Drive devices

Abstract: A drive device comprises driving and driven members (20),(19), and first and second elements (10), (7), one of the elements being movable with respect to the other. Energy derived from the coming together of the elements is stored (31), preferably hydraulically, and transferred to the driving member (20). Advantageously, the drive device is applied to a gun whereby the device may be used to drive the breech opening and closing mechanism (18) and/or the loading tray (73). The first and second elements include the beating plate (10) and a part of the breech structure (7). Energy to be stored and transferred is obtained from the recuperation of the gun after firing.

Description: This invention relates to drive devices and more particularly, but not exclusively is concerned with drive devices for actuating artillery mechanisms such as automatic or semi-automatic systems for the operation of the breech mechanisms of field artillery. The current trend in military philosophy is to use highly trained mobile forces which can be rapidly deployed to any troublespot. In order to operate effectively when deployed, they must be supplied with the appropriate equipment to enable them to complete their mission. In the case of ground forces, this often means field artillery and, to meet this requirement, new ultra lightweight equipment has been developed. A feature of this equipment is that it can be transported, either as a single load by a medium-size battlefield helicopter, or in dismantled sections by smaller helicopters. In order to achieve the ultra lightweight required, radical new design concepts have been evolved. In some cases these concepts have required design modifications or new ideas to give the minimum overall weight and most ergonomically usable design. For example conventional breech opening mechanisms use a cam and lever arrangement and normally can open the breech only to the 90° position (B on Figure 2 of the accompanying drawings). When the gun is horizontal (0°), as shown in Figure 2, 90° opening is acceptable (though not ideal), but when the gun is at high elevation (e.g. +70°), it is far from convenient. The access problem is compounded if the breech is well forward of the trunnion bearing in the run out position. While the cam and lever system can open the breech (to 90°) using run out energy, the problems created by the length of the levers required due to the run out position of the gun, the need for access to inspect the barrel during loading, and the difficulty actually of closing the breech when the gun is at high angles of elevation, make the conventional system unacceptable. A further disadvantage of the cam and lever system is that the breech must be closed by human intervention to disengage the cam and lever and reset it for the next cycle of operation. This involves physical effort. As an alternative to the cam and lever system, a hand-pumped hydraulic mechanism has been developed. Though this works well, it is slower in its operation than ideally required. It is a strategy of highly mobile forces, as herein before mentioned, to arrive unexpectedly, deliver a lightning 'surgical' strike (which could include a heavy artillery barrage) in order to achieve their objective, and then depart. Clearly, in such a situation, the maximum rate of fire achievable is required. DE-A-2519850 is concerned with self-powered automatic guns, such as heavy calibre machine guns, which require a source of external power. The type of ammunition envisaged in this citation is relatively light in comparison with that of the present invention and is fed into the gun in a continuous manner. The aim of this citation is to capture and store recoil energy hydraulically and supply it in a controlled manner to an external motor to drive the gun. GB-A-11616 discloses a hydraulic device which is intended to enable semi-automatic operation of the breech mechanism of large calibre guns. The energy is derived from a hydraulic accumulator which is energised during the running-out of the gun barrel and is recovered by the relative movement of two pistons of different diameters working in a common chamber. GB-A-14279 relates to a semi-automatic breech mechanism in which the breech is automatically opened while the gun is moving forward after recoil. A ram in the rear of a cylinder fast with the gun actuates the breech mechanism as the gun returns to its original position after firing and a rod and arm arrangement, operated manually allows closure of the block once a shell has been loaded. There is thus a need for an ultra lightweight, quick-acting breech opening and closing mechanism which requires the minimum of physical effort and which can be fully or semi-automatic requiring only the pressing of buttons or operation of simple control levers, i.e., where negligible physical effort is required. It is an object of the present invention to provide a drive device suitable for use in such a mechanism. According to the present invention there is provided a gun comprising: (i) a first element comprising a beating plate; (ii) a second element comprising a breech assembly moveable relative to the first element during recoil and recuperation of the gun on firing, between a first position at which the first and second elements abut and a second position at which the first and second elements are spaced apart, the arrangement being such that the second element approaches and contacts the first element on returning to the first position; (iii) a power operated breech mechanism to open and close the breech; (iv) a drive device operative to actuate said breech mechanism, comprising a driving member connected to the breech mechanism, the driving member being connected to the first element and the driven member being connected to the second element so that the driving member and the driven member are separable as the elements move between their first and second positions and re-engageable as the elements move between their second and first positions, and (v) means of storing energy and transferring energy to the driving member thereby to drive the driven member when the driving member and driven member are engaged. Preferably, the driving member is connected to the first element and the driven member is connected to the second element so that the driving member and the driven member are separable and re-engageable as the elements move between their second and first positions. In a preferred embodiment the connection between said driving