GB2221019A - Arming system for a fuze - Google Patents

Abstract

In an arming system for a fuze, e.g. a bomb fuze, a turbine 1 is drivingly engaged to a spring 5 via a primary differential 10 and a secondary differential 17 to wind it up, for a time set by a timing mechanism 6 which also appropriately locks the differentials via locks 18, 18' and 19 to produce the driving engagement. Once the set time is over, the timing mechanism releases lock 19, so that either a fast or slow arming can take place to move a detonator carrier 11 to complete an explosive train, with a selectable delay. In the slow arming mode lock 18 is released but lock 18' is engaged so that turbine 1 is disengaged from the spring 5 which unwinds, and the detonator carrier is moved, at a rate determined by an escapement 9. In the fast arming mode lock 18 is engaged and lock 18' released by a solenoid 27 so the turbine drives the differential 10 in addition to the spring 5, thus increasing the rate of arming. The solenoid is controlled by a counter 15 which causes it to select the fast arming mode until a selectable number of pulses produced by a pulse generator 16 have been counted. In a modification of the system, (Fig. 6 not shown) the turbine directly winds a spring and all the energy required for both slow and fast arming is derived only from the spring. <IMAGE>

Description

ARMING SYSTEt.d The prevent invention relates to safety and arming systems and is particularly related to the use of such systems in fuzes, for example bomb fuzes.

In a fuze for an explosive device such as a bomb it is usual to insert a safety and arming system so that premature firing of the detonator will not result in premature firing of the explosive. A barrier which provides physical separation or interruption is incorporated in the explosive train of the device and this barrier is removed by the safety and arming system.

Such systems are often operated by simple timing mechanism initiated b suitable environmental inputs. For example a typical bomb fuze uses a safety and arming mechanism driven from a turbine in the tail of the bomb. This turbine provides power for the safety and arming timer and represents an environmental input since, unless the bomb i9 exposed to a high speed airflow, no power input is applied to the safety and arming mechanism and no movement of th detonator can occur.

It has been proposed to provide fuzes, for weapons such as bombs, which are programmable for different manners of operation and it is an object of this invention to provide an improved safety and arming mechanism suitable for such fuzes.

According to the invention there is provided an arming system! for a fuze, including means for storing energy from an environmental input, means for completing arming sequence after a delay dependent on the rate of supply of energy thereto, first means for supplying to the sequence completing means at least a portion of the said stored energy at z first rate to complete the sequence after a first delay, second means for supplying to the sequence completing means additional energy derived from the environmental input to speed the sequence to be completed after a second, shorter and variable delay, and means for controlling the supply of energy by the second means to select the delay to be used.

In one example of the system, the additional energy is derived directly from the environmental input.

In another example, the additional energy Is supplied by the storing means.

In order that the invention may be clearly understood and readily carried into effect it will now be described by way of example with reference to the accompanying drawings of w'r,ich:- Figure 1 is a bloc diagram illustrating one example of an arming system of the invention, Figures 2 to 4 show a mechanical arrangement of that example of the arming system, in three modes of operation, Figure 5 is a block diagram illustrating another example of the arming system, and Figures 6 to 8 show a mechanical arrangement of that other example in three modes of operation.

One proposal for a programmable fuze allows the choice between different modes such as impact or proximity fuzing or delayed firing and the choice of different post impact delays.

The choice may be made when loading the weapon onto an aircraft or may be made on the aircraft prior to release.

In such fuzes for which it is possible to modify the arming time a new problem arises. That is in certain circumstances the fuzed device may reach target impact before the arming procedure is complete. In that event the arming turbine will cease to rotate and the weapon will not fire. Of course the arming turbine could be dispensed with in favour of a permanent power supply. However it is desirable to retain this system since the environrnental input which it provides is a very useful safety feature.

It is therefore proposed to use the input energy from the turbine in the first few seconds of flight to store energy for a timer which can continue to run, if necessary, even after impact. This can be achieved, for example, by winding a spring which operates a mechanical timer.

