Wheel dolly with large lifting capacity

Abstract

A wheel dolly is described for use in lifting the wheel of a vehicle and supporting the wheel on casters. The wheel dolly includes a motion conversion mechanism operative to convert rotational motion at a drive shaft into relative linear motion of two bodies that act to lift the wheel. The motion conversion mechanism can include a worm gear and lead screws. Actuation of the wheel dolly may be accomplished using a rotary power tool such as a drill or impact wrench so that the wheel dolly becomes power assisted.

Description

[0001] WHEEL DOLLY WITH LARGE LIFTING CAPACITY

[0002] FIELD OF THE INVENTION

[0003] The present invention relates generally to wheel dollies, and, more particularly, to power- assisted wheel dollies capable of lifting heavy loads utilizing a motion conversion mechanism for actuation.

[0004] BACKGROUND OF THE INVENTION

[0005] United States Patent No. 4,854,803, entitled “Apparatus and Method for Jacking and Dollying an Affixed Vehicle Wheel Assembly,” issued to A.V. Coccaro, discloses a wheel dolly designed to lift a vehicle’s wheel off the ground, enabling the vehicle to be repositioned. The invention features a “bidirectional, double pawl, lever ratchet mechanism” that, when the user pumps an actuation lever, drives two opposed rollers against the vehicle’s wheel, lifting it off the ground. With the vehicle supported by four such wheel dollies, it can be easily moved using the casters attached to the dollies.

[0006] While manually operated wheel dollies relying on levers and pawls have gained widespread commercial success, they may not be suitable for lifting exceptionally heavy vehicles. For these heavy vehicles, power assisted wheel dollies with larger lifting capacities are desired.

[0007] SUMMARY OF THE INVENTION

[0008] Embodiments of the present invention address the above-identified needs by providing wheel dollies with larger lifting capacities than prior art designs.

[0009] In accordance with an aspect of the invention, an apparatus comprises a left body portion, a right body portion, and a drive portion. The left body portion comprises a left pair of casters, while the right body portion comprises a right pair of casters. The drive portion is configured to translate the left body portion and the right body portion toward and away from each other in response to rotation of a drive shaft. The left body portion and the right body portion are configured to lift a wheel between them such that the wheel is supported on the left pair of casters and the right pair of casters.

[0010] The above-described apparatus thereby forms a wheel dolly. Conforming wheel dollies offer significant advantages over traditional designs, including exceptional leverage and lifting capacities, with the ability to lift loads of 3,000 pounds (1,360 kilograms) or more. They can accommodate large wheels using dual roller sets and can be operated with power tools, reducing manual effort. Moreover, these wheel dollies are highly resistant to unwinding under load, allowing them to securely hold heavy wheels in position without additional locking mechanisms or brakes.

[0011] BRIEF DESCRIPTION OF THE DRAWINGS

[0012] These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:

[0013] FIG. 1 shows a perspective view of a wheel dolly in accordance with an illustrative embodiment of the invention in combination with a wheel and a handheld drill;

[0014] FIGS. 2 and 3 show perspective views of a drive portion in the FIG. 1 wheel dolly;

[0015] FIGS. 4-8 show perspective views of a left body portion in the FIG. 1 wheel dolly;

[0016] FIG. 9 shows a perspective view of a right body portion in the FIG. 1 wheel dolly; and

[0017] FIGS. 10-12 show a sequence of side views of the FIG. 1 wheel dolly while the wheel dolly is being used to lift a wheel.

[0018] DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention will be described with reference to illustrative embodiments. For this reason, numerous modifications can be made to these embodiments, and the results will still come within the scope of the invention. No limitations with respect to the specific embodiments described herein are intended or should be inferred.

[0020] As used herein and in the appended claims, “attached to” and “coupled to” means connected to with or without intervening elements. A “tubular member” may be round tubular or square tubular. A “rotary power tool” comprises a motor-driven device that generates rotational motion such as, but not limited to, drills and impact wrenches. A “roller” is a cylindrical element sized and shaped to make direct contact with a wheel’s surface. A roller may or may not rotate.