member and said first element and between said driven member and said second element permit, when the driving and driven members are engaged, said driving and driven members to execute a rotary motion about an essentially common axis. Generally, the kinetic energy generated by the coming together of said elements is stored for subsequent use when said driving and driven members are fully re-engaged. Advantageously, the energy is stored in the form of pressure energy by the compression of a working fluid by a means operated by the coming together of said elements. In this case, the compressing means is preferably such as to reset itself when said elements are separated. Advantageously, a shock absorber is incorporated in said device to protect said device, and components connected thereto, from excessive forces arising during the coming together of said elements. The drive device is particularly useful for actuating mechanisms in a gun. Accordingly, a second aspect of the present invention provides a gun including a power-operated mechanism and a drive device as hereinbefore defined for actuating said mechanism. In a first embodiment of this aspect of the invention, the mechanism to be actuated is a loading tray for feeding ammunition into the breech of the gun. In a second embodiment of this aspect of the invention, the mechanism to be actuated is the breech operating mechanism of the gun. In this case, the drive device is used to provide a power train from the cradle to the breech mechanism. In such an application, when the gun is fired, the barrel and breech mechanism recoil along the cradle and recuperation and run out systems return the moving mass to its preset position. At this preset position, the driving and driven members of the device re-engage so that a drive train is re-established whereby power may be transmitted from an energy store on the cradle to the breech operating mechanism for the purposes of opening and closing the breech. In this embodiment, the first element, to which the driving member is connected, is a beating plate in the cradle. The second element, to which the driven member is connected, is a part of the breech structure of the gun. When the recuperation/run out is complete, this part of the breech structure comes to rest in hard contact with the beating plate; this contact thus defines the juxtapositioning of the driving and driven members and hence their re-engagement. Preferably, the drive transmission occurs via rotation of the driving member causing an equal angular rotation of the driven member about an essentially common axis. It is further preferred that the energy to be transmitted via the driving and driven members is generated by the movement of a piston in a cylinder compressing hydraulic fluid into a gas-filled accumulator. The cylinder is preferably fixed, e.g. in relation to the beating plate, and the piston is extendable outwards from the cylinder, e.g. by a spring, during the recoil and forced back into the cylinder during the recuperation via contact with the breech structure. Advantageously a shock absorbing means is incorporated into the piston rod which drives the piston to minimise the risk of damage due to shock loading, e.g. possible impact with the breech structure during the recuperation motion. The driving and driven members may be of block, part circular or part annular shape. Preferably, they separate and re-engage in a first direction and are held firmly together in the engaged position so that said driving member may impart rotary motion to said driven member with both said driving and driven members rotating about an essentially common axis lying in a second direction. Advantageously, said first and second directions are essentially at right angles to each other. Rotary motion may be provided to said driving member via a gearwheel mounted coaxially fast with said driving member and rotatable about said essentially common axis. A gear rack may be provided to mesh with said gearwheel to provide said rotary motion to said driving member, said gear rack being movable in both a first sense to cause rotary motion of said gearwheel in a first sense and in a second sense to cause rotary motion of said gearwheel in a second sense opposite to that of said first sense. The energy required to move said gear rack in said first and second senses is supplied from that obtained and stored by virtue of the coming together of said two elements. The driving and driven members may have concave part-circular inner faces extending for less than half the circumference of a circle and be disposed about the input drive shaft of the breech operating mechanism. Adjusting bolts are preferably provided so that the driving and driven members are in direct, or close, contact with each other. The driven member is fast with the input drive shaft of the breech operating mechanism so that, when the driving member is caused to rotate, the driving and driven members and the shaft all turn together essentially as a solid body about the axis of the shaft. When the gun is fired, the breech operating mechanism and the driven member move away under the recoil leaving the driving member static on its mounting in relation to the cradle and beating plate. When the run out is complete and the breech structure is hard against the beating plate, the driven member becomes re-engaged with the driving member via the adjusting bolts. Generally, the line of engagement of the driving and driven members is parallel to the axis of the gun and the common axis of the breech operating mechanism input drive shaft and the rotation of the driving and driven members is perpendicular to the axis of the gun resulting in an angle of essentially 90° between the two axes. In this preferred example, the driving member is fast with the gear wheel which meshes with the gear rack forming part of a hydraulically operated actuator. The actuator is fast with the cradle of the gun so that the axis of rotation of the gear wheel and driven member is essentially the same as the axis of the breech operating mechanism input shaft. Thus hydraulic actuation in one direction will rotate the gearwheel, driving member, driven member and shaft in a first direction to unlock and open the breech and actuation in the opposite direction will close and lock the breech. The hydraulic power for the operation of the actuator is derived from the stored supply created in the gas-filled accumulator by the action of the piston driven by the movement of the breech