Abstract:
A detachable push plate assembly for hand trucks is disclosed. A user applies downward pressure on a lever arm causing a push plate to move forward and discharge cargo, or to discharge the hand truck out from underneath cargo from the bottom of the hand truck. The push plate assembly comprises four major components: a one piece integral housing; a push plate; a projection bar connected to the push plate; and a one piece pedal assembly coupled to the projection bar. The assembly also comprises a spring that biases the push plate to a retracted position when not in use, and a wear plate or shim to prevent deterioration of the housing base. Alternatively, the push plate assembly may have an electrically driven gear wheel engaging the projection bar, the limits of travel being defined by a limit switch actuated by stops on the gear wheel.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This Application is a Continuation-in-part of application Ser. No. 09/878,049 “Push Plate Assembly”, filed on Jun. 8, 2001, in the name of Joseph Boyanich. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates to assemblies that attach to existing pushcarts and that make it easier for a user to discharge cargo from the bottom chisel plate of a pushcart. It relates in particular to electrically actuated assemblies.  
         BACKGROUND OF THE INVENTION  
         [0003]    Over the years many designs for hand trucks have been created. Some of these have included devices or assemblies incorporated for the purpose of easing the unloading of freight from hand trucks. Some of these assemblies were freestanding contraptions.  
           [0004]    A problem with past push plate assemblies was the expense of producing the push plate assembly. The previous assemblies were costly to manufacture and it was difficult to alter the original design of the assemblies without incurring more costs.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention is an assembly that may be attached to a variety of different hand trucks to ease the unloading of freight such as a box or carton from the chisel of the hand truck. A user may operate it by applying downward pressure on a lever arm. The push plate is connected to the arm and moves forward so as to discharge cargo from the chisel. Alternatively, a foot pedal may be used in place of the lever. A spring then returns the push plate to a rest position at the rear of the chisel. In yet a further alternative, the lever or foot pedal may be replaced by an electric motor operating a gear operably connected to the push plate.  
           [0006]    The advantage of the current invention is that it has a lower production cost, because the housing and pedal assembly are each one-piece. They are each stamped out of a sheet of metal and then molded to a desired shape. The entire push plate assembly comprises four major components: (1) a one piece integral housing, (2) a push plate, (3) a rack connected to the push plate, and (4) a one piece pedal assembly. The invention also includes a spring to return the push plate to a rest position, and a wearplate or shim to prevent deterioration of the housing base. However, neither addition is necessary to operate the assembly. They simply make operation more convenient. With the electrically actuated push plate, the gear has cams that trip a limit switch to define the extremes of travel of the push plate. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a perspective view of a housing of a push plate assembly for a hand truck;  
         [0008]    [0008]FIG. 2 is a perspective view of a push plate with a projection bar attached thereto in a first embodiment of the invention;  
         [0009]    [0009]FIG. 3 is a side view of a pedal assembly in the first embodiment;  
         [0010]    [0010]FIG. 4 is a perspective view of the housing showing the insertion of the projection bar therein in the first embodiment;  
         [0011]    [0011]FIG. 5 is a partially cut away side view of the first embodiment of the push plate assembly;  
         [0012]    [0012]FIG. 6 is a side view of a pedal assembly in the second embodiment;  
         [0013]    [0013]FIG. 7 is a cross-section viewed along  7 - 7  of FIG. 6;  
         [0014]    [0014]FIG. 8 is a perspective view of a portion of the projection bar in the second embodiment, showing also a portion of a cable engaged therewith;  
         [0015]    [0015]FIG. 9 is a perspective view of a cable bracket affixed to an end of the cable;  
         [0016]    [0016]FIG. 10 is a partially cut away side view of the second embodiment of the push plate assembly;  
         [0017]    [0017]FIG. 11 is a rear view of the housing;  
         [0018]    [0018]FIG. 12 is a rear view of the first embodiment of the push plate assembly;  
         [0019]    [0019]FIG. 13 is a rear view of the push plate assembly attached to the hand truck;  
         [0020]    [0020]FIG. 14 is a top view of a portion of the housing and attachment members for securing the housing to the hand truck;  
         [0021]    [0021]FIG. 15 is a side view of the push plate assembly attached to the hand truck, with the push plate in a retracted position;  
         [0022]    [0022]FIG. 16 is a side view of the push plate assembly attached to the hand truck, with the push plate in an extended position;  
         [0023]    [0023]FIG. 17 is a side view of the hand truck with the push plate assembly configured to transport an elongate load;  
         [0024]    [0024]FIG. 18 is a side view of the hand truck with the push plate assembly configured to transport an oversized load;  
         [0025]    [0025]FIG. 19 is a top view of a blank for fabricating the housing;  
         [0026]    [0026]FIG. 20 shows elements of the second embodiment, including an upwardly curved projection bar in the retracted position;  
         [0027]    [0027]FIG. 21 shows elements of the second embodiment, including the upwardly curved projection bar in the extended position;  
         [0028]    [0028]FIG. 22 is a rear view of portion of a third embodiment wherein an electrically driven gear wheel engages the projection bar;  
         [0029]    [0029]FIG. 23 is a partially cut away side view of a portion the third embodiment;  
         [0030]    [0030]FIG. 24 is a similar view to FIG. 23, showing also a propulsion gear, with the gear wheel in a push position;  
         [0031]    [0031]FIG. 25 is the view of FIG. 24, showing the gear wheel in a drive position. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0032]    Referring to the drawings, all of which are schematic and not necessarily to a consistent scale, the present invention is a push plate assembly  100  for a typical hand truck  110  with spaced struts  112 , a bottom chisel  114  and wheels  116 . It is essentially directed to a mechanism for moving an upright push plate  120  between retracted position and an extended position. Actuation of the push plate  120  assists in discharging cargo from the hand truck  110 .  
