US2170521A

US2170521A - Alarm lock

Info

Publication number: US2170521A
Application number: US62610A
Authority: US
Inventors: Joseph R Rodth
Original assignee: Individual
Current assignee: Individual
Priority date: 1936-02-06
Filing date: 1936-02-06
Publication date: 1939-08-22
Anticipated expiration: 1956-08-22

Description

Aug. 22, 1939. J. R. RODTH 2,170,521

. ALARM LOCK Original Filed Feb. 6 193s 4'Sheets-Sheet 1 lNvlEeitlfgR BY Qfr 153a ATTORNEY} Aug zz, 1939. J. R RODTH 1 2,170,521

'1 ALARM LOCK Original Fiieie Feb. e, 1936 4 Sheets-Sheet 2 I lNVE/Eljl'gR ATTORNEY;

Aug. 22, 1939. J R RQDTH 2,170,521

ALARM LOCK Original Filed Feb. 6, 1936 4 Sheets-Sheet 5 1 l ATTQRNEY E Patented Aug. 22, 1939 UNITED STATES PATENT OFFiCE Application February 6, 1936, Serial No. 62,610 Renewed January 19, 1939 9 Claims.

The present invention relates to looks and more particularly to alarm looks, that is locks so constructed that they cause an alarm to sound when subjected to unauthorized tampering.

It is a general object of the invention to provide a novel lock of this kind that is particularly suitable for doors to apartments although it will be evident that the use of the invention is not so limited since it can be used under various conditions and for various purposes.

One object of the invention is to provide an alarm lock that makes unauthorized access to homes and the like by any of the methods involving relatively little demolition difficult or impossible without setting off the alarm.

Another object of the invention is to provide such a lock in which both the locking and the alarm mechanisms are protected against unauthorized access and in addition to provide such a lock which, in addition to affording such protection, is of such construction that it can be readily installed by relatively unskilled persons.

A further object of the invention is to provide such a lock which can be so installed without altering the door or other adjacent construction.

Additional objects of the invention, including the special provision against certain of the more common methods of unauthorized entry, will ap- SQ pear from the following detailed description.

', appended claims.

In the accompanying drawings there is illustrated a. preferred embodiment of the invention, certain details of which may be varied without departing from the invention as defined by the In these drawings:

Figure l is a front elevation showing a lock comprising the invention attached to a door;

Figure 2 is a transverse, substantially central vertical sectional view through the lock of Figure 1, taken on line 22 thereof;

Figure 3 is a horizontal sectional view through the lock of Figure 1, taken on line 3-3 of Figure 5;

Figure 4 is a wiring diagram showing also cer tain of the mechanical parts associated in the several circuits;

Figure 5 is a longitudinal vertical sectional view through the lock of Figure 1 and taken on the line 5--- Figure 3;

Figure 6 is an enlarged detail front view of one of switches, the view being taken on line 6--6 of Figure 5;

Fi ure 7 is an enlarged detail bottom view of another switch, this view being taken on line "5-1 of Figure 8;

Figure 8 is a. longitudinal sectional view through the same switch taken on line 8-8 of Figure 7;

Figure 9 is a transverse sectional view through the same switch taken on line 9-9 of Figure '7;

Figure 10 is an enlarged detail horizontal sectional view through a portion of the lock housing taken on line Iii-ii) of Figure 5 and showing the lock bolt operation control cam;

Figure 11 is a longitudinal sectional view through the lock housing taken on line H-l i of Figure 3;

Figure 12 is a vertical sectional view taken on the line l2l2 of Figure 2, and

Figure 13 is an enlarged horizontal sectional view through one of the switches and taken on line I3I3 of Figure 11.

Referring in detail to the drawings, a box-like shell or housing H is provided, is open on one side, this opening being by the door surface when the lock is in place, and in its other side has an opening in which there is fitted a lock door l2 and a series of slotted openings I 3, behind which a shield plate l0 prevents access through the openings E3 to the alarm and its associated mechanism. Into this shell there is fitted a locking knob it which operates the bolt 45, as hereinafter described, independently of the key operation of the lock cylinder, and opposite and independent of the knob is a lock cylinder 38. The bolt I5 has pivoted to it an arm l5, which has an end having a. circular opening fitting over the pin it on knob arm 20, and having a forked portion opposite the pin 19, for engagement with the pin 3? on cam arm 35 of the lock cylinder. The knob pin [9 moves through clockwise as viewed in Figure 5, and returns counterclockwise to the position of Figure 5. Lock cylinder pin 3? moves through 360", and during half its movement moves the bolt I 5 by engaging in the forked end of arm IS.

