Electrical Contact Socket Having Improved Contact Spring

Abstract

Stamped and formed electrical contact socket which is adapted to receive a contact pin has an improved integral contact spring in the form of a cantilever formed from the body of the socket and extending inwardly and obliquely towards the socket axis. The cantilever has a generally helicoid surface so that upon insertion of the pin, the cantilever is flexed in torsion to provide increased contact force for a given spring length material.

Description

BACKGROUND OF THE INVENTION

A commonly used type of stamped and formed electrical contact socket is provided with an integral cantilever spring formed from the body of the socket and extending generally obliquely towards the socket axis. When a contact pin is inserted into the socket, the spring is resiliently flexed as a cantilever beam to establish the contact force at the electrical interface between the parts.

Known types of sockets having cantilever springs are satisfactory under many circumstances, however, there are conditions under which a sufficiently high contact force and/or deflection cannot be established with previously known spring designs. For example, if the designer is faced with a problem of producing an extremely small contact socket from a given material, say a conventional brass of given thickness, he may find that it is impossible to design a cantilever type spring which will impose the necessary contact force on an inserted pin. Under such circumstances, the designer can substitute a material, such as berillum copper or phosphor bronze, having improved spring characteristics but if he does so, he immediately increases the cost of the terminal and sacrifices some of the current carrying ability of the contact. He may also provide a separate contact spring of high grade material such as a stainless steel, but this alternative would greatly increase the cost of the contact terminal for the reason that it would require a separate assembly operation in the manufacture of the contact.

The instant invention is directed to the achievement of an improved contact spring for one-piece stamped and formed terminals which will provide increased contact force, other things being equal, at the electrical interface between the contact socket and an inserted pin-like member. The invention thus provides the terminal designer with a wide range of design alternatives as regards contact size, cantilever spring lengths, stock material thickness and composition, so that he can determine his final dimensions and material on the basis of electrical or cost considerations rather than on the basis of minimum spring requirements.

It is accordingly an object of the invention to provide improved electrical contact socket. It is a further object to provide a stamped and formed contact socket having an improved cantilever-type spring. It is a further object to provide a contact socket having a contact spring which will produce improved contact force, other things, such as material composition and size and spring length being equal. It is a further object to provide an electrical contact socket having improved contact spring characteristics which has an anti-overstress feature so that it cannot be readily damaged.

These and other objects of the invention are achieved in a preferred embodiment thereof, which is briefly described in the foregoing abstract, which is described in detail below, and which is shown in the accompanying drawing in which:

FIG. 1 is a perspective view of an electrical contact socket and an electrical contact pin, the contact socket having a contact spring in accordance with the invention.

FIG. 2 is a view similar to FIG. 1 but showing the pin and socket coupled to each other.

FIGS. 3, 4 and 5 are views taken along the lines 3--3, 4--4 and 5--5 of FIGS. 1 and 2.

FIG. 6 is a top plan view of a contact socket in accordance with the invention as shown in FIG. 1.

FIGS. 7-15 are a series of perspective views showing the successive steps in the formation of an electrical contact socket in accordance with the invention from a flat blank.

FIGS. 1-6 show an electrical contact socket and pin, the socket incorporating a contact spring in accordance with the invention, both the pin and socket having retention lances which may be formed in accordance with the invention as will be explained below.

The pin 4 has a generally cylindrical contact end 6 of reduced diameter and a conical tip 8. The cylindrical section 6 merges with a conical transition 9 which, in turn, merges with a cylindrical collar 12 of slightly greater thickness than the tip 6 and other portions of the terminal. The collar 11 adjoins a cylindrical section 10 of reduced thickness and an additional collar 12 is integral with the section 10 at its rearward end. Section 12 may be provided with outwardly formed embossment as shown for the purpose of positioning the terminal in an insulating housing. A crimp 14 is provided adjacent to the collar 12 between the terminal and the insulating core of a wire and an additional crimp 16 is provided, at the rearward end of the terminal, between the terminal and the insulation of the wire 18. The intermediate cylindrical section 10 is provided with outwardly formed lances 20 by means of which the terminal may be retained in a cylindrical cavity in a connector housing. These retention lances may have a helical form if desired as described below with reference to the contact springs 34.

