CA1332024C - Shock absorber band - Google Patents

Abstract

ABSTRACT
Polymeric Film Material and its Production Orientable thermoplastic polymeric film material is provided with at least one stretched zone in which the material has been stretched in a first direction and, adjacent to the opposite sides of the zone, unstretched zones in which the material is substantially unstretched.
The material is of particular value for preventing rupture of bags containing the material, especially when the zones are adjacent a seam in a filled sack and/or in the gusset of a gusset bag.

Description

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13~202~
60/28~6~/01 Polymeric F~lm Ma~erial and lt~ Produ~tion Wh~n forming bags and other articles from orientable thermoplastic polymerle film material, varlo~s way~ are S known and us~d for en~urln~ that the ~il~ mate~ial has adequate stren~th for th~ p~rpo~es to which the ~ag will be subjected. Pe~pi~e this, there i5 always a rlsk that the ~in~l arti~le wil~ rupture during use when it is :~ s~e~ted to sudden forces. ~r instance ~ sack ~hat has be~n ~illed ~ith powder or granules may rupture when dropped, ~he ~enden~y i~ greater with relati~ely rigid polyme~s (considering the ~odulus of elasticity) such ~-~polypropylene or high deneity polyethylene than ~ith less rigid polymers such as low dens$ty pol~ethylQne~ but even the low rigidlty polymers have a tendency to r~pt~re when ~ubjected to imp~ct. ~.
It would be desirable to ~ind a way of reducing ~e -.
tendencv for the ~ilm materi~l ~or article formed ~rom it) to rupture undar impact, and to lncrease the energ~
20 absorption properties of th~ article. ~:
The prQsent ln~ention is concerned with ways Of ;:~
~preading ~he ten~ion and other ~o~ces in a ilm material in ~uch a wa~ AS to mini~lse the rlsk of rupture. ::
In so~e instances, it would ~e desirable fox a ~ajor 2S proportion of the article, or even the entire article, to ~: be ~o~fied in th~s ~anner. ~o~ ;ns~ance it ca~ be ~:
~esirabl~ to modify. strapping formed fro~ ori~ntable film ~: mat~ri~l, especially strapping for parachute~, in order to ~ini~isc the risk of ~pture under impact or to reduce the 1 ~ act on the loa~ which the strapping is ln~end~d to carry, or for si~ila~ reasons it can ~e desirable tO
~od~fy the entire sur~ce area (o~ parts o~ the entire surfac~ are~) of large sheets, such as the hood of a :
pa~achute.

133202~

In oth~r cases it i5 desira~le to modify ~inor proportions of the film in selected areas. Thus particular problems a~ise ~ith sacks or bags since generally there is a particular zone in the bag ~t which 5 the bag is liable to star~ rupturin~, ~nd I re~e~ to this :~
as the rupture 20ne. It ~ould be p~ticularly ~esira~le :~
~o mod~f~ the bag in the rupt~re zone. Once ruptur~ng has b~en initiated, the rupturing is l~able _o be :propogated out of the rupt~e zone. The rupture zone, I
~ 10 ~or any partlcular con5truct~o~ ~f bag, can be postulated : from theoretlcal consideration~ or, in a ~ore practical aspect, can be deter~ined exper~entally bv dxopping so~e ¦
f~ ag~
The rupture zone is often a~soc~ated wi~h a seam in ;
15 the bag ln that the fil~ m~terlal ~d~acent tO a se~ is :~
often more liable to rupture than ~ aterial elsewhere in the bag. It appears that the act of forming the seam can adver~ely af~ect the propertles of the ~ material ln the areas adjacent to the 6eam. Howe~er lt should be .~
ZO~ noted~ tbat the rupture zone may not extend acros~ the i, ent~re length of ~he ~eam slnce in a conventlonal ~ag the .:~
r~pture zone ~ay be locatQ~ pri~ar~ly ln the ar~a mid-way etween:the ends of the seam.
WSen the bag ls ~ g~ssetted bag that h/as an end 52al ` ;;~:
and tha~ compxise~ oppo~ea ou~er facesfinterconnQcted at t~e~r side jedges~ b~f side ~u~sets,there tends to be particula~ rupt~e 20~e at the junc~ion bet~een ~he side `~
gusset6 and the seam.
bag ma~ have ~ore than one rupture zone. For --30 instance ~ ~ the ~ag is 6ea~ed at top and bottom then : there wS 11 generally be a r~pture ~one associated with each sea~ ~and at ~hl~h rupture is liXely durlng edge drops) and if the bag ha~ side gussets then there will generally bc a particular rupture zone also a~ ~he ~:

'~ 3 1 3 3 2 0 2 4 junction between the side gussets and the sea~ ~and at ~ich rupture is likely during flat ~rops).
It i~ of cou~ very well known to su~c~ the film material from which the bag is made to v~rious S oxientation and other treatment steps ~o as to impart optimum propertles to lt but conventionalt~ the film throughout the entire ~ag is of substantially unif4r~
properties, I~ i5 aleo ~ell known to em~oss the surface of the fil~ either or visual app~arances or to fa~ilitate ~t~cking of the fllm. Rowever conventional ov~rall emhossing technl~ues do not give the ~mp~ovements that would be de~ira~le~
Ori~ntable ther~oplas~ic poly~eric ~ aterial a~cord,ing to the invention has at l~ast one stretched lS zone in whiçh the material has ~een s~retched in a ~irst direction and adjaeent to oppo3ite sides o~ this or each zone, unstretched zones that ex~end ~,bstantially ln the said ~lrst direction a~d in which ~he material is 3ubs~antially ~n~tretch~d.
~h~q in the ~vention ~he ~ilm ma~e~al i5 not of unif~r~ stretch but is ins~ead given ~arlable de~rees of stretch so ~s to provld~ the ~t least one stretched zone and the plurAlity of substantially un,stretched zones.
~:~ These unstretched zones have a degree of stretch significantly less than the stretch of the stretched ~ zone, ~ut they may be stretc~,ed slightly more ~han tha:~ origin~l fil~ ~aterial, before the stretchlng in the stretch~d ~one. ~refera~ly there are a plurali~y of these unstretched zones, eaah located betw~en a pair of stretch,ed zone~.
! Generally the degree o~ stretch in stretched 20ne is at least 10~ and genQrally a~ l~ast '0~, for in~tan,ce ~p to 30 or 40~ or more relative ~o the initial film materlal and preferably ~he ~ilm ~aterial in the substantlally unstrstched, zones has little or no stretch, 1~32024 relative to the initial film material. The initial '~1 material must be orientable, but it may already have ~een .
oriented to a limited extent.
It is therefore necessary that, within each :
~tretched zone, the fi~m materlal ~hould have a longer length than the adjacent unstretched zone. ~he film material in thc st~etched z~ne ~ay co~pri~e a ~eries of regularly or irregularly ar~anged pleats that extend trans~erçel~ to the length o~ the stretched zone. A ~:
10 convenient way o forming each stretched zone comprises ~-:
pro~idlng a series of transver6ely extendinq positions at :
which the fil~ materi~l is stretched (i.e. it is ~tre~ched ln the said first dire~tion of the st~etched one). In parti~ular, thi~ is ~est a~hie~ed by 15 ~tretching each zone by embo~sing the film material in - :`
that zone with tec~h that ~xtena tran3versely to t~ne first direction. Often the ~tretched zones ~re longitudinal and extend in the first d~rcct~on. :~
he invention can be ~ppliea to the e~ti~e area of a :~
sheet material in which e~ent, as indicated, there are preferably a pl~rality of the stretched and uns~retched ~ ~
~o~es alternat~ng with one another. Each unstretch~d ` .
: zone may be in thQ form of a ri~bon that may ~e rectil~near or zi~-~ag and which ~ay have a wid~h 25 typically of 5 to 150~ of the width of each stretched -~:
zone. Typically each un3tretched 20ne ~s a~ 'east O.~m ~:
wide and each stretched zone is ~t least 2mm and preferabl, at leas~ 5mm ~-ide. When the unstre~ched ~anes ~: ~ a~e alt~rnating with the stretched zones, the unstretched 30 zones are generally not ~ore than abou~ Smm or ~ometi~es :~
10~ wide although they can be ~ide~, whilst the :::
st~etchea zones car. fre~uently be up to 20mm or 30mm wid~, or mo~e. ;~
:~ The in~ention is of particular ~alue when applied to .
the avoidance of rupture of bags ~hat may be sacks1.
...~.

s 1332024 In ~his aspect of the invention, tubular orien~able thermop~astic polymeric film matexlal th~t is or can be s~aled ~o form a clo~ed bag havlng a ruptu~e zone at which Xupture is lia~le to occur when th~ ~ag is S s~bjected to rupture force~ by beln~ dropped when full is provid~d and the film m~terial adjacent the rup~ure zone in~ludes shocX absorbing zone compri3in~
at 1 east one str~tched z~ne that e~tends in a directlon leading sub~tantially away ~ro~ the rupt~re zone and in whioh the film material has b~n ~tretched s~bstantially in that tirect~on, and a plurality o~ sub~tan~ially unstret~he~ zones ~d~acent ~o and extend~ng in subs~antially ~he sa~e d~rec~ion as the or each ~tretched zone, whereby the r~pture forc~s are tran~mitted away from ~: the rupture zone by the un~tre~ched zone~ and in'o the : stretched zone or zone~.
~he tubular material of the in~ention ma~ be a clo~ed bag, an open bag or an open tube that can ~e sealed ~o form an open bag. ~or lnstan~e it may be a~
ena:ess tube that can b~ sealed and cut to eor~ a pl~rality of tubes. The material is generally e~ended in tubular form, ~ut if ~esired a shee~ ~ay be ~ide ~S seale~ ~o ~or~ the tubul~r ~aterial.
In ~hi~ aspect o~ the inven~ion the rup~ur~ 20ne is preferaSly along a heat ~eal0d o~ stitched sea~ in the final b~g, and thc shock a~sor~ing zone is pre~erably a shoc~ absorber band t"SAB") tha~ ls separated from the sea~ by ~n unstretohed area thro~h whi~h the rupt~re force~ can ~e trans~itte~ in~o the shocX a~sorbe~ ba~d, : and the band comprise~ a plurality of ribbons of ~ub~tantially un6tretched ma~erial extending sub~tantially in th~ dire~tion of ~orce~ ~eting on the ~eam ~which norm~lly will ~e substantially perpendi~ular 6 1332o2~

to ~he seam) separated by strips of f ilm materlal that ha~e be~n stretched s~bstantially in the sa~e direction (i,e. nor~all~t 6ub~tanti~11y pcrpendicular to the seam).
~he ~idth of each unstretched ribbon does, for optlmum p~operties, depend upon the partic~lar fil~ m~ter~als being used but is typically in ~he ran~e 5 to 150~ of the width of each adjacent stretched strip. As mentioned, the direction of force~ ac~ing on the seam is ~ormall~
substa~t~ally perpendicul~ to the ~ea~. An e~ception to this are seams made on the ~a~ in gussets.
Each ~stretched ribbon preferably e:~tends cont~nuously ac~oss the entlre depth o~ the shocX
absorber band, in the diversion of the band perpendicular to the associated seam. It may extend as a substantially straight line or as a zig-zag line 15 provided the changes of direction within the zig-zag line are not so great as to prevent the transference of the load forces along the length of the line.
~ hen the ~upture zone is the se~, it ~s desirable fo~ the shoc~ absor~e~ band to be displaced ~ short di~ance, for instance at lea~t l~m and o~ten at least 3cm $rom the seam, in order th~t the rupture forces at or ~djacent the sea~ can be dictributed over a ~seful width of the shoek absorbing band. ~enerally, good ~esults are obtained uhen th~ di~placem~nt is for instance not more 2S than lOc~ and often not more than 5 or 6cm. The depth of the shock abso~bing band, i,e., the distance from ~ts edge adjace~t the seam to its further~ost edge, is typically ~n the range 3 to lOcm.
:: ~he parts of the seam where the ruptu~e forces are 30 most liablc to cause rupt~re are ~hose that are inwardly displ~ced ~ro~ the side edges of the bag, in con~entional bag desiqns, and eo it ca~ ~e ~nnecessary for the shoc~
ab~orbing ban~ to ext~nd to the o~termost edses.
Instead it ~ay ext~nd be~ween side positions tha~ are displaced ~nwardly from the edge~ of the ba~.

