GB2357195A

GB2357195A - An electrical socket

Info

Publication number: GB2357195A
Application number: GB9928828A
Authority: GB
Inventors: Tony Smith
Original assignee: THERMAPRO Ltd
Current assignee: THERMAPRO Ltd
Priority date: 1999-12-06
Filing date: 1999-12-06
Publication date: 2001-06-13
Also published as: GB9928828D0

Abstract

An electrical socket (30) for receiving a plug (140), in particular in the field of electrical or electronic devices having removable plug in components. The socket (30) has a spring (100) disposed within a housing (40) that is adapted to guide the inserted plug pin (140) towards the socket electrical contact (70) and to bias the two contacts together.

Description

2357195 AN ELECTRICAL SOCKET This invention relates to an electrical

socket.

Electrical sockets are found in many devices. For example, electrical sockets are often used in electric al or electronic devices that have plug in removable components. An example is a thermocouple device in which the thermocouple probe is removably coupled to a control unit.

In electrical socket connectors, into which male type electrical connectors are plugged, it is important that it is easy to plug the connectors in and that a good low resistance contact between the two connectors is achieved. Known electrical socket devices have sought to achieve a good contact between the electrical connectors by biasing the connectors together using spring devices. Figures 1 and 2 show two such known devices. In Figure 1, a C-clamp 10 passes around two conductors 12 which are arranged to receive a plug in electrical contact between them, the C- clamp 10 biases the two electrical contacts 12 together. A guide portion 30 is provided to facilitate insertion of the male type connector. In Figure 2, a coil spring 20 is used to bias the conductors 12 together.

With the continual reduction in size of electrical and electronic components it is often the mechanical parts associated with them that determine the overall size of a device. There is therefore an increasing demand to reduce the size of these associated mechanical parts in order to decrease the overall size of the device. In the case of electrical sockets, the overall size of the socket may to a large extent be governed by the size of the biasing spring. The C-clamp illustrated in Figure 1 passes around the conductors outside the width of the contact thereby leading to an increase in the width of the socket. The coil spring illustrated in Figure 2 is also not a compact device.

Furthermore, both devices require separate guide portions to aid insertion of the electrical connectors.

In the field of thermocouple devices, narrow electrical contacts are preferred as this aids the provision of polarised connectors in a small space. In these devices a low resistance contact is also required over a narrow contact region. Furthermore, in the field of thermocouples, the electrical pathway must be formed from a single metallic

2 element or alloy. As the materials forming the thermocouple tend not to make good springs, the springs, which are usually made from spring steel, need to be outside the electrical pathway. Thus, the springs holding the contacts together in a thermocouple act from outside to push the contacts together.

In accordance with the present invention there is provided a socket for receiving a plug having a plug electrical contact, the socket comprising: a housing having an inlet leading to a recess; a socket electrical contact disposed within the housing; an insertion pathway bound by the inlet, at least a portion of the recess and at least a portion of the socket electrical contact; and a spring disposed within the housing, the spring having a portion biased to project into the insertion pathway, the biased portion being arranged such that on insertion of a plug electrical contact the biased portion directly touches the plug electrical contact, guides the inserted plug electrical contact towards the socket electrical contact and biases the plug electrical contact against the socket electrical contact.

The socket of the present invention alleviates the disadvantages of the sockets of the prior art, by providing a socket having a spring for biasing the contacts together whose biased portion acts both to guide the inserted plug electrical contact and to supply the biasing force whilst directly touching the inserted contact.

In prefer-red embodiments the biased portion of the spring converges towards the socket electrical contact away from the inlet. Owing to this arrangement of the biased portion of the spring it is well adapted to act as a guide to the inserted plug obviating the need for additional guide means and thereby increasing the compactness and reducing the cost of manufacturing the device.

Although the housing may be a unitary piece, in preferred embodiments the housing comprises an upper and a lower portion. The provision of a two piece housing enables the socket to be easily assembled.

Advantageously the spring is disposed within the recess. This is a compact construction, the recess acting to hold the spring in place.

Preferably, the spring further comprises a first and a second linear portion extending substantially parallel to one another in a first plane; and wherein the biased 3 portion comprises an arc, at least a portion of which overlies but does not extend beyond the part of the first plane that lies between the two linear portions.

This spring formation is both robust and compact while still providing a good biasing force. The positioning of the resiliently biased arc above and inside of the linear portions enables a narrow contact to be able to operate the spring.

