GB1582078A

GB1582078A - Device for welding together juxtaposed faces of thermoshrinkable sheet material

Info

Publication number: GB1582078A
Application number: GB23468/79A
Authority: GB
Original assignee: Nippon Telegraph and Telephone Corp; Sumitomo Electric Industries Ltd
Current assignee: Nippon Telegraph and Telephone Corp; Sumitomo Electric Industries Ltd
Priority date: 1976-11-05
Filing date: 1977-11-03
Publication date: 1980-12-31

Description

(54) A DEVICE FOR WELDING TOGETHER JUXTAPOSED FACES OF THERMOSHRINKABLE SHEET MATERIAL (71) We, NIPPON TELEGRAPH AND TELEPHONE PUBLIC CORPORATION, a Japanese Company, of No 1-6, 1-chome, Uchisaiwaicho, Chiyoda-ku, Tokyo, Japan and SUMITOMO ELECTRIC INDUSTRIES, LIMITED, a Japanese Company, of No. 15, Kitahama5-chome, Higashi-ku, Osaka, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a device intended to weld together juxtaposed faces of thermoshrinkable synthetic resin sheet material which is used, for example, for covering a joint between electric wires or cables, or plastics or steel pipes.

Conventionally, in order to protect a joint, either a synthetic resin tape is wound around a joint between electric wires or cables, or a thermoshrinkable synthetic resin sleeve is shrink-fitted about the joint. The former method, however, greatly reduces the operational efficiency when the working space is limited, while the latter method not only requires the preparation of a variety of sleeves to suit different sizcs of cables, but also makes it difficult to repair an old joint.

In view of the above defects, it has been proposed to cover a joint with a synthetic resin sheet, weld the two ends thereof together by the application of heat to form a sleeve, and thereafter, if necessary, thermally shrink the sleeve. However, the ends of the sheet will not be sufficiently sealed simply by heat-welding, resulting in lack of strength of the sealed portion. Moreover, when a thermoshrinkable synthetic resin sheet is used, the welded ends and adjacent zones are deformed due to the shrinkage, arising from the application of heat during welding, so that the sleeve will not tightly fit about the cable joint.

Copending Application No. 45834/77 (Serial No. 1,582,077), from which the present application is divided, aims to obviate or significantly reduce the above defects, and discloses a method of welding together juxtaposed faces a thermoshrinkable synthetic resin film or sheet material which enables a reliable seal to be obtained, and minimizes the influence of heat adjacent the sealed portion. The said copending application claims a method of welding together juxtaposed faces of portions of monoaxially oriented thermoshrinkable sheet material of crosslinked polyethylene or ethylene copolymer comprising inserting an uncrosslinked polyethylene or ethylene copolymer tape, containing a crosslinking agent comprising a peroxide, and a polyfunctional monomeric additive, between juxtaposed faces of the portions of the sheet material to be welded together, securing a heat-resisting adhesive tape to the outer faces of the said portions on opposite sides of the firstmentioned tape, and applying heat and pressure to said portions via the heat-resisting adhesive tape.

In order to efficiently perform the above welding of the sheet material, there is required a device having a compact operating mechanism, which is relatively easy to carry, is operable in a limited space, and is capable of exerting a substantial pressure on the juxtaposed portions of the sheet material during welding.

It is an object of the present invention to provide a device which is primarily although not necessarily intended for use in the above method, and which is capable of meeting the various requirements mentioned above.

According to the present invention, there is provided a device for use in welding together juxtaposed faces of monoaxially oriented thermoshrinkable sheet material, comprising a pressure plate having a heater, a sheet material-receiving plate, a first link pivotally connected at one end to one end of the sheet material-receiving plate and at the other end to the pressure plate an operating lever pivoted at one end of the sheet material-receiving plate, a second link pivotally connected to the free end portion of the operating lever and to the first link, the first and second links and the operating lever constituting a power amplifying mechanism by which a turning force, when exerted on the operating lever, is translated into an increase in the pressure applied by the pressure plate.

In order that the present invention may be more readily understood, reference will now be made to the accompanying drawings, in which : - Figs. 1 to 4 are sectional views through juxtaposed portions of various thermoshrinkable sheets, illustrating different weld configurations; Figs. 5 to 7 are perspective views illustrating cable joints covered with thermoshrinkable sheets formed into sleeves; Fig. 8 is a side elevation showing a welding device embodying the invention; and Fig. 9 is a perspective view of the device of Fig. 8 in use, welding the juxtaposed end portions of a sheet which is formed into a sleeve and covers a cable joint.

Throughout the drawings, simiuar parts and elements are designated by the similar reference numerals and letters.

