US2837999A - Base detonating fuze - Google Patents

Description

l.lune 1o, 1958v H. B. LINDSAY 2,837,999

BASE DETONATING FUzE Filed July 26, 1954 Fzl.. 23 43V l63 7/ 3;] 24 Iza 56% \f, 7 7a I l a ,69

2 l l 5 9/ 132' 2;7) \66 64 L6 /5 5/ 7/ 56 X/ ff /3/ 6/ A9 j 34 2a INVENTOR United 'States Patentfce 2,837,999 BASE DETONATING FUZE Harvey B. Lindsay, Oakland, Calif. Application July 26, 1954, serial No. 445,852

` claims. (ci. 1oz- 75) This invntion relates to base detonating fuzes for projectiles, and more particularly towards a base detonating fuze in which means are incorporated for effecting tletonation of the projectile only after a short period of time has elapsed after initial impact.

Fuzes falling into the above classification are used in modern warfare where it is desirable to have detonation of the projectile occur only after full or partial penetration of the target. This is of course readily distinguishable from a point detonating fuze which effects detonation substantially simultaneously with impact. A point detonating fuze will render a projectile ineffective lagainst armor plate, thick concrete Walls or earthwork f fortifications possessing substantial depth, as the detonation or explosion occurs in a non-vulnerable'area. Con versely, if the projectile is provided with `an armor piercing nose portion as well as a delay type of base fuze, the shell will rst penetrate the protective armor or other target covering and then explode, thereby in-l flicting far greater damage on the target.

Heretofore, the majority of delay fuzes were lixed with respect to the elapsed time interval between initial impact and subsequent explosion. In general, the delay was provided by utilizing either intricate mechanicalmeans or by a successive train of ignitions or explosions until finally the main detonating or projectile burster charge was reached and., exploded. With this xed delay period, once impact occurs, the mechanism or chemical train is initiated, Vand irrespective of the nature of the With the foregoing in mind,it is an object `of theV present invention to provide -a base detonating fuze for 1 projectiles arranged to effect explosion of the projectilev at substantially the point of greatest penetration of the projectile in a target whereby optimumresults .may bev obtained. j V Another object of my invention is to provide a fuze of the character described in which the time interval penetration may be several The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of the preferred form ofl the invention which isillustrated in the drawing iaccompanying and-forming part of the specification. lt is to be understood, however, that variations in the showing made by. the said drawing and description may be adopted within `the scope of the invention as set forth l in the claims.

Referring to saiddrawing:

Figure l is a longitudinal cross-sectional view of the fuze of -the `present invention, with the parts shown in their respective positions before firing.

Figure 2 is a view similar to Figure 1, but illustrating the parts in the positions they assume during flight.

Figure 3 is another View similar to Figure 1, but here indicating the positions of the parts after impact of the projectile has commenced.

Figure 4 is a cross-sectional view taken substantially in the plane indicated by line 4-4 of Figure 2.

Figure 5 is a cross-sectional view taken through the rotor assembly, the general plane of the view being indicated by line 5 5 of Figure 3.

Figure 6 is a cross-sectional view taken substantially at the plane represented by line 6-6 of Figure 3.

Figure 7 is a portional view of a slightly modified form lof detonating arrangement.

The fuze about to be described is readily distinguishable from 'the point detonating fuze disclosed in my copending application, Serial No. 435,678, filed June l0, 1954, now U. S. Patent No. 2,808,000, as the latter fuze was 'l designed to effect detonation substantially simultaneously between initial impact and subsequent explosion is automatically variable and dependent upon thev physical` characteristics of the target. l I

A further object of this invention is to provide a fuze as hereinabove described which will remain in a safe unarmed position until impact of the projectile on the target notwithstanding blows or shocks resulting from handling, transporting or firing the projectile.

Yet another object of this invention is to providev a fuze of the above type which is extremely reliable and,v accurate in operation, but which may be produced at alower Cost than its Cgnvenfionalgwuntenart.a, e

with even the slightest impact, while the present fuze, as above explained, is arranged to permit detonation aftera period of time has elapsed after impact so as to permit-thepro'jectile to penetrate the target to the fullest extent possible before explosion occurs.

