Abstract:
A low profile seat suspension includes a bottom frame adapted to be mounted on a vehicle, and a top frame located above the bottom frame for supporting a seat cushion and seat back thereon. A substantially fully collapsible scissors linkage is interconnected between the bottom frame and the top frame enabling the bottom frame and the top frame to move relative to each other substantially in parallel. A biasing arrangement is disposed between the top frame and the bottom frame and has a preload force urging the top frame away from the bottom frame. A first adjustment mechanism is located in the top frame and selectively enables fore and aft adjustment of the top frame relative to the bottom frame. A second adjustment mechanism is located between the bottom frame and the top frame and selectively enables an adjustment on the biasing arrangement in accordance with the weight of an occupant in the seat by translating a horizontal force applied to an adjustment plate into a vertical force effecting the preload force of the biasing arrangement. The invention is improved wherein an adjustment knob is positioned at a front of the seat and the knob is enabled to move along with the top frame irregardless of the fore and aft adjustment of the top frame relative to the bottom frame.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application is based on an claims priority from provisional U.S. Patent Application Ser. No. 60/477,618 filed Jun. 11, 2003. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates broadly to a vehicle seat suspension assembly and, more particularly, pertains to a fore and aft seat adjustment mechanism and a seat occupant weight compensation adjustment which collectively provide a vehicle seat suspension having a relatively low profile.  
       BACKGROUND OF THE INVENTION  
       [0003]     As is well known, vehicles, and in particular large trucks, are provided with scissors-type suspensions capable of cushioning extremely heavy loads unlike those normally encountered in the smoother ride of a passenger car. In order to isolate the driver from fatigue and discomfort induced by the vehicle vibrations, it is normal practice to provide seat suspension systems incorporating various spring arrangements which protect the driver from vibrations at the expense of consuming a considerable amount of physical space beneath the seat. This is especially applicable to spring suspension systems which can be adjusted according to the weight of the seat occupant. Some of these seats include slide provisions which enable a fore and aft or longitudinal adjustment of the seat relative to the floor of the vehicle. When a seat is provided with both of the aforementioned adjustments, it must locate its seat frame a considerable distance above the vehicle floor to accommodate them. In addition, the partial collapsibility of the scissors linkage used in the suspensions also contributes to the distance at which the seat is mounted. Often, this distance becomes prohibitively high to be utilized in certain vehicles having relatively small space limitations between the floor and the ceiling. Accordingly, it remains desirable to provide a seat suspension incorporating both a seat occupant weight compensation adjustment and a fore and aft seat adjustment which together with a substantially fully collapsible scissors linkage will ensure a relatively low profile for the seat.  
         [0004]     One such seat suspension is disclosed in U.S. Pat. No. 5,765,802 issued Jun. 16, 1998 and U.S. Pat. No. 5,871,198 issued Feb. 16, 1999, both of which are assigned to the assignee of this application. In these patents, a seat suspension includes a fore and aft seat adjustment mechanism and a weight compensation adjustment mechanism in combination with a substantially fully collapsible scissors linkage. While the designs from these patents have performed satisfactorily, improvements can be made to further enhance the performance, ease of adjustment and economy of cost for the seat suspension. For example, in the aforementioned patents, the weight compensation adjustment mechanism is located on the left side of the seat such that upon a forward seat adjustment it is sometimes difficult to access the adjustment knob which may have moved rearwardly beyond the reach of the seat occupant. Moving the adjustment knob to the front of the seat however requires that the weight compensation adjustment mechanism allow the adjustment knob to move back and forth with the fore and aft seat adjustment.  
         [0005]     It is a principal object of the present invention to provide a suspension mechanism that is simply constructed and relatively inexpensive while still meeting manufacturers&#39; ever increasing demands for compactness and comfort.  
         [0006]     It is also an object of the present invention to provide a suitable suspension unit which will reduce the shocks and vibration transmitted from the vehicle to the driver via the driver&#39;s seat.  
         [0007]     It is a further object of the present invention to provide a seat suspension having an adjustable preload to suit the weight of the seat occupant.  
         [0008]     It is another object of the present invention to provide a seat suspension utilizing a scissors linkage having slide channels which serve as guides for the longitudinal adjustment of the seat.  
         [0009]     Yet another object of the present invention to provide a seat suspension having a substantially fully collapsible scissors linkage.  
         [0010]     It is also an object of the present invention to provide a seat suspension with a weight compensation adjustment which is always accessible irregardless of the longitudinal adjustment of the seat.  
