ANTI-JAMMING DEVICE FOR SECURITY SCREENS

Abstract: An anti-jamming device for a security screen arrangement, in which a security screen is able to be rapidly fired from a rest position to an upper position at which passage of a person from one side of the screen to another is not possible, includes sensors (24, 26) for detecting whether the screen is at the rest position or the upper position. The device also includes a valve for lowering a screen when it does not reach the upper position, due to the screen having been jammed, and for reactivating the firing of the screen. The screen may be repeatedly fired until the obstruction is cleared.

Description: This invention relates to security screens for use in banks, savings and loan premises, building society offices and the like, and in particular, relates to an anti-jamming device for such screens. European patent No. 0171950 and European published patent application No. 0334395 - and equivalent United State patents Nos. 4,748,914 and 4,831,939 are equivalents thereof - describe security screens of the aforementioned type. Such a screen is also described in EP-A-0178240. A bank till shield has an armoured movable panel mounted under a cover, and is driven upwards by a pneumatic cylinder. Screens of the aforementioned type are adapted to rapidly ascend from counters when a robbery is detected, thus screening staff and currency from the robbers. There is a concern that such screens may jam, rendering them ineffective. One existing approach to counteract security screen jamming is to use a collapsible bulkhead. In such an arrangement the bulkhead is constructed to collapse when a screen is jammed by having something placed over it. Whilst this approach is effective, there are a number of disadvantages. Once the bulkhead has collapsed, a major rebuild must be undertaken before the premises are able to operate normally. Furthermore, the aesthetic design of the bulkhead is greatly limited. In addition, when an existing security screen system is upgraded, the cost of a collapsible bulkhead is prohibitive, Finally, a collapsible section of at least the reach of the screen is required over and above the lower level of- the bulkhead. This amount of room is rarely available. Another prior manner of overcoming screen jamming consists of a flap covering the opening from which the screen emerges, the flap is hinged on the front edge. When the screen is activated the flap flips forward theoretically knocking away the jamming device if it falls within a length that will be hit by the flap. If it is too long the flap will fail to open, if it is too short the flap will miss completely. It is an object of this invention to provide an anti-jamming device for a security screen. The invention provides an anti-jamming device according to EP-A-178 240 for use with means for rapidly firing a security screen from a lower rest position to an upper operative position at a predetermined height above said rest position and for returning the screen to its rest position, said device being characterised by a "screen-up" sensor and a "screen-down" sensor for indicating when a screen has reached its operative and rest positions respectively and means, operable in the absence of an expected indication from the "screen-up" sensor, to initiate operation of the lowering and raising means alternately until an indication is received from the "screen-up" sensor that the operative position of the screen has been reached. The invention also provides a security screen arrangement according to EP-A 178 240 in which the screen is to be rapidly fired from a rest position to a predetermined height above said rest position, characterised by an anti-jamming device comprising a "screen-up" sensor for detecting the presence of at least part of said screen at said predetermined height, and a "screen-down" sensor for detecting the presence of a screen at or near said rest position, means for lowering said screen from a fired position which is short of said predetermined height due to jamming of the screen and means for reactivating the firing of said screen when said "screen-down" sensor detects that the screen is at or near said rest position until said screen reaches said predetermined height. An embodiment of the invention will be described in detail hereinafter, with reference to the accompanying drawings, in which:- Figure 1 is a schematic diagram of an embodiment of an anti-jamming device in accordance with the present invention. The diagram of Figure 1 is intended to be read in conjunction with the general disclosures of European patent No. 0171950, European published patent application No. 0334395 and United States patents Nos. 4,748,914 and 4,831,939, which are incorporated into this specification by reference. The anti-jamming device of the embodiment of Figure 1 involves features which will, in conjunction with the security screen arrangement, provide anti-jamming operation of such an arrangement. The features include:- 1. A sensing service to detect that each security screen has reached a safe height which is preferably the "fired" height less 200mm. 2. A system to isolate the screen that has not reached its safe height, including (a) a timing device, (b) a flow detector on pneumatic rams used to fire the screen, and (c) a proximity switch. 3. A valve to quickly drop the isolated security screen. 4. A sensing device to reactivate the screen and the reset cycle, including (a) a timing device, (b) a proximity switch, (c) a micro switch. The above can be achieved either electrically, pneumatically or with a combination of both. One other consideration is the requirement for the provisional additional air storage (in a pneumatically-operated system) to ensure that the system can handle multi-part firings. In Figure 1, a prior art system of the type disclosed in the aforementioned European and United States patents and patent application is shown enclosed by a rectangular border and marked 10. Some features of the prior art system are master components 12 and screen components 14, the latter including an air tank 16 and pneumatic rams 18. The device of this embodiment of the invention includes a reserve air tank 28 (to allow for repeated screen firings), isolators 20, a timer 22, a 'screen down' sensor 24 and a 'screen up' sensor 26. The arrow at lower left indicates a pneumatic connection to other screens. The device of Figure 1 operates as follows. When the screens are fired in accordance with the prior art disclosures, the device detects jamming - that is, the placement of an article or a person or part of a person between the top of the security screen and, for example, a bulkhead - by the failure, within a predetermined time, of sensor 26 to detect the presence of a screen at a predetermined height, and thus to send a 'screen up' signal. Preferably, such sensor 26 is located at such a position that a screen reaches within 200mm of an upper bulkhead, it is considered to be up. The space of 200mm is considered sufficient to prevent a person lying on the screen from suffering repeated blows as the screen is activated. When jamming is so detected, isolators 20 isolate the screen from other non-jammed screens, lower the screen until sensor 24 detects that the screen is down by detecting its presence at a predetermined height, at which time the screen is reactivated. It is considered that most jamming situations will be resolved by one such cycle, with any jamming device falling or being expelled when the screen is dropped or reactivated. Should this not occur, the cycle will continue. If the jamming device is supported in some way, the screen will continue to fire, rapidly, making it impossible for a person to attempt to jump over it. Of course, eventually the air supply will be exhausted, hence the desirability of having additional capacity (tank 28) but it is considered that by then robbers would have been sufficiently deterred to flee the premises.

