Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS3706090 A
Publication typeGrant
Publication dateDec 12, 1972
Filing dateOct 12, 1970
Priority dateOct 12, 1970
Publication numberUS 3706090 A, US 3706090A, US-A-3706090, US3706090 A, US3706090A
InventorsCallaghan James I
Original AssigneeCallaghan James I
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Burglar alarm triggered by breaking of a magnetic circuit
US 3706090 A
Abstract
A burglar alarm for use on a window in which the alarm is triggered by breaking of a magnetic circuit across the window. The magnetic circuit is defined by a pair of movable bar magnets carried on opposite sides of the window. One bar magnet is carried by a window screen or other movable member which when displaced carries it away from the window to break the magnetic circuit. The other bar magnet then moves to close an electrical alarm circuit.
Images(2)
Previous page
Next page
Description  (OCR text may contain errors)

[22] Filed:

United States Patent Callaghan [s41 BURGLAR ALARM TRIGGERED BY BREAKING OF A MAGNETIC CIRCUIT [72] Inventor: James I. Callaghan, 11229 Camaril- 10 St., North Hollywood, Calif. 91602 i Oct. 12, 1970 [2]] Appl. No.: 79,832

52 us. 01. .l ....340/274, 49/13, zoo/61.84,

' 340/273 51 1111. c1. ..G08b 13/08 [58] Field of Search...340/274, 273', 174 PM;

[56] References Cited UNITED STATES PATENTS 3,539,741 11/1970 Volandm, ZOO/61.62

11 1' 3,706,090 1451' Dec. 12, 1972- Qualheim ..200/61 .62

2,877,361 3/1959 Chase ..340/274 700,812 5/1902 Peyton ..335/205 3,281,735 10/ l 966 Blumish ..335/207 Primary Examiner-John w. Caldwell Assistant Examiner-Glen R. Swann, lll Attorney-Nilsson, Robbins, Wills & Berliner ABSTRACT A burglar alarm for use on a window inwhich the alarm is triggered by breaking of a magnetic circuit across the window. The magnetic circuit is defined by a pair of movable bar magnets carried on opposite sides of the window. One barmagnet is carried by a window screen or other movable member which when displaced carries it away from the window to break the magnetic circuit. The other bar magnet then moves to close an electrical alarm circuit.

17 Claims, 13 Drawing Figures PA'TENTED nu: 12 I972 SHEET 1 UF 2 INVENTOR. 56 Cmmsw/v pmminnmzmz 3.706.090

SHEU 2 BF 2 INVEN'i'OR- dimes Cmmemq/v FIELD OF THE INVENTION The field of art to which the invention pertains includes the field of burglar alarms, particularly sound generating alarms.

BACKGROUND AND SUMMARY OF THE INVENTION The present invention provides a low cost, compact, self-contained burglar alarm unit which can be utilized on any window to provide a tamper proof alarm. The unit can operate on batteries and the alarm generating components can be installed entirely on the inside of a window.

In accordance with this invention, a burglar alarm is provided in which the components define a magnetic circuit across a window, or the like, whereby upon breaking the circuit an alarm is triggered. Specifically, an alarm unit is disposed on the inside of the window and includes a magnet which cooperates with a second magnet on the opposite side of the window. The second magnet can be carried by a movable member such as a window frame or a flat sheet of plexiglass or other transparent member which acts as a barrier obstructing access to the window. The magnets cooperate to define a magnetic circuit and movement of the barrier results in displacement of the second magnet to break the magnetic circuit.

The magnet on the inside of the window is disposed at an alarm set position. A signal generating circuit cooperates with this magnet so as to energize a signal generator when the magnet is moved to an alarm position. The magnet is continuously urged to the alarm position either by the force of gravity or by attraction to paramagnetic or magnetic material disposed at the alarm position. In a particular embodiment, the alarm circuit includes spaced contacts at the alarm position defining the circuit as open and the magnet when displaced to that position bridges the spaced contracts to thereby close the alarm circuit and trigger the alarm. In another embodiment, the alarm circuit includes a switch, such as a micro-switch which is spring loaded to close the signal generator circuit but carried by the first magnet against the force of the spring at the alarm set position so as to open the signal generator circuit. Upon breaking of the magnetic circuit, the first magnet moves away from the alarm set position, by gravity or otherwise, allowing the switch to close the signal generator circuit thereby triggering the alarm.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevational view of a window incorporating a burglar alarm in accordance with this invention;

FIG. 2 is a cross-sectional view taken on line 2-2 of FIG. 1, in the direction of the arrows;

FIG. 3 is a perspective view of a particular alarm unit shown open and partially broken away;

FIGS. la-care schematic representations of the manner of operation of the burglar alarm unit of FIG.

