Shrink cap and method of manufacturing shrink cap

Abstract

To provide a mechanically stable, airtight and highly voltage-resistant shrink cap which reduces the risk of causing damage or injury.SOLUTION: The invention relates to a shrink cap (10) for sliding onto a temperature-dependent switch (12). The shrink cap (10) comprises an open first end (18) for sliding onto the switch (12), and a closed second end (20) which is closed by a welded or embossed seam (22) that extends from a closed end face (24). The closed end face (24) is arranged in the area of the second end (20) and results from the welded or embossed seam (22). In the area between the first end (18) and the end face (24), the shrink cap (10) is substantially mirror-symmetrical with respect to a first plane of symmetry (30). The welded or embossed seam (22) is arranged parallel to the first plane of symmetry (30) at the end portion (34) adjacent to the end face (24).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a shrink cap and a method for manufacturing the shrink cap.The present invention further relates to a temperature dependent switch comprising a shrink cap according to the invention. [Background technology]

[0002] A typical shrink cap and a typical method for producing such a shrink cap are disclosed in European Patent 0 857 562.

[0003] Such shrink caps are usually held in bulk, pressed onto the electrical device to be protected, such as a temperature dependent switch, and then shrunk using hot air to create a covering that protects the device from dirt, moisture and electrical contact with other components. The connecting elements of the device, often configured as strands or cables, protrude from this covering.

[0004] Such shrink caps are usually manufactured by first cutting a section of heat shrink tubing to a given length and then forming a welded or embossed seam at one of its ends. For this purpose, the section of heat shrink tubing is pressed together at said ends and the welded or embossed seam is formed, for example, by two welding stamps acting on the ends of the section of heat shrink tubing from opposite sides by pressure and heat.

[0005] Because the welded or embossed seam is formed by pressing one end of the heat shrink tubing together and joining the longitudinal halves of the heat shrink tubing that are pressed together, the welded or embossed seam is typically about twice the wall thickness of the remainder of the heat shrink tubing. This results in a relatively stiff and rigid welded or embossed seam.

[0006] The welded or embossed seam protrudes from the closed end formed by the welded or embossed seam on the heat shrink tubing or shrink cap, respectively. Due to the manufacturing process, the protruding free end of the welded or embossed seam usually has a very sharp edge that remains when the shrink cap is shrunk onto the device it is protecting.

[0007] In both the assembly of the shrink-capped device and the subsequent processing of the shrink-capped device, many process steps are typically performed manually and the people performing these process steps are unable to wear protective gloves because they are required to perform very delicate motorized operations.

[0008] Due to the sharp edges of the welded or embossed seams, this type of manual work can subject people to repeated injuries, which of course is a major drawback.

[0009] Therefore, to avoid these injuries, people often grab the covered element with the connecting cable rather than grabbing the covered element with the shrink cap itself, which often weakens the connection between the connecting cable and the covered element or breaks completely during further manipulations that are required, and devices made from such elements often malfunction.

[0010] In particular, if the device is a temperature-dependent switch, for example protecting a coil from overheating, the switch housed in the shrink cap will be in direct contact with the coil of, for example, an electric motor. The switch is electrically connected in series with the coil and interrupts the electric circuit if the temperature of the coil exceeds a predefined value. For this purpose, in a known manner, a bimetallic switching mechanism is arranged inside the temperature-dependent switch.

[0011] To ensure this protective function, the switch must be located inside the coil, or at least very close to it. Sharp edges on the shrink cap could cause damage to the coil, which is of course a disadvantage.

[0012] According to EP 0 857 562 the above mentioned problems are solved by re-processing the shrink cap after the welded or embossed seam has been formed, during which the welded or embossed seam is folded over with a forming punch. This bending causes the sharp free edges of the welded or embossed seam to be rolled up or folded over, in other words, so that they no longer protrude straight out from the front face of the shrink cap.

[0013] This measure effectively prevents the aforementioned personal injury problems and the risk of damage to other equipment.

