IL34850A - A mechanical delay system - Google Patents

Description

34850/2 n'aaa n»»nwrt nDTyn A mechanical delay system THE STATE OP ISIAEL, MINISTRY OF DEFENCE Inventors? :ο*κ*.ίοη Jakhin Boaz Popper *iais r ia =' Raphael Gohen ?nD «ai Dan Hayon Ρ'π n 54850/2 -.l-LSb- This invention relates to an improved mechanical delay system and is particularly but not exclusively concerned with a delay system designed to introduce. a predetermined time-delay in the functioning of a fuse and particularly in the arming mechanism of the fuse.

In the operation of the arming mechanism of the fuse it is often necessary to provide for a fixed and relatively short time delay between the various stages of the arming mechanism and for this purpose various time delay mechanisms have been employed or proposed. In the design of such time delay mechanisms account must be taken of the fact that the mechanism must be capable of withstand created ing the set back forces as a result of high accelerations and for this purpose various types of delay mechanisms have been proposed suoh as clock work or pyrotechnic delay mechanisms· Clockwork delay meohanisms whilst essentially accurate and capable of providing time delays within very harrow limits are, nevertheless, usually complicated and expensive to produce. On the other hand pyrotechnio delaya are relatively inaccurate and operate within very wide ranges and are also not capable of non-destructive testing* It is an object of the present invention to provide a new and improved mechanical delay system which is capable of application, inter-alia in a time delay fuse and in which the. above referred to disadvantages are substantially reduced or overcome.

According to the present invention there is provided a mechanical delay system comprising at least two members, biasing means for biasing at least one of said members in respectively transverse main directions of motion, an abutment system associated with said members and serving releasably to articulate said members together and releasable retaining means associated with said members so as to inhibit movement thereof, the arrangement being such that upon release of the retaining means one of the members is displaced along its main direction of motion, its displacement being accompanied by a reciprocating motion of .edrttrwr said one member displacement of said one member along its main direction by a predetermined amount resulting in releasing the reciprocal displacement of the slider member along its main direction of motion.

Preferably said abutment system consists of providing the plate-like member with a pair of serrated edges and providing the slider member with a pair of toothed abutments between which the plate-like member passes, said toothed abutments abutting alternately said serrated edges.

In accordance with a preferred aspect of the present invention the abutment system can form part of a mu ti stage delay system in accordance with our, 'copending'.:■·-$ Patent Application Serial No. at least two delay 'and comprising said spring biased slider/elements constituted by serrated plates and associated toothed abutments referred to above dlsplaceable at a predetermined rate with respect to the first member and releasably articulated thereto, releasable retaining means for releasably retaining said delay elements against displacement, means for initiating the displacement of a first delay element constituted by the initial displacement of the slider upon initiation of arming and triggering means associated with the first and subsequent (but not the final) delay element/s and so designed that upon a predetermined displacement of a delay element and its resulting de-articulation from the first member, the retaining means of the subeequent delay elemen is released.

. . For a better understanding of the various aspects of the present invention and especially the underlying theoretical concepts thereof reference will now be made to the accompanying drawings, in which: Fig, 1 shows schematically one form of mechanical delay device in accordance with the present invention; Fig, 2 is a model illustrating mathematically the embodiment shown in Fig. 1; Fig* 3 shows schematically a modified form of mechanical delay device in accordance with the , | invention; ! ' Fig, 4 shows on an enlarged scale a portion of the serrated plate shown in Fig, 35 ' Fig. 5 shows a model which when taken together with the model shown in Fig. 2 illustrating mathematically the embodiment shown in Fig. 4; Fig. 6 is a partially sectioned side elevation of a shell fuse showing the mechanical dela device illustrated in Fig, 3 incorporated in an arming mechanism thereof; Fig, 7 is a perspective view of a two-stage mechanical delay device shown prior to the initiation > of the delay; Fig, 8 is a perspective view of the delay device shown in Fig, 7 during the first stage of the delay, and Fig. 9 ia a perspective view of the delay device shown in Fig. 7 after completion of the first stage of the delay and during the second stage of the delay.

