Abstract:
A connector terminal is disclosed including a cylindrical socket body with a spring contact inserted therein. The spring contact has a distal portion that establishes a press fit with the socket body. The socket body may be crimped over the distal portion to more securely hold the spring contact in the socket body. The spring contact further has a plurality of fingers which taper forwardly and inwardly to resiliently grab a male pin as it enters the socket.

Description:
RELATED APPLICATION 
     This application is a continuation-in-part of my application Ser. No. 09/104,733 filed Jun. 25, 1998 entitled Hoodless Electrical Socket Connector which was abandoned on Feb. 4, 2000. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to electrical contacts, and more particularly, it is directed to a hoodless socket contact and method for making the same. 
     BACKGROUND OF THE INVENTION 
     Electrical contacts are present in all avionics, military and aerospace equipment environment such as in helicopters, missiles and planes. Such equipment may have dozens or even hundreds or even thousands of electrical connections that must be made between electronic power supplies, sensors, activators, circuit boards, bus wiring, wiring harnesses, to provide the electrical pathways or highways needed to transport electricity in the form of control signals and power. The hardware reliability requirements for operating in an avionics environment are stringent as a failure can have catastrophic consequences. As such, the electrical components and circuitry, as well as the connectors and contacts therein employed to electrically connect these items, must work in a wide range and wide variety of environmental conditions such as mechanical, vibration, wide temperature ranges, humidity and corrosive elements, etc. For example, military standards (also known in the industry as mil specs) for aircraft avionics equipment require that contacts be able to mate and unmate a minimum of five hundred times without a failure during all anticipated environmental and mechanical conditions. In addition, the contact assemblies must be protected to withstand repeated handling without significant distortion or damage to the interconnecting parts which could lead to a lack of electrical continuity. 
     One example of a high-amperage power socket contact or terminal is illustrated in U.S. Pat. No. 5,376,012 “Power Port Terminal” to Clark which includes a contact socket receiving portion and an integral mounting portion. The socket includes a web with a plurality of beams thereon. Each of the beams has a curved surface with a bend, which beams cooperate to form an axially extending tubular socket region which accepts a pin terminal of any desired length. Disadvantageously, the beams are exposed and therefore subject to damage. Additionally, the beams of the socket contact are not protected from entry of an oversize male contact, which may bend the beams beyond their elastic limit thereby damage the connector so that it will not perform electrically. 
     Another example of a socket contact is illustrated in U.S. Pat. No. 4,906,212 entitled “Electrical Pin and Socket Connector” to Mixon, Jr. which includes a socket have a cylindrical mating portion defined by cantilever beams having one or more blades wherein one or more of the blades include a rearwardly extending free end. The pin includes a mating portion having a bullet nose at one end and a wire barrel at another end. This connector suffers from the same limitations as the Clark connector and therefore is an undesirable alternative in environments where high reliability is critical. 
     A prior art female contact which is used in non-critical and in non-aerospace applications is shown in FIG. 1 which contact includes a cylindrical member  10  having holes  12  and  14  in the ends thereof. A spring member  16  is inserted in one of the ends, the spring member tapering rearwardly into the hole  12 . Accordingly, a male pin contact inserted into the cylindrical member  10  would be grasped by the spring member  16  relatively deeply within the hole  12  which is disadvantageous. The distance from the free end  15  of the socket to the point of engagement  17  with a male contact or pin is designated by the letter “l” in FIG. 1 (and in FIG.  2 ). The particular connector halves in which the male and female contacts are used (and the positioning of the connector halves on the equipment, e.g., trays and black boxes) may result in a lesser or greater penetration of the male pins into the socket body. Furthermore, there is no mechanical structure to ensure that the spring member  16  will remain in place and as such the spring may “walk out” of the hole during vibration or during mating and unmating cycles. Mil specs require that a spring member which provides the electrical continuity must be able to withstand the separation force during the unmating cycle (i.e., 500) without being dislodged under all anticipated environmental conditions including vibration. The arrangement of the spring  16  socket member  10  could be potentially hazardous if used in avionics environments where high reliability is a must for human safety. 
     Another example of a socket contact that is successfully manufactured and sold by the assignee of the present invention is shown in FIG.  2 . This contact  20 , sometimes referred to as a hooded socket contact, includes a tubular socket body  22  having a plurality of tines  24  for receiving a male contact or pin. A hood  26  is inserted over the tines  24  and rear portion of a contact to protect the tines from damage. The hood is generally made of stainless steel with a wall thickness of only 0.004 to 0.010″ for economic and reliability reasons. The hood is press fit over the cylindrical shoulder portion  28  at the rear of the contact. This press fit arrangement, due to the hood&#39;s wall thickness, requires precision manufacturing. Improper sizing of the socket body shoulder may result in damage to the hood during the press fit operation or the hood may come loose during use. Plating of the contact may exacerbate the press fit step during manufacturing. Furthermore, a stainless steel hood may not be tolerated in certain applications where interference with magnetic fields is a problem. In summary, the manufacturing steps necessary to insure reliable performance of the hooded type contact shown in FIG. 2 may result in a fairly expensive contact when mass produced. 