The shell or housing II is attached to the door 23 by means of four wood screws 2d. The invention includes means hereinafter described for setting the alarm in action if these screws are tampered with when the bolt is in locked position. There is also provided keeper 2%, to be attached to the jamb 21. The lock can be operated from the outside by means of a standard lock cylinder 30 which is attached to the door and is free of the lock itself. A fiat connecting rod 34 attached to and rotatable with the lock cylinder 30 passes through the slotted opening provided for it in the cam disk 36, carmetal which closed Lil rying the arm 35 and eccentrically fixed pin 51, which, when the cylinder 3! is turned, engages the bolt arm i6 and causes the bolt I5 to move back and forth as desired. This locking mechanism is per se not new, and for the purposes of the invention need not be of the specific design shown in the drawings; the invention includes the various devices which comprise the alarm system in combination with the essential elements of such a locking mechanism.

The invention in its entirety thus includes an alarm and means for causing the alarm tobe set off when the door is pried, or the lock is pried, cut or otherwise tampered with. The actual alarm may be an electric bell, and in structures carrying out the invention to what is now considered the best advantage, the lock itself forms part of the alarm or bell circuit. In the embodiment here shown as an example, carried inside the housing H is an electric bell id, in itself of ordinary construction, which is attached to the back plate ii which is fixed to the lock housing by a screw 62 threaded into the guide post 58, and positioned by abutments 38 formed in the housing. The bell is completely insulated from the lock, the current source derived from dry cell batteries id attached to the same plate and located within. the lock housing, where, without the key hereinafter referred to, they cannot be reached without setting off the alarm. As shown in Figure 4, from one terminal of the batteries i -l conductor 5% leads to conductor 5 l, which leads to the terminal 45 of one end of the magnet coil 52 of bell 40. From the other terminal of the batteries M conductor 53 leads to conductor I65, which, extending to the left as viewed in Figure 4, is attached at 53 to the housing II with which look bolt i5 is at all times in contact. To the right of conductor 53, conductor E55 leads to fixed terminal I64.

The electrical energy is thus transmitted to the bolt l5 and through the bolt to the conductor spring 51 carried by the bolt and which when in normal or bolt unlocked position bears against one end of a notch 59 in a contact plate 60, secured to the bolt l5 by two screws 63 which pass through insulating collars 65 and hold the plate to the bolt by means of the insulating washers 61 (Fig. 3). The insulating member 69 serves to keep the plate Ell out of electrical contact with the bolt.

A pin 12 (Figs. 4, 5, 7, 8) fixed in plate 6!], has its outer end fixed to the slide member 8 5 of the double switch shown in detail in Figs. '1, 8 and 9. This switch includes three fixed slotted insulating

members

88, 89 and 95 held together by hollow rivets 92, through which screws 93 pass securing the plates to the housing II. To these plates are fastened two slotted metal guides 85 and Si by rivets 91. The movable metal conductor slide 8? is held in place by guide 85 and the cooperating sliding member 99 is held in place by the guide SI. The sliding member 99 is located opposite sliding member 8d, and is provided with a slot 592, through which passes pin 12. The three fixed

insulating members

88, 89, 90 have slots I54, and the pin 12 passes through these slots also.

When the conductor 84 is moved completely forward (that is, to the left as viewed in Figs. 4, 7 and 8) by the movement of the pin. 12, which will occur when the bolt I5 is in locked position, it is forced between the two points I83 and IE9 of the terminal i I0, which is fixed to the insulating member 83 and connected by a conductor 35 to the line M8 thus closing the circuit hereinafter described. The other sliding conductor 99 has the slotted hole I02, permitting the pin 12 to pass through it, so located that when the pin 12 is moved forward it will cause the conductor 99 to engage between the springs IIS, [I1 constituting terminal I20, which is secured to the insulating member 99 and connected to line I15 of the circuit hereinafter described, at the same time as the other conductor B l contacts terminal Ill]. However, when the pin. 12 moves back, that is, to the right as viewed in Figs. 4, '1 and 8, carrying the conductor 8 with it, and thereby immediately opening the circuit through terminal lit and slide 34, the conductor 99 remains in place in contact with terminal I28 until the pin 12 travels to the other end of the slot IE2, whereupon the pin 12 moves slide 99 enough to the right to break its contact with terminal I20, thus opening the circuit through that terminal and conductor slide 99. The conductor spring strip l25 passes through the fixed insulating

members

88, 89, 9!], and insures the flow of current between the traveling slides 84 and 99 the closed position of Fig. 8.