An important safety requirement for such a programmable safety and arming system is that, in the event of a failure somewhere in the system, the mechanism reverts to the longest time delay. This implies that the stored energy timer naturally runs for the maximum arming time and that further energy must be added to the system to shorten the arming time.

Of course other energy supplies can be used to provide this further energy. However if these are other than the environmental inputs there exists the possibility that the other energy supplies may of themselves be capable of arming the system.

Thus it is desirable for the other energy supplies to be environmental inputs. In the preferred embodiment of this invention both the initial and further energy inputs are provided by an environmental input in the form of an arming turbine.

Figure 1 shows in block diagrammatic form one example of an arrangement for implementing this invention.

An air vane or arming turbine 1 is arranged on the weapon so as to be rotated by an airflow past the weapon after release thereof. A locking mechanism 2 prevents operation of vane 1 or transmission of power therefrom prior to weapon release. Such release is indicated by a tug on a lanyard, not shown, and the transmission to the weapon of an aircraft separation pulse. In the presence of both of these as indicated by an 'AND' gate 3 the mechanism 2 is unlocked, probably by a gas motor. At release therefore the vane 1 can operate, via a speed governor 4, a spring mechanism 5 in which energy is stored.

A primary timer 6 determines the period for which the spring mechanism 5 is wound and after the required period removes the drive from the spring mechanism and transfers it to the clutch 7 the output of which can be positively locked by brake 8 when the clutch is disengaged. The clutch 7 and brake 8 form part of a mechanism for controlling the rate of completion of the arming sequence after winding.

tÇhen the drive to spring mechanism 5 is removed, the spring unwinds at a rate determined by secondary timer 9 (e.g. an escapement) connected thereto and provides an input to differential gear 10 so that the spring energy is used to operate a detonator carrier 11, to move the detonator into the explosive train and complete arming. This operation, controlled by unwinding of the spring 5, is completed in the maximum allowed arming time provided the weapon has been released, as indicated by a direct safety interlock 12 unlocked by the separation pulse.

To reduce the arming time, to suit operational requirements, a command input is accepted at 13 from a control, perhaps in the aircraft cockpit or fro a memory device in the fuze, and interpreted by a decoder 1, which sets a preset count into a down counter 15. An OR gate 155 senses whether the counter contains any number greater than zero, and the output of the OR gate controls a solenoid 27 which is arranged to disengage the clutch 7 and apply the brake 8 when the down counter 15 contains all zeros, and te engage the clutch 7 and remove the brake 8 when the down counter contains any binary number greater than zero. Hence, if a number greater than zero is set in the down counter 15, when the primary timer 6 removes the turbine drive from the spring 5, the turbine 1 will drive the detonator carrier 11 via the clutch 7 the pulse generator 16 and the differential 10, this turbine drive being additional to the drive by the spring 5. This rotational input via the clutch 7 continues until sufficient pulses have been produced by the pulse generator 16 to cause the down counter 15 to register zero. This rotational input via the clutch 7 is applied to the differential 10, and the detonator carrier 11 is rotated at a rate equal to the sum of the rates of rotation'of the clutch 7 and the secondary timer 9.Therefore, by varying the number set in the down counter 15, the time during which faster rotation of the detonator carrier occurs, and hence the arming time can be controlled.

It will be understood that Figure 1 is merely a schematic diagram illustrative of one sequence of operation to implement the invention and the actual sequence described may be altered as desired.

Figures 2 to 4 show one example of a mechanical system for implementing the invention, in which the reference numerals common with Figure 1 have the same signIficance as in Figure 1.

For clarity items such as the detents, the carrier 11, and the decoder 14 are not shown.

