Abstract:
A load lifting mechanism including a telescoping mechanism, a pump lever operable to extend the telescoping mechanism, and a drive apparatus operably coupled to the pump lever, and wherein the drive mechanism is operable to actuate the pump lever so the telescoping mechanism is extended to lift a load.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This is a Continuation-In-Part application of International Application Number PCT/AU2005/001182 having an International Filing Date of 08 Aug. 2005 Aug.8, 2005and which claims priority of Australian patent application Serial No. 2004904424 filed on 06 Aug. 2004 Jun.8, 2004. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates to improved lifting mechanisms for vehicular applications and particularly to lifting mechanisms for use where forces in such ranges as 500 kg, 1000 kg or 1500 kg are to be developed.  
       BACKGROUND  
       [0003]     The alternatives presented for those in the market for small load capacity lifting mechanisms for application to vehicles are limited. Large load capacity lifting mechanisms utilizing hydraulic or pneumatic rams have been described for applications such as tray lifting mechanisms for tip trucks, heavy load lifting cranes, systems for lifting refuse bins onto trucks have been described, amongst many others. However, their adaptation to light or low load lifting vehicular applications may involve over-engineering and excessive costs.  
         [0004]     For example, where hydraulics are considered for use in a lifting mechanism, the cost, weight and complexity of providing and controlling a flow of hydraulic oil under pressure to the actual force-generating devices such as hydraulic cylinders can be prohibitive in small sizes. Maintenance costs can also be excessive.  
         [0005]     In some applications where comparatively small loads are to be lifted, winch-based mechanisms optionally powered by an electric motor or by a vehicle&#39;s electrical system have been proposed. However, winch mechanisms are poorly adapted to many applications such as, for example, tray-tiliting mechanisms.  
         [0006]     Accordingly, there is a need for alternative small load lifting mechanisms for vehicular applications such as the provision of tilting-tray facilities on small vehicles and towed trailers, and it is an object of the present invention to provide such mechanisms.  
         [0007]     The above description of the prior art is not intended to be, nor should it be interpreted as, a statement or admission as to the common general knowledge in the art in Australia.  
       SUMMARY OF THE INVENTION  
       [0008]     The invention provides a load lifter for use in vehicular applications comprising.  
         [0009]     a ram having a telescoping means and a pump lever operable to extend said telescoping means;  
         [0010]     drive means operably coupled to the pump lever, and means for mounting the ram to a structural part of a vehicle, wherein the drive means is operable to actuate the pump lever so that the telescoping means is extended to lift a load.  
         [0011]     Preferably, the load lifter has a load lifting capability less than or equal to about 1.5 tonnes, particularly less than or equal to about 1 tonne, and more particularly less than or equal to about 500 kg.  
         [0012]     In the preferred embodiment of the invention, the ram is one of a hydraulic ram and a pneumatic ram, the ram comprises a cylinder and the telescoping means comprises a piston movable within the cylinder.  
         [0013]     The ram may be of the telescopic type. That is, the telescoping means may comprise a plurality of pistons concentric with one another so as to be extendable telescopically.  
         [0014]     The pump lever is preferably rotatable about a pivot point associated with the cylinder and operatively coupled to a pump.  
         [0015]     It is particularly preferred that a pump is associated with the cylinder and operable by the pump lever to pump a fluid into the cylinder whereby to extend the telescoping means.  
         [0016]     The load lifter may further comprise control means having positions selectable by a user to cause actuation of the pump lever to either extend or retract the telescoping means.  
         [0017]     The load lifter may comprise control means operable to permit bleeding of the fluid from the cylinder so that a load acting on the telescoping means retracts the telescoping means.  
         [0018]     The drive means may comprise one of an internal combustion engine and an electric motor. However, it is especially preferred that the drive means comprises an electric motor and further comprises means for powering the electric motor from an electrical system of the vehicle.  
         [0019]     In one embodiment, the pump lever is movable by a linearly reciprocating component of the drive means connected by one or more linkages to the pump lever.  
         [0020]     Preferably however, the drive means in use causes rotation of a crank and a link connects the crank to the pump lever whereby to impart a reciprocating movement to the pump lever.  
         [0021]     Preferably the ram is secured to a support component that is pivotally mountable either to the said structural part of the vehicle or to a base part mounted to the said structural part of the vehicle.  
         [0022]     Advantageously, the drive means is secured to at least one of the said support component and the ram so as to be in a fixed position relative to the ram. This simplifies the connection of the drive means to the pump lever.  
