Patent Application
20120038123
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 dolly and four-wheeled transportation board, 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 have 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 have to unload and reposition the bully 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.
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 a 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 hand-free manner.
Another advantage of the invention is to provide a hand truck, which does not require to alter 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.
Additional advantages and features of the invention will become apparent from the description which follows, and may be realized by means of the instrumentalities and combinations particular point out in the appended claims.
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 at the first operation position, the wheel units are switched in parallel for enabling the frame body to move at a back-and-forth direction, and at the second operation position, the wheel units are switched to align with each other for enabling the frame body to move at a left-and-right direction.
Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings.
These and other objectives, features, and advantages of the present invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims.
Referring to
As shown in
The adjustable wheel assembly comprises two wheel units 20 spacedly supported at the handle 12 of the frame body 10 to switch between a first operation position and a second operation position for enabling the frame body 10 to be tilted backward to transport the load. Accordingly, at the first operation position, as shown in
Accordingly, the wheel units 20 are located at two outer sides of the frame body 10 to maximize the distance between the wheel units 20 so as to enhance the stability of the hand truck during the transportation. In particular, the wheel units 20 are located at the rear side 102 of the handle members 121 of the frame body 10 respectively.
Each of the wheel units 20 comprises a steerable wheel 21 and a switching shaft 22 which is upwardly extended from the steerable wheel 21 and is adjustably rotated with respect to the frame body 10. Therefore, when the steerable wheels 21 are switched in parallel at the first operation position, the frame body 10 is adapted to be moved at the back-and-forth direction, and when the steerable wheels 21 are switched in an aligned planar manner at the second operation position, the frame body 10 is adapted to be moved at the left-and-right direction. In particular, each of the wheel units 20 is turned 90 degrees to switch between the first and second operation positions.
In addition, each of the steerable wheel 21 comprises a wheel housing 211, preferably having a U-shaped cross section, and a wheel member 212 rotatably held at the wheel housing 211, wherein the switching shaft 22 is upwardly extended from the wheel housing 211 of the steerable wheel 21 such that when the switching shaft 22 is rotated, the wheel member 212 of the steerable wheel 21 is driven to rotate correspondingly. In other words, at the first operation position, the wheel members 212 are coaxial and parallel with each other and are located at the outer sides of the frame body 10 at the rear side 102 thereof such that the frame body 10 can be moved at the back-and-forth direction. A the second operation position, the wheel members 212 are aligned side-by-side at the outer sides of the frame body 10 at the rear side 102 thereof such that the frame body 10 can be moved at the left-and-right direction, i.e. the sideward direction of the frame body 10.
As it is mentioned above, the frame body 10 is preferably tilted backward in order for the user to move the frame body 10 at the back-and-forth direction. Each of the switching shafts 22 is inclinedly supported with respect to the handle 12 of the frame body 10 to enable the frame body 10 being tilted backward for transporting the load. Since the switching shafts 22 are inclinedly supported at the rear side 102 of the frame body 10 when the frame body 10 is moved at an upright position, the switching shafts 22 can be moved perpendicular to the ground surface when the frame body 10 is tilted backward.
It is worth mentioning that when the frame body 10 is tilted backward, the frame body 10 can be moved at the back-and-forth direction when the wheel units 20 are switched at the first operation position, or can be moved at the left-and-right direction when the wheel units 20 are switched at the second operation position.
The wheel assembly further comprises two wheel frames 30 spacedly and rearwardly extended from the frame body 10 for retaining the wheel units 20 in position. Accordingly, the wheel frames 30 are rearwardly extended from the handle members 121 of the frame body 10 respectively. As shown in
The two retention walls 31 are embodied as an outer retention wall and an inner retention wall which preferably parallels to the outer retention wall. Each of the retention walls 31 has a front edge extended from the rear side 102 of the frame body 10 and a slanted rear edge such that each of the retention walls 31 has a trapezoid shape. Accordingly, the switching shaft 22 is received along the guiding channel 32 between the outer and inner retention walls 31 at a position that the switching shaft 22 is aligned with the slanted rear edge of each of the retention walls 31.
It is worth mentioning that each of the guiding channels 32 has a bottom opening formed between the bottom sides of the retention walls 31 such that each of the steerable wheels 21 is located underneath the respective wheel frame 30.
The wheel assembly further comprises two retention units 40 for retaining the wheel units 20 being switched between the first and second operation positions respectively, wherein each of the retention units 40 forms a position lock to lock up the respective wheel unit 20 between the first and second operation positions.