         [0011]     In one aspect of the invention, a low profile seat suspension includes a bottom frame adapted to be mounted on a vehicle, and a top frame located above the bottom frame for supporting a seat cushion and seat back thereon. A substantially fully collapsible scissors linkage is interconnected between the bottom frame and the top frame enabling the bottom frame and the top frame to move relative to each other substantially in parallelism. A biasing arrangement is disposed between the top frame and the bottom frame and has a preload force urging the top frame away from the bottom frame. A first adjustment mechanism is located in the top frame and selectively enables fore and aft adjustment of the top frame relative to the bottom frame. A second adjustment mechanism is located between the bottom frame and the top frame and selectively enables an adjustment on the biasing arrangement in accordance with the weight of an occupant in the seat by translating a horizontal force applied to an adjustment plate into a vertical force affecting the preload force of the biasing arrangement. The adjustment plate has a cam engaged therewith and the horizontal force slidably moves the adjustment plate and cams a resilient element of the biasing arrangement in a vertical direction. The invention is improved wherein an adjustment knob of the second adjustment mechanism is positioned at a front of the seat and the knob is enabled to move along with the top frame irregardless of the fore and aft adjustment of the top frame relative to the bottom frame.  
         [0012]     Various other objects, features and advantages of the invention will be made apparent from the following description taken together with the drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The drawings illustrate the best mode presently contemplated in carrying out the invention. In the drawings:  
         [0014]      FIG. 1  is a perspective view of a vehicle seat employing the seat suspension of the present invention and showing a fore and aft seat adjusting mechanism, and a weight compensation adjusting mechanism;  
         [0015]      FIG. 2  is an exploded, perspective view of the seat suspension in  FIG. 1 ;  
         [0016]      FIG. 3  is a bottom view of the seat suspension of  FIG. 1  in assembled form with portions of the base plate removed;  
         [0017]      FIG. 4  is a sectional view taken on line  4 - 4  of  FIG. 3  showing the weight compensation mechanism in an initial setting;  
         [0018]      FIG. 4A  is a view like  FIG. 4  showing a forward adjustment of the seat supporting frame and the manner in which the adjustment knob and the rod of the weight compensation adjusting mechanism move therewith;  
         [0019]      FIG. 5  is a view like  FIG. 4  showing the weight compensation adjusting mechanism in a subsequent setting;  
         [0020]      FIG. 6  is a sectional view taken on line  6 - 6  of  FIG. 3  showing the weight compensation adjustment mechanism in the setting of  FIG. 4 ;  
         [0021]      FIG. 7  is a view like  FIG. 6  showing the weight compensation adjustment mechanism in the setting of  FIG. 5 ;  
         [0022]      FIG. 8  is an exploded view of the scissors linkage of the seat suspension;  
         [0023]      FIG. 9  is a perspective view of  FIG. 8  in an assembled condition; and  
         [0024]      FIG. 10  is an exploded view of the seat back. 
     
    
     DETAILED DESCRIPTION  
       [0025]     Referring now to  FIG. 1 , a vehicle seat suspension embodying the present invention and generally identified by the reference numeral  10  is shown incorporated into the base or bottom portion of a vehicle seat  12  which is anchored to a floor  14  of the vehicle. As is well known, the vehicle seat  12  includes a seat cushion  16  and a seat back  18  which may be either fixed or pivotally adjustable with respect to the seat cushion  16 . A first adjusting mechanism  20  is provided to longitudinally adjust the position of the vehicle seat  12  relative to the floor  14  of the vehicle. A second adjusting mechanism  22  is provided to alter the resilient suspension of the vehicle seat  12  according to the weight of the seat occupant. As will be described, the arrangement of components in the seat suspension  12  results in the seat having a relatively low profile desirable to purchasers of such suspensions.  
         [0026]     Turning to the exploded view in  FIG. 2 , the vehicle suspension  10  includes a top frame  24 , a bottom frame  26  and a substantially fully collapsible scissors linkage  28  interposed between the top frame  24  and the bottom frame  26 . The first adjusting mechanism  20  is conveniently isolated in the top frame  24  and comprises a pair of adjustment channel assemblies  30 . The second adjusting mechanism  22  is located between the top and bottom frames  24 ,  26 , respectively, and comprises a suspension spring  32 , a cam assembly  33  defined by a cam follower  34  and a cam  36 , an adjustment paddle or strap  38 , a weight adjusting arm assembly  40 , a cylindrical coupling  41  with a throughhole  42 , a clevis pin  43 , and a long rod  44  attached to a weight adjustment knob  46 .  
