Abstract:
A linkage assembly for expandable rooms for recreational vehicles to affect the coordinated movement of parallelogram linkage members through the actuation of a glide arm that will extend or retract the expandable room. The glide arm is powered by a hydraulic cylinder and moves generally vertically along a vehicle frame member as the hydraulic cylinder rod extends or retracts to move the expandable room relative to the vehicle frame. The glide arm is pivotally connected to one link in each of two pairs of parallelogram linkage members, the linkage members extending between points of pivotal attachment with a second structural member, such as an expandable room member, and the vehicle frame member.

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 generally straight motion parallelogram linkage. 
     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. 
     An example of an improved type of linkage utilized in these expandable rooms is disclosed in co-pending patent application Ser. No. 09/682,874 filed Oct. 26, 2001 and entitled “Straight Motion Parallelogram Linkage”, now U.S. Pat. No. 6,568,734. It is the object of this invention to provide an improved linkage mechanism for expandable rooms for vehicles which mechanism is relatively inexpensive to manufacture, reliable in use, lightweight, and which will allow for maximum space inside the vehicle. It is a further object to provide a braced parallelogram linkage that permits motion of linkage 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 disposed for convenient housing of the mechanism in the floor. Finally, it is an object of the present invention to provide such a parallelogram linkage mechanism wherein a force assist means such as, for example, a hydraulic cylinder, electric drive, or pneumatic control system may drive the movement of the braced parallelogram linkage, and where the linkage mechanisms are provided on both sides of the room, they are synchronized. 
     SUMMARY OF INVENTION 
     The present invention includes a linkage assembly that can be manually operated or powered by a hydraulic cylinder, electric drive or pneumatic or other similar control system, to affect the coordinated movement of parallelogram linkage members through the actuation of a glide arm or rolling support arm. The glide arm 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 glide arm is pivotally connected to one link in each of two pairs of parallelogram linkage members, the linkage members extending between points of pivotal attachment with a second structural member, such as an expandable room member, and the vehicle frame member. The glide arm is constructed to accommodate movement of the glide arm past the ends of the linkage members that are operatively attached to the vehicle frame member. 
     Thus, each pair of linkage assemblies comprises a main link attached at one end to rollers that move within a vehicle frame member and at the other end to the expandable room member. A first linkage member is pivotally attached at one end to the vehicle frame member and at the other end to the main link midway between its ends. A second linkage member in turn is pivotally attached to the first linkage member and at its other end is pivotally attached to and moveable with the glide arm. This double linkage arrangement improves the mechanical advantage in moving the expandable room inwardly and outwardly. Movement of the glide arm causes the main link and the first linkage member to move and pivot thus extending or retracting the room. During extension and retraction of the room, the linkage assemblies create an improved mechanical advantage in extending and retracting the room. Preferably, a pair of upper and lower linkage assemblies is employed on each side of the expandable room, and 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 an expandable room and showing the linkage mechanisms when the room is retracted and the linkage mechanisms are extended; 
     FIG. 2 is an interior side view similar to FIG. 1 but showing the expandable room extended and the linkage mechanisms retracted; 
     FIG. 3 is an end view showing the linkage mechanism on both sides of the expandable room; 
     FIG. 4 is a side elevation view of a portion of the mechanism and showing a vehicle frame and glide arm when the linkage mechanism is extended and the room retracted; 
     FIG. 5 is a side elevation view similar to FIG.  4  and showing only the glide arm mechanism; 
     FIG. 6 is a front elevation view of that portion of the mechanism shown in FIG.  4  and thus showing a vehicle frame and glide arm when the linkage mechanism is retracted and the room extended; 
     FIG. 7 is a front elevation view similar to FIG.  6  and showing only the glide arm mechanism; 
     FIG. 8 is a top view looking in the direction of the arrows  8 — 8  of FIG.  3  and showing the pivotal connection of the vehicle frame member and the second linkage member and showing the torsion bar connection; 
     FIG. 9 is a cross-sectional view taken on the line  9 — 9  of FIG.  3  and showing the pivotal connection of the first linkage member to the vehicle frame member; 
     FIG. 10 is a cross-sectional view taken on the line  10 — 10  of FIG.  1  and showing the pivotal connection of main link and the first linkage member; 
     FIG. 11 is a cross-sectional view taken on the line  11 — 11  of FIG.  1  and showing the pivotal connection of the first and second linkage members; 
     FIG. 12 is an enlarged view of detail A—A of FIG.  3  and showing the pivotal connection of the first linkage member and the vehicle frame; 
     FIG. 13 is a cross-sectional view taken on the line  13 — 13  of FIG.  3  and showing the pivotal connection of the second linkage member and the glide arm; and 
     FIG. 14 is a cross-sectional view taken on the line  14 — 14  of FIG.  3  and showing the pivotal and rolling connection of the main link and the channel. 
    
    
     DETAILED DESCRIPTION 
     Referring first to FIGS. 1,  2  and  3 , there is illustrated an expandable room for a recreational vehicle, for example, which has an opening formed in its side wall to accommodate an expandable room indicated generally by the reference numeral  20 . 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  20  in its extended position to provide 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  20  is retracted as shown in FIG. 1 so that the end wall  22  of the expandable room  20  is generally flush with an exterior wall  24  of the recreational vehicle. As is also well known to those skilled in the art, the expandable room  20  typically extends from the side of the recreational vehicle. 
