Abstract:
A steering device for decreasing a turning radius of a pallet jack is disclosed. The steering device comprises a first portion fixedly connected to the pallet jack between a main wheel and the extensible roller thereof. A second portion pivotally attaches to the first portion. A spring disposed within the first portion urges the second portion to remain in a selected position. A wheel disposes within the second portion. Positioning the pallet jack towards the lowered position, the wheel engages the ground causing the extensible roller to disengage the ground whereupon the main wheel and the wheel define a second turning radius which is lesser than the first turning radius. Upon the wheel contacting a lower cross member of a pallet, the second portion is urged against the biasing force of the spring to pivot relatively upwards and over the lower cross member.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/176,185 entitled STEERING DEVICE FOR PALLET TRUCK, filed on 7 May 2009, which is hereby incorporated herein by reference. 
    
    
     BACKGROUND OF INVENTION 
     The present invention generally relates to pallet jacks. In particular, the present invention relates to a device for decreasing a turning radius of a pallet jack. 
     In the art of material handling, pallets jacks (or pallet trucks) typically include wheeled devices intended for the manual lifting of a pallet, with a load resting thereon, to transport the pallet and load from one work area to another. U.S. Pat. No. 4,589,669 discloses an exemplary pallet jack, or hydraulic pallet truck. Pallet jacks typically include forked support arms upon which extensible rollers are mounted at terminal ends. The opposing ends of the forked support arms are typically connected to one another and attached in some fashion to a pivotal wheel with a hydraulic lift. The pivotal wheel allows the user to steer the pallet jack when either pushing or pulling the pallet jack. The hydraulic lift is operatively connected the wheel and the extensible rollers to raise and lower the support arms to engage and transport the pallet or to disengage the pallet jack from the pallet. 
     Due to the relatively heavy loads pallet jacks are intended to transport, and the size of the pallets themselves, the length of the forked arms are designed to provide the greatest support and stability when in contact with the pallets. Therefore, to maximize stability, the roller of each fork is terminally positioned on each fork to maximize the distance each roller is from the main wheel. However, by positioning the rollers at such a distance from the main wheel, the pallet jack is sometimes difficult to steer in tight or crowded work areas due to the fact that the turning radius of the pallet jack is defined by the distance between the main wheel and the rollers. The turning radius of the pallet jack becomes especially problematic when the work area does not provide for adequate space, as is the case with crowded warehouses or storerooms. Also, because the steerable wheel is positioned at one end and the rollers are positioned at the opposite end, the center of curvature of the pallet jack is virtually positioned between the rollers at the terminal ends of the forked arms. Therefore, positioning the forked arms to engage the pallet is made difficult because very little lateral movement occurs at the terminal ends of the forked arms relative to lateral movement made at the opposing end having the main steering wheel. 
     U.S. Pat. Nos. 7,226,060 and 7,427,075 teach the use of a device for decreasing the turn radius of an empty pallet jack. It has been discovered, though, that such devices have a tendency to impede the ability of inserting the support arms of a pallet jack within certain pallets for the lifting and moving thereof. As most pallets commonly include a lower cross-beam over which the support arms of the pallet jack must travel to position the pallet jack to lift the pallet, the rigid devices as taught in the aforementioned patents are sometimes difficult to pass over said cross-beams. 
     BRIEF SUMMARY OF INVENTION 
     The present invention includes a device attachable to a pallet jack for facilitating steering and positioning of the pallet jack while in a lowered position. The device includes a first member fixable to an underside of a support leg of the pallet jack. A second member containing a roller or wheel for contacting the ground pivotally attaches to the first member. A spring disposed within the first member provides bias against the second member to maintain the second member at a first position relative to the second member. The second housing member further includes a forward skid plate for contacting and slidably disposing upon a lower cross-beam of a pallet structure. 
     The pallet jack is positionable between a raised position and a lowered position by means of a hydraulic mechanism. The hydraulic mechanism connects to a main wheel and extensible rollers terminally positioned on each support leg. While in the raised position, the extensible rollers and the main wheel contact the ground, defining a first turning radius of the pallet jack. Upon lowering the pallet jack, the roller of each steering device engages the ground while the extensible rollers disengage the ground. Because the steering device is positioned between the main wheel and the terminally positioned extensible rollers, the resulting turning radius of the pallet jack is decreased thus allowing for better control and positioning of the pallet jack. 
