GB2075262A - Switch mechanisms - Google Patents

Abstract

A switch mechanism includes a cam follower member (6) having at least one protrusion with a convex surface. The cam member (6) is operatively connected to a switch actuator (5) and a grooved cam actuator (7) is provided for the convex surface of the cam member (6). The cam actuator (7) has at least two bridging members (8) bridging the groove thereof and when the switch is in its "on" position the convex surface of the cam member (6) is positioned between the bridging members (8) within the groove of the cam actuator (7). When so positioned, any rectilinear movement of the cam actuator (7) causes rotation of the cam member (6) so that the switch is turned to its "off" position. When the switch is in its "off" position it cannot be returned to its "on" position by rectilinear movement of the cam actuator (7) because there is abutment of the cam member (6) against at least one of the bridging members (8). The mechanism removes the danger of reactivating apparatus controlled by the switch mechanism after it has been switched off in, for example, an emergency. <IMAGE>

Description

SPECIFICATION Pullkeys The present invention relates to pulikeys and more particularly relates to pullkey switch mechanisms.

Pullkeys, or mechanical switches, are well known in the art and are used to switch on and switch off various apparatus such as conveyors. For example, a plurality of such pull keys can be spaced along the length of a conveyor, the pullkeys being intercon nected by pull wires. Operation of a pullwire oper ates a switch in an adjacent pullkeywhich can be used to switch off the conveyor. Alternatively, a single pulikey with pullwires extending in opposite directions can be used.

In known pullkeys, the danger exists that the pullwire may be accidentally operated a second time thereby switching the conveyor on again and thus possibly causing injury or damage.

Pullkeys incorporating the mechanism of the pre sent invention overcome the above mentioned dan ger in that after the switch has been switched off by one pull on the pullwire, a second pull on the pullwire cannot turn the switch on again.

Accordingly, the present invention provides a pullkey switch mechanism including a cam member having at least one protrusion with a convex surface, the cam member being operatively connected to a switch actuator, and a respective grooved cam actuator for the, one of the, or each convex surface, the or each cam actuator having at least two bridging members bridging across the groove there of, at least part of the or each convex surface of the cam member when the switch is in the "on" position being positioned between said bridging members within the groove of the respective cam actuator in such manner that linear movement of the or each cam actuator causes rotation of the cam member so that the switch is turned to its "off" position in which position movement of the switch to its "on" position by any linear movement of the or each cam actuator is prohibited by abutment of the cam member against at least one of said bridging members of the respective cam actuator.

It is preferred that the cam member has two protrusions, each with a convex surface, and the -mechanism is therefore in this case provided with two cam actuators each of which is associated with one of the protrusions. However, it should be understood that on a single ended pullkey only one cam actuator need by provided. In a particularly preferred embodiment, the two protrusions are diametrically opposed and each conveniently has a concave surface opposite its convex surface. In this most preferred embodiment, the cam member is substantially S-shaped.

Preferably, the or each grooved cam actuator has two bridging members, each of which advan tageously is in the form of a roller and preferably each cam actuator is operatively connected to an actuating shaft which may be spring loaded, and which normally projects externally of the pullkey housing whereby a pullwire may be conveniently connected thereto.

The present invention is further illustrated with reference to the accompanying drawings in which: Figure 1 is a plan view, partly in cross section of a pulikey, with the lid removed, incorporating a preferred switch mechanism of the present invention when in its "off' position; Figure 2 is a continuation of Figure 1 from the line A-A in the direction of the arrows: Figure 3 is a part view of the switch mechanism shown in Figure 1, but in the "on" position; Figures 4, Sand 6 are plan, end and side views respectively of one of the cam actuators shown in Figure 1 with the bridging members removed therefrom; Figures 7 and 8 are plan and side views respectively of the bridging members shown in Figures 1 and 3 but on twice the scale; and Figure 9 is a schematic side view of a waterproof fitting for attaching a knob to a switch actuator in the form of a spindle, the pulikey itself being the same as shown in Figure 1.

Referring to Figures 1 to 3, the pullkey has a box 1 which is adapted to receive a lid. Inside the box 1 is an electrical switch 2 which is connected by wires 3, 31 to a junction box 4. The switch 2 has a switch actuator in the form of a spindle 5 and to this spindle is operatively connected a cam member 6 which has two diametrically opposed protrusions, each with a convex and a concave surface, and which is substantially S-shaped. The cam member 6 is restrained from upward and also twisting movement on the spindle 5 by a retaining member 6a. Associated with each protrusion of the cam member 6 is a cam actuator 7, each of which is provided with two bridging members 8 which are in the form of rollers.

Each cam actuator 7 is operatively connected to an actuating shaft generally designated 9. Each shaft 9 is spring loaded by means of two springs 10 and 11 and is slidably mounted in a hollow actuator bush 12 which projects on either side of the box 1. As may be seen from Figure 1 the shaft 9 is divided into several parts, and referring to Figure 2, the end of the shaft 9 receives a looped member 13 which is screwed therein and to which, in use, the pullwire is attached.

It should be understood that in this embodiment of the present invention, the pullkey has two loop members 13, but only one has been shown for clarity.

