US3298310A - Escapement mechanism for clockwork fuzes - Google Patents

Description

Jam 17, 1967 D. e. COLLINS ETAL 3,298,310

ESCAPEMENT MECHANISM FOR CLOCKWORK FUZES Filed Oct. 14, 1964 3 Sheets-Sheet l INVENTORS DONALD G. COLLINS JOHN SEIFNER CLARENCE W. WANDREY ATTORNEYS Jan. 17"

, 1967 D. 5. COLLINS ETAL 3,298,310

ESCAPEIVIEIIIT MECHANISM FOR CLOCKWORK FUZES Filed Oct. 14, 1964 3 Sheets-Sheet 2 INVEN TOR S DONALD G. COLLINS JOHN SEIFNER CLARENCE W. WANDRE Y QLC ATTORNEYS n- 1967 D. G. COLLINS- ETAL 3,

ESCAPEMENT MECHANISM FOR CLOCKWORK FUZES Filed'Oct. 14, 1964 s Sheets-Sheet a INVENTORS DONALD G. COLLINS JOHN SE/FNER CLARENCE W. WANDREY x' W ATTO NEYS United States Patent 3,298,310 ESCAPEMENT MECHANISM FOR CLOCKWORK FUZES Donald G. Collins, Deerfield, Mass., and John Serfner,

Chicago, and Clarence W. Wandrey, Wheaton, Ill., assignors, by mesne assignments, to the United States of America as represented by the Secretary of the Army Filed Oct. 14, 1964, Ser. No. 403,957 1 Claim. (Cl. 102-84) This invention relates to improvements in escapement mechanisms and, more specifically, to a simplified time delay escapement mechanism for use with fuze armmg devices.

Fuzes which contain mechanisms to delay the arming of the fuze after a projectile has been fired to insure the safety of the person firing the projectile are well known and take a variety of different forms. One conventional method of providing an added time delay for a f-uze involves the use of a driving element, such as a pinion or escape wheel, rigidly attached to a spring-driven rotor, and .a mating driven element, such as a gear or pallet mounted on a stator portion of the fuze proper, which is usually the rotor housing. This conventional approach, however, creates a need for very close mechanical tolerances. which is not compatible with the loose assembly tolerances normally provided for assembling a rotor to a fuze.

Another common expedient for providing a substantial time delay in fuzes requires the use of a gear train to provide sutficient angular displacement of an escape wheel. In such time delay escapement mechanisms, a first gear is usually affixed to the rotor shaft, and a pinion meshes with this gear to provide the necessary rotary motion to an escape wheel. The escape wheel then meshes with a pellet pivoted to. operate in an oscillatory motion, thus providing in combination, the required delay. However, the space requirements for these additional components require modifications to the basic fuze to keep within the existing fuze dimensions. Also, to maintain the necessary rotor torque, a thicker rotor spring is often necessary, which also adds to the space requirements.

In designing a fuze for projectile use it is important to have a certain minimum arming distance. The arming distance is normally considered to be the distance a projectile travels from the time it is fired to the time it is armed, jor ready to be exploded. With projectiles or shells having large muzzle velocities, a substantial time delay before arming is not of great importance because a safe distance is quickly achieved. However, with shells having smaller muzzle velocities, it is very important to provide a time delay sufiicient to allow the shell to travel a minimum safe distance before it is armed. Such a time delay protects the person expending the shell and is necessary to meet minimum arming distances specified for particular shells.

In order to increase the time for arming a fuze after firing, it has been suggested to use a setback-arming device having a sequential leaf system to permit a projectile to get beyond a safe distance before it is armed. The static arming time of such a system usually works wellwith higher muzzle velocity projectiles but is inadequate. for low and intermediate muzzle velocity am- 3,298,310 Patented Jan. 17, 1967 ever, the time delay added by such increase in rotor travel is not sufficient to meet the minimum distance requirements for low muzzle velocity projectiles.