Figs. 1 and 2 each show a monoaxially oriented film or sheet 1 the end or edge portions of which are overlapped, and are to be welded together. Each sheet 1 is formed of a crosslinked polyethylene or ethylene copolymer such as ethylene vinyl acetate copolymer ethylene ethyl acrylate copolymer, an ethylene glycidacrylate ethylacrylate copolymer, or a mixture thereof.

As shown, initially, the juxtaposed faces of the end portions to be welded are cleaned, and inserted between them is a piece of uncrosslinked polyethylene or uncrosslinked ethylene copolymer tape 2, which contains 0.5 to 5% by weight, and preferably 2 to 3% by weight, of at least one peroxide, such as dicumyl peroxide, 1, 3-bis(t-butyl peroxyisopropyl) benzene, 1,1-dit-butyl peroxy-3,3,5-trimethyl cyclohexane, t-butyl cumyl peroxide, 2,5-dimethyl-2,5 di-(t-butyl peroxy)-hexane, or 2,5-dimethyl-2,5-di-(t-butyl peroxy)-hexane-3, or a mixture thereof. In addition to the peroxide, the tape contains at least one polyfunctional monomer, such as diallyl phthalate, trimethylool propan trimethylacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, or allyl acrylate, or a mixture thereof. The amount of this monomer is 0.5 to 5% by weight, and preferably 2 to 3% by weight.

In addition, as shown in Fig. 2, the juxtaposed faces to be welded, and/or both faces of the tape 2, may be coated with a crosslinking agent comprising a liquid or paste peroxide 3, such as t-butyl cumyl peroxide, 2,5-dimethyl-2,5 di-(t-butyl peroxy)hexane, or 2,5-dimethyl-2,5-di-(t-butyl peroxy)-hexane-3, or a mixture thereof.

Prior to welding, heat resisting adhesive tapes 4 made of, for example, glass fibre, aluminium, polytetrafluoroethylene such as Teflon (Registered Trade Mark), or epoxy resin impregnated paper or cloth are secured to the outer faces of the overlapping portions and adjacent zones, where the heat is to be applied. The tapes 4 prevent separation of the end portions of the sheet 1, and also hold the tape 2 in place, prior to welding.

The above assembly is then subjected to pressure and heat, applied to the outer faces of the heat-resisting tapes 4, thus welding together the end portions of the sheet 1.

During welding, since the zones of the sheet adjacent the weld zones are covered by the heat-resisting adhesive tapes 4, these adjacent zones are protected from direct heat, and can be maintained below the temperature at which heat-shrinkage occurs, thus making it possible to prevent the sheets from partially shrinking as a result of welding.

Furthermore, the tapes 4 avoid the necessity of applying a releasing agent to the heating and pressure plate of the device which is used to weld the sheet, and the necessity of providing the pressure plate with a specific material for the purpose of preventing the sheet 1 from adhering to the pressing plate.

The welding may be performed at 150 to 250"C, and preferably at about 210 C, at a pressure of 0.5 to 5.0 kg/cm2, and preferably about 3 kg/cm2, for 1 to 60 minutes, and preferably about 4 minutes.

Fig. 3 shows an embodiment in which the end portions of the sheet 1 are turned outwardly from the plane of the sheet, i.e. are upturned as viewed in this Figure, and are welded together after application of a single piece of tape 4.

Fig. 4 illustrates an embodiment in which the overlapping portions which are welded together are central portions, not end portions, of sheet 1. The juxtaposed portions of the sheets 1 in Figs. 3 and 4 are welded together by substantially the same method as previously described with reference to Figs. 1 and 2, with substantially the same results. As seen in the case of Fig. 2, a liquid or paste peroxide 3 can be interposed between the tape 2 and the juxtaposed faces of the sheet 1 in Fig. 3 or 4.

When the sheet 1 of each of the previously described embodiments, after welding, was subjected to a peeling test, the material of the sheet was found to tear, without any peeling apart occurring at the interface of the welded portions.

Figs. 5 and 6 illustrate joints between electric cables A and A1 which are covered by a respective sheet 1 formed into a sleeve or tube by welding together the end portions thereof, utilizing the abovementioned method, with the oriented direction of the sheet being circumferential. The sleeve, after welding, is thermally shrunk to cause it to fit tightly about its associated joint. Heat shrinking is effected by subjecting the sleeve to a temperature of 120 to 300"C for 1 to 20 minutes.

In Fig. 5, both ends of the sheet 1 are welded together by the method described with reference to Fig. 1, in which the end portions overlap one another. In Fig. 6, the end portions are out-turned as in Fig. 3.

In Fig. 7, the end portions of the sheet 1 are welded together in a similar manner to Fig. 1, and in addition, the opposed intermediate portions of the sheet 1 between the two branches formed by the cables A' are welded together by the method of Fig. 4.