To illustrate the operation of the system, Figures 2 to 4 show the system for the three main operational modes, winding, slow arming and fast arming. The clutch 7 is provided by a secondary differential gear 17 and lock 18, and brake 8 is provided by lock 18', while differential 10 is referred to as a primary differential gear 10 in the following. Each differential comprises, in kr.own manner a housing 10', 17' which is rotatable, and has differential pinions 10", 17" coupled to shafts and to the housing. Differential 10 has two input shafts 71 ad 75 connected to the pinions 10", whilst differential 17 has an input shaft 73 and an output shaft 75 coupled to the pinions 17".

The primary timer 6 comprises in the system of Figures 2 to 4 a mechanical arrangement which locks and unlocks the housing of both the differentials 10 and 17 to control the winding time.

The controlling mechanism including the solenoid 27 controls the slow and fast unwinding by controlling the lock 18 on the housing 17' and the brake 18' on the output shaft 75'.

The timer 6 includes a gear 60 drivingly engaged to the output shaft of the speed governor 4, and a timing plate 61 including a notch 62, connected to the gear 60. A timing shaft 63 biased (upwards in the Figures) by a spring 64, has a toe 65 trapped under the plate 61 until the notch 62 releases it.

The locks 18 and 18 are controlled in dependence on the portion of the shaft 63 and the state of the solenoid 27 which is supported on the shaft 63,the locks being coupled to the solenoid by pivoted links 65 and 67. Link 67 is pivoted to the shaft and has slots on either side of its pivot coupled respectively to the solenoid 27 and to the link 66.

A further lock 19 is provided fo locking the housing 10' of differential 10 against rotation, thus preventing movement of the detonator carrier 11, which is coupled to housing 10'.

This lock 19 which is biassed away from the differential 10 by a spring is controlled by an abutment 68 on the shaft 63.

Referring now to Figure 2, this figure shows the arrangement in the initial winding mode in which spring unit 5 is being wound, for a time typically from zero to 1.5 seconds after release, controlled by the primary timer 6. The housing of the secondary differential gear 17 is locked by brake 18 and the brake 18' is unlocked so that the shaft rotation is transferred through the differential 17, being reversed in direction thereby, to primary differential 10 via a gearbox. The housing of the primary differential gear 10 is also locked by the lock 19 so that rotation is transferred through the differential 10, with a further reversal, to wind the spring.The toe 65 of the primary timer (Figure 2) flies through the notch 62 out of engagement with plate 61 at 1.5 seconds (in this example) and removes both the lock 18 from the housing of differential 17 and the lock 19 from the housing of the primary differential 10 allowing unwinding of the spring 5.

In Figure 3 there is shown the mode of slow arming. The housing of differential 17 is released by lock 18 so as to be free to rotate but the output shaft 75' is locked by lock 18' under the control of solenoid 27. Thus the motion from turbine vane 1 is not transferred via the gearbox to primary differential 10. The housing of the differential gear 10 is itself unlocked which is not only necessary to allow the gearbox shaft to be locked without locking the spring 5 but transfers the slow unwinding motion of spring mechanism 5 to the detonator carrier 11 as shown. This unwinding is then effective from 1.5 seconds to whatever is the maximum delay time unless further action is taken.

If the fast arming is to be brought into operation to speed the arming sequence, the down counter 15 causes the solenoid 27 to change state and change over the secondary differential locks 18 and 18' to provide the mode shown in Figure 4. This allows the motion of turbine vane 1 to be once more transmitted to primary differential gear 10, which however is left unlocked.

This has two effects; first that the motion of the turbine vane is still transferred to the detonator carrier 11 and second that there is no reversal at 10 and the motion is still a movement of the detonator carrier to complete the arming sequence. At the differential 10 the unwinding motion of the springs is added to the motion of the turbine vane so that the arming proceeds more quickly. This mode can complete the unwinding at such a speed that in a typical arrangement, the total arming time can be completed in less than three seconds if a suitable number is contained in down counter 15. It can be made longer by reducing the time period of the mode of Figure 4 and allowing the remaining stroke of the detonator carrier to occur at the slower rate of the mode of Figure 3.