[0014] Nevertheless, there is still potential for improvement in the manufacture of such shrink caps. For example, as described in European Patent 0 857 562, it has been shown that shrink caps with welded or embossed seams bent more than 90° become mechanically unstable and therefore break more easily. This can lead to open areas in the shrink cap, which can result in a fundamental loss of the protective function of the shrink cap. Furthermore, this can impair the voltage or high voltage resistance of the shrink cap, which is an important property that must be guaranteed by the shrink cap, especially when used for temperature-dependent switches. Summary of the Invention [Problem to be solved by the invention]

[0015] It is therefore an object of the present invention to provide a shrink cap and a method for manufacturing such a shrink cap which makes it possible to eliminate or at least reduce the above-mentioned problems, thereby in particular reducing the risk of damage or injury which may be caused by such a shrink cap and at the same time ensuring a mechanically stable, tightly sealed and voltage-resistant shrink cap. [Means for solving the problem]

[0016] According to the invention, this object is solved by a shrink cap which slides over the temperature-dependent switch, the shrink cap having an open first end which slides over the switch and a closed second end which is closed by a welded or embossed seam extending from the closed end face, the closed end face being arranged in the region of the second end and arising from the welded or embossed seam, the shrink cap being approximately mirror symmetrical with respect to a first plane of symmetry in the region between the first end and the end faces, the welded or embossed seam being arranged offset parallel to the first plane of symmetry at the end adjacent to the end face.

[0017] According to a further aspect of the present invention, the above object is achieved by a method for manufacturing a shrink cap comprising the steps of: a) providing a shrink tubing section having a first opening at a first end and a second opening at a second end, the shrink tubing section being substantially mirror symmetric about a first plane of symmetry; b) pressing the heat shrink tubing portions together at the second end to create a welded or embossed seam to close the second opening and to create a closed end surface adjacent the welded or embossed seam in the region of the second end, the welded or embossed seam being created offset parallel to the first plane of symmetry; c) forming portions of the welded or embossed seam such that at least a portion of the welded or embossed seam is bent;

[0018] In other words, the welded or embossed seam is not produced in the center of the first plane of symmetry of the heat shrink tubing section from which the shrink cap is made, but is offset off-center with respect to this first plane of symmetry.

[0019] This has the advantage that the welded or embossed seam can be relatively large and does not protrude laterally beyond the edge of the shrink cap after molding. The welded or embossed seam is preferably not folded or rolled, but simply bent in one direction. By offsetting the welded or embossed seam, there is relatively more space in which the welded or embossed seam can be bent. For example, if the welded or embossed seam is provided on an end face that is offset upwards in a parallel manner from the first plane of symmetry, there is relatively much more space below the welded or embossed seam in which the welded or embossed seam can be bent.

[0020] Even if the welded or embossed seam is bent exactly 90° and is longer than half the height of the shrink cap, it still does not protrude laterally from the shrink cap, i.e. across the first plane of symmetry. In particular, the free, usually sharp edge of the welded or embossed seam does not protrude laterally from the shrink cap. Subsequent cutting or shortening of the welded or embossed seam can therefore be omitted.

[0021] All of this can be effected by locating the welded or embossed seam off-center or offset, even if the welded or embossed seam has a relatively large surface area. The large area configuration of the welded or embossed seam increases the tightness of the seam and makes it easier to handle when manufacturing the welded or embossed seam.

[0022] In this way, the above objective is completely achieved.

[0023] In one refinement, the interface plane of the welded or embossed seam at the end of the welded or embossed seam adjacent the end face is offset parallel to the first plane of symmetry.

[0024] "Faying surface" as used herein refers to the surface along which two longitudinal halves of a heat shrink tubing that are pressed together and joined are connected to one another when a welded or embossed seam is produced.

[0025] This faying surface or faying plane extends parallel to the first plane of symmetry after the welded or embossed seam is created. However, since only a portion of the welded or embossed seam is formed in accordance with the present invention, the above definition of parallel offset arrangement of faying surfaces refers to "only the ends of the welded or embossed seam adjacent to or located on the end surface."

[0026] In a further refinement, the inner mating surface of the shrink cap defines a boundary line that curves into a circular arc.

[0027] This boundary line is the beginning of the joint surface and is visible from the inside, i.e. through the first opening.

[0028] In a further refinement, the end face has a height measured perpendicular to a first plane of symmetry and the welded or embossed seam is located at an end adjacent the end face offset parallel to the first plane of symmetry by at least 1 / 10 of the height, preferably at least 1 / 5 of the height.

