CA1253309A - Method and injection molding tool for producing link belts - Google Patents
Method and injection molding tool for producing link beltsInfo
- Publication number
- CA1253309A CA1253309A CA000524710A CA524710A CA1253309A CA 1253309 A CA1253309 A CA 1253309A CA 000524710 A CA000524710 A CA 000524710A CA 524710 A CA524710 A CA 524710A CA 1253309 A CA1253309 A CA 1253309A
- Authority
- CA
- Canada
- Prior art keywords
- link
- cavities
- mold
- cross
- injection molding
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000001746 injection moulding Methods 0.000 title claims abstract description 35
- 238000000034 method Methods 0.000 title claims abstract description 11
- 239000012768 molten material Substances 0.000 claims abstract description 16
- 238000001816 cooling Methods 0.000 claims abstract description 6
- 238000002347 injection Methods 0.000 claims description 19
- 239000007924 injection Substances 0.000 claims description 19
- 229920002994 synthetic fiber Polymers 0.000 claims description 17
- 239000000463 material Substances 0.000 claims description 6
- 238000007711 solidification Methods 0.000 claims description 5
- 230000008023 solidification Effects 0.000 claims description 5
- 238000003780 insertion Methods 0.000 claims description 2
- 230000037431 insertion Effects 0.000 claims description 2
- 239000002699 waste material Substances 0.000 claims description 2
- 230000000875 corresponding effect Effects 0.000 claims 3
- 238000007493 shaping process Methods 0.000 claims 1
- 230000005540 biological transmission Effects 0.000 abstract description 2
- 238000005266 casting Methods 0.000 abstract 1
- 238000000465 moulding Methods 0.000 abstract 1
- 229940090044 injection Drugs 0.000 description 12
- 238000006073 displacement reaction Methods 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 239000004952 Polyamide Substances 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 229920002647 polyamide Polymers 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 229930188970 Justin Natural products 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 150000002148 esters Chemical class 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 239000011796 hollow space material Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000036961 partial effect Effects 0.000 description 1
- 229920000728 polyester Polymers 0.000 description 1
- -1 polypropylene Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 229920000136 polysorbate Polymers 0.000 description 1
- 239000012209 synthetic fiber Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/17—Component parts, details or accessories; Auxiliary operations
- B29C45/26—Moulds
- B29C45/27—Sprue channels ; Runner channels or runner nozzles
- B29C45/2701—Details not specific to hot or cold runner channels
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/14—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor incorporating preformed parts or layers, e.g. injection moulding around inserts or for coating articles
- B29C45/14549—Coating rod-like, wire-like or belt-like articles
- B29C45/14565—Coating rod-like, wire-like or belt-like articles at spaced locations, e.g. coaxial-cable wires
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/16—Two dimensionally sectional layer
- Y10T428/169—Sections connected flexibly with external fastener
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/18—Longitudinally sectional layer of three or more sections
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
- Y10T428/24273—Structurally defined web or sheet [e.g., overall dimension, etc.] including aperture
Abstract
TITLE OF THE INVENTION
METHOD AND INJECTION MOLDING TOOL FOR PRODUCING LINK BELTS
ABSTRACT OF THE DISCLOSURE
A link chain or string is produced in an injection molding tool in such a way that a plurality of links threaded onto a string or cable are molded simultaneously, for example in the form of spheres. In order to avoid the transmission of axial forces to the links, which forces might disturb the axial spacings from link to link, the injection molding tool is provided with restric-tions which reduce the cross-sectional area of molten material flow channels to a minimum. Preferably, the restricted area is located directly at the respective link. The channels all lead to a common injection molding channel to which the molten material is supplied for thus simultaneously casting or molding of a plurality of links to strings or cables. The restrictions make sure that any forces result-ing from shrinkage during the cooling and solidifying cannot shift the balls or links even if the latter are not yet completely solid-ified internally. Thus, errors in the on-center spacing between adjacent links are avoided.
METHOD AND INJECTION MOLDING TOOL FOR PRODUCING LINK BELTS
ABSTRACT OF THE DISCLOSURE
A link chain or string is produced in an injection molding tool in such a way that a plurality of links threaded onto a string or cable are molded simultaneously, for example in the form of spheres. In order to avoid the transmission of axial forces to the links, which forces might disturb the axial spacings from link to link, the injection molding tool is provided with restric-tions which reduce the cross-sectional area of molten material flow channels to a minimum. Preferably, the restricted area is located directly at the respective link. The channels all lead to a common injection molding channel to which the molten material is supplied for thus simultaneously casting or molding of a plurality of links to strings or cables. The restrictions make sure that any forces result-ing from shrinkage during the cooling and solidifying cannot shift the balls or links even if the latter are not yet completely solid-ified internally. Thus, errors in the on-center spacing between adjacent links are avoided.
Description
~2~33l~9 1 FIEI.D OF T~E INVENTION
The invelltion relates to a method and to an injection molding tool for producing link belts or chains to which links of synthetic ma-terial are secured. The term "]ink belts" is used in its broadest meaning to include a flexible string or a cable to which synthetic chain links are secure(l at spaced intervals, whereby thcse links are injection molded onto a strinq or cable or belt or the like.
DESCRIPTION OF THE PRIOR ART
sall or link chains are known, comprising a flexible string on which balls are threaded or lined up at uniform spacings. Such ball or link chains or simply ball chains have a wide range o use, particularly because the ball chains can be bent or turned in any desired direc-tion, whereby they may serve in many instances for a synchroneous drive or control, or they may serve as force transmitting elements.
