Abstract:
A pneumatically supported bunk assembly is dynamically leveled using compressed air provided by the vehicle. Level sensors determine deviation from the horizontal. Extension sensors associated with the pneumatic cylinders prevent over or under extension of the pneumatic cylinders.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to vehicle bunks and, more particularly, to a dynamically leveled bunk for use on a truck. 
     2. Description of the Problem 
     Extended cab trucks afford room for a bunk behind the operator&#39;s seat allowing the driver a place to sleep when on break. Patents directed to such bunks have focused on providing motion damping for the bunk making the bunk more comfortable for a relief driver while the truck remains in motion. Examples of the such patents include U.S. Pat. No. 4,713,851 to Rosquist; U.S. Pat. No. 4,868,939 to Tagtow; and U.S. Pat. No. 6,493,886 to Vanpage et al. The Vanpage reference provides a mattress suspension including a support device attached between a lower frame attached to the cab floor and an upper frame which carries the mattress. The support device is described as an air sleeve or air cushion capable of providing an upward force to the upper frame. Air is supplied through a fluid connection to the vehicle&#39;s air system. The amount of air in the support device is user controlled. 
     While the art cited above attempts to deal with road shock and noise encountered by a moving vehicle, this art does not address the discomfort and disorientation experienced by operators attempting to sleep on a non-level mattress. The extensive under bed support arrangements taught by the prior art also compromise use of the space under the bunk mattress for internal storage. 
     SUMMARY OF THE INVENTION 
     According to the invention there is provided a bunk assembly having pneumatic supports distributed around the perimeter of a platform which support a mattress. The pneumatic supports provide full two axes leveling of the platform and mattress. Deviation of the mattress from the horizontal is detected by first and second level sensors mounted with respect to the platform in the plane of the platform. Different extensions of the supports are adjusted using vehicle compressed air. Control is automatic and is implemented using microcontroller technology. The leveling algorithms executed by the microcontroller filter and the level sensor input slow changes in orientation. 
     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 an extended cab truck partially cut away to show a bunk fitted aft of the forward seating area; 
     FIG. 2 is a perspective view of the cab interior; 
     FIG. 3 is a perspective view of a bunk assembly in accord with a preferred embodiment of the invention; 
     FIG. 4 is an exploded perspective view of the bunk assembly of FIG. 3; 
     FIG. 5 is an elevation of an air cylinder and mating joint used with the bunk assembly of the invention; 
     FIG. 6 is a block diagram of the invention; and 
     FIG. 7 is a flow chart of a program executed by the microcontroller of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the figures, in FIG. 1 is depicted a truck  10  having a cab  14  mounted on a pair of frame side rails  12  (passenger side only shown). Truck  10  is depicted as a cab over design, although the invention is equally applicable to engine forward designs, recreational vehicles or any other vehicle having bunks. Cab  14  comprises four exterior sidewalls, including a front sidewall  60 , a driver sidewall (not visible), a passenger sidewall  62  and a backwall  17 , which enclose an interior space  16 . Cab  14  provides a usable aft area  40  and a forward operator area  41  where front seats  42  and  44  are located. Operator area  41  includes a driver seat  42  having access to a steering wheel  46  and an instrument and control panel  48 . The driver seat  42  and passenger seat  44  are positioned to have good views through windshield  50  and to be next to doors  52  and  54  for easy egress from the vehicle. A bunk  18  is located in aft area  40  resting on floor or deck  28  and positioned snugly against the interior face of backwall  17  for use by an off duty driver/operator. 
     FIG. 2 is a perspective view of a modular bunk and storage assembly  118  in accord with a preferred embodiment of the invention. Bunk assembly  118  is visible behind driver seat  42 . Bunk assembly  118  rests on a bulkhead support  113  and provides a mattress  101  as a sleeping surface for a vehicle occupant. Bulkhead support  113  in turn is attached to floor or deck  28  and may be further attached to interior trim walls, or through the trim walls to the cab frame or sidewalls. A closet  103  located near one end of bulkhead  113  and encloses controller box  107 . Controller box  117  comprises a microcontroller and air valves used in implementing leveling of mattress  101 . An air hose  109  from a compressed air supply  105  may be introduced through one side of closet  103  to controller box  107 . A bundle air lines  111  emerge from the other side of controller box  107  to locations within bunk assembly  118  and under mattress  101  to connect with mattress leveling air cylinders. Controller box  107  includes valves used to direct air into and exhaust air from the air cylinders. Mattress  101  overlies a platform which doubles as a cover for storage compartments within bulkhead  113  (not shown). Implementing the leveling function requires minimal, if any, modification to many bunk bulkhead supports. 
     Referring now to FIG. 3, the features of bunk assembly  118  are described with greater particularity. Mattress  101  is a conventional coil spring mattress resting on a support assembly  129 . A mattress retaining flange  123  extends upwardly along a front face  131  of support assembly  129 . A shin guard  125  edges the upper lip of mattress retaining flange  123 . Bulkhead  113  may take a number of forms, the only requirement being those that are conventionally met in providing a raised platform for a bed. Bulkhead  113  is a generally rectangular support of sturdy construction. Support assembly  129  rests when lowered on storage compartment bulkheads  119 ,  117  and on side framing  115 . Bulkhead  113  is divided into two storage compartments by a recessed bunk storage area  121  accessible from the front face of bulkhead  113  under support assembly  129 . 
