Abstract:
A leveling jack for a vehicle, such as a recreational vehicle, includes a leveling piston and cylinder, a bi-directional, reversible pump, and a reservoir within a common sealed housing that does not require exterior fluid connections. The piston is extended from the housing to contact the ground and effect leveling by operating the pump in one direction, and is retracted into the cylinder by operating the pump in the other direction. Accordingly, the leveling jack is a self-contained unit, and does not require a central hydraulic unit and the necessary hoses between the jack and the central hydraulic unit as needed in the prior art.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims domestic priority based upon U.S. Provisional patent application Ser. No. 61/205,668, filed Jan. 22, 2009, the disclosure of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a leveling and stabilization system for a motor vehicle, such as a recreational vehicle. 
     2. Description of the Background of the Invention 
     When a recreational vehicle is parked for use, it is desirable that the vehicle be leveled and stabilized for the convenience of the inhabitants. Accordingly, it has become common to provide stabilization and leveling systems for recreational vehicles. Commonly, these systems provide multiple leveling jacks (usually four) located on opposite corners of the vehicle. A centralized hydraulic system mounted within the vehicle is used to effect leveling and stabilization. The centralized hydraulic system includes a pump, reservoir, and appropriate hydraulic lines connecting the pump to the jacks located at each corner of the vehicle. Such systems are shown in U.S. Pat. Nos. 4,061,309; 4,165,861; 4,597,584; 4,743,037 and 4,746,133. In addition to the foregoing, which disclose hydraulic leveling systems, electric leveling jacks have also been used, as shown in U.S. Pat. No. 6,722,635. 
     The hydraulic leveling systems using a centralized hydraulic system are relatively complex in construction and operation, and are costly to install and maintain. Furthermore, hydraulic lines connecting the pump to the jacks are exposed to damage on the exterior of the vehicle. Furthermore, the pump, hydraulic manifold, hydraulic valves (usually four or more), all hydraulic hose assemblies and fittings, pressure switches, wiring harness, etc., are relatively bulky and the space needed inside the vehicle to house the centralized hydraulic system used is not insignificant. In addition, the centralized hydraulic system requires the user to top off hydraulic fluid and to bleed air from the system. 
     SUMMARY OF THE INVENTION 
     The present invention provides a leveling jack for leveling and stabilizing a vehicle of the above-described type in which a leveling cylinder, a pump, and a fluid reservoir are all sealed within a common housing. It is contemplated that four of these jacks will be used as described above; however, since each of the jacks is a sealed unit, no hoses or fittings are necessary to connect the jacks to a centralized hydraulic system, and since both the pump and reservoir are within each sealed unit, the hydraulic manifold, centralized pump, and centralized reservoir are not needed. The piston within the housing of the present invention includes a piston rod which extends from the housing to engage the ground surface (the housing itself is mounted on the surface of the body of the vehicle) the pump is a reversible, bi-directional pump that extends the piston rod from the housing when the pump is operating in one direction and retracts the piston rod into the housing when the pump is operating in the reverse direction. According to a second embodiment of the invention, a second adult single-acting piston includes a rod extending from the housing to engage ground surface and a spring which retracts the rod. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a leveling jack made pursuant to the teachings of the present invention; 
         FIG. 2  is a cross-sectional view taken substantially along lines  2 - 2  of  FIG. 1 , taken through the piston intermediate the top and bottom portions of the apparatus; 
         FIG. 3  is a view taken substantially along line  3 - 3  of  FIG. 2 ; 
         FIG. 4  is a view taken substantially along line  4 - 4  of  FIG. 2 ; 
         FIG. 5  is a view taken substantially along line  5 - 5  of  FIG. 2 ; 
         FIG. 6  is a view similar to  FIG. 1 , but illustrating a different embodiment of the invention; 
         FIG. 7  is a schematic illustration of the hydraulic system used in the embodiment of  FIGS. 1-5 ; and 
         FIG. 8  is a schematic illustration of the hydraulic system used in the embodiment of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     Referring now to  FIGS. 1-5  of the drawings, the leveling jack  10  includes a housing  12  consisting of a leveling cylinder  14 , a pump unit  16 , and an end cap  18  extending between the leveling cylinder  14  and the pump unit  16 . Although the leveling cylinder  14 , pump unit  16 , and end cap  18  are illustrated as separate components, housing  12  may be made as a single cast unit. Leveling cylinder  14  is defined by a circumferentially extending outer wall  20  which slidably receives a piston  22 , to which a piston rod  24  is attached, which extends out of lower end  26  of the leveling cylinder  14 . The end of the piston rod  24  extending out from the housing is attached to a ground engaging plate  28 , which rests on ground when the leveling jack is used. A mounting bracket  30  is attached to the outer surface of the outer wall  20 , and is aperatured to facilitate attachment to an exterior surface of a vehicle, such as a recreational vehicle, which uses the leveling jack  10 . The exterior surface is defined herein as a first surface, and the ground is defined as a second surface. 
     The cap  18  is attached to the top of the leveling cylinder  14  by bolts  32 ,  34 , and  36 . Bolts  32  and  34  are conventional, but bolt  36  is provided with a transverse passage  38  which intersects with longitudinal passage  40 . A passage  42  of about the same diameter as the bolt  36  extends along outer wall  20  and is provided with an opening  43  that extends through the wall  20  to permit fluid communicated through the passage  38  and  40  of the bolt  36  to communicate in the annular retraction chamber  44  defined between the piston rod  24  and the inner circumferential surface of the outer wall  20 . Piston  22  cooperates with the end cap  18  to define an extension chamber  46 . When fluid pressure is communicated into extension chamber  46 , piston  20  and piston rod  24  are urged downwardly viewing the Figures, thereby extending the lower end of piston rod  24  out of the leveling cylinder  14 . Conversely, when pressure is communicated into the annular retraction chamber  44 , the piston  20  is urged upwardly viewing the Figures, thereby withdrawing the piston rod into the cylinder  14 . The pump unit  16  includes a housing or cylinder  48  in which a bi-directional, reversible pump  50  (which will be hereinafter described) and a bi-directional, reversible motor  52  for driving the pump  50  are mounted. The motor  52  is connected to the pump  50  to operate the latter. The pump  50  cooperates with end cap  18  to define a reservoir  54  therebetween. A pair of tubes  56 ,  58  (only the tube  56  being shown in  FIG. 2 ) extend through the reservoir  54  to communicate the pump  50  to passages  60 ,  62  ( FIG. 3 ) extending within the end cap  18 . 
     Relief valves  64 ,  66  prevent over-pressure in the passages  60 ,  62 . Passage  60  is communicated into the extension chamber  46  through opening  68 , and the passage  62  is communicated into the annular retraction chamber  44  through the passages defined within the bolt  36 . Check valves  70 ,  72  are mounted in the passages  60 ,  62  and permit flow into the corresponding pressure chambers  44 ,  46 , but normally prevent flow from the pressure chambers. Shuttle piston  74  is slidable within a bore extending between the passages  60 ,  62  and is provided with offset faces  76 ,  78 , which are exposed to the pressure levels in the passages  60 ,  62  respectively. Accordingly, when passage  60  is pressurized, the shuttle  74  is shifted to hold the check valve  72  open, thereby permitting fluid to vent from the annular retraction chamber  44 , and when the passage  62  is pressurized, the shuttle piston  74  shifts to hold the check valve  70  open, thereby permitting fluid to vent from the extension chamber  46 . 
     Referring now to the pump  50 , a commutator  80  is non-rotatably mounted in a pump block  82  and is circumscribed by a rotor  84  which is mounted in pump block  82  for rotation relative to the commutator  80 . A roller bearing  86  is mounted in the pump block  82  and circumscribes the rotor  84 , but the center of rotation of the rotor  84  is offset from the center of the roller bearing  86 . Accordingly, the clearance between the rotor and the roller bearing at point A ( FIG. 5 ) is greater than the clearance between the rotor and the rotor bearing at point B, and the clearance tapers between points A and B. Notches  88 ,  90  are provided in the commutator  80  and are communicated to the tubes  56 ,  58  respectively. Circumferentially spaced pistons  92  are mounted in corresponding circumferentially spaced bores  94  and slide relative to the rotor. Accordingly, as each piston  92  approaches the point of maximum clearance A, fluid is drawn in through notch  90  and passage  58 , and as the rotor continues rotation, the corresponding piston is urged inwardly, toward the commutator, thereby discharging fluid through the corresponding notch  88  and tube  56  assuming rotation in the clockwise direction. The pistons are maintained in contact with the inner race of the bearing  86  by centrifugal force. Accordingly, when the motor is reversed in the opposite (counterclockwise) direction, fluid is drawn in through notch  88  and its corresponding tube and is discharged through notch  90  and its corresponding tube. A pin  95  drives the rotor by its connection with plate  98  that is turned by the motor  52 . Passages  96  extend through the pump block  82  to communicate make-up fluid to the rotor  84 . 
     Referring to  FIG. 7 , operation of the leveling jack is illustrated diagrammatically. The dashed lines connecting the check valve  70  with tube  58  and check valve  72  and tube  56  represent the operation of the shuttle piston  74 . Check valves  98  are located in passages  96 , but are not shown in other drawings, to permit fluid to be withdrawn from the reservoir  54  by the pump  50  when necessary. A valve  100  connects the tube  56  to reservoir  54  through a relief valve  102 . The valve  100  is a pressure operated valve and is connected to the pressure in tubes  56 ,  58 . When the piston  22  is being retracted into the extension chamber  46 , a greater amount of fluid is discharged from chamber  46  than is admitted into chamber  44 , because of the volume consumed by piston rod  24 . Accordingly, when the pressure in tube  58  indicates the chamber  44  is being pressurized, valve  100  is switched to permit communication into the reservoir, but when the pressure chamber  46  is being pressurized, valve  100  is in the position illustrated, blocking communication to the reservoir  54 . 
     The embodiment in  FIG. 6  is substantially the same as that of  FIGS. 1-5 , except that a single-acting piston is used instead of the double-acting piston illustrated in  FIGS. 1-5 . Accordingly, in the embodiment in  FIG. 6 , the annular chamber  44  is vented to atmosphere, and the piston is returned when pressure in extension chamber  46  is released by a spring  106 . Accordingly, tube  58  is stubbed off, and the pump  50 , when driven in one direction, pressurizes extension chamber  46  to drive the piston rod outwardly and when the pump is driven in the reverse direction, pressure in tube  58  holds check valve  70  open, thereby releasing the pressure in chamber  46 , permitting the spring  106  to withdraw the piston into the housing. 
     This invention is not limited to the details above, but may be modified within the scope of the following claims.