Abstract:
A device for suspending the cab of a vehicle includes a U-shaped main torsion bar ( 5 ) and a main actuator ( 3 ). The U-shaped main torsion bar ( 5 ) is positioned more or less along the longitudinal axis of the vehicle.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention is of particular use in suspending cabs of all-terrain vehicles, which are subjected to high-amplitude shocks. 
         [0002]    One particular application of the invention is the suspension of cabs of all-terrain materials-handling vehicles, particularly the cabs of handling vehicles with telescopic arm. 
       BACKGROUND OF THE INVENTION 
       [0003]    In the known way, the cab suspension of telescopic-arm handling vehicles comprises three or four mounting points fitted with rubber mounts. These rubber mounts provide limited filtration of vibrations in the low frequencies, in high-magnitude shocks with an amplitude of the order to one decimetre. 
         [0004]    Another suspension system used on agricultural tractors or all-terrain machines involves linear-travel spring-damper assemblies which have a degree of freedom in the direction of vertical translation. Such a suspension system does, however, entail stabilizing the other degrees of freedom through the use of link rods or parallelograms. However, the independence of the mounting points and the weight distribution allow disruptive coupling between the bouncing, pitching and rolling movements of the cab. 
         [0005]    In order to avoid these undesirable movements, stabilizing torsion bars that limit the coupling may be provided. It is also possible to provide active systems comprising actuators and sensors driven by the on-board computer system of the machine comprising the cab. 
         [0006]    Document FR 2 749 265 describes a main suspension with just one single U-shaped torsion bar to limit the connections between the chassis and the suspended bodyshell. The bar is secured by fixings at its base and by two rotational articulations at the respective ends of its arms. The reduction of noise bridges between the chassis and the driving cab of the vehicle means that the cab can be very well soundproofed at low cost. The use of the U-shaped torsion bar which constitutes one sole main suspension member thus means that the cost of suspending the cab can be reduced. However, in order to avoid pitching movements a U-shaped secondary torsion bar is provided, interposed between the cab and the chassis. This U-shaped secondary torsion bar is positioned in such a way that its base runs parallel to the axis of the vehicle and its arms run transversely to the said axis. 
       SUMMARY OF THE INVENTION 
       [0007]    It is a first object of the invention to improve on the prior art that is known, notably from document FR 2 749 265, by proposing a suspension device that is compact, easy to manufacture and has a reduced number of moving parts. 
         [0008]    It is a second object of the invention to avoid coupling between the bouncing, pitching and rolling movements. 
         [0009]    One subject of the invention is a device for the suspension of a vehicle cab comprising a U-shaped main torsion bar and a main actuator, characterized in that the U-shaped main torsion bar is positioned more or less along the longitudinal axis of the vehicle, to keep the cab in a stable position and reduce the pitching thereof. 
         [0010]    According to other alternative features of the invention:
       the ends of the U-shaped torsion bar may be fixed to the front and to the rear of the cab, or the ends of the U-shaped torsion bar may be fixed to the chassis of the vehicle;   the main actuator is advantageously positioned at the rear of the cab;   the main actuator is preferably chosen from the group including: a conventional assembly comprising coil spring and telescopic hydraulic damper, a passive pneumatic or oleopneumatic system, an active hydropneumatic system coupled to an electronic computer, a magnetor rheological variable-damping system, and an elastomer spring;   at least one end of the U-shaped torsion bar may be connected to the cab via a damper means;   the damper means may be an elastomer damper means;   the damper means may be an inertia damper;   the damper means may be a telescopic hydraulic damper;   the device may comprise a mechanism controlling the relative displacement of the top and bottom points of a deformable quadrilateral formed by the points of articulation of an arm and of the U-shaped torsion bar.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The invention will be better understood through the description which will follow, which is given by way of nonlimiting example with reference to the attached drawings in which: 
           [0020]      FIG. 1  schematically depicts a perspective view of a cab suspension device incorporated into an all-terrain vehicle. 
           [0021]      FIG. 2  schematically depicts a rear view of a suspension device of  FIG. 1  according to the invention. 
           [0022]      FIG. 3  schematically depicts a rear view of another device according to the invention. 
