GB2146156A - An alarm - Google Patents

Abstract

The alarm comprises a source of fluid 1 e.g. a CO2 cylinder, which supplies a circuit including a horn or the like 17 and a series of outlets 31 which are openable by disengaging respective seals 32 therefrom carried by, say doors and windows of premises. Removal of any seal will cause pressure to fall in the circuit to cause the horn 17 to operate. The circuit is placed in a ready condition by one of a pair of valves 12. <IMAGE>

Description

SPECIFICATION An alarm The invention relates to an alarm and is particularly but not exclusively concerned with an intruder alarm for the protection of property.

Over recent years with increasing instances of burglary there has been a great demand for intruder alarms which will deter burglars.

Numerous types of alarm have been proposed which will be actuated e.g. by breaking or opening windows or doors, by movement of persons inside rooms, by heat and so on.

Such systems usually actuate a loud audible device outside and/or inside the property concerned. Certain problems have arisen with alarms over the years. One of the most common, particularly with sophisticated movement or heat sensing alarms, is that they can be triggered inappropriately, say, by a pet animal moving around in the property, and can give a false alarm. Usually the alarm is powered by mains electricity and much to the annoyance of neighbours may continue to sound for several hours until it is switched off by the returning owner of the premises. Also, alarms operated by mains electricity cannot normally be installed in boats, touring caravans and garden tool sheds.

An object of the present invention is to provide an improved alarm.

According to the invention there is provided an alarm comprising a source of fluid, a circuit supplied by fluid from said source, and alarm means, said circuit being arranged to permit the alarm means to be actuated in response to a change in fluid pressure in the circuit.

Preferably the change in fluid pressure causes operation of valve means which permits fluid in the circuit to flow through a logic unit to actuate the alarm. The logic unit may be a NOT unit. Flow through the logic unit preferably prevents fluid fow through a second logic unit whereby any opposite change in pressure will have no effect on fluid flow through the first logic unit so as to maintain actuation of the alarm means. The second logic unit may be a NOT unit. Flow through the first logic unit may cause a gradual change of pressure to occur in part of the circuit which at a predetermined level prevents fluid flow through the second logic unit.

Further valve means may be arranged in a section of the fluid circuit, operation of said further valve means being arranged to place the fluid circuit in a ready condition. Preferably operation of said further valve means causes fluid pressure in said section of the circuit to be relieved. Said further valve means may comprise a plurality of further valves connected to the fluid circuit via a logic element. The logic element may be an OR element whereby actuation of any of said further valves will place the fluid circuit in a ready condition.

Preferably means is provided which is operable to allow said change in pressure in the circuit to permit actuation of the alarm means or to prevent said change in fluid pressure.

Said means may comprise a fluid port in communication with said fluid circuit and a seal carried by a movable member for sealing the port, removal of the seal causing said change of fluid pressure to occur. A plurality of said means is provided whereby unsealing of any of said ports will cause the said change in fluid pressure. The said means may be spaced apart to enable them to be located at strategic points. The ports may, in such a case, be spaced apart along a conduit, e.g. a flexible plastics tube. The or each port may be defined by an open end of a pipe in communication with the fluid circuit. The or each pipe may be formed as a T to enable it to be connected by a conduit to the fluid circuit.

Preferably flow control means is provided to ensure that fluid from said source cannot replenish a part of the fluid circuit which includes the said means at a rate equal to or greater than the rate at which fluid can pass through said means to cause the said change in pressure.

The source of fluid may be a fluid cartridge or cylinder e.g. CO2 cartridge or cylinder. The CO2 is preferably arranged to power the alarm means, e.g. a horn. With such an arrangement, the alarm will operate only for the duration of the CO2 cartridge which may be up to approximately 30 minutes depending on the size of the cylinder. Also the use of a CO2 cylinder permits the alarm to be installed in buildings, boats etc. where there is no mains electricity available and the invention is highly advantageous in that respect.

An alarm in accordance with the invention will now be described by way of example with reference to the accompanying drawings in which Figure 1 is a diagram of the alarm, and Figure 2 is a cross section through part of a door post showing the interrelation between a fluid outlet on the post and a seal on the door.

A CO2 cylinder 1 is connected to a pressure reducing valve 3 the outlet of which terminates at a port A of a key-operable isolating valve 4. The valve 4 has a port B connected to a pilot P1 of an arming valve 5, a port C connected to exhaust and a port D connected to port E of valve 5, a pressure relief valve 6, a port J or a logic NOT unit 9 and a timer 16.

