WO2008111041A2

WO2008111041A2 - Combination dolly-pallet

Info

Publication number: WO2008111041A2
Application number: PCT/IL2007/000341
Authority: WO
Inventors: Nir Hadar
Original assignee: Polymer Logistics B.V.
Priority date: 2007-03-15
Filing date: 2007-03-15
Publication date: 2008-09-18
Also published as: WO2008111041A3

Abstract

A combination dolly-pallet device has wheel elements attached in fixed relation to a load bearing deck portion. A transition from pallet to dolly is performed by bringing support elements closer to the deck portion until weight is transferred from the support element to the wheel elements. Three embodiments are described, each based upon motion of wedge elements. In a low-angle wedge embodiment, a screw-drive actuator converts the device between pallet and dolly configurations by use of an external source of rotational power. A higher-angled wedge embodiment provides gravity-assisted manual operation to convert from pallet to dolly. A yet higher angled wedge embodiment provides automatic pallet-to-dolly conversion which is selectively inhibited by a manually releasable retention mechanism.

Description

Combination Dolly-Pallet

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to devices used for conveyance of goods and, in particular, it concerns a combination dolly-pallet. Conveyance of many types of retail goods from their source (e.g., agricultural producer, factory or importer) through distribution channels to retailers is typically performed using pallets or containers without wheels, referred to generically herein as "pallets". These pallets can be handled by a wide range of lifting gear, forklifts and roller-based conveyor systems particularly suited to efficient conveyance of large quantities of produce, and are also convenient for storage on racks or other tiered storage systems.

On reaching the delivery point for a retail outlet, it is often preferably to provide wheeled transport decks or containers, referred to generically herein as "dollies," to allow convenient handling of the goods, for example, guiding them along relatively narrow aisles, without requiring a dedicated pallet jack or the like. Dollies are not generally acceptable for the earlier stages of transportation since the wheels may interfere with conveyor systems or with stacking, and the mobility of the loads is considered problematic for storage in racks. As a result, use of dollies at the retail outlet typically requires labor-intensive manual transfer of the goods, item by item or box by box, from a pallet to a dolly.

It has been suggested to combine the functionality of pallets and dollies into a single device. Specifically, various devices have been proposed in which a set of wheels are mounted retractably so that the device functions as a regular pallet with the wheels retracted during distribution and then, on reaching the retail outlet, the wheels are lowered to convert the pallet to a dolly.

While this approach is theoretically very promising, devices of this sort tend to suffer from various disadvantages. Specifically, the mechanism for lowering the wheels is subject to very high stress since it must lift up the entire pallet with its load sufficiently to provide rolling clearance for the wheels. This requires a robust lifting mechanism which typically adds undesirably to the weight and cost of the pallet, and may be unreliable. Alternatively, a simpler retractable wheel configuration may be employed if an external lifting device such as a pallet jack is used to lift the pallet while the wheels are lowered. However, this too is inconvenient.

There is therefore a need for a combination dolly-pallet which would facilitate the transition from pallet functionality to dolly functionality without requiring lifting of the load bearing surface and its load. It would also be highly advantageous to provide a combination dolly-pallet device employing a relatively simple wedge-based mechanism.

SUMMARY OF THE INVENTION

The present invention is a combination dolly -pallet device. According to the teachings of the present invention there is provided, a combination dolly-pallet device for supporting a load above an underlying surface, the device comprising: (a) a load bearing deck portion; (b) a plurality of wheel elements attached in fixed relation to the load bearing deck portion; (c) at least one retractable support element having a downward facing contact surface, the retractable support element being linked to the load bearing deck portion; (d) at least one wedge element disposed so as to assume a first position in which the at least one wedge element is interposed between the load bearing deck portion and the retractable support element, thereby maintaining a position of the retractable support element such that the contact surface is deployed below the wheel elements so that at least of portion of the combination dolly-pallet device is supported by contact of the contact surface with the underlying surface, the wedge element being displaceable to a second position in which the retractable support element is retractable to a retracted state in which the contact surface is raised so that at least a portion of the combination dolly-pallet device is supported by contact of the plurality of wheel elements with the underlying surface.

According to a further feature of the present invention, the load bearing deck portion forms part of a walled container.