There is provided a means for maintaining a normally open circuit between the leaf spring 5'? and the plate Bil, and for closing the circuit to set off the alarm when certain tampering operations are attempted. To this end, as here shown as an example, in. the bolt I5 there is an axially movable pin I38 which operates lengthwise of the bolt, and which, when the bolt is in locked position, is forced back against coil spring l33 by a set screw E35 attached to the rear inside wall of the strike 28, so that the right hand end of the pin thrusts spring 51 out of contact with plate G l and into the notch 59 thereof to open the alarm circuit. The set screw i395 is adjustable to vary the throw of conductor leaf spring 51 out of contact with plate 65; the less the throw, the less tampering movement of the door or bolt is necessary to close the circuit and sound the alarm when an unauthorized entry is attempted. For example, an attempt to insert an implement between the door and jamb would result in moving both door and bolt to the right, as viewed in Figs. 3, 4 and 5, away from set screw I35, whereupon the pin. I30 is moved by coil spring 633 a corresponding distance to the left within bolt l5. As soon as the pin has moved whatever slight distance the device is set for, conductor leaf spring 51 returns to contact with plate Bi! and closes the alarm circuit. The set screw H5 is preferably threaded into the keeper 26, and is locked in adjusted position by the lock nut I38.

The same result would occur if the jamb were cut away by some implement such as a chisel, and the bolt sawed through, for any such operation would break the thrust of pin I35 against conductor leaf spring 51 which holds it out of contact with plate 60.

The same result would occur if the door were to be removed from its hinges, for this would close the circuit through spring 51.

When an authorized person provided with the proper key moves the bolt I5 to locked position, spring 51 is moved by pin I30 to open circuit position. The double switch of Figs. '7 and 8 is so arranged that, immediately after spring 51 moves to open circuit position, conductor plate 84, moved by pin 12, closes the circuit through terminal III].

The terminal I It] (Fig. 4) is connected by conductor I45 with conductor I48 which leads to one end of magnet coil I50, the other end of which is connected battery 44.

Upon any attempt to insert an implement between the door and jamb, or on any attempt to saw through the bolt I5, switch 51 closes the circuit from the bolt I5 to the plate 60, and causes the alarm to sound, the circuit being traceable as follows: from battery 44 through conductor 53, conductor I66 to bolt terminal 58, through the bolt I5, spring 51, plate 60, pin 12, conductor plate 84 of the double throw switch to terminal II 0 thereof; thence through conductor I45 and conductor I48 to magnet coil I50, thence through conductor 50 to the other terminal of battery 44. This energizes the magnet coil I50.

Associated with the magnet coil I50 is a reis actuated by energizing by conductor 50 with the lease mechanism which of magnet coil I50 to cause a closing of the alarm bell circuit. The release mechanism includes a bell crank lever rockable on a fixed pivot I and having the core arm I56 and the release arm I51, the latter being provided with the holding catch I58 and passing through a limited opening 59 in the spring switch I60. The spring switch IE0 is connected by conductor I62 and with the terminal I63 of the bell circuit, and is normally held by catch 558 of the bell crank lever in open circuit position, that is, spaced away from its other terminal I64, which is connected toone terminal of the battery 44, by conductors I66 and 53. The other terminal 45 of the bell circuit, leaving magnet coil 52, is connected to the other battery terminal by conductors 5| and 50. The alarm bell and bell circuit may be of ordinary or usual construction and are so shown in the drawings.

The operation of the release mechanism is as follows: upon the energizing of coil I50, the core arm I56 of the release lever is moved about the fixed pivot I55, (clockwise, as viewed in Fig. 4) thereby causing catch I58 to release the spring switch I 60, which thereupon springs to closed circuit position, thus closing the alarm bell circuit through spring switch terminal I64, and

causing the alarm bell to sound as aresult of the unauthorized attempted entry.