structure in the recuperation/run out phase. Forward and reverse valving is provided to control the direction of operation of the actuator, i.e. to open or close the breech. The hydraulic circuits include all the appropriate non-return valves, pressure relief valves, etc., plus a hand pump for initial pressurisation of the system. Preferably, a shock absorber is provided between the end of the piston rod and the point of contact with the second element (i.e the aforesaid part of the breech structure). The recuperating motion may result in a significant impulse when the breech structure strikes the end of the piston rod (which drives the piston in the cylinder to generate the pressurised working fluid). The shock absorber may consist of spring, hydraulic or pneumatic means, or combinations of these means. The shock-absorber is such as to generate a reaction to commence movement of the piston rod before metal-to-metal contact with the breech structure actually occurs. Preferably a means is provided to react to the re-establishment of hard contact between the elements (the breech structure and the beating plate) and the re-engagement of the driving and driven members such that the hydraulic actuator may not be operated prematurely. This means may be in the form of a safety valve in the hydraulic circuit which blocks all fluid flow to and/or from said hydraulic actuator until said driving and driven members are fully re-engaged. Alternatively said means may be a device to operate the hydraulic actuator as soon as said driving and driven members are fully re-engaged to open the breech ready for reloading. A further means may be provided to close the breech after the gun has been loaded by initiating the operation of the hydraulic actuator once a preset point of the loading cycle has been reached. In a preferred design, the final few millimetres of the run out, i.e. just as hard contact is being re-established between the breech structure and the beating plate, operates a safety valve, e.g. by pressing a plunger, to open the hydraulic circuits to the flow of fluid when the actuating valve(s) are opened, e.g. by manual means. Alternatively, the plunger movement may be used to initiate the breech opening cycle, e.g. via a mechanical, hydraulic or electrical link, i.e. semi-automatic operation. A similar device may be incorporated elsewhere on the cradle to react to a later point in the reloading cycle, e.g. the return to its rest position of the shell loading tray, and operate the hydraulic circuit to close the breech to provide a fully automatic operation. If desired, means may also be included for providing a quantity of more permanently stored energy to actuate the driving member before the first firing of said gun or at any other time when the energy derived from the coming together of the elements is inadequate. For a better understanding of the invention and to show how the same may be put into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:- Figure 1 is a block schematic representation of an ultra lightweight field howitzer in accordance with the invention, Figure 2 is a diagram of the breech end of the barrel of the howitzer of Figure 1, showing the breech in the open and closed positions, Figure 3 is a diagrammatic sectional elevation of the breech end of the barrel of the howitzer of Figures 1 and 2, Figure 4 is an elevation showing a dog-clutch forming part of the breech operating mechanism of the howitzer of Figure 3, Figure 5 is an elevation showing part of the dog clutch of Figure 4 and its connection to a double acting hydraulic rotary actuator, Figure 6 is a flow diagram of the hydraulic circuit in which the actuator shown in Figure 5 is incorporated, Figure 7 is a sectional elevation of a shock-absorbing mechanism incorporated in the breech mechanism of the howitzer of Figures 1 to 6, and Figure 8 is a diagrammatic representation of a modification of the howitzer of Figures 1 to 7 incorporating a power-operated loading tray in accordance with the invention. In this description, the same reference number is used for identical components fulfilling the same role in different figures. Figure 1 shows a block diagrammatic representation of an ultra lightweight field howitzer comprising a barrel 1, mounted in a cradle 2, and supported via a trunnion bearing 3, in a chassis 4 with support/recoil legs 5. The barrel 1 terminates in a breech assembly 7 having a forward face 6 and the chassis 2 includes a beating plate 10 having a rearward face 9. In use, the forward face 6 and the rearward face 9 are juxtaposed and, for reasons of clarity, barrel 1 is shown removed from chassis 2 so that the juxtaposition of the forward face 6 can be shown, via dotted line 8, in relation to the rearward face 9. Two headed arrow 11 indicates the movement of barrel 1 in use. On firing, the barrel recoils violently rearwards, indicated by the double arrow 11A and then the barrel 1 recuperates forwardly more sedately, as indicated by arrow 11B to its run out position. In the fully run out position, the front face 6 of the breech assembly 7 is hard against the rear face 9 of beating plate 10, as indicated by line 8. Figure 2 shows the breech end of barrel 1 of the howitzer. The juxtaposition of faces 6 and 9 is again shown with barrel 1 passing through a hole 12 in beating plate 10. The actual breech block consists of an obturator 13 and a member 16 and engages with mating screw threads in breech assembly 7. The screwing arrangement is such that limited rotational movement of member 16, about barrel axis 14 e.g. through angle ° will fully lock or fully unlock the breech block. Though member 16 rotates about barrel axis 14 to lock or unlock, mechanism 18 which actually operates the locking/unlocking of the breech block is driven from a rotational input via axis 15. As shown in Figure 2, axis 15 is located at right angles to and above axis 14. Referring to Figure 3, the breech operating mechanism 18 is connected to a driven member 19 which can engage with a driving member 20 such that rotation of the driving member 20 about axis 15 though ° firstly unscrews the breech block. Further rotation about axis 15 then opens the breech, moving members 13, 16 together in an arc 17. Designation A (Figure 2) shows the normal closed position of the breech block 13, 16 both when the block is fully screwed home and fully unscrewed, i.e., equivalent to rotations of both 0° and ° of the driven member 19 about axis 15. A further rotation of 90° by the driven member 19 