Abstract:
A push-pull drive chain mechanism and scissors linkage assembly and lifter assembly all powered by hydraulic cylinders 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, and then horizontally as the hydraulic cylinders extend or retract to move the expandable room relative to the vehicle frame. The lifter assembly assists in raising and lowering the expandable room so that when the room is extended, the floor of the expandable room will be substantially flush with the floor of the vehicle.

Description:
BACKGROUND OF INVENTION 
   The invention relates to a linkage arrangement for moving members together or apart in a substantially horizontal motion without a substantial shift in a direction perpendicular to the desired linear motion while still allowing the members to move a limited distance vertically under controlled conditions. 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. Other known arrangements teach a linkage arrangement of the “X” or scissors type for moving members relative to one another in a substantially linear motion. The present invention utilizes a chain driven linkage arrangement for moving the members horizontally relative to each other while allowing for controlled and limited vertical movement. 
   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 traveling over the road and along 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 U.S. Pat. No. 6,568,734 entitled “Straight Motion Parallelogram Linkage”, U.S. Pat. No. 6,729,670 entitled “Linkage for Expandable Rooms” and U.S. Pat. No. 6,679,541 entitled “Chain Driven Linkage Assemblies for Room Extensions”. 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 chain-drive assembly that provides for improved motion of structural members together or away from one another in a substantially linear path while allowing limited 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. It is also 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. Finally, it is an object of the invention to provide a lifting mechanism that allows the expandable room to be flush with the floor of the vehicle when extended and then raised to be positioned on top of the vehicle floor when the expandable room is retracted. 
   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. A pair of chains are utilized, one on each side of the room. The drive chains move generally vertically along structural members, such as vehicle frame members on each side of the room, and then the chains are redirected for horizontal travel as the hydraulic cylinders are actuated to extend or retract to retract the expandable room. The drive chains are pivotally connected at the proper place on the vehicle structural members, and are constructed and guided to provide the required force for extending and retracting the room. 
   There preferably are drive chain mechanisms on each side of the expandable room. Use of two chain mechanisms, one on each side of the expandable room, improves the mechanical advantage in moving the expandable room inwardly and outwardly. As the room extends outwardly, a lifting system, comprised of a lifter mechanism on each side of the room, controls vertical movement of the room so that when the room is fully extended, the floors of the vehicle and the expandable room will be substantially flush. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is an interior side elevational view of the chain-linkage assembly and master lifter mechanism for an expandable room and showing the linkage when the room is retracted; 
       FIG. 2  is an interior side elevational view similar to  FIG. 1  but showing the expandable room expanded: 
       FIG. 3  is a view taken on the line  3 — 3  of  FIG. 1  with some components not shown for purpose of clarity; 
       FIG. 4  is an interior side elevational view of the chain-linkage assembly similar to  FIG. 1  but showing the slave lifter mechanism for an expandable room and showing the linkage when the room is extended; 
       FIG. 5  is an interior side view similar to  FIG. 4  but showing the expandable room retracted; 
       FIG. 6  is an side enlarged elevational view of the master lifter mechanism and the lower portion of the chain-linkage assembly; 
       FIG. 7  is an enlarged side elevational view of the slave lifter mechanism and the lower portion of the chain-linkage assembly; 
       FIG. 8  is a top view of the master lifter mechanism; 
       FIG. 9  is a perspective exploded view of the major components that comprise the master lifter mechanism; 
       FIGS. 10   a  through  10   e  are a series of side elevational views of portions of the structure that illustrate the movement of the lifter mechanism while the expandable room moves from a retracted to an extended position in which the floor of the expandable room lowers to the level of the vehicle floor; and 
       FIG. 11  is a schematic diagram of the hydraulic system that controls the drive chain-linkage assembly and lifter mechanisms. 
