Patent Publication Number: US-2007116548-A1

Title: Fork-type pallet-lifting device

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to the general art of material and article handling, and to the particular field of hoists or loading equipment with means for additional movement.  
      2. Description of the Related Art  
      Material and articles are often handled by a vehicle such as a fork lift truck. Such trucks generally have a mast to which forks are movably attached. These forks generally move up and down in a vertical direction to move material, pallets and the like from one level to another.  
      However, there are many instances when simple vertical movement of the forks is not sufficient. For example, if the vehicle cannot be maneuvered into a certain orientation with respect to the load, the forks may not be properly oriented. Still further, some loads, such as pallets, may not fit on forks that are oriented at a specific distance with respect to each other. In some instances, a pallet may be loaded in an asymmetric manner, in which case, a fork lift that has symmetrically oriented forks may not be as efficient as possible.  
      Therefore, there is a need for a fork lift having forks that can be moved in a horizontal direction with respect to each other. There is also a need for a fork lift wherein the length of the forks is adjustable.  
     PRINCIPAL OBJECTS OF THE INVENTION  
      It is a main object of the present invention to provide a fork lift having forks that can be moved in a horizontal direction with respect to each other.  
      It is another object of the present invention to provide a fork lift having forks wherein the length of the forks is adjustable.  
     SUMMARY OF THE INVENTION  
      The improvements of the fork-type pallet-lifting device of the present invention comprise frame means, a steering wheel unit, a fork unit, fork-displacing means, hydraulic means, and control means.  
      The frame means includes a steering wheel-mounting mechanism having a vertically oriented axis, a fork-supporting means, and a horizontally oriented crossbar with an upper surface and with two sets of vertically oriented throughbores wherein the fork-supporting means includes: a horizontally oriented support element, first and second vertically oriented supporting elements suspended from the horizontally oriented support element, the first and second vertically oriented supporting elements being fixedly connected to the fork front end of a respective one of hereinafter described first and second fork elements, each of the vertically oriented supporting elements including a horizontally oriented plate having at least one throughbore, each plate being spaced adjacently to the upper surface of the crossbar wherein the at least one throughbore is alignable with a selected throughbore of a respective one of the two sets of throughbores, and a pair of pins, each removably insertable through the at least one throughbore of a respective one of the plates and through an aligned selected throughbore of a respective one of the two sets of throughbores to thereby selectively lock the lateral spacing of the hereinafter described first and second fork elements relative to each other.  
      The steering wheel unit is mounted to the steering wheel-mounting mechanism to pivot about the vertically oriented axis.  
      The fork unit, which is mounted to the fork-supporting means, includes opposing first and second fork elements, each having a fork front end and a fork rear end, wherein each of the opposing first and second fork elements includes a first fork portion, a second fork portion, and fastening means, and wherein the first and second fork portions are telescopically slidable longitudinally relative to each other, and wherein the fastening means selectively fixes the respective overall length of the first fork portion in combination with the second fork portion.  
      The fork-displacing means, which is mounted to the frame means, is structured to selectively and separately allow lateral displacement of the first and second fork elements relative to each other. The fork-displacing means includes the first and second vertically oriented supporting elements being slidably mounted on the horizontally oriented support element to thereby allow the first and second fork elements to be horizontally and laterally displaced relative to each other. The fork-displacing means further includes a pair of displacing handles, one mounted on each of the first and second vertically oriented supporting elements.  
