Abstract:
The present invention relates to a method and a device for clearing mines deployed on or in the ground using a mechanical demining vehicle operating on the rotary cultivator principle in a way that prevents major damage to the demining tool ( 6 ) or the engine ( 5  ). The basis of the present invention is that the demining tool ( 6 ) is enabled to deflect away from large mine detonations whereby the demining tool ( 6 ) moves in coordination with the engine so that neither it nor its drive function suffers any major damage.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a method for rapid clearance of landmines located freely on the surface of the ground or buried in the upper ground layer whereby major damage to the demining vehicle and the demining tool mounted thereon is avoided. The present invention also incorporates a dedicated design of the demining vehicle. 
     The expression ‘landmines’ used herein denotes both smaller types of anti-personnel (AP) mines as well as the significantly larger anti-vehicle and anti-tank mines. 
     As there is usually a mix of both types of mines in a mined zone one must be prepared to neutralise both types when demining mined zones. 
     To be able to neutralise buried mines of the above types the ground needs to be comprehensively worked down to a sufficient depth in the upper ground layer. Previously, most interest has been focused on military requirements for demining vehicles for rapid breaching of routes through minefields, while the final demining of minefields after the end of a conflict has been performed by the time consuming method of using probes or electromagnetic mine detectors. The latter are very reliable provided individual mines each contain at least some quantity of metal, but the number of false alarms owing to metal fragments in the ground can be considerable, especially in areas where battles have previously been fought. Electromagnetic mine detectors are, in fact, highly sensitive and require, moreover, trained personnel. This type of mine clearance is thus very time consuming and labour intensive. as is the use of probes, and is also very costly. 
     In latter years, however, various quarters have started to show an interest in developing mechanical mine clearance vehicles that operate in a similar way to mechanical rotary cultivators and which, in suitable ground, have displayed a capability for clearing considerably greater areas per unit of time than has been possible previously. 
     Demining devices operating like rotary cultivators—by means of toothed rollers, demining discs or some other type of tool—either ‘chew’ or tear apart any mines in their path or cause them to detonate either in or under the demining tool. The larger types of mines, however, often cause such extensive damage to the demining tool that it must be repaired or replaced before demining operations can continue. The mounting and/or driveline for the demining tool may also be damaged and may be much more difficult to rectify than the tool itself which can usually be replaced fairly easily, but each work stoppage should preferably be avoided, especially if they involve costs for irreparable materiel. 
     The desire to avoid as far as possible damage to the demining tool, its mount and drive function must, however, be combined with enablement of a sufficiently large mass and force on the demining tool that it constantly reaches the desired, pre-determined operating depth. This places major—and partially contradictory—demands on the design. 
     SUMMARY OF INVENTION 
     The present invention now offers a combined demining tool and drive-motor mount for demining vehicles of the type herein mentioned that enables a large mass to be exerted on the demining tool while also minimising damage to the demining tool in the event of any large mine detonations in or under the tool, and that also prevents damage to the tool&#39;s drive function and engine. 
     As claimed in the present invention the demining vehicle&#39;s demining tool that operates in the ground similar to a rotary cultivator or, to be more precise, the mounts which carry the rotating demining tool are interconnected with the engine that drives the tool, and in the present case also drives the demining vehicle, to form a longitudinal (in relation to the vehicle) interactive unit. This unit in turn is mounted on the chassis of the demining vehicle via a torsion shaft transverse to the longitudinal axis of the chassis which shaft is located at the same height as the engine and is so located longitudinally that a necessary part of its dead weight bears on the demining tool. The angle setting of the complete unit relative to the ground surface is in turn determined by dedicated devices that lift the ends of the demining tool that bear most of the dead weight of the unit. The tilt of the demining tool relative to the ground surface is what determines the operating depth of the tool in the ground. The mounting of the demining tool / engine unit around a torsional shaft transverse to the longitudinal axis of the chassis in combination with a lifting function journalled at the ends of the demining tool that bear most of the combined weight of the unit mean in turn that any mine detonation in or under the demining tool initiates an upwards swing of the demining tool / engine unit which will minimise the damage effect of the detonation on the demining tool itself, its mounts and drive function. The complete basic concept thus provides a method for reducing the effect of a mine detonation in or under the demining tool by means of a weighted-load counter-spring of the active system in which the engine—which must be present and must provide high output—constitutes the main constituent of the counter-weight. As the demining tool and the engine constitute a coordinate unit in the longitudinal axis of the demining vehicle, the load on the drive coupling between the engine and demining tool is also reduced. 
     As claimed in a preferred variant of the demining vehicle in the present invention, the demining vehicle is equipped with further devices for as far as possible eliminating the negative effects of any mine detonations on the demining tool and its mounts and engine. 
     The demining tool mounts in the inverted cradle supporting the demining tool have thus been designed to be spring-loaded so that some of the stresses on the demining tool caused by any mine detonation can be assimilated immediately by the mounts. 
     Furthermore, the demining tool cradle is united with the engine of the above mentioned coordinate unit journalled around the transverse shaft by shock absorbers mounted between them with a great capability for assimilating stresses caused by any mine detonations. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The method and device as claimed in the present invention is defined in the Patent Claims below, and shall now be described in more detail with reference to the appended figures: 
     FIG. 1 shows a diagonal projection of a demining vehicle as defined in the present invention, 
     FIG. 2 shows a side projection of the same general vehicle, 
     FIG. 3 shows the chassis and drive tracks of the same vehicle, and 
     FIG. 4 shows a top projection of the same general vehicle. 
    
    
     DETAILED DESCRIPTION 
     Corresponding parts on the various figures have the same designation on each figure. 