The system of Figures 1 to 4 relies on the continuous operation of the turbine or air vane 1 to reduce the delay in arming. However in some situations, the turbine reliably operates only over a short period of time. For example, if the turbine is placed at the tail of a bomb equipped with a retarder, the turbine will operate reliably only for a short time after the bomb is released from the aircraft because thereafter the action of the retarder significantly reduces the airflow past the turbine. Accordingly, the modified system of Figures 5 to 8 is provided, in which the turbine 1 is used only to wind up the spring 5, all the energy to drive the detonator carrier in both the slow arming and fast arming modes being derived from the spring.

Referring to Figure 5, in which the reference numerals have the same significance as in Figure 1, the air turbine 1 winds up the spring 5 via the locking detent 2 and the speed governer 4 (e.g. an escapement), the detent 2 and the speed governer operating in the same way as in Figures 1 to 4. The primary timer 6, however, operates to prevent spring 5 unwinding and thereby driving the detonator carrier, during a predetermined period in which the spring is wound. This period Is chosen to be within the period of reliable operation of the turbine (in this example 0.75s). Thereafter the primary timer allows the spring to unwind, (but does not prevent the spring being wound).

As in Figures 1 to 4, the spring 5 drives the detonator carrier 11 via the differential 10 at a rate determined by the secondary timer 9 in the form of an escapement for example.

However, unlike the system of Figures 1 to 4, the spring 5 also provides the additional drive to the differential 10 to reduce the delay in completing the arming sequence. The delay is selectable in exactly the same way as in Figure 1 using pulse generator 16, input 13, decoder 14, down counter 15, OR gate 155, and solenoid 27 controlling clutch 7 and brake 8 as described hereinbef ore.

Figures 6 to 8 show a mechanical arrangement for implementing the system shown in Figure 5. The reference numerals used in Figures 6 to 8 have the same significances as in Figure 1 to 5. Figures 6 to 8 show the system in the three operational modes, winding, slow arming, and fast arming.

Referring to Figure 6, in the winding mode, the turbine 1 winds the spring mechanism 5 via a gearbox and optionally via a torque limiter 70 to prevent overwinding. A speed governer 4 regulates the rate of winding. In this example winding proceeds alone for 0.75 seconds from release of the bomb after which the spring can unwind. This time is controlled by the primary timer 6. A mechanism such as a ratchet may be provided between the turbine 1 and the spring 5 to allow the spring to be wound, but to prevent the spring driving the turbine.

The timer 6 has a shaft 53 upwardly (in the Figures) biassed by a spring 64. The upper end of the shaft has a toe 65 trapped under a timing plate 51 connected to a gear 60 drivingly engaged to the output shaft of the turbine 1. The plate 61 includes a notch 62 which after 0.75 seconds is rotated to the toe, which flies through the notch allowing the spring to unwind.

During the period of winding alone, with the toe 65 trapped under plate 61, the housing of differential 10 (to which the detonator carrier 11 is coupled) is locked by lock 19, and the housing of the differential 17 is similarly locked by lock 18.

The input shaft 71 from the spring mechanism 5 to the differential 10 is drivingly coupled by a drive shaft 72 to the input shaft 73 of the differential 17 via an idler gear 74.

With the dIfferentIals 10 and 17 locked by locks 19 and 18, and the shafts 71 and 73 coupled by shaft 72 and gear 74, any tendency of the spring to unwind is resisted. This is because such unwinding action tends to cause the differentials to rotate the shaft 75 between them in opposite directions.

Once the toe 65 flies through notch 62, the slow arming mode begins as shown in Figure 7.

As shown the brake 18 is released from the differential 17 but its output shaft 75 is locked by brake 18', thus preventing the shaft 75 from being driven by the spring mechanism 5 via the drive shaft 72.

