CA2127310C

CA2127310C - Beverage cup lid having an annular flange extension for increased cap retention force and method of manufacture

Info

Publication number: CA2127310C
Application number: CA002127310A
Authority: CA
Inventors: Jonathan E. Rush; Thomas R. Toczek
Original assignee: James River Corp of Virginia
Current assignee: Dixie Consumer Products LLC
Priority date: 1993-08-04
Filing date: 1994-07-04
Publication date: 1999-07-06
Anticipated expiration: 2014-07-04
Also published as: CA2127310A1; US5460286A

Abstract

ABSTRACT OF THE DISCLOSURE

A beverage cup lid is disclosed that comprises a circular closure panel, circumscribed by a side wall that terminates in a resilient, restricted diameteredge for capturing a brim of a beverage cup, and a frustro-conical skirt connected around the restricted diameter edge for increasing the hoop strength of the edge, and an extended diameter flange circumscribing the free edge of the skirt for further increasing the hoop strength of the restricted diameter edge such that the edge retains the brim with a force of at least 1 pound. The invention is particularly applicable to beverage cup lids formed by a plastic web machine that applies heat to only those areas that are deformed into structural components on the lid (such as the side wall, restricted diameter edge, and skirt), and which consequently results in some, amount of wall thinning in the skirt, and hence some reduction in the hoop strength that the skirt gives to the restricted diameter edge that retains the cup brim. The radial extent of the flange is large enough to increase the hoop strength, and hence retaining force of the restricted diameter edge by between .5 and 1.0 pounds.

Description

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Background Of The Invention This inventioll generally relates to lids for beverage cups, and LS
~re~ifie~lly ~oncerned with a disposable beverage lid having a reduced diameter edge that snap-fits over the brim of a drinl~g cup, wherein the retemion force of the edge around the cup br m is incre~sed by the provision of an eYterl~ed dianeter flange that increases the hoop slrength of the reduced diameter edge.
Disposable beverage cup lid~s are well lcnown in the prior art. Such, cup ~ids are formed from a fusible plastic sheet material, and are d~
to snap-fit over the top of a disposable beverage cup to keep the liquid cQn~çnt~ of such cups ~om spilling dunng ~ransport. In ~he past, such lids were the~rnrJf~rmed into plastic sheet material by applying radiant heat ulliÇu~ l,Y ~oughout a si~gle piece of sheet material to soften the sheet m~t~ l at all points, and then pnP~lm~tir~lly pl~S5il3g the sof~Pn~d sheet of material against a plurali~ of lid molds by the creation of a parual vacuum between the sheet material and the molds. After the molding operating was completed~ the vacuum pre~.ule be~een the sheet material and the molds was norrnalized so that the sheet could be easily pulled l~rom the molds, and the resulting lid blanks were then individually cut out of the sheet by means of a trim press having a rnech~nir~l action similar to that of a co~non hole punching ~n~ehine for paper.
2S An example of a snap-on lid manu~actured by ~his process is disclosed in U.S. Patent 4,877,151 assigned to James Rivêr Corporat;on. Such lids generally comprr,e a clrcular closure panel circumscribed by a side wall tha~