~ 1332~2~

n ~ seco~d aspect of the invention, th~ orientable ~ilm materi~1 is in the form o~ a bag compri~ing opposed o~ter fa~es in~erconne~ted at thcir ~ide edges b~ side gussets. In thi4 case th~re ~s a par~icular rupture zo~e 5 at thc junction betweon the side gusse~s and a heat scaled or s~itched end se~m tending to cau~e rupture ~hen the bag is dropped on one of its f~at face3. Part or all of the side gussets ~ay be in ~he form of one or more of th~ described ~retched zones of logitudinally ~tret~hed material whilst the uns~ret~hed zones of su~s~antially unst~etched material may be ~it~in the gussets, ~or instance alternatlng with s~retchea zones or at ~he cent~e fold of the g~siset~, or may be at the extreme edges of the ~us~ets or at the edges of the outer faces lS of the ~ack, or may be displaced inwardly fro~ the outer ed~e~ of the sack. This cons~ruc~ion means that load is taken by ~he unstretched long$tudinal zones in o~
a~acen~ to the gussets but the otretched l~ngitudinal zones in the gusset6 absorb shock and so protect ~he ju~c~ions fro~ ruptu~e.
I now dlscuss in ~ore detail the avoldance of rupture along a sea~. ~he i~pact strength of a seam in ~: a bag u~ually is one of the ~ost critic~l propext~es of the bag. "Impact 6trength" here re~ers to drop test~
;~ 25 ~erfor~ed on th~ ~a~ filled wi~h the powaer or granule~
: for whlch ~t is ~nt~nded. ~orm~lly it will n~ ~e possi~le to produce an adequate, simple "peel-type" heat 6eal (as opposed to the ~ore co~plicated "shear-type~
: he.at seals) in bags ~de 4ro~ relativel~ rigid poly~ers I(re~errlng to the modulus of elasticity) such as polyprop!rlene or hi~h densitv polyethylene, even ~hen the mentioned ~o polymers have ~een modified ~y addition of elastomer~ in amounts econo~ically and practically acceptable, ~:

. ~ 1332024 The peel strength of ~uch heat seals, measured at th~ l~w veloel~ie~ ~7hich are customary for tensile testing, normally ~111 show v~lues at g~nerally th~ same level or e~n hi~he~ than a h~at seal of low densi~y polyethylen~ o~ slmilar thicknes~, while the impact strength o~ ~he polypro~lene or high density polyethylene seals is very inferior comp~red to low density polyethylene ~eals.
By a study o~ these problems, I have Lound that the 1~ poor impact ~trength is conne~ed wi~h a pheno~enon that may be e~uivalent to notch effect, namely, the conc~ntration o4 peelin~ forces in a ~arrow linear are~
around the boundary of the contact-ace of the seal.
Add~ionally, th~re will often be a real no~ch effect due ~o imperfection in the shape o~ the ~eater bars ~sed for formlng a heat seal. Where ~he ten~ile for~es are concentrated, orien~ati~n will star~. If the peeling action i3 slow this orien~ation will gradually de~elop aw~ from the ~tarting line and will improve the stren~th i~ this area. If, however, the rate of th~ peelin~
action e~ceeds a certaln ~rit~cal range, dependent on the ....
~aterial a~d of paxam~ters of the pre~ious heat seal -operation, the progres~ of the orie~tation ~which is a time dependent process) will ~ema~n co~flnad to a very :~
limited line~r zon~ in~tead of qradually w~de~ng this zone. ~h~ high ~nergy action on an extre~ely limited zone almo6t instantly causes a rupt~re~ .
I believe ~h- d~ 4ferent character o~ the o~ientation proces~ when e~ected ~elow and above th~ ~ritical range of peeling rates m~inly is a ~atter of heat developed ~y ,: ~ the ~tretching, the heat produced by the internal ~riction being high when the polymer is rigid. ~t ra~es be~ow the critical range I believe there is tlme fo~ the heat to be condueted into adjace~t por~ions of the film 60 as tO ~elp the orlentat~on to develop gradually and '~. ..

1332~24 smooth'y. ~Qntrar~W~se~ a~ rates abo~e the critical ran~q thQre ~ ~ not time enough 40r the heat to be conducted away from th~ narro~ zone which is under the influence o~ ~notch ef~ect~ (or similar) and the polymer S will al~ost iD~tantly ~elt ~ithin this zone.
2crforat~ on8 c~use~ by the ~titchin~ ln a stitched seal ~ay also ca~se wea~ne3ses a~d in ~his c~6e the resifitace to rupt~re ~s very dependent on the velocity.
In the in~en~ion I ~ttempt to alter the ~haracterist~ of the bag material in a region near to .. the sea~ with the aim that the energy released by dropping the fllled bag sXould be guided to attack another, prede~ermi~d and less sensitive ~a~t of the bag ~; conatruction.
It should be note~ that the described deficiency in heat sealed bag~ from ri~id materials i9 particularly pronounced i~ the ~aterial i~ oriented ~y stretchinq below its melting point. I~ ~his connect~on it is known that cross lami~ates of ~niaxially oriented high density .
poLyethylene or poly~ro W lene ~wh~ ch may contain minor ~: ~mounts o elastomer) with a suita~le, not too strong bonding establlshed b~ween the plies, exhi~it high tear propagation and impact stren~th ~alues in the film t3elf, and glued bsgs ~ainly valve ba~s) o~ such cro~s ~ ~ 25 laminates have ~ouna ~mportant commer~ial uses. It is noted that xigidity, per se, is a desirable praperty for a baq ~aterial. It is also Xnown that heat sealslin these cross laminates ~how good peel strength when ~easured at thc rates normally used in tenslle tes~ing, however, the imp~ct-peel-stre~th ~f such seals is :~particularly lo~ maXing these otherwlse verr usef~1 :
materials comple~ely u~eles~ for simple ~elded ~ag co~structions.
By ~tudies and theoretical ~ork ~ith oriented film 35 mate~ial, I have found thlat the above mentioned notch ~

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- lO 133202~

effect (or similar) is adversely co~ple~e~ted by the loss o~ orientation in the area i~ediately adjacent to the heat sealed area. ~he orientation, of co~rse, i.s also lost in the ~eale~ a~ea itself, but sinc~ this area is thicker this seems to be immaterial in this connection.) In ~he oriented material i~self there is a hlgh resistance against ~ur~her orlentatlo~ de~eloping, but not so in the unoriented lineary zone adjacent to the seal. ~herefore, not only the notch e~fect (or t~e like) b~t also the ruin~ng of orientation ca~ses the impact action or rupture forces to be confined to a very narrow zone. As a re~ult, even material ~uch less rigid than high de~sity polye~hylene or polyprop~lene, but in oriented state, ~ecomes useless for the sealed ~ag constructions here 1~ dealt with. -U,S, patent no.4,039,364 concer~s a ~ethod o prs~ucing ~ cross laminate of a type 2i~iferent rom theC~055 la~lnates mentioned ~bove. Rere each ply is biaxially oriented, and instead of criss-crossing of 2~ direc~ions o unia:~ial orientation there is established c~iss crossing of "graln of polymer~, which grai~ is primarily proa~ced during the extrusion, but then through the sequence of stretching steps, deflected to a desirable zig~ag cou~se. As stated in the mentioned patent, ~hese cxoss lamlnate6 generally are ~lell suited ~or heat sealing, a matter ~hich can be explained partly the shrin~abil~ty ~ h~oh the heat sealed and the a~jace~t areas increase in thickness, and pa~tly by the special zig-~agging ~ra~ n of polymer. Nevertheless, i~provement of ~he heat seals of such cross laminates are sti~l de~irable, ~s the examples of ~hei pre6ent zpecification will sho~.
F~rther, ac to ~he adverse ~ole of material r:gidity in co~ection ~ith the impact strength o~ a seal, it ~hould ~e borne ln mlnd that what ma'~ers here is the 33202~

ri~idity at the temperatures exis~ing when the filled bag is dropped, by inten~ or ~ccident. Thus, ~ven nor~al low dsnsit~ polyethylene ls relativel~ rigid, e.g., at -20C, and the drop strength ~ simple heat seals of lo~
S den6i~y polyeth~lene ~ags a~ that t~mperatures has been fo~nd significantly inferior to tha~ esta~lished at roo~
~emp~atures. How~ver, -20~C and even lower temperatu~es in many cases are normal ~or handling of bags and, thereforeO there also exists a n~ed to r~$nforce ~he seals of low density polye~hylene bags.
~ preferred ba~ (or tu~ula~ material for orming a bag) ao¢ording to the in~entlon ~omprises, in combination wtth a s~am, a ~rlpe pattern o~ embossmen~ along the s~a~ adjacent but spaced ~rom the seam. The embossed pattern consi~t~ of row6 o~ ~eeth-like indentations, in ~hich the fil~ is elongated malnly in the direction of ~he ~orce~ o~o~rring during a cr~tic~l type of drop, i.e.
nor~ally mainly perpendicularly to the seam, separat~d ~y ri~bon~ of ~ubstantlally unaltered ~ material, ~o ~ause a shock abso~b~ng affect which protects the seam ~tself, when ~he filled bAg is dropped. The embossment cau~es stretching.
The rlbbons of subst~ntially unalter~d film material should b~ 6ufficiently narrow loo~pared to the teeth-like indentations), and the degree of local elongation produced by ~he embossment should be sufficiently high, to ~ecure ~hat the descrlbed shock ab orbing effect really is establishod a~d acts to retard the peeling action, so that a certa~n orienta~ion can "calml~
d~velop in the area jus~ ad~acent to the seam. The optimu~ design of thQ pattern ~which will hereafter be callsd n tho shoc~ ab60rber band") depends on the per~ormanee ~quirement~, the film chara~teristics, the dimen~ion~ of the bag, ~he material which will be filled in~o the ~a~, ~he degree of filling, the sealin~ or 133202~

