US2274870A - Burglar alarm - Google Patents

Description

March 3, .1942. F. F. Rlcl-IIARDSI 2,274,870

BURGLAR ALARM 'y Filed oct, 8, 1940 2f f 2f 5 3,0, 2,1/

Inventor Fred f.- fic/yards" A torney Patented Mar. 3, 1942 @Tra 6 fClaims.

My invention relates to improvements in burglar alarms', and particularlyto an arrangement of this character which is operated-by displacement of a stretched-string or wire connected to a switch mechanism, and the primary object of the invention istoprovide a simple, eicient arrangement of this character which although rugged construction is extremely sensitive.

Other important objects and advantages of my invention will be apparent from a reading of thev following description taken in connection withI the drawing, wherein for purposes of illustration I have shown a preferred embodiment of: my invention.

In the drawing:

Figure l is a general. top plan View oil the embodiment.

Figure 2 isa side elevational view ofV Figure l.

Figure 3 is a left hand end' elevational View oflFigure'2l Figure 4 isv a vertical. longitudinal. sectional view.

Figure 5iis. a bottom plan view of Figure l showing diagrammatically the electrical connections thereto of the alarm circuit.

Referring in detail to the drawing; the' numeral 5 generall'ydesignates an elongated. generally rectangular insulating material casing which is open at its bottom as indicated by the numeral 6, the Saidppening to face the support, suchas'a'window Casement or the like onwhich the switch mechanism is' to be mounted, the casing 5 being adapted to be attached or suspended in place by the half elliptical shaped projection 1 on one end thereof which is. provided'withahole 8 to` receive a screw or other attaching means. The opposite end of the casing is provided with a keyhole-shaped opening 9.

Supported in a groove I in the sides of the keyhole openingi is a U-shaped conductiveplate I1 which has a longitudinal extension I2 providing acontact I3` for engagement by one of the terminals of a shielded cable containing the burglar alarm system wires through a suitable opening in the side of the casing. Extending through the aperture I4 in the conductive plate II is a rod or heavy wire I5 which has respective eyes I5 and I1 on its opposite ends, the eye I6 being adapted for connection to a Wire or cable or string or the like I8 which is stretched across the object to be protected, such as a window opening, with the free end of the wire I3 attached to a suitable anchor such as a hook I9 on a support remote from the casing 5 and on a line with the conductive wire I5.

To the eye I1 on the conductive wire I5 istattached one end of a contractilespring 21'l which has its opposite end engaged through a hole 22 in the foot portion 23' of an L-shaped bracket 24 which has threaded through the standard portion 25 thereof the adjusting screw 25 which turns in a smooth opening 21 in the end wall of the casing and has a head 23 bearing against the outer side of the end ofthe casing so that the screw may be turned to adjust the position of the bracket 23 in the opening G'of the-casing 5 and thereby adjust the tension'otthe spring ZI and hence the position of the conductive disks 29 and 3i] relative to the conductive'vpl'ate II. The conductive disks 29 and 39 are iixedly` secured to the conductive rod I51on opposite sides of the conductive plate I1 and these disks are of suiiicient diameter and suflicientspacing relative to thel sides of the conductive plate IIV so that a relatively small deflection of the rod I5 through disturbance of the stretched wire I8 will bring about engagement with the conductive plate I I of either or both of the conductive disks 29 and 3B or therod I5 itself so as to close the burglar alarm circuit. Electrical' connection with the'rod' I5 is made bymeans of a flexible conductor 3l which is connected with a contact 32 paired4 with ther contact I3 and reached .by a terminal of the shielded cable through an openingfin'the side of the casing as indicated. It will beY observed that in thek unoperated condition the conductive disks andtherod I5 are cleanly j and `completely separated from 'engagement with the conductive plate I'I but that they.l are so arranged'that only a relatively small deflection is required to engage any of them with the conductive plate to closethe circuit, and thereby setf the alarm intov action.

The circuit contemplated for operation bythe aboveV described switch mechanism comprises the wire 33Y which leads from'l thecontact I3 to one side of the battery' 34- or. other suitable source of current. A wire 35connects the remaining side off the battery with. one' endof the Winding on the electro-magnet 35, the remaining end of this winding being connected to the wire 31 which leads to the contact 32. 'The wire 31 also connects with the contact point 38 which is paired with the contact point 39 adapted for bridging by the armature 40 which is pivoted at 4I in a position over the end of the core of the electro-magnet 35. The contact point 39 is connected to one side of the alarm bell or other alarm device 42, theremaining side of the alarm device loe-ing connected .by the wire 43 with the wire 35 and hence with the battery 34. A switch 44 is connected in the wire 35 between the magnet and the wire 43 so that the alarm circuit can be opened after it has once been set in operated position by the operation of the switch mechamsm.

