GB1576123A - Electrical connector - Google Patents

Description

(54) ELECTRICAL CONNECTOR (71) We, SIEMENS AKTIENGESELL- SCHAFT, a German Company, of Berlin and Munich, Federal Republic of Germany, 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: The invention relates to an electrical connector having a contact disposed in an insulating casing, the contact having a pair of contact arms arranged for establishing a releasable electrical contact with a contact pin or other contact member, e.g. for multipolar plug connectors.

In electronic equipment such as data processing systems, structural elements are often combined to form assemblies which can individually be plugged in, to facilitate production and maintenance. For this purpose, circuit boards made of moulded laminated plastic and having etched or printed conductor paths are commonly used. These conductor paths are interconnected either directly via so-called plug connecting elements or, when a higher transmission quality is required, via plug connectors which are arranged on the circuit boards.

Owing to the packing density and the dense concentration of the structural elements resulting therefrom, the contact clearances of the contact sockets in the plug connectors are also very small. However, in order to secure sound functioning of the contact arms, they have to satisfy the following conditions: The spring opening should differ just slightly from the insertion opening of the spring chamber, otherwise the sping will be upset on insertion of the contact pin, and thus ruined. Moreover, the contact arm requires sufficient clearance within the spring chamber, so that on insertion or withdrawal of the corresponding contact pin, the contact arms and the contact pin do not become hooked or butt against something.

Moreover, it is required of a contact arm that the fluctuations of the spring force resulking from variations in dimensions due to manufacturing tolerances are as small as possible. The contact force of the spring should not fall below a minimum value, as otherwise a reliable electrical connection can no longer be ensured. But, on the other hand, the contact force should not be excessively large because this could result in the abrasion of the surface coating of the contact (for example of gold) being unduly increased, Despite the small size of the individual contact sockets, they often have to be manufactured in such a way that they can be connected by the crimp technique. When employing this technique, contacts are mechanically contacted by means of pressing together a connecting part of the contact with the wire to be connected. In addition to this the connecting part has to be designed in such a way that therewith soldering is made possible. However, in the event of soldering, the entire connector socket becomes relatively rigid, and the required clearance of the connector socket in the spring casing is reduced.

A further demand on the contact arms.

with regard to their contact force is their appropriate adaptation to the various contact surfaces. In this context, it is well-known to employ different contact arms for different contact forces.

U.S. patent specification No. 3,646,500 discloses a contact spring which is clamped at one end into a spring chamber of a multipolar plug connector and has one or more points of contact. Here, the contact spring is, when no contact pin is inserted, biased against a firm support connected to the spring chamber, and on insertion of the contact pin, the contact spring is lifted from said support just shortly before completing the inserting process, whereby that part of the contact spring which is situated between the point of support and at least one point of contact, functions as a spring.

However, a contact spring of this kind has the disadvantage that its construction is relatively complicated and, moreover, it requires a special design for the spring cham- ber. A connecting technique corresponding to the crimp technique is hardly possible for easily replaceable contact elements.

According to the present invention there is provided an electrical connector comprising an insulating casing and a contact disposed in a chamber therein, the contact having a body portion secured in said casing and from which extends a pair of spring arms, the distance between the arms having a minimum at a region intermediate their ends whereby insertion therebetween of a contact member urges the arms apart at said region, in which the contact is so disposed in the casing that, upon insertion of a contact member, initial movement of the arms takes place without deformation of the outer end portions of the arms whilst upon further movement the free ends of the arms contact the casing and said outer end portions are deformed whereby the effective stiffness of the arms is increased, and in which the contact includes a flexible portion disposed between the pair of spring arms and a connecting portion thereof.

By "minimum" we mean not "the least possible", but a mathematical minimum i.e. a region in which the facing surfaces of the arms converge and then diverge.

In a preferred embodiment of the invention, the minimum region is formed by arms of sheet material at least one of which has a convex portion.

By means of simple measurements with regard to the bending technique, the contact spring arms can be adapted to the various requirements on the contact and insertion force in accordance with the materials used.

For this purpose, on the one hand, the insertion force can be reduced by forming out the distance element to a greater extent but, on the other hand and independent of this, it is possible to achieve a high contact force by deforming the spring leaves, for example, by forming out further the upper part of the contact sprints, so that they butt against the casing when the pin is inserted. Thereby the spring characteristic of that part of the spring element which rests against the casing wall between the point of contact and the point of support is altered and the contact force is increased.

In order that these advantageous spring characteristics do not fluctuate in dependence upon the connecting technique used, the spring system and the connecting region of the contact are decoupled via a flexible portion.

Preferably the contact is formed from a single stamped metal part.

An exemplary embodiment of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows a partially cut-away perspective view of a connector acording to one embodiment of the present invention; and Figure 2 shows a graph of the curve of forces on a spring leaf in dependence upon the deflection.