~ewin~ procQ~s and the temperature at which the drop~ are envisaged to take place. In any case, however, this design will cau~e no principal problems for a skilled person working by trial and error.
S In the accompanying drawings:
Figure 1 ahowR, on ~cale about 1:3, an open-mouth pillow-bag, oupplied with two ~hock-absorber-bands, one near the heat-~eal at the bottom, and one at the top near the region predetermined for closing either by heat-~ealing or by sewing.
Figures 2A and B are details on approximately true scalo of the bottom of the ~ack of Figure 1, A being a horizontal vlew of the bag, and B a longitudinal, vertical section pas~ing through a row of indentations.
Figure 3 i8 a modification of the shock-absorber-band of Figure 2A, al80 shown in horizontal view and on about true scale.
Figure 4A are strain/stress diagrams taken on 5 specimen~
from the shock-absorbQr-band zone of a sack produced a~
described in Example 4.
, Figure 4B ar- strain/stress diagrams for aompari~on, taken on 5 specimen~ f:rom the samQ sack, but out~ide th ~shock~absorb~r-band~ zone.
;~ Flgures 5A and B on the same sheet as Figure 1 ~how dlfferent sections of a set of embossment whee}~ (rollers) ~`suitable for making the shock-absorber-band. Figur SA is a ~` 25 ~ection through b-b of Pigure SB, and Figure 5B i~ a section through a-a of Figure 5A.
Figure 6 i8 a per~pective view on approximately true ~cale showing a corner of a gussetted bag, in which the gusset i~
supplied with an embossment to eliminate the critical ten~ion which otherwise occurs at the intersection between the seam and the innermost fold of the gusset.
The ribbon~ of unaltered fil~ material may be generally ~traightline ribbon~ (reference to Figures 1 and 2a) or may be generally sig-sagging a~ by staggered embossment (referena- to .

133202~
- 12a -Figure 3) The former ~ake6 the machining of embos~mQnt tool~
easiQr, while the latter enables the ~ost e~ficient ~hock absorption effQct, which may be needed wh~n th~ material i~
particularly rigid or particularly oriented S In the dQscription above, the invention has been de6cribed with a particular view to "peel-type~ heat seals However, a similar problem of low impact strength often exist~ for ~ovorlap~ ~Qal~ in ca~e~ wh-n heat sealing of th ~atorial i~
diffieult, in particular whon the polym~r is oriontod Probl~
of a ~imilar nature can also ~ccur with overlapping seam~ bonded by a ~elt adhesiv- and with super~onically produced soams The invention therefore is useful in all such cases Furtherf the invention i8 very advantageous in connection with a sewn seam The strength of a ~ewn seam is essentiaily lS~ dependent on the toar propagation strength in the film, which aqain for stiff and/or oriented material is critically dependont on th~ voloGity of tearing Thi~ also i~ true for tho abovo ~entioned two kind- of Gro~s laminates, which both show a high toar propagation strength up t~ a certain critical range of tearing rat-, but genorally poor tear propagation strength above thi~ rang- The ~hock absorber band~ therefore ean advantaqeou~ly be used to take up tho top of the impact aetion, redueing the toaring rat- to a valuo below the critical rango ~;
,,, i I ~ ' ` ' "':~ ' ;
:
.'~ ,.
~' ~

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~ _~ 13 1332024 The shock abso~be. band is applicable to top and bottom seams as well as side seams~ It hls been 'ound ~hat the forces exerted n~ar the corners of a ~illed bag when the bag i~ dropped are alway~ xelatively small, ~onsequently ~he "shock ab~orber band" neQds not evtend right to the ~dge~ of th~ ba~.
~ he in~Qntion further concerns the ~e~hod of combining ~ea~ing o~ a bag with embossment in the specific pattern which appears from the above d~scription of the product, and ~o the combination of Seaming and em~o~sing apparat~l~ for ¢arrying o~ ~his ~ethod.
Th~ shock ~bsorber band can be produced prior to, simultaneous with o~ subsequen~ to the seaming process.
Thus, the shock absorber b~nd can ~e em~ossed either (al on ~ilm be~ore tubing, or tb) on tube before bag making, or ~c) on ~he bag before $illing, ox (d) on the filled bag before thG f~nal sea~ is made, or ~e) after ~aking : the ~inal seam. The invention also cover~ bag~ and pre-stages of a bag (e,g., tubes for ~orm-and-fill) with shoc~ absorber ~and alone, correctly located in relation to a seam ~hich i 8 not yet made but intended to be made later, ~his will us~ally be the top seam or both top and bo~om seams ~ade in connec~ion with the ~illi~g process. ~ag machines or form-~nd-fill ~achines using pre ormed tu~e wi~h ~hock absorber b~nd can be supplied with qy~ch~onisation devl~s SO as to ma~e the sea~s a~
the corr~ct locatlon~ in relation to the band~.
As mentlonod, a ~hock absorbe~ ~nd for the ~op seam o~ an open mouth bag c'an be made a~ter the ~illing process, in connection ~ith sea~ing of ~he bags. The seami~g will ~s~ally take place by a conventional band sealer or a conventional sewing machi~e, and in su~h cases the shock absorber band is prefera~ly produced continuou~ly between a set of emboss~ent wheels oÇ which one can be ~upplied with a ~ala sur~ace pattern and the oth~r with ~ corresponding female surface patt~rn. (See Figure 5a nd b.) In other case~ it will often be preferable to carry ou~ the embossment $ntermittently, e.g., by use o~ a hydraulic or pneumatic pre~s, still between male and ~emale formed sur~ace patterns.
If a transver~e 6hock absorber band is made b~l embos~ment of tubular ~ilm, it may be dif~icu~t, witho~t special measures, to open the ~ube for filling.
~heref~re, it is often advan~ageous to make at least the s~ock absorber band ~or the top seam o~ an open mouth bag whll~ the ba~ material i~ a fl~ film, and then convert the flat film ~o B tube. In su~h cases, the m~chinery ~or embossm~nt ~an convenien~y be combined and nchroniJed either wlth a printing machine or directly 15 with the bag making ~achine.
In this ca6e th~ slde seam i6 formed subseque~t to the embossing of the shock absorber band for bottom ~: andlor top s~am~ and when the 6ide seam i~ produced either by appli~atlon 0~ hot melt adhesive ar by heat :20 seallng~ the applicat~o~ of hea~ will eause ~he embos6ment to di~appear ~t the ~pot where the shoc~
abso~ber band Lnt~r~e~t~ with the side seam. Ho~er, ~his dQes not h~e ~n~ adver~e e~e~t provided the side s~am i~ located very close to one edge of the ba~ since . 2S ag ~entlon~d above the impact actlon is relatively 10W
~ .
nea~ to the corners of the ~aq .
he fact that only the unalt~red ribbons in the shock-a~sor~er-band have to carxy the tensions perpand~cula~ly to the ~eam, mean~ that the coefficient of elasticity in ~hi~ band appears to be ~i~nificantl~
reduced, so that the band so to say acts a~ a rubb~r band, and at the same time the all-over yield force in he band will be red~ced. Both features wlll be further explai~ca in conneet~on with Figure~ 1 to 4. ~he reduction of yiald force can lead to permanent . 15 deformations of the m~terial within the shock-absorber-band ~v~n durin~ normal handl~ng or storage of the bag, bu~ these deformations no~mall~ will be r~latively un~mpo~tar~t, Aince they ~re con~lned .o the 5 rlaxrow band and, g~nerally speaking, terminate when the bo~ses have be~ome straightened out. The ~alance between the ne~ds for good drop performance and sufficien~ resistance to yield is an intpor~ant factor to consider in ~he choice of optlmurn pat~ern.
If the bag is intende~ to be carried ~anually and maint~in ~ts ~hape a~ter this, the shock-absorber-band 6hou~d preferably ~ot traverse the bag sur~ace ~rom edge to edge, but portion near the edges shoula be left unembossed, ~hese ~eing of a width su~ficient to avoid any sub~tantial deforma~ion when the filled b~ is llf~ed a~ the corner~. As ~entioned earlier, there is no essential need ~or ~hock~absorption effect at these locat~ons, since in any case the peel forces will be relat~vely lo~ ~ere when the bag is dropped.
In order t~ achieve a sufficiently important shoc~-ab40rbing ~ffect, the pa~ern and depth of exbos~mQnt should be adapted to give no l~ss than 15~ and prefexably ~ore than 2$~ i~pro~emen~ of ncritical drop height" for one drop cycle. ~Critical drop height" here ~:~25 ig de~ined as the drop hei~ht ~hi~h, statistically, is the li~it be~een no-failu~e and failure, ~hen One bag :~ith the relev~nt contents o~ powdere~ or granulated : ~goods is dropped 6 time~ in the fol~owing cycle~
lat surface, ~) 2nd flat surfac~, (3~ 1st edge, (4) 2nd edge, (5) ~ot~om, ~6) top~
~`~owe~ex, w~th suita~le selection of pat~ern and dep~h of embossment ~guidelines ~or this ~e~ection given ~:in sonnection with Fig~res 1 to 4~ th~ incr~ase in critical drop helght for one drop cycle can in many cases ~e 50~ or 100~ or even more, withou~ causing any ~':

' ` 16 ~33202 4 essential damage of the capability to resiQt deormation during handling and ~torage of the bag, ~mbossment of the film materi~l in ba~s is ~nown ~or the purpose of improving the anti~sl~p ch~ra~tQristlcs, which are lmportant for stacking. For this purpose, how~ver, it is important to select a type o e~bossmen~ whi~h onl,r creates ~inimum reduction in coefficient of ela~ticlt~
and yield ~orce ~refer~ing ~o the apparent values as further explained in connection wi~h Figures l ~o ~). A
1~ bag with the ~hock-absor~er-band can also, in order to ~mprove ~he anti-slip praperties, be supplied with an additional embossment in other ~elected areas or generally all-over, b~t in ~uch c~ses the pattern a~d dep~h of emboss~ent ~n the shoc~-absorbcr-b~nd ~ust be lS adapted to produce ~ subst~n~lally higher shock absorption e~fec~. ~T~e basic features of ~hock a~sorption ef~ect are expla~ned ~ore quantitativel~ in : connection with the graphs in Figur~s 4A and 4~.) A~ mentionQd in the introduction, gussetted sacks ~ith button and/or top heat seals have a particular, : spot-~ormed rupture zone in or im~ediately adjacent to each of he interse~tlcns between the lnnermos~ folds of the gussets and ~he bottom o~ top heat seal. The rupture in ~hese zones mainly occur3 when the fille~ sacX is ~S dropp~d on one of its ~lat ~aces. There are two reasons for the tendency ~ pture in these spQts~ one ~hi~h one ~ i~ the ~udden ch~nge in th~ckne6s hetween the gussatted, : 4-ply, part o~ the s~ck and the part which i~ not : gusse~ted, i.e. ~s 2-ply. This change o~ thick~ess makes thc heat-sealing particularl~ critical. Ano~her reason ,~. wh~ ruptur~ tends to occur in these ~pots is that, when ~he sack h~s ~een filled and the gusset there~ore has unfolded to g~ve the sac~ brick-form, the p~ll on the gusset at each corner o~ the sack has to ~e taken-up m~inly by th¢ narrow spot ~here the heat-seal int~rsects 1~ 1332~2~

