Patent Application
20070114079
1. Field of the Invention
This invention relates to a front wheel stabilizing device for an electric motor-driven wheeled vehicle, more particularly to a front wheel stabilizing device to prevent tipping of the wheeled vehicle.
2. Description of the Related Art
A conventional electric motor-driven wheelchair is generally provided with a front wheel stabilizing device to improve tracking upon undulating or irregular surfaces and to provide anti-tip stability.
Each of the front stabilizing devices 15 includes a support rod 151 which extends through an insert hole 112 formed in a front upright post 111 of the main frame 11 and which is secured to the front upright post 111 by means of screw fasteners 16 that extend through lock holes 113 formed in the front upright post 111, a cantilever arm 152 which is pivotally mounted on the front upright post 111, a stabilizing wheel 153 which is mounted on the cantilever arm 152, and a compression spring 154 which is disposed between a front segment 1511 of the support rod 151 and the cantilever arm 152.
Due to the provision of the front stabilizing devices 15, when the wheelchair 10 travels over undulating or irregular surfaces, the compression springs 487 provide a damper effect to the cantilever arms 152 and the stabilizing wheels 153 so as to improve anti-tip stability. However, the upright posts 111 need to be formed with the insert holes 112 for passage of the support rods 151, and the lock holes 113 for securing the support rods 151 to the upright posts 111, thereby resulting in weakening of the structure of the main frame 11 and complicating the manufacturing process. Moreover, as the front segments 1511 of the support rods 151 extend forwardly of the main frame 11 for the compression springs 154 to be mounted thereon, they are liable to be damaged as well as unsightly.
U.S. Pat. No. 5,848,658 and U.S. Pat. No. 6,460,641 also disclose electric power wheelchairs, which, however, suffer from the aforesaid drawbacks as well.
The object of the present invention is to provide a front wheel stabilizing device which can be assembled conveniently to a main frame of an electric motor-driven wheeled vehicle without weakening the structure of the main frame, and which has an improved anti-tipping stability.
According to this invention, the front wheel stabilizing device includes a mount adapted to be secured to a front side of a main frame of an electric motor-driven wheeled vehicle, and having two side plates which are spaced apart from each other in a transverse direction. An axle is disposed between the side plates, and extends along a pivot axis in the transverse direction to interconnect the side plates. A wheel mounting member has a tubular head which is sleeved on and which is rotatable relative to the axle about the pivot axis, and a cantilever arm which extends from the tubular head forwardly to terminate at a wheel -carrying end. A stabilizing wheel is rollably mounted on the wheel-carrying end to be rollable about a stabilizing wheel axis parallel to the pivot axis, and can yield under a jolting force that arises as a result of movement of the stabilizing wheel over an uneven ground surface so as to displace from a more tractive position, where the stabilizing wheel travels with more traction, to a less tractive position. A torsion spring has a coiled segment which is wound on the tubular head about the pivot axis, and two urging ends which are connected to opposite sides of the coiled segment, and which abut against the mount and the cantilever arm, respectively, so