US3444815A - Canister timer for mechanical time fuse - Google Patents

Description

May 20, 1969 c, YEAGLEY $444,815

CANISTER TIMER FOR MECHANICAL TIME FUSE Filed July 20, 1967 FIG 4 INVENT OR Clarence R. Yeag/ey 3a 62 34 5a 46 /2 BY ATTORNEY 3,444,815 CANISTER TIMER FOR MECHANICAL TIME FUSE Clarence R. Yeagley, Lancaster, Pa., assignor to Hamilton Watch Company, Lancaster, Pa., a corporation of Pennsylvania Filed July 20, 1967, Ser. No. 654,821

Int. Cl. F42c 9/04 US. Cl. 10283 8 Claims ABSTRACT OF THE DISCLOSURE The time fuse comprises a clock mechanism driving a cam having a lever in following engagement therewith, the lever being mounted on a rotatable shaft. A cylindrical plunger having ignition material disposed in a cavity in the end of the plunger is spring biased for sliding movement from a cocked position to a firing position. The rotatable shaft engages in a reduced diameter portion of the plunger to retain the latter in the cocked position. The rotatable shaft has a cut-out portion which registers with the plunger to release the same in response to a predetermined rotation of the shaft, such rotation being controlled by the cam and lever arrangement. The cavity in the plunger housing the ignition material has a lateral bore which registers with a blow hole only when the plunger slides into the firing position. A safe wire having a reduced diameter portion prevents rotation of the shaft to the plunger release position.

Background of the invention This invention relates to a time fuse and more particularly to a mechanical time fuse having improved timing accuracy and safety features.

A wide variety of time or delayed action fuses have been proposed and manufactured. A number of these have been electrically or chemically actuated and these types have proven satisfactory although are somewhat limited in their employment due to their relatively higher cost, limited dependability and wear life, and, in the case of chemical fuses, the always present danger of mixing their volatile ingredients. Mechanical time fuses have many advantages in comparison with electrical and chemical fuses among which include ruggedness, durability, and operability in practically any environmental condition, as well as comparative simplicity and safety of operation.

Conventional mechanacal time fuses often employ a clock mechanism driving a cam which, through a series of linkages, releases a plunger after a predetermined time interval and rotation of the cam to actuate ignition material or a percussion cap which, in turn, detonates the explosive charge. The plunger is normally spring biased to the ignition position and is releasably retained in a cocked position by the linkage, the force applied to the linkage by the restrained spring biased plunger being transmitted to the cam surface. The linkage normally has a cam follower which bears on the cam surface with a force comparable to the spring force acting on the plunger and, accordingly, considerable drag is introduced in the clock mechanism which directly drives the cam. This drag force effects the timing accuracy of the clock mechanism and is a problem to my knowledge heretofore unappreciated or solved.

These conventional mechanical time fuses additionally employ a variety of safety mechanisms to lock-up the linkage to preclude displacement of the plunger. One of these safety features normally comprises a wire or rod which engages the linkage to prevent movement thereof thereby preventing release of the plunger. Accordingly, the safety rod or wire must be removed to unlock the linkage 3,444,815 Patented May 20, 1969 and permit normal functioning of the timer cam linkage and plunger. Accidental setting of the timer mechanism to zero (the firing position) and the subsequent removal of the safety wire or pin from its linkage locking position, would immediately release the plunger and actuate the fuse. Mechanical time fuses having safety features of this type, however, must still be handled with extreme care particularly with respect to the time setting on the clock mechanism as the safety rod or wire must not be removed if the timer is accidentally or otherwise set to the zero firing position. If this occurred, the fuse would immediately be actuated resulting in substantially simultaneous detonation of the attached explosive charge.

In many conventional mechanical time fuses, the plunger is retained in cocked position opposite the ignition material which is in free communication via a blow hole with the explosive charge to which the fuse is attached. If the fuse is dropped, jarred, heated or otherwise adversely affected, the ignition material may be actuated even with the plunger retained in the cocked position. Premature actuation of the ignition material in these conventional fuses will automatically cause detonation of the explosive charge in view of the free communication between the fuse and charge and it has been a problem to prevent detonation of the explosive charge by premature or accidental actuation of the ignition material while simultaneously providing for such detonation only in response to displacement of the plunger.