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terminates in a reduced diameter edge. The reduced diameter edge is (1irnencioned so tha~ it is capable of snap-fitting over the annular brim that circumscribes the open end of a disposable drinldng cup. To provide the reduced ~ m~ter edge with s~ffi(~ie~t resiliency to achiev~ its purpose9 a S plurality of flutes are provided in the side wall shat circurnscribes the central, circular panel of the lid. A frustro-conically shaped slcirt is in~e~ally conn~cte-l to the reduced ~ s~nptçr edge. ~s skirt flares oul~dly and dvwllw~dly from ~he edge, and not ~nly increases the hoop ~ n~ of the reduced diameter edge, but also advantageously receives, guides, arld wedgingly snaps the reduced edge of the lid over the annnlar brim of the drinking cup when it is pressed d-3wllwaldly over the open end of the cup.
The free edge of the frustro-conical skirt is typically circumsc;ibed by a very short flange having a radial length of only about .030 inches. Ideally, it was, thought that the flange that circurnscribes the ou~er edge of s~he frustro-conical skirt should be elimin~tçd altogether, as it served no Si~ .9~l purpose in the lid. However, in view of the tolerances associated with the operation of ~he t im press9 it was necessary to leave some small amount of flange to insure that no parts of the skirt were inadverlently cut during the g operation.
While the snap-on lid disclosed and claimed in U.S. Patent 4,877,151 represented a substantial advance in the art, the inventors observed that when lids of this design were manufactured in certain types of therrnoforming machinery, the retention force between the lid and the cup fell to lower than optimal levels (i.e., in some cases, under 1 pound of force). In particular, theapplicants observed that~ when such cups were made by way of plastic web rnachine, which applied localized, contact-type hea~ing to only those por~ions of the sheet ma~erial which were going to be deformed by the mold, the resultant stretching in the side wall area wes~kçn.od the hoop strength of th~
res~ricted diameter edge that snap-fits over ~he brim of the beverage cup, ,'',.

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which in turn resul~ed in a lower than opnmal re~en~ion force between thelid and the cup.
While the applicants recoEni7ed that it would be possible to increase the hoop strength of the restricted diameter edge by either decreasing the 5 rli~meter of the edge, or modii~ying the pattern of flutes in the side wall which deterTninPs the resilien~y of the restricted edge, or even len~henin~ the frustro-conical skirt that is integrally conn~cted to ~he edge, any of these approaches would n~c~ e an experlsive re-m~rhinin~ opera~ion on eash of the lid molds. ~ ition~lly~ if ~he restricted diameter were made ~m~ or, 10 or the skir~ were made longer, it might be difficult, if not impossible, to remove the lid blanlcs from the mold. Still another solution that the applicants contemplated was to make the sheet material which forrrLs ~he lids thicker. While ill actual ~ests this approach sucreeded in increasing the hoop strength of the restricted diameter without the need for making e~y~
15 changes in the lid molds, it nPcec~jt~ted the use of larger amounts of plastic material to produce the lid, which in turn resulted in a sllbst~nti~l increase manufacturing cost.
Clearly, what is needed is a way to increase the hoop strength of the restTicted ~ m~ot~r to at least a 1.5 pounds without the need for an expe~sive 20 re-machining of the molds, and without the use of thicker sheet mateAal.

Summary Of The Invention Generally speaking, the inven~ion is an improved beverage cup lid of the type manufacnlred by a partial thermal-forming process which compensates for the reduced hoop strength given to the restricted (li~meter 2~ edge by the fmstro-col~ical skirt by 2he provision of a flange t?Ytencion that circurrlscribes the free edge of the skirt. The radial extent of the ~laDge extension is chosen so as to increase the hoop strength of the frustro-conical 2~27~3~

