GB2048581A - Electrical socket - Google Patents

Abstract

An electrical socket for providing electrical and mechanical contact to a mating electrical pin includes an elongate metallic box which receives the pin contact. An elliptical spring (14) is secured in the box by ear pairs (40,42) projecting from the opposing ends of the elliptical spring (14). A pair of cantilevered beams (26,28), integral with the top of the box, are bent slightly downward and have their free ends in contact with the ends of the elliptical spring (14). The cantilevered beams (26,28) thus form a pair of single leaf springs. The elliptical spring (14) and the cantilevered beams (26,28) cooperate with each other to provide a suitable force on the inserted pin over a wide range of deflections of the springs. <IMAGE>

Description

SPECIFICATION Improved electrical socket This invention relates to improved electrical sockets.

More particularly, it relates to improved electrical sockets especially suitable for use in telecommunication and computer connectors, the sockets having greatly improved constancy of spring force per unit length of deflection of a spring means contained therein.

Electrical sockets or receptacles, as they are sometimes referred to, are essential elements of electrical connectors. Normally one end of the socket terminates a cable conductor by using solder or some other technique. The other end is open and is adapted to receive a corresponding electrical pin contact such as a wire-wrap post which is mounted in a member for completing a circuit. Socket contacts are designed to ensure low and stable electrical resistance through the connector, as well as mechanical integrity for the connection. Sockets have been made to provide these features by using a stamped and formed sheet metal box with a single elliptical spring fixed in the box for providing spring force downward on the pin.

An example of such a socket is shown in U.S.

Patent No. 3,370,265. This patent shows a stamped and formed rectangular box receiving a cruciform tapered elliptical spring. The spring is held in the box, in one embodiment by the use of ears on each end of the spring, and in another embodiment by lateral ears in the middle of the spring. The use of tapered elliptical springs in sockets is also taught in Mechanical Design and Systems Handbook, Section 33.31, copyrighted in 1964 by McGraw-Hill, Inc., Library of Congress Catalog No.62-21118. One drawback of the design shown in the above mentioned Patent is that in order to obtain acceptable force on the inserted pin over a range of spring deflection, a beryllium copper alloy is normally used as the spring material. This alloy is expensive to use.

Another example of the use of an elliptical spring to provide mechanical and electrical contact to a pin is taught in U.S. Patent No. 3,140,141. This shows a machined socket body rather than a stamped box, and provides a single elliptical spring held in the socket body by a shroud.

Stamped sockets have also been provided which utilize spring arms extending into the cavity of the box to provide a spring contact directly with the pin.

Examples of such contacts are shown in U.S. Patents 3,955,689 and 4,076,369. Each of these patents show socket contacts having spring arms integral with the main body of the socket, with the free ends of the arms facing inwardly towards the centre of the contact.

U.S. Patent 3,384,866 shows a socket having a spring member with a flat portion adapted to engage a corresponding electrical pin, and a pair of reversely turned arms integral with the flat portion of the spring, for providing spring pressure on the pin. As in U.S. Patent 3,140,141, the socket is machined rather than stamped.

It is an object of the invention to provide an improved electrical socket contact.

The invention and preferred embodiments thereof provide sockets having improved electrical and mechanical characteristics, and in particular improved uniformity of spring force per unit distance of deflection of a spring contained in the socket. The desired spring contact force in the socket is preferably to be obtained over a wide range of spring deflection without the use of exotic and expensive material. The socket of the invention may have acceptable mechanical and electrical characteristics and yet may be made with less expensive materials than most prior art sockets.

A preferred embodiment of the invention is in the form of a sheet metal stamped and box and contact which are inexpensive to manufacture and which have improved characteristics.

In one of its aspects the invention provides a plurality of sockets on a carrier using inexpensive materials.

According to a first aspect of the invention there is provided an electrical socket comprising an elongate box-shaped metallic member, said box-shaped member being open on at least one end for receiving an electrical pin contact; a first spring means received in and held in said box-shaped member adapted to make spring contact with the pin; and a second spring means associated with said boxshaped member and acting in conjunction with said first spring means, said second spring means providing additional spring force for enhancing the electrical mechanical contact between said socket and the pin contact.

According to a second aspect of the invention there is provided an electrical socket comprising an elongate metal housing open at at least one end for receiving an electrical pin; a beam projecting from one side of said housing, said beam forming an incline with respect to the longitudinal axis of said socket such that said beam is slightly bent inwardly so that the free end of said beam is closer to the longitudinal axis of the housing than its fixed end when the electrical pin is not received in the socket, said beam being compressed outwardly upon the insertion of an electrical pin into said socket; and an elongate spring member received in said housing, said spring member being in contact with said free end of said beam.

