GB2424764A

GB2424764A - A call point

Info

Publication number: GB2424764A
Application number: GB0506447A
Authority: GB
Inventors: Laurence John Sharman William
Original assignee: MAXHUNT Ltd
Current assignee: MAXHUNT Ltd
Priority date: 2005-03-31
Filing date: 2005-03-31
Publication date: 2006-10-04
Anticipated expiration: 2025-03-31
Also published as: GB0506447D0; GB2424764B

Abstract

A call point comprising a displaceable or frangible element 5 which is displaceable in order to actuate a plurality of switches 8-11 to indicate an alarm condition, the element 5 being moveable from a set position in which the switches 8-11 are held by the displaceable or frangible element 5 in a first position to an activated position in which the displaceable or frangible element 5 no longer holds the switches 8-11 in said position, at least two of the switches 8-11 opposing each other so that the displaceable or frangible element 5 holds them both in said first position when the call point is set and allows both of the pair to move to their activated positions when the call point is activated. The switches 8-11 may be microswitches.

Description

Call Points This invention concerns call points particularly but not

exclusively for use in fire or intruder alarm systems.

GB2404494-A describes a call point for use in fire or intruder alarm systems in which a displaceable or frangible element which is manually displaceable in order to actuate a microswitch to indicate an alarm condition. The microswitch is actuated when the displaceable or frangible element moves from its first position to its second position, a spring biasing the displaceable or frangible element from its first to its second position.

A latch having an abutment which is engageable against the displaceable or frangible element maintains the displaceable or frangible element in its first position against the action of the spring. The latch is rotatable by a key from an active position, where the abutment engages the displaceable or frangible element, to an inactive position where the displaceable or frangible element is free to move to its second position under the action of the spring, in order to actuate the microswitch and thus test the alarm system.

The call points described in GB2404494-A enable a single microswitch to be actuated by pushing the displaceable or frangible element from its first position to its second position. However, there are situations where actuation of more than one electrical circuit is required when the call point is actuated, and it has been proposed hitherto to place two or more microswitches alongside each other so that a single edge of the displaceable or frangible element simultaneously maintains all of the switches in the same state until the displaceable or frangible element is moved to its second position. Furthermore, there are situations where, due to the physical constraints within the housing of the call points, it is impossible to increase the number of adjacent microswitches. In general this imposes a limit of three on the number of microswitches which can be placed side by side within standard call point housings.

Whilst three simultaneously actuateable microswitches is sufficient in many situations, there are some in which it is desirable to actuate four or more such switches.

According to the present invention there is provided a call point comprising a displaceable or frangible element which is displaceable in order to actuate a plurality of switches to indicate an alarm condition, the element being moveable from a set position in which the switches are held by the displaceable or frangible element in a first position to an activated position in which the displaceable or frangible element no longer holds the switches in said position, at least two of the switches opposing each other so that the displaceable or frangible element holds them both in said first position when the call point is set and allows both of the pair to move to their activated positions when the call point is activated.

Call points in accordance with the present invention can be used for a variety of purposes but they are of particular use in fire or intruder alarm systems.

Displaceable elements are preferred over frangible elements because displaceable can be reset rather than having to be replaced, which is generally the case with frangible elements.

An embodiment of call point in accordance with the present invention will now be described with reference to the accompanying drawings in which:Fig. 1 shows a front view of the call point ready for operation; Fig. 2 corresponds to Fig. 1 with the front cover of the call point removed; Fig. 3 corresponds to Fig. 2 with the call point having been activated; Fig. 4 shows a portion of Fig. 2 to an enlarged scale; and Fig. 5 shows a portion of Fig. 3 to an enlarged scale.

The call point as shown in Fig. 1 has a front cover 1 with a window aperture 2, the cover 1 being attached to a switch box 3.

A lock 4 serves to hold the cover 1 on the switch box 3 to prevent unauthorised access to the interior of the call point.

A key (not shown) can be used to open and/or close the lock 4.