Referring to figure 1, a connector for flat cable assemblies comprises an insulating casing 1 having chambers 2 in which are disposed contact sockets. Each contact has been prepared from one piece of metal by stamping. Two spring arms 3 for receiving a contact pin 15 are provided with arched formations 4 in the vicinity of their contact surfaces. These arched formations serve to open the prestressed springs according to the width of the applied contact pin 15, in order to attain thereby a small insertion force for the connecting pin. The arched formations 4 are arranged at the edge of the contact surfaces and, at the same time, serve as guidance for the contact pin 15 to be inserted.

The spring arms 3 are secured at one end via an elastic transverse element 5. The elastic transverse element 5 together with the rear part of the spring arms 3 form a Ushaped spring, the arms 6 of which can be resiliently urged together. Due to this springing together of the arms 6 it is possible to lock the contact bush in the plug connector or its spring chambers 2 in a simple manner.

This takes place by virtue of the fact that on insertion of the contact into the spring chamber 2, the contact arms (3, 6), i.e. the spring arms 3 together with the arms 6, are urged together by virtue of an inclined face 7 situated in the chamber 2. When the contact is in the working position, the arms 6 open again and lock behind a locking edge 8. The contact may thus be snap-fitted into the connector. The inserting region of the contact bush into the spring chamber is limited by a further locking edge 9 which abuts the transverse element 5. Attention is drawn to our co-pending U.K. patent application No. 10170/78 (serial No. 1576122) which is concerned with contacts having this snap-fit feature.

Removal of the contact for replacement may be effected by inserting a knife-shaped tool 14 into the spring chamber 2.

A flexible portion 11 is arranged between an actual connecting portion 10 of the contact and the contact region (3, 6). This flexible portion 11 consists of an S-shaped bent connecting piece between the transverse element 5 and the connecting portion 10 and serves to decouple mechanically the actual connecting region (10) from the contact region (3, 6). Due to this decoupling, the spring system can conform to the respective pin position of the connecting pin within the scope of the tolerances in the spring casing.

Moreover. by means of such a decoupling it is possible to dimension the spring system as well as the connecting zone independently of one another. This is- important when, as shown here, by using flexible connecting wires connection is effected by pressing the line 12 into the connecting piece 10. On the other hand, the wire 12 may be soldered to the connecting portion 10, or connecting piece 10 itself may be soldered directly to a circuit board.

Figure 2 shows a graph where in dependence upon the deflection width (abscissa) of a spring leaf 3, the force of reaction (ordinate) acting on insertion has been plotted. In order to keep the insertion force and thus the wear and tear of a plug connector low, the spring arms 3, while installed, are advantageously prestressed just below the opening for operation (V). This takes place, as already described, by means of the arched formations 4, which serve also as guidance of the contact surface of the spring leaves 3.

The described connector thus includes an electrical contact having contact arms which show a high contact force in the presence of a relatively low insertion force. The contact arms should be designed in such a way that by means of simple measures, they can be adapted to different contact forces of different contact materials.

If various contact surfaces are required for different variants of embodiments, e.g.

gold for commercial use and tin for consumer electronics, then in dependence upon these materials it is necessary to alter the contact force. Thus, a contact force of 0.8 N is applicable as optimum for contact surfaces of gold, whereas the contact force should be higher than 2N for surfaces of tin.

In applications requiring only a low contact force, it may be convenient to use a contact arrangement in which, upon insertion of a contact pin or other member, the contact arms 3 are forced apart to a reduced extent such that they do not come to rest against the casing wall so that only the re sion between Point V and Point A, shown in the graph, is utilised. If the contact force is to be increased when using, for example, tin for the surface material of the spring leaves 3. this can be achieved by bending over further the upper edge 13 of the spring arms 3, so that this upper edge 13 comes to rest against the spring chamber, wherebv the knee in the chnracteristic shown in the graph is caused. That part of the spring leaf 3, which is situated between the point of support and the point of contact, acts as an additional spring element now, so that on insertion of a connecting pin the contact force is promptly increased up to the desired value B. Instead of bending further the spring leaves 3, it is also possible to use a thicker connecting pin.

Thus the above described embodiment of connector has the advantage of employing a contact which may be used in low contact force connectors as well as connectors in accordance with the invention in which the knee in the force curve is utilised. Obviously this can reduce the number of different patterns of contact which need to be produced for a range of connectors.

WHAT WE CLAIM IS:- 1. An electrical connector comprising an insulating casing and a contact disposed in a chamber therein, the contact having a body portion secured in said casing and from which extends a pair of spring arms, the distance between the arms having a minimum at a region intermediate their ends whereby insertion therebetween of a contact member urges the arms apart at said region, in which the contact is so disposed in the casing that, upon insertion of a contact member, initial movement of the arms takes place without deformation of the outer end portions of the arms whilst upon further movement the free ends of the arms contact the casing and said outer end portions are deformed whereby the effective stiffness of the arms is increased, and in which the contact includes a flexible portion disposed between the pair of spring arms and a connecting portion thereof.