Referring to the accompanying drawing, the fuze of the `present invention-will be seen to include a suitable casing 12, here shown as generally cylindrical in form, whose rear end portion may be threadedly attached to a rear blocl 13 which is further threaded for attachment to the base 14 of a shell or projectile (not shown). As is Well known in the art, base detonating fuzes of this general character are carried entirely within the rear portion of a shell and along the longitudinal axis thereof in proximity to the burster charge, with the fuze arranged to actuate-the latter.

Casing 12 and rear block 13 partially define an axially extending chamber 16 whose front end is substantially enclosed by a rotor assembly, generally indicated by the numeral 17. A passage 18, the function and details of which will be later described in detail, extends along chamber 16 dfrom block 13 to the rotor assembly so :is to provide communication therebetween.

Rotor assembly 17 consists of a generally cylindrical rotor block 19 having a transverse bore 21 provided therein, with the axis of such bore lying in the plane of the longitudinal axis of chamber 16 and substantially perpendicular to such axis. The outer peripheral surface of block 19 may be threaded as shown at 22 for attachment to the forward end of casing 12. Preferably, in order to facilitate manufacture and assembly of the entire rotor assembly, the block 19 is made in two portions, 3A and 24, each ofthe portions having a semi-cylindrical figurative, ,which, when the portions are brought together andecuredby. pres s t dowel pins 26, lcooperate to dc- Patented June 1G, '1958 A I. .1 fine the rotor bore 21. As bore 21 terminates inwardlyf the opposed surfaces of the block and is aligned with a pair of smaller bores 27 whose function will be presently explained.- Y, I'ffl Mounted for rotation in'bore 21 is a cylindricalfrotor, 28 having axial projections in thenature of axles; 29: which arerrotatable in the bores 27v of thevblock. It will' thus be seen that rotor.28 is fixed against movement' transverse to the casing axis, but is freely rotatable about a transverse axis wherebyl it may rotate ,from a first` position illustrated in Figure 1 to a second position shown in Figure 3.

Rotor 28 is designed to carry the primer (if required) and the detonator of the fuze, which as here illustrated comprise a generally cylindrical pellet 31 of primer mixture, azide, or the like. Pellet 31, is disposed within a diametrical bore 32 provided medially of the ends ofthe rotor so that such pellet will lie on the axis of the casing when the rotor is in armedposition.' More particularly, a tubular member 33 is tixedly secured in ther bore `32 with one end thereof extending;l beyond the rotor pe riphery, with such member defining a pellet chamber 34.

t abscess will best be seen in Figure 5,H

the passage 18, the stops 41 and/or 38 may be moved forwardly against the pellet, detonating the latter, and resulting in ignition or explosion into the ash duct and consequent explosion of the main charge in the shell.

In order to hold the rotor in the above described safe and armed positions, a pair of notches 51 are provided on the outer periphery of the rotor, such notches being spaced apart 90 degrees and being sequentially engageable by a spring detent 52, which is preferably suciently pellet for exploding the latter when the rotor is in its with two or more spaced peripheral grooves v,36, such grooves being adapted to receive pellet stops 37 and 38.5

The latter are constructed from thin spring metal whose shape is best seen in Figure 6. They may be perforated or carry a projection as will be hereinafter discussed. The opposed portions 39 have a slightly` greater diameter than the diameter of the grooves 36 sothat when seated in the grooves, the stops will be under compression bending stress and flex into the curvate shape' shown. A pair of grooves, and thus the front and rear stops 37 and. 38, are spaced apart slightly greater than the length; of the detonating pellet to retain the same in fixed position in pellet chamber 34. As will be later explained, detonation of the pellet occurs when the rear stop 38 is struck and forcibly moved against the pellet. It might be wellV to here explain that where a lead azide detonator is.,

used, actuation requires the piercing by a .sharp instru' ment which causes friction heating in the crystals resulting in initiation of a flash and shock wave. With this type of pellet, the arrangement illustratedin Figurev 7 may be used. As shown, a third spring metal element 41 is tlexed into a groove spaced rearwardly of the stop 38 groove, and is provided with a piercing point 42.