Then, escapement mechanisms were introduced into the fuzes to increase the time delay. As mentioned above, such added escapement systems required more space than was generally available, and were also quite complex, expensive, as well as time consuming and difiicult t manufacture. 7

As a result of the inadequacies of the present time delay systems, a need has arisen to provide means for use with a fuze which is extremely simple, has very low space requirements, and has a high degree of ruggedness. As far as possible, the machining costs for producing such a time delay in fuzes should be kept to a minimum, while maintaining high reliability. Further, such a time delay should be produced which requires little or no modification of the basic fuze design. Finally, the time delay mechanism should be able to withstand high accelerations without a degradation of performance.

In accordance with the present invention, novel means have been provided to permit a time delay of sufiicient magnitude for safe firing of low muzzle velocity projectiles. By virtue of the present invention, a fuze would not be armed until the minimum safe distance has been covered. Also, the time delay escapement mechanism of the present invention requires very little space in the projectile.

It is accordingly a primary object of the present invention to provide novel time delay escapement means.

It is still another important object of the present invention to provide a novel time delay escapement system which is simple and extremely rugged.

It is a further object of the present invention to provide a novel time delay escapement mechanism that provides a substantial time delay in a smaller space and with greater simplicity of design than is usual for mechanisms providing time delays in this range.

It is still another important object of the present invention to provide mechanical time delay means for fuzes which employ only an escape wheel and an oscillating member as the delay elements that act in conjunction with a three-quarter turn displacement of a spring-driven rotor.

It is a further important object of the present invention to provide novel time delay escapement means for explosive fuzes which make possible sufiicient angular displacement of the escape wheel in a small device with sufficient time delay, but without the use of a gear train.

It is still another object of the present invention to provide a rugged time delay escapement mechanism designed to assure proper component orientation with a minimum of space and complexity.

It is a further object of the present invention to provide a time delay escapement mechanism of relatively few component parts requiring little modification in the basic design of the fuze with which it is used.

It is still another object of the present invention to provide a time delay escapement mechanism for use with a fuze which can withstand high acceleration without performance degradation.

It is still a further object of the present invention to provide a time delay escapement system for use with a fuze having a heavy rotor wherein the combination produces a smoother rotation without disturbing the actual time delay resulting from the escapement wheel-pallet action.

These and other important objects and advantages of 3 the present invention will become more apparent in con,- nection with the ensuing description and appended claims, as Well as the attached drawings wherein:

FIGURE 1 is a front elevation view of the fuze and escapement mechanism emboding the principles of the present invention;

FIGURE 2 is a side elevation view of the fuze and escapement mechanism shown in FIGURE 1;

FIGURE 3 is a rear elevation view of the fuze and escapement mechanism shown in FIGURE 1;

FIGURE 4 is a sectional view of the fuze taken along the line 44 of FIGURE 2;

FIGURE 5 is a partial enlarged section showing the time delay escapement mechanism of the present invention;

FIGURE 6 is a vertical sectional view on line 6-6 of FIGURE 5; and

FIGURE 7 is an exploded perspective view of the essential parts of the time delay mechanism.

As previously indicated, the present invention involves novel time delay escapement means, and in particular, a time delay escapement mechanism for fuzes used in projectiles.

The operation of the time delay escapement means of the present invention is based on an escape wheel-pallet principle. Preferably, the escape or star wheel is connected to a rotating member and is caused to rotate a portion of a full turn. The pallet, which is essentially an oscillating mass, is designed to engage the teeth of the escape wheel to provide the necessary time delay. The escape wheel is connected to a heavy mass which slows the acceleration of the escape wheel due to its inertia, and the rotational inertia of the pallet also is high. The pallet is provided with an opening a given distance from its axis of pivot and two wedge-shaped teeth project into 'the opening in position to engage the teeth of the escape wheel. Upon rotation of the star wheel, the pallet oscillates while the rotor inertia tends to maintain the rotation smooth by alternately helping and hindering the action of the escape wheel and pallet combination without disturbing the actual time delay. Thus, there is provided simple means for causing a time delay. In addition to this broad concept, the present invention contemplates more specific concepts including the provision of particular structural elements which are peculiarly well adapted to effect the broad objects of the present invention, as will be more particularly described hereinafter.

