Abstract:
A suspension for a vehicle seat having four bellcranks which guide the seat substantially vertically, oscillate on a central pivot on elevated stationary pivots mounted on a lower frame, with upper arms of the bellcranks pivotally attached to a seat cushion upper frame and the lower arms indirectly attached to adjustable tension springs that are attached to the upper frame; the lower ends with substantial inward offsets so as to rotate downwardly toward the mounting deck of the vehicle while clearing the lower frame and adjustable sliders; the bellcranks being coupled longitudinally and laterally to stay in phase and keep the upper frame level.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention is directed to a seat suspension apparatus effective on rough riding vehicles to absorb high jolts with minimum fore/aft movement.  
       BACKGROUND OF THE INVENTION  
       [0002]     Seat suspension mechanisms support a person sitting on the seat while providing maximum comfort. These mechanisms are designed to provide comfort to the occupant while minimizing and absorbing or dampening bumps and jolts due to uneven, rough or rugged terrain the vehicle encounters. Design criteria include seat vibration and frequency of the seat and suspension of the seat and the vehicle, space limitation under the seat and above the seat to overhead restraints, the type of terrain likely to be encountered, limits of seat travel up and down to absorb shocks during operation, components costs, durability, and the like. The design criteria are particularly critical and generally more complicated for off-road vehicles, such as tractors, lift-trucks, heavy equipment, earth moving vehicles, and the like. These off-road vehicles have either relatively heavy-duty or no shock absorbing suspensions between the wheels and the chassis that do not prevent jolts, bumps, vibrations, and shocks from reaching the driver. Thus for these vehicles the seat and seat suspension must safely dampen and absorb these transmitted jolts in a safe manner while providing comfort and reducing fatigue. Such prior art suspensions have not adequately provided horizontal stability to enable the driver to maintain control when encountering rough terrain. As an example, it is not safe for the driver to be thrown fore-and-aft as the seat moves up and down due to rough terrain.  
         [0003]     Typical prior art suspension mechanisms are illustrated and described in U.S. Pat. No. 4,241,894 to Okuyama, FIGS. 3a, 3b, and /3c. Other prior art suspension mechanisms, as illustrated in FIG. 1c of Okuyama employ a parallelogram arrangement of bi-arm linkage with one pair of adjacent ends of the arms pivotally connected to a bracket extending downwardly from the cushion frame and the opposite ends of the arms pivotally connected to the deck frame of the vehicle, with all pivot connections in a single plane. Biasing springs connected to the cushion frame or to arms and to the deck provide a cushioning effect. These prior art figures and description from Okuyama are incorporated herein by reference thereto. Still other prior art suspension mechanisms employ a scissors arrangement of bi-arm linkage with one pair of adjacent ends of the arms pivotally connected to the cushion frame and the opposite ends of the arms pivotally connected to the deck frame of the vehicle. Again biasing springs provide a cushioning effect by dampening the jolting movement of vehicle caused by roadway undulations and bumps. An attempt is made to choose the spring characteristics to bias rather than match the amplitude and frequency of the road bumps, in an effort to smooth the ride to avoid a bouncing effect.  
         [0004]     Another typical prior art seat suspension apparatus in used on KUBOTA® vehicles includes four bellcranks connecting springs to bias movement of the seat frame. As illustrated in the schematic drawing of a side view of one of the bellcranks  11  of the KUBOTA® apparatus shown in  FIG. 8 , pivot point  12  is connected to and located down at the base, the angle  15  between lines from pivot point  12  to connecting point  13  to the seat frame and from point  12  to connecting point  14  to the spring bias opens upwardly, and the spring biasing connecting point  14  is on an upper directed arm form the pivot point. As the seat is lowered and raised bellcrank  11  rotates through angle β with up and down movement c of the seat frame due to the weight of the person sitting on the seat and jolts from a rough roadway, angle  15  moves counter-clockwise as the seat is compressed and unfavorably the seat also moves fore-and-aft distance b, which is common. The bellcranks of the Kubota apparatus pivot from a non-upraised pivot point on the base frame with the two arms of each of the bellcranks extending upwardly at an acute angle from each other. A spring bias pulls horizontally from a distal end of one of the ends against force applied to the distal end of the second upright arm in an opposite direction as the seat frame is depressed. No portion of this bellcrank moves into spaces between the slide rails below the lower frame or into the set cushion area and so has only about one-half as much vertical travel for similar profile height. All of these elements of these prior art bellcranks are essentially opposite or contrary to the present invention, resulting in, among other deficiencies, the substantial fore and aft movement during compression and decompression of the suspension mechanism as well as higher spring bias per distance of movement close to upper position and lower bias per distance of movement as the seat moves toward the lowest position, resulting in a harsher ride. Other limitations of these seat suspension mechanisms and the ones that follow include complexity, high weight, higher costs, and relatively high profile inasmuch as the height of the seat above the vehicle frame is almost always at a premium, either to provide space under the seat or due to restricted head room for safety of the operator. One of the reasons the prior art suspension mechanisms have a high profile is that they have separate upper and lower frames/brackets.  