         [0023]     In one embodiment, the load to be lifted may be or include a movable part of the vehicle, the load lifter being secured to the vehicle structural part and operable to raise and lower the movable part. The movable part of the vehicle may be a load tray pivotally mounted to the vehicle, the load lifter being operable to raise the tray to a tilted position from a lowered position.  
         [0024]     Preferably in this embodiment the load lifter has an intermediate movable element mounted to the vehicle and able to be moved between first and second positions by the ram, the said element being connected to the said movable part of the vehicle by at least one connecting link.  
         [0025]     This movable element may comprise an elongate boom with the telescoping means being pivotally secured to the boom at a point partway along the length of the boom.  
         [0026]     In some applications, it has been found advantageous for the boom to be of curved shape and concave downward.  
         [0027]     It is particularly preferred that the load lifter be based on use of a hydraulic jack. Thus, in a further aspect, the invention provides a load lifter comprising: 
        a hydraulic jack having a piston slidable in a cylinder, a pump for pumping oil into the cylinder below the piston whereby to raise the piston and a pump lever adapted for operation of the pump;     drive means operably coupled to the pump lever; and     means for mounting the jack to a structural part of a vehicle,     wherein the drive means is operable to actuate the pump lever so that the piston or a piston rod secured thereto is extended to lift a load thereon.        
 
         [0032]     Preferably in this aspect, the drive means is adapted to rotate a crank arm that is connected by a link to the pump lever, so that rotation of the crank arm reciprocates the pump lever of the jack.  
         [0033]     In another aspect, the present invention is a tipping unit for a vehicle comprising: 
        a base mountable to a body of the vehicle;     one or more connector members attachable to a tipping platform of the vehicle;     a boom arm pivotally connected at a first end to the base and pivotally connected at a second end to the one or more connector members;     a hydraulic jack pivotally mounted to said base and having a piston slidable in a cylinder and a pump for raising said piston, the piston being connectable at a distal end to the boom arm; and     a drive unit mounted to said base and operably coupled to a lever of the pump to drive the pump,     wherein raising of the piston causes the boom arm to move between a first position wherein said tipping platform is substantially horizontal for carrying a load and a second position wherein said tipping platform is angled to the horizontal.        
 
         [0040]     In yet another aspect, the present invention is a tipping assembly for a vehicle comprising: 
        a base frame mountable to a body of the vehicle;     a support frame hingedly attached to the base frame at one end and configured to receive a tipping platform of a vehicle; and     a tipping unit mounted to said base frame and said support frame, said tipping unit having; 
            a boom arm pivotally connected at a first end to the base frame and pivotally connected at a second end to the support frame;     a hydraulic jack pivotally mounted to said base frame and having a piston slidable in a cylinder and a pump for raising said piston, the piston being connectable at a distal end to the boom arm; and     a drive unit mounted to said base frame and operably coupled to    
            a lever of the pump to drive the pump,     wherein raising of the piston causes the boom arm to move between a first position wherein said support frame is substantially horizontal and a second position wherein said support frame is angled to the horizontal.       