Summary of the invention One aspect of the present invention provides a mechanical time fuse having a unique disposition of parts for releasably retaining the plunger firing mechanism in the cocked position such that the accuracy of the clockwork is substantially unaifeceted thereby. Specifically, the firing mechanism comprises a cylindrical plunger having a cavity at one end housing ignition material and axially slidable in a chamber from a first cocked position to a second firing position whereat the ignition material strikes a fixed firing pin and ignites. The plunger has a diametrically reduced portion which receives a release shaft extending normally to the plunger. The release shaft mounts a lever on one end which bears against a cam rotatably driven by a clockwork, the shaft being mounted in the fuse housing and retaining the plunger in its first or cocked position. The lever is spring biased into following engagement with the rotatable cam whereby the lever drops off the cam after a predetermined time interval. The shaft has a laterally opening cutout portion through which the plunger slides when the shaft is rotated to a position corresponding to the rotary position of the lever after it drops from the cam and swings through a predetermined angle under the bias of the lever spring. In this manner, the rotary shaft positively retains the firing mechanism in the cocked position until the shaft is rotated to a predetermined position defined by the rotary position of the clockwork controlled lever and cam.

By this unique disposition of the fuse parts, the drag force imparted to the cam by the lever can be virtually eliminated such that the accuracy of the clockwork is practically unaffected by the firing release mechanism. To this end, the rotary shaft is located in the diametrically reduced portion of the plunger such that the axis of the shaft is spaced outwardly of the cylindrical surface of the plunger. In this manner, a torque is applied to the shaft by the spring biased plunger in a direction opposite the torque applied thereto by the spring biased lever, which latter torque maintains the lever in following engagement on the cam. By providing the lever and plunger with properly counterbalanced springs, the drag force imparted by the lever on the cam can be minimized to the extent that the clockwork is practically insensitive to such drag force. By this unique arrangement, a larger spring, and hence a larger spring force, can be applied to the plunger to drive the same against the firing pin thus assuring actuation of the fuse material with the assurance that the larger spring force does not in any way affect the clockwork.

Another aspect of the present mechanical time fuse is the provision of multiple safety features. One of such safety features provides for positive and independent actuation of the clockwork subsequent to the setting of the timer to the desired time interval. A spring biased plunger is maintained in its cocked position by a safety pin and is operably connected, in this latter position, to the clockwork to preclude actuation thereof. The safety pin must be withdrawn before the clockwork can be actuated.

Another safety feature of the present invention renders the fuse inoperative when the fuse is accidentally or otherwise set to the zero firing position and the safety pin is removed. Specifically, a safe wire, operable externally by withdrawing the same from the fuse housing, is provided and has an inner diametrically reduced end portion passing through a diametrical bore formed in the rotary shaft. The wire is substantially in axial alignment with the bore when the lever bears against the cam and the plunger is retained in the first or cocked position. If the timer is set to zero, the lever drops from the cam and rotates the shaft such that the bore is misaligned with the axis of the wire. The length of the reduced diameter portion of the wire relative to the diameter of the rotary shaft is such that the shaft is prevented from full rotation to the plunger release position by the locking action of the shoulder formed between the full and reduced diameter portions of the wire against the shaft. This unique locking action also prevents withdrawal of the wire from the fuse housing, thus maintaining the fuse inoperative and indicating to the operator that the timer setting is zero and that the fuse is otherwise ready for firing.

A further safety feature hereof resides in preventing free communication between the ignition material and the explosive charge when the fuse is in the cocked position so that premature actuation of the ignition material does not detonate the explosive charge. To this end, a radial bore into the cavity housing the ignition material is formed and located such that, when the plunger is in the cooked position, the bore is misaligned with a blow hole opening through the fuse housing thus preventing communication between the ignition material and the explosive charge through the blow hole. The radial bore is only aligned with the blow hole when the plunger slides into the firing position thus placing the cavity housing the ignition material in communication with the explosive charge.

Accordingly, it is a primary object of the present invention to provide a mechanical time fuse having an improved actuating mechanism.

It is another object of the present invention to provide a mechanical time fuse having improved timing accuracy.

