Abstract:
A shock-mitigating damper apparatus for vertical shocks has a scissor linkage extending vertically between a base and an object. A damper is also connected between the base, the object, and is mounted to the base for substantially horizontal reciprocating damper motion. An articulated arm assembly connects one end of the damper to the object at a point substantially in vertical alignment with an intermediate pivot point for the scissors.

Description:
The present invention relates to an apparatus for preventing vibrational shocks from being passed from a base to an object resiliently mounted to the base. It has particular applicability, for example, as a mount for seats in vehicles, such as earth-moving vehicles, which travel over rough and uneven terrain. 
     BACKGROUND OF THE INVENTION 
     It is well recognized that shock-absorbing systems may be interposed between a base structure, such as a vehicle or ship body or superstructure, and a structure or equipment mounted to the base to provide isolation of the so-mounted equipment. In vehicles and ships, for example, such isolating mechanisms are used to support seats and seating systems, such that the driver or pilot of the vehicle or craft, as well as passengers, can be in some manner isolated from the buffeting resulting from travel over rough terrain or seas. 
     Human factors engineering recognizes both a dynamic response index (“DRI”), a measure of a peak acceleration realized by a human when subjected to a known forcing function, as well as a summation of equivalent static compressive stress realized by a human model, denoted as S e . The significance of the S e  variable is that it is a cumulative measure of stress over a normalized period of time. 
     Accordingly a purpose of the present invention to provide a shock-absorbing system, particularly adapted to provide appropriate isolation to a human, which represents an attempt to minimize both DRI and S e . 
     BRIEF DESCRIPTION OF THE INVENTION 
     In accordance with the foregoing, a shock-mitigating apparatus of the present invention comprises a scissors support for a load, such as a vehicle seat and occupant, with respect to a base structure to which the apparatus is mounted. Shock-absorption is provided by the parallel arrangement of a damper and spring, the damper being connected to an accumulator having an adjustability feature to allow the damper to be preloaded as appropriate for the static load of the seat and occupant. 
     The parallel combination of spring and cylinder are arranged horizontally between the attachment points of the scissor support and to the base. One end of the spring/damper assembly is mounted to the base, while the other end is connected to the load through a rocker arm assembly that similarly lies within the footprint of the base. The resulting construction is of a compact size and therefore may be easily retrofitted into existing equipment, which may include other shock-mitigating devices, without the need for repositioning or reorienting the load. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A fuller understanding of the present invention will be acquired upon consideration of the following detailed explanation of a preferred but nonetheless illustrative embodiment of the invention when reviewed in conjunction with the annexed drawings, wherein: 
         FIG. 1  is an exploded perspective view of the scissors support portion of a shock-mitigating apparatus of the present invention; 
         FIG. 2  is a perspective view of the spring/damper and associated support and rocker arm assembly of the invention; 
         FIG. 3A  is a simplified side elevation view of the invention depicting the orientation of the spring/damper assembly in an equilibrium position; 
         FIG. 3B  is a view similar to that of  FIG. 3A  showing the orientation of the assembly when in a compressed orientation resulting from the absorption of a shock by the shock; 
         FIG. 4  is a bottom perspective view of the spring/damper and rocker arm assembly; and 
         FIG. 5  is a bottom perspective view, partially exploded, illustrating the accumulator associated with the damper element. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With initial reference to  FIGS. 1 and 3A , shock-mitigating apparatus  10  comprises a top pan  12 , to which an object, such as a vehicle seat, is mounted for shock absorption protection. The top pan  12  is supported for vertical travel with respect to bottom pan  14 , mounted to the deck or chassis of the vehicle receiving the shocks to be mitigated. The top and bottom pans are joined together through scissor linkage assembly  16 . A pair of pillow blocks  18  positioned between the arms of the scissors linkage assembly and mounted to the underside of the top pan by mounting bolt assemblies  20  provides a connection point for a spring/damper assembly as depicted in  FIG. 2 . The spring/damper assembly is mounted within a base housing  22 , on which the bottom pan  14  sits, which in turn is mounted to the substrate, such as a vehicle chassis or vessel superstructure, through which shocks would be transmitted to the supported object. 