     When positioning the pallet jack to engage a pallet, the extensible wheels are positioned slightly off the ground and each leg is inserted within the pallet structure between a bottom base board and upper supporting board. Upon positioning each leg further within the pallet structure, the forward skid plate of each steering device engages the bottom base board of the pallet structure. Upon applying appropriate force and further positioning the pallet jack within the pallet structure, the biasing force of the spring against the second member is overcome and the second member is urged upward relative to the ground to permit the second member and wheel to travel over the bottom base board. Upon traveling past the bottom base board, the second member is urged by the bias force of the spring back to its home position and the pallet jack is fully positionable within the pallet structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a steering device of the present invention. 
         FIG. 2  is a perspective exploded view of a steering device of the present invention. 
         FIG. 3  is a perspective view of a pallet jack utilizing the steering device of the present invention before engaging a pallet. 
         FIG. 4  is a perspective view of an underside of a pallet jack with the steering device of the present invention. 
         FIG. 5  is a cross-sectional view of a support member containing the steering device of the present invention. 
         FIG. 6  is a side profile view of a support member of a pallet jack containing a device of the present invention attached thereto upon being inserted into a pallet. 
         FIG. 7  is a side profile view of a support member of a pallet jack containing a device of the present invention being urged upward and over a lower board of a pallet. 
         FIG. 8  is a side-view of a pallet jack in a raised position and a lowered position (dashed lines). 
     
    
    
     DETAILED DESCRIPTION 
     A steering device of the present invention is generally indicated at  10  in  FIGS. 1 and 2 . The steering device  10  is preferably used in conjunction with material handling equipment, for example, a pallet jack  12  as illustrated in  FIG. 3 . The pallet jack  12 , or hydraulic pallet truck, is a material handling device known to those skilled in the art of material handling for moving pallets  14  within a work area, such as a warehouse, storage room or within a manufacturing facility. For purposes of the present description, an exemplary pallet jack  12  includes leg members  16  having extensible rollers  18  attached to an A-frame  20  having a positionable main wheel  22 . A hydraulic lifting mechanism  24  for raising and lowering the pallet jack  12  connects to the main wheel  22  and the extensible rollers  18 . In the lowered position, the pallet jack  12  can be positioned such that the leg members  16  are disposable within the pallet  14  resting on the ground. Actuating the hydraulic lifting mechanism  24  positions the pallet jack  12  toward the raised position resulting in the leg members  16  engaging the pallet  14  and lifting the pallet  14  from the ground, whereby the pallet  14  can be transported to the desired portion of the work area. 
     Referring back to  FIGS. 1 and 2 , the steering device  10  of the present invention includes a base member  26  attachable to an underside of a leg member  16 . The base member  26  generally includes a first half  28   a  and a corresponding second half  28   b  locked together by a key  30 . The key  30  is generally “L”-shaped and includes a vertical locking tab  32  and horizontal locking tabs  34  extending therefrom. Each half  28   a ,  28   b  is constructed to include a top portion  36   a  and  36   b , respectively, with a downwardly extending wall  38   a  and  38   b , respectively. Rectangular apertures  40   a  and  40   b , respectively, are positioned through each wall  38   a ,  38   b  to receive the horizontal locking tabs  34  extending from the key  30  while apertures  42   a  and  42   b , respectively, are positioned on the top portion  36   a ,  36   b  of each half  28   a ,  28   b  to receive the vertical tab  32 . Apertures  43   a  and  43   b , respectively, are positioned within the top portions  36   a ,  36   b  of each half  28   a ,  28   b  to permit corresponding bolts  44  to be fitted through apertures  45  machined in the leg member and threadably engage burrs  46 . 
     The steering device  10  of the present invention further includes a positionable member  48  pivotally connected to the base member  26 . The positionable member  48  contains a wheel or roller  50  for engagement with the ground when the pallet jack  12  is in a lowered position and not carrying a load. The wheel  50  rotatably attaches to and disposes between opposing side walls  52  by means of an axial member  54  and corresponding screws  56 . It should be noted, however, that other attaching means known to those skilled in the art is well within the scope of the present invention. 