If the alarm has been set off, its circuit can be opened by depressing knob I10 of spring switch I60, which cams the holding catch arm I51 of the bell crank lever to the left, whereupon a leaf spring I12 causes it to hold the spring switch I in the open circuit position. The invention provides a construction however, such that the knob I10 can be reached only by an authorized person.

The double throw switch of Fig. 4 is constructed to prevent sounding of the alarm when the bolt is moved to unlocked position by the proper key. It will be recalled that conductor plate 84 of the double throw switch did not contact terminal IIO until after spring 51 had been moved by pin I30 out of contact with plate 60. Consequently, the coil I50 of the release mechanism circuit was not energized, since the circuit was opened by spring 51 before it was closed at terminal H0. Upon movement of the bolt I5 toward unlocked position, the reverse action takes place, and the release mechanism circuit is opened at terminal IIO before it is closed by spring 51, the opening of the circuit at terminal H0 occurring upon initial movement of conductor plate 84 by pin 42. The alarm bell circuit is thus maintained open throughout normal operation of the look by a person using the proper key.

The invention includes means for causing the alarm to sound in the event the door is cut through for the purpose of unlocking the bolt by operating the bolt knob I 4, and the knob is operated by an unauthorized person. This means is optionally settable by operation of a switch by an authorized person, the switch being accessible only to such a person.

This means includes the sliding member 99 of the double throw switch, above referred to, which contacts terminal I20 when the bolt reaches its maximum throw into locked position. The terminal I20 is connected by a conductor I15 to a switch terminal I 18 (Figs. 4, 5). The vertically movable plate I80 is normally forced upwardly by the coil spring I82, surrounding its lower end, the plate and spring being carried and guided within a housing I 84 fixed to the lock casing II. Carried by the plate I80 is the terminal bridging member I86, having a finger actuated end I88 extending through a slot I89 in the lock casing II. The plate I80 has a projecting lug I92, extending through the housing I84, by means of which the plate I80 is held down against the action of its coil spring I82, with the bridging member I86 closing the circuit across switch terminals I18 and I93.

Fig. 12 shows the means for holding the bridging member I86 across the terminals when its finger actuated end I 88 is depressed. Attached to the back plate 4| is a guide I91 in which slides the holding plate I99 provided at one end with the holding lug 20I, which is movable with the holding plate into and out of a position over the lug I92 on holding plate I80, in which position it holds down the bridging member I86 in contact with the terminals I18 and I 93.

The holding lug 2! is formed with a beveled upper edge cam 203, and is held in the right hand position of Fig. 12 by the leaf spring 205 which has one end fixed at 201 and its other end bearing against the holding plate I 99 and urging it toward the right as viewed in Fig. 12. When the plate I80 is depressed, its lug I92, bearing down on cam 203, forces the holding plate and lug 29I to the left as viewed in Fig. 12, and as soon as the lug I92 passes below the lug 28H, spring 205 forces the lug to the right above the lug I92 so that the lug I82 is held in lower position with the terminals H18 and 93 bridged by member I86 and the circuit closed across these terminals.

It will be noted that only the finger actuated end 88 of the terminal bridging member I86 protrudes from the lock casing; and that when the circuit is thereby closed, the bridging member cannot be lifted to break the circuit, because of the holding mechanism just described, even if such an attempt be made by an intruder cutting through the door.

The mechanism includes means for breaking this circuit when the bolt E5 is moved to unlocked position by operation of the lock with its proper key, so that the optionally operable circuit closing mechanism will thereby be returned to normal inoperative, or open circuit, position.

