Abstract:
A cart includes a projecting load receiving platform mounted on a slide frame in turn mounted for vertical movement on a main frame. A spring mechanism urges the slide frame and platform to an elevated position so that objects may be stacked on the platform without placing them on the floor. As the weight of the stack on the platform increases the platform starts to descend until the cart is full. Conversely as items are removed from the top of the stack the platform elevates so the operator doesn&#39;t have to pick up an object from the floor. The spring mechanism uses a plurality of air springs each with a different load rating and operating in a cascading fashion. A pivoting weight operated latch holds the platform in its bottom position until released by a kick plate.

Description:
DISCLOSURE  
       [0001]     This invention relates generally as indicated to a transfer cart, and more particularly a wheeled cart for transferring a stack of relatively heavy items without requiring the user to place or pickup any of the items on or from the floor or surface on which the cart is moved.  
       BACKGROUND OF THE INVENTION  
       [0002]     Many back injuries are sustained when someone has to pick up or place a relatively heavy object either from, or on the floor. This is particularly so if the lifting or placing has to be done repeatedly.  
         [0003]     Many such objects or items are transferred from a truck, for example, to a customer, or sometimes to or from a warehouse. A two wheeled dolly or cart known as a hand truck is often used for such purposes. For example, a beverage distributor will remove cases or kegs from a truck and stack them one at a time on the projecting shelf at the bottom of the cart and build a stack. When the cart is full the stack is tilted back and wheeled into a customer&#39;s business, for example, usually to be stacked again in a storage area. The case at the top of the stack is the easiest to place or transfer because it can be moved or placed without bending over.  
         [0004]     It would accordingly be desirable if a cart or dolly could be provided where the stack on the cart or dolly is formed on or removed from the cart without bending over.  
       SUMMARY OF THE INVENTION  
       [0005]     The invention relates to a cart having a platform on which a stack of items may be built. As the weight of the stack increases the platform incrementally descends. In this manner the stack may be built by placing each item at an elevated position. The stack thus drops from under the user as the stack is built. Conversely, as an item is lifted from the top of the stack the platform elevates avoiding the necessity to pick or place any item with respect to the floor.  
         [0006]     The cart includes an air or gas spring mechanism achieving four positions of the platform with three springs and an interconnecting slide block mechanism. The gas springs may each be rated differently increasing in load rating top to bottom, so that they operate in a cascading fashion.  
         [0007]     In a hand cart form, a bottom fixed stabilizing platform is provided extending forwardly of two wheels so that the cart will be stabilized and stand upright on a floor or flat surface. In one embodiment the platform is latched in its lowermost position and will remain there until the latch is released. In this manner the platform may be unloaded while down and then returned to its elevated position when wholly or partially unloaded.  
         [0008]     The present invention has wide utility in the transfer of stackable items. A few of the examples are cardboard boxes used by movers, or for the storage or shipment of files, beverage cases or kegs, or bottles of water, luggage, sacks of cement, feed, or anything else stackable as discrete loads.  
         [0009]     To the accomplishment of the foregoing and related ends the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these 
    being indicative, however, of but a few of the various ways in which the principles of the invention may be employed.   
 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a rear elevation of a cart in accordance with the present invention;  
         [0012]      FIG. 2  is a side elevation of the cart as seen from the right hand side of  FIG. 1 ;  
         [0013]      FIG. 3  is a top plan view of the cart;  
         [0014]      FIG. 4  is a section taken from the inside of the rear cover plate as seen from the line  4 - 4  of  FIG. 3 ;  
         [0015]      FIG. 5  is a section taken from the line  5 - 5  of  FIG. 3 ;  
         [0016]      FIG. 6  is an exploded perspective view of the load spring balancing and slide block mechanism;  
         [0017]      FIG. 7  is a top plan view of the main frame;  
         [0018]      FIG. 8  is a broken side elevation of the main frame;  
         [0019]      FIG. 9  is a broken front elevation of the main frame;  
         [0020]      FIG. 10  is a front elevation of the slide frame which rides in the main frame;  
         [0021]      FIG. 11  is a side elevation of the slide frame;  
         [0022]      FIG. 12  is a plan view of the slide frame;  
         [0023]      FIG. 13  is a view like  FIG. 4 , but showing the slide frame having descended one increment;  
         [0024]      FIG. 14  is a similar view with the slide frame descended to the next increment;  
         [0025]      FIG. 15  is a similar view with the slide frame fully down;  
         [0026]      FIG. 16  is a fragmentary side elevation of another embodiment showing a platform latch when in the lowermost position;  
         [0027]      FIG. 17  is a fragmentary rear elevation showing the transverse kick release for operating the latch; and  
         [0028]      FIG. 18  is a fragmentary view looking down on the latch and also showing the kick release plate. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0029]     Referring initially to  FIGS. 1-5 , there is illustrated a stack loading and unloading cart shown generally at  20  which includes a main upright frame  21  having a forwardly projecting base stabilizing plate  22  secured to the bottom thereof as indicated at  23 . Also secured to the bottom of the main upright frame is a vertically extending heel plate  25  shown more clearly in  FIG. 5 .  
