Abstract:
A truck cab suspension system provides improved lateral location of the cab and restrains the cab from detachment from the vehicle chassis during accidents. The suspension system offers simplification over the prior art by providing a lateral locating wheel set in a vertical travel between the chassis and the vehicle cab. The travel provides a backup link between cab and chassis. The locating wheel is cushioned to provide bumper like protection for lateral, and both up and down vertical shocks.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a cab suspension system for a truck and, more specifically, relates to a suspension providing lateral location for the cab on the chassis and for restraining the cab from detaching from the vehicle chassis during high acceleration events. 
     2. Description of the Problem 
     Vehicle cab suspensions isolate occupants of the cab from shock to and vibration of a truck&#39;s frame. Many proposed suspensions have been characterized by great mechanical complexity, resulting in added maintenance costs, and by excessive bulk, making it difficult to fit the suspension within the space allowed between the cab and the frame. A factor contributing to the size and complexity of some of these suspensions is the need to proved lateral control over cab position relative to the frame. In addition, some suspensions have required separate components to provide a restraint against cab detachment in accidents. Lateral positioning has been provided on some vehicles by equipping the vehicles with a lateral tracking or locating link, sometimes called a Panhard rod, between the cab and the chassis. Alternatively, lateral rubbing pads have been provided between cab and chassis which bind when the sprung and unsprung masses roll relative to one another. 
     In U.S. Pat. No. 6,168,229, vander Kooi et al. proposed an alternative suspension system directed to providing lateral positioning of the cab. This system proposed the use of a square metal tube positioned under the aft section of a vehicle cab. The tube is attached to a chassis cross member and is oriented transversely with respect to the direction of elongation of the vehicle. A rubber encased torsion bar is set through the tube and the cab is attached to the free ends of the bar, extending from the tube&#39;s opposed open ends. 
     Means must also be provided for preventing cabs from detaching from frames during catastrophic events. Such means have often been provided with by attaching metal straps between the cab and the vehicle&#39;s frame. 
     SUMMARY OF THE INVENTION 
     According to the invention there is provided a vehicle having a suspended cab. The vehicle has a chassis with elongated side frame rails and cross members connected between the side frame rails. One cross member is provided as a support for the back of a vehicle cab. A cab attachment plate is supported above the cross member and provides an attachment point for the floor of the cab. A pair of air springs is disposed between cab attachment plate and the cross member for supporting the cab. A pair of shock absorbers are attached between the cab attachment plate and the cross member for damping vertical movement of the cab. Lateral positioning of the cab and limits to the vertical travel of the cab are provided by a lateral locating wheel mechanism. The lateral locating wheel mechanism includes a roller attachment bracket which may be mounted upwardly from the cross member. A roller contact bracket is mounted downwardly from the cab attachment plate, with the cab attachment plate providing an upper limit to linear travel defined by the roller contact bracket, which defines a vertical guide in which the roller can move up and down. A roller mechanism is mounted to the roller attachment bracket and through the roller contact bracket. In the preferred embodiment the roller mechanism further comprises a single roller having a relatively rigid core and an overmolded rubber shell shaped spherically to provide a non-linear spring rate upon compression. 
     Additional effects, features and advantages will be apparent in the written description that follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a perspective view of a truck incorporating the suspension of the present invention showing placement thereof relative to a truck cab and chassis, which are illustrated in phantom. 
     FIG. 2 is a detailed perspective view of the suspension of the present invention. 
     FIG. 3 is an elevation view of the suspension of the present invention. 
     FIG. 4 is a perspective view of a combination Panhard wheel, rebound and bump stop and collision restraint mechanism, which is an integral part of the suspension. 
     FIG. 5 is a schematic of an alternative embodiment of a roller for use in the mechanism of FIG.  4 . 
     FIG. 6 is a schematic of an alternative embodiment of a contact bracket and roller for use in the mechanism of FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the figures and more particularly to FIG. 1, there is illustrated a vehicle  10  incorporating a cab suspension  16  according to a preferred embodiment of the present invention. Cab suspension  16  is positioned between a cab  12  and a frame  14  of a truck, and is mounted between side frame rails  18 . 
     Suspension system  16  includes a cross member  20 , which is attached at its respective ends to right and left siderails  18 . Suspended above the cross member  20  is a cab attachment plate  22 , which may be connected by appropriate fasteners to a floor  24  of, or framing for, cab  12 . 
     FIGS. 2 and 3 illustrate cab suspension  16  in greater detail. Cross member  20  is positioned latitudinally oriented between frame siderails  18  at a position under the intended installation point for the aft portion of vehicle cab  12 . Cross member  20  includes a pan  34  which provides a base for supporting two air springs  30  which are located aligned with one another perpendicular to the direction of elongation of frame  14 . A Panhard wheel mechanism  32  is located between air springs  30 . Panhard wheel mechanism  32  maintains lateral positioning of the cab  12  on the vehicle frame  14 . Panhard wheel mechanism  32  comprises an upper roller contact bracket  36  and a lower roller attachment bracket  38  which are centered between side rails  18 . 