The basic fuze environment for the time delay escapement means of the present invention is best illustrated in FIGS. 1-4. As shown therein, and especially FIG. 2, the fuze proper consists of three minor sub-assemblies, namely, a spring driven rotor 10, a sequential-leaf set back release mechanism 12, and an arming delay mechanism 14. A rotor housing assembly and an aluminum shield assembly, both of which are not shown for the sake of clarity, complete the fuze structure.

The rotor 10, which is a single machined piece, has a passageway 16 for receiving an electric detonator which arms the fuze. As shown in FIG. 3, a spring biased pin 18 extends from the larger diameter portion of the rotor to provide the electrical contact necessary between the electric detonator and power source for fuze arming. A locking-pin slot 20 is formed in the rear face of the rotor 10 along with a blow-through hole 22 leading to the passageway 16 in the rotor 10. The rotor 10 is mounted on a shaft 24 which extends through the release mechanism 12 and the arming delay mechanism 14. As shown in FIG. 1, the outer end of the shaft 24 is slotted to form a groove 26 to accept one end 27 of a rotor spring 28. The other end 29 of the rotor spring 28 is attached to a front bearing plate 44. Flats 31 are formed on the outer end of the shaft 24 to provide a loose keyed fit with the star wheel of the time delay escapement mechanism as will be more specifically described hereinafter. As shown most clearly in FIG. 4, a small pin 30 extends from the front face of the rotor 10 to lock the rotor in its one angular position, which is the safe position for the fuze.

The release mechanism 12 comprises a base plate 32 having a 270 slot 34 formed therein and holes 36 for receiving attaching screws, a pair of which are indicated by reference numerals 38. The base'plate 32 also contains a pair of holes 40 adapted to receive spring retaining pins 42 and 43. A front bearing plate 44 forms the outer portion of the release mechanism 12 and is attached to the base plate 32 by means of the screws 38 which pass through sleeves 46 to space the plates.

A setback-actuated arming device comprising three interlocked sequentially operating leaves 48, 50, and 52 is used to arm the fuze after a projectile containing the fuze has been fired. As best shown in FIG. 4, the leaf 48 is restrained by a spring 54 mounted on the pin 42, while the leaf 50 is restrained by a spring 56 mounted on the pin 43. Sleeves 58 are provided on the pins 42 and 43 to prevent the springs 54 and 56 from sliding and losing their engagement with the leaves 48 and 50. An antireset spring 60 is attached to the base plate 32 by rivets 62 to prevent the leaf 52 from rebounding to the safe position and relatching the rotor in high acceleration shells.

The leaf 48 is pivotally mounted on a pin 64 and contains an enlarged opening 66 to allow leaf movement about this pivot. The leaf 50 is pivotally mounted on a pin 68 and contains an enlarged opening (not shown) to accomrnodate its movement around the pivot pin 68. The leaf 50 also contains a pin 70 which bears against the upper corner of the leaf 48 as shown in FIG. 4, when the fuze is in its safe position. The leaf 52 contains a pin 72 (FIG. 2) which bears against the upper corner of the leaf 52 in a similar manner. An extension 74 of the leaf 52 holds the rotor pin 30 in the fuze safe position as shown in FIG. 4. Thus it can be seen that the three leaves are interlocked, and when the fuze is in its safe position, the interlocking of the springs prevents arming of the fuze if the shell were to be dropped or mishandled.

In operation a sustained acceleration of at least 2500 g is required to cause the leaf 48 to pivot in a clockwise direction (FIG. 4) under the influence of the acceleration. The leaf 48 pivots around the pin 64 against the force of the spring 54- and allows pivoting of the leaf 50, which is interlocked with the leaf 48, around the pin 68 against the force of spring 56. This sequential set back of the leaves 48 and 50, removes the bias force from the leaf 52. The rotor spring 28, which urges the rotor 10 in a clockwise direction, provides a force sufficient to overcome the restraint of the extension 74 of leaf 52 against the rotor pin 30, causing the rotor 10 to rotate 270. The rotor pin 30 travels this distance in the slot 34 of the base plate 32 and when rotor pin 30 is in its extreme clockwise position in the slot 34, the pin 18 of the fuze detonator is in position to arm the fuze.