         [0027]     Top frame  24  is a generally U-shaped, steel tubular structure for supporting seat cushion  16  thereon. A forward portion of the tubular structure  24  includes a transverse support strap  48 , and a pair of slide channels  50  extending between the strap  48  and the front of the tubular structure  24  on respective bottom surfaces thereof. Ends of the channels  50  define front and rear limits of travel for components of the scissors linkage  28  to be described later. An indicating and rod holding bracket  52  having a recess  53  ( FIG. 3 ) is welded to the front of the tubular structure  24 . A rear portion of the tubular structure  24  includes a recessed, planar mounting bracket  54  having a pair of spaced apart, upstanding mounting walls  56  interconnected by a rear cross brace  58 . As will be explained hereafter, the mounting walls  56  facilitate pivotal attachment of a seat back frame  60  ( FIG. 10 ) thereto. The seat back frame  60  has a support  57  for supporting a foam back  59  over which a cover  61  is slipped to form seat back  18 . The spaced apart channel assemblies  30  are attached to a bottom surface of the mounting bracket  54  on opposed sides thereof, and are operably tied together by a connecting wire  62  in  FIG. 3 .  
         [0028]     With reference to  FIGS. 2 and 3 , each top frame channel assembly  30  includes an elongated adjusting channel  64  which is C-shaped in cross section and has a bottom wall formed with a number of slots  66  along its length. Each channel  64  also has a front ear  68  and a rear ear  70  formed with aligned circular openings. A comb  72  which is U-shaped in cross section, has a bottom wall formed with a plurality of teeth  74 , and also has a front tab  76  and a rear tab  78 . Each adjusting channel  64  is juxtaposed relative to its comb  72  such that the teeth  74  of comb  72  are receivable in slots  66  of adjustment channel  64 , and openings formed in ears  68 ,  70  are aligned with apertures formed in tabs  76 ,  78 . On each adjustment channel assembly  30 , an elongated release rod  80  extends through the aligned openings and apertures. The release rod  80  on the left side of the vehicle seat  12  includes an extension  82  which runs beyond the front end of the seat  12  and terminates in a handle  84  accessible to the seat occupant outside the left front corner of the seat  12 . The forward end of each release rod  80  includes a U-shaped turning channel  86  fixed thereto which abuts front tab  76  on comb  72 . As seen in  FIG. 3 , the rear end of each release rod  80  projects beyond rear tab  78 , and is received in a wire eye  88  carrying connecting wire  62 . A torsion latch spring  90  ( FIG. 2 ) surrounds a forward portion of release rod  80  and is interposed between front ear  68  of adjusting channel  64  and front tab  76  of comb  72 . Each torsion latch spring  90  is positioned to normally retain teeth  74  of each comb  72  in the slots  66  of its respective adjusting channel  64 .  
         [0029]     Referring back to  FIG. 2 , the bottom frame  26  is a generally H-shaped steel base plate  92  having bent side edges  94  which form opposite side channels  96 . Holes  98  formed in the corners of base plate  92  can be used to receive studs (not shown) extending upwardly from the vehicle floor  14  and nuts (not shown) can be screwed onto the studs so as to fix the base plate  92  relative to the vehicle floor  14 . The base plate  92  has a pair of mounting segments  100  carrying suitable fasteners  102  to enable a connection to a portion of the scissors linkage  28 . The base plate  92  is also provided with a central opening  104  ( FIG. 6 ) which receives a nut  106  used to secure the base plate  92  with the suspension superstructure.  
         [0030]     With reference to  FIGS. 2, 8  and  9 , top frame  24  and bottom frame  26  are connected one above the other in parallel by scissors linkage  28  formed by a pair of inner links  108 ,  110 , and a pair of outer links  112 ,  114 . The inner links  108 ,  110  are formed by the bent side portions of a generally rectangular inner arm assembly  116  having a steel support plate  118  and bent front and rear portions  120 ,  122 , respectively.  FIG. 3  shows that on one side of the inner arm assembly  116 , a reinforced tube  124  extends between the respective front and rear portions  120 ,  122 . On the other side, an inner arm reinforcement tab  126  projects upwardly from the plate  118 , and a pair of aligned openings  128  ( FIG. 2 ) are formed in the respective front and rear portions  120 ,  122  to receive the long rod  44  of the weight compensating adjustment mechanism  22 . A protrusion  130  ( FIG. 3 ) extends upwardly from the plate  118  and has a hole aligned with the openings. The protrusion  130  carries a rotatable bearing  131  through which the rod  44  is passed. The cylindrical coupling  41  and the clevis pin  43  also extend downward from the plate  118 . A rear corner area of the plate  118  is cut out at  132  to accommodate a portion of the weight adjusting arm assembly  40 . Inner link  108  has a coupling-nut  134  welded to it and the reinforcement tube  124 , and extends laterally through and outside the link  108 . The opposite inner link  110  has a coupling nut  136  welded to it and to the inner arm reinforcement tab  126 , and extends laterally through and beyond the link  110 . Forward ends of the inner links  108 ,  110  carry pins  138  for mounting a first pair of slide blocks  140  slidably received in the slide channels  50  at the front of top frame  24 . Rearward ends of the inner links  108 ,  110  have holes and nuts (one being seen at  111  in  FIG. 2 ) welded to the inner surfaces of the inner links  108 ,  110  to receive the fasteners  102  in the mounting segments  100  of base plate  92 .  