           [0023]      FIG. 4  schematically depicts a perspective view of a piece of an all-terrain handling vehicle equipped with a second cab suspension device according to the invention. 
           [0024]      FIG. 5  schematically depicts a perspective view of a third cab suspension device incorporated into an all-terrain vehicle. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    With reference to  FIGS. 1 to 5 , elements that are identical or functionally equivalent are identified by identical reference numerals. 
         [0026]    In  FIG. 1 , an all-terrain handling vehicle, for example a handling vehicle with telescopic arm, comprises a self-propelled chassis ( 1 ) and a cab ( 2 ) that is suspended with respect to the self-propelled chassis ( 1 ). 
         [0027]    The chassis ( 1 ) comprises a reinforcement ( 1   a ) and the cab ( 2 ) comprises a mount ( 2   a ). 
         [0028]    A damping member ( 3 ), for example an oleopneumatic member ( 3 ), and a suspension arm ( 4 ) are mounted between the self-propelled chassis ( 1 ) and the cab ( 2 ) that is suspended with respect to the self-propelled chassis ( 1 ). 
         [0029]    Advantageously, the oleopneumatic cylinder ( 3 ) is mounted on two pivot pins ( 3   a ,  3   b ), whereas the arm ( 4 ) is mounted on one pivot pin ( 4   a ) and the aforementioned pivot pin ( 3   b ) which is common to the oleopneumatic cylinder ( 3 ). 
         [0030]    The pivot pin ( 4   a ) and the pivot pin ( 3   a ) are secured to the chassis ( 1 ) while the pivot pin ( 3   b ) is secured to the cab ( 2 ). 
         [0031]    A U-shaped main torsion bar ( 5 ) having a base ( 5   a ) and two lateral arms ( 5   b ,  5   c ) is mounted between the cab ( 2 ) and the chassis ( 1 ). 
         [0032]    The U-shaped main torsion bar ( 5 ) is articulated at its ends to two pivot pins ( 6  and  7 ) of the cab and by its central part ( 5   a ) on bearings ( 8 ) of the chassis ( 1 ). 
         [0033]    The points of articulation ( 3   b ,  4   a ,  7  and  8 ) define a deformable quadrilateral of which two points ( 4   a  and  8 ) are located on the chassis ( 1 ) and two more points ( 3   b  and  7 ) are located on the cab ( 2 ). 
         [0034]    The suspension member ( 3 ) essentially vertically filters shocks and vibrations as the all-terrain handling vehicle moves around. 
         [0035]    The triangle formed by the vertices ( 3   a ,  3   b  and  4   a ) deforms, thereby filtering the vibrations and movements of the cab ( 2 ) in pitch and roll. 
         [0036]    The cab ( 2 ) is kept in a stable position by the 
         [0037]    U-shaped torsion bar ( 5 ) comprising the elements ( 5   a ,  5   b ,  5   c ). 
         [0038]    The articulation ( 6 ) is positioned more or less above the plane defined by the elements ( 5   a ,  5   b ) of the U-shaped torsion bar. 
         [0039]    The U-shaped torsion bar ( 5 ) thus includes an element ( 5   c ) which is bent upward, so that the point ( 6 ) of articulation to the cab is notably higher up than the point ( 7 ) of articulation situated at the rear of the cab. 
         [0040]    By providing a U-shaped torsion bar ( 5 ) that is very stiff, the vertical and transverse loadings are fully absorbed by the elastic damping member ( 3 ). 
         [0041]    Reactions are transmitted between the front and the rear of the cab ( 2 ) by the torsion bar ( 5 ) interacting with the front ( 6 ) and rear ( 7 ) articulations. 
         [0042]    The stiffness of the U-shaped torsion bar ( 5 ) allows reactions to be transferred between the front and the rear of the cab ( 2 ) in order to damp the pitching of the cab ( 2 ). 
         [0043]    The suspension device according to the invention is depicted in the neutral position in  FIG. 2 . 
         [0044]    The suspension device according to the invention comprises the mount ( 2   a ) secured to the cab ( 2 ), the reinforcement ( 1   a ) secured to the chassis ( 1 ), the damping member ( 3 ), and the U-shaped torsion bar ( 5 ) articulated to the pivot pins ( 6  and  7 ) at its two ends. 