FIG. 5 is a front elevational view of an alternative system utilizing a burglar alarm of this invention;

FIG. 6 is a cross-sectional view taken on line 6-6 of FIG. 5, in the direction of the arrows;

FIG. 7 is a view similar to that of FIG. 6 but in a displaced position wherein the alarm is triggered;

FIG. 8 is a schematic, perspective view, partially broken away, of a portion of an alternative alarm embodiment of this invention;

FIG. 9 is a schematic, perspective view, partially broken away, of a portion of another alternative alarm embodiment of this invention;

FIG. 10 is a schematic, cross-sectional view of still another alternative alarm embodiment of this invention; and

FIG. 11 is a perspective view of a connector which can be utilized in accordance with an embodiment of the invention.

DETAILED DESCRIPTION As required, detailed illustrative embodiments of the invention are disclosed herein. However, it is to be understood that these embodiments merely exemplify the invention which may take many forms radically different from the specific illustrative embodiments disclosed. Therefore, specific structural and functional details are not to be interpreted as limiting, but merely as a basis for the claims which define the scope of the invention. Somewhat in this regard, the illustrative embodiments herein comprise self-contained alarms operating off batteries. However, it is to be emphasized that the construction herein is readily adaptable to the utilization of line current such as household current. Furthermore, the embodiments disclosed utilize a sound generator as an alarm signal, but the concepts herein are applicable to visual alarms and to remotely signaling alarms.

Referring now to FIGS. 1 and 2, there is illustrated one manner of utilization of an alarm unit 10 in accordance with the present invention. There is illustrated a window 12 secured within its sash 14 which also carries a window screen 16 in its frame 18. A flat, rigid transparent sheet 20 of plexiglass, or the like is carried centrally of the window screen 16 by means of a pair of oppositely disposed springs 22 and 24 clamped to side members 26 and 28 of the screen frame 18 and to opposite side edges 30 and 32 of the plexiglass sheet 20. A bar magnet 34, which can be encased in plastic, is secured centrally of the plexiglass sheet 20, by adhesive or the like, so as to abut the windowpane 12 when the window screen 16 is in its normal position. The alarm unit 10 is carried on the other side of the windowpane 12 so as to effect a magnetic circuit with the bar magnet 34, as will hereinafter be described in more detail.

The alarm unit 10 is completely self-contained in that it includes a source of current and a sound generator and is responsive to a break in the magnetic circuit to generate a loud sound to signal such a break. The magnetic circuit is broken by displacement of the bar magnet 34 which occurs by a movement of the plexiglass sheet 20, such as by attempting to remove or cut the window screen 16. The result is that an attempt to burglarize by entering the window 12 is foiled by the triggering of the alarm unit 10.

Referring now to FIG. 3, the unit-10 is illustrated in more detail. The alarm unit 10 includes a plastic case 36 having two halves 38 and 40 opening on a hinge 42 along its bottom edge and closing by means of matingly engageable clasp halves 44 and 46. The alarm unit includes a three volt horn 48 which is serially connected over the line 50 to a pair of penlight batteries 52 and 54, interconnected by a line 56. The born 48 is connected over the line 58 to an electrically conductive strip 60 and the penlight battery 54 is connected over a line 62 to another electrically conductive strip 64 spaced from the first mentioned strip 60. Referring briefly to FIG. 4a, each electrically conductive strip 60 and 64 is supported via electrical insulation 66, such as rubber or the like, on a bar 68 of paramagneticmaterial. The strips 60 and 64 are formed of nonmagnetic material, such as copper, aluminum, brass, or the like. The bar 68 may be ferromagnetic and made of iron, steel or the like; alternatively, it may be a bar magnet, e. g. constructed of Alnico metal.