about axis 15 opens the breech block 13, 16 to position B. This is the normal position for a conventional mechanical cam/lever system for operating the breech opening mechanism. By means of the present invention the breech block 13, 16 can be opened further to about 130°, as shown by position C. This additional degree of opening, greatly improves access to breech assembly 7 and into the bore of barrel 1, and is achievable only by means of a power-operated system. A simple visual estimation of the size, and hence mass, of breech block 13, 16, and the distance of their centres of mass from axis 15 will indicate that a massive turning moment must be applied to driven member 19 rotating about axis 15 in order to open the breech to position B, if the gun is nearly horizontal, or to close it to position A, if the gun is at a high angle of elevation. In order to supply the necessary turning moment to driven member 19 about axis 15, a manually operated hydraulic pump has been used. However, hand pumping is time-consuming and physically exhausting and a system driven from a separate power source would be a great advantage. However, as the breech 7, 13, 16 and operating mechanism 18, 19 are integral with barrel 1, they are subject to violent recoil 11A and less violent recuperation 11B forces and movements. It is thus inappropriate to locate any form of hydraulic system on breech assembly 7, unless it is capable of withstanding the recoil forces. This would require a massive, robust system which would, of course, be incompatible with the requirements of the ultra lightweight design principles. A simple hand pump could be used, but this is too slow and physically exhausting to the operator. The solution to this problem, in accordance with the present invention, is to provide a hydraulic power system in or on cradle 2 with a power transfer mechanism which is separable as the breech recoils, but is re-established by a mechanical connection when the recuperation is complete and the gun is fully run out. Figure 3 shows the principle of the separable mechanical drive connection. The breech operating mechanism includes an input shaft 25 rotatably mounted about axis 15. Surrounding shaft 25 are driven and driving members 19, 20 (respectively) having substantially semi circular concave inner faces. Driven member 19 is fast with shaft 25 and is also fast with the breech of the howitzer, i.e. with members 18, 13, 16 and 7; this connection is shown schematically by arrow 21. Driving member 20 is integral with actuator 26 (Figures 5 and 6) which is fast with cradle 2 and hence with beating plate 10, as indicated schematically by arrow 22. The spacing between members 19 and 20 can be accurately set by means of adjustable spacer bolts 23 (Figure 4) which are provided with lock nuts 24. Member 20 is rotatably mounted and is rotated by a hydraulic power system, as will be described hereinafter. Adjusters 23, 24 are thus set so that member 20 may rotatably drive member 19, and hence shaft 25, about axis 15 in either the clockwise or the anti-clockwise sense. If the adjusters 23, 24 are exactly set, there will be no relative motion between the heads of bolts 23 and surface 19A of member 19. As this is difficult to achieve, in practice, and to maintain on a field howitzer, faces 19A and the heads of bolts 23 are preferably made from hardened steel and lubricated, for example, with grease, to accommodate any minor degree of misalignment. Preferably a small gap for example of about 1 mm (not shown) is provided between the heads of bolts 23 and faces 19A so that no mechanical shock occurs on completion of the run out, i.e. when faces 6 and 9 come into contact. The presence of this gap does not significantly affect the rotary drive between members 19 and 20. Two headed arrow 11 indicates the relative movement of barrel 1 and breech members 7 and 16, including driven member 19, input shaft 25 and the breech opening mechanism 18. It will be apparent from Figures 3 and 4 that, on firing the howitzer, members 7, 16, 19 and 25 move violently to the left (arrow 11A) leaving members 20, 23 and 24 (relatively) stationary. After the recoil and during the recuperation, members 7, 16, 19 and 25 move steadily back to the right (arrow 11B) to re-establish the positions shown in Figures 3 and 4. The contact between face 6 of breech assembly 7 and face 9 of beating plate 10 defines the rest position at which the adjusting bolts 23 and nuts 24 are set. The word 'relatively' above is placed in parentheses to recognise that, though driving member 20 remains stationary relative to members 19 and 25, the whole gun, i.e., including cradle 2, chassis 4 and legs 5, undergoes considerable movement, vibration and the like during firing and absorbing the recoil and, to a lesser extent, during recuperation and run out. The arrangement of driving member 20 and driven member 19, via bolts 23 disposed about input shaft 25 and axis 15, has been described. This unit is referred to as a 'dog clutch'. From previous reference to the turning moments required to open and close breech block 16, 13, an indication has been given of the large torques which must be applied to shaft 25 and hence transmitted by driving member 20 and driven member 19. It will be noted that there is no direct mechanical connection between members 19 and 20 to provide the reaction forces. There is, however, a mechanical reaction path from driving member 20, via the mounting (arrow 22) and cradle 2 (not shown) to beating plate 10. Similarly, arrow 21 indicates the mounting of driven plate 19 on breech assembly 7. Thus, the relative location of members 19 and 20 in the (barrel) axial direction 14, corresponding to arrow 11, is determined by whether or not face 6 of breech assembly 7 and face 9 of beating plate 10 are in direct contact. Similarly the relative location of members 19 and 20 in planes at right angles to that of arrow 11 are determined by the freedom of movement of the barrel 1 in cradle 2. The recuperator and run out systems (not shown) of the howitzer exert a considerable force. Clearly as the run out proceeds, the actual axial force applied decreases as the gas volume of the recuperator increases and its pressure consequently falls. However, even at maximum run out, i.e., with faces 6 and 9 in hard contact, the net force pressing the two faces 6 and 9 together is still of the order of tonnes. Thus, unless the howitzer has been seriously damaged, or suffered a major failure, the recuperator pressure will be more