In order to prevent the separation of the intermediate connecting portions when the sheet 1, consisting of crosslinked polyethylene or ethylene copolymer, is thermally shrunk, it is preferable to use for the sheet, a material of which the gel content ranges from 20 to 65% by weight.

In a modification, a tube or sleeve is prepared by welding together the end portions of a sheet 1 by a method as previously described, whereafter the welded sleeve is slid over one of the cables A, Al to be joined. After the cables have been joined to each other, the sleeve is slid over the joint, and is then heat-shrunk.

When the tube is heat-shrunk in any of the above embodiments, the heat-resisting adhesive tapes 4 can be left in position.

However, preferably, they are peeled off, since a tape of this kind is relatively stiff and lacks flexibility, so that it will not closely fit to the sleeve upon heat-shrinking thereof, and is prone to change its color due to the heat, which can result in a bad appearance.

Figs. 8 and 9 show a device for use in welding the sheet 1. As shown, a base in the form of a stationary lower jaw 10 has an anvil or receiving plate 11 secured thereto for receiving the juxtaposed portions of the sheet 1 which are to be welded together. The sheet-receiving plate 11 is cooperable with a movable upper jaw 12, which may be opened and closed relative to the lower jaw 10, and has a pressure plate 13, which incorporates a heater 14, secured thereto. Electrical wires 24 are connected to the upper jaw 12 to supply power to the heater 14. A thermosensitive element 15 may be incorporated within the upper jaw 12 to control the heater 14, and therefore the temperature of the pressure plate 13.

A bracket 16 extends upwardly from the rear or right-hand end of the lower jaw 10, and to the upper end portion of this bracket is pivotally connected one end of a link 17.

The other end of the link 17 is pivoted to the central part of the upper jaw 12 so that the latter will be displaced bodily towards or away from the lower jaw 10 upon pivotal movement of the link 17 relative to the bracket 16.

A forked operating lever 18 is pivotally connected by its lower end portion of the bracket 16. Into the free or upper end of the lever 18 is threaded a manually adjustable screw 19. By rotating the screw 19, the lower end of the screw moves upwardly or downwardly to adjust the pressure between the jaws as will be explained hereinafter.

The upper end of the lever 18 is pivotally connected to the link 17 by a link 20 so that, when the lever 18 is pivoted, the link 17 is caused to pivot through the intermediary of the link 20, thus allowing the upper jaw 12 to move towards or away from the lower jaw 10. A pivot on the upper end of the link 20 engages in a slot 23 in the lever 18, and the lower end of the screw 19 engages the upper curved end of the link 20, so that adjustment of said pivot within and along the slot 23 will be effected by rotation of the screw 19. Further, the lever 18, link 20 and link 17 form a toggle mechanism, constituting what may be termed a power amplifying mechanism, which provides a mechanical advantage when the pressure plate 13 is pressed against the sheet-receiving plate 11. Stops 21 and 22 are provided on the link 17 and bracket 16, respectively, for defining the limits of the pivotal movement of the lever 18.

Though not shown in the drawings, a heat insulating material may be interposed between the upper jaw 12 and pressure plate 13, and between the lower jaw 10 and sheet-receiving plate 11.

In operation of the device, the screw 19 is initially rotated so as to adjust the position of the pivot in the slot 23, thus adjusting the fulcrum of the link 20 in relation to the lever 18. In this way, the pressure applied by the pressure plate 12 relative to the sheet-receiving plate is set.

With the mechanism positioned as shown in broken lines in Fig. 8, i.e. with the jaws 10 and 12 open and the lever 18 inclined rearwardly, as shown in Fig. 9 the lower jaw 10 is inserted between the joint between the cables A, Al and the overlapping portion of the sheet 1 which covers the joint. The upper jaw 12 is then aapplied to the overlapping end portions by pivoting the lever 18 in the direction of the arrow, the end portions to be welded or sealed being pressed by the pressure plate 13 against the sheet-receiving plate 11, and heated by the heater 14, thus effecting the welding. The pressure applied by the pressure plate 13 becomes a maximum when the fulcra at both ends of the link 20 and that of the lever 18 are aligned. However, if the stop 21 is positioned slightly leftwardly of that position of maximum pressure, so that the lever 18 will be slightly over-centre when it engages the stop 21 as shown by the solid lines in Fig. 8, the lever 18 will remain in that position, and will not inadvertently pivot to the right.

