ROCKETS USED IN

FUNCTIONING

ARMED CONDITION

ARMING TIME

MAX. BODY DIAMETER

OVERALL LENGTH

COLOR

MATERIAL

DESCRIPTION:

This fuze, called the "Kealy Fuze", has been designed for use with rocket projectiles, particularly where numbers of rounds are to be fired in salvos from multiple launchers. It is adapted for automatic setting on the launcher through the medium of electric impul-ses transmitted from a control point, increase or decrease of set being rapidly applied at will. Setting of individual fuzes by hand may also be effected by a time ring.

For automatic fuze setting, the launcher is fitted with two pairs of electric magnets for each set of rails, the pole pieces of the magnets extending to within 1/4 inch of the outside of the rounds. One pair of magnets on each set of rails serves to increase the fuze set; the other to reduce it. The fuze incorporates two soft iron cruciform arma-tures, so positioned that when the round is loaded on the launcher the ends of each armature are in close proximity to the poles of a magnet. The arrangement is such that an armature will undergo a partial rotation against the action of a spring when an elec-tric impulse passes through the coils of the proximate electric magnet, and will be re-turned by the spring at the end of the current pulse. Each such oscillation causes mo-vement of a ratchet mechanism associated with the armatures and changes the fuze setting by half a second.

It will be apparent that no electrical or mechanical connection exists between the fuze and the launcher. The setting is effected by the magnetic flux passing from the pole pieces of the magnets, through the intervening air gap and fuze casing, to actuate the armatures. To ensure correct positioning of the armatures with respect to the elec-tro-magnet poles when the round is loaded on the launcher, there is provided on the fuze an external mark, which must be aligned with one of the tail fins on assembly.

Timing is effected by a clockwork train and escapement, which is ordinarily preven-ted from running by a spring-loaded detent capable of setting back on projection. The rate of retraction of the detent is so controlled by the escapement that an accelera-tion sustained for about 0.4 second must be applied before the fuze will arm. When the detent has completed the setback movement, it allows a spring-loaded shutter to move and uncover the detonator and at the same time lock the detent in position.

When the fuze is set "safe" the detent is locked, the detonator is moved out of the path of the striker, and any automatic setting which may have been applied is cancel-led. In addition, with the time ring moved beyond the "auto" position for manual setting, any automatic setting is cancelled and the automatic gear put out of action.

The percussion element will fire on impact with relatively light structures such as are encountered in aircraft.

OPERATION:

The base of the fuze receives the boss of the gaine, which is held in position with screws. The latter may be loosened to permit alignment of the fuze with the round for automatic setting on the launcher. The base carries the detonator shutter which is provided with lugs bearing in the surfaces of the projections on the ring. When the fuze is set "safe", the lower lug bears on the lower portion of the projection, but movement of the ring to the "auto" position causes the lower portion of the projection to clear the lower lug and brings the upper portion into contact with the upper lug, rotating the shutter until the detonator is in line with the axis of the fuze beneath the striker. Si-multaneously, the lobe of the shutter moves out of the path of the arming detent, thereby allowing the fuze to arm on projection.

The base of the fuze supports the timing and release mechanism, which is carried by a number of plates and arranged axially around the hollow striker. The mechanism is en-closed in a brass casing held in position by a ballistic cap of bakelite, which is screwed over the top flange of the internal fuze mechanism. The forward end of the ballistic cap carries the percussion element, consisting of a striker, sleeve, and detonator.

The clockwork train, which times the fuze, is controlled by an escapement, move-ment of which in the unarmed position is impeded by the arming detent extending into the path of the pallet arm. The arming detent is removed from the pellet on setback, starting the clockwork. Rate of movement of the detent is governed by a gear train and escapement through the medium of a pinion engaging on a rack on the edge of the de-tent. This control is such that displacement is completed in about 0.4 seconds when the fuze is subjected to a mean acceleration of 60 g. A safety shutter carried on a spindle pivotted in the base of the fuze is normally held under the striker by its arcuate arm, which bears against the side of the detent. When the latter has moved to its fully setback position, the arcuate arm is allowed to move into a slot in the detent, moving the safety shutter under the action of the shutter spring out of the path of the striker and locking the detent in position. A small initial movement of the detent suffices to re-lease the pallet arm and thus allow the clockwork timing train to start with a minimum delay on projcetion, but the fuze will remain safe until full displacement of the detent permits movement of the arming shutter.