with the in~er~os~ ~old of the gusset. Then ~hen the sack i8 dropped on o~e o~ its fl~t faces, the contents becomes thrown out against ~he corner o~ the sacX, and ths re~ultant pull on the ~usset in this corner concentrates ln ~he narrow spot of intersec~ion.
Consequently, gussetted sacks ~annot ~ithstand ~lat drop~
from the sa~e maximum h~ights as simple "pillo~ 6acks" of ~imilar materi~l, unl~os sp~cial precautions are taken.
Th~s applies ~lso to gussetted sacks fro~ soft and read~ly heat-seala~le materi~ u~h as ~DPE or LDP~.
In the known art, this problem i9 solved by supplying each gussetted corner with two extra, rectilinear heat-seal~, each one sealing one si~e of the gusset to th~ corresponding outer ply of the ~a~k, and 1~ ~ach s~arti~g in the mentloned spot of intersection and extending on bias, normally inclined 4S~ to the : longitudinal direc~ion o the sack. ~ith these extra heat-6eals, the gusset ~ill still ~old in the normal way in the corner and ~ill give the sack ~ri~k-shape durlng ~illing, but now the ~orces on the gusset in the corner dur~ng a fl~t ~rop will become distributed ove~
th~ ent~re len~th of the two e~ra heat-s~als instead of concent~ating on one spot.
A drawba~k of th~s com~only used precaution is the r~latively long ti~e needed ~or the special ex~ra ~ heat-6ealing, which necessarily ~ncludes a ~ool~ng step `~ before the ~wo ~ide6 of ths gusset meet each other again, slnce otherwise they would fuse ~o~ether and f~rm one ~ngle se~
` 30 Therofo~e, the ext~a sealing procedur/ 3s more conveniently, accordinq to this invention, su~stitut~d by ap~lication of S-A-B to the gusse~s in the co~ne~s o~ the sa~k~ Th~s S-A-s shoula not, in ~ssence, e~end into the two outer plie6 of the sack, but be confined ~o the ~ ~ la 1332024 gusset near the corner (hara refer~ing to the structure ' o~ the sack hefo~e unfolding of ~he gus~et).
Ideally, the unstretchQd ~ones or ~riSbons" in the S-A-~ should all poin~ in the direction of the spot of S interscction ~o as to point the same wa~ as the tens~ons in the un~olded gu6~et ~ut in order to make the con~truction of the toolG ~mplex the pattern of embossm~nt can ~e li)ce in example 3, in which t},~
~ribbons" all ~xtend in the logitudinal direction of the 10 saclc. At least the "ribbons" near the innermost fold o~
tho gusset then malnly point towards the spot of intersection.
A3 an add~ional advanta~e, the apparent s~rong reduction of coeffi~ient of elasti~ity effe~ted by the 15 eTnbossment of the gusset~ near the corners of the sack helps th~ ~ontents better to ~ill out the space ln the corners and there~y the bri~k-shape becomes perfected.
Shoc3c-absorber band~ can optionally be ~sed in :~ combina~c~oJl ~ith the em~os~ment of the gusse~ here 20 descri~ed. Thus, the oombined use of "gusset embo~smen~" ~na ~ sho~k-absorber-band" described in example 3 gave improv~ment ln critical drop height b~ a fa~tor exceeding thr~e. The "gusse~ embossMent" i5 preferably carried out on ~lat ~ilm b~fo~e tubin~ or on ~lat tub~ before gussetting, but can also be calried out : af~er gussetting, and even a~er bag maklng, provided ~he ~nte~nal o~ the bag is convenientl~ a~cessible.
An alternat~ve, and in so~e cases slmpler precaution, which doe~ not t~uly fall under the above montioned definition of shock-absor~er-band but utili~es an analogous effect consists in stretching by e~bossment the innermost fold o~ the gus~et lmmediately adjacent to the bot~om andtor top seals, Thu~ tha gusset and the adjacent ~aces of th~ ba~ can be cons~dere~ to be a special form o~ the shocX a~sorblng ~on~ o~ the .~", ~ :;

invention, which may extend from ~ position at or close to the junction betwee~ the seam and ~he side gu~sets and ~hich need not extend substantially acro~ the width o~
the gusset~. The edges of the outer f~ces o~ the bag and/or parts withln the gus~ may ser~e a~ the substantially unstretched zone9 adj~cent t~ the stre~che~
zone, that i6 part or all o~ the area within the gussets.
Simultaneous embossment of the outer pli~s of ~he sack may do no harm, but ma~es the procedure ~impler. This embossm~nt in ~he gussets must be sufficientl~ deep and/or ~ufficiently close to the seal, to pro~uce the ~ffect that a tension applied to the fold is essen~ially ~arr~ed ~way from the spot of intersection ~whe~e the heat-s~aling as mentloned tends to be critical) and into a part Oc the heat-~eal closer to the ed~e-face o~ the sack.
Prefera~ly, this e~bos3ment should gradually fade-off in the direction to~rds the edge in s~ch a ~nner as ~ distrib~te the forces up on the ~nnermost fold of the gus~e~ over a wider part of the bottom or top seal .
In ord~ ~o ensure a preclse location o~ this embossm~n~ relati~e to the ~pot of int~rsection bet~een ~he inn~rmost fold and the bottom or top seal, this e~ossment is mor~ convenicn~ly ~arried o~t slmultaneously with the heat-sealing on the ~ame apparatus, whlch may compri~e m~ans to detect the tran~verse location of the innermost ~old and accordingly ~or auto~atic transv~rse ~djust~en~ or the loca~ion of embossment.
~ 3 alrQady ment~oncd, the shock-ab~orb~r-band is very suited for bags made ~rom the cro~-lam~na~e~
described in U.8. patent n~.4,039,~4. The ~ame ls true ~or the "gusset embossment~ desc~ibed above. u.S.
patent no,4,629,525 discloses improved compo~io~s for 133202~

cross-laminates of this type, consisting of two or more plies, of which each normally has a main layer, a layer to facilitate lamination, and a seal layer. The two embossment systems according to the present invention can advantageously be used, separately or in combination, on bags from these compositions. Thus, a particularly preferred main layer for use in such laminated sheet for the bag of the invention is formed of a blend of high molecular weight high density polyethylene with significantly lower molecular weight low density polyethylene, the latter preferably being selected from copolymers and/or branched polyethylenes which have the io same or higher elongation of break (tested at room temperature under slow s~retching) as the high molecular weight polyethylene and which are capable of distinctly segregating, while forming a distinct microphase, from the high molecular weight polyethylene on cooling of a molten homogeneous blend of the components. The blending ratio of the ;~ 15 polyethylenes is preferably 25:75 to 75:25. The inclusion of polypropylene having significantly lower molecular weight than the high molecular weight polyethylene can also be advantageous, in amounts from 0 to 70%, based on the combined weight of polypropylene and both polyethylenes.

> `~
21 ~332024 The high molecular weight high density polyethylene (HMHDPE) preferably has a melt flow index of about 0.2 or lower by ASTM D1238 condition E, and the low density polyethylene is preferably linear low density polyethylene (LLDPE).
In Figures 1 through 3, (1) are rows of teeth-like indentations and (2) unaltered (or substantially unaltered) ribbons~ (1) and (2) together forming the shock-absorber-band (hereinafter abbreviated to S-A-B). (3) ; is the heat-seal at the bottom. At the top, (4) indicates the zone where the bag is predetermined to become closed either by heat-sealing or by 0 sewing. There are relatively long distances X, and X2 from the S-A-B's to (3) and (4) respectively, the lengths of which will be discussed below.
At each corner of the bag, a zone Y is preferably kept free of embossment. Y should be calculated so that ::

, ~ .~

2~ 1332024 it is sufficient to avoid any essential deformatisn when the filled bag is ~arried by the corner3 in ~he way by Which it is intended tO be handl~d, Edg~-droE~ is by ~ar the mos~ cri~ical kind of 5 dropping 'or top - and bo~tQm hea~-seals or sewn seams in pillow baqs. (For gu~setted ba~s flat drop is rnore critical due to the ~peci~l problem dealt with in ~orlr~ection with Fig~lre 6, ana for longitudinal seams bottom-drop and top~drop are most critic~l). When the ed~e o~ the bag f~lled with powder or gr~nules hits the g~ound, th~ ~ontents are with great force spread horizont~lly. A~ the moment ~he bag hits ~he ground, the spxeading is ~onfined ~o take pla~e almost entire~y perp~ndi~ularly to the len~h o~ ~he ba~, ~nd near top and bottom the impaot on the ~lat surfaces o~ ~he bag the~ will cause a high lon~itudinal pull, that ~eans ~trong peeling action on top and ~ottom seams. I have found that this peeliny action is hlghest near the middle of the seams, or somewha~ closer to the edge which hits the ground. It is ver~l understandable tha~ the peeling is near zero at t~e oorner. which aO no~ hit th~ g~ound, but rather suxprising that i~ also is lo~ nea~ tho corners which d~ hit the g~ound.
~he improYements achie~ed b~ use of the S-A-~ are 25 best understood bS~ ob~a~ation ~ the gxaphs in Figures 4A and B.
~ he ed~es of each of the specimens 11 to 14, of the inv0n~ion, for the graphs in Figure 4A have been out through the middle line of two unaltered ribbons (2) ar~d 30 each spe~ilnen comprises two rows o teethlike indenta~lons ~1) with an unaltered ribbon ~2) hatween.
In total therefore, each specimen con~ists of two rows o~
teethlike indentations (1) and two unaltered ribbons ~2).
~hs speoimen width ~s 22mm~ The initial distance betw~en the jAWS o the tensile testlng appaxatus is 133202~