         [0005]     U.S. Pat. No. 5,014,960 to Kimura discloses a seat suspension mechanism directed to absorbing horizontal fore-and-aft impact or jolting applied to the seat. U.S. Pat. No. 4,520,986 to Liljequist et al disclosed a seat assembly with reduced elevational space requirements. U.S. Pat. No. 5,014,960 to Harney discloses a seat adjustor mechanism with bellcrank with angles between diverging lines from the pivot point to the two connecting points of the bellcranks greater than 90 degrees and a pivot point that is not raised above the seat frame. U.S. Pat. No. 5,222,709 to Culley, Jr. et al discloses a scissor-type suspension mechanism with a bellcrank used for adjustment. U.S. Pat. No. 6,264,158 to Downey et al discloses a support structure for a vehicle seat assembly with fore-aft adjustment. U.S. Pat. No. 6,520,474 to Toshida et al discloses a slice mechanism for a vehicle seat. U.S. Patent Application Publication 2003/0201660 to Janscha et al discloses a seat suspension mechanism with a bellcrank with angles between diverging lines from the pivot point to the two connecting points of the bellcranks greater than 90 degrees and a pivot point that is not raised to extend above the seat frame. U.S. Pat. No. 5,938,164 to. Kargol et al discloses a seat adjuster for vehicle seat assemblies. U.S. Pat. No. 6,695,275 to Schuler et al discloses a device for longitudinal adjustment for vehicle seats. U.S. Patent Application Publication 2005/0006937 to Takata et al discloses a lifter for adjusting the height of a vehicle seat frame with a magnetic damper. U.S. Patent Application Publication 2005/0001133 to Bostrom et al discloses a scissor-type seat suspension mechanism for motor vehicles. U.S. Pat. No. 5,794,911 to Hill discloses a suspension seat using a parallelogram suspension mechanism. U.S. Patent Application Publication 2004/0144906 to Hill et al discloses a vehicle suspension mechanism with a bellcrank that operates differently and does not include the elements of the bellcranks of the present invention. U.S. Pat. No. 6,755,469 to Akaike et al discloses a typical parallelogram suspension mechanism. U.S. Pat. No. 6,851,753 to Akaike et al discloses a suspension system similar to his prior patent except for pivot members from the seat frame to a slide connection in the base frame. U.S. Pat. No. 6,830,297 to Gordon discloses a suspension seat with a link between the spring and the suspension mechanism similar to the prior art described above. U.S. Pat. No. 6,773,049 to Rupiper et al. discloses a suspension seat using a parallelogram suspension mechanism. U.S. Pat. No. 6,776, 384 to Igarashi discloses a seat suspension using a typical scissor cross-member suspension mechanism.  
         [0006]     None of these devices disclose or even suggest the use of the bellcranks and suspension apparatus of the present invention, nor do they satisfy the needs of the prior art described herein above or attain the objects of the present invention provided herein below.  
       SUMMARY OF INVENTION  
       [0007]     Important elements of an embodiment of a vehicle seat suspension of this invention include a plurality of, preferably four in number, bellcranks, each pivotally connected at a proximate median point of the bellcrank, to a pivot member raised above and structurally connected to a base frame adapted to be attached on mounting deck of a vehicle at a pivot point which is elevated above said base frame to a height that is above a seat cushion frame when the seat cushion frame is lowered due to the weight of a person sitting on the cushion or to a jolt from the roadway. These elevated pivot points preferably require that that the pivot members be positioned laterally so as to not contact the seat cushion frame when cushion frame is lowered and each pivot member extends above the seat cushion frame, and also a hollow opened from below into the cushion for each pivot member be provided so that when the cushion frame is lowered and each pivot member extends above the seat cushion frame, the cushion will not engage the pivot member.  