[0029] It is particularly preferred that the height of the welded or embossed seam, measured perpendicular to the first plane of symmetry, is greater than half the height of the end face, measured from the end of the welded or embossed seam adjacent to the end face to the free end of the welded or embossed seam.

[0030] This enables the welded or embossed seam, in its final formed state, to have a height, measured perpendicular to the first plane of symmetry, that is greater than half the height of the end face, such that the seam does not protrude laterally beyond the end face.

[0031] In a further refinement, the welded or embossed seam is formed such that a formed portion of the welded or embossed seam lies directly against the end face or with an intervening bonding agent.

[0032] In contrast to what is proposed in EP 0 857 562, the welded or embossed seam is therefore not only bent, folded or rolled over by more than 90° towards the end face of the shrink cap, but is also formed so as to at least partially contact the end face. Preferably, the welded or embossed seam is folded over by approximately 90° and positioned relative to the end face of the shrink cap such that at least a portion of the welded or embossed seam is directly against the end face of the shrink cap or indirectly against the end face of the shrink cap by means of an intervening bonding agent.

[0033] This has several advantages. Firstly, the shrink cap and thus the device in which it is used (e.g. temperature dependent switch) are shorter. This small size is advantageous both in terms of bulk storage of the shrink cap and in terms of handling and mounting options for the shrink cap. Furthermore, it has been shown that by attaching the welded or embossed seam to the end face of the shrink cap, the risk of injury and damage is further reduced since the sharp edges of the welded or embossed seam can be completely attached to the end face of the shrink cap, so that the seam no longer protrudes from the shrink cap and is therefore almost inaccessible. Furthermore, it has been shown that the welded or embossed seam on the edge further increases the wall thickness of the end of the shrink cap, so that a kind of double or multiple wall is formed at the end of the shrink cap. This not only provides an additional mechanical stability, but initial tests by the applicant have also shown that the high voltage resistance of the shrink cap is significantly improved. Whereas conventional shrink caps exhibit high voltage resistance in the region of 1.5-2.5 kV, the shrink cap according to the invention can achieve high voltage resistance of 3.5 kV and above.

[0034] In a refinement, the welded or embossed seam has a free end and an end adjacent the end face, and the formed portion of the welded or embossed seam abuts the end face directly or with an intervening bonding agent and extends over the area between the free end and the end adjacent the end face.

[0035] Thus, the welded or embossed seam preferably contacts the end face of the shrink cap at least in a central portion extending between the free end and the end adjacent the end face.

[0036] In a further refinement, it is preferred that more than 50% of the area of ​​one side of the welded or embossed seam that abuts the end face abuts the end face either directly or with an intervening bonding agent.

[0037] In other words, it is preferred that the majority of the welded or embossed seam abuts the end face of the shrink cap, which further improves the mechanical stability and high voltage resistance of the shrink cap.

[0038] It is particularly preferred that the welded or embossed seam completely abuts the end face either directly or indirectly by means of an intervening bonding agent.

[0039] The welded or embossed seam is preferably bent 90° and placed on one side relative to the end face of the shrink cap. The welded or embossed seam preferably does not protrude beyond the outer edge or circumference of the shrink cap. This method ensures the greatest possible mechanical stability and high voltage resistance. At the same time, the risk of injury and damage caused by the shrink cap is reduced to a minimum.

[0040] In a further refinement, the formed part of the welded or embossed seam is pressed against the end face.

[0041] This preferably results in a seamless and essentially wrinkle-free welded or embossed seam being applied to the end face of the shrink cap. Part or all of the welded or embossed seam is preferably thermoformed or hot formed by heating with external hot air and / or a thermoforming die and then pressed onto the end face of the shrink cap. This results in a very compact shrink cap, which has a high level of stability and high voltage resistance, especially in the region of the end face.

[0042] In a further refinement, the formed part of the welded or embossed seam is fixed to the end face by means of a material lock.

[0043] For example, a welded or embossed seam may have a formed portion glued or welded to the end surface of the shrink cap after the seam is manufactured and formed, such that the formed portion of the welded or embossed seam remains permanently attached to the end surface as it is additionally secured thereto.