In operation, whenever the conductive plate I I is engaged by either one of the disks 29 and 30 or the rod I5, or any of them, the switch 44 being closed, current will flow through the electro-magnet 36, causing the armature 40 to be attracted by the electro-magnet so that the contact points 38 and 39 are bridged and the bell or the like alarm device 42 is thrown into circuit with the battery 34. A shunt 45 is connected between the binding post I3 and the battery 34 with the wire 33, the remaining end of the shunt being connected with the conductive armature 40. By reason of this arrangement even though the switch mechanism become restored to open and inoperative position, the alarm device will continue to give the alarm and will not shut off until the switch 44 be opened.

Similarly should the connection of the shielded cable terminals with the contacts I3 and 32 be disturbed, the alarm will be set off.

Although I have shown and described herein a preferred embodiment of my invention, it is to be denitely understood that I do not desire to limit the application of the invention thereto, except as may be required by the scope of the subjoined claims.

Having described the invention, what is claimed as new is:

l. A device for closing a normally open burglar alarm or other circuit, said device comprising a dielectric casing adapted to be anchored to a support, a longitudinal conductive rod extending through an opening formed in an end of said casing in spaced relation to the sides of said opening, a contractile spring connected to the end of the conductive rod within said casing, a longitudinally adjustable bracket connected to the opposite end of said spring, a stationary conductive plate on said casing, said plate being formed with an aperture aligned with said opening and freely passing said conductive rod, conductive disks fixed on said conductive rod on opposite sides of said conductive plate, and a cord connected at one end to an anchor remote from said rod but substantially axially aligned with and connected to the outer end of said conductive rod, said bracket being longitudinally adjustable to space said conductive disks close to the opposite sides of said aperture in the stationary conductive plate whereby lateral or longitudinal deflection of said rod produced by disturbance or disruption of said cord engages any of said conductive disks and/or said conductive rod with said stationary conductive plate, and means for connecting said rod and said plate in the burglar alarm or other circuit.

2. A circuit closer comprising a dielectric chamber, an anchor at one side of said chamber,

an element having one end secured to said anchor, an elongated conductive rod having its inner end secured to the remaining end of said element, said conductive rod projecting spacedly through an opening formed in the opposite side of said chamber, a contact on said opposite side of the chamber and having portions on three sides of said opening projecting inwardly from the corresponding edges of said opening. said portions extending in laterally spaced relation to said conductive rod, a cord connected to the outer end of said conductive rod, said cord being normally stretched to hold said conductive rod out of engagement with the said contact, whereby breaking or substantial lateral deflection of said cord engages said conductive rod with said contact.

3. A circuit closer comprising an elongated hollow dielectric housing, an anchor secured to one end wall of said housing, an element connected, to said anchor, an elongated conductor having its inner end secured to said element, the remaining end wall of said housing being formed with an opening through which said conductor spacedly extends, a contact mounted on said remaining end Wall and having edge portions surrounding and projecting laterally into said opening from at least three sides of said opening and in spaced relation to said conductor, a cord connected to the outer end of said conductor, said cord normally being stretched in a direction to hold said conductor out of engagement with said edge portions, whereby slackening or substantial lateral deflection of said cord permits electrical engagement of said conductor with the edge portions of said contact.

4. A circuit closer according to claim 3 wherein said housing is formed with an access opening in a longitudinal side thereof. said access opening extending through the said remaining end wall and communicating with the first mentioned opening, said edge portions of the contact being discontinuous at the point of communication of the two openings to permit lateral Withdrawal of the conductor through the point of communication.

5. A circuit closer according to claim 3 wherein said element comprises a contractible spring and said conductor comprises a pair of longitudinally spaced contactors located on opposite sides of said edge portions of the contact, said contactors being disengaged from said contact only while said cord is in a stretched and undeflected condition.

6. A circuit closer according to claim 2 Wherein said' element comprises a contractile spring and said conductive rod has a pair of longitudinally spaced radial contactors located on opposite sides of the said portion of the Contact, said contactors being arranged to be disengaged from the said portions of said contact only While said cord is in a stretched and undeiected condition.

FRED F. RICHARDS.

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