US3887909A

US3887909A - Alarm device

Info

Publication number: US3887909A
Application number: US248050A
Authority: US
Inventors: John L Beiswenger; Leland Devon Jorgensen
Original assignee: National Presto Industries Inc
Current assignee: National Presto Industries Inc
Priority date: 1972-04-27
Filing date: 1972-04-27
Publication date: 1975-06-03
Anticipated expiration: 1992-06-03
Also published as: AU4948872A; GB1385927A; JPS4923599A; AU468636B2

Abstract

An alarm device having an extendible cord control element the outer end of which is attached to an object, such as a window or door, to place the cord in predetermined tension with the cord acting directly on a switch arm to effect an alarm signal upon a change in tension of the cord resulting from breaking or pulling thereof.

Description

United States Patent 1191 Beiswenger et al. 1 June 3, 1975 54] ALARM DEVICE 2,780,689 2/1957 La Cavera 340/276 x [75] inventors: John L. Beiswenger, Pacific 52:2? gig 2 i Palisades; Leland Jorgensen, 317131132 1/1973 Tonkow i c h lill...........::::l: 340/274 x v Chippewa Falls, both of Wis. [73] Assignee: National Presto Industries, Inc., Eau FOREIGN PATENTS B APPLICATIONS Claire, Wis 1,068,127 5/1967 United Kingdom 200/153 H [22] Filed: 1972 Primary Examiner.l0hn W. Caldwell [21] App], No; 248,050 Assistant Examiner-Scott F. Partridge Attorney, Agent, or Firm.lohnson, Dienner, Emrich & Wagner [52] US. Cl. 340/274; ZOO/61.62; 340/276 [51] Int. Cl G08b 13/00; G08b 13/08 [58] Field of Search 340/274, 276, 283, 273, [57] ABSTRACT 340/420 232; 200/6139 An alarm device having an extendible cord control element the outer end of which is attached to an object, [56] References cued such as a window or door, to place the cord in prede- UNITED STATE PATENTS termined tension with the cord acting directly on a 763,386 6/1904 Fitch 340/276 switch arm to effect an alarm signal upon a change in 793,775 7/1905 Esser 340/276 tension of the cord resulting from breaking or pulling 1,238,532 8/1917 Lemberg 340/283 UX thereof 1,452,500 4/1923 Galerman 340/274 2,767,268 10/1956 Levine ZOO/61.39 11 Claims, 5 Drawing Figures v /6 l8 =5555555e ji ,4, 1 55555555 I188 uazssssss n n u u u n u n u 1' [l2 7,0

M L 2% l2 1* M ALARM DEVICE BACKGROUND OF THE INVENTION The present invention relates generally to alarm devices, and more particularly to a burglar alarm device having novel switch means operative in response to the change in tension of a control element to effect an alarm signal.

Burglar alarm devices are known which employ trip wire means attachable to a window or the like such that unauthorized opening or entry will effect an alarm signal. For example, U.S. Pat. Nos. 118,199 to Cock and Guest, 1,238,532 to Lemberg, and 1,937,134 to Stout disclose burglar alarm mechanisms utilizing trip cord or chain means which are connected to an object such that a change in tension of the cord as through movement of the object effects an alarm signal. The present invention provides an improved alarm device of this general type which includes novel structural and functional advantages over the prior art devices.

SUMMARY OF THE INVENTION In accordance with a preferred embodiment of the present invention, an alarm device is provided having housing means which encloses electrically operative alarm signal means and a source of electrical energy to selectively energize the signal means. The energy source is connected to the alarm signal means through a circuit which includes a control switch having a contact arm movable to contact either of a pair of spaced fixed contacts. The contact arm is supported for pivotal movement about the rotational axis of a reel which has a length of cord wrapped therearound. The cord directly engages the contact arm and has magnetic attachment means on its outer end allowing it to be led from the reel and attached to an object such as a window or door or the like. The reel is manually adjustable from outside the housing to place the cord under a predetermined tension and position the contact arm intermediate the fixed contacts. When the cord is pulled or broken by unauthorized movement thereof, the contact arm is caused to contact one of the fixed contacts and energize the alarm signal means. A key may be removably inserted into the housing to open the circuit to the alarm signal means during adjustment of the reel and contact arm. Thermostat means are preferably connected in circuit with the alarm signal means to establish an alarm when the ambient temperature surrounding the housing reaches a danger level such as in the case of fire.