It is still another object of the present invention to provide a mechanical time fuse having a clock mechanism wherein the drag force imparted thereto by the plunger release mechanism is virtually eliminated.

It is a related object of the present invention to provide a mechanical time fuse having a plunger carrying ignition material wherein the force driving the ignition material against a firing pin can be adjusted without affecting the timing accuracy of the clock mechanism.

It is a further object of the present invention to provide a mechanical time fuse having an improved safety feature whereby the fuse is rendered inoperative upon inadvertent setting of the timer to the zero or firing position.

It is yet a further object of the present invention to provide a mechanical time fuse wherein the ignition material is maintained in an out-of-line position relative to 4 an explosive charge whereby premature or accidental firing of the ignition material will not detonate the explosive charge.

These and further objects and advantages of the present invention will become more apparent upon reference to the following specification, claims, and appended drawrngs.

Description of the drawing figures FIGURE 1 is a perspective view of a mechanical time fuse constructed in accordance with the present invention and shown with parts broken away and in section for ease of illustration;

FIGURE 2 is an end elevational view thereof with parts broken away and in section;

FIGURE 3 is a fragmentary longitudinal view thereof illustrating the plunger firing mechanism in a cocked position;

FIGURE 4 is a fragmentary longitudinal view illustrating the plunger firing mechanism in a firing position;

FIGURE 5 is a fragmentary view of a safety feature hereof illustrating the bore of the rotary shaft in axial alignment with the safe wire; and

FIGURE 6 is a fragmentary view similar to FIGURE 5 showing the rotary shaft in a locked position.

Description of a preferred embodiment Referring to the drawings, and particularly to FIGURE 1, there is shown a mechanical time fuse comprising a housing or canister, generally designated 10, including a box-like bod portion 12 having a side wall 14 spaced therefrom to form a lateral chamber 15 open at its upper end. A clock mechanism 16 is suitably mounted within body portion 12 and operably connected to a pair of dials 17 and 18 mounted within chamber 15 by a pair of concentric shafts 19 and 20 respectively, the latter shafts being suitably journaled through a side wall of body portion 12. The surface of outer dial 17 is inscribed with time interval indicia or calibrations and dial 17 is fixed to the larger knurled inner dial 18. A tab portion 22 of side wall 14 is bent to overlie calibrated dial 17 and, by rotating knurled dial 18, the fuse can be set to a predetermined time interval by aligning the dial calibrations with the edge 24 of tab portion 22 thereby to actuate the fuse at the expiration of such predetermined time interval in a manner as will presently become clear.

Clock mechanism 16 preferably comprises a conventional clockwork having a Junghans escapement for time regulation and a mainspring both of which are not shown as they are conventional. Shaft 19 is operably connected by gearing, not shown, to the mainspring and it will be seen that clockwork 16 is wound by rotation of setting dial 17 to the predetermined time interval. Rotation of the setting dial 17 thus serves a dual purpose in setting a predetermined time interval into the fuse and winding the mainspring of clockwork 16. Outer concentric shaft 20 is operably connected by suitable gearing, not shown, to the driven arbor of clockwork 16 as is conventional in clock mechanism. The outer end of shaft 20 is in frictional driving connection with knurled dial 18 whereby dial 18 slips about shaft 20 as setting dial 17 is rotated. A cam 28 is fixed on the inner face of knurled dial 18 for rotation therewith and has an outer cam surface 30 for purposes as will presently become clear.

As best illustrated in FIGURES 1, 3, and 4, body portion 12 is provided with a longitudinally extending cylindrical chamber 32 containing a cylindrical plunger 34 slidable lengthwise therein. Plunger 34 has a threaded bore or cavity 36 opening through one end thereof for threadedly receiving encapsulated ignition material indicated at 38 and which may be of any suitable well known type. Plunger 34 is biased to the position illustrated in FIGURE 4 by a spring 40 engaging between the opposite end of the plunger and an end wall of chamber 32. An enlarged set screw 42 having a firing pin 44 projecting from its inner face is threaded in a suitable bore through body portion 12 such that firing pin 44 projects into chamber 32 in axial registry with bore 36 and encapsulated ignition material 38.

