Stackable cart assembly

A stacking member for stacking one hamper cart on another hamper cart is provided that is easily installed, removed, and stored nested with other like stacking members. The stacking member is strong, yet relatively light weight, and functions, among other things, (1) to distribute the weight of the stacked cart evenly and to a major portion of the length of each sides and ends of the upper frame of the supporting cart, (2) index itself for quick installation in the proper position on the upper frame of the supporting cart, (3) orient and index the supported cart on the stacking member, (4) secure the stacked cart on the stacking member to prevent sliding or movement during transport by pinching or gripping the shifting, fixed axis center caster wheels, and (5) allow imprecise transverse placement of the stacked cart on the stacking member.

FIELD OF INVENTION 
The present invention relates to stackable cart assemblies and, more 
particularly, to stackable carts and devices facilitating the stacking one 
cart on to another for transportation or storage of the stacked cart 
assemblage. As used herein the term cart includes wheeled hampers, hamper 
trucks, rod type hand trucks or other similar wheeled carts. The terms 
stacked cart and supporting cart refer to the upper and lower carts, 
respectively, of an assembled stack. 
BACKGROUND 
Carts comprising a lower frame and a top frame connected by a series of 
upstanding flexible resilient metal rods with a vinyl or canvas lining 
have become popular for a variety of applications primarily because of 
these carts low manufacturing costs and strength-to-weight benefits. 
Recent advancements, such as those disclosed U.S. Pat. No. 5,611,554, 
issued Mar. 18, 1997, entitled "Cart", and owned by the same assignee 
hereof, include increased strength and rigidity for these types of carts. 
These improvements have increased the number of different applications to 
which these carts may be used. One application includes the long distance 
transportation of certain scrap goods such as recycled fiber products. 
Typically a large number of these carts, each filled with several hundred 
pounds of scrap materials are rolled into a truck for transport to another 
location. Although the floor of the truck can be almost completely covered 
with carts, only one layer of these carts is transported. Accordingly, the 
majority of space within the truck is free space which increases the 
shipping costs, fuel, and labor on a per unit cart basis. 
Similarly, conventional carts must be stored or moved about individually, 
which also wastes vertical space in a warehouse or work area, makes it 
economically impractical to use a fork lift to move an individual cart, 
and requires two trips to move two carts which increases labor costs. 
Accordingly, a need exists for an assembly that enables two or more carts 
to be vertically but stacked securely and quickly to prevent shifting or 
damage during transport. 
SUMMARY OF EXEMPLARY EMBODIMENT OF THE PRESENT INVENTION 
An exemplary assembly, according to the principles of the present 
invention, includes a cart that includes side and end structures that can 
support a predetermined load that is several times the weight of 
anticipated two stacked and fully loaded carts. 
According to one aspect of the present invention, a stacking member is 
provided that is easily installed, removed, and stored nested with other 
like stacking members. The stacking member is strong, yet relatively light 
weight, and functions, among other things, (1) to distribute the weight of 
the stacked cart evenly and to a major portion of the length of each side 
and end portions of the upper frame of the supporting cart, (2) index 
itself in the proper position on the upper frame of the supporting cart, 
(3) orient and index the supported cart on the stacking member, (4) secure 
the stacked cart on the stacking member to prevent shifting, sliding or 
movement during transport, and (5) allow imprecise transverse placement of 
the stacked cart on the stacking member. 
In one example, the stacking member includes a number of strengthening 
members, preferably box tubes, angle irons, and flat corner plates and 
longitudinal mid-length plates welded together. The corner plates support 
the corner casters of the cart above and the mid-length plates locate 
under the fixed axis center wheels of the cart above. The thickness of the 
corner plates is selected so that the weight of the loaded upper cart is 
distributed to the end casters and center casters of the stacked upper 
cart. 
Transverse rails preferably welded to the mid-length plates are spaced so 
that substantially all the weight borne through the stacked cart center 
wheels are taken up by the transverse rails. This aspect of the invention 
enables a fork lift operator to lower the above cart on to the stacking 
plate slightly off center in the transverse direction. The rails also 
pinch or grip the center caster wheels and prevent lateral movement of the 
above cart on the stacking member during cornering by the truck or 
movement by a fork lift, or the like. 