         [0008]     An embodiment of the invention is a seat suspension apparatus adapted to be attached to a mounting deck of a vehicle, said apparatus including a lower frame comprising a pair of longitudinal side members and four pivot members structurally attached and extending upwardly from the side members of the lower frame. The term “frame” is not limited as to shape and includes square rigid frames as pictured, but also other shapes. The term “longitudinal” is used to define relative directions and does not limit the length of the side members. These pivot members are generally referred to as providing elevated pivot points, centers, or connections for the median pivot connection of the bellcranks. The apparatus also includes four bellcrank members disposed to pivot or rotate in vertical planes, each bellcrank member including a median pivot section each pivotally connected to a distal end of the four pivot members an upper bellcrank arm comprising a distal end, and a lower bellcrank arm comprising a distal end. The apparatus further includes an upper seat cushion frame pivotally connected to the distal ends of the four upper bellcrank arms, and spring biasing means pivotally connected to the distal ends of the four lower bellcrank arms to provide spring biasing against downward movement of the seat cushion frame. When the upper seat cushion frame is depressed, the median pivot sections of the bellcrank members extend above an upper edge of the upper seat cushion frame and the distal ends of the lower bellcrank arms rotate to a height below a lower edge of the lower frame.  
         [0009]     It is preferred that the distal ends of the lower bellcrank arms of the bellcranks be offset laterally inwardly. It is also preferred that the four bellcranks be physically coupled together maintaining them in a phase relationship to each other. It is further preferred that the spring biasing means pivotally connected to distal ends of the lower bellcrank arms include a pair of tension springs connected to the upper seat cushion frame, although connection to the lower frame operates well. It is also preferred that an angle between two diverging lines each from a central axis of a pivot connection on the median pivot section of the bellcrank to central axes of pivot connection points on the distal ends of the upper and lower arms be less than ninety degrees. It is more preferred that the angle between the two diverging lines be in the range of 30 to 90 degrees and most preferred in the range of 40 to 70 degrees. It is also preferred that the upper and lower arms of the bellcranks rotate through proximate equal angles relative to each other above and below a median position corresponding to median height position of the upper seat cushion frame. It is further preferred that apparatus further include an adjustment means to adjust the spring bias force. It is also preferred that the spring biasing means include a pair of springs each attached at one pair of ends to the distal ends of the lower bellcrank arms and that the apparatus further include adjustment means that includes connecting a second pair of ends of the springs to a screw shaft extending through an opening in the upper seat cushion frame and terminating in an adjustment knob to turn the shaft to adjust the spring bias. It is further preferred that apparatus further include a seat cushion attached on top of the seat cushion frame, the cushion including a hollow space above the frame to receive the median pivot sections of the bellcrank members upon downward movement of the seat cushion frame. It is also preferred that apparatus further include a seat cushion attached on top of the seat cushion frame wherein the seat cushion includes four cavities cut out from below to receive the median pivot sections of the bellcrank members upon downward movement of the seat cushion frame. It is further preferred that the apparatus further include spacer mounting means adapted to attach the lower frame to the mounting deck at a height above the mounting deck sufficient to allow the distal end of the lower arm of the bellcranks to clear the mounting deck when rotated fully downwardly. It is also preferred that apparatus further include a fore and aft slide means that includes laterally spaced longitudinal sliding rails adapted to be attached onto the mounting deck of a vehicle, said means to support the lower frame and allow said frame to slide longitudinally to a multiplicity of longitudinal positions.  
         [0010]     A second embodiment of the invention is a seat suspension apparatus adapted to be attached to a mounting deck of a vehicle, said apparatus including a lower frame including longitudinal side members and spacer mounting means adapted to attach the lower frame to the mounting deck at a height above the mounting deck. The apparatus further includes four pivot members structurally attached to and extending upwardly from outer edges of the side members of the lower frame. The apparatus also includes four bellcrank members disposed to pivot in vertical planes, each bellcrank including a median pivot section pivotally connected to an outer surface of a distal end of the pivot members, an upper arm and a lower arm. The apparatus further includes an upper seat cushion frame pivotally connected to distal ends of the upper bellcrank arms, and spring biasing means pivotally connected to distal ends of the lower bellcrank arms to provide spring biasing against downward movement of the seat cushion frame. The height of the distal ends of the pivot members is sufficient that when the upper seat cushion frame is depressed, the median pivot sections of the bellcrank members extend above an upper edge of the upper seat cushion frame and the distal ends of the lower bellcrank arms rotate to a height below a lower edge of the lower frame. Further, the height of the lower frame above the mounting deck is sufficient to allow the distal ends of the lower arms of the bellcranks to clear the mounting deck when rotated fully downwardly. The above-preferred embodiments, where applicable, apply equally to this embodiment.  
