Patent Publication Number: US-6334605-B1

Title: Pantagraph-type jack

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a pantagraph-type jack and, in particular, an improved pantagraph-type jack, in which outer ends of a pair of lower arms disposed in a V-shaped manner whose inner ends are swingably connected to a base and outer ends of a pair of upper arms disposed in an inverted V-shaped manner whose inner ends are swingably connected to a load bearing platform are connected via first and second connecting shafts, and a threaded rod supported on the first connecting shaft in a rotatable but axially non-movable manner is screwed into a threaded bore provided in the second connecting shaft. 
     2. Description of the Prior Art 
     Such a pantagraph-type jack is already known as disclosed in, for example, Japanese Patent Publication No. 3-6120. 
     In such a pantagraph-type jack of the art, the degree of lift of the load bearing platform is increased by increasing the lengths of the lower arms, the upper arms and the threaded rod. However, when the lengths of the lower arms, the upper arms and the threaded rod are increased, the size of the jack increases and thus it is difficult to store it in a small storage space in an automobile, etc. 
     SUMMARY OF THE INVENTION 
     The present invention has been carried out in view of the above-mentioned circumstances, and it is an objective of the present invention to provide a compact pantagraph-type jack in which the degree of lift of the load bearing platform can be increased without increasing the lengths of the lower arms, the upper arms and the threaded rod. 
     In order to achieve the above-mentioned objective, the present invention provides firstly a pantagraph-type jack in which outer ends of a pair of lower arms disposed in a V-shaped manner whose inner ends are swingably connected to a base and outer ends of a pair of upper arms disposed in an inverted V-shaped manner whose inner ends are swingably connected to a load bearing platform are connected via first and second connecting shafts, and a threaded rod supported on the first connecting shaft in a rotatable but axially non-movable manner is screwed into a threaded bore provided in the second connecting shaft, wherein the base comprises an upper base member and a lower base member which are connected to each other relatively movably in a vertical direction, inner ends of the pair of lower arms are swingably connected to the upper base member via a pair of lower pivots arranged in a horizontal direction, lower sector gears are formed on outer peripheries of the inner ends of the two lower arms, and a lower rack which meshes with the lower sector gears is disposed in the vertical direction and secured on the lower base member. 
     In accordance with the above-mentioned first feature, when the threaded rod is rotated in a clockwise direction so as to erect each pair of lower arms and upper arms around the lower pivots and the upper pivots respectively in order to erect the collapsed or contracted jack, since the lower sector gears formed on the outer peripheries of the inner ends of the two lower arms rotate at the same time so as to ascend the lower racks, the upper base member having the lower pivots lifts relative to the lower base member having the lower racks. Therefore, the total amount of lift of the jack becomes the sum of the amount of lift of the load bearing platform due to the erection of the lower arms and the upper arms and the amount of lift of the upper base member relative to the lower base member, and thus the amount of lift can be increased in comparison with a jack of the prior art in which the amount of lift of the load bearing platform is determined only by the erection of the lower arms and the upper arms. Moreover, since it is unnecessary to specially increase the lengths of the lower arms, the upper arms and the threaded rod, the size of the jack is not made larger. 
     The present invention provides secondly a pantagraph-type jack in which the outer ends of a pair of lower arms disposed in a V-shaped manner whose inner ends are swingably connected to a base and outer ends of a pair of upper arms disposed in an inverted V-shaped manner whose inner ends are swingably connected to a load bearing platform are connected via first and second connecting shafts, and a threaded rod supported on the first connecting shaft in a rotatable but axially non-movable manner is screwed into a threaded bore provided in the second connecting shaft, wherein the load bearing platform comprises a lower load bearing platform member and an upper load bearing platform member which are connected to each other relatively movably in a vertical direction, inner ends of the pair of upper arms are swingably connected to the lower load bearing platform member via a pair of upper pivots arranged in the horizontal direction, upper sector gears are formed on the outer peripheries of the inner each of the two upper arms and an upper rack which meshes with the upper sector gears is disposed in the vertical direction and secured on the upper load bearing platform member. 
