Connector For Plug In Field

Abstract

A terminal is provided for use in interconnecting the magnet wire of a field coil of an electric motor to another circuit element such as a lead wire. The terminal is insulatively mounted on the field core, preferably before winding the coils. The terminal includes a channel part adapted to be crimped to the magnet wire and a socket part adapted to receive the circuit element.

Description

The present invention relates to field sub-assemblies for universal electric motors and specifically to a field coil terminal for use in such sub-assemblies.

In the copending application of Wendell B. Leimbach, James W. Marshall and Salvatore R. Abbratozzato, Ser. No. 140,374; filed May 5, 1971, and assigned to the assignee of this invention, the disclosure of which is incorporated herein by reference, a field sub-assembly is disclosed which includes a plurality of insulative terminal blocks mouted on the core of an electric motor field. The block provides a mounting location for terminals, each of which receives one end of the coils of wire which are wound on the field. The function of these terminals is to mechanically secure the wire of the coils while the wire is still under tension, to make electrical connection to the wire and to provide for later connection of a lead wire or another circuit element.

As set forth in that application, the system and method disclosed therein provide a number of advantages over the devices shown in the prior art, particularly in the case of a machine-assembled field, including a simplified and lower cost assembly as well as the ability to handle and test the field without the inconvenience caused by either loose magnet wire ends or extended lead wire. It is the purpose of the present invention to provide an improved terminal for use in the assembly described in the aforementioned application.

Briefly, in accord with a preferred embodiment of this invention, a terminal is provided for use in interconnecting the magnet wire of a field coil of an electric motor to another circuit element such as a lead wire. The terminal is insulatively mounted on the field core, preferably before winding the coils. The terminal includes a channel part adapted to be crimped to the magnet wire and a socket part adapted to receive the circuit element.

In accord with the present invention, the channel portion includes two segments, one of which is for mechanically securing the wire as soon as it is placed in the channel while the other is for making electrical connection to the magnet wire at a subsequent stage in the process.

In further accord with this invention, the socket includes a tang which is formed from a socket wall and which is curved so that it first extends outside and then reenters the socket. The end of the tang inside the socket allows insertion of a wire from one direction but holds the wire against withdrawal. The end of the tang may be shaped to optimise its holding power against the surface of a wire. The curvature of the tang outside the socket increases the effective length of the lever arm, thus increasing the force on the wire surface without increasing the overall size of the socket.

In the drawings:

FIG. 1 is a side elevation of a field subassembly for a universal motor incorporating the connector of the present invention;

FIG. 2 is a perspective view of a connector in accord with this invention; and

FIGS. 3 and 4 are views of the connector illustrating the function of specific portions thereof.

In FIG. 1, a field 10 for a universal motor is illustrated which comprises a stack of laminations 11 and a plurality of coils of wire, one of which can be seen at 12, wound therein. The field may be of any conventional type including internally extending pole tips which define slots in which the coils are wound. Also visible in FIG. 1 are the ends of slot liners 13 which insulate the stack of laminations from the coil. Mounted on one end of the stack 11 are a pair of insulating terminal blocks 14. These may be of any insulating material having suitably stable thermal and mechanical characteristics such as polysulphone.

Mounted in the terminal blocks are a plurality of connectors 15 in accord with the present invention. The total number of connectors corresponds to the total number of coil leads, for example four. The connectors 15 are inserted in appropriately shaped recesses in the insulator blocks. In the illustrated case, since polysulphone is transparent, the portion of the connectors extending within the block can be seen in the elevational view.

The conductive connector itself is illustrated in FIG. 2. Each of the connectors includes a generally channel shaped portion 16 and a sleeve-shaped portion 17. The sleeve portion may include a dimple 18 which engages with a corresponding recess in the plastic to hold the terminal in place.

As described in the above-noted application, the channel part of the connector is used to mechanically secure the starting and ending leads of the coil 12 and to provide for electrical connection thereto. In use, the terminal block is mounted on the stack of laminations 11, the coil is wound in the slots and the starting and ending leads are laid in the channel portion to provide for such connection. In developing this process, it was determined that it is difficult to perform the crimping operation at the same station where winding of the coils is performed. Therefore, in accord with the present invention, the channel portion 16 is provided with a first, crimping portion 19 and a second, holding portion 20. In the process of preparing the subassembly, the coils are wound and the starting and ending leads 21 are placed in the channel portion so that the wire extends through both portions 19 and 20. At the winding station, a small pair of pinching chucks are applied to the holding portion 20 to squeeze its sides together as shown in FIG. 3. Then, the field subassembly can be removed from the winding station without losing control over the wound coils. If control is released, several turns can spring away from the pole pieces, necessitating a hand operation to rewind them. When these leads are held by portion 20, the field is delivered to the next processing station where the crimp portion 19 is engaged by suitable dies and crimped to the lead 21. As soon as the lead is securely held by the crimped portion, the holding portion 20 can be severed since it no longer serves any useful purpose. The resulting connection is illustrated in FIG. 4.