Originally such ball chains were made of metal. I~owever, balls made of synthetie materials have also become known. Ball chains with balls of synthetic material have been produced heretofore in such a way that the balls were individually injection molded onto a string or cable, whereupon the string or cab1e was trans~ortQtl hy a ~et~d advance in accordance with a pr~deterlninetl on-ccnter spacinc3 be-tween two neighborill(3 balls. Such a production methoc1 is very slow and not suitable for mass production.
The simultaneous production of a plurality of balls injection molded onto a string or cable in an injection mold for synthetic material has failed heretofore due to the fact that spacing errors occurred
The invelltion relates to a method and to an injection molding tool for producing link belts or chains to which links of synthetic ma-terial are secured. The term "]ink belts" is used in its broadest meaning to include a flexible string or a cable to which synthetic chain links are secure(l at spaced intervals, whereby thcse links are injection molded onto a strinq or cable or belt or the like.
DESCRIPTION OF THE PRIOR ART
sall or link chains are known, comprising a flexible string on which balls are threaded or lined up at uniform spacings. Such ball or link chains or simply ball chains have a wide range o use, particularly because the ball chains can be bent or turned in any desired direc-tion, whereby they may serve in many instances for a synchroneous drive or control, or they may serve as force transmitting elements.
Originally such ball chains were made of metal. I~owever, balls made of synthetie materials have also become known. Ball chains with balls of synthetic material have been produced heretofore in such a way that the balls were individually injection molded onto a string or cable, whereupon the string or cab1e was trans~ortQtl hy a ~et~d advance in accordance with a pr~deterlninetl on-ccnter spacinc3 be-tween two neighborill(3 balls. Such a production methoc1 is very slow and not suitable for mass production.
The simultaneous production of a plurality of balls injection molded onto a string or cable in an injection mold for synthetic material has failed heretofore due to the fact that spacing errors occurred
- 2 -~ 330~
1 due to heat shrinkage. Such spacing exrors are unaccep-table in con-nection with the use of such ball chains for the synchroneous drive or for control purposes. It has been found that connecting lands leading to the individual ballsdue to the injection molding and which lands extend from a common injection molding land, cause, due to any heat shrinking during cooling, a slight displacement of the balls along the string or cable because the inside of the balls has not yet fully cooled. Such displacement of the balls results in spacing inaccuracies in the finished ball chain. The larger the number of balls which were injection molded simultaneously, the larger became `0 the inaccuracy. The spacing errors became the larger the further the balls were removed from the center of the injection molding land.
OBJECTS OE' T~IE INVENTION
In view of the foregoing it is the aim of the invention to achieve the following objects singly or in combination:
to provide a method for the mass production of link belts or link chains also referred to as ball chains, comprising a plurality of links made of synthetic material, wherein the links may be balls, and whereby the mentioned spac.illg error is avo.i~ed;
to provide a method and apparatus in which the type of 0 link belt or chain as described above can be produced in a multiple injection mold in an efficient and economic manner; and to produce such belt or chains with link elements having any desired shape not ~ust spheres.
1'~533t)9 SUMM~RY OF 'rllE INVENTION
~ccording to the invention the method is characterizedin that there is provided at least one common longitudinal injection molding land extending in parallel to the string or cable for the simultaneous injection molding of a plurality of links onto said string or cable.
The method further comprises providing connecting lands or passages extending laterally away from the common longitudinal passage toward the individual links, whereby the connecting paths or lands are made so weak and/or the cross-section thereo~ at least at one location, is O made so small that a force transmission,after the injection molding has been completed,is prevented and thus a displacement of the links along the string or cable due to heat shrinkage of the common injec-tion molding land or path is avoided.
Due to the provision of the thin wall or weak connection between the injection molded links, especially balls, and the respective connect-ing lands, the relatively massive common injection molding land can-not exert any displacement force on the links or balls in the longi-tudinal direction of the string or cable. This holds true even though the relatively massive common injection molding land is subject to O material shrinka~3e whe~n the moltent m~terial soli.difies.
The material shrinkage is unavoidal~le in connection with synthetic materials. Such shrinkage is relatively large comparecl to the shrink-age of metals, in the longitudinal direction of the common injection molding land. Yet, as a result of the present teaching the shrinkage of the common injection molding land can only cause a slight bending of the relatively thin lands an~orofthe relatively weakrestriction justin frontofthe link or ball. When the links or balls just after the " ., l~S33~3~
injection molding operation have not yet completely cooled down on the inside due to their mass, these links or balls do not yet rigidly enclose, nor do they solidly adhere to the string or cable. However, the weak connecting location pre-vents that a change in the position of the links or balls in the longitudinal direction of the string or cable can take place.