     The second positional member  48  pivotally attaches to the first base member  26  by means of a machined spacer  58  and an axial member  60 . As best shown in  FIG. 2 , the machined spacer  58  includes a central portion  62  having a first diameter, as well as terminal portions  64  of lesser diameter. Each wall  38   a ,  38   b  of the base member  26  contains opposing apertures  66   a  and  66   b , respectively, to receive the terminal portions  64  of the spacer  58 , and the central portion  62  of the spacer  58  abuts against opposing inner surfaces  68  of the base member walls  38   a ,  38   b  thereby providing support to the walls and preventing any inward biasing. A through-bore  70  contained within the spacer  58  receives the axial member  60 . Each wall  52  of the positionable member  48  in turn contains an aperture  74  for accepting the respective terminal ends  72  of the axial member  60 , thereby securing the positional member  48  to the base member  26 . This arrangement permits the pivotal movement of the positionable member  48  about the base member  26  without the walls  38   a ,  38   b  of the base member  26  engaging with the walls  52  of the positionable member  48 , and vice versa. However, to limit the amount of travel the positionable member  48  is permitted about the base member  26 , each wall  38   a ,  38   b  of the base member  26  contains slotted apertures  76   a  and  76   b , respectively, for receiving a guide post  78  extending between each wall  36   a ,  36   b  of the base member. Terminal ends  80  of the guidepost  78  seat within opposing apertures  82  of the positionable member  48 . The guidepost  78  slidably engages each slotted aperture  76   a ,  76   b  which defines end limits of the positioning of the positionable member  48 . 
     To retain the positionable member  48  at one of the end limits, or home position, a spring  84  is provided to exert a biasing force against the positionable member  48 . As shown in  FIG. 2 , a proximal end  86  of the spring  84  connects to the base member  26  and the positionable member  48  by means of a cap member  88  disposed on the guide post  78 . A nub  90  extending from the cap  88  disposes partially within the proximal end  86  of the spring  84 . An opposing distal end  92  of the spring  84  abuts against a lower leg  94  of the key  30 . When positioned against the lower leg  94  and the cap member  88 , the spring  84  is compressed and provides a biasing force against the positionable member  48 . This biasing force urges the guidepost  78  to engage each slotted aperture  76   a ,  76   b  at the end limit, or home position. 
     The compressive force of the spring  84  also assists in locking the halves  28   a ,  28   b  together by means of the key  30 . As described, the key  30  contains both vertical  32  and horizontal tabs  34 . When assembling the base member  26 , the two halves  28   a ,  28   b  are brought together, along with the spring  84 , cap member  88 , key  30 , spacer  58  and axial member  60 . The key  30 , the lower leg  94  of which is abutted against the spring  84 , is then positioned to align the vertical tab  32  with its respective apertures  42   a ,  42   b  and the horizontal tabs  34  with their respective slots  40   a ,  40   b . In so positioning the key  30 , the spring  84  is compressed. Upon further positioning the key  30  to compress the spring  84 , the horizontal tabs  34  travel to align with their respective slots  40   a ,  40   b . When proper alignment of the key  30  occurs, the two halves  28   a ,  28   b  are positioned further inward to dispose the horizontal tabs  34  of the key  30  within their respective slots  40   a ,  40   b . The key  30  is then released which causes the biasing force of the spring  84  to urge the walls  38   a ,  38   b  between hooked portions  96  of the horizontal tabs  34 , thereby locking the two halves  28   a ,  28   b  together. 
     The second positionable member  48  further includes a forward skid plate  98  and rearward skid plate  100 . Each skid plate  98 ,  100  extends between each side wall  52 . Each skid plate  98 ,  100  is constructed in such a fashion to be at an angle relative to the horizontal when the device  10  is attached to a leg  16  of the pallet jack  12 . The wheel  50  is positioned between each skid plate  98 ,  100  and extends past walls  52  of the positionable member so that engagement with the ground is possible without the walls  52  or either skid plate  98 ,  100  contacting the ground. The skid plates  98 ,  100  are designed to engage a lower board member  102  of the pallet  14  upon positioning the pallet jack  12  to engage or disengage the pallet  14 , as will be discussed in further detail. 
     The steering device  10  of the present invention is designed to affix to an underside of each fork member  16 , as illustrated in  FIGS. 4 and 5 . It is preferable that a single steering device  10  be attached to each fork member  16 , but not absolutely necessary to practice the present invention. When attaching the steering device  10  onto each fork member  16 , it is preferable to position each steering device  10  directly opposite one another. It is also preferable to position each steering device  10  approximately half the distance between the extensible roller  18  of each arm and the main wheel  22 , however, each steering device  10  can be positioned opposite one another at any desirable point along the underside of the respective fork member  16 . 