Accordingly, one of the primary objects of the present invention is to provide an alarm device having novel means for establishing an alarm signal upon unauthorized movement of a control element of the device.

Another object of the present invention is to provide an alarm device which employs a novel contact switch arrangement responsive to unauthorized movement of a control cord having an outer end secured to an object such as a window or door or the like.

Another object of the present invention is to provide an alarm device as described wherein the control cord is supported on a rotatable reel and acts directly on a contact arm movable in response to a change in tension in the cord to contact one of a pair of fixed switch contacts and thereby energize alarm signal means.

A further object of the present invention is to provide an alarm device which is relatively inexpensive to manufacture and highly efficient in operation.

A feature of the present invention is a provision of a circuit disabling key which may be removably inserted into the housing to disable the circuit during adjustment of the control cord and movable contact arm.

Further objects and advantages of the present invention, together with the organization and manner of operation thereof, will become apparent from the following detailed description'of a preferred embodiment of the invention when taken in conjunction with the accompanying drawings wherein like reference numerals designate like elements throughout the several views.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of an alarm device in accordance with the present invention illustrated as being operatively connected to a window to detect unauthorized movement thereof;

FIG. 2 is an enlarged front view of the alarm device of FIG. 1, the cover of the housing being removed to show the internal elements;

FIG. 3 is a longitudinal sectional view taken generally along the line 33 of FIG. 2 but showing the cover of the housing in assembled position;

FIG. 4 is a transverse sectional view taken generally along the line 44 of FIG. 3: and

FIG. 5 is a schematic circuit diagram of the control circuit utilized in the alarm device of FIGS. 1-4.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the drawings, and in particular to FIG. 1, an alarm device in accordance with the present invention is indicated generally at 10 and is shown in conjunction with a conventional double-hung window, indicated generally at 12. For purposes of illustration, the alarm device 10 is shown in FIG. 1 in substantially greater size relative to the window 12 than the size of the actual production unit which is approximately three by five inches, considered in front elevation as in FIGS. 1 and 2. As will become more apparent hereinbelow. the use of the alarm device 10 in conjunction with the window assembly 12 exemplifies but one possible use of the alarm device. In general, the alarm device 10 may be employed to generate an alarm system responsive to the unauthorized movement of an object to which a control element is attached, or signal the movement of the control element when positioned in a passageway or the like so as to be obstructed by movement of a person in the passageway.

The alarm device 10 includes a rectangularly shaped housing indicated generally at 14, having a removable cover plate 16. Noting FIG. 3, the cover plate 16 is retained on the top of the rectangularly shaped housing 14 by a retaining screw 18 the lower end of which is threadedly secured in an upstanding boss 20 formed integral with or otherwise suitably secured to the lower wall 22 of the housing 14. The housing 14 is preferably made of a lightweight material such'as a suitable thermoplastic material. The cover plate 16 of the alarm device 10 has a plurality of openings 24 therethrough to facilitate the transmission of an audible alarm signal from the alarm device as will be described more fully hereinbelow.

With reference to FIG. 2, taken in conjunction with FIGS. 3 and 4, the alarm device 10 includes alarm gen erating means, indicated generally at 26, which, in the illustrated embodiment, comprises a Klaxon steady signal electrically operated audible alarm 28 of known design. The alarm 28 has a mounting bracket 30 secured to the lower surface thereof (FIG. 3) which is suitably secured to and supported by an upstanding boss 32 formed integral with the bottom 22 of the housing 14. A conductor strip 34 has one end thereof interposed between the mounting bracket 30 and the boss 32 and extends along the bottom 22 of the housing to an upturned end portion 36 which forms a contact for a conventional C size alkaline DC battery cell, indicated in phantom at 38. The mounting bracket 30 of the alarm 28 serves as the negative or ground terminal for the alarm control circuit to be described more fully below. While the alarm generating means 26 is described and illustrated herein as being an audible tone generating means, it will be understood that the alarm means may comprise a visual signal device such as a light, or may comprise means providing an output signal for a remote indicating means.