[0021] FIG. 1 shows a perspective view of a wheel dolly 100 in accordance with an illustrative embodiment of the invention, while the wheel dolly 100 is being used to lift a wheel 1000 of a vehicle. The wheel dolly 100 is being actuated by a handheld drill 1005. When combined with three other such wheel dollies, the wheel dolly 100 may be used to lift and move a four-wheel vehicle within tight spaces or when the vehicle is disabled.

[0022] The wheel dolly 100 comprises three main portions: a drive portion 105, a left body portion 110, and a right body portion 115. The drive portion 105 spans between the left body portion 110 and the right body portion 115. FIGS. 2 and 3 show aspects of the drive portion 105, with the figures each showing a perspective view along a respective view angle indicated in FIG. 1. FIG. 2 is also partially broken.

[0023] A central tubular member 120 is square tubular. A drive mechanism housing 125 is attached to the central tubular member 120 via a housing bracket 130 near the center of the central tubular member 120. The drive mechanism housing 125 supports a drive mechanism 135.

[0024] In the present illustrative embodiment, the drive mechanism 135 comprises a worm gear that includes a drive shaft 140, a worm 145, and a worm wheel 150. Worm gears are commonly used in mechanical systems to convert rotational motion into linear motion, particularly where compactness and high gear reduction are desired. Their geometry typically involves a helical worm engaging with a toothed wheel, producing smooth and continuous motion transfer. Design considerations such as lead angle, tooth profile, friction reduction, load handling, and lubrication are well understood in the field and are described in various technical publications, including: Crosher, William P., Design and Application of the Worm Gear, New York, American Society of Mechanical Engineers, 2002. For countries / regions that recognize incorporation by reference, this publication is incorporated herein by reference to provide additional background on worm gear configurations, performance characteristics, and application-specific adaptations.

[0025] The worm 145 comprises a gear in the form of a screw with helical thread, while the worm wheel 150 comprises a gear with teeth cut to mesh with the worm 145 in combination with an axle 155. The worm 145 and the worm wheel 150 are arranged perpendicular to each other. The drive shaft 140 allows the worm 145 to be rotated, which, in turn, rotates the worm wheel 150. Thrust washers 160, roller bearings 165, and washers 170 are arranged about the drive shaft 140, the worm 145, and the worm wheel 150 to reduce friction and handle axial and rotational loads. The drive shaft 140 is adapted for coupling to a rotary power tool such as the drill 1005.

[0026] The axle 155 of the worm wheel 150 is coupled to a left lead screw 175 via a left shaft coupling 180, and is coupled to a right lead screw 185 by a right shaft coupling 190. The lead screws 175, 185 may, for example, have trapezoidal thread. Arranged in this manner, rotating the drive shaft 140 causes the left lead screw 175 and the right lead screw 185 to rotate in coordinated motion so that rotational motion of the drive shaft 140 can ultimately be translated into linear motion of the left body portion 110 and the right body portion 115.

[0027] In this manner, the drive mechanism 135 and the left and right lead screws 175, 185 combine to form a motion conversion mechanism operative to convert rotational motion at the drive shaft 140 into linear motion at the left and right body portions 110, 115.

[0028] Aspects of the left body portion 110 are further described in FIGS. 4-8, with FIG. 4 showing the entire left body portion 110, and FIGS. 5-8 showing portions of the left body portion 110. FIGS. 4 and 6 are intact perspective views. FIGS. 5 and 7 are exploded perspective views. Finally, FIG. 8 is a partially exploded, partially broken perspective view.

