US3763795A

US3763795A - Alarm condition sensor

Info

Publication number: US3763795A
Application number: US00267008A
Authority: US
Inventors: L Wetz
Original assignee: Mosler Safe Co
Current assignee: Mosler Safe Co
Priority date: 1972-06-28
Filing date: 1972-06-28
Publication date: 1973-10-09
Anticipated expiration: 1990-10-09

Abstract

An alarm condition sensor for enclosing a device to be protected, such as a vault, which will change its electrical properties and thereby facilitate an alarm indication when a person tampers with the sensor and/or attempts to cut, burn or otherwise penetrate the protected device to gain access thereto. The alarm condition sensor includes frangible, opaque panels adhesively secured to the exterior surface of the protected device to completely enclose it. The panels have a printed circuit on the inside surface thereof which is electrically insulated from the exterior of the protected device, and due to the opaqueness of the panel is not visible from the outside. Attempts to pry, fold, bend, or otherwise remove the frangible panel prior to penetration of the protected unit itself will cause the panel, by virtue of its brittleness, to break, interrupting the electrical continuity of the printed circuit formed thereon. Similarly, attempts to drill, cut, or otherwise penetrate the protective panel, which necessarily occur prior to penetration of the protected unit, either interrupt the electrical continuity of the printed circuit or at least shortcircuit it to ground via the vault which is typically of conductive material. In either case, a change in the electrical circuit occurs which can be sensed and an alarm indication provided prior to the point in time when the protective device is actually penetrated.

Description

United States Patent 1191 Wetz, Jr.

[ Oct. 9, 1973 ALARM CONDITION SENSOR Leonard R. Wetz, Jr., Fairfield, Ohio [73] Assignee: The Mosler Safe Company,

Hamilton, Ohio [22] Filed: June 28, 1972 [21] Appl. No.: 267,008

[75] Inventor:

109/38, 24; 340/273, 256, 276; ZOO/DIG. 12; 161/196, 200, DIG. 7

[56] References Cited UNITED STATES PATENTS 1,223,583 4/1917 Hitchcock 109/42 R8,874 8/1879 Chester 109/42 181,078 8/1876 Larned 200/D1G. 12 587,931 8/1897 Coleman 340/273 1,536,804 5/1925 Mason 109/42 1,559,380 10/1925 Roe 340/273 UX 2,726,625 12/1955 Evans 109/31 X 3,409,886 11/1968 Davis et a1. 340/273 3,643,756 2/1972 Soreghy 340/273 X Ill" [5 7] ABSTRACT An alarm condition sensor for enclosing a device to be protected, such as a vault, which will change its electrical properties and thereby facilitate an alarm indication when a person tampers with the sensor and/or attempts to cut, burn or otherwise penetrate the pro tected device to gain access thereto. The alarm condition sensor includes frangible, opaque panels adhesively secured to the exterior surface of the protected device to completely enclose it. The panels have a printed circuit on the inside surface thereof which is electrically insulated from the exterior of the protected device, and due to the opaqueness of the panel is not visible from the outside. Attempts to pry, fold, bend, or otherwise remove the frangible panel prior to penetration of the protected unit itself will cause the panel, by virtue of its brittleness, to break, interrupting the electrical continuity of the printed circuit formed thereon. Similarly, attempts to drill, cut, or otherwise penetrate the protective panel, which necessarily occur prior to penetration of the protected unit, either interrupt the electrical continuity of the printed circuit or at least short-circuit it to ground via the vault which is typically of conductive material. In either case, a change in the electrical circuit occurs which can be sensed and an alarm indication provided prior to the point in time when the protective device is actually penetrated.

1 Claim, 1 Drawing Figure 1 ALARM CONDITION SENSOR This invention relates to protection of devices against unauthorized access, and more particularly to the protection of vaults, safes and the like against access to the interior thereof by cutting, drilling, burning or otherwise penetrating the walls thereof.

A common method of gaining unauthorized access to the interior of a vault, safe or similar storage device is to make a hole in the wall of the device by drilling, cutting, burning or otherwise penetrating it. Different approaches to defeating unauthorized access of the type indicated are possible. In accordance with one approach, the material from which the vault or safe is fabricated is of a type which physically resists penetration to a degree sufficient to effectively prevent unauthorized access. In accordance with another approach, sensor means are provided on the vault or safe to detect when an effort is being made to penetrate it, whereupon an alarm indication, such as an audible signal, is activated, bringing the police to the scene, who are then in a position to halt the unauthorized activity.