Another aspect of the present invention includes a stacking member of the 
type described in which angle members are provided having one leg resting 
on the upper frame of the supporting cart and the other leg extending down 
around the outside of the upper frame of the supporting cart to simply and 
precisely index or position the stacking member. Since the great majority 
of damage to the upper cart frames result in inward projections or dents, 
the outside indexing can cooperate with even most of the upper frame 
damaged carts. The ends of the depending legs are preferably rounded for 
safety and to avoid tearing canvas or vinyl liners. 
A further aspect of the present invention is to distribute the static 
weight and dynamic loads of the upper cart to substantially the entire 
upper frame and all of the upstanding rods or sides and ends to the lower 
frame of the supporting cart. 
Yet a further aspect of the present invention includes a stacking member of 
the type described that can be nested with other like stacking members to 
reduce the vertical height required for storage or transport. 
Another aspect of the present invention is to provide a cart of the type 
described with reinforced side and end rods to increase the supporting 
strength and stackability under dynamic load conditions.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENT OF INVENTION 
With reference to FIGS. 1 and 2, stacking member 10 comprises an H-frame 
formed of two longitudinal struts 12 and 14 and a transverse strut 16 
welded to the sides of struts 12 and 14 at their mid-lengths. Struts 12, 
14, and 16 can be formed of angle pieces, U-pieces, or round tubing or any 
other suitable profile. However, box tubing for struts 12, 14, and 16 is 
preferred. Four corner plates 18 are welded to the sides of the end 
portions of struts 12 and 14 and extend laterally and longitudinally 
therefrom. Struts 12 and 14 and plates 18 are dimensioned to locate corner 
plates 18 above the corner regions of the supporting cart such that a 
mid-region of plate 18 contacts and supports the corner swivel caster of 
the stacked cart as described below. The outer corners of plates 18 can be 
rounded to follow the profile if the upper frame of the supporting cart, 
for safety reasons, and to avoid tearing the cart liner. 
Stacking member 10 further comprises end struts 20 and side struts 22 
welded to the outside edge regions of plates 18 and the ends of struts 12 
and 14 to strengthen member 10 and distribute static and dynamic support 
loads through to the top frame of the supporting cart. End and side struts 
20 and 22 also function to quickly index member 10 into the precise 
installed position on the upper frame of the supporting cart. In one 
example, struts 20 and 22 comprise angle irons having their top leg welded 
beneath the outer edges of corner plates 18 and having their depending leg 
overhanging the outside of the end and side tubes of the supporting cart 
top frame, generally as shown. The lower outer corners of the depending 
legs of struts 20 and 22 are rounded to avoid tearing the canvas or vinyl 
liner and for safety. 
As better seen in FIGS. 1 and 5, a pair of transversely extending and 
longitudinally spaced rails 26 are welded to the outside of struts 12 and 
14 and the top surface of side struts 22. A further piece should be 
connected between rails 26 to provide further longitudinal strength 
therebetween. Preferably, plate 30 is welded to each rail pair generally 
as shown for this purpose and can have its inner portion welded to cross 
strut 16 and side struts 12 and 14 and its outer edge welded to side 
struts 22, as shown, for further strengthening of member 10. Rails 26 can 
be any suitable shape such as angle iron, U-shaped, etc., however, the box 
tube as shown is preferred. 
The longitudinal spacing of rails 26 is predetermined to pinch fit or grip 
the center, fixed caster wheel of the stacked cart. It is preferred that 
such spacing will cause the rails to support substantially all of the 
weight of the stacked cart and its load and dynamic load forces that are 
and become transferred through that respective fixed center caster of the 
stacked cart. Accordingly, in a static mode, rails 26 cause the bottom of 
caster wheel 32 to be slightly raised above plate 30. In this way, rails 
26 serve as fore and aft orienting and positioning stops to precisely 
longitudinally position the stacked cart when placed by a fork lift or 
other mechanism and to longitudinally secure the stacked cart. Thus, the 
four swivel corner casters resting on plates 18 need not be secured. 
