CA2063007A1

CA2063007A1 - Heat-shrinkable products and method for manufacturing same

Info

Publication number: CA2063007A1
Application number: CA002063007A
Authority: CA
Inventors: Christian Kipfelsberger; Uwe Brudermann; Axel Figge; Bernd Selbach; Werner Figge
Original assignee: Individual
Current assignee: RXS Schrumpftechnik Garnituren GmbH
Priority date: 1991-03-15
Filing date: 1992-03-13
Publication date: 1992-09-16
Also published as: EP0503463B1; JPH0569488A; EP0503463A1; AU650326B2; AU1291392A; DE59201427D1; ATE118730T1; GR3015167T3; ES2068622T3

Abstract

ABSTRACT OF THE DISCLOSURE
A method for manufacturing heat-shrinkable products includes providing a base product of heat-shrinkable material, and applying a stitched seam to the base product to modify the shape of the base product. Stitched seams can be used to change the shape of the base product itself, or to attach additional shaped parts to the base product.

Description

2~63~

TITLE

"HEAT-SHRINKABLE PRODUCTS AND METHOD FOR MANUFACTURING"

TECHNICAL FIELD
The present invention relates to heat-shrinkable products, and to a method for manufacturing heat-shrinkable products by applying a stitched seam in a base product of shrinkable plastic.

BACKGROUND OF THE INVENTION
German OS 31 01 256 discloses cylindrical and longitudinally slotted heat-shrinkable products. The products include closure elements (i.e., hook-and-loop fastening strips) that are sewn along the longitudinal edges of a generally flat, heat-shrinkable base product or "band". The methods used in manufacturing the disclosed product o~fer several advantages over previously known methods, since a simple band can be extruded, onto which a great variety of additional closure elements can be applied as needed. However, the disclosed method fails to provide any way to modify the actual shape of the extruded, plate-shaped article.
In addition, such heat-shrinkable products are usually divided with a longitudinal slot, so that they can be installed over uncut, elongated articles, such as cables.
Corresponding longitudinal closures must be arranged along the iongitudinal slo~, such that the closures can be brought into engagement with one another a~ter plarement of the product over the article.
Furthermore, it is often necessary for the heat-shrinkable product to have heat-shrinkable, individually-shaped parts, such as branching rnernbers or caps. For example, in high-voltage technology, heat-shrinkable shaped parts having a plurality of outlets are often required. These shaped parts currently require extremely complicated and involved manufacturing methods using newer injection molding and widening tools : 1 20~3~7 and additional auxiliary devices. With known methods, manufacturing such parts is extremely complicated and expensive.
Other closure methods are known in addition to the hook-and-loop fastener discussed hereinabove. For example, in communications technology, heat-shrinkable, hose-shaped envelopes are provided to enclose cable splices and the like. These envelopes have longitudinal slots that have usually been closed with the assistance of metallic rails, with edge re~ions along the longitudinal edges of the polymeric envelope including appropriate profile elements. In order to prevent the profile elements from sliding out of the metal rails when heat is applied, the elements must be manufactured with extremely narrow tolerances. This places extremely highly demands on the extrusion technology, since the profile elements have significantly different extrusion resistances than the rest of the envelope.

SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a simple and inexpensive method for manufacturing heat-shrinkable products It is another object of the present invention to provide a heat-shrinkable product that can be easily modified in order to maximize its potential uses.
These and other objects are achieved by providing a rnethod in which at least one stitched seam is applied to a basic product. The stitching allows the shape of the resultant heat-shrinkable article to be easily modified.
The advantages of the present invention lie in that articles having a complicated shape can be manufactured by ~irst fabricating a simply shaped base product, for example by extrusion or by injection molding, and then using simple additional steps to further process the base product into relatively complicated shapes.
The additional steps include applying stitched seams to the base products. The stitched seams can be applied to the basic product in the form of tie-offs, of separating stitched seams, or of any suitable arbitrary shapes, such that the base produc~is 2~63~7 configured to meet any desired functions.
In one exemplary embodiment, a base product is provided in the form of a simple through-sleeve of heat-shrinkable material. A parting stitched seam is applied to gather wall parts of the basic product together, for example at opposite points on an output end of the sleeve. The original opening can be divided into further openings, so that the new product, modified by the stitched seam, can be used as a branching sleeve or as a dividing cap. Up to now, additional components parts, usually clamps, have been required as parting elements for this purpose.
In addition to modifying a base product's shape, stitched seams can be used to attach additional shaped parts to the base products. For example, additional parts can be stitched to longitudinal closures along parting edges of the shrinkable product.
This facilitates ease of manufacture of the heat-shrinkable prodLlcts, since the base product does not have to be fabricated with a special profile to be adapted to receive attachments. Moreover, stitched seams can be used to combine and secure together components of different materials, allowing the ~Itimate article to be optimally adapted to its intended specialized use.
The present invention uses technical sewing threads in the manufacture and fabrication of heat-shrinkable articles. In general terms, the present invention resolves longstanding problems by simplifying the time-consuming and expensive manufacture of heat-shrinkable products having a complicated design. Moreover, heat-shrinkable products having various properties and intended for various uses can be manufactured by employing stitched seams having appropriately selected technical threads.
The technical fibers or threads are selected so that~the~ can be easily manipulated in the sewing process. Ideally, these threads should be highly elastic, resistant to abrasion, mechanically strong, and, most importantly, stable whe subjected to high temperatures. Threads having these characteristics include threads of glass, combinations of glass and polytetrafluorethylene, aramid, carbon, metal, combinations of rnetal and aramid, combinations of metal and cotton, or any known 2~3~