According to a third aspect of the invention there is provided an electrical socket comprising a substantially box-shaped member open on at least one end for receiving an electrical pin; and compound spring means in contact with said box and adapted to be in contact with an electrical pin when inserted into said box, whereby a substantial force is applied by said compound spring means onto said pin when said pin is inserted into said box.

According to a fourth aspect of the invention there is provided an electrical socket comprising an elongate metal box open on at least one end for receiving an electrical pin; a first spring means attached to said box; and a second spring means in said box and adapted to come into contact with the pin; said first spring means acting with said second spring means whereby the combined action of said first and second spring means provide substantial force on an inserted electrical pin.

According to a fifth aspect of the invention there is provided an electrical socket comprising an elongate metal box having two side walls, a base and a top portion; a pair of cantilevered beams integral with said top portion and having free ends projecting away from said top portion at an angle; a substantially elliptical spring member having two end portions and mid-portion; and means for securing said spring member inside of said box, said midportion of said spring member being closerto said base than said end portions, said free ends of said cantilevered beams being in contact with said substantially elliptical spring member near said end portion whereby upon insertion of a pin into said socket, said elliptical spring member and said cantilevered beams are deflected, causing said end portions of said elliptical spring to slide near said free ends of said cantilevered beams, thereby providing substantial force on said pin by the combined action of said elliptical spring member and said cantilevered beams.

According to a sixth aspect of the invention there is provided an electrical socket and carrier system comprising a plurality of electrical sockets, said sockets being open at both ends, each end being adapted to receive a pin contact and a carrier including a pair of elongate rails, each socket having a corresponding pair of tails extending from respective ends of said socket, each of said tails being integral with one of said rails; and at least one of said sockets having at least one of its tails offset from the longitudinal axis of rail socket.

According to a seventh aspect of the invention there is provided an electrical socket comprising an elongate box shaped metallic member, said boxshaped member being open at at least one end for receiving an electrical pin contact; a bowed spring member received in said box-shaped member adapted to make spring contact with the pin; means for holding said bowed spring member inside said box-shaped member; and at least one cantilevered beam associated with said box-shaped member and having its free end in contact with said bowed spring member, said cantilevered beam providing additional spring force for enhancing the electrical and mechanical contact between said socket and the pin.

Figure 1 is a side elevational view of the socket contact showing some of the features of the present invention.

Figure 2 is a top view of the socket contact of Figure 1; Figure 3 is a cross-sectional side elevational view of the socket contact in Figure 2 taken along line 3-3; Figure 4 is an end elevational view of the socket contact of Figure 1; Figure 5 is a top view of the curved spring member utilized in the socket contacts shown in Figures 1-4; Figure 6 is a perspective view of the socket contact shown in Figure 1; Figure 7 shows the cross-sectional view of the socket contact of Figure 3 with a corresponding pin contact inserted in the socket; Figure 8 is a graph of spring deflection v. force comprising some prior art sockets with a socket incorporating some of the features of the present invention; and Figure 9 is a plan view of a plurality of sockets, one of which being shown in Figure 2, on a carrier.

Figure 1 shows an electrical socket 10 comprising an elongate body member or box 12 and an elliptical 4 spring member 14. As better illustrated in Figure 4, the socket box includes a pair of side walls 16 and 18 and a base 20. Figures 2 shows that the box further includes a top 22 which, in this embodiment, acts only as a partial covering of the remaining side of the box. The box 10 is made by stamping and forming flat sheet metal and is held together along a seam 24, which is along the top of the box. These sockets may be provided on a carrier which is shown in Figure 9 and which will be discussed below. A pair of cantilevered beams 26 and 28 are integral with and thus a part of the body of the socket box. The ends 30 and 32 of the box are open, forming rectangular entryways, either of which is adapted to receive a pin contact.The box is designed to receive pins of various shapes, such as round or square, for exam ple, 0.635 mm by 0.635 mm. The extension 33 from the base 20 of the box is adapted to have electrical conductor 35 terminated thereto. In this embodiment conductor 35 is wedged into termination slot 80, which has been stamped in straight end 78 of extension 33.

An elliptical spring 14, such as the one shown in FigureS, is received in the box. Elliptical spring 14 is tapered from a wide mid-section 34 down to narrow ends 36 and 38. Each end of the elliptical spring includes ear pairs 40 and 42. As shown in Figure 2, these ear pairs are disposed in slots 44 and 46 of the socket box for retaining the spring in the box.