[0044] In a further refinement, the end face of the shrink cap is convexly curved. Particularly preferably, the end face is curved when viewed in a longitudinal section of the shrink cap.

[0045] This further minimises the risk of injury and damage caused by shrink caps.Furthermore, this shape is particularly suitable for receiving temperature dependent switches, which are typically cylindrical or round.

[0046] In a further refinement, a formed portion of the welded or embossed seam extends substantially parallel to the convexly curved end face.

[0047] Thus, the formed part of the welded or embossed seam fits flush against the front surface of the shrink cap like a second wall, which further improves the compactness, mechanical stability, high voltage resistance and rigidity of the shrink cap.

[0048] As mentioned above, the improvements mentioned above and those defined in the claims do not only relate to the shrink cap itself, but also to the temperature-dependent switch comprising such a shrink cap. They likewise relate to the method for manufacturing the shrink cap according to the invention. This in particular leads to the following further improvements to the manufacturing method according to the invention:

[0049] In one embodiment, in step b), the welded or embossed seam is generated offset from a first plane of symmetry of the shrink tube portion, such that the welded or embossed seam generated in step b) is substantially mirror symmetric with respect to a second plane of symmetry offset parallel to the first plane of symmetry.

[0050] In a further refinement, in step b) the welded or embossed seam is generated offset from a first plane of symmetry of the shrink tube portion, and in step b) the welded or embossed seam generated is substantially mirror symmetrical with respect to a second plane of symmetry, the second plane of symmetry being offset from the first plane of symmetry by at least 1 / 10 of the height, preferably at least 1 / 5 of the height, measured orthogonally to the first plane of symmetry.

[0051] In a further refinement, a portion of the welded or embossed seam is formed in step c) such that the formed portion of the welded or embossed seam is located directly on the end face or is located on the end face with the aid of an intervening bonding agent.

[0052] In a further refinement, the welded or embossed seam includes a free end and an end adjacent the end face, with a formed portion of the welded or embossed seam abutting the end face directly or with an intervening bonding agent and extending over the area between the free end and the end adjacent the end face.

[0053] In a further refinement, a portion of the welded or embossed seam is formed in step c) such that more than 50% of the area of ​​one side of the welded or embossed seam abutting the end face abuts the end face directly or with an intervening bonding agent.

[0054] In a further refinement, a portion of the welded or embossed seam is formed in step c), the welded or embossed seam being fully abutted against the end face directly or with an intervening bonding agent.

[0055] In a further refinement, a portion of the welded or embossed seam is pressed against the end face in step c) or after step c).

[0056] In a further refinement, the cross section of the welded or embossed seam is fixed to the end face in step c) or after step c) by means of a material lock.

[0057] In a further refinement, the end face is convexly curved.

[0058] In a further refinement, a portion of the welded or embossed seam is formed in step c) such that the formed portion extends approximately parallel to the convexly curved end face.

[0059] In a further refinement, a welded or embossed seam is formed in step c), in which the free end of the welded or embossed seam does not protrude beyond the end face in a direction perpendicular to the first plane of symmetry.

[0060] It is understood that the features mentioned above and those to be described below can be used not only in the combinations indicated in each case, but also in other combinations or by themselves, without departing from the scope of the invention. [Brief description of the drawings]

[0061] Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. [Figure 1] 3A-3D are schematic representations of intermediate states during the manufacture of a shrink cap according to the invention in some figures; [Figure 2A] FIG. 2 is a side view of a shrink cap according to a first embodiment of the present invention. [Figure 2B] FIG. 2B is a cross-sectional view of the shrink cap shown in FIG. 2A. [Figure 3A] FIG. 11 is a side view of a shrink cap according to a second embodiment of the present invention. [Figure 3B] FIG. 3B is a cross-sectional view of the shrink cap shown in FIG. 3A. [Figure 4] 5A-5C are several schematic manufacturing steps for producing a shrink cap according to the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0062] 1 shows, in various schematic views, intermediate states achieved during the manufacture of a shrink cap according to the invention. The shrink cap as a whole is designated by the reference numeral 10.