In summary, therefore, the present invention may be considered as providing a method for simultaneously injection molding two link chains, each link chain having an elongated flexible member and a series of synthetic material link elements having a given cross-sectional dimension and being molded at equal spacings from one another to their respective elongated flexible member, comprising the following steps: a) using an injection mold having two rows of mold cavities, each row including a series of equally spaced cavities for simul-taneously forming the series of link elements on each link chain as a row along each link chain, grooves for the elong-ated flexible member interconnecting the cavities to form the two rows of cavities, and molten material supply channels including a main channel located between the two rows of cavities and individual branching channels leading individ-ually from the main channel to each cavity on both rows, b) providing each individual branching channel with a throat of reduced cross-sectional dimension corresponding to less than about 10% of the given cross-sectional dimension of the link elements, c) locating the reduced throat directly at the res-rn/rm lZS3309 -5a-pective link forming cavity, d) inserting one elongated flexible member into each row of cavities and grooves and closing the mold, e) introducing molten material into the cavities through the main channel and the individual channels, and f) restricting a cross-sectional dimension of a land, formed in the individual channel by the throat of reduced cross-sectional dimension, to such an extent that force components resulting Erom material shrinking during the cooling of the synthetic material in the main channel, are substantially prevented from displacing the link elements along the respective elongated flexible member, whereby the equal spacings between neighboring link elements are assured even if the chain is removed from the mold before solidifica-tion of the link elements.
The above method may be carried out by way of an injection mold for simultaneously injection molding two link chains, each link chain having an elongated flexible member and a series of synthetic material link elements molded at equal spacings from one another to their respective elongated flexible member to simultaneously form one row of link elements along each respective elongated flexible member, com-prising a lower mold plate, an upper mold plate, two rows of equally spaced cavities in each row in the mold plates for simultaneously forming the link elements as two rows of a series of link elements, the cavities having cross-sectional dimensions corresponding to respective dimensions of the link elements, grooves for insertion of the elongated flexible rn/rm lZ~;~3(~9 -5b-member, the grooves interconnecting the cavities in each row, molten material supply channel means in the mold plates, the channel means including a central main channel between the central main channel, the central main channel and the two rows of grooves including the cavities extending substantially in parallel to each other and in the longitudinal direction of the two link chains, and individual channels leading away from the central main channel in opposite directions to each of the cavities in each row, so that the individual channels and the central main channel form two ladder type individual channel configurations for producing the two link chains, each indi-vidual channel having a throat with a reduced cross-sectional flow area corresponding to less than 10% of the cross-sectional dimension of the cavities for forming the link elements of the molten material, the reduced cross-sectional flow area of each throat preventing shrinking forces from distorting the equal spacings.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be clearly under-stood, it will now be described, by way of example, withreference to the accompanying drawings, wherein:
Fig. 1 is a top plan view of two ball chains which are connected to a common injection molding land through individual connecting lands which must later be removed;
Fig. 2 is a top plan view onto a portion of a mold plate of the injection molding tool;
Fig. 3 is a sectional view along section line III -rn~rm 5~3309 -5c-III in Fig. 2;
Fig. 4 illustrates one example embodiment of molded links having the shape of disks with conical projections in the direction of the string or cable;
Fig. 5 is another example embodiment in which the links are formed as fork-type elements; and r n/ r~?" ~
33~)~
Fig. 6 shows still another example embodiment in which the links comprise groups of balls spaced by links in the form of eyelets.
DETAILED DESCRIPTION OF PREFERRED EX~MPLE EMBODIMENTS ~ND OF TEIE
BEST MODE OF TI~E INVENTION
Fig. 1 shows an injection molded part 1 made of synthetic material including two ball chains manufactured simultaneously. Two par-tial lenqths of such chains are shown. As a result of the injection molding the chains still are interconnected by lands 5 leading from O each ball 2 to a cor~mon injection molding land 4. Due to the injection molding the balls 2 are permanently bonded to the strings or cables 3. After the injection molding and after the cooling the lands 5 are separated from the balls 2 at the point 7 which designates the narrowest cross-section of the lands S. Thus, the lands 5 and the common injection molding land 4 are separated from both ball chains and are removed as waste while the two chains remain as the result of the injection molding. Due to the reduced cross-sections 7 any forces in the axial direction resulting from the shrinkage especially of the land 4, cannot be transmitted to the balls 2 so O that these halls remain uniformly spaced alonc3 th(?ir resp~ctive striny or cable 3. The balls or similar eLelllc?nts are rigidly secured to the respective string or cable 3 as a result of the solidification and curing of the synthetic material.
Fig. 1 sl~ows two strings 3 each carrying sixteen spheres 2. Ilowever, more than two strings3 ~y be stepped through the in}ection mold and the number of balls produced along each string section in each injec-tion molding step may also be substantially larger, for example, lZS331~9 1 forty to fifty balls have ~een found to be easily made simultaneously along each section of string or cable 3. The feed advance of the strings or cable 3 in steps through the injection molding tool is not part of the invention. After the initial ins~rtion of the required number of strings or cables into the injection mold, the feed advance may continue until the entire length of the cable or string has been used up. Thus, the total length of a link chain or belt according to the invention is practically determined only by the total length of the available string or cable 3.
0 ~s shown in Figs. 2 and 3 the multiple injection mold comprises two mold plates 18 and 20 having recesses therein corresponding to the mold cavities and to the passageways for supplying the molten material into the mold cavities. ~ hollow space or channel 12 serves for the introduction of the molten material into the mold. The channel 12 extends in parallel to a groove 13 which is intended to receive the string or cable 3. The above mentioned land 4 is formed in the channel 12. Recesses 16, for example, of cylindrical shape, are formed at spaced intervals in the mold plate 18 along the channel 12 for forming studs 6 also shown in Fig. 1. These studs 6 also help 0 reducing the effects of any shrinkage when the injected material is coolin~ because the studs 6 tie the lands 4 to the molcl plate 1~.
