Abstract:
A hydraulic synchronization system for a slide-out portion of a recreational vehicle has two cylinders spaced apart and reversed in orientation with respect to one another at opposite sides of the slide-out portion. The bore sides of the cylinders are connected and the rod sides of the cylinders are connected such that fluid is pumped from the rod side of one cylinder to the rod side of the other cylinder and from the bore side of one cylinder to the bore side of the other cylinder upon extension and retraction of the slide-out portion to keep the slide-out portion synchronized.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims benefit to U.S. Provisional Patent Application No. 60/658,679 filed Mar. 4, 2005. 
     
    
     STATEMENT CONCERNING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not applicable.  
       FIELD OF THE INVENTION  
       [0003]     This invention relates to the field of expandable vehicles, and particularly to synchronization of the movement of a slide-out room of a recreational vehicle.  
         [0004]     Slide-out operating mechanisms for moving rooms in and out in recreational vehicles are well known. Such a mechanism may have two telescopic rails spaced apart that are powered in and out to move the room in and out, out to expand the living space of the recreational vehicle, and in to contract it for over-the-road travel. Other mechanism also exist that have cables, or the room is directly driven in and out. In any case, the movement of the two sides of the room must be synchronized to one another, or else the room will become canted, possibly resulting in damage to the vehicle. In a rack and pinion system, synchronization is accomplished by pinions at opposite ends of a shaft meshing with racks on two rails or on the room. In such mechanisms, any of a number of means may be used to power the rails in and out, including an electric motor that drives the pinions, a hydraulic cylinder, a lead screw, cables or linkage mechanisms.  
         [0005]     The present invention provides an alternative for synchronizing the movement of a slide-out room.  
       SUMMARY OF THE INVENTION  
       [0006]     Synchronization of the movement of a slide-out room is accomplished using two hydraulic actuators, one on each side of the room. One of the actuators is arranged so as to extend when the room is extended and the other is arranged so as to retract when the room is extended. The bore sides of the cylinders of the two actuators are connected with a hydraulic line and the rod sides of the two cylinders of the actuators are also connected with a hydraulic line. As such, the bore sides exchange fluid with one another and the rod sides exchange fluid with one another, but the bore sides do not exchange fluid with the rod sides. Thus, extension of one cylinder causes an equal and opposite retraction of the other cylinder, and vice versa. Thus, both sides of the slide-out move in and out in synchronization with one another. This system could be applied to the top and bottom of the room as well, to synchronize the top and bottom movement rather than or in addition to the side to side movement.  
         [0007]     Such a system is completely passive, in that it needs no power to keep the sides in synchronization with one another. In addition, any means may be used to power the slide-out in and out, including manual power with it just being pushed in and out by a human or cranked in and out if the manual input is a crank or other means. Alternatively, an electric drive could be used using a rack and pinion arrangement or a lead screw, or a hydraulic cylinder could be used, for example a single cylinder mounted between the two synchronization cylinders or elsewhere, or a cable system could be used, a chain system, a different type of mechanical link system or any system for powering the room in and out. Since the hydraulic cylinders are separate from the drive systems and passive, they will always work to keep the two sides of the slide-out in synchronization with one another no matter what type of drive is used or where it is applied to the room.  
         [0008]     The foregoing and other objects and advantages of the invention will appear in the detailed description which follows. In the description, reference is made to the accompanying drawings which illustrate a preferred embodiment of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a perspective view of a slide-out room of a trailer in a retracted position;  
         [0010]      FIG. 2  is a view like  FIG. 1  of the slide-out in an extended position;  
         [0011]      FIG. 3  is a perspective view of a prior art slide-out operating mechanism for the slide-out of  FIGS. 1 and 2 ;  
         [0012]      FIG. 4  is a hydraulically powered variation of the slide-out mechanism of  FIG. 3 , that is also prior art;  
         [0013]      FIG. 5  is a hydraulic slide-out synchronization system of the present invention;  
         [0014]      FIG. 6  is a schematic view of the hydraulic synchronization system of  FIG. 5 ; and  
         [0015]      FIG. 7  is a view like  FIG. 6  of a variation. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]      FIGS. 1-4  are described in U.S. Pat. No. 5,758,918 and the description therein respecting those figures is hereby incorporated herein by reference.  FIGS. 1-3  of the current application correspond to  FIGS. 1-3  of U.S. Pat. No. 5,758,918, and  FIG. 4  of the current application corresponds to  FIG. 14  of U.S. Pat. No. 5,758,918.  
         [0017]     Briefly, a vehicle body  10  has mounted thereon an expandable, telescopic slide-out section  12 , shown retracted in  FIG. 1  and extended in  FIG. 2 . Slide-out section  12  is rectangularly configured and includes a pair of side walls  14 , a front wall  16  with two windows  18 , a bottom wall  20  and a roof  22 . An arrangement for supporting and controlling the slide-out section  12  is adapted to be mounted beneath the vehicle body  10  by the mechanism illustrated in  FIG. 3  or in  FIG. 4 .  