For this purpose, the plate I99 pivotally carries the spring pressed lug 259, constantly urged into the position of Fig. 12 by a spring 2H also carried by the plate I99. The lug 259 has an abutment edge 2I3 and a slip cam edge 255, and is located adjacent to and in the path of travel of a cam 2i9 carried by the cam disk 36 operated by cylinder 39 above described. When the lock cylinder is operated by its proper key in a clockwise direction as viewed in Fig. 12 to move the bolt to unlocked position, cam 2I9 contacts with the abutment edge 2I3 of pivoted lug 222, and forces it, with the plate I99 and holding lug 29I to the left, as viewed in Fig. 12, against the pressure of spring 295, thereby releasing plate I89, whereupon the plate I80 is forced upwardly by coil spring I82, carrying with it the bridging member it'd and thereby breaking the circuit across terminals I18 and I93.

this circuit is closed by the bridging memby depression of the finger end I88, before the rocking operation, the cam 2I9 in its rotary movement simply slides over the slip cam edge 2H3 of lug 299, depressing it against the action of leaf spring 2H, and having no'eifect on the circuit. 1

If the circuit is not closed across terminals I18 and I99 action the same, since the parts are normally maintained in the position of Fig. 12 whether this circuit has been closed or not.

ihe cam 2I9 makes one complete revolution in the locking operation, and one complete revolution in the opposite direction in the unlocking operation of the lock cylinder. If the circuit across terminals I18 and I93 has not been optionally closed, movement of the plate I99 to the cit by cam 2I9, as viewed in Fig. 12, is merely an idie movement, as is its return movement to the right caused by spring 295 when the cam 2 I9 passed spring pressed pivoted lug 299.

By the means just described, when the circuit across terminals I18 and I93 has been optionally closed, this optionally operable circuit closing mechanism is always returned to normal open circuit position by the unlocking operation with the proper key. Moreover, the parts are proportioned and positioned so that the circuit is broken across terminals I18 and I93 by unlocking motion with the proper key before the bolt has moved far enough toward unlocked position for spring 51 to close the alarm circuit and cause sounding of the alarm. That is, the pin 31 and the cam 2Ii are located substantially at right angles to each other, sothat before the pin 31 engages arm IS, the cam 2I9 will have engaged lug 229, which causes. plate I99 to move back and release lug I92 before the bolt has moved more than a very short distance.

The invention provides means associated with the mechanism just described for closing another part of this circuit by the moving of the lock bolt to closed position by its proper key from outside the door after the door is closed, and for keeping the circuit closed despite unlocking movement of knob I i from within, so that even if an intruder cut through the door, he could not unlock it without sounding the alarm even if he should be able to reach and should actually turn knob It in the unlocking direction. The invention thereby provides alarm protection even against this manner of attempted entry, and the optionally operable -nechanisrn may therefore be used by an apartment resident if he so desires whenever he is the East to leave. But opening of the door from outside by means of the proper key, however, breaks the alarm circuit across terminals I18 and I93, as already described, before spring 51 closes the alarm circuit.

Referring to this means (Figs. 4, 12 and 13), a switch 232 comprises a pair of spaced terminals 232 and 23 i spaced apart and insulated from each other by an insulating mounting 235 secured to the lock casing back plate M and insulated therefrom. Means for closing the circuit across these terminals includes the bridging contactor 236 carried by an insulator 238 secured to a slide 240 reciprocable in a casing 242 secured to the lock casing back plate M. The terminal 234 is provided with the binding post 248, from which a conductor 259 runs to the magnet coil I59 already described.

The terminal 232 is provided with the binding post 252, connected by conductor 254 with terminal I93 of the optionally operable switch, whose cooperating terminal I18 is connected by the conductor I15 with switch I29 as already described. As viewed in Fig. 12, the left hand position of plate 248 closes the circuit through switch 239, and the right hand position thereof opens the circuit at said switch.

The sliding plate 249 pivotally carries a pair of

opposed lugs

260 and 262. The lug 299 has an operating abutment edge 264 and an adjoining slip cam edge 2%, and is normally maintained in the position of Fig. 12 by one arm 268 of a leaf spring 219 carried by the plate. The oppositely directed lug 222 has an operating abutment edge 212 and an adjoining slip cam edge 214, and is normally maintained in the position of Fig. 12 by the other arm 21% of the leaf spring 219.

Both lugs 25% and 252 lie in the path of the cam M9, by which the switch 239 is opened and closed. The parts are so arranged and proportioned that spring 51 opens the alarm circuit before switch is closed, upon locking movement by the key, during which the cam 2I9 moves counterclockwise, as viewed in Fig. 12; and upon the reverse or unlocking movement of said cam by the key the switch 230 is opened before the alarm circuit is closed by spring 51. Movement by the proper key, therefore, does not cause actuation of the alarm.

