Patent Publication Number: US-7591028-B2

Title: Automatic futon frame

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to sofa-bed frames for adjustably supporting a futon mattress, and more particularly to a futon mattress frame having seat and back portions automatically adjustable between a sofa position and a bed position. 
     BACKGROUND OF THE INVENTION 
     Manually operated futon frames having a seat and a back linked to the seat for guided relative motion to permit adjustment between a sofa position and a bed position are well known in the art. In a common futon frame arrangement, the seat and back are pivotally connected to each other, and the back is connected to each adjacent side of the frame by respective link arms having one end pivotally connected to the back and another end pivotally connected to the associated side of the frame. In another common arrangement, pairs of follower bearings extend from the back for travel within corresponding pairs of guide channels provided in each side of the frame. With either type of arrangement, manual adjustment from a sofa position to a bed position is made by sliding the seat forward such that back is caused to follow and assume a horizontal position level with the seat. Manual adjustment from a bed position to a sofa position is carried out by pushing the seat backward at a slight downward angle to force the back into a generally vertical position. U.S. Pat. No. 5,129,114 illustrates this type of construction. 
     Heretofore, various attempts have been made to automate the adjustment operation of futon frames by providing a single stationary drive motor as means for indirectly driving a follower bracket connected to impart adjustment motion to the seat and back. Examples may be seen in U.S. Pat. Nos. 3,458,877; 4,563,784; and 4,937,900. 
     A primary challenge encountered in the design of an automatically adjustable futon frame is that a relatively large force is required to initiate backward movement of the seat to dislodge the back from its horizontal position. Prior art automatic frames have typically relied on complex multiple-bar linkages and/or brute power in the electric motor to meet this challenge. Drawbacks of a complex linkage system include added manufacturing cost, increased frame weight, and decreased reliability. Drawbacks of using a single high-powered motor include complexities in the drive train necessary to evenly transmit force to each side of the frame for smooth adjustment motion, with corresponding increase in manufacturing cost. Consequently, despite the long-recognized desirability of an automatically adjustable futon frame, as evidenced by the patents mentioned above, such item is not widely available to consumers at a reasonable price. 
     U.S. Pat. Nos. 5,790,993; 6,061,848; and 6,138,299, owned by the assignee of the present application and invention, disclose various configurations aimed at providing a commercially acceptable automatic futon frame. These configurations are based on a dual-motor design having a pair of motors mounted one on each opposite side of the seat to drive a respective pinion mated with an inclined rack fixed to the associated side of the frame. While these designs represented and advancement toward the goal of a commercially viable automatic futon frame, the dual-motor design proved costly, and synchronization and balance of drive forces were difficult to achieve in practice. 
     SUMMARY OF THE INVENTION 
     Therefore, it is an object of the present invention to provide an automatically adjustable futon frame which is relatively inexpensive to manufacture, operates smoothly and quietly during position adjustment, and is reliable. 
     In furtherance of this object, an automatically adjustable futon frame is provided that generally comprises first and second opposing sides connected by front and rear support members extending laterally between the first and second sides. A back is situated between the first and second sides, and the back has first and second side members respectively adjacent to the first and second frame sides. A seat is pivotally connected to the back for folding along a laterally extending axis, and the seat has first and second side members. First and second racks are respectively fixed to the first and second sides of the frame, and a motor is fixed to the seat. The motor includes a drive shaft rotatable about a laterally extending drive axis, and first and second pinions are mounted on the drive shaft for rotation with the drive shaft, wherein the first pinion engages the first rack and the second pinion engages the second rack. A first link arm is pivotally coupled to the first side member of the back and to the first side of the frame, and a second link arm is pivotally coupled to the second side member of the back and to the second side of the frame. Consequently, the motor is operable to automatically adjust the back and the seat between a sofa position and a bed position. 
     In an embodiment of the invention, the motor is fixed to the first side member of the seat, the drive shaft extends through respective passages in first and second side members, and the opposite ends of the drive shaft are received in respective channels in the first and second sides of the frame. A pair of limit switches may be provided on the first side of the frame adjacent opposite ends of the rack for engagement by the drive shaft to shut off the motor upon reaching the sofa position and the bed position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The nature and mode of operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying drawing figures, in which: 
         FIG. 1  is an isometric view of an automatic futon frame formed in accordance with an embodiment of the present invention, in its bed position; 
         FIG. 2  is an elevational view showing a first side of the futon frame as viewed from a second opposite side of the futon frame, wherein a back and a seat of the frame are shown in phantom line in their sofa position; 
         FIG. 3  is an elevational view similar to that of  FIG. 2 , however the back and the seat are shown in their bed position; 
         FIG. 4  is an elevational view showing the second side of the futon frame as viewed from the first side of the futon frame, wherein the back and seat of the frame are shown in phantom line in their sofa position; 
         FIG. 5  is an elevational view similar to that of  FIG. 4 , however the back and the seat are shown in their bed position; 
         FIG. 6  is a top plan view showing a motor drive system of the futon frame; and 
         FIG. 7  is a schematic block diagram showing electrical circuitry of the motor drive system. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a futon frame  10  formed in accordance with an embodiment of the present invention. Futon frame  10  comprises a pair of opposite sides  12 A,  12 B connected by a front support member  14  and a rear support member  16  extending laterally between sides  12 A,  12 B. Frame  10  further comprises a back  18  situated between sides  12 A,  12 B and including first and second side members  20 A,  20 B (see also  FIG. 6 ) near respective sides  12 A,  12 B, and a seat  22  situated between sides  12 A,  12 B and having first and second side members  24 A,  24 B near respective sides  12 A,  12 B. As best seen in  FIG. 6 , seat  22  is pivotally connected to back  18  for folding along a laterally extending axis by pivot pins  25 A,  25 B joining first side members  24 A and  20 A and second side members  24 B and  20 B of the seat and back. A first link arm  50 A is pivotally coupled to first side member  20 A of back  18  and to first side  12 A by pivots  52 A and  54 A, respectively. Likewise, a second link arm  50 B is pivotally coupled to second side member  20 B of back  18  and to second side  12 B by pivots  52 B and  54 B, respectively. Link arms  50 A,  50 B may be straight, rigid members. Seat  22  includes a pair of support legs  26 A and  26 B generally near a front portion of the seat. The legs may include wheels  27  (the term “wheels” including casters, rollers, and the like) at their bottom ends for engaging a floor on which frame  10  is situated in a manner which minimizes friction. 
