US2849956A - Dummy fuze - Google Patents

Description

P 2, 1 c5. w. JOHNSON ETAL 2,849,956 DUMMY FUZE- Filed Feb. 26, 1957 INVENTORS, I H Bent-Q's lfianuvski I I g] BY Ui'hnMJuhnsun sults.

United States Patent DUMlVIY FUZE Otho W. .lohnson and George J. Ganovski, Baltimore,

Md., asslgnors to the United States of America as represented by the Secretary of the Army Application February 26, 1957, Serial No. 642,624

3 Claims. (Cl. 102-70) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to a dummy fuze, and more particularly to an inert device assembled to resemble a live fuze of the type carried by the projectile fired from the 120 mm. automatic gun having automatic fuze setting equipment.

Dummy fuzes are attached to target practice ammunition where a full functioning fuze is not required. Fuzes of this type may be fabricated from burned out or rejected inert parts of service fuzes, or manufactured especially for the purpose for which they are intended. Whether fabricated from disused parts or especially manufactured, the assemblies are completely inert. In general, the fuzes are intended to simulate a specific model, or one type of service fuze. The contour and weight of the service fuze which is to be simulated are approximated closely in the dummy fuze for use with practice ammunition, and to give the proper feel when used with drill ammunition. This policy also permits the use of drill ammunition in conjunction with fuze setters for training in preparing ammunition in conjunction with fuze setters for firing and in servicing the piece. Most dummy fuzes are extremely simple in construction but essential features of the simulated service fuze are incorporated in some types.

Heretofore, existing dummy fuzes for use with the 120 mm. projectile have produced unsatisfactory re- After being used for only three or four operations, these fuzes became unserviceable due to wear and tear at points of adjustment and thereby incurred great expense through the necessity of providing a large number of dummy fuzes.

This wear and tear upon the dummy fuzes is caused chiefly by their employment in checking the M18 and M19 automatic fuze setters. Fuzes of this type generally have a base upon which the time setting indicia is engraved. A rotatable lower cap is rigidly secured to an upper cap for rotation as a unit therewith. On the lower cap and on the base, there is provided a setting grove, one each, into which the setting jaws of the fuze setter fits in order to rotate the lower cap in a clockwise direction to the desired time delay setting for arming. The groove in the lower cap is subject to more wear than the groove in the base due to the fuze setter moving the lower cap. Another point of wear is the safety set screws usually found on fuzes of this type. The screws prevent rotation between the base and lower cap during handling and the possibility of premature arming of the fuze. After a very short period of use, wear at these points rendered the fuze useless and it was necessary to either replace the lower cap or obtain a new assembly entirely. With the present invention, it is proposed to eliminate these objectionable features by providing a readily replaceable insert of hardened tool steel to replace the existing setting groove and to ice incorporate the set screws in a setting groove cut in the insert, thus providing long and continuous. use of the fuze. It is further proposed to provide an adjustable means to provide the proper torque between the base and the rotatable lower cap portions of the fuze.

It is therefore a principal object of this invention to provide a dummy fuze capable of long and continuous use.

It is another object of the invention to provide a dummy fuze for use by anti-aircraft units in training for checking the M18 and M19 automatic setters.

A further object is to provide a fuze having a replaceable hardened tool steel insert at the area of the set screws holding the rotatable parts of the fuze and to provide adjustable torque means to provide relative rotation between the fuze setting elements. of the fuze.

The invention will be best understood from a consideration of the following detailed description taken in connection with the accompanying drawing, it being understood however, that the invention is not limited by the specific illustration or description but that uch illustration and description constitutes a preferred embodiment of the invention.

In the drawing: I

Fig. 1 is a longitudinal section taken along line 11 of Fig. 2, illustrating in assembled relation the dummy fuze of the invention,

Fig. 2 is a side elevation of the fuze,

Fig. 3 is a detail section taken along line 3-3 of Fig. 2, and,

Fig. 4 is a perspective view of the hardened metal insert.

Referring more particularly to the drawings in which 1 indicates generally a dummy fuze constructed in accordance with the invention having a base member generally indicated as at 2, a lower cap member indicated generally by 3 and an upper cap 4. Base 2, lower cap 3 and the upper cap 4 are identical to the parts of the fuze which the fuze of the invention is intended to simulate. The base 2 comprises an annular body having a rearward externally threaded portion 5 for attachment to a projectile (not shown) when desired, an intermediate forwardly tapering portion 6 of larger diameter than portion 5 constituting the time setting ring of the fuze and a forwardly reduced portion 7. The base 2 is provided with a rearward axial bore 8, a forward axial bore 9 and a reduced axial bore 10 communicating between the forward and rearward bores. The lower cap 3 comprises an annular member having a forwardly tapered rearward portion 11 and a forwardly extending externally threaded portion 12. The lower cap 3 is provided with a rearward axial bore 13, of a diameter to permit the reduced portion 7 of the base 2 to rotate therein, a forward axial bore 14 and an intermediate reduced axial bore 15 communicating between bores 13 and 14. The upper cap 4 which servesv as the windshield is internally threaded as at 16 at its rearward end and is adapted to threadably engage the threaded portion 12 of lower cap 3 for rotation therewith.

