CA2481726C

CA2481726C - Article transfer device and method

Info

Publication number: CA2481726C
Application number: CA 2481726
Authority: CA
Inventors: Dan S. Jones; Edward G. Ostertag
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 2004-10-12
Filing date: 2004-10-12
Publication date: 2008-07-08
Anticipated expiration: 2024-10-12
Also published as: CA2481726A1

Abstract

Disclosed herein is a cart comprising a support frame portion, a pair of swivel wheels and a pair of non swivel wheels, the swivel and non swivel wheels lying in a common plane to roll along a common ground surface, lifting means having at least one non swivel support wheel and being operable to transfer the support wheel between a first position above the common plane and a second position below the common plane, the lifting means further comprising actuating means to displace the at least one support wheel between the first and second positions , the at least one support wheel being operable in the second position to displace either the swivel wheels or the non-swivel wheels off the ground surface.

Description

ARTICLE TRANSFER DEVICE AND METHOD
BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
The present invention relates to the transfer of articles and more particularly to carriers therefor.

2. DESCRIPTION OF THE RELATED ART
Manufacturing, assembly, distribution and warehousing facilities usually involve extensive transfers of materials and articles from one location to another. This is commonly done by carriers such as wheeled carts, which are typically arranged with a pair of caster wheels on one end and a pair of fixed axle wheels on the other. Advances in plastics have provided an impressive range of resilient plastic wheels which are capable of withstanding the punishing wear and tear that these wheels undergo when used on these kinds of carts. However, the use of the resilient plastic wheels can increase the forces needed to move the carts.
In recent years, there has been an increasing focus on improving the ergonomic aspects of different processes used in manufacturing, assembly, distribution and warehousing facilities. An important facet of these ergonomic studies is the reduction of injuries such as back injuries.
With this in mind, the transfers of articles using carriers or carts which involve physical exertion by an operator are significant sources of such injuries.
It is therefore an object of the present invention to improve the transfer of articles.
SUMMARY OF THE INVENTION
In one of its aspects, the present invention provides a cart comprising a support frame portion, a pair of swivel wheels and a pair of non swivel wheels, the swivel and non swivel wheels lying in a common plane to roll along a common ground surface, lifting means having at least one non swivel support wheel and being operable to transfer the support wheel between a first position above the common plane and a second position below the common plane, the lifting means further comprising actuating means to displace the support wheel between the first and second positions below the common plane, the support wheel being operable in the second position to displace either the swivel wheels or the non-swivel wheels off the ground surface.

Preferably, the common plane is fixed relative to the support frame portion, but may be adjustable relative thereto if desired.
In an embodiment, the lifting means is located centrally between the non-swivel wheels and the swivel wheels and includes an undercarriage supporting a pair of fixed axle support wheels. Preferably, the undercarriage is movable relative to the support frame portion.
In an embodiment, the support frame portion further comprises positioning means to position the undercarriage relative to the support frame portion. In this case, the support frame portion has a pair of longitudinal central frame members and a pair of frost undercarriage support flanges oppositely mounted on, and inwardly extending from, the central frame members. The undercarriage has a pair of outwardly extending second undercarriage support flanges, each extending along a corresponding side of the undercarriage. The second undercarriage support flanges are positioned for slidable movement along the corresponding first undercarriage support flanges. The positioning means further provides a number of threaded fasteners, each extending through a corresponding one of a series of matching passages formed in the first undercarriage support flange.
In an embodiment, the undercarriage includes displacement means to displace the undercarriage relative to the support frame portion. The displacement means includes a threaded rod which is threadably engaged between the undercarriage and the support frame portion, by one or more threaded support flanges.
However, an alternative embodiment is also provided in which displacement means includes an electrical, hydraulic or pneumatic motor and/or a gear arrangement which is operable between the undercarriage and the support frame portion.
In an embodiment, the actuating means includes an electrical, hydraulic and/or manual motor portion and a transmission portion operable in response thereto, for delivering an actuating force to the support wheels.
In one example, the transmission portion includes a ram portion, but may include other arrangements, such as gear assemblies, linkages and the like.
In an embodiment, the support wheels are mounted for rotation on an axle member. The ram portion further comprises an hydraulic ram acting between the support frame portion and the support wheels and the motor portion includes an hydraulic pump for displacing the hydraulic ram, the hydraulic ram and the hydraulic pump being operably joined by a hydraulic fluid circuit. In this example, the actuating means further comprises a pair of link members each pivotally mounted to the undercarriage and supporting a corresponding support wheel. A cross member extends across the undercarriage and each of the link members includes an end plate fixed to a corresponding end of the cross member. Each support wheel is thus mounted on a corresponding end region.

In an embodiment, the actuating means includes a bleed unit for bleeding the hydraulic ram for progressively returning the support wheels to the first position. The bleed unit includes a variable valve in the hydraulic fluid circuit, the hydraulic ram or the hydraulic pump. A first foot pedal is provided which is movable between a first operable position and a second operable position for pressurizing the hydraulic fluid circuit for advancing the hydraulic ram. A spring portion biases the first foot pedal to its first operable position.
In an embodiment, a releasing means is provided for depressurizing the hydraulic fluid circuit for retracting the hydraulic ram. The releasing means is activated by a second foot pedal.
In an embodiment, the actuating means includes return means for returning the support wheels to the first position, preferably following activation of the releasing means.
In an embodiment, each support wheel includes a ground engaging portion formed from a substantially non resilient material. Preferably, the non resilient material includes one or more of steel, bronze and aluminum, but may include other materials as desired.
In an embodiment, each of the swivel and non swivel wheels includes a ground engaging portion formed from a resilient material.
In an embodiment, the cart further comprises a hitch portion which is operable between a first position and a second position, wherein in the first position the hitch portion is arranged to connect to an adjacent cart and/or a tow vehicle. In one example, the hitch portion includes a hitch arm which is generally horizontal in the first position and generally upright in the second position.
A further embodiment provides safety means which is responsive to the hitch portion to cause the actuating means to displace the support wheels to the first position when the hitch portion is displaced toward the first position or when the hitch portion reaches the first position or a position between the first and second positions.
1n a further embodiment, the actuating means further comprises a trigger assembly for triggering the motor portion for deploying the transmission portion. The cart is provided, in one example, with a cart handle and the trigger assembly may, if desired, be mounted on the cart handle, or another suitable location on the cart, as desired. The motor portion includes a hydraulic pump which is responsive to a switch portion operably coupled to the trigger assembly. The trigger assembly also desirably includes a trigger latch which is positioned adjacent the cart handle to be actuated when the cart handle is gripped by an operator. A power source supplies a power signal to the hydraulic pump.