         [0031]     The outer links  112 ,  114  are joined at rearward ends by a transfer shaft  142 . The rearward ends of the outer links  112 ,  114  are provided with pins  144  for mounting adjusting blocks  146  slidably received in the adjustment channel assemblies  30  on the top frame  24 . The forward ends of the outer links  112 ,  114  are equipped with pins  148  for mounting a second pair of slide blocks  150  which are slidably accommodated in the side channels  96  on bottom frame  26 . A midportion of each outer link  112 ,  114  is operably connected to a midportion of each inner link  108 ,  110  by a bolt  152  threaded into one of the coupling nuts  134 ,  136 .  
         [0032]      FIGS. 2-7  illustrate the unique weight compensation adjustment mechanism  22 . Cylindrical coupling  41  and clevis pin  43  extend vertically downwardly from the underside of formed inner arm plate  118 . Coupling  41  passes through a notched hole  154  formed by a continuous wall  156  on a distal end of adjustment strap  38  in underlying contact with the plate  118 . The peripheral size of the hole  154  is larger than the diameter of the coupling  41  so that the coupling  41  lies in spaced relationship to wall  156 . A proximal end of the adjustment strap  38  is joined to the weight adjusting arm assembly  40 . More particularly, the assembly  40  has a pair of spaced apart, arms  158  held together by a rivet  159  and defining a pair of bifurcated legs  160  between which a clevis nut  162  is rotatably mounted. The proximal end of the adjustment strap  38  is received between the arms  158  and retained by a clevis pin  164  and a cotter pin  166  such that there is freedom for relative movement between the adjustment strap  38  and the spaced apart arms  158 . The arms  158  have two aligned holes for receiving the clevis pin  43  in order that the arms  158  may rotate thereon. The coupling  41  also passes through the cam  36 , the cam follower  34  and at least a portion of the spring  32 . The cam  36  is oriented into the notched hole  154  on the adjustment strap  38  such that a boss on the cam  36  aligns with the notch in the hole  154  to prevent rotational movement of the cam  36  relative to the adjustment strap  38 . The cam  36  has a cavity so as to enable relative motion between the cam  36  and the coupling  41 . The cam  36  contains a series of inclined wedges or ramps  168  engageable with complimentary ramped surfaces  170  on cam follower  34 . Extending outwardly from the base of the cam follower  34  is a lip  172  which serves to seat small or upper end of the spring  32  that encircles the cam follower  34 . The spring  32  includes a large or lower end which is seated against the base plate  92 . Spring  32  is installed with a predetermined preload force which urges top frame  24  away from bottom frame  26 . An upstop or fastener  174  is inserted through the coupling throughhole  42  and has a threaded end which is received in the nut  106  fitted into base plate  92  so as to hold together the scissors linkage  28 , the adjuster strap  38 , the weight adjustment arm assembly  40 , the cam  36 , the cam follower  34 , the spring  32  and the base plate  92 . The fastener  174  is threaded into the nut  106  for such a distance as to set the maximum distance between the seat  16  and the base plate  92 . It should be appreciated that the fastener  174  passes through the neutral axis of the spring  32  and counteracts the load pressure thereof to allow lighter components in the suspension. By offsetting the load, these light weight components remain straight and functional. Use of the fastener  174  facilitates not placing the base plate  92  in a bending load.  