To retain plunger 34 in the cocked position illustrated in FIGURE 3 and released the same for axial sliding displacement to the firing position shown in FIGURE 4 in response to the expiration of the predetermined time interval set into clockwork 16 by setting dial 17, plunger 34 is provided with a reduced diameter portion 46 forming a peripheral flange 48 adjacent the spring biased end thereof. A shaft 50 having an axis extending at right angles to the axis of plunger 34 is suitably journalled at opposite ends in body portion 12 such that an intermediate portion thereof extends within reduced diameter portion 46 of plunger 34 to abut peripheral flange 48 thereby retaining plunger 34 in the cocked position shown in FIG- URE 3 against the bias of spring 40. The intermediate portion of shaft 50 has a lengthwise laterally opening cutout or slot 52 having a sufiicient depth such that when shaft 50 is rotated to the position shown in FIGURE 4, slot 52 registers with flange portion 48 to release plunger 34 for axial sliding movement under the influence of biasing spring 48 from the plunger position illustrated in FIGURE 3 to the position shown in FIGURE 4.

A lever 54 is fixed at one end of shaft 50 and has a finger 56 at its other end bent to engage against cam surface 30. A spring 58, suitably mounted at one end to body portion 12 and at its other end to lever 54, biases finger 56 into following engagement against cam surface 30 in the direction of the arrows seen in FIGURE 4. It is thus seen that the rotary position of shaft 50 and cutout 52 is dependent upon the rotary position of cam 28 and that cam surface 30 is correlated with the time indicia on dial 17 such that, when the cam 28 and dials 17 and 18 are rotatably driven by clockwork 16 in the direction of the arrow in FIGURE 1 to align the zero dial setting with edge 24 of tab 22, lever 54 drops from the cam surface 30 and rotates shaft 50 to register cutout 52 with peripheral flange 48 thereby to release plunger 34. In this manner, plunger 34 is released from the cocked position shown in FIGURE 3 for spring biased movement into the firing position shown in FIGURE 4. It will be noted that lever 54 must swing through an angle of approximately 60 after disengagement of finger 56 from cam surface 30 to fully rotate shaft 50 to a position locating cutout 52 in registry with flange 48 to release plunger 34 for reasons as will become apparent.

A radial bore 60 is provided through the lower side of plunger 34 into cavity 36 and a blow hole 62 is provided through the bottom of body portion 12 into chamber 32. Axial displacement of plunger 34 into the firing position shown in FIGURE 4 aligns bore 60 with blow hole 62 whereby the heat generated by firing ignition material 38 is transmitted through the aligned bore and blow hole to an explosive charge, not shown. In order to insure that bore 60 and blow hole 62 will not be circumferentially misaligned one from the other when plunger 34 is in the firing position, an elongated slot 64 is formed lengthwise along the surface of plunger 34 and receives the inner end of a pin 66 suitably fixed to body portion 12. Pin 66, accordingly, prevents rotation of plunger member 34 during sliding movement of the latter thereby maintaining bore 60 in a fixed rotary position for registry with hole 62.

A plunger 70 extends through body portion 12 and is biased outwardly by spring 72. A safety pin 74 engages laterallly through body portion 12 and engages in a suitable bore, not shown, formed through plunger 70 to maintain the latter in the depressed position substantially as shown against the bias of spring 72. Plunger 7 t) is suitably connected to the gear train of the clockwork movement in a like manner as the stem in a conventional stopwatch to prevent running of the clockwork when plunger 70 is depressed as shown. Release of plunger 70, as

by the withdrawal of safety pin 74, releases the clockwork movement to drive shaft 20 in a timed relation under the influence of the mainspring. It is thus seen that with plunger 70 retained in the depressed position by pin 74, clockwork 16 is rendered inoperative and will not rotate cam 28 even when the mainspring thereof is wound by the rotation of setting dial 18.

To actuate the mechanical time fuse, a predetermined time interval is set into the fuse by rotating setting dial 17 such that the time calibration corresponding to the predetermined time interval is rotated to an aligned position with edge 24 of tab 22, the rotation being in the clockwise direction as seen in FIGURE 1. Rotation of the setting dial 18 also winds the mainspring of clock mechanism 16 through shaft 19 as well as positioning cam 28 in the proper rotary position corresponding to the predetermined time interval. It will be noted that the frictional engagement between setting dial 18 and shaft 20 allows dial 18 to rotate relative to shaft 20 in the dial setting direction such that the clockwork movement per se is not affected by winding the mainspring thereof through shaft 19. At this point, the fuse is still inoperative as actuation of the clockwork mechanism is prevented by the depressed plunger 70.