     In accordance with the above-mentioned second feature, when the threaded rod is rotated in the clockwise direction so as to erect each pair of lower arms and upper arms around the lower pivots and the upper pivots respectively in order to erect the collapsed jack, since the upper sector gears formed on the outer peripheries of the inner ends of the two upper arms rotate at the same time so as to push up the upper racks, the upper load bearing platform member having the racks lifts relative to the lower load bearing platform member having the upper pivots. Therefore, the total amount of lift of the jack becomes the sum of the amount of lift of the load bearing platform due to the erection of the lower arms and the upper arms and the amount of lift of the upper load bearing platform member relative to the lower load bearing platform member, and thus the amount of lift can be increased in comparison with a jack of the prior art in which the amount of lift of the load bearing platform is determined only by the erection of the lower arms and the upper arms. Moreover, since it is unnecessary to specially increase the lengths of the lower arms, the upper arms and the threaded rod, the size of the jack is not made larger. 
     The present invention further provides a pantagraph-type jack in which outer ends of a pair of lower arms disposed in a V-shaped manner whose inner ends are swingably connected to a base and outer ends of a pair of upper arms disposed in an inverted V-shaped manner whose inner ends are swingably connected to a load bearing platform are connected via first and second connecting shafts, and a threaded rod supported on the first connecting shaft in a rotatable but axially non-movable manner is screwed into a threaded bore provided in the second connecting shaft, wherein the base comprises an upper base member and a lower base member which are connected to each other relatively movably in a vertical direction, inner ends of the pair of lower arms are swingably connected to the upper base member via a pair of lower pivots arranged in a horizontal direction, lower sector gears are formed on outer peripheries of the inner ends of the two lower arms, and a lower rack which meshes with the lower sector gears is disposed in the vertical direction and secured on the lower base member, and the load bearing platform comprises a lower load bearing platform member and an upper load bearing platform member which are connected to each other relatively movably in a vertical direction, inner ends of the pair of upper arms are swingably connected to the lower load bearing platform member via a pair of upper pivots arranged in the horizontal direction, upper sector gears are formed on the outer peripheries of the inner ends of the two upper arms, and an upper rack which meshes with the upper sector gears is disposed in the vertical direction and secured on the upper load bearing platform member. 
     In accordance with the above-mentioned third feature, when the threaded rod is rotated in a clockwise direction so as to erect each pair of lower arms and upper arms around the lower pivots and the upper pivots respectively in order to erect the collapsed jack, since the lower sector gears formed on the outer peripheries of the inner ends of the lower arms rotate at the same time so as to ascend the lower racks, the upper base member having the lower pivots lifts relative to the lower base member having the lower racks, and since the upper sector gears formed on the outer peripheries of the inner ends of the upper arms rotate at the same time so as to push up the upper racks, the upper load bearing platform member having the racks lifts relative to the lower load bearing platform member having the upper pivots. Therefore, the total amount of lift of the jack becomes the sum of the amount of lift of the load bearing platform due to the erection of the lower arms and the upper arms, the amount of lift of the upper base member relative to the lower base member and the amount of lift of the upper load bearing platform member relative to the lower load bearing platform member, and thus the amount of lift can be increased to a great extent in comparison with a jack of the prior art in which the amount of lift of the load bearing platform is determined only by the erection of the lower arms and the upper arms. Moreover, since it is unnecessary to specially increase the lengths of the lower arms and the upper arms, the size of the jack is not made larger. 
     In addition to any one of the first to the third features, the present invention fourthly provides a pantagraph-type jack, wherein the rack comprises a plurality of pins which are inserted in a vertical array on the corresponding one of the lower base member and upper load bearing platform members, and both sides of these pins are made to mesh with a corresponding pair of sector gears. 
     In accordance with the above-mentioned fourth feature, one rack which is shared by a corresponding pair of sector gears will suffice and thus the arrangement can be simplified. 
     The above-mentioned objectives, other objectives, characteristics and advantages of the present invention will become apparent from an explanation of a preferable embodiment which will be described in detail below by reference to the attached drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a pantagraph-type jack of an embodiment of the present invention. 
     FIG. 2 is a partially cut away front view showing a state in which the jack is collapsed. 
     FIG. 3 is a partially cut away front view showing a state in which the jack is erected. 
     FIG. 4 is a cross-sectional view taken along a line  4 — 4  in FIG.  2 . 
     FIG. 5 is a cross-sectional view taken along a line  5 — 5  in FIG.  2 . 