According to a further feature of the present invention, the plurality of wheel elements includes four wheel elements attached to the load bearing deck portion.

According to a further feature of the present invention, the at least one retractable support element is implemented as two retractable support elements extending along a majority of the width of two opposing sides of the load bearing deck portion, and wherein the at least one wedge element is implemented as two wedge elements, each of the wedge elements cooperating with a corresponding one of the retractable support elements. According to a further feature of the present invention, the wedge elements and the retractable support elements are configured to provide an opening for insertion of a tine of a pallet-lifting device from each of the two opposing sides.

According to a further feature of the present invention, at least two of the wheel elements are caster wheels.

According to a further feature of the present invention, the at least one retractable support element is resiliently biased towards the retracted state.

According to a further feature of the present invention, the at least one wedge element is implemented as two wedge elements, each of the wedge elements cooperating with at least a corresponding one of the retractable support elements.

According to a further feature of the present invention, the two wedge elements move in opposite directions during displacement from the first position to the second position. According to a further feature of the present invention, there is also provided a screw-drive actuator for displacing the at least one wedge element bidirectionally between the first position and the second position.

According to a further feature of the present invention, the screw-drive actuator includes an externally accessible power-input port for receiving a rotatable tip of a power tool for driving the screw-drive actuator.

According to a further feature of the present invention, the at least one wedge element has an effective wedge angle in the range from 10 degrees to 30 degrees. According to a further feature of the present invention, there is also provided a manually operable mechanical linkage configured for displacing the at least one wedge element from the first position to the second position, and wherein the at least one wedge element has an effective angle of at least 35 degrees such that a load applied to the load bearing deck portion facilitates operation of the mechanical linkage.

According to a further feature of the present invention, the manually operable mechanical linkage includes a manually displaceable actuator lever configured to be displaceable along an actuating path of length greater than a path of the at least one wedge element from the first to the second position. According to a further feature of the present invention, the at least one wedge element has an effective wedge angle no greater than 55 degrees.

According to a further feature of the present invention, the at least one wedge element has an effective angle of at least 55 degrees such that, when a load is applied to the load bearing deck portion, the load biases the at least one wedge element to move from the first position to the second position, the device further comprising a manually releasable retention mechanism deployed to prevent displacement of the at least one wedge element from the first position towards the second position until the retention mechanism is manually released. According to a further feature of the present invention, the manually releasable retention mechanism includes a rotatable element mounted so as to be rotatable about an axis of rotation and mechanically linked to the at least one wedge element, and at least one blocking element selectively deployable to engage both the rotatable element and a fixed element so as to prevent relative rotation between the rotatable element and the fixed element, the at least one blocking element being located at a distance from the axis of rotation of no less than a quarter of a minor dimension of the load bearing deck portion.

According to a further feature of the present invention, the manually releasable retention mechanism includes a rotatable disk mounted so as to be rotatable about an axis of rotation and mechanically linked to the at least one wedge element, a fixed surface mounted in fixed relation to the load bearing deck portion and at least one ball deployed in complementary recesses in the rotatable disk and the fixed surface to as to prevent relative rotation between the rotatable disk and the fixed disk.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein:

FIGS. IA and IB are isometric views of a first embodiment of a combination dolly-pallet device, constructed and operative according to the teachings of the present invention, in its pallet state and its dolly state, respectively;

• FIGS. 2A and 2B are lower isometric views of the combination dolly- pallet device of Figures IA and IB in its pallet state and its dolly state, respectively;

FIG. 3 is a bottom view of the combination dolly-pallet device of Figures IA in its pallet state; FIGS. 4 A, 4B and 4C are cross-sectional views taken along the lines A-A, B-B and C-C, respectively, in Figure 3;

FIG. 5 is an exploded isometric view of the combination dolly-pallet device of Figures IA and IB; FIG. 6 is a cut-away isometric view of the combination dolly -pallet device of Figures IA and IB illustrating the operation of a screw-drive actuator;

FIG. 7 is an isometric view of a second embodiment of a combination dolly-pallet device, constructed and operative according to the teachings of the present invention, in its dolly state; FIG. 8 is an isometric view of the combination dolly -pallet device of

Figure 7 with an upper deck surface removed to reveal a manually operable mechanical linkage;