slcirt such that the restricted diameter edge that ~,dp~ es the brim of the beverage cup seQlres the brim with a force of at least 1~5 pounds. This also pro~rides a more coIlveniently grippable surface than the previously-used short flange that f~ e5 the removal of ~he lid by the finger of a user.
S ~n the l~lefelled embodimer~t, the radial extent of the flange is between about 0.020 to û.040 inches, and the radial extent of the ~ ge ~oytencion is between abou~ 0.032 and 0.052 inches such that th ~ange cion increases the reeeIItion force of the lid around the bri n by betwee .25 and 50 pounds.
In the method of the 3nvention, a lid is formed from a sheet of heat fusible, plastic sheet rnaterial by first selectively applying heat to only those poruons of the sheet material that will be deformed imo the side wall, the reduced ~ met~r edge, and tbe ~rustro-conical skirt of the lid, deforming said, - -selectively heated portions into said side wall, restricted diameter edge~ and frustr~conical skirt, and then creating both the flange and the flange eYtencion by making a circular cue in the sheet material around the outer edge of the skirt. The cut is spaced apart from the outer edge of the skirt such that the aforemPntion~od 9ange and ~lange extersion is ~ormed that increases the hoop strength of the restricted ~ meter edge such that it retains the brim tha~ circurnscribes the cup with a ,force of at least 1.25 pounds.
In the preferred method of th~ invention, the side wall, r~stricted diameter edge, and skirt of the lid is formed by rneans of a plastic web m~t~hinf~ of the type that applies heat to only the portions of the fusible 2S plastic sheet material th~t are deformed with respect to the circular closure panel that constitutes most of the lid, and the trimming step is implemented by an integral trim press of the type that can Cut circular holes in plastic sheet material o~ any one of a number of selected diameters. The use of a trim press to create an ex~ended flang,e having the properties heretofore . CA 02127310 1999-03-05 described, provides a cup lid with a restricted diameter edge that is c~r~le of grasping the brim of a drinking cup with the same retention force as a cup lid m~mlf~c~lred by a co..Yc.,l ;on~l thermal forming ~roce~s without the need for m~kina any iuconvenient, time concllmin~, and eYr~enciye toolillg changes 5 or using thicker and more expensive sheet material.

Brief Descri~tion Of The Several Figures Figure lA is a plan view of the beverage cup of the invention;
Figure lB is a partial cross-sectional side view of the cup lid of Figure 1~ illustrating how the restricted diameter in the side wall of the lid s~aps 10 over the brim of the open end of a disposable beverage cup;
Figure lC is an enlargement of the portion of the lid contained within, the dotted cirde in Figure lB, and Figure 2 is an enlarged, cross-sectional side view of the lid of the invention, illustrating the strengthening extension of the peripheral ~ange that15 serves to increase the hoop strength of the restricted diameter portion of the side wall.

Detailed Description Of The Preferred Embodiment Witb reference now to Figures lA lB, and lC, the lid 1 of the invention is designed to be snap-fitted over a beverage cup 3 (shown in 20 Figure lB) of the type having a brim 5 circurnscribing its open end. The lid 1 generally comprises a circular closure panel 7 having a side wall or bead 9 which circumscribes its periphery. One end of the side wall 9 is integrally connected with the edge of the panel 7, while the other end terrninates in a restricted diameter 11 that is designed to snap over and capture the brim 5 25 of a cup 3 in the manner shown in Figure lB. To give the restricted diameter 11 the flexibility it requires in order to resiliently snap-fit over the brim 5, a plurality of flutes 13 are integrally molded into the side wall 9, as may best be seen in Figure 1C. While any one of a number of different types of flutes can 5 provide the restriction diameter 11 with the resiliency it needs, the flute pattern disclosed in U.S. patent 4,877,151 assigned to the James River Corporation, is preferred. A frustro-conical skirt 15 is integrally connected to the restricted diameter 1 1 that circumscribes the bottom edge of the restricted diameter 1 1. The frustro-conical skirt performs a variety of functions, including guiding, and 10 wedgingly snap-fitting the restricted diameter 11 of the side wall 9 over a brim 5 when a user pushes the lid 1 over the open end of a cup 3. The frustro-conical skirt 15 also helps to provide hoop strength to the restricted diameter 11 of the side wall 9, thereby increasing the reiention force by which the restricted diameter 11 captures and retains the brim 5 of cup 3.
With reference now to Figures 1 A and 2, the closure panel 7 preferably includes a relatively shallow, annular recess around its mid portion as shown. Integrally formed within the annular recess 20, are four V-shaped stacking lugs 21 a-d located at 90~intervals around the circumference of the recess. Each of these V-shaped lugs 21 a-d includes an inner side wall 22, an outer side wall 24, 20 and a bottom wall 26. The purpose of these V-shaped lugs 21a-d is to allow the lid 1 to be stacked with identical lids 1' in the manner illustrated in Figure 2 in such a manner that the lids 1 and 1 ' do not stick together. It should be noted that any one of a variety of different lug designs may be employed with the present invention, as such lugs do not form part of the instant invention. Disposed at the -6a-very center of the closure panel 7 is a circular depression 30 having an arcuate straw slot 32 that defines a straw punch-out region 33. The provision of the depression 30 prevents any of the liquid contents of the cup 3 that runs out on 5 top of the lid 1 when a -7- 2~27~