         [0045]    The damping member ( 3 ) in this example comprises an outlet ( 3   c ) for height adjustment, should the operator of the all-terrain handling vehicle wish to alter the attitude or height of the cab ( 2 ) for the job in hand. 
         [0046]    The pivot pins ( 6  and  7 ) are secured to the cab ( 2 ) in this embodiment. 
         [0047]    The suspension device inclined with respect to the vertical direction of loading means that a horizontal loading due, for example, to braking, or a combined horizontal and vertical loading due, for example, to passage over rough terrain, can be partially damped. 
         [0048]    The arms ( 5   b  and  5   c ) may differ in length in order to introduce a particular dynamic response in stiffness and in damping depending on the positioning of the articulation point ( 6 ). 
         [0049]    An auxiliary damping member ( 19 ) as depicted in  FIG. 5  may also be mounted between the cab ( 2 ) and the chassis ( 1 ), at the front of the cab ( 2 ) in order to make up for the lack of intrinsic damping of the torsion bar and of its rubber bearings. 
         [0050]    In  FIG. 3 , another device according to the invention comprises an arm ( 4 ) that is articulated between the chassis ( 1 ) and the cab ( 2 ), a U-shaped torsion bar ( 5 ) mounted via its ends ( 6  and  7 ) to the cab ( 2 ) and articulated on the bearings ( 8 ) of the chassis ( 1 ), and a damping element ( 13 ). 
         [0051]    The damping element ( 13 ) comprises a coil spring ( 13   a ) and a telescopic hydraulic damper ( 13   b ). 
         [0052]    The points ( 3   b ,  4   a ,  8  and  7 ) of articulation define a deformable quadrilateral the deformation of which is damped by the damping element ( 13 ). 
         [0053]    The damping element ( 13 ) comprising the coil spring ( 13   a ) and the telescopic hydraulic damper ( 13   b ) may be replaced by any equivalent system without departing from the scope of the present invention. 
         [0054]    Thus, any elastic or damping element may be mounted in place of the member ( 3 ) or of the damping element ( 13 ), for example: a passive pneumatic system with no height adjustment, a passive oleopneumatic system with no height adjustment, an active hydropneumatic system coupled to an electronic computer, a magnetor rheological variable damping system or a simple elastomer spring. 
         [0055]    The choice of main elastic damping element is made by the person skilled in the art according to the desired level of performance sought for the suspension device. 
         [0056]    In the example depicted, the points ( 6  and  7 ) of articulation of the ends of the U-shaped torsion bar ( 5 ) are positioned on either side of the cab ( 2 ), it being possible for this arrangement to be modified without departing from the scope of the invention. 
         [0057]    Where there is a desire to incorporate a system having greater flexibility in roll, or even where there is a desire to impose a pendular motion, the two articulation points ( 6  and  7 ) are sited in the corresponding positions. 
         [0058]    In order to ensure the stability of the cab ( 2 ), at least one of the articulation points ( 6  or  7 ) is preferably positioned above the plane (P) containing the centre of gravity of the cab. 
         [0059]    In  FIG. 4 , another embodiment of the all-terrain handling vehicle according to the invention comprises a suspension device having a U-shaped torsion bar ( 5 ) and a deformable quadrilateral defined by the articulation points ( 4   a ,  3   b ,  7  and  6 ), and a damping element or member ( 3 ). 
         [0060]    The ends ( 7  and  8 ) of the U-shaped torsion bar ( 5 ) are not fixed rigidly to the cab ( 2 ) but are connected via an additional damping device ( 9 ) to a fixed point of the cab ( 2 ). 
         [0061]    The presence of the elastic elements ( 9 ) ensures greater lateral flexibility. Where it is desired to impose a pendular motion, while at the same time limiting the rolling motion of the cab ( 2 ), provision may be made for a link rod mechanism ( 10 ) to be fitted to control the relative displacement of the top ( 3   b ) and bottom ( 7 ) points of the deformable quadrilateral ( 3   b ,  4   a ,  8  and  7 ). 
         [0062]    The mechanism ( 10 ) thus allows control over the motion when the suspension device according to the invention is in operation. 
