Hand truck with adjustable wheel assembly

A hand truck includes a frame body and a wheel assembly including two wheel units spacedly supported at the frame body to switch between a first operation position and a second operation position for enabling the frame body to be tilted backward to transport a load. In the first operation position, the wheel units are oriented in parallel planes for enabling the frame body to move in a back-and-forth direction, and in the second operation position, the wheel units are oriented to align with each other in a common plane for enabling the frame body to move in a left-and-right direction. Therefore, the hand truck provides two modes of movement for two-dimensional movement.

BACKGROUND OF THE PRESENT INVENTION

1. Field of Invention

The present invention relates to a dolly with adjustable wheel assembly, and more particularly to a dolly with adjustable wheel assembly which provides movement of the dolly along two perpendicular axes.

2. Description of Related Arts

Hand trucks, such as dollies and four-wheeled transportation boards, are commonly used for carrying and transporting a load, especially heavy and bulky load, from one place to another. One type of conventional dolly includes a frame for holding a load and two wheels for movement along the axis of the frame. When a user uses the dolly to transport a heavy load and has to make a turn, the whole dolly, which includes the frame and the wheels, has to be turned together. That is to say, the user has to hold and turn the dolly which carries the heavy load in order to make a turn.

There are some major drawbacks for this kind of conventional dolly. First, the user has to turn the heavy load on the dolly when making a turn and without any displacement and without making any progress of movement. Second, the heavy load may be dislodged from its original position and collapsed while making a turn. Third, when the load is bulky and the space is not sufficient for making a turn, a user has to unload and adjust the position of the heavy and bulky load manually and reposition the dolly with respect to the load. For example, a rectangular bulky load is carried with the dolly across a L-shaped corridor. When the user approaches the corner of the L-shaped corridor, he or she has to unload and reposition the bulky load at the corner, and then moves the dolly to fit the load in order to pass through the corner. The lack of any mechanism in the conventional dolly to facilitate movement in two perpendicular directions makes it really inconvenience and ineffective as a transportation tool. Since building structures, either residential or commercial, usually will not provide a huge corridor and cannot avoid having corner points in the building structures, the need of making a turn at the corner is real and the problem of failing to provide any mechanism to solve the problem is a vital drawback.

Another type of hand truck is a four-wheeled transportation board, which is very primitive in the sense that there is no mechanism to secure a load on the transportation board and no handle or navigation means for the user to hold and move the board around, or to stop the board. There is simply no control or handle arrangement for this kind of four-wheeled transportation board.

SUMMARY OF THE PRESENT INVENTION

The invention is advantageous in that it provides a hand truck which includes a wheel assembly for providing two modes of movement such that the hand truck is capable of providing two-dimensional movement.

Another advantage of the invention is to provide a hand truck which comprises a wheel assembly comprising two wheel units being controlled to switch and lock into two different positions to move at two different perpendicular axes of the hand truck.

Another advantage of the invention is to provide a hand truck, wherein the two wheel units are selectively switched between the first and second operation positions in a hands-free manner.

Another advantage of the invention is to provide a hand truck, which does not require altering the original structural design of the hand truck, so as to minimize the manufacturing cost of the hand truck incorporating with the adjustable wheel assembly.

Another advantage of the invention is to provide a hand truck, wherein no expensive or complicated structure is required to employ in the present invention in order to achieve the above mentioned objects. Therefore, the present invention successfully provides an economic and efficient solution for not only providing a rigid configuration for the hand truck to carry and transport the load but also enhancing the practical use of the hand truck with two different directional movements.

According to the present invention, the foregoing and other objects and advantages are attained by a hand truck, comprising:

a frame body, having a L-shaped cross section, comprising a load platform for carrying a load thereon, and a handle upwardly extended from the load platform; and

a wheel assembly which comprises two wheel units spacedly supported at the handle of the frame body to switch between a first operation position and a second operation position for enabling the frame body to be tilted backward to transport the load, wherein in the first operation position, the wheel units are oriented in parallel planes for enabling the frame body to move in a back-and-forth direction, and in the second operation position, the wheel units are oriented to align with each other in a common plane for enabling the frame body to move in a left-and-right direction.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring toFIG. 1of the drawings, a hand truck, such as a dolly, according to a preferred embodiment of the present invention is illustrated, wherein the hand truck comprises a frame body10and an adjustable wheel assembly20provided at the frame body10for providing two dimensional movements. Therefore, the hand truck can be moved in a first direction and a second direction which is perpendicular to the first direction. In other words, the hand truck can be moved back-and-forth, or left-and-right as desired.