The electrical contact socket 2 comprises a cylindrical receptacle portion 22 which is adapted to receive the contact portion 6 of the terminal 4. The socket 2, like the pin 4, is formed from metal having a contoured profile so as to provide a collar 24 of relatively thick stock metal at the forward end of the terminal, an intermediate collar 25, and a collar 26 of relatively thick metal stock adjacent to the wire crimp 28. The terminal 2, like the pin terminal 4, is also crimped onto the insulation 32 of the wire as shown at 30.

The forward socket portion of the terminal has inwardly directed contact springs 34 which are described in greater detail below, and the cylindrical portion of the terminal behind the collar 25 provided with outwardly directed lances 36 which, like the lances 20, function to retain the terminal in a cavity in an electrical housing.

The contact springs 34 are integral with the cylindrical portion 22 of the socket adjacent to the collar 24 as shown best in FIG. 6 and extend rearwardly towards the axis of the socket as is apparent from this Figure. These springs are not simple cantilevers but are formed with a helical twist along their lengths as indicated at 42 so that their opposed edges 44 are normally offset from each other as shown in FIG. 4. The ends of these springs are disposed within the confines of the cylindrical portions 22 and surface portions adjacent to the ends of the contacts are coined as shown at 46 so that these surface portions overlap the external surface portions of the springs. On the opposite sides 47 of the springs, the surfaces of the springs overlap the opening in the cylindrical section 22 so that this opposite side cannot be forced outwardly beyond the internal surface of the cylindrical contact receptacle section 22. This overlap as indicated at 47 of one side of each spring and the internal surface of the receptacle section 22 results from the fact that the contact springs are helically formed after they are struck from the body of the terminal as will be described below.

When the contact pin 6 is inserted into the receptacle, the primary mode of stressing the contact springs will be in torsion; that is the springs will be deflected along their lengths until their internal surfaces are substantially cylindrical, rather than helical, and are disposed against the external surface 6 of the contact 4 as shown in FIG. 5. This torsional stressing mode has the advantage of loading the spring with a high degree of efficiency so that a high contact force can be developed with a given material as regards thickness, spring length, physical properties, heat treatment, etc.

It should be added that the springs 34 can be designed to be stressed both torsionally and as simple cantilever springs if desired. A compound spring of this type will thus be flexed outwardly as a simple cantilever when the pin is inserted to give rise to one type of internal stressing in the spring which results in the imposition of a contact force being imposed by the spring on the inserted pin. Insertion of the pin also has the tendency to straighten the spring and cause a second mode of stressing which gives rise to additional contact forces being imposed on the pin. The terminal designer will not necessarily always utilize both types of stresses in a particular design but will design the spring such that it will impose the desired contact force on the inserted pin. In other words, it is not always desirable to design the spring such that it will develop its maximum capability for imposing contact stresses or forces on the pin. It is advantageous, however, that the disclosed type of spring is capable of imposing a relatively high force on the inserted pin when it is deflected. Because of this fact, spring design is not then the limiting factor when a specific terminal is being designed.

The retention lances 20 can also be designed such that they will be torsionally stressed rather than stressed as cantilever beams when the terminals 2, 4 are inserted into the housings. Ordinarily, however, the design and performance of these lances is less critical than the design and performance of the contact springs.

As previously noted, the contact terminals in accordance with the invention are advantageously manufactured by stamping and forming so that they can be produced in large volume and at low cost. FIGS. 7-15 illustrate the successive stages in forming of a blank to produce a contact socket in accordance with the invention. In these Figures the reference numerals used to identify specific portions of the finished contact socket 2 are also used to identify the portions of the blank which correspond to the finished structural features of the terminal, the reference numerals in FIGS. 7-15 being differentiated by prime marks.

As shown in FIG. 7, the blank 48 is of stock metal having three relatively thick ribs 24', 26', 25' which become the collars 24, 25, and 26. The blank is first curled along its edges as shown in FIG. 8 and openings are subsequently punched to define the retention lances in the contact springs. In addition to the openings, the blank is sheared as indicated to define the ends of the springs and lances. The portions of the blank adjacent to the ends of the contact springs are then coined as shown in FIG. 10 to define the surface portions 46 shown best in FIG. 5. The contact springs are then formed inwardly from the plane of the blank as shown in FIG. 11. Subsequently, the center portions of the blank is formed upwardly as shown at 50 in FIG. 12 and the sides are formed arcuately upwardly as shown at FIG. 13. In the next step, FIG. 14, the contact springs are formed to their final helical shape so that the sides of these springs will overlap the one side of the opening in the blank as shown at 47'. The final forming steps are then carried out as shown in FIGS. 15 and 16 in which the blank is rolled until it is generally cylindrical with an axially extending seam as shown. The retention lances may be formed outwardly during these final steps.