     Accordingly, there is a need for an improved socket contact that is simple to manufacture yet reliable in performance and that can be made in mass quantities at relatively low cost. 
     SUMMARY OF THE INVENTION 
     The foregoing mentioned disadvantages are avoided by providing a hoodless socket or female contact for engaging a male pin contact. The female contact includes a socket body with two ends, each end having an axially oriented hole or bore. A spring for making an electrical connection with a male contact or pin is located in one of the holes. The spring is arranged for resiliently engaging the male pin contact in close proximity to the hole entry point or free end of the socket body. Means are provided for securely holding the spring in the hole, which may be established by a press fit of the spring within the hole coupled with an extension of the socket body overlaying a portion of the spring thereby preventing the spring from exiting from the socket body. 
     Alternatively, the spring may be securely coupled in the socket body by crimping the socket body onto the spring. Preferably, this is achieved by crimping a portion of the socket body into a peripheral annular groove in the spring. Barbs on the spring, which engage the inner wall of the hole of the socket body, may also be employed, with or without crimping, to provide additional security. 
     The hole at the other end of the socket body is sized and shaped to receive a conductor such as a insulated copper wire. The conductor may be electrically and mechanically secured together with the socket body by crimping the socket body onto the conductor. 
     The construction and operation of preferred embodiments of the contact of the present invention may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which like components or features are designated by the same or primed reference numbers. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side cross-sectional view of a prior art contact; 
     FIG. 2 is a side cross-sectional view of another prior art contact; 
     FIG. 3 is a side cross-sectional, partially broken away side view of a socket contact in accordance with the principles of the invention illustrating the two parts of the socket contact prior to assembly; 
     FIG. 4 is a side cross-sectional, partially broken away side view of the contact parts of FIG. 3 assembled together; 
     FIG. 5 is a side view of a stamped out spring prior to roll forming; 
     FIGS. 6A and B are cross-sectional views illustrating a spring made from roll forming (“seam type”) or deep drawn (“seamless type”) processes, respectively; 
     FIG. 7 is a side cross-sectional view of the spring with dimples; 
     FIGS. 8A-C are partial side cross-sectional views of the back end of the spring with optional groove configurations therein; 
     FIG. 9 is a cross-sectional side view of an assembled socket contact that has been crimped; 
     FIG. 10 is a cross-sectional view of another assembled socket contact wherein the two parts are assembled together and in additional are also retained by barbs and a pin terminal is inserted into the socket contact; 
     FIG. 11 is a cross-sectional side view illustrating the two parts of the socket contact prior to assembly with an electrical conductor; 
     FIG. 12 is a cross-sectional side view of the socket contact with metal stands of an insulated conductor wire inserted into the rear portion of the socket body prior to crimping, and 
     FIG. 13 is a partially broken away side view of the socket contact with the rear portion of the socket body crimped onto the wire strands. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings and more particularity to FIGS. 3 and 4, there is shown a socket contact generally indicated by reference number  30 . The socket contact, sometimes hereinafter referred to as a hoodless socket, is made from two parts including a socket body  32  and a spring  34 . The socket body  32  consists of a cylindrically or tubularly shaped member  36  having two ends, with an axially disposed male-contact-receiving hole or bore  38  extending from one of the ends  40  (i.e., free end) into the socket body a preselected distance and a conductor or wire receiving hole of bore  39  at the other end  41  thereof. See FIG.  11 . The socket body  32  may be made of an electrically conductive material such as a brass/copper alloy. The male-contact-receiving hole  38  may have an inwardly projecting shoulder  42  that provides a back stop for the seating of the spring  34 . 
     The spring  34  contains a forward male contact receiving portion  44  and a rear mounting portion  46 . The contact receiving portion  44  includes a plurality of fingers or tines  50 . The fingers are arranged around the longitudinal axis  52  of the spring  34  and are separated by gaps or slots  54  between adjacent fingers. Each of the forwardly extending fingers tapers inwardly to define together a tubularly shaped contact region  56  and  58  which engages a male pin inserted  3  therebetween and to provide a reliable electrical connection therebetween under anticipated adverse conditions. The portion of the fingers forward of the contact region  56  bend outwardly to form a flared region  57  which acts as a centralizer for guiding the insertion of a male pin. The tubularly shaped contact region  56  at the bends define a plane curved contact surface which surface may be in radial plane such as the an annular contact surface  58  at a preselected point  60  along a longitudinal axis  52 . The preselected point for annular contact surface  58  of the spring  34  is spaced within about 0.020 to 0.045 inches, and preferably about 0.035 inches maximum, from the free end  40  of the socket body when the spring contact is secured therewith, i.e., equals about 0.020″ to 0.045″ and preferably about 0.035″ maximum. The distance from the free end  40  of the socket body to the annular contact surface  58  is designated by the letter “ ” in FIG.  4 . The aforedescribed arrangement between the socket body and spring thus allows electrical contact to be made with a male contact close to the end  40  of the socket body. This advantageously provides electrical contact to be made immediately essentially upon coupling a male contact (not shown) to the hoodless female contact  30 , as required by the applicable mil specs. 