3 1n another of its aspects, the present invention provides a carrier for transporting an article comprising a support frame portion, a first undercarriage including a plurality of first wheels to roll along a ground surface and having rolling contact points lying in a common plane, a second undercarriage located centrally within the first undercarriage and including one or more second wheels, actuating means for actuating the second undercarriage from a position with the one or more second wheels above the common plane to a position beyond the common plane which is sufficient to displace one or more of the first wheels of the first undercarriage off the ground surface.
In an embodiment, one or more of the first and/or second wheels are swivel wheels. However, if desired, one or more of the first and/or second wheels may be non-swivel wheels.
In an embodiment, one or more of the first and/or second wheels are fixed axle wheels.
In an embodiment, the second undercarriage is inclined relative to the first undercarriage.
In one embodiment, the support frame portion has a longitudinal axis and the second undercarriage is operable to adjust the position of the one or more second fixed axle wheels relative to the longitudinal axis.
Preferably, the second undercarriage is movable in a direction substantially parallel with or substantially perpendicular to the longitudinal axis, or both, though other movements at other angles relative to the longitudinal axis are also contemplated.
In still another of its aspects, the present invention provides a method of transporting an article, comprising - a step for providing a carrier for supporting the article;
- a step for providing a first undercarriage including a plurality of first wheels to roll along a ground surface with rolling contact points of the first wheels lying in a common plane, - a step for providing a second undercarriage located centrally within the first undercarriage and including a pair of second fixed axle wheels, - a step for displacing the second undercarriage so that the second fixed axle wheels are above the common plane, - a step for transferring the carrier from an originating location to a destination location;
- and after the carrier arrives near the destination location, a step for actuating the second undercarriage from the position with the second fixed axle wheels above the common plane to a

4 r position beyond the common plane sufficient to displace one or more first wheels off the ground surface; and - manipulating the carrier for the article to be in a predetermined orientation at the destination location.
In yet another of its aspects, the present invention provides a method of improving the transfer of an article between an originating location and a destination location, comprising the steps of:
a) providing a carrier for supporting an article during transfer;
b) providing the carrier with a first wheeled undercarriage having a plurality of first wheels on which to displace the carrier between the originating and destination locations;
c) arranging the first wheels to roll on a ground surface with rolling contact portions of the first wheels lying in a common plane;
d) selecting a predetermined characteristic of the first wheels to optimize the transfer of the article between the originating location and destination locations;
e) transferring the carrier between the originating and destination locations on the first wheels, f) providing a second undercarriage with at least one second fixed axle support wheel;
g) selecting a predetermined characteristic of the at least one second fixed axle support wheel to optimize the manipulation of the carrier at the destination location;
h) and after step e), actuating the at least one second fixed axle support wheel from a position above the common plane to a position beyond the common plane, sufficient to raise at least one selected first wheel of the first undercarriage off the ground surface;
and i) manipulating the carrier for the article to be in a predetermined orientation at the destination location.
In one embodiment, the step d) includes the step of selecting the first wheels with a ground engaging portion formed from a resilient material, while step g) includes the step of selecting the second fixed axle wheels with a ground engaging portion formed from a substantially non-resilient material.

5 In still another of its aspects, the present invention provides a kit for converting a cart of the type having a support frame portion, a pair of swivel wheels and a pair of non swivel wheels, the swivel and non swivel wheels lying in a common plane to roll along a common ground surface, the kit comprising lifting means having at least one non swivel support wheel and being mountable on the support frame portion for transferring the at least one support wheel between a first position above the common plane and a second position below the common plane, the lifting portion further comprising actuating means mountable between the support frame portion and the at least one support wheel to displace the at least one support wheel between a first position above the common plane and a second position below the common plane, the at least one support wheel being operable in the second position to displace either the swivel wheels or the non-swivel wheels off the ground surface In still another of its aspects a cart comprising a support frame portion, a pair of swivel wheels and a pair of non swivel wheels, the swivel and non swivel wheels lying in a common plane to roll along a common ground surface, a lifting portion having at least one rolling support element and being operable to transfer the at least one rolling support element between a first position above the common plane and a second position below the common plane, the lifting portion further comprising an actuating portion to displace the at least one rolling support element between the first and second positions, the rolling support element being operable in the second position to displace either the swivel wheels or the non-swivel wheels off the ground surface.
In one embodiment, the at least one rolling support element includes one or more rollers and/or wheels.
1n one embodiment, the cart has two non swivel wheels and two swivel wheels.
This arrangement is suited to carts which are towed from one location to another, among other methods of transport. However, other wheel an-angements may be used. For instance, all wheels may be of the swivel or non swivel variety.
Some wheels may be swivel in one operative mode and non swivel in another operative mode. The rolling support elements may similarly be provided in a number of possible combinations. For example, the rolling support elements may be all swivel wheels, non-swivel wheels, rollers or be provided in other arrangements as desired.
In still another of its aspects, the present invention provides a cart comprising a support frame portion, a pair of swivel wheels and a pair of non swivel wheels, the swivel and non swivel wheels lying in a common plane to roll along a common ground surface, a lifting portion having at least one rolling support element and being operable to transfer the at least one rolling support element from a first position relative to the common plane and a second position below the common plane, the lifting portion further comprising an actuating portion to displace the at least one rolling support element between the first and second positions,

6 the rolling support element being operable in the second position to displace either the swivel wheels or the non-swivel wheels off the ground surface.
In an embodiment, the first position is either above the common or in the common plane.
In an embodiment, the at least one rolling support element is operable in the first position to contact the common ground surface together with the swivel and non swivel wheels.
In another embodiment, the at least one rolling support element includes a suspension arrangement for permitting the at least one rolling support element, in the first position, to accommodate changes in the common ground surface.
BRIEF DESCRIPTION OF THE DRAWINGS
Several preferred embodiments of the present invention will now be described, by way of example only, with reference to the appended drawings in which:
Figure 1 is a fragmentary perspective view of a cart;
Figure 2 bottom plan view of the cart of figure 1;
Figure 3 is a side view of the cart of figure 1 in a first operative position;
Figure 4 is a side view of the cart of figure 1 in a second operative position;
Figure 5 is another side view of the cart;
Figure 6 is a fragmentary perspective view of a portion of the cart of figure 2 in one operative position;
Figure 6a is another fragmentary perspective view of the portion shown in figure 6;
Figure 6b is another fragmentary perspective view of the portion shown in figure 6, in this case in another direction;
Figure 7 is a fragmentary perspective view of a portion of the cart of figure 2 in another operative position;
Figure 8 is a fragmentary perspective view of another portion of the cart of figure 1;