The foregoing components are contained in'one-half 38 of the case 36, the other half 40 being empty except for a loosely contained bar magnet 70 which is supported by the lower edge 72 of the case half 40. The bar magnet 70 is of Alnico metal of rectangular shape and of a length sufficient to bridge the spaced conductive strips 60 and 64. With the case halves 38 and 40 closed, the bar magnet 70 would be magnetically drawn to the case half 38 by means of the bar 68 of paramagnetic or magnetic material. In use, however, the unit 10 is disposed with the bar magnet 70 opposite and aligned with the aforementioned bar magnet 34 (FIG. 2) on the opposite side of the windowpane 12. The bar magnet 70 is thus held spaced from the conductive strips 60 and 64, albeit continuously urged toward the strips 60 and 64 as a result of the presence of the paramagnetic or magnet bar 68.

Referring to both FIGS. 2 and 3, the alarm unit 10 is positioned so that the case half 40, containing the bar magnet 70, is facing the windowpane 12 and is secured to the windowpane 12 by means of double sided adhesive strips 74, or the like. Initially, to set the alarm, the unit 10 is positioned with the case halves 38 and 40 opened and the bar magnet 70 manually disposed into magnetic engagement with the bar magnet 34. Thereafter, the case 36 is closed and the alarm is set.

Referring additionally to FIG. 4, the manner of operation of the unit 10 is schematically illustrated. As shown in FIG. 4a, a magnetic circuit is effected between the bar magnets 34 and 70 whereby the bar magnet 70 is secured in an alarm set position spaced from the electrical conducting strips 60 and 64. Referring to FIG. 4b, upon movement outwardly of the outside bar magnet 34, as indicated by the arrow 76, the magnetic circuit is broken and the inside bar magnet 70 is drawn by attraction to the paramagnetic or magnetic bar 68, as indicated by the arrows 78 to abut the electrically conductive strips 60 and 64. The bar magnet 70 thus bridges the strips 60 and 64 to close the alarm circuit, thereby energizing the 3-volt-horn 48. The horn is selected so as to generate a piercing sound, warning the occupants of the building that entrance has been attempted and thwarting the burglary by giving clear inwith the magnetic bar 34. Alternatively, the bar 68 and adjacent material of the inner case half 38 can be formed with aligned openings 80 and 82 through which is thrust a thin rod 84, as indicated by the arrow 86 to push the inner bar magnet 70 against the case half 40 in alignment with the outside bar magnet 34.

It will be appreciated that the outside magnet 34 can be replaced by a bar of paramagnetic material which has sufficient attraction for the internal bar magnet 70 so asto function in the manner'described. Alternatively, the internal bar magnet 70 can be replaced by a'bar of paramagnetic material provided the bar 68 supporting the spaced conductive strips 60 and 64 is constructed of magnetic material. Other changes and modifications can be madeconsistent with the foregoing concepts. It will also be appreciated that when the alarm is not used it is in a quiescent state and does not draw current from the batteries 52 and 54. It is only when an alarm is generated that current is drawn with the result that the alarm unit 10 has a lifetime as long as the storage life of the batteries. Periodic testing is easily accommodated by simply opening the case and momentarily bridging the strips 60 and 64 with the bar magnet 70. In place of the 3-v.olt horn 48, one could utilize any signaling means in that the lines and 58 leading to the horn 48 can instead lead to any signaling device, on the premises or remote.

