Abstract:
A push-pull drive chain mechanism and scissors linkage assembly powered by a hydraulic cylinder to affect the coordinated, linear movement of an expandable room in a recreational vehicle. The drive chain moves generally vertically along a first structural member, such as a vehicle frame member, as the hydraulic cylinder extends or retracts to move the expandable room relative to the vehicle frame. The drive chain is pivotally connected at the proper place on the scissors-type linkage assembly, the links that form the scissors extending and crossing for pivotal attachment to a structural member of the vehicle body and a structural member of the expandable room. The drive chain is constructed and guided to provide the required force for opening and closing the scissors assembly.

Description:
BACKGROUND OF INVENTION 
     The invention relates to a linkage arrangement for moving members together or apart in a substantially linear motion without a substantial shift in a direction perpendicular to the desired linear motion. Typical linkages that are commonly used for a variety of purposes involve a pair of parallel members attached pivotally to a pair of parallel linkage members to form a parallelogram. If one of the parallel members is fixed, then motion of the parallelogram linkage results in an angular motion—in or out and up or down rather than simply in or out. The present invention relates to a linkage arrangement of the “X” or scissors type for moving members relative to one another in a substantially linear motion. 
     The invention disclosed herein is particularly useful as a control mechanism for expandable rooms in habitable structures, especially room structures that are telescopically slideable between retracted and extended positions for motorized or towed vehicles. A variety of recreational vehicles are known and used that have a room or a room portion that may be moved from a retracted position while the vehicle is moving over the road to an extended position when the vehicle is stationary in order to provide additional internal space. This type of an arrangement provides adequate space to accommodate users when a recreational vehicle is parked for habitation while still keeping the vehicle within governmental regulations that impose width limitations for vehicles on roads and highways. When these vehicles are stationary, they are frequently used for habitation for extended periods of time, and when so used, it is highly desirable to be able to maximize the available living space. This is done in a variety of ways in which the user can move a “nested” portion of the expandable room out to its extended or expanded position, typically under hydraulic or electrical power. 
     These expandable room portions usually comprise a structure that includes a floor, a roof, an external end wall (typically generally parallel to the vehicle side wall), an open (or openable), interior end wall, and one or more side walls (typically generally perpendicular to the vehicle side wall). These components are typically made of frame members and wall panels. In the retracted position, the roof, floor and side walls are typically concealed from exterior view and the room exterior end wall forms a portion of the vehicle side wall. A large factor in the purchase of a vehicle of this type is the amount of useable space that is available inside the vehicle. Thus, it is desirable that the mechanism for extending and retracting the room take up a minimum of space. 
     The prior art for expanding and retracting expandable rooms generally employs hydraulic arms that are housed inside the vehicle or under the floor of the vehicle. The hydraulic arms contained within the vehicle require a housing unit when they are in their retracted position. This housing unit remains intact when the room is extended taking up space within the vehicle. The hydraulic arms that are housed under the floor are generally complex, relatively expensive, and may be unduly heavy. Further, when the room is in the retracted position, otherwise available storage space under the floor is lost. The additional weight also adversely affects the fuel economy of the vehicle. With the highly competitive market in these recreational vehicles, not only weight and space but also cost and reliability of operation are important factors. 
     Examples of improved types of linkage utilized in these expandable rooms are disclosed in co-pending patent applications Ser. No. 09/628874 filed Oct. 26, 2001 and entitled “Straight Motion Parallelogram Linkage”, and Ser. No. 10/065509 filed Oct. 25, 2002 and entitled “Linkage for Expandable Rooms”. It is the object of this invention to provide another type of mechanism for expanding rooms for vehicles which mechanism is reliable in use, lightweight, has fewer components and which will allow for maximum space inside the vehicle. It is a further object to provide a scissor type linkage that provides for motion of structural members together or away from one another in a substantially linear path without substantial movement of the members in a direction perpendicular to said path. It is a further object to provide a mechanism for the expansion and retraction of expandable rooms or structures when the rooms or structures are not designed for convenient housing of the mechanism in the floor. Finally, it is an object of the present invention to provide a mechanism wherein a force assist means such as, for example, a hydraulic cylinder, electric drive, or pneumatic control system can be used to drive the movement of a push-pull chain that in turn moves an expandable room, and if needed, such a chain can be provided on both sides of the room and synchronized. 
     SUMMARY OF INVENTION 
     The present invention includes a push-pull drive chain mechanism that can be powered by a hydraulic cylinder, electric drive or pneumatic or other similar control system, to affect the coordinated linear movement of an expandable room in a recreational vehicle. The drive chain moves generally vertically along a first structural member, such as a vehicle frame member, as the hydraulic cylinder extends or retracts to move the expandable room relative to the vehicle frame. The drive chain is pivotally connected at the proper place on the structural members, and in a preferred embodiment the chain is connected to one link of a scissors-type linkage assembly, the links that form the scissors extending and crossing between points of pivotal attachment with a structural member of the vehicle body and a second structural member of the expandable room. The drive chain is constructed and guided to provide the required force for opening and closing the scissors assembly. 