Adjustable means are provided to apply sufiicient torque between the base and the lower cap for relative rotational movement therewith and consists of a cap screw 17, flanged adapter bushing 18, Belleville spring 19, a pair of fiat washers 20 and 21 and safety nuts 22. These members are assembled in the manner illustrated in Fig. 1. The flanged adapter bushing 18 fits into the bore 15 and has an axial bore 23 of the same diameter as bore 10, both bores 10 and 15 adapted to receive the cap screw 17. Means preventing wear in the setting groove of the lower cap 6 and safety screws is provided which consists of a mortise 24 (see Fig. 3) cut in the giving long and continuous use.

rearward portion of the peripheral surface of lower cap 3. Mortise 24 is intended to replace the existing setting groove in the lower cap and is located exactly in this area. An insert 25 of hardened tool steel fits snugly within the mortise 24 and is provided with a setting groove 26. As the tool setter to be employed for this type of fuze is rotated clockwise insetting the fuze,

the lands of the insert are of different heights. The left land 27 is cut lower than the land 28 to provide a vertical face 29 for engagement with lugs on a fuze setter (not shown) to engage, thu insuring only a clockwise movement of the lower cap. Threaded holes 30 are provided in the floor of the setting groove'26 and are counter bored as at 31 to provide a planar surface to the groove 26 receiving screws 32. Suitable indicia 33 is etched on the tapered surface of the base member 2 and a setting mark 34 is etched on the lower cap (see Fig. 2) which serves as the time training ring of the fuze. The base member 2 is also provided with a setting groove 35 for use when setting the fuze by automatic setters.

In operation, the torque means may be adjusted by turning the cap screw 17 to provide the amount of torque for the rotation between the lower cap 3 and base 2. If it is desired, the fuze may be screwed to a projectile after the torque adjustment has been completed. As the ramming and setting operation of the automatic 120 mm. gun are completely automatic and the setting desired is transmitted by a director to the fuze setter electrically, no hand setting is necessary. The jaws of the fuze setter (not shown) will fit into setting grooves 26 and 35 and will automatically rotate the lower cap about the base until the predetermined setting for time delay is reached.

The fuze of the invention is also adaptable to practicing hand setting. In this operation a hand setter (not shown) is applied on the lower cap until its lug engages the setting groove 26 and the bore may be held against rotation with a fuze wrench (also not shown) by engaging whench grooves 36 in base 2. The lower cap is then turned with one hand while the other hand holds the base against rotation by the fuze wrench until the mark 34 registers with the desired index line of the indicia 33.

It is apparent from the foregoing that a highly practical training fuze has been devised which is capable of The fuze of the invention has provided a training fuze that is easily adjustable for torque to provide the right amount of force to be applied to rotation in setting the fuze. As the fuze has eliminated wear and tear at the points of manipulation, an almost indestructible training device has been attained.

It is to be understood that the form of the invention herewith shown and described, is to be taken as a preferred example of the same, and that variou changes to a projectile, a rotatable lower cap and an upper cap rigidly secured to said lower cap, said base having forward and rearward axial bores and a reduced axial bore communicating between said forward and rearward bores, said cap having forward and rearward axial bore and a reduced axial bore being of larger diameter than said reduced bore in said base, and means for securing said base and said rotatable lower cap in coaxial relation comprising a flanged bushing having a bore of substantially the same diameter as said reduced bore in said base, a cap screw received in said reduced bore in said base and said bore in said bushing and means for providing adjustable rotational torque between aid base and said lower cap comprising an adjustable nut threadably engaging the forward end of said cap screw and a Belleville spring disposed on said cap screw between said flanged bushing and siad nut.

2. In a dummy fuze, a base for attachment to a projectile, said base defining a forwardly extending annular reduced portion, a lower cap adapted to receive the forwardly extending reduced portion of said base for rotation therein, an upper cap rigidly secured to said lower cap for rotation therewith, pivot for said lower cap centrally disposed within said base and said lower cap holding said base and said lower cap in coaxial alignment and said lower cap for rotation about said reduced portion on said base and a hardened metal insert adapted to be inserted in a mortise provided in the rearward peripheral surface of said lower cap, said insert being milled to define a longitudinal setting groove having a planar floor and smooth vertical side walls, the height of one wall being less than the other said highest wall to provide a fuze setter engaging surface, said insert being bored and counterbored to receive set screws piercing said lower cap to engage the peripheral surface of said reduced portion on said base.

3. In a dummy fuze having a longitudinal axis of symmetry, a base member for attachment to a projectile, a rotatable lower cap, an upper cap rigidly attached to said lower cap for unitary rotation therewith, pivot means securing said base and said lower'cap in coaxial alignment and for rotation about said base, said means being disposed axially within said base, a spring adjustably associated with said pivot means to permit the application of relative rotational torque between said lower cap and said base and a detachable fuze setter engaging member adapted to be received in a mortise provided in the rearward peripheral surface of said lower cap.

References Cited in the file of this patent UNITED STATES PATENTS 1,707,414 Pfafi Apr. 2, 1929 2,262,068 Towner Nov. 11, 1941 2,397,055 Sekella Mar. 19, 1946 2,461,793 Whitehead Feb. 15, 1949 2,709,963 Butterworth June 7, 1955

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