A glass or plastics plate 5 with an upper edge 6 and a lower edge 7 situated behind the front cover 1 fills the window aperture 2.

Within the switch box 3 are four microswitches 8, 9, 10, and 11, three of the microswitches 8, 9 and 10 being secured above the plate 5, and the fourth switch 11 being positioned below the plate 5. Each of the switches 8-10 has a body portion 12 and an actuator button 13. The actuator buttons 13 are spring biased away from the respective body portions 12. Operation of the individual switches can then be effected by pushing the actuator buttons 13 towards the associated body portion 12, thereby changing the switch from one state to another, that is from off to on, or from on to off.

Fig. 2 shows the call point in its set position with the plate 5 positioned between the switches 8-10 and the switch 11. The lower edge 7 of the plate 5 rests on and pushes in the actuator button 13 of the lower switch 11, and the upper edge 6 of the plate 5 pushes in the actuator buttons 13 of the switches 8-10.

The lower right hand corner portion 14 of the plate 5 as seen in Figs. 2 and 3 rests on a projection 15 from the interior of the switch box 3 and serves to stabilise the plate 5 in the position shown in Fig. 2.

Actuating the illustrated call point involves pushing the plate inwardly from the position shown in Fig. 2 to the position shown in Fig. 3. In doing so, the plate 5 is moved inwardly of the cover 1, and of the actuator buttons 13 of the switches 8-11, to a point where the plate 5 no longer holds the actuator buttons 13 in their fully pushed in positions and allows the switches 8-11 to change state from on to off, or off to on, depending on the internal configurations of the respective switches 8-il.

Actuation of the microswitches 8-11 can be seen more clearly from Figs. 4 and 5 which show the lower left hand corner of the call point to an enlarged scale.

As can be seen in Fig. 4, the call point in its set configuration has the actuator button 13 of the microswitch 11 pushed in by the plate 5. In this condition of the call point, the remaining microswitches 8-10 similarly have their actuator button buttons 13 pushed into their respective bodies 12 by the plate 5.

Activation of the call point by pushing the plate 5 inwardly causes the plate 5 to take up a position behind the actuator button buttons 13 as shown in Fig. 5, thereby allowing the actuator button buttons 13 to change the state of the switches 8-11. Although not shown in Fig. 5, the actuator button buttons 13 of the switches 8-10 are similarly released from engagement with the plate 5 when the edge 6 of the plate 5 slides past the actuator button buttons 13 in a similar manner to that shown for switch 11.

As can be seen from Figs. 2 and 3, the dimensions of the switches 8-11, which are conventional microswitches, relative to the internal dimensions of the switch box 2 only allow for three of the switches to be located above the plate 5. However, the present invention allows for a fourth switch 11 to be positioned below the plate 5. It will also be appreciated that there is sufficient room within the switch box 3 for a fifth switch to be positioned adjacent to switch 11.

Claims

Claims 1. A call point comprising a displaceable or frangible element

which is displaceable in order to actuate a plurality of switches to indicate an alarm condition, the element being moveable from a set position in which the switches are held by the displaceable or frangible element in a first position to an activated position in which the displaceable or frangible element no longer holds the switches in said position, at least two of the switches opposing each other so that the displaceable or frangible element holds them both in said first position when the call point is set and allows both of the pair to move to their activated positions when the call point is activated.
2. A call point according to claim 1, wherein the switches are microswitches.
3. A call point according to claim 1 or claim 2, wherein in the set position the displaceable or frangible element is in contact with actuator means of the respective switches.
4. A call point according to any of the preceding claims, wherein one of the said at least two opposing switches has at least one further switch adjacent thereto, the at least one further switch being held in said first position by the displaceable or frangible element when said one of the said at least two opposing switches is held in said first position.
5. A call point according to any of the preceding claims, wherein in said first position the displaceable or frangible element is supported by support means within the call point.
6. A call point substantially as herein described with reference to the accompanying drawings.