Processing the end of a wound resistance wire

Abstract

 Upper and lower portions of an exposed portion 37 at an end portion of a wound resistance wire 36 are heated and compressed, thereby embedding a resistance wire element into both upper and lower portions of a core 30.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] This invention relates to a method for processing an end of a wound resistance wire. The wire comprises a resistance wire element wound onto a core of a thermoplastic resin. An insulating member covers an outer periphery of the wire element. A wound resistance wire can be used, for example, in the wiring of an ignition plug system in a vehicle.

[0002] A wound resistance wire can be produced by winding a resistance wire element onto a core of a thermoplastic resin such as a fluoro rubber. An insulating member is then extruded onto an outer periphery of the wire element-wound core.

2. Description of Related Art

[0003] The end of a wound resistance wire can be processed by an end processing apparatus as shown in Fig. 6. In Fig. 6, the end processing apparatus comprises a cutting section 10 for cutting a continuously-fed wound resistance wire 15 into a predetermined length, a stripping section 11 for removing an insulating member from opposite ends of a cut length of wound resistance wire 15, thereby forming exposed portions each defined by a core having a resistance wire element wound thereon, a heating/compressing section 12 for heating and compressing each exposed portion, a dag coating section 13 for coating the thus heated and compressed, exposed portions with dag, and a dag drying section 14 for drying the dag coated onto the exposed portions. Cutting by section 10 and stripping by section 11 are effected by conventional techniques.

[0004] Heating/compressing section 12 is similar to that disclosed in Japanese Patent Unexamined Publication No. 3-70416 filed by the Applicant of the present application. As shown in Figure 7, section 12 comprises a lower die 17 fixed at a predetermined position, and an upper die 18 vertically movable between an upper position indicated by a solid line and a lower position indicated by a broken line (see Fig. 7). The upper die 18 contains a heater (not shown) for heating upper die 18. When upper die 18 is held in its upper position, an end portion of the exposed portion 19 of wound resistance wire 15 is placed on the upper surface of the lower die 17. Then the upper die 18 moves downward to its lower position to compress only an upper portion of a distal end portion of the exposed portion 19 in the vertical direction. At the same time, exposed portion 19 is heated by die 18. As a result, the distal end portion of the exposed portion of resistance wire element 20 is embedded into core 21 of thermoplastic resin so as to tightly wrap the core to prevent loosening of the wire element 20 as shown in Fig. 8.

[0005] Exposed portion 19 is compressed in the vertical direction by the upper and lower dies 18 and 17. Heating is effected only by upper die 18. As a result, resistance wire element 20, pressed by the upper die 18, is embedded deeply into the upper side of the core 21. However, resistance wire element 20 is not embedded as deeply into the lower side of the core 21. As a result, the resistance wire element 20 can become loosened at the lower side. A dag 23 of an electrically-conductive carbon coating must be applied to assure that element 20 is tightly wrapped to prevent loosening at the lower side of core 21. The electrically-conductive carbon coating of the dag is coated onto exposed portion 19 as shown in Fig. 9. A blast of hot air is blown onto the coated dag 23 to dry the same as shown in Fig. 10 to prevent loosening of resistance wire element 20.

SUMMARY OF THE INVENTION

[0006] The method of processing described above with reference to Figures 6-10, requires a coating dag 23. The steps of coating and drying dag 23 make the process complicated and increase the cost of processing apparatus.

[0007] It is an object of the present invention to provide a simple method of processing an end of a wound resistance wire to prevent loosening of the resistance wire element.

[0008] The present invention provides a method of processing an end of a wound resistance wire comprising a resistance wire element wound on a core of a thermoplastic resin, and an insulating member covering an outer periphery of the wire element-wound core. The method comprises the steps of: removing insulating member from an end portion of the wound resistance wire, thereby forming an exposed portion comprising an exposed core portion having a wound resistance wire element; and heating and compressing both upper and lower portions of the exposed core portion to embed wound resistance wire element into both upper and lower portions.

[0009] In the above method of processing, both upper and lower portions of the exposed portion are heated and compressed. The core is thermoplastically deformed at upper and lower sides of the exposed portion so that the resistance wire element is embedded in both the upper and lower sides of the core.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] 

Fig. 1 is a perspective view of a wound resistance wire;

Fig. 2 is a schematic plan view showing one preferred embodiment of an end processing apparatus of the invention;

Fig. 3 is a front-elevational view showing a heating/compressing portion of the end processing apparatus;

Fig. 4 is an enlarged, plan view of a portion of an opposite-side heating/compressing portion;

Fig. 5 is a cross-sectional view showing a contact portion of the wound resistance wire, heated and compressed by the opposite-side heating/compressing portion;

Fig. 6 is a schematic plan view showing a conventional end processing apparatus;

Fig. 7 is a front-elevational view showing a heating/compressing portion of the conventional apparatus;

Fig. 8 is a cross-sectional view showing a contact portion of a wound resistance wire heated and compressed by the heating/compressing portion of the conventional apparatus;

Fig. 9 is a view showing a dag coating portion of the conventional apparatus; and

Fig. 10 is a view showing a dag drying portion of the conventional apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0011] One preferred embodiment of an end processing apparatus for performing a method of the invention is described with reference to Figures 1-5 of the drawings.