[0029] The left tubular member 200 is square tubular and partially overlaps the central tubular member 120 so that the left tubular member 200 can slide over the central tubular member 120. A left translation bracket 205 is attached to a top of the left tubular member 200. The left translation bracket 205 supports a left clevis bracket 210, which is formed of two spaced-apart, parallel plates. A hexagonal opening in one plate is aligned with a corresponding hexagonal opening in the other plate. These hexagonal openings accommodate a left coupling element 215 in the left clevis bracket 210 and inhibit the left coupling element 215 from rotating. In the present illustrative embodiment, the left coupling element 215 comprises an elongated nut. A left U-shaped insert 220 fits between the two plates of the left clevis bracket 210 and engages vertical notches in the left coupling element 215, stopping the left coupling element 215 from translating within the left clevis bracket 210.

[0030] The left coupling element 215 threadably engages the left lead screw 175. Rotating the left lead screw 175 thereby causes the left coupling element 215 to translate on the left lead screw 175, creating a leadscrew (or lead screw) arrangement. This translation of the left coupling element 215 on the left lead screw 175 causes the left body portion 110 to translate towards or away from the right body portion 115. A left lead screw guard 225 is attached to the left clevis bracket 210 and encompasses and protects the left lead screw 175 outboard of the left coupling element 215.

[0031] To help reduce friction between the left tubular member 200 and the central tubular member 120, several left friction-reducing inserts 230 are placed in holes in the left tubular member 200 and held in place by the left translation bracket 205. The left friction-reducing inserts 230 are slightly thicker than the sidewalls of the left tubular member 200 so that they push the inner surface of the left tubular member 200 away from the outer surface of the central tubular member 120, thereby minimizing direct contact and reducing binding and friction between these members 120, 200 during translation. The left friction-reducing inserts 230 preferably contain a hard, high-strength metal with a low friction coefficient and superior wear resistance such as, for example, bronze.

[0032] A left arm 235 is attached to the left tubular member 200 and is oriented perpendicular thereto. The left arm 235 supports a left lower set of rollers 240 and a left higher set of rollers 245. The left lower set of rollers 240 are supported on a left roller bracket 250 attached to the left arm 235 so that the left lower set of rollers 240 are positioned lower and inboard (i.e., towards the right body portion 115) of the left higher set of rollers 245. The left roller bracket 250 is attached to the left arm 235 via a left lower plate 255 and a left upper plate 260, which occupy opposite sides of the left arm 235 and are bolted together through the left arm 235 with first bolts 265 and first nuts 270.

[0033] The left higher set of rollers 245 rotate on a left set of inside rings 275. A left proximal stop 280 and a left distal stop 285 keep the left higher set of rollers 245 in position on the left arm 235. The left proximal stop 280 is welded in place, while the left distal stop 285 is held in place by a second bolt 290 and a second nut 295, facilitating removal of the left higher set of roller 245 when desired.

[0034] A left pair of casters 300 are mounted on opposite ends of the left arm 235.

[0035] FIG. 9 shows a perspective view of the right body portion 115. The right body portion 115 is essentially a mirror image of the left body portion 110 with a similar grouping of elements. Readily visible in FIG. 9 are, for example: a right tubular member 400, a right translation bracket 405, a right clevis bracket 410, a right coupling element 415, a right lead screw guard 420, right friction-reducing inserts 425, a right arm 430, a right lower set of rollers 435, a right higher set of rollers 440, and a right pair of casters 445. These various elements in the right body portion 115 are designed, arranged, supported, and function in the same manner as those elements with corresponding names in the left body portion 110, but, of course, as mirror images thereof as necessary.

[0036] FIGS. 10-12 shows a sequence of side views of the wheel dolly 100 as wheel dolly 100 is utilized to lift the wheel 1000. To lift the wheel 1000 in a manner like that shown in FIG. 1, the wheel dolly 100 is positioned so that the left arm 235 and the right arm 305 occupy opposite sides of the wheel 1000 (FIG. 10). The drill 1005 (or impact wrench) may then be used to spin the drive shaft 140 and actuate the wheel dolly 100. Rotating the drive shaft 140 in one direction moves the left body portion 110 and the right body portion 115 towards each other. This allows the rollers 240, 245, 435, 440 to get under the wheel 1000 and lift the wheel 1000 off the ground. The lower sets of rollers 240, 245 engage the wheel 1000 first (FIG. 11), and then, after the wheel 1000 is lifted somewhat, the higher sets of rollers 435, 440 engage the wheel 1000 and continue lifting (FIG. 12). After being lifted, the wheel 1000 will be supported on the casters 300, 445. Rotating the drive shaft 140 in the other direction causes the left body portion 110 and the right body portion 115 to move away from each other, allowing the wheel 1000 to be lowered back to the ground, after which, the wheel dolly 100 can be disengaged from the vehicle.