As seen in Fig. 1 of the drawings a mechanical delay device consists of an elongated slider member 1 whioh is slidable along its longitudinal direction in a guide way 2 formed in a frame member 3 and a plate member 4 having serrated longitudinal edges 4a and 4b and which is displaceable, under the influence of a biasing means 5» normally with respeot to the longitudinal axis of the slider member 1 and between a pair of toothed abutment ribs la and lb formed integrally with the slider member 1· The plate member 4 is constrained to move only in its longitudinal direction by guideway 6 formed in the frame member 3 and cannot move in a transverse direction* In consequence the upward displacement of the plate 4 is accompanied by a reciprocating movement of the slider 1 (along its longitudinal direction) until (after the predetermined time delay) the plate member has moved out of the region of the toothed abutment ribs la and lb whereupon , the articulated connection between the plate and slide members is released. Thus the time delay achieved is determined by the time it takes forthe plate member to be displaced by a sufficient amount for the articulation between the two members to be released.

In the following discussion the following symbols will be employed :- L = Plate length X = Depth of serration P = Biasing force Xo = Stroke of slider P = Average biasing force ^ = Angle of serration 3 = Pitch of the serrations Δ = Sum of tolerance T = Time delay = Slider wight n =s Number of serrations u;a;3:= Various coefficient: per edge of friction With the upward movement of the plate 4 under a biasing force ^ a resulting force 2 = ^^- i will operate on the slider' ( ^ is a constant to be defined below) and the slider will perform n pairs of reciprocal movements.

Now the force opposing the movement of the slider 1 arises out of the frictional resistance to movement of the slider in its guideway (coefficient of friction β) and therefore the acceleration of the slider is given by:- see e, we d a t in the by an element II and a =» coefficient of friction of the plate with reapect to its pathway, and μ = coefficient of friction between the elider and the plate then i In order to ensure that the plate does not lock with respect to the slider the angle of serration must be chosen so that and this determines an upper limit for As is evident from the relationship (l) the greater the number (n) of serrations per edge and the greater the stroke path XQ the greater should be the maximum delay which is obtainable.

However XQ is not independent of n Thus 3 ■ 2X cot ^ and therefore n = L = L tan Ψ (4) S 2X In other words T cc 1 ΥΓ and therefore in order to achieve a maximum time delay, X (serration depth) must be reduced to a minimum.

However, the reduction of X brings in its train the ratio of the sum of the tolerances Δ to the stroke path of the slider and as this increases the ef ective stroke path X is reduced o so that X = X - Δ ο and Τ α ν*Χ -« Δ X In oonsequenoe the maximum delay time T is obtained when X = 2Δ (5) i. e. when the serration depth is double the sum of the tolerances and therefore the slider stroke path is reduced to one half the serration depth.

Any increase in the magnitude of the angle ^ is accompanied by a decrease in. (see relationship (2)) and i consequence the biasing orce P^ must be inoreased so as to displace the slider* Such an increase is un- . desirable from many points of view and it can be shown that a condition for effective operation is K^inin) X P1(min) > V pmax (6) The optimum value of 1 can be obtained from the above relationships by means of a computer.

In one particular numerical example it can be shown that with a serrated plate with the following dimensions W = 15 gr P, = 20 ÷ 30 gr ·■ y : JT = 35 mm a =» 0.2 * 0.3 β = 0.1 + 0.15 - 0.2 + 0.3 A S o.£ mm ■ = 8 X « 0.8 mm '■ ; n a 35 "". ' , ..·' ' · :: · ■' . a maximum time delay o T = 1.08 sees can be obtained.

In the modification illustrated in Fig, 3 of the drawings there is again provided, as before, slider and plate members 11 and 12 but in this case the slider member is provided w ith biasing means 13 which exert a force -j on the slider whioh acts alternately with and against the force Pg = K^P^ originating wit the plate member.

In consequence therefore of the provision of the biasing means 13, the plate is constrained to displace the slider in one direction against the biasing force and in the other direction with the biasing force. As clearly seen in Fig. 4 of the drawings the serrations on eaoh side of the plate are defined by two angles and r*2. Now (p , is the angle defining those portions of the serrations which are engaged during movement of the slider against the biasing foroe whilst ^ 2 is the angle defining those portions of the serrations which are engaged during movement of the slider in the direction of the biasing. The condition ,set out in relationship (3) for the serration angle Vappliee only totyl whilst the other angle jf 2 can be greater and this is in fact the case as seen in Pig. 3 of the drawings, and in detail in Pig. 4 thereof.

