US3489121A

US3489121A - Detonating burglar alarm

Info

Publication number: US3489121A
Application number: US692755A
Authority: US
Inventors: Barkman C Mccabe; John R Foss
Original assignee: Burglar Blast Inc
Current assignee: Burglar Blast Inc
Priority date: 1967-12-22
Filing date: 1967-12-22
Publication date: 1970-01-13
Anticipated expiration: 1987-01-13
Also published as: GB1222168A

Description

Jan. 13, 1

Filed Dec. 22, 1967 B, C. M CABE ET AL DETONAT ING BURGLAR ALARM 3 Sheets-Sheet 2 .ZM/EN Toes.

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United States Patent 3,489,121 DETONATING BURGLAR ALARM Barkman C. McCabe and John R. Foss, Los Angeles, Calif., assignors to Burglar Blast, Inc., Los Angeles, Calif., a corporation of Nevada Filed Dec. 22, 1967, Ser. No. 692,755 Int. Cl. G08b 13/08 US. Cl. 116-88 7 Claims ABSTRACT OF THE DISCLOSURE A burglar alarm of the type in which a blank cartridge or primer cap is fired to make a very loud report when an intruder opens a window or door or enters an unauthorized area with which the alarm is associated. The alarm employs a spring biased firing member for detonating the cartridge or cap. An improved means for releasably retaining the firing member in a cocked position and for triggering the same to actuate the alarm is described.

BACKGROUND OF THE INVENTION This invention relates generally to a burglar alarm and, more particularly, to a detonating burglar alarm which fires a blank cartridge or primer cap upon actuation of the alarm by an unauthorized person.

Detonating type burglar alarms have been known in the art for many years. In the conventional detonating burglar alarm, the firing member is generally a plunger which is slidably mounted in a barrel having a blank cartridge positioned at the forward end thereof. The end of the plunger adjacent to the cartridge carries a firing pin. The firing pin end of the plunger is biased toward the blank cartridge by means of a coil spring surrounding the plunger and engaging an annular flange adjacent to the forward end of the plunger. A mechanism is pro vided for releasably retaining the plunger in a cocked position wherein the firing pin is remote from the blank cartridge. Release of the retaining means permits the plunger to be thrust by the force of the coil spring toward the forward end of the barrel to fire the blank cartridge.

In a common form of a detonating burglar alarm, the mechanism for retaining the plunger of the alarm in its cocked position comprises a triggering pin engaging aligned transverse bores in the plunger and barrel wall.

A cord, such as a household string, connects the pin to a movable object, such as a window sash or door, which might be opened by an intruder. Opening of the door or window by an intruder forcibly withdraws the triggering pin, thereby firing the alarm. A very powerful coil spring must be employed in a detonating burglar alarm in order to provide sufiicient force against the plunger to insure firing of the cartridge mounted in the barrel of the alarm. When employing such a spring in the aforementioned common detonating alarm, as may well be appreciated, a substantial amount of force is required to withdraw the triggering pin from the transverse bores in the plunger and barrel. As a consequence, when the door or window attached by a cord to the triggering pin is opened by an intruder, the cord might break rather than efiect removal of the pin from the alarm. Also, the resistance to movement of the door or window caused by the connection thereof to the alarm might be felt by the intruder before the alarm is triggered or the alarm might be pulled loose from its mounting without being triggered.

Thus, what is needed is a detonating burglar alarm which may be triggered by a relatively small amount of force, even though the alarm employs a heavy spring for actuating the firing member against the blank cartridge or other detonating element employed in the alarm,

yet which is positively secured against accidental release until triggered, as by an intruder.

SUMMARY OF THE INVENTION The principal object of the present invention is to provide a detonating burglar alarm which may be triggered by a relatively small amount of force, yet which is positively secured against accidental release;

A further object of the invention is to provide a detonating burglar alarm which is readily triggered by a cord connecting the device to a window, door, or other object which might be moved by an intruder, or by an intruder entering an unauthorized area.

Another object of the invention is to provide a detonating burglar alarm having means for easily reloading the device and resetting the firing member of the alarm in its cocked position after the alarm has been triggered.

