US 3521266 A
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MELMHMH MUMWB July 21, 1970 HALL 3,521,266
BURGLAR ALARM SYSTEM HAVING PLURAL VIBRATION DETECTORS WITH ACTUATION INDICATORS Original Filed May 17, 1967 ALARM INVENTOR. ROBERT A. HALL EM- -J A ATTORNEYS United States Patent M 3 521,266 BURGLAR ALARM SYSTEM HAVING PLURAL VIBRATION DETECTORS WITH ACTUATION INDICATORS Robert A. Hall, Montclair, N.J., assignor to Guardian Industries, Inc., Springfield, N..I., a corporation of New Jersey Original application May 17, 1967, Ser. No. 639,181, now Patent No. 3,392,246, dated July 9, 1968. Divided and this application May 1, 1968, Ser. No. 725,757
Int. Cl. G08h 13/02 US. Cl. 340-261 1 Claim ABSTRACT OF TI-m DISCLOSURE A burglar alarm system comprises a plurality of vibration detection devices mounted on one or more surfaces to be protected at a plurality of spaced-apart locations to detect vibration thereof. An alarm in circuit with the devices responds to actuation of any one of the devices. Each of the vibration detection devices includes an actuator for actuating such device upon the occurrence of vibrations exceeding a predetermined intensity. In addition, the actuating means maintains such actuated device in an actuated condition to facilitate identification of the actuated device among a plurality of devices. The devices are manually engageable for resetting.
CROSS-REFERENCE TO RELATED APPLICATION This is a division of my copending application Ser. No. 639,181, filed May 17, 1967, now Pat. No. 3,392,246, for Vibration Detection Device.
BACKGROUND OF THE INVENTION Field of the invention This invention relates to a burglar alarm system and, in particular, to a novel and highly-improved burglar alarm system including a plurality of devices the sensitivity of each of which is adjustable independently of the force with which first and second break contacts are normally pressed together. Means are provided for maintaining each device of the system in such condition following actuation as to facilitate ready identification of the device as having been actuated.
Description of the prior art Vibration detectors are known and are used, for example, for burglary detection. In such use, vibration detectors are typically mounted on windows, doors, or walls and are designed to open momentarily normally-closed electrical contacts when vibration results from an attempt to break through the protected surface. Conventional vibration detectors have, however, a number of serious disadvantages. For example, they are typically prone to produce false or spurious alarms after installation, and their design is such that it is extremely diificult to locate the malfunctioning detector or detectors in a typical multidetector burglar alarm installation.
One reason for the difliculty in detecting an improperly adjusted device is that the contacts opened by, for exam ple, nearby vehicular traffic promptly close again after the passage of the disturbance so that inspection of the devices fails to reveal which of them actuated the alarm.
Another shortcoming of conventional devices is that the force with which the contacts are normally held together is a function of the adjustment of the sensitivity. For a sensitive adjustment, a light force is necessary, which means that dry circuit phenomena including resistive ox- 3,521,266 Patented July 21, 1970 SUMMARY OF THE INVENTION An object of the present invention is to remedy the shortcomings noted above. In particular, an object of the invention is to provide a burglar alarm system comprising a plurality of rugged, simple, inexpensive, compact vibration detection devices in which the relatively movable contacts are strongly held in their normal relative posi tions irrespective of the sensitivity adjustment and which, once actuated, remain in a condition adapted to facilitate ready verification of the fact of actuation.
The foregoing and other objects are attained in accordance with the invention by the provision of a burglar alarm system comprising a plurality of vibration detection devices mounted on surfaces at a plurality of spacedapart locations to detect vibration thereof and alarm means in circuit with such devices responsive to actuation of any one of such devices to produce an alarm, the vibration detection devices respectively including a plurality of actuating means for (a) actuating the respective devices upon the occurrence of vibrations of the respective surfaces exceeding predetermined intensities and (b) maintaining the actuated devices in an actuated condition, to facilitate identification of actuated devices without employment of separate alarm circuits therefor. Manually engageable means is provided for resetting the devices.
BRIEF DESCRIPTION OF THE DRAWING An understanding of other aspects of the invention may be gained from a consideration of the following detailed description of representative embodiments of the invention and of the accompanying figures of the drawing, in which:
FIG. 1 is a side elevational view, partly in section, of an exemplary embodiment of a device suitable for use in accordance with the invention;
FIG. 2 is a fragmentary perspective View, on an enlarged scale, of the apparatus of FIG. 1;
(FIG. 3 is a fragmentary elevational view, on the same scale as FIG. 1, of the apparatus of FIG. 1 in an actuated condition; and
FIG. 4 is a schematic diagram of a plurality of devices according to FIGS. 13 in an alarm circuit according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows apparatus 10 constructed in accordance with my copending application identified above. The ap paratus includes an insulating base 12 mounted on a surface 14 to be protected. The surface 14 is typically the surface of a wall, door, window, floor, or ceiling.
A first electrically conducting strip, which may be of brass, is mounted on the insulating base 12. The electrically conducting strip 16 has a terminal portion 18 and a contact portion 20. The terminal portion 18 is electrically connected to a lead 22 by a terminal screw 24. The contact portion 20 of the strip 16 is preferably formed with a contact 26 which is normally closed with a second contact 28.
The contact 28 is formed on a second electrically conducting member 30, which may also be of brass. The conducting member 30 is preferably a flexible spring mounted in cantilever fashion, the free end 32 accommodating the contact 28 and the other end 34 being supported by an insulating mounting 36 in insulated relation from the conducting strip 16 and serving as a second terminal portion.