In further accord with the present invention, the socket part of the connector 15, preferably a sleeve as shown, is adapted to receive and hold the end of a circuit element such as a lead wire. As described in the aforementioned application, a resilient tang is preferably formed from the side wall of the sleeve to engage the surface of the wire and prevent its withdrawal. In accord with the present invention, the tang 22 is shaped so that it first extends outwardly from the sleeve, at 23, then curves to reenter the sleeve, at 24. Prior to insertion of the lead wire 25, the tang extends substantially to the opposite wall of the sleeve. When the wire is inserted, as can be seen from FIG. 4, the tang is resiliently moved out of the way. Upon full insertion of the lead wire 25, the inner end 26 of the inwardly extending portion 24 engages the surface of the lead wire and is held against it by the resiliency of the tang.

The determining factor for the spring force exerted by the tang against the lead wire is the effective length of the tang. The length of the tang would appear to be limited by the length and diameter of the sleeve. However, in accord with the present invention, the effective length of the tang is substantially increased, without increasing the overall size of the connector, by means of the curved portion of the tang which extends externally of the sleeve. In this manner, the pivot point of the tang is moved substantially from the position it would take if the tang were simply bent inwardly from the wall of the sleeve and thus the force holding the lead wire in position is substantially increased. This feature is of basic importance in a field such as that illustrated in FIG. 1 since, otherwise, the required increase in the size of the connector could extend the plastic beyond the boundaries of the field stack and this would introduce a significant cost increase in providing for the mounting of the field in a motor housing.

While a specific embodiment of this invention has been illustrated and described, it will be clear to those skilled in the art that many changes and modifications can be made therefrom without departing from the true spirit and scope of this invention. For example, further refinements in the precise design of the connector, such as providing ribs in portion 20 of shaping the inner end 26 of the tang 22, can be made to increase the holding force applied to the lead wire without departing from the concept disclosed herein; also, the configuration of the socket or channel can be modified as required. It is also noted that the described connector can be used with other coils such as transformers. Accordingly, it is intended that the appended claims cover all such changes and modifications as come within the purview of this invention.

Claims

I claim:

1. A terminal to facilitate the connection of an electrical conductor wire thereto, comprising: an insulating block having a hole therein; and a one-piece electrically conductive terminal connector having offset first and second portions joined by a joining portion; said first portion having a generally tubular form and being inserted into said hole and frictionally held therein; said second portion being located outside said block and being a generally U-shaped channel to receive said conductor wire, and having collapsible side walls and a base portion, said base portion being generally tangent to said first portion and all imaginery lines passing longitudinally along said channel parallel to said base being located outside said first portion, and said side walls having opposed notches therein near the extremity of said second portion to form a main segment of sufficient length to securely hold said conductor wire and a severable segment whereby said conductor wire may first be temporarily gripped by collapsing said side walls of said severable segment.

2. A terminal as claimed in claim 1 wherein said first portion includes a tang extending diagonally across said first portion and joined to one side of said first portion, said tang including a curved portion extending outside of said first portion for increasing the effective force exerted by said tang against an element inserted in said socket.

3. The terminal as claimed in claim 1 further including a conductor wire lying in said second portion between said side walls with said conductor wire having an end being at least partially enveloped by the side walls of the severable segment.

4. A method of securing an electrical conductor to a one-piece electrical terminal connector having a U-shaped channel to receive said conductor and having a terminal contact portion, said channel having a main portion and a severable portion, said method comprising the steps of: positioning said conductor in said channel so that a portion of the conductor to be severed is positioned in the severable portion of the connector; crimping the walls of said severable portion causing them to collapse against the conductor thereby to temporarily secure the conductor in the channel, crimping the main portion of the channel to secure the conductor therein and to complete the electrical connection between the conductor and the connector; and severing the severable portion of the connector and the portion of the conductor held therein.