     FIG. 6 is a cross-sectional view taken along a line  6 — 6  in FIG.  1 . 
     FIG. 7 is a cross-sectional view taken along a line  7 — 7  in FIG.  1 . 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     A preferred embodiment of the present invention is explained below by reference to the attached drawings. 
     In FIG. 1 a jack  10  is of the so-called pantagraph type in which four link arms are connected in a pantagraph state and comprises a base  11 , a load bearing platform  12  provided just above the base  11 , a link mechanism  13  for linking the base  11  and the load bearing platform  12  and a threaded rod  14  for lifting the load bearing platform  12  up and down by driving the link mechanism  13 . 
     As shown in FIG. 2, FIG.  4  and FIG. 5, the aforementioned base  11  comprises an upper base member  11   a  and a lower base member  11   b  which are connected to each other relatively movably in the vertical direction. The upper base member  11   a  is formed by bending a sheet of steel into a U shape and comprises a pair of side walls  30 ,  30  which oppose to each other in the depth direction, that is to say, in the direction of the width of the jack  10  and a top part  31  which connects upper ends of the side walls  30 ,  30  integrally with each other. The lower base member  11   b  is also formed by bending a sheet of steel into a U shape and comprises a pair of side walls  32 ,  32  which oppose to each other in the depth direction with a gap wider than that of the two side walls  30 ,  30  of the upper base member  11   a  and a bottom part  33  which connects lower ends of the side walls  32 ,  32  integrally with each other, and the upper base member  11   a  is provided inside the lower base member  11   b  in a vertically movable manner. Ground supports  33   a ,  33   a  are integrally formed with the bottom part  33  of the lower base member  11   b  so as to extend from the right and left ends of the bottom part  33 . 
     The aforementioned load bearing platform  12  comprises a lower load bearing member  12   a  and an upper load bearing member  12   b  which are connected to each other relatively movably in the vertical direction. The lower load bearing platform member  12   a  is formed by bending a sheet of steel into a U shape and comprises a pair of side walls  37 ,  37  which oppose each other in the depth direction and a bottom part  38  which connects the lower ends of the side walls  37 ,  37  integrally with each other. The upper load bearing platform member  12   b  is also formed by bending a sheet of steel into a U shape and comprises a pair of side walls  37 ,  37  which oppose to each other in the depth direction with a gap wider than that of the two side walls  35 ,  35  of the lower load bearing platform member  12   a  and a top part  38  which links the lower ends of the side walls  37 ,  37  integrally with each other, and the lower load bearing platform member  12   a  is provided inside the upper load bearing platform member  12   b  in a vertically movable manner. A load bearing channel  38   a  is formed in the depth direction on the top part  38  of the upper load bearing platform member  12   b . When an automobile body is jacked up, the sidesill of the body is borne by the load bearing channel  38   a.    
     The above-mentioned link mechanism  13  comprises a pair of right and left lower arms  17 ,  17  which are disposed in a V-shaped manner, the inner ends thereof being swingably connected to the upper base member  11   a  via a pair of right and left lower pivots  15 ,  15 , a pair of right and left upper arms  18 ,  18  which are disposed in an inverted V-shaped manner, the inner ends thereof being swingably connected to the lower load bearing platform member  12   a  via a pair of right and left upper pivots  16 ,  16 , a first connecting shaft  19   a  for swingably connecting the outer ends of lower arm  17  and upper arm  18  on one side and a second connecting shaft  19   b  for swingably connecting the outer ends of lower arm  17  and upper arm  18  on the other side. 
     Each lower arm  17  is made from a sheet of steel and comprises a pair of side walls  26 ,  26  which oppose to each other in the depth direction and a bottom part  27  which connects the lower edges of the side walls  26 ,  26  integrally with each other, and the inner ends of the two side walls  26 ,  26  are inserted between the side walls  30 ,  32  of the upper and lower base members  11   a ,  11   b  and connected to the side walls  30 ,  30  of the upper base member  11   a  via the corresponding aforementioned lower pivot  15 . 
     Each upper arm  18  is also made from a sheet of steel and comprises a pair of side walls  28 ,  28  which oppose to each other in the depth direction and a top part  29  which connects the upper edges of the side walls  28 ,  28  integrally with each other, and the inner ends of the two side walls  28 ,  28  are inserted between the side walls  35 ,  37  of the lower and upper load bearing platform members  12   a ,  12   b  and connected to the side walls  35 ,  35  of the lower load bearing platform member  12   a  via the corresponding aforementioned upper pivot  16 . 