From the above description, it can be seen that the only delay from the time that the projectile is fired to the time the fuze is fully armed in the time it takes the sequential leaves 48, 50, and 52 to move from their safe position to unlock the rotor 10, plus the time it takes the rotor pin 30 and the rotor 10 to rotate 270. As pointed out above, in high muzzle velocity shells this small delay may be sufficient, but in low muzzle velocity shells an added time delay is required.

The arming delay mechanism 14 provides the necessary arming delay required for the low and intermediate muzzle velocity shells. As shown in the drawings, especially FIGS. 5-7, this mechanism consists essentially of a plate or pallet 76 and a star or escape wheel 78. In FIG. 7, it can be seen that the pallet 76 comprises a flat plate having a large opening 80 formed therein. A pair of wedge-shaped teeth 82 and 84 are formed on opposite sides of the opening 80 and project into the opening in position to engage the teeth 86 of the star wheel 78. The teeth 86 of the star wheel are contoured to approximate an involute curve to produce a relatively constant separating force between the star wheel 78 and the pallet 76 as the star wheel is rotated. The pallet 76 has a tab 88, which isbent below the plane containing the opening 80 and contains a hole 90 formed therein to pivotally connect the pallet to a screw 104 secured to the front bearing plate 44. At the other end of the pallet 76 a slot 92 is formed to receive a bent over finger 94 of the star wheel bracket 96. To increase the mass of the pallet 76 without increasing the space requirement and to utilize the space present in the fuie, the other end of the pallet is bent overto form a flange 98. Thus, the center of gravity of the pallet:76 is placed relatively far from its pivot point to maximize the rotational inertia of the pallet.

The star wheel 78 is mounted in an opening 100 in the bracket 96. An aperture 102 is provided on a lowered end 103 of the bracket 96 to accommodate the screw 104 attaching the star, wheel-pallet assembly to the front bearing plate 44. t A washer 106 is provided between the head of screw 104 and the lowered end 103.

The star wheel and bracket assembly is put together by placing the. upper portion of the star wheel 78 through the opening 100 in the bracket 96. The hub 110 of the star wheel 78 .fits within the opening 100 and the reduced end portion 108 of the star wheel 78 is rolled over a washer 112 as shown in FIG. 6 to fix the star wheel against axial movement while leaving it free to rotate.

A slot 116 is formed in the bore of the star wheel 78 to loosely. key it to the flats 31 on the outer end of the shaft 24..

The assembly of the time delay escapement mechanism on the fuze is a simple operation. The tab 88 of the pallet 76 is first placed on the front bearing plate 44 with the main portion of the pallet 76 lying above the rotor spring 28 because the tab 88 is bent downward. The bracket and star wheel assembly is then placed over the pallet 76 with the star wheel 78 dropping into the opening 80. Since the end 103 of the bracket 96 is also bent downward it can be seen that the central portion of the star wheel and bracket assembly lies above the pallet 76. The screw 104 with the washer 106 thereon is then placed through the aligned holes 102 and 90 of the bracket 96= and the pallet 76 and screwed into the threaded opening 107 of the front bearing plate 44. The bent over finger 94 of the bracket 96 fits into the slot 92 of the pallet 76 .to restrict the amplitude of oscillation of the pallet. The fully assembled time delay escapement mechanism isshown in FIGS. 5 and 6. To complete the assembly, the shaft 24, with the inner end 27 of the spring 28 positioned in the slot 26, is then passed upwards through the slot 116 of the star wheel 78 in the opening 80.

With the above arrangement of parts in mind, it is apparent that the pallet 76 is pivotally mounted with respect to the front bearing plate 44 and the remainder of the fun to oscillate in a plane substantially perpendicular to the shaft 24. As seen in FIG. 5, when the rotor shaft 24 rotates in the clockwise direction, urged by the rotor spring 28, the teeth 82 and 84 will engage and disengage the teeth 86 of the star wheel 78 to oscillate the pallet from side to side about the screw 104.