     FIGS. 1 and 2 show the linkage assemblies, each indicated by the reference. numeral  25 , for extending and retracting the expandable room  20 . As shown in FIG. 3, there is a pair of assemblies  25  on each side of the room  20 , an upper assembly and a lower assembly, but it should be understood that in some applications, it may be necessary to use only a single assembly  25  on each side. Since the assemblies  25  are substantially identical and function is the same manner, only one of the assemblies  25  will be described in detail and will be described as used in connection with an expandable room for a recreational vehicle. It will be understood, however, that these assemblies can be used in other application where it is desired repeatedly to move and retract a large object along a limited linear distance. 
     FIG. 1 shows the linkage assembly  25  in the extended position with the room  20  retracted while FIG. 2 shows the linkage assembly  25  in the retracted position with the room  20  extended. The linkage assembly  25  includes a glide arm  26  that is housed within and slidable along a frame member  28  which forms a part of the exterior wall  24  of the recreational vehicle. As best seen in FIGS. 8 and 9, frame member  28  is a standard structural channel member and therefore is open along one side. The linkage assembly  25  also includes a main link  30  and first and second linkage members  32  and  34 . The main link  30  has one end pivotally connected to a mounting bracket  36  that is secured to the frame structure of the expandable room  20  at a point inwardly from the end wall  22 . The other end of the main link  30  is pivotally connected to rollers  38  that roll inside the channel frame member  28  of the vehicle as the link  30  pivots. This connection is shown in detail in FIG.  14 . As shown in FIG. 10, the first linkage member  32  has one end pivotally connected to the main link  30  at the center of the link  30 , while the other end of the first linkage member  32  is pivotally connected to the channel frame member  28  of the vehicle (FIG.  9 ). The second linkage member  34  has one end connected to the first linkage member  32  (see FIG. 11) while the other end of the second linkage member  34  is pivotally connected to the glide arm  26  which rides on rollers  40  within the channel frame member  28  as illustrated in FIG.  13 . Thus, as glide arm  26  moves up and down, the second linkage member  34  will move with the glide arm  26 , riding on the rollers  40  which roll inside the channel frame member  28  of the vehicle. As the second linkage member  34  is moved upwardly and downwardly with the glide arm  26 , it will cause the first linkage member  32  to pivot which in turn will force the main link  30  to pivot and move the expanded room outwardly to an extended position or inwardly to a retracted position, as the case may be. As the linkage assembly  25  thus moves from its extended position of FIG. 1 to its retracted position of FIG. 2 the expandable room  20  is pushed from its retracted position within the recreational vehicle to its extended position outwardly from the exterior wall  24  of the vehicle. Similarly, when the linkage assembly  25  moves from its retracted position of FIG. 2 to its extended position of FIG. 1, the expandable room  20  is pulled from its extended position outwardly from the exterior wall  24  of the vehicle back to its retracted position within the vehicle. 
     In order to power movement of the linkage assemblies  25  and thus move the expandable room  20 , a hydraulic cylinder  42  having an operating rod  44  is mounted at the lower end of and within the channel frame member  28  of the vehicle as shown in FIGS. 1-7. The operating rod  44  has its outer end attached to the lower end  46  of the glide arm  26 . The glide arm  26  is formed of parallel spaced apart walls  50  joined together at the lower end  46  and upper end  48  thus providing a longitudinal opening between the lower end and upper end  48 . This allows the glide arm  26  to move upwardly and downwardly within the channel frame member  28  of the vehicle without interference with the pivot attachment of the first linkage member  32  to the channel frame member  28 . This is shown in FIG.  9 . The closed lower end  46  of the glide arm  26  also provides for connection of the operating rod  44  of the hydraulic cylinder  42  to the glide arm  26 . 
     In the preferred embodiment shown in the drawings, there are a pair of linkage assemblies  25  on each side of the expandable room  20 . The single hydraulic cylinder  42  powers both the upper and lower linkage assemblies by interconnecting the glide arm  26  of each assembly  25 . This is illustrated in FIGS. 1-7 which shows the upper end  48  of the glide arm  26  of the lower assembly connected to the lower end  46  of the upper assembly  25  by a connecting pin  52 . 
     The glide arm  26  for each linkage assembly  25  is shown to be nested and slidable within the channel frame member  28 . Of course, depending on glide arm  26  or frame member  28  configurations, the glide arm  26  may be disposed in any convenient arrangement to move generally along the frame member  28 . 
     In the preferred embodiment, there are a pair of linkage assemblies  25  on each side of the expandable room  20 . In order to synchronize movement of the assemblies  25  on opposite side of the room  20  and therefore maintain proper alignment of the expandable room  20  relative to the exterior wall  24  of the vehicle, there is shown in FIGS. 3 and 8 a torsion bar  54 . The upper linkage assemblies  25  are connected by the torsion bar  54  which is attached at its ends to the top of each assembly  25  as shown in FIG.  8 . If one side of the expandable room  20  advances ahead of the other side, the torsion bar  54  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 the torsion bar  54  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. 
     Although the preferred embodiments as described herein includes reference to a force assist element in the form of hydraulic cylinders, the present invention can also employ a manual force assist element. Without any force assist element, the room may be manually pushed or pulled using the principles of the invention. It is preferred to employ room locks to secure the room in the extended or retracted position. Of course, the linkage assemblies could be reversed with mounting of the hydraulic cylinders along the expandable room exterior side wall in which case the mechanism would push the room outwardly and pull the room inwardly. Mounting the mechanism to a vehicle frame member 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.