[0063] The shrink cap 10 is used in particular to receive a temperature-dependent switch 12, the outer connection 14 of which is shown here in simplified form as a twisted wire. Such temperature-dependent switches 12 are used to monitor electrical devices. In particular, they are used for this purpose to de-energize the electrical device to be monitored in the event of overheating. Here, the switch 12 is usually installed inside the switch housing and comprises a temperature-dependent switching mechanism consisting of a bimetallic part. This bimetallic part changes its shape when a response temperature is exceeded, whereby the switching mechanism is moved from its closed position to its open position. The electrical circuit in which the switch 12 is installed is then opened. If the device to be monitored is then cooled again below the so-called reset temperature of the bimetallic part, this in turn snaps back into its initial position, whereby the switch is returned to its closed position. In this way, the temperature-dependent switching behavior of the switch 12 is realized.

[0064] The shrink cap 10 according to the present invention functions, among other things, to provide external protection and electrical shielding for the switch 12. The shrink cap 10 is placed over, attached to, or shrunk onto the switch 12 so that, in the final state, the shrink cap 10 surrounds the switch 12 on all sides.

[0065] However, it is understood that the shrink cap 10 according to the invention is in principle also suitable for receiving other devices and is not limited to receiving a temperature dependent switch as shown in the present case.

[0066] Shrink cap 10, the cross section of which is shown at 16, has a first end 18 slid onto switch 12 and then shrunk onto switch 12 using hot air so that only outer connection portion 14 protrudes from the sheath thus formed. First end 18 is thus configured as an open end including a first opening 19.

[0067] A second end 20 of the shrink cap 10 opposite the first end 18 is closed. Here, the shrink cap 10 comprises a welded or embossed seam 22 provided in the region of the second end 20. By means of this welded or embossed seam 22, the shrink cap 10 is completely closed in the region of its second end 20. Due to the welded or embossed seam 22, the shrink cap 10 comprises, in the region of its second end 20, a closed end surface 24, which adjoins the welded or embossed seam 22.

[0068] Due to the manufacturing process, the welded or embossed seam 22 is configured as a fold or edge that projects straight out from the end surface 24 of the shrink cap 10. This fold or edge is relatively rigid or inflexible and has a relatively sharp edge 28 at its front free end 26.

[0069] FIG. 1 shows the state of the shrink cap 10 after the welded or embossed seam 22 has been created (before the welded or embossed seam 22 has been formed). In this state, the shrink cap 10 is substantially mirror symmetrical with respect to a first plane of symmetry 30 in the region between the first end 18 and the second end 20. Preferably, the shrink cap 10 is substantially mirror symmetrical with respect to this first plane of symmetry 30, except for the welded or embossed seam 22. The term "substantially mirror symmetrical" is used in this case to indicate that in practice there is no absolutely exact mirror symmetry. However, in principle this mirror symmetry exists and slight deviations that occur in practice due to the manufacturing process, which are usually in the range of millimeters or tenths, can be neglected.

[0070] However, the shrink cap 10 is not substantially mirror symmetrical overall with respect to the first plane of symmetry 30. The welded or embossed seam 22 is disposed offset parallel to this first plane of symmetry 30. More specifically, in the state shown in FIG. 1, the welded or embossed seam 22 is substantially mirror symmetrical with respect to a second plane of symmetry 70 that is parallel to and spaced apart from the first plane of symmetry 30.

[0071] In other words, the welded or embossed seam 22 is not created in the center of the shrink cap 10 but is offset in height relative to the plane of symmetry 30 .

[0072] The right side of FIG. 1 shows a top view of the shrink cap 10 from the front through the first opening 19. Here, the welded or embossed seam 22 can be seen as an offset line parallel to the first plane of symmetry 30. This line is formed by a joining surface 68 along which the two longitudinal halves of the heat shrink tubing that are pressed together and joined are joined when the welded or embossed seam 22 is produced. This joining surface 68 extends parallel to the first plane of symmetry 30 when the welded or embossed seam 22 is produced. The joining surface 68 lies in a second plane of symmetry 70 with respect to which the welded or embossed seam 22 is substantially mirror symmetric and parallel to the first plane of symmetry 30.