         [0033]    The push plate  120  is arranged generally parallel with the axis of the wheels  116 . Its lower edge is closely spaced to the top face of the load-carrying tongue or chisel  114  of the hand truck  110 . This push plate  120  preferably extends sideways to an extent to be in front of the wheels  116 . It is essentially a rectangular ⅛″ steel plate, having stamped indentations  122  such as those shown in FIG. 2 which provide enhanced strength. A housing  140  essentially carries a mechanism for projecting the push plate  120 . This mechanism has a projection bar  160  and a pedal assembly  180 . The housing  140  can be removably secured to the hand truck frame, so as to permit the push plate  120 , together with the actuating mechanism of the present invention, to be sold as an accessory for existing hand trucks. In a first embodiment, the projection bar  160  and the pedal assembly  180  engage through a rack-and-pinion mechanism. In a second embodiment, the projection bar  160  and the pedal assembly  180  would be coupled with a length of flexible cable  220 .  
         [0034]    The housing  140  is an integral, solitary piece of material. It is made from a ⅛″ thick stamped steel plate, which is cut to produce a blank  200  illustrated in FIG. 19. The blank  200  is then bent and shaped until it reaches the final configuration shown in FIG. 1.  
         [0035]    The housing  140  includes a pair of flanges  142 , a pair of sidewalls  144 , a bottom  146  and a pair of opposed pedal mounts  148 . The sidewalls  144  and the bottom  146  form an open-ended channel  150  for accommodating the projection bar  160  and the pedal assembly  180 .  
         [0036]    The flanges  142  are sized to contact the struts  112  of the hand truck  110 . Note that each flange  142  has an extension  152  having a hole  156 .  
         [0037]    As shown in FIG. 19, the blank  200  from which the housing  140  is formed is a generally rectangular flat piece of rigid sheet metal having opposed first edges  204  and opposed second edges  208 . By rigid is meant that the material holds its shape absent an externally applied force but that it can be bent or shaped by applying a force of the magnitude which is typically applied in sheet metal working. A generally rectangular recess  202  extends from one of the second edges  208  is symmetrically disposed between the first edges  204 . Each of a pair of first bend lines  206  defines the boundary between one of the intended sidewalls  144  and the intended bottom  146 . They extend from the recess  202  to the non-recessed second edge  208 . Each of a pair of second bend lines  210  defines the boundary between a sidewall  144  and a corresponding flange  142 . The extensions  152  are joined to the first edges  204 , and are partly separated therefrom by slits  158 .  
         [0038]    To form the housing  140 , the blank  200  is bent along the first bend lines  206  until the sidewalls  144  are essentially parallel with each other. As depicted in FIG. 19, the intended sidewalls  144  would be bent towards the viewer. Assuming, only for descriptive purposes that the blank  200  is still flat as depicted in FIG. 19, the sidewalls  144  and flanges  142  would then be bent away from the second bend lines  210  relative to the viewer. Note that in the performance of this operation, each extension  152  remains entirely coplanar with its corresponding flange  142 , as is permitted by the existence of the slits  158 .  
         [0039]    It is understood that while the bottom  146  is shown in the drawings as being essentially flat, it can equally well be curved; instead of forming a right angle along each of the first bend lines  206 , the bending operation can instead lead to a smooth curvature between the first bend lines  206 , the final shape nevertheless providing that the sidewalls  144  are essentially parallel.  