The striker is held cocked against the action of the striker spring by a catch pivoted on the top plate carried by the upper sleeve, to which is attached the inner end of the time train spring. The catch engages a groove in the striker. A downwardly extending finger of the catch, resting against the edge of the firing plate, prevents movement of the catch, under action of the catch spring, and release of the striker, until movement of the timing train brings the finger into a position adjacent to the slot in the firing plate. The time of release of the striker is thus determined by the initial position of the slot in the firing plate relative to the catch finger. Since contact of the finger with the firing plate during the setting operation would introduce undesirable friction, the catch is provided with a stud which serves to lift the finger from the firing plate by initially engaging a ramp carried by a fixed plate of the fuze. The stud rides off the ramp during the early stages of the movement of the timing train.

Automatic setting of the fuze is accomplished by a pair of iron cruciform armatures arranged for limited rotary movement in opposite directions under the influence of mag-netic impulses and against the action of the armature springs. The upper armature car-ries a spindle of an upper pawl tending to be forced by the pawl spring into contact with the ratchet wheel. The ratchet wheel is carried on the same sleeve that carries the firing plate. Normally, the upper pawl is held out of contact with the ratchet wheel by a depending leg on the pawl abutting against an arm A attached to the lower sleeve, to which is also fixed the lower armature. Movement of the upper armature against the action of its spring will first break the contact of the leg and arm and per-mit the upper pawl to engage the ratchet wheel and by continued movement turn the ratchet wheel through a distance of one tooth against the action of the ratchet wheel spring. The lower pawl, having two deending legs, which engages the ratchet wheel when the fuze is set on "auto" retains the ratchet wheel while the upper armatrue is allowed to return to its original position. Repetition of the movement of the armature will cause the ratchet wheel to move a distance of one toeth for each oscillation and as each tooth corresponds to half a second, the fuze setting will be reduced from the maximum of 30.5 seconds by the corresponding number of oscillations. Reverse move-ment of the ratchet wheel is automatic setting is effected by oscillation of the lower armature and its attached sleeve, which carries arm A and arm B. Movement of arm A releases the upper pawl which then bears on the ratchet wheel halfway between two teeth, while movement of arm B serves to lift the lower pawl away from the ratchet wheel thorugh the medium of the leg. The arms A and B are so designed that the upper pawl bears on the ratchet wheel before the lower pawl is lifted. The ratchet wheel is thus allowed to move back the distance of half a tooth under the action of its spring. When the lower armature is allowed to return, the lower pawl first engages the ratchet and then the upper pawl is raised, thereby permitting the ratchet wheel to move back-ward a further distance of half a tooth. Thus each oscillation of the lower armature re-sults in backward movement of the ratchet wheel to the extent of one tooth and con-sequently results in an increase of half a second in the fuze setting.

It will be noted that when the fuze time ring is moved to the "auto" position for au-tomatic setting, the short leg of the lower pawl then rests in a cut-away portion or re-cess of the camplate, and the lower pawl bears on the ratchet wheel. However, when the time ring is moved to the "safe" or the manual setting, the short leg will ride in the outer edge of the camplate, and the lower pawl will be out of contact with the ratchet wheel. The latter will then be free to return under action of its spring, thus cancelling any setting given by automatic means.

Manual setting of the fuze is effected by movement of the time ring, graduated in half-seconds from 0-30. The time ring carries an internal gear which meshes with a pi-nion assembly to rotate a pinion and its associated pinion sleeve and the camplate. The latter has an upwardly extending stud which is adapted to engage a lever mounted for free movement about the axis of the fuze. The ratchet wheel is provided with a similar stud extending downwards into the path of the lever. Movement of the time ring will cause counter-clockwise movement of the camplate until the short leg of the lower pawl rises from the recess of the camplate, raising the lower pawl from the ratchet wheel. The ratchet wheel spring then returns the ratchet wheel to the maximum set-ting, in which position the pin on the ratchet wheel bears on the stop, and the cam-plate stud forces the lever into contact with the ratchet wheel stud. Further movement of the timing ring will cause the ratchet wheel and its associated firing plate to move as one with the camplate.

Functioning of the fuze on impact is caused by operation of a striker and detonator arranged in the nose cap. The striker is held by a metal cap designed to collaps under about 150 lbs. pressure. The upper end of the striker bears on the closing plate. On im-pact the plate forces the striker into the detonator, crushing the cup. The flash from the detonator passes down the central tube and through the hollow striker. If the fuze is armed, the shuttered detonator will be set off by the blast. If the fuze is not armed, the lower detonator will be sealed off by the safety shutter.