      The hydraulic means, which is mounted to the frame means, includes supporting wheel means having opposing supporting wheels which, in cooperation with the steering wheel unit, is structured to selectively and vertically displace and suspend the first and second fork elements at a selected elevation above an underlying supporting surface; a horizontally oriented axle; a hydraulic motor structured to selectively rotate the horizontally oriented axle, and a linkage arrangement connecting the horizontally oriented axle to the opposing supporting wheels. The linkage arrangement includes a pair of first lever arms, each having a proximal end and a distal end; a pair of second lever arms, each having a proximal end and a distal end; a pair of third lever arms, each having a proximal end and a distal end; a pair of fourth lever arms, each having a proximal end and a distal end; and a pair of elongate links, each having a proximal end and a distal end, and each including a first link portion, a second link portion, and fastening means wherein the first and second link portions are slidable longitudinally relative to each other, and wherein the fastening means selectively fixes the respective overall length of the first link portion in combination with the second link portion, and wherein the proximal end of the first lever arm is longitudinally slidable along, but not radially pivotal about, the horizontally oriented axle; the distal end of the first lever arm is fixedly secured to the proximal end of the second lever arm, the distal end of the first lever arm and the proximal end of the second lever arm are pivotally connected to the frame means, the distal end of the third lever arm is fixedly secured to the proximal end of the fourth lever arm, the distal end of the third lever arm and the proximal end of the fourth lever arm are pivotally secured to a respective one of the first and second fork elements, each of the opposing supporting wheels is rotationally secured to the distal end of a respective one of the fourth lever arms, the relative lengths of the first and second lever arms and the angular relationship therebetween, and the relative lengths of the third and fourth lever arms and the angular relationship therebetween and relative to the lengths and angular relationship of the first and second lever arms are dimensioned such that the elevation of the fork front ends of the first and second fork elements above an underlying supporting surface is always substantially equal to the elevation of the fork rear ends of the first and second fork elements above the underlying supporting surface, and the proximal end of each of the elongate links is pivotally connected to the distal end of a respective one of the second lever arms and the distal end of each of the elongate links is pivotally connected to the proximal end of a respective one of the third lever arms.  
      The control means, which controls the hydraulic motor, includes a main handle pivotally mounted to the steering wheel-mounting mechanism about a horizontally oriented axis, the main handle being structured to activate the hydraulic motor, a biasing mechanism structured to bias the main handle to an upright position, and a release mechanism structured to cause the hydraulic motor to allow the horizontally oriented axle to freely rotate such that the first and second fork elements return to their lowermost positions. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
       FIG. 1  is a side elevational view of a pallet-lifting apparatus in accordance with the present invention.  
       FIG. 2  is a top plan view of the pallet-lifting apparatus.  
       FIG. 3  is an end elevational view of the pallet-lifting apparatus.  
       FIG. 4  is an enlarged and fragmentary, side elevational and cross-sectional view of a vertically oriented supporting element, a horizontally oriented plate, and a pin of the pallet-lifting apparatus.  
       FIG. 5  is a fragmentary top plan view of the pallet-lifting apparatus showing first and second fork elements thereof displaced inwardly toward each other to accommodate a narrow skid, and also showing the first and second fork elements retracted to accommodate a short skid.  
       FIG. 6  is a fragmentary top plan view of the pallet-lifting apparatus showing the first and second fork elements thereof displaced outwardly away from each other to accommodate a wide skid, and also showing the first and second fork elements extended to accommodate a long skid.  
       FIG. 7  is a fragmentary side elevational view with parts removed for purposes of clarity, showing the pallet-lifting apparatus lowered relative to an underlying supporting surface.  
       FIG. 8  is a fragmentary side elevational view with parts removed for purposes of clarity, showing the pallet-lifting apparatus elevated relative to an underlying supporting surface.  
       FIG. 9  is an enlarged and fragmentary top plan view with portions cut away to reveal details of a fastening means of one of the fork elements of the pallet-lifting apparatus, in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Other objects, features and advantages of the invention will become apparent from a consideration of the following detailed description and the accompanying drawings.  
      A fork-type pallet-lifting apparatus  10  as shown in  FIGS. 1 through 9 . The pallet-lifting apparatus  10  includes frame means  13 , a steering wheel unit  15 , a fork unit  17 , fork-displacing means  19 , hydraulic means  21 , and control means  23 .  