straw is pushed through ~he pumch out 33 from run~ing over the sides of ~he lid 1 and ge~ng on the clothes of the user.
With reference now to Figure 2, the flange 17 of the lid 1 inJ~ es a~
in~egrally i~ormed~ aml~llar strerl~h~ninS~ to~encion 35 as shown that is S rlim~on~ion~d to increase the retention force of the restric~ed diameter 11 of the side wall 9 to an average value of at least 1.25 pounds, and morP
preferably 1.45 pounds. In a cup lid $hat does not embody the present Lllven~iOrl, if the outer ~ oter of the brirn S of the cup 3 is between 3.499 and 350~ inches, and the inner diame~er of the restricted diameter 11 is between 3.426 and 3.430, and the cap 1 is formed from high impact polystyrene plastic sheet matçrial having a thickness of 9 mils in ~be molds of a plastic web m~hin~ m~nllf~lred by James El~iver of ~lorw~lk Conn~ t, the radial extent L1 of the peripheral flange 17 would be .030, inches The restricted ~ mpter of such non-inventi~e lids have an average retention force of orlly about 1.08 pounds around the brim 5 of a cup 3. By contrast, when a strengthening extension 35 is integrally fo~ned with the flange 17 ~hat has a radial length I2 of .043 inches, the ~otal radial exten~ ofthe ~ange 17 increases from .030 to .07'~ inches, which in nlrn increases the retention force of ~he restric~ed diameter 11 around the brim 5 from an average value of about 1.08 pounds to an average value of about 1.4~ pounds.
The radial extent I3 of the skirt 15 is on the average û.079 inches, and another way of viewing the invention is in terms of the ratio of the total radial extent of the flange 17 ~ith and wichout che flange extension 35.
Specifically, the radial extent of the flange 17 by itself is only about 38% of 2S the radial extent of the slcirt 15. By con~rast, the radial extent of the flange 17 in combination with the exte~sion 35 is 91% of the radial extent of ~he skirt 1~. The increased radial length of the resulting flange 17 has been further found to facilitate removal of the lid by a user by providing a larger grasping surface for the finger of such a user.

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In the method of the ~vention, a lid is formed from a sheet of heat fusible, plastic sheet material of the type and ~lim~ncionc as heretofc,l~
descr~bed. The plastic sheet material is fed into the previously referred to plastic web machine. Such m~-~hin~s include a co~tact heater having a S smooth, coll~uuled heating surface tha~ over~ies an arrangement of female lid molds. The plastic sheet material is fed between the surface of ~he contact heater, and the lid molds so that the sheet material is placed ~to contact with the heating surface. The contace heaeer then proceeds to apply a pattern of heat to the sheet rnaterial only on those portio~s of the mateIial which will10 be deformed by the lid molds. After hea~ from the contact heater has selectively so~tened those portions to be deformed by the lid molds, a partial vacuum is drawrl between the sheet material and the molds, while at the same tirne air pressure is applied between the co~tact heater and the sheet, ma~elial in order IO draw the sheet material tightly agaLTlst the surfaces of the 15 lid molds. The lid molds then proceed to defonn the sheet material into an array of lid blan};s, each having a profile as shown in Figure 2 with the exception that the free end of the ~ustr~conical skir~ 11 tern~inates in unused shee~ material between adjacent lid blanks, instead of in the flange 17. In the final steps of the me~hod of the invention, the lid blanlcs that ase . ~
20 in e~fect embossed in the sheet material are each aligned with the circular cutter of an i~e~ral trim press, which proceeds to punch the finished lids out in much the same fashion as a paper punch. The circular cutters of the trim press are each adjusted so that the length of the flange 17 and ~lange extension is on the order of .072 inches for all the reasons heretofore 2~ described. The diameter of the holes punched by such trim presses may be adjusted by the manufacturing facili~v by ~h~n~ina ~he trim tools so ~hat the radial length of the resulting flange 17 is .07~ inches. This can be accomplished by boring the existing dies larger and manufacturing new larger punches.