         [0011]     A third embodiment of this invention is a seat suspension apparatus adapted to be attached to a mounting deck of a vehicle, said apparatus including: a lower frame that includes a pair of longitudinal side members and four pivot members structurally attached and extending upwardly from the side members of the lower frame. The apparatus further includes four bellcrank members disposed to rotate in vertical planes, each bellcrank member including a median pivot section each pivotally connected to a distal end of the four pivot members an upper bellcrank arm including a distal end, and a lower bellcrank arm including a distal end offset laterally inwardly. The apparatus further includes an upper seat cushion frame pivotally connected to the distal ends of the four upper bellcrank arms, and spring biasing means pivotally connected to the distal ends of the four lower bellcrank arms to provide spring biasing against downward movement of the seat cushion frame. As the upper seat cushion frame is depressed, the median pivot sections of the bellcrank members extend above an upper edge of the upper seat cushion frame and the distal ends of the lower bellcrank arms are sufficiently offset to allow rotation to a height below a lower edge of the lower frame. The above-preferred embodiments, where applicable, apply equally to this embodiment.  
         [0012]     Other important elements preferably include a plurality of bellcranks, each bellcrank with an angle less than ninety degrees between diverging lines from the pivot point to two separated connecting points, one point adapted to be pivotally connected to a biasing spring and the second point adapted to be pivotally connected to the seat cushion frame. It is most preferably in the range of 40 to 70 degrees. It is also preferred that the connecting point for the spring bias be on a downwardly extending arm from the pivot point. It is also preferred that the angle between the diverging lines from the pivot point to two separated connecting points of each bellcrank move pivot downwardly as the seat frame is lowered.  
         [0013]     A fourth embodiment of this invention is a seat suspension apparatus comprising four offset bellcranks, each including an upper arm with a proximal end and a distal end and a lower arm with a proximal end and a distal end, wherein the proximal ends are structurally joined, a central pivot opening through the proximal ends, which are in a vertical first plane with the distal end of the upper arm, a first opening through the distal end of the upper arm adapted to be pivotally connected to a seat frame, a second opening through the distal end of the lower arm adapted to be pivotally connected to a spring biasing means, an offset extension of the lower arm extending from a median section proximately horizontally from the first plane to a distal section of the lower arm extending perpendicular therefrom in a second plane parallel to the first plane, and wherein a first line drawn through the center points of the central pivot opening and the first opening and a second line drawn on the first plane through the center point of the central pivot opening and the central axis of the second opening are at an angle of less than 90 degrees and greater than 30 degrees.  
         [0014]     A fifth embodiment of this invention is a seat suspension apparatus including four offset bellcranks, each including: an upper arm with a proximal end and a distal end and a lower arm with a proximal end and a distal end, wherein the proximal ends are structurally joined, a central pivot opening through the proximal ends, which are in a vertical first plane with the distal end of the upper arm, a first opening through the distal end of the upper arm adapted to be pivotally connected to a seat frame, a second opening through the distal end of the lower arm adapted to be pivotally connected to a spring biasing means, an offset extension of the lower arm extending from a median section proximately horizontally from the first plane to a distal section of the lower arm extending perpendicular therefrom in a second plane parallel to the first plane, and wherein a first line drawn through the center points of the central pivot opening and the first opening and a second line drawn on the first plane through the center point of the central pivot opening and the central axis of the second opening are at an angle of less than 90 degrees and greater than 30 degrees.  
         [0015]     It is an object of an embodiment of the present invention to provide a seat suspension apparatus for a vehicle that utilizes a low profile between the seat cushion and the mounting deck of the vehicle.  
         [0016]     It is a further object of an embodiment of the present invention to provide a seat suspension apparatus for a vehicle that utilizes a low profile between the seat cushion and the mounting deck of the vehicle when it is not feasible to adjust pre-existing longitudinal fore and aft slide rails used to support the seat suspension apparatus and allow the apparatus to slide back and forth to a multiplicity of positions.  
         [0017]     It is an additional object of an embodiment of the present invention to provide a seat suspension apparatus for a vehicle that utilizes a low profile between the seat cushion and the mounting deck of the vehicle when it is feasible to laterally adjust longitudinally aligned fore and aft slide rails used to support the seat suspension apparatus and allow the apparatus to slide back and forth to a multiplicity of positions.  
         [0018]     It is a further object of an embodiment of the present invention to provide a seat suspension apparatus for a vehicle that dampens the jolts of a rough terrain and does not require inclusion of a standard dampening mechanism, such as a shock absorber.  
