Abstract:
This invention relates to seat pivoting mechanisms of the type that would be used on industrial vehicles such as forklift trucks, for example. The pivoting seat mechanism permits locking the seat in a forward facing position, as well as allowing the seat to pivot or rotate through a fixed, controlled angle. The seat pivot system is compact and does not unnecessarily add height to the seat structure, thereby conserving headroom within a vehicle cab or protective cage.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    The present application claims the benefit of U.S. Provisional Application Serial No. 60/416,165 filed on Oct. 4, 2002, which is hereby incorporated by reference in its entirety. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates generally to a seat pivot system for a work vehicle and more particularly to a low profile seat pivot system for a forklift vehicle.  
         BACKGROUND OF THE INVENTION  
         [0003]    The location of the operator&#39;s seat in a forklift truck presents a number of problems in the design of a seating system. Because of the design of most forklifts, the operator&#39;s seat must be located directly above the engine housing. Further complicating the design is the protective cage or cab which limits the size of any seating suspension or pivot system.  
           [0004]    A typical forklift truck as shown in FIG. 1 has a fixed seat facing the direction of the forks. During normal operation of the vehicle, this design mandates that many operations be performed operating the vehicle in reverse. With the forklift unloaded, the operator has a clear forward view and may operate the vehicle in the forward direction. When the vehicle is loaded, however, the operator&#39;s forward view may be obstructed by the load forcing the operator to drive the vehicle in reverse. During a typical 8 hour shift, a forklift truck operator may spend as much as 70% of his or her time operating the vehicle in reverse.  
           [0005]    The operator&#39;s ability to turn towards the rear of a typical forklift is limited by the layout of the vehicle. First, the operator&#39;s legs must remain forward to allow the operator to manipulate the vehicle&#39;s foot pedals. Second, the seat belt restricts the amount an operator may turn his hips with a standard, forward-facing seat. These limitations force the operator to rotate or twist his neck and upper spine to look toward the rear of the vehicle. Over time, this repeated twisting may lead to an increased incidence of neck and back pain as well as muscle fatigue and/or injury.  
           [0006]    Most seats used on forklifts, tug tractors, tow motors, cranes, skid-steer loaders, ground support equipment and the like are fixed in a forward-facing position. In addition to lacking the ability to turn, these seats force the operator to sit in a fixed posture for the duration of a particular operation. Because fixed seats do not allow spinal movement, performing a task for an extended period of time against a rigid back support without variety in movement can cause muscles to weaken and atrophy, and joints to become inflexible.  
           [0007]    Traditionally the solution to this problem has been to provide the work vehicle with a pivotable seat; however, forklift trucks have not been amenable to typical seat pivoting systems such as those using ball bearing turntables. The operator seat in a typical forklift is located directly above the engine housing. The desire to keep the forklift compact prevents relocating the seat with respect to the housing. Further complicating the matter is the fact that most forklifts have a rollover and falling material protection system in the form of a protective cage surrounding the operator which must be a minimum of 35 inches above the H-point of the seat in order to provide sufficient headroom to allow even tall operators to sit upright. Again, the desire to retain a compact design which allows the forklift to pass through doorways and other openings dictates this protective cage be as low as possible. This low height of the protective cage prevents the use of most larger seat pivoting systems in forklifts or vehicles of this type.  
           [0008]    The present invention is directed towards overcoming the problems set forth above by providing a compact pivotable seat mechanism and method that allows a vehicle operator to turn the seat in order to relieve muscle tension and to permit an easier view to the rear of the vehicle when moving the vehicle in reverse.  
         SUMMARY OF INVENTION  
         [0009]    One object of the present invention is to provide a work vehicle seat pivot system which allows the operator to rotate the seat from a forward facing position during normal operation of a typical work vehicle.  
           [0010]    Yet another object of the present invention is to provide a work vehicle seat pivot system which incorporates a seat suspension system to dampen harmful vibration generated by the operation of the vehicle.  