Referring now to FIGS. 5-7, a modification of the alarm system is illustrated. In this embodiment, the window 86 is not provided with a window screen but is protected by a large sheet 88 of plexiglass or of heavy screen material, as desired. The sheet 88 substantially covers the window 86 and is supported at its upper corners only by means of springs 90 and 92 securing the upper comers to the window frame 94. The sheet 88 thus hangs downwardly in front of the window 86. A bar magnet 96 is pivotally secured by means of a linkage 98 to a coupling volt 100 centrally through the sheet 88. An alarm unit 102, identical to the alarm unit 10 of FIGS. 1-4, is secured to the opposite side of the windowpane 86 so that its internal bar magnet is aligned with the external magnet 96. When the sheet 88 is moved away from the window 86, the bar magnet 98 is caused, by the linkage 96, to drop downwardly, not only breaking the magnetic circuit, but thereby making replacement of the bar magnet 96 a difficult procedure. In the arrangement depicted in FIGS. 1 and 2, it might be possible to turn off the alarm by realigning the external bar magnet 34 and jostling the windowpane 12 to I draw the internal bar magnet 70 back into magnetic endication to the burglar that his presence has been degagement with the external bar magnet 34. In the arrangement illustrated in FIGS. 5-7, such an attempt is made much more difficult and generally would require the use of a long rod or the like to hold the external bar magnet 96 up against the window, making realignment by jostling more unlikely.

Referring now to FIG. 8, there is illustrated an alternative embodiment. The alarm unit 104 is contained within a plastic case 106 which cannot be snapped open as the case 36 depicted in FIG. 3. A pair of electrically conductive strips 108 and 110 are secured, by adhesive, or otherwise, against the rear wall 112 of the case and are connected via lines 114 and 116 to an alarm (not shown) in a manner similar to the arrangement depicted in FIG. 3. In this embodiment, the electrically. conductive strips are constructed of paramagnetic material, such as tin, so as to magnetically attract a bar magnet 118 movably disposed on the front wall 120.

The bar magnet 118 is pivotally secured in the case by means of a hinge 122 which allows the bar magnet 118 to pivot into bridging engagement with the electrically conductive strips 108 and 110. In operation, when an external magnet such as the bar magnet 34 or 96, as previously described, is placed in proximity to the front wall 120 in alignment with the forward position of the bar magnet 118, it secures the bar magnet 118 in an upright position spaced from the conductive strips 108 and 110. Upon breaking of that magnetic circuit by removal of the external bar magnet 34 or 96, the bar magnet 1 18 is then attracted to the electrically conductive strips 108 and 110 and pivots, as shown by the arrow, into bridging engagement with the strips 108 and 110 to thereby close the alarm circuit, signaling the fact that the external bar magnet 34 or 96 has been displaced.

To return the bar magnet 118 to its original position, the external bar magnet 34 or 96 is realigned in its alarm set position and a shaft similar to the shaft 84 depicted in FIG. 4c is inserted within an opening 124 defined through the rear case wall 112 until engagement with the bar magnet 1 18 whereupon the shaft and magnet 118 can be pushed forward until the magnet 118 is in its upright position.

As further modification to the alarm unit 104 of FIG. 8, a spring can be located between the bar magnet 118 and front case wall 120 urging the bar magnet 118 to an alarm position, the force of the spring being insufficient to overcome the magnetic attraction between the bar magnet 118 and the external bar magnet 34 or 96. In this case, the electrically conductive strips 108 and 110 can be made of non-magnetic material, such as copper, etc.

Referring now to FIG. 9, another alternative embodiment is illustrated in which an alarm unit 126 is provided in the form of a closed case 128 of plastic or the like. Spaced electrically conductive strips 130 and 132 are secured to the rear case wall 134 and a bar magnet 136 is loosely disposed within the case 128. The bar magnet 136 is shaped rectangularly and is of such dimension as to be prevented from rotating within the case 128. Thus the case 128 can be jostled and vibrated without significant change in the relative position of the bar magnet 136 within the case 128.

In this embodiment the electrically conductive strips 130 and 132 are of nonmagnetic material such as copper and the like but a plate 138 of magnetic or paramagnetic material is pivotally connected by a hinge 140 to the top wall 142 of the case 128. The plate 138 can thus be positioned adjacent the conductive strips 130 and 132 but insulated therefrom by the rear case wall 134 and attract the internal bar magnet 136 when the external bar magnet 34 or 96 is removed. When this occurs, the electrically conductive strips 130 and 132 are bridged by the bar magnet 136, closing the alarm circuit. In this embodiment, the alarm circuit is disposed exteriorly of the case 128 as indicated by the lines 144 and 146 leading from the conductive strips 130 and 132 via openings such as 148 formed in the bottom case wall 150. The alarm circuit can be similar to the circuit depicted in the unit of FIG. 3, or the lines 144 and 146 can lead to a remote signaling device.