50m~ and the specimen has S-~-B throughout this space.
~Th~ width o the S-A-B is also ~mm, see exampl~ 4.) ~he testin~ ~eloçity i~ 500mm/min ~ looo~ elongation per min. In the graph~, lOm~ on t~e abscissa corr~ponds to 20% elongatlon.
~ he comparative set of graph~ Figure 4B ~as als~
made from 22m~ wid~ specimens 16 to 19 c~t fro~ parts of the sack that are frRe of ~ho~k ab~orber band.
In the ran~e from ZQro to the deflexion point Y, the ~ibbons become elong~ed in el~s~ical manner, but b~gin to y~eld at Y. In this range, ~mpari~on he~ween ~he two sets of graphs shows that the 510pe in c~rves A is almo~t qxactly half that o the curves s, in accordance ~ith the fact that ~ach ~i~bon in the S~A-~ in ~hi~
actual case (see e~a~ple 4) has been made with the sa~e w~dth as each row of indentations, so th~t al~os~ exactly half the width o~ the ~pecimen ~s under load. ~he ~lope in th~ s range i~ a meaq~re of the coef~ic~nt of el~ticity - for th~ e~bos~ed samples it is more correc~
to ~ay ~ppar~nt coe~icient o elasticity - and t~e ~r~ph~ d~monstra~e how the S-A-B make~ the ma~erial appear mo~e rubber-like.
~ ith the fllm compositlon ussd in example 4, the ratio between width o ri~bon and dl~lsion ih the ~-A-~
could also h~ve been somewhat ~igher ~han the actuallyu~ed rat~o l: ~ and still w w ld ha~e ~iven satis~actory im~rov~ments, while lt can be nece$sary to make the ratio much low0r ~n case of m~ch s~ er composition~, e.g., to : mak~ it 1~10 G~ even 1~20 ~s~e e~ample 1 in ~hich it was necessary to use ratio 1:10).
!. Between defle~ion point Y and ~he next defl~xion poin~ A, the ribbons are yielding, while ~.he indentations still are ~lacX. A~ point A, ~he indentations are ~traightened out and b~gin to ~longate el~st~cally, while 24 ~33~024 the ri~bons continue yielding. ~t the last defle~ion point B, th~ former Lndentations also start yielding.
The elongation in percent a~ A ~s ess~ntially equal to th~ origihal str~tch ratio ~n the row of indentatio~s, S in this case a~ou~ 28~ e~ualling ratlo 1.28 One important factor for the ~unc~ion ~f the S-A-B
i~ the apparcnt reductio~ of coefficient of ela~ticity and yield poi~t, dealt ~th abo~e, which invltes the impact to a~tack ~he S-A-B instead of at~acking the se~m.
Another i~po~tant ~actor is the energy absorbed ~y the S-A-~ from zero ~o deflexion po~nt ~, which I call ~S-A-B
energy". ~his mu~t be sufficiently big to "paci~y" the i~pact ~aused by the edge drop, so ~hat, after the S-A-B
ha~ng been in effect, the at~ack on the seam will not ~e strong enough ~o ruin the latter.
The indenta~ions sho~ld pre~erabl~ be made as deep a$ practically possible ~ ., the stretching ratio in thc rows of ~ndentations highest po~sible) ~o that ~he S-A-B ~nergy ~er width of ~he S-A-B becomes highest pos6~1e Ifor an~ given pattern of embossm~nt) however, t~ere a~ the fvllowing practical l~mitations:
(a~ the li~ited st~etchabil~ty of ~he film, in connection with the required high process v~locities, ~b) the weakness of the teeth ~in&~ o~ ~he embos3men~
2~ devices.
~ ith the t~pes o~ cross-la~inates ~hich are described ~n the examples, and wh~ch already ha~e been stretchea in both direc~i~ns before the embos~ment in ratios b~t~een about 1.4;1 and 1.6sl, I h~e fo~nd lt di~f~cult to exceed rati~s 1.3sl or 1.4:1 when ma~in~ ~he i n~lenéatlons, unless preheatin~ of the film is used in th~ areas whlch are to be embossed, and rlormally I would avold preheating ~hich i9 a complication o~ the proces~.
: Stretch ratios lower than a~out 1.3:1 are also applica~le when ~aking the ro~s o indentation~, provided at least '~.` 25 2 0 2 ~
15~, ~ut pre~erably ~ore than 25% i~provement in critical drop h~ight of the bag (as this term is defin~d above) c~n be a~hieved.
~he optlmum length of S~A-B an~ ra~io betw~en the width of e~ch ribbon and the divi6ion in the S-~-B ( to~al width of a ribbon and a row of indentations) mu~t be ~ss~bli6hed by syste~ati~al ~xperimen~s or general ~xperience, and depends, a3 already mentioned in th~
summary o~ the invention, on the p~rformance 1~ requirements, the ~ilm characte~is~ics, the d~en~ions o~
the ba~, the material which will be ~illed into the b~g, the degree of filin~, the sealing or sewing process, and She temp~ra~ure at which the drops are envisa~ed to ~ake place. As re~axds performance requirements, the ba1ance be~we~n the neQd for ~ood arop performance and the need for form 6tab~1ity of the bag is particularly import~nt~
In Figures l to 3, the Lndentations are shown obl~ng, with t~eir long~tudinal direction pexpendicular to the lon~itudin~l direction of the ribbons 12). This structure w~ll normalty be ad~antageous, but it is als~
~o~s~ble to ~ubsti~ute e~ch oblong inden~ation with two or mor- g~nerally circular indentations, although Shis : will require more complicat~d apparatus ~or the ~ embo~smen~. In some ca~e5, when only a small S-A-3 : 25 effe~t is ai~ed at, ~inqle row~ of gene~ally circular indentation~ can be used in al~ernatlon ~rith the ribbons ~2J~
The divl~ion o~ the lnden~at~ on5 in each ro~ should pr-fer~bly be as small as practically possible, the lo~er li~it being determined by the obtainable strength of the ~! 1 t,eQth (ribs) in the app~ratus ~or ~bo~sment and~ the pr~c~i~ally obtainable accuracy of thi~ apparatu~. ~or bag~ ~rom very thin ~ilm, thi~ division aan be down to abo~t l.Smm, while suitable values for heavy-duty bag~
~:: 35 . ., ~ .

` `` 26 13320~

gener~ are between abou~ 2.0 - 4.0mm, although somewh~t bigger divisions also are applicable.
It has already been mentloned that the indentations mu~ no~ rt immedia~ely adjacent ~o the seam (i,e., the di~tance x-O). I~ that ease ea~h ~ibbon ~2) would pull almo~t with lts full force on a corresponding po~ion of the seam, and prac~t~ally no improvement w~uld be achieved.
In order to even out the forces on the seam, x should never be les~, generally ~peak~g, than abo~t the same as the dis~ance be~ween two n~ighbour "ribbons", i.e., ~he width of each row 4 indentations, and pre~erably x sho~ld ~e a few times, e.g., 2 - 6 times this d~ ~tance. X can al~o be lon~er, but since ~he ten~ions, when th~ bag h~ts ~he ground on edge, are concent~ated near top ~nd botto~, the en~ire S-A-B should gener~lly be confined to a zone within a dis~ance from the seam ~or loca~ion predetermined to ~ecome seam) not e:~ceeding 25e and preferably ~ot ex~eeding 15~ o~ the total length o4 the bag ~or, in Ga~e the S-A B i5 mada fox protection of the side-seam, of the ~idth of ~he bag).
In F~gures 5~ ~nd B, both wheels ~5) and ~6) are driven with the same ~ircu~erential velo~it~, and ~he susface~ of both are foxmed as circular fins and ~roove~, the fins on one wheel fit~ing into ~he grooves of the other, with ~pace left between for ~he bag material, so that the bag, wh~n passing between the intermeshing fins, is stretched perpen2icularly to the direction of advaneing~ Whil~ the fins on ~5) are continuously circular, the fins on ~6) are formed in dent-shapes as 6hown. ~ orners and edge~ which get into contact wi~ the ba~ ~re carefully rounded and ground to avoid puncturing of tha material.

~33202~

The ba~ is pass~d through the embossin~ de~ice in a direction parallel to the top or bottom seam, whereby the top or bottom S-A-B shown in ~igure 1 is formed. ~o~h can of course be formQd ~imultaneou~ly by us~ of two sets of embossing wheel~.
At the inlet, the appara~us is p~efera~ly supplied with guide ~he~ls ~rollers~ acting to ~e~p the ~ag straightened out while aounte~a~ting the dx~gging ~owa~ds the ~iddle o~ the wh~els (not shown)~
~he set o~ wheel9 ~5 p~e~er~bly made to op~n and ~lose, so that embossing can ~e avolded near each corner.
~ h~ ~eeding of th~ bag into the device, and op~ning an~ clos~ng of ~he wh~el~, can be done m~nually, :: semi-auto~atically or fu~ly automatically. Imm~diately ~rior to the embossing and wor~lng in line ~ith the wheels, there ~ay be provided a pre-hea~ing de~ice ~hich sel~ctl~ely heats the ~icinity of the ~oming S-A-B.
Thls can, e.g., be a device similar to a band-se~ler, but operated at a temp~rature at which sealing does ~o~
occur. After the embossing, there may be ~ calendering step to reduce ~ulk.
The device here described i~ the simplest and cheapest ~pparatus ~or producin~ the S-A~
Alt~r~ati~e~y, a prcss can ~e used having simllar intermeshing fins, ~ut of course in rectillnear instead of circular arr~ngement. Thi 5 will be the apparatus normally used, if th~ process i~ car~ied out be$sre bas-m~ing.
With refe~nce to Figure 6, which illustrates the ~ussetted ba~ aspect of the i~vention, the location (7) 1~ where the heat-seal (B~ lntersect~ the innermo~t fold ~9) :: of the gussQt ~s very critical when th~ bag is dropped on ~: one o the major ~urfaces ~flat drop). ~hlle the co~tents spread o~t horizontally, the gusset material adjac~nt to (9) comes under a particula~ly high ~ension, , . ' 28 ' 133202~ ~

which tends to start tearing along the sealin5~ at location ~7).
I have solved this pro~lem bv stret~hing a por~ion ~10) of the gus~e~ in a dlrection parallel to th~
longitudinal dirRctlon of ~he bag~ This stretchln~ is çarried out by em~ossment bet~een ~utuall~ in~rmeshing f~ns, mo~t pract~cally before the gusset has been for~ed.
It is confined ~o plies ~11) and (12) which ~orm the gusset, ~h~le the two o~termos~ plies ~13) and ~14) are 1~ not ombossed. I refer to ~h~s localised strotching as "Gusset Embossment~ elimina~es or reduces the tensions at location (~) and can thereby, in case the bag : ~aterial i9 a relatively rigid or an oriented film, incre~se the critical drop helght by a ~actor o~ 2 or or even more ~bee example 3).
The drawing shows the Gusset Em~ossment as a number o~ indenta~ion~, and ~o~ as a pat~ern li~e ~he S-A-B, where row~ of indentation6 al~ernate wi~h unaltered ribbon~. However, eu~h Alternating ~attern is also 2~ u~e~ul, bu~ not ~andatory, for ~he Gusse~ ~mbossm~nt.
In th~ foregoin~, the invention has bee~ des~ribed ~lmo~t e~tirely with a v~e~ ~o ~ack ~pplicatlons, ~here the need i~ to build in shock-a~sorbing propcrtie6 in~o a selec~ea are~ near to a se~m. ~o~ever, it has b~ie~
beon ment~oned that there also can exist a need to modify a m~or propoxtion of or even the en~ire article, : espe~ially in connection with manufact~re o~ parachutes.
Th~s applies in pa~ticular ~o cheap, disposable parachutes for parachu~ing o~ materials such as vehicles or containers. I~ ifi usually desirahle ~hat the unfoldln~ o~ the parachute i~ postponed as much as po8sl~1e, ~ut the impa~t f orce~ on the load and ~n the;~
parachute it~elf when the parachutQ unÇolds sets th~
limit f~r how late thi6 can be. : :

, 133~02~

Therefore, parachutes are often supplie~ with ~hock-absorbing device~. The pres~nt invent~on, ho~ever, enables particularly ef~icient shock-a~orption by ~imple and cheap me~ns. ~hus, the s~rapping can be made from film material (prefera~ly as~embled from sever~l lay~rs, which may be only loosely held together) which o~er a suitably long length is suppli¢d with a ~sttern of stretched and unstr¢tched zones ~ccordin~ to the invent~on. Alte~natlvely, the parachute, cloth can ~:
10 be made from p~ly~eric material which is supplied with a ~:-pattern o~ 6tretchea and un8tretched zones according to the in~ention over an essenti~l part of its area, which nay b~ almost the full area.
:~ ~he di~ection of the ~ub~tantially unstretched zone~ :
15 in thl~ patte~n should prefera~ly be mainly parallel to the local directions of force when the parachute unfolds ~nd ~hould preferably ~e in the form of a plurality of ribbons. ;
It is w~l kno~n ~hat orient~ble polymer~
20 :especiall~ the highly crystallne and stif~ ones such as h~gh aen~ity polyethylene or polypropylene, ex~i~it high : yield poln~ and at the same t~e, if drawn slowly, a high ;:~
elongation at break (up ~o about 10 times) and a high ult~mate ~ensile strength. Therefore, the energy ~ 25 abso~ption up to She breaking poin~ is also very high :~- when the polymers are slowly drawn, b~t during very quick drawiPg they may rupture sImost wi~hout any permanein~
~: de~or~tion. By application o~ the present in~ention, ~:~
the physi~al charac~eristic~ can be changcd very :~
~ign~ficantly 80 ~h~t, e~e~ under the wo~st impact co~ditions, a permanent defo~ation can s~art at almost ;~
~; zero ten~ion dnd progress in predetermined way ~nder increas~ l~g resi~tance to a hl~h degree of elonga~ion and to a f~rce clo~e to the ultimate tensile force obtained .
du~lng slow dra~ng. ~-~
' ~'.