           [0011]    A further object of the present invention is to provide a work vehicle seat pivot system which may be easily retrofit to existing work vehicles, particularly forklift trucks.  
           [0012]    Yet another object of the present invention is to provide a seat pivot system which is compact to allow for use in work vehicle protective cages without the loss of operator headroom.  
           [0013]    Further objects, embodiments, forms, benefits, aspects, features and advantages of the present invention may be obtained from the description, drawings, and claims provided herein.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0014]    [0014]FIG. 1 is a side view of a forklift vehicle for use in describing the embodiments of the present invention.  
         [0015]    [0015]FIG. 2 is a side view of a vehicle seat incorporating a pivoting seat apparatus in accordance with an embodiment of the present invention.  
         [0016]    [0016]FIG. 3 is top plan view of one component of a vehicle seat pivoting apparatus in accordance with an aspect of the present invention.  
         [0017]    [0017]FIG. 4 is a perspective view of the component shown in FIG. 3, further illustrating an exploded view of one embodiment of a seat locking mechanism.  
         [0018]    [0018]FIG. 4A is a detailed view of the seat locking mechanism shown in FIG. 4, illustrated in an assembled state.  
         [0019]    [0019]FIG. 5 is a perspective view of a portion of the component shown in FIG. 3, further illustrating an exploded view of a seat position release mechanism in accordance with the present invention.  
         [0020]    [0020]FIG. 5A is a detailed view of the release mechanism of FIG. 5, illustrated in an assembled state.  
         [0021]    [0021]FIG. 6 is a top plan view of another component of a vehicle seat pivoting apparatus in accordance with an aspect of the present invention.  
         [0022]    [0022]FIG. 7 is a top plan view of a component of a vehicle seat pivoting apparatus similar to that shown in FIG. 6, illustrating another aspect of the present invention.  
         [0023]    [0023]FIG. 8 is a perspective exploded view showing the assembly of a portion of the seat pivoting apparatus in accordance with an aspect of the present invention.  
         [0024]    [0024]FIG. 8A illustrates the portion of the seat pivoting assemble shown in FIG. 8, shown in an assembled state.  
         [0025]    [0025]FIG. 9 is a perspective exploded view showing the assembly of another portion of the seat pivoting apparatus in accordance with an aspect of the present invention.  
         [0026]    [0026]FIG. 9A illustrates the portion of the seat pivoting assemble shown in FIG. 9, shown in an assembled state.  
         [0027]    [0027]FIG. 10 is a perspective exploded view showing the assembly of another embodiment of a seat pivoting apparatus in accordance with the present invention.  
         [0028]    [0028]FIG. 10A shows the seat pivoting apparatus of FIG. 11 in an assembled state.  
         [0029]    [0029]FIG. 11 is an exploded side elevational view of one embodiment of a seat pivoting apparatus in accordance with an aspect of the present invention, illustrating its assembly to a vehicle.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0030]    For the purposes of promoting understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is hereby intended and alterations and modifications in the illustrated device, and further applications of the principles of the present invention as illustrated herein being contemplated as would normally occur to one skilled in the art to which the invention relates.  
         [0031]    The present invention relates to a seat pivot system for a work vehicle, such as a forklift truck  10  as shown in FIG. 1. Forklift truck  10  includes an engine or motor housing  12  (which will also include the transmission and other components), wheel assemblies  14 , which are supported by a suspension system (not shown). Forklift mechanism  16  is mounted to the front of engine housing  12  and incorporates forks  18  and lifting drive  20  of a conventional, known design. A representative load  22  is shown in place on forks  18 . Seat  24  is mounted to housing  12  via mounting structure  26 , which may include the seat pivoting apparatus of the present invention such as will be described in detail below, as well as other components such as seat adjustment rails and suspension parts. Also shown in FIG. 1 are steering wheel  28 , a representative operation pedal  30 , and protective operator shield  32 , which may be a cage or enclosed cab, for example.  