     The gap between the side walls  26 ,  26  of each of the right and left lower arms  17 ,  17  is made so as to be wider than the gap between the side walls  28 ,  28  of each of the right and left upper arms  18 ,  18 , and the outer ends of the side walls  28 ,  28  of each of the two upper arms  18 ,  18  are interposed between the outer ends of the side walls  26 ,  26  of each of the two lower arms  17 ,  17  and these outer ends are connected to each other via the first and second connecting shafts  19   a ,  19   b.    
     The lower pivots  15 ,  15  slidably penetrate two pairs of right and left long bores  40 ,  40  which are vertically elongated and are provided on each of the two side walls  32 ,  32  of the lower base member  11   b , and in order to prevent the pivots  15 ,  15  from falling out they have expanded ends  15   a ,  15   a  at both ends which are in contact with the outer surfaces of the above-mentioned two side walls  32 ,  32 . 
     The upper pivots  16 ,  16  slidably penetrate two pairs of right and left long bores  41 ,  41  which are vertically elongated and are provided on each of the two side walls  37 ,  37  of the upper load bearing platform member  12   b , and in order to prevent them from falling out they have expanded ends  16   a ,  16   a  at both ends which are in contact with the outer surfaces of the above-mentioned two side walls  37 ,  37 . 
     Lower sector gears  20 ,  20 ;  20 ,  20  which oppose to each other are formed symmetrically on the outer peripheries of the inner ends of each of the two side walls  26 ,  26 ;  26 ,  26  of the right and left lower arms  17 ,  17 , and lower racks  42  which mesh with the lower sector gears  20 ,  20 ;  20 ,  20  are provided in the vertical direction on the lower base member  11   b . These lower racks  42  comprise a plurality of pins  43  . . . (three pins in the illustrated embodiment) which are provided at vertically identical intervals with both ends supported on the two side walls  32 ,  32  of the lower base member  11   b , and the right and left lower sector gears  20 ,  20 ;  20 ,  20  mesh with both the sides of these pins  43  . . . . Here, elongated hole-shaped notches  46 ,  46  are provided on the two side walls  30 ,  30  of the upper base member  11   a  in order to avoid interference with each of the pins  43  . . . . Each of the pins  43  . . . has expanded ends  43   a ,  43   a  at both ends which are in contact with the outer surfaces of the lower base member  11   b  in order to prevent them from falling out. 
     Upper sector gears  21 ,  21 ;  21 ,  21  which oppose to each other are also formed symmetrically on the outer peripheries of the inner ends of each of both the side walls  28 ,  28 ;  28 ,  28  of the right and left upper arms  18 ,  18 , and upper racks  44  which mesh with the upper sector gears  21 ,  21 ;  21 ,  21  are provided in the vertical direction on the upper load bearing platform member  12   b . These upper racks  44  comprise a plurality of pins  45  . . . (three pins in the illustrated embodiment) which are provided at vertically identical intervals with both ends supported on both the side walls  37 ,  37  of the upper load bearing platform member  12   b , and the right and left upper sector gears  21 ,  21 ;  21 ,  21  mesh with both the sides of these pins  45  . . . . Here, elongated hole-shaped notches  47 ,  47  are provided on the two side walls  35 ,  35  of the lower load bearing platform member  12   a  in order to avoid interference with each of the pins  45  . . . . Each of the pins  45  . . . has expanded ends  45   a ,  45   a  at both ends which are in contact with the outer surfaces of the upper load bearing platform member  12   b  in order to prevent them from falling out. 
     As shown in FIG.  6  and FIG. 7, the first connecting shaft  19   a  is made from a hollow tube and is provided at its centre with a shaft hole  22  which is orthogonal to its axis. The second connecting shaft  19   b  is solid and is provided at its centre with a threaded hole  23  which is orthogonal to its axis, one end of the threaded rod  14  is fitted rotatably into the above-mentioned axis hole  22 , and the other end of the above-mentioned rod  14  is screwed into the threaded hole  23 . 