It has been an objective of this invention to provide reliable, and yet economical, means for protecting a vault, safe or the like which will facilitate generating an alarm indication when penetration of the vault or safe to gain access thereto is attempted. In a preferred embodiment of this invention, this objective has been accomplished by completely enclosing the vault with opaque panels of frangible material each having a printed circuit on the inner surface thereof, the panels being secured to the exterior surface of the vault with adhesive which electrically insulates the printed circuit and vault. The brittle nature of the frangible panel results in its breaking, thereby interrupting the electrical continuity of the printed circuit, when an effort is made to pry, fold, bend, or otherwise remove the protected panel adhered to the vault exterior. Similarly, attempts to 'drill, cut or otherwise penetrate the vault results in interrupting the electrical continuity of the printed circuit, or at least short-circuiting it to ground via the vault which is typically conductive. In either case, the change in the electrical condition of the printed circuit occurs, is sensed, and an alarm provided, prior to actualpenetration of the protected unit itself.

By virtue of the opaqueness of the protective, circuitbearing frangible panels, the location of the printed circuit cannot be ascertained from the exterior thereof, and one attempting to penetrate the protected unit is unlikely to be successful without grounding or interrupting the electrical continuity of at least one portion of the printed circuit. Notwithstanding the brittle or frangible character of the protective panel which is located exteriorly of the printed circuit, the panel nevertheless has sufficient durability to withstand normal abuse without requiring additional protection. Finally, by reason of using an electrically insulative adhesive to mount the circuit-bearing surface of the frangible panel to the exterior surface of the vault, not only is the protective panel easily secured in place on the vault, but the circuit is maintained electrically insulated from the vault and hence will not, absent penetration, be shortcircuited by contact with the vault wall which, as noted, is typically fabricated of electrically conductive material.

These and other advantages and features of the invention will become more readily apparent from a detailed description of the preferred embodiment thereof in which the figure is a perspective view, partially exploded, of a vault provided with the protective panel of this invention.

With reference to the figure, a conventional vault is shown of the type with which the protective panel of this invention is useful. The vault includes sidewalls l0 and 12, rear wall 14, bottom wall or floor l6 and top wall or ceiling 18. A door 20 hinged along one vertical edge and provided with a suitable combination lock 22 selectively closes an access opening in the front of the vault. The walls and door of the vault are relatively thick, and preferably fabricated of hard, tough material such as steel, and accordingly inherently possess a high resistance to penetration by drilling, burning, cutting, or the like.

The alarm condition sensor of this invention is designed to facilitate provision of an alarm indication in the event that an attempt is made to gain unauthorized access to the interior of the vault, and includes a plurality of

protective panels

10a, 12a, 14a, 16a, 18a and 20a secured to the exterior surfaces of side walls 10 and 12,

rear wall 14, bottom and

top walls

16 and 18, and front door 20, respectively. The

protective panels

1011,1211, 14a, 16a, 18a and 20a are identical in structure, although in certain cases differently sized to completely enclose their respectively differently sized associated vault wall surfaces. in view of such identity, only side wall protective panel 12a is described.

Protective panel 12a includes a relatively thin frangible, or brittle, substrate or'layer 26. The substrate 26' vault wall 12a to which it is secured will result in the at tacked portion of the substrate breaking away from the remaining portion of the substrate. For reasons to become apparent hereafter, the substrate 26 preferably is opaque.

Secured to the inner surface 28 of the frangible panel 26 and integral therewith is an electrically conductive element 30, preferably of the printed type, in the form of an electrically conductive pattern of foil, conductive laminate, or other conductive material formed according to well known techniques utilizing photography, etching, plating, or the like. The printed circuit pattern, or conductive element, preferably is in the form of an elongated continuous conductor arranged'in serpentine or zig-zag fashion with closely spaced adjacent sections 30a, 30b, and having

opposite end terminals

31 and 32 to which flexible electrical leads 33 and 34 are secured.

The protective panel 26 is permanently secured in place on the vault, completely enclosing the exterior surface of side wall 12a, using an adhesive layer 36. Adhesive layer 36 preferably is electrically insulative to prevent short-circuiting of adjacent sections 30a, 30b, of the printed circuit 30 by the exterior wall of the vault 12a which is usually fabricated of electrically conductive material such as steel or the like. The adhesive layer 36 may take the form of a double-sided plastic foam tape, the opposite surfaces of which have adhesive qualities, and the body of which is electrically insulative. The electrical leads 33 and 34 connected to the

ends

31 and 32 of the printed circuit 30 are preferably located remote from the peripheral edge of the panel 26 such as in the center of the panel as shown in the figure. When so located, the electrical leads 33 and 34 are not readily accessible for tampering. To facilitate connection of the electrical leads 33 and 34 of the printed circuit 30 to a suitable electrical sensing and alarm condition indicating circuit (not shown) located inside the vault,

holes

38 and 40 are provided in the adhesive layer 36 and in the vault wall 12 through which the leads are inserted for connection to the sensing and indicating circuit (not shown) inside the vault.

