Abstract:
An operator seat suspension apparatus includes a seat having a seat structure including longitudinal, upright flanges and a vehicle having a frame including longitudinal, upright flanges spaced away from the longitudinal, upright flanges of the seat structure. A set of isolators is fixed to and connects between the upright flanges of the seat structure and the upright flanges of the vehicle frame. The isolators are adapted to allow displacement in shear in the vertical and the longitudinal directions in response to shock forces in either direction.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/768,839 filed on Feb. 25, 2013, which is incorporated herein by reference. 
     FIELD 
     This invention relates to an apparatus for suspending an operator&#39;s seat for a working vehicle that traverses moderately rough terrain such as a riding mower. 
    
    
     BACKGROUND 
     Riding mowers and other vehicles that traverse moderately rough terrain have long been known for transmitting vibrations to the operator. This problem is particularly acute for riding mowers. Because riding mowers must follow terrain variations in order to properly cut turf and because the cutting decks of riding mowers are typically carried by the frame of a riding mower. Because of this, when riding mowers do have suspension systems between the wheels and the frame, the range of relative motion between the wheels and the frame are usually limited so that the quality of the cut is not compromised. Accordingly, various suspension systems have been interposed between mower frames and operator seats or operator platforms in order to isolate operators from terrain variations. All suspension systems rely on the fundamental property of inertia. Accordingly, if the operator and the operator&#39;s seat can be at least partially decoupled from the vehicle frame, then the operator and the operator&#39;s seat would generally continue their motion and direction of motion regardless of sudden variations in the path of the mower. Further, since the direction of motion of a riding mower is generally in the longitudinal or “x” direction, the path variations which are most likely to cause discomfort for an operator are in the vertical or “y” direction as well as, and nearly as importantly, in the longitudinal or “x” direction. The ability to absorb displacements in the longitudinal or “x” direction is particularly important for riding mowers having relatively short wheel bases. When such “short coupled” riding mowers encounter a bump, the mower will suddenly rotate about a generally transverse axis causing “back slap” (when the back of the operator seat to slaps the operators back). If the operator&#39;s seat can translate in the longitudinal direction, then back slap can be reduced. Yet, most prior art riding mower suspension systems employ a spring element which compresses only in response to vertical forces. Also, suspension systems having compression springs or elastomeric compression elements usually have a limited range of motion. Accordingly, what is needed is an operator seat suspension system that is compliant in the vertical or “y” direction, as well as being compliant in the longitudinal or “x” direction and with a generous range of motion in both the “x” and “y” directions. Further, it would be advantageous if such a suspension system had a means for dampening responsive relative motions between the operator seat and the vehicle frame in the vertical or “y” direction and in the longitudinal or “x” direction. 
     SUMMARY 
     An operator seat suspension system for vehicles that traverse moderate rough terrain includes an operator seat and a suspension system interposed between the operator seat and the frame of the vehicle. The suspension system includes transverse elastomeric isolators which connect between first members fixed to a seat frame and second members fixed to a vehicle frame. An optional dampener may be connected between a member fixed to the vehicle frame and the seat. The elastomeric isolators connect transversely between the seat frame flanges and the vehicle frame flanges. The isolators are not adapted to deform in compression but are adapted to respond in shear to both vertical and longitudinal forces. The isolators are arranged to be relatively unresponsive either in compression or tension. Thus, compliance in the transverse direction, which results in either compression or tension in the isolators, is significantly less than compliance in either the longitudinal or vertical directions. Accordingly, in this example, the seat may move up and down in response to sudden vertical accelerations or forward and back in response to sudden longitudinal accelerations but will be significantly less responsive to the relatively less common side to side accelerations. However, as noted above, such side to side accelerations are not significant during normal operations. 
     In this example, an optional dampener may be connected between the seat and the vehicle frame and is oriented to primarily dampen vertical displacements and to a lesser degree, longitudinal displacements. Thus, the dampener is adapted to rapidly reduce cyclic displacements of the seat relative to the frame, particularly if those cyclic displacements are in the vertical direction. 
     The overall effect of the suspension system described above is to allow the operator to move along a path that will have vertical displacements but will have vertical displacements that are smoother and more gradual than the vertical displacements experienced by the vehicle frame when the vehicle frame is traversing an uneven surface. Moreover, while the vehicle may rock and tip about a transverse axis, the suspension system will tend to prevent the seat from changes in orientation in response to the sudden or rapid oscillations of the vehicle frame as the vehicle traverses an uneven surface, such as a washboard surface. Yet the suspension system will permit the seat to change its orientation, by following the orientation of the vehicle frame, in response to more gradual changes in pitch as might occur when the vehicle begins to climb a slope. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an operator seat mounted to a vehicle frame with the present suspension system. 