Now the force acting on the slider so as to displace it in ie direction of the arrow A is K1P1 " P3 On the other hand when moving in the reverse direotion !ΐ.θ. in the direction of the arrow B the spring biasing of the plate must be overcome by a force which is given as ^2fi ωά therefore the force displacing the slider in the direction of A is given as P3 ~ K2P1 There can therefore be deduced an expression for the time delay T which can be obtained, i.e.

Now from Fig* 4 we can deduce that n = L X (ootf+ dotf2 ) and a relationship can be deduced for and Kg as follows ¾ » 1- - ta ^ (μ+β) (β) tan^ (l-ia)-¾u+a Consideration will now be given to the various factors leading to maximum delay times* The serration depth for maximum delay will again be as given in relationship (5).

The calculation of the optimum values for the angles ^ and Furthermore, the biasing force P.., must be suffice :iently strong to displace the slider after the delay time to its ultimate location and therefore it cannot be reduced arbitrarily.

There can therefore be set out the following conditions for operation.

F3 max ^ ¾ min (10) P- min Optimal values can be obtained by means of a computer as in the following example* With the same values as before W, L, α, β, μ, then the slider Bpring is given a value 3 = 30 i 42 gr. and P. « 704 100 gr. max = 0.846 2 min = 0.188 n = 24 T = 0.316 sec Δ = 0.4 X * 0.8 · In practice, however, the time delay achieved exoeeds this value which has been calculated seeing that a maximum sum of tolerances rarely, if ever, occur in practioe. Furthermore, the slider acquires upon each stroke a momentum which tends to make it continue in its displacement even after the abutting serration ceases to press it forward.

Thus the effective stroke will be slightly greater than . the calculated stroke as will in consequence be the time delay.

As can be seen fcbove therefore the time delay which can be achieved can be raised or lowered oonvenlently by adding or reducing the number of serrations* Adding the number of serrations, however, increases the overall length of the plate and this may not be practicable in view of space limitations. Under these circumstances, and as will be described in cetail below a multi-stage delay system in accordance with our co-pending Patent Application Serial: No. 1¾9 , can be devised utilizing successively the delaying effect of a plui-ality of such plates. , Reference will now be made to Fig. 6 of the drawings which shows the incorporation of a mechanical delay device as shown in Fig. 3 of the drawings in the arming meohanism of a shell fuse.

As seen in Fig. 6 the shell fuse comprises a conical portion 21 and a cylindrical body portion 22 and an intermediate screw threaded portion 23 whioh enables the fuse to be screw fitted in a shell. Located within the cylindrical body portion 22 is a slider housing 24 consisting of an upper portion 24a and a lower portion 24b, the two portions being juxtaposed and fitting together by means of : projections and recesses and defining between them a slider guide way 25 in which is slidable an elongated metallic slider 26 of construction similar to the slider 11 described with reference to Pig, 3 of the drawings« In order to reduce the coefficient of friction between the slider 26 and the wall of the guideway 25 the slider is provided with Teflon bearings 27· A serrated plate 28 is located within a guideway 29 formed in the lower slider housing portion 24b and is biased upwardly by means of a compression spring (not seen) in the direction of a corresponding guideway 31 aligned with the lower guideway 29 and located in the upper slider housing portion 24a. As shown, the serrated plate 28 is located between a pair of toothed abutment ribs 26a and 26b which are respectively and alternately arranged to be located in the successive serrations 28a and 28b of the serrated late 28.

A compression spring 32 biases the slider member against an arming element 33· As can be seen rom the drawing the uppermost tooth 34 ^hereinafter referred to as the retaining tooth) Of the serrated edge 28b is inset with respect to the remaining teeth whilst the lowermost tooth 35 (hereinafter referred to as 1he beyond the remaining teeth.