         [0019]     It is an additional object of an embodiment of the present invention to provide a seat suspension apparatus for a vehicle wherein the stiffness of the spring bias against downward movement of the seat is reduced as the seat moves downward also reducing the strain on the spring attachments, and resulting in a softer, more comfortable ride.  
         [0020]     It is an additional object of an embodiment of the present invention to provide a seat suspension apparatus for a vehicle wherein adjustment of the spring bias tension is handy and may be safely and easily reached by the driver while sitting on the seat.  
         [0021]     It is a further object of an embodiment of the present invention to provide a seat suspension apparatus for a vehicle that utilizes a part of the seat, namely a standard seat frame, as part of the suspension apparatus to save parts and vertical space below the seat.  
         [0022]     It is an additional object of an embodiment of the present invention to provide a seat suspension apparatus for a vehicle that utilizes a low profile between the seat cushion and the mounting deck of the vehicle without structural interference problems or sacrificing comfort of the driver sitting on the seat.  
         [0023]     It is an object of an embodiment of the present invention to provide a seat suspension apparatus that allows minimal fore and aft movement as the seat frame moves up and down due to rough terrain.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]      FIG. 1  is a front plan view of a vehicle seat with the suspension apparatus of the present invention supporting the seat.  
         [0025]      FIG. 2  is a left side elevational view of said vehicle seat with the apparatus.  
         [0026]      FIG. 3  is a top view of said apparatus with the seat removed.  
         [0027]      FIG. 4  is an enlarged front plan view of said apparatus with the seat cushion and sides of knob cut-away. (note to John: the seat cushion is cross-sectioned and some of the knob is missing)  
         [0028]      FIG. 5  is a right side plan view of said apparatus with the seat cushion in its uppermost position of travel and partially cut-away.  
         [0029]      FIG. 6  is a right side plan view of said apparatus with the seat cushion in its almost lowermost position of travel and partially cut-away.  
         [0030]      FIG. 7  is provided on four sheets,  7 A,  7 B,  7 C, and  7 D and is an exploded perspective view of said apparatus without seat cushions.  
         [0031]      FIG. 8  is a perspective view of a typical bellcrank of the prior art.  
         [0032]      FIG. 9  is an enlarged perspective view of a preferred bellcrank of the present invention.  
         [0033]      FIG. 10  is top view diagram of a second embodiment of a seat apparatus of the present invention with the seat removed.  
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0034]     Preloading the spring bias is to balance the weight of the particular operator so that he is statically positioned approximately at mid-height of the vertical travel limits of the seat suspension system.  
         [0035]     Seat suspension apparatus  10  of the present invention uses seat frame  22  as the upper frame of the suspension apparatus providing a lower silhouette. As shown in  FIGS. 1, 2 , and later figures, seat back  16  including a hidden frame with foam and covering and seat cushion  17  including foam and covering are all securely attached to seat frame  22 . Standard seat belt latch  19  and seat belt retractor  18  are securely attached to frame  22 . The seat is adjustable and slides  46  and  46 ′ slide frontwardly and rearwardly and locked in a chosen position using standard mechanisms with seat position release lever  28 , which disengages seat position release latch  29  pivoting on release pivot connection  30  as shown on  FIG. 3 . Throughout the drawings, where there are two essentially identical parts or elements the right side part of the two is without a prime and the identical part on the left is affixed with a prime (′). Further, throughout the drawings, where there are four essentially identical parts or elements the right front side part of the four is without a prime and the identical part on the right rear is affixed with a prime (′). Continuing with the four essentially identical parts including right and left hand versions where applicable, the parts or elements the front left side of the four is affixed with a double prime (″) and the identical part on the right rear is affixed with a triple prime (′″). As shown on  FIGS. 1 through 3 , four bellcranks,  25  (for the purpose of clarity and simplicity the remaining three essentially identical elements, including but not limited to the other bellcranks,  25 ′,  25 ″, and  25 ′″, are not listed but are included by the reference to “four” parts). As the seat moves up and down the four bellcranks  25  pivot on four pivot centers  24 , located on four vertical pivot posts  23 , which are securely connected to and extend upwardly from two longitudinal side members  53  and  53 ′ of base frame  21 . All of the pivot connections of the four bell cranks  25 , that is four pivotal connections to four bellcrank pivot centers  24 , four pivotal connections to four spring bias connection centers  36 , and four pivotal connections to four seat frame connection centers  38 , utilize a total of twelve shoulder bolts  37  though the respective holes and secured