Heat-shrink crimping device and method

Abstract: In order to establish a low-electrical resistance between two wires (14, 15), a heat-shrinkable hollow tube (11) is prepared. Three or more small-diameter conductors (12.1-12.4) are attached to the inner surface of the hollow tube, such as by means of an epoxy adhesive. These conductors run parallel to the axis of the tube along its entire length (L). Each of the two wires is inserted into an opposite end of the tube. The tube is then heated to a sufficient temperature, such that when it cools it collapses and grasps both of the wires firmly, whereby the resulting electrical conductance between them (aided by the conductors) is enhanced.

Description: Field of Invention This invention relates to devices using heat-shrinkable tubes for establishing low-electrical-resistance connections between wires, and to methods for establishing such connections. Background of Invention In order to establish low electrical-resistance connections (i.e., good electrical connection, high electrical conductance) between wires, the prior art has taught a variety of devices and methods. For example, one well-known method involves using a crimping tool for mechanically crimping together a pair of wires at room temperature . This method, however, is difficult to perform in an environment where physical access to the wires with the crimping tool is not easy, such as in tight spaces ("close quarters") of relatively small electronic devices. For another example, soldering the wires together requires heating them while their ends are overlapping each other. This heating typically requires a temperature of at least approximately 182°C (= 360°F). Such a temperature can damage not only devices to which the wires are already connected at their other ends (because of the thermal conductance of the wires) but also devices that are present nearby. G.B.-A-1134240 discloses a method of establishing a low electrical resistance connection as defined in the preamble of claim 1. Therefore, it would be desirable to have a device and a method for connecting a pair of wires together that mitigates some or all of the problems of prior art. Summary Of Invention The inventive method is set forth in claim 1. Preferred forms of the method are set forth in claims 2-4. The inventive device is defined in claim 5. An embodiment of the inventive device is set forth in claim 6. Brief Description Of the Drawing FIG. 1 shows a perspective view of a heat-shrink crimping device for connecting a pair of wires together, in accordance with a specific embodiment of the invention; and FIG. 2 shows a perspective view, partly cut away and partly in cross section, of a pair of wires that have been connected together in the device shown in FIG 1, in accordance with a specific embodiment of the invention. Only for the sake of clarity none of the drawings is to any scale. Detailed Description Turning to FIG. 1, a heat-shrink crimping device 10 includes a hollow tube 11 in the form of a hollow circular cylinder made of a heat-shrinkable material. The tube 11 need not be circular, but can be elliptical, oval, square, rectangular, or other shapes -- or it can have different ones of these shapes at various locations along the length L of the device 10. In other words, any long hollow tube of heat shrinkable material will do for the tube 11. At any rate, the tube 11 has an inner surface 11.1. Four exemplary conductors 12.1, 12.2, 12.3, and 12.4 (hereinafter, "12.1 - 12.4") are attached to this inner surface 11.1 of the hollow tube 11. The cross section of each of the conductors 12.1 - 12.4 typically is a solid circular cylinder. Typically an epoxy adhesive is used for this attachment purpose: the epoxy is applied to the inner surface 11.1 and is partially set to a tacky state, and the conductors 12.1 - 12.4 are inserted into the tube 11 and are adhered to its inner surface 11.I. Alternatively, the attachment is achieved by heating either the conductors 12.1 - 12.4 or the hollow tube 11, or both, to a temperature sufficient for direct adherence of the conductors 12.1 - 12.4 to the heat-shrinkable material of the inner surface 11.1 of the hollow tube 11 while the conductors 12.1 - 12.4 are contacting the inner surface 11.1 of the tube 11 and are being held in place by a metal or ceramic mandrel. Advantageously each of these four conductors runs substantially parallel to the axis of the hollow tube 11. Also, each of the conductors 12.1 - 12.4 typically runs along the entire length L of the tube 11. Wires 13 and 14 (FIG. 2) are to be joined together after their being inserted into opposite open ends of the tube 11, as described in greater detail below. Advantageously each of the four conductors 12.1, 12.2, 12.3, and 12.4 is made of copper, tin, or gold. The diameter of each of these conductors 12.1 - 12.4 advantageously is less than approximately one-third the inner diameter of the hollow tube 11 (i.e., the diameter of the inner surface 11.1). Thus there is at least enough empty space between opposing conductor pairs -- namely between opposing conductor pair 12.1 and 12.3, and between conductor pair 12.2 and 12.4 -- for the insertion therein of the wires 13 and 14. In order to enable the wires 13 and 14 to have a low-resistance connection, they are inserted into opposite open ends of the tube 11 with the (near) end surfaces 13.5 and 14.5 of these wires 13 and 14 , respectively, either in close proximity with each other (FIG. 2), abutting each other (not shown), or overlapping each other (not shown). After insertion of the wires 13 and 14 into the tube 11 as aforementioned, the tube 11 is heated to a temperature T sufficient to cause the heat-shrink material of this tube 11 to shrink after cooling to such an extent that after cooling the heat-shrink material forces the conductors 12.1, 12.2, 12.3, and 12.4 to collapse and thus to grasp the wires 13 and 14. Advantageously the grasping is with sufficient compressive force to enable the conductors to break through at least some of any insulating material that may be present on the surfaces of the wires 13 and 14. In this way, a low-electrical-resistance connection is established between the wires 13 and 14 via the conductors 12.1, 12.2, 12.3, and 12.4. It is enough, of course, that both of the wires 13 and 14 establish low-resistance connections with only one, but each with the same one, of these conductors. For example, the heat-shrink material of the tube 11 is essentially a Teflon- or a vinyl-based material, and the temperature T is approximately 66°C(=150°F). Although the invention has been described in detail in terms of a specific embodiment, various modifications can be made without departing from the scope of the invention. Prior to inserting the wires 13 and 14 into the tube 11, the length of this tube together with the conductors 12.1- 12.4 can be considerably longer than the length L, typically at least approximately three times as long as L, and the tube together with the conductors can be cut into one or more pieces, each having a length approximately equal to L, when it is decided how long a length L is desired for each of the piece(s) to accommodate the demands of the task(s) at hand. Also, instead of four conductors 12.1, 12.2, 12.3, 12.4, there can be more than four or as few as one, but preferably at least three. One or both of the wires 13, 14 can be coated with an insulator layer (not shown) in regions outside the tube 11. Also, the two wires can be inserted into one and the same end of the tube. In such a case, the other end of the heat-shrinkable tube advantageously is closed, instead of being open, and contains an electrically conductive metallic plug at the closed end At least three (parallel) conductors extend over a separate peripheral portion of the plug. Thereby each of the conductors spaces apart a separate peripheral portion of the plug from a separate portion of the inner cylindrical surface of the hollow tube at its closed end. In this way, each of the conductors contacts at least one of the wires and connect the two wires together via the plug, thereby providing a lower resistance connection between the two wires via these conductors and the plug.