threads that are resistant to high-temperature. With such threads and suitable sewing equipment ffor exarnple, shoemaker's sewing machines), heat-shrinkable products, even heat-shrinkable products having thick walls, can be sewn to one another or to other non-polymeric materials. The temperature stability of the sewing threads must be high enough to guarantee adequate strength at the stretching and shrinking temperatures of the shrinkable article. The elasticity of the sewing threads must be such that the tightness, and thus the durability, of the stitched seams does not deteriorate at the stretching and shrinking temperature of the product. The resistance to abrasion of the thread must be at least as high as that of the sewn product.
A further advantage of the present invention is that the base product and th0 separate attachments can be differently cross-linked, either chemically or with high-energy irradiation, dependent upon the application.
As set forth hereinabove, the manufacture of heat-shrinkable, individually shaped parts (such as branching members, caps and the like) has been relatively difficult with known methods. The present invention allows such articles to be manufactured significantly more simply by sewing injection molded or extruded ~abricated materials either before or a~ter cross-linking. Furthermore, if an expansion process is used to fabricate the base product, the present invention also allows sewing to be performed either before or after expans;on.
The present invention offers advantages in manufacturing heat-shrinkable articles to be used in communications technologies. The method of the present invention simplifies production, and allows the special attachments ~o be extruded in, for example, a special tool, while the envelope itself is separately manufactured as a flat web. The special attachments can be joined to the flat webs with appropriate ~hreads in additional stitched seams.
The present invention offers several advantages over known methods. For example, since attachments to the base product can be extruded separately, the extruded shapes are relatively simple, thus requiring correspondingly simpler extrusion 20~3~7 tooling. Furthermore, the base product and attachments can be fabricated from diFferent thermoplastic elastomeric materials. It is also possible to fabricate the heat-shrinkable alticle, or its attachmen~s (either by extrusion or by injection molding), such that a metal rail for closure is superfluous, i.e. that the article or attachment thernselves form the closure.
With proper thread selection, (e.~. non-polymeric threads), metallic closures or other closure arrangements can be sewn onto the article, so that metal rails are no longer required.
The present invention offers several advantages with respect to production engineering that are of particular significance in fabricating heat-shrinkable shaped parts having a plurality of outlets for use in high-voltage technologies. The complexity of tooling required is greatly reduced when the shaped parts, for example, are injected, cross-linked, and widened in two halves, then subsequently sewn to one another in their widened condition. By implementing the principles of the present invention, a relatively complex multi-outlet part can be fabricated from a very simple base product having a stitched seam.
Different materials having different cross-linking characteristics can also be employed. Moreover, the ability to independently cross-link and configure the base product allows the base product to be widened or altered, or attachments to be sewn onto the base product, after the base product and attachments have been cross-linked.
With appropria~e thread selection, heat-shrinkable products having relatively large or varying wall thicknesses can be sewn to one another, or to attachments fabricated from other non-polymeric materials. This is also true o~ articles or attachments ~abricated from different polymers, for example amorphous or semi-crystalline materials, and of differently cross-linked materials.
When polymer profile elements are required for closing a longitudinally slotted envelope with a metal rail, the profile elements can be separately manufactured, and -20~3~07 sewn on either before or after the stretching of the basic product.
Non-polymeric materials (for example, metals and the like) are also suitable for manufacturing separate closure elements.
Injection molded or extruded closure elements can also be manufactured of some other polymeric material that differs from the material of the basic product. The polymeric material may be cross-linked or non-cross-linked. Such injection molded or extruded shaped parts or attachments can be secured to the base product either before or after cross-linking, and either before or after widening. Similarly, the application of a shape-modifying stitched seam in the basic product csn occur either before or after cross-linking, and either before or after widening.
In addition, adhesion promoters, glues, peroxide bands, and the like can be applied in the re~ion of the stitched seams, in order to enhance the tightness and integrity of the sewn edges.
Other objects and advantages of the present invention will be apparent upon reference to the accompanying description when taken in conjunction with the following drawings.

