Abstract:
The invention provides a self-propelled mobile system that is characterized by a lightweight space frame chasis on which is mounted a large caliber artillery piece. The weight of the system is preferably less than 8.000 kg and the artillery piece preferably has a calibre of up to a 155 mm 52 caliber gun. The artillery piece may include a lightweight elevating and traversing mass and gun chasis mounted on a space frame vehicle, such vehicle having a weight which does not exceed 3,800 kg.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a self-propelled mobile system. Although for convenience, the description describes such a system that includes an artillery gun, such as a howitzer, mounted onto a vehicular platform for rapid deployment in the battlefield, it should be appreciated that the invention need not include such an artillery gun. In particular, the system is lightweight and maneuverable.  
         BACKGROUND OF THE INVENTION  
         [0002]    The emerging trend in today&#39;s battletield is to employ a rapid deployment force, which is lighter, more lethal and less dependent on logistic talls. A highly agile and capable force must be sufficiently versatile to substain a high operating tempo and defeat the opponent with minimum losses. They must then quickly re-position, refocus and execute subsequent missions against an opponent by employing asymmetric means.  
           [0003]    Currently, artillery support brigades operate large artillery weapons, such as howitzers which are towed. These howitzers are not integrated with the vehicles by which they are towed but may have auxiliary power units that are capable of propelling them to a maximum speed of about 20 km/h on paved roads and half that speed off-road. An example of such a system is the 155 mm/52 calibre FH2000 self propelled howitzer, which consists of a howitzer mounted with an auxiliary power unit (APU). These howitzer systems are relatively heavy and may need to be supported by a tow vehicle and ammunition supply train during long-distance operations. The main problem with such equipment is its limited maneuverability, which largely depends on the tow vehicle and the ability of the logistics support train to re-equip. Loading onto fixed-wing aircraft is also difficult due to its weight and bulk and/or the need for it to be towed into the aircraft. Other howitzer systems may be tracked, but these are unable to attain high speeds of say, up to 80 km/h and are not capable of being airlifted.  
           [0004]    In today&#39;s battlefield, the lack of mobility can well mean a lower survival probability, as shoot and scoot capability is important. It is with this motivation that the present invention of a lightweight self-propelled howitzer was conceptualized.  
         SUMMARY OF THE INVENTION  
         [0005]    It is an object of the present invention to provide a field artillery system that has improved firepower, in terms lethality and accuracy.  
           [0006]    It is another object of the invention to provide a field artillery system that is mobile, both strategically and tactically, whether in the air or on the ground.  
           [0007]    It is also on object of this invention to provide a field artillery system that has improved survivability in the field of operations and which requires minimal logistics support.  
           [0008]    According to one aspect of the present invention, there is provided a self-propelled mobile artillery system characterized by a lightweight space frame chassis on which is mounted a large caliber artillery piece.  
           [0009]    An artillery system in accordance with the invention has the advantage that it is lighter, faster and more maneuverable than existing long range artillery systems such as those discussed above.  
           [0010]    Preferably, the weight of tho system is less than 8,000 kg, and the artillery piece has a caliber of up to 155 mm 52 calibre. Furthermore, it is advantageous for the artillery piece to have a firing system which includes an elevating and traversing mass and gun chassis mounted on the space frame vehicle having a weight which does not exceed 3,800 kg.  
           [0011]    In the preferred embodiment, tho system includes dual-purpose hydro-pneumatic cylinders which provide suspension damping of the rear wheels and also are operable to move the rear wheels away from the ground for firing of the artillery piece. This has the advantage that stability of the system is improved during firing. The stability may be further improved by provision of retractable outriggers built at the rear of the gun chassis, each of which has a spade on its free end, the outriggers being operable to engage the ground with the spades embedded therein upon firing of the artillery piece. This will result in the transfer of most of the recoil load to the ground.  
           [0012]    Front wheels of the system are preferably mounted on the chassis by means of a multi-link independent suspension system. Advantageously, each such suspension system includes a hydro-pneumatic strut, which preferably utilizes nitrogen gas as a spring and hydraulic fluid as a damper, connected to a suspension arm which not only absorbs both shock and vibrations from the front wheels which arise during transit of the system and counter-recoil forces which arise during firing or the artillery piece, but also can have their length adjusted to vary the ride height of the system. This has the advantage that the ground clearance of the chassis can be adjusted to suit the particular terrain over which it is traveling and also to enable it to be loaded more easily onto transport vehicles such as fixed or rotary wing aircraft. A lower gun elevation can also be attained to enable the gun to fire at a lower elevation angle. This will contribute to the direct fire capability of the gun.  