7 Figure 9 is another fragmentary perspective view of the portion shown in figure 8;
Figure 9a is a fragmentary perspective view of another portion of the cart of figure 1;
Figure 9b is a fragmentary schematic vie taken on plane 9b-9b of figure 9;
Figure 10 is a fragmentary plan view of an alternative portion to that shown in figure 9a;
Figure 11 is a fragmentary perspective view of another cart; and Figure 12 is a partly schematic plan view of the cart of figure I 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, particularly figures 1 and 2 there is provided a cart shown at 10 having a support frame portion 12 with a load supporting deck 14, a pair of swivel (or otherwise known as castered) wheels 16, 18 on one end and a pair of non swivel (or otherwise known as fixed axle) wheels 20, 22 on an opposite end. As can be seen in figure 3, the wheels 18 and 22 have lowermost points 26 and 30 respectively (as do wheels 16 and 20 though not shown in figure 3) which lie in a common plane 32 so that they can roll along a ground surface 34 for the transfer of a load shown in phantom at 36. The load 36 may include such things as manufactured articles, materials and the like. In this case the common plane 32 corresponds with the ground surface 34.
Referring to figures 2 and 3, lifting means is generally shown at 42 with at least one, in this case two, non swivel support wheels 38, 40. As can be seen in figures 3 and 4, the lifting means 42 is operable to transfer the support wheels 38, 40 between a first position above the common plane 32 (figure 3) and a second position below the common plane 32 (figure 4). Thus, in figure 4, for the sake of illustration, the common plane 32 is now shown as being situated parallel to and above the ground surface 34. However, in this particular example, the cart 10 will tend to support the load 36 on the support wheels 38, 40 and either on the swivel wheels 16, 18 or non-swivel wheels 20, 22 respectively. Thus, in the particular arrangement shown in figure S, the cart 10 is operable to roll on the ground surface 34 on the support wheels 38, 40 and the swivel wheels 16, 18.
Referring to figure 2, it can be seen that the support wheels 38, 40 are located relatively closer to a central longitudinal axis 'A' of the cart 10 in comparison with the swivel and non-swivel wheels 16, 18 and 20, 22.
If desired, each of the support wheels 38, 40 can be substantially aligned with their neighboring swivel and non swivel wheels along a common corresponding longitudinal edge region of the cart, the position of the support wheel 38 in this case being shown in phantom generally at 38'. For that matter, the support wheels 38, 40 may also be positioned beyond the swivel and non-swivel wheels 16, 18 and 20, 22 relative to the longitudinal axis A, if desired, as shown (for the support wheel 40) in phantom generally at 40'. Further, it will be understood that the spacing between the support wheels 38, 40 may be increased or decreased to provide a desired level of lateral stability to the cart 10. For instance the wider the stance of the support wheels 38, 40, the greater the stability of the cart 10 when the support wheels 38, 40 are in the second position against the ground surface 34.
Still further, the support wheels 38, 40 may be replaced by a single rolling support element, either in the form of one or more than one wheel or one or more than one roller (as shown in phantom at 39) whose lateral dimension is selected to provide the required degree of stabilized for the cart 10 or some other form of rolling support as desired.
In this example, the common plane 32 is fixed relative to the support frame portion 12. However, the position of the common plane 32 may be adjustable relative to the support frame portion 12, if desired.
This may be achieved, for example, through the use of height adjustable axle support structures (not shown) supporting one or both pairs of swivel or non-swivel wheels 16, 18, or 20, 22 respectively.
Referring now to figure 3, the lifting means 42 provides an actuating means shown generally at 44 to cause the support wheels 38, 40 to pass through the common plane 32 for lifting either pair of swivel or non-swivel wheels 16, 18 and 20, 22 off the ground surface 34.
1n this example, the lifting means 42 is centrally located with the non-swivel wheels 20, 22 on one side and the swivel wheels 16, 18 on the other. In this case, the specific location of the lifting means 42 may be adjusted relative to the support fi-ame portion 12 to accommodate variations in the load 36 and its position on the deck 14. As shown in figure 2, this may be achieved by way of an undercarriage 46 which is mounted on the support frame portion 12 for movement thereof as shown by the double arrow.
Though not necessary in all examples of the cart 10, the ability provided by the undercarriage 46 to adjust the location of the lifting means 42 is particularly beneficial in situations wherein changes to the load 36 or its position on the deck 14 alter the location of the centre of gravity of the cart 10, as shown at 48 in figure 3. A shift in the load's centre of gravity may thus cause a corresponding shift in the centre of gravity 48 of the cart 10. Thus, the undercarriage 46 may be adjusted to maintain the centre of gravity 48 on one side of the support wheels 38, 40 so that the swivel wheels 16, 18 remain in contact with the ground surface, regardless of the orientation, shape or weight of the load 36 on the deck 14.
However, if desired, the centre of gravity 48 may be centered on the support wheels 38, 40.

Referring to figure 6, the support frame portion 12 has a pair of longitudinal central frame members 50 and a pair of first undercarriage support flanges 52 oppositely mounted on, and inwardly extending from, the central frame members 50. The undercarriage 46 has a pair of outwardly extending second undercarriage support flanges 54, each being part of a right angled frame member 56 extending along a corresponding side of the undercarriage 46. The second undercarriage support flanges 54 are positioned for slidable movement along the first undercarriage support flanges 52.
As shown in figure 6a, one or more additional first and/or second support flanges 58, 60 may be provided adjacent the corresponding first and second support flanges 52, 54, as desired to enhance the coupling between the support frame portion 12 and the undercarriage 46.
Referring again to figure 6, the support frame portion 12 has a positioning means 62 to position the undercarriage 46 relative to the support frame portion 12. In this case, the positioning means 62 is provided in the form of a number of threaded fasteners 64 each extending through a corresponding one of a series of matching passages 66 formed in the first undercarriage support flange 52. The positioning means may also include such things as clamping members (not shown) and the like to secure the undercarriage 46 to the support frame portion 12.
As shown in figure 2, the undercarriage 46, may also be provided with displacement means 68 to displace the undercarriage 46 relative to the support frame portion 12. The displacement means 68 may, for example, take the form of a threaded rod 70 which is threadably engaged between the undercarriage 42 and the support frame portion 12, by one or more threaded support flanges 72 or the like. Alternatively, the displacement means 68 may include other arrangements such as an electrical, hydraulic and/or pneumatic motor (as shown schematically at 74), gear arrangements (not shown) or the like. In this case, the motor 74 may be responsive to an external controller as will be described. While the undercarriage 46 allows the position of the lifting means to be adjusted along the longitudinal axis 'A' in relation to the support frame member 12, the lifting means may alternatively be fixed in position relative to the support portion 12.
The actuating means 44 is best shown in figures 6, 6a, 6b and 7 and includes an hydraulic ram 76, including a housing portion 78 and a ram portion 80 extending outwardly therefrom and acting between the undercarriage 46 and the support wheels 38, 40. The housing portion 78 has one end region which presents the ram portion 80 and an opposite end region which is pivotally mounted by a first pivot pin 82, to a pair of first flanges 84 extending from the undercarriage 46. The ram portion 80, is pivotally mounted at a remote end region thereof by way of a second pivot pin 86 (figure 6b) to a pair of second flanges 88 mounted on a cross member 90.