BRIEF DESCR~PTION ~F THE DRAWINGS
FIG. 1 illustrates a perspective view of a heat-shrinkable article manufactured in accordance with the principles of the present invention.
FIG. 2 illustrates a modification of the exemplary embodiment of ~IG. 1.
FIG. 3 schematically illustrates the manufacture of a heat-shrinkable product of FIGS. 1 and 2.
FIGS. 4 through 10 illustrate a variety of sewn-on longitudinal closures in accordance with the principles of the present invention.
FIG. 11 illustrates a perspective view of a heat-shrinkable article manufactured in accordance with the principles of the present invention and havin~ a sewn-on distributor member.

2~0~7 DETAILI~D DESCRIPTI~N OF THE PREFERRED EMBODIMENT~
FIG. 1 illustrates a stitched seam ~ tha~, in accordance with the principles of the present invention, is applied to an originally purely cylindrical, heat-shrinkable base product 1. The stitched seam 2 is a "tie-off" that rnodifies the shape of the base product 1, and adapts the base product 1 to a variety of additional uses. Specifically, the stitch-modified base product 1 of FIG. 1 can now be employed as a branching article, with two smaller openings 5 Iying parallel to one another having been formed from an original, large opening 4 by sewing the stitched seam 2 with threads. The opposite walls of the base product 1 are held together without the use of any auxiliary components (e.g. clamps) whatsoever. The base product 1 is fabricated from a generally planar sheet joined together at opposite edges at a longitudinal seam or closure arrangement 6. Specifics of the closure arrangement 6 shall be set for~h in greater detail with respect to FIGS. 3 through 10.
FIG. 2 illustrates a base product similar to that illustrated in FIG. 1., with a U-shaped or wedge-shaped incision 7 between the branches of the stitched seam or "parting stitch" 2. The incision 7 permits a greater degree of branchin~ between the openings 5.
FIG. 3 schematically illustrates the method by which the articles o~ FIGS. 1 and 2 are formed. Initially, a generally planar sheet provided with a pair of closure elements in the form of beads 9 at opposite longitudinal edges. The sheet is formed into a through-sleeve by a longitudinal closure arrangement 6 including a metal rail 10 slipped over the beads g. An inside flap 19 underlies the closure 6 on the interior of the through-sleeve. In this example, the beads 9 at the longitudinal sides have be~n ~ormed integrally with the base product 1, as is conventional.
The arrows 8 indicate that opposite walls of the base product 1 are presse~l together until they touch one another in a central regior) 3, shown in dashed line. The stitched seam 2 is applied as described hereinabove, thus forming the two branch openings 5.

2 0 6 ~

As discussed in the Background of the Invention, the conventional construction of the beads 9 shown in FIG. 3 is problematic ~or several reasons, including structural weakness due to the different extrusion forces exerted during manufacture. In addition to the formation of branches shown in FIGS. 1 through three, the principles of the present invention can also be applied to forming closure elements.
The longitudinal closures shown in FIGS. 4 through 10 are formed separately from the base product 1 and, in conformity with a further aspect of the present invention, are applied to the base product with stitched seams. Consequently, the base product 1 and the separate closure elements are much easier to manufacture, since each of the components can be manufactured to have different optimum wall thicknesses. Moreover, the components can be manufactured out of different optimal materials, as set forth in the Summary of the Invention.
FIG. 4 illustrates a pa~ially broken-away view of a heat-shrinkable article manufactured in accordance with the principles of the present invention. The base product 1 of the article is provided as a planar sheet without any beads or other projections. In all of the illustrated embodiments, the shape-modifying stitched seams can be applied onto the base product 1. Additionally, in the exemplary embodiments of FIGS. 4 through 10, the closure elements 9 in the closure arrangement 6 are formed separately from the base product 1, and are attached to the base product 1 with suitably configured stitched seams 11. The closure elements 9 are provided \Nith seating surfaces to abut the base product 1. In the FIG. 4 embodiment, the outermost edge of the base product 1 extends beyond one of the closure elements 9, forming an inside flap 19. After the article to be protected has been enveloped, a closure rail is pulled over the closure elements 9.
FIG~ 5 illustrates an exemplary embodiment wherein the inside flap 19 is formed by one of the closure elements 9, which extends beyond the outermost edge of the basic product 1. Otherwise, this embodiment is identical to that illustrated in Fl(~i. 4.
FIG. 6 illustrates an exemplary embodiment in which the closure elements 9 are B