Some salient advantages of the invention are discussed generally above but can be restated here by way of summation. A contact socket in accordance with the invention is highly resistant to damage to its contact springs 34 by virtue of the fact that the sides of these springs cannot be deflected outwardly beyond the internal surface of the socket. As shown in FIG. 5, the coined section 46 of the socket wall overlaps one side of each spring and the other side of each spring overlaps the adjacent internal surface of the wall by virtue of the fact that the springs are displaced helically within the socket. It follows that the springs 34 cannot be over-stressed by being bent outwardly and any gross abuse which would overstress the contact springs would also destroy the socket to the point where it would be obviously unsuited for further use.

As was stated generally in the foregoing description, contact springs in accordance with the invention offer the design engineer a high degree of freedom of choice as regards the dimensions of the contact he is designing, the material from which he can make the contact, and the temper or hardness of the material. For example, in the embodiment shown, the ends of the springs 34 are relatively close to the socket axis as shown in FIG. 4 so that upon insertion of the contact pin 6, the ends of the springs will be deflected outwardly for substantial distance, almost to the surface of the socket. If, however, it is desired to reduce the contact force imposed on an insert pin, the springs 34 can be formed such that their ends will be spaced from the axis of the socket by a distance greater than that of the embodiment shown so that insertion of the contact pin would cause less deflection and, therefore, a low contact force. It follows that a contact socket of given dimensions can be designed with a wide variety of materials and can be designed to develop a contact force on the inserted pin within a wide range of values.

The helical surfaces of the springs provide a smooth, gradual guide surface or lead-in for the contact pin during insertion, a feature which is of importance when a large number of contact pins and sockets are provided in a multi-contact electrical connector assembly. The gradual lead-in surfaces serve to correct minor misalignments of the pins and to ensure smooth and easy coupling of the two connector parts.

The individual contact springs can be designed if desired, to contribute to the contact force by virtue of cantilever deflection as well as helical torsional deflection. The two modes of deflection can be utilized in series if desired, to permit accommodation of a larger range of pin sizes for a socket of given dimensions of what otherwise would be possible.

The principles of the invention can be used on a wide variety of contact terminals as regards contact size or specific design configuration. Contacts in accordance with the invention do not, for example, require the dual thickness stock of the disclosure embodiment but can be manufactured from stock metal of a uniform thickness throughout its width. The principles of the invention are particularly applicable to extremely small contact terminals where efficient utilization of the material is of paramount importance.

Claims

What is claimed is:

1. An electrical contact socket which is adapted to be disengageably coupled to a complementary contact pin, said contact socket comprising:

a stamped and formed tubular body which is adapted to receive said contact pin,

a contact spring, said contact spring comprising a cantilever spring arm which is integral at its fixed end with said tubular body, said spring arm having spaced-apart side edges which are substantially coextensive, said spring arm having a free end,

said spring arm extending obliquely inwardly towards the axis of said tubular body from said fixed end to said free end whereby said arm is adapted to be deflected by an inserted contact pin in the manner of a cantilever spring,

said spring arm being helically deformed along its length from said fixed end to said free end whereby said spring arm is adapted to be torsionally deflected by an inserted contact pin whereby,

electrical contact between said socket and in inserted contact pin is established by both the torsional stressing of said contact spring arm and the deflection of said spring arm as a cantilever arm.

2. A stamped and formed contact socket as set forth in claim 1 said free end of said spring being offset relative to the axis of said socket.

3. A stamped and formed contact socket as set forth in claim 1, said receptacle having an opening from which said spring arm was struck, edge portions of said opening extending laterally beyond edge portions of said free end of said spring arm whereby said spring arm cannot be moved through said opening and is thereby protected against overstressing.

4. A stamped and formed contact socket as set forth in claim 3, said edge portions of said openings being coined so that they extend over said free ends of said spring arm.