The battery 38 is connected in circuit with a second DC battery, indicated at phantom at 40, identical to the battery 38 to provide a source of electrical energy for the alarm generating means 26. To this end, the positive terminal 42 of the battery 38 contacts an upstanding conductor strip 44 which is of a configuration to cooperate with the upstanding end 36 of the conductor strip 34 to resiliently receive the battery 38 therebetween. Suitable battery support plates 46 are formed integral with the housing 14 and serve to cradle the batteries 38 and in operating position within the housing. The conductor strip 44 has an integral conductive arm portion 48 adjacent the bottom 22 of the housing 14 which normally resiliently contacts a second conducting arm 50 formed integral with an upstanding conductive strip 52 which provides the ground contact for the battery 40. The conductive strips or

contacts

44 and 52 are secured to the lower or bottom plate 22 of the housing means 14 through suitable means such as

rivets

54 and 56, respectively.

The housing 14 is preferably provided with a suitable opening 58 which receives an elongated end portion 60 of a circuit disabling key 62 made of a non-conducting material such as plastic. The elongated end 60 of the disabling key 62 may be selectively inserted through the opening 58 in the housing 14 and caused to separate the normally contacting

conductive arms

48 and 50 and thereby open the series circuit between the

batteries

38 and 40 to open the circuit to the alarm generating means 26.

The positive terminal 64 of the battery 40 contacts a conductive strip 66 which is secured to a nonconducting support plate 68. The support plate 58 is of planar rectangular configuration and is slidably received between and supported by inwardly directed projections 70 formed integral with the housing 14 and having slots along their lengths to receive the opposite edge portions of the support plate 68 as shown in FIG. 2 such that the support plate may be removed from the housing 14.

The support plate 68 supports switch means, indicated generally at 72, which is connected in circuit between the source of electrical energy comprising the

batteries

38 and 40 and the alarm generating means 26 to effect selective energizing of the alarm generating means. The switch means 72 includes a pair of

fixed contacts

74 and 76 which comprise conductor strips formed integral with the conductive strip 66, the

fixed contacts

74 and 76 being formed to extend downwardly from the top edge of the support plate 68 and upwardly from the bottom edge thereof, respectively, as illustrated in FIGS. 3 and 4. The switch means 72 further includes a movable contact arm 78 which has a suitable opening mid-length thereof to allow the contact arm to be pivotally mounted on a support pin 80 secured in normal relation to the support plate 68 generally centrally thereto. The support pin 80 has a threaded end portion 82 which is received through a suitable opening in the support plate 68 and has a nut 84 secured thereon to retain the support pin 80 in fixed relation on the support plate 68. A compression spring 86 is disposed about the support pin 80 between a reel 88 to be described more fully hereinbelow, and the movable contact arm 78 which engages an enlarged head portion 90 of the support pin 80. The opposite ends of the contact arm 78 are formed to establish

leg portions

92 and 94 which lie in planes perpendicular to the plane of the main arm portion 78.

Noting FIG. 4, a tension spring 96 has its opposite ends connected, respectively, to the inwardly turned leg portion 92 of the movable contact arm 78 and to a projection 98 formed integral with and projecting outwardly from the support plate 68 adjacent the upper edge thereof. The tension spring 96 is adapted to urge the movable contact arm 78 in a counter-clockwise rotational direction, as considered in FIG. 4, to effect engagement of the end leg portion 94 with the fixed contact 76. As will be described below, the contact arm 78 is also rotatable in a clockwise direction to effect engagement of the leg portion 94 with the other fixed contact 74.

The support pin 80 is made of a metallic conducting material so as to be conductively connected to the movable contact arm 78, which in turn is made of a conductive metallic material. The support pin 80 is conductively connected to a conductor 100 adjacent the threaded end 82 and nut 84, the conductor 100 having its opposite end connected to a metallic terminal 102 through a screw 104 received through a suitable opening in the bottom 22 of the housing 14 and having a nut 106 secured on the lower end thereof to retain the terminal 102 against a raised boss formed on the bottom 22 of the housing. A conductor 108 connects the conductor 100 to a terminal 109 of the alarm 28 to complete a circuit from the alarm generating means 26 through the

batteries

38 and 40 and back to the alarm 28 through the conductor 108 when the movable contact arm 78 is contacting either of the

fixed contacts

74 or 76.