FIG. 9 is an isometric exploded view of the combination dolly-pallet device of Figure 7; FIG. 10 is a bottom view of the combination dolly-pallet device of Figure

7;

FIGS 1 IA and 1 IB are cross-sectional views taken along the lines G-G and E-E, respectively, in Figure 10;

FIGS. 12A and 12B are top isometric views of the combination dolly- pallet device of Figure 7 with the upper deck surface removed and showing the manually operable mechanical linkage in the pallet state and the dolly state, respectively;

FIG. 13 is an isometric cut-away view of the combination dolly-pallet device of Figure 7; FIGS. 14A and 14B are end views of the combination dolly-pallet device of Figure 7 in the pallet state and the dolly state, respectively;

FIG. 15 is an isometric view of a third embodiment of a combination dolly-pallet device, constructed and operative according to the teachings of the present invention, in its pallet state; FIG. 16 is an isometric exploded view of the combination dolly-pallet device of Figure 15;

FIG. 17 is a bottom view of the combination dolly -pallet device of Figure 15; FIGS. 18 A, 18B and 18C are cross-sectional views taken along the lines

I-I, H-H and K-K of Figure 17, respectively;

FIG. 19A is a lower isometric view of a two wedge elements and part of a retention mechanism from the combination dolly-pallet device of Figure 15;

FIG. 19B is an upper isometric view similar to Figure 19A with addition of two retractable support elements cooperating with the wedge elements;

FIG. 20 is an upper isometric view of the combination dolly-pallet device of Figure 15 with an upper deck surface removed to show the deployment of the retention mechanism;

FIG. 21 is a .cut-away isometric view of the combination dolly-pallet device of Figure 15; and

FIGS. 22A and 22B are schematic illustrations of an implementation of the combination dolly-pallet device of the present invention in which the load bearing deck portion is part of a walled container.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is a combination dolly-pallet device.

The principles and Operation of combination dolly-pallet devices according to the present invention may be better understood with reference to the drawings and the accompanying description.

By way of introduction, the present invention will be exemplified by reference to three particular embodiments. The three embodiments share a common conceptual approach to implementing a combination dolly-pallet device, namely, that the wheel elements are attached in fixed relation to a load bearing deck portion, and the transition from pallet to dolly is performed by bringing a support element closer to the deck portion until weight is transferred from the support element to the wheel elements. As a result, the height of the deck portion above an underlying surface decreases during the transition from pallet to dolly, so the load on the deck portion of the device actually facilitates this transition. The transition from dolly back to pallet, which requires some degree of lifting of the deck portion, is typically performed when the deck is unloaded.

The three embodiments presented herein also have in common that they employ particularly simple mechanisms based upon motion of wedge elements to maintain the support elements in position to provide the pallet functionality. The various embodiments differ primarily in the structure and functionality of how the wedge is held in position or moved.

Specifically, a first embodiment described with reference to Figures 1 A-6 employs relatively low-angle wedge elements driven bidirectionally by a screw- drive actuator, allowing conversion of the dolly-pallet device from a pallet to a dolly and back to a pallet by use of an external source of rotational power, such as an electric screwdriver. A second embodiment described with reference to Figures 7-14B employs higher-angled wedge elements to provide gravity-assisted operation of a manually operable mechanical linkage for converting the pallet to a dolly. A third embodiment described with reference to Figures 15-21 employs yet higher angled wedge elements to provide a structure which tends under an applied load to convert itself from a pallet to a dolly, but is prevented from doing so by a manually releasable retention mechanism. These different embodiments will now be described in turn. Referring now to the drawings, Figures 1A-6 show a first embodiment of a combination dolly -pallet device, generally designated 10, constructed and operative according to the teachings of the present invention, for supporting a load above an underlying surface. In general terms, device 10 has a load bearing deck portion 12 to which a plurality (typically four) of wheel elements 14a, 14b are attached in fixed relation. At least one retractable support element 16 having a downward facing contact surface 18 is linked to the load bearing deck portion. At least one wedge element 20 is disposed so as to assume a first position (Figures IA and 2A) in which the at least one wedge element 20 is interposed between load bearing deck portion 12 and retractable support element 16, thereby maintaining a position of retractable support element 16 such that contact surface 18 is deployed below wheel elements 14a, 14b and supports at least part of combination dolly -pallet device 10. Wedge element 20 is also displaceable to a second position (Figures IB and 2B) in which retractable support element 16 is retractable to a retracted state in which the contact surface 18 is raised. In this state, at least part of combination dolly-pallet device 10 is supported by contact of wheel elements 14a, 14b with the underlying surface.