     As illustrated in  FIG. 5 , each fork member  16  is typically formed to include downwardly extending side members  104  to provide overall rigid support to the fork member  16 . The downwardly extending side members  104  include flange portions  106  extending therefrom. Disposed along a center underportion of each fork member  16  is a connecting member  108  which operatively connects the hydraulic lifting mechanism  24  with the respective extensible roller  18 . As described, each device is preferably bolted to the underside of each leg, but other means of attachment are well within the scope of the present invention, including welding or riveting. 
     As illustrated in  FIG. 3 , when engaging the pallet  14 , the pallet jack  12  is positioned such that the pallet  14  is capable of receiving each leg  16  of the pallet jack  12 . As illustrated in  FIG. 6 , upon inserting each leg  16  within the pallet  14  structure, the forward skid plate  98  engages the lower board member  102  of the pallet  14 . Further positioning of each leg  16  into the pallet  14  causes the skid plate  98  to urge the positionable member  48  relatively upwards against the biasing force of the spring  84 . Thus, in instances where the gap between the bottom board  102  and upper board  110  of the pallet  14  into which each leg  16  is being inserted is less than the height of each leg  16  with the wheel  50  of the device  10  engaging the ground, the positionable member  48  is permitted to be urged upward and over the lower board member  102 , as is illustrated in  FIG. 7 . Also, upon removing the pallet jack  12  from the pallet  14 , the rear skid plate  100  performs the same function when engaging the lower board member  102 , thereby allowing the positionable member  48  to be urged up and over the board member  102  against the biasing force of the spring  84 . Upon removal of the pallet jack  12  from the pallet  14 , the biasing force of the spring  84  urges the positionable member  48  back to the home position. The biasing force provided by the spring  84  is such that the positionable member  48  will remain at the home position when the pallet jack  12  is lowered and the wheel  50  is engaged with the ground. 
     In operation, and as exemplified in  FIG. 8 , the pallet jack  12  is positionable between a raised position and a lowered position (dashed lines). As is known in the art, while in the raised position, the extensible roller  18  of each leg  16  and the main wheel  22  contact the ground and the steering device  10  is disengaged from the ground. This permits the pallet jack  12  to be used in a conventional manner when transporting pallets  14 . As such, the turning radius of the pallet jack  12  while in the raised position is defined by the distance between the main wheel  22  and the extensible rollers  18 . However, upon lowering the pallet jack  12 , the wheels  50  from each steering device  10  contact the ground, and further actuation from the lifting mechanism  24  causes the respective extensible roller  18  to be drawn up even further and eventually disengage from the ground. At this point, only the rollers  50  of the respective steering device  10  and the main wheel  22  contact the ground. Thus, upon lowering the pallet jack  12  a new turning radius is defined by the distance between the positioning of the steering devices  10  and the main wheel  22 . Because the steering devices  10  are positioned closer to the main wheel  22  than the extensible rollers  18 , the turning radius of the pallet jack  12  is decreased. The decreased turning radius permits the pallet jack to be more maneuverable, especially in tight or congested spaces. 
     When the pallet jack  12  is in the lowered position, the steering device  10  is in contact with the ground and the rollers  50  permit the pallet jack  12  to be pushed or pulled in much the same manner as when the extensible rollers  18  are in contact with the ground. Each device  50 , by way of the spring  84 , also provides shock absorbing qualities which make the positioning of the pallet jack  12  much smoother. When in the lowered position, the pallet jack  12  is also maneuverable to pivot about the steering devices  10  with relation to the main wheel  22 . This facilitates in positioning of the pallet jack  12  to align the legs  16  with pallet  14 . Also, when the steering devices  10  are positioned on each leg member  16  in the preferred position, the turning radius of the pallet jack  12  is approximately halved in comparison to the turning radius of the pallet jack  12  when it is in the raised position. In that respect, the steering device  10  of the present invention acts in much the same manner as described in commonly owned U.S. Pat. Nos. 7,226,060, 7,427,075 and 7,475,887, each of which are hereby incorporated herein by reference. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.