GB2125134A

GB2125134A - Improvements in and relating to safety devices

Info

Publication number: GB2125134A
Application number: GB08318843A
Authority: GB
Inventors: Robin Mumby
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-07-12
Filing date: 1983-07-12
Publication date: 1984-02-29
Also published as: GB2125134B; GB8318843D0

Abstract

A safety device 10 includes a plug member 12 arranged to engage with a socket member 11, the plug member including projecting terminals 15a, 16a connected together by a bridging link 19. The plug member 12 is mounted on the safety guard 14 of a machine, and the socket member 11 on the machine front 13. The socket member has recessed terminals 15, 16 which are arranged to contact the projecting terminals 15a, 16a when the plug and socket members are interengaged, so as to complete the power supply to the machine. With the guard open and the plug and socket parts separated, the recessed nature of terminals 15, 16 acts to deter attempts to bridge the terminals. <IMAGE>

Description

SPECIFICATION Improvements in and relating to safety devices This invention relates to improvements in safety devices, in particular but not exclusively for use in large industrial machines.

It is known that large machines have to comply with various safety regulations which may involve some form of safety guard and a safety switch.

The switch may be the 'on'-'off" type operable independently of the safety guard.

Alternatively, the switch may work in conjunction with the safety guard. There are many such safety devices already on the market; one such device comprises a push-button arrangement biased in its off position. When the safety guard is closed, it depresses the push-button thus completing the circuit. However, in practice these switching devices can be quite readily overridden by, referring to the same example, adhering tape over the push-button hence making it possible to operate the machine without the safety guard being in its correct position. Other more sophisticated switching devices may be overridden using a screwdriver or the like.

It is an object of the invention to provide a safety switching device which cannot be readily overridden.

The present invention provides a safety device comprising first and second interengageable connector parts, the first connector part including two resilient terminals projecting from a surface of the part and being electrically connected together, the second connector part including an opening arranged to receive the first connector part and having two recessed terminals positioned within the opening so as to engage respective ones of the resilient terminals when the connector parts are interengaged, the recessed terminals of the second connector part acting to deter attempts to bridge the terminals other than by interengagement with the first connector part.

In the preferred arrangement, a plug member carries the two resilient projecting terminals which are connected together, and the two recessed terminals are provided in a corresponding socket member, the terminals being recessed in a direction generally perpendicular to the direction of insertion of the plug member.

In order that the present invention may be more readily understood, embodiments thereof will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a schematic cross-sectional view of a first embodiment; Figure 2 is a view similar to that of Figure 1, but of a developed embodiment; and Figure 3 shows a cross-sectional view of an alternative plug part.

Referring to Figure 1, the device 10 as shown comprises an open-ended socket member 11 made from suitable non-conductive material in any shape, and a plug member 12 capable of being received within said socket member.

Advantageously, the socket member 11 is mounted on the front of the machine 13 or similar, and depending on the arrangement adopted, the plug member 12 is mounted on the safety guard 1 4 of the machine. When the guard is fully closed, the plug member 1 2 is received within the socket member 11, in the direction of arrow A.

The socket member 11 includes two recessed terminals 1 5 and 16 mounted thereon with their upper ends protruding externally for connection by cable 1 7 to the appropriate part of the machine.

When the terminals are wired up accordingly, a safety cover 1 8 including a hole through which the cable 1 7 is fed is placed securely over the terminals for preventing anyone connecting the upper ends of the two terminals together. The purpose of the recessed terminals 15, 1 6 is to make it awkward for someone to bridge the terminals without using the corresponding plug member 12. These recessed terminals may be mounted anywhere on the socket member 11 provided the terminals cannot be bridged by a screwdriver or the like, but it is preferable that they are aligned adjacent each other, and also that they are recessed generally perpendicular to the direction of insertion of the plug member 1 2.

The plug member 12 comprises two springloaded connectors 1 spa and 1 6a connected together at their lower ends by a conductive member 1 9 such as a brass bridging connector and held substantially completely within the plug member 12. Each connector 1 spa, 1 6a protrudes slightly from the surface of the plug member so that when, in use, the plug member is inserted in the socket member, the end of each connector 1 5a, 16a fits into the recess of the corresponding terminal 1 5, 1 6 producing a connection therewith; it effectively connects the two terminals 1 5 and 1 6 together.These terminals will be connected via the main power feed to the machine or similar, so that power is cut off when the plug and socket members are apart.