     As may be seen in  FIGS. 2 through 5 , a first toothed rack  30 A is fixed to first opposing side  12 A and a second toothed rack  30 B is fixed to second opposing side  12 B. Racks  30 A and  30 B slope downwardly as they extend front to rear on respective sides  12 A,  12 B. 
     Referring also now to  FIG. 6 , a motor  32  is fixed to seat  22  and includes a gearbox  33  and a drive shaft  34 . In the embodiment depicted, motor  32  is fixed to first side member  24 A of seat  22 , however motor  32  may be mounted to the seat at other locations. Motor  32  is operable to rotate drive shaft  34  about a laterally extending drive axis  35 . First and second pinions  36 A,  36 B are mounted on drive shaft  34  near opposite ends of the drive shaft for rotation therewith. The first pinion  36 A is arranged to mate with first rack  30 A, while second pinion  36 B is arranged to mate with second rack  30 B. In the embodiment shown, drive shaft  34  extends through respective passages  38 A,  38 B in first and second side members  24 A,  24 B of seat  22 . A rotary bearing  40  may be mounted on second side member  24 B of seat  22  for rotatably supporting drive shaft  34 . Sides  12 A and  12 B are provided with respective channels  41 A,  41 B extending parallel to first and second racks  30 A,  30 B, wherein each of the channels receives a respective opposite end of drive shaft  34  to maintain pinions  36 A,  36 B in mated engagement with racks  30 A,  30 B. Attention is also directed now to  FIG. 7 . A control switch  42 , which may be a rocker switch or other switch mechanism mounted on first side  12 A in a location accessible to a user, is operable to connect a power supply  44  to motor  32  by way of leads  43  and  45  and capacitor  49  to selectively energize the motor for rotation in a desired direction. In a forward position of switch  42 , drive shaft  34  and first pinion  36 A will rotate in a clockwise direction as viewed in  FIG. 2  to cause seat  22  to move forward such that back  18  folds out (rotates counterclockwise) relative to seat  22  toward the bed position shown in  FIG. 3 . In a reverse position of switch  42 , drive shaft  34  and first pinion  36 A will rotate in a counterclockwise direction as viewed in  FIG. 3  to cause seat  22  to move backward such that back  18  folds in (rotates clockwise) relative to seat  22  toward the sofa position shown in  FIG. 2 . 
     In an aspect of the invention, link arms  50 A and  50 B reside at a slight positive angle of at least 1° relative to horizontal when the frame is adjusted to the bed position as shown in  FIGS. 3 and 5 , with pivots  52 A,  52 B being slightly higher than their counterpart pivots  54 A,  54 B. In this way, the frame does not “lock up” when seat  22  is forced backward to begin adjustment to the sofa position. 
     A forward limit switch  46  and a reverse limit switch  48  may be arranged on frame side  12 A near at opposite ends of first rack  30 A such that each limit switch disconnects motor  32  from power source  44  upon being engaged by drive shaft  34 . As may be understood from  FIG. 2 , when seat  22  and back  18  reach their sofa position, reverse limit switch  48  is engaged by drive shaft  34  and is thereby actuated to cut power to motor  32  and prevent further rotation in the reverse direction only. Similarly, as may be understood from  FIG. 3 , when seat  22  and back  18  reach their bed position, forward limit switch  46  is engaged by drive shaft  34  and is thereby actuated to cut power to motor  32  and prevent further rotation in the forward direction only. It is possible to mount control switch  42  and limit switches  46 ,  48  on second side  12 B, however such an arrangement is not favored because it would require a more complicated wiring scheme for hard wired communication between the switches and motor  32 , which is associated with first side  12 A of frame  10 . 
     In a prototype embodiment of the present invention, an alternating current PSC reversible gearmotor manufactured by Molon Motor and Coil Corporation under Part No. QAM-6005-X, having a 100:1 gear train reduction providing 6 rpm at drive shaft  34 , was found to be suitable as motor  32 . Power source  44  in the prototype embodiment was a standard 115V AC power source, and 10 microfarad capacitors were used for capacitors  47  and  49 . In the prototype embodiment, McMaster-Carr Part No. 5174T11 was used to make racks  30 A,  30 B, and McMaster-Carr Part No. 5172T16 was used to make mating pinions  36 A,  36 B. Also in the prototype embodiment, racks  30 A,  30 B were inclined at an angle of 12 relative to horizontal. Rotary bearing  40  was embodied by Triangle Manufacturing Co. Part No. FLB-8 for accommodating the half-inch diameter drive shaft of the Molon motor. Wiring in the prototype was routed through grooves formed in first side  12 A. While the prototype embodiment demonstrated the utility of the present invention, it is recognized that more sophisticated motor control electronics may be used to provide advanced features, for example predetermined intermediate position settings (in the manner of an automobile seat) and remote control capability. 
     Modifications and other embodiments of the invention described herein will be apparent to persons skilled in the art to which the invention pertains. Therefore, it is understood that the invention is not limited to any specific embodiment described herein, and that modifications and other embodiments are intended to fall within the scope of the appended patent claims.