To initiate the running of the predetermined set time interval, safety pin 74 is withdrawn from plunger 70 and the latter is spring biased outwardly to release the clockwork movement for operation under the influence of its mainspring. Clockwork 16 drives cam 28 through shaft 20 and lever 54 follows the movement of cam surface 30 under the bias of spring 58. At the expiration of the set predetermined time interval, lever 54 drops from cam surface 30 as indicated by the dashed lines seen in FIGURE 4 and rotates through an angle approximating 60 under the bias of spring 58 to the full line position shown in FIGURE 4 to register cutout 52 with peripheral flange 48, thereby releasing plunger 34 for sliding movement into firing position under the influence of spring 40. Opening 60 is thus aligned with blow hole 62 and ignition material 38 is ignited upon impact against firing pin 44- Whereby the generated heat therefrom is transmitted through the aligned hole 62 and bore 60 to an explosive charge, not shown.

It is a significant feature of the present invention that the frictional drag force imparted by finger 56 against cam surface 30 is practically eliminated leaving the accuracy of clockwork 16 virtually unaffected by the dynamic forces of the plunger release mechanism. To accomplish this, shaft 50 is located such that its axis is outwardly spaced from the periphery of plunger 34 whereby the force applied to shaft 50 by peripheral flange 48 acts along a chord line of the shaft below the axis thereof as seen in FIGURE 3. In this manner, a torque is applied to shaft 50 by spring 40 in a direction opposite to the torque applied thereto by spring 58 acting on lever 54. Springs 40 and 58 are counter-balanced such that the net torque applied to shaft 50 tends to rotate lever 54 in a counterclockwise direction as seen in FIG- URES 3 and 4 with finger 56 in following engagement against cam surface 30 but with minimal frictional contact therebetween. The frictional drag force applied to cam surface 30 by lever 54 can thus be minimized and controlled by a proper choice of springs 40 and 58 as not to practically affect the torque applied by clockwork 16 to cam 28 by shaft 20. The accuracy of the clockwork movement remains virtually unaffected by the plunger release mechanism. Moreover, with the foregoing arrangement, various combinations of spring sizes can be utilized and a large spring can be employed to drive the plunger 34 to the firing position, thus assuring ignition of the ignition material 38 without affecting the accuracy of the clockwork movement.

The mechanical time fuse hereof is provided with an additional safety feature which prevents instantaneous actuation of ignition material 38 by the accidental or inadvertent setting of the calibrated dial to zero and withdrawal of safety pin 74. To this end, an additional safety wire 76 is provided and extends through body portion 12 terminating at its outer end in a loop or handle 78 and at its inner end in a reduced diameter portion 80 as best seen in FIGURES and 6. A diametrical bore 82 is formed through shaft 50 adjacent an end thereof, bore 82 having a diameter sufiiciently large to accommodate the passage of wire 76. The reduced portion 80- of wire 76 is received within bore 82 and, with the shaft 52 in the position illustrated in FIGURES 1 and 2, it is seen that bore 82 is in axial alignment with wire 76 whereby wire 76 may be withdrawn from shaft 50. However, as seen in FIGURE 6, rotation of shaft 50 will cause misalignment between bore 82 and wire 76 and continued rotation thereof to approximately the rotary position whereat lever 54 drops from cam 28 (corresponding to the zero or firing position of the fuse) causes the shoulder 84 to bear against the shaft about bore 82. Loop 78 bears against the body portion 12 and cooperates with shoulder 84 to thereby lock the shaft from further rotation. Shaft 50 cannot therefore swing through the are shown by the arrows in FIGURE 4 into the plunger release position even after lever 54 drops off cam 28. With the foregoing arrangement, accidental or inadvertent setting of the calibrated dial 18 to zero or to the firing position and the removal of safety pin 74 will not by themselves actuate the fuse since full rotation of shaft 50 to the plunger release position is prevented by safety wire 76. It will be seen, therefore, that both safety pin 74 and wire 76 must be withdrawn from the body portion 12 before the fuse can be actuated.