By virtue of the fact that the slider member 26 oannot move to the right under the influence of the oom- -pression spring 32 owing to the presence of the armin element 33, the toothed rib 26a is firmly lodged on the uppermost retaining tooth 34 and as a consequence the serrated plate 28 is prevented f rom moving upwardly under the influence of the compresaion spring 30.

As soon, however, as the arming of the fuBe is initiated (by means which do not form part of the present invention and are therefore not described herein) the arming element 33 will no longer abut the slider member and as a consequence the latter is free to move forward under the influence of the compression spring 32 for a limited amount until the toothed abutment 26b bears against the uppermost tooth of the serrated edge 28a. The serrated plate 28 is now freed for upward displacement and this displacement is accompanied by a reciprocal movement of the slider along its longitudinal direction, this reciprocal movement oontinues until the serrated edges of the plate 28 has been displaced beyond the toothed abutting ribs 26a and 26b whereupon the articulation between the serrated plate 28 and the slider 26 is released and, assuming that only a one-stage mechanical delay is involved the slider is free to move forward into a fully armed position* As indicated above the time delay achieved with a single plate of such dimensions which can be readily accommodated in the available space may not be adequate for the purpose Required and under these circumstances a multi-stage delay device such as forms the subject of our oopending Patent Application Serial Wo.41239 , oan be employed. Such a; multi-stage delay device is shown schematically in Figs. 7, 8 and 9 of the drawings and is in fact foreshadowed in the embodiment shown in Fig. 6 i of the drawings wherein the serrated plate 28 is provided with a trigger tooth 35 for a purpose now to be explained.

As seen in Figs. 7 to 9 of the drawings a slider member 41 is associated with a pair of serrated plates 42 and 43» the plate 42 being located between a pair of toothed abutment ribs 41a and 41b whilst the serrated plate 43 is located between a pair of similar toothed abutment ribs 41'a and^l b^^the latterpair being, hoverer, staggered rearwardly with respect to the direction of movement of the slider. The serrated plate 42 is biased upwardly by means of a compression spring 44» the upper end of which is designed to bear against a lug 45 formed integrally with and bent outwardly from the serrated plate 42 whilst the serrated plate 43 is biased upwardly by means of a compression spring 46, the upper end of which bears against a corresponding lug 47.

The slider member 41 is slidable with respect to a fixed support frame 48 and is spring biased by means of a compression spring 49 against an arming element 50. A stop element 51 integral with the frame 48 bears on the lug 47 of the serrated plate 43 and in the initial condition of the device inhibits the upward movement of the plate 43 under the influence of the compression spring 46.

When as in the embodiment described with reference to Fig. 6 of the drawings the arming element 50 is in position, the slider 41 is pressed against this arming element and the serrated plate 42 is prevented from moving upwardly under the influence of the compression spring 44 in view of the fact that the toothed abutment rib 41a is firmly lodged on the upper recessed retaining tooth of the serrated edge 42a of the serrated plate 42.

When, as a result of the displacement of the arming element 50, the arming process begins the slider moves forward under the influence of the compression spring 49 into the position shown in Fig. 8 of the drawings whereupon the serrated plate 42 is freed for upward motion under the influence of the compression spring 44 and this upward motion involves the slider element in a reciprocating motion along its longitudinal direction* It is to be noted, however, that the stroke of this reciprocal movement is not so great as to displace the lug 47 from under the stop element 1 and in consequence the serrated plate 43 is prevented from moving upwardly under the influence of its compression spring 46.

This state of affairs continues until the serrated plate 42 has been almost entirely displaced upwardly under the influence of the compression spring 44 with the lowermost trigger tooth. of the serrated edge 42a bearing against the toothed abutment rib 41a. As a consequence the slider member 41 is displaced to the right with sufficient force to displace the lug 47 from beneath the stop member 51 amd thereby to allow the initiation of the upward displacement of the serrated plate 43 and therefore the initiation of the second stage of the delay.

It will thus be seen that with the completion of the first stage of the delay, i.e. when the first serrated plate 42 is de-articulated with respect to the slider, the second stage of the delay is automatically initiated and the second serrated plate 43 begins its upward motion and carries with it the continued reciprocating motion of the slider 41 as seen in Fig. 9.