[0073] The free front edge 28 of the face side of the welded or embossed seam 22 is curved in the shape of a circular arc when viewed from above (see the upper center part of FIG. 1 ). This is due to the manufacturing process, since, as will be explained in more detail below, the shrink cap 10 is produced by pressing together in the region of its second end 20 and then welding or embossing the initially still open end (opening 21) of a cylindrical shrink tube to produce the welded or embossed seam 22.

[0074] At 16, the shrink cap 10 is illustrated as being oval or elliptical in cross section. However, the shrink cap 10 may be approximately circular when viewed in cross section. The starting material used for the shrink cap 10 in the form of heat shrink tubing is typically circular or round in cross section, i.e., generally cylindrical.

[0075] The end surface 24 of the shrink cap 10 resulting from the welded or embossed seam 22 is configured to be convex, as can be seen particularly from the top view from above the center top of FIG. 1 and the side view from the bottom of FIG. 1. It is understood that the shape of the end surface 24 shown here is shown diagrammatically. In reality, this end surface 24 is usually convexly curved, but typically not exactly round or regular as shown in this figure. However, as mentioned above, the manufacturing process results in an arc-like rounding or curvature of the end surface 24. Depending on the shape of the switch 12 onto which the shrink cap 10 is to be shrunk, the end surface 24 may also be angled or substantially flat, and the welded or embossed seam 22 may extend along a straight line. However, a round or curved welded or embossed seam 22 is advantageous for receiving a switch 12 that is mostly round.

[0076] If the shrink cap is used in the condition shown in FIG. 1 and not further treated, there is a relatively high risk of damaging the component of the machine in which the temperature dependent switch 12 is installed together with the shrink cap 10 due to the relatively sharp edges 28 at the end faces 26 of the welded or embossed seam 22.

[0077] Thus, according to the invention, the shrink cap 10 is further processed starting from the intermediate state shown in FIG. 1. Here, the welded or embossed seam 22 can be formed such that at least a formed portion 32 of the welded or embossed seam 22 is in contact with the end face 24 of the shrink cap 10. In other words, the welded or embossed seam 22 can be bent by about 90° or slightly more and placed at least in part against the end face 24. The formed portion 32 of the welded or embossed seam 22 placed against the end face 24 of the shrink cap 10 can be placed against the end face 24 directly or indirectly by means of an intervening bonding agent. In principle, support against the end face 24 is advantageous, but is not necessarily required according to the invention. For example, the welded or embossed seam 22 can also be bent by 90° without being applied to the end face 24 of the shrink cap 10 (i.e. without being in contact with the end face 24 of the shrink cap 10).

[0078] Starting from the intermediate state shown in Figure 1, the welded or embossed seam 22 is bent by 90° and partially or completely affixed to the end surface 24, and the sharp edges of the welded or embossed seam 22 no longer protrude laterally or downwardly from the shrink cap 10 due to the upwardly offset welded or embossed seam 22 (see Figures 5A and 5B). Furthermore, no further reworking, such as shortening of the welded or embossed seam, is necessary. The risk of injury or damage is minimized.

[0079] In Figures 2A, 2B, 3A and 3B two different embodiments of the shrink cap 10 according to the invention are shown in their final state. Figures 2A and 3A show the shrink cap 10 in a side view. Figures 2B and 3B respectively show the shrink cap 10 in a longitudinal cross section. The cross sections are in each case perpendicular to a first plane of symmetry 30, which is shown in dashed line in Figure 1.

[0080] In the first embodiment shown in Fig. 2A and 2B, the welded or embossed seam 22 is folded over and partially glued to the end face 24 of the shrink cap 10. In the region of the end 34 of the welded or embossed seam 22 adjacent to the end face 24, a smaller bead can be created by folding back the welded or embossed seam 22, which protrudes slightly forward from the end face 24. Overall, however, the effective length of the shrink cap 10 is significantly shortened by the folded arrangement of the welded or embossed seam 22 against the end face 24. Furthermore, the sharp edge 28 of the welded or embossed seam 22 no longer protrudes from the front of the shrink cap 10. The risk of injury and damage is therefore significantly reduced. Moreover, in the region of the folded over welded or embossed seam 22, the welded or embossed seam 22 forms, so to speak, an additional layer in this portion 32, which increases the wall thickness and therefore also the high voltage resistance of the shrink cap.