An additional safety feature hereof prevents detonation of the explosive charge due to premature or accidental actuation of ignition material 38 when the plunger member 34 is in the cocked position shown in FIGURE 3. It will be noted that bore hole 60 is formed such that it is aligned with and closed by the walls of chamber 32, and that hole 62 is aligned with and closed by plunger 34 when plunger 34 is cocked. Thus, any heat generated by premature or accidental ignition of material 38 is confined to the cavity 36 and the end of chamber 32 containing firing pin 44, since plunger 34 blocks blow hole 62 and prevents communication of such heat to the adjacent explosive charge. It is only when plunger 34 is moved to the firing position that bore hole 60 and blow hole 62 are aligned and only then can the heat generated by ignition of material 38 be in communication with the explosive charge.

It is thus seen that the objects of my invention are fully accomplished in that there is provided a mechanical time fuse wherein the accuracy of the clockwork mechanism is not affected by the dynamics of the firing mechanism and wherein the spring forces in the firing mechanism can be adjusted to larger or smaller magnitudes as desired. Moreover, additional safety features are provided in that accidental actuation of the fuse upon inadvertent setting of the timer to Zero is precluded and detonation of the explosive charge in response to premature actuation of the ignition material is prevented.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof.

What is claimed and desired to be secured by United States Letters Patent is:

1. A mechanical time fuse comprising a housing having a chamber and a member slidable in said chamber between first and second positions, spring means biasing said member for sliding movement into said second position, an igniter, means responsive to sliding movement of said member into said second position to actuate said igniter and means releasably retaining said member in said first position including timer means adapted to be set to a predetermined time period, a cam operably connected with said timer means for rotation during the set predetermined time, a shaft, a lever carried by said shaft and having an end portion engaging against said cam, spring means biasing said lever end portion in following engagement with said cam for rotating said shaft in response to rotation of said cam, a lengthwise portion of said shaft being cut out to form a slot opening laterally of said shaft, said member having a shouldered portion bearing against said shaft to retain said member in said first position, said shaft being rotated to register the slot thereof with said shouldered portion in response to the elapse of the set predetermined time period to release said member for movement into said second position, said shouldered portion of said member bearing against said release shaft at a point thereabout to impart a torque to said shaft opposite the torque applied thereto by said spring biased lever thereby counter-balancing said lever spring means such that said lever end portion applies minimal drag force to said cam.

2. A mechanical time fuse comprising a housing having a chamber and a member slidable in said chamber between first and second positions, spring means biasing said member for sliding movement into said second position, an igniter, means responsive to sliding movement of said member into said second position to actuate said igniter and means releasably retaining said member in said first position including timer means adapted to be set to a predetermined time period, a cam operably connected with said timer means for rotation during the set predetermined time, a shaft, a lever carried by said shaft and having an end portion engaging against said cam, spring means biasing said lever end portion in following engagement with said cam for rotating said shaft in response to rotation of said cam, a lengthwise portion of said shaft being cut out to form a slot opening laterally of said shaft, said member having a shouldered portion bearing against said shaft to retain said member in said first position, said shaft being rotated to register the slot thereof with said shouldered portion in response to the elapse of the set predetermined time period to release said member for movement into said second position, said chamber and member being cylindrical and said member having a reduced diameter portion extending lengthwise therealong, said release shaft and cylinder being substantially normally disposed one to the other, said release shaft extending within the confines of the cylinder at the reduced diameter portion thereof such that the axis of said release shaft is spaced outwardly from the circumference of the cylinder a distance less than the radius of said shaft, said shouldered portion comprising an annular portion of said cylindrical member defined between the periphery of the cylinder and the reduced diameter portion thereof whereby a torque is applied to said release shaft opposite the torque applied thereto by said spring biased lever.