At this stage, it will already be appreciated that the present invention provides a particularly simple and advantageous combination dolly-pallet device 10. Specifically, the provision of fixed wheel elements together with retractable non-rolling support elements ensures that conversion of the combination dolly- pallet device from a pallet to a dolly corresponds to lowering rather than raising the load bearing deck portion. As a result, any load on the device helps rather then hinders conversion to a dolly, thereby simplifying the pallet-to-dolly conversion which is normally required when the pallet is fully loaded at the retail outlet. Furthermore, the use of a wedge-based mechanism provides a reliable and cost effective solution for transferring the load bearing forces in the pallet state. These and other advantages of the present invention will become clearer from the following more detailed description. Although not limited to such a case, the present invention is typically implemented with four wheel elements 14«, 146 attached to load bearing deck portion 12 to provide full dolly functionality. Most preferably, two of these wheel elements, designated 14α, are caster wheels, i.e., free to swivel about a vertical axis. In this context, it should be noted that caster wheels are also considered to be "fixed" wheel elements relative to the load bearing deck portion, both because their mounting is fixed and because they are at constant vertical spacing from the deck. It is typically preferred that two of the wheel elements are non-swiveling wheels 14b. The retractable support element(s) may be implemented in a number of forms. According to one option, a separate retractable support element may be provided for each wheel. Alternatively, a single retractable support element may be configured as a lower frame to support the entirety of the dolly-pallet device in the pallet state. In the particularly preferred implementations illustrated here, the at least one retractable support element is implemented as two retractable support elements 16 each extending along a majority of the width of two opposing sides of load bearing deck portion 12. The at least one wedge element is most preferably also implemented as two wedge elements 20, each cooperating with a corresponding retractable support element 16. In the preferred configurations shown here, the two wedge elements 20 move in opposite directions during the transition from pallet to dolly, both being drawn inwards towards the center of the device. As the wedges move inwards, retractable support elements 16 are freed to move vertically upwards, and are preferably resiliently biased upwards towards their retracted state. In the case shown here, this resilient bias is provided by a set of compression springs 22 which are mounted around guide rods 24 (see Figures 4B and 5). Guide rods 24 delineate a vertical path of motion for retractable support elements 16 while compression springs 22 bear upwards and tend to force retractable support elements 16 towards their fully raised "retracted" position. Turning now to the mechanism for displacing wedge elements 20, this embodiment features a screw-drive actuator, best seen in Figures 4A, 5 and 6, for displacing wedge elements 20 bidirectionally between their first (pallet) and the second (dolly) positions. Specifically, the screw-drive actuator includes a central actuator bolt 26 with regions of left- and right-handed threading 28 which engage correspondingly threaded sleeves 30 embedded in wedge elements 20. At one or both ends of actuator bolt 26 is an externally accessible power-input port 32. Power-input port 32 is preferably configured for receiving a rotatable tip of a power tool, such as an electric screwdriver, for rotating the actuator bolt 26 so as to simultaneously displace wedge elements 20 inwards or outwards, as illustrated in Figure 6.

Clearly, a screw-drive actuator of- the type illustrated is capable of developing sufficient force to displace wedge elements 20 in either direction, either forcing the wedge elements 20 outwards so as to lower retractable support elements 16 and raise the load off the wheels or drawing wedge elements 20 inwards so as to allow retraction of support elements 16 and leave the load resting on wheel elements 14α, 146. Most preferably, the bulk structural components of the dolly -pallet device 10 are produced from low-cost polymer materials. If it is contemplated that the mechanism may be used to convert from a dolly back to a pallet when heavily loaded, it is preferable to implement wedge elements 20 and retractable support elements 16 with a relatively small effective wedge angle so that stress and frictional forces on the polymer materials are kept within acceptable ranges. Most preferably, the effective wedge angle is chosen to be within the range from 10 degrees to 30 degrees, and typically about 15 degrees. Optionally, materials with wear-resistant or friction-reducing additives or coatings may be employed.