     The spring  34 ′ may be of the seam type in which case it is made in a flat configuration, as illustrated in FIG. 5, and then roll formed into the form of a sleeve. A small gap  37  is formed between the edges  51 , as shown in FIG.  6 A. This gap may visually disappear as a result of the roll formation and press fit steps. Alternatively, the spring  34 ′ may be of the seamless type made, for example, by deep drawing process well known in the art, as shown in FIG.  6 B. 
     While the fingers  50  described hereinabove provide good electrical continuity to a male terminal, increased electrical contact may be established by providing the contact region  56  with inwardly disposed dimples  62 , as shown in FIG.  7 . While the dimples could be disposed on the same radial plane, preferably the dimples  62  are staggered on the fingers  50 , i.e., disposed at different axial distances from the free end of the socket body as shown more particularity in FIG.  5 . This advantageously reduces the insertion force needed to insert a male pin between the fingers  50  than when the dimples  62  are all on the same radial plane, while increasing the retention force provided by the fingers  50 . Additionally, by staggering the dimples  62 , the resonance point of the individual fingers  50  will vary during vibration, thus mitigating open circuit faults. Fingers having different widths “W”, as illustrated in FIG. 5, also aid in overcoming the resonance problem encountered with conventional spring contacts. The dimples  62  further assure that a gas-tight connection is established between the fingers and a male contact. Such a gas-tight connection seals out corrosive gases and thereby prevents formation of films or corrosives on the surfaces interconnecting the mating male/female contacts that could degrade the electrical conductivity therebetween and cause failures in the connection. It should be noted that dimples or fingers having differing widths may not be necessary in many applications. 
     The spring  34  may be retained within the hole  38  of the socket body  32  by inserting the contact into the socket body with a press fit configuration and thereafter rolling the free end of the socket body radially inwardly to form an annular shoulder  53  which will engage end  35  of the spring in the event that a sufficient force is applied to the spring tending to pull the spring out of the socket body. See FIG.  4 . Alternatively, or in addition thereto, the rear mounting portion  46  of the spring contact may have an annular groove  70  therein, shown with more particularity in FIG.  8 A. After assembly, the wall of the socket body  32  may be roll crimped such that a portion  59  of the socket body wall is rolled into the groove  70 , as shown in FIG.  9 . The rear mounting portion  46  of the spring  34  may have a variety of groove configurations, as shown with more particularity in FIGS. 8A-C. 
     Another means for retaining the spring in the socket body is shown in FIG.  10 . In this embodiment, the rear mounting portion  46  of the spring has a plurality of outwardly extending spring retention barbs  80 . The barbs  80  resiliently compress inward upon insertion of the spring  34  into the hole  38 , but dig into the inner wall  38  of the hole to resist removal. As further illustrated in FIG. 10, the pin portion  92  of a male contact  90  is inserted between fingers  50  which spread to resiliently grasp the pin portion  92  via the dimples  62 . It should be noted that the dimples  62  are optional. 
     FIGS. 11-13 illustrate an attachment mechanism for electrically connecting the socket body  32  to an electrical conductor  102 , such as a conventional insulated copper wire, for example. The socket body  32  includes a forward (first) tubular portion  32   c  and a rearward (second) tubular portion  32   d  separated by a solid center section  32   a . The second or rearward portion  32   c  forms a wire receiving end  41  which opens to a rear hole or blind bore  39  which receives the copper strands  100  of insulated wire  102 . The first or forward tubular portion  32   c  includes the male contact receiving blind bore  38  discussed previously. The front and rear bores  38  and  39  are closed by end walls  38   a  and  39   a , respectively, formed by center section  32   a  of the socket body. The socket body  32  includes a pair of spaced radially extending shoulders  32   b.    
     As is shown in FIG. 12, the wire strands  100  of the conductor  100  are inserted a predetermined distance into hole  39 , which insertion may be aided by a small viewing hole  104  (shown in FIG.  13 ). The distal end wall  39   a  of the hole  39 , in any event, limits the insertion distance of the wire. A selected portion  106  of the socket body  32 , extending over the wire strands  100 , is crimped onto the wire strands to make good electrical contact therewith and mechanically hold the wire strands  100  in the socket body  32 , as shown in FIG.  13 . Advantageously, the socket body while serving to hold and protect the spring also provides for direct attachment to conductor wires and the like without the need for additional parts. It should be noted that while it is preferable to provide separate front (first) and rear (second) holes,  38  and  39 , respectively, separated by a center section  32   a  of the socket body, the hole or bore could be continuous, i.e., one long bore. 
     There has thus been described an improved contact arrangement which can be cost effective manufactured on a repetitive basis. This spring is protected from damage by the socket body. The dimples, when utilized, provide an increased gas tight point(s) of contact, allowing thinner or less noble electrical conductive plating to used on the fingers. Optionally, staggering the dimples reduces the overall mating and unmating force while maintaining a desired gas tight seal between the fingers and the male contact. Accordingly, various modifications of the hoodless socket, and processes involved in manufacturing the contact terminal, will occur to persons skilled in the art without involving any departure from the spirit and scope of the invention as set forth in the appended claims.