   

   DETAILED DESCRIPTION 
   Referring first to  FIGS. 1–5 , 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 horizontal frame member  10  and a lower horizontal frame member  12  that form a part of an interior side wall of an expandable room. The upper surface of the frame members  12  define the floor of the expandable room. Each of the side walls formed by the upper and lower frame members  10  and  12  are connected by a vertical frame member  14  that forms a part of the interior end wall of the expandable room. Similarly, the outer ends of the upper and lower frame members  10  and  12  are connected by vertical frame members (not shown) that form the outer end wall  17  of the expandable room. The side walls shown in  FIGS. 1–5  are interconnected by lateral support members (not shown) that form a box-like structure that defines the expandable room. The expandable room nests within the vehicle between vertical supports  16  that form a part of the vehicle side wall structure. An example of an expandable room for a recreational vehicle of the general type to which the invention relates is shown in U.S. Pat. No. 6,067,756. The basic structure of expandable rooms of various sizes are well know to those skilled in the art and therefore all the details of the vehicle and expandable room structures will not be described.  FIGS. 2 and 5  show 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 ( FIGS. 1 and 4 ) so that the outer end wall of the expandable room is generally flush with the exterior wall of the recreational vehicle that includes vertical support members  16 .  FIGS. 2 and 5  show the expandable room structure in the extended position with the frame members  14  that form part of the interior end wall of the expandable room positioned adjacent the vehicle support members  16 . 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, but the principles of the invention are applicable to the expansion and retraction of a movable structure in other applications as well. 
     FIGS. 1 and 2  are elevational views that illustrate one side of the expandable room which is termed the “master” side, while  FIGS. 4 and 5  are similar views that illustrate the “slave” side. Both sets of figures,  FIGS. 1–2  and  FIGS. 4–5 , illustrate the main push-pull chain system that provides for horizontal movement of the room. Since these push-pull chain mechanisms are the same for both the master and slave sides of the expandable room, the components and operation will be described for one side with the identical reference numerals applied to both the master and slave sides of the expandable room. 
   Mounted in the vehicle vertical support  16  is a hydraulic cylinder  18  having an operating rod  20  to which is connected a bracket  22  that is in turn connected to the end of a lower chain  24 . Extending vertically inside the vertical support  16  adjacent the hydraulic cylinder  18  are a pair of parallel rods  26  which are secured to the bracket  22  so as to connect the end of the lower chain  24  with the end of the upper chain  28 . This provides for simultaneous movement of both chains  24  and  28  when the operating rod  20  moves to either push or pull the chains  24  and  28 . The chains  24  and  28  are guided for limited vertical movement between the rods  26 , and the chains  24  and  28  exit the vertical support  16  through a guide member  30  that turns the chains  24  and  28  from vertical to horizontal where the other ends of the chains are connected to the vertical frame members  14  that form a part of the interior end wall of the expandable room. Each of the drive chains  24  and  28  are comprised of consecutive links pivotally connected to each other and are of a type that allow the drive chains  24  and  28  to flex in one direction only thereby allowing the chain to be pushed from one end link to the other end link as well as being pulled. A chain of this type is well known to those skilled in the art and is more specifically described in U.S. Pat. No. 6,679,541. Thus, as the operating rod  20  of hydraulic cylinder  18  travels vertically, chains  24  and  28  are pushed or pulled to move the expandable room horizontally between a retracted position or an extended position. 
   Secured to the bottom of the vertical frame member  14  of the expandable room is a bracket  32  having actuating pins  33  which interface with a toggle in the lifting mechanism, indicated generally by the reference numeral  34 , and which will now be described in detail. 
   Referring now to  FIGS. 1 ,  2 ,  6 ,  9  and  10 , it will be seen that the lifting mechanism  34  is mounted beneath the level of the vehicle floor  36  on a support member  38  that is secured to the vehicle frame and to the vehicle vertical support  16 .  FIGS. 1 ,  2 ,  6  and  9  show the master side of the room in which a hydraulic lifter cylinder  40  is pivotally mounted at its cap end  42  to the support member  38 . The operating rod  44  of cylinder  40  is pivotally connected to a toggle  46  by pin  47 , the toggle  46  being turnable about pin  48  secured to the support member  38 . The toggle  46  has generally upwardly extending fingers  50 . The toggle  46  is connected by spacer pin  55  and stiffener  57  to a secondary toggle bracket  56  that supports a slide block  52  turnable about pin  54 . Pin  54  extends through toggle  46 , the secondary toggle bracket  56  and bracket  59 . The slide block  52  serves as one of the supports for the expandable room by being engageable with the horizontal frame member  14 . 