In operation, the magnetic or paramagnetic plate 138 is raised, as indicated by the arrow, and the unit 126 mounted, via adhesive strips 152 to a window to be protected in a manner similar to the arrangement illustrated in FIGS. 1 and 2 or FIGS. 5-7. After alignment and completion of a magnetic circuit with an external bar magnet 34 or 96, the plate 138 is swung into contact with the rear case wall 134 so as to thereby continuously urge the internal bar magnet 136 to a rearward, alarm position, but resisted by the force of the external bar magnet 34 or 96. Upon removal of the external bar magnet 34 or 96, the internal bar magnet 136 is propelled across the case 128 into bridging contact with the conductive strips and 132, closing the alarm circuit. To reset the alarm, the plate 138 is raised and the external bar magnet 34 or 96 is replaced drawing the internal bar magnet 136 back into its alarm set position.

Referring now to FIG. 10, there is illustrated still another alternative embodiment of this invention in which an alarm unit 154 is provided which incorporates a microswitch 156 to close the circuit between a set of batteries 158 and a low voltage horn 160. The unit 154 includes a case 162 having a rear wall 164 formed with an opening to accommodate the horn and defining a compartment 168 for the batteries 158. The microswitch 156 is spring loaded to close the alarm circuit but, when disposed in an alarm set position, has its button 170 depressed against the force of its spring 172 to open the alarm circuit. The microswitch 156 is carried by an aluminum support member 174 which is pivotally secured at its bottom end by a hinge 176 internally of the case 162 so as to pivot toward the rear case wall 164.

The case 162 is open at its front end and is positioned against a windowpane 178. A bar magnet is secured to the forward surface of the support member 174 and the microswitch 156 is so positioned with respect to the magnet 180 that its button 170 is depressed by the windowpane 178 when the magnet 180 abuts the windowpane 178.

In operation, the alarm unit 154 is situated with its open front confronting the windowpane 178 and its internal magnet 180 against the window pane 178 thereby opening the circuit on the microswitch as above described. An external bar magnet 182 is secured to a window screen 184 by means of a bolt 186 and is magnetically aligned with the internal bar magnet 180 so as to define a magnetic circuit therewith and bias the support member 174 to an alarm set position. Upon removal of the external bar magnet 182, the internal bar magnet 180 is pulled rearwardly and downwardly by the force of gravity, releasing the spring loaded microswitch button 170, thereby closing the alarm circuit to sound the horn 170 indicating an intrusion attempt.

Referring now to FIG. 11, there is illustrated an alternative method of securing an external bar magnet 188 to a window screen 190 without requiring bolts or a barrier sheet. The bar magnet 188 is secured at its outer surface 192 to a bracket 194 which is formed with a channel 196 of U-shaped cross section. The bracket channel 196 is designed to fit within the window screen frame channel 198, and, in turn, tightly receive the window screen frame 200. By such means, the barmagnet 188 can be disposed against the window, between the window and screen 190 so that when the screen 190 is removed it carries the magnet 188 out of magnetic engagement with the alarm unit on the other side of the window.

I claim 1. A burglar alarm comprising, in combination:

an alarm signal generator;

a first magnetically attractable member movable between spaced positions of alarm set and alarm and continuously urged to said alarm position;

a second magnetically attractable member disposed in spaced proximity to said alarm set position;

at least one of said first and second members being magnetic, said first and second members cooperating to define a first magnetic circuit at said alarm set position whereby to maintain said first member at said alarm set position, said first and second members being relatively movable whereby to break said first magnetic circuit releasing said first member to move to said alarm position; and

circuit means connected to said signal generator comprising electrical contacts, spaced from one another and fromsaid first member at said alarm set position, defining said circuit as open, said first member effecting electrical contact and bridging of said spaced contacts when said first member is moved to said alarm position thereby closing said circuit.