[0037] Wheel dollies in accordance with aspects of the invention (“conforming wheel dollies”) have several advantages over prior art designs. More particularly, conforming wheel dollies can be configured to provide extreme leverage and lifting capacities. Lifting capacities of 3,000 pounds (1,360 kilograms) or greater are readily achievable. By using lower and higher sets of rollers, very large wheels can be accommodated. Conforming wheel dollies can also be actuated by power tools (e.g., drills or impact wrenches) rather than relying solely on manual effort. Conforming wheel dollies may therefore be power assisted and their operation may be less physically demanding.

[0038] Moreover, worm gears in combination with lead screws with trapezoidal thread are typically very resistant to unwinding or backdriving under load due to self-locking and friction. Conforming wheel dollies are thereby able to hold loads in position securely without the need for added locking mechanisms or brakes. That is, in the apparatus 100, with a force urging the left body portion 110 away from the right body portion 115, the left body portion 110 and the right body portion 115 will not move apart without a user intentionally rotating the drive shaft 140. Wheel dollies that rely on pawls and ratchets for actuation do not typically have this advantage and need some kind of mechanism to act as a brake under load.

[0039] Conforming wheel dollies may also be configured with different drives for different applications, making the design highly scalable. In a prototype wheel dolly 100 conforming to that shown in the figures, the drive mechanism 135 had a ratio of 20: 1, meaning that twenty rotations of the drive shaft 140 and the worm 145 had the effect of turning the worm wheel 150 and the left and right lead screws 175, 185 by one rotation. The left and right lead screws 175, 185 were configured to translate the left and right coupling elements 215, 415 by one-eighth of an inch (0.32 centimeters (cm)) per rotation of the lead screws 175, 185. Stated another way, the lead of the lead screws 175, 185 was one-eighth inch (0.32 cm). Accordingly, it took about 80 rotations of the drive shaft 140 to move the left and right body portions 110, 115 towards each other by one inch (2.5 cm) (each body portion 110, 115 moved towards the other by one-half inch (1.3 cm) to give a total of one inch (2.5 cm) of relative movement). Nevertheless, this configuration is merely by way of example and very different configurations can be utilized and still fall within the scope of the invention.

[0040] Manufacture of the wheel dolly 100 will be familiar to one having ordinary skill in the art from the description provided herein. In some embodiments, the wheel dolly 100 may comprise metal components made from steel, aluminum, or the like. Gears and components for the drive mechanism 135 are commercially available from several sources, including, as just one example, MCMASTER-CARR® (Elmhurst, IL, US).

[0041] In summary, the wheel dolly 100 (an apparatus) comprises the drive portion 105, the left body portion 110, and the right body portion 115. The drive portion 105 comprises the central tubular member 120, the left lead screw 175, the right lead screw 185, and the drive mechanism 135 attached to the central tubular member 120 and configured to drive the left lead screw 175 and the right lead screw 185 in coordinated motion in response to rotation of the drive shaft 140. The left body portion 110 comprises the left tubular member 200 slidably coupled to the central tubular member 120, the left coupling element 215 threadably engaged with the left lead screw 175 and operatively coupled to the left tubular member 200 such that translation of the left coupling element 215 along the left lead screw 175 causes translation of the left tubular member 200 relative to the central tubular member 120, the left arm 235 attached to the left tubular member 200, and the left pair of casters 300 attached to the left arm 235. The right body portion 115 comprises the right tubular member 400 slidably coupled to the central tubular member 120, the right coupling element 415 threadably engaged with the right lead screw 185 and operatively coupled to the right tubular member 400 such that translation of the right coupling element 415 along the right lead screw 185 causes translation of the right tubular member 400 relative to the central tubular member 120, the right arm 430, and the right pair of casters 445 attached to the right arm 430. Rotating the drive shaft 140 in a first direction moves the left body portion 110 and the right body portion 115 towards each other. Rotating the drive shaft 140 in a second direction moves the left body portion 110 and the right body portion 115 away from each other. The wheel dolly is operative to lift the wheel 1000 and support the wheel 1000 on the left pair of casters 300 and the right pair of casters 445.