The switch 239 is closed by cam 2I9 which is operated by the proper key of the lock and slides over the slip cam edge 214 of lug 262, depressing the lug against spring 210, and then contacts the abutment edge 214 of lug 269 and moves plate 239 to the left causing contactor 236 to bridge the terminals 232 and 234. In the unlocking movement of cam 2 I 9 caused by the key, the cam slides over slip cam edge 266 of lug 269, depressing the lug against spring 219, and then contacts the abutment edge 212 oflug 262 and forces the lug and plate 242 to the right, thereby opening the switch 239.

By this time the bolt I has moved considerably toward completely unlocked position, at the beginning of which movement the spring 51 moved to closed circuit position. The alarm was not operated, however, because the circuit was first opened between switch terminals I93 and I18 before spring 51 moved to closed circuit position, as already described.

Since the pin 31 is operated only when the lock cylinder 39 is turned by the key, the foregoing mechanism, when operated by the key, will not cause the alarm to sound.

If, however, after the optionally operable safetly mechanism has been set as above described, an attempt be made to move the bolt I5 to unlocked position by operating knob l4, the circuit will not be broken at switch 230, or across terminals I18 and I93, since the lock cylinder will not be turned and the cam 2I9 will not move because the knob operation of the bolt I5 is independent of the key operation.

If the optionally operable safety mechanism has been set as above described, and the door be cut through and the knob operated to unlock the door, the first unlocking movement of the bolt will close the alarm circuit at spring 51, and since the rest of the circuit remains closed until key operated, the alarm will sound.

In such event, the actuating circuit through magnet coil I50 to close the alarm circuit is as follows: from battery 34, conductor 53, conductor I66 to casing It to bolt I5, through spring 51, plate 60 and pin 12 to slide 8i, spring strip I25 to slotted conductor plate 99 (which plate remains in contact with the terminals of switch I26 and keeps this switch closed even though initial knob movement of the bolt has opened switch II thence through switch I23, conductor I15, terminal I18, bridging member I85, terminal I93, conductor 254, switch 239 (which is opened and closed only by key movement of the lock cylinder, and which was closed when the door was locked by the key from outside), thence by way of conductors 256 and M8 through magnet coil I50 to conductor 55 and thereby to the other battery termina. Energizing of coil I50 causes sounding of the alarm through the closing of the alarm circuit already traced.

But key actuated unlocking movement of the bolt I will not cause the alarm to sound, for the circuit just traced will thereby be broken first by the release of bridging member I86 caused by cam 2I9 acting on lug 20S, and thereafter by the opening of switch 230 caused by cam 2I9 acting on lug 262. It will be noted that switch 230 is closed every time the door is locked by the key, and opened every time the door is unlocked by the key; while holding plate 199, though it is given a circuit opening movement every time the door is unlocked by the key, is given no movement during locking by the key. The circuit opening movement of holding plate I99 is effective to open the circuit by releasing bridging member I86 only in the event the finger end I88 thereof has been depressed.

The invention provides means for giving access to the interior of the lock casing to a person with the proper key and only to such person. For this purpose, the door i2 is provided on the lock casing I I, being hinged thereto at 282 and 284, and having the cylinder lock 286 by which it is held closed and locked to the casing I4. The lock 286 may be operable by the same key that operates the bolt I5, or may be operable by a different key. Opening of the door I2 gives access to the interior of the lock casing I4 to replace the batteries 44, and to open the alarm circuit by depressing knob I10 of the spring switch I60. This construction prevents the stopping of the alarm by any one who has not the proper key.

It has been pointed out how the optionally operable mechanism may be set to cause the alarm to sound by knob operation of the bolt from the inside of the door, for example, by any one cutting through the door in order to open it by reaching and turning the knob I4. It is to be noted that the lock casing is secured to the door by ordinary wood screws, so that any householder or apartment resident can affix the lock in place by a screw driver. It is to be noted that if the door has been locked, any attempt at removal of the look from the door by removing the screws 24 will cause the alarm to sound, for as soon as the lock is loosened, pin I30 will no longer hold the spring 51 in open circuit position, with the result that it will move to closed circuit position 5 and cause the alarm to sound as soon as the lock is loosened whatever amount the pin I30 has been set for.

The invention provides safety release means for preventing the alarm from sounding when the door is open by preventing both knob and key operation of the bolt i5 when the door is open unless the safety release means is manually held in look release position.