As shown inFIG. 1, the frame body10, having a generally L-shaped cross-section, comprises a load platform11for carrying a load thereon, and a handle12upwardly extended from the load platform11. Accordingly, the frame body10defines a front side101that the load platform11is frontwardly extended from the handle12, and a rear side102that a user is able to stand at the rear side102of the handle12to operate the hand truck. The handle12preferably comprises two parallel handle members121, wherein upper portions of the handle members121form a handle portion of the frame body10while the load platform11is extended from lower portions of the handle members121.

The adjustable wheel assembly comprises two wheel units20spacedly supported at the handle12of the frame body10to switch between a first operation position and a second operation position for enabling the frame body10to be tilted backward to transport the load. Accordingly, in the first operation position, as shown inFIG. 2A, the wheel units20are oriented in parallel planes for enabling the frame body10to move in a back-and-forth direction. In the second operation position, as shown inFIG. 2B, the wheel units20are oriented to align with each other in a common plane for enabling the frame body10to move in a left-and-right direction. In other words, the frame body10can be selectively moved in two dimensional directions.

Accordingly, the wheel units20are located at two outer sides of the frame body10to maximize the distance between the wheel units20so as to enhance the stability of the hand truck during the transportation. In particular, the wheel units20are located at the rear side102of the handle members121of the frame body10respectively.

Each of the wheel units20comprises a steerable wheel21and a switching shaft22which is upwardly extended from the steerable wheel21and is adjustably rotated with respect to the frame body10. Therefore, when the steerable wheels21are oriented in parallel planes in the first operation position, the frame body10is adapted to be moved in the back-and-forth direction, and when the steerable wheels21are oriented in an aligned common planar manner in the second operation position, the frame body10is adapted to be moved in the left-and-right direction. In particular, each of the wheel units20is turned 90 degrees to switch between the first and second operation positions.

In addition, each of the steerable wheel21comprises a wheel housing211, preferably having a U-shaped cross section, and a wheel member212rotatably held at the wheel housing211, wherein the switching shaft22is upwardly extended from the wheel housing211of the steerable wheel21such that when the switching shaft22is rotated, the wheel member212of the steerable wheel21is driven to rotate correspondingly. In other words, in the first operation position, the wheel members212are coaxial and parallel with each other and are located at the outer sides of the frame body10at the rear side102thereof such that the frame body10can be moved in the back-and-forth direction. In the second operation position, the wheel members212are aligned side-by-side at the outer sides of the frame body10at the rear side102thereof such that the frame body10can be moved in the left-and-right direction, i.e. the sideward direction of the frame body10.

As it is mentioned above, the frame body10is preferably tilted backward in order for the user to move the frame body10in the back-and-forth direction. Each of the switching shafts22is inclinedly supported with respect to the handle12of the frame body10to allow the frame body10to be tilted backward for transporting the load. Since the switching shafts22are inclinedly supported at the rear side102of the frame body10when the frame body10is moved in an upright position, the switching shafts22can be moved perpendicular to the ground surface when the frame body10is tilted backward.

It is worth mentioning that when the frame body10is tilted backward, the frame body10can be moved in the back-and-forth direction when the wheel units20are switched in the first operation position, or can be moved in the left-and-right direction when the wheel units20are switched in the second operation position.

The wheel assembly further comprises two wheel frames30spacedly and rearwardly extended from the frame body10for retaining the wheel units20in position. Accordingly, the wheel frames30are rearwardly extended from the handle members121of the frame body10respectively. As shown inFIGS. 3A to 3C, each of the wheel frames30comprises two retention walls31rearwardly extended from the handle12at the respective outer side thereof to define a guiding channel32between the retention walls31. The switching shaft22is rotatably received in the respective guiding channel32to enable the wheel units20to be switched between the first and second operation positions.