Referring to figure 6, the cross member 90 has a central angled portion 92 and a pair of link members 93 in the form of end plates 94 welded on corresponding opposite ends thereof. Each end plate 94 has a first passage 96 to receive a third pivot pin 98, for pivotally mounting the end plate 94 to a corresponding frame member 56. In addition, the corresponding frame member 56 has an adjustable stopping means 100 to provide a limit for the cross member 90 to arrive at a predetermined end location when the support wheels 38, 40 are deployed to the second position. The stopping means 100 includes a first pair of stop blocks 102, each fixed to a corresponding frame member 56. A threaded fastener, in this case a bolt 106, is threaded into each first stop block 102 extending outwardly therefrom. The bolt 106 has a head which is positioned to intercept a corresponding second stop block 104 (figure 6) which itself is fixed to an inner side of a corresponding end plate 94. Each end plate 94 has a second passage 108 to receive an axle member 110, itself supporting the support wheels 38, 40 at opposite ends thereof. Thus, the first and second stop blocks 102, 104 are operable to limit the travel of the end plate 94 and thus the support wheels 38, 40 beyond the second operating position thereof.
While the cross member 90 provides a secure positioning of the link members 93 (in their preferred form as end plates 94), the cross member 90 may be replaced by a direct coupling of the hydraulic ram 76 to the link members 93. The link members 93 may in turn each be pivotally secured to the undercarriage 46, in a manner permitting them to support the axle member 110 without the need of the cross member 90. If desired, the axle member 110 may be replaced by axle segments (not shown), each fixed to a corresponding link member 93.
Referring to figure 6, a return means 112 is also provided for returning the support wheels 38, 40 to the first position above the common plane 32. In this case, the return means 112 is provided in the form of a double spring rod arrangement 114 involving a pair of opposed rods 116 extending through a first support flange 118 on the housing portion 78 and fixed at one end to a second support flange 120 (figure 7) by way of fasteners 122. The second support flange 120 is in turn fixed to the ram portion 80 at a location near its end region. Each rod 116 is provided at its other end with an anchor fastener 124 to cooperate with the first support flange 118 to position a compression spring 126 therebetween. A
commercial version of the hydraulic ram 76 is available from NORTHRIDGE METAL FABRICATORS, New Lowell, Ontario CANADA.
Referring to figures 8 and 9, the actuating means 44 is further provided with a motor means 128 in the form of an hydraulic pump 136 having first and second foot pedals 130 and 132 respectively. The first foot pedal 130 operates the hydraulic pump 136, while the second foot pedal 132 operates a release means 134, which is integrally formed with (and operable to release) the hydraulic pump 136 to displace the support wheels 38, 40 toward their first position above the common plane 32. A
commercial version of the hydraulic pump 136 is available from STAR HYDRAULIC under model number FP3AC-PL. Thus, the first foot pedal 130 is operable in two reciprocating movements, the first movement when it is moved from its first operable position to its second operable position to pressurize the hydraulic pump 136 and thus the hydraulic ram 76 by way of a hydraulic fluid circuit 138. The second movement occurs when the second foot pedal returns to its first operable position, in this case under the action of a spring 139. The hydraulic circuit 138 is provided in the form of first and second hydraulic hoses 140, 142. The release means 134 is provided, in one example, as a release valve which is responsive either to the second foot pedal 132 or a predetermined limit function. The latter is operable to avoid damage when the fluid pressures in the hydraulic fluid circuit 138 exceed a predetermined upper pressure limit. The predetermined limit function is a built in function of the commercial version of the hydraulic pump 136 described herein, but may be external to the hydraulic pump 136, if desired.
Refen-ing to figure 9a, the actuating means 44 also provides a bleed unit 144 for bleeding the hydraulic ram 76 from the extended position (figure 6) in which the support wheels 38, 40 are at or near their second position below the common plane 32 in order to return the support wheels 38, 40 toward the first position.
The bleed unit 144 provides, in this case, the substantial equivalent of an imperfect hydraulic seal on a high pressure side of the hydraulic ram 76. This has the effect of causing a gradual leakage of hydraulic fluid from the hydraulic chamber (not shown) of the hydraulic ram 76. This is provided by a variable valve 146, which is located in the hydraulic fluid circuit between the hydraulic ram 76 and the second hydraulic hose 142. If desired, the bleed unit function may be provided elsewhere, such as in the hydraulic fluid circuit or the hydraulic pump 136 itself. The bleed unit 144 is operable to insure that the actuation means 44 is not deployed beyond a reasonable dwell time. This allows the operator to deploy the support wheels 38, 40 to raise the cart 10 and then, within a predetermined dwell time, to manipulate the cart with the support wheels 38, 40 gradually traveling toward their first position, as seen by a gradual lowering of the cart 10.
For example, the bleed unit 144 may be configured by making an appropriate adjustment to the variable valve 146 by way of an adjustment portion 146a to completely retract the support wheels within about two minutes for an unloaded cart 10 (which may in one case weigh in the order of about 250 pounds) and within about 30 seconds for a loaded cart (which may in one case weigh in the order of about 1350 pounds).
When fully retracted to their first position, the support wheels 38, 40 may provide ground clearances in the order of about 1 inch to about 8 inches. When the support wheels 38, 40 are fully deployed they may be about 0.5 inch below the common plane 32, though other specific ground clearances or deployments may be used as desired. If desired, the variable valve unit 146 may be responsive to an electrically, pneumatically or hydraulically powered actuator shown schematically at 146b which in turn may be responsive to a switch 146c located on a control pod 147 (figure I) at a suitable location on the cart 10 such as a cart handle 148 shown in figure 1. If desired, the control pod 147 may also be provided with one or more other control functions by way of one or more buttons, graphical readouts and the like, as shown schematically at 147a to control other functions of the cart 10. For instance, the control functions may include the adjustment of the undercarriage by way of the motor shown at 74 in figure 2 as described earlier, and the operation of the hydraulic ram 76 by way of an electric motor (not shown).
The swivel and non swivel wheels 16, 18 and 20, 22 are conveniently equipped with ground engaging portions formed from resilient materials such as urethanes and other plastics, though other suitable materials may of course be employed, depending on, for instance, the operating weight of cart 10 and the nature of the ground surface 34. The support wheels 38, 40 are preferably equipped with ground engaging portions which are of a substantially non resilient wheel material, such as steel, bronze, aluminum and the like. This has the benefit of ensuring the forces needed to displace the cart when the support wheels 38, 40 in their second position are substantially reduced since the rolling friction of the support wheels 38, 40 should, by consequence, generate lower frictional forces compared with the higher frictional forces generated by the resilient material of the swivel and non swivel wheels, 16, 18 and 20, 22.
The support wheels 38, 40 are also desirably provided with a set of bearings (not shown) which provide an improved reduction of rolling friction. Examples of suitable bearings for use on the support wheels 38, 40 are available from CANADIAN BEARINGS.
However, other materials may be used, as desired. Moreover, the same materials or different material may be employed for one or more of the wheels, including resilient material for the support wheels and substantially non resilient materials for the swivel or non swivel wheels, as desired. For example, suitable support wheels, swivel and non swivel wheels are available from COULSON.
As seen in figure 1, the cart handle 148 is configured to assist the operator in maneuvering the cart 10 and includes an inverted U-shaped support member fixed to the frame 12 adjacent a hitch arm 150. The hitch arm I50 is operable for connecting the cart 10 to an adjacent cart or a tow vehicle, as shown in fragmented fashion at 153 in figure 3. In figure 8 and 9, a safety means 152 is operably coupled to the hitch arm 150 and is responsive to movements thereof to release the hydraulic ram 76 to return the support wheels 38, 40 to their first position above the common plane 32. The safety means 152 includes a cable assembly 154 having a cable 155 which is coupled to a lower region of the hitch arm 150 by way of a fastener 154a and at an opposite end to the second foot pedal 132 by way of anchor member 154b. The cable assembly 154 has a pair of cable supports 156, 158 which secure the cable assembly 154 to the cart frame 12. Of course other hitch portions may be used in place of the hitch arm 150, such as ball and socket, or loop and hook coupling units. Though not specifically illustrated herein, another safety means may include an "inertia"
switch which activates based on relative movement between a switch and its associated contacts. In this case, when a load is pulled, a short movement in the hitch forward will cause the "inertia" switch to release the hydraulic pressure.