[0081] In the second embodiment shown in Figures 3A and 3B, the welded or embossed seam 22 is applied almost completely or at least partially to the end face 24 of the shrink cap to a greater extent than according to the second embodiment (see Figures 2A and 2B). Preferably, the welded or embossed seam 22 is pressed against the end face 24. This preferably results in a seamless and essentially wrinkle-free welded or embossed seam 22 that is applied to the end face 24 of the shrink cap 10. The formation of the above-mentioned type of welded or embossed seam 22 is preferably carried out under the influence of heat, as will be explained in more detail below.

[0082] Depending on the intended application, the portion 32 of the welded or embossed seam 22 that is affixed to the end surface 24 is preferably either loosely affixed to the end surface or connected to the end surface by an additional welding or bonding process.

[0083] Particularly preferably, the formed portion 32 of the welded or embossed seam 22 according to the second embodiment shown in Figures 3A and 3B has at least a majority (i.e., 50% or more of its area) of the bottom surface 36 folded over the end surface 24 positioned in contact with the end surface 24.

[0084] In principle, however, the welded or embossed seam 22 does not necessarily have to contact the end face 24 and can be bent downwards by 90° or less than 90° without touching the end face 24 .

[0085] The end 34 of the welded or embossed seam 22 adjacent to the end face 24 is preferably offset from the first plane of symmetry 30 by at least 1 / 10 of the height h1, more preferably by at least 1 / 5 of the height h1, and particularly preferably by more than 1 / 3 of the height h. Said height h1 means the dimension of the shrink cap 10 measured perpendicularly to the first plane of symmetry 30 in the region of the first end 18. In FIG. 1, said offset is indicated by the symbol x.

[0086] FIG. 4 illustrates generally how the shrink cap 10 according to the present invention may be manufactured from heat shrink tubing 38.

[0087] First, short heat shrink tubing sections 40 having open ends 18, 20, each end including an opening 19, 21, are cut from the heat shrink tubing 38. These heat shrink tubing sections 40 are then slid, one after the other, onto a profile 42 placed on a turntable 44.

[0088] After being pressed onto the profile 42, the turntable 44 is rotated 90° in the direction indicated by the arrow 46 in FIG. 4 (here clockwise) so that each heat shrink tubing segment 40 reaches a welding position 48.

[0089] At the welding position 48, the heat shrink tubing section 40 is heated and preformed by hot air, indicated at 50, and two welding punches 52 simultaneously act on the second end 20 of the heat shrink tubing section 40, thereby closing the second opening 21 in the heat shrink tubing section 40 and creating the welded or embossed seam 22.

[0090] One of these two welding stamps 52 is shown diagrammatically in Figure 4. Also shown at 54 is the position where the welding stamp 52 engages the heat shrink tubing section 40. Generally, the welding stamp 52 comes from above and below, thereby pressing the ends of the heat shrink tubing together, and the welded or embossed seam 22, as shown in Figure 1 or Figure 4, is produced by heating.

[0091] The shrink cap 10 now has the intermediate state shown in FIG.

[0092] Now, the turntable 44 is rotated another 90° in the direction of the arrow 46 so that the shrink cap 10 reaches a forming position 56. Here, the welded or embossed seam 22 is preferably heated again by hot air 58 to facilitate its formation. At the same time, a forming or pressing punch 60 is pressed forward against the welded or embossed seam 22 to bend the seam 22 and, if desired, affix or press the seam 22 to the end surface 24 of the shrink cap 10.

[0093] A forming or pressing punch 60 is shown diagrammatically on the right hand side of FIG. 6 in both a top view and a side view, the side view being equipped with a heater 62 which can be used instead of hot air 58 to heat the welded or embossed seam 22 with high precision before or during forming.

[0094] The forming or press punch 60 preferably includes a forming area 64 having arcuate flanks to conform to the curvature of the end face 24 of the shrink cap 10 .

[0095] As already mentioned, the welded or embossed seam 22 may be additionally connected to the end surface 24 during this manufacturing process, i.e., additionally welded or glued.

[0096] Finally, the turntable 44 again rotates 90° in the direction of the arrow 46, so that the finished shrink cap 10 reaches an ejection position 66 where it is ejected, for example by compressed air. The shrink cap 10 thus produced can be stored as bulk material until it is used, for example to house a temperature dependent switch.

