GB1571601A - Electric contacts - Google Patents

Description

(54) ELECTRIC CONTACTS (71) We, BIcc-BURNDY LIMITED, a British Company of Parr, St. Helens, Merseyside, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to resilient electric contacts and more especially to contacts for separable electric connectors. More particularly it relates to contacts having cantilever springs or other resilient fingers. One important form of the invention is a socket contact suitable for use in a multi-pole twopart connector, especially one of small size.

Connectors often involve small and relatively fragile components, which are easily damaged if, from minor misuse or inevitable dimensional discrepancies, the contacts of a pair are misaligned when the connectors are brought together or disconnected. One form of damage that is, from a practical point of view, irreparable, arises when a resilient member of a contact is bent in the intended direction but by an excessive amount, so that some part of it is deflected beyond its elastic limit and so the member is permanently deformed. Cantilever springs and other resilient fingers are particularly susceptible to damage of this kind, and proposals have been made over many years (see for example British Patent Specification 451990) to provide contacts that rely on such springs with various kinds of projection designed to engage the free end of the cantilever before permanent deformation occurs and to provide additional support to resist further deflection.

We have found that such projecting supports are not always reliable, particularly when the contact is made from thin sheet metal.

Furthermore, it is of course necessary to control the contact force so as to keep it within a range determined by the electrical and mechanical performance required and this may be difficult especially in the smaller sizes. In some cases it is found impracticable within the limitations imposed by the space available and the material of the resilient finger, to obtain sufficient force from a true cantilever, that is a resilient finger which operates with one end free and unsupported.

In such cases it may be desirable to use a resilient spring finger with an arched form and with its free end bearing in normal operation upon a fixed, rigid part of the structure. In this way, the operation of the spring is converted from that of a cantilever to that of an arched beam, supported but free to move longitudinally at one end. This type of spring will give a larger restoring force on deflection than a true cantilever spring of comparable dimensions made from the same material, and has a better deflection range than an arched spring with both ends fixed.

There are, therefore, two possible reasons why a designer of electrical connectors may wish to provide a rigid support to engage the free end of a resilient spring finger. Firstly he may do so as a safety measure to prevent damage or, secondly, he may do so in order to effect a fundamental change in the mode of operation of the spring.

In accordance with the present invention, an electric contact is made from sheet metal and includes at least one resilient finger integrally connected to a body member of the contact at one of its ends and at one end of an aperture in the body member. The finger overlies the aperture and extends beyond it so that the free end of the finger overlies a part of the body member that is directly supported on both sides (as distinct from a projection in the body supported in cantilever from one side or one end only) and is engaged with it or can be engaged with it by resilient deflection of the finger.

It will be appreciated that the finger will be formed by part or all of the metal blanked out to create the aperture, and that it will need to be elongated if the parts of the sheet bounding the aperture remain planar. A preferred method of manufacture is the subject of our copending Application No.

28239/76 (Serial No. 1571602) filed on the same day as this application, and entails first severing a part of the sheet from which the spring is to be formed from the remaining part of the sheet along its sides only, with or without removing metal, so that it remains attached at both ends, simultaneously or subsequently stretching and bowing that part to elongate it significantly, and afterwards severing one end of the spring from the sheet and reducing its curvature until that end overlies a part of the sheet from which it was severed.

One imporant instance of the application of this invention is a female contact or socket of tubular form with the resilient finger extending into the bore thereof, which may be circular, square, rectangular or any other convenient cross-section. Preferably two resilient fingers are formed in opposite walls of the socket, both of which will make electrical contact with a pin or other male contact when the latter is inserted in the female contact. The contact may also include a crimping barrel, wire wrap pillar, or other means for connection of a wire or other conductor; and a resilient detent or other means may be provided for securing the contact in an insulating housing.

The invention will be further described, by way of example, with reference to the accompanying drawings in which Figure 1 is an isometric drawing of a preferred form of socket contact in accordance with the invention; Figure 2 is a fragmentary cross-section in the plane of the chain line 2 in figure 1; and Figure 3 is an isometric cut-away drawing of another form of contact in accordance with the invention.

The contact of figures 1 and 2 is formed from a single piece of resilient sheet metal and consists of a crimping bucket section 3 (of conventional design) and a socket section 4.

The socket section is basically rectangular, with an unseamedjoint 5 down the middle of one face (the seam could be welded, soldered or bonded with adhesive if the cost were justified in particular cases by the use of thinner metal or otherwise). The opposite face has stamped out of it a latching spring 6 which is designed to snap over and engage a shoulder in an insulating housing when the contact is pushed, mating-end 7 first, into a bore in the housing so securing the contact against withdrawal, the end 7 of the contact will usually engage a further shoulder to ensure that the contact cannot pass right through the bore, nor move too far forward in it.

In accordance with the invention, resilient contact fingers 8 stamped from the other two faces of the socket and bowed to project into the interior thereof overlap at their free ends 9 (as best seen in figure 2) with the parts 10 of the sheet that are directly supported on both sides 11 12 (figure 1). The ends 9 may or may not touch the parts 10 in the free state of the socket contact; if not they will do so after a predetermined deflection of the respective contact finger by an inserted pin contact. In the design shown the corners of the socket have been cut away adjacent to the contact fingers; the extra clearances so obtained simplify tooling design.