Thus, the second foot pedal 132 may be activated to release the hydraulic pressure in the hydraulic fluid circuit 138, either by directly depressing the second foot pedal 132 or by lowering the hitch arm 150. In the latter case, as the hitch arm 150 is moved from its upright position as shown in figure 8 to its horizontal operative position as shown in figure 9. The hitch arm 150 thus draws the cable 155 outward in the region of the fastener 154a, as seen by the arrow adjacent thereto causing a proportional displacement of the anchor member 154b and thus the second foot pedal 132. Thus, the safety means 152 may be operable when the hitch arm 150 reaches the first position, or in between the first and second position and/or when the hitch arm 150 leaves the second position.
Thus, the cart 10 may be used as follows. The cart 10 is first assembled as shown and is positioned with the supporting wheels 38, 40 in their first position above the common plane 32 to receive a load 36 on the deck 14. The load 36 may, in this case, include a rack or fixture containing a number of manufactured or assembled articles or components for later manufacture or assembly into a finished article, such as a vehicle.
It is preferable that the load 36 be located so that the centre of gravity 48 of the cart is just to the left of the support wheels 38, 40 (figure 5) when in their second position, in order to have the majority of the load resting on the support wheels 38, 40 for reasons to be described. If desired at the time of placing the load 36 on the deck 14 (or at a later stage in or following the transfer of the load 36), the undercarriage 46 may be adjusted as desired by rotating the threaded rod 70 or by displacing the motor 74, to bring the centre of gravity 48 to a desirable location relative to the support wheels 38, 40. For instance, the load 36 may be positioned so that about 55 percent of the load is located on the swivel wheel side of the support wheels 38, 40.
With the load 36 in position, the cart is then transferred from an originating location to a destination location. For example, the originating location might be the output of a vehicle component storage or manufacturing area and the destination location might be a site on an assembly line where the vehicle component is to be installed on a vehicle. The transfer of the cart 10 is conducted by a tow vehicle 153 which is connected to the hitch arm 150 in its horizontal position as shown in figure 3. It will be understood that, with the swivel and non swivel wheels 16, 18 and 20, 22 having a resilient ground surface engaging portion, the frictional forces generated between the ground surface 34 and the ground wheel engaging portions requires a relatively high "push pull" force to be exerted by the tow vehicle 153 on the hitch arm 150. The term "'push pull" force is intended to mean the minimum force needed to overcome the collective static friction generated at the swivel and non swivel wheels 16, 18 and 20, 22. This term can be considered to include the forces needed to twist the swivel wheels 16, 18 from a transverse or "sideways"
position to a position in line with the longitudinal axis A. Of course, this "push pull" force would be significant if an operator were to attempt to displace the load bearing cart 10 by exerting forces on the cart handle 148 and doing so would risk back injury. Of course, these forces would not pose a problem for the tow vehicle 153 in most practical cases.
The tow vehicle 153 delivers the cart 10 to a location near the destination location and the hitch arm 150 is thus disconnected from the tow vehicle 153 and raised to its upright storage position as shown in figure 1.
While grasping the cart handle 148 for support, the operator depresses the first foot pedal 130 in a reciprocating fashion, first to depress the pedal 130 and then to allow the force of the spring 139 to return the first foot pedal 130 to an upper position. With each stroke of the first foot pedal 130, the hydraulic ram 76 is extended causing the hydraulic ram 76 to displace the cross member 90 which in turn displaces the support wheels 38, 40 toward, and then beyond, the common plane 32. With the location of the load 36 on the swivel wheel side of the support wheels 38, 40, continued displacement of the support wheels 38, 40 beyond the common plane 32 brings the non swivel wheels 20, 22 off the ground surface 34 with the vast majority of the weight of the load being carried by the support wheels 38, 40.
These wheels, in their most preferred form, are steel and thus have substantially non resilient ground surface engaging portions, which means that the forces needed to overcome the rolling friction of the support wheels 38, 40 are also significantly reduced. Thus, with the support wheels 38, 40 in their deployed position as shown in figure 5, the operator may grasp the cart handle 148 and manipulate the cart 10 to position the load 36 in its proper orientation at the destination location.
Meanwhile, the bleed unit 146 slowly reduces the pressure in the hydraulic ram 76 resulting in the support wheels 38, 40 slowly retracting toward their position above the common plane 32. The speed of this retraction is, of course, adjustable and is intended to provide the operator sufficient time to manipulate the cart 10 to its desired position at the destination location while ensuring that the cart 10 will not remain with the support wheels 38, 40 fully deployed. It will be understood that the cart 10 may be used without the bleed unit 146, if desired.
Should the operator wish to release the pressure in the hydraulic ram 76, the operator depresses the second foot pedal 132 which activates the release valve located within the hydraulic pump 136. Should the operator opt to connect the hitch arm 150 with a tow vehicle 153, the corresponding swinging of the hitch arm 150 from the upright position toward the horizontal position displaces the cable 155 which in turn similarly depresses the second foot pedal 132 to release the pressure in the hydraulic ram 76. Of course, other variations of the cart 10 are intended without necessarily using the release means as described herein.
Once the pressure is released from the hydraulic ram 76, the support wheels 38, 40 will travel toward the common plane 32. In the case where the return means 112 is utilized (figure 6), the support wheels 38, 40 will return to their first position above the common plane 32 under the action of compression springs 126.

