AU730032B2

AU730032B2 - Pressing cushion

Info

Publication number: AU730032B2
Application number: AU20646/00A
Authority: AU
Inventors: Walter Halterbeck; Ralf Kaldenhoff
Original assignee: Thomas Josef Heimbach and Co GmbH
Current assignee: Heimbach GmbH and Co KG
Priority date: 1999-03-03
Filing date: 2000-03-03
Publication date: 2001-02-22
Anticipated expiration: 2020-03-03
Also published as: AU2064600A; CZ295281B6; ATE203953T1; PL189937B1; DE59900190D1; ES2162499T3; EP1040909B1; CZ2000668A3; HUP0000938A3; CN1265972A; DK1040909T3; PL338720A1; PT1040909E; HUP0000938A2; EP1040909A1; HU0000938D0

Abstract

A pressing cushion (1) comprises two outer layers (3, 4) and cushioning layer (8), which is elastic in the thickness directi arranged between the two outer layers. The outer layers are constituted by two plies of a spacer textile (2) with spacer threads connecting the plies. The spacer threads are configured as thermally conductive threads.

Description

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AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION NAME OF APPLICANT(S): Thomas Josef Heimbach Gesellschaft mit beschrankter Hlaftung &Co.

ADDRESS FOR SERVICE: DAVIFS COLUISON CAVE Patent Attorneys 1 Little Collins Street, Melbourne, 3000.

INVENTION TITLE: Pressing cushion The following statement is a full description of this invention, including the best method of performing it known to me/us:- The invention concerns a pressing cushion for use in laminating presses, having two outer layers and a cushioning layer that is arranged therebetween and is elastic in the thickness direction.

The manufacture of layered materials, for example decoratively coated particle boards, is performed in laminating presses that can be configured as low- or high-pressure multiplaten presses or as shortcycle presses. To ensure that the pressure of the press plates is transferred uniformly onto the pressed material over its entire surface, pressing cushions are inserted between the pressed material and the press plates. The pressing cushions must be capable of withstanding high pressures as well as the temperatures that occur in such presses, and they must be capable of transferring the heat proceeding from the press plates quickly and without major losses onto the pressed material. It is also desirable to be able to process pressed materials in different e e 15 formats in succession with one pressing cushion.

The pressing cushions of the kind cited initially are layered °ee° •designs. For example, DE-A-26 27 442 describes a pressing cushion in which a matted nonwoven fabric is coated on both sides with a silicone elastomer. The generic EP-A-0 235 582 discloses a pressing cushion in eeo° 20 which a silicone elastomer film is coated on both sides with a parting eoee film. US-A-3 723 3320 also shows a pressing cushion made of a silicone film that can additionally be equipped with a parting film.

S Also known are pressing cushions that are made of or contain a eee °fabric. DE-B-23 19 593, for example, discloses a pressing cushion whose basis is a metal sieve fabric that is enclosed in a matrix made of a silicone elastomer. The pressing cushion according to DE-A-23 38 749 has a glass fiber fabric in which individual or all threads are impregnated or coated with a plastic, for example a silicone elastomer, so that these threads form the cushioning. The teaching of DE-A-26 50 642 is similar. EP-A-0 493 630 proposes a pressing cushion made of a textile fabric in which the fabric is composed of aromatic polyamide threads and of metal threads. DE-U-297 18 204 discloses a pressing cushion in which one portion of the threads has a silicone elastomer and a further portion can be configured as metal wire. DE-U-94 18 984.6 describes a pressing cushion in which the threads can be made of various materials, in particular of rubber, silicone elastomer, or metal, and combinations P:AOPERAxl2 O646OO-sp.doc-OI/12AO -2thereof. Lastly, DE-U-297 21 495 and DE-U-297 21 494 depict pressing cushions made of a fabric in which the individual threads are configured in a particular fashion.

The coated pressing cushions have the disadvantage that satisfactory thermal conductivity cannot be achieved. With the pressing cushions in which a fabric is used, compromises must be made between thermal conductivity and dimensional stability, so that an optimum result in terms of those properties cannot always be obtained.

The invention advantageously provides for the configuration of a pressing cushion in such a way that it is characterized by dimensional stability and that the thermal conductivity can be adjusted within wide limits; in terms of the .cushioning as well, a wide range of possible variations is to be 15 provided for designing the pressing cushion in accordance with requirements.

According to the present invention, there is provided a pressing cushion for use in laminating presses, having two outer layers and a cushioning layer that is arranged therebetween and 20 is elastic in the thickness direction, wherein the outer layers are constituted by two plies of a spacer textile having spacer threads connecting the plies, at least some of the spacer threads being configured as thermally conductive threads.

