GB2157041A - Thermal alarm system - Google Patents

Abstract

A thermal alarm system for safes 10 and the like wherein at least one thermal switch 12, 14 is concealed within the safe in a position to be influenced by external heat, such as that produced by a cutting torch of a burglar 37 or by accidental fire in the vicinity of the safe, to sound an alarm 40, preferably remote from the safe and connected to the switch by concealed wiring 32, to summon the proper authorities. <IMAGE>

Description

SPECIFICATION Thermal alarm system This invention relates to alarm systems for safes and the like, and more particulary the heat sensitive alarm systems for safes and the like, arranged to signal an alarm when the heat of a burglar's cutting torch is applied to the safe or when the external temperature rises significantly, such as in the case of accidental fire in the premises.

Burglars all over the world, in spite of the impressive and higly sophisticated techniques and devices available to prevent burglaries (electronic and micro-wave detectors and alarms), continue to break safes and vaults in banks, jewellery shops, private or government institutions and the like, using the oxy-hydrogen/acetylene flame.

Highly ingenious systems used by these"professionals" doaway with the most elaborate protection methods. Detectors, alarm systems, closed T.V. circuits, etc. can be deactivated, neutralised or eluded by them, leaving the strength of the armour of the safe as the ultimate barrier to their goal.

Access to the premises where the safe/vault is located can be gained through unprotected connecting buildngs, sewage systems, etc. thus bypassing the detectors/aiarms installed in the premises leading to the safe. Once this is done, the protection of the safe against the oxhydrogen/ acetylene flame will only depend on the strength of its own structure. Burglars equipped with powerful welding torches and having plenty of time at their disposal will do away with the strongest armoured structures.

The object of the present invention is to provide protection for the safe itself; which is built within its own structure and thus is out of the reach of the burglars yet will set the alarm off as soon as heat is applied to the external walls of the safe. Its construction is simple and its functioning dependable. The built-up thermic alarm system proposed in this application will pose the burglars with such difficulties to destroy, and imminent risk of being detected as soon as they apply heat to the safe, that they will give up any attempt if they know what they are up against. If they don't, the trap will function without their having the slightest suspicion. A notice attached to the safe, warning of the existence of the thermic alarm system inside the safe might discourage any prospective offender.

The invention is premised on the recognition that modern day safes are clad with an armor so difficult to penetrate by any means other than a cutting torch, that a effective protection system for a safe or the like can be prudently restricted to one which is heat sensitive but which does not require that any part of the safe or the alarm system be permanently destroyed in order to effect operation of the alarm.

The invention provides an alarm system comprising switch means arranged to be concealed within a safe, vault, or the like, an alarm arranged to be in communication with the switch means, and heat responsive switch- actuating means arranged to be disposed in a position within the said safe, vault, or the like to operate the switch means between open and closed conditions in response to heat, the switch means being actuated to one of its conditions by the switch-actuating means to activate the alarm when heat applied to the external surface of the said safe, vault, or the like rises above the said predetermined temperature level.

Various forms of alarm system constructed in accordance with the invention will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a safe including one form of the alarm system; Figure 2 is a view of a heat sensitive switch, used in the system shown in Fig. 1, to a larger scale than Fig. 1; Figure 3 is a cut away, partly schematic, vertical cross sectional view showing the general arrangement of another form of alarm system; Figure 4 is a schematic perspective view showing alternative wiring arrangements which may be used in the alarm system; and Figure 5 is a cross-sectional view of one arrangement of wires that may be used in the alarm systems, toa larger scale than Fig. 4.

Referring to the accompanying drawings, the principle involved in that a built-in thermometer, preferably of the bi-metal spiral type (or a thermostat), placed within the structure of the safe (door, walls, roof, bottom) is arranged to set off an alarm as soon as excessive heat is applied to the exterior of the safe. The increase in temperature produced by a flame will trigger the connecting alarm.

A safe may be equipped by its manufacturer with one or more thermometers or thermostats according to the size and design of the safe, and so on. Referring to Fig. 1, in one form of safe 10 two thermal switch means 12, 14 have been installed, one of them within the metal structure of the door 16 and another in the back wall 18 of the safe. Although the switch means 12, 14 could be installed on the internal surfaces of the door, walls, etc. it is preferred to have them embedded in the safe structure so that no one knows about their existence and location. This will reduce the risk of accidental damage or even deliberate tampering by eventual intruders.