[0012] As shown in Fig. 1, the wound resistance wire 36 includes a resistance wire element 31 wound on a core 30 made of a fluoro rubber containing ferrite. An insulating member 32 is extruded onto an outer periphery of the wire element-wound core 30.

[0013] As shown in Fig. 2, the end processing apparatus for processing the wound resistance wire comprises a cutting section 33, a stripping section 34, and an opposite-side heating/compressing section 35, which are arranged in this order or sequence from an upstream side (that is, from an upper side) in Fig. 2. Cutting section 33 and stripping section 34 are of conventional construction. The resistance wire 36 is continuously fed from the left. The wire 36 is cut into a predetermined length by the cutting section 33. A cut length of wound resistance wire 36 is transferred to stripping section 34 where part of insulating member 32 is removed from opposite end portions of the cut portion to form exposed portions 37 each defined by core 30 having resistance wire element 31 wound thereon (see Fig. 1).

[0014] Thereafter, the length of wound resistance wire 36 is transferred to opposite-side heating/compressing section 35 where upper and lower portions of each exposed portion 37 are heated and compressed.

[0015] As shown in Fig. 3, opposite-side heating/compressing section 35 comprises a cylinder 42 mounted on an upper portion of an upper base 41, an upper die 44, which is mounted on a distal end of a piston rod 43 of the cylinder 42, and containing a heater (not shown), a lower die 47, which is mounted through a heat-insulating member 46 on a lower die base 45 provided generally centrally of the height of the upper base 41, and containing a heater (not shown), and a temperature control section 48 for controlling the temperature of the heaters contained respectively in the upper and lower dies 44 and 47.

[0016] Upper die 44 is moved upwardly and downwardly by cylinder 42 by means of piston rod 43 between an upper position (indicated by a solid line in Fig. 4) above the lower die base 45 and a lower position (indicated by a broken line in Fig. 4) close to the lower die base 45. When upper die 44 is in an upper position, each exposed portion 37 of the wound resistance wire 36 is placed on lower die 47, and upper die 44 is moved to its lower position. As a result, a distal end portion of exposed portion 37 is heated and compressed by the lower surface of upper die 44 and the upper surface of the lower die 47, so that resistance wire element 31 is embedded into both upper and lower sides of core 30, thus forming a compressed portion 37b.

[0017] Resistance wire element 31 at each exposed portion 37 is embedded onto both upper and lower sides of core 30. Resistance wire element 31 cannot become loosened. Further, no dag coat is required to prevent loosening as is required with wire ends produced by a conventional method such as shown in Figures 6-10. Therefore, end processing according to the invention can be carried out by the use of a simply constructed apparatus.

[0018] Core 30 is shown as made of fluoro rubber containing ferrite. However, core 30 may be any other suitable thermoplastic resin such as chlorinated polyethylene, polyolefin resin, ethylene-propylene-diene terpolymer or silicone rubber. Temperature of upper die 44 and lower die 47, as well as thickness of the compressed portion 37b, can be changed in accordance with the material used for core 30 and with the diameter of the core. In the embodiment shown, core 30 is composed of fluoro rubber containing ferrite. When the core diameter is 1.3 mm, temperature of the upper and lower dies 44 and 47 is set to 120°C, and thickness of the compressed portion 37b is set to 0.5-0.7 mm. When the diameter of the core 30 is 1.1 mm, the temperature of the two dies is set to 80°, and the thickness of the compressed portion 37b is set to 0.5∼0.7 mm.

[0019] Resistance wire element 31 is wound on that portion of the exposed portion 37 extending from its lengthwise central portion to its proximal end. Only the distal end portion of exposed portion 37 needs to be heated and compressed as shown for resistance wire element 31 to make electrical contact when a terminal is clamped to the end portion of the wire.

[0020] As described above, upper and lower portions of the exposed portion are heated and compressed, and therefore the resistance wire element is embedded into the upper and lower sides of the core, thereby effectively preventing loosening of the resistance wire element. The conventional step of coating dag can be omitted. Resistance wire element loosening is prevented solely by the simple end processing method of the invention.

Claims

1. A method for processing an end of a wound resistance wire comprising:

removing an insulating member portion from an end of a wound resistance wire, thereby forming an exposed portion comprising an exposed core portion having a wound resistance wire element; and

heating and compressing both upper and lower portions of the exposed core portion to embed wound resistance wire element into both upper and lower portions.

2. The process of claim 1, wherein said wound resistance wire is cut into a length with two end portions and insulating member portions are removed from both end portions of the cut portions to form exposed end portions each defined by an exposed core portion defined by wound resistant wire portions.

3. The method of claim 1, wherein said heating and compressing step comprises transferring said wound resistance wire to an opposite-side heating/compressing section of an end processing apparatus where upper and lower portions of each exposed portion are heated and compressed.

4. An end processing apparatus for processing a wound resistance wire, comprising: a cutting section, a stripping section and an opposite side heating/compressing section, wherein the opposite-side heating/compressing section comprises an upper heatable die and a lower heatable die.

5. The apparatus of claim 4, wherein said opposite-side heating/compressing section comprises a cylinder mounted on an upper portion of a base, said upper die mounted on a distal end of a piston rod of said cylinder and said lower die mounted through a heat-insulating member on a lower die base.

6. The apparatus of claim 4, wherein the opposite-side heat/compressing section additionally comprises a temperature control section for controlling temperature of said upper and lower dies.

Drawing