     As shown in FIG. 4 the roller is divided into disks  9  which have a combined width greater than the width of chassis  1 . The demining vehicle in question comprises a chassis  1 , two drive tracks  2  and  3 , an armoured spring-mounted control cab  4 , and an engine compartment  5  incorporating an engine which is not illustrated in detail but which drives the demining vehicle as well as the rotatable demining tool  6  mounted at the front of the vehicle. The demining tool  6  comprises a central, mainly horizontal roller  7  fitted with a large number of demining discs  9  incorporating teeth  8  around their periphery. The demining tool  6  is in turn mounted and journalled for rotation in an inverted cradle  10 . As previously mentioned these mounts should preferably be sprung. Level with the horizontal cross-piece  11  of the cradle  10  there is a mitre-wheel gear  12  driven by the engine in the engine compartment via a drive shaft  13 . The power output from the mitre-wheel gear  12  is a second drive shaft  14 , which may be fitted with a torque limiter, that provides drive to the demining tool  6  at one outer end of the cradle  10  via an enclosed chain-drive  15 . FIGS. 1 and 2 illustrate two alternative designs of the enclosure of the mitre-wheel gear  12  and chain-drive  15 . 
     Propulsion of the demining vehicle over the ground is driven, as indicated previously, by the same engine as the demining tool  6 , but in the version illustrated in the figures propulsion is via enclosed hydraulic motors. 
     The demining tool  6  can be raised and lowered and can also be inclined or tilted relative to the horizontal plane by the same motor-driven hydraulics. 
     As previously described the drive shaft  13  is driven by the engine in the engine compartment  5 . Drive shaft  13  drives gear  12  which in turn drives second drive shaft  14  to drive the tool  6  which is mounted in cradle  10 . Thus, the various structures such as drive shaft  13 , gear  12 , drive shaft  14  and cradle  10  might be considered as mounting structure which connects the engine to the demining tool for rotating the demining tool and for creating an interconnected unit of the engine and the demining tool. 
     As claimed in the present invention the engine compartment  5  (the ‘5’ also denotes the engine therein) and the demining tool  6  and its cradle  10  are interconnected to form a functionally coordinate unit of previously described type in the longitudinal axis of the demining vehicle, which unit is journalled around the transverse shaft  16  which is located transverse to the longitudinal axis A of the vehicle (see FIG.  4 ). 
     The transverse shaft  16  mountings on the demining vehicle chassis are designated  17  and  18  in FIG. 3 whereof  18  is concealed from view in the figure. 
     The combined engine compartment and demining tool unit has its centre of gravity longitudinally ahead of the transverse shaft  16 . This means that more than half of the combined weight of the unit is concentrated over the demining tool  6 . 
     There are two hydraulic lift pistons (which could be considered as lift structure)  19  and  20  ( 20 , however, is concealed in the figures) that control the operating depth of the demining tool  6  in the upper ground layer. These two-hydraulic lift pistons incorporate damping functions that dampen the oscillation of the engine compartment and demining tool. The upper mounts  21  and  22  of the hydraulic lift pistons  19  and  20  are located in the combined unit, i.e. inside the engine compartment  5  ( 22  is concealed in FIG.  2 ), and the lower mounts  23  and  24  are located on the chassis  1  (see FIG.  3 ). 
     The demining tool  6  can also be inclined or tilted relative to the demining vehicle to enable small undulations in the upper ground layer to be followed. Tilting is controlled by two hydraulic tilt pistons  27  and  28  which also incorporate shock absorbers  25  and  26 . For lateral control of the cradle  10  of the demining tool  6  there is a further shock absorber  29  mounted between the chassis  1  and the cradle  10  designed to assimilate lateral oscillation between the chassis and cradle. 
     The cradle  10  of the demining tool  6  is also fitted with lateral supports, different designs of which are shown in FIGS. 1 and 2. 
     In FIG. 1 the lateral support consists of a pair of tubular lateral supports  30  and  31  located on each side of the demining vehicle that are mounted via journals both in the cradle  10  and in the vehicle chassis level with the transverse shaft  16 . 
     In FIG. 2 the same lateral support function is comprised instead of a rigid beam  32  journalled in the cradle  10  and similarly journalled level with the transverse shaft  16  in which latter mounting point one end of a support beam  33  is also journalled and which incorporates al least one shock absorber  34  and whose other end incorporates a twin link  35  and  36  via which it is mounted on the cradle  10 . The purpose of the twin link is to prevent twisting of the roller  7  when it is tilted. 
     The functioning of the complete demining vehicle is as follows. The operating depth of the demining tool  6  in the upper ground layer is controlled by the hydraulic lift pistons  19  and  20 . More than half of the weight of the engine compartment  5  and demining tool  6  and its cradle  10  bear on the demining tool. When the demining tool starts to operate the demining discs  9  work down to the desired depth and as the demining vehicle moves forwards the demining tool works through the upper ground layer. The objective is that mines encountered will either be ‘chewed’ into small harmless fragments or will be made to detonate. The tilt function enables the demining tool to follow any undulations in the ground so that it operates at a constant depth. 
     If a large mine such as an anti-vehicle or anti-tank mine is made to detonate in or under the demining tool, the resultant stresses are absorbed by the demining tool  6 , partially by the spring mounts in the cradle  10 , partially by the shock absorbers  25  and  26  located between the cradle and the engine, and partially by an upswing by the entire engine compartment and demining tool unit. 
     By means of this arrangement damage to the demining tool  6  is usually restricted to only one or two demining discs  9 , even in the case of very powerful mine explosions. and individual demining discs or sections thereof are relatively easy to replace. In an extreme case the complete demining tool  6  can be replaced. What is vital is that there is no damage to the cradle  10  or driveline of the demining tool.