 
     
    
       [0049]     In order that the invention may be better understood, and further inventive features disclosed, there will now be described, a preferred embodiment as shown in the attached Figures, of which:  
         [0050]      FIG. 1  is an elevation of a hydraulic ram and a drive unit;  
         [0051]      FIG. 2  is a schematic side view, omitting some mechanical details) of a trailer provided with a tipping tray using the invention;  
         [0052]      FIG. 3  is a perspective view of a part of the trailer shown in  FIG. 2 ;  
         [0053]      FIG. 4  is a schematic side view, omitting some mechanical details, of a tipping tray of a trailer or vehicle and its actuating mechanism, according to the invention;  
         [0054]      FIG. 5  is a perspective view of a portion of the actuating mechanism as shown in  FIG. 4 ;  
         [0055]      FIG. 6  is a pair (marked a and b) of elevations of a hydraulic ram and an actuating mechanism therefore, according to a further embodiment of the invention;  
         [0056]      FIG. 7  is a side elevation of a further lifting apparatus according to the invention;  
         [0057]      FIG. 8  is an elevation of the apparatus shown in  FIG. 7 , as seen looking in the direction of arrow “Q”;  
         [0058]      FIG. 9  is a cross sectional view of a component of the apparatus shown in  FIG. 7 , the section being taken at station “XX”;  
         [0059]      FIG. 10  is a side elevation of a tipping unit according to one embodiment of the present invention;  
         [0060]      FIG. 11  is a side elevation of the tipping unit shown in  FIG. 10  with the tipping unit in a retracted position;  
         [0061]      FIG. 12  is a side elevation of a tipping assembly according to another embodiment of the present invention; and  
         [0062]      FIG. 13  is a side elevation of the tipping assembly shown in  FIG. 12  in an extended position.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0063]      FIG. 1  shows a hydraulic ram  1  and a drive unit  19  that actuates ram  1  according to the invention. Ram  1  is of a type widely used as a jack and suitable for use in practice of the present invention. Ram  1  has a cylinder and piston (not shown) in a casing  2  and a telescoping piston rod  3  secured to the piston, and which can raise a load as oil is pumped into the cylinder below the piston. Casing  2  is secured to a base plate  4 . A reciprocating piston-type pump  5  is mounted to casing  2  and can pump oil into the cylinder from an oil chamber (not shown) within the casing  2 . Pump  5  is operable by a pump lever  6  that is pivotally secured to a plunger  7  of pump  5  and to a link  8 . Link  8  in turn is pivotally mounted to the base plate  4 . A valve  9  is provided for bleeding oil from the cylinder back into the oil chamber so as to allow retraction of the jack. Valve  9  is operable by rotation of a control rod  10 .  
         [0064]     Some jack-type rams provide, instead of or additionally to such a valve, means whereby oil can optionally be pumped into a space (not shown) above the piston so that retraction can be achieved by this means instead of or in addition to applying a force to the piston rod. Still other rams provide multiple concentric pistons that telescope within one another to achieve a greater ratio of lift stroke to cylinder length than is possible with a single piston. These rams too are usable with the invention.  
         [0065]     Jacks that combine a cylinder and telescoping piston with an oil (or other working fluid) reservoir, a lever-actuated pump and suitable control valve(s) are especially convenient for practice of the present invention. However, it is not intended to imply that such jacks are the only form of rams that may be used in practice of the invention.  
         [0066]     An advantage of rams such as ram  1  is that they require no connection to an external hydraulic oil supply. This can greatly simplify the provision of lifting device that is compact and powered by means other than manual means.  
         [0067]     Drive unit  19  comprises an electric motor  11  coupled to a speed reducer  12 . Speed reducer  12  is preferably a gear type speed reducer, whose output shaft rotates a crank arm  13 . Crank arm  13  is pivotally connected to one end  14  of a link rod  94  whose other end  15  is pivotally connected to pump lever  6 . The result is that when motor  11  is driven from a suitable electric power supply (not shown), point  14  describes a circular path  16  and lever  6  is pumped up and down as shown by arrow  17 , thus actuating ram  1  to lift a load applied downwardly to the piston rod  3 .  
         [0068]      FIGS. 2 and 3  show the application of the invention to a vehicle-towable road trailer  20  provided with a load tray  21  that can tilt to dump its load. Referring to  FIG. 2 , from which unnecessary mechanical detail has been omitted, there is shown a trailer  20 , suitable for towing by an automobile or the like with a hitch connection  121 . Trailer  20  includes a frame  22  mounted on wheels  23 . Tip tray  21  is hingedly connected to the frame  22  by a  10  pair of hinges  24  at the rear of the frame  22 .  
         [0069]     A ram  25  is provided for raising and lowering tray  21  and is shown in two positions in  FIG. 2 , position “A” corresponding to the raised position of tray  21  and position “B” corresponding to the lowered position of tray  21 . Piston rod  32  of ram  25  is connected to tray  21  at pivot  41 .  
         [0070]     Referring now to  FIG. 3 , ram  25  is mounted to a bar  26  that extends between a pair of spaced generally upright members  27 . Members  27  are hingedly mounted to side girders  28  of frame  22  at hinged connections  29  so that the bar  26  is free to pivot about an axis  30  through hinged connections  29 . Thus, ram  25  can pivot about axis  30 . This arrangement allows ram  25  to change its angle relative to frame  22  and tray  21  as tray  21  is raised and lowered. The arrangement further allows suitable positioning of axis  30  along the length of ram  25  so as to provide advantageous geometry throughout the stroke of ram  25  and to avoid possible buckling of ram  25  at full extension of its piston rod  32 .  