     There may be a scissors linkage assembly and drive chain mechanism on each side of the expandable room, each linkage assembly having a first link attached at one end to a vehicle frame member and at its other end to a structural member of the expandable room. The other link of the scissors linkage assembly is pivotally attached at one end to the vehicle frame member and at the other end to a structural member of the expandable room, the links crossing and being pivotally connected midway between their ends. The drive chain mechanism for each of the linkage assemblies is then attached to one of the links to expand or collapse the assembly and cause the expandable room to extend or retract. Use of two linkage assemblies, one on each side of the expandable room, improves the mechanical advantage in moving the expandable room inwardly and outwardly. Preferably, a torsion bar interconnects the linkage assemblies to equalize the pressures on the assemblies and thereby assure smooth, synchronized operation. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is an interior side view of the scissors linkage assembly for an expandable room and showing the linkage when the room is retracted; 
     FIG. 2 is an interior side view similar to FIG. 1 but showing the expandable room extended and the linkage assembly retracted; 
     FIG. 3 is an end view showing the linkage assembly on one side of the expandable room; 
     FIG. 4 is a sectional view of a portion of the assembly taken on the line  4 — 4  of FIG.  2  and showing a vehicle frame and expandable room member when the linkage assembly is retracted; 
     FIG. 5 is a sectional view of a portion of one of the links taken on the line  5 — 5  of FIG.  1  and showing the connection to the pivot plate that is attached to the expandable room; 
     FIG. 6 is a sectional view of a portion of the other link taken on the line  6 — 6  of FIG.  1  and showing the connection to the vehicle frame; 
     FIG. 7 is a sectional view of a portion of one of the links taken on the line  7 — 7  of FIG.  1  and showing the pivotal connection to the expandable room structure; 
     FIG. 8 is an end elevational view looking in the direction of the arrow A of FIG.  1  and showing the drive chain; 
     FIG. 9 is an enlarged view of a portion of the drive chain; 
     FIG. 10 is an enlarged view showing the connection of the drive chain to the operating rod of the hydraulic cylinder, with the frame member broken away for clarity; and 
     FIG. 11 is an enlarged view of the drive chain connection to the link of the scissors linkage assembly. 
    
    
     DETAILED DESCRIPTION 
     Referring first to FIGS. 1,  2  and  3 , there is illustrated a portion of the framework for an expandable room for a recreational vehicle which, as is well know to those skilled in the art, has an opening formed in its side wall to accommodate an expandable room having an upper frame member  10  and a lower frame member  12  that form a part of the interior end wall of the expandable room. An example of an expandable room for a recreational vehicle is shown in U.S. Pat. No. 6,067,756. Such expandable rooms of various sizes are well know to those skilled in the art and therefore additional details of the vehicle and room will not be described. FIG. 2 shows the expandable room structure in its extended position so that there will be additional living or storage space inside the recreational vehicle when the vehicle is stationary, such as at a campsite. As is well known to those skilled in the art, when the vehicle is traveling over the road, the expandable room is retracted so that the outer end wall of the expandable room formed is generally flush with an exterior wall (not shown) of the recreational vehicle. FIG. 2 shows the expandable room structure in the extended position with the frame members  10  and  12  that form the interior end wall of the expandable room positioned adjacent the vehicle frame members. As is also well known to those skilled in the art, the expandable room typically extends outwardly from a side wall of the recreational vehicle. 
     FIGS. 1 and 2 show a scissors-type linkage mechanism for extending and retracting the expandable room. Although use of the scissors linkage is the preferred way of utilizing the principles of the invention, it should be understood that the drive chain mechanism described hereinafter could be suitably attached directly to a rigid frame member of the expandable room. In either event, there may be a drive chain mechanism on each side of the room, and in some applications, it may be necessary to use only a single mechanism on one side. Therefore, only one of the drive chain mechanisms will be described in detail and will be described as used in connection with a scissors-type linkage assembly as used in connection with an expandable room for a recreational vehicle. It will be also understood, however, that these mechanisms and linkage assemblies can be used in other applications where it is desired repeatedly to move and retract a large object along a limited linear distance. 