         [0032]    As can be seen in FIG. 1, a large load such as load  22  can easily obscure an operator&#39;s forward view when operating forklift truck  10 , particularly when forks  18  are in a raised position necessary for moving the forklift truck  10 . As cab  32  cannot exceed a height that would prevent forklift truck  10  from passing through doors and under overhead objects, an operator will often decide to drive forklift truck  10  in reverse to obtain a better view of objects and people approaching the moving forklift truck  10 .  
         [0033]    In accordance with an aspect of the present invention, seat mounting structure  26  comprises a seat pivoting mechanism  34  that permits the operator to turn seat  24  within a prescribed range in order to obtain a better rearward facing view while reducing the amount of neck and back twisting that is required. The construction and operation of seat pivoting mechanism  34  will be described in greater detail below.  
         [0034]    [0034]FIG. 3 illustrates one component of seat pivoting mechanism  34 , namely a seat plate  36 . Seat plate  36  may be manufactured of a variety of materials, such as stamped sheet metal, aluminum, or other materials that are strong and preferably lightweight. Seat plate  36  incorporates a number of holes  38  for mounting seat plate  36  to a vehicle seat for use in vehicles such as forklift  10 . Holes  38  are placed in a variety of locations to facilitate retrofitting seat pivoting mechanism  34  to a range of models and vehicles from different manufacturers. Mounting of seat plate  36  to a vehicle seat such as forklift  10  may be by any known means, such as screws or bolts, for example. Holes  38  may also be countersunk to reduce the overall height of mechanism  34 . The seat plate  36  shown in FIG. 3 also has material removed to form a central hole  40  that may accommodate a spring or other suspension component and additionally to reduce the weight of seat plate  36  and hence the overall weight of seat pivoting mechanism  34 . Seat plate  36  also incorporates pivot pins  42  which extend perpendicular to the surface of seat plate  36 . A portion of seat locking guide  44  is also shown in FIG. 3.  
         [0035]    The construction and operation of seat locking guide  44  is shown in FIG. 4, which also shows more clearly the structure of pivot pins  42 . Seat locking guide  44  includes a pair of tabs  46 , extending substantially perpendicular from seat plate  36 . Tabs  46  are illustratively shown as being cut and bent from the material of seat plate  36 , but they may be separately attached members. Tabs  46  incorporate through holes  48  which are adapted to receive locking pin  50 . A biasing member illustratively shown as a compression spring  52  is located between the two tabs  46  so that locking pin  50  passes through spring  52  when locking pin  50  is inserted through holes  48  of tabs  46 . A C-clip  54  is used to hold locking pin  50  in place after insertion through holes  48  of tabs  46 , but other types of clamps or holding means would be suitable as well. FIG. 4A shows seat locking guide  44  in an assembled state with locking pin  50  passing through holes  48  of tabs  46  and spring  52 , and being held in place by C-clip  54 .  
         [0036]    [0036]FIG. 5 illustrates an exploded view of one embodiment of the assembly and operation of a release mechanism for locking pin  50 . Lever arm  56  incorporates a C-shaped channel  58  which fits around the shaft  60  and below the head  62  of locking pin  50 . C-channel  58  is dimensioned to be smaller than the diameter of head  62 . Lever arm  56  is shown illustratively mounted to seat plate  36  via bolt  64  and nut  66 , although other means of attaching lever arm  56  to seat plate  36  would be equally suitable.  
         [0037]    Attached to, and extending outwardly from lever arm  56  is a handle  68  on which is placed a handle cover  70 . Handle  68  provides a means to impart a torque moment to lever arm  56  in order to rotate or pivot lever arm  56  about bolt  64 . FIG. 5A shows this release mechanism in an assembled state. In operation, when handle  68  is moved in direction A (as shown in FIG. 5A), lever arm  56  rotates around bolt  64  and moves locking pin  50  in direction B.  