[0097] It will be appreciated that the present drawings merely illustrate the shrink cap 10 and its manufacture in a schematic manner, and that various further geometric or manufacturing modifications may be made without departing from the scope of the invention as defined by the appended claims.

Claims

1. A shrink cap (10) configured to receive a temperature dependent switch (12) and having an open first end (18) and a second end (20) closed by a welded or embossed seam (22) extending from a closed end surface (24), the closed end surface results from a welded or embossed seam (22), and the shrink cap (10) is substantially mirror symmetrical about a first plane of symmetry (30) in a region between the first end (18) and the end surface (24); A shrink cap, characterized in that an end (34) of the welded or embossed seam (22) adjacent the end face (24) is disposed offset parallel to the first plane of symmetry (30).

2. 2. The shrink cap of claim 1, wherein an interface surface (68) of the welded or embossed seam (22) at an end (34) of the welded or embossed seam (22) adjacent the end surface is offset parallel to the first plane of symmetry (30).

3. 3. The shrink cap of claim 2, wherein the mating surface (68) on the inside of the shrink cap (10) defines a boundary line that is curved in an arc.

4. 2. The shrink cap of claim 1, wherein the end face (24) has a height (h1) measured perpendicular to the first plane of symmetry (30), and the welded or embossed seam (22) is disposed at an end (34) adjacent the end face (24) and offset in parallel to the first plane of symmetry (30) by at least 1 / 10 of the height (h1).

5. 5. The shrink cap of claim 4, wherein a height (h2) of the welded or embossed seam (22), measured perpendicular to the first plane of symmetry (30), from an end (34) of the welded or embossed seam (22) adjacent the end face (24) to a free end (26) of the welded or embossed seam (22) is greater than half the height (h1) of the end face (24).

6. 2. The shrink cap of claim 1, wherein the welded or embossed seam (22) is formed such that a formed portion (32) of the welded or embossed seam (22) abuts the end surface (24) directly or with a bonding agent interposed between the welded or embossed seam (22) and the end surface (24).

7. 7. The shrink cap of claim 6, wherein a free end (26) of the welded or embossed seam (22) does not protrude laterally from the shrink cap (10) in a direction perpendicular to the first plane of symmetry (30).

8. 7. The shrink cap of claim 6, wherein the welded or embossed seam (22) has a free end (26), and the formed portion (32) of the welded or embossed seam (22) abuts the end face (24) directly or with an intervening bonding agent and extends over the area between the free end (26) and the end (34) adjacent the end face (24).

9. 7. The shrink cap of claim 6, wherein more than 50% of the area of ​​one side (36) of the welded or embossed seam (22) that abuts the end face (24) abuts the end face (24) directly or with an intervening adhesive, or the welded or embossed seam (22) completely abuts the end face (24) either directly or with an intervening adhesive.

10. The shrink cap of claim 6, wherein the formed portion (32) of the welded or embossed seam (22) is pressed against the end surface (24).

11. The shrink cap of claim 6, wherein the formed portion (32) of the welded or embossed seam (22) is secured to the end surface (24) in a material-locking manner.

12. 2. The shrink cap of claim 1, wherein said end surface (24) is convexly curved.

13. 7. The shrink cap of claim 6, wherein the end surface (24) is convexly curved and the shaped portion (32) of the welded or embossed seam (22) extends parallel to the convexly curved end surface (24).

14. A temperature dependent switch comprising a shrink cap according to any one of claims 1 to 13.

15. A method of manufacturing a shrink cap (10), comprising the steps of: a) providing a heat shrink tubing section (40) having a first opening (19) at a first end (18) and a second opening (21) at a second end (20), the heat shrink tubing section (40) being substantially mirror symmetric about a first plane of symmetry (30); b) pressing the heat shrink tubing portions (40) together at the second ends (20) to create a welded or embossed seam (22) closing the second opening (21) and creating a closed end face (24) in the region of the second ends (20), the welded or embossed seam (22) being created offset parallel to the first plane of symmetry (30); c) A method of manufacturing a shrink cap (10) comprising forming a portion (32) in the welded or embossed seam (22), and bending the portion (32) of the welded or embossed seam (22).

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