With the completion of the second stage, i.eV the complete upward displacement of the second serrated plate 43» this plate is de-articulated from the slider and the slider is now completely free to move forward into its fully armed position under the influence of the compression spring 49.

It will therefore be realized that the total time delay involved in the arming of the mechanism after its initiation, i.e. the displacement of the arming element, , is the sum of the time delays associated with the upward displacement of each individual serrated plate and in this way an extended time delay can be achieved without the necessity of using an unduly long serrated plate which could not be conveniently accommodated in the available space. 34850/2

Claims (1)

1. CLAIMS A mechanical delay comprising at least two biasing means for biasing at least one of said respectively transverse directions of abutment system associated with said members and serving releasabl to articulate members together and releasable retaining means associated with said members so as to inhibit movement arrangement being such that upon release of the retaining means one of the members is displaced along its main direction of its displacement being accompanied by a reciprocating motion of sa d one member transverse to its main direction of motion the displacement pf said one member along its resulting main direction by a predetermined releasing the articulation of said A mechanical delay to Claim 1 wherein said abutment system consists of at least one serrated edge formed on one member and at least one toothed abutment Carried by the other member so as to abut successive serrations of said upon relative movemen of the two A mechanical delay system aocordin to Claim 2 where of said members being biased by said biasing means is formed as a elongated member having a pair of edges and wherein the other member is provided with a of toothed abutments between which the member said toothed abutments abutting alternately said serrated A mechanical delay system aocording to Claim 3 wherein both serrated edges have substantially serration angles whose magnitude less than a critical value so as to avoid A mechanical delay system according to Claim 3 wherein further biasing means is provided for biasing the other member towards said and wherein the serrations on each side of the plate are defined by first and second a first of which defines those portions of the serrations which are engaged during movement of slider against the biasing force whils the second angle defines those portions of the serrations which are engaged during movement of the slider in the direction of biasing said first angle having a magnitude less than a critical value so as to avoid locking and wherein the othe angle has a magnitude which can critical A mechanical delay system substantially as hereinbefore described by way of example and with referenoe to the accompanying An arming system for a shell fuse comprising a mechanical delay system according to any one of the precedin claims wherei of said is constituted by a spring biased slider member and the other of said members is constituted by a said abutment system bein so arranged that the displacement member along its main direction of motion is accompanied by a reciprocal displacement the slider member along its direction of An arming system according to Claim 7 when dependant Claim wherein said releasable retaining means is constituted by an arming element against which said slider member spring biased and an uppermost recessed retaining serration o one of serrated edges in which one of said toothed abutments is the arrangement being suc that upon displacement of said armin element the slider member moves downwardl spring biasing so as to disengage the toothed abutment from the retaining serratio thereby freeing the serrated plate for An arming system according to Claim 8 wherein said slider slldeable a guideway defined between a pair juxtaposed interengaging slider housing portions and said member is dlsplaceable in a pair of aligned recesses formed in said A delay system accordance with Claim 1 of copending Application Serial and comprising a first at least two delay elements at a predetermined rate with respect to the first member and releasably ar thereto eac delay element comprising a meohahloal delay system according to any of Claims 2 to 5 and said first membe being constituted by the other one of said retaining means for releasably retaining said delay elements agains for initiating the displacement of a first delay element and triggering means associated with the first and subsequent not the delay and ι so designed that upon a predetermined displacemen of a delay element and its resulting from the A delay system according to Claim 10 when dependant on Claim 5 and wherein the last serration of one serrated edge of at least one said plates projects beyond the remaining serrations o said edge and engages with a corresponding toothed abutment member so as to displace the sufficiently or the release of a subsequent spring biased serrated An arming system for a shell fuse comprising a delay system according to Claim 10 or 11 wherein said one member is constituted by a slider member 13 An arming system according to when dependant o Claim wherein said releasable retaining means is constituted by an arming element agains which said slider member is spring biased and an uppermost recessed retaining serration of one of said serrated edges in which one of toothed abutments is the arrangement being such that Upo displacement of said arming element slider member moves forwardly under spring biasing so as to disengage the toothed abutment from the retaining serration thereby freeing the plate arming system a shell fuse substantially as hereinbefore by way of example and with reference to the accompanying or Applicants insufficientOCRQuality