         [0030]     A pair of pneumatic tire wheels seen at  27  and  28  are mounted on transverse axle  29  outboard of the main upright frame  21  as seen in  FIG. 1 . The axle  29  is supported by wheel brackets  30  and  31  secured to the back of the frame. Generally L-shaped skid braces  33  and  34  are mounted on the axle  29  at their lower end and fastened to the back of the upright frame at their upper ends as indicated at  35  more clearly in  FIG. 5 . Each of the skid braces is provided with a skid plate as seen at  36  and  37 , respectively. The skid plates enable the cart to be pulled over a step or a curb, for example. It is also noted that the two skid braces are interconnected by a horizontal rod shown generally at  39  which serves as a foot brace. The operator may simply place a foot on the brace when tilting the cart backwardly or to the left as seen in  FIGS. 2 and 5  for transportation of a stack formed thereon.  
         [0031]     The top rear of the upright frame also includes a horizontally extending handle indicated at  41  which includes bent ends, in turn secured to handle brackets  42  and  43  secured to the upper end of the rear of the upright frame  21 .  
         [0032]     The sides of the upright frame  21  are formed by relatively closely spaced generally tubular frame members seen more clearly for example in  FIGS. 2, 5 ,  7  and  8 . These frame members are shown at  45  and  46  for one side and at  47  and  48  for the opposite side. Each of the parallel upright frame members on the respective sides of the frame is interconnected by a relatively short horizontal frame as seen at  50  and  51 . Transversely, the parallel upright side frames are interconnected by the transverse frame  52  at the top and the plate  22  at the bottom.  
         [0033]     The parallel upright side frames form tracks which accommodate rollers mounted on the vertically movable slide frame shown generally at  54 . The slide frame is shown in its uppermost position in  FIGS. 1, 2 , and  5  and is shown in detail in  FIGS. 10 through 12 . As can be seen more easily with reference to  FIGS. 10-12 , the slide frame includes vertically extending side frame members  56  and  57  interconnected at the top by a transverse frame member  58 . The bottom of the side frame members are interconnected by a shelf or platform structure seen at  60 . The shelf structure includes a horizontally projecting plate  61  extending forwardly from the lower end of a relatively short vertical plate  62  which is in turn connected to the forward edge of relatively short horizontal plate  63  in turn fastened to the vertical slide frame members  56  and  57 . The plate  63  is provided with a rearwardly opening cutout or notch  65  to accommodate the spring biasing mechanism hereinafter described.  
         [0034]     The slide frame side member  56  is provided with projecting rollers  66 ,  67 ,  68 , and  69 , while the opposite side frame  54  is provided with oppositely projecting rollers  71 ,  72 ,  73 , and  74 . The rollers  66  and  67  are both vertically and horizontally offset as are the rollers  68  and  69 . The same is true for the rollers on the opposite side of the frame. The rollers may be mounted on bronze bushings or journals on stub shafts projecting from the side frame members of the slide frame.  
         [0035]     The frame members for both the upright vertical frame and the slide frame may be extruded aluminum or other metal structures of essentially square or tubular configurations, and a standard form may include an x-shape core with a slot in each face. Such shapes may come in square, half-round, or quarter-round configurations and are ideal for fabricating the frames illustrated. The rollers illustrated may ride in the slots in the inside faces of the vertically extending slide frame members of the main upright frame. In this manner the slide frame member is confined for vertical movement in the tracks provided by the upright main frame.  