Almost any type of thermal switch means or thermostat could be used for this purpose. Thermometers based on liquids, for example, alcohol or mercury, might, however, be broken by the high temperatures and have to be replaced after each attempt made by the burglars. Because of its simplicity, sturdiness, low cost, durability and dependability, the helicoidal, bi-metal type switch 16 as shown in Fig. 2 is preferred. A metal thermostat would be equally satisfactory.

Because of the replacement problem of liquid heat- responsive elements, the combination of a safe or the like and re-usable element, such as the helicoidal- bi-metal type switch actuator 18 and switch means 20, 22 shown in Fig. 2, or metal ther mostats, is preferred. Such actuators function to operate the switch means between open and closed condition or vice versa in response to heat above or below a predetermined temperature level applied to the external surface of the safe or the like.

The thermal conductivity of steel is high. Should an oxyhydrogen or acetylene flame be applied to any external spot of the safe, the temperature of the entire body of the safe would increase in a matter of seconds. This would set off the alarm, as follows: the bi-metal band 18 of the switch of Fig.

2 would expand and uncoil with the heat, its free end 20 moving outwards. This displacement is caused by the expansion of one of the metal bands bound together in the spiral, having a higher coefficient of expansion than the other, which is the basis on which such thermometers function. As a result of this outward movement, the free end of the spiral will bridge terminals 22 and close a electric circuit, switching on the connecting alarm.

Oxyhydrogen/acetylene flames produce temperatures of several thousand degrees centigrades, whereas the thermic alarm system can be set to function with a temperature only slightly above room temperature. In fact, the thermal switch can be adjusted so that a small increase of, say, 15 to 20 centigrade above the historical absolute maximum registered in the place (or the maximum temperature registered during the hottest month of the year) will set the alarm in action. For instance, if the highest temperature registered in the room where the safe is located is 35", the thermometer could be set at 50 . This will allow for a reasonable safety margin. In the case of air-conditioned premises, the highest temperature to be reached should be taken as a basis for adjusting the thermometer.

Obviously enough, the thermic alarm system proposed here will also detect any abnormal increase in room temperature, such as that caused by accidental fire. Quick response of the alarm after the flame is applied will enable prompt intervention of the police and less damage to the safe.

Fig. 3 schematically shows a possible installation of the wires connecting the thermal switches with external alarms. As can be seen, wires 24, 26 connected to the switches 12, 14 emerge through the bottom wall of the safe 10 and are concealed by being embedded in the concrete floor 28. Fig. 4 shows other possible exits for the wires which can be tailored to the existing physical environment and type and size of the safe. For example, wires 28, 30, 32 could emerge through the roof, side walls or bottom wall of the safe, whichever locations offer the least risk that the wires will be spotted and reached by intruders. As a further precaution, a safe can be partially embedded in surrounding concrete building strucutres, such as walls or a roof, as shown, for example, in Fig. 4, where the rear portion 34 of the safe 10 is embed ded in a vertical building wall 36.Thus, burglars would be obliged to carry out heavy demolition work at the rear wall of the safe to uncover the outside wiring 28 leading from the safe into the wall 36. This would require the use of heavy and noisy demolition equipment, thus increasing the likelihood of the burglars being detected. Separate concrete structures could also be built to surround the safe. Further possibilities of increasing the protection of safes are discussed below with a view to making a safe practically invulnerable to burglars.

As to the type of alarm to be used, this decision should be made by the interested beneficiary (bank, jewellery shop, private or government institution, private manager, and so on.) The market offers a wide variety of alarms, from the simple bellalarm public system 40 which includes a battery 42 as shown in Fig. 3, to more sophisticated alarms, such as those connected with police headquarters as shown generally at 44 in Fig. 3.

From the description of the thermic alarm system, it follows that the cost of installing it is negligible as compared with the expected benefits.

Manufacturers incorporating the thermic alarm system in their safes will be able to streamline and simplify their models. Heavy and costly armouring will not be an indispensable requirement and may even become redundant with the use of the thermic alarm system. Existing safes and vaults can be equipped with systems according to the invention at very low cost. Thermometers could be installed on the internal surfaces of the safe (walls, door, roof) and orifices drilled to install any necessary connecting wiring.

From the description given above, it follows that the alarm system of the invention can only be frustrated by destroying the wiring installation outside the safe. In fact, the switches and wiring inside the safe are totally out of the reach of burglars. Assuming that the burglars were aware of the existence of the thermic alarm system and would still decide to go ahead with their plans knowing that the exteral wires were embedded in the floors or walls, they would be compelled to undertake heavy demolition work requiring the use of heavy demolition equipment, electrically driven, and a high risk of being detected by the noise and vibration caused in the building.