         [0040]    On completion of the bending operation, the extensions  152  overlap so that holes  156  are aligned, allowing the flanges  142  to be secured together with a fastener such as a bolt  159 . It is understood, however, that the flanges  142  could equally well be secured by other means such as welding together the extensions  152 .  
         [0041]    The one-piece pedal assembly  180  is stamped from one sheet of metal. It includes a drive segment  182  and a lever or treadle  184 . The lever  184  includes a twist  186 , which is added after the pedal assembly  180  is stamped to correctly orient a foot-bearing surface  188  and also to provide structural strength. The assembly  180  could equally well be designed to operate with a hand lever.  
         [0042]    The projection bar  160  projects forwardly beyond the housing  140 , and is secured by one or more pins  124  to a bracket  126  attached to the rear of the push plate  120  and projecting rearwardly therefrom. This method of attachment provides for convenient replacement of either the push plate  120  or the projection bar, should there be a need to replace only one of these components. If this is of no concern, the projection bar  160  can simply be welded to the bracket  126  or directly to the push plate  120 .  
         [0043]    When only one pin  124  is used, it is oriented transversely across the width of the projection bar  160 , and the push plate may pivot about the pin  124 . Beneath the pin  124 , a stop  128 , which is L-shaped in cross section, is welded or suitably secured to the back of the push plate  120  so that it can contact the bottom of the projection bar  160 . As will be seen later, the ability of the push plate  120  to pivot enhances the ability to handle bulky objects. In the remainder of this disclosure, it is understood that a single pin  124  is used and that the push plate  120  is therefore free to pivot.  
         [0044]    The projection bar  160  slides over the bottom  146  of the housing  140  between the two flanges  142 . Resting on the bottom  146  is a wear plate or shim  154 , preferably made of bearing metal. The shim also has two flaps, one at either end, that hold it in place while the projection bar  160  slides back and forth across the top of it. The end flanges are used to secure the shim into place on the housing  140  during movement of the projection bar  160 .  
         [0045]    In a rest or retracted position, the stop  128  is removably engaged with the bottom of the projection bar  160  and is normally held in engagement with the projection bar  160  by a helical tension return spring  170 . When the push plate  120  pivots about the pin  124 , it can do so in only one direction starting from its normal position essentially parallel to the chisel  114  as indicated in FIG. 16, removing the stop  128  from contact with the projection bar  160 . The stop  128  precludes rotation in the opposite direction. The spring  170  is arranged below the housing  140  and has its back end hooked through an opening  172  in a spring mount  174  projecting from the housing bottom  146 . The spring mount  174  is essentially stamped as an indentation in the metal of the housing  140 .  
         [0046]    The front end of the spring  170  is hooked through a hole  178  of an attachment member  176  which is welded to the push plate  120  directly beneath the stop  128 . It is understood, however, that other methods may be used to attach the spring  170  to the housing  140  and the push plate  120 .  
         [0047]    The pedal assembly  180  pivots about an axle  192 , which extends between the pedal mounts  148 . The lever  184  actuates the drive segment  182 .  
         [0048]    Alternative dispositions of the spring  170  are possible. For example, it may be housed in a spiral fashion, with one end anchored at the axle  192  and the other end anchored to a point of the pedal assembly  180  spaced apart therefrom.  
         [0049]    In the first embodiment, the drive segment  182  has teeth  190  which mesh with teeth  162  which project upwardly form the projection bar  160 .  
         [0050]    In the second embodiment, the drive segment  182  has a perimeter groove  230 , which can receive the flexible cable  220 , as indicated in FIGS. 6 and 7. The cable typically has multiple twisted individual strands of wire. The projection bar  160  has an upwardly facing groove  232  to receive the cable  220  as shown in FIG. 8. As indicated in FIGS.  9 , the ends of the cable  220  are fixedly attached to cable brackets  222 , for example by welding or crimping. One bracket  222  is attached to the drive segment  182  and the opposed bracket is attached to the projection bar  160 . The brackets are attached for example by clamping or bolting to the appropriate member. Other methods may be used to attach the cable to the drive segment  182  or projection bar  160 , for example by passing the cable through an opening and securing it by forming a securely closed loop. The cable is sized so that no significant slack is present when the push plate  120  is in the retracted position.  