         [0036]     Referring now more particularly to  FIGS. 1, 5 , and  6 , there is illustrated a gas spring biasing mechanism which urges the shelf or platform  61  to its uppermost position. This spring biasing mechanism is shown generally at  80 . With reference to such figures it will be seen that the spring biasing mechanism comprises a bottom mounting plate  82 , a lowermost slide block  83 , an intermediate slide block  84 , a further intermediate slide block  85 , an uppermost slide block  86 , and a top mounting plate  87 . The slide blocks  83  and  86  may be identical, but the slide block  86  is inverted. Similarly, the slide blocks  84  and  85  may be identical but the slide block  85  is inverted. The bottom mounting plate  82  is secured by the fasteners illustrated in  FIG. 1  to the bottom of the main upright frame. The top mounting plate  87  is secured to the underside of the lateral frame member  58  at the top of the slide frame  54 .  
         [0037]     In the spring biasing mechanism illustrated, three gas springs in the form of piston-cylinder assemblies are employed and they are illustrated at  90 ,  91  and  92 . Preferably, the gas spring cylinders are each rated for a different load. For example, the uppermost gas spring  92  may be rated at 50 lbs. The intermediate gas spring  91  may be rated at 75 lbs., while the lowermost gas spring  90  is rated at 100 lbs. The loading of the gas springs may vary depending upon the uses to which the cart is placed, but normally the loading will increase in descending order.  
         [0038]     The uppermost gas spring  92  has its blind end connected to the block  85  by knurled nut  94 , while the rod  95  is connected at  96  to the top mounting plate  87 .  
         [0039]     The cylinder  92  telescopes through the hole  98  in block  86 . Thus the gas spring  92  controls the spacing between the block  85  and the top mounting plate  87 .  
         [0040]     The gas spring  91  is mounted at its blind end in block  83  with knurled nut  100 , the cylinder telescopes through hole  101  in block  84  and the rod  102  projects through hole  103  in block  85  and is secured with knurled nut  104  to the block  86 . The gas spring  91  thus controls the spacing between the lowermost slide block  83  and the uppermost slide block  86 .  
         [0041]     The gas spring  90  has its cylinder mounted on the bottom mounting plate  82  and its rod  106  telescopes through the slide block  84  and is connected by knurled nut  107  to the slide block  85 . The cylinder  90  of the lowermost gas spring telescopes through the slide block  83  at  108 . The gas spring  90  thus controls the spacing between the bottom mounting plate  82  and the slide block  85 .  
         [0042]     The center section of the spring biasing mechanism formed by the slide blocks  83 ,  84 ,  85  and  86  is formed in two parts which are relatively moveable with respect to each other. The upper slide block  86  and the lower most intermediate slide block  84  are interconnected by tie-rods shown at  112  and  113 . The tie-rods are connected by the fasteners shown at  114  to the slide blocks  86  and  84  and telescope through the slide block  85 . This requires that the slide blocks  86  and  84  move in unison.  
         [0043]     Similarly, the slide block  85  and the slide block  83  are interconnected by tie-rods  116  and  117  which are secured to the blocks by the fasteners seen at  118  requiring that the blocks  85  and  83  move in unison.  
         [0044]     As seen when comparing  FIGS. 1 and 5  with  FIG. 6 , when all of the gas springs are fully extended the slide block  84  is positioned closely below the slide block  85 .  
         [0045]     As seen more clearly in  FIGS. 1 and 5 , the gas spring biasing mechanism projects through the notch  65  in the top plate of the shelf or platform and that portion of the biasing mechanism below the notch is enclosed in a boot or bellows seen at  122 . The top of the boot or bellows may be secured at the notch  65 .  
         [0046]     The upright frame is provided with a rear cover  124  as well as side covers  126  and  127 . The front of the vertical frame from which the platform or shelf  61  projects is not provided with a cover.  
         [0000]     Operation  
         [0047]     Referring now more particularly to  FIGS. 4, 13 ,  14  and  15 , the various vertical positions of the shelf or slide frame are illustrated. In  FIG. 4  the slide frame is in its uppermost position and in such position the shelf or platform  61 , in the illustrated embodiment, is approximately 34 inches above the floor which is a bit better than at desk or table height. It is also noted that the projecting platform  61  of the shelf is slightly more narrow but projects a bit further than the base plate  22 . With the slide frame and platform in its elevated position the cart will stand vertically upright in a stable fashion, as seen for example in  FIG. 2 .  