2~3~7 sewn to cooperating plates 12. The closure elements 9 are disposed ~n one side of the base product 1, and the cooperating plates 1~ are disposed on an opposite side of the base product 1. This arrangement provides increased strength in the closure region of the finished article.
FiG. 7 illustrates an exemplary embodiment in which each of the closure elements 9 includes a longitudinal channel 13. The channels 13 receive the respective edges of the base product 1 along their full length, after which stitched seams 11 are applied to secure the closure elements 9 to the base product 1. This arran~ement provides a double-sided reinforcement along the closure region of the finished article.
FIG. 8 illustrates an exemplary embodiment having a longitudinal closure 6 in which the closure rail is replaced by an interengaging hook arrangement. One side of the closure system 6 includes a row of closure elements that are fashioned as hooks or bent-over clips 15. The clips 15 are disposed on a band 14 that is sewn onto the base product 1. A second, opposite side of the longitudinal closure 6 includes a plurality of openings 18 disposed on a band 16 that is sewn onto the base product 1.
The openings are of sufficient size to receive the clips 15.
In order to close the base product 1, the bent-over clips 15 are inser~ed through the corresponding openings 18 in hooking fashion. As described with reference ~o FIG. 4, an inside flap 19 covers the closure region.
FIG. 9 illustrates another alternative to the previously-described closure rail arrangements. In this exemplary embodiment, the longitudinal closure 6 includes ~
band 20 that is sewn onto the base product 1, and upon which is dispos~d a row of openings 21. A second sewn-on band 22 includes a pluraiity of arcuate closure elements 23. As with the FIG. 8 embodiment, the openings 21 are of sufficient size to receive the closure elem0nts 23.
In order to close the base product 1, the closure elements 23 are inserte~
through the corresponding openings 21 in hooking fashion. As described with reference to FIG. 4, an inside flap 19 covers the closure region.

20~3~7 FIG. 10 illustrates yet another alternative to the previously-described closure rail ~rrangements. The longitudinal closure 6 includes a first sewn-on band 24 having a plurality of T-shaped hook elements 2~ with respective head portions and shank portions, and a second sewn-on band 26 having a plurality of retaining elements 27.
The retaining elements 27 are spaced apart from one another so that the individual spaces between the retaining elements 27 are narrower than the head portions of the hook elements 25, but wider than the shank portions of the hook elements 2~.
In order to olose the base product 1, the hook elements 25 are engaged with the corresponding retainin~ elements 27 such that the heads of the hook elements 25 are retained behind the retaining elements 27, and the shank portions extend through the spaces between the retaining elements 27.
Finally, FIG. 11 illustrates an exemplary embodiment in which an attachment or shaped part 28 is sewn to the base product 1 with a stitched seam 11. In the illustrated example, the shaped part 28 is a branched distributor element having four branching outlets 29. The manufacturing methods required in fabricating the distributor section integrally with the through-sleeve are extremely complicated, due to ~he differing configurations, wall thicknesses, and required physical properties of these sections. By allowing the base product to be manufactured separately frorn the shaped part, the present invention facilitates the use of more economical manufacturing methods, since it permits the use of manufacturing techniques and materials specifically suited to each of the parts. Although the ~IG. 11 embodiment shows a distributor attachment, the present invention conternplates that virtually any part or attachment can be applied to a ba~e product with the use of sti~ched seams, thereby providing an extremely broad range of application.
As already mentioned, appropriate sealing agents ~such as 01ue or the like) can be introduced into all stitched seam regions. It is also contemplated that the stitched seam could itself be cross-linked, for example by inserting a peroxide band.

2~6~7 Although the principles of our invention have been set forth hereinabove with refererlce to specific embodiments, it is to be understood that these are by way of illustration, and that variations and modifications rnay be eFfected without departing from the scope and spirit of the invention as defined by the appended clairns.

Claims

1. A method for manufacturing heat-shrinkable products, said method comprising the following steps:
providing a base product of heat-shrinkable material having a predetermined shape; and applying a stitched seam to said base product to modify said shape of said base product.