The pressure relief valve 6 is connected to a length of flexible plastics conduit 30 along which are five or any other desired number of spaced apart outlets 31 closable by respective seals 32. The outlets and seals constitute the aforesaid elements designated generally at 15. At shown in Fig. 2, the outlet or port 31 comprises the open end of a small bore (dia.

approx. 0.75 mm) tube 33 connected to a plate 34 located in a door jamb 35. The tube 33 locates in a small groove 37 in the jamb and is T-shaped for connection to adjacent sections of conduit 30. A door 38 carries the seal 32 which is formed, e.g. from rubber.

When the door is closed, the seal 32 closes the open end 31 of the tube 33. The elements 15 are located strategically, e.g. at all doors and windows of a house, and the conduit extends around the house hidden behind the edges of carpets or neatly secured to skirting boards. The conduit will generally be transparent but, of course, it can be painted once installed to match existing paintwork.

The conduit 30 is connected to a port M of a diaphragm amplifier valve 8, the latter having a port N connected to a port K of the NOT unit 9 and a port P connected to a port R of a further logic NOT unit 10 and to an indicator 11. The NOT unit 10 has a port S connected to a port H of arming valve 5 and a port T connected to a pressure vessel 40, the timer 16 and a port Loathe NOT unit 9. The timer 1 6 is connected to a fluid-operable horn 1 7.

The arming valve 5 has a port F connected to a pair of valves 12 and associated indicators 14 and has a port G connected to exhaust. The valves 1 2 are connected via a logic OR unit 1 3 to a pilot P2 of arming valve 5.

Various components are housed as shown in Fig. 1 within a box 2 drawn in broken lines. The conduit 30 is a push-fit on nipples 41 on the exterior of the box. Similar nipples 41 are provided to enable the valves 1 2 and horn 1 7 to be connected by flexible tubing to the box. The connections between the components inside the box comprise flexible plastics tubing or small bore metal pipework.

The operation of the alarm will now be described, Fig. 1 showing the alarm in an inoperative condition with the pressure relief valves 3 and 6 and the timer 1 6 pre-set.

Operation of the key 4 allows CO2 gas to apply pressure at ports A and D thereby pressurising the conduit 30, port M of amplifier valve 8, the timer 1 6 and port J of NOT unit 9. Pressure is also applied to port E of arming valve 5 and hence to port F and the port of the fluid circuit upstream of the valves 12. Provided that all the openings 31 are sealed, the pressure at port M will be sufficient to operate the amplifier valve 8 and allow pressure from port K of NOT unit 9 (port L being unpressurised) to pressurise port R of NOT unit 10 through ports N and P of the amplifier valve. In that condition, indicators 11 and 14 will show that the system is pressurised. Any entry/exit door may be used when leaving the premises, the drop in pressure resulting in conduit 30 simply causing valve 8 to close momentarily until the door is re-closed.After closing the door, either of the valves 1 2, which are located on the exterior of the premises, are operated by means of a push button 42 to allow pressure through the OR unit 1 3 to operate the arming valve 5 thereby placing the circuit in a ready condition. In that condition, pressure at E is applied through H to port S of the NOT unit 10.

However, pressure at port R prevents pressure at S being applied to port T. Simultaneously, pressure in the external circuit containing valves 12 is relieved as operation of the arming valve 5 connects port F to exhaust port G. Therefore, any subsequent tampering with the push buttons 42 will have no effect whatsoever on the operation of the alarm.

If an intruder opens a door or window, a drop in pressure will result in conduit 30 as the seal 32 disengages the tube 33. The restrictor 7 ensures that fluid from the cylinder 1 cannot replenish the conduit 30 at a rate sufficient to compensate for the fluid lost through the unsealed opening. The fall in pressure causes amplifier valve 8 to close and pressure at port R of NOT unit 10 is lost thereby allowing fluid to flow from port S to port T, through the pre-set timer 16 and then to the horn 1 7. Build-up pressure downstream of port T and hence at port L of NOT unit 9 is controlled by the pressure vessel 40.At a given pressure the NOT unit L switches off the supply to amplifier valve 8 from port K so that subsequent closing of the door and resumption of pressure in conduit 30 cannot cause the NOT unit 10 to switch off the supply of fluid to the horn 1 7. The system is, therefore self latching.