In the preferred examples illustrated here, the upper surfaces of wedge elements 20 are configured to slide horizontally, i.e., parallel to the deck surface, while the inclined wedge surfaces face correspondingly inclined cooperating surfaces of retractable support elements 16. It should be noted that the invention is not limited to this configuration, and that part or all of the inclination of wedge elements 20 may optionally be implemented on an upward facing surface with corresponding adjustment of the cooperating surfaces of the deck portion 12 and retractable support elements 16. Where inclined surfaces are used on both upper and lower faces, an "effective wedge angle" is defined as the angle of a single angle wedge which would provide the same ratio of vertical-to-horizontal displacement. In quantitative terms, the effective angle is the arctangent of the sum of the tangents of the upper and lower wedge angles. In most cases, the use of upper surfaces sliding parallel to the deck surface is considered advantageous for its mechanical simplicity.

Turning now to Figures 7-14B, these illustrate a second embodiment of a combination dolly -pallet device, generally designated 100, constructed and operative according to the teachings of the present invention, for supporting a load above an underlying surface. Generally speaking, device 100 is structurally and functionally similar to device 10 described above, with functionally equivalent elements being designated with similar reference numerals incremented by 100. Device 100 differs from device 10 primarily in the mechanism employed to displace the wedge elements 120 and the corresponding mode of use.

Specifically, device 100 includes a manually operable mechanical linkage configured for displacing wedge elements 120 from their first position (Figure 12A) to their second position (Figure 12B). In the non-limiting preferred case illustrated here, the mechanical linkage includes an elongated primary lever arm 134 pivotally mounted at a central pivot point 136 of the device and coupled so as to displace two secondary displacement arms 138 linked to wedge elements 120. When primary lever arm 134 assumes the position of Figure 12A, secondary displacement arms 138 are forced outwards thereby maintaining wedge elements in their outward-most positions corresponding to the pallet state of the device. Most preferably, primary lever arm 134 reaches a position slightly beyond the straight-line alignment of the points of linkage so as to generate mechanical locking to resist inward displacement of wedge elements 120. Additionally or alternatively, a notch or other retaining feature may be deployed to help prevent inadvertent dislodging of primary lever arm 134 from the pallet state position. Primary lever arm 134 may then be manually displaced, typically through a small impact delivered by a user's foot, towards the position of Figure 12B so that secondary displacement arms 138 draw wedge elements 120 inwards. Once this motion starts, any load on the deck portion tends to help displace the wedge elements and facilitates completion of the motion. For this purpose, it is preferable that wedge elements 120 have an effective wedge angle of at least 35 degrees, although typically no more than 55 degrees.

It will be noted that the manually displaceable portion of primary lever arm 134 is displaceable along an actuating path of length significantly greater than the path of travel of wedge elements 120. This provides mechanical force amplification which further facilitates manual displacement of the mechanism.

As mentioned earlier, the reverse transition from dolly to pallet is not typically required while the device is loaded with goods. Once all the goods have been sold or otherwise removed, in the absence of a load on the deck portion of the device, primary lever arm 134 may readily be returned to its pallet state by manual displacement of primary lever arm 134 in the opposite direction, thereby rendering the device ready for re-use as a pallet.

Turning now to Figures 15-21, these illustrate a third embodiment of a combination dolly-pallet device, generally designated 200, constructed and operative according to the teachings of the present invention, for supporting a load above an underlying surface. Generally speaking, device 200 is structurally and functionally similar to device 10 described above, with functionally equivalent elements being designated with similar reference numerals incremented by 200. Device 200 differs from device 10 primarily in the mechanism employed to displace the wedge elements 220 and the corresponding mode of use.