           [0013]    The drive of the system is preferably provided by a turbo-charged intercooled diesel engine which is coupled to a hydromechanical transmission. One drive line, preferably the rear wheel drive, may then be effected by use of radial piston in-hub motors in the rear wheels, which have the advantage that they provide good spatial configuration for mounting the weapon platform and allow the weapon recoil force to be fully transferred to the ground. As a result, there is a smaller overall loading on the vehicle structure so that further weight saving is possible.  
           [0014]    Front wheel drive may also be provided by means of a hydromechanical gearbox which drives the front wheels. A microprocessor may also then be provided to enable drive modes to be switched between front wheel drive, rear wheel drive and four wheel drive modes to suit the particular terrain and circumstances.  
           [0015]    Other improvements and advantages of the invention will become apparent from the specific embodiment described below.  
           [0016]    It will be convenient to hereinafter describe an embodiment of the present invention with reference to the accompanying drawings which illustrate one form of a mobile artillery system incorporating the invention. It is to be understood that the particularity of the drawings and the related description is not to be understood as superseding the generality of the broad description of the invention as defined in the claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 is a perspective view of a mobile artillery system according to one embodiment of the invention.  
         [0018]    [0018]FIG. 1 a  is a perspective view of only the space frame of the mobile artillery system of FIG. 1 with all the other parts removed.  
         [0019]    [0019]FIG. 2 is a side view of the mobile artillery system looking from position A of FIG. 1.  
         [0020]    [0020]FIG. 3 is a side perspective view of the mobile artillery system of FIG. 1.  
         [0021]    [0021]FIG. 4 is a side view of the mobile artillery system, including shock isolators.  
         [0022]    [0022]FIGS. 5 a  to  5   c  illustrate the travelling positions of the rear wheels of the mobile artillery system from an extended to a fully retracted position.  
         [0023]    [0023]FIG. 6 is a side view of the mobile artillery system illustrating the suspension system.  
         [0024]    [0024]FIG. 7 is an enlarged view of the suspension system of the mobile artillery system.  
         [0025]    [0025]FIG. 8 is a schematic diagram illustrating the various components of the drive mechanism of the mobile artillery system.  
         [0026]    [0026]FIG. 9 is a diagrammatical representation of the components of a hydromechanical transmission comprising a mechanical transmission and hydrostatic transmission used in one embodiment of the invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0027]    Incorporation of a Space Frame Chassis  
         [0028]    [0028]FIG. 1 is a perspective view of a mobile artillery system according to one embodiment of the invention. The system includes a light weight vehicle  10  with a chassis  12  that comprises primarily of a space frame structure  14 . The space frame structure can be more clearly seen from FIG. 1 a , wherein all the other parts of the mobile artillery system have been removed. The space frame  14  requires less material to manufacture and makes the whole structure light-weight. The lightweight space frame design makes the complete system both air-portable and heli-portable. The design of the space frame  14  can thus be relatively light but achieve both structural and dynamic rigidity. The space frame  14  not only has to carry the intended payload, but can also withstand the stress and fatigue from prolonged travelling on off-road terrain.  
         [0029]    The space frame  14  of the vehicle  10  is reinforced at the points where the load is being transferred. The members of the space frame  14  are positioned to achieve maximum torsional and structural rigidity. The vehicle may be powered by a 125 kW turbo-charged intercooled diesel engine. The engine and necessary transmission lines are held on the vehicle chassis  12  via the space frame  14 . This is to reduce the weight of the complete system.  
         [0030]    The chassis  12  has front wheels  16  and rear wheels  17  mounted to it, and a driver compartment  18  towards the front of the vehicle  10  for steering the vehicle. A compartment for ammunition storage  20  may be incorporated to the chassis  12 .  
         [0031]    Mounted on top of the vehicle chassis  12  and integrated with the vehicle chassis  12  is a weapons system including a howitzer gun  22 , supported by a cradle  24  and saddle  26 . The howitzer gun  22  includes a barrel  28  and muzzle brake  30 . A barrel clamp  32  clamps the barrel  28  to the space frame  14  when the howitzer gun  22  is not in use.  
         [0032]    At the rear of the vehicle, a pair of outriggers  34  are mounted for stabilising the system structure during firing. The outriggers  34  are movable and retractable using hydraulic pistons (not shown) such that they may be raised in the position shown or lowered to engage the ground when in the firing position.  