Figure 9b shows an alternative safety means wherein a satellite hydraulic release valve 160 is located adjacent a lower region of the hitch arm 150. The release valve 160 is provided with an activator 162 and is in fluid communication with the hydraulic fluid circuit 138 (figure 9) by way of satellite fluid circuit portion 164. In this case, the hinge arm I50 is provided with a cam portion 150a to engage the activator 162 to release the hydraulic pressure in the hydraulic fluid circuit 138 when the hitch arm I50 is moved from its upright storage position to its horizontal operative position.
An alternative to the hydraulic ram 76 is shown in figure 10. In this case, a hydraulic ram 170 and a tension spring assembly 172 are separately mounted between a cross member 174 (supporting a pair of support wheels not shown) and a lateral frame member 176 (of an undercarriage not shown) by way of a respective set of pivot pins 178, 180, each held by a corresponding pair of mounting flanges 182, 184 respectively. The hydraulic ram 170 is fluidly coupled to a hydraulic fluid circuit 186 and is thus operable to displace the support wheels as described earlier. In this case, the hydraulic ram 170 is separate from the tension spring assembly 172 and the latter is operable to return, the support wheels 38, 40 to their first position above the common plane 32 as described earlier.
It may be desirable in some cases to provide a cart which does not rely on a manual pumping of a hydraulic pump as necessary in one version of the cart 10 as described above. Thus, with reference to figure I 1 and 12, an alternative cart is shown at 200, having a cart handle 202 which is mounted on a cart frame 204.
Mounted on the cart handle 202 is a trigger assembly 206, operably coupled with an hydraulic actuator assembly 208, by way of a cable 210. The trigger assembly 206 has a trigger latch 212 which is responsive to the gripping hand of an operator as when gripping the cart handle 202 to maneuver the cart 200. The trigger assembly 206 thus emits an actuating signal to the hydraulic actuator assembly 208 when the operator grips the cart handle 202 and displaces the trigger latch 212. In this case, the hydraulic actuator assembly 208 includes a switch portion 214 which is operably coupled with the cable 210 to receive the actuating signal. A hydraulic pump 216 receives a corresponding actuating power signal from the switch portion 214 to pressurize or depressurize a hydraulic fluid circuit shown at 218. The hydraulic fluid circuit 218 includes a hydraulic ram (not shown) which is operably coupled with a pair of support wheels (not shown) as described above. The hydraulic pump 216 is powered by a power supply 220 in this case in the form of a battery pack 222. In this case, then, the cart 200 is operable to actuate the support wheels when the operator grips the handle and thus depresses the trigger latch 212. The cart 200 is also operable to retract the support wheels when the operator releases his grip on the cart handle 202 thus releasing the trigger latch 212, which causes the hydraulic pump 2I6 to depressurize the hydraulic circuit 218.
Figure 12 shows another variation of the cart 200 in which the hydraulic pump 216 is positioned locally to the hydraulic ram and receives power from the battery pack 222 by way of a power cable 224.

Y
While the present invention has been described for what are presently considered the preferred embodiments, the invention is not so limited. To the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
If desired, the support wheels and the hardware providing the actuating means may be provided in a kit for retrofitting existing wheeled carts.
While the cart 10 is provided with an undercarnage 46 which is capable of adjustments along the longitudinal axis "A", the undercarriage 46 may, if desired, be arranged to provide lateral adjustment, that is, perpendicular to the longitudinal axis "A". This may be necessary or desired, in some cases, to accommodate lateral imbalances caused by a misplacing of a toad on the deck 14, for example as shown schematically in dashed lines at 36' in figure 2. The lateral adjustment may, if desired, be provided in addition to the longitudinal adjustment, or as an alternative thereto.
Furthermore, the undercarriage may be inclined relative to the support frame portion, as shown in chain-dotted lines at 42' in figure 3. In this case, deployment of the support wheels between their first and second positions may be made by displacing the undercarriage 42' along an inclined axis B (as shown by the chain dotted arrow) which is at an angle relative to the support frame portion. This displacement includes a component, in this case a vertical component as viewed in figure 3, which may be selected to provide the necessary displacement of the support wheels without additional displacement of the support wheels 38, 40 relative to the undercarriage 42'. In other words, in this case, the support wheels 38, 40 may be fixed relative to the undercarriage 42, if desired.
While the cart 10 has one or more rolling support elements which are positioned above the common plane in the first position, there may be cases where the one or more rolling support elements need not be above the common plane. For instance, the one or more rolling support elements may be in fact located at one of a number of locations relative to the common plane. For instance, the one or more rolling support elements may in fact be located in the common plane in the first position, provided the one or more rolling support elements do not unreasonably limit the maneuverability of the cart 10 beyond its intended use.
Furthermore, though not specifically illustrated herein, the one or more rolling support elements may be provided with a suspension arrangement, permitting them to accommodate variations in the common ground surface. A suspension arrangement may also be provided for the swivel and non swivel wheels.

Furthermore, the hydraulic fluid circuit may be arranged to override the suspension arrangement when the one or more rolling support elements are displaced from the first position to a second position, thus making the one or more rolling support elements static or "inflexible" or less flexible to changes in the common ground surface. Thus, the first position may be above the common or in the common plane, or for that matter both if the rolling support elements are movable by way of a suspension arrangement. The one or more rolling support elements may thus be operable in the first position to contact the common ground surface together with the swivel and non swivel wheels. Thus, the suspension arrangement may permit the one or more rolling support elements, in the first position, to accommodate changes in the common ground surface. If desired, the undercarriage 46 and/or hydraulic fluid circuit 138 may be configured to provide the suspension arrangement.