The contact of figure 3 has a single contact finger struck from the base of a channel -member, and closely resembles one half of the contact of figure 1; the same reference numbers have been used for corresponding parts. This can be used as a male resilient contact entering a rigid rectangular socket, or to engage a contact on a printed circuit board.

WHAT WE CLAIM IS: 1. An electric contact made from sheet metal and including at least one resilient finger integrally connected to a body member of the contact at one of its ends and at one end of an aperture in the body member, the finger overlying the aperture and extending beyond it so that the free end of the finger overlies a part of the body member that is directly supported on both sides and is engaged with it or can be engaged with it by resilient deflection of the finger.

2. A female electric contact made from sheet metal and including at least one resilient finger integrally connected to a tubular body member of the contact at one of its ends and at one end of an aperture in the body member, the finger extending into the bore of the contact, overlying the aperture and extending beyond it so that the free end of the finger overlies a part of the body member that is directly supported on both sides and is engaged with it or can be engaged with it by resilient deflection of the finger.

3. A female electric contact made from sheet metal and including two resilient fingers formed in opposite walls of a tubular body member of the contact and each integrally connected to the body member at one of the ends of the finger and at one end of an aperture in the respective wall, each finger overiying the respective aperture and extending beyond it so that the free end of the finger overlies a part of the body member that is directly supported on both sides and is engaged with it or can be engaged with it by resilient deflection of the finger.

4. A contact as claimed in any one of the preceding claims including a resilient detent or other means for securing the contact in an insulating housing.

5. A socket contact substantially as

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. subsequently stretching and bowing that part to elongate it significantly, and afterwards severing one end of the spring from the sheet and reducing its curvature until that end overlies a part of the sheet from which it was severed. One imporant instance of the application of this invention is a female contact or socket of tubular form with the resilient finger extending into the bore thereof, which may be circular, square, rectangular or any other convenient cross-section. Preferably two resilient fingers are formed in opposite walls of the socket, both of which will make electrical contact with a pin or other male contact when the latter is inserted in the female contact. The contact may also include a crimping barrel, wire wrap pillar, or other means for connection of a wire or other conductor; and a resilient detent or other means may be provided for securing the contact in an insulating housing. The invention will be further described, by way of example, with reference to the accompanying drawings in which Figure 1 is an isometric drawing of a preferred form of socket contact in accordance with the invention; Figure 2 is a fragmentary cross-section in the plane of the chain line 2 in figure 1; and Figure 3 is an isometric cut-away drawing of another form of contact in accordance with the invention. The contact of figures 1 and 2 is formed from a single piece of resilient sheet metal and consists of a crimping bucket section 3 (of conventional design) and a socket section 4. The socket section is basically rectangular, with an unseamedjoint 5 down the middle of one face (the seam could be welded, soldered or bonded with adhesive if the cost were justified in particular cases by the use of thinner metal or otherwise). The opposite face has stamped out of it a latching spring 6 which is designed to snap over and engage a shoulder in an insulating housing when the contact is pushed, mating-end 7 first, into a bore in the housing so securing the contact against withdrawal, the end 7 of the contact will usually engage a further shoulder to ensure that the contact cannot pass right through the bore, nor move too far forward in it. In accordance with the invention, resilient contact fingers 8 stamped from the other two faces of the socket and bowed to project into the interior thereof overlap at their free ends 9 (as best seen in figure 2) with the parts 10 of the sheet that are directly supported on both sides 11 12 (figure 1). The ends 9 may or may not touch the parts 10 in the free state of the socket contact; if not they will do so after a predetermined deflection of the respective contact finger by an inserted pin contact. In the design shown the corners of the socket have been cut away adjacent to the contact fingers; the extra clearances so obtained simplify tooling design. The contact of figure 3 has a single contact finger struck from the base of a channel -member, and closely resembles one half of the contact of figure 1; the same reference numbers have been used for corresponding parts. This can be used as a male resilient contact entering a rigid rectangular socket, or to engage a contact on a printed circuit board. WHAT WE CLAIM IS:

1. An electric contact made from sheet metal and including at least one resilient finger integrally connected to a body member of the contact at one of its ends and at one end of an aperture in the body member, the finger overlying the aperture and extending beyond it so that the free end of the finger overlies a part of the body member that is directly supported on both sides and is engaged with it or can be engaged with it by resilient deflection of the finger.

2. A female electric contact made from sheet metal and including at least one resilient finger integrally connected to a tubular body member of the contact at one of its ends and at one end of an aperture in the body member, the finger extending into the bore of the contact, overlying the aperture and extending beyond it so that the free end of the finger overlies a part of the body member that is directly supported on both sides and is engaged with it or can be engaged with it by resilient deflection of the finger.

3. A female electric contact made from sheet metal and including two resilient fingers formed in opposite walls of a tubular body member of the contact and each integrally connected to the body member at one of the ends of the finger and at one end of an aperture in the respective wall, each finger overiying the respective aperture and extending beyond it so that the free end of the finger overlies a part of the body member that is directly supported on both sides and is engaged with it or can be engaged with it by resilient deflection of the finger.

4. A contact as claimed in any one of the preceding claims including a resilient detent or other means for securing the contact in an insulating housing.

5. A socket contact substantially as

described with reference to and as shown in figures 1 and 2 of the drawings.

6. A contact substantially as described with reference to and as shown in figure 3 of the drawings.