A further object of the invention is to provide an improved cartridge or primer cap holder which presents virtually no encumbrance to the noise produced by a detonated cartridge or cap in the alarm, and also means for preventing assembly of the holder with the cartridge or cap therein to the remainder of the alarm unless the spring biased firing member in the alarm is latched in its cocked position.

According to the principal aspect of the present invention, there is provided an improved means for releasably retaining a spring biased firing member of a detonating burglar alarm in its cocked position. Such means includes a trigger element adapted to be slidably mounted in a set position in either the body member of the alarm, or the firing member. A cord, cable, wire, or the like, connects the trigger element to a window, door, or other object which might be moved by an unauthorized person entering a room or building, or across a walkway or other area from which it is desired to restrict unauthorized persons. When the trigger element is in its set position, it retains a rollable latch element carried by one of the members in shouldered engagement with the other member, thereby retaining the firing member in its locked position. When the door or window associated with the alarm is opened by an unauthorized person, or when the person enters the restricted area, the cord connected to the trigger element withdraws the latter from the alarm, thereby releasing the latch element and permitting the firing member to be thrust toward a blank cartridge or primer cap in the alarm by the force of the spring associated with the firing member.

Since the latch element which serves to retain the firing member in its cocked position is rollable, a relatively small amount of force is required to mount the trigger element in either the body member or firing member, and to position the latch element in shouldered engagement with the other member. Even more importantly, a relatively small amount of force is required to withdraw the trigger element to fire the alarm, even though a relatively strong spring is employed for forcing the firing member toward the cartridge or cap in the alarm. As a consequence, the cord connected to the trigger element in the present invention will not break, as may occur in the above described common detonating burglar alarm; the resistance to movement of the cord due to its connection to the trigger elementis sufficiently low so as not to be observed by an intruder; and the alarm will not be pulled loose from its mounting. Nevertheless, the latch element serves to retain the firing member safely in its cocked position against accidental release.

According to another aspect of the invention, there is provided a tool for facilitating the resetting of the firing member of the alarm to its cocked position where the firing member is a spring biased plunger slidably mounted Patented Jan. 13, 1970 in a barrel. One end of the tool engages a slot in the rear end of the plunger, while an intermediate portion of the tool engages a fulcrum provided on the barrel adjacent to the end of the plunger. The upper portion of the tool extends substantially beyond the fulcrum so that substantial mechanical advantage is provided for moving the plunger in a rearward direction to its cocked position against the substantial force of a coil spring which urges the plunger toward the forward end of the barrel.

In accordance with another feature of the invention, a holder for the cartridge or primer cap is provided which is threadedly engaged to the main body portion of the alarm. The holder is designed to provide a barrier to blast or wadding expelled from the detonating element, yet embodies a sufficiently large cavity and open space in the walls thereof so as not to muflle the noise produced by a fired detonating element. In a preferred embodiment of the invention, the firing member protrudes into a threaded bore in the body of the alarm which receives the holder so that the holder and detonating element therein cannot be assembled to the body unless the firing member is safely latched in its cocked position. Consequently, there is no langer of the detonating element being fired by accidentally releasing the firing member when Setting it in its cocked position as might occur if the detonating element could be assembled in the alarm piror to latching of the firing member in its cocked posi tion.

The detonating burglar alarm of the present invention may be utilized in homes, factories, farms, or ofiice buildings by connecting the cord attached to the trigger element of the alarm to doors, windows, machinery, gates, etc., and may be used in connection with vehicles, such as boats, trucks, airplanes, etc. The alarm may also be employed for any other application wherein it is desired to prevent unauthorized persons from moving certain objects. The alarm may further be utilized to prevent unauthorized persons from entering restricted areas by eX tending the cord connected to the trigger element a short distance above the ground across an entranceway, walk- Way, etc., into the area so that an intruder will strike the cord and thereby actuate the machanism. The present invention can be used outdoors without danger of being rendered inoperative by dampness as from rain, fog, dew or the like, because the shotgun shell primer caps employed therein are obtainable fully waterproofed, whereas prior devices of this type generally could not be used outdoors because the blank cartridges required to be used therein quickly became inoperative under damp condi tions.