      The frame means  13  includes a steering wheel-mounting mechanism  29  having a vertically oriented axis  31  and a fork-supporting means  33 , which includes a horizontally oriented support element  35  and a horizontally oriented crossbar  37 . The steering wheel unit  15  is mounted to the steering wheel-mounting mechanism  29  to pivot about the vertically oriented axis  31 .  
      The fork unit  17  is mounted on the fork-supporting means  33  and includes opposing first and second fork elements  41 ,  43 , each having a fork front end  45  and a fork rear end  47 . The fork-supporting means  31  includes first and second vertically oriented supporting elements  49 ,  51 , which are suspended from the horizontally oriented support element  35  and which are fixedly connected to the fork front end  45  of a respective one of the first and second fork elements  41 ,  43 .  
      The fork-displacing means  19  includes the first and second vertically oriented supporting elements  49 ,  51  being slidably mounted on the horizontally oriented support element  35  to thereby selectively and separately allow horizontal lateral displacement of the first and second fork elements  41 ,  43  relative to each other.  FIGS. 1, 3  and  5  show the first and second fork elements  41 ,  43  moved inwardly toward each other in order to accommodate a narrow skid, and  FIG. 6  shows the first and second fork elements  41 ,  43  displaced outwardly away from each other in order to accommodate a wide skid. The fork-displacing means  19  includes a pair of displacing handles  53 , one mounted on each of the first and second vertically oriented supporting elements  49 ,  51  for slidably displacing the respective first and second vertically oriented supporting elements  49 ,  51  horizontally along the horizontally oriented support element  35 .  
      Each of the first and second vertically oriented supporting elements  49 ,  51  has a horizontally oriented plate  55  spaced adjacently to an upper surface  57  of the crossbar  37 . Each of the plates  55  has at least one throughbore  59  that can be aligned with selected ones of corresponding sets of vertically oriented throughbores  63 ,  65  through the crossbar  37 . A pair of pins  67  are removably inserted through bores  59  and through selected ones of the sets of bores  63 ,  65 , to thereby selectively lock the lateral spacing of the first and second fork elements  41 ,  43  relative to each other.  
      The hydraulic means  21  is mounted on the frame means  13  and includes supporting wheel means  71  which, in cooperation with the steering wheel unit  15 , is structured to suspend the first and second fork elements  41 ,  43  at a selected elevation above an underlying supporting surface  73 . The hydraulic means  21  is structured to selectively and vertically displace the first and second fork elements  41 ,  43  relative to the underlying supporting surface  73 .  
      The hydraulic means  21  includes a hydraulic motor  75 , that is structured to selectively rotate a horizontally oriented axle  77 , the supporting wheel means  71  which includes opposing supporting wheels  81 , and a linkage arrangement  83 . The linkage arrangement  83  includes a pair of first lever arms  85 , each having a proximal end  87  and a distal end  89 , and a pair of second lever arms  91 , each having a proximal end  93  and a distal end  95 . The distal end  89  of each first lever arm  85  is fixedly secured to the proximal end  93  of the respective second lever arm  91 . The proximal end  87  of each first lever arm  85  is longitudinally slidable along, but not radially pivotal about, the horizontally oriented axle  77 . For example, the cross-section of the axle  77  is non-circular or ribbed, or has any other cross-sectional profile that prevents rotation of the first lever arms  85  relative to the axle  77 . The distal end  89  of each first lever arm  85  and the proximal end  93  of the respective second lever arm  91  are pivotally connected to the frame means  13  about an axis  97 .  
      The linkage arrangement  83  also includes a pair of third lever arms  101 , each having a proximal end  103  and a distal end  105 , and a pair of fourth lever arms  107 , each having a proximal end  109  and a distal end  111 . The distal end  105  of each third lever arm  101  is fixedly secured to the proximal end  109  of the respective fourth lever arm  107 . The distal end  105  of each third lever arm  101  and the respective proximal end  109  of the fourth lever arm  107  are pivotally secured to a respective one of the first and second fork elements  41 ,  43  about an axis  113 . Each of the opposing supporting wheels  81  is rotationally secured to the distal end  111  of a respective one of the fourth lever arms  107 .  
