Abstract:
A seat back linking mechanism includes a base frame having a pivot portion; a back frame pivotally connected to the base frame; an actuation member slidably coupled to the back frame; a linkage having a first link and a second link pivotally coupled together, the first link and the second link being respectively pivotally coupled to the pivot portion of the base frame and the actuation member, and a driven slot; and a drag member having a drag pin adapted for dragging the driven slot of the linkage.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to seat technology, and more particularly to a seat back linking mechanism that allows the seat back to be adjusted between a sitting posture and a reclining posture. 
     2. Description of the Related Art 
     U.S. Pat. No. 7,296,856 discloses a reclining seat with movable back support for wheelchair, which comprises a reclining seat assembly 10 comprising a back support translation mechanism 90 that comprises a first portion, namely, the support member 102 and a second portion 110, wherein the support member 102 is pivotally coupled to a back frame 60 and the second portion 110; the second portion 110 is pivotally coupled to a base 40. Adjustment of the reclining seat to a predetermined reclined angle is subject to sliding movement of the support member 102 along two followers 130 of two tracks 80 and the relative pivoting motion between the support member 102 and pivot components of the second portion 110. 
     The linking mechanism used in this prior art design of reclining seat is functional, however it has a complicated structure, not facilitating the deployment of the installation location and space allocation. Further, the actuation and stop stability of the linking mechanism are to be improved 
     SUMMARY OF THE INVENTION 
     The present invention has been accomplished under the circumstances in view. The technical concept of the present invention is to provide a seat back linking mechanism, which has the advantages of simple structure, accurate operation and high positioning stability and, facilitates space allocation. 
     To achieve this and other objects of the present invention, a seat back linking mechanism of the invention comprises a base frame comprising a pivot portion; a back frame pivotally connected to the base frame; an actuation member slidably coupled to the back frame; a linkage comprising a first link and a second link pivotally coupled together, the first link and the second link being respectively pivotally coupled to the pivot portion of the base frame and the actuation member, and a driven slot; and a drag member comprising a drag pin adapted for dragging the driven slot of the linkage. 
     By means of the operation of the first link and second link of the linkage to move the actuation member, the drag member can drive the first link and second link of the linkage to move the actuation member accurately. Further, the arrangement of the first link and second link of the linkage and the drag member facilitates space utilization, achieving the expected effects and objects of the present invention. 
     Other advantages and features of the present invention will be fully understood by reference to the following specification in conjunction with the accompanying drawings, in which like reference signs denote like components of structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is an oblique top elevational front view illustrating a seat back linking mechanism used in a wheelchair and set in a first status in accordance with the present invention. 
         FIG. 2  is an oblique top elevational rear view of  FIG. 1 . 
         FIG. 3  is an explode view of  FIG. 2 . 
         FIG. 4  is an exploded view of the seat back linking mechanism shown in  FIG. 3 . 
         FIG. 5  is a schematic side view illustrating the seat back linking mechanism in the first status in the wheelchair in accordance with the present invention. 
         FIG. 6  is an enlarged view of a part of the seat back linking mechanism in the first status in accordance with the present invention. 
         FIG. 7  is an oblique top elevational front view illustrating the seat back linking mechanism in a second status in the wheelchair in accordance with the present invention. 
         FIG. 8  is a schematic side view illustrating the seat back linking mechanism in the second status in the wheelchair in accordance with the present invention. 
         FIG. 9  is an enlarged view of a part of the seat back linking mechanism in the second status in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1-4 , a seat back linking mechanism  20  in accordance with the present invention is shown used in a wheelchair  1 . The wheelchair  1  comprises a seat back  11 , a seat  13  and at least two chair wheels  15 . The seat back linking mechanism  20  is coupled between a back side of the seat back  11  of the wheelchair  1  and the seat  13  and disposed near the chair wheels  15 . 
     The seat back linking mechanism  20  comprises: 
     two base frames  21  respectively pivotally coupled to respective outer edges of two opposite lateral sides of the seat  13  of the wheelchair  1 , each comprising a pivot portion  23 ; 
     a back frame  31  mounted at the back side of the seat back  11  of the wheelchair  1 , comprising two actuation members  33  respectively disposed adjacent to the two base frames  21 ; 
     two drag members  35  that are, in the present preferred embodiment, fixedly mounted at and swing-linked to the back frame  31 , each comprising a drag pin  351 , which is, in the present preferred embodiment, a guide rod where the guide rods of the two drag members are arranged in parallel or adapted for the mounting of rollers; 
     a driving device  41 , which is, in the present preferred embodiment, a retractable rod assembly, comprising a first pivot connection portion  43  pivotally coupled with the back frame  31 , a second pivot connection portion  45  pivotally coupled with the two base frames  21 , and a third pivot connection portion  47 ; 
     two linkages  51  each comprising a first link  53 , which comprises a first pivot portion  532  and a second pivot portion  534 , and a second link  55 , which comprises a first pivot portion  552 , a second pivot portion  554  and a driven slot  556 . In this embodiment, the driven slots  556  of the two second links  55  of the two linkages  51  are guide slots arranged in parallel. The actuation members  33  of the back frame  31  are respectively pivotally coupled to the first pivot portions  532  of the first links  53  of the linkages  51 . The pivot portions  23  of the base frames  21  are respectively pivoted to the first pivot portions  552  of the second links  55  of the linkages  51 . The drag members  35  are respectively pivoted to the driven slots  556  of the second links  55  of the linkages  51 . The second pivot portions  534  of the first links  53  of the linkages  51  are respectively pivoted to the second pivot portions  554  of the second links  55  of the linkages  51 . 