Specifically, device 200 employs relatively high angle wedge elements 220, preferably with an effective angle of at least 55 degrees, and most preferably about 60 degrees. As a result, when a load (not shown) is applied to load bearing deck portion 212, the load biases wedge elements 220 to move from the first (pallet) position to the second (dolly) position. In other words, the geometry of the wedge surfaces is such that the pallet state is inherently unstable and would independently transform to the dolly state through the action of gravity if not prevented from doing so. Device 200 further includes a manually releasable retention mechanism deployed to prevent displacement of wedge elements 220 from the first position towards the second position until the retention mechanism is manually released. This embodiment thus renders conversion from pallet to dolly particularly easy and convenient, requiring minimal force applied by the user. The reverse transition, on the other hand, may require lifting of deck portion 212 or use of a dedicated tool. It is envisaged that this embodiment is primarily to be employed in the context of a service provider maintaining a service point via which device 200 passes for cleaning and maintenance after each use. In this case, part of the maintenance cycle is the resetting of device 200 back to its pallet state ready for the next round of use.

Turning now to the details of the manually releasable retention mechanism, the non-limiting preferred implementation illustrated here is best understood with reference to Figures 16, 17, 18C, 20 and 21. The mechanism includes a rotatable disk 240 mounted so as to be rotatable about an axis of rotation 242 relative to an adjacent fixed surface 244. In this case, fixed surface 244 is an integral part of a lower part of a two-part load bearing deck portion 212, and rotatable disk 240 is sandwiched between the upper and lower parts. A short central hub portion 246 extends below rotatable disk 240, passing through the lower part of deck portion 212 and connects to two actuator rods 248 which link to wedge elements 220, as best seen in Figures 17 and 19 A.

Rotatable disk 240 has at least one, and preferably two, through bores 250 each receiving a blocking element, preferably in the form of a ball 252. The height of the blocking elements, in this case the diameter of balls 252, is greater than the thickness of rotatable disk 240. In selected positions on fixed surface 244 are corresponding recesses 254 (Figures 16 and 21) for accommodating at least part of the excess height of the balls when bores 250 and recesses 254 are aligned. A locking element, in this case implemented as an elongated bar 256 pivotally mounted at axis 242, selectively overlies rotatable disk 240 opposite recesses 254.

When bores 250 and recesses 254 are aligned and together house balls 252, elongated bar 256 is deployed overlying bores 250. In this state, rotatable disk 240 is locked against rotation by the overlap of balls 252 between rotatable disk 240 and fixed surface 244, as seen in Figure 21. When elongated bar 256 is then displaced to as to no longer overlie bores 250 (Figure 20), balls 252 are free to ride up out of recesses 254, thereby allowing rotation of rotatable disk 240. A clearance between rotatable disk 240 and the facing lower surface of the upper part of deck portion 212 is preferably smaller than the diameter of balls 252 to prevent the balls from escaping from bores 250. The weight of a load, or of deck portion 212 alone, acting on the relatively high-angled wedge element 220 is then sufficient to displace wedge elements 220 and cause corresponding rotation of rotatable disk 240 until device 200 assumes its dolly state. Springs 222 (Figure 18A) also contribute to this transition.

Most preferably, balls 252 are located further from the axis of rotation than the linkages to actuator rods 248, thereby providing a step-down ratio of forces acting on the balls when locked. Preferably, this step down ratio is at least 2:1, more preferably at least 5:1, and in the preferred example illustrated here, at least about 10:1. In certain preferred implementations, a distance from axis of rotation 242 to balls 252 is no less than a quarter of a minor dimension of load bearing deck portion 212.

This embodiment also illustrates an optional feature of the present invention equally relevant to the embodiments described previously whereby retractable support elements 216 and wedge elements 220 are configured to provide an opening 260 (Figures 15 and 18A) for insertion of a tine of a pallet- lifting device from the sides of the device along which they extend. For this purpose, each wedge element 220 is configured as a U-shaped element with two localized wedge surfaces 262 cooperating with corresponding regions 264 of retractable support element 216. In all other respects, the structure and operation of device 200 may be understood by analogy to device 10 described above.

Turning finally to Figures 22A and 22B, as mentioned earlier, the load bearing deck portion 12, 112, 212 may be part of a walled container, variously referred to as a bin, box or crate, of various types employed in conveyance. By way of one non-limiting example, Figures 22A and 22B show an example of a shipping and display bin, constructed and operative according to the teachings of the present invention, implemented as a combined dolly-pallet device mechanically similar to device 100 described above. Figure 22A shows the "pallet" state of the bin while Figure 22B shows the "dolly" state of the bin.