Relerring particularly to Fig. 10, pivotally secured at 299 on the inside front face of lock casing iI is a bell crank lever 292 having a cam arm 294 and a lock release arm 295. A leaf spring has one end secured to the bell crank lever, and its other or free end 304 bearing on the inner front face or the lock casing. The spring 355 urges the bell crank lever in a clockwise direction about its pivot 290, thereby causing the cam arm 294 to protrude slightly through an opening 3:36 provided for it in the lock casing opposite the keeper 26. When the door is closed, cam arm 294 is carnmed by the keeper 25 in a direction toward the back plate M, which moves lock release arm 295 clear of a stop lug 358 on the under side of the bolt I5 (Fig. 5), which, in the unlocked position or the bolt I5, occupies the dotted line position of Fig. 10. Thus, when the door is closed, the lock may be moved into and out or' locked position by the knob E4 or its key.

When the door is open, however, spring 350 forces bell crank lever 292 in a clockwise direction until the cam arm 294 protrudes to its limit from the lock casing opening 308. This brings the lock release arm into the path of the stop lug 308 on the bolt, and prevents movement of the bolt into locked position.

The lock release means can be manually operated to permit moving the bolt to locked posi tion when the door is open by depressing cam arm 294, to test the alarm, for example. Whenever the door is closed, the release means is automatically operated to free the bolt for locking movement by depression of the cam arm 294 by the keeper 26. It will be noted that whatever attempt be made, successfully or not, to manipulate the safety release means after the door has been locked, it will have no effect whatever upon the functioning of the alarm resulting from an attempted entry without the proper key.

From the foregoing description it will be seen that the invention provides an alarm lock that can be applied to a door or other closure by screws and a screw driver; that can not be operated unintentionally when the door is open; and that functions to sound the alarm when entry is attempted in a number of ways without the proper key, including inserting a wedging instrument between door and jamb in an effort to force the bolt back, sawing through the bolt, actuating the bolt knob by cutting through the door to reach it, unscrewing the bolt casing from the door, unscrewing the keeper, removing the door from its hinges, separating the lock casing from the strike by bursting open the door, and in any other way which results in movement of spring 57 to closed position except by using the proper key or by the bolt knob when it is not elected to use the optionally operable safety mechanism. Moreover, the circuit cannot be tampered with because it is wholly contained in the lock casing and cannot be reached without the proper key, and the same is true of the alarm bell, the batteries, and all the mechanism of the invention which could otherwise be tampered with to prevent the alarm signal from functioning in its intended way.

What I claim is:

1. An alarm lock for doors and the like, including a lock housing, a bolt member movable therein to locked and unlocked position, an alarm circuit in said housing, a source of current therefor, an audible alarm associated therewith in said housing and set in action by closing of said circuit, circuit closing means carried by said bolt member and movable to circuit closing position by unlocking movement of said bolt member, and means for opening said circuit before circuit closing movement of said bolt member comprising a key actuated switch in said circuit.

2. An alarm lock for doors and the like, including a lock housing, a bolt member movable therein to locked and unlocked position, an alarm circuit in said housing, a source of current therefor, an audible alarm associated therewith in said housing and set in action by closing of said circuit, circuit closing means carried by said bolt member and movable to circuit closing position by unlocking movement of said bolt member, and means for opening said circuit before circuit closing movement of said bolt member comprising a switch in said circuit and a bolt actuating knob and means associated therewith for controlling said switch.

3. An alarm lock for doors and the like, including a lock housing, a bolt member movable therein to locked and unlocked position, an alarm circuit in said housing, a source of current therefor, an audible alarm associated therewith in said housing and set in action by closing of said circuit, circuit closing means carried by said bolt member and movable to circuit closing position by unlocking movement of said bolt member, means for opening said circuit before circuit closing movement of said bolt member comprising a key actuated switch in said circuit and a key controlled housing closure for said lock housing.

i. An alarm lock for doors and the like comprising a lock housing having a key controlled closure, and, within said housing, an audible alarm, an alarm circuit for actuating said alarm when said circuit is closed, a source of current therefor, a normally open switch in said alarm circuit, means for closing said switch including a control circuit, a bolt member movable to locked and unlocked position, key controlled means for moving said bolt, knob controlled means for moving said bolt, means for opening said control circuit after the bolt has moved into locked position. and before completion of its looking movement comprising a bolt actuated switch in said control circuit movable to circuit closing position at the beginning of bolt unlocking movement, and switch mechanism in said control circuit movable to closed circuit position by said key controlled means and said knob controlled means upon opening of said control circuit by said bolt actuated switch and movable to open circuit position by said key controlled means and said knob controlled means prior to closing of said circuit by the bolt actuated switch at the beginning of bolt unlocking movement.