2. The invention according to claim 1 in which said first and second members are both magnetic.

3. The invention according to claim 1 in which said spaced contacts are nonmagnetic.

4. A burglar alarm comprising, in combination;

an alarm signal generator;

a first magnetically attractable member movable between spaced positions of alarm set and alarm;

a second magnetically attractable member disposed in spaced proximity to said alarm position;

at least one of said first and second members being magnetic, said first and second members cooperating to define a first magnetic circuit at said alarm set position whereby to maintain said first member at said alarm set position;

a third, magnetically attractive, member in proximity to said alarm position, at least one of said first and third members being magnetic, said first and third members cooperating to define a second magnetic circuit at said alarm position and thereby continuously urge said first member to said alarm position whereby upon breaking of said first magnetic circuit said first member is magnetically drawn to said third member; and

circuit means connected to said signal generator and cooperating with said first movable member for energizing said signal generator when said first movable member is at said alarm position;

said first and second members being relatively movable to break said first magnetic circuit whereby said first member is moved by said continuously urging means to said alarm position.

5. A burglar alarm comprising, in combination:

an alarm signal generator;

a first magnetically attractable member movable between spaced positions of alarm set and alarm, said alarm position being spaced below said alarm set position whereby said first member is continuously urged to said alarm position by the force of gravity;

a second magnetically attractable member disposed in spaced proximity to said alarm set position;

at least one of said first and second members being magnetic, said first and second members cooperating to define a first magnetic circuit at said alarm set position to maintain said first member at said alarm set position, said first and second members being relatively movable to break said first magnetic circuit releasing said first member to move to said alarm position; and i circuit means connected to said signal generator and cooperating with said first movable member for energizing said signal generator when said first movable member is at said alarm position.

6. A burglar alarm comprising, in combination:

an alarm signal generator;

a first magnetic member movable between spaced positions of alarm set and alarm and continuously urged to said alarm position;

a second magnetic member cooperating with said first magnetic member to define a magnetic circuit at said alarm set position to maintain said first magnetic member at said alarm set position, said first and second magnetic members being relatively movable to break said first magnetic circuit releasing said first magnetic member to move to said alarm position; and

circuit means connected to said signal generator comprising electrical contacts, spaced from one another and from said first magnetic member at said alarm set position, defining said circuit as open, said first magnetic member contacting and bridging said spaced contacts when moved to said alarm position to close said circuit.

7. The invention according to claim 6 including a third magnetic member spaced further than said electrical contacts from said first magnetic member and disposed to continuously urge said first magnetic member to said alarm position.

8. A burglar alarm comprising, in combination:

an alarm signal generator;

a first magnetic member movable between spaced positions of alarm set and alarm;

a second magnetic member;

said first and second magnetic members cooperating to define a magnetic circuit at said alarm set position to maintain said first member at said alarm set position; and

means for cooperating with said first magnetic member to define a second magnetic circuit at said alarm position and thereby continuously urge said first magnetic member to said alarm position whereby upon breaking of said first magnetic circuit said first magnetic member is magnetically drawn to said means, said means comprising circuit means connectedto said signal generator and cooperating with said first magnetic member for energizing said signal generator when said first member is at said alarm position;

said first and second members being relatively movable to break said first magnetic circuit whereby said first member is moved by said continuously urging means to said alarm position.

9. The invention according to claim 8 in which said 10. The invention according to claim 8 in which said means additionally comprises a third magnetic member in proximity to said alarm position.

11. A burglar alarm comprising, in combination:

an alarm signal generator;

a first magnetic member movable between spaced positions of alarm set and alarm, said alarm position being spaced below said alarm set position whereby said first member is continuously urged to said alarm position by the force of gravity;

a second magnetic member cooperating with said first magnetic member to define a first magnetic circuit at saidalarm set position to maintain said first magnetic member at said alarm set position, said first and second members being relatively movable to break said first magnetic circuit and release said first member to move to said alarm position; and

circuit means connected to said signal generator and cooperating with said first magnetic member for energizing said signal generator when said first magnetic member is at said alarm position.