         [0033]    In order to preserve the integrity of the lightweight space frame structure  14 , the recoil force is isolated by means of shock isolators  36  positioned between the gun chassis and the vehicle structure. They can also dampen vibration when the vehicle is travelling from point to point. The shock isolators are sized and mounted onto the space frame structure  14  by four mounting brackets. These mounting brackets are preferably welded onto the space frame  14  as shown in FIGS. 3 and 4. Two shafts (not shown) run the length of the gun chassis through the holes of the shock isolators  36 . The vehicle chassis  12  will then be supported by these shock isolators which help to reduce the amount of force that is being transmitted to the space frame structure  14 . During firing, the recoil load is transmitted from the trunnion to the gun chassis, shock isolator shafts and finally to the shock isolator  36 . The shock isolators  36  serve to isolate the firing load that is being transmitted to the space frame  14 , thereby protecting it from damage. FIGS. 3 and 4 show only one embodiment of the shock isolators  36  and the mounting brackets mounted to the space frame. It should be apparent that other embodiments are possible, wherein the firing load is transmitted to the space frame  14 . As such the vehicle structure can be optimized to be as light as possible and yet able to handle the tremendous firing load.  
         [0034]    In addition, roll-over bars  38  are designed to surround the driver compartment  38  to protect the driver and passengers in the event the vehicle rolls over, for example in undulating terrain. Each outrigger  34  has a spade structure  35  at its end. The spade structure  35  is self-embedding once the outrigger  34  is lowered by the hydraulic pistons. The embedding of the spade structure  35  enhances the stability of the howitzer gun  22  once deployed to be fixed to the ground and enables the first shot to be fired at high accuracy.  
         [0035]    [0035]FIG. 2 is a side view of the mobile artillery system looking from position A of FIG. 1. FIG. 3 is a side perspective view of the mobile artillery system of FIG. 1.  
         [0036]    The capability of the system to be both lightweight and attain structural rigidity enhances the effectiveness of the rapid deployment force to respond quickly to an emerging crisis in less time from base to a global theatre of operation. The integrated system offers high ground tactical mobility because of its capability to move rapidly about the battlefield. The howitzer  22  can thus be rapidly deployed to critical areas immediately upon landing so as to exert influence on the battlefield. Likewise, the howitzer  22  has the capability to evacuate from critical areas immediately. In the battlefield, high mobility means higher survival probability. The system, including the howitzer gun  22  also functions as the tow vehicle and logistics train, thus eliminating the dependency on a separate tow vehicle and logistics train.  
         [0037]    There are two operating modes of tho artillery firing system, the travelling mode and the firing mode. In the travelling mode, the elevation of the gun barrel  28  is kept low and passes through the cab of the vehicle (see FIG.  1 ). The safety roll-over bar  38  is hinged at both sides of the vehicle. It can be opened up from the midline at the top to allow traversing and elevation of the gun barrel  28  (see FIG. 2). In the firing mode, the outriggers  34  are lowered so that the spade structure  35  engages the ground to stabilize the howitzer gun  22  during firing, and the rear wheels  17  are lifted off the ground using trailing arms powered by hydro-pneumatic cylinders ( 72  in FIGS. 5 a - 5   c ) which function also as a rear wheel suspension. This lowers the rear end of the chassis  12  together with the gun platform to touch the ground.  
         [0038]    Rear Wheel Assembly  
         [0039]    [0039]FIGS. 5 a  to  6   c  illustrate the travelling positions of the rear wheels from a retracted position wherein the wheels are in contact with the ground, to a fully extended position, wherein the wheels are lifted off the ground.  
         [0040]    The rear wheels  17  are mounted onto specially designed wheel arms  70 . The wheel arms  70  are pivotally attached to the chassis  12 . Alternatively, it could be pivotally attached to the structure of the space frame  14 . Adjacent to the point of attachment of the wheel arm  70  to the chassis  12 , side hydro-pneumatic struts  72  are pivotally connected to the wheel arms  70 . As can be observed, extension and contraction of the side hydro-pneumatic struts  72  result in the raising and lowering of the rear wheels  17  in a leveraged arrangement. Between the side hydro-pneumatic struts  72 , a centre hydro-pneumatic strut  74  is positioned to provide an additional force to ensure that the rear wheels  17  are fully raised when the side hydro-pneumatic struts  72  are extended. The side hydro-pneumatc struts  72  and centre hydro-pneumatic strut  74  are interconnected by a portion of the space frame  14 .  