Elliptical spring 14 is bowed inwardly towards the centre of the socket box. The wide central portion 34 of this spring 14 is approximately aligned with a dimple 48, which is formed by a embossment in the base 20 of the socket. The dimple may include a gold dot 49 as a cap to prevent oxidation and to improve electrical conductivity between the pin and the socket.

As can be seen in Figure 3, each of the cantilevered beams 26 and 28 are pre-biased or deflected downwardly from the horizontal as indicated by the angle a, the horizontal being represented by the flat plane of top 22 of the socket. The bends 50 and 52 of the beams occur approximately at the junction between the beams and the top of the socket box. These cantilevered beams thus form a pair of single leaf spring members with the free ends 54 and 56 being respectively in contact, in this embodiment, approximately with the ends of the ear pairs 40 and 42 of the elliptical spring 14. As will be explained below, the cantilevered beams and the elliptical spring member cooperate with each other to provide improved electrical and mechanical contact with an inserted electrical pin. The beams also help to retain the elliptical spring in the box.

Figure 7 illustrates an electrical pin contact 58 which has been inserted in the cavity of socket box 12. As can be seen, this particular pin contact is of a slightly oversized diameter and of a length to fully deflect upwardly to the horizontal both the elliptical spring member 14 and the cantilevered beams 26 and 28. Normal and smaller sizes of pins may also be used by taking advantage of the cooperation between the elliptical and cantilevered springs. Since there is substantial deflection of the elliptical spring member 14, it has been straightened out, forcing the eared free ends 40 and 42 near the free ends 54 and 56 of the cantilevered beams. Thus, in this embodiment, the elliptical spring is designed to remain within the limits of the cantilevered spring ends.The beams exert substantial force down on these elliptical springs approximately at positions 60.and 62 on the elliptical spring, or wherever such contact occurs depending on the relative lengths of the beams and elliptical spring, their bend angles, and the type of materials used. Thus, the forces provided by the combination of the cantilevered beams and the elliptical spring bear down on the pin to provide a greatly improved electrical and mechanical contact with the pin when inserted in an electrical socket. As can be seen, with the deflection upwardly of the cantilevered beams the angle a between the beam and the horizontal top 22 goes to approximately zero degres, again depending on the size of the pin.

Figure 8 illustrates a graph showing the calculated spring force on the pin versus the deflection of spring means, comparing a socket with an elliptical spring only against the embodiment of the present invention shown in Figures 1 to 7 utilizing a pair of cantilevered beams and an elliptical spring. The force per unit deflection contribution of the cantilevered beams above is also illustrated. As can be seen, line 64, which illustrates the use of the cantilevered beams only, does not provide sufficient force to meet minimum electrical contact require ments. Line 66, which illustrates the use of an elliptical spring without the cantilevered beams, shows that an acceptable force range of from 0.250 lb. (0.113 kg) to 0.400 lb. (0.181 kg) may be met through deflections from about 0.0038 in. (0.096 mm) to about 0.0073 in. (0.185mm).However, by the use of the socket of the subject invention, particularly using the dual cantilevered beams and the elliptical spring, as indicated by line 68, the same range of acceptable forces is achieved through a much larger range of spring deflection, i.e. from about 0.0047 in. (0.1 19mm) to about 0.0091 in. (0.231 mm). This is particularly important when oversized pins, such as the one shown in Figure 7, are used.

The spring stress is much lower as the spring force becomes more constant over a given range of deflection. A decrease in stress will increase the life expectancy of the spring. Clearly line 68 shows a more constant force than line 66. Thus the force to deflection ratio is lower using the socket of the subject invention when compared to a single leaf spring socket. Thus, since pin contacts come in various sizes or diameters, due to manufacturing variations, the socket of the subject invention is capable of performing acceptably with a far greater degree of flexibility.

The socket contact illustrated above has been formed by known sheet metal stamping and forming procedure with the socket box 12 made of nickelcopper (CA 725) alloy and the elliptical spring made of a 510 phos-bronze alloy (CA 510). Simple 48 was gold plated. The angle of curvature of the elliptical spring was approximately 25 degrees from its tangent and the angle of deflection ofeach of the cantilevered beams was approximately 10 degrees from horizontal.

Thus, it can be seen that independent spring forces have been combined to achieve a greatly improved electrical contact socket. Furthermore, the forces on the pin may be easily adjusted by simply varying the angle a, that is the amount of spring bias in the cantilevered beams, thus making a readily adjustable socket.