     The first link  53  of each linkage  51  comprises a stop portion  56 . The second link  55  of each linkage  51  also comprises a stop portion  56 . The stop portions  56  are adapted to provide a stop effect in a swinging action. Broadly speaking, the first link  53  or second link  55  of each linkage  51  comprises at least one stop portion  56 . 
     After understanding of the structures of the component parts of the preferred embodiment of the present invention, the main features and effects of the present invention are outlined hereinafter: 
     Referring also to  FIGS. 5 and 6  where the seat back linking mechanism  20  is shown in a first status. At first, when the base frames  21 , back frame  31 , driving device  41  and linkages  51  of the seat back linking mechanism  20  are moved relative one another to a first angle, the first links  53  of the linkages  51  are kept in a vertical status relative to the second links  55  of the linkages  51  due to the effect that the second pivot portions  534  of the first links  53  of the linkages  51  are respectively pivotally coupled to the second pivot portions  554  of the second links  55  of the linkages  51 . Further, because the drag members  35  are respectively pivotally coupled with the driven slots  556  of the second links  55  of the linkages  51 , moving the drag members  35  to a first position (not indicated by any reference sign) to bias the driving device  41  of the seat back linking mechanism  20  to the first angle can give a support to the actuation members  33  of the back frame  31  to hold the actuation members  33  in the first position, and thus the seat back can support the back of the user in a sitting position. 
     Referring also to  FIGS. 7-9  where the seat back linking mechanism  20  is shown in a second status. At first, when the base frames  21 , back frame  31 , driving device  41  and linkages  51  of the seat back linking mechanism  20  are moved relative one another to a second angle, the first links  53  of the linkages  51  and the second links  55  of the linkages  51  are received together due to the effect that the second pivot portions  534  of the first links  53  of the linkages  51  are respectively pivotally coupled to the second pivot portions  554  of the second links  55  of the linkages  51 . 
     Further, because the drag members  35  are respectively pivotally coupled with the driven slots  556  of the second links  55  of the linkages  51 , moving the drag members  35  to a second position (not indicated by any reference sign) to bias the driving device  41  of the seat back linking mechanism  20  to the second angle can give a support to the actuation members  33  of the back frame  31  to hold the actuation members  33  in the second position, and thus the seat back can support the back of the user in a reclined position. 
     Except the embodiment disclosed above, the invention can also be various embodied as follows: 
     For example, except the above-described design that the seat back linking mechanism  20  comprises two base frames  21 , the seat back linking mechanism  20  can be defined comprising at least one base frame  21 . 
     Further, except the above-described design that the back frame  31  of the seat back linking mechanism  20  comprises two actuation members  33 , the back frame  31  can be defined comprising at least one actuation member  33 . 
     Further, in the above-described design, the driving device  41  is pivotally coupled to the back side of the back frame  31  of the seat back linking mechanism  20 . Alternatively, the driving device  41  can be pivotally coupled to the back side of the seat back  11  of the wheelchair  1 . 
     Further, in the above-described design, the driving device  41  is pivotally coupled with the two base frames  21 . Alternatively, the driving device  41  can be defined pivotally coupled to at least one of the base frames  21 . 
     Further, in the above-described design, the seat back linking mechanism  20  comprises two linkages  51 . Alternatively, the seat back linking mechanism  20  can be defined comprising at least one linkage  51 . 
     Further, instead of the design of the drag members  35  for synchronous movement with the back frame  31 , the drag members  35  can be made movable by the driving device  41  or other linking means. 
     Further, in the above-described design, the driven slot  556  of the second link  55  of each linkage  51  of the seat back linking mechanism  20  is a guide slot. Alternatively, the driven slot  556  can be a guide groove of a predetermined depth formed in the second link  55  and extending in direction from an outer end along the body thereof. 
     Further, the driven slots  556  of the linkages  51  are not limited to the design of guide slots; the drag pins  351  of the drag members  35  are not limited to the design of guide rods. The design of the driven slots  556  of the linkages  51  and the design of the drag pins  351  of the drag members  35  can be exchanged. 
     In conclusion, by means of the functioning of the first links  53  and second links  55  of the linkages  51  to move the actuation members  33  and the functioning of the drag members  35  to drag the first links  53  and second links  55  of the linkages  51 , the actuation member  33  can be accurately moved; further, the arrangement of the first links  53  and second links  55  of the linkages  51  and the arrangement of the drag members  35  facilitate space utilization; the parallel arrangement of the drag pins  351  of the drag members  35  mates with the parallel arrangement of the driven slots  556  of the linkages  51 , enhancing actuation stability and achieving the expected effects and objects of the present invention. 
     Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.