Semispherical recesses 8 are provicled in each mold plate 18 and 20.
Side channels 10 in the mold plate 18 connect the molten material main suppl~ channel 12 to the recesses or cavities 8 in the mold plates 18 and 20. These side channels 10 result in the formation of the con-necting lands 5 havinc3 relatively thin walls. The side channels 10 are so shaped that the cross-sections of these lands 5 decrease,as ......
~Z533U9 1 the spacing from the injection molding land 5 increases. Direc-tly where the side channels 10 enter into the ball shaped recesses or cavities 8,the side channels 10 are provided with a substantially reduced cross-section 14, whereby the resulting land 5 has its smallest cross-section at this point for limiting or eliminating an effect of any axial forces resulting from the solidification and cooling of the synthetic material, on the balls or links 2. The axial direction in this connection is the longitudinal direction of the strings or cables 3. These reduced cross-sectional areas7Of the 0 connecting lands 5 which are caused, according to the invention, by the restrictions 14, thus make sure that a longitudinal displacement of the balls 2 is prevented as lo~g as is necessary, namely until the balls 2 are completely solidified. Thus, the balls will not shift, even after they have been removed from the mold, although they have not yet completely solidified on the inside.
In a practical example embodiment the cross-sectional dimension of the restriction 14 is less than 10~ of the diameter of the balls 2.
The cross-sectional area of these restrictions 14 is less than 1 mm2.
Where the ball diameter is q.5 mm, the cross-section of the restric-o tion 14 is about 1/6 of 1 mm2. The cross-section of the injection molding lan~ 4 is substantially lar~er thall the cross-sec~ioll of the individual connectinc3 lands 5 where these l~nds 5 merc3e into the land 4, for example, the cross-sectional area of the land 4 may be three times the cross-sectional area of the land 5 at the location where the lands 5 join the land 4.
The second or upper mold plate 20 which closes the mold has recesses compatible or similar to the recesses in the mold plate 18, except i2533V9 1 that the side channels 10 and the injection molding channel 12 have a flat, narrow side 21. ~ddition~lly, the mold plate 20 has at least one inlet channel 21' for introducin~ the molten material into the mold channel 12. The molten material is, for example, polyamide, polyester or the like, synthetic material.
The string or cable 3 passes centrally through each ball. The string is preferably made also of synthetic fibers such as polyamide, poly-ester, polypropylene fibers, or the like. For special purposes, the string or cable 3 may be made of a steel wire or wires encased by the ~0 mentioned synthetic materials or a steel cable may be used which is not encased.
As shown in Figs. 4, 5, and 6, the elements 2 need not be balls.
These elements may have almost any desired shape as illustrated in Figs. 4, 5, and 6. In Fig. 4 the elements have a central disk 24 flan~ed by two truncated conical sections In Fig. 5 the elements have a fork-type configuration 22. In Fiy. 6 groups of balls 2 alternate with eyelet elements 23.
As mentioned above, the production efficiency and economy i improved by holding simu]taneously more tllall two string~, for example, four or ) six string sections may be molded witll linlcs in a respectively formed mold. Further, the length shown in Fig. 1 is merely an example and the above mentioned number of links for each mold section is quite practical.
_ g _ l~S33~g 1 ~lthough the invention has been described with reference to specific example embodiments, it will be appreciated, that it is intended to cover all modifications and equivalents within the scope of the appended claims.
- 1 0 - i ....~ ~b
1 due to heat shrinkage. Such spacing exrors are unaccep-table in con-nection with the use of such ball chains for the synchroneous drive or for control purposes. It has been found that connecting lands leading to the individual ballsdue to the injection molding and which lands extend from a common injection molding land, cause, due to any heat shrinking during cooling, a slight displacement of the balls along the string or cable because the inside of the balls has not yet fully cooled. Such displacement of the balls results in spacing inaccuracies in the finished ball chain. The larger the number of balls which were injection molded simultaneously, the larger became `0 the inaccuracy. The spacing errors became the larger the further the balls were removed from the center of the injection molding land.
OBJECTS OE' T~IE INVENTION
In view of the foregoing it is the aim of the invention to achieve the following objects singly or in combination:
to provide a method for the mass production of link belts or link chains also referred to as ball chains, comprising a plurality of links made of synthetic material, wherein the links may be balls, and whereby the mentioned spac.illg error is avo.i~ed;
to provide a method and apparatus in which the type of 0 link belt or chain as described above can be produced in a multiple injection mold in an efficient and economic manner; and to produce such belt or chains with link elements having any desired shape not ~ust spheres.
1'~533t)9 SUMM~RY OF 'rllE INVENTION
~ccording to the invention the method is characterizedin that there is provided at least one common longitudinal injection molding land extending in parallel to the string or cable for the simultaneous injection molding of a plurality of links onto said string or cable.
The method further comprises providing connecting lands or passages extending laterally away from the common longitudinal passage toward the individual links, whereby the connecting paths or lands are made so weak and/or the cross-section thereo~ at least at one location, is O made so small that a force transmission,after the injection molding has been completed,is prevented and thus a displacement of the links along the string or cable due to heat shrinkage of the common injec-tion molding land or path is avoided.