Claims

CLAIMS.

1. A cart comprising a support frame portion, a pair of swivel wheels and a pair of non swivel wheels, the swivel and non swivel wheels lying in a common plane to roll along a common ground surface, lifting means having at least one non swivel support wheel and being operable to transfer the support wheel between a first position above the common plane and a second position below the common plane, the lifting means further comprising actuating means to displace the at least one support wheel between the first and second positions, a hitch portion which is operable between a first position and a second position, the hitch portion being arranged in the first position to connect to an adjacent cart and/or a tow vehicle and to be generally upright in the second position, and a safety means responsive to the hitch portion to cause the actuating means to displace the at least one support wheel to the first position when the hitch portion is displaced toward the first position or when the hitch portion reaches the first position or a position between the first and second positions.

2. A cart as defined in claim 1, wherein the at least one support wheel includes a pair of fixed axle support wheels.

3. A cart as defined in claim 1, wherein the common plane is fixed relative to the support frame portion.

4. A cart as defined in claim 1, wherein the lifting means is located centrally between the non-swivel wheels and the swivel wheels.

5. A cart as defined in claim 1, wherein the lifting means comprises an undercarriage, the undercarriage being movable relative to the support frame portion.

6. A cart as defined in claim 5, wherein the support frame portion further comprises positioning means to position the undercarriage relative to the support frame portion.

7. A cart as defined in claim 6, wherein the support frame portion has a pair of longitudinal central frame members and a pair of first undercarriage support flanges oppositely mounted on, and inwardly extending from, the central frame members.

8. A cart as defined in claim 7, wherein the undercarriage has a pair of outwardly extending second undercarriage support flanges, each extending along a corresponding side of the undercarriage, the second undercarriage support flanges being positioned for slidable movement along the corresponding first undercarriage support flanges.

9. A cart as defined in claim 8, wherein the positioning means includes a number of threaded fasteners, each extending through a corresponding one of a series of matching passages formed in the first undercarriage support flange.

10. A cart as defined in claim 5, wherein the undercarriage includes displacement means to displace the undercarriage relative to the support frame portion.

11. A cart as defined in claim 10, wherein the displacement means includes a threaded rod which is threadably engaged between the undercarriage and the support frame portion, by one or more threaded support flanges.

12. A cart as defined in claim 10, wherein the displacement means includes an electrical, hydraulic or pneumatic motor and/or a gear arrangement which is operable between the undercarriage and the support frame portion.

13. A cart as defined in claim 2, wherein the actuating means includes an electrical, hydraulic and/or manual motor portion and a transmission portion operable in response thereto, for delivering an actuating force to the support wheels.

14. A cart as defined in claim 13, wherein the transmission portion includes a ram portion.

15. A cart as defined in claim 14, wherein the support wheels are mounted for rotation on an axle member.

16. A cart as defined in claim 15, wherein the ram portion further comprises an hydraulic ram acting between the support frame portion and the support wheels and the motor portion includes an hydraulic pump for displacing the hydraulic ram, the hydraulic ram and the hydraulic pump being operably joined by a hydraulic fluid circuit.

17. A cart as defined in claim 16, wherein the actuating means further comprises a pair of link members each pivotally mounted the undercarriage and supporting a corresponding support wheel.

18. A cart as defined in claim 17, wherein the actuating means further comprises a cross member extending across the undercarriage, each of the link members including an end plate fixed to a corresponding end of the cross member.

19. A cart as defined in claim 18, wherein the actuating means further comprises an axle member having a pair of end regions and extending between the end plates, each support wheel being mounted on a corresponding end region.

20. A cart as defined in claim 16, wherein the actuating means includes a bleed unit for bleeding the hydraulic ram for progressively returning the support wheels to the first position.

21. A cart as defined in claim 20, wherein the bleed unit includes a variable valve in the hydraulic fluid circuit, the hydraulic ram or the hydraulic pump.

22. A cart as defined in claim 16, further comprising a first foot pedal for pressurizing the hydraulic fluid circuit for advancing the hydraulic ram.

23. A cart as defined in claim 22, the first foot pedal moveable between a first operable position and a second operable position, further comprising a spring portion for biasing the first foot pedal to first operable position.

24. A cart as defined in claim 16, further comprising a releasing means for depressurizing the hydraulic fluid circuit for retracting the hydraulic ram.

25. A cart as defined in claim 24, further comprising a second foot pedal for activating the releasing means.

26. A cart as defined in claim 2, the actuating means including return means for returning the support wheels to the first position.

27. A cart as defined in claim 24, the actuating means including a return means for returning the support wheels to the first position, following activation of the releasing means.

28. A cart as defined in claim 2, each support wheel including a ground engaging portion formed from a substantially non resilient material.

29. A cart as defined in claim 28, wherein the non resilient material wheel includes one or more of steel, bronze and aluminum.

30. A cart as defined in claim 2, wherein each of the swivel and non swivel wheels includes a ground engaging portion formed from a resilient material.

31. A cart as defined in claim 13, wherein the actuating means further comprises a trigger assembly for triggering the motor portion for deploying the transmission portion.

32. A cart as defined in claim 31, further comprising a cart handle, the trigger assembly being mounted on the cart handle.

33. A cart as defined in claim 32, wherein the motor portion includes a hydraulic pump which is responsive to a switch portion operably coupled to the trigger assembly.

34. A cart as defined in claim 32, wherein the trigger assembly includes a trigger latch which is positioned adjacent the cart handle to be actuated when the cart handle is gripped by an operator.

35. A cart as defined in claim 33, further comprising a power source for supplying a power signal to the hydraulic pump.

36. A carrier for transporting an article comprising a support frame portion, a first undercarriage including a plurality of first wheels to roll along a ground surface and having rolling contact points lying in a common plane, a second undercarriage located centrally within the first undercarriage and including one or more second wheels, actuating means for actuating the second undercarriage from a position with the one or more second wheels above the common plane to a position beyond the common plane which is sufficient to displace one or more of the first wheels of the first undercarriage off the ground surface, a hitch portion which is operable between a first position and a second position, the hitch portion being arranged in the first position to connect to an adjacent cart and/or a tow vehicle and to be generally upright in the second position, and a safety means responsive to the hitch portion to cause the actuating means to displace the second undercarriage above the common plane when the hitch portion is displaced toward the first position or when the hitch portion reaches the first position or a position between the first and second positions.