         [0041]    [0041]FIG. 5 a  shows the aide hydro-pneumatic struts  72  in a retracted position and the rear wheels  17  lowered to be in contact with the ground. FIG. 5 b  shows the side hydro-pneumatic struts  72  in an extended position such that the rear wheels  17  are rotated counter-clockwise and are raised off the ground. In this position, the rear wheels  17  are still not fully retracted. FIG. 5 c  shows the rear wheels  17  in a fully retracted position. The centre hydro-pneumatic strut  74  has been extended to push the axle  76  further so that the wheel arm  70  is almost horizontal and the rear wheels  17  are brought further towards the front of the vehicle.  
         [0042]    Multi-link Suspension System  
         [0043]    [0043]FIG. 6 is a side view of the mobile artillery system giving an overview of the suspension system associated with the front wheels  16 . A multi-link suspension  80  is incorporated to the front wheels  16 .  
         [0044]    [0044]FIG. 7 is an enlarged view of the multi-link suspension system of the mobile artillery system. The suspension system utilizes a multi-link independent suspension comprising a lower link  82  and an upper link  84  with hydro-pneumatic struts  86  for optimum off-road performance. The front wheel  16  is attached to the front wheel hub  90 . The suspension system is designed for three functions. The main function is to damp as well as to absorb the shock that is present from the undulating off-road terrain. The hydro-pneumatic struts  86  may use nitrogen gas as their spring and hydraulic fluid as the damper. Some of the advantages of incorporating the multi-link suspension with the hydro-pneumatic suspension are:  
         [0045]    1) small space requirement;  
         [0046]    2) a kinematic or elasto-kinematic toe-in change tending towards understeering;  
         [0047]    3) easier steerability with existing drive;  
         [0048]    4) low weight;  
         [0049]    5) independence by there being no mutual wheel influence;  
         [0050]    6) ability to counteract the change of wheel camber due to roll pitch of the vehicle body;  
         [0051]    7) Higher off-road mobility and speed;  
         [0052]    8) Larger wheel travel;  
         [0053]    9) Progressive suspension characteristics allow for high driving speeds while providing improved comfort for driver and crew.  
         [0054]    The secondary function of the suspension system is to serve as a shock absorber for the counter-recoil force during firing. The gun recoil force during firing causes the front of the vehicle to lift off the ground. A counter-recoil force is usually generated after gun recoil due to a whip-lash effect. As the counter-recoil force is tremendous, the suspension at the front of the vehicle has to be sized to absorb and damp the shock so as to prevent damage to the vehicle instrumentation and other systems on-board.  
         [0055]    The third function of the suspension system is to provide height adjustment control of the vehicle. This is accomplished by depressurizing the fluid in the cylinders of the hydro-pneumatic struts  86  by means of relief valves (not shown) that are incorporated into the cylinders and thus allow the cylinders to be compressed. The reason for allowing the height adjustment is to enable the howitzer gun  22  to fire at a lower elevation angle. This will contribute to the direct fire capability of the gun. The height adjustment control will also provide more height clearance in situations where lower height is required, eg. when the vehicle is loaded onto a C-130 airplane.  
         [0056]    It should be appreciated that hydro-pneumatic struts using hydro-pneumatic cylinders can also be added to the rear suspension. One advantage of doing so is that the height of the rear of the vehicle is adjustable. This will be very useful for clearing obstacles or difficult terrain.  
         [0057]    Hydraulic Drive System  
         [0058]    [0058]FIG. 8 is aschematic diagram illustrating the various components of the driving mechanism of the mobile artillery system. The system includes a turbo-charged inter-cooled diesel engine  100  which is coupled to a rear pump  102 , auxiliary pump  104  and steering/brake pump  106 . The rear pump  102  is operatively connected to a manifold  120  and to radial in-hub motors  112  towards the rear of the vehicle via fluid drivelines.  
         [0059]    There is a switch on the driver&#39;s instrumental panel (not shown) which allows the driver of the vehicle to select between front wheel drive mode (on-road), four-wheel drive mode (off-road) and automatic mode. Front wheel drive mode allows the vehicle to travel on roads at higher speeds. Four-wheel drive mode allows the vehicle to travel off-road up to a maximum speed of about 25 km/h, depending on the hydraulic radial piston in-hub motor. The automatic mode allows the vehicle to travel in a mixed configuration of four wheel drive and two wheel drive depending on the speed of the vehicle. A vehicle speed below 25 km/h will have a four wheel drive configuration while a speed above 25 km/h will have a two wheel drive configuration. The switching of these two modoes is controlled automatically by a microprocessor  122 . The turbo-charged diesol engine  100  drives a hydromechanical tansmission  108  comprising  2  shafts: 1) a hydrostatic transmission and 2) a mechanical transmission. The hydromehanical transmission is connected to a differential  110  which drive propeller shafts  18  to which the front wheels  16  are attached.  