     The scissor linkage assembly  16 , which may be part of the original support structure in which the present invention may be retrofitted, includes a first pair of parallel arms  24  pivotally joined to a second pair of parallel arms  26  at pivot axis  28 . The two first arms  24  and second arms  26  are maintained in a spaced relationship from each other by cylindrical spacers  30  at a first end of the arm pairs and by scissor links  32  at their second ends. The arm ends are pivotally joined to the spacers and links, and to the top and bottom pans  12 ,  14 , by mounting bolts  34  and corresponding nuts  36 . A conventional air spring  38  may be mounted to the bottom pan  14  with a spring arm  41  that contacts the bottom of top pan  12  to provide a degree of initial buffering of downward displacements of the top pan with respect to the bottom pan as shocks are experienced. The air spring may be part of the original support structure. 
     Spring/damper assembly  40 , detailed in  FIG. 2 , also interconnects the top pan  12  to the base or chassis to which it is mounted. As shown in  FIG. 2 , the assembly includes a pair of parallel shock links  42  that extend along opposed sides of spring/damper unit  44  which typically comprises a hydraulic damper cylinder  46  and a co-axial spring  48 . The unit  44  may be, for example, a unit of a size capacity appropriate to the load supported and the shock magnitudes intended to be experienced, as determined by those knowledgeable in the art, manufactured by Taylor Devices Inc. with a 2-inch stroke. The cylinder  46  is provided with a first mounting collar  50  at its distal end, while the cylinder&#39;s piston arm  52  is provided with a second mounting collar  54  at the proximal end. The spring/damper unit is connected to the shock links  42  by pivotally connecting the second mounting collar  54  to a pair of spaced, bored lugs  56  located on the shock links  42  by mounting bolt assembly  58 . 
     Shock links  42  also support a pair of guide links  60  pivotally mounted between pairs of mounting blocks  62  on the shock links. At the opposite ends of the shock links, pairs of similar mounting blocks  64  are provided for pivotable mounting of a pair of bell crank arms  66 . The bell crank arms in turn support a pair of fork links  68  likewise mounted to the bell crank arms for pivotable rotation with respect thereto. Each of the mounts for the pivotable elements may be provided with bearing elements as known in the art to provide low friction connections. 
     With further reference to  FIGS. 4 and 5 , it may be seen that spring/damper assembly  40  is mounted within base  22 , to the top of which is mounted bottom pan  14 . Base  22  may be in the general form of a rectangular box with mounting flanges  70  at its lower end to allow it to be mounted to the appropriate support structure, such as a vehicle chassis. The mounting collar  50  of cylinder  46  is mounted to an end wall of the base assembly through spaced mounting flanges  72  on the base wall. The opposite end of the spring/damper assembly  40  mounted through the guide links  60  to sets of mounting flanges  74  on the underside of the top  76  of the base. 
     The bell crank arms  66  and attached fork links  68  extend upwardly through receiving apertures in the top  76  to connect to the top pan  12  through the pillow blocks  18  mounted to the bottom surface of the top pan. See  FIG. 1 . 
     With further reference to  FIGS. 4 and 5 , spring/damper assembly  40  includes accumulator  78 , which is operatively connected to the damper cylinder  46 , and is mounted to base  22  by bracket and clamp assembly  80 . Accumulator  78  is provided with a gauge  82  by which the pressure in the accumulator may be monitored such that its equilibrium pressure may be adjusted as appropriate to compensate for the tare weight of the apparatus to be supported by the spring/damper assembly. 
     With reference to  FIGS. 3A and 3B , in a static equilibrium position, as depicted in  FIG. 3A , the weight of top pan  12  and the object mounted thereon (not shown) rotates bell crank arms  66  generally clockwise, whereby the point of linkage between the bell crank arms and the shock links  42  moves to the left in the Figure. Leftward travel of the shock links in turn moves the piston arm  52  inwardly into the cylinder, until an equilibrium force point is reached. The equilibrium point may be adjusted by varying the accumulator pressure which provides the opposing hydraulic force within the cylinder. Guide links  60  connecting the shock links to the base insure that the motion of the shock links is essentially horizontal, and maintains the spring/damper assembly  40  in an essentially horizontal orientation and within the footprint of the base during operation. When a shock is experienced relative acceleration between the top and bottom pans, driving the pans towards each other, is experienced. This causes the bell crank arms to further rotate clockwise, further attempting to drive the piston into the cylinder, which force is resisted by the hydraulic back pressure and spring  48 , whereby damping is accomplished. As the shock is dissipated, the spring and hydraulic pressure subsequently returns the pan and mounted load to the equilibrium position.