In addition, the pinch fit between rails 26 and caster wheel 32 provides 
lateral restraint since wheel 30 is well secured by friction and gripping 
of the pinch fit. Thus, when in a cornering tractor trailer or truck, or 
when carried by a fork lift, the stacked cart will not slip or shift 
sideways on member 10. 
Rails 26 further enable the stacked cart to be imprecisely positioned in 
the transverse direction particularly in view of the transverse dimensions 
of plates 18 and rails 26. Accordingly, the dimension from the centermost 
points 25 of rails 26 on one side of member 10 to the outermost points 27 
of rails 26 on the other side of member 10 should be slightly more than 
the distance between the inside of one center wheel 32 of stacked cart 40 
to the outside of the other center wheel 32 of cart 40. In this way, if 
for some unlikely reason cart 40 shifts laterally on rails 26, the inside 
of one wheel 32 will abut against the outside of strut 12 or 14 before the 
other wheel 32 slips off the outer edges 27 of the other pair of rails 26. 
In addition plates 18 are dimensioned to support the corner casters 34 
even if cart 40 assumes this extreme lateral position on rails 26 shown in 
FIG. 5. 
As better seen in FIG. 1, all four rails 26 and struts 12 and 14 terminate 
short of the edge of the underlying side struts 22 and end struts 20 
respectively. This allows an adjacent stacking member 10 of the same 
design and dimensions to nest with member 10 in the shortest vertical 
space. See FIG. 6 where the side struts and end struts 20 contact the 
corresponding side and end struts of an adjacent, nested stacking member. 
With reference to FIG. 4, the lower or supporting cart is preferably 
strengthened during manufacture by welding a diagonal flexible metal rod 
42 to the underside near one corner of the upper frame and the top of 
opposite corner of the bottom frame. Similar diagonal rods should be 
welded on the opposite side and both end sections of the cart. If desired, 
rod 42 can be welded to each upstanding rod 43 as well. 
When stacking is desired, stacking member 10 is placed on to the canvas or 
vinyl covered top frame of supporting cart 41. The fact that cart 41 has 
only two or four wheels touching a flat supporting surface at any one time 
is insignificant. Flanges 21 and 23 aid in the quick and accurate 
placement of member 10. The end sections of cart 41 and the end sections 
of member 10 are shorter than the side sections for most standard carts. 
Member 10 requires no front-back orientation with cart 41. 
A fully or partially loaded stacked cart 40 is raised by a fork lift or 
other mechanism and oriented so that the long side of cart 40 generally 
aligns with the long side of cart 41 and casters 32 and 34 are above 
member 10. Standard fork lift tongues extend under and lift cart 41 at the 
bottom frame zones marked 44. Once lifted, the fork lift operator 
approaches cart 41 from the side and aligns the center, fixed axis caster 
wheel 32 with rails 26. Once aligned, the operator lowers cart 40 until 
wheels 32 are indexed between and supported by rails 26. The only lateral 
requirement for cart 40 placement is that both wheels 32 lie outside 
struts 12 and 14. This alignment can be easily seen by the operator by 
watching that the two corner wheels 34 closest to the operator descend 
onto plates 18. The thicknesses of plates 18 are selected to support the 
four swivel cart wheels 34 notwithstanding the standard one-eighth inch 
vertical off-set of the center fixed caster 32 relative to the swivel 
casters 34. With wheels 32 and 34 so supported on member 10, the operator 
can lower and withdraw the fork lift tongues. The carts are ready for 
storage or transport. 
If desired, the assembly can be transported locally by a standard fork lift 
that slides tongues under the bottom frame of cart 41 and engages at zones 
46. In this way, both carts can be lifted simultaneously in their 
positions shown in FIG. 4 and transported by fork lift truck. Cart 41 
remains longitudinally and transversely secured by member 10 as described 
above during lift and transport. Alternately, the assembly of carts 40, 41 
and stacking member 10 can be manually walked and controlled by pushing 
cart 41 in the usual manner. 
It should be understood that various modifications may be made to the 
herein disclosed exemplary embodiment without departing from the teachings 
and concepts of the present invention.