with twelve nuts  43 , with bushings  40  allowing the pivotal connections to freely pivot. Where the parts are not clearly shown on  FIGS. 1 through 6 , they are found on the exploded views of  FIG. 7 . For example the four bellcranks  25  pivotally connect through four seat frame connection central axes  38  to seat frame  22  through horizontal holes  59  in four vertical flanges  58  depending downwardly from frame  22 . While two tension support springs  31  and  31 ′ pull on four pivotal connections  36  on four lower end sections  50  of the four bellcranks  25 , the four pivotal connection central axes  38  on four upper end sections  48  of four bellcranks  25  push upward on four seat frame connection flanges  58  welded to seat frame  22 . As shown in  FIG. 6 , the tension in springs  31  is increased and reduced by rotating weight adjustment knob  20  to adjust for the weight of the rider. The four bellcranks  25  are phased longitudinally by phase links  35  and  35 ′ pivotally connected at the front ends to pivot connections  36  and  36 ′ respectively and at the rear ends to pivot connections  36 ′ and  36 ′″ respectively thereby maintaining pivotal connections  38  at the same height. Similarly, as shown in  FIG. 7B , rear bellcranks,  25 ′ and  25 ′″, are phased together by real lateral phase link connecting member  27  welded at its ends to bellcrank off-set sections  52 ′ and  52 ′″ and front bellcranks,  25  and  25 ″, are phased together by front lateral phase link connecting member  26  welded to bellcrank off-set sections  52  and  52 ″, to keep the four bell cranks  25  at the same angular relationship. These lateral and longitudinal phase links coordinate to always maintain a “level” seat frame  22  and seat  17 . As shown in  FIGS. 7A  &amp; C, front hook ends  63  and  63 ′ of tension springs  31  and  31 ′ respectively hook into holes  61  and  61 ′ through spring connection flange  60  through which screw shaft  32  threadably extends horizontally through threaded nut  65  welded to flange  60  so that flange  60  moves forward or rearward as knob  20  is rotated. Rear hook ends  64  and  64 ′ of springs  31  and  31 ′ respectively hook into holes  62  and  62 ′ through spring attachment cross-member  33 , which is welded transversely between rear sections of longitudinal phase-link members  35  and  35 ′. Cross-member  33  moves fore/aft and up/down with seat  17  up/down motions, but it does not rotate which would cause extra, damaging stresses in the spring end hooks being frictionally urged to follow such rotation. As shown in  FIG. 7D , base frame  21  may be of relatively thin gauge metal as it is supported and reinforced by upper fore/aft slides  46  and  46 ′ threadably attached by bolts  47  through base frame  21 , upper slides  46  and  46 ′ having a box-shaped cross-section with a lengthwise lower slot to slideably receive lower fore/aft lower slides  45  and  45 ′ respectively, which have a “U” cross-sectional shape with lengthwise outwardly extending flanges to engage the bottom lengthwise inward extending flanges of upper slides  46  and  46 ′. Lower fore/aft slides  45  and  45 ′ are attached by bolts  44  though vertical holes in the bottom wall of the slides to mounting deck of the vehicle, not shown. Although not shown, bumpers to provide cushioning end points by meeting phase bars and the like. Of particular interest is  FIG. 9  together with  FIGS. 5 and 6  showing the elements of bellcrank  25 , which is identical to rear right bellcrank  25 ′ and is the mirror image of front left bellcrank  25 ″ and rear left bellcrank  25 ′″. Bellcrank  25  rotates on pivot connection  24  located on vertical post  23  extending upwardly from lower base frame  21 . Bellcrank  25  rotates on pivot connection  24  around horizontal central axis  34  of horizontal hole  55  through the bellcrank located in median section  49  of the bellcrank. As seat frame  22  is lowered and raised bellcrank  25  rotates through angle a with up and down movement distance c′ of the seat frame due to the weight of the person sitting on the seat and jolts from a rough roadway; and most favorably the seat only moves fore-and-aft a small distance b′. Force is applied to bellcrank  25  by the downward movement of upper seat frame  22  through the arc of angle α of connection  38  and countervailing force is applied by the spring bias through the arc of angle α of connection  36 . For a suspension apparatus of the present invention a total movement up/down of about one and one-half inches results in a fore/aft movement of only about an almost negligible one-eighth inch. Bellcrank  25  is pivotally connected to the seat frame  22  through pivotal connection  38 , which is horizontal hole  57  through a distal end of upraised arm  48  of bellcrank  25 , the hole with horizontal central axis  39 . Bellcrank  25  is pivotally connected though connection  36  to the longitudinal phase-link  35  essentially connecting it to the spring bias pivotal connection  36  including horizontal hole  56  through a distal end of lower arm  50  of bellcrank  25 , the hole with horizontal central axis  54 . Lower arm  50  is off-set horizontally from the plane of pivotal connections  34  and  39  and is connected to median section  49  by horizontal arm  52 . A slot is shown cut laterally across about half the width of arm  48  proximate median section  49  to facilitate bending during some manufacturing processes, but is not necessary nor desirable