         [0033]     An adjuster screw  176  has external threads engageable with internal threads of a clevis nut  162 , and has a forward end engaged against the bearing  131 . The adjuster screw  176  has an internal hex  178  ( FIG. 4A ) which matingly receives a hex-shaped periphery of the long rod  44 . Rotating the rod  44  will thus turn the adjuster screw  176  relative to the clevis nut  162  yet will allow the long rod  44  to freely slide through adjuster screw  176  when fore and aft adjustment is made. A jam nut  180  is threaded onto a rearward end of the adjuster screw  176  to act as a travel limitation device for the clevis nut  162 . The long rod  44  is assembled into the adjuster screw  176  by passing the rod  44  through openings in the respective front and rear portions  120 ,  122  of the inner arm assembly  116  and the hole in the protrusion  130 . As seen best in  FIG. 4 , the weight compensation knob  46  is mechanically fastened with a jam nut  182  to a forward end of the long rod  44  so as to transmit rotational motion. The long rod  44  is inserted into a hole formed in the bracket  52  at the front of the tubular structure  24 . A spacer  184  and a spring pin  186  are located in such a way so as to hold the knob  46  in a position relative to seat tube  24 . A weight adjusting nut  188  is attached to the long rod  44  and has an extension  190  which projects into aligned grooves on the bracket  52  and an arm-like, weight adjusting indicator  192 .  
         [0034]     With the above structure, the inner links  108 ,  110  and the outer links  112 ,  114  can be spaced from each other such that the first pair of slide blocks  140  are almost at the same level as the second pair of slide blocks  150  when scissors linkage  28  is substantially fully collapsed. In such position, the spring  32  is compressed by applying a heavy load on seat cushion  16  such that the spring coils are tightly bounded together upon one another. Arranging the links  108  through  114  and the spring  32  in a particular fashion will create additional clearance which places the seat  12  in a particularly low profile.  
         [0035]     In use, let us assume it is desired to change the fore and aft position of the seat  12  from the rearward position of  FIG. 4  to the forward position of  FIG. 4A . One grasps handle  84  and against the bias of spring  90  lifts and rotates the extension  82  and release rod  80  on the left front side of seat  12  which rotational motion is transferred by connecting wire  62  to the right side of seat  12 . Such rotation moves the teeth  74  on combs  72  out of engagement with the slots  66  on adjusting channels  64  allowing the adjusting blocks  146  to slide in the adjusting channel  64  and permitting the first pair of slide blocks  140  to slide in the top front channels  50 . Once a desired slide position is reached, handle  84  is released and latch spring  90  will rotate and return each release rod  80  such that the teeth  74  will again engage slots  66  thereby locking seat  12  in position. By this construction, top frame  24  holding seat cushion  16  can be selectively adjusted forwardly and rearwardly relative to scissors linkage  28  which is connected to the bottom frame  26 .  
         [0036]     As a feature of the invention, the long rod  44  of the weight compensation adjustment mechanism  22  slides freely through the interior  178  of the screw  176  as the fore and aft adjustment is made ( FIG. 4A ). This allows the adjustment knob  46  to travel with the front edge of the top frame  24  on which seat cushion  16  is mounted so that the knob  46  is always easily accessible to the seat occupant irregardless of the seat fore and aft position.  
         [0037]     Now assume it is desired to change the preload force on the suspension spring  32  from the lower setting of  FIG. 6  to the higher setting of  FIG. 7  depending on the weight of the seat occupant. One conveniently turns the adjustment knob  46  outside the right front edge of seat  12 . As the knob  46  is turned in such a manner to increase the preload, a rotation of long rod  44  will cause rotation of the adjuster screw  176  and cause the clevis nut  162  to move in a direction towards the jam nut  180 . The motion of the clevis nut  162  causes a rotation in adjuster arms  158  and applies a horizontal force to adjuster strap  38  through clevis pin  43 . The movement of adjusting strap  38  moves the cam  36  in relation to the cam follower  34  causing the latter to rise over cam  36  and increase the compression or preload of spring  32  resulting in a stiffer ride.  
         [0038]     It should be noted that as the knob  46  is rotated, the invention provides a relative indication of the weight compensation adjustment. In particular, rotation of the knob  46  and nut  188  causes the arm-like indicator  192  to move relative to the recess  53  formed in the bracket  52 . The amount of surface area of the indicator  192  seen through the recess  53  gives a visual indication to the seat occupant of the amount of the weight compensation adjustment.  
         [0039]     While the invention has been described with reference to a preferred embodiment, those skilled in the art will appreciate that certain substitutions, alterations and omissions may be made without departing from the spirit thereof. Accordingly, the foregoing description is meant to be exemplary only, and should not be deemed limitative on the scope of the invention set forth with the following claims.