Other objects, aspects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is an elevational view of a wall of a room having one embodiment of the burglar alarm device of the present invention secured to the wall and connected by means of a cord to a sash of a window in the wall;

FIGURE 2 is a side elevational view of the burglar alarm in FIGURE 1, with the plunger thereof being in its cocked position;

FIGURE 3 is a top plan view of the burglar alarm in FIGURE 1;

FIGURE 4 is an enlarged view of the rear end of the burglar alarm in FIGURE 1;

FIGURE 5 is a partial vertical section taken along line 55 of FIGURE 3, with the plunger in its cocked position;

FIGURE 6 is a fragmented partial horizontal section taken along line 6-6 of FIGURE 5;

FIGURE 7 is a partial vertical sectional view similar to FIGURE 5, but showing the plunger of the alarm in its released position after the alarm has been triggered,

and with a plunger setting tool disposed for retracting the plunger to its cocked position;

FIGURE 8 is a fragmented partial horizontal section taken along line 88 of FIGURE 7, with the plunger setting tool removed;

FIGURE 9 is a side elevation of the plunger setting tool for the alarm in FIGURE 1;

FIGURE 10 is a top plan view of the plunger setting tool;

FIGURE 11 is a fragmented partial vertical longitudinal section through a second embodiment of the burglar alarm, with the plunger thereof being in its cocked position;

FIGURE 12 is an elevational view of the rear .end of the burglar alarm in FIGURE 11;

FIGURE 13 is a transverse vertical section taken along line 13-13 of FIGURE 11;

FIGURE 14 is a transverse vertical section taken along line 1414 of FIGURE 11; and

FIGURE 15 is a fragmented partial vertical longitudinal section similar to FIGURE 11, but showing the plunger of the alarm in its release position after the alarm has been triggered.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings in detail, wherein like reference characters designate like parts throughout the various views, there is shown in FIGURES 1-10, one form of a detonating burglar alarm according to the present invention, generally designated 10. The alarm is secured to a wall 11, and connected by means of a cord 12 to a window sash 14 in the wall so that upon opening of the sash by an intruder, the alarm will be actuated to fire a blank cartridge or primer cap therein.

The alarm comprises a barrel 16 mounted to a generally flat base 18 by means of two vertical supporting

plates

20 and 22. The

plates

20 and 22 are spaced apart to provide a slot 24 in which the plunger setting tool 26, illustrated in FIGURES 9 and 10, may be positioned as shown in dotted lines in FIGURE 2 when not in use. Two

vertical bores

28 and 30 are provided in the base 18 adjacent to the opposite ends thereof for mounting the alarm by means of wood screws or the like, not shown, to the wall 11 adjacent to the Window sash 14, or elsewhere, as may be convenient.

A cylindrical bore 32 is formed in the barrel and opens at the rear end 34 thereof. As seen in FIGURES 4 and 5, a cylindrical sleeve 38 is positioned at the rear end of the barrel 16. A key 40 is slidably mounted in longitudinally extending, vertical aligned

key slots

42 and 42a which are formed in the wall 43 of the bore 32 and in the sleeve 38, respectively, and open at the rear end 34 of the barrel. The key 40 prevents any rotational movement of the sleeve 38 within the bore 32. As seen in FIGURE 6, a set screw 44 threaded in the wall of the barrel 16 engages a notch 45 in the outside cylindrical surface 38a of the sleeve 38 to prevent relative longitudinal movement of 'the sleeve with respect to the barrel 16.

The sleeve 38 slidably mounts a cylindrical plunger 48 which is coaxial with the bore 32. The plunger 48 has a forward reduced diameter section 49 which is separated from the rear, main body section 50 of the plunger by means of an annular flange 51. A firing pin 52 is provided at the forward end 53 of the plunger.

The firing pin 52 is centrally positioned at the forward end 53 of the plunger. This form of firing pin is employed when a shortgun shell primer cap, as indicated by numeral 54, or other center fire-type of detonating device is employed. However, if desired, a rim fire cartridge, such as a .22"caliber blank cartridge, could be utilized, in which case the plunger would have an eccentrically positioned firing pin. The primer cap 54, blank cartridge or other detomating device will hereafter be referred to as a detonatin element.

The forward section 49 of the plunger is slidably mounted in a bore 55 which is coaxial with the bore 32. The bore 55 extends from the end 56 of the bore 32 to a threaded bore 58 opening at the forward end 60 of the barrel 16.