Even more importantly, however, the decreased force to deflection ratio caused by the cantilevered beams permit the use of material in the elliptical spring which have lower modulii of elasticity and yield strength than prior sockets, such as the socket previously described in U.S. Patent 3,370,265 and are much cheaper materials. For example, 510 phos-bronze which is used as a material in the preferred embodiment, has a modulus of elasticity of about 17.5 x 106 PSI(1.23x106 kg/cm2) and a yield strength of about 92 to 108 x 106 Pal(6.47 to 7.59 x 106 kg/cm2) while 170 beryllium copper, which is referred to in U.S. Patent 3,370,265 has a modulus of elasticity of about 18.5 x 106PS1(1.30 x 106kg/cm2) and a yield strength of about 120 to 140 x 106 PSl(8.44to 9.84 x 106 kg/cm2).The alloy 170 beryllium copper current costs between twice and three times as much as 510 phos-bronze. The socket design of the subject invention thus enables one to manufacture a socket which performs better than prior art sockets, and for a much lower cost.

As stated previously, the socket may be provided on a carrier such as carrier 70, as shown in Figure 9.

A plurality of sockets 22 are coupled to each rail 72 and 74 of the carrier through tails 76 and 78, which extend from respective ends of the socket. As stated previously, the socket 22 is symmetrical and thus capable of receiving a corresponding pin in either end. Thus the tails 76 and 78 extend from either end.

However, when the socket 22 is to be inserted into an electrical connector, one of the tails of course, must be clipped off. The tail for each socket acts as an electrical conductive path or transition between the socket and an electrical conductor. It has been found that it is advantageous to terminate the electrical conductor to the tail by the use of a slot such as slot 80. Of course, if tail 78 were utilized then a slot could also be punched in tail 78. As can be seen, a portion of tail 76 is offset from the longitudinal axis of socket 22, while tail 78 is not offset. Thus one may used a socket having an offset tail or a straight tail depending on the need, particularly since, as stated previously, the socket may receive a pin contact from either end. The reason for the offset tail or transition element is in order to provide for the difference between the distance between electrical conductors in a flat cable and sockets in a connector. Furthermore, the width of the tails 76 and 78 are wide enough so that the slot which is punched therein provides sufficient holding strength to hold the conductor which is to be inserted in the slot for proper termination. The carrier tails and socket, except for spring 14, are made from a single strip of nickel-copper alloy (CA 725). It has been found quite unexpectedly that this nickel-copper alloy with a thickness of approximately 0.15 mm. is of sufficient hardness and thickness, and in the case of the tails, the proper width, to provide the desired beam spring characteristics in the socket, as well as the desired characteristics for terminating the wire to a tail or transition member. The carrier socket box and tails are stamped from this roll of nickel-copper using known stamping techniques. Holes 82 provide indexing during the stamping process.

Claims (26)

1. An electrical socket comprising an elongate box-shaped metallic member, said box-shaped member being open on at least one end for receiving an electrical pin contact; a first spring means received in and held in said box-shaped member adapted to make spring contact with the pin; and a second spring means associated with said boxshaped member and acting in conjunction with said first spring means, said second spring means providing additional spring force for enhancing the electrical and mechanical contact between said socket and the pin contact.

2. An electrical socket as claimed in Claim 1, wherein said second spring means includes at least one cantilevered beam, the free end of said beam being in contact with said first spring means near the opposing end thereof.

3. An electrical socket as claimed in Claim 1 or 2, wherein said first spring means is elliptical in shape and bowed.

4. An electrical socket as claimed in any preceding Claim, wherein said first spring means is held inside said box by a pair of ears on each end of said first spring means, and a pair of slots is provided in each end of said box for receiving said ears.

5. A socket as claimed in any preceding Claim, further including a base on said box-shaped member, said base including a dimple projecting inside said box-shaped member, said first spring means being tapered from the middle of said spring towards its ends, with the middle of said spring being approximately at the same longitudinal position inside said box-shaped member as said dimple.

6. An electrical socket as claimed in any preceding Claim, wherein said box includes a top portion which is substantially parallel to the longitudinal axis of said socket, said top portion covering only a part of a side of said socket; and a pairofcantilevered beams integral with said top portion and projecting away from said top portion forming free ends, said beams forming an incline with respect to said top portion, said free ends being in contact with portions of said first spring means.

7. An electrical socket as claimed in any preceding Claim, wherein said first spring means is made from a phos-bronze alloy.

8. An electrical socket as claimed in any preceding Claim, further including a metallic tail extending from one end of said contact, a slot being provided in said tail for terminating an electrical conductor thereto.

9. A plurality of electrical sockets as claimed in any preceding Claim coupled by coupling means to a carrier.

10. An electrical socket comprising an elongate metal housing open at at least one end for receiving an electrical pin; a beam projecting from one side of said housing, said beam forming incline with respect to the longitudinal axis of said socket such that said beam is slightly bent inwardly so that the free end of said beam is closer to the longitudinal axis of the housing than its fixed end when the electrical pin is not received in the socket, said beam being compressed outwardly upon the insertion of an electrical pin into said socket; and an elongate spring member received in said housing, said spring member being in contact with said free end of said beam.