Claims: A method of establishing a low electrical resistance connection between first and second wires (13,14) by providing a heat-shrinkable hollow tube (11), the hollow tube (11) having a length L and at least one open end and an axis, and containing at least one conductor (12.1) extending parallel to the axis, inserting the first wire (13) into the at least one open end and the second wire (14) into the at least one open end or into another open end of the tube, heating the heat-shrinkable hollow tube to a sufficiently high temperature whereby, upon cooling, the inner diameter of the tube is reduced and the tube forces the at least one conductor to grasp the two wires (13, 14) firmly, wherein establishing the connection is characterized in the step of, attaching the at least one conductor (12.1) to the inner surface of the hollow tube (11) along the entire length L of the tube. The method of claim 1, characterized in that prior to the step of inserting the wires into the at least one open end, the following steps are performed: providing a long heat-shrinkable hollow tube (11) having at least one conductor (12.1) extending parallel to the axis, the length of the long hollow tube and the at least one conductor being at least 3L; and cutting the long heat-shrinkable tube into a desired length L. The method of claim 1 in which at least three conductors (12.1, 12.2, 12.3) are attached to the inner surface of the hollow tube (11), said at least three conductors running parallel to the axis of the hollow tube. The method of claim 1, whereby at least three conductors (12.1, 12.2, 12.3) are provided extending parallel to the axis of the hollow tube (11), the second wire (14) is inserted into the at least one open end and an opposite end of the hollow tube is closed, an electrically conducting plug is provided at the closed end, the electrically conducting plug being connected to the at least three conductors (12.1, 12.2, 12.3) so that the two wires (13, 14) are connected together via the electrically conducting plug even if each conductor only contacts one of the wires. A device for establishing a low electrical resistance connection between two wires (13, 14) comprising a heat-shrinkable hollow tube (11), the tube having at least one open end and an axis, and at least one conductor (12.1) attached to the inner surface of the tube and running parallel to the axis, characterized in that , the at least one conductor (12.1) runs along the entire length L of the hollow tube. The device of claim 5 characterized in that the tube (11) has a closed end and only one open end, and that it contains an electrically conducting plug at the closed end and at least three conductors (12.1, 12.2, 12.3), each of the conductors being attached to the inner surface of the tube and extending to and spacing apart a separate peripheral portion of the plug from the inner surface of the hollow tube, each of the three conductors running along the entire length L of the tube parallel to the axis of the tube and electrically connected to the electrically conducting plug so that the two wires are connected together via the electrically conducting plug even if each conductor only contacts one of the wires.

Inventors: BLONDER GREG E, BLONDER, GREG E.
Applicants: AT & T CORP, AT&T CORP.
Application year: 1995
Main classification: H01R4
IPC codes: H01R4, H01R43