A CONNECTOR CLIP FOR MAGNET WIRE

Abstract: A connector clip (10) having a crimp section (15) whose wire-engaging surface (20, 21) is serrated to bite through the insulation on magnet wire.

Description: A Connector Clip for Magnet Wire This invention relates to a connector clip, and more particularly, to a connector clip to be connected to magnet wire. Magnet wire is single strand wire that is stiff and is coated with an insulative material. Its principal use is in windings for motors, magnets and the like wherein it is desirable to compact as many wire turns as possible in a small space. As a conse¬ quence, the wire is insulated with a varnish that enables strands to be wound upon strands while- main¬ taining an insulative barrier between adjacent strands. The clips to be connected to such wire have a receptacle that is to be forced upon a pin to provide electrical contact and a ferrule that clamps about the wire. The ferrule normally has two sections: a crimp section adjacent the receptacle that is to clamp upon the wire and make electrical connection with respect to it, and a clamp for the insulation surrounding the wire. These clips may be mounted in a cluster assembly wherein three equiangularly-spaced clips are mounted in a cluster block, the clips being connected directly to the magnet wire from a motor used in a hermetically-sealed compressor. The problem presented by the magnet wire and clip combination has been the making of good electrical contact between the clip and the magnet wire. A conventional wire-engaging clamp, when clamped upon magnet wire, remains insulated for failure to penetrate the insulative coating. One solution to the problem has been to provide apparatus for applying to the wire an insulative sleeve and using a laser beam to cut that insulative sleeve. The laser beam is also used to burn off the insulation at the end of the wire. That apparatus is expensive and does not always work reliably. An objective of the present invention has been to provide a clip having a crimp section that makes good electrical contact with the magnet wire when it is clamped onto the wire in a conventional way. The objective of the invention is attained by providing, on the wire-engaging surface of the crimp section, a series of transverse serrations or alternating ribs and grooves. The ribs penetrate the insulation when the crimp section is applied to a magnet wire and thus provide electrical contact as well as a good grip on the wire. It has been found that the ribs must have side walls lying at an angle of about 20° to a trans¬ verse plane perpendicular to the crimp section. When the ribs and hence the grooves are so configurated, a desired slicing action on the insulation and copper wire occurs such that the top of the rib strips off and drives insulation below the original surface of the wire. The penetration of the rib, carrying with it that portion of insulation, bares a portion of the wire and the side wall of the rib lies against it in intimate electrical contact. Another feature of the invention resides in making the grooves adjacent the receptacle deeper than the grooves at the other end of the crimp section with the depth of the grooves gradually becoming more shallow as the grooves become more remote from the receptacle. This tapering of the groove depth permits the deeper grooved section to penetrate deeply into the wire to form the best electrical contact. That deep penetration, however, would tend to weaken the wire if applied uniformly so that the wire might not stay attached to the clip. The shallower grooves, remote from the receptacle, provide less contact by a less damaging grip to the wire so that the wire is securely held to the clip by the shallower section. In the forming of the crimp section, burrs are inevitably left on the corners of the ribs. Normally, such burrs would be cleaned away but, in accordance with the present invention, it has been found that those burrs improve the insulation stripping function of the ribs to provide good electrical contact. Finally, at least the crimp section of the clip is plated with tin to a thickness in the range of 0.0001 inch - 0.0003 inch. It has been found that this post-plating, although an expensive operation, has been necessary in order to obtain a satisfactorily consistent millivolt drop across the connection. It is believed that the plating not only protects against the oxidation of the phosphor bronze from which the clips are formed, but additionally assists in the formation of a mechanical bond which is free of oxygen and permits a tin migration to form a chemical bond as well as the mechanical bond. The several objectives and features of the invention will become more readily apparent from the following detailed description taken in conjunction with the accompanying drawings in which: Fig. 1 is a perspective view of a clip formed in accordance with the present invention; Fig. 2 is a cross-sectional view taken along lines 2-2 of Fig. 1; Fig. 3 is a perspective view of the clip applied to magnetic wire; and Fig. 4 is a cross-sectional view taken along lines 4-4 of Fig. 3. The clip of the present invention is shown at 10 in Fig. 1. It has a receptacle 11 and a ferrule 12. The receptacle has an opening 13 through which a pin passes by which the clip makes electrical contact to a power source. The ferrule has a crimp section 15 and an insulation gripping section 16. ~ The ferrule is adapted to receive one or two magnet wires. The crimp section is best illustrated in Fig. 2. It has a series of transverse grooves 20 alternating with ribs 21. The grooves and ribs are tin plated with a thickness in the range of 0.0001 inch - 0.0003 inch indicated at 22. The burrs 23 created on the corners of the ribs in the serrating process are left on the ribs to provide assistance in penetrating through the insulative coating of the magnet wire. Each rib is trapezoidal in cross section to provide sides 24. The sides lie at an angle of about 20° to a transverse plane 26 perpendicular to the crimp section. The grooves at the receptacle end are deeper than the grooves adjacent the insulation gripping section 16. At the receptacle end, the grooves are about from .006 inch - .007 inch deep. The grooves at the shallow end are .002 inch - .003 inch deep. The grooves are on .020 inch centers. The grooves are about .010 inch wide. The operation in clamping about a wire is illustrated in Fig. 4. The ribs, in penetrating into the wire during the crimping operation, bite off a chunk of insulation as indicated at 30 in Fig. 4, the insulation being carried by the top 31 of the rib below the original surface of the wire. The shearing away of that insulation causes the wire to be bared along the sides of the rib and to create an intimate electrical contact at the interface between the rib and wire indicated at 32. At the end with the deeper grooves, the penetration is deep in order to provide the good electrical contact. That depth of penetration, however, tends to weaken the wire. Hence, at the other end of the crimp section, the grooves are shallow so that the penetration is not as deep. While there is a sacrifice of electrical contact, there is a gain in the strength of the wire so that the wire will always be held tightly gripped by the clip. From the above disclosure of the general principles of the present invention and the preceding detailed description of a preferred embodiment, those skilled in the art will readily comprehend the various modifications to which the present invention is susceptible. Therefore, I desire to be limited only by the scope of the following claims and equivalents thereof:

Claims: What is claimed is: 1. In a connector clip having a receptacle to receive connector pins and a ferrule adapted to receive magnet wire having an insulative coating on its surface, said ferrule including a crimp section to receive said wire comprising, said crimp section being channel-shaped and presenting a channel-shaped surface to receive said wire, said channel-shaped surface having a series of transverse grooves alternating with transverse ribs, said grooves being deep adjacent said receptacle and gradually growing shallow as said grooves are spaced away from said receptacle, whereby the deeper grooves permit said ribs to bite deeply into said wire past said coating and the shallower grooves provide good gripping of said wire. 2. A connector clip as in claim 1 in which the depth of said grooves ranges from about 0.007 inch to about 0.002 inch. 3. A connector clip as in claim 1 in which each said rib is a trapezoid whose sides are at an angle of about 20° to a transverse plane perpendicular to said crimp. 4. A connector clip as in claim 1 in which said ribs have, at their corners, burrs that penetrate said coating. 5. A connector clip and coated magnet wire combination comprising, a receptacle, a wire-gripping ferrule including a wire crimp, and a magnet wire disposed in said crimp, said crimp having a series of transverse grooves alternating with transverse ribs, said ribs having sides lying at about 20° angles to a transverse plane perpendicular to said crimp, said crimp being clamped tightly about an end portion of said wire, said ribs penetrating said coating and a portion of said wire to provide metal-to-metal contact along at least a portion of the sides of said ribs. 6. The combination of claim 5 in which the grooves closer to said receptacle are deeper than those remote from said receptacle, whereby the area of deeper grooves takes a deeper bite and provides greater contact, whereas the area of the shallower grooves provides better grip on the wire. 7. In a connector clip adapted to receive magnet wire having an insulative coating on its surface, a crimp section to receive said wire com¬ prising, said crimp section being channel-shaped and • presenting a channel-shaped surface to receive said wire, said channel-shaped surface having a series of transverse grooves alternating with transverse ribs, each said rib being a trapezoid in cross section and having sides at an angle of about 20° to a trans¬ verse plane perpendicular to said crimp, whereby, when said crimp section is clamped about a coated :ire, the ribs will penetrate the coating and a portion of said wire to provide metal-to-metal contact along at least a portion of the sides of said ribs.

Inventors: HEIMBROCK HENRY H, HEIMBROCK, HENRY, H.
Applicants: STANDEX INT CORP, STANDEX INTERNATIONAL CORPORATION
Application year: 1988
Main classification: H01R4
IPC codes: H01R4