DE9010609U1 - Cap-like heat-recoverable hollow article - Google Patents

Description

Description

The invention relates to a bucket-like hollow, heat-recoverable base made of a cross-linked polymer...with an internal coating made of a filler or sealant that becomes liquid when heated.

So-called end caps are required to seal pipes, cables and lines against moisture. These are usually made of heat-recoverable plastic, are placed on the end and shrink under the influence of heat. When the material is shrink-heated, an adhesive on the inner surface of the cap softens, which ensures that the cap is bonded to the cable and that it is sealed against moisture ingress.

The production of the caps is very complex. First, a cap is produced using an injection molding process. Since the plastic is cross-linked during production, injection molding is a lengthy process. An injection molding machine can produce around 6 to 10 caps per minute. In the next step, the caps are heated again, expanded while heated, and cooled while expanded. Finally, a layer of hot-melt adhesive is applied to the inner surface.

In order to avoid the lengthy injection molding process, attempts have already been made to cut short ends from a continuously produced tube, close one end and then expand it. In order to achieve the desired tightness by closing it, the still uncrosslinked blank was closed by welding or gluing. The blank was then crosslinked (e.g. by radiation crosslinking), expanded and finally coated on the inside. This procedure also requires many individual, time-consuming work steps.

The present invention is based on the object of specifying a cap-like object of the type mentioned at the beginning which is significantly simpler and thus cheaper to manufacture and yet fully meets the requirements with regard to sealing.

This huge task is solved by the fact that the object consists of a piece of hose, one end of which is sealed by heating with the aid of a molded piece, a deformed part or similar.

The main advantage is that one starts from a length of hose that is produced by extrusion, cross-linking, expanding and adhesive coating, whereby at least the first three process steps are carried out in a continuous manner, the desired length is cut off from this hose length and one end of the cut length is sealed with a molded part and this area is shrinked by heating. The surface pressure required for permanent sealing is achieved by the increase in wall thickness that occurs during shrinking, as a result of which the liquid adhesive during the shrinking process is forced into all possible

cavities. After cooling, the adhesive hardens.

According to a particularly advantageous embodiment of the invention, a plug is inserted into the end, onto the outer surface of which a certain length of the hose is shrunk. The outer diameter of the plug must be equal to or larger than the inner diameter of the hose after extrusion, but

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cylindrical part made of plastic. Such parts are inexpensive and can be obtained as waste items.

The advantage of such a design is that the transition from the sealing point to the diameter of the hose is uniform.

It is also possible to make the plug from cross-linked plastic. A strand is extruded with a diameter equal to c*em the inner diameter of the extruded tube. Pieces are cut off from this strand and placed in a

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Outer diameter increases to the inner diameter of the expanded tube. In this design, the base part of the cap, i.e. the plug, shrinks to the same extent as the tube when heated. This design is closest to the cap produced by injection molding.

Simpler than the version with an inserted plug and completely sufficient for most applications is an object whose end is sealed with a crimping tool. The end is usually flattened or compressed. The crimping tool can be a jaw tool that prepares the ends at the factory. The hose end is heated, compressed with the jaw tool and cooled in the tool.

It is also possible to compress the hose end first and then heat it.

The squeezing tool can also be a clamp that is placed on the hose transversely to the longitudinal axis of the hose, where the length of the clamp legs is at least equal to the width of the hose in the collapsed state.

A clamp with three legs can also be used

the other two legs rest on the opposite side of the hose. The crimping tool can also be a buckle with at least three bars around which the hose end is alternately guided.

Alternatively, the squeezing device can be a metal tube deformed into a flat nozzle.

The clamp, buckle and flattened metal tube are crimping devices that can be removed after the end is sealed or left on the object.

The hose is preferably made of a plastic that shrinks at a temperature of less than 100 ^° C. This measure makes the item suitable for applications where high temperatures must be avoided. Shrinkage without the use of flames, e.g. with warm air, is also possible.

To achieve a secure seal, the length of the sealing area should be at least 5 mm.