3. A fuse according to claim 2 wherein said release shaft has a diametrical bore, means releasable externally of said housing and operable to restrain said release shaft from rotation to said member release position, said restraining means including a wire having a reduced diameter portion extending through said bore and forming an annular shoulder for abutting the surface of said release shaft adjacent said bore to prevent rotation of said release shaft to said member release position, a plunger extending through said housing, spring means biasing said plunger outwardly, said timer means being actuated in response to outward movement of said plunger to initiate running of the set time period, a safety pin releasably restraining said plunger from outward movement, said member having a cavity opening through an end thereof and having a lateral bore opening into said cavity, a blow hole opening through said housing into said chamber and adapted to communicate with an explosive charge, said bore being axially displaced from said blow hole when said member is in said tfirst position, said bore and blow hole registering one with the other in response to movement of said member into said second position, ignition material carried within said cavity, a firing pin mounted on said housing and projecting into said chamber in axial alignment with the cavity formed in said member to thereby actuate said ignition material in response to movement of said member into said second position, a slot formation extending lengthwise along a side of said member and a guide pin fixed to said housing and engaging in said slot to prevent rotation of said member in said chamber.

4. A mechanical time fuse comprising -a housing having a chamber and a member slidable in said chamber between first and second positions, spring means biasing said member for sliding movement into said second position, an igniter, means responsive to sliding movement of said member into said second position to actuate said igniter and means releasably retaining said member in said first position including timer means adapted to be set to a predetermined time period, a cam operably connected with said timer means for rotation during the set pre determined time, a shaft, a lever carried by said shaft and having an end portion engaging against said cam, spring means biasing said lever end portion in following engagement with said cam for rotating said shaft in response to rotation of said cam, a lengthwise portion of said shaft being cut out to form a slot opening laterally of said shaft, said member having a shouldered portion bearing against said shaft to retain said member in said first position, said shaft being rotated to register the slot thereof with said shouldered portion in response to the elapse of the set predetermined time period to release said member for movement into said second position, means releasable externally of said housing and operable to restrain said release shaft from rotation to said member release position, said release shaft having a lateral bore, said restraining means including a wire having a reduced diameter portion extending through said bore and forming at least one radially extending annular shoulder for abutting the surface of said release shaft adjacent said bore to prevent rotation of said release shaft to said member release position.

5. A time fuse for igniting an explosive charge comprising a housing having a chamber, a blow hole opening through said housing into said chamber and adapted to communicate with an explosive charge, a plunger movable axially in said chamber between first and second positions, said plunger having a cavity and a lateral bore opening into said cavity, said bore being axially displaced from said blow hole when said plunger is in said first position, ignition material carried within said cavity, first spring means biasing said plunger for movement into said second position thereby locating said bore and said blow hole in registry one with the other to establish communication between said cavity and the explosive charge, means releasably retaining said plunger in said first position including a timer means adapted to be set to a predetermined time period, a cam operably connected with said timer means for rotation during the set predetermined time, a shaft, a lever carried by said shaft and having an end portion engaging against said cam, second spring means independent of said first spring means biasing said lever end portion into following engagement with said cam for rotating said shaft in response to rotation of said cam, a lengthwise portion of said shaft being cut out to form a slot opening laterally of said shaft, said plunger having a shouldered portion bearing against said shaft to retain said plunger in said first position, said shaft being rotated to register the slot thereof with said shouldered portion in response to the elapse of the set predetermined time period to release said plunger for movement into said second position.

6. A fuse according to claim 5 including a second plunger extending through said housing, spring means biasing said second plunger outwardly, said timer means being actuated in response to outward movement of said second plunger to initiate running of the set time period and means releasably restraining said second plunger from outward movement.

7. A time fuse according to claim 5 including means constraining said plunger fro-m rotation to preclude misalignment of said bore opening with said blow hole.

8. A time fuse according to claim 7 wherein said constraining means includes a slot formation extending lengthwise along a side of said plunger and a fixed guide carried by said housing, said guide engaging in said slot to prevent rotation of said plunger in said chamber.

References Cited UNITED STATES PATENTS 896,135 8/1908 Meigs et al 10282 2,232,714 2/1941 Mathsen et a1 102-84 2,449,170 9/1948 MacLean et a1. lO2-'84 2,485,949 10/1949 Wilson et a1. 102-84 2,900,908 8/1959 Burrell 10282 X 2,982,209 5/1961 Borcher 10284 X 3,261,293 7/1966 Webb 10282 BENJAMIN A. BORCHELT, Primary Examiner.

G. H. GLANZMAN, Assistant Examiner.

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