         FIG. 2  is a side view of an operator seat mounted to a vehicle frame with the present suspension system. 
         FIG. 3  is a front view of an operator seat mounted to a vehicle frame with the present suspension system. 
         FIG. 4  is a top view of an operator seat mounted to a vehicle frame with the present suspension system. 
         FIG. 5A  is a front view of an isolator in a first neutral position. 
         FIG. 5B  is a front view of an isolator in a second downwardly deflected position as might occur with the added weight of an operator. 
         FIG. 5C  is a front view of an isolator in a third upwardly deflected position as might occur if the frame of the vehicle were to suddenly translate down relative to the operator seat. 
         FIG. 5D  is a front view of an isolator in a fourth downwardly deflected position as might occur if the frame of the vehicle were to suddenly translate up due to a sudden bump. 
         FIG. 6A  is a top view of an isolator in a first neutral position. 
         FIG. 6B  is a top view of an isolator in a second rearwardly deflected position as might occur if the frame of the vehicle were to suddenly translate forward relative to the operator seat. 
         FIG. 6C  is a top view of an isolator in a third forwardly deflected position as might occur if the frame of the vehicle were to suddenly translate backward relative to the operator seat. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings,  FIGS. 1-4  illustrate a vehicle operator seat  5  mounted to a vehicle frame  2  with a suspension system  10  interposed between seat  5  and vehicle frame  2 . In this example, vehicle frame  2  is a portion of the frame of a working vehicle for traversing moderately rough terrain such as a riding mower. Those skilled in the art will readily understand the general configuration of a vehicle such as a riding mower and will readily understand the types of displacements experienced by a riding mower during typical operations as the mower traverses moderately rough terrain. Seat suspension system  10  generally includes isolators  12  and  14  generally connecting between seat  5  and vehicle frame  2  and dampeners  22  which also generally connect between a structure connected to vehicle frame  2  and operator seat  5 . 
     As can be seen in  FIG. 1 , in this example, operator seat  5  is rigidly mounted to a seat pan  5 A which presents two spaced apart generally longitudinal, upright seat flanges  5 B. In this example seat flanges  5 B extend from the forward end of seat  5  toward the back of seat  5 . Yet, the skilled reader should understand that seat flanges  5 B are shown and described here by way of example only. Seat flanges  5 B should be understood as structural members which are at least indirectly mounted to seat  5  and which are fixed in relation to seat  5 . Vehicle frame  2  includes two spaced apart generally longitudinal, upright frame flanges  2 A which are generally parallel to and spaced away from seat flanges  5 B. In this example, frame flanges  2 A are shown to be spaced outboard of seat flanges  5 B but could also be spaced inboard of seat flanges  5 B. Further, the skilled reader should understand that upright frame flanges  2 A are merely examples of suitable members for mounting isolators  12  and  14  to a vehicle. Upright frame flanges  2 A should be understood as any structural member which presents a suitable, generally upright longitudinal surface for mounting an isolator which is either part of a vehicle frame or which can be mounted to a vehicle frame and fixed in relation to a vehicle frame. In this example, elastomeric isolators  12  and  14 , including forward isolators  12  and rear isolators  14 , are located adjacent to the forward and rear ends of seat  5  respectively and extend transversely and connect between frame flanges  2 A and seat flanges  5 B. Thus, isolators  12  and  14  extend transversely and are adapted to deform in shear in response to vertical forces between a neutral position shown in  FIG. 5A  and a downwardly displaced position shown in  FIG. 5D . It is also possible, should frame  2 A suddenly accelerate downward, for isolator  12  to deform in an upwardly displaced manner as shown in  FIG. 5C . Further, to a different degree, with a different spring rate, isolators  12  and  14  are capable of deforming in shear in response to longitudinal forces between a neutral position shown in  FIG. 6A , a forward position shown in  FIG. 6C  and a rearwardly displaced position shown in  FIG. 6B . 
     One of isolators  12  is shown in detail in  FIGS. 5A-6C . The skilled reader should understand that isolator  12  is generally similar in design to isolator  14 . As can be better seen in  FIGS. 5A-6C , isolator  12  includes an outboard flange  12 A, an elastomeric isolator body  12 B and an inboard flange  12 C. Isolator body  12 B is bonded to flanges  12 A and  12 C by a strong, durable adhesive. In this example, outboard and inboard flanges  12 A and  12 C are flat plates which, in this example, are fashioned from a strong material such as steel or a high grade aluminum alloy. Flanges  12 A and  12 C may be replaced by L shaped brackets or the like as long as generally upright flanges are present for supporting isolator body  12 B. In this example, four fasteners  12 F fasten flanges  12 A and  12 C to frame flange  2 A and seat flange  5 B respectively. The purpose of these structural elements is to mount an isolator, on one side of the isolator, to a generally first upright, longitudinal surface of a member which is fixed in relation to seat  5  and to also mount the isolator, on its opposite side, to a second upright, longitudinal surface of a member which is fixed in relation to the vehicle frame. 