Due to the provision of the thin wall or weak connection between the injection molded links, especially balls, and the respective connect-ing lands, the relatively massive common injection molding land can-not exert any displacement force on the links or balls in the longi-tudinal direction of the string or cable. This holds true even though the relatively massive common injection molding land is subject to O material shrinka~3e whe~n the moltent m~terial soli.difies.
The material shrinkage is unavoidal~le in connection with synthetic materials. Such shrinkage is relatively large comparecl to the shrink-age of metals, in the longitudinal direction of the common injection molding land. Yet, as a result of the present teaching the shrinkage of the common injection molding land can only cause a slight bending of the relatively thin lands an~orofthe relatively weakrestriction justin frontofthe link or ball. When the links or balls just after the " ., l~S33~3~
injection molding operation have not yet completely cooled down on the inside due to their mass, these links or balls do not yet rigidly enclose, nor do they solidly adhere to the string or cable. However, the weak connecting location pre-vents that a change in the position of the links or balls in the longitudinal direction of the string or cable can take place.
In summary, therefore, the present invention may be considered as providing a method for simultaneously injection molding two link chains, each link chain having an elongated flexible member and a series of synthetic material link elements having a given cross-sectional dimension and being molded at equal spacings from one another to their respective elongated flexible member, comprising the following steps: a) using an injection mold having two rows of mold cavities, each row including a series of equally spaced cavities for simul-taneously forming the series of link elements on each link chain as a row along each link chain, grooves for the elong-ated flexible member interconnecting the cavities to form the two rows of cavities, and molten material supply channels including a main channel located between the two rows of cavities and individual branching channels leading individ-ually from the main channel to each cavity on both rows, b) providing each individual branching channel with a throat of reduced cross-sectional dimension corresponding to less than about 10% of the given cross-sectional dimension of the link elements, c) locating the reduced throat directly at the res-rn/rm lZS3309 -5a-pective link forming cavity, d) inserting one elongated flexible member into each row of cavities and grooves and closing the mold, e) introducing molten material into the cavities through the main channel and the individual channels, and f) restricting a cross-sectional dimension of a land, formed in the individual channel by the throat of reduced cross-sectional dimension, to such an extent that force components resulting Erom material shrinking during the cooling of the synthetic material in the main channel, are substantially prevented from displacing the link elements along the respective elongated flexible member, whereby the equal spacings between neighboring link elements are assured even if the chain is removed from the mold before solidifica-tion of the link elements.
The above method may be carried out by way of an injection mold for simultaneously injection molding two link chains, each link chain having an elongated flexible member and a series of synthetic material link elements molded at equal spacings from one another to their respective elongated flexible member to simultaneously form one row of link elements along each respective elongated flexible member, com-prising a lower mold plate, an upper mold plate, two rows of equally spaced cavities in each row in the mold plates for simultaneously forming the link elements as two rows of a series of link elements, the cavities having cross-sectional dimensions corresponding to respective dimensions of the link elements, grooves for insertion of the elongated flexible rn/rm lZ~;~3(~9 -5b-member, the grooves interconnecting the cavities in each row, molten material supply channel means in the mold plates, the channel means including a central main channel between the central main channel, the central main channel and the two rows of grooves including the cavities extending substantially in parallel to each other and in the longitudinal direction of the two link chains, and individual channels leading away from the central main channel in opposite directions to each of the cavities in each row, so that the individual channels and the central main channel form two ladder type individual channel configurations for producing the two link chains, each indi-vidual channel having a throat with a reduced cross-sectional flow area corresponding to less than 10% of the cross-sectional dimension of the cavities for forming the link elements of the molten material, the reduced cross-sectional flow area of each throat preventing shrinking forces from distorting the equal spacings.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be clearly under-stood, it will now be described, by way of example, withreference to the accompanying drawings, wherein:
Fig. 1 is a top plan view of two ball chains which are connected to a common injection molding land through individual connecting lands which must later be removed;
Fig. 2 is a top plan view onto a portion of a mold plate of the injection molding tool;
Fig. 3 is a sectional view along section line III -rn~rm 5~3309 -5c-III in Fig. 2;
Fig. 4 illustrates one example embodiment of molded links having the shape of disks with conical projections in the direction of the string or cable;
Fig. 5 is another example embodiment in which the links are formed as fork-type elements; and r n/ r~?" ~
33~)~
Fig. 6 shows still another example embodiment in which the links comprise groups of balls spaced by links in the form of eyelets.
DETAILED DESCRIPTION OF PREFERRED EX~MPLE EMBODIMENTS ~ND OF TEIE
BEST MODE OF TI~E INVENTION
Fig. 1 shows an injection molded part 1 made of synthetic material including two ball chains manufactured simultaneously. Two par-tial lenqths of such chains are shown. As a result of the injection molding the chains still are interconnected by lands 5 leading from O each ball 2 to a cor~mon injection molding land 4. Due to the injection molding the balls 2 are permanently bonded to the strings or cables 3. After the injection molding and after the cooling the lands 5 are separated from the balls 2 at the point 7 which designates the narrowest cross-section of the lands S. Thus, the lands 5 and the common injection molding land 4 are separated from both ball chains and are removed as waste while the two chains remain as the result of the injection molding. Due to the reduced cross-sections 7 any forces in the axial direction resulting from the shrinkage especially of the land 4, cannot be transmitted to the balls 2 so O that these halls remain uniformly spaced alonc3 th(?ir resp~ctive striny or cable 3. The balls or similar eLelllc?nts are rigidly secured to the respective string or cable 3 as a result of the solidification and curing of the synthetic material.