     FIGS. 4 ,  5  and  7  show the slave side of the expandable room. As shown in these figures, support member  38  contains a slave hydraulic lifter cylinder  70  with an operating rod  72  that is pivotally connected to a toggle  74  substantially identical to the toggle  46  on the master side of the expandable room. Toggle  74  is pivotally mounted about pin  76  on the support member  38  and has upwardly extending fingers  78 . Pivoted to the toggle by pin  80  is a slide block  82  which is another support for the expandable room, being engageable with the horizontal frame member  12 . 
   The lifter mechanism  34  also includes a switch mechanism indicated generally by the reference numeral  58 . Switch mechanism  58  includes a switch arm  60  pivotally attached to a main switch member  62  that is turnable about pin  48 . Switch mechanism  58  also includes an actuating arm  64  turnable about pin  51 . Bracket  59  holds the switch mechanism  58  inside the lifting mechanism  34 . With the toggle  46  in the raised position, the switch arm  60  is located between the fingers  50  of the toggle  46  and therefore can be engaged by the leading roller pin  33  on bracket  32  as the room moves from a retracted to an extended position. Since the main switch arm  62  is pivoted about the same pivot pin  48  about which the toggle  46  rotates, this allows the switch mechanism  58  to operate independently of the toggle  46 . Main switch member  62  carries a pin  65  ( FIG. 6 ) that engages the curved inner surface of the actuating arm  64  of switch mechanism  58  and thus holds the arm  64  in the same position as the pin  65  travels along the curved surface. The lifter support member  38  supports a valve block  66  containing an unlock switch  68  that is engageable by the actuating arm  64  as the arm rotates (See  FIG. 6 ). As will be more fully described hereinafter, the switch mechanism  58  provides a safety feature that assures that the expandable room will not drop suddenly as it is extended, which drop could cause damage to the room or the vehicle floor. 
     FIGS. 10   a    10   e  illustrate the action of the lifter mechanism  34  as the expandable room moves from a retracted to an extended position, while  FIG. 11  is a schematic diagram of the hydraulic system of the preferred embodiment of the invention. When the expandable room is fully retracted, the main cylinders  18  as well as the lifter cylinders  40  and  70  are all extended.  FIG. 10   a  shows the expandable room retracted but starting to move to an extended position from right to left of  FIG. 10 . In this position, the expandable room is supported above the coach vehicle floor  36 , and as the expandable room is extended, the slide blocks  52  and  82  engaged by the horizontal frame members  12  support the room as it moves. As previously described, the bracket  32  that is secured at the lower end of the interior end wall vertical frame member  14  contains actuating roller pins  33 . As the expandable room continues to move to an extended position, the first or leading pin  33  on the bracket  32  makes contact with the switch arm  60  to depress it and cause rotation of the main switch member  62  which in turn pivots the actuating arm  64  that engages and depresses unlock switch  68  on the valve block  66 . Once switch  68  is thus unlocked, hydraulic fluid is allowed to flow back to pump-manifold  84 . At this time, and as long as switch  68  remains unlocked, only residual fluid pressure exists in the lifter cylinders  40  and  70 . As the main drive chain mechanism through the action of cylinders  18  continues to extend the expandable room, the pins  33  on the brackets  32  engage the toggle fingers  50  and  78  of their respective lifter mechanisms  34 . As the room continues to move to an extended position, the toggles  46  and  74  will be rotated about their respective pivot pins  48  and  76  carrying with them the slide blocks  52  and  82  which are supporting the lower horizontal frames  12  of the expandable room. When the slide blocks  52  and  82  are moved to a position substantially vertical over the toggle pivot pins  48  and  76  (see  FIG. 10   c ), further outward movement of the expandable room will rotate the toggles  46  and  74  over center and then downwardly as the weight of the expandable room pulls the room downwardly. The drive chains  24  and  28  resist the free fall of the room and control the speed of descent. The toggles  46  and  74  control the downward path of the room as it is lowered in an arcing motion, and the main drive chain mechanism through cylinders  18  controls the speed at which the expandable room descends.  FIG. 10   d  shows the toggles  46  and  74  over center while  FIG. 10   e  shows the room fully descended so that the floor of the expandable room is level with the vehicle floor  36 . 