To render the possibility of reaching the external wires even more remote, some complementary steps might be considered which would make the attempt still more risky and difficult for the intruders. These are the following: i) To install alternate wiring for each thermal switch so that is one set is destroyed during the demolition stage, the remaining ones would still do the job. Each set of wires could emerge from different places of the safe and follow different routes through the concrete structures of the build ing, as in Fig. 4. To make sure that all the emerg ing wires had been destroyed, the burglars should have to isolate the safe completely from all the adjoining concrete structures (walls, roof, floor) and though this might be possible with safes of small size, it would almost be impossible with safes of greater size and weight.

ii) Dummy wiring emerging from various places of the safe could be used to deceive the burglars.

iii) The use of an independent supplementary alarm system, whose wiring 46 would be inter twined with the wiring 26 of the thermic alarm system as shown in Fig. 5. This new alarm system would operate only when its wires are cut-off. It could consist of a simple electric circuit, fed by a battery and having a small electro- magnet. The moment the electricity is cut-off, a metal spring would detach itself from the magnet and switch on the alarm. There is no need to go into further description as this is a well-known device. The use of such an independent supplementary alarm with its wires fully intertwined would leave no valid alternative to the intruders. In fact, if they cut the wires during the demolition job, the magnetoperated alarm would set the alarm. If they did not, the thermic alarm system would do the job, just the same.

iv) The use of a wireless, remote-control alarm system, could be connected to the thermic alarm proposed here. The remote control would activate the alarm as soon as the demolition work leaves one of the external walls of the safe unprotected.

As this is a supplementary suggestion, there is no need to enter into full details.

To prevent tampering with the building's power supply feeding the alarm systems, independent sources of power should be used. The use of batteries or electricity from a circuit different from the one installed in the building will afford safety.

Claims (15)

1. An alarm system comprising switch means arranged to be concealed within a safe, vault, or the like, an alarm arranged to be in communication with the switch means, and heat responsive switch-actuating means arranged to be disposed in a position within the said safe, vault, or the like to operate the switch means between open and closed conditions in response to heat, the switch means being actuated to one of its conditions by the switch-actuating means to activate the alarm when heat applied to the external surface of the said safe, vault, or the like rises above the said predetermined temperature level.

2. An alarm system as claimed in claim 1, wherein the switch-actuating means is arranged to actuate to the other of its conditions when the applied heat falls below the said predetermined temperature level.

3. An alarm system as claimed in claim 1 or claim 2, wherein the heat-responsive switch-actuating means and the said switch means are arranged to be embedded in wall means of the safe, vault, or the like.

4. An alarm system as claimed in any one of claims 1 to 3, wherein the alarm means is arranged to be located in a position remote from the safe, vault, or the like.

5. An alarm system as claimed in any one of claims 1 to 4, wherein the heat-responsive switchactuating means is arranged to be concealed behind an outer surface of wall means, of the safe, vault, or the like.

6. An alarm system substantially as hereinbefore described with reference to, and as shown in Figs. 1 and 2, or Fig. 3, or Fig. 4, or Figs. 4 and 5 of the accompanying drawings.

7. A safe, vault, or the like having an alarm system as claimed in any one of claims 1 to 6.

8. A safe, vault, or the like as claimed in claim 7, wherein the alarm is connected to the switch means by concealed wiring.

9. A safe as claimed in claim 7 or claim 8, including building means having a floor and at least one wall, the safe being supported on the floor and having at least a portion therof embedded in the said at least one wall.

10. A safe as claimed in claim 9 when dependent upon claim 8, wherein the wiring is concealed by being embedded in the wall and by passing from the wall to that portion of the safe embedded in the wall for connection to the switch means.

11. A safe as claimed in claim 9 when dependent upon claim 8, wherein the wiring is concealed by being embedded in the floor of the building means for connection to the switch means.

12. A safe as claimed in any one of claims 9 to 11, wherein the heat-responsive switch-actuating means is within heat receiving relationship of the portion of the safe embedded in the said wall.

13. A safe, vault, or the like as claimed in any one of claims 7 to 12, which includes door means in heat transmitting relationship with the heat-responsive switch-actuating means.

14. A safe substantially as hereinbefore described with reference to, and as shown in, Fig. 1, or Fig. 3, or Fig. 5 of the accompanying drawings.

15. A safe as claimed in claim 14, modified substantially as hereinbefore described with reference to, and as shown in, Fig. 2, or Fig. 4, or Fig. 2 and Fig. 4, of the accompanying drawings.