The female contact of current commercial pin and sleeve electrical connectors, in one common form, has two opposing, semi-cylindrical fingers (or "beams" as they are sometimes called). Together, they form an elongated, cylindrical socket or female receptacle for a male connector pin, both fingers being integral with and extending from a common base in cantilever. Thus, each of the fingers extends from a common base, outwardly in a semi-cylinder to a distal end. Together they form a split cylinder--i.e., the socket. The semi-circular distal ends of the two fingers form an inlet opening to the socket through which the pin is placed in making a connection.
A cylindrical sleeve is located around the outer edges of the fingers and it extends from the base of the fingers to a location short of the outermost or distal ends of the fingers. In other words, the outermost ends of the fingers, in the prior art, extend out of the sleeve at the location where they receive the connector pin in mating coupling. The cylindrical sleeve thus limits the outward flexing of the fingers at their base, but it leaves the inlet ends free, where damage can occur.
Typically, connectors of this type have two through five or more poles, each pole being represented by a mating pin of a male connector and a corresponding socket of a female connector. All of the connector elements for both the male and the female connectors are held in place by a plastic body called an insert. An electric cable having a conductive wire for each pole is assembled to each male and female connector, with a wire attached to each connector element; and a covering or sheath of soft insulating plastic is molded to bridge the jacket of the cable to the insert, thereby enclosing and sealing the connections of the electrical wires to the connector elements. Thus, these connectors are frequently referred to in the industry as "molded" connectors.
In connectors of this type, the primary mechanism for limiting the diameter of a pin being inserted is the opening formed in the plastic insert body just beyond the outer-most extension of the fingers. However, the insert body, being formed of a pliable, molded plastic, deforms under force, so that it is not uncommon for a person to attempt to assemble a male connector having oversized pins into a corresponding female connector. This may lead to damage.
Experience has shown there are two problems with the female connector in the prior art structure. It must be realized that molded connectors are typically used in industrial or commercial applications and that they experience rugged conditions of use. The pins may be stepped on or otherwise mishandled so that one or more of the pins become misaligned (i.e., out of parallel) with the other pins of the male connector. During assembly to a female connector, a misaligned pin may cause damage to the socket. In assembling the male connector to a female connector, even if the pins are not misaligned, molded connectors are frequently subjected to rough handling so that one or more of the pins of the male connector are not properly aligned with the axis of the associated female socket into which it is being inserted. This can also cause damage to the socket elements.
Thus, a common failure is caused by misalignment of the pin during insertion. This can cause a bending of the flexible finger at the inlet opening of the socket because the finger extends beyond, and is therefore not supported by, the surrounding metal cylindrical sleeve. The damage is exacerbated because of the shape of the fingers (i.e., semi-cylindrical) and because of the characteristics of the type of brass material from which these contacts are conventionally made. That is, they are machined from a brass alloy which is somewhat brittle so that it rather easily is deflected beyond its normal stress-deflection characteristic. When this occurs, the metal is overstressed and may even tear. In either case, it will lose its resilient characteristic; and its ability to establish reliable electrical continuity is then lost.
A second problem which also results from the stiffness and shape of the semi-cylindrical fingers of the prior art construction is that they are susceptible to damage if a pin having a diameter larger than that for which the female connector is designed, is inserted into the female socket. Again, the rugged conditions of industrial applications must be borne in mind. It is not uncommon for a user to force an oversized pin into a smaller socket. If an oversized pin is attempted to be assembled to a smaller female socket, the inlet ends of both semi-circular fingers are bent outwardly and about the edge of the protecting sleeve where failure occurs if the fingers are bent with sufficient force.