         [0038]    In accordance with an aspect of the present invention, FIG. 6 illustrates a pivot or bearing plate  72  which may be manufactured from a variety of suitable materials, preferably an ultra high molecular weight (UHMW) plastic such as UHMW polyethylene. This material is sold commercially under a number of brand names including Trilon AR® by Tri Star Plastics Corp. of Shrewsbury, Mass. and Tivar® by Poly-Hi Inc. of Fort Wayne, Ind. UHMW plastics exhibit excellent abrasion resistance, zero moisture absorption, resistance to UV light and low friction. Preferably the bearing plate will also be impregnated with solid and/or liquid lubricants such as silicone or graphite to further reduce friction between the bearing plate and the seat plate. Bearing plate incorporates a central hole  74  which will correspond in position with hole  40  of seat plate  36 , as well as arcuate slots  76  having a curved or elliptical shape, and mounting holes  78 . Also shown in FIG. 6 are rotation stops  80  separated by slot  82 . The function of rotation stops  80  and slot  82  will be explained below.  
         [0039]    [0039]FIG. 7 illustrates a similar bearing plate  72 ′ having a central hole  74 ′, arcuate slots  76 ′, mounting holes  78 ′, rotation stops  80 ′ and  84 , and slot  82 ′. The distal end of rotation stop  84  extends further than the end of stop  80 ′, compared to rotation stops  80  in FIG. 6 which are similarly dimensioned. As will be explained in greater detail below, stop  84  is designed to permit seat pivoting mechanism  34  to pivot or rotate only in one direction.  
         [0040]    [0040]FIG. 8 illustrates the assembly of pivot or bearing plate  72  with base plate  86 . Bearing plate  72 ′ could be substituted for bearing plate  72  without changing the manner of assembly shown in FIG. 8. Base plate  86  may be made from the same or similar material to that of seat plate  36 . Base plate  86  also incorporates arcuate slots  88 , a central hole  90 , and a number of mounting holes  92  for mounting or attachment to a vehicle such as forklift  10 . Base plate  86  also incorporates holes  94  through which are passed bolts  96 . Bolts  96  pass through holes  94  in base plate  86  and holes  78  in bearing plate  72  and are secured by nuts  98 . Holes  78  are shown as being countersunk so that nuts  98  will not extend above the upper surface of bearing plate  72 . FIG. 8A illustrates the assembly of bearing plate  72  and base plate  86 .  
         [0041]    In FIG. 9, the base plate  86  and bearing plate  72  assembly is shown being assembled to seat plate  36 . Pivot pins  42  of seat plate  36 , illustratively shown as being threaded, pass through corresponding arcuate slots  76  and  88  of bearing plate  72  and base plate  86 , respectively. One or more wing nuts  100  are illustratively shown as being threaded onto pins  42  to securely attach seat plate  36 , bearing plate  72  and base plate  86  together.  
         [0042]    As can be more easily seen in the assembled view of FIG. 9A, the end of locking pin  50  fits into slot  82  between rotation stops  80  of bearing plate  72  and maintains the bearing plate and base plate assembly in fixed position with respect to seat plate  36 . When handle  68  is moved so as to rotate lever arm  56  and as a result pull locking pin out of engagement with slot  82 , seat plate  36  is then allowed to rotate through the angular range determined by the amount that pivot pins  42  are allowed to move within the confines of arcuate slots  76  and  88 . Rotation is accomplished by way of bearing plate  72  sliding against seat plate  36 . The use of bearing plate  72 ′ instead of bearing plate  72  would allow the bearing plate/base plate assembly to rotate in one direction only, as the end of pivot pin  50  would not extend beyond the end of rotation stop  84  due to its increased length compared to rotation stops  80 . Positioning pivot pins at one extreme of the respective arcuate slots of bearing plate  72  and base plate  86  could also be used to control the direction and/or the degree of rotation. As an illustrative example, the arcuate slots are dimensioned to permit the rotation of a vehicle seat by 15°, although other angles of rotation are of course possible. When handle  68  is released, pivoting or rotation of the bearing plate/base plate assembly will continue until the bearing plate is rotated back to its “home” position where spring  52  will cause pin  50  to again engage slot  82 .  