The two retention walls31are embodied as an outer retention wall and an inner retention wall which preferably parallels to the outer retention wall. Each of the retention walls31has a front edge extended from the rear side102of the frame body10and a slanted rear edge such that each of the retention walls31has a trapezoid shape. Accordingly, the switching shaft22is received along the guiding channel32between the outer and inner retention walls31at a position that the switching shaft22is aligned with the slanted rear edge of each of the retention walls31.

It is worth mentioning that each of the guiding channels32has a bottom opening formed between the bottom sides of the retention walls31such that each of the steerable wheels21is located underneath the respective wheel frame30.

The wheel assembly further comprises two retention units40for retaining the wheel units20, respectively, while the wheel assemblies are in the first and second operation positions, wherein each of the retention units40forms a position lock to lock up the respective wheel unit20between the first and second operation positions.

As shown inFIGS. 3A to 3C, each of the retention unit40has a first locking slot41formed between the retention walls31and a second locking slot42formed at a bottom edge of one of the respective retention walls31. Accordingly, the first locking slot41is formed at the bottom side of the respective wheel frame30at a position between two slanted rear edges of the retention walls31. The second locking slot41is preferably formed at the bottom edge of the outer retention wall31.

The retention unit40further comprises a retention member43upwardly protruded from the respective steerable wheel31, wherein when the switching shaft22is rotated to move the retention member43to the first locking slot41, the steerable wheel21is switched and locked in the first operation position. When the switching shaft22is rotated to move the retention member43to the second locking slot42, the steerable wheel21is switched and locked in the second operation position. Accordingly, the retention member43has a block-like structure, such as a cube structure, a rectangular block, a hexagonal block or the like.

As shown inFIGS. 3A to 3C, the retention member43is upwardly extended from the wheel housing211of the steerable wheel21, wherein the retention member43has a shape and size matching with each of the first and second locking slots41,42.

In particular, each of the switching shafts22is slidably and rotatably retained in the respective guiding channel32such that each of the steerable wheels21is adapted to be downwardly pushed to disengage the retention member43from each of first and second locking slots41,42so as to enable the steerable wheel21to be switched between the first and second operation positions. As shown inFIG. 3A, the steerable wheel21is locked in the first operation position that the retention member43is engaged with the first locking slot41.

In order to switch the steerable wheel21from the first operation position to the second operation position, the steerable wheel21is downwardly pressed to drive the respective switching shaft22moving downwardly within the guiding channel32so as to disengage the retention member43from the first locking slot41. Once the retention member43is dropped down at a position below the bottom edge of the outer retention wall31, the steerable wheel21can be turned with respect to the rotational movement of the switching shaft22within the guiding channel32, as shown inFIG. 3B. When the steerable wheel21is turned to align the retention member43with the second locking slot42, the downward pressing force at the steerable wheel21can be released. Therefore, the steerable wheel21will be lifted upward to engage the retention member43with the second locking slot42so as to lock up the steerable wheel21in the second operation position, as shown inFIG. 3C. In other words, the hand truck, or the dolly can be moved back and forth, or left and right without rotating the frame body10, as desired.

It is worth mentioning that the height of the retention member43is about 1 cm and the depth of each of the first and second locking slots41,42is about 1 cm. In other words, the steerable wheel21can be downwardly pressed with a displacement of 1 cm in order to disengage the retention member43with each of the first and second locking slots41,42. In addition, since each of the wheel units20is supported at an inclined position when the frame body10is moved at the upright position, there is a clearance between each of the wheel units20and the ground surface for enabling the wheel unit20to be moved downwardly for switching the wheel unit20between the first and second operation positions. When the frame body10is moved in the upright position, the weight of the load is substantially applied at the load platform11of the frame body10but not at the wheel units20. Therefore, the user is able to easily press each of the wheel units20downward for switching its position by the downward pushing force in no relation to the weight of the load. Thus, the two wheel units20are rearwardly located at the rear side102of the frame body10, such that the wheel units20form two rear stands for supporting on the ground surface when the frame body10is moved in the upright position. The wheel units20further form two pivot points to move the frame body10from the upright position to the tilted position with minimum rear pulling force at handle12of the frame body10by the user.