5. An alarm lock for doors and the like comprising a lock housing having a key controlled closure, and, within said housing, an audible alarm, an alarm circuit for actuating said alarm when said circuit is closed, asource of current therefore, a normally open switch in said alarm circuit, means for closing said switch including a control circuit, a bolt member movable to locked and unlocked position, key controlled means for moving said bolt, knob controlled means for moving said bolt, means for opening said control circuit after the bolt has moved into locked position and before completion of its locking movement comprising a bolt actuated switch in said control circuit movable to circuit closing position at the beginning of bolt unlocking movement, switch mechanism in said control circuit movable to closed circuit position by said key controlled means and by said knob controlled means upon opening of said control circuit by said bolt actuated switch and movable to open circuit position by said key controlled means and by said knob controlled means prior to closing of said circuit by the bolt actuated switch at the beginning of bolt unlocking movement, and means to prevent said knob controlled means from so moving said switch mechanism to open circuit position comprising optionally settable switch holding mechanism released by key operation of the bolt.

6. Alarm lock mechanism for doors and the like including a keeper, a variably positionable regulator associated therewith, a lock housing and, within said lock housing, an audible alarm, circuit means for operating said alarm, a source of current therefor a bolt movable to locked and unlocked positions, key controlled means for moving said bolt, knob controlled means for moving said bolt, a bolt controlled switch in said circuit means having spring means normally urging it toward closed position, a switch opener carried by the bolt and movable to switch opening position by contact with said variably positionable regulator on completion of bolt movement into locked position, and switch means in said circuit means opened by said key controlled means and by said knob controlled means by bolt unlocking movement thereof and closed by bolt locking movement thereof.

7. Alarm lock mechanism for doors and the like including a keeper, a variably positionable regulator associated therewith, a lock housing and, within said lock housing, an audible alarm, circuit means for operating said alarm, a. source of current therefor, a bolt movable to locked and unlocked positions, key controlled means for moving said bolt, knob controlled means for moving said bolt, a bolt controlled switch in said circuit means having spring means normally urging it toward closed position, a switch opener carried by the bolt and movable to switch opening position by contact with said variably positionable regulator on completion of bolt movement into locked position, switch means in said circuit means opened by said key controlled means and by said knob controlled means by bolt unlocking movement thereof and closed by bolt locking movement thereof, a key lockable closure for said lock housing, and a manually operable switch in said circuit means accessible by key opening of the housing closure.

8. Alarm lock mechanism for doors and the like including a lock housing having therein a bolt, an electrically operable audible alarm and circuit means including a current source therefor, a keeper for said bolt, means associated therewith providing a switch movement regullator, a switch in said circuit means movable to circuit closing alarm operating position by relative movement of said switch and said regulator toward each other and by relative movement of said bolt and regulator away from each other, a'bolt carried switch opener cooperable with said switch and said regulator, key controlled means and knob means for actuating the bolt, and means for preventing operation of the alarm during normal operation of the lock comprising key controlled and knob controlled switch mechanism in said circuit means.

9. Alarm lock mechanism for doors and the like including a lock housing having therein a bolt, an electrically operable audible alarm and circuit means therefor, a keeper for said bolt means associated therewith providing a switch movement regulator, a switch in said circuit means movable to circuit closing alarm operating position by relative movement of said switch and said regulator toward eachother and by relative movement of said bolt and regulator away from each other, a bolt carried switch opener cooperable with said switch and said regulator, key controlled means and knob means for actuating the bolt, means for preventing operation of the alarm during normal operation of the lock comprising key controlled and knob controlled switch mechanism in said circuit means, and 0ptionally settable means for causing operation of the alarm by bolt unlocking movement of said knob means comprising manually settable switch closer associated with said circuit means and movable to un-set or switch opening position upon bolt unlocking movement of said key controlled means.

JOSEPH R. RODTH.