     FIG. 1 shows the linkage assembly, indicated generally by the reference numeral  14 , in the extended position with the room structure retracted while FIG. 2 shows the linkage assembly  14  in the retracted position with the expandable room structure extended. The linkage assembly  14  is comprised of a first link  16  secured by suitable fasteners such as bolts  17  to a pivot plate  19  (FIG. 5) that in turn is pivotally attached at its lower end by pin  20  to rollers  22  that roll inside a vertically extending frame member  18 . Frame member  18  is affixed to the lower frame member  12  which forms a part of the structure for the interior end wall of the expandable room. As best seen in FIG. 7, frame member  18  is a channel-type member open along one side to receive the pin  20  and rollers  22 . Pin  20  pivotally connects the pivot plate  19  and thus the link  16  to the frame member  18  through rollers  22 . The upper end of the first link  16  is pivotally attached to the upper end of the vertical structural member  24  of the vehicle body. As best seen in FIG. 4, the link  16  is pivotally attached by a pivot pin  26  turnable in bushings  28  in the structural member  24 . The linkage assembly  14  also includes a second link  30  pivotally attached at its lower end to rollers  34  rollable inside the lower end of the vertical structural member  24  of the vehicle body. As best seen in FIG. 6, link  30  is turnable on pivot pins  32  each of which support a roller  34 . Two pivot pins  32  are used so that the central portion of the structural member  24  is open to received a hydraulic cylinder  36  (not shown in FIG.  6 ). The second link  30  has its upper end pivotally connected to the upper frame member  10  of the expandable room. As best seen in FIG. 4, link  30  is turnable on a pivot pin  38  mounted to the upper frame member  10  in bushings  40 . The second link  30  intersects and is pivotally connected to the first link  16  at their respective centers by a pivot pin  42  to form the scissors linkage assembly  14 . 
     The linkage assembly  14  is expanded and collapsed by a chain drive mechanism shown in FIGS. 1-3 and in detail in FIGS. 8-11. A drive chain, indicated generally by the reference numeral  44 , has one end attached to link  16  at a point above the pivotal connection of link  16  with link  30 . FIG. 11 is an enlarged view of the connection when viewed from the side and shows the end link  46  secured by bolt  48  to the link  16 . A bracket  50  reinforces the connection. The end link  52  at the other end of drive chain  44  is affixed to the end of the operating rod  54  of the hydraulic cylinder  36  as shown in FIG.  10 . Hydraulic cylinder  36  is mounted vertically inside the vertical structural member of the vehicle body and is suitably connected to the hydraulic system of the vehicle by hydraulic line  56 . The end link  52  is also secured to the operating rod  54  of the hydraulic cylinder  36  so that the link  52  remains rigid when the hydraulic cylinder  36  extends and retracts. As shown in FIG. 10, a guide plate  59  is mounted inside the structural member  24  for easy movement and for guiding the links  58  of the drive chain  44 . The drive chain  44  is comprised of consecutive links  58  pivotally connected to each other by pins  60  and extending between the end links  46  and  52 . Each chain link  58  has a pair of rollers  62  held by the pins  60  and extending from the drive chain  44 . Rollers  62  facilitate movement of the chain  44  as it bends outwardly from the structural member  24  toward the first link  16  of the linkage assembly  14 . As suitable guide member (not shown) can be secured to the structural member  24  at the place where the chain  44  exits. As best seen in FIG. 9, the links  58  of the drive chain  44  each have a forward flat edge  64  that engages with a corresponding rear edge  66  of the adjacent link  58 . The edges  64  and  66  allow the drive chain  44  to flex in one direction only so that the links  58  provide a rigid configuration with any two consecution links thereby allowing the chain to be pushed from one end link  52  with the pushing force carried by the chain links  58  to the other end link  46 . The chain can thus be pushed or pulled, and by its connection with the linkage assembly  14  as described, will cause the assembly to expand or collapse. Because the linkage assembly is pivotally connected between the structural members of the expandable room and the vehicle body, pushing of the drive chain  44  by the hydraulic cylinder  36  will expand the linkage assembly  14  and cause the expandable room to retract into the vehicle body as shown in FIG.  1 . Similarly, when the drive chain  44  is pulled by the hydraulic cylinder  36 , the linkage assembly  14  will collapse and extend the expandable room away from the vehicle body as shown in FIG.  2 . 
     In a preferred arrangement, there are a pair of linkage assemblies  14  on each side of the expandable room. In order to synchronize movement of the assemblies  14  on opposite sides of the room and therefore maintain proper alignment of the expandable room relative to the exterior wall of the vehicle, there may be provided a torsion bar suitably connected to the structural members of the vehicle body and the expandable room. With such an arrangement, if one side of the expandable room advances ahead of the other side, the torsion bar will twist and slow down the faster side to allow the slower side to “catch up” and thus equalize the pressure. Although the use of a torsion bar is a simple way of equalizing the pressure, a synchronizing cylinder in the hydraulic system can be used for the same purpose or a synchronizing system using electronics can also be employed, all as is well known to those skilled in the art. 
     Although the preferred embodiment as described herein includes reference to a force assist element in the form of hydraulic cylinders, the present invention can also employ a pneumatic cylinder and system or an electrically powered motor to drive the drive chain. Also, it is possible not to employ any force assist element, in which case the room would be manually pushed or pulled using the principles of the invention. Of course, the linkage assembly  14  could be reversed with mounting of the hydraulic cylinder  36  in the structural members of the expandable room. Also, the hydraulic cylinder  36  may be inverted from the position shown in the drawings with the drive chain  44  secured to the first link  16  near its lower end. Mounting the mechanism to a vehicle frame member in the manner illustrated is preferred since this arrangement requires less space. 
     Having described the invention in reference to the preferred embodiments thereof, it will be understood by those skilled in the relevant art that various modifications and revisions may be made and that such modifications and revisions are intended to be within the scope of the invention as claimed below.