     A cab attachment plate is positioned atop of air springs  30  and is further attached to the top of the Panhard wheel mechanism  32  by the upper roller contact bracket  36 . Cab attachment plate  22  is an elongated plate which terminates at each of two ends in downwardly oriented brackets  26 , which in turn provide points of attachment for two shock absorbers  28 . Shock absorbers  28  are located at the outside ends of cross member  20  and cab attachment plate  22  outside of air wrings  30  and are pivotally attached at one end each to the brackets  26  located at the opposite ends of the cab attachment plate and at their opposite ends to opposite ends of cross member  20 . Air springs  30  are inflated by a pump (not shown) in response to changes from a desired spacing between the cross member  20  and the cab attachment plate  22 . A valve, positionable to admit or discharge air from air springs  30 , may be controlled by an appropriate lever mechanism positioned in response to the changes in the spacing between-the cross member  20  and the attachment plate  22 . 
     FIG. 4 illustrates Panhard wheel mechanism  32  in greater detail. The Panhard wheel mechanism  32  restrains the cab  12  from excessive lateral movement relative to the frame  14  of vehicle  10 , and while the Panhard wheel allows some up and down movement of the cab, it also provides stops defining the limits of the cab&#39;s up and down travel. It further provides cushioning on impact of the roller  40  at the top and bottom of the travel of the wheel in the roller contact bracket  36 . Lastly, Panhard wheel mechanism  32  provides a restraint against detachment of the cab  12  from the frame  14  of the vehicle  10 . 
     Panhard wheel mechanism  32  includes three major components, an upper roller contact bracket  36 , a lower roller attachment bracket  38 , and a roller  40 . Upper roller contact bracket  36  is a generally U-shaped member having support wings  42  extending outwardly from its sides. The interior surfaces of the upper roller contact bracket  36  serve as a vertically oriented guide in which roller  40  rides and which restrain the roller from lateral movement. Bracket  36  can be attached to either the upper sprung mass, as shown in the preferred embodiment, or to the lower, unsprung mass. The top surface  44  of bracket  36  is flat for attachment by welding or fasteners to the bottom surface of the cab attachment plate  22 . Support wings  42  provide strength and an increased area for surface contact with the cab attachment plate  22  to better brace the bracket on the attachment plate. The interior U-channel provides a linear travel in the vertical direction for roller  40  relative to attachment plate  22 , the upper limit of which is defined by the cab attachment plate  22  and the lower limit of which is the bottom of the “U”. 
     Roller  40  is fitted through upper roller contact bracket  36  and has an axis or rotation in the plane of the vehicle centerline, parallel to the side frame rails  18 . The fit between roller  40  and the walls of the U-shaped channel defined by upper roller contact bracket  36  is not a snug one in the preferred embodiment, there being allowance for some side to side play to allow the roller to turn. Roller  40  is preferably a single wheel of two or three part construction with a rigid interior section  44 , preferably made of a hard plastic, and a softer, elastic exterior shell  46 , which has a generally spherical shape for contact with the contact bracket  36 . Exterior shell  46  is generally made of an elastomeric polymer, such as rubber. The spherical shape of shell  46  gives the shell a non-linear, increasing spring rate with compression. This preserves the isolation between the sprung and unsprung masses. In a three section embodiment, roller  40  has an inner metal sleeve  50  to provide a point of tight grip for a retaining bolt used to assemble the roller. It also provides a better bearing surface for the plastic inside the rubber and reduces rattles from the bolt and roller. 
     The lower roller attachment bracket  38  has a generally C-shaped footprint, with two wedge shaped plate sections at the ends connected by an intermediate section. Roller  40  is mounted for rotation between the two wedged shaped sections. Lower roller attachment bracket  38  retains the roller  40 , and may be attached to either the unsprung mass, as illustrated, or to the sprung mass. 
     FIG. 5 illustrates an alternative to a single roller  40 . Two counter rotating rollers  52  and  54  are set inside the U-shaped channel of a roller contact bracket  36 . Rollers  52  and  54  are snugly positioned in the channel for more accurate lateral location of the cab. However, vibration isolation of this arrangement is inferior to single roller embodiments of the invention. 
     FIG. 6 illustrates yet another embodiment of the Panhard wheel mechanism in which the cushioning materials are from the roller  140  are replaced with a liner applied to an interior channel in the contact bracket  136 . Here the vertical linear travel of the roller  140  is lined with a rubber liner  142 . 
     The invention provides lateral location of the suspended cab. It also provides a non-linear cushioned rebound and bump stop. All of this is achieved while effecting excellent isolation between the relatively unsprung chassis and the sprung cab. The size of the mechanism in minimal and it is mechanically simple, while providing good mechanical resistance against separation. 
     While the invention is shown in only one of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit and scope of the invention.