In normal operation, the pullkey is turned on (reset) by rotation of the spindle 5 in the appropriate direction by means of, for example, a knob attached thereto. Turning of the knob, of course, also causes the cam member 6 to rotate in the same direction. In an emergency there is not normally sufficient time to reach the aforementioned knob and the pullwire connected to one of the looped members 13 is pulled. Referring specifically now to Figure 3 in which the mechanism is shown in its "on" position, movement of the shaft 9 and thus the cam actuator 7 in either direction of arrows C will cause the cam member 6 to rotate in the direction of arrow B to its "off" position as shown in Figure 1.Thus, pulling the pullwire will cause the cam actuator 7 to move in the direction Cl thereby causing rotation of the cam member 6 by means of the convex surface riding on the roller 8 which is furthest from the shaft 9.

Alternatively, -should the pullwire, which is normally set up in a tensed state, snap, the spring 11 will bias the cam actuator 7 in the direction of arrow C11 thereby causing rotation of the cam member 6 by means of the convex surface riding on the roller 8 which is nearest to the shaft 9. Thus, by either of the above processes, the switch is switched off and the cam member 6 achieves the position shown in Figure 1.As may be seen from Figure 1, any linear movement of the cam actuators 7 will not cause the necessary clockwise rotation of the cam member 6 to turn the switch on again since any inward movement thereof, with respect to the container 1 cannot cause the necessary rotation of the cam member 6 because of abutment thereof with a roller 8, and if the pullwire is pulled hard enough for the cam actuator 7 to slidingly contact the cam member 6, it has to be moved such a distance that any clockwise rotation of the cam member 6 is prevented by abutment thereof against one of the roilers 8.

Although it is preferred that the cam actuators 7 and the cam member 6 be fabricated in brass to substantially remove the need for lubrication thereof, they may, of course be manufactured from any other suitable material such as stainless steel or a plastics material.

Although the preferred embodiment described above with reference to the accompanying Figures 1 to 8 empioys a switch activator which turns the switch off by anti-clockwise movement, it will be appreciated that a clockwise set up may be used if desired.

Referring to Figure 9, pullkeys incorporating a switch mechanism according to the present invention, as has been described with reference to Figure 1 are adapted to receive a lid, and part of such a lid is shown in Figure 9 and is designated by reference numeral 90. The spindle 5 previously referred to is upstanding and terminates adjacent the undersurface of the lid 90. The lid 90 has a hole 91, and inserted in this hole 91 is a member having a sealing annularflange 92 and a skirt 93 depending therefrom. A knob generally designated 94 has an-upper portion 95 which is that part which is turned by the operator in use, a lower portion 96 and an annular flange portion 97 adapted to seat on the flange 92.

Disposed about the lower portion 96 are three sealing rings of resilient and waterproof material 98, 99 and 100. In addition the knob 94 is adapted to receive the spindle 5 by provision of a hole (not shown) in the lower portion 96. The position shown in the drawing is just before insertion of the knob 94.

When actually inserted, the lower portion 96 receives the top of the spindle 5 whereby there is operative connection therebetween, the sealing rings 99 and 100 form a waterproof seal between the lower part 96 and the inner circumference of the skirt 93 whilst the sealing ring 98 forms a waterproof seal between the lower part 96 ad the inner circumfer ence of the flange 92. In addition, the underside of flange 97 seats on the top of flange 92.

Claims (11)

1. A pullkeyswitch mechanism including a cam member having at least one protrusion with a convex surface, the cam member being operatively connected to a switch actuator, and a respective grooved cam actuator for the, one of the, or each - convex surface, the or each cam actuator having at least two bridging members bridging across the groove thereof, at least part of the or each convex surface of the cam member when the switch is in the "on" position being positioned between said bridg ing members within the groove of the respective cam actuator in such manner that linear movement of the or each cam actuator causes rotation of the cam member so that the switch is turned to its "off" position in which position movement of the switch to its "on" position by linear movement of the or each cam actuator is prohibited by abutment of the cam member against at least one of said bridging members of the respective cam actuator.

2. A pullkey switch mechanism as claimed in claim 1 wherein the cam member has two protru sions, each with a convex surface.

3. A pullkey switch mechanism as claimed in claim 2 wherein the two protrusions are diametrical ly opposed.

4. A pullkey switch mechanism as claimed in claims 2 or claim 3 wherein each protrusion has a concave surface opposite the convex surface thereof.

5. A pullkey switch mechanism as claimed in any of claims 2 to 4 wherein the cam member is substantially S-shaped.

6. A pulikey switch mechanism as claimed in any of claims 1 to 5 wherein the or each grooved cam actuator has two bridging members.

7. A pullkey switch mechanism as claimed in any of claims 1 to 6 wherein the or each bridging member is in the form of a roller.

8. A pullkey switch mechanism as claimed in any of claims 1 to 7 wherein each cam actuator is operatively connected to an actuating shaft.

9. A pullkey switch mechanism as claimed in claim 8 wherein each actuating shaft is spring loaded.

10 A pullkey switch mechanism as claimed in claim 8 or claim 9 wherein each actuating shaft projects externally of the pulikey housing.

11. A pullkey switch mechanism substantially as herein described with reference to, and as shown in the accompanying drawings.