      The relative lengths of the first and second lever arms  85 ,  91  and the angular relationship therebetween, and the relative lengths of the third and fourth lever arms  101 ,  107  and the angular relationship therebetween and relative to the lengths and angular relationship of the first and second lever arms  85 ,  91 , are dimensioned such that the elevation of the fork front ends  45  of the first and second fork elements  41 ,  43  above the underlying supporting surface  73  is always substantially equal to the elevation of the fork rear ends  47  of the first and second fork elements  41 ,  43  above the underlying supporting surface  73 .  
      The linkage arrangement  83  further includes a pair of elongate links  115 , each having a proximal end  117  and a distal end  119 . The proximal end  117  of each of the elongate links  115  is pivotally connected to the distal end  95  of a respective one of the second lever arms  91 , and the distal end  119  of each of the elongate links  115  is pivotally connected to the proximal end  103  of a respective one of the third lever arms  101 . Each elongate link  115  comprises a first link portion  121  and a second link portion  123  that are slidable longitudinally relative to each other. First fastening means  125 , such as a bolt and nut through appropriately spaced throughbores for example, selectively fixes the respective overall length of the elongate links  115 .  
      Each of the first and second fork elements  41 ,  43  comprises a first fork portion  127  and a second fork portion  129  that are telescopically slidable longitudinally relative to each other. Second fastening means  131  selectively fixes the respective overall length of the first and second fork elements  41 ,  43 . An example of the second fastening means  131  is shown in  FIG. 9 .  
      The control means  23  is structured to control the hydraulic means  21  and includes a main handle  133  pivotally mounted to the steering wheel-mounting mechanism  29  about a horizontally oriented axis  135 . A biasing mechanism  137 , such as a compression coil spring  139 , is structured to bias the handle  133  to an upright position, as shown in  FIG. 1 . The control means  23  includes a release mechanism  141  that is structured to cause the hydraulic motor  75  to allow the horizontally oriented axle  77  to freely rotate such that the first and second fork elements  41 ,  43  return to their lowermost positions, as shown in  FIGS. 1 and 7 .  
      In an application of the present invention, the first and second fastening means  125 ,  131  are used to adjust the lengths of the elongate links  115  and the lengths of the first and second fork elements  41 ,  43  to accommodate the lengths of short skids (see  FIG. 4 ) and long skids (see  FIG. 5 ) to be handled by the pallet-lifting apparatus  10 . Similarly, the pins  67  are temporarily removed from the bores  59 ,  63 ,  65  to adjust the distance between the first and second fork elements  41 ,  43  by pulling or pushing on the displacing handles  53 , thereby sliding the proximal ends  87  of the first lever arms  85  along the axle  77  in order to accommodate the widths of narrow skids (see  FIGS. 2, 3  and  5 ) and wide skids (see  FIG. 6 ) to be handled by the pallet-lifting apparatus  10 . With the elevation of the first and second fork elements  41 ,  43  in their lowermost position (see  FIGS. 1 and 7 ) and using the main handle  133  to steer and maneuver the first and second fork elements  41 ,  43  into the void of a skid to be handled by the pallet-lifting apparatus  10 , the release mechanism  141  is closed, and the main handle  133  is pumped up and down, causing the hydraulic motor  75  to rotate the horizontally oriented axle  77 , thereby elevating the first and second fork elements  41 ,  43  and accordingly lifting the skid clear of the underlying supporting surface  73  (see  FIG. 8 ). After the skid has been relocated as desired, the release mechanism  141  is opened, allowing the first and second skid elements  41 ,  43  to return to their lowermost positions. The main handle  133  is then used to pull the pallet-lifting apparatus  10  from the void of the skid.  
      It is to be understood that while certain forms of the present invention have been illustrated and described herein, it is not to be limited to the specific forms or arrangements of parts described and shown.