Such point, upon forward movement of element 41,

passes through a central aperture in stop 38, and pierces the pellet 31.

Returning now to the rotor block, it will-be noted that the forward end thereof is provided with an axial passage 46 which serves as a flash duct between the detonator pellet and the projectile booster or burster charge. The rear end is provided with an aligned axial passage 47 which receives the leading end of passage 18. Also,.to permit rotation of the radially extending pellet receiving member 33 upon rotation of its associated rotor, an arcuate cut-out portion 48 is provided in the block. In this manner, the rotor in the position shown in Figures 1 and 2, renders the fuze in its safe or unarmed position, for there is no communication between passage 18 and the detonating pellet, nor is there any communication between the latter and the ash duct 46. However, to further render the fuze safer, even if the pellet should explode when the rotor is in its unarmed position, I

provide a safety passage 49 which connects pellet chamy ber 34 and casing chamber 16 so that the effect of premature detonator explosion will be dissipated in the relatively large casing chamber rather than permitting high explosive pressures building up in the pellet chamber- Y itself. o

Upon rotation of the rotor 28 and member 33 to the position illustrated in Figure 3, the member 33 willfbealigned with and connect passage 18 and flash ductf4v6l andthus, upon movement of-the Iiring'element through armed position. Block 13 has a central opening 56 in which a metal ball 57 is disposed. The ball, which actually will assume the duties of a conventional tiring pin, is normally retained in opening 56 by a clip 58 screwed or otherwise secured to a plug 59 which forms the rear closure for opening 56. It might be mentioned at this time that the arrangement is such that only an impact force of substantial magnitude can belease the ball from clip 58 and permit it to advance towads passage 18, and ultimately strike the pellet and/or its stops 41 and/or 38. However, to prevent premature release of the ball, a transverse bore 61 is provided in bloclf` 13 in which a pair of detents 62 are positioned and normally arranged to close o access to passage 18 by springs 63. The detents 62 are suiciently close to the normally held position ofthe ball, that it the ball should start to be accidentally released from clip 58, it would engage one or both of the detents and be urged back into the resilient converging arms of the clip.

To facilitate manufacture and assembly, the rear end of passage 18 may be secured to an annular plug 64 which can be threadedly secured to the front end of block 13, and in communication with an axial bore 66 provided in the block.

From the foregoing description, it should be clear that in the normal position of the fuze, the pellet detonating ball 57 is restrained from movement by clip 58 and detents 62. Further, even if the ball was free to move forwardly, it could merely strike the solid portion of rotor 2S, and even if the pellet was detonated by this shock, the explosive force would escape through the safety exhaust passage 49 and not be directed into flash duct 46.

The design of passage 13 which interconnects rear block passage 66 with rotor block passage 47 is of utmost importance in the operation of the fuze. As will later be explained in detail, when the shell, travelling at a speed say of approximately 2000 F. P. S., hits a target which stops further movement in a very short distance, any freely movable object in the shell will, due to its inertia, continue to travel at an extremely high rate of speed. Thus, with the rotor in its armed position and the detents 62 in their retracted position as shown in Figure 3,l the balls inertia will carry it through the passage. If the passage were straight, the ball would merely travel forwardly at substantially the same rate of speed as the shell velocity in ight at the instant of the balls release, and offer but a very slight delay before pellet detonaton, which would not to any appreciable extent be variable depending on the target characteristics. For this reason, the passage is illustrated in the form of a helix or spiral, decreasing in pitch from the rear to front, and the reasons for such an arrangement, and possibly variations therefrom will be discussed in connection with a description of the physical reactions of the parts upon target impact.