2. A method according to claim 1, wherein said step of applying a stitched seam comprises applying a tie-off.

3. A method according to claim 1, wherein said step of applying a stitched seam comprises applying a parting seam.

4. A method according to claim 1, wherein said step of applying a stitched seam comprises applying said stitched seam with a sewing machine.

5. A method according to claim 1, wherein said step of applying a stitched seam comprises applying said seam using a high-temperature resistant sewing thread having high elasticity and resistance to abrasion.

6. A method according to claim 1, further comprising the following steps:
cross-linking said base product, using a method selected from a group consisting of chemical cross-linking and high-energy irradiation cross-linking; and stretching said base product after said step of cross-linking.

7. A method according to claim 1, wherein said step of applying a stitched seam comprises sewing an additional shaped part onto said base product.

8. A method according to claim 1, further comprising the step of applying adhesion promoters, preferably peroxide bands, in the region of said stitched seam.

9. A method according to claim 1, wherein said step of applying a stitched seam comprises applying said stitched seam along an opening of said base product such that said opening is subdivided into a plurality of openings.

10. A method according to claim 9, wherein said step of applying a stitched seam comprises applying said stitched seam as a U-shaped or wedge-shaped tie-off.

11. A method according to claim 1, wherein said step of providing a base product comprises providing said base product as an injection molded part.

12. A method according to claim 1, wherein said step of providing a base product comprises providing said base product as an extruded part.

13. A heat-shrinkable product comprising:
a base product; and at least one stitched seam applied to, and modifying the shape of, said base product.

14. A heat-shrinkable product according to claim 13, wherein said base product is an injection molded part.

15. A heat-shrinkable product according to claim 13, wherein said base product is an extruded part.

16. A heat-shrinkable product according to claim 13, wherein said at least one stitched seam comprises technical sewing thread composed of glass.

17. A heat-shrinkable product according to claim 13, wherein said at least one stitched seam comprises technical sewing thread composed of combinations of glass and polytetrafluorethylene.

18. A heat-shrinkable product according to claim 13, wherein said at least one stitched seam comprises technical sewing thread composed of aramid.

19. A heat-shrinkable product according to claim 13, wherein said at least one stitched seam comprises technical sewing thread composed of carbon.

20. A heat-shrinkable product according to claim 13, wherein said at least one stitched seam comprises technical sewing thread composed of metal.

21. A heat-shrinkable product according to claim 13, wherein said at least one stitched seam comprises technical sewing thread composed of combinations of metal and aramid.

22. A heat-shrinkable product according to claim 13, wherein said at least one stitched seam comprises technical sewing thread composed of combinations of metal and cotton.

23. A heat-shrinkable product according to claim 13, wherein said at least one stitched seam comprises technical sewing thread is high-temperature resistant and exhibits mechanical stability at at least a stretching or shrinking temperature of said base product.

24. A heat-shrinkable product according to claim 13, wherein said at least one stitched seam comprises technical sewing thread having sufficient elasticity to allow the base product to be subjected to stretching or shrinking processes without substantially affecting the tightness or durability of said at least one stitched seam.

25. A heat-shrinkable product according to claim 13, wherein said at least one stitched seam comprises technical sewing thread having a resistance to abrasion least as high as a resistance to abrasion of said base product.

26. A heat-shrinkable product according to claim 13, wherein said base product has different wall thicknesses adjacent to said at least one stitched seam

27. A heat-shrinkable product according to claim 13, further comprising at least one shaped part sewn to said base product.

28. A heat-shrinkable product comprising:
a generally cylindrical, heat-shrinkable base product including a longitudinal slot;
a longitudinal closure arrangement closing said slot; and a stitched seam applied to said base product such that at least one end face of said base product is subdivided into at least two openings.

29. A heat-shrinkable product according to claim 28, wherein said closure arrangement comprises first and second closure elements attached to said base product with respective stitched seams.

30. A heat-shrinkable product according to claim 29, wherein said first closure element comprises hook elements, and said second closure element comprises catch elements adapted to selectively receive and retain said hook elements.

31. A heat-shrinkable product according to claim 28, wherein said closure elements comprise beads adapted to receive a closure rail.

32. A heat-shrinkable product according to claim 29, wherein said closure elements are composed of metal.

33. A heat-shrinkable product according to claim 29, wherein said closure elements are composed of polymeric material.

34. A heat-shrinkable product according claim 28, further comprising a layer of material applied to said base product at an area adjacent said stitched seam, said layer being composed of a material chosen from a group consisting of sealants, adhesion promoters, and adhesives.

35. A heat-shrinkable product according to claim 28, further comprising peroxide bands applied to said base product at an area adjacent said stitched seam.