   As previously described, during extension of the expandable room, the lifter cylinders  40  and  70  will contain only residual pressure after the unlock switch  68  actuates the valve block  66  to allow the hydraulic fluid in the cylinders to flow back to the pump-manifold  84 . The lifting mechanism  34  will function without the switch mechanism  58 , but for the safety reason mentioned, we prefer that the switch mechanism  58  be included in the system. Before the room is later retracted and raised by the main drive chain mechanism and the lifter mechanism  34 , the components of the switch mechanism  58  are returned to their original position by action of a spring  86  (see  FIG. 6 ). 
   When it is desired to retract the room, the main chain drive mechanism and lifter mechanisms  34  work in reverse to that just described for extending the expandable room, with the lifter mechanisms  34  lifting the expandable room upward while the main drive chain mechanism controls the speed of movement of the expandable room. The lifter cylinders  40  and  70  are connected in series and share only a single common connection to the hydraulic system on the cap side of the pump (see  FIG. 11 ). Because the lifter cylinders  40  and  70  share connection with the cap side of the main cylinders  18 , cylinders  40  and  70  are pressurized and the toggles  46  and  74  begin to rotate (counter clockwise in the drawings) as the main cylinders  18  are pressurized to extend and therefore retract the room by extending the chains  24  and  28 . Because the pins  33  on the room brackets  32  are interfaced with the toggles  46  and  74 , the room will start moving upwardly and inwardly. The room will remain substantially horizontal as it pivots independently of the toggles  46  and  74  about the pivot pins  54  and  80  that support the slide blocks  52  and  82 . Once the toggles  46  and  74  are in the fully raised position, the interface with the pins  33  of the room brackets  32  disengages and the room continues to travel horizontally under power of the main chain drive mechanism. 
     FIG. 11  is a schematic diagram of the hydraulic system of the invention. As shown in  FIG. 11 , the main hydraulic cylinders  18  on both the master and slave sides are connected to a synchronizing cylinder  88  that assures movement of both sides of the room simultaneously to prevent any lateral movement which would bind the room as it is extended and retracted. The master hydraulic cylinder  40  is connected in series to the slave hydraulic cylinder  70  and the cylinders are synchronized in any suitable manner, such as a poppit (not shown) that maintains the volume of hydraulic fluid between the cylinders constant. This assures that the two cylinders  40  and  70  will move at the same rate. In the alternative, the lifter cylinders may be connected in parallel and synchronized by a synchronizing cylinder similar to cylinder  88 . As previously described, when the operating rods  20  of the main cylinders  18  are extended, this causes the drive chains  24  and  28  to extend and move the room to a retracted position. Because the master lift cylinder  40  and the slave lift cylinder  70  share a common connection through pump-manifold assembly  84 , they are all under the same pressure. During room retraction, when the master lifter cylinder  40  and slave lifter cylinder  70  are actuated, the toggles  46  and  74  are thus rotated simultaneously. As previously described, the interface between the toggles  46  and  74  and the pins  33  on the brackets  32  controls the curved path of the room upward and downward during both extension and retraction of the room. 
   Although the preferred embodiments describe the use of master and slave lifter mechanisms on opposite sides of the room, it should be understood that the system of the invention will function if either the “slave mechanism” or “master mechanism” is used on both sides of the room. Having thus described the invention in connection with the preferred embodiments thereof, it will be evident to those skilled in the art that various revisions can be made to the preferred embodiments described herein without departing from the spirit and scope of the invention. It is our intention, however, that all such revisions and modifications that are evident to those skilled in the art will be included within the scope of the following claims.