The loading of the fuze is accomplished, simply, as follows: Into the tubular member 33 of the rotor 28, one or more stops intended to be located rearward of the detonating'pellet, as for example stop 38, are pushed, preferably with a gauge-rod, through any intervening seating grooves36 to seat in their respective such grooves. The detonating pellet is then inserted in place, and the clos l f y apego??? ing forward stop pushed into position in its groove. Itk is to be noted that this loading may readily be done either v ing sequence: The ball 57 is engaged in the clip 5.8 and plug 59 screwed tightly into block 13 with its detents in place; enclosed passage 18 is now firmly affixed to block 13 and inserted in casing 12 which is then rigidly secured Ito block 13. On the forward endof enclosed passage 18 is pushed (with a tight sliding t) a centering Washer 70 having peripheral openings 71 therethrough (to permit passage of hot gases in event of pre-detonaton). Rotor bloclf` 19, loaded or unloaded, is now screwed into casing 12 to a snug seat of the end of enclosed passage 18 in the opening of passage 47 in the rotor block. The fuze is now completely assembled, quickly and at low cost. lf an auxiary fuze or booster is utilized, it may be attached to the front of the fuze by the threads 69, and the tuze is then inserted in and secured to the shell base .by the aforementioned threaded connection.

When the shell is fired, the fuze will be exposed directly to the lpropulsion force and does notreceive the bcnet of the small but definite cushioning of the force received by a point detonating fuze resulting from the elasiicity of the shell walls. Consequently, the instant fuze is sufhciently sturdy and simple in construction to withstand this force without damage to its proper. functioning. Thus, the set-back force resulting from propulsion, merely urges ball 57 against the closed back of its clip, the detents 62 are bound in their normally closed position, and tubular member 33 bears against the rotor block, placing no stress on the rotor detent.

During the initial acceleration of the shell in the gun box, bind holds all of the moving parts'in their above mentioned position. However, as acceleration .ceases so does the bind force, and consequently, the centrifugal force set up by the high rotation of the shell (approxi-v mately 200 to 250 revolutions per second) causes the detents 62 to be moved outwardly against the action of their respective springs 63 to clear the passage 66. As will be seen in Figure 2, all of the other parts of the fuze remain in their original position, as both the ball and rotor arev centered on the axis of rotation of the shell. Although the member 33 is off-center, it is already in the ultimate position. that centrifugal force would direct it, and consequently no further movement results. During this condition of normal Hight and gradual deceleration the creep force, or the continuous inertia force resulting from deceleration of the projectile caused by air resistance, there is a tendency for movable fuze parts to move forwardly. However, the clip 58 and rotor detent 52 areJ each suicient strong to resist either release of the ball or rotation of the rotor into itsL armed position.

While the shell is in flight, and just prior to target impact, its forward velocity will usually be in the range of 1,500 to 2,000 feet per second, depending on the initial muzzle velocity, trajectory, etc. Immediately after 'impact, the parts of the fuze are subjected to what might be aptly called set-on force in contradistinction to the set-back force occasioned by initial firing. This seton force, resulting from the forward inertia of the fuze parts, is considerably greater than the set-back forces, as the shells velocity is decelerated to zero in a lesser distance than the dista-nce required to accelerate the shell to such velocity. Consequently, the magnitude of the set-on force is extremely high.

The set-on force as above described is more than ample to perform two tasks substantially simultaneously. First, the ball is forced from its retaining clip and into passages 66 'and,18, and in this connection, it should be pointed out that even after initial impact, the shell continues to rotate, and in any event, the set-on force produced by shell stoppage will bind the detents in their openA position. Second, the off-center member 33 will snap the rotor out of engagement with its detent 52 and effect a 90 degree rotation so that the rotor bore will be aligned Withpas'sage 18 and flash duct 46. Further rotation is prevented, as the member 33 engages a surface 71 on the block and detent 52 enters the other of the rotor notches. Rotor bind due to impact is effectively prevented by providing the rotor with a small diameter .axle as described and sufficient clearance between the rotor periphery and surrounding block surfaces to prevent contact. The clip 58 and rotor detent 52 are each only suiciently strong retentively to withstand a set-on force produced by stoppage of a shell velocity in the neighborhood of 200 to 300 feet per second, and hence target impact at a materially higher speed will easily effect release.