12. A burglar alarm, comprising:

an alarm signal generator;

a housing having spaced front and rear walls;

a first magnetically attractable member between said front and rear housing walls, spaced from one thereof and movable between spaced positions of alarm adjacent said one wall and alarm set adjacent the wall opposite said one wall;

a second magnetically attractable member disposed externally of said housing front wall, at least one of said first and second members being magnetic, said first and second members cooperating to define a first magnetic circuit at said alarm set position whereby to maintain said first member at said alarm set position;

magnetically attractive means in said housing adjacent said opposite wall for cooperating with said first magnetic member to define a second magnetic circuit at said alarm position and thereby continuously urge said first magnetic member to said alarm position whereby upon breaking of said first magnetic circuit said first member is magnetically drawn to said means, said means comprising circuit means connected to said signal generator and cooperating with said first member for energizing said signal generator when said first member is at said alarm position;

said first and second members are both magnetic.

. The invention according to claim 2 in which said alarm position is adjacent said rear wall.

15. A burglar alarm system, comprising:

a glass window;

a window cover movably disposed adjacent one side of said glass window and covering substantially all of the area of said glass window on said one side;

a first magnetically attractable member on a side of said glass window opposite said first side and occupying a first minor portion only of the region of said glass window on said opposite window side;

a second magnetically attractable member on said window cover adjacent said first window side and occupying a second minor portion only of the region of said window cover, said first and second minor portions at least overlapping;

at least one of said first and second members being magnetic, said first and second members cooperating to define a magnetic circuit;

alarm means on said opposite window side responsive to a break in said magnetic circuit whereby to generate an alarm signal; and

means for connecting said second member to said window cover for movement therewith whereby movement of said window cover effects a break in said magnetic circuit.

16. The invention according to claim 15 wherein said window cover comprises a window screen having screen material defining said second minor portion.

17. A burglar alarm system, comprising:

a glass window;

a flat transparent member movably disposed adjacent one side of said window;

a first magnetically attractable member on a side of said window opposite said first side and occupying a first minor portion only of the region of said glass window on said opposite window side;

a second magnetically attractable member on said first window side and occupying a second minor portion only of the region of said second window side, said first and second minor portions at least overlapping;

at least one of said first and second members being magnetic, said first and second members cooperating to define a magnetic circuit;

alarm means on said opposite window side responsive to a break in said magnetic circuit whereby to generate an alarm signal; and

means for connecting said second member to said transparent member for movement therewith whereby movement of said transparent member effects a break in said magnetic circuit.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US700812 *Jun 1, 1901May 27, 1902Guy M PeytonElectric alarm.
US2877361 *Apr 12, 1957Mar 10, 1959Holmes Electric Protective ComBurglar alarm system
US3281735 *Apr 14, 1965Oct 25, 1966Thomas BlumishMagnetic switch having swingably supported permanent magnet actuating means
US3513273 *Sep 19, 1968May 19, 1970Qualheim Harold JMagnetically-controlled safety switch for food slicers
US3539741 *Aug 8, 1969Nov 10, 1970Mallory & Co Inc P RMagnetically activated door switch
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3899784 *May 17, 1973Aug 12, 1975Omni Spectra IncGlass breakage detector
US3973095 *Jun 16, 1975Aug 3, 1976Greene Ted RIntrusion detector sensitive to resonant frequency of breaking glass
US4160972 *May 18, 1978Jul 10, 1979Adco Venetian Blind CompanyAlarm apparatus for movable barrier members
US4222032 *Oct 3, 1977Sep 9, 1980Speer Gary DVehicle cover alarm
US4292629 *Dec 10, 1979Sep 29, 1981Teledyne Industries, Inc.Alarm system
US4347502 *May 27, 1980Aug 31, 1982Johnson Pet-Dor, Inc.Early warning electrical sound alarm system for pet door structure
US4686792 *Mar 3, 1986Aug 18, 1987Terrian Barbara CCombination storm window and security system
US4814750 *Nov 20, 1987Mar 21, 1989Pace Window & Door Corp.Window screen alarm
US4971130 *Dec 20, 1989Nov 20, 1990Bentley Richard PWeather seal covering assembly for a window
US6226165Apr 14, 1999May 1, 2001Dell Usa, L.P.System and method for securing a computer system
US7265672Oct 7, 2004Sep 4, 2007Lou GuaragnaMagnetic sensor for a double-hung window
Classifications
U.S. Classification340/547, 49/13, 200/61.84
International ClassificationG08B13/02, G08B13/08
Cooperative ClassificationG08B13/08
European ClassificationG08B13/08