The timer 1 6 provides sufficient time to enter the premises and switch off the valve 4 by means of the key. In the event of unauthorised entry, the horn will continue to operate only for the duration of the gas cylinder 1.

It is envisaged that instead of using elements 15, the conduit 30 could communicate with the interior of a sealed double-glazing unit. When operational, the interior of the sealed unit would be pressurised by the CO2 and if the sealed unit were smashed by an intruder the resulting fall in pressure would cause the horn to be actuated. The alarm could also be housed in a gas-tight showcase which would be pressurised internally by the CO2. In the event of the showcase being smashed to remove valuables, the fall in pressure would cause the horn to be actuated.

The conduit 30 may include a branch 50 of flexible plastics tubing for location at high firerisk points. In the event of a fire, the branch 50 would burn through and cause the horn to be actuated.

It will be appreciated from the foregoing description that the alarm is self powered and requires no external electrical power source.

Even the indicators 11, 14 are fluid operable.

Therefore the alarm is idealy suited for use on boats and touring caravans as well as in buildings.

If desired the horn 1 7 could be electrically operable and pressure from port T could be arranged to operate, say, a solenoid switch on the alarm. The electricity supply from the alarm could be derived from a battery to avoid the need for mains electricity.

Instead of using CO2 cylinder or cartridge the pressure could be derived from a portable air compressor.

It is also envisaged that the alarm could be vacuum operated.

Claims (22)

1. An alarm comprising a source of fluid, a circuit to be supplied by fluid from said source, and alarm means, said circuit being arranged to permit the alarm means to be actuated in response to a change in fluid pressure in the circuit.

2. An alarm according to Claim 1 in which the change in fluid pressure causes operation of valve means which permits fluid in the circuit to flow through a logic unit to actuate the alarm.

3. An alarm according to Claim 2 in which the logic unit is a NOT unit.

4. An alarm according to Claim 2 or 3 in which flow though the logic unit prevents fluid flow through a second logic unit whereby any opposite change in pressure will have no effect on fluid flow through the first logic unit so as to maintain actuation of the alarm means.

5. An alarm according to Claim 4 in which the second logic unit is a NOT unit.

6. An alarm according to Claim 4 or 5 in which flow through the first logic unit causes a gradual change of pressure to occur in part of the circuit which at a predetermined level prevents fluid flow through the second logic unit.

7. An alarm according to any preceding claim in which further valve means is arranged in a section of the fluid circuit, operation of said further valve means being arranged to place the fluid circuit in a ready condition.

8. An alarm according to Claim 7 in which operation of said further valve means causes fluid pressure in said section of the circuit to be relieved.

9. An alarm according to Claim 7 or 8 in which said further valve means comprises a plurality of further valves connected to the fluid circuit via a logic element.

10. An alarm according to Claim 9 in which the logic element is an OR element whereby actuation of any of said further valves will place the fluid circuit in a ready condition.

11. An alarm according to any preceding claim in which means is provided which is operable either to allow said change in pressure in the circuit to permit actuation of the alarm means or to prevent said change in fluid pressure.

1 2. An alarm according to Claim 11 in which said means comprises a fluid port in communication with said fluid circuit and a seal carried by a movable member for sealing the port, removal of the seal causing said change of fluid pressure to occur.

1 3. An alarm according to Claim 1 2 in which a pluraity of said means is provided whereby unsealing of any of said ports will cause the said change in fluid pressure.

1 4. An alarm according to Claim 1 3 in which said means are spaced apart to enable them to be located at strategic points.

1 5. An alarm according to Claim 1 4 in which said ports are spaced apart along a conduit.

1 6. An alarm according to any of Claims 1 2 to 1 5 in which the or each said port is defined by an open end of a pipe in communication with the fluid circuit.

1 7. An alarm according to Claim 1 6 in which the or each pipe is formed as a T to enable it to be connected by conduit to the fluid circuit.

1 8. An alarm according to any of Claims 11 to 1 7 in which flow control means is provided to ensure that fluid from said source cannot replenish a part of the fluid circuit which includes the said means at a rate equal to or greater than the rate at which fluid can pass through said means to cause the said change in pressure.

1 9. An alarm according to any preceding claim in which the source of fluid is a fluid cylinder or cartridge.

20. An alarm according to Claim 1 9 in which the alarm means is powered by the fluid.

21. An alarm according to Claim 19 in which the alarm means is powered electrically and the fluid operates a switch to switch on the alarm means.

22. An alarm constructed and arranged substantially as described herein with reference to the accompanying drawings.