The alarm device 10 includes switch operating means for cooperation with the movable contact arm 78 to selectively effect movement of the switch arm to engage the fixed contact 74 or allow movement of the switch arm to engage the fixed contact 76 under the influence of the biasing spring 96. Such switch operating means includes a control element 110 comprising a trip wire or cord, preferably made of a monofilament nylon line, which acts directly on the movable contact arm 78 and is adapted to be secured to an object under a predetermined tension to position the contact arm intermediate the fixed

contacts

74 and 76. To this end, the control element 110 is wound upon the aforenoted reel 88 which is made of a nonconductive thermoplastic material and is supported on the support pin 80 for rotational movement thereon-The reel 88 is urged toward the support plate 68 by the compression spring 86. The reel 88 has a peripheral surfaceportion-which extends through a suitable rectangular opening 112 in the cover 16 of the housing 14 such that the reel 88 may be rotated on the support shaft 80 by one s thumb from outside the housing 14. The reel 88 is adapted to hold approximately 30 feet of the control element line 110 and allows the control element line to be played outwardly from the reel whereupon the control element line is passed through an opening 114 in the leg portion 94 of the movable contact arm 78 and through an opening 116 formed in the sidewall of the housing 14. The opening 114 in the movable contact arm 78 and the opening 1 16 in the housing have smooth peripheral surfaces to allow free sliding movement of the control element line 110. Theouter end of the control element 110 has a magnet 118 secured thereto for magnetically attaching the endof the control element to a metallic plate 120 affixed to an L-shaped bracket 122 to the vertical leg portion of which has a pressureadhesive surface 124 providing means to secure the bracket 122 to an object such as the horizontal window frame member 126 of the window assembly 12 shown in FIG. 1. It will be understood that the outer end of the control element 110 may be secured to the window frame member 126 or other object through any suitable means alternative to the magnet 118 and bracket 122.

As noted, the control element 110 may be played-out from the reel 88 to allow the magnet 118 to be secured to the bracket 122 which is attached to an object removed from the alarm device 10. To prevent free rotation of the reel, a flange portion 128 thereof has one or more V-shaped projections or teeth 130 projecting outwardly therefrom toward the opposing surface of the support plate 68. The teeth 130 cooperate with a plurality of circularly disposed V-shaped teeth 132 formed integral with the support plate 68 and lying on a circle having a radius equal to the radial distance of the teeth 130 from the axis of the flange 128 of the reel. In this manner, the compression spring 86 urges the reel 88 in a direction to position the teeth 130 intermediate the spaced teeth 132thereby providing resistance to rotasupported within a suitablev opening in an end wall 136 of the housing 14. The thermostat means 134 has a pair of terminals .138 and 140. The terminal 130 is connected through conductors-142 and 144 to the conductive strip 66 so as to be in circuit with the

batteries

38 and 40. The terminal 140 of the thermostat means 134 is connected through a conductor 146 to a positive terminal 148 on the bottom of the alarm 28. The thermostat means 138 is of known design and is responsive to a predetermined termperature rise to close the circuit between the

batteries

38 and 40 and the alarm 28 to energize the alarm and effect an alarm signal when the temperature surrounding the ala rm device reaches a danger condition such as would result from a fire.

, FIG. 5 schematically illustrates the circuit for selectively electrically connecting the alarm 28 of the alarm generating means 26 to the energy source comprising the

batteries

38 and 40, and shows that with the disabling key 62 removed to effect connection between the

conductive arms

48 and 50, the alarm 28 may be energized through closing of the normally open thermostat switch means 134 or through engagement of the movable contact arm 78 with either of the fixed

contacts

74 and 76.

Having thus described a preferred embodiment of the present invention, its operation will now be briefly described. With the elements of the alarm device 10 assembled as hereinabove described, the housing 14 may be secured to a wall or window frame adjacent a window, door or passageway in which unauthorized movement it to be detected. In the application of the alarm device as illustrated in FIG. 1, the bracket 122 would then be secured to the horizontal window frame member 126 and the control element withdrawn or played-out from the reel to allow the magnet 110 to be magnetically attached to the metallic plate of the bracket 122. When mounting the alarm device 10 in an operating position, the disabling key 62 is inserted through the opening 58 to separate the

contact arms

48 and 50 and thereby open the circuit to the alarm 28 through the

batteries

38 and 40. After connecting the magnet 118 to the bracket 122, the reel 88 is moved by the operators thumb in a rotational direction to tighten the control element line 110 until the end leg 94 of the movable contact arm 78 is positioned intermediate the fixed