than adequate to maintain the relative axial location of faces 6 and 9 and hence of members 19 and 20. It will also be noted that this large force, acting normally via face 6 onto face 9, provides a high frictional component to resist any reaction forces generated in planes at right angles to axis 14 (Figure 2) due to the torque transmitted between members 20 and 19. The main means of locating the barrel 1 in the cradle 2 is via lugs (not shown) which slide in axial guides (not shown). This means of location allows barrel 1 to move axially 11, but not radially. However, though both lugs and guides are precision machined, there must be some clearance if sliding motion is to occur and this clearance, possibly magnified by geometric factors, may have some affect on the alignment of members 19, 20 in planes radial to axis 11. However, any misalignment arising from this cause is unlikely to be more than 1-2 mm. A further factor which will affect the alignment of members 19 and 20 is thermal expansion of the breech assembly 7 after a number of shells has been fired. The maximum likely increase in the bulk metal temperature is about 100°C. This is sufficient to cause radial expansion of breech assembly 7 and so cause driven member 19 and shaft 25 to move radially outwards (i.e., upwards as shown on Figure 3) relative to driving member 20 mounted in relation to the cooler beating plate 10. Thus the means of transmitting the rotary motion must be capable of working under conditions of limited misalignment. The hardened bolt heads 23, bearing on hardened surfaces 19A, are ideally adapted to this and lubrication can be provided to minimise scuffing damage. Dog clutch 19, 20 must be 'double-acting' as effort is required to close as well as open the breech. For example, in the situation shown in Figure 2, lower bolt 23 (Figure 4) applies the force to unscrew the breech block and open it to positions B and C. On closing, lower bolt 23 controls the descent of breech block 13, 16, but the upper bolt 23 ensures that the obturator 13 is fully home before the block is screwed tightly closed. When the barrel 1 is at high angles of elevation, e.g., up to +70°, the division of the effort between the two bolts 23 will be different. As indicated above, the howitzer employs a hydraulic power system to store energy obtained from the recoil of the barrel 1 and to transfer that energy when desired to impart rotary motion to the driving member 20 in order to open and/or close the breech 13,16. The method by which the rotational drive is applied to driving member 20 will now be described with reference to Figures 5 and 6. The double-hydraulic actuator 26 includes piston(s) 27 which are fast with a rack gear 28 which in turn meshes with a gearwheel 29 which is fast with driving member 20. Gearwheel 29 and driving member 20 rotate about axis 15A. If all the alignments are precise, axis 15A will coincide with axis 15. However, in practice, even perfect alignment when various components are cold may be slightly out when the components are hot for example, after firing, so that minor misalignment can be accommodated via bolts 23 and surface 19A, as hereinbefore mentioned. It is, however, particularly desirable for gearwheel 29 and member 20 to be mounted in robust bearings (not shown) so that any reaction forces due to misalignment, etc. will not substantially affect the meshing of gear wheel 29 and rack 28. A suitable hydraulic circuit is illustrated in Figure 6. It should be noted that the sense of rotation 30 to open the breech is opposite to that shown in Figures 2, 3, 4 and 5. Energy is stored in the hydraulic system by pressurisation of the system and after each opening or closing of the breech, the hydraulic system must be repressurised. This pressurisation could be achieved solely by means of a hand pump 50. However, due to the pumping effort required and the resulting fatigue of the operators this would limit the rate of fire to approximately 3 rounds per minute, whereas by means of the hydraulic system described hereinafter a burst rate of fire of 4 rounds per minute can be achieved. It will, of course, be appreciated that in this art speed of operation is a particularly important factor. Thus, in practice the hand pump 50 is used only for initial pressurisation to operate the breech mechanism before the first round is fired. Hand pump 50 draws fluid from sump 46 via pipe 51 and non-return valve 52 and pressurised fluid is passed via pipe 53 and non-return valve 54 into accumulator 31. In an emergency, only sufficient fluid need be pumped to open the breech to 90° (Position B) and shut it again; pressure gauge 55 indicates when pumping has reached the required level. When the hydraulic system is pressurised the breech can be opened by moving lever 32 to the left to open valve 33 thereby allowing direct flow 33A from accumulator 31, through connections 34 to safety valve 35. In the illustrated embodiment safety valve 35 can allow hydraulic fluid to pass only when plunger 36 has been moved to the right against return spring 37. As shown in Figure 3, plunger 36 is mounted in, or close to, the beating plate 10 and is moved to the right only when breech assembly 7 is hard against the beating plate 10. On firing, the spring 37 returns the valve 35 to the closed position, as shown in Figure 6, and it will not re-open until faces 6 and 9 are in contact again. After passing through safety valve 35, hydraulic fluid enters dual overcentre valve 38 via pipes 39 and the pressure builds up until, at a desired pressure, flow of fluid through internal port 40 causes outlet valve 41 to move to the right and allow flow out of actuator 26 via pipe 26A. Under these conditions, hydraulic fluid flows through non-return valve 43 and pipe 26B into actuator 26, causing piston(s) 27 to move to the right and displace hydraulic fluid which leaves actuator 26 via pipe 26A and outlet valve 41. Dual over centre valve 38 appears very complicated, but produces a smooth flow of hydraulic fluid through actuator 26 to ensure a uniform rate of rotation of gear wheel 29 and smooth opening (or closing) of the breech block 16, 13. Movement of piston(s) 27 to the right causes gear wheel 29 to rotate anti-clockwise, as shown 30, and driving member 20 to operate the breech opening mechanism. Hydraulic fluid displaced from actuator 26 leaves via pipe 26A, outlet valve 41, pipe 48, safety valve 35, connector 34, valve 33A and pipe 45 to sump tank 46. Symbols 47 indicate that long pipe runs could be