         [0048]     It will be appreciated that the cart of the present invention may be employed to stack and transport a wide variety of items which may have various weights. For example, the operator may place a first item on the projecting shelf or platform  61  and the spring biasing mechanism may not move. It depends on the weight of the item positioned on the platform. After the operator places the next or even a further item on the forming stack, when sufficient weight is on the platform the top gas spring will yield causing the slide frame to move to the position seen in  FIG. 13 . In this position only the top gas spring has responded to the load but the platform has nonetheless moved downwardly in response to the load. In the  FIG. 13  position the rod  95  of the upper gas spring  92  has simply retracted. The intermediate frame has remained in position with the upper and lower parts fully separated.  
         [0049]     As the operator continues to build the stack or load on the platform, the next gas spring  91  will yield moving the slide frame to the second intermediate position seen in  FIG. 14 . The upper part of the intermediate slide block assembly has moved downwardly as the rod  102  retracts into the intermediate cylinder  91 . Continued building of the stack then causes the slide frame to move to the lowermost position seen in  FIG. 15  when the rod  106  of the gas spring  90  retracts moving the shelf or platform to its lowermost position. In  FIG. 15  all three gas cylinders are retracted.  
         [0050]     When the platform is in its lowermost position and the cart has received the stack built from the top, the operator simply tilts the cart backwardly or to the left as seen in  FIG. 2  and transports the stack to another location. At such other location the stack is unloaded from the top. As the weight of the stack decreases as the operator removes each item from the top of the stack, the gas springs will again extend but in reverse order of their retraction. Initially the bottom spring extends to move the platform up to the first position seen in  FIG. 14 . Continued removal of items from the top of the stack moves the stack to the intermediate position seen in  FIG. 13  and the complete removal of the bottom items in the stack moves the platform to its fully elevated position seen in  FIG. 4 . The gas springs thus act in cascading fashion to move the forming or disappearing stack through the increments shown.  
         [0051]     In some situations it is desirable that the platform  61  remain down even though all or part of the stack load is removed. Referring now to the embodiment shown in  FIGS. 16, 17  and  18 , the cart includes a latch shown generally at  132  which automatically locks the platform down when it bottoms out so that the operator may then unload the cart while the platform remains in place. With a readily accessible kick plate shown at  133 , the latch is released and the unlocked platform is elevated by the gas spring assembly.  
         [0052]     As seen more clearly in  FIGS. 17 and 18 , the latch assembly comprises two levers  135  and  136  with the kick plate  133  spanning between the tops of the levers. The levers are pivoted at  138  and  139  to brackets  141  and  142  respectively secured to the interior of frame members  45  and  47 .  
         [0053]     The brackets extend vertically in a space between the platform reinforcing structure such as plates  62  and  63  with the reinforcing gussets and vertical plate  144 .  
         [0054]     The assembly of the two levers  136  and  137  together with the kick plate  135  is such that it will fall back against the top edge of plate  144  in its at rest condition. As seen in  FIG. 16  the levers are provided with triangular notches  146  in which the upper edge of the plate seats. This holds the latch in the position shown in  FIG. 16 .  
         [0055]     As the platform descends, the framework of the platform will engage the angled front or left side of the levers seen in  FIG. 16 , pivoting them and the kick plate to an upright position.  
         [0056]     As the platform continues down, the top plate  63  will clear the lower ends of the levers, and the assembly then falls back to the position shown with the lower ends  147  of the levers projecting over the top of the back edge of plate  63 . In this position the platform is latched down against the force of the gas springs. If desired all or part of the stack may be unloaded.  
         [0057]     In order to release the latch the operator kicks the plate  133  forward to pivot the assembly to a vertical or upright position clearing the platform for vertical elevation.  
         [0058]     The cart of the present invention may be used for stacking and transporting a wide variety of items such as cases, beverage containers, kegs, bottles, file cases, or even luggage for that matter. The projecting shelf may be tailor made to inter-fit and support cylindrical objects such as water bottles or kegs, for example.  
         [0059]     It can now be seen that there is provided a transfer cart having a platform on which a stack of items may be built. As the weight of the stack increases the platform incrementally descends. In this manner the stack may be built by placing each item in an elevated position. The stack thus drops from under the user as the stack is built. Conversely, as an item is lifted from a stack the platform elevates avoiding the necessity to pick or place any item with respect to the floor.  
         [0060]     The cart includes a cascading gas spring mechanism achieving four incremental positions of the platform with three springs and an interconnecting slide block mechanisms. The gas springs may be rated differently increasing in load rating top to bottom. The cart is particularly useful for transporting many stackable items.  
         [0061]     Although the invention has been shown and described with respect to certain preferred embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification. The present invention includes all such equivalent alterations and modifications, and is limited only by the scope of the claims.