In order to enhance the switching operation of each of the steerable wheel21, each of the wheel frames30further comprises a resilient element33coaxially coupling with an upper portion of the respective switching shaft22for applying an upward pulling force thereat so as to ensure the retention member43being engaged with one of the first and second locking slots41,42. As shown inFIG. 3A, the resilient element33is embodied as a compression spring coaxially coupling with the upper portion of the switching shaft22within the guiding channel32. A lower affixing holder34is affixed to a surrounding wall of the guiding channel32and is coaxially and slidably coupled with the switching shaft22. An upper movable holder35is slidably coupled with the surrounding wall of the guiding channel32and is coaxially coupled with the switching shaft22. Accordingly, the resilient element33is supported between the lower affixing holder34and the upper movable holder35at a position that the lower and upper ends of the resilient element33bias against the lower affixing holder34and the upper movable holder35respectively. Therefore, when the switching shaft22is slid downwardly within the guiding channel32, the resilient element33will be compressed. When the downward pressing force at the steerable wheel21is released, the resilient element33will be restored to its original form to apply the upward pulling force against the switching shaft22. In other words, the upward pulling force of the resilient element33will ensure the retention member43to be engaged with one of the first and second locking slots41,42so as to ensure the steerable wheel21being locked in one of the first and second operation positions.

According to the preferred embodiment, the wheel assembly30further comprises two foot pedals36sidewardly extended from the wheel units21respectively to selectively switch each of the wheel units21between the first and second operation positions in a hands-free manner.

Accordingly, each of the foot pedals36is an elongated foot step sidewardly extended from the wheel member212at the center thereof. The foot pedal36is arranged for the user to step thereon for applying the downward force at the steerable wheel21. Therefore, when the frame body10is moved in the upright position, the user is able to apply the downward force at the steerable wheel21by the foot of the user to switch the steerable wheel21between the first and second operation positions. It is appreciated that the user is able to slightly push the frame body10forward by hands of the user to minimize the downward force applied at the foot pedal36by the foot of the user. Preferably, the two wheel units21are identical in structure except the provision of the foot pedals36.

The wheel assembly further comprises a reinforcing frame50for reinforcing the structure of the wheel units20with respect to the frame body10. The reinforcing frame50comprises a first reinforcing arm51extending between two inner retention walls31of the two wheel frames30and a second reinforcing arm52extending between two outer retention walls31of the two wheel frames30.

Referring toFIG. 4of the drawings, since the hand truck of the present invention provides two different operation positions for two-dimensional movement, two or more of the hand trucks of the present invention can be co-operatively used together to carry a big and bulky load. For example, as shown inFIG. 4, four hand trucks can be used for all four sides of the load, wherein two hand trucks are set in the first operation position that the two hand trucks are positioned at two longitudinal sides of the loads respectively. The other two hand trucks are set in the second operation position that the two hand trucks are positioned at two transverse sides of the loads respectively. Therefore, the load can be moved in either back-and-forth direction or left-and-right direction. It is worth mentioning that the handles12of the hand trucks form four boundary frames of the load such that by tightening the handles12together via a cable or the like, the load can be securely retained and supported by the hand trucks. Since the hand trucks are located at four sides of the load respectively, any size of the load can fit to be supported by the hand trucks without the limitation of the supporting surface of the hand truck.

FIG. 5illustrates the operation of the hand truck for cornering without repositioning the orientation of the frame body10. As shown inFIG. 5, the load is placed at the frame body10while the steerable wheels21of the wheel assembly20are shifted in the first position. Therefore, the hand truck can be moved in the back-and-forth direction. During cornering, the frame body10will be remained at the same orientation while the steerable wheels21of the wheel assembly20are shifted in the second position. Therefore, the hand truck can be moved in the left-and-right direction. It is worth mentioning that the user does not have to dislodge the load at the frame body10or turn the frame body10for cornering. By switching the steerable wheels21of the wheel assembly20between the first and second positions, the frame body10can be moved at any narrow corridor.