This invention relates to a switch actuating mechanism switch and more particularly to an electric switch mechanism for use in association ith an electric switch for monitoring the position of a fluid control valve. In various fire sprinkler installations it is considered at least desirable and in some instances compulsory due to legislation to monitor that various valves of the hydraulic system are in a normal operating position and are not in some other position that might render them ineffective. Thus, a water supply line for a sprinkler system ma be fitted with an on-off valve which can be put to the off position for various maintenance reasons. However, for the sprinkler s stem to be effective that valve must be returned to the on position after the maintenance is completed. Since errors might occur it has become at least desirable that a means is provided for monitoring whether that valve is in the on or off position. Such monitoring may be conducted remotely such as at a distant fire station. It is relatively easy matter to provide an electrical circuit incorporating a switch which can be actuated by some movement of a valve operator to become an open or closed circuit. However, maintenance on the s itch itself may be required or the switch may need to be removed for some reason and it is conceivable that a human error might occur rendering the sprinkler system unable to operate but which, to a casual observer, appears to be in full working order. In many other instances besides fire sprinkler systems similar problems may arise such as at oil refineries and on ships . Accordingly, the present invention seeks to provide a switch having a self disabling feature when various work is done on the switch itself. The present invention provides an electrical s itch mechanism comprising a housing, a switch actuator within the housing, biasing means biasing the switch actuator towards a first position, an operator member adapted to undergo a

movement to cause the actuator to move against said biasing means to a εecond position, a removable access cover for providing access within the housing and means responsive to removal of said cover adapted to put the mechanism in a condition such that said movement is incapable under normal conditions of use of moving the actuator to said second position. A specific construction of a switch incorporating a switch mechanism in accordance with the present invention will now be described with the aid of the accompanying drawings in which:- Fig- 1 is a perspective view of a s itch housing incorporating a switch actuating mechanism, with cover removed; Fig. 2 is a cross-se tional view on the line 2-2 of Fig. 1; Fig. 3 is a cross-sectional view on line 3-3 In Fig. 1, and Fig. 4 is a view similar to Fig. 3 showing the mechanism in the inoperative position. The switch shown in the drawings comprises a housing comprised of a body 1 and a cover 2. The bod 1 has an access hole 3 for electrical cable and mounting lugs 4. Within the body is a partition 6 which divides the bod into a connections chamber 7 and a switch chamber 8. In use of the switch a terminal block (not shown) is provided in the connections chamber 7 and wires of a cable (not shown) which pass through the hole 3 are connected to the terminal block and further wires (not shown) pass from the terminal block to a switch 5. The wires to the switch 5 are embedded in a sealant compound (not shown) which alεo serves to seal the chambers 7 and 8 from one another. The switch 5 is a normally open circuit switch and is provided with an actuator lever 23. The actuator lever 23 can be moved b a pivoted actuator 24 which is mounted to pivot on pivot pin 26 (Fig. 2). The pivoted actuator 24 is biased by a spring 27 so that the switch 5 is in its normally open circuit condition

(Fig. 4) but can be moved against that bias by an operator 28 so as to cause the switch 4 to become closed circuit. In Fig. 3 the s itch 5 is sho n in the closed circuit condition . In use, the operator 28 which is a small piston which slides in a bore in the wall of the body, may be associated with a fire sprinkler valve such that when the valve is open the operator 28 will normally be moved upwardly to cause the switch 5 to be closed circuit as shown in Fig. 3 and when the valve is closed the operator 28 will be moved downwardly such that the switch 5 is open circuit. The body 1 is chamfered at 42 to facilitate actuation of the operator 28. Clearl the switch 5 could be of opposite type such that when the actuator 24 pushes the actuator lever upwardl , aε sho n in Fig. 3, the s itch 5 is in an open circuit condition and is closed when the actuator 24 moves down but this depends entirely on the nature of the external supervisory circuit to which the switch is connected. The ends of pivot pin 26 "sit" in respective U-shaped cradles in end wall members 25 and thus the pivot pin 26 is urged upwardly towards the open ends of the cradles by the spring 27. Adjacent reεpective ends of the pin 26 discs 31 bear on the pin 26 to retain the ends downwardly in the cradles and the discs 31 are on the bottom ends of respective pushrodε 36. The pushrods 36 slide in tubu lar members 32. Downwardly depending pins 37 are part of the lid 2 and when the lid is in position on the body 3 the pins 37 extend downwardly in respective tubular members 32 and, b contacting the top ends of the respective pushrods 36 cause the pin 26 to be retained in its lowermost or operating position. When the cover 2 is removed the spring 27 will serve to move the pin 26 upwardly whereby the axis about which the pivoted actuator 24 ma pivot will be moved so that movement of the operator 28 of the type which can be expected in normal service will not move the pivotted actuator 24 at all or insufficientl to cause the switch 5 to become closed circuit. The above described switch will find utilitv at least

- 4 -

1 in fire εprinkler installations in that removal of the cover

2 2 or failure to replace the cover 2 can be indicated by the

3 switch 4 being open circuit or changing to the oppoεite

4 condition to what it is in when everything is in order.

5 A modification (not shown in the drawings) of the above

6 involves replacing the switch 5 with an electronic switch

7 having a light emitter and a light detector and in which the

8 pivotted actuator 24 iε used to interrupt a light path

9 between the emitter and the detector.

10 The above described switch may be used with the valve

11 spindle 51 and iε mounted in cloεe proximity to the εpindle

12 51, aε shown, using the mounting lugs 4.

13 The valve spindle 51 haε an aperture 52 within which is

14 located a spring loaded pin 38. The εpring urges the pin

15 outwardly of the spindle 51.

16 In normal use the pin 38 ill extend to contact the

17 operator 28 cauεing the εwitch 5 to be closed circuit.

18 However, if the εpindle 51 is rotated or iε moved

19 axially a εhort diεtance, the pin 38, guided in itε movement

20 by the chamfer 42, will become out of contact with the

21 operator 28 εo causing the εwitch 4 to become open circuit.

22 Appropriate electrical circuitry can be provided to

23 indicate when the switch 5 is open circuit to thus indicate

24 that the spindle 51 is not in its operative position or that

25 the switch has been tampered ith or not put back to its

26 operative condition...

27 It will be evident that the "floating pivot" of the

28 actuating mechanism as described above provides a unique way

29 of operating the switch when either the valve spindle iε

30 moved away from a poεition wherein the valve iε "open", or

31 the εwitch cover is removed or not properly replaced. The

32 invention enables a single micro-switch to be utilized to

33 monitor both circumstances and is therefore less complicated

34 and lesε coεtly to manufacture than known devices of the

35 kind in question.