         [0071]     Also mounted to the pivot bar  26 , is a drive unit  33  comprising an electric motor  34  and geared speed reducer  35 . Drive unit  33  is mounted to the pivot bar  26  by a main bracket  135  and a stabilizing cross strut  36  in combination adapted to fix the drive unit relative to the pivot bar  26  and therefore to ram  25 . The combination of drive unit  33  and ram  25  is similar to the arrangement shown in  FIG. 1 , and operates in the same way. By securing drive unit  33  and ram  25  to bar  26 , the relative positions of drive unit  33  and ram  25  are preserved at all operating positions of ram  25 .  
         [0072]     Pump lever  37  of ram  25  is shown as curved and this assists in provision of a compact arrangement for driving ram  25  with drive unit  33 . However a straight pump lever could be used instead.  
         [0073]     The motor  34  is powered, via an electrical cable  38 , from the electrical system of the towing vehicle (not shown) or any other suitable electrical supply. A suitable electrical switch (not shown) is provided, preferably on trailer  20  itself, to switch motor  34  on and off.  
         [0074]     To raise tray  21 , the motor  34  is switched on and rotates the crank  39  whereby a link  40  reciprocatingly actuates the pump lever  37  and in turn operates the pump  139  of ram  25  to extend piston rod  32 .  
         [0075]     The pivot  41  may be located towards the front of the underside of the tip tray  21  to lessen the load on the ram  25  or may be placed at a position intermediate the length of the tip tray  21  to allow use of a shorter ram  25 .  
         [0076]     To lower tray  21 , a user operates a release valve  42  that is connected by an extension  43  to a knob  44  which is mounted to the bar  26  and below frame  22  out of the way of the descending tip tray  21 . The user may control the descent of the tip tray  21  whereby to permit it to gently return to its lowermost position where it can be secured to the frame  22  optionally by a latch or clamp device (not shown).  
         [0077]     Other positions of controls for release valve  42  may be chosen, but may require an articulated extension (unlike rigid extension  43 ) to accommodate the changing orientation of the ram  25  relative to the frame  22 . A flexible cable may also be provided as an alternative to operate release valve  42 , for example a so-called “Bowden” cable having a flexible cable in a flexible supporting sheath.  
         [0078]     The drive unit  33  may be enclosed in a cover (not shown) both for aesthetic and practical purposes, that is to keep the mechanism free of dust, mud and grime to which the trailer  20  may be exposed in use.  
         [0079]     Another way to provide a tilting tray facility for a trailer or vehicle using the invention will now be described.  FIG. 4  is a schematic side view (i.e. with unimportant mechanical detail omitted) of a tray  50  that is pivotally mounted by hinges  49  to a fixed frame (represented by a symbol  51  in  FIG. 4 ) that may be a trailer frame (like frame  22 ) or a chassis of a road vehicle (not shown) such as a small utility vehicle. Tray  50  is shown in raised and lowered positions in  FIG. 4 .  
         [0080]     Also hingedly connected to the frame at a pivot  53  is a beam  54 . Beam  54  is pivotally connected to one end  55  of a link  56  and the other end  57  of link  56  is connected pivotally to tray  50 . Pivotally connected to beam  54  is upper end  58  of a piston rod  59  of a ram  60 . Ram  60  is itself connected to the frame at a pivot  61  in a way described below. Position “A” of ram  60  in  FIG. 4  corresponds to the raised position of tray  50  and position “B” corresponds to the lowered position of tray  50 .  
         [0081]     Beam  54  is shown in  FIG. 4  as having a bend  62 , but persons skilled in the art will recognize that this is not essential. Beam  54  happens to provide a compact arrangement, which is important in tray raising applications.  
         [0082]     Comparison of  FIGS. 2 and 4  shows that a shorter ram can be used in the arrangement of  FIG. 4 . The arrangement shown in  FIG. 4  can also be proportioned to provide a better match between the available thrust on piston rod  59  and the effort required to raise the tray  50  from its lowered position to its raised position.  
         [0083]      FIG. 5  shows the mechanical arrangement for mounting and actuation of ram  60 . Only a part of the frame is shown, namely transverse beams  64  and  65 . Ram  60  is mounted on a platform  63  that is in turn pivotable about pivot  61 , so that the combination of ram  60  and platform  63  pivots together about pivot  61 .  
         [0084]     A drive unit  66 , comprising an electric motor  67  and gear-type speed reducer  68  is secured by brackets  69  and  70  so as be in a fixed position relative to ram  60  irrespective of the position of ram  60 . Brackets  69  and  70  are secured to the ram  60  and the platform  63  respectively.  
