US 3871737 A
This invention relates to a socket contact which provides a layer of conductive elastomer material along at least one wall of the socket hole. A contact in which a complete electrical circuit is established only when the pin and socket are fully mated may be provided by utilizing a conductive elastomer material which is conductive only when placed under compression.
Claims available in
Description (OCR text may contain errors)
United States Patent I 11 Dorrell et al.
SOCKET CONTACT WITH CONDUCTIVE ELASTOMER CONTACTING SURFACE Inventors: Robert Francis Dorrell, Des Plaines; Norman Richard Anderson, Cicero, both of I11.
Bunker Ramo Corporation, Oak Brook, 111.
Filed: June 5, 1974 Appl, No.: 476,612
Related U.S. Application Data Continuation of Ser. No. 323,867, Jan. 15, 1973, abandoned.
U.S. Cl. 339/255 R, 339/DIG. 3 Int. Cl. H0lr 13/12 Field of Search 339/147, 255, 256, 278,
References Cited UNITED STATES PATENTS 9/1960 Myers 338/100 1 Mar. 18, 1975 Evanicsko, Jr 338/99 Cooney 339/256 R Harshman et a1 338/99 DuRocher 338/114 Primary Examiner.loseph H. McGlynn Attorney, Agent, or Firm-Norton Lesser; Frederick M. Arbuckle ABSTRACT This invention relates to a socket contact which provides a layer of conductive elastomer material along at least one wall of the socket hole. A contact in which a complete electrical circuit is established only when the pin and socket are fully mated may be provided by uti lizing a conductive elastomer'material which is conductive only when placed under compression.
2 Claims, 2 Drawing Figures a 2 J2 /19a 19 C5 SOCKET CONTACT WITH CONDUCTIVE ELASTOMER CONTACTING SURFACE This is a continuation of application Ser. No. 323,867, filed Jan. 15, 1973, abandoned.
This invention relates to socket contacts for electrical connectors and, more particularly, to a socket contact having a conductive elastomer contacting surface.
BACKGROUND OF INVENTION Electrical connectors normally consist of a male element having one or more projecting pin contacts and a female element having a like number of socket contacts. These socket contacts have a pin-receiving hole in their forward face. Some sort of a metallic spring member is normally either mounted in the hole in engagement with the walls thereof or is formed from the walls of the contact member itself. These springs serve to perform the dual function of physically retaining a pin in the socket and providing good electrical contact between the pin and socket,'the springs also serve to compensate for any slight misalignment of a pin with its sockets.
While the springs presently utilized in socket contacts adequately perform the required functions, they do suffer from certain shortcomings. First, these springs normally engage the pin at a point or, at best, over a relatively small area, thus providing a relatively high contact resistance. The relatively small area of physical contact also creates high bearing forces thereby generating excessive wear and galling on thin electro-deposited precious metals normally applied on contact surfaces. With repeated use, or as a result of pin misalignment, these springs may also become bent and distorted resulting in potential spurious open circuit conditions. Finally, the forming and/or inserting of the springs is one of the more difficult and expensive operations involved in making a socket contact. It would, therefore, be preferable ifa simpler, less expensive, more reliable, technique could be developed for providing physical and electrical contact with a pin inserted in the socket contact. Such a technique should be adapted for providing contact over as large an area of the pin as possible while not creating a critical pin alignment condition.
Another problem with existing electrical connectors is that electrical connection is normally effected as soon as the pin comes into contact with the spring element in the socket even though the two connector elements have not been fully mated. Where live lines are being connected, current may start flowing when only a point contact has been established resulting in arcing and/or potential burn-out damage to the contacts. In these situations, electrical contact should not be established until the connector elements are fully, orat least substantially, mated. While connectors having this capability do exist, they are generally relatively complicated and expensive. A simple, inexpensive technique for preventing electrical circuit from being established through a connector until its elements have been fully mated is thus required.
SUMMARY OF THE INVENTION In accordance with the above, this invention provides a socket contact for an electrical connector which contact has a metallic contact body with a forward face having an elongated hole formed therein, the hole extending from the forward face. In place of the springs of the prior art, this invention provides a layer of conductive elastomer material which is positioned in the hole along atleast one wall thereof. Where the layer of elastomer material is positioned only along the rear wall of the hole and the material is of the type which is conductive only when placed under compression, a circuit is completed through the socket contact only when the connected elements are fully mated.
The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention as illustrated in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cut-away side view of a socket contact of a preferred embodiment of the invention with a mating pin positioned therein.
FIG. 2 is a cut-away side view of an alternative embodiment of the invention.
DETAILED DESCRIPTION Referring now to FIG. 1, it is seen that a socket contact 10 having a metallic body 11 is provided which contact has a wire crimp pocket 12 formed in its rear end and a pin-receiving hole 14 in its forward face. A flange 16 is provided on the contact for use in retaining .the contact in a connector. It should be noted that pocket 12 and flange 16 do not form part of the present invention. Thus, any suitable means for permitting the connecting of a wire or other current carrying element to the contact may be utilized in place of pocket 12 and flange 16 may be replaced by any other suitable contact retention element or may be eliminated completely.