     A yoke joint  24  is secured by welding to one end of the threaded rod  14  on the side corresponding to the first connecting shaft  19   a , a thrust bearing  25  is mounted so as to adjoin the yoke joint  24 , and the threaded rod  14  can be connected to the first connecting shaft  19   a  in an axially non-movable manner by positioning the thrust bearing  25  and an extrusion  50  formed on the outer peripheral surface of the threaded rod  14  so as to be in contact with both the side surfaces of the first connecting shaft  19   a.    
     As shown in FIG.  4  and FIG. 5, recesses  48 ,  49  for receiving one portion of the outer peripheral surface of the threaded rod  14  when the jack  10  is collapsed are formed on the upper wall part  31  of the upper base member  11   a  and the bottom wall part  36  of the lower load bearing platform member  12   a , and thus it is possible to reduce the height of the collapsed jack  10  as much as possible. 
     Next, the operation of the present embodiment is described. 
     When the jack  10  is in a collapsed state as shown in FIG. 1 (the solid line) and FIG. 2, by rotating the threaded rod  14  in the clockwise direction by means of a rotation tool (not illustrated) connected to the yoke joint  24  the first and second connecting shafts  19   a ,  19   b  approach each other, thereby resulting in the lower arms  17 ,  17  and the upper arms  18 ,  18  starting to erect around the lower pivots  15 ,  15  and the upper pivots  16 ,  16  respectively to lift the load bearing platform  12 . 
     Simultaneously, while the lower arms  17 ,  17  are erecting around the lower pivots  15 ,  15 , since the lower sector gears  20 ,  20  rotate so as to ascend the lower racks  42  as shown in FIG. 3, the upper base member  11   a  having the lower pivots  15 ,  15  lifts relative to the lower base member  11   b  having the lower racks  42 . While the upper arms  18 ,  18  are erecting around the upper pivots  16 ,  16 , since the upper sector gears  21 ,  21  rotate so as to push up the upper racks  44  as shown in FIG. 3, the upper load bearing platform member  12   b  having the upper racks  44  lifts relative to the lower load bearing platform member  12   a  having the upper pivots  16 ,  16 . 
     As a result, the total amount of lift of the jack  10  becomes the sum of the amount of lift of the load bearing platform  12  due to the erection of the lower arms  17 ,  17  and the upper arms  18 ,  18 , the amount of lift of the upper base member  11   a  relative to the lower base member  11   b , and the amount of lift of the upper load bearing platform  12   b  relative to the lower load bearing platform  12   a , and thus it is possible to increase the amount of lift to a great extent in comparison with that of a lack of the art in which the amount of lift of the load bearing platform  12  is determined only by the erection of the lower arms  17 ,  17  and the upper arms  18 ,  18 . Moreover, since there is no special need to increase the lengths of the lower arms  17 ,  17 , the upper arms  18 ,  18  and the threaded rod  14 , the size of the jack  10  can be prevented from increasing. 
     Since the lower racks  42  comprise a plurality of pins  43  . . . which are provided at vertically identical intervals and whose both ends are supported on the two side walls  32 ,  32  of the lower base member  11   b  and the right and left lower sector gears  20 ,  20  mesh with both sides of these pins  43  . . . , only one set of lower racks  42  which is shared by the right and left lower sector gears  20 ,  20  will suffice. Since the upper racks  44  comprise a plurality of pins  45  . . . which are provided at vertically identical intervals with both ends supported on the two side walls  37 ,  37  of the upper load bearing platform member  12   b  and the right and left upper sector gears  21 ,  21  mesh with both sides of these pins  45  . . . , only one set of upper racks  44  which is shared by the right and left upper sector gears  21 ,  21  will suffice. Thus, the arrangement can be simplified. 
     When the jack  10  is in an erect state, by rotating the threaded rod  14  in the reverse direction, the lower arms  17 ,  17  and the upper arms  18 ,  18  collapse around the lower pivots  15 ,  15  and the upper pivots  16 ,  16  respectively due to an action opposite to the above-mentioned action, the upper base member  11   a  descends relative to the lower base member  11   b , the upper load bearing platform member  12   b  descends relative to the lower load bearing platform member  12   a , and thus it is apparent that the jack  10  collapses. 
     The present invention is not limited to the above-mentioned embodiment and can be modified in a variety of ways without departing from the spirit and scope of the invention.