involved and connectors 34 are quick-release devices that minimise loss of fluid. They are used to allow the howitzer to be separated into a small number of major components for ease of transport. The long pipe runs 47 allow components, such as the sump tank 46, to be located at the most appropriate positions on the howitzer. To close the breech block lever 32 is moved to the right to bring reverse flow section 33B into operation. Flow is now into pipes 48 causing outlet valve 42 to open via pressure in internal port 45. Fluid now flows via non-return valve 44, moving piston(s) 27 to the left, and out via pipe 26B and outlet valve 42 back to sump 46. Vent 49 on the sump tank 46 eliminates the build up of back pressure or suction head. It will be noted from Figure 2 that the breech block 16, 13 must open to a 90° angle (Position B) to give clear access to the bore of barrel 1. This is the normal position for a mechanical opening system. However, when the hydraulic power is (relatively) unlimited, breech block 13, 16 can be opened a further 40° to point C (Figure 2). This greatly improves access to the bore of barrel 1, especially when the howitzer is at high angles of elevation. In this case, the total angular movement of breech block 13, 16 is 90° + 40° = 130°. The hydraulic system includes a piston 57 which moves in a cylinder 59. The piston 57 has a piston rod 58 and is biased by a biasing means such as a spring 56. The piston rod 58 is so disposed that in the runout position when the face 6 of the breech assembly 7 abuts the face 9 of the beating plate 10, the piston is held to the right in Figures 3 and 6 such that spring 56 is extended. When the howitzer is fired, breech assembly 7 recoils in direction 11A from beating plate 10. This allows spring 56 to urge piston 57 and piston rod 58 to the left in cylinder 59, drawing in hydraulic fluid from sump tank 46 via a non-return valve 60. When the recoil 11A is complete, breech assembly 7 will start to move in direction 11B under the effect of the recuperation and face 6 will contact piston rod 58 which, by virtue of spring 56, is at this stage extended fully out of cylinder 59. The result is that piston rod 58 is forced to the right driving piston 57 to force fluid out of cylinder 59 into pipe 61. As valve 60 will shut under positive pressure in pipe 61, the fluid can flow only via pipe 62 and non-return valve 63 into accumulator 31. A pressure relief valve 64 protects against over pressurisation and discharges any excess fluid to sump 46. When recuperation 11B is complete, there is a high residual pressure in pipes 61, 62. Valve 65 is a throttle check valve comprising non-return valve 60 and a variable throttle 66. The residual pressure in pipes 61, 62 escapes to tank 46 via throttle 66. The use of throttle 66 allows the shock absorber to reset itself preferentially as described hereafter. It will be apparent to those skilled in the art that whilst the recoil 11A is violent, the recuperation 11B is also rapid so that face 6 of breech assembly 7 will strike the extended end of piston rod 58 with a significant impulse. As piston rod 58, piston 57 and the hydraulic fluid in cylinder 59 cannot instantaneously start moving with a velocity equal to that of breech assembly 7, without serious risk of buckling piston rod 58, a means is required to absorb the initial impulse and provide a small time interval during which piston rod 58 may be accelerated up to the velocity of breech assembly 7. Figure 7 illustrates a suitable shock absorbing mechanism for this purpose. A machined cylindrical cap 67 is provided which fits closely over the end of piston rod 58, as shown in Figure 7. A spring 68 is disposed between end 58A of piston rod 58 and the flat inner end 67A of cap 67. When the howitzer is fired, breech assembly 7 recoils in direction 11A and, free from its compressive loads, spring 56 moves piston 57 to the left with respect to cylinder 59. The rating of spring 56 and the resistance against which it operates is such that the motion is fully complete in the time interval between firing and the contact of faces 6 and 67B near the end of the recuperation and run out phase of the barrel motion. As described below, spring 68 will be fully extended before the howitzer is fired. When face 6 strikes face 67B in the recuperation motion 11B, cap 67, which is light and strong, immediately starts to move to the right with the same velocity as that of face 6. In doing so, spring 68 is compressed. Thus the force of spring 68 acts on face 58A of piston rod 58 to cause it to start to move to the right. As the recuperation 11B continues, the compression on spring 68 increases as does the force on face 58A. The design ideal is that piston rod 58, and everything that it is driving, is accelerated to the velocity of face 6 before metal-to-metal contact 67A-68-58A occurs but, in practice, any significant acceleration imparted to piston rod 58 before hard impact with face 6 will greatly minimise the mechanical shock and consequent stress in piston rod 58. Spring 68 is stronger than spring 56 so that, on completion of the run out, spring 68 extends causing further stretching of spring 56 and further movement of piston 57 to the right displacing further fluid via pipe 61 and throttle 66 to tank 46. The advantage is that the shock absorber is fully deployed and thus able to protect piston rod 58 from damage as soon as the next round is fired. If cap 67 is a close fit over piston rod 58, the air 60 inside will not be able to escape quickly through annulus 69. Thus pneumatic pressure will also act on face 58A to supplement the action of spring 68. As an alternative to the shock absorbing mechanism described, a hydraulic shock absorber or any combination of spring, hydraulic or pneumatic devices may be used. As has been mentioned, the drive device of the invention has been primarily designed for use in an ultra lightweight howitzer. Although it is quite possible to design a piston rod 58 so robustly that the axial impacts from breech assembly 7 cause no undue stress, the magnitude of the axial impacts will generate considerable additional reaction forces, e.g. at the mounting points of cylinder 59 and on the guides in which barrel 1 slides. To accommodate these additional reaction forces, stronger structures are required, i.e., of more massive or better (more costly) materials. The use of a shock absorbing mechanism thus makes a substantial weight saving to the system and also contributes to the overall life