A cartridge holder, generally designated 62, has a rear threaded boss 64 engaged in the threaded bore 58. The dettonating element 54 is positioned with its cylindrical shank 66 mounted in a cylindrical bore 68 opening through the end 70 of the boss 64 of the cartridge holder. The head 72 of the detonating elemen is clamped between the end 70 of the boss 64 and the annular shoulder 73 at the end of threaded bore in the barrel 16. By this arrangement, detonating elements may be easily mounted in a fixed position in the barrel 16 to be fired by the firing pin 52 on the plunger 48. Preferably, there is relatively loose tolerance between the shank 66 of the detonating element and the bore 68 so that the element may be readily removed from the barrel even if it expands somewhat upon being detonated.

The cartridge holder 62 includes a cylindrical body 74 and a front end 75. As seen in FIGURES 5 and 7, a

plurality of horizontal bores 76 are provided in the front end 75 of the holder. The bores are sufiiciently small so that the front end 75 will prevent the blast or wadding from the detonating element 54 from doing any damage to adjacent objects or persons upon firing thereof.

A plurality of circumferentially spaced, longitudinally extending, elongated slots 77 are formed in the cylindrical body 74 of the cartridge holder. As seen in FIGURES 5 and 7, the inner diameter of the cylindrical body 74 is substantially larger than the diameter of the bore 68 in which the detonating element 54 is positioned. Preferably, the inner diameter of the body 74 is at least twice as great as the diameter of the bore 68. As a consequence, the slots 77 may be made relatively wide, that is, substantially wider than the diameter of the bores 76, and sufiiciently wide to provide a total peripheral open space in the holder which is substantially greater than the periphery of the bore 68 securing the detonating element 54. Due to the large cavity provided in the holder and the substantially open wall of the cylindrical body 74 thereof, the holder presents virtually no encumbrance to the noise from the detonating element 54. Nevertheless, due to the relatively large size of the cylindrical body 74, sufficient material is provided between the relatively wide slots 77 so that the holder remains a strong, rigid unit.

The relatively large diameter of the body 74 and the serrated-like surface of the body provided by the slots 77 facilitate easy gripping and rotation of the holder When it is necessary to disengage the same from the end of the barrel to insert or remove the detonating element 54,

A coil spring 80 surrounds the main body section 50 of the plunger 48 between the front end 82 of the sleeve 38 and the flange 51 of the plunger. The plunger 48, in the position illustrated in FIGURES 2 to 6, is in its cocked position wherein the coil spring 80 is compressed and the firing pin 52 is spaced from the detonating ele ment 54.

The plunger 48 is releasably retained in said cocked position by a mechanism, generally designated 90. Such mechanism includes a trigger element 92' and a rollable latch element 93, best seen in FIGURES 4 and 6. The trigger element 92 is a generally straight, flat member which is slidably mounted in a longitudinally extending slot 94 formed in the wall 43 of the bore 32 adjacent to the rear end 34 of the barrel. The rollable latch element 93, preferably a ball bearing, is positioned in a transverse opening 98 extending completely through the wall of the sleeve 34, and normal to the longitudinal axis of the plunger 48. A curved recess 100 having a forwardly facing shoulder 101 is formed in the surface 102 of the main body portion 50 of the plunger. When the trigger element 92 is in its set position, that is, positioned in the slot 94 as illustrated in FIGURES 4 and 6, it shifts the ball bearing 93 into shouldered engagement with the shoulder 101 in the plunger, thus retaining the plunger in its cocked position.

The plunger 48 may be locked in its cocked position, and the trigger element in its set position, by means of a safety pin 106. The pin 106 passes through a passage 108 in the barrel 16, a passage 110 in the trigger element 92, a passage 112 in the sleeve 38, and a passage 114 in the plunger 48, all of which passages are transverse to the longitudinal axis of the plunger and are aligned when the plunger is in its cocked position, as seen in FIG- URE 6.