Whilst, in Figure 9, by way of example, the welding device is shown as being used to weld together overlapping portions of sheet, such as are shown in Figure 5, it will be understood that the device could equally well be employed to weld together out-turned portions, such are shown in Figure 6. In the latter case the cable Al will be disposed along side the device with the out-turned edges oriented to project generally horizontally towards the device and between the plates 11 and 13. The device could similarly be employed to weld together the out-turned portions shown in Figure 3, by orienting the sheets 1 so that the out-turned portions project generally horizontally towards the device and between the plates 11 and 13.

As described hereinbefore in detail, since the device incorporates a power amplifying mechanism for increasing the pressing force, i.e. possesses a mechanical advantage, and incorporates adjustment means therefor, it is possible to obtain a suitable pressure in accordance with different sheet thicknesses.

thus enabling the increase of reliability of the welded or sealed portions. Furthermore, the device is compact, and it is suitable for carrying, and operating in a limited space.

WHAT WE CLAIM IS:- 1. A device for use in welding together juxtaposed faces of monoaxially oriented thermoshrinkable sheets material, comprising a pressure plate having a heater, a sheet material-receiving plate, a first linke pivotally connected at one end to one end of the sheet material-receiving plate and at the other end to the pressure plate, an operating lever pivoted at one end of the sheet material-receiving plate, a second link pivotally connected to the free end portion of the operating lever and to the first link, the first and second links and the operating lever constituting a power amplifying mechanism by which a turning force, when exerted on the operating lever, is translated into an increase in the pressure applied by the pressure plate.

2. A welding device as claimed in claim 1, wherein a thermosensitive elcment is incorporated in the pressure plate to control the operation of the heater.

3. A welding device as claimed in claim 1 or 2, wherein the operating lever has adjustment means for adjusting a fulcrum of the second link.

4. A welding device as claimed in claim 3, wherein the adjustment means comprises a manually rotatable screw threaded in the free end of the operating lever, and a pivot forming the fulcrum of the second link is inserted in a slot provided adjacent the free end of the operating lever, the end of the screw abutting the free end of the second link and being operable, upon rotation, to move said pivot along the slot.

5. A welding device as claimed in any preceding claim, wherein a stop is provided on one end of the sheet material-receiving plate and on the first link so as to define the limits of the pivotal movement of the operating lever 6. A welding device as claimed in any preceding claim, wherein the sheet materialreceiving plate is mounted on a base, said plate and base being dimensioned to be received between a member or members and sheet material disposed about the member or members during a welding operation.

7. A welding device as claimed in any preceding claim, wherein the pressure plate is mounted on a movable jaw, pivotally connected to a stationary base on which the sheet material-receiving plate is mounted, and wherein a heat insulating material is interposed between the pressure plate and movable jaw, and between the sheet materialreceiving plate and stationary base.

8. A welding device substantially as hereinbefore described with reference to Figs. 8 and 9 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. engages the stop 21 as shown by the solid lines in Fig. 8, the lever 18 will remain in that position, and will not inadvertently pivot to the right. Whilst, in Figure 9, by way of example, the welding device is shown as being used to weld together overlapping portions of sheet, such as are shown in Figure 5, it will be understood that the device could equally well be employed to weld together out-turned portions, such are shown in Figure 6. In the latter case the cable Al will be disposed along side the device with the out-turned edges oriented to project generally horizontally towards the device and between the plates 11 and 13. The device could similarly be employed to weld together the out-turned portions shown in Figure 3, by orienting the sheets 1 so that the out-turned portions project generally horizontally towards the device and between the plates 11 and 13. As described hereinbefore in detail, since the device incorporates a power amplifying mechanism for increasing the pressing force, i.e. possesses a mechanical advantage, and incorporates adjustment means therefor, it is possible to obtain a suitable pressure in accordance with different sheet thicknesses. thus enabling the increase of reliability of the welded or sealed portions. Furthermore, the device is compact, and it is suitable for carrying, and operating in a limited space. WHAT WE CLAIM IS:-

1. A device for use in welding together juxtaposed faces of monoaxially oriented thermoshrinkable sheets material, comprising a pressure plate having a heater, a sheet material-receiving plate, a first linke pivotally connected at one end to one end of the sheet material-receiving plate and at the other end to the pressure plate, an operating lever pivoted at one end of the sheet material-receiving plate, a second link pivotally connected to the free end portion of the operating lever and to the first link, the first and second links and the operating lever constituting a power amplifying mechanism by which a turning force, when exerted on the operating lever, is translated into an increase in the pressure applied by the pressure plate.

5. A welding device as claimed in any preceding claim, wherein a stop is provided on one end of the sheet material-receiving plate and on the first link so as to define the limits of the pivotal movement of the operating lever

6. A welding device as claimed in any preceding claim, wherein the sheet materialreceiving plate is mounted on a base, said plate and base being dimensioned to be received between a member or members and sheet material disposed about the member or members during a welding operation.