of the howitzer for little additional complexity. The method of operation of the howitzer will now be described. Firstly it will be assumed that the howitzer has been moved to near the battlefield and initial preparations to fire have been completed e.g. the legs 5 (Figure 1) have been deployed, the shells have been brought up, etc. The breech operating mechanism is initially pressurised by means of hand pump 50 until the pressure 55 in accumulator 31 is adequate to open the breech preferably to position C, or at least to position B, and close it fully afterwards. The howitzer is then aimed and fired. Breech assembly 7 recoils in direction 11A allowing spring 56 to contract and move piston 57 and piston rod 58 to the left drawing hydraulic fluid from sump 46 via valve 60 and pipe 61 into cylinder 59. The spring 56 will have completed its travel by the time face 6 of breech assembly 7 has returned, in its recuperation phase, to strike outer face 67B of cap 67. The final part of the recuperation motion 11B causes the piston 57 to pump fluid through pipes 61, 62 and valve 63 into accumulator 31. Excess pressure is relieved via valve 64. When the gun has been fully run out, the residual pressure in pipes 61, 62 is relieved via throttle 66, allowing spring 58 to reset itself. It will be noted that the pressurisation of accumulator 31 occurs during the final part of the run out phase. The howitzer is never fired unless fully run out, i.e., with faces 6 and 9 in intimate contact, so that piston 57 will have completed its stroke. It is possible for a howitzer to be fired with less than a full charge. In such a case, the howitzer would not recoil to its fullest extent, but would recoil sufficiently to enable piston 57 to complete its full leftward travel so that, on recuperation, accumulator 31 would be fully recharged. Thus after initial pressurisation by hand pumping 50, the firing of each round leaves the system fully charged to open and close the breech for the next round. Hard contact between faces 6 and 9 aligns and brings into contact the driving and driven members 20, 19 of the dog clutch as well as moving plunger 36 to the right to open safety valve 35. This allows lever 32 of valve 33 to be moved to the left to open the breech to position C. Barrel 1 is then swabbed out and reloaded and the breech is closed manually by lever 32 which moves valve 33 to the right 33B. The howitzer can now be re-aimed and fired and the above sequence is then repeated. Valve 33 may be manual, semi-automatic or fully automatic, as required. In the manual version, shown in Figure 6, a spring 72 biases the valve to the central 33C shut position. In this position, a spring loaded pin (not shown) locks into a hole (not shown) so that the valve 33 cannot be operated without lifting the pin (not shown) and simultaneously moving lever 32, i.e. a two handed operation. Such a mechanism is known as a "detent" and minimises the risk of accidental, unintentional operation. For semi-automatic operation, a link 71 is provided between safety valve 35 and the operation of the valve 33. In this case, when the run out is fully complete, movement of plunger 36 causes valve 33 to be moved to position 33A, which opens the breech to position C. After reloading, the breech 13, 16 is closed manually by lever 32 (33B) in conjunction with the "detent". Link 71 may be mechanical, electrical, hydraulic or pneumatic. Fully automatic operation of the breech is also possible. In such a case, a second link 71A is used. This is operated by a hydraulic or electrical switch (not shown) activated by a suitable member on completion of its operation, e.g. by the return of the loading tray 73 (Figure 8) to its rest position after loading the shell into the breech. On completion of firing, the barrel 1 is cleaned, and oiled and the breech is closed manually by lever 32, and valve 33. Valves (not shown) to release residual hydraulic pressure to sump 46 may be operated, if required. The above description discloses how the invention may be put into effect in one particular application where extremely high reliability is required. Variations of the embodiment disclosed and other arrangements offering, for example, lower levels of reliability will be apparent to the man skilled in the art and, all fall within the scope of the present invention. The above described principle of taking some of the energy of the recoil, which is stored temporarily for use in the recuperation/run out, and converting it into a more permanent form of stored energy for use after the barrel has been fully run out, has other applications, for example in the operation of the shell loading mechanism, as shown diagrammatically in Figure 8. Referring to Figure 8, the loading tray 73 is mounted on cradle 2 by a parallel arm linkage 74A and 74B which can pivot about mountings 75A and 75B respectively. Fast with linkage arm 74A is gearwheel 29A and both share a common axis of rotation 75A. Gearwheel 29A is rotated via actuator 26 and rack 28, as hereinbefore described, to cause loading tray 73 to move from its rest position D to its loading position E (shown dashed), and back again. The operation of the actuator 26 is controlled by a hydraulic control system 77, for example similar to that shown in Figure 6, which derives its supply of pressurised fluid from the movement 11A and 11B of piston 57 in cylinder 59, as described hereinbefore. In this variation of the howitzer, no dog clutch 19, 20 is required, as the loading tray remains at position D, stationary with respect to cradle 2, while the recoiling mass 1, 7 passes below and returns to its location at the beating plate 10. In the example shown in Figure 8, in its rest position the tray 73 is located above barrel axis 14 but movement up from below or laterally from one side is equally possible. Location of the tray 73 above the axis 14 is preferred as, due to the low height of axis 14 above ground level, it is convenient to use, particularly when the howitzer is at high angles of elevation. Movement of tray 73 from position D to position E is rapid so that shell 76 gains considerable kinetic energy via shell stop 78; this, possibly in conjunction with other means, flicks the shell 76 into the breech, as shown. Tray 73 then returns to position D, where it operates a switch 79 to send a signal via linkage 71A to cause the breech control system (Figure 6) to close the breech. Thus, this provides a fully automatic system, though manual overrides may be provided, as required.