Claims: An anti-jamming device for use with means for rapidly firing a security screen from a lower rest position to an upper operative position at a predetermined height above said rest position and for returning the screen to its rest position, said device being characterised by a "screen-up" sensor (26) and a "screen-down" sensor (24) for indicating when a screen has reached its operative and rest positions respectively and means, operable in the absence of an expected indication from the "screen-up" sensor (26), to initiate operation of the lowering and raising means alternately until an indication is received from the "screen-up" sensor (26) that the operative position of the screen has been reached. An anti-jamming device according to claim 1, further characterised by timing means (22) to provide a delay sufficient for a screen to reach, under normal circumstances, said predetermined height, on each firing thereof. An anti-jamming device according to claim 1 or 2, for use with a plurality of security screens, further characterised by means (20) to isolate a jammed screen from other, non-jammed security screens, An anti-jamming device according to any preceding claim, characterised in that a cycle of state detection, screen lowering and screen firing reactivation is carried on until said predetermined height is reached. An anti-jamming device according to claim 4, characterised by pneumatic firing means and an additional source of air (28), said cycle operating until said predetermined height is reached or until such air is exhausted. A security screen arrangement in which the screen is to be rapidly fired from a rest position to a predetermined height above said rest position, characterised by an anti-jamming device in accordance with any preceding claim, comprising a "screen-up" sensor (26) for detecting the presence of at least part of said screen at said predetermined height, and a "screen-down" sensor (24) for detecting the presence of a screen at or near said rest position, means for lowering said screen from a fired position which is short of said predetermined height due to jamming of the screen and means for reactivating the firing of said screen when said "screen-down" sensor detects that the screen is at or near said rest position until said screen reaches said predetermined height.

Inventors: CARDINAL, MICHAEL JOHN
Applicants: SAFETELL SECURITY SCREENS LIMITED
Application year: 1990
Main classification: E05G5
IPC codes: E05G7, E05F15