         [0063]    In  FIG. 5 , another embodiment of the all-terrain handling vehicle according to the invention comprises a suspension device having a U-shaped torsion bar ( 5 ), a deformable quadrilateral defined by articulation points ( 4   a ,  3   b ,  17  and  18 ), and a damping element or member ( 3 ). 
         [0064]    The chassis ( 1 ) comprises a reinforcement ( 1   a ) and the cab ( 2 ) comprises a mount ( 2   a ). 
         [0065]    An oleopneumatic damping member ( 3 ) and a suspension arm ( 4 ) are mounted between the self-propelled chassis ( 1 ) and the cab ( 2 ) that is suspended with respect to the self-propelled chassis ( 1 ). 
         [0066]    Advantageously, the oleopneumatic cylinder ( 3 ) is mounted on two pivot pins ( 3   a ,  3   b ), whereas the arm ( 4 ) is mounted on one pivot pin ( 4   a ) and the aforementioned pivot pin ( 3   b ) that is common to the oleopneumatic cylinder ( 3 ). 
         [0067]    The pivot pin ( 4   a ) and the pivot pin ( 3   a ) are secured to the chassis ( 1 ), whereas the pivot pin ( 3   b ) is secured to the cab ( 2 ). 
         [0068]    A U-shaped main torsion bar ( 5 ) comprising a base ( 5   a ) and two lateral arms ( 5   b ,  5   c ) is mounted between the cab ( 2 ) and the chassis ( 1 ). 
         [0069]    The U-shaped main torsion bar ( 5 ) is articulated by its central part ( 5   a ) to bearings ( 18 ) of the cab ( 2 ) and at its ends to two pivot pins ( 16  and  17 ) of the chassis ( 1 ). 
         [0070]    The articulation points ( 3   b ,  4   a ,  17  and  18 ) define a deformable quadrilateral of which two points ( 4   a  and  17 ) are located on the chassis ( 1 ) and two other points ( 3   b  and  18 ) are located on the cab ( 2 ). 
         [0071]    The suspension member ( 3 ) essentially vertically filters shocks and vibrations as the all-terrain handling vehicle moves around. 
         [0072]    The triangle formed by the vertices ( 3   a ,  3   b  and  4   a ) deforms, thereby filtering vibrations and movements of the cab ( 2 ) in pitch and roll. 
         [0073]    The cab ( 2 ) is kept in a stable position by the U-shaped torsion bar ( 5 ) comprising the elements ( 5   a ,  5   b ,  5   c ). 
         [0074]    The articulation ( 16 ) is positioned more or less level with the plane defined by the elements ( 5   a ,  5   b ) of the U-shaped torsion bar. 
         [0075]    The U-shaped torsion bar ( 5 ) comprises an element ( 5   c ) substantially parallel to the element ( 5   b ), so that the point ( 16 ) of articulation to the cab is more or less level with the articulation point ( 17 ) situated at the rear of the cab. 
         [0076]    By providing a U-shaped torsion bar ( 5 ) that is very stiff, vertical and transverse loadings are fully absorbed by the elastic damping member ( 3 ). 
         [0077]    The differences in reaction are transmitted between the front and the rear of the cab ( 2 ) by the torsion bar ( 5 ) interacting with the front ( 16 ) and rear ( 17 ) articulations. 
         [0078]    The stiffness of the U-shaped torsion bar ( 5 ) allows the reactions to be transferred between the front and the rear in order to damp the pitching of the cab ( 2 ). 
         [0079]    The damping member ( 3 ) in this example comprises an outlet ( 3   c ) for a height adjustment, should the operator of the all-terrain handling vehicle wish to alter the attitude or height of the cab ( 2 ) for the job in hand. 
         [0080]    The pivot pins ( 16  and  17 ) are secured to the chassis ( 1 ) in this embodiment. 
         [0081]    An auxiliary damping member ( 19 ) may also be mounted between the cab ( 2 ) and the chassis ( 1 ), at the front of the cab ( 2 ), in order to make up for the lack of intrinsic damping of the torsion bar and of its rubber bearings. 
         [0082]    The invention described with reference to a number of embodiments is not in any way restricted to those embodiments but rather covers any modification in form and any variant embodiment that falls within the scope of the attached claims.