     Referring now to FIG. 4, an exploded perspective view of bunk assembly  118  illustrates the major mechanical features of the dynamic leveling feature of the invention. Mattress  101  rests on support assembly  129  which comprises in turn a rectangular base frame  141  and a rectangular mattress platform  143 . Platform  143  and base frame  141  lie in generally horizontal planes, with platform  143  resting on four air cylinders  133  located near each of its four corners. Air cylinders  133  can be individually extended and retracted by adding or exhausting air therefrom through air lines  111 . Air lines  111  may be positioned on shelf  135  and run to a point on the shelf along the rear face of base frame  141  before leaving the shelf for connection to the controller box  107 . The location of the air lines  111  on shelf  135  allows support assembly  129  to be lifted open on hinge  145  without stretching the lines. By appropriate adjustment of the degree of extension of air cylinders  133 , platform  143  may be kept level even when the vehicle bunk assembly  118  is installed on is not on a level surface, leaving base frame  141  shifted from a strictly horizontal orientation. Air cylinders  133  are mounted on a shelf  135  extending inwardly from a perimeter rail  137  of base frame  141 . Horizontally extending hinge  145  is attached to a rear face of perimeter rail  137  and provides attachment points for connection to an interior wall of a vehicle or to bulkhead  113 . Mattress retaining flange  123  is an upwardly turned extension from a front edge of mattress platform  143 . Shelf  135  provides a platform supporting the four air cylinders  133 . 
     FIG. 5 depicts a representative air cylinder  133  which includes a conventional piston shaft  151  extending from the cylinder body  157 . Shaft  151  moves upwardly and downwardly depending upon the load on the cylinder and the quantity of air introduced to the cylinder. Shaft  151  terminates in a ball  153  which fits a cup  155  to form a ball joint. This ball joint is attached to the underside of a mattress platform  143  allowing the platform to be freely moved up and down independently at each corner. Air cylinders  133  not only allow the height of platform  143  to be independently adjusted at each corner, but also isolate the platform from some road noise and shocks. 
     FIG. 6 depicts the control arrangement for the dynamically leveled bunk. A microcontroller  160  which opens one of a set of four air valves  162  to allow air into any one of air cylinders  133  through one of air lines  111  or to exhaust air from any one of cylinders  133 . Valves  162  may of course simply be held closed to keep the quantity of air in any of the cylinders constant. Associated with each air cylinder is a cylinder extension sensor  166 , which may be implemented using a rheostat or similar device. Each of four cylinder extension sensors  166  is connected to return its signal to controller  160 . The four air cylinders  133  are attached to and modify the orientation of mattress platform  143  relative to the horizontal. The orientation of platform  143  relative to the horizontal is also changed by changes in vehicle orientation. The orientation of platform  143  with respect to the level is sensed by two level sensors  168  which are mounted on the base perpendicularly with respect to one another. Controller  160  levels platform  143  by adjusting the air in air cylinders  133 , with the limitation that the total extension of the air cylinders measured by the four extension sensors  166  remains constant. Movement of support assembly  129  toggles a lift switch  144 , which disables changes in the level orientation of mattress platform  143  by controller  160 . 
     Referring now to FIG. 7, a flow chart of an exemplary program which can be implemented by controller  160  of FIG. 6 to maintain a mattress platform  143  which is supported at each of its four corners by an air cylinder  133  in a horizontal orientation. At step  200  the program initially collects data from level sensors  168  and uses the new sample data to update a running average of samples. The average may reflect a time decay of older samples or a simple weighted sum of the latest sample with the combined result from the prior sample period. Such averaging or combination is done to reduce the responsiveness of the horizontal leveling system to highly transient changes in orientation. This avoids abrupt shifts in bunk position. The result indicates which, if any corner of the bunk is the lowest and which is the highest relative to horizontal. Next, at step  202  the degree of extension of the extension sensors is determined for each of four sensors. It may be noted that the lowest corner of the platform  143  may be associated with the air cylinder  133  which is most extended. The results are averaged for each cylinder. Again by “averaged” it is meant the latest result is arithmetically combined with prior period results in a way which reduces the responsiveness of the system to a comfortable level for an occupant of the bunk. After averaging of the extension measurements is completed the averages are summed at step  204 . At step  206  it is determined from the samples relating to orientation with respect to level of the bunk determined at step  200  indicate if the bunk is level. If YES, step  208  is executed to determine if the sum of air cylinder extensions determined at step  204  is nominal. If YES, processing returns to step  200  to collect a new set of samples. If NO, step  210  provides that a quanta of air is added to or subtracted from all of cylinders  133  to move the bunk up or down and bring the extension of the cylinders into line with the desired amount. 
     If at step  206 , it were determined that platform  143  was not level, than the updated information from the level sensors determined at step  200  is analyzed to find the high and low corners of the platform relative to the true horizontal. Next, at step  214  it is determined if the total extension of the air cylinders determined at step  204  is nominal. If the total extension is nominal, the YES branch from decision step  214  is taken resulting in air being exhausted from the air cylinder associated with the highest corner (step  216 ) and air being added to the lowest corner cylinder  218 . Program execution then returns to step  200  to collect additional samples. If at step  214  it was determined that the total extension of the air cylinders was not nominal, step  220  following along the NO branch is used to determine if the total extension was too small. If YES, step  222  is executed to add a quantity of air to the air cylinder associated with the lowest corner. If NO, step  224  is executed to exhaust air from the air cylinder associated with the highest corner of platform  143 . After either of steps  222 ,  224  program execution returns to step  200 . 
     The invention provides a simple bunk leveling system easily installable with new or existing extended cab bunk assemblies. The invention preserves space under the bunk assembly in a supporting bulkhead for use as a storage area. It will be appreciated by those skilled in the art that alternative arrangements of the air cylinder are possible, including, by way of example, three cylinders arranged as a tripod support, or from cylinders disposed to support the mattress platform along its edges. 
     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.