[0042] It should again be emphasized that the above-described embodiments of the invention are intended to be illustrative only. Other embodiments can use different types and arrangements of elements for implementing the described functionality. These numerous alternative embodiments within the scope of the appended claims will be apparent to one skilled in the art.

[0043] It is, for example, contemplated that a wheel dolly falling within the scope of the invention be manually actuated using a handle or hand tool coupled to the drive shaft of the drive mechanism rather than actuated by a power tool. The handle or hand tool will preferably be removable to allow a power tool to be substituted in its place as desired, providing a user with maximum flexibility in using the apparatus.

[0044] All the features disclosed herein may be replaced by alternative features serving the same, equivalent, or similar purposes, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

Claims

CLAIMSWhat is claimed is:

1. An apparatus comprising: a left body portion comprising a left pair of casters; a right body portion comprising a right pair of casters; and a drive portion configured to translate the left body portion and the right body portion toward and away from each other in response to rotation of a drive shaft; wherein the left body portion and the right body portion are configured to lift a wheel between them such that the wheel is supported on the left pair of casters and the right pair of casters.

2. The apparatus of claim 1, wherein the drive portion comprises: a left lead screw; a right lead screw; and a drive mechanism adapted to rotate the left lead screw and the right lead screw in coordinated motion in response to rotation of the drive shaft.

3. The apparatus of claim 2, wherein rotation of the drive shaft by one rotation rotates the left lead screw and the right lead screw by less than one rotation.

4. The apparatus of claim 2, wherein the left lead screw and the right lead screw each have a trapezoidal thread profile.

5. The apparatus of claim 2, wherein: the drive mechanism comprises a worm gear comprising; a worm; and a worm wheel; rotating the drive shaft rotates the worm; rotation of the worm rotates the worm wheel; and the left lead screw and the right lead screw are rotationally coupled to the worm wheel.

6. The apparatus of claim 5, wherein: the worm comprises a helical gear; and the worm gear comprises a gear with teeth cut to mesh with the worm.

7. The apparatus of claim 2, wherein the left body portion further comprises a left lead screw guard that encompasses a portion of the left lead screw.

8. The apparatus of claim 2, wherein the left body portion further comprises a left coupling element threadably engaged with the left lead screw and operatively coupled to a remainder of the left body portion such that translation of the left coupling element along the left lead screw causes translation of the left body portion.

9. The apparatus of claim 1, wherein: the drive portion comprises a central tubular member; and the left body portion further comprises: a left tubular member slidably coupled to the central tubular member; and a left arm attached to the left tubular member and oriented perpendicular thereto, the left pair of casters mounted to the left arm.

10. The apparatus of claim 9, wherein the central tubular member and the left tubular member are square tubular.

11. The apparatus of claim 1, wherein the left body portion further comprises a left higher set of rollers.

12. The apparatus of claim 11, wherein the left higher set of rollers are operative to rotate.

13. The apparatus of claim 11, wherein the left body portion further comprises a left lower set of rollers positioned lower and inboard of the left higher set of rollers, wherein inboard is towards the right body portion.

14. The apparatus of claim 1, wherein the drive shaft is adapted for coupling to a rotary power tool.

15. The apparatus of claim 1, wherein, with a force urging the left body portion away from the right body portion, the left body portion and the right body portion will not move apart without a user intentionally rotating the drive shaft.

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