         [0060]    The input from The engine is split by using two gears (not shown). The hydrostatic transmission consist of a variable displacement pump which is closely coupled to a fixed displacement motor or variable displacement motor. The mechanical transmission consists of a set of planetary gears and a clutch. The purpose of the clutch is to engage and disengage the hydroulatic and mechanical modes.  
         [0061]    The hydrostatic transmission and mechanical transmission will now be described with reference to FIG. 9. In the hydrostatic transmission, when the engine flywheel rotates a gear G 1  in the clockwise direction (as seen from the engine), another gear G 2  will rotate in the anti-clockwise direction. The rotation will be transmitted via a shaft S 1  to a gear G 3 . A shaft S 2  will drive the input of hydrostatic transmission (pump) and the output will be shaft S 3  (from the motor). The torque from the motor will subsequently be transmitted to gear G 8  by gear G 4 . The direction of Gear G 8  is the same as the engine rotation. The speed of the hydrostatic transmission can be varied by adjusting the swash plate in the variable displacement pump. As the angle of the swash plate in the pump is increased, more flow results and the motor will turn faster. This will increase the speed of gear G 4  and eventually to the output speed N o .  
         [0062]    In the mechanical transmission, rotation of gear G 5  is effected by gear G 3 . Gear G 5  rotates the shaft S 4  in the same direction. Shaft S 4  is directly connected to the planetary carrier. The rotation of the planetary carrier will cause all the planetary gears G 6  to rotate. Since the sun gear G 7  is in direct contact with the planetary gears, the sun gear will also rotate together with the planetary gears, which will in turn cause the shaft S 5  to rotate in the same direction. With the clutch engaged (hydromechanical mode), this rotation will be transmitted to gear G 8  via shaft S 6 . Gear G 8  will then rotate gear G 9  via a shaft. The rotation from the gear G 9  will be transmitted to the ring gear, which will eventually cause the output shaft to the differential to rotate at the speed of N o .  
         [0063]    There are three different drive modes: i) the hydrostatic mode whereby the swashplate is varied to cause the motor to rotate with the clutch disengaged; ii) the hydromechanical mode whereby the swashplate is varied and the clutch is disengaged; iii) the swashplate is at zero displacement (no flow to the motor) and the clutch is engaged (fully mechanical).  
         [0064]    The front wheels  16  are steerable via a steering system  116  and steering pump  106 . The rear pump  102  also transmits power to a pair of in-hub radial piston motors  112 , each of which drives a rear wheel  17 . A brake pump  106  is operatively connected to brake callipers  112  which control brake discs  114  at the front and rear wheels  16 , 17 . The components of the system are generally controlled by a microprocessor  122 .  
         [0065]    The use of the radial piston in-hub motors  112  provide good spatial configuration for the mounting of the weapon platform and allow the weapon recoil force to be fully transferred to the ground through an integrated firing platform. Due to this design, there are fewer requirements on the strength of the space frame  14 , thus allowing for weight savings.  
         [0066]    The vehicle can move at up to speeds of 80 km/h on 4×2 drive (front wheel drive) on paved roads and the two rear wheels  17  can be activated for 4×4 drive off-road. The vehicle is capable of being deployed and displaced within 30 seconds to 1 minute. It can move 500 meters within 30 seconds and can be ready for firing in less than 30 seconds from the deployed position.  
         [0067]    During highway travelling, the hydromechanical transmission is used to drive the front wheels  16  while the rear radial piston motors  112  are allowed to freewheel. During off-road travelling, all the four wheels  16 , 17  are activated to optimize wheel traction.  
         [0068]    The extensive application of lightweight materials such as titanium alloys further helps to reduce the weight of the whole system and enhance its operational mobility.  
         [0069]    While a particular embodiment of the invention has been shown and described, it will be appreciated by these skilled in the art that changes and modifications of the present invention may be made without departing from the invention in broadest aspects. As such, the scope of the invention should not be limited by the particular embodiment and specific construction described herein but should be defined by the appended claims and equivalents thereof. Accordingly, the aim in the appended claims is to cover all such changes and modifications as fall within the spirit and scope of the invention.