         [0085]     Drive unit  66  when operated from a suitable electric supply rotates a crank arm  71  that is pivotally connected to one end  72  of a link  73 . The other end  74  of link  73  is pivotally connected to pump lever  75  of ram . 60 . Lever  75  actuates a plunger-type pump  76  that is integral with ram  60 .  
         [0086]     Drive unit  66  is mounted substantially beside ram  60  (i.e. so that lever  75  extends approximately transversely to the direction of travel  77  of the vehicle) for compactness and approximately constant ground clearance. (In contrast, in the arrangement in  FIGS. 2 and 3 , drive unit  33  will have a ground clearance that varies as bar  26  swings during raising and lowering of tray  21 .)  
         [0087]     Although not shown in  FIG. 5 , a suitable protective cover can be mounted (for example from brackets  69  and/or  70 ) in a position fixed relative  5  to drive unit  66  to protect drive unit  66  from mud, dust and the like.  
         [0088]     A release valve (comparable to valves  9  and  42  above) is not shown in  FIG. 5 , but a suitable arrangement for operating such a valve may be provided in ways similar to those described above.  
         [0089]     It will be apparent to persons skilled in the mechanical art that the  10  drive-unit-and-ram arrangements described above may be readily adapted to applications other than the raising and lowering of load trays of trailers and utility and other vehicles. For example, they could be applied to the raising of booms in cranes and the like and generally to applications where a load has to be raised and lowered. The use of hydraulic or pneumatic rams having integral or permanently associated pumps operated by levers, for example those sold as jacks, allows effective load lifting devices to be made in comparatively small sizes, for example where the ram is required to develop a force of in the 500 kg, or 1 tonne or 1.5 tonne ranges, without the expense and complexity of providing, and later maintaining, external hydraulic power supplies.  
         [0090]     It is not essential that a rotary motor be used in the drive units as described above. Referring now to  FIGS. 6   a  and  6   b , the linkages involved in a lifting mechanism using a motor  80  having a linearly reciprocating plunger  81  is shown. The plunger  81  is connected to one end  82  of a link  83  whose other end  84  is pivotally connected to a pump lever  85  of a ram  86 . It can be seen that by the reciprocation of the plunger  81  up and down that the pump lever  85  is also pivoted up and down whereby to operate a pump associated with ram  86 .  
         [0091]      FIGS. 7 and 8  show a further lifting apparatus  100  of the invention that has been found useful. Apparatus  100  is a particular embodiment of apparatus shown in  FIG. 4  and  5 , and has a ram  101  foot-mounted on a platform  102  similar to platform  63  ( FIG. 5 ) that is able to pivot about a pivot  103 , and piston rod  104  of ram  101  is pivotally connected to a boom  105  at pivot  106 , boom  105  being pivotally connected by a pivot  111  to a base  112 . Links  107  are pivotally connected to boom  105  and to load supports  108  as shown in the Figures. Apparatus  100  is suitable for mounting to a supporting structure such as a vehicle chassis or frame  109  and load supports  108  are secured to a load  110 . (Load  110  is here assumed to be secured movably or guided by additional means not shown, for example pivotally secured to structure  109 , and in particular could be a tilting tray as in the earlier-described embodiments. A drive unit  118  is provided that is similar to drive unit  66  of  FIG. 5  and actuates pump lever  119 . (Drive unit  118  is shown in  FIG. 8 , but for clarity not in  FIG. 7 .)  
         [0092]     Boom  105  is curved, with its concave side downwards. It has been found that the use of such a curved boom can allow for achieving a compact arrangement with comparatively high load capacity and a short stroke ram. In particular, where limited vertical clearance is available between a vehicle chassis frame and the base of a tilt tray, the arrangement shown in  FIGS. 7 and 8  can be advantageous.  FIG. 9  shows a cross sectional view of boom  105 , which can conveniently be made using channel-section structural section(s). The curved shape of boom  105  can be achieved in manufacture by bending in suitable cases, or by the use of short straight sections welded to produce a similar geometry.  
         [0093]      FIGS. 10 and 11  show an arrangement similar to that shown in FIGS.  7  to  9 , whereby the boom  122  is shaped in an arc through welding of a plurality of short straight sections. In the embodiment as shown, the arrangement is in the form of a tilting/tipping unit  120  for incorporation into a vehicle, such as a trailer, utility vehicle or the like. Such vehicles typically comprise a tray (not shown) for receiving a load, which can be tipped/tilted to assist in depositing the load from the tray, and/or positioning the load on the tray.  