         [0051]    In the second embodiment, the projection bar  160  can be curved. In FIGS. 20 and 21 which show the projection bar  160  with upward curvature, essential elements of the assembly  100  such as the cable  220 , and of the truck  110  such as the struts  112  are omitted for clarity. When the lever  184  is near its extended position, it contacts the upwardly curved portion of the projection bar  160  and pushes downward thereon. The curvature of the projection bar  160  permits it to tilt; in doing so, it can cause the push plate  120  to tilt in the manner of FIG. 21. This provides an additional forward component to the movement of the push plate  120 , giving added impetus for unloading cargo from the hand truck  110 .  
         [0052]    A third embodiment, illustrated in FIGS.  22 - 25 , is electrically actuated. A gear wheel  382  has teeth  390  meshing with the teeth  162  of the projection bar  160 . The gear wheel  382  is driven by a drive gear  302  mounted on a drive shaft  304  of an electric motor  300 , which is attached to the housing  140  by suitable fasteners such as bolts. The gear wheel  382  is mounted on a shaft  384 , which in turn is rotatably mounted in bearings  386  held in bearing apertures  388  of the housing  140 .  
         [0053]    Preferably, the motor  300  is a 12V motor powered by a rechargeable battery  310 , such as is used for power tools. The battery is removably held in a casing  312  attached to the housing  140 . Preferably, the casing  312  is a single piece of molded plastic which can be any type of plastic commonly used in bodywork for appliances. The casing  312  can be affixed to the housing by any suitable fastening means such as bolts. Electrical control circuitry is provided on a circuit board  306 , which has electrical conductors  308  connected to the battery  310 , to the motor  300  (the motor connections are not shown), and to a control switch (not shown) which can be conveniently mounted for example on one of the struts  112 . The circuitry and the control switch provide for the drive shaft  304  to be selectably rotated in either direction when the electric motor  300  is energized; thus the push plate  120  can be moved between the retracted and extended positions. As seen in FIG. 23, the push plate  120  is precluded from moving beyond either of its extreme positions by stops  392  affixed at predetermined positions on the gear wheel  382 . The positions of the stops  392  are selected relative to a limit switch  316  that is fixedly attached inside the housing  140 . The stops  392  move in an arc as the gear wheel  382  rotates. When the position of the gear wheel  382  corresponds to an extreme position of the push plate  120 , the appropriate stop  392  actuates the limit switch  316  and de-energizes the electric motor  300 , precluding further movement until the operator actuates the control switch to operate the electric motor  300  in reverse from its previous direction. Appropriate electrical circuitry being known, it will not be further described.  
         [0054]    In addition to actuating the push plate  120 , the electric motor  300  can optionally be used to provide powered assistance for moving the hand truck  110 . As seen in FIGS. 24 and 25, the bearing apertures  388  are elongate, allowing the bearings  386  and the shaft  384  to be reversibly moved between lower and upper positions by means such as a lever  394 , an end of which is pivotally attached to the housing  140 , the lever  394  also pivotally engaging the shaft  384 . The lever  394  has a locking mechanism (not shown) which can take various known forms to retain the shaft in the selected lower (push) or upper (drive) position. For example, the locking mechanism may include a spring loaded pin engaging either of two holes in the housing  140 , depending on which position is selected.  
         [0055]    When the bearings  386  are in the lower position, the gear wheel  382  engages the projection bar  160 . When the bearings  386  are in the upper position, the gear wheel  382  is disengaged from the projection bar  160  and engages a propulsion gear  397  mounted on a propulsion shaft  396 . Note that when thus raised, the gear wheel  382  nevertheless still engages the drive gear  302 . The propulsion shaft  396  is transversely mounted in bearings (not shown) attached to the struts  112  by any suitable means. At the extremities of the propulsion shaft are propulsion wheels  398  that frictionally engage the wheels  116  of the hand truck  110 . Both the hand truck wheels  116  and the propulsion wheels  398  are made of a material such as rubber conducive to good frictional contact, preferably with a suitable tread. Thus when the electric motor  300  is energized, it now assists the movement of the hand truck  110 . The stops  392  are disposed in such a way that when the gear wheel  382  is in the upper position, the arc in which the stops  392  travel clears the limit switch  316 . By contrast, when the gear wheel  382  is in the lower position, the arc intercepts the limit switch  316 , the stops  392  thus defining the rotational limits of the gear wheel  382 .  
         [0056]    Optionally, the gear wheel  382  may be clutched in order to provide the operator with better control.  
         [0057]    To summarize, then, the gear wheel  382  has selectable lower and upper positions for actuating the push plate  120  via the projection bar  160  and driving the handcart wheels  116  via the propulsion gear  397 , respectively.  
         [0058]    As previously indicated, the invention can be largely fabricated from sheet metal. This is especially desirable for the housing  140 , which can be conveniently and inexpensively formed from a single flat piece. In the second embodiment especially, the pedal assembly can be conveniently and inexpensively molded from a hard plastic.  