~'~` 30 1 3 3 2 Ecpe~ially for these uses, the substant1ally u~stretched ribbons should pre~e~ably be very narrow, and the degree of stre~ching in the ~ndividual bo6s on the film very smoo~hly v~ied from zero at the boundAry of th~ ribbon to the ~aximum value nea~ the middle of the boss ~e~ween two ribbons.
Mate~ial v~ry suited for such strapping is high densi~y polyethyle~e and polypro~lene, which both may be used unblended. For the parac~ute cloth ~or hood) oPe can u~e cross-lamlnates of the biaxially oriented type and ganexally si~ilar composltion as the sa~k material used in example~ 3 and 4. Additionally, the blends ~an contain polypropyl~ne.
ExamPle L
This example demon~ rates the i~provements achieved with shock-ab~orber-~and on heat-6ealed pillow-bags from polypropylene-based, b~xially oriented cros~-laminates at O~C. At this temperature, the heat ~eal will act ~o ~: fragile ~ithou~ a S-A-~, that such ma~erials cannot be used ~or heavy auty bags wlth simple hcat-seals.
A cross-laminate ba~ed on gas-phase-type polyp~opylen~ was produced generally as in E~ample ~ of my ~,~. patent no.l,526,722 ~nd the ~orresponding U.s, patent no.4,039,364, h~wever with the following es~ential d~fferences~
:~ (a) 4~ply instead of 3-ply, wi~h the an~les of main d~c~ion: ~45, t~0C~ -300, -450, (b) Gauge 90gsm inst~ad of 72g~m.
c) The admixture to the polypropylene in the ~iddle -~- 30 layer o~ the ~oextruded film ~as 20~ lineary low denslty polyeth~Ien~ ~LLDP~) in6tead of 14~VA.
(d) ~e surface layers of the ~oextruded fiLm were lends o~ polypropylene and ethylene-propylene-dimer rubber lEPD~) instead of EVA.

~_~ 31 1332024 The cross-laminate was tubed b~ use of an extruded melt-adhesive for the slde-seam, and the tube ~as cut into lengths o~ about l.Om. Flat width: 500mm. The s~de-seam was positioned very close to the edge. ~he S ~ottom seam~ for the open-mouth ba~ w~re produced manually ~y impulse~sealing. In order to allow shrinkage to take place in the heat-seal and thereb~ a ~rowth o~ its th~c~ness, the cooling period in the sealing p~ocess was set at ~ero, so that all cooling took : lO place after release of t~e press~re on the jaws.
The reason for pla~lng the 6ide-seam very close to :~ one cdge ls that I have found the ln~ersection ~etween ~; ~ hea~-s~al and s$de-seam mos~ prone to ctart o~ tearing along ~he heat-seal (on edge-dropping). ~ore correc~ly, lS the weak zone ~s not in the side-seam itself, bu~
immediately adjacent to the latter, where the seal is adcquate. It was hypothetically assumed that the edge drop cau~es only low peel-forces near the ~dge which hits : th- ground co~pared to the peel forces at the middle of ; : Z~ the seal - and of course the peel ~orces ~ill be nearly zero near the other edg- - so lt was assu~ed ~hat h~ghest crit~cal drop height~ i6 achieved with the s~de-~eam :near to one o2 the ed~es. The proo~ hereof is given i~
Examp~e 2. .
25~ach bag was fillcd with 25~g polyethylene granules, and a pie~e of the top was cut off to leave about 11 -2c~ free ~pace over the evened-out level of the contents (b~ag~ stand n~ upright, majo~ bag faces folded over th~
level:of the contcnts~:to the ~iddle, free space measured h~reover). The ba~ was closed by overtap~ng with reinforced j adhesi~c t~pe. In practical productio~ it s~ hould be closed either by heat-sealin~ or ~cwin~, and a S-A-~ provided also at the top, but it ~as judged that ~; thc effect o~ the S-A-3 Q~ se best can be dete~mlned by r~ `
~ 2 1332024 investigations onl~ o~ ueh heat-seals or s~wn seams which are made prior to fllling.
~h~ drop-te~ting was carrl~d ou~ a~ ambient tempe~ature O~C, and the content~ of th¢ ~ags (the 5 polyeth~lene granules) were precooled to this temperat~re.
In a series of initial trial~, the applicahle ratios between widths of "unalter~d ribbons" and "rows of indentatlons" were determi~ed as ~ollo~s: A primitive 10 laboratory press wa~ made for embossment o~ one row only of indent~tions, con~isting of 15 single indentation~, each lOmm long, with row di~i~ion (~is~ance between top of two neighbour inden ations) ~ing 3.0mm, The S-A-3 was made from ~dge to edge ~y repetitio~ of embossment, lS row by ro~ The ~ri~bons" were kept ~ constant width ~ithin eaGh bag, but dif~erent rihbon-wi~ths were trie~.
The str~tc~ing ratio, correspo~ding to the depth o.
e~bo~sment, i~ belie~ed to have ~een ~out 1.20:1, and in any ¢ase was ~he same for all emSo~ment~. The S-A~
20 was s~arted 30mm ~rom the heat^seal.
I~ was ~ound ~hat the w~dth of ~he "r~bbons" had to ~e down at about Zmm to gi~e a significant i~prove~ent, and lmm was estimated to be the optimu~.
~n embossing apparatus as 6hown in Figure~ SA and B
25 ~a~ made ~or xibbon-width l~mm, ~ow-width lO.mm, row~len~th (~ width of the S-A-B~ is 50mm, division of each row 3.mm, and 17 ~ndenta~ions in each ro~. Start of S-A-B 30mm fro~ the heat-seal, It e~tend~d the wid~h o ~he bag.
A The em~ossm~n~w~s c~rried out at room temperature, with the fins/ o~ the wheels practicalltl in full engageme~t ~exactly the same engagemsnt in all trials) which i~ believed to have corresponded ~o ~tretch ratic about 1.2:1.

~3 ,. 1 3 3 2 0 2 ~
The strength o the heat~seal wi~h and without e~bo~sme~ ~as determined as the critical drop heigh~
which statistically, 19 the limit between no-failure a~d failure, ~hen o~e bag with the relevant ~o~tents is S dropp~d 6 times in th~ following cycle: (1) 1st ~lat ~ur~ace, ~2) 2nd ~lat su~face, (3) 1st edge, ~4) 2n2 edge, (S) bottom, ~6) top.
However in order to simplify the testing wor~ for heat-sealed p~llo~-ba~s, the determ~'nation has been ~odifie~ 50 that only one drop is carried out per bag, ~amely an edge -drop on the edge closest to the side seam. ~he ju~tification ~or this ~implL~ication is my experience tcon~ined to the bi~xially stretched type o cross-l~minates) that when a bag has passed one edqe-drop, ~he ~eak, dlsoriented line adjacent ~o the heat-sea~ will be rein~orced by an orientation caused by the drop. Therefore, subsequent drops of the same bag from the same height will in any case give positive results and are needless. Further, drops ~1 ) and (2) of the above-mentioned cycle (the flat drops) have been 20 found, practically speaking, neither to weaken nor to reinforce the heat-seal of a pillow bag. This simplificaiton of testing procedure is not applicable to either gussetted, or sewn bags.

. ~ l .,<~ .

34 ~332024 Table of results, indicating for each trial, drop height in cm, and passed = P or failed = F.
With~ h SA9 Bag No. Drop H~lgh~ Result Bag No. Prc~ Height Result 140 F 17 240 p 1~ 120 F 16 240 F
13 1~0 F 6 220 1~ lO~ F 9 ~00 P
~00 F
ll 200 P
lS 2 190 P
Since only one bag without S-A-B has passed, namely no. (4~ from 140c~, whils 3 bag~ ~rom 120cm and 2 from lOO~m ha~e failed, it i~ be~ieved that no. 4 wa~ no~ a straight edge drop but ~hould be disca~ded. The ~0 ~riti~al edge drop value th~re~or2 will be lower ~han lOOcm ~or th~ bag without S-A-8, while ~t i9 estimat~d to be about 220cm for the b~ with S-A-~.
Example 2 ~he objective of th~s ex~mple is an elaborate 2S drop-strength compariJ~n a~ room tempera~ur~ between heas-sealed bags with and without S-A-B, made from biaxially orient~d crOss-~amin2teC of two different compositiong, one based on p~lypropylene, and the ~ther on polyethylen~. In each c~se, drop-test comparison are also ~ade between bags ha~ing the side-seam ;Sc~ fr~m a~
edge, and bags ~ith the side seam adjacent ~o sn edge.
~he polypropylene-based cross-laminate was a 9imilar 4-ply as in Example 1, e~cept ~ha~ the addition ~o the polypropylene in the mlddle la~r ~f the coex.truded film 3$ no~ was 10~ EPDM. The gauge still was 90gSm, ~he ~5 1332024 polyeth~lene-based cross-lamina~e ~as a combination o ~-high-molecular-weight-hi~h-den~ity-polyethylene ~M~DPE) and lineary lo~ densi~y polye~hylene ~L~DPE), namely the 2-ply oross-laminate designated a~ "Rl" in Example 3 o~
U.S. patent ~o.4,62g,5~5.
~u~ing and ba~ making was carried out like in example 1. ~he bag width was 490mM for the polypropylene based b~g~ and 560mm for the polyeth~lene~ased b~gs.
The pattern of 5-~-E, its distance ~xom the heat-seal, the em~os6me~t apparatus and the en~aqement between the fins of the lattex were al60 ~xactly as ln ~xample 1. The S-A-3 e~te~ded the bag width. It is ,be,lleved that the stre~ch ratio has bee~ about 1.20-1.
The ba~s were filled with 50kg of PVC gra~ules plus sand, and the top closure ~s ~ade with a self-adhesive rein~orc~d tap~ e in ~ample 1.
Free space 11 - 12cm li~e in Example 1.
The critical drop height was determ,ined in the ~am~
8impli~ied manner as in Example 1.
In the ~able below:
Film Typ~ A i~ polypropylen~ 90 gsm ::.;
~ilm Type 9 is polye~hylene 70 gsm :~
Sack T~pe S is a bag without SAB and side ~,eam 15 cm from edge Sack Type C i~ a simila~ bag to S b~t wi~h side ~eam at corner ~
SacX Type C I SAB ~ s a simil ar bag to C but ~ith one:;, -S~B
Sack Type C + ~SAB is a si~ilar bag to C but with ;~
~wo SA~ , ;' ' Edge ~xop Tests recorded the height OL drop and :
wheth~r the sack pa~sed P failed ~, just ~ailed (F) ; .
with a spli~ below 10~ or split at the SAB, ':~
p~oba~ly due to p~nctu~e ~uring the embossing (F~) ', -' i::
.. . ...