An opening 116 is provided near the rear end 118 of the trigger element 92. The cord 12 is connected at one end to the window sash 14 and at its other end to the trigger element 92 by being tied through the opening 16 in the element. When it is desired to place the alarm in condi tion for firing upon the opening of the sash 14, the safety pin 106 is removed from the

passages

108, 110, 112 and 114. If the window sash 14 is opened by an intruder, the cord 12 will .pull the trigger element 92 out of the slot 94, thus allowing the ball 93 to be cammed free of the shoulder 101 as seen in FIGURE 8, and permitting the plunger 48 to be thrust toward the forward end of the barrel 16 by means of the spring to the position illustrated in FIGURES 7 and 8. In such position, the firing pin 52 on the forward end of the plunger engages the detonating element 54, firing the same and producing a very loud report.

After the alarm has been fired in the manner described hereinabove, the cartridge holder 62 is removed from the forward end of the barrel 16 to replace the detonating element 54, the large serrated-like surface of the body 74 enabling easy removal of the holder 62 from the barrel, and the loose mounting of the detonating element in bore '68 facilitating ready removal of the element from the holder.

It is an important feature that the latch element 93 be rollable and that the trigger element 92 have a straight rolling track 92a on the side contacting the latch element and, hence, present an unshouldered surface which will ride smoothly along the latch element when the trigger element is removed from the slot 94. It is preferred, in addition, that the trigger element have a uniform crosssection along its longitudinal length. As a consequence, the trigger element may be easily withdrawn from the slot 94 without substantial force. Yet, when the trigger element 92 is positioned in the slot 94, the shouldered engagement of ball 93 with the shoulder 101 on the plunger serves to positively retain the plunger 48 in its cocked position. Hence, substantially less force is required to trigger the alarm 10 of the present invention than would be required if the plunger were retained in its cocked position by means of a transversely extending trigger pin, as in conventional forms of detonating burgular alarms, yet the plunger is still safely retained in its cocked position against accidental release by the plunger retaining mean Because of the substantial force of the spring 80, it is desirable to provide means to facilitate the resetting of the plunger 48 from its release position shown in FIGURES 7 and 8, back to its cocked position shown in FIGURES 5 and 6. Such means includes the plunger setting tool 26 illustrated in FIGURES 9 and 1 0, a fulcrum, generally designed 130, and a slot 132 adjacent to but spaced from the rear end 133 of the plunger. The slot 132 extends generally vertically and has forward and

rear walls

134 and 136 which converge toward each other at their lower ends, thereby providing an inverted, trapezoidal-shaped slot.

The fulcrum is provided by means of a projection 140 which extends above the upper surface 142 of the barrel and beyond the rear end 34 thereof. The projection 140 has a vertical groove 144 therein. The groove 144 and slot 132 in the plunger 48 are so disposed that they will be generally vertically aligned when the plunger is in the released position illustrated in FIGURE 7.

The plunger setting tool 26, as best seen in FIGURES 9 and 10, preferably is an elongated, generally flat metal rod having a body 146 with a curved finger engaging portion 148 at one end and a hook-shaped extension 150 at the other end. In using the tool 26, it is positioned as illustrated in FIGURE 7, with the hook-shaped extension 150 passing through the slot 132 of the plunger 48 and with the tip 152 of the tool underlying the lower surface of the plunger. In such position, the body 146 of the tool engages the vertical groove 144 of the fulcrum 130, The tool 26 has substantially greater length between the fulcrum 130 and the handle 148 than between the fulcrum and the hook-shaped extension 150 engaging the slot 132, so that substantial mechanical advantage will be derived upon forward pivotal movement of the handle 148 about the fulcrum. By this lever arrangement, one may easily retract the plunger 48 into its cocked position. While holding the plunger in such position by means of the tool 26, the trigger element 92 is slid forwardly into the slot 94 to shift the ball 93 into shouldered engagement with the shoulder 101 in the plunger. After the plunger is thus set in its cocked position, the tool 26 may be removed from the slot 132 in the plunger and stored in the slot 24 provided between the

vertical plates

20 and 22 below the barrel 16 in the position illustrated in dotted lines in FIGURE 2.

If it is desired to utilize the alarm again, it is reset as illustrated in FIGURE 1 If it is desired to render it temporarily inoperative, the safety pin 106 is inserted through the

passages

108, 110, 112 and 114 to lock the plunger securely in its cocked position.

A second embodiment of the invention is illustrated in FIGURES 1115. In this embodiment, the basic structure is as previously described, and like numbers primed are used to indicate like or corresponding parts.

In the alarm a single plate 20" supports the barrel 16' on the base 18. Screws 170' secure the three parts together.