Fig. 1 sl~ows two strings 3 each carrying sixteen spheres 2. Ilowever, more than two strings3 ~y be stepped through the in}ection mold and the number of balls produced along each string section in each injec-tion molding step may also be substantially larger, for example, lZS331~9 1 forty to fifty balls have ~een found to be easily made simultaneously along each section of string or cable 3. The feed advance of the strings or cable 3 in steps through the injection molding tool is not part of the invention. After the initial ins~rtion of the required number of strings or cables into the injection mold, the feed advance may continue until the entire length of the cable or string has been used up. Thus, the total length of a link chain or belt according to the invention is practically determined only by the total length of the available string or cable 3.
0 ~s shown in Figs. 2 and 3 the multiple injection mold comprises two mold plates 18 and 20 having recesses therein corresponding to the mold cavities and to the passageways for supplying the molten material into the mold cavities. ~ hollow space or channel 12 serves for the introduction of the molten material into the mold. The channel 12 extends in parallel to a groove 13 which is intended to receive the string or cable 3. The above mentioned land 4 is formed in the channel 12. Recesses 16, for example, of cylindrical shape, are formed at spaced intervals in the mold plate 18 along the channel 12 for forming studs 6 also shown in Fig. 1. These studs 6 also help 0 reducing the effects of any shrinkage when the injected material is coolin~ because the studs 6 tie the lands 4 to the molcl plate 1~.
Semispherical recesses 8 are provicled in each mold plate 18 and 20.
Side channels 10 in the mold plate 18 connect the molten material main suppl~ channel 12 to the recesses or cavities 8 in the mold plates 18 and 20. These side channels 10 result in the formation of the con-necting lands 5 havinc3 relatively thin walls. The side channels 10 are so shaped that the cross-sections of these lands 5 decrease,as ......
~Z533U9 1 the spacing from the injection molding land 5 increases. Direc-tly where the side channels 10 enter into the ball shaped recesses or cavities 8,the side channels 10 are provided with a substantially reduced cross-section 14, whereby the resulting land 5 has its smallest cross-section at this point for limiting or eliminating an effect of any axial forces resulting from the solidification and cooling of the synthetic material, on the balls or links 2. The axial direction in this connection is the longitudinal direction of the strings or cables 3. These reduced cross-sectional areas7Of the 0 connecting lands 5 which are caused, according to the invention, by the restrictions 14, thus make sure that a longitudinal displacement of the balls 2 is prevented as lo~g as is necessary, namely until the balls 2 are completely solidified. Thus, the balls will not shift, even after they have been removed from the mold, although they have not yet completely solidified on the inside.
In a practical example embodiment the cross-sectional dimension of the restriction 14 is less than 10~ of the diameter of the balls 2.
The cross-sectional area of these restrictions 14 is less than 1 mm2.
Where the ball diameter is q.5 mm, the cross-section of the restric-o tion 14 is about 1/6 of 1 mm2. The cross-section of the injection molding lan~ 4 is substantially lar~er thall the cross-sec~ioll of the individual connectinc3 lands 5 where these l~nds 5 merc3e into the land 4, for example, the cross-sectional area of the land 4 may be three times the cross-sectional area of the land 5 at the location where the lands 5 join the land 4.
The second or upper mold plate 20 which closes the mold has recesses compatible or similar to the recesses in the mold plate 18, except i2533V9 1 that the side channels 10 and the injection molding channel 12 have a flat, narrow side 21. ~ddition~lly, the mold plate 20 has at least one inlet channel 21' for introducin~ the molten material into the mold channel 12. The molten material is, for example, polyamide, polyester or the like, synthetic material.
The string or cable 3 passes centrally through each ball. The string is preferably made also of synthetic fibers such as polyamide, poly-ester, polypropylene fibers, or the like. For special purposes, the string or cable 3 may be made of a steel wire or wires encased by the ~0 mentioned synthetic materials or a steel cable may be used which is not encased.
As shown in Figs. 4, 5, and 6, the elements 2 need not be balls.
These elements may have almost any desired shape as illustrated in Figs. 4, 5, and 6. In Fig. 4 the elements have a central disk 24 flan~ed by two truncated conical sections In Fig. 5 the elements have a fork-type configuration 22. In Fiy. 6 groups of balls 2 alternate with eyelet elements 23.
As mentioned above, the production efficiency and economy i improved by holding simu]taneously more tllall two string~, for example, four or ) six string sections may be molded witll linlcs in a respectively formed mold. Further, the length shown in Fig. 1 is merely an example and the above mentioned number of links for each mold section is quite practical.
_ g _ l~S33~g 1 ~lthough the invention has been described with reference to specific example embodiments, it will be appreciated, that it is intended to cover all modifications and equivalents within the scope of the appended claims.