~ 3~ 1332024 . .
~he seal is formed ~y a Star Impulse Sealer at the Weld Time and He~t Ra~ing Settings quoted, except for the o ~erles ~ealed with a Poboy ~and S~ler.
-~ A6 it appears from the ta~1~, the move of the siae-seam to ~h~ edge genera!ly lead to about 50%
improveme~t of the critical drop height, and the use of S-~-B fur~her le~d to about 50~ improvement. Use of a second S-A-~ close to the first one ga~e no significant extra improvement.

: 25 ~ JrRde J~4~k ~

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, ~~ 3B 1332024 ExamPle 3 The objeetive of th~ example is ~o investiga~e the improvements in drop-performance of gussetted b~gs by use of the n Gussett ~mbos~ment" alone and ln com~ination with S th~ S-A-B. The material for the bags lnve~ti~a~ed ~as thç ~R1" cross~lamlnate also used in e::ample 2, e~cept that the ~LDPE of example 2 has Seen the octene copolyme~
of ethylene, but in this example ~as its copolymer with b~ne. T~e gua~e of the cross-laminate no~ ~as 80 gam.
Tubing was carried our as in ~xamp'e 1, t~ tu~e width being 56cm before ~ussetting. A 50mm deep gusset was ~olded b~ hand, and hea'c-sealed bags made by use of lmpulse sealing. The ~onditions ~o~ sealing were op~imizéd ~d no cooling per~od applied. Tha sealing condition~ ~ere the ~ame ~or all bag~ tested.
The Gu~set Em~o~sment was carried out on the tube before gussetting, while the S-A-~ pattern was em~o~sed into the laminate after guss~tting.
For both types of em~ossment, the same embossment wheels, and the same pattern was used dS in examples 1 and 2, w~th t~e modification that the wh~els now were tightly screwed towards e~ch other ~o inc~ease the stretch ratio. A depth o~ embossment w~s measured corresponding to stretch ratlo abouk 1,30 : l. The heat-~eal was made about 20cm from the start of t~e Gusset Embossment, and the S-A-st which ~omprised gusset as well as outer faces of the bag, was embossed immediately adjacent to the Gusset Embossment on the side of the la~ter which was oppo~ite to the heat-seal.
It should ~e born in mind ~see example l) that the :~ , width of "unaltered rib~'ons" were l.Omm~ width of rows of indentations 10 mm, and width of the S-A-B (now aLso of the Gusset Embossment) 5~ mm.
The bags were filled with 50 kg salt (sodium chloride). ~t the top, ~he gusset was straightened out to ~ive the ~ag its Cull width 56 c~, and the bag was closed with a reinfox~ed self adhesive tape. Free spa~e over ~he level o~ contents was 10 cm.
The ollowing test-cycle was appliedz ~1) fla~ drop one side, (2) flat drop on the other ~.de, (3) drop on o~e edge, (4) d~op on the other ~dge. It was considered ne~dless to carry out bottom and top-~rop~, since the latter would not cause or further develop ruptures, The first bag kested w~s without a~y emhossment, neither Gusset Embo6~ment nor S-A~ t was dropped flat ~rom 90 c~ height and the ~ir~t d~op produced a split about 1~ cm long at each o~ the two critieal location~
~ee ~73 is ~igure 6). ~h~ drop cycle was interrupted after thls first drop.
lS A second bag tested ~s with out Gusset Embossmen~
and S-A-B, and was ~rled in ~he abo~e men~ioned cycle of four drops from 400 ~. After ~he two fla~ drops there was observed very small tea~-~ at the ~wo criti~al locat~ons, and after the subs~uent two ed~e-drops the ~ length o~ tearLng wa~ measured to be lOmm and 12 m~.
A third ~ag, also with both Gusset Embossment a~d S-~-B was ~ested in th~ same cycle of four drop~, bu~
~rom 300 cm. ~her~ occured no ~earing at all.
It i~ ~here~ore jud~ed that the Gusset Embossmen~
2~ and S-A-~ together ha6 improved th~ p~r~orman~e of the bag by a factor higher than ~ou~.
A ~ourth ba~ was produced ~ith ~he Gusset Em~o~men~, but without 5-A-B and ~a~ tested in one single fl~t drop from 400 cm. There was observ~d a 5~m tea~ a~ one and a 8mm tear at the other critical location w~ich in any case is less than the damage of bag no. 1 ! te5ted ~rom 90 cm onl~ and also ~n one flat drop only~
As an interesting further ~eature o~ the bags with ~u89et ~mbossment, it wa6 observed tha~ the filled b~

, 1332024 ~ 40 `:; ' !
exhibited clearly better block shape a~ the botto~ than the gussetted sac~s with the Gu6~et Embossment.
E~amPle 4 The objective of this example is to demons~ra~e the l~provements which the S-A-3 causes ~n a ~ag with sewn tOp and/or bottom sea~.
~ he bags were made from the bi.axially oriented cross-la~inate, which which is designated as ~R2" in exa~ple 3 of ~.S. patent no. 4.629.525. ~his is stiffer : 10 than u~l~ u6ed in e~amples 2 and 3, and connected with this highe~ sti~ne~s ex~ibit6 a higher tear propagation :resistance. For further impro~ements of stitching ~:~ st~ength, thQ spiral cutti~g angle 45 used in the ~entioned example of the U.S. patent, was substituted by spiral cutting angle 30. ~he stretching and lamination of the plies we~e carried out by the improved method described in example 3 of Canadian Patent 1,316,320. The stretch ratios were 1.40: 1 in both directions, and gauge 70 gsm.

Tubing was carr~ed out as in e~ample 1, to give bag wi~th S6cm~ The side seam was positioned 6-7c~ from the edge, whloh was the closest that could be ~ade cont~nuously on the tubes actually used. ~he bottom o~
the ba~ sewn, while using over-folding of the bag mater~a1 ~n the seam and o~er-~aping with crepe paper.
The distance betwecn the stitches ~as 8 mm.
The S-A-B ~as embossed in the pattern and by the ~ app~ratus descri~ed in example 1, e~cept that the pa~tern -~ wa~ modified so that Uribbon~ w~dth equaled Uinden~ation"
3~ length, b~t still giving the same total, namely 11~ ~the isiion of the s-A-s)~ and the S-~-3 was stlill 50 mm ~ide. Th~ change of embossment pattern was made, not particularly because sewing should be applied, but : because the other pat~ern, which was developed for a ~ 35 ... ~
~ . Y
~',~

.. ~ 41 1~32024 polyp~opylene composition, was eons1dered les~ suit~ble for the p~lyethylen~ composition.
Strain/s~xess diagrams taken in the S-A-B are shown in Figure 4A and similar di~gram~ fro~ the unembo~ed ~ross-laminate in ~i~ure 4~. Comparison between these diagrams and e~planatlon of the significance a~e given in the descript~on o~ these fisure~. As mentioned here, it appears irom Fig~re 4A that the ~retch ratio ln the tows o~ indentations has ~een 1.26:1, a ~alue whi~h also with Rpproxi~ation is estimated from the observed shape and mea~u~ed di~ensions of the ind~ntations.
The bags were ~ d with 20kg polyethylene granules and closed by ~ve~taping with rein~o~eed seld adhesive tape. ~he free space ~etween the top leYel and the closure, ~easured as indicated in example 1, was 11 cm.
Four bags with, and four without, S-A-B were dxop-~estea around the val~es ~hich beforehand were judged to bo their critlca~ drop heights. There was used the same d~op-test cycle as in example 3. By these tr~al~, the ba~s ~ithou~ S-A-~ were est1mated to have critical drop heigh~ 120cm and the ~ags with 5-A-B ~50 cm.
If bags are ~nder a particularly high p~essure in a stack, the S-A-B can conceiva~ly become stretched so much thas the embossment disappears, bl~t the latter will be to some extend rever~ when the pre~sure has been releas~d.
Fu~ther, the stretching cau~ed by the pr~ssure will have oriented the disor~ented weak line adjacent to the heat-seal (in the case of heat-sealed bags3 so that the sea~ in any case is relnforced. With prope~ly ~elected dimensions for the S-A-B, the deformation when the ~mbossmen~ disappears, will not be serious for the : ~uality of sta~king. Thus, in ~11 o~ the e~amples, full 3S for~e ~o el~minate the emSoss~ent will ~ause only 20-30~

42 1~3202~

elongation ~ a ~ em wide S-A-~, or with one S-A-B at top al~d one at bottom, a total ~longation o~ about or less than 3 cm. Since normal length ~or ~ 50 kg bag is ~out 1 ~ Om or slightly less, the t.otal elon~ation of the bag 5 c~used by ~ull stretching-out of til~e two S-A-~ ' g will be about 3-43 at the highest, all provided the need for ~-A-B e~fect do~s not exceed the improvem~nts which have been demonstrated ~y the~e ~xamples.
1~ '' ~ ', 3~

;, .

Claims (30)

1. A tube for forming a tubular bag closed at at least one end by a generally transverse seam at a predetermined generally transverse locus along the length of the tube, said seam resulting in a rupture zone adjacent thereto which is susceptible to rupture when subjected to impact stress, said tube being formed of generally continuous orientable thermoplastic polymeric material, the film material of said tube including adjacent the predetermined locus of said rupture zone a shock-absorbing band of limited depth perpendicular to said predetermined locus which is separated from said locus by a region of unstretched film material and extends in width over a significant portion of the transverse dimension of the tube, said shock absorbing band comprising:
a plurality of discrete stretched zones of film material stretched in a direction generally perpendicular to the locus and alternating one by one with a plurality of generally narrow stripes of substantially unstretched film material with the stripes extending lengthwise in substantially the same generally perpendicular direction, whereby impact stress forces applied to the tube material adjacent said rupture zone are transmitted away from said rupture zone and absorbed by said shock absorber band to thereby significantly improve the resistance of the tube to impact stress applied to said rupture zone.

2. The tube of claim 1 wherein said seam is a heat sealed or stretched seam.

3. The tube of claim 2 wherein the stretched zones of said shock absorber band are formed as stripes extending lengthwise generally perpendicular to said predetermined generally transverse locus with the film material of said stretched stripes being stretched in said generally perpendicular direction.

4. The tube of claim 3 wherein said unstretched stripes each extend generally perpendicularly of said predetermined generally transverse locus in a substantially straight or zig-zag direction substantially through the band perpendicular to said predetermined generally transverse locus.