A terminal screw 38 connects a second electrically conducting lead 40 to the portion 34 of the spring 30-.
The contacts or contacting portions 26 and 28 and normally pressed firmly together so that minor heating or warping of the surface 14 or the formation of oxides on the contacts will not cause the generation of spurious signals. The spring 30 is not provided with a weight, as in typical conventional devices, so the contact 28 tends to follow the vibration of the surface 14 just as does the contact 26.
Actuation of the device to separate the contacts 26 and 28 is effected by a biased lever 42. The biased lever is pivotally mounted and biased by means such as a tension coil spring 44. The upper end 46 of the lever is normally retained by a notch 48 formed in a leaf spring 50. Those skilled in the art will readily understand that other retaining means can be employed in lieu of the notch 48. For example, the lever 42 could be provided with pins insertable within holes formed in the spring 50.
As FIG. 2 best shows, the spring 44 is anchored at its lower end 44a in a boss 12a formed on a plate 12b securely attached to the base 12. At its upper end 44b, the spring 44 is secured through an eye 42a formed in a tab 42b on the lever 42. A wall portion 120 integral with the plate 12b is formed with a slot 12d permitting pivoting movement of the lever 42, as will hereinafter become evident.
The notched spring 50 tends to remain stationary notwithstanding vibration of the surface 14 because of the inertia of a weight 52 mounted thereon. The position and, if desired, the magnitude of the weight 52 are adjustable to adjust the sensitivity of the device. In addition, the sensitivity of the device is adjustable by a threaded screw 54 adapted to bear on the spring 50 at a point 56. The spring 50 is flexible, and the force with which the screw 54 bears on the spring 50 adjusts the tendency of the notch 48 to follow downward movement of the lever 42 as seen in FIG. 1.
The adjustment screw 54 is mounted in a threaded aperture 58 formed in a spring retainer 60. The spring retainer '60 and the end 62 of the spring 50 are secured by the terminal screw 38 to the insulating mounting 36.
A dust cover 64, preferably formed of an insulating material, forms a snap-on engagement at 66 with the base 12 and protects the apparatus from dust.
The dust cover 64 is formed with a slot 68, and the lever 42 has a protruding portion 70 which extends exteriorly of the dust cover 64 to facilitate manual engagement for resetting the device after actuation. The protruding portion 70 of the lever 42 also facilitates ready verification of the fact that a device has been actuated and makes it possible to identify one or more vibration detection devices of a plurality of such devices arranged in circuit with an alarm which may be generating spurious alarm signals.
Specifically, in operation, when the surface 14 and base 12 vibrate, the portion 46 of the lever 42 (see especially FIG. 2) engaging the notch 48 in the spring 50 will, if the intensity of the vibration exceeds a predetermined magnitude which is a function of the position and mass of the weight 52 and of the adjustment of the screw 54, move out of engagement with the notch 48, so that the spring 44 pivots the lever 42 clockwise as seen in FIG. 1 and the end 72 separates the contacts 26 and 28, as shown in FIG. 3.
Inasmuch as the lever 42 remains in the actuated condition shown in FIG. 3 until it is reset, the portion extending at an angle of about 45 to the horizontal, the fact that the device has been actuated is readily determined upon visual inspection.
In accordance with the present invention, a plurality of such devices A, B, C, and N is arranged in circuit with an alarm 74 between leads 76 and 78. If experience shows that one of the devices is adjusted so that it repeatedly gives a spurious indication of an attack upon the protected surface, the device may be rendered less sensitive by adjustment of the screw 54. Any detector which has been actuated can be manually reset by manual engagement of the portion 70 of the lever 42 to move the lever 42 to a position normal to the base member 12.
Thus there is provided in accordance with the invention a novel and highly-eifective burglar alarm system. The apparatus of the invention is rugged, simple, compact, and inexpensive to manufacture and repair. A relatively large contact force of, say 12 to 20 grams may be provided notwithstanding a very sensitive adjustment of the device.
Many modifications within the spirit and scope of the invention of the representative embodiments disclosed herein will occur to those skilled in the art. For example, vibration detectors, other than the one specifically illustrated, may be employed in accordance with the invention. Accordingly, the invention is to be construed as including all of the embodiments thereof within the scope of the appended claim.
1. A burglar alarm system comprising a plurality of vibration detection devices mounted on surfaces at a plurality of spaced-apart locations to detect vibration thereof and alarm means in circuit with said devices responsive to actuam'any one of said devices to produce an alarm, each of said vibration detection devices including a lever, each of said levers (a) actuating the vibration detection device with which it is associated upon the occurrence of vibrations of the surface protected by said device exceeding a predetermined intensity and (b) maintaining said actuated device in an actuated condition, said levers being mounted to be visible at least in part from outside said respective devices and the appearance of said levers facilitating identification of actuated devices among said plurality of devices without employinent of separate alarm circuits therefor, and said levers respectively including portions manually engageable for resetting said devices.
References Cited UNITED STATES PATENTS 640,273 1/ 1900 Coleman. 1,192,312 7/1916 Hopkins 340-261 1,903,584 4/ 1933 Wettengel. 2,942,456 6/ 1960 Hardway 73-71 3,333,073 7/ 1967 Ohlson ZOO-61.45
JOHN W. CALDWELL, Primary Examiner D. L. TRAFTON, Assistant Examiner US. Cl. X.R. 340-276