Thus, as shown in Figure 3, the effect of target impact results in arming of the rotor and release of the ball for forward movement through passage 18. When the ball strikes the pellet stop or stops 38 and 41, the stops will be displaced against the pellet with suilicient force to detonate the same with resulting flash or shock wave in flash duct 46 for explosion of the burster and main charge in the shell.

As hereinabove mentioned, the design of passage 18 is of importance, and in order to understand its purposes and design, an understanding must first be had of the forces acting upon ball 57 during its forward travel.

Primarily, the set-on force is the motivating factor which causes the ball to leave the clip and travel forwardly in the passage. The intensity of this force will be principally dependent upon the rate of stoppage of the shell, which in turn is controlled by the nature of the target. The residual set-on force at any instant may be measured by the difference between the respective absolute velocities of the ball and fixed portions of the shell. Thus, if the-shell is stopped quickly, as by hitting a hard target, the set-on force will be greater, though for a lesser duration, than if the shell was stopped more slowly, as in the case of a softer target. Therefore, the speed of the ball will vary in effect as the hardness of the target varies.

It was previously mentioned that a straight passage to the detonator would be unsatisfactory in providing the desired delay, indeed it would be irnpracticable for other than a quick detonating form of my invention. If the ball enters the passage at a speed of say 1500 F. P. S. or more, as it well may, and friction is reduced to a relatively negligible minimum, it would take for example a passage some ft. long to cause a delay of 1A@ of a second. Friction, on the other hand, by whatever means designed for' this purpose, is fatally uncontrollable and uncertain, not only because of changes due to temperatures, chemical surface changes, etc., but also because of the varying obliquity of impact of the shell on the target.

Now, in the embodiment of my invention shown in the foregoing, having reduced friction as near as possible to a minimum by making my firing element a hard smooth heavy ball of lesser diameter than the passage-also having a hard smooth surface, there are three remain ing retardant factors which I use and can control very closely, as they are all subject to known and immutable physical laws. These factors may be listed as follows:

(1) Centrifugal force, which is applicable only when the ball leaves the axis of rotation of the shell. Ihis force, of course, tends to drive the ball to the point of greatest distance possible from said rotational axis.

(2) lThe resistance created by the continuous angular incidence of the ball on the passage wall, emphasized by the screw-back effect of the clockwise rotation of the conduit or passage; mathematically both are reductions of the axially forward set-on force, dependent on the angle of incidence (from 0 to 90).

(3) Gyroscopic resistance created by the constant change of the plane of rotation of the ball.

Of these the first two are the most important, but it is essential to note that in all of them the retarding effect 7 is increased as the steepness of the helical slope is increased, until when the helix became a reducing planetary spiral in a plane normalto the axis of the fuze, the angle of incidence would counterbalance set-on force still existing though not the balls reducingA momentum while-I Gyroscopic action would be active likewise, though a` lesser factor of retardation, as long as the 'ball is rolling in the` curved passage.

It is therefore seen that the balls retardation and consequently the delay of the fuze can be closely controlled merelyby a change in the shape of one partthe passage r staats 'gitudinally extending casing adapted for attachment to a shell along the rotational axis thereof, a base member secured to the rear end portion of said casing said base member having an axial bore extending from the front end of thev member rearwardly, a ball, means for relaas-f i ably holding said ball in said bore, block means on the front end of said casing substantially closing the same provided with an axial bore therethrough and further having Ia generally cylindrical chamber, the axis of said chamber intersecting the block means bore at substantially right angles, a rotor journalled in said chamber for `rotation about an axis transverse to the axis of said casing,

means defining a diametrical bore in said rotor which in .one position ofV said rotor is substantially normal to said axial bore and in another position of rotor rotation is aligned with said axial bore, means for releasably holding provided for the ball or firing elementi However, whatt ever the range of relay provided, it is to. be remembered, as previously noted, in penetrating a hard target, set-on is more intense and the ball enters thepassage at a pro portionately higher speed with consequently less resultant delay in detonation than in penetrating a soft target; and in the former case the shell reaches the point of deepest penetration in a proportionately shorter time. Thus this fuze automatically adjusts its delay of detonation to the nature of the target. A i

Obliquity of impact in entering the target has negligible effect on the travel of the ball through the passage, due

principally to its excessively low coefficient of frictionV even at the instant of greatest deflection stress. i l Y The complete absence of operating springs, sliding parts and relay ignitions, in this fuze, as well as the` extreme simplicity and sturdiness of parts, uniquely increase the sureness and accuracy of operation.