     As noted above, isolators  12  and  14  may be configured to have differing spring rates in the vertical and longitudinal directions. By way of example, isolators  12  and  14  may be configured so that an operator weighing 200 lbs will notice that seat  5  translates down approximately ½ or 2 inches when the operator sits in seat  5 . Thus, all four isolators may have a combined spring constant in the vertical direction of approximately between 100 to 200 lbs/inch. A different spring rate may be selected for the longitudinal direction. Isolators  12  and  14  are much less responsive to transverse or side to side forces. However, if vehicle frame  2  was to suddenly rock or rotate about a longitudinal axis (when, for example, wheels on one side of the vehicle encounters a bump), isolators  12  and  14  on one side would deflect downwardly while isolators  12  and  14  on the opposite side might deflect upwardly or at least deflect toward the neutral position under the weight of an operator thereby allowing seat  5  to generally remain in its orientation during such rocking motion. As can be appreciated by those skilled in the art, a riding mower is not likely to experience significant sudden side to side (transverse) displacements. 
     Various deflection modes for isolators  12  and  14  are shown in FIGS.  4  and  5 A- 5 C. Since the deflection modes of isolators  14  are essentially identical to the deflection modes of isolators  12 , the deflection modes for right front isolator  12  are shown in  FIGS. 5A-6C .  FIGS. 5A-5D  illustrate what occurs when relative vertical displacements occur between vehicle frame  2 A and seat frame  5 B. As can be seen in  FIG. 5A , which is a front view of isolator  12 , isolator  12  is in a first neutral position as might occur when the vehicle is not moving and operator seat  5  is empty. In  FIG. 5B , isolator  12  is in a second downwardly deflected position as might occur when an operator is sitting in seat  5 . In  FIG. 5C , isolator  12  is in a third upwardly deflected position as might occur if the vehicle is in motion and frame  2 A suddenly translates downwardly. And finally, in  FIG. 5D , isolator  12  is in a fourth downwardly deflected position in which seat frame  5 B is displaced downwardly to a degree which is larger than in the second downwardly deflected position shown in  FIG. 5B . The fourth downwardly deflected position might occur when frame  2 A is suddenly displaced upwardly as might occur when the vehicle encounters a bump. Isolators  12  and  14  may be configured to have differing spring rates in the vertical and longitudinal directions. By way of example, isolators  12  and  14  may be arranged so that an operator weighing 200 lbs may notice seat  5  translates down approximately between ½ and 2 inches much as shown in  FIG. 5B . 
       FIGS. 6A-6C  illustrate what occurs when relative longitudinal displacements occur between vehicle frame  2 A and seat frame  5 B. As can be seen in  FIG. 6A , which is a top view of isolator  12 , isolator  12  is in a first neutral position as might occur when the vehicle is not moving. In  FIG. 6B , isolator  12  is in a second rearwardly deflected position as might occur when frame  2 A suddenly accelerates forward relative to seat frame  5 B as might occur when a short coupled vehicle in motion encounters a bump and the vehicle frame is rotating forward around a transverse axis. In  FIG. 6C , isolator  12  is in a third forwardly deflected position as might occur when a short coupled vehicle in motion encounters a bump and the vehicle frame is rotating backward around a transverse axis. Such backward and forward displacements which occur with greater amplitudes in short wheel base vehicles causes the “back slap” condition noted above. By allowing operator seat  5  to be displaced in the longitudinal direction relative to frame  2 A, backslap may be reduced or even substantially eliminated. 
     As can be seen in  FIGS. 1 and 4 , in this example, two optional dampeners  22  are connected between stanchions  20  mounted to frame  2  and the extreme rear corners of seat pan  5 A. Dampeners  22  are pivotally mounted at both ends and are operable to dampen vertical oscillations of seat  5  and to a lesser degree to dampen longitudinal oscillations of seat  5 . The dampening coefficient of the dampeners may be tuned to permit displacements to counter jolts in the ride, but to also minimize the oscillations of seat  5  after the vehicle encounters a bump. 
     It is to be understood that while certain forms of this invention have been illustrated and described, it is not limited thereto, except in so far as such limitations are included in the following claims and allowable equivalents thereof.