The cross-sectional shape of hole 14 may be circular, square, or any other desired shape with the peripheral surface I7 of the hole 14 extending from one end 17a of said body 11. The shape of the hole 14 depending on the cross-section of the metal pin or male contact 18 with which socket contact 10 is to be mated. Pin 18 has a peripheral surface 19 and a radial or transverse forward end surface 190. The cross-section of hole 14 is slightly larger than that of the pin and the leading edge of the hole is tapered so as to permit easy insertion of the pin, and to permit the socket to accept slightly misaligned pins. Along the rear transverse surface or wall 20 of hole 14 is a layer 22 of a conductive elastomer material. Layer 22 may, for example, be an electrically conductive silicone elastomer or other known conductive elastomer which is normally conductive. However, for certain applications it is preferable that layer 22 be of a material such as Pressex, manufactured by Essex International, which material conducts electrical current only when compressed. Where Pressex or a similar conductive elastomer is utilized for the layer 22, an electrical circuit is not established between socket 10 and pin 18 until the pin has been fully (or at least substantially) inserted into the socket, compressing layer 22 to render it conductive under the axial pressure of said pin against layer 22 and the hole rear metal surface 19a defining the rear axial end of the hole. Thus, electrical contact over the entire contacting area is established before the electrical circuit is completed, preventing possible arcing'or burn-out where live circuits are being connected.
Layer 22 may be rammed into hole 14 and held in by friction, may be molded to the wall 20, or may be otherwise secured in the hole. However, regardless of how the elastomer is placed in the hole, the operation is relatively simple and inexpensive. Further, the conductive elastomer is not subject to deformation or other permanent distortion as the result of use, pin misalignment, or other factors and, covering the entire rear wall of hole 14, the conductive elastomer makes contact with the pin over a-relatively large area. Thus, the socket of this invention is adapted for making reliable, relatively low resistance electrical contact with an inserted pin even after repeated use, and possible misuse, of the socket.
FIG. 2 shows an alternative embodiment of the invention which differs from the embodiment shown in 7 FIG. 1 only in that hole 14 has a conductive elastomer layer 24 positioned therein which layer covers both the rear wall and the side walls of the hole. The space 26 between the side-wall layers of conductive elastomer is substantially less than the cross-section of pin 18, so that the elastomer on the side walls is also deformed when a pin is inserted. This assures good electrical contact between the pin and the conductive elastomer over substantially the entire length of the pin which is in hole 14. If a Pressex-type conductive elastomer is utilized with the embodiment of the invention shown in FIG. 2, the opening 26 will have to be made quite small so as to assure adequate pressure on the conductive elastomer along the side walls to render the elastomer conductive. The portion of the conductive elastomer layer near the front of the hole 14 is tapered slightly for ease of pin insertion and to reduce the tolerances on pin alignment.
An improved socket contact has thus been provided. While the invention has been particularly shown and described above with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and detail may be made therein without departing from the spirit and scope of the invention.
What is claimed is:
1. A socket contact for use in an electrical connector adapted to receive a metal pin, said pin having a peripheral surface and a transverse forward end surface for establishing an electrical connection between said pin and contact comprising:
a metallic contact body having an elongated hole formed therein with an elongated axis, said hole extending from one end of said body and defined by an axially extending peripheral surface portion, a rear metal surface on said body at a position spaced in one direction from said one end of said body to define a rear axial end of said hole;
an axially extending layer of conductive elastomer material positioned in said hole with said layer of elastomer material having a peripheral surface extending axially of said hole and engaging said peripheral surface portion of said hole throughout the axial extent of the peripheral surface of said layer of elastomer material;
a rear surface on said layer of elastomer material engaged with the rear metal surface defining the rear axial end of said hole; and
a forward surface on said layer of conductive elastomer material spaced from the one end of said body and transverse to the axis of said pin and hole with the forward surface of said layer of elastomer material terminating the peripheral surface of said layer and having an area corresponding to the area of said transverse forward end surface of said pin and placing said layer of elastomer material under the axial pressure of said pin between the rear axial end of said hole and said transverse forward end surface to establish said electrical connection as a low resistance electrical path through the transverse forward end surface of said pin and the forward surface of said layer of elastomer material transverse to the axis of said pin without deformation of either said pin or socket contact in response to the insertion of said pin in said hole to engage said layer of elastomer material under said axial pressure.
2. A contact as claimed in claim 1 wherein said layer of conductive elastomer material has an annular portion integrally formed on said layer of elastomer mate rial engaging the peripheral surface portion of said hole with said annular portion extending toward the one end of said body and defining an axially extending recess for receiving and engaging the peripheral surface of said pin.