When the guard is fully closed, the plug member 1 2 is received within the socket member 11 and the connectors 1 5a and 1 6a fit into the corresponding recessed terminals 1 5 and 1 6.

Thus the machine will only operate with the guard in position.

The guard may be a hinged door operating arcuately and the plug member may be mounted horizontally perpendicular thereto. To ensure that the plug member can be readily received by the socket member, the socket member has an opening wide enough to receive the plug member at an angle and the socket member is preferably tapered away from the opening to allow ready insertion of the front of the plug member. The whole assembly could readily be incorporated into a door latch, hinge or similar, which would make individual installation easier.

Figure 2 shows a modified arrangement 20.

The general principle is similar to that of Figure 1, but includes two improvements.

Firstly, the second connector 26a to be inserted when plug and socket parts are brought together is arranged to protrude more prominently than the first connectors 25a; the corresponding recessed terminal 26 is further recessed than the other terminal 25. The effect of this is to prevent springloaded connector 25a from contacting terminal 26 as the plug member is initially inserted into the socket member. Such contact might be detrimental in certain circumstances.

Secondly, the socket member also includes a terminal guard member 27 to further protect terminals 25, 26 from tampering. The terminal guard member 27 is slidably mounted within the socket opening and includes an aperture 28 and spring 29 so positioned that the terminals 25, 26 are both covered when the plug member is not in place. Insertion of the plug member pushes the guard member against spring bias until aperture 28 is aligned with terminal 25, and the forward edge of the guard member 27 is clear of aperture 26. The connectors 25a, 26a can then make contact with the recessed terminals 25, 26. This second modification can be included with or separate from the first modification.

Figure 3 shows an alternative type of plug member 32 in which the resilient connectors 31 a, 32a are formed by the ends of a suitably shaped pressed metal spring 30. The centre portion is moulded within the plug member and the projecting ends 31 a, 32a are shaped to engage the recessed terminals. As shown, the end 32a projects more than the end 31 a so as to be compatible with the Figure 2 socket member, but this need not be so whereupon the plug member would be compatible with the Figure 1 socket.

The plug and socket members in any of the previously-described arrangements are made of suitable material, such as moulded plastics material. They may be generally cylindrical or of any other suitable shape.

Claims

1. A safety device comprising first and second interengageable connector parts, the first connector part including two resilient terminals projecting from a surface of the part and being electrically connected together, the second connector part including an opening arranged to receive the first connector part and having two recessed terminals positioned within the opening so as to engage respective ones of the resilient terminals when the connector parts are interengaged, the recessed terminals of the second connector part acting to deter attempts to bridge the terminals other than by interengagement with the first connector part.

2. A safety device according to claim 1, wherein said recessed terminals are recessed in a direction generally perpendicular to the direction of insertion of the first connector part within the opening in the second connector part.

3. A safety device according to claim 2, wherein said recessed terminals and said resilient terminals are aligned in said direction of insertion.

4. A safety device according to claim 1,2 or 3, wherein one of said resilient terminals projects more than the other, and the corresponding recessed terminal is recessed to a greater extent that the other.

5. A safety device according to any preceding claim, wherein the second connector part includes a spring-loaded slidable shielding member arranged to shield the recessed terminals when the connector parts are not engaged and to allow contact between respective resilient and recessed terminals when the connector parts are interengaged.

6. A safety device according to any preceding claim, wherein the second connector part includes a terminal cover disposed over the parts of said recessed terminals where connection to wiring is made.

7. A safety device according to any preceding claim, wherein the resilient terminals comprise projecting portions of a resilient conductive member, a centre portion of which is within the first connector part.

8. A safety device according to claim 7, wherein the resilient conductive member comprises a pressed metal spring.

9. A safety device according to any of claims 1 to 6, wherein the resilient terminals comprise spring-loaded terminals connected by a conductive bridging link within the first connector part.

1 0. A safety device according to any preceding claim, wherein the first connector part is mounted on the guard of a machine or the like, and the second connector part is mounted on the machine front.

11. A safety device substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.