         [0043]    [0043]FIG. 10 illustrates another aspect of the present invention in which the seat pivoting mechanism also incorporates vibration dampening structure such as that disclosed in co-pending U.S. patent application Ser. No. 10/253,042, filed Sep. 23, 2002, which claimed priority from Provisional Application No. 60/324,142, filed Sep. 21, 2001, both being incorporated by reference herein.  
         [0044]    In FIG. 10 there is shown a first base plate  102  and a second base plate  104 . Base plate  102  forms an assembly with a bearing plate (not shown) and a seat plate  106 . The bearing plate and seat plate  106  may be similar or identical to bearing plate  72  and seat plate  36  previously described. Base plates  102  and  104 , in addition to the elements included in base plate  86  such as arcuate slots, mounting holes, and a central hole, also incorporate leaf spring elements  108 , which provide vibration dampening in the manner described in co-pending application Ser. No. 10/253,042. Base plates  102  and  104  are shown illustratively attached to each other by way of bolts  110  and nuts  112 . FIG.  10 A shows a completed seat pivoting assembly, incorporating vibration dampening, in its assembled form.  
         [0045]    [0045]FIG. 11 shows a simplified side exploded view that illustrates the various components of a seat pivoting mechanism in accordance with the present invention. A representative forklift housing  12 , which could also be a truck bed, or other vehicle mounting seat mounting base, is illustratively shown as the base on which the pivoting mechanism is mounted. Sliding rails  114  are also shown as an example of additional components that could be included. Rails  114  allow the vehicle seat to move forward and backward to permit operators to obtain a desired seat position, through the use of adjustment handle  116 , for example. Base plate  86  mounts onto rails  114  through conventional means, while bearing plate  72  and seat plate  36  are assemble together as described above. Seat plate  36  in turn attaches to vehicle seat  24  through conventional means as well. Release arm  68  and pivot pins  42  can also be seen in connection with seat plate  36  in FIG. 11.  
         [0046]    Other embodiments are of course possible. The examples shown illustrate seat pivoting mechanisms or systems having a single bearing plate. The present invention also contemplates a seat pivot system having a greater number of pivot plates and having pivot or bearing plates that are of different shapes and sizes. Additionally, the wide variety of operator&#39;s seats available may require different methods of attachment than are described herein. The present invention contemplates seat plates adapted to a variety of means for securing an operator&#39;s seat including, but not limited to, such methods as bolts, screws, pins, and clasps. Similarly, the attachment of the base plate to a vehicle may be by similar or other means. Mechanisms allowing for slidable positioning of a seat are well known in the art and may be incorporated between the base plate of the seat pivot system of the present invention and the work vehicle, such as the sliding rails shown in FIG. 11, although other adjustment means could be employed.  
         [0047]    As the size of forklift or other suitable vehicle seats vary, the dimensions of the seat plate, the pivot or bearing plate and the base plate will vary according to the particular application. The overall height of a seat pivot system according to the present invention is minimized to allow for use in a forklift truck while maintaining as much room as possible for the operator between the seat surface and the forklift&#39;s protective cage. According to one embodiment of the present invention, the overall height of the pivot system is no greater than 0.5 inches. As forklift configurations vary, other heights are contemplated by alternate embodiments of the present invention.  
         [0048]    While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes, modifications and equivalents that come within the spirit of the inventions disclosed are desired to be protected. The articles “a”, “an”, “said” and “the” are not limited to a singular element, and include one or more such elements.