- 1 0 - i ....~ ~b
Claims (8)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for simultaneously injection molding two link chains, each link chain having an elongated flexible member and a series of synthetic material link elements having a given cross-sectional dimension and being molded at equal spacings from one another to their respective elongated flexible member, comprising the following steps:
a) using an injection mold having two rows of mold cavities, each row including a series of equally spaced cavities for simultaneously forming said series of link elements on each link chain as a row along each link chain, grooves for said elongated flexible member interconnecting said cavities to form said two rows of cavities, and molten material supply channels including a main channel located between said two rows of cavities and individual branching channels leading individually from said main channel to each cavity on both rows, b) providing each individual branching channel with a throat of reduced cross-sectional dimension corresponding to less than about 10% of said given cross-sectional dimension of said link elements, c) locating said reduced throat directly at the respective link forming cavity, d) inserting one elongated flexible member into each row of cavities and grooves and closing the mold, e) introducing molten material into said cavities through said main channel and said individual channels, and f) restricting a cross-sectional dimension of a land, formed in said individual channel by said throat of reduced cross-sectional dimension, to such an extent that force components resulting from material shrinking during the cooling of the synthetic material in said main channel, are substantially prevented from displacing said link elements along the respective elongated flexible member, whereby said equal spacings between neighboring link elements are assured even if the chain is removed from the mold before solidification of said link elements.
a) using an injection mold having two rows of mold cavities, each row including a series of equally spaced cavities for simultaneously forming said series of link elements on each link chain as a row along each link chain, grooves for said elongated flexible member interconnecting said cavities to form said two rows of cavities, and molten material supply channels including a main channel located between said two rows of cavities and individual branching channels leading individually from said main channel to each cavity on both rows, b) providing each individual branching channel with a throat of reduced cross-sectional dimension corresponding to less than about 10% of said given cross-sectional dimension of said link elements, c) locating said reduced throat directly at the respective link forming cavity, d) inserting one elongated flexible member into each row of cavities and grooves and closing the mold, e) introducing molten material into said cavities through said main channel and said individual channels, and f) restricting a cross-sectional dimension of a land, formed in said individual channel by said throat of reduced cross-sectional dimension, to such an extent that force components resulting from material shrinking during the cooling of the synthetic material in said main channel, are substantially prevented from displacing said link elements along the respective elongated flexible member, whereby said equal spacings between neighboring link elements are assured even if the chain is removed from the mold before solidification of said link elements.
2. The method of claim 1, further comprising dimensioning said throats in said branching channels so that said reduced cross-sectional dimension is within the range of about 0.1 to 1mm2, using for said elongated flexible members strings made of at least partly of synthetic material, shaping said cavities as hemispheres to form said link elements as spheres having a diameter of about 4.5 mm, removing both chains from said mold after sufficient solidification of said initial molten material, and severing said spheres from waste at said throat.
3. An injection mold for simultaneously injection molding two link chains, each link chain having an elongated flexible member and a series of synthetic material link elements molded at equal spacings from one another to their respective elongated flexible member to simultaneously form one row of link elements along each respective elongated flexible member, comprising a lower mold plate, an upper mold plate, two rows of equally spaced cavities in each row in said mold plates for simultaneously forming said link elements as two rows of a series of link elements, said cavities having cross-sectional dimensions corres-ponding to respective dimensions of said link elements, grooves for insertion of said elongated flexible member, said grooves interconnecting said cavities in each row, molten material supply channel means in said mold plates, said channel means including a central main channel between said central main channel, said central main channel and said two rows of grooves including said cavities extending substantially in parallel to each other and in the longitudinal direction of said two link chains, and individual channels leading away from said central main channel in opposite directions to each of said cavities in each row, so that said individual channels and said central main channel form two ladder type individual channel configurations for producing said two link chains, each individual channel having a throat with a reduced cross-sectional flow area corresponding to less than 10% of said cross-sectional dimension of said cavities for forming said link elements of said molten material, said reduced cross-sectional flow area of each throat preventing shrinking forces from distorting said equal spacings.
4. The injection mold of claim 3, wherein said throat having a reduced cross-sectional flow area is located directly at the entrance of each of said individual channels to said cavities.
5. The injection mold of claim 3, wherein said throat cross-sectinal flow area is maximally 1 mm2.
6. The injection mold of claim 3, wherein said throat cross-sectional flow area is within the range of about 0.1 to 0.2 mm2.
7. The injection mold of claim 3, wherein said two rows have hemispherical mold cavities in each of said mold plates for simultaneously forming two series of ball element grooves for producing two ball chains simultaneously.