In place of the helical passage shown, it be appre-I"` ciated that the conduit could bedisposed ina 'single planej with a generally V-shaped configuration intermediatethe endsthereof. The apex ofthe V would producethe maximum centrifugal delay effect. Likewise,` any other"- passage in which a portion was spaced .from4 the axis Vofu rotation .would produce al` degree of` comparable results.V But my preferred form of helix, or a combination of part planetary spiral, or straight for` quick-actingfuze requirements, provides the best results. i l, It will therefore be appreciatedthat the invention is sturdy, uniquely safe, economical to produce, positive'in action, and possesses the unique characteristic'of automatically delaying explosion of the shell until maximum penetration is reached.

What is claimed is: l. A base detonating fuze for shells comprising a longitudinally extending casing adapted for attachment to a shell along the rotational axis thereof, a base member secured to the rear end portion of said casing and having an axial passage therein, airing element in the` form of a ball normally positioned'within -said passage,

resilient means for releasably holdingsaid ball insaid i passage until impact, means secured to the front end por-- tion of said casing having an axial bore therethrough air-1dl further provided with a generally cylindrical chamber whose axis is normal to and coplanar with said bor'e'a rotor journalled in said chamber for rotation about'an axis transverse to the axis of said casing, means defining a diametrical bore in said rotor which in one'position of said rotor is normal to said axial bore and in another position of rotor rotation is aligned with said axial bore,

means on said rotor for receiving a detonator in said diametrical bore, and longitudinally extending conduit means communicating between said axial passage and said axial bore through which said ball may Amove upon 1 release thereof from said resilient means'.

2. Abase detonating fuze for sheils compri si nga"lon 'means is provided with a safety passage interconnecting the interior of said casing and said rotor bore when said rotor is in said one position.

4. A fuze as set forth in claim 2 in which said block means is provided with an arcuate passageway extending for approximately 90 degrees of are along which the:l

portion of said tubular member extending outwardly from said rotor may pass.

5. A base detonating fuze for shells comprising a `longitudinally extending casing adapted for attachment to a shell along the rotational axis thereof, a base member secured to the 'rear end portion of said casing, said base .member having an axial bore extending from the front end of the member rearwardly, a ball, means for releasably holding said ball in said bore, block means on the frontend of 4said casing substantially closing the same provided with an axial bore therethrough and further having a generally cylindrical chamber, the axis of said chamber 4intersecting the block means bore at substantilly right angles, a rotor journalled in said chamber for rotation about an axis transverse to the axis of said casing, ,i n. means detini'nga diametrical bore in said rotor of a size 'fuze' of this sufficient to receive said ball which in one position of said rotor is substantially normal to said axial bore and in another position of rotor rotation is aligned with said axial bore, means for releasably holding said rotor in each of said positions, said rotor having a tubular member extending outwardly from said diametrical bore, means in said tubular member for receiving a detonator, and means defining a longitudinally extending passage interconnecting the bores of said base member and t block means along which said ball may roll when released by said holding means, a ball detent in juxtaposition to said ball holding means and normally disposed within saidbase member bore so as to prevent said ball from I l leaving said'holding means, said ball detent being mov-f able'out of said bore upon `rotation of said fuze.

References Cited in the le of this patent UNITED STATES PATENTS i 1,316,607 watson sept. 23, 1919 1,327,600 Lukens Jan. 6, 1920 1,570,630 Crawell Jan. 26, 1926 1,999,747 Aragone Apr. 30, 1935 2,465,395 ORear Mar. 29, 1949 2,609,753 Rosenberg Sept. 9, 1952 v FOREIGN PATENTS f241,930 Great Britain May 13, 1926 "685,607 France Apr. l, 1930

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