11. An electrical socket comprising a substantially box-shaped member open on at least one end for receiving an electrical pin; and compound spring means in contact with said box and adapted to be in contact with an electrical pin when inserted into said box, whereby a substantial force is applied by said compound spring means onto said pin when said pin is inserted into said box.

12. An electrical socket comprising an elongate metal box open on at least one end for receiving an electrical pin; a first spring means attached to said box; and a second spring means in said box and adapted to come into contact with the pin; said first spring means acting with said second spring means whereby the combined action of said first and second spring means provide substantial force on an inserted electrical pin.

13. An electrical socket comprising an elongate metal box having two side walls, a base and a top portion; a pair of cantilevered beams integral with said top portion and having free ends projecting away from said top portion at an angle; a substantially elliptical spring member having two end portions and mid-portion; and means for securing said spring member inside of said box, said midportion of said spring member being closer to said base than said end portions, said free ends of said cantilevered beams being in contact with said substantially elliptical spring member near said end portion whereby upon insertion of a pin into said socket, said elliptical spring member and said cantilevered beams are deflected, causing said end portions of said elliptical spring to slide near said free ends of said cantilevered beams, thereby providing substantial source on said pin by the combined action of said elliptical spring member and said cantilevered beams.

14. An electrical socket and carrier system comprising a plurality of electrical sockets, said sockets being open at both ends, each end being adapted to receive a pin contact; and a carrier including a pair of elongate rails, each socket having a corresponding pair of tails extending from respective ends of said socket, each of said tails being integral with one of said rails; and at least one of said sockets having at least one of its tails offset from the longitudinal axis of rail socket.

15. An electrical socket and carrier system as claimed in Claim 14, wherein said carrier, said tails and at least a portion of said sockets are made from the same material.

16. An electrical socket and carrier system as claimed in Claim 15 wherein said material is a nickel-copper alloy.

17. An electrical socket and carrier system as claimed in any one of Claims 14to 16, further including a slot in at least one tail extending from each socket, said slot being adapted to receive and terminate an electrical conductor.

18. An electrical socket and carrier system as claimed in any one of Claims 14 to 17, wherein each of said sockets includes an elongate box shaped metallic member, said box-shaped member being open at at least one end for receiving an electrical pin contact; a first spring means receved in and held in said box-shaped member adapted to make spring contact with the pin contact; and a second spring means associated with said box-shaped member and acting in conjunction with said first spring means, said second spring means providing additional spring force for enhancing the electrical and mechanical contact between said socket and the pin contact.

19. An electrical socket comprising an elongate box shaped metallic member, said box-shaped member being open at at least one end for receiving an electrical pin contact; a bowed spring member received in said box-shaped member adapted to make spring contact with the pin; means for holding said bowed spring member inside said box-shaped member; and at least one cantilevered beam associated with said box-shaped member and having its free end in contact with said bowed spring member, said cantilevered beam providing additional spring force for enhancing the electrical and mechanical contact between said socket and the pin.

20. An electrical socket as claimed in claim 19, wherein said at least one cantilevered beam includes a pair of cantilevered beams, the free end of each of said beams being in contact with said bowed spring nearthe opposing ends of said bowed spring.

21. An electrical socket as claimed in Claim 19 or 20, wherein said bowed spring means is elliptical in shape.

22. An electrical socket as claimed in Claim 19,20 or 21, wherein said means for holding said bowed spring member inside said box includes a pair of ears on each end of said spring member and a pair of slots in each end of said box for receiving said ears.

23. An electrical socket as claimed in any one of Claims 19 to 22 further including a base on said box-shaped member, said base including a dimple projecting inside said box-shaped member, said bowed spring member being tapered from the middle of said spring towards its ends, with the middle of said spring being approximately at the same longitudinal position inside said box-shaped member as said dimple.

24. An electrical socket as claimed in Claim 20 wherein said box includes a top portion which is substantially parallel to the longitudinal axis of said socket, said top portion covering only a part of a side of said socket, said pair of cantilevered beams being integral with said top portion and projecting away from said top portion forming free ends, said beams forming an incline with respect to said top portion, said free ends being in contact with portions of said bowed spring member.

25. An electrical socket as claimed in any one of Claims 19 to 24, wherein said first spring means is made from a phos-bronze alloy.

26. An electrical socket substantially as herein described with reference to any one of the embodiments illutrated in the accompanying drawings.