As shown in
The retention unit 40 further comprises a retention member 43 upwardly protruded from the respective steerable wheel 31, wherein when the switching shaft 22 is rotated to move the retention member 43 at the first locking slot 41, the steerable wheel 21 is switched and locked at the first operation position. When the switching shaft 22 is rotated to move the retention member 43 at the second locking slot 42, the steerable wheel 21 is switched and locked at the second operation position. Accordingly, the retention member 43 has a block-like structure, such as a cube structure, a rectangular block, a hexagonal block or the like.
As shown in
In particular, each of the switching shafts 22 is slidably and rotatably retained in the respective guiding channel 32 such that each of the steerable wheels 21 is adapted to be downwardly pushed to disengage the retention member 43 from each of first and second locking slots 41, 42 so as to enable the steerable wheel 21 being switched between the first and second operation positions. As shown in
In order to switch the steerable wheel 21 from the first operation position to the second operation position, the steerable wheel 21 is downwardly pressed to drive the respective switching shaft 22 moving downwardly within the guiding channel 32 so as to disengage the retention member 43 from the first locking slot 41. Once the retention member 43 is dropped down at a position below the bottom edge of the outer retention wall 31, the steerable wheel 21 can be turned with respect to the rotational movement of the switching shaft 22 within the guiding channel 32, as shown in
It is worth mentioning that the height of the retention member 43 is about 1 cm and the depth of each of the first and second locking slots 41, 42 is about 1 cm. In other words, the steerable wheel 21 can be downwardly pressed with a displacement of 1 cm in order to disengage the retention member 43 with each of the first and second locking slots 41, 42. In addition, since each of the wheel units 20 is supported at an inclined position when the frame body 10 is moved at the upright position, there is a clearance between each of the wheel units 20 and the ground surface for enabling the wheel unit 20 to be moved downwardly for switching the wheel unit 20 between the first and second operation positions. When the frame body 10 is moved at the upright position, the weight of the load is substantially applied at the load platform 11 of the frame body 10 but not at the wheel units 20. Therefore, the user is able to easily press each of the wheel units 20 downward for switching its position by the downward pushing force in no relation to the weight of the load. Thus, the two wheel units 20 are rearwardly located at the rear side 102 of the frame body 10, such that the wheel units 20 form two rear stands for supporting on the ground surface when the frame body 10 is moved at the upright position. The wheel units 20 further form two pivot points to move the frame body 10 from the upright position to the tilted position with minimum rear pulling force at handle 12 of the frame body 10 by the user.
In order to enhance the switching operation of each of the steerable wheel 21, each of the wheel frames 30 further comprises a resilient element 33 coaxially coupling with an upper portion of the respective switching shaft 22 for applying an upward pulling force thereat so as to ensure the retention member 43 being engaged with one of the first and second locking slots 41, 42. As shown in
According to the preferred embodiment, the wheel assembly 30 further comprises two foot pedals 36 sidewardly extended from the wheel units 21 respectively to selectively switch each of the wheel units 21 between the first and second operation positions in a hand-free manner.
Accordingly, each of the foot pedals 36 is an elongated foot step sidewardly extended from the wheel member 212 at the center thereof. The foot pedal 36 is arranged for the user to step thereon for applying the downward force at the steerable wheel 21. Therefore, when the frame body 10 is moved at the upright position, the user is able to apply the downward force at the steerable wheel 21 by the foot of the user to switch the steerable wheel 21 between the first and second operation positions. It is appreciated that the user is able to slightly push the frame body 10 forward by hands of the user to minimize the downward force applied at the foot pedal 36 by the foot of the user. Preferably, the two wheel units 21 are identical in structure except the provision of the foot pedals 36.
The wheel assembly further comprises a reinforcing frame 50 for reinforcing the structure of the wheel units 20 with respect to the frame body 10. The reinforcing frame 50 comprises a first reinforcing arm 51 extending between two inner retention walls 31 of the two wheel frames 30 and a second reinforcing arm 52 extending between two outer retention walls 31 of the two wheel frames 30.
Referring to
One skilled in the art will understand that the embodiment of the present invention as shown in the drawings and described above is exemplary only and not intended to be limiting.
It will thus be seen that the objects of the present invention have been fully and effectively accomplished. It embodiments have been shown and described for the purposes of illustrating the functional and structural principles of the present invention and is subject to change without departure from such principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims.