2. A connector as claimed in claim 1, in which the flexible portion of the contact is of S-shaped form and couples a transverse element connecting the spring arms to the connecting portion.

3. A connector as claimed in claim 1 or 2, in which the minimum region is formed by arms of sheet material at least one of which has a convex portion, and couples a transverse element connecting the spring arms to the connecting portion.

4. A connector as claimed in claim 1, 2 or 3, in which the contact is formed from a single stamped metal part.

5. A connector as claimed in any one of the preceeding claims in which the spring arms are resiliently joined by a transverse element of said body portion whereby at least one of the arms serves as a locking element which engages an abutment within said chamber.

6. A connector as claimed in claim 5 in which the transverse element and the ends of the arms secured thereto form a Ushaped resilient portion, and an end edge of an arm serves to engage the abutment.

7. A connector according to claim 5 or 6 in which the chamber has a tapered portion which narrows toward a wider portion

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

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. when, as shown here, by using flexible connecting wires connection is effected by pressing the line 12 into the connecting piece 10. On the other hand, the wire 12 may be soldered to the connecting portion 10, or connecting piece 10 itself may be soldered directly to a circuit board. Figure 2 shows a graph where in dependence upon the deflection width (abscissa) of a spring leaf 3, the force of reaction (ordinate) acting on insertion has been plotted. In order to keep the insertion force and thus the wear and tear of a plug connector low, the spring arms 3, while installed, are advantageously prestressed just below the opening for operation (V). This takes place, as already described, by means of the arched formations 4, which serve also as guidance of the contact surface of the spring leaves 3. The described connector thus includes an electrical contact having contact arms which show a high contact force in the presence of a relatively low insertion force. The contact arms should be designed in such a way that by means of simple measures, they can be adapted to different contact forces of different contact materials. If various contact surfaces are required for different variants of embodiments, e.g. gold for commercial use and tin for consumer electronics, then in dependence upon these materials it is necessary to alter the contact force. Thus, a contact force of 0.8 N is applicable as optimum for contact surfaces of gold, whereas the contact force should be higher than 2N for surfaces of tin. In applications requiring only a low contact force, it may be convenient to use a contact arrangement in which, upon insertion of a contact pin or other member, the contact arms 3 are forced apart to a reduced extent such that they do not come to rest against the casing wall so that only the re sion between Point V and Point A, shown in the graph, is utilised. If the contact force is to be increased when using, for example, tin for the surface material of the spring leaves 3. this can be achieved by bending over further the upper edge 13 of the spring arms 3, so that this upper edge 13 comes to rest against the spring chamber, wherebv the knee in the chnracteristic shown in the graph is caused. That part of the spring leaf 3, which is situated between the point of support and the point of contact, acts as an additional spring element now, so that on insertion of a connecting pin the contact force is promptly increased up to the desired value B. Instead of bending further the spring leaves 3, it is also possible to use a thicker connecting pin. Thus the above described embodiment of connector has the advantage of employing a contact which may be used in low contact force connectors as well as connectors in accordance with the invention in which the knee in the force curve is utilised. Obviously this can reduce the number of different patterns of contact which need to be produced for a range of connectors. WHAT WE CLAIM IS:-

1. An electrical connector comprising an insulating casing and a contact disposed in a chamber therein, the contact having a body portion secured in said casing and from which extends a pair of spring arms, the distance between the arms having a minimum at a region intermediate their ends whereby insertion therebetween of a contact member urges the arms apart at said region, in which the contact is so disposed in the casing that, upon insertion of a contact member, initial movement of the arms takes place without deformation of the outer end portions of the arms whilst upon further movement the free ends of the arms contact the casing and said outer end portions are deformed whereby the effective stiffness of the arms is increased, and in which the contact includes a flexible portion disposed between the pair of spring arms and a connecting portion thereof.

2. A connector as claimed in claim 1, in which the flexible portion of the contact is of S-shaped form and couples a transverse element connecting the spring arms to the connecting portion.

3. A connector as claimed in claim 1 or 2, in which the minimum region is formed by arms of sheet material at least one of which has a convex portion, and couples a transverse element connecting the spring arms to the connecting portion.

4. A connector as claimed in claim 1, 2 or 3, in which the contact is formed from a single stamped metal part.

5. A connector as claimed in any one of the preceeding claims in which the spring arms are resiliently joined by a transverse element of said body portion whereby at least one of the arms serves as a locking element which engages an abutment within said chamber.

6. A connector as claimed in claim 5 in which the transverse element and the ends of the arms secured thereto form a Ushaped resilient portion, and an end edge of an arm serves to engage the abutment.

7. A connector according to claim 5 or 6 in which the chamber has a tapered portion which narrows toward a wider portion

whereby the contact may be snap-fitted into the chamber.

8. A connector substantially as herein described with reference to the accompanying drawings.