In preferred embodiments the length ftirther comprises: a first helical portion extending from the first linear portion to a first end of the arc and a second helical portion extending from the second linear portion to a second end of the arc, the helical portions acting to resiliently bias the arc away from the first plane.

Helical portions are particularly well adapted at producing a sizeable resilient force from a compact volume.

Although the helical portions may be at an angle to the first plane containing the two linear portions it is preferred that their transversal cross sections are substantially perpendicular to this first plane.

Advantageously, the helical portions are substantially coaxial. This arrangement provides a uniform force across the width of the are.

In preferred embodiments the socket further comprises a nut and a bolt for attaching a connecting wire to the socket electrical contact, the nut being located within a matching recess in the housing such that rotational movement of the nut is inhibited.

The nut is held in a matching recess within the housing to inhibit rotational movement while allowing vertical movement. Thus, as the bolt is tightened the nut rises without rotating. This means that if the connecting wire is placed between the nut and the electrical contact, tightening of the bolt to hold the wire in place will not result in a twisting force being transmitted to the wire. This obviates the need for any additional intermediate washer type parts for protecting the wire from any twisting force.

In preferred embodiments the socket electrical contact is a stamped metal plate, the chanifered edges of which face towards the insertion pathway.

Metal stamping is a convenient way of producing the socket electrical contact, while having the charnfered edges facing the insertion pathway aids insertion of a plug.

4 Advantageously, the plug comprises a stamped metal plate that is substantially the same as the stamped metal plate forming the socket electrical contact, the plug being arranged such that its chamfered edges face towards the chamfered edges of the socket electrical contact. By having plug and socket electrical contacts that are substantially the same means that they can be produced by an identical process, manufacturing costs are thereby significantly reduced. Furthermore, by placing the chamfered edges facing each other, insertion of the plug into the socket is made easier.

Although the socket is suitable for many applications in the electronic field where removable devices having electrical contacts need to be plugged together, it is particularly well adapted to biasing together the contacts of a thermocouple.

Thermocouples require good electrical contact between the contacts; finthermore, they are often compact devices. Thus, the socket of the present invention is very well suited for use in this field.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 illustrates a conventional C-clamp device for biasing electrical contacts together; Figure 2 illustrates a conventional coil spring device for biasing electrical contacts together; Figure 3 illustrates a plan view of two electrical socket devices according to an embodiment of the invention with associated plug in electrical connectors; and Figure 4 illustrates a transverse cross section of two electrical socket devices according to an embodiment of the invention with associated plug in electrical connectors.

With reference to Figure 3, two sockets 30 according to an embodiment of the invention are shown. Each socket is essentially identical with the other one, though of slightly different dimensions, one being the positive contact and the other the negative.

The different widths of the two sockets prevent the wider plug being inserted into the narrower socket and thereby prevent mismating of the two pole plug and socket contact pair. In the embodiment illustrated, the sockets shown are for connecting a thermocouple probe to a control unit. In the following description just one of the two sockets will be considered.

Figure 4 shows a transverse view of this socket. The socket 30 comprises a plastic housing with an upper portion 40 and a lower portion 45, the housing having a recess 50 and an inlet 60. A conducting plate 70 (socket electrical contact) is located in a recess in the lower part of the socket body 45 and is prevented from vertical movement by the upper part of the socket body 40. The two parts of the socket housing are connected together by screw 42. A bolt 80 passes through the conducting plate 70. A nut 85 attached to the bolt is held in a matching recess which inhibits rotational movement of the nut while allowing it some vertical movement. The socket is electrically connected to the rest of the device via a wire 90 (see Figure 4) which is connected to the underside of the conducting plate 70, by the nut 85 and bolt 80. The wire 90 is located between the conducting plate 70 and the nut 85, this ensures that as the bolt is tightened there is no twisting force transmitted to the wire.

The socket 30 ftu-ther comprises a spring 100. The spring is arranged within the recess 5 0 of the housing 40. The spring has two linear portions 110 each connected to helical torsion spring portions 120 which bias an arc 130 away from the two linear portions 110. The spring 100 is arranged within the recess 50 of the housing 40 underneath the conducting plate 70. Thus, an electrical connecting plug 140 inserted through the inlet 60 passes between the spring 100 and the conducting plate 70, and contacts the arc 130 of the spring 100. As it travels further in it is pushed by the arc of the spring 100 up against the conducting plate 70, thereby ensuring a good contact between the two contacts. The form of the spring 100 is such that it sits within the footprint of the conducting plate 70 and the electrical connector plug 140. The use of this type of spring reduces the width occupied by the spring. This leads to a compact socket. Furthermore, the helical torsion springs 120 enable a high con tact force to be obtained from a small volume. The positioning of the helical torsion springs 120 inside of the linear portions 110 mean that the width of the arc 13 0 is small, so that narrow connector plugs can still operate the spring 100.