contacts

74 and 76 as illustrated in FIG. 4. After roughly tensioning the control element 110, the disabling key 62 is removed and the reel 88 further rotated, if necessary, to assure placement of the contact arm 76 intermediate the fixed

contacts

74 and 76. The compression spring 86 serves to maintain friction engagement of the teeth on the reel flange 128 between the opposing teeth 132 on the support plate 68 such that the reel will remain in its set position with the control element 110 being under a corresponding predetermined tension to establish the intermediate position of the contact arm 78.

With the alarm device 10 so installed, if the lower window of the window assembly 1 12 should be opened upwardly in an unauthorized manner, the tension in the control element 110 will be reduced to allow the biasing spring 96 to move the contact arm 78 into engagement with the fixed contact 76 and thereby energize the alarm 28 giving an alarm signal. Alternatively, if the control element 110 and its associated magnet 118 are secured to the lower window when in a desired raised position, unauthorized lowering of the window will increase the tension on the control element 110 and cause the movable contact arm 76 to engage the fixed contact 74 and close the circuit to the alarm 28 to establish an output alarm signal. Similarly, if the alarm device 10 is placed adjacent a floor area close to a passage through which people pass, the control element 110 may be placed across the passage area and secured in a predetermined tension to place the contact arm 78 intermediate the

contacts

74 and 76. Thereafter, should anyone effect an unauthorized passage through the passageway and contact the control element 110, it would either place the control element in greater tension to effect movement of the contact arm 78 with the contact 74 to establish an alarm signal, or would pull the magnet 118 from the associated bracket 122' to slacken the control element sufficiently to allow move ment of the contact arm 78 into engagement with the contact 76 to again close the circuit to the alarm 28 and establish an alarm signal. Similarly, if the control element 110 is cut, broken, or burned after having been installed in the aforedescribed manner, an alarm will be established.

While a preferred embodiment of the present invention has been illustrated and described, it will be understood that changes and modifications may be made therein without departing from the invention in its broader aspects.

We claim:

1. An alarm device for use in detecting movement of an object, comprising, in combination, housing means, electrically operated alarm generating means supported by said housing means, a source of electrical energy supported by said housing means, circuit means selectively electrically connecting said alarm generating means to said source of electrical energy, said circuit means including switch means having a pair of spaced fixed contacts and a movable contact arm therebetween and biasing means urging the movable contact arm to one and away from the other of said fixed contacts, said movable contact arm and fixed contacts being connected in said circuit such that said circuit means is closed when said contact arm is contacting either of said fixed contacts and open when said contact arm is disposed intermediate said fixed contacts, a rotatable reel member, means including a length of cord wound about said rotatable reel memher, and releasable clutch means for resisting rotation of said reel member, said cord means acting directly on said movable contact arm and having its free end adapted to be secured to the object, said clutch means being releasable to permit unwinding of said cord means from said reel member to facilitate attachment of said cord means to the object and to take up slack in said cord means to place said cord means under tension of an amount sufficient to resist the force of the biasing means and hold said contact arm intermediate and out of engagement with said fixed contacts, whereby when said cord means is pulled, broken or otherwise disturbed said contact arm will be caused to contact one of said fixed contacts and to energize said alarm generating means.

2. An alarm device as defined in claim 1 wherein said movable contact arm has an opening therein, and wherein said cord means passes through said opening and acts upon said contact arm to effect movement thereof when the tension in said cord is varied from said tension placed thereon.

3. An alarm device as defined in claim 1 wherein said reel member is mounted within said housing and includes a flange portion extending outwardly of said housing to allow said reel member to be rotated through movement of said flange portion externally of said housing.

4. An alarm device as defined in claim 1 wherein said source of electrical energy comprises a pair of DC batteries normally connected in series, said circuit means having a pair of separable contacts normally connecting said batteries in series, and including means adapted to be inserted between said last mentioned contacts to separate the same and open said series connection between said batteries.

5. An alarm device as defined in claim 1 wherein said reel member is mounted within said housing for rotation about its longitudinal axis, and wherein said movable contact arm of said switch means is mounted for pivotal movement about the axis of rotation of said reel.