8. The injection mold of claim 3, wherein said central main channel comprises a plurality of cylindrical recesses spaced relative to each other along said central main channel.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH5185/85-4 | 1985-12-05 | ||
| CH518585 | 1985-12-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1253309A true CA1253309A (en) | 1989-05-02 |
Family
ID=4289348
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000524710A Expired CA1253309A (en) | 1985-12-05 | 1986-12-05 | Method and injection molding tool for producing link belts |
Country Status (8)
| Country | Link |
|---|---|
| US (1) | US4806405A (en) |
| EP (1) | EP0225846B1 (en) |
| JP (1) | JPH0651323B2 (en) |
| AT (1) | ATE72168T1 (en) |
| CA (1) | CA1253309A (en) |
| DE (1) | DE3683738D1 (en) |
| ES (1) | ES2029798T3 (en) |
| GR (1) | GR3004424T3 (en) |
Families Citing this family (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5005280A (en) * | 1987-01-15 | 1991-04-09 | Emerson Electric Co. | Method of manfacturing a foldable ladder structure |
| US5279876A (en) * | 1990-09-29 | 1994-01-18 | Volkswagen Ag | Limited compressibility support structure |
| US5480604A (en) * | 1991-01-23 | 1996-01-02 | Asten, Inc. | Molded seam for papermakers fabric and method |
| US5560884A (en) * | 1992-11-23 | 1996-10-01 | Esterline Technologies Corporation | Method of producing a molded woven cable |
| US5588209A (en) * | 1994-05-04 | 1996-12-31 | The Tempered Spring Company Limited | Method and apparatus to manufacture stabilizer bars |
| DE19606490A1 (en) * | 1996-02-22 | 1997-08-28 | Merck Patent Gmbh | Device for the manual production of pearl cord-shaped pharmaceutical implants |
| FR2781714B1 (en) * | 1998-07-29 | 2000-09-22 | Europ De Fabrications Ind Sefi | METHOD FOR MANUFACTURING A REMOTE CONTROL DEVICE INCLUDING A MOBILE CONTROL CABLE IN A SHEATH |
| US6514063B2 (en) * | 1999-01-07 | 2003-02-04 | International Business Machines Corporation | Tooling for forming a stent |
| FI112455B (en) * | 1999-02-24 | 2003-12-15 | It Innovations Finland Oy | Process and plant for processing workpieces in a manufacturing process |
| CA2364508A1 (en) * | 1999-03-09 | 2000-09-14 | Thomas Skorch | Method and apparatus for improving gate removal from a mold |
| US7807247B1 (en) | 1999-10-29 | 2010-10-05 | Bromley Robert L | Flexlock with headed pintle and conical buttressing |
| JP4807718B2 (en) | 1999-10-29 | 2011-11-02 | サムソナイト アイピー ホールディングス エス．エー．アール．エル． | Method for producing a non-fiber structure |
| FI109105B (en) * | 1999-11-26 | 2002-05-31 | Jari Ruuttu | Method and apparatus for processing injection-molded workpieces during the manufacturing process |
| DE102006024529A1 (en) * | 2006-05-23 | 2007-11-29 | Werner Sand | Production of chain of clips for fixing car seat coverings in position comprises injection molding them at fixed distances on to flexible cord |
| KR100827843B1 (en) | 2007-01-10 | 2008-05-07 | 이동원 | Cast for injection molding and injection molding goods |
| US7686609B2 (en) | 2007-03-23 | 2010-03-30 | Kent Byron | Apparatus for molding proppants and method |
| US8117725B2 (en) * | 2008-10-31 | 2012-02-21 | The Gillette Company | Method of manufacturing a plurality of molded components |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE261113C (en) * | ||||
| CH228767A (en) * | 1941-03-07 | 1943-09-15 | Szanto Sandor | Process for the production of cords with shaped bodies separated from one another by spaces and a pressing tool for carrying out the process. |
| US2386697A (en) * | 1942-08-13 | 1945-10-09 | Harold J Lynch | Injection molding of plastic materials |
| US2920354A (en) * | 1957-08-14 | 1960-01-12 | Viso S A | Process for making spaced reinforcements on shaped elongate structures from fiber-forming materials |
| CH621177A5 (en) * | 1973-09-01 | 1981-01-15 | Walter Huegin | Device for fastening a spacer cord on the vertical lamellae of a window hanging |
| JPS52132069A (en) * | 1976-04-27 | 1977-11-05 | Ashimori Ind Co Ltd | Method and device for producing long article secured with synthetic resin molded materials at predetermined interval |
| US4176149A (en) * | 1976-02-20 | 1979-11-27 | Textron Inc. | Apparatus and method of manufacture of trains of slide fastening elements |
| DE2633583A1 (en) * | 1976-07-27 | 1978-02-02 | Irving Levine | Beads injection moulding device - has two symmetrical moulds provided with bead cavities co-linear with twine or wire supply ducts and sprue breaking pins |
| JPS5855898A (en) * | 1981-09-30 | 1983-04-02 | 株式会社東芝 | Closing device of reactor main steam nozzle |
| JPS602458A (en) * | 1983-06-15 | 1985-01-08 | 株式会社トスカ | Sealing tool and manufacture thereof |
| JPS6027608U (en) * | 1983-07-29 | 1985-02-25 | 荒井 力雄 | Submersion rings such as rice straw |
-
1986
- 1986-11-20 ES ES198686810531T patent/ES2029798T3/en not_active Expired - Lifetime
- 1986-11-20 EP EP86810531A patent/EP0225846B1/en not_active Expired - Lifetime
- 1986-11-20 DE DE8686810531T patent/DE3683738D1/en not_active Expired - Fee Related
- 1986-11-20 AT AT86810531T patent/ATE72168T1/en not_active IP Right Cessation
- 1986-12-02 US US06/936,821 patent/US4806405A/en not_active Expired - Lifetime
- 1986-12-04 JP JP61287860A patent/JPH0651323B2/en not_active Expired - Fee Related
- 1986-12-05 CA CA000524710A patent/CA1253309A/en not_active Expired
-
1992
- 1992-04-21 GR GR920400757T patent/GR3004424T3/el unknown
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0651323B2 (en) | 1994-07-06 |
| US4806405A (en) | 1989-02-21 |
| JPS62132625A (en) | 1987-06-15 |
| EP0225846B1 (en) | 1992-01-29 |
| DE3683738D1 (en) | 1992-03-12 |
| EP0225846A2 (en) | 1987-06-16 |
| EP0225846A3 (en) | 1989-02-08 |
| GR3004424T3 (en) | 1993-03-31 |
| ES2029798T3 (en) | 1992-10-01 |
| ATE72168T1 (en) | 1992-02-15 |
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