In this embodiment, the rollable latch element 93" is carried by the plunger 48 rather than by the sleeve 38, as in the device illustrated in FIGURES 110, and the sleeve 38' is composed of two parts, 172 and 174. The part 172 is in the form of a hollow cylinder having a forward wall 176 and an open rear end 178 aligned with the rear end 34 of the barrel. A slot 180 formed in the upper portion of the cylindrical part 172 extends from the forward wall 176 to the rear end 178. The sleeve part 174 is positioned rearwardly in the part 172, with its rear end 182 aligned with the ends 34' and 178. The

sleeve parts

172 and 174 are fixedly secured in the barrel bore 32' by means of screws 184 seen in FIGURE 14.

Parts

172 and 174 have coaxial, longitudinally extending

bores

186 and 188, respectively, in which the main body section 50' of the plunger 48' is slidably mounted.

A longitudinal cylindrical passage 190 is provided in the plunger 48, and opens at the rear end 133' thereof. The passage is flared adjacent to the end 133 to facilitate insertion of the trigger element 92 into the passage.

The latch element 93', preferably a ball bearing, is positioned in an opening 192 in the plunger. This opening extends upwardly from the passage 190 to the outer surface of the plunger. A vertical bore 194 passing through the wall of the sleeve part 174 is positioned so as to be in longitudinal registry with the opening 192 in the plunger when the latter is in its cocked position, as seen in FIG- URE 11.

The outer end of the bore 194 is closed by a thin, elongated element 196. This element has a curved crosssection such that the element may slide longitudinally in the arcuate slideway 198 defined by the sides of the slot 180 in the sleeve part 172, the wall of the bore 32', and the outer surface of the sleeve part 174. The bore 194, closed at its outer end by element 196, provides a recess 8 199 that opens at the wall of the bore 188 in the sleeve part 174; such recess provides a rearwardly facing shoulder 200.

The element 198 is spaced from the upper surface of the plunger 48' by an arcuate spacer 201, so that the element is in longitudinal alignment with the slideway 198. An arcuate segment 202 is positioned on the element 196 above the spacer 201 and is slidable in a longitudinally extending, vertical slot 204 in the barrel 16. A screw 206 secures the arcuate segment 202, elongated element 196, and spacer 201 to the plunger. The arcuate segment 202 and elongated element 196 cooperate with the sides of the

slots

204 and 180, respectively, to maintain the plunger so oriented that the opening 192 therein, and the recess 199, will be aligned when the plunger is in its cocked position. The segment 202 includes an upwardly extending projectiong 216 for facilitating resetting of the plunger to its cocked position after it has been fired.

The trigger element 92" is formed of a cylindrical rod, shaped to provide a straight shank 210 and an end loop 212. The diameter of the shank is such as to permit it to slide freely in the cylindrical passage 190 in the plunger. When the trigger element is in its set position as illustrated in FIGURE 11, the shank 210 shifts the ball hearing 93 outwardly into shouldered engagement with the shoulder 200 on the recess 199, thus retaining the plunger in its cocked position.

It is preferred that the depth of the recess 199-that is, the distance between the wall of the bore 188 and the lower surface of elongated element 196-be less than the radius of the ball bearing 93'. Thus, when the trigger element 92' is in its set position, a majority of the ball bearing is disposed in opening 192 in the plunger. Hence, when the trigger element is withdrawn from the passage 190, it will be assured that the shoulder 214, provided by the rear wall of opening 192 in the plunger, will function to cam the ball bearing free of the shoulder 200 on recess 199 during forward movement of v the plunger by the spring The alarm 10' is utilized in the same manner as alarm 10, a cord 12 being secured to the loop 212 on the end of the trigger element 92'. When the trigger element is pulled out of the passage the ball bearing is cammed away from the shoulder 200 and becomes lodged in the opening 192 in the plunger, as seen in FIGURE 15, thus permitting the plunger to be thrust forwardly in the barrel 16' to fire the detonating element 54'.

It is seen that the trigger element 92', like element 92, is provided with a straight rolling track 92a, that contacts the latch element 93', by virtue of the fact that the shank 210 has a straight cylindrical, unshouldered surface. Also, because the' cylindrical shank 210 has a uniform crosssection, the trigger element 92' may be easily withdrawn from passage 190, yet the trigger element in cooperation with the ball bearing 93' and shoulder 200 positively retain the plunger in its cocked position when the trigger element is in its set position.