It will be appreciated that the above descriptions are intended only to serve as examples, and that many other embodiments are possible within the scope of the present invention as defined in the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A combination dolly-pallet device for supporting a load above an underlying surface, the device comprising:

(a) a load bearing deck portion;

(b) a plurality of wheel elements attached in fixed relation to said load bearing deck portion;

(c) at least one retractable support element having a downward facing contact surface, said retractable support element being linked to said load bearing deck portion;

(d) at least one wedge element disposed so as to assume a first position in which said at least one wedge element is interposed between said load bearing deck portion and said retractable support element, thereby maintaining a position of said retractable support element such that said contact surface is deployed below said wheel elements so that at least of portion of the combination dolly-pallet device is supported by contact of said contact surface with the underlying surface, said wedge element being displaceable to a second position in which said retractable support element is retractable to a retracted state in which said contact surface is raised so that at least a portion of the combination dolly-pallet device is supported by contact of said plurality of wheel elements with the underlying surface.

2. The device of claim 1, wherein said load bearing deck portion forms part of a walled container.

3. The device of claim 1, wherein said plurality of wheel elements includes four wheel elements attached to said load bearing deck portion.

4. The device of claim 3, wherein said at least one retractable support element is implemented as two retractable support elements extending along a majority of the width of two opposing sides of said load bearing deck portion, and wherein said at least one wedge element is implemented as two wedge elements, each of said wedge elements cooperating with a corresponding one of said retractable support elements.

5. The device of claim 4, wherein said wedge elements and said retractable support elements are configured to provide an opening for insertion of a tine of a pallet-lifting device from each of said two opposing sides.

6. The device of claim 3, wherein at least two of said wheel elements are caster wheels.

7. The device of claim 1, wherein said at least one retractable support element is resiliently biased towards said retracted state.

8. The device of claim 1, wherein said at least one wedge element is implemented as two wedge elements, each of said wedge elements cooperating with at least a corresponding one of said retractable support elements.

9. The device of claim 8, wherein said two wedge elements move in opposite directions during displacement from said first position to said second position.

10. The device of any of claims 1 to 9, further comprising a screw- drive actuator for displacing said at least one wedge element bidirectionally between said first position and said second position.

11. The device of claim 1O₅ wherein said screw-drive actuator includes an externally accessible power-input port for receiving a rotatable tip of a power tool for driving said screw-drive actuator.

12. The device of claim 10, wherein said at least one wedge element has an effective wedge angle in the range from 10 degrees to 30 degrees.

13. The device of any of claims 1 to 9, further comprising a manually operable mechanical linkage configured for displacing said at least one wedge element from said first position to said second position, and wherein said at least one wedge element has an effective angle of at least 35 degrees such that a load applied to said load bearing deck portion facilitates operation of said mechanical linkage.

14. The device of claim 13, wherein said manually operable mechanical linkage includes a manually displaceable actuator lever configured to be displaceable along an actuating path of length greater than a path of said at least one wedge element from said first to said second position.

15. The device of claim 13, wherein said at least one wedge element has an effective wedge angle no greater than 55 degrees.

16. The device of any of claims 1 to 9, wherein said at least one wedge element has an effective angle of at least 55 degrees such that, when a load is applied to said load bearing deck portion, the load biases said at least one wedge element to move from said first position to said second position, the device further comprising a manually releasable retention mechanism deployed to prevent displacement of said at least one wedge element from said first position towards said second position until said retention mechanism is manually released.

17. The device of claim 16, wherein said manually releasable retention mechanism includes a rotatable element mounted so as to be rotatable about an axis of rotation and mechanically linked to said at least one wedge element, and at least one blocking element selectively deployable to engage both said rotatable element and a fixed element so as to prevent relative rotation between said rotatable element and said fixed element, said at least one blocking element being located at a distance from said axis of rotation of no less than a quarter of a minor dimension of said load bearing deck portion.

18. The device of claim 16, wherein said manually releasable retention mechanism includes a rotatable disk mounted so as to be rotatable about an axis of rotation and mechanically linked to said at least one wedge element, a fixed surface mounted in fixed relation to said load bearing deck portion and at least one ball deployed in complementary recesses in said rotatable disk and said fixed surface to as to prevent relative rotation between said rotatable disk and said fixed disk.