The angling of the arc 130 of the spring 100 towards the conducting plate 70 is such that it starts from a low point close to the helical portions thereby leaving a 6 substantial gap at this point between the spring 100 and the conducting plate 70. As the spring 100 is arranged such that the helical torsion springs 120 are near the inlet 60 of the housing 40, this gap occurs adjacent to the inlet 60 forming a natural opening into which a connecting plug 140 can be inserted. This opening narrows as you travel into the housing 40 and the arc 130 of the spring 100 rises up towards the conducting plate 70. Thus, the spring 100 acts as a natural guide for insertion of the plug 140. If metal stamped conducting plates 70 are used, this guiding function can be further aided by using the natural chamfer from the stamping of the connector plates 70, so that the conducting plate 70 has a rounded end 72 on its lower side and the connecting plug 140 has a rounded end 142 on its upper side.

In the embodiment illustrated, the conducting plate 70 is offset on one side of a centre line and the connector plug 140 on a different side. This enables them to be stamped from the same machine, conducting plate 70 being conducting plate 140 rotated through 1801. This also means that the chamfering occurs on different sides such that the chamfered sides (72, 142 of Figure 4) connect when the plug is inserted and aid the insertion action.

In the embodiment illustrated the two sockets shown are offset to different sides of the centre line and have different widths. Both the offset and the different widths aids polarisation in the thermocouple device, i.e. the plug in device can only be inserted one way round.

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Claims

1. A socket for receiving a plug having a plug electrical contact, the socket comprising:

a housing having an inlet leading to a recess; a socket electrical contact disposed within the housing; an insertion pathway bound by the inlet, at least a portion of the recess and at least a portion of the socket electrical contact; and a spring disposed within the housing, the spring having a portion biased to project into the insertion pathway, the biased portion being arranged such that on insertion of a plug electrical contact the biased portion directly touches the plug electrical contact, guides the inserted plug electrical contact towards the socket electrical contact and biases the plug electrical contact against the socket electrical contact.

2. A socket according to claim 1, wherein the biased portion of the spring converges towards the socket electrical contact away from the inlet.

3. A socket according to any one of the preceding claims, wherein the housing comprises an upper and a lower portion.

4. A socket according to any one of the preceding claims, wherein the spring is disposed within the recess.

5. A socket according to any one of the preceding claims, wherein the spring further comprises a first and a second linear portion extending substantially parallel to one another in a first plane; and wherein the biased portion comprises an arc, at least a portion of which overlies but does not extend beyond the part of the first plane that lies between the two linear portions.

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6. A socket according to claim 5, wherein the spring further comprises a first helical portion extending from the first linear portion to a first end of the arc and a second helical portion extending from the second linear portion to a second end of the arc, the helical portions lying between the two linear portions and acting to resiliently bias the arc away from the first plane.

7. A socket according to claim 6, wherein respective transversal cross sections of the helical portions are substantially perpendicular to the first plane.

8. A socket according to any one of claim 6 or clairn 7, wherein the helical portions are substantially coaxial with each other.

9. A socket according to any one of the preceding claims, the socket further comprising a nut and a bolt for attaching a connecting wire to the socket electrical contact, the nut being located within a matching recess in the housing such that rotational movement of the nut is inhibited.

10. A socket according to any one of the preceding claims, wherein the socket electrical contact is a stamped metal plate, the chamfered edges of which face towards the insertion pathway

11. A socket according to any one of the preceding claims, wherein the socket is for connecting a probe of a thermocouple to a display device.

12. A plug and socket, comprising a socket as claimed in any one of the preceding claims.

13. A plug and socket, comprising a socket according to claim 10, the plug comprising a stamped metal plate that is substantially the same as the stamped metal plate forming the socket electrical contact, the plug being arranged such that its chamfered edges face towards the chamfered edges of the socket electrical contact.

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14. A socket substantially as hereinbefore described with reference to Figures 3 and 4 of the accompanying drawings.

15. A plug and socket substantially as hereinbefore described with reference to Figures 3 and 4 of the accompanying drawings.