5. The tube of claim 1 wherein the dimension of said shock absorber band perpendicular to said predetermined generally transverse locus is in the range of about 3 - 10 cm.

6. The tube of claim 1 having generally opposed front and rear faces joined along side edges and wherein said shock absorber band terminates at its lateral ends inwardly of the side edges of said bag.

7. The tube of claim 1 having generally opposed front and rear faces joined along side edges and wherein said shock absorber band is present on each of such faces adjacent each such locus.

8. The tube of claim 1 wherein each unstretched stripe has a transverse dimension parallel to said locus which is equal to about 5 - 150% of the corresponding dimension of each of the stretched zones.

9. The tube of claim 1 wherein the film material in each such stretched zone is stretched into a plurality of embossments by engagement between a plurality of intermeshing embossing teeth, said teeth being interrupted at spaced points to form the unstretched stripes.

10. The tube of claim 9 wherein said embossments are oblong in shape with their greater dimension extending parallel to the seam.

11. A method of manufacturing from generally continuous orientable polymeric film material a bag having a generally transverse seam at a predetermined location defining at least one end of the bag, which comprises, before or after the seam is made, embossing the film material along a generally band-shaped zone adjacent to but separated from the location of the seam with a pattern of discrete localized indentations in which the film material is stretched mainly in a direction perpendicular to the length of the seam, said indentations being arranged in a plurality of rows generally perpendicular to the seam length which are separated by ribbons of unstretched film material.

12. The method of claim 11 wherein said indentations have a generally undulating configuration when viewed in cross-section through one of said rows thereof.

13. The method of claim 12 wherein said indentations are elongated generally parallel to the length of the seam.

14. A tube for bag-making formed of a sheet of continuous orientable thermoplastic polymeric film material, said sheet having two opposite side edges which are seamed together to form longitudinal seam and having adjacent said longitudinal seam a rupture zone susceptible to undergoing rupture when subjected to impact stress, the film material of said tube including adjacent each said rupture zone a shock-absorbing band which is separated from said longitudinal seam by a region of unstretched film material and extends along a significant portion of the seam length, said shock absorbing band comprising:
a plurality of discrete stretched zones of film material stretched in a direction generally perpendicular to the seam alternating one by one with a plurality of stripes of substantially unstretched film material with the length of said stripes extending in a direction generally perpendicular to the seam, whereby when the rupture zones are subjected to impact stress, the stress forces are transmitted away from said rupture zone and absorbed by said shock absorber band to thereby significantly improve the resistance of the rupture zones to such stress.

15. A tubular gussetted bag having at least one generally transverse seam defining an end thereof, being formed of generally continuous orientable thermoplastic polymeric film material, said bag comprising opposed generally rectangular front and back panels of film material united along side edges of such panels and having corresponding side margins of respective ones of said panels adjacent said side edges each tucked inwardly along a central fold line and held in such tucked position by said seam to create a gusset to give a generally rectangular shape in transverse cross-section to the bag when expanded, the gussetted bag being susceptible to rupture under impact stress at a junction of each said fold line and said seam, the tubular bag therefor being provided on the tucked side margins of each said gusset adjacent to each said rupture junction with a localized stress-relieving zone, each said stress-relieving zone comprising:
at least one elongated zone of stretched film material formed by stretching the film material in a direction generally perpendicular to the end seam along at least one line intersecting the center fold line of at least one of said gussets and extending on either side of the center fold line into the tucked side margins of the gusset, whereby impact stress applied to said at least one gusset is prevented from being concentrated at the rupture junctions by said stress-relieving zones to thereby significantly improve resistance of such rupture junctions to rupture under such stress.

16. The gussetted bag of claim 15 wherein there are a plurality of said elongated zones of stretched film material in spaced parallel relation which together have a generally undulating configuration in cross-section taken longitudinally through such zones parallel to the central fold line.

17. The gussetted bag of claim 15 wherein each such elongated zone of stretched material is interrupted along its length by a plurality of ribbons of unstretched material.

18. In a method of manufacturing from generally continuous orientable thermoplastic polymeric film material a gussetted bag having opposed front and back faces, each such face having opposite side edges with the corresponding side edges of the faces being united and having opposite side margins adjacent such side edges, the corresponding side margins of the respective faces being tucked inwardly along a central fold line to form a gusset, said bag having across at least one end thereof a generally transverse seam which extends across the inwardly tucked side margins of the gusset to secure such inwardly tucked side margins in their inwardly tucked condition, the end seam intersecting with each central fold line to define at such intersection a point of susceptibility to rupture under impact stress, the improvement which comprises the step of embossing selective regions of said inwardly tucked side margins generally adjacent to each rupture point along at least one line which intersects the corresponding central fold line in generally perpendicular relation and extends into the tucked side margins on either side of such central fold line to form in the gusset a transverse zone of stretched film material adjacent each rupture point which zone is capable of relieving impact stress on that rupture point.

19. The method of claim 18 wherein each such embossed zone is interrupted at at least one spaced point along the transverse direction thereof to form generally parallel links of unstretched film material passing through each such zone in a direction generally parallel to said central fold line.

20. The method of claim 18 wherein the side margins of said front and back faces in their inwardly tucked position are overlaid by corresponding side portions of such faces to form a four-ply sandwich of said film material and the resultant four-ply sandwich is subjected to embossing adjacent the end seam to form said transverse zones of stretched film material simultaneously in all four plies of said four-ply sandwich.

21. The method of claim 18 wherein said inwardly tucked side margins are embossed in selective regions thereof generally adjacent to each rupture point along a plurality of lines which intersect said center fold line in generally perpendicular relation and extend into the tucked side margins on either side of said central fold line to form a plurality of spaced parallel transverse zones of stretched film material in the gusset which are capable of relieving impact stress on the rupture point.

22. In a parachute having a canopy and strapping connected at one end thereof at points spaced around the periphery of said canopy, at least one of said canopy and strapping being formed of orientable thermoplastic polymeric material, the improvement comprising a shock absorber band of said polymeric material provided in at least one of said strapping or in regions of said canopy adjacent to the points of connection of said strapping thereto, said shock absorber band being comprised of a plurality of ribs of stretched film material extending generally transversely of the length direction of said lines, said ribs being interrupted along their transverse length at a plurality of spaced points by generally parallel stripes of unstretched film material which are generally perpendicular to the rib length, said shock absorber band being capable of absorbing tension when the parachute opens.

23. In a bag formed from continuous orientable polymeric film material and having at least one generally transverse seam defining an end of the bag which seam is susceptible to rupture when stressed, the improvement comprising a pattern of discrete localized embossed indentations in the film material defining a generally band-shaped zone extending generally parallel to said seam in a location adjacent to but separated from the seam, the film material of said embossed indentations being stretched mainly in a direction perpendicular to the length of the seam, said indentations being arranged in a plurality of rows generally perpendicular to the seam length which are separated by ribbons of unstretched film material, whereby the resistance of the seam to rupture under stress is significantly increased.

24. A tube formed of generally continuous orientable thermoplastic polymeric film material for forming a tubular gussetted bag closed at at least one end thereof by a generally transverse seam, each such seam being located at a predetermined generally transverse locus along the length of the tube, said gussetted bag comprising opposed generally rectangular front and back panels of film material united along side edges of such panels and having corresponding side margins of respective ones of said panels adjacent said side edges each tucked inwardly along a central fold line and held in such tucked position by said seam to create a gusset to give a generally rectangular shape in transverse cross-section to the bag when expanded, the gussetted bag being susceptible to rupture under impact stress at a junction of each said fold line and said seam, the improvement wherein the film material of the tube for said gussetted bag is provided at a locus which corresponds to the tucked side margins of each said gusset of the gussetted bag and is adjacent to each of the rupture junctions with a localized stress-relieving zone, each said stress-relieving zone comprising:
at least one elongated zone of stretched film material formed by stretching the film material in said zone in a direction generally perpendicular to the predetermined generally transverse locus of the end seam along at least one line which intersects the center fold line of at least one of said gusset-of the gussetted bag and extends on either side of such center fold line generally parallel to said predetermined locus of said end seam, whereby impact stress applied to the gussets of the gussetted bag is prevented from being concentrated at the rupture junctions by said stress-relieving zones to thereby significantly improve the resistance of such rupture junctions to rupture under such stress.

25. The tube of claim 24 wherein the film material in each elongated zone of stretched film material constituting one of said stress-relieving zones is formed as a plurality of spaced apart stripes extending lengthwise generally perpendicular to said predetermined generally transverse locus of the end seam with the film material of said stretched stripes being stretched in said direction generally perpendicular to said predetermined locus of the end seam.

26. The tube of claim 25 wherein the stripes of stretched film material are separated by stripes of unstretched film material each extending in a direction generally perpendicularly of said predetermined generally transverse locus in a substantially straight or zig-zag direction substantially through each said stress-relieving zone perpendicular to said predetermined generally transverse locus.

27. The tube of claim 24 wherein said stress-relieving zone is constituted of a plurality of said elongated zones of stretched film material in spaced relation parallel to said predetermined generally transverse locus which together have a generally undulating configuration in cross-section taken longitudinally through such zones parallel to the central fold line.

28. A tubular bag closed at at least one end by a generally transverse seam, said seam resulting in at least one rupture zone adjacent thereto which is susceptible to rupture when subjected to impact stress, said bag being formed of generally continuous orientable thermoplastic polymeric material, the film material of said bag including adjacent each such rupture zone a shock-absorbing band of limited depth perpendicular to said seam which is separated from said seam by a region of unstretched film material and extends generally parallel to said seam over a significant portion of the seam length, said shock absorbing band comprising:
a plurality of discrete stretched zones of film material stretched in a direction generally perpendicular to the seam alternating one by one with a plurality of generally narrow stripes of substantially unstretched film material with the stripes extending lengthwise in substantially the same generally perpendicular direction, whereby impact stress forces applied to the bag material adjacent said rupture zone are transmitted away from said rupture zone and absorbed by said shock absorber band to thereby significantly improve the resistance of the bag to impact stress applied to said rupture zone.

29. The bag of claim 28 wherein each said shock absorber band extends in depth from a position separated from said end seam by at least one cm to a position not more than 25% of the length of the bag perpendicular to said seam.

30. A tubular bag having a generally transverse seam at one end and a generally longitudinal seam along at least one side thereof, said bag being formed of continuous orientable thermoplastic polymeric film material, said bag having adjacent said longitudinal seam a rupture zone susceptible to undergoing rupture when subjected to impact stress, the film material of said tube including adjacent said rupture zone a shock-absorbing band which is separated from said longitudinal seam by a region of unstretched film material and extends generally parallel to said longitudinal seam over a significant portion of the length of said longitudinal seam, said shock absorbing band comprising a plurality of discrete stretched zones of film material stretched in a direction generally perpendicular to the longitudinal seam alternating one by one with a plurality of stripes of substantially unstretched film material with the length of said stripes extending in a direction generally perpendicular to said longitudinal seam, whereby impact stress forces applied to said rupture zone are transmitted away from said rupture zone and absorbed by said shock absorber band to thereby significantly improve the resistance of the rupture zone to such stress.