37. A carrier as defined in claim 36, wherein one or more of the first and/or second wheels are fixed axle wheels.

38. A carrier as defined in claim 36, wherein one or more of the first and/or second wheels are swivel wheels.

39. A carrier as defined in claim 39 wherein one or more of the first and/or second wheels are non-swivel wheels.

40. A carrier as defined in claim 36 wherein one or more of the first and/or second wheels are fixed axle wheels.

41. A carrier as defined in claim 39 wherein the support frame portion has a longitudinal axis and the second undercarriage is operable to adjust the position of the one or more second fixed axle wheels relative to the longitudinal axis.

42. A carrier as defined in claim 40 wherein the second undercarriage is movable in a direction substantially parallel with or substantially perpendicular to the longitudinal axis, or both.

43. A carrier as defined in claim 36 wherein the second undercarriage is inclined relative to the first undercarriage.

44. A method of transporting an article, comprising:

- a step for providing a carrier for supporting the article, - a step for providing a first undercarriage including a plurality of first wheels to roll along a ground surface with rolling contact points of the first wheels lying in a common plane, - a step for providing a second undercarriage located centrally within the first undercarriage and including a pair of second fixed axle wheels, - a step for displacing the second undercarriage so that the second fixed axle wheels are above the common plane, - a step for providing a hitch portion with the carrier, - a step for arranging the hitch portion to be operable between an inclined first position and an upright second position, - a step for arranging the hitch portion in the inclined first position to connect to an adjacent cart and/or a tow vehicle, - a step for providing a safety arrangement to be responsive to the hitch portion to actuate the at least one support wheel to the first position when the hitch portion is displaced toward the first position or when the hitch portion reaches the first position or a position between the first and second positions, - a step for transferring the carrier from an originating location to a destination location;

- and after the carrier arrives near the destination location, a step for actuating the second undercarriage from the position with the second fixed axle wheels above the common plane to a position beyond the common plane sufficient to displace one or more first wheels off the ground surface; and - manipulating the carrier for the article to be in a predetermined orientation at the destination location.

45. A method of improving the transfer of an article between an originating location and a destination location, comprising the steps of:

a) providing a carrier for supporting an article during transfer;

b) providing the carrier with a first wheeled undercarriage having a plurality of first wheels on which to displace the carrier between the originating and destination locations;

c) arranging the first wheels to roll on a ground surface with rolling contact portions of the first wheels lying in a common plane;

d) selecting a predetermined characteristic of the first wheels to optimize the transfer of the article between the originating location and destination locations, e) providing a hitch portion with the carrier, f) arranging the hitch portion to be operable between an inclined first position and an upright second position, g) arranging the hitch portion in the inclined first position to connect to an adjacent cart and/or a tow vehicle, h) providing a safety arrangement to be responsive to the hitch portion to actuate the at least one support wheel to the first position when the hitch portion is displaced toward the first position or when the hitch portion reaches the first position or a position between the first and second positions, i) transferring the carrier between the originating and destination locations on the first wheels, j) providing a second undercarriage with at least one second fixed axle support wheel;

k) selecting a predetermined characteristic of the at least one second fixed axle support wheel to optimize the manipulation of the carrier at the destination location;

l) and after step e), actuating the at least one second fixed axle support wheel from a position above the common plane to a position beyond the common plane, sufficient to raise selected first wheels of the first undercarriage off the ground surface; and m) manipulating the carrier for the article to be in a predetermined orientation at the destination location.

46. A method as defined in claim 45, wherein step d) includes the step of selecting the first wheels with a ground engaging portion formed from a resilient material.

47. A method as defined in claim 46, wherein step g) includes the step of selecting the at least one second fixed axle wheel with a ground engaging portion formed from a substantially non-resilient material.

48. A kit for converting a cart of the type having a support frame portion, a pair of swivel wheels and a pair of non swivel wheels, the swivel and non swivel wheels lying in a common plane to roll along a common ground surface, the kit comprising lifting means having at least one non swivel support wheel and being mountable on the support frame portion for transferring the at least one non swivel support wheel between a first position above the common plane and a second position below the common plane, the lifting means further comprising actuating means to displace the at least one support wheel between a first position above the common plane and a second position below the common plane, the at least one non swivel support wheel being operable in the second position, a hitch portion which is operable between a first position and a second position, the hitch portion being arranged in the first position to connect to an adjacent cart and/or a tow vehicle and to be generally upright in the second position, and a safety means responsive to the hitch portion to cause the actuating means to displace the at least one support wheel to the first position when the hitch portion is displaced toward the first position or when the hitch portion reaches the first position or a position between the first and second positions.

49. A cart comprising a support frame portion, a pair of swivel wheels and a pair of non swivel wheels, the swivel and non swivel wheels lying in a common plane to roll along a common ground surface, a lifting portion having at least one rolling support element and being operable to transfer the at least one rolling support element between a first position above the common plane and a second position below the common plane, the lifting portion further comprising an actuating portion to displace the at least one rolling support element between the first and second positions, the rolling support element being operable in the second position, a hitch portion which is operable between a first position and a second position, the hitch portion being arranged in the first position to connect to an adjacent cart and/or a tow vehicle and to be generally upright in the second position, and a safety means responsive to the hitch portion to cause the actuating portion to displace the at least one support element to the first position when the hitch portion is displaced toward the first position or when the hitch portion reaches the first position or a position between the first and second positions.

50. A cart as defined in claim 49, wherein the rolling support element includes one or more rollers and/or wheels.

1. A cart comprising a support frame portion, a pair of swivel wheels and a pair of non swivel wheels, the swivel and non swivel wheels lying in a common plane to roll along a common ground surface, a lifting portion having at least one rolling support element and being operable to transfer the at least one rolling support element from a first position relative to the common plane and a second position below the common plane, the lifting portion further comprising an actuating portion to displace the at least one rolling support element between the first and second positions, the rolling support element being operable in the second, a hitch portion which is operable between a first position and a second position, the hitch portion being arranged in the first position to connect to an adjacent cart and/or a tow vehicle and to be generally upright in the second position, and a safety means responsive to the hitch portion to cause the actuating portion to displace the at least one support element to the first position when the hitch portion is displaced toward the first position or when the hitch portion reaches the first position or a position between the first and second positions.

52. A cart as defined in claim 51 wherein the first position is either above the common or in the common plane.

53. A cart as defined in claim 52 wherein the at least one rolling support element is operable in the first position to contact the common ground surface together with the swivel and non swivel wheels.

54. A cart as defined in claim 53 wherein the at least one rolling support element includes a suspension arrangement for permitting the at least one rolling support element, in the first position, to accommodate changes in the common ground surface.