After firing the alarm 10', the plunger may be reset to its cocked position by pushing rearwardly upon a vertical projection 216 on the arcuate segment 202 fixed to the plunger. While the plunger is positioned with the opening 192 therein aligned with the recess 199, the trigger element 92' is slid into passage 190 to shift the ball bearing 93' into shouldered engagement with the shoulder 200 in the recess. A safety pin, not shown, may be inserted through a transverse passage 218 near the forward end of the barrel, such passage passing through the bore 55 behind the detonating element 54' and in front of the firing pin 52' on the plunger. Thus, if the trigger element 92' is accidentally released, the pin in passage 218 will prevent the firing pin from striking the detonating element.

It will be noted that in the embodiment of the invention illustrated in FIGURES 1-10, the cartridge holder 62, together with the detonating element 54, may be assemb d 9 h barrel 16 before cocking the plunger 48, since the length of the forward section 49 of the plunger is such that the firing pin 52 extends only slightly forward of the shoulder 73 after the alarm has been fired. As a consequence, it is possible that the detonating element 54 could be accidentally fired if the user of the alarm permitted the plunger to slip when retracting it to its cocked position.

This problem is overcome in alarm by making the forward section 49' of the plunger sufliciently long so that after the cartridge holder 62' is removed from the barrel 16' after firing of the alarm, the firing pin end of the plunger will extend a sufiicient distance into the bore 58, as seen in phantom lines in FIGURE 15, so that the threaded boss 64' of the cartridge holder cannot be threaded into the barrel if a detonating element is positioned in the holder. Thus, the length of the forward section 49 of the barrel is such that the annular flange on the plunger 51' does not engage the end 56' of bore 32 until after the holder 62 has been removed from the barrel to withdraw the fired detonating element. From the foregoing it can be seen that the detonating element cannot be assembled in the alarm 10' until the plunger is latched in its cocked position. Hence, the alarm 10 cannot be accidentally fired while retracting the plunger to its cocked position as may occur in alarm 10.

While it is preferred to utilize a ball as the latching element in both embodiments of the invention, it is understood that other rollable elements, such as a cylindrical roller, could be utilized with similarly improved success.

While the releasable retaining means of the present invention, which includes the trigger elements 92 and 92' and rollable elements 93 and 93', has been described as being associated with a slidable plunger-type of burglar alarm, it is understood that the retaining means could be utilized in other types of detonating alarms. For example, the retaining means could be employed in an alarm having a pivoted, spring biased hammer for detonating a blank cartridge or cap associated therewith. In such an alarm, the latch element would engage a shoulder on the pivoted hammer, and the trigger element would be slidably mounted in a slot in the supporting body for the hammer, or the latch element would be carried by the hammer and engage a shoulder on the supporting body.

Although we have herein shown and described our invention in what we have conceived to be the most practical and preferred embodiments, it is recognized that departures may be made therefrom within the scope of our invention, which is not to be limited to the details disclosed herein, but is to be accorded the full scope of the claims so as to embrace any and all equivalent structures and devices.

We claim:

1. A detonating burglar alarm including a body member, means for supporting a detonating element in said body member, a spring biased firing member arranged to fire said detonating element when said firing member is released, and means for releasably retaining said firing member in a cocked position remote from said detonating element, wherein the improvement comprises: said retaining means including a rollable latch element and a trigger element; said trigger element being mounted for slidable movement in one of said members between a set position and a release position; said trigger element in said set position locating said rollable latch element in shouldered engagement with the surface of the other of said members to retain said firing member in said cocked position; and said trigger element in said release position allowing said spring biased firing member to fire said detonating element.

2. A burglar alarm as set forth in claim 1, wherein said trigger element has an operative potrion engageable between said rollable latch element and a surface of said one of said members, said portion having a substantially straight rolling track engageable with said rollable latch element.

3. A burglar alarm as set forth in claim 2 wherein said operative portion of said trigger element has a substantially uniform cross section along its longitudinal length.