According to the present invention, the above advantage may be achieved in the that the outer layers are constituted by the two plies of a spacer textile, for example a woven spacer fabric or knitted spacer fabric, having spacer threads connecting the plies, at least some of the spacer threads being configured as thermally conductive threads which improve the thermal conductivity of the pressing cushion in the thickness direction. A spacer textile of this kind, also called a doublewall textile, forms a composite fabric having two textile plies that are configured substantially as a complete woven fabric or S T s\ knitted fabric and into which is additionally incorporated a thread system that alternates between the two textile plies, the

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(OFV~<76 p OPE RU 0d 21-)(--0(s.c.d-08/12A2 -2Asegments extending between the textile plies forming the spacer threads. These spacer threads define the maximum spacing between the two textile plies. The spacing can, in this context, be adjusted within wide limits in accordance with the particular requirements, and a spacing that is uniform over the surface area can be guaranteed by way of the spacer threads.

Spacer textiles of this kind have previously been used in other industrial sectors, for example in the groundwater protection sector (cf. Dr. G. Schwarz, Girmes GmbH, paper no. 344 at Techtextil Symposium 1990; EP-B-0-450 154).

A pressing cushion of this kind is characterized by high dimensional stability. The flat and very uniform surfaces having a large *o *oo o o g *o o* o o•* o go *oooo number of contact points result in good contact with the heated press plates. In this way, and by way of the plurality of spacing threads, good heat transfer and rapid heat transport through the pressing cushion can be achieved; the thermal conductivity can be adapted within wide limits, in accordance with the particular requirements, by way of the number of spacer threads and their material. In this context, not all the spacer threads need to be configured as thermally conductive threads. Rather they can alternate with spacer threads of high mechanical and thermal strength, for example made of aramids, polyimides, or a combination thereof.

In an embodiment of the invention, provision is for thermally conductive threads which are at least partially metallic, for example are made of aluminum, bronze, stainless steel, copper, or brass or contain such a metal as well as other materials, to be present.

"s 15 Provision can also be made for the spacer textile to have, in addition o° to the spacer threads, further thermally conductive threads that are made of or contain a material such that the thermal conductivity is thereby improved, so that provision is thus also made for good thermal transfer at the surfaces of the pressing cushion. These further threads cole 20 as well can be at least partially metallic.

o" ~A wide variety of embodiments are suitable for configuring the elastic cushioning layer. For example, the cushioning layer can have at least one ply of cushion threads that are elastic in the thickness direction, such as are known in the pressing cushions that are made of woven fabrics. The cushion threads can be made entirely of an o elastomeric material, for example a silicone elastomer, i.e. as a silicone monofilament or a metal powder-filled silicone monofilament.

The cushion threads can, however, also each have a core thread, for example a plastic multifilament made of aramid, polyimide, etc., or a metal wire made, for example, of copper, that is surrounded by an elastomeric thread sheath, in this case once again preferably made of a silicone elastomer. The core threads can be configured as wires, monofilaments, multifilaments, spun fiber yarns, twisted yarns, strands, braids, cords, ribbons, or the like, and of combinations thereof. To improve thermal conductivity, the cushion threads can also be at least partially surrounded by a metal wire that is wound, stranded, or braided around the thread sheath. Because of its high thermal conductivity, copper is especially suitable as the metal, but aluminum, bronze, stainless steel, and brass can also be used.

In the spacer textile, the cushion threads can be arranged running next to one another in the same direction; they are then present as a layer and thus guarantee dimensional stability. The cushioning layer can, however, also have a polymer sealing compound, for example made of a silicone elastomer or a fluorosilicone elastomer; metal particles in the form of powder or short cut fibers can be added to the sealing compound.

The polymer sealing compound is first introduced in the liquid state between the plies of the spacer textile. Once the desired position has been achieved, the final elastic mechanical properties are brought about by crosslinking or by curing. Metal powder or short cut metal S 15 fibers can also be embedded in the sealing compound.

Plastic foams are also suitable. It is not excluded in this context to embody the cushioning layer in multiple plies and to configure each ply differently, i.e. to provide combinations of different embodiments of plies.

20 Lastly, provision is made according to the invention for the pressing cushion to have edge thickenings in order to ensure uniform contact pressure over the entire surface area.

The invention is illustrated in more detail, with reference to exemplary embodiments, in the drawings, in which: FIG. 1 shows a portion of a pressing cushion having a woven spacer fabric, in an oblique view; FIG. 2 shows a plan view of a portion of the upper side of the woven spacer fabric shown in FIG. 1; FIG. 3 shows a side view of a cushion thread with wire overbraiding; FIG. 4 shows a cross section through the cushion thread shown in FIG.

3; FIG. 5 shows a portion of a pressing cushion with a knitted spacer fabric, in an oblique view; FIG. 6 shows a plan view of a portion of the upper side of the knitted spacer fabric; and FIGS. 7 through 9 show cross sections through pressing cushions having edge thickenings.