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Claims

1. An improved lid detachably affixable over the brim of a beverage cup of the type formed from a plastic sheet material and having a generally circular closure panel circumscribed by a side wall that terminates in a resilient, restricted diameter edge for capturing a brim of a beverage cup between said edge and said side wall and retaining said lid over said cup; a frustro-conical skirt connected around said restricted diameter edge for increasing the hoop strength of said restricted diameter edge and for guiding said cup brim into said edge and wedgingly snap-fitting it around said brim, said skirt having a free edge terminating in a flange, wherein the thickness of the sheet material forming the skirt is less than the thickness of the sheet material forming the circular panel, and the radial extent of said flange is between about 30 and 46% of the radial extent of said skirt wherein the improvement comprises a flange extension circumscribing the flange of said skirt and having a radial extent of between about 40 and 60% of the radial extent of said skirt for increasing the hoop strength of the restricted diameter edge such that said edge retains said brim with a force of over 1.25 pounds, and for providing a surface that facilitates removal of the lid by the finger of a user.

2. A lid as described in claim 1, wherein said lid is formed from a single piece of resilient, fusible plastic sheet material, in a plastic web machine that causes the thickness of the sheet material forming the skirt to be less than the thickness of the plastic forming the closure panel.

3. A lid as described in claim 1, wherein the radial extent of the flange is between about .020 to .040 inches, and the radial extent of the flange extension is between about .032 to .052 inches.

4. A lid as described in claim 1, wherein the radial extent of the flange is between about .025 to .035 inches, and the radial extent of the flange extension is between about .037 to .047 inches.

5. A lid as described in claim 1, wherein said frustro-conical skirt has a small diameter end that is integrally connected to said restricted diameter edge, and a large diameter end, and wherein said flange is integrally connected to said large diameter end, and said flange extension is integrally connected to the outer periphery of said flange.

6. A lid as described in claim 1, wherein said flange extension increases the retention force of said lid around said brim by between .27 and .47 pounds.

7. A method of manufacturing a lid from a sheet of heat fusible, plastic sheet material that is detachably affixable over a brim that circumscribes the open end of a beverage cup, wherein said lid includes a generally circular closure panel circumscribed by a side wall that terminates in a resilient, restricted diameter edge for capturing said brim of said cup andfor retaining said cap over said cup, and a frustro-conical skirt connected around said restricted diameter edge for increasing the hoop strength of said restricted diameter edge and for guiding said cup brim into said edge, said skirt terminating in an outer edge having an annular flange, comprising the steps of:

selectively applying heat to only those portions of said sheet material to be deformed;
deforming said heated portions of said sheet material into a lid having said side wall, restricted diameter edge, and said skirt, wherein the thickness of the deformed portions of the sheet material is less than the thickness of undeformed portions of the sheet material and trimming the resulting lid out of said sheet material by making a circular cut around said outer edge of said skirt, said cut being spaced apart from said skirt edge such that an annular extension is provided around said flange that increases the hoop strength of said restricted diameter edge such that it retains said brim with a force of over 1.25 pounds.

8. A method of manufacturing a lid as described in claim 7, wherein the flange around the free end of the skirt has a radial extent of between about 30 and 46% of the radial extent of said skirt, and the flange extension has a radial extent of between about 40 and 60% of the radial extent of said skirt.

9. A method of manufacturing a lid as described in claim 7, wherein the radial extent of the flange is about .020 to .040 inches, and the radial extent of the flange extension produced by said trimming step is between about .032 and .052 inches.

10. A method of manufacturing a lid as described in claim 7, wherein said extended flange increases the retention force of said lid around said brim by between about .27 and .47 pounds.