in most constructions. Angle  51  is between straight line  67  drawn from bellcrank pivot central axis  34  and seat frame connection central axis  39  in the vertical plane of upright arm  48  and straight line  69  drawn in the same vertical plane parallel with straight line  68  drawn from central axis  54  of connection  36  to spring bias in the plane of arm  50  to an extension of central axis  34  is less than ninety degrees. This angle is more preferably in the range of ninety degrees to thirty degrees, and most preferably in the range of 50 to 80 degrees. For bellcranks of the present invention where arm  50  is not offset and all three connections are in one vertical plane, this angle is described as the angle between line  67  from connection pivot central axis  34  to connection seat frame central axis  39  and line  68  from connection pivot central axis  34  to connection spring bias central axis  54 . For the purpose of clarity and simplicity, in the specification and in the claims, whether on the non offset or the offset versions of the bellcranks, the said angle is defined by and named by the following language: “an angle between two diverging lines each from a central axis of a pivot connection on the median pivot section of the bellcrank to central axes of pivot connection points on the distal ends of the upper and lower arms”. Since the rotation of the bellcrank and the angular movements of the connection points are not affected by the offset, this simpler description of the relative positions of the connection axis includes the versions with the connections in the same plane, that is on a flat piece of metal, as well as the offset version illustrated in  FIG. 9 . Actually, the bellcranks as illustrated in  FIGS. 5 and 6  show the movement of non offset versions and the angle described above. For the sake of brevity the elements and the movement of the balance of the essentially identical bellcranks are not further described although they are illustrated in the balance of the figures. In  FIG. 5  seat  17 , including foam seat cushion  42  and seat frame  22 , is in the full up position with springs  31  and  31 ′ in minimum tension and arms  48  and  48 ′ in full up-right position. As seat  17 , including seat frame  22 , is depressed in  FIG. 6  to an almost full downwardly position, arms  48  and  48 ′ rotate downwardly, springs  31  and  31 ′ are in increased tension providing spring bias, and the upper ends of pivot posts  23  and  23 ′ and median sections  49  and  49 ′ of bellcranks  25  and  25 ′ now extend into cavities  41  and  41 ′ of foam seat cushion  42 . It should be observed that the fore/aft position of seat frame  22  is hardly different between  FIGS. 5 and 6 . A reason for this advantage is that bellcrank  25  moves through almost equal angles from top to mid to bottom positions. Thus, the seat frame positions fore/aft in full upward and full downward positions are essentially identical and only slightly rearward of mid height position. The rotational travel of seat frame connections  38  and  38 ′ are nearly symmetrical above and below the mid height of the seat frame connection. It is preferred that line  68  never rotate more than ninety degrees from the force line of action of the spring bias in its most stretched condition, as a ninety degree angle produces the maximum restoring torque to urge the seat and rider back upwards during the oscillatory travel of the seat. If this angle of line  68  rotates past ninety degrees the restoring torque is lessened and detracts from the rider&#39;s comfort. As shown in  FIG. 6  the distal ends of arms  50  and  50 ′, pivotal connections  36  and  36 ′ of the bellcrank to the spring bias, and phase link  35  all move downwardly below the upper edges of slide track  46  as the seat frame moves toward its most downward position. As it is important for the phase links and the pivotal connections be as low as possible, the offset of arm  50  inwardly by horizontal offset arm  52  allows the distal ends of arms  50  and  50 ′ and phase links  35  and  35 ′ to move unimpeded between slide tracks  46  and  46 ′ below the height of the slide tracks. These offsets of the bellcrank connection arms allow them to connect to the spring bias means and allow full vertical travel with a higher spring bias throughout the movement with the full bellcrank rotation. In the above embodiment the pairs of slide tracks  45 / 46  and  45 ′/ 46 ′ are about a foot long and about a foot apart and the offset bellcranks are preferred. An embodiment is shown in  FIG. 10 , a diagram to illustrate the present invention adapted to be used on a mounting deck of a vehicle with no slide tracks to adjust the seat position longitudinally front to back. In this embodiment flat bellcranks of this invention are used. On these vehicles holes are typically provided through the deck on which to bolt the seat apparatus and here the same holes are used that were used to attach the above slide tracks. In this embodiment four spacer mounting pad washers  79  are used to raise frame  21 ′ off the deck about an inch when bolted onto the deck with bolts  47 ′. The side views of this embodiment are essentially identical to those illustrated in  FIGS. 5 and 6  with the diagonal lines showing the off-set removed and the movement, attachment and connection of the various parts are essentially identical. Four vertical pivot cantilever posts  77 , essentially identical to the four posts  23 , extend upwardly