Claims: A gun comprising: (i) a first element (10) comprising a beating plate; (ii) a second element (7) comprising a breech assembly moveable relative to the first element (10) during recoil and recuperation of the gun on firing, between a first position at which the first and second elements (10),(7) abut and a second position at which the first and second elements (10),(7) are spaced apart, the arrangement being such that the second element (7) approaches and contacts the first element (10) on returning to the first position; (iii) a power operated breech mechanism to open and close the breech; (iv) a drive device operative to actuate said breech mechanism, comprising a driving member (20) connected to the breech mechanism, the driving member (20) being connected to the first element (10) and the driven member (19) being connected to the second element (7) so that the driving member (20) and the driven member (19) are separable as the elements move between their first and second positions and re-engageable as the elements move between their second and first positions, and (v) means of storing energy and transferring energy to the driving member (20) thereby to drive the driven member (19) when the driving member (20) and driven member (19) are engaged. A gun as claimed in claim 1, wherein the respective connections between said driving member (20) and said first element (10) and between said driven member (19) and said second element (7) permit when the driving and driven members are engaged, said driving and driven members to execute a common motion about an essentially common path (15). A gun as claimed in claim 2, wherein the motion is rotary motion about an essentially common axis. A drive device as claimed in claim 1, 2 or 3, including a means of storing energy (57,58,59,31) operative to store kinetic energy generated by the coming together of said elements (7,10) and to release said energy for use when the driving and driven members (20),(19) are fully re-engaged. A drive device as claimed in claim 4 wherein the means of storing energy includes a working fluid and a compression means (57,58,59) operative to compress the working fluid, whereby the means of storing energy is operative to convert the kinetic energy into the form of pressure energy and to store the pressure energy. A gun as claimed in claim 5, wherein the compression means includes biasing means (56) operative to reset the compression means when the elements (10),(7) are separated. A gun as claimed in any preceding claim, wherein shock absorbing means (67), (68) are incorporated into the drive device to protect the device, and components connected thereto, from excessive forces arising during the coming together of the first and second elements (10),(7). A gun as claimed in any preceding claim, wherein the gun is mounted in a cradle (2) and the drive device is operative to provide a power train from the cradle (2) to the breech mechanism. A gun as claimed in claim 8, wherein the cradle (2) includes a beating plate (10). A gun as claimed in claim 9, wherein the driving member (20) is disposed in fixed relation to the beating plate (10) and wherein the driven member (19) is disposed in fixed relation to a part of the breech structure (7). A gun as claimed in claim 9 or 10, wherein the first position represents the point at which the gun is fully run out and the breech structure (7) is maintained in hard contact with the beating plate (10), and the second position represents a position of the second element adopted during recoil of the gun in which the breech structure (7) and the beating plate (10) are spaced apart. A gun as claimed in any of claims 2 to 11, wherein rotation of the driving member (20) causes an equal angular rotation of the driven member (19) about a substantially common axis (15). A gun as claimed in claim 12, wherein the driving and driven members (20),(19) separate and re-engage along a first direction and wherein the substantially common axis (15) lies in a second direction substantially perpendicular to the first direction. A gun as claimed in claim 12 or 13, including a rack (28) and a gearwheel (29) wherein the gearwheel is mounted coaxially fast with the driving member (20), is rotatable about the substantially common axis (15) and meshes in said rack (28), and wherein the stored energy is transferred to the rack (28) such that the rack is operable to move in a first sense to cause rotary motion of the gearwheel (29) in a first rotary sense and in a second sense to cause rotary motion of the gearwheel (29) in a second rotary sense opposite to the first rotary sense. A gun as claimed in any of claims 12 to 14, wherein the breech mechanism includes an input drive shaft (25), the driving and driven members (20), (19) are disposed in confronting relation about said input drive shaft (25) and the driven member (19) is rotatably fast with said input drive shaft (25). A gun as claimed in claim 15, wherein the driving and driven members (20), (19) each include an inner face having a concave part-circular inner portion adapted to receive said input shaft (25), each inner portion extending for less than half the circumference of the shaft (25). A gun as claimed in claim 16, wherein adjustable bolts (23) are provided on one of said inner faces whereby the driving and driven members (20), (19) are in direct, or close, contact with each other through said bolts (23). A gun as claimed in any of claims 5 to 17, wherein the means of storing energy comprises an accumulator (31), and the compression means comprises a working fluid, a piston (57) and cylinder (59), wherein the working fluid is compressed into the accumulator (31). A gun as claimed in claim 18, wherein the cylinder (59) is fixed in relation to the beating plate (10), the piston (57) is biased to extend outwards from the cylinder (59) and is acted upon by the breech structure (7) during recuperation. A gun as claimed in claim 19, wherein the piston includes shock absorbing means (67), (68). A gun as claimed in claim 14 and any of claims 18 to 20 , wherein the gun further includes a hydraulic actuator (26) operative to move the rack (28), and forward and reverse valving (33),(40),(41), (42),(43),(44),(45) operative to control the flow of compressed working fluid to the hydraulic actuator (26) and thereby to control the sense of movement of the rack (28). A gun as claimed in any of claims 12 to 21 including a safety means (35), (36) operative to prevent rotation of the driving member (20) until the first and second elements are in hard contact. A gun as claimed in claim 22, wherein the safety means (35),(36) comprises a valve (35) operative to prevent flow of the compressed working fluid to the hydraulic actuator (26) until the driving and driven (20), (19) members are fully engaged. A gun as claimed in any preceding claim, wherein the drive device further operates a mechanism to actuate a loading tray (73) for feeding ammunition (76) to the breech of the gun.

Inventors: GORST JOHN BAILEY, GORST, JOHN BAILEY
Applicants: VICKERS SHIPBUILDING & ENG, VICKERS SHIPBUILDING & ENGINEERING LIMITED
Application year: 1993
Main classification: F41A5
IPC codes: F41A5