- 6. An alarm device comprising, in combination, housing means, electrically operated alarm generating means supported by said housing means, a source of electrical energy supported by said housing means, circuit means selectively electrically connecting said alarm generating means to said electrical energy source, said circuit means including switch means comprising a pair of fixed contacts and a movable contact arm swingable therebetween, and biasing means urging the movable contact arm to one of said fixed contacts and away from the other, a rotatable reel having a length of cord wound thereabout and spring-biased, releasable clutch means for resisting rotation of said reel, said cord passing through a provided opening in one end of said contact arm and having its free end adapted for attachment to an object, said clutch means being releasable to permit unwinding of the cord therefrom to facilitate attachment of said cord to such object and to take up slack in the cord sufficiently to place the cord under tension and hold the contact arm out of engagement with the fixed contacts and against the force of the, biasing means whereby when the cord is pulled, broken or otherwise disturbed the contact arm will be caused to contact one of the fixed contacts and to energize the alarm generating means.

7. An alarm device as defined in claim 6 wherein said free end of the cord has a magnet attached thereto.

8. An alarm device as defined in claim 6 wherein the circuit means includes a pair of separable contacts aligned with an opening in the housing through which a removable electrical insulating member is insertable to separate the contacts and open the circuits to disable the alarm device.

9. An alarm device as defined in claim 6 wherein the reel and movable contact arm are mounted to independently turn on a common axis located to one side of and spaced from the opening in the contact arm through which the cord passes, said housing having a further opening therein spaced from and to the opposite side of said opening in the contact arm through which the cord is also threaded, said opening being so related that the reel may be rotated on its axis to take up slack in the cord and thereby to center the contact arm spaced between the fixed contacts.

10. An alarm device as defined in claim 6 including thermostat means supported by said housing means and connected in circuit with said circuit means, said thermostat means being adapted to effect energizing of said alarm generating means when a predetermined temperature surrounding said thermostat means is reached.

11. An alarm device as defined in claim 10 wherein said thermostat means is connected in parallel with the portion of said circuit having said switch means therein so that said alarm generating means may be energized by said thermostat means while said swith means is open.

Claims

1. An alarm device for use in detecting movement of an object, comprising, in combination, housing means, electrically operated alarm generating means supported by said housing means, a source of electrical energy supported by said housing means, circuit means selectively electrically connecting said alarm generating means to said source of electrical energy, said circuit means including switch means having a pair of spaced fixed contacts and a movable contact arm therebetween and biasing means urging the movable contact arm to one and away from the other of said fixed contacts, said movable contact arm and fixed contacts being connected in said circuit such that said circuit means is closed when said contact arm is contacting either of said fixed contacts and open when said contact arm is disposed intermediate said fixed contacts, a rotatable reel member, means including a length of cord wound about said rotatable reel member, and releasable clutch means for resisting rotation of said reel member, said cord means acting directly on said movable contact arm and having its free end adapted to be secured to the object, said clutch means being releasable to permit unwinding of said cord means from said reel member to facilitate attachment of said cord means to the object and to take up slack in said cord means to place said cord means under tension of an amount sufficient to resist the force of the biasing means and hold said contact arm intermediate and out of engagement with said fixed contacts, whereby when said cord means is pulled, broken or otherwise disturbed said contact arm will be caused to contact one of said fixed contacts and to energize said alarm gEnerating means.

6. An alarm device comprising, in combination, housing means, electrically operated alarm generating means supported by said housing means, a source of electrical energy supported by said housing means, circuit means selectively electrically connecting said alarm generating means to said electrical energy source, said circuit means including switch means comprising a pair of fixed contacts and a movable contact arm swingable therebetween, and biasing means urging the movable contact arm to one of said fixed contacts and away from the other, a rotatable reel having a length of cord wound thereabout and spring-biased, releasable clutch means for resisting rotation of said reel, said cord passing through a provided opening in one end of said contact arm and having its free end adapted for attachment to an object, said clutch means being releasable to permit unwinding of the cord therefrom to facilitate attachment of said cord to such object and to take up slack in the cord sufficiently to place the cord under tension and hold the contact arm out of engagement with the fixed contacts and against the force of the biasing means whereby when the cord is pulled, broken or otherwise disturbed the contact arm will be caused to contact one of the fixed contacts and to energize the alarm generating means.