         [0059]    Although the push plate assembly  100  can be attached to the hand truck  110  in a variety of ways, such as bolting it directly thereto, it is preferably designed to be attached without in any way modifying the hand truck  110 . An attachment bracket  130  is welded or otherwise affixed to each of the flanges  142 . The brackets  130  are spaced apart and sized to be readily disposed adjacent the struts  112  in the manner shown in FIG. 14. Each attachment bracket  130  has at least one threaded hole (not shown) for accepting a bolt  132 . Once the bolts  132  are tightened against the adjacent struts, the assembly  100  is secured to the hand truck  110 . The invention is used in the following manner. A load such as a box or stack of boxes is loaded on the hand truck  110  in the usual way, with the push plate  120  in the retracted position. The load is essentially supported by the bottom chisel  114  and by the vertical spaced struts  112  of the hand truck  110 . The load is then placed at a desired location such as against the wall of a transport truck. To release the load and retrieve the hand truck  110 , the operator simply pushes downward on the lever  184 . Through the drive segment  182  and rack  160 , the push plate  120  is pushed forward against the load which is thus ejected from the chisel  114 . If load is already against the wall or against other relatively immovable cargo, the action of the push plate  120  against the load impels the hand truck  110  to move back and leave the load behind.  
         [0060]    When the hand truck  110  is withdrawn the operator releases the lever  184  and the return spring  170  pulls the push plate  120  back to its retracted position. This also moves the rack  160  rearward along the wear plate  154  and rotates the drive segment  182  so as to return the lever  184  to its inoperative (rest) position. During this movement, the push plate  120  is held upright by virtue of the L-shaped stop  128  between it and the bottom of the rack  160 , this stop  128  being held by the helical tension spring  170 .  
         [0061]    For special service such as transporting an elongate carton  240 , the drive segment  182  is provided with a hole  194  that comes into register with a pair of cross holes  196  in the sidewalls  144  when the treadle  184  is in its fully depressed position. In this position, these registering holes  194  and  196  are adapted to receive a locking pin  198 , which secures the push plate  120  in its extended position.  
         [0062]    When such a carton is to be transported, the lever  184  can be fully depressed by the operator so that the hole  194  in the drive segment  182  comes into register with the cross holes  196  in the sidewalls  144 . The operator can then slip the locking pin  198  through these registering holes  194  and  196  so that the push plate  120  is fixed in its fully projected position. In this position, the hand truck frame can be placed in a lateral position with its handles or grips on the ground for loading the elongate carton loaded thereon. The carton is loaded so that one end is supported by the push plate  120 , and the other end rests on the struts  112 . The push plate  120  can tilt about the pin  124  against the opposition of the spring  170  to conform with the angle of the carton  240 . The stop  128  is free to leave the bottom of the projection bar  160  for this purpose. The carton is transported with the hand truck inclined at a relatively small angle from the horizontal. The push plate  120  supports a relatively large area of the carton, instead of a carton wall having to rest on and possibly be damaged by the end of the chisel  114 .  
         [0063]    A differently shaped oversized carton  242 , while not excessively long in a single direction, may be too bulky to be easily balanced on the chisel  114  while being loaded onto the hand truck  110 ; in this case, the push plate  120  can be rotated about the pin  124 , against the opposition of the spring  170 , in the direction indicated by the curved arrows in FIG. 16, to assume a position roughly parallel to the chisel  114 . The spring  170  now tends to urge the push plate  120  as a whole toward the struts  112 , but lacks sufficient moment about the pin  124  to restore the push plate  120  to its former position unassisted. The push plate  120  can now receive and support the oversize carton  242 .  
         [0064]    The electrically actuated embodiment is used in generally the same manner, except of course for energizing the electric motor  300  to move the push plate  120  in either direction. When the option of powered assistance for moving the hand truck  110  is available, the lever  394  is used to move the gear wheel  382  between the push and drive positions. Typically, the rechargeable battery  410  is removed from the casing  412  and charged at a charging station when the hand truck  110  is not in use. Normally, the charging station would be at a convenient location such as a loading dock where the hand truck  110  is normally used. On the hand, the hand truck  110  may be intended to accompany a delivery vehicle, in which case the charging station could be on board the vehicle.  
         [0065]    The stamping of the major components of the push plate assembly  100  as single pieces is an advantage of the invention as it provides a manufacturing economy.  
         [0066]    While the invention has been described with reference to preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation of material to the teachings of the invention without departing from the scope of the invention. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope and spirit of the appended claims.