The invention is explained in more detail using the embodiments shown schematically in Figures 1 to 4.

% Figures 1 to 3 show sections through various

f: hollow objects, whereas Figure 4 is a plan view of

&Kgr; shows a hollow object.

Figure 1 shows a hose 1 made of cross-linked polyethylene, which has, for example, an outer diameter of 12 mm, a wall thickness of 1 mm and a length of 210 mm. The hose 1 is made of a continuously extruded cross-linked and

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On the inner surface of the hose 1 there is an unspecified layer of an adhesive that softens when heat is applied Ii, preferably a so-called

Hot melt adhesive.

To produce a hollow, closed-end &igr;

cap-like object, a plug 2, preferably made of plastic, is inserted into one of the ends of the tube 1 and the end area is heated. The heating causes the adhesive on the inner surface to soften and the end area to shrink to the surface of the plug 2, increasing its wall thickness. After

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It is essential that the outer diameter of the plug is larger than the inner diameter of the unexpanded hose 1. The plug 2 can still be S not shown with in the circumferential direction

m running beads, which provide improved

i£ mechanical connection and better sealing effect

achieve.

Figure 2 shows an embodiment in which the

% end of the hose to be sealed 1 a clamp 3

I- is attached. After attaching the clamp 3,

'j as described above, the end area is heated and

% to shrink. When cooling, the

£: opposite surfaces of the collapsed end

% with each other. The essential thing about this design is that

the distance between the fingers of the clamp 3 is less than twice the wall thickness of the shrunk tube x, so that the necessary contact pressure for bonding and sealing can be applied. The clamp 1 can be removed after the actual sealing process, ie after cooling, or it can remain on the end.

Figure 3 shows the hose 1 with a sealed label as described above. The squeezing tool here is advantageously a jaw tool (not shown) which acts on a supplied length of hose. The length of the sealing area is ±1 ^twice as long as for a cap-like object, at least 10 mm. To produce the caps, the hose is severed in the sealing area and between two sealing areas.

After completion of the sealing areas, the parting plane in the sealing area 4 can be formed in a circular arc, as shown in Figure 4, in order to avoid points and sharp edges 7.1.1 =

Since the melting or softening point of the adhesive should or must be lower than the shrinking temperature, the sealing area 4 should be avoided from being heated again when shrinking on the C-',2nstand, e.g. a cable end. For this purpose, a marking 5 is provided on the hose 1, e.g. a colored ring, beyond which the heating should not go. This precautionary measure can be dispensed with if, for example, the clamp 3 or a similar type of crimping tool remains on the sealing area 4.

Claims (10)

Protection claims 1. Cap-like hollow heat-retaining article made of a cross-linked polymer, with an inner coating of an adhesive or sealant which becomes liquid when heated, characterized in that it consists of a piece of tubing (1), one end of which is sealed by heating with the aid of a shaped piece (2), a deformed part (3) or the like. 2. Article according to claim 1, characterized in that a plug (2) is introduced into the end, onto the outer surface of which a certain length of the hose (1) is shrunk down. 3. Article according to claim 2, characterized in that the plug (2) is a cylindrical plastic part. 4. Article according to claim 1, characterized in that the end is sealed by a crimping tool (3). 5. Article according to claim 1 or 4, characterized in that the squeezing tool is a clamp (3) which is placed on the hose (1) transversely to the longitudinal axis of the latter, the length of the clamp legs being at least equal to the width of the hose (1) in the collapsed state. ittt-. 6. Article according to claim 5, characterized in that the clamp has three legs. 7. Article according to claim 1 or 4, characterized in that the squeezing mechanism is a buckle with at least three bars. 8. Article according to claim 1 or 4, characterized in that the squeezing device is a metal tube forged into a liquid. ^ 9. Article according to one of claims 1 to 8, characterized in that the hose (1) consists of a plastic which shrinks at temperatures below 100 ^° C. 10. Article according to one of claims 1 to 9, characterized in that the length of the sealing region is at least 5 mm.