In operating the device, the rotor spring 28 is wound by rotating the rotor 10 relative to the remainder of the fuzeh As shown in FIG. 4, the fuze is held in its wound safe position by the extension 74 of the leaf 52 which bears against the pin 30 to hold the rotor in place. The fuze isthen assembled and placed into a projectile with the rotor axis perpendicular to the longitudinal axis of a the projectile and the end containing the screw 104 extending toward the rear of the projectile. The interlocked leaves 48, 50, and 52, keep the rotor pin 30 and the fuze itself in the safe position until the projectile is fired and large acceleration forces sequentially depress the leaves until the final leaf 52 unlatches the rotor 10 by releasing the rotor pin 30, as previously described. Thereafter,

the spring 28 with its one end 27 retained in the slot 26 in the shaft 24, rotates the rotor in a clockwise direction as viewed in FIG. 4 and the shaft 24 rotates the star wheel 78 since it is keyed to the shaft. The teeth 86 of the star wheel 78 engage the teeth 82 and 84 of the pallet 76 to oscillate the pallet. The spring 28 provides a relatively constant input force to drive the star wheel 78, and the repeated reversal and re-acceleration of the pallet 76 retards the acceleration of the star wheel to produce relatively uniform motion. The relatively heavy mass of the rotor 10 which is connected to the star wheel through the shaft 24 tends to slow the acceleration of the star wheel because of its inertia. In other words, the rotors inertia tends to maintain its rotational speed alternately helping and hindering the action of the star wheel and pallet combination to produce a smoother rotation without disturbing the actual time delay resulting from the star wheelpallet action. Thus the time required for the input torque supplied by the spring 28 to move the rotor 10 through the desired 270 angle of rotation is added to the time delay introduced by the star wheel 78 and pallet 76 to achieve the desired total time delay.

When the rotor 10 completes its 270 turn, the pin 18 of the detonator in the rotor completes an electrical circuit which arms the fuze at a distance far enough away from the point of firing to preclude any damage if the projectile were to explode.

Thus, with the time delay escapement mechanism of the present invention, a substantial time delay is provided in a smaller space and with greater simplicity of design than is usual for time delay mechanisms in this range. Only an escape wheel and an oscillating mass are provided as the delay elements, which act in conjunction with a 270 displacement of a spring driven rotor in the fuze. A gear train is not required and the relatively long time delay is achieved by the novel pallet design in which the rotational inertia has been increased by completely encircling the escape wheel.

The simple design of the present invention enables both of the moving parts in the escapement to be mounted on a single rigid support, thereby assuring the required close control over assembly tolerances. The required relative motion between the two parts is achieved by loosely keying the driving element into a rectangular slot in the escape wheel. This loose keying arrangement permits normal free assembly of the rotor, while still maintaining tight tolerance control of the escapement. Further, the larger mass of the rotor provides a more favorable operation of the time delay mechanism without an increase in the space requirement. The present escapement mechanism can be added to a standard production fuze in the available small space with little modification of the basic fuze design. Further, the mechanism can withstand high acceleration without any performance degradation.

This invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restricted, the scope of the invention being indicated by the appended claim rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claim are therefore intended to be embraced therein.

What is claimed is:

A projectile fuze having a rotor of relatively heavy mass and a shaft with two ends extending therefrom; a plate surrounding said shaft and being substantially perpendicular to said shaft; an escape wheel concentrically mounted on said shaft on one end of said shaft, said mounting including a rectangular portion on one end of said shaft and a rectangular slot formed in said escape wheel, said escape wheel having a plurality of teeth, said teeth being contoured to approximate an involute curve; a substantially fiat rectangularly shaped pallet member surrounding said escapement wheel, said pallet member having two ends, one of said ends connected to said plate to allow said pallet to pivot about said one end, the other of said ends being downwardly turned to increase the moment of inertia of said pallet about said one end, said pallet having two opposed pawls to mesh with said teeth of said escapernent Wheel, said pallet further having a slot formed adjacent said turned down end; a bracket connected to said plate at said pallet pivot point and being substantially parallel to said plate and said pallet, said bracket having a finger thereon to cooperate with said pallet slot to limit the pivotal amplitude of said pallet.

References Cited by the Examiner UNITED 10 BENJAMIN A. BORCHELT, Primary Examiner.

G. H. GLANZMAN, Assistant Examiner.

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