The brake 19 is released from differential 10 however, allowing the spring mechanism 5 to drive the detonator carrier. This slow arming is effective from 0.75 seconds after release of the bomb until the maximum arming time.

If the arming time is to be reduced, the fast arming mode is selected as shown in Figure 8. In this mode, the state of the solenoid is changed to apply brake 18 to the differential 17 but release brake 18'. This allows the drive shaft 72 to cause shaft 75 to be driven by the spring. This causes the housing of the differential 10 coupled to the detonator carrier to rotate at a rate which is the sum of the rates of rotation of the shafts 71 and 75.

As described before, the period of fast arming is controllable by selecting the number stored in down counter 15.

Claims (1)

1. What we claim is:-

   1. An arming system, for a fuze, including: means for storing energy from an environmental input, means for completing an arming sequence after a delay dependent on the rate of supply of energy thareto, first means for supplying to the sequence completing means at least a portion of the said stored energy at a first rate to complete the sequence after a first delay, second means for supplying to the sequence completing means additional energy derived from the environmental input to speed the sequence to be completed after a second, shorter and variable delay, and means for controlling the supply of energy by the second means to select the delay to be used.

   2. A system according to Claim 1, wherein the additional energy is derived directly from the environmental input by the second means.

   3. A system according to Claim 1, wherein the additional energy is derived from the storing means by the second means.

   4. A system according to Claim 1, 2 or 3 wherein the arming sequence completing means comprises:- a carrier for carrying a device to complete an explosive train; and a differential gear mechanism having a housing coupled to the carrier to move it and two differential pinions coupled to the housing to rotate it and also connected to be driven by respective input shafts, the first means being coupled to one of the input shafts, and the second means being coupled to the other of the input shafts.

   5. A system according to Claim 4, wherein the second means includes a further differential gear mechanism having a rotatable housing and two differential pinions coupled to the housing, one of the pinions being connected to an input shaft for receiving the said additional energy derived from the environmental input, and the other pinion being connected to an output shaft drivingly coupled to the said other. of the input shafts of the. differential gear mechanism of the arming sequence completing means.

   6. A system according to claims 3, 4 and 5 in combination, wherein the storing means is coupled te means for providing energy from the environmental input and is further coupled to the said one of the input shafts of the differential gear mechanism of the arming sequence completing means and to a drive shaft which is coupled to the said input shaft of the further differential gear mechanism.

   7. A system according to any preceding claIm comprising timing means for causing energy to be stored in the storing means and not released therefrom for a predetermined period and for allowing the stored energy to be released from the storing means after that period.

   8. A system according to claim 7 when appended to claims 4 and 5 or when appended to claim 6, wherein the timing means comprises means for locking the housing of the differential gear mechanisms against rotation during the said predetermined period in which energy is stored in the storing means.

   9. A system according to any preceding claim, wherein the controlling means selects and controls the time for which the second means supplies the additional energy to the sequence completing means.

   10. A system according to claim 9, wherein the controlling means comprises an input for receiving an indication of the desired time for which the additional energy is to be supplied to the sequence completing means, means for producing an indication of the actual time of supply of the addional energy and means responsive to the indications to allow the supply of the additional energy until the actual and desired times are equal.

   11. A system according to claim 9 or 10, when appended to claims 4 and 5, or when appended to claim 6 or 8, wherein the controlling means comprises means for selectively releasing the locking of the housing of the further differential gear mechanism and locking the output shaft thereof against rotation.

   12. A system according to claim 4 or any one of claims 5 to 11 when appended to claim 4, wherein the storing means comprises a spring mechanism arranged to be wound by the environmental input, the spring mechanism being coupled to the said one of the input shafts of the differential gear mechanism of the arming sequence completing means.

   13. An arming system substantially as hereinbefore described with reference to Figures 1 to 4 of the drawings.

   16. An arming system substantially as hereinbefore described with reference to Figures 5 to 8 of the drawings.