A device to be protected, such as a vault, safe or the like, completely enclosed with the protective panels of this invention will provide an electrical condition change, which can be sensed and used to activate an alarm indicator, prior to actual penetration of the walls of the protected unit, such as side wall 120. If an attempt is made to drill, burn, cut, or otherwise make a hole in the vault wall 12 to gain access to the interior of the vault, the cutting implement must necessarily pass through the protective panel 26 and in doing so passes through the printed circuit 30. This either interrupts the electrical continuity of one or more of the conductive sections 30a, 30b, thereof, or connects one or more of the sections to ground via the cutting implement and vault wall. Interruption of the electrical continuity or grounding of any single section 30a, 30b destroys the electrical continuity or alters the resistance between the

terminals

31 and 32 thereof which, via leads 33 and 34, can be sensed by conventional electrical continuity or resistance sensing circuits inside the vault to activate an alarm.

Alternatively, should an unauthorized attempt be made to remove the protective panel 12a prior to cutting a hole in the vault wall 12, the electrical continuity of the printed circuit 30 will be interrupted and via leads 33 and 34 this condition sensed by a circuit (not shown) to provide an alarm. Specifically, any effort to peel, pry, chip, or otherwise remove the substrate 26 will, because of the frangible or brittle nature thereof, cause the attacked portion of the substrate to breakaway from the remaining portion which is not under attack. When the attacked portion of the substrate 26 breaks away, the printed circuit portion adhered thereto breaks away with it, destroying the electrical continuity of the printed circuit 30.

The protective panel of this invention has a number of advantages. First, it represents an extremely inexpensive method of protecting a vault inasmuch as the cost of materials, namely, the frangible substrate 26,

printed circuit 30 and adhesive layer 36, is quite modest. Also the cost of assembly, which involves little more than providing substrate 26 with a printed circuit 30 and adhering the interior surface 28 thereof to the vault wall via the double-sided adhesive 36, can be quickly and easily accomplished without sophisticated tools or prior training. Additionally, by virtue of the opaqueness of the substrate 26, the printed circuit pattern 30 is not visible from the outside, reducing the likelihood that it can be penetrated without either interrupting the continuity of the circuit or grounding it. Further, since the substrate 26 is itself fabricated of reasonably tough and rugged material, it is unnecessary to provide the protective panel 12a with an additional housing, skin, or the like to protect it against physical damage occasioned in the normal course of routine use. Finally, the protective panel of this invention provides a sensible change in its electrical characteristics when an attempt is made to penetrate the vault, prior to the point in time when the vault is actually penetrated. Thus, a warning alarm can be provided before the unauthorized party has actually had access to the contents of the vault.

Having described the invention, what is claimed is:

1. A penetration-responsive protected assembly comprising:

a vault having walls completely enclosing and thereby defining a protected interior, said walls having an exterior surface and being relatively thick to inherently inhibit access to said interior by making a hole therethrough, at least one of said walls being electrically conductive,

a protective panel located exterior of said one electrically conductive vault wall, said panel including a. an opaque substrate of brittle electrically nonconductive material which is relatively thin and which inherently possesses low resistance to penetration, said substrate having an inner surface, an electrically conductive circuit path secured to said inner surface of said substrate and having predetermined electrical characteristics,

c. an electrically insulative adhesive bonding said circuit-bearing inner surface of said substrate to said one exterior wall surface to preclude removal of said brittle substrate without altering the electrical characteristics of said printed circuit, and

d. an electrical sensing circuit electrically connected to said circuit path to detect interruption of said path and/or short -circuiting of said circuit path to said one electrically conductive vault wall.

Claims

1. A penetration-responsive protected assembly comprising: a vault having walls completely enclosing and thereby defining a protected interior, said walls having an exterior surface and being relatively thick to inherently inhibit access to said interior by making a hole therethrough, at least one of said walls being electrically conductive, a protective panel located exterior of said one electrically conductive vault wall, said panel including a. an opaque substrate of brittle electrically non-conductive material which is relatively thin and which inherently possesses low resistance to penetration, said substrate having an inner surface, b. an electrically conductive circuit path secured to said inner surface of said substrate and having predetermined electrical characteristics, c. an electrically insulative adhesive bonding said circuitbearing inner surface of said substrate to said one exterior wall surface to preclude removal of said brittle substrate without altering the electrical characteristics of said printed circuit, and d. an electrical sensing circuit electrically connected to said circuit path to detect interruption of said path and/or shortcircuiting of said circuit path to said one electrically conductive vault wall.