from the outer edges of longitudinal side members  71  and  71 ′ of base frame  21 ′. Four vertical flat bellcranks  70  pivot in vertical planes on pivot connections at the distal ends of four posts  77 . Springs  31  ″ and  31 ′″ connect at the front ends to spring connection flange  72 , which is essentially identical to flange  60  and operates and is connected to the adjusment mechanism in the same manner as are all of the attachment members and the phase links of this embodiment. Single parts that are essentially identical to the corresponding parts of the first embodiment are marked with a prime (′) and are not called out herein. The rear ends of the springs are connected to cross-member spring attachment member  74 , which, with its extended length, is attached to longitudinal phase links  76  and  76 ′, which are pivotally connected on both ends on the outside of the bellcrank lower arm pivot connections. Front lateral phase link member  73  is rigidly connected to the lower arms of the front bell cranks  70  and  70 ″. Rear lateral phase link member  75  is rigidly attached to the lower arms of rear bellcranks  70 ′ and  70 ′″. The distal ends of the upper arms of the four bellcranks  70  are pivotally connected to upper seat frame through four connections  78 .  
                                             List of Reference Numbers Emboldened in Text                                    10   seat suspension apparatus of this invention           11   bellcrank of prior art           12   pivot point           13   connecting point on seat frame           14   connecting point on spring bias           15   angle between lines from pivot to connecting               points           16   seat back, covered foam and frame           17   seat, covered foam and frame           18   seat-belt retractor           19   seat-belt latch           20   knob for spring tension adjustment           21   base frame           22   seat frame           23   vertical pivot posts (four)           24   pivot connections (four)           25   bellcranks (four)           26   front lateral phase-link           27   rear lateral phase-link           28   seat position release lever           29   seat position release           30   release pivot connection           31   tension support springs (two)           32   threaded spring tension rod           33   cross-member spring attachment           34   central axis for pivot connections (four)           35   longitudinal phase-links (two)           36   pivotal connections bellcrank to spring bias               (four)           37   shoulder bolts (twelve)           38   pivotal connections bellcrank to seat frame               (four)           39   central axis for connection 38           40   bushings on shoulder bolts to facilitate pivoting           41   cavities in foam cushion for bellcranks (four)           42   foam seat cushion           43   nuts for shoulder bolts (twelve)           44   bolt connections to vehicle floor deck           45   lower fore/aft slides (two)           46   upper fore/aft slides (two)           47   bolt/nut connection upper slide to base frame           48   arms of bellcranks connected seat frame (four)           49   central sections of bellcranks at pivot               connections (four)           50   arms of bellcranks connected to spring bias               (four)           51   angle on bellcranks between lines from pivot               point to spring bias and seat frame connection               points           52   bellcrank off-set section           53   longitudinal side members of frame 21           54   central axis of connection 36           55   holes through pivot section of bellcranks           56   holes through spring-bias section of cranks           57   holes through seat-frame section of cranks           58   seat frame connection flanges (four)           59   holes through flanges           60   spring connection flange           61   holes through flange for spring connection           62   holes through cross member for spring connection           63   hooks on front ends of springs           64   hooks on rear ends of springs           65   support for tension rod           66   horizontal holes in pivot posts           67   line from central axis 34 to central axis 39           68   line from central axis 34 to central axis 54           69   line parallel to line 68 through central axis 34           70   non off-set bellcranks (four)           71   longitudinal side members of frame 21′ (two)           72   spring connection flange           73   front lateral phase-link           74   cross-member spring attachment           75   rear lateral phase-link           76   longitudinal phase-links (two)           77   vertical pivot posts (four)           78   connections bellcrank to seat frame (four)           79   spacer mounting pads (four)           b′   fore/aft movement as seat lowers and raises           c′   up and down movement of seat           α   angle of rotation of bellcrank           β   angle of rotation of prior art bellcrank           b   fore/aft movement of prior art           c   up and down movement of prior art seat                      
 
         [0036]     While this invention has been described with reference to specific embodiments disclosed herein, it is not confined to the details set forth and the patent is intended to include modifications and changes, which may come within and extend from the following claims.