4. A burglar alarm as set forth in claim 1, wherein said body member is a barrel having a forward end, a rear end and a bore therethrough extending between said ends; said firing member being a plunger having a forward end and a rear end, said plunger being slidably mounted in said bore and carrying a firing pin at the forward end thereof; spring means biasing said plunger toward said forward end of said barrel; said detonating element supporting means being located adjacent to said forward end of said barrel and adapted to position a detonating element so as to be fired upon rapid movement of said plunger toward said forward end of said barrel; and said retaining means retaining said plunger, while in said cocked position, rearwardly in said bore wherein said firing pin is remote from said detonating element; and a sleeve fixedly mounted rearwardly in said bore; said sleeve having a bore therethrough slidably receiving said plunger; said sleeve having an opening extending transversely through the wall thereof, said rollable latch element being positioned in said opening; a slot between said sleeve and barrel, said slot communicating between said rollable latch element and the exterior of said barrel; and said trigger element being slidably mounted in said slot.

5. A burglar alarm as set forth in claim 1, wherein said body member is a barrel having a forward end, a rear end and a bore therethrough extending between said ends; said firing member being a plunger having a forward end and a rear end, said plunger being slidably mounted in said bore and carrying a firing pin at the forward end thereof; spring means biasing said plunger toward said forward end of said barrel; said detonating element supporting means being located adjacent to said forward end of said barrel and adapted to position a detonating element so as to be fired upon rapid movement of said plunger toward said forward end of said barrel; and said retaining means retaining said plunger, while in said cocked position, rearwardly in said bore wherein said firing pin is remote from said detonating element, and a sleeve fixedly mounted rearwardly in said bore; said sleeve having a bore therethrough slidably receiving said plunger; said plunger having a longitudinally extending passage therein opening at the rear end of said plunger; an opening in said plunger extending from said passage to the outer surface of the plunger; said rollable latch element being positioned in said opening; and said trigger element being slidably mounted in said passage.

6. A burglar alarm as set forth in claim 1, wherein said body member is a barrel having a forward end, a rear end and a bore therethrough extending between said ends; said firing member being a plunger having a forward end and a rear end, said plunger being slidably mounted in said bore and carrying a firing pin at the forward end thereof; spring means biasing said plunger toward said forward end of said barrel; said detonating element supporting means being located adjacent to said forward end of said barrel and adapted to position a detonating element so as to be fired upon rapid movement of said plunger toward said forward end of said barrel; said retaining means retaining said plunger, while in said cocked position, rearwardly in said bore wherein said firing pin is remote from said detonating element; and said detonating element supporting means comprising a separate holder having a threaded portion with a bore therein adapted to slidably receive the shank of a detonating element; said bore in said barrel being threaded adjacent to said forward end thereof and adapted to receive said threaded portion of said holder; said forward end of said plunger, after said plunger is released by said trigger element, extending a sufiicient distance into said threaded barrel bore so that said threaded portion of said holder, when the holder has a detonating element mounted therein, cannot a 1 1 be engaged in said threaded barrel bore until said plunger is latched in its cocked position.

7. A detonating burglar alarm comprising: a body having a. threaded bore therein opening at the surface of said body, said bore terminating in an annular shoulder; a holder for a detonating element; said holder having front and rear ends, said rear end having a threaded boss engageable in said threaded bore; a cylindrical bore in said rear end of said holder coaxial with said threaded bore and adapted to slidably receive therein the shank of a detonating element; said holder being adapted to clamp the annular head of the detonating element between the end of said boss and said shoulder; spring biased firing means associated with said body for firing the detonating element after the head thereof is clamped between said boss and said shoulder; said holder including a hollow cylindrical portion between said front and rear ends and generally coaxial with said bores, the inner diameter of said cylindrical portion being substantially greater than the diameter of said cylindrical bore; and a plurality of circumferentially spaced, longitudinally extending, elongated slots in said cylindrical portion.

References Cited UNITED STATES PATENTS 1,005,844 10/1911 Jones 116-89 1,192,893 8/1916 Harvey l1688 1,328,559 1/1920 Brown 11687 1,435,969 11/ 1922 Marcotte 11689 2,167,456 7/ 1939 Hooper 11634 2,570,438 10/1951 Flagge et a1 11681 2,970,560 2/ 1961 Perrin 116-88 LOUIS J. CAPOZI, Primary Examiner