Pressing cushion 1 depicted in FIG. 1 has a woven spacer fabric 2 that comprises two cover plies 3, 4 and spacer threads (labeled 5 by way of example) connecting them. As is evident from FIG. 2, cover ply 3 is woven from warp threads 6 (shown in solid black) and weft threads 7 in a plain weave; warp threads 6 form spacer threads 5 and alternate between oooe s15 the two cover plies 3, 4, thus yielding the rows of spacer threads visible in FIG. 1. oo Cushion threads (labeled 8 by way of example) are laid between the rows of spacer threads 5, the spacing of cover plies 3, 4 being adapted to the thickness of cushion threads 8. Cushion threads 8 have a stranded 20 wire (labeled 9 by way of example) that are [sic] respectively surrounded by a thread sheath (labeled 10 by way of example). Cushion threads 8 provide elastomeric characteristics for pressing cushion 1 in the thickness direction.

~FIGS. 3 and 4 depict a particular cushion thread 11. It also has as its core thread a stranded wire 12 made of copper, which is surrounded by a thread sheath 13 made of a silicone elastomer. Thread sheath 13 is additionally overbraided on its outer side with copper wires (labeled 14 by way of example). This improves the thermal conductivity with respect to cushion threads 8.

FIG. 5 shows a pressing cushion 15 that differs from pressing cushion 1 in that what is provided is not a woven spacer fabric but a knitted spacer fabric 16. This knitted spacer fabric 16 also has two cover plies 17, 18 that are interconnected at a defined spacing by spacer threads 19 arranged in rows. As is evident from the detail shown in FIG. 6, cover plies 17, 18 of knitted spacer fabric 16 each form a warp-knit fabric having loop threads (labeled 20 by way of example), -6pile threads (labeled 21 by way of example), which alternate between cover plies 17, 18 and thereby form spacer threads 19, additionally being introduced.

Here as well, cushion threads (labeled 22 by way of example) are laid between the rows of spacer threads 19; they are identical to cushion threads 8 in pressing cushion i, so that the description there may be referred to. Cushion threads 22 provide elastomeric characteristics in the thickness direction of pressing cushion 1.

FIGS. 7 through 9 show outline cross sections of pressing cushions 23, 24, 25 which have edge thickenings 26, 27, 28, 29, 30, 31. Edge thickenings 26, 27, 28, 29, 30, 31 can be produced by using additional cushion threads, increasing the stitch density, introducing ribbons, or forming loops. In the exemplary embodiment shown in FIG. 9, edge thickenings 30, 31 are formed by turning over the edges.

15 Edge thickenings 26, 27, 28, 29, 30, 31 ensure uniform contact pressure over the entire surface area all the way into the edge regions.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion

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that that prior art forms part of the common general knowledge in Australia.

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Claims

1. A pressing cushion for use in laminating presses, having two outer layers and a cushioning layer that is arranged therebetween and is elastic in the thickness direction, wherein the outer layers are constituted by two plies of a spacer textile having spacer threads connecting the plies, at least some of the spacer threads being configured as thermally conductive threads.

2. The pressing cushion as defined in Claim i, wherein the spacer textile is configured as a woven spacer fabric or knitted spacer fabric. 15

3. The pressing cushion as defined in Claim 1 or 2, wherein thermally conductive threads which are at least partially metallic are present.

4. The pressing cushion as defined in any one of Claims 1 20 through 3, wherein the spacer textile has, in at least one of the two plies, further thermally conductive threads in oo addition to the spacer threads. •ego

5. The pressing cushion as defined in Claim 4, wherein the co o• 25 further thermally conductive threads are at least partially metallic.

6. The pressing cushion as defined in any one of Claims 1 through 5, wherein the cushioning layer has at least one ply of cushion threads that are elastic in the thickness direction.

7. The pressing cushion as defined in Claim 6, wherein the cushion threads each have a core thread that is surrounded by an elastomeric thread sheath. 'C~T_

8. The pressing cushion as defined in Claim 7, wherein the thread sheath is made of a silicon elastomer.

9. The pressing cushion as defined in Claim 7 or 8, wherein the cushion threads are at least partially surrounded by metal wire.

The pressing cushion as defined in any one of Claims 7 through 9, wherein the cushion threads run next to one another in the same direction.

11. The pressing cushion as defined in any one of Claims 7 through 9, wherein the cushion threads are present as a layer.

12. The pressing cushion as defined in any one of Claims 1 Sthrough 11, wherein the cushioning layer has a polymer sealing compound, for example made of a silicone elastomer or a fluorosilicone elastomer.

13. The pressing cushion as defined in any one of Claims 1 Sthrough 12, wherein the cushioning layer is made of a plastic foam. 25

14. The pressing cushion as defined in any one of Claims 1 through 13, wherein the pressing cushion has edge thickenings. A pressing cushion substantially as hereinbefore described with reference to the drawings. DATED this 1 1 t h day of December 2000 Thomas Josef Heimbach Gesellschaft mit beschrankter Haftung Co. f US7by DAVIES COLLISON CAVE SPatent Attorneys for the Applicants