         [0094]     The tipping/tilting unit  120  can be readily installed in the vehicle and has a base  121  which is secured against a chassis or frame of a vehicle, and one or more connector members  123  which are pivotally secured to the tray of the vehicle. In this arrangement, the tipping/tilting unit  120  is secured between the chassis of the vehicle and the tray of the vehicle.  
         [0095]     The boom  122  is pivotally mounted at one end to the base  121 , and is able to pivot about this point through action of the ram  124 . As described above with regard to the alternative embodiments of the present invention, the ram  124  linearly drives a piston rod  127 , which is pivotally connected to the boom  122  at a pivot point  128 . Extension of the piston rod  127  from the ram  124  causes the boom  122  to extend as shown in  FIG. 10 . As the boom  122  extends, the ram  124  also pivots to ensure that the piston rod moves in a freely moves in a linear manner. To facilitate this pivot action of the ram  124 , the ram  124  is mounted on a platform  125  that is able to pivot about a pivot point  126 .  
         [0096]     The other end of the boom  122  is attached to the connector members  123  by way of a link  129 . The links  129  are pivotally connected to the end of the boom  122  and the connector members  123  to enable the tray to pivot between a tilted position as depicted in  FIG. 10 , and a flat or level position, as depicted in  FIG. 11 .  
         [0097]     In the position as shown in  FIG. 11 , the tipping/tilting unit  120  is compactly arranged such that it fits between the chassis of the vehicle and the tray. As shown, the piston rod  127  is retracted into the ram  124  and as such that ram  124  is pivoted into a retracted position as shown.  
         [0098]     A drive unit  130  is provided to operate the ram  124  such that the piston rod  127  can move between its extended and retracted positions. The drive unit  130  may be in the form of motor as discussed previously, which operates a pump lever  131  of the ram  124 .  
         [0099]     It will be appreciated that the tipping/tilting unit  120  can be easily supplied for installation in a vehicle. However, in many instances, it may be necessary to provide associated support frames about the tipping/tilting unit  120  such that the arrangement can be easily incorporated into the structure of the vehicle, without requiring onerous installation techniques to ensure that the tipping/tilting unit  120  is orientated correctly to tilt the tray of the vehicle.  
         [0100]     For this reason, the arrangement  140  of  FIGS. 12 and 13  has been proposed. As shown, in the arrangement  140 , the tipping/tilting unit  120  is mounted between a base frame  135  and a support frame  138 . The base frame  135  can be constructed such that it can be easily mounted to the chassis of the vehicle through existing mounting means, such as bolts and the like. Similarly, the support frame  138  can have appropriate mounting means to receive a tray, upon which a load can be supported. Both the base frame  135  and the support frame  138  are pivotally connected at a pivot point  133  such that when the tipping/tilting unit  120  is operated, the support frame  138  is moved with respect to the base frame  135 , which in turn causes the tray to tilt/tip with respect to the chassis of the vehicle.  
         [0101]     It will be appreciated that such an arrangement  140  enables the present invention to be simply installed in a vehicle between the chassis and the tray of the vehicle, without requiring precision positioning and mounting of the individual components of the tipping/tilting unit  120 .  
         [0102]     In the arrangements shown in  FIGS. 2 and 3 ,  4  and  5 ,  7  and  8 ,  10  and  11 , and  12  and  13 , drive units  33 ,  66 ,  118 , and  130  are supported in fixed positions relative to the rams  25 ,  60  and  124  respectively. However, where only limited movement of a ram is required in a mechanism, it may be practical to hold a drive unit in a fixed position while the ram pivots. In this case, simple pivots (for example at the ends of links  40  or  73 ) may have to be replaced by ball-and-socket pivots.  
         [0103]     Still other variations may be made without exceeding the spirit and scope of the invention.  
         [0104]     In this specification the terms “vehicle” and “vehicular” are meant to be interpreted as being applicable both to self-propelled vehicles such as light trucks, utility vehicles and the like, and also to trailers intended for towing by other vehicles.  
         [0105]     In this specification, the word “comprise” and its derivatives when used in relation to a set of integers, elements, items or steps is to be taken to mean that the integers, elements, items or steps are present but not to be taken to preclude the possibility that other integers, elements, items or steps are or may be present also.