         [0018]     The mechanism  24  in  FIG. 3  for extending and retracting the slide-out section  12  includes a pair of substantially parallel, hollow outer rail members  26  fixed to the frame of the RV. A rail member  42  is slideably telescoped in each of the rail members  26 . The outer ends of the rail members  42  are attached to the slide-out section by brackets  56  at the outer ends  54  of the rails  42 . In the embodiment shown in  FIGS. 3 and 4 , each of the inner rails  42  has welded or otherwise secured on its bottom wall a gear rack and a pinion gear beneath each respective rail  42  is in driving engagement with the gear rack. The two pinion gears are connected by the shaft  84 . In the embodiment of  FIG. 3 , the motor  119  drives the two pinion gears to move the rails  42  in and out. Manual drive handles  140  may also be provided. The two pinion gears rotate together because they are connected by the shaft  84 , and therefore the two rails  42  are synchronized in their extension and retraction motions.  
         [0019]     In the embodiment of  FIG. 4 , a hydraulic cylinder  148  and pump  146  are used to extend and retract a slide-out room, but the racks connected to the rails and the pinions connected to one another by the shaft  84  synchronize the movement of the rails  42 .  
         [0020]     The present invention provides a hydraulic solution to the synchronization of the rails  42  and eliminates the synchronizing mechanisms such as the racks, the pinions and the connecting shafts.  
         [0021]     Referring to  FIGS. 5 and 6 , a system  200  of the invention includes a pair of hydraulic actuators  202 ,  204  having cylinders  202 ,  204 , a first hydraulic line  206  connecting the bore sides of the two cylinders  202  and  204  and a second hydraulic line  208  connecting the rod sides of the cylinders  202  and  204 . As illustrated in  FIG. 5 , the cylinders  202  and  204  may be incorporated inside of the hollow tubes that make up the rails  42  and  26 . However, that need not be the case.  
         [0022]     Each actuator  202 ,  204  includes a cylinder  210 ,  212  respectively and a rod, or piston rod  214 ,  216 , respectively. The bore end (or other part) of the cylinder  210  is fixed to the frame  220  of the RV, analogous to item  34  or  36  in  FIG. 3 , or any other fixed member of the RV. It may be fixed to the rail  26 , which is fixed to the frame of the RV. Likewise, the bore end (or other part) of cylinder  204  is fixed to the stationary frame  220  of the RV, and may be fixed to the rail  26 . The rods  214  and  216 , on the other hand, are secured to the slide-out, so that they move with the rails  42 .  
         [0023]     As is clear from  FIGS. 5 and 6 , the mounting of the cylinders  202  and  204  is reversed, such that extension of the room causes extension of one of the cylinders and retraction of the other, and retraction of the room causes retraction of the one cylinder and extension of the other. Thus, fluid is pumped back and forth between the rod side chambers of the cylinders  210  and  212  and the bore side chambers of the cylinders  210  and  212  as the room extends and retracts, which keeps the two sides of the room synchronized. This is so because the cylinders  210  and  212  are the same size, and the bore sides of both cylinders are in closed fluid communication with one another, and the rod sides of both cylinders are in closed fluid communication with one another.  
         [0024]     Thereby, a system of the invention is completely passive, not requiring any power input to keep the two sides of the rooms synchronized as the room is moved in and out. However, power input is required to move the room, and that may be accomplished by a gear drive, a hydraulic cylinder as in  FIG. 5 , a screw driven mechanism, cables, a manually driven mechanism or any other type of mechanism for moving the room in and out.  
         [0025]      FIG. 7  discloses the embodiment of  FIG. 6 , with a modification to keep both hydraulic circuits full of hydraulic fluid at all times. In this modification, an accumulator  250  having a pressurized fluid chamber is in communication with each of the circuits  206  or  208  through a one way check valve, which only permits fluid to flow from the accumulator to the respective circuit  206  or  208 . Thereby, if fluid leaks out of either of the circuits, it will be replenished by the accumulators  250 , and reverse flow from the circuits  206  or  208  to the accumulators  250  is prevented by the check valve.  
         [0026]     A preferred embodiment of the invention has been described in considerable detail. Many modifications and variations to the preferred embodiment described will be apparent to those skilled in the art. For example, in  FIG. 6 , the end of the rod  216  of actuator  204  could be stationary (fixed to RV frame or stationary rail  26 ) and the bore end of cylinder  212  could be attached to the movable rail  42 , which would result in the cylinder  212  and hydraulic lines  206 ,  208  moving with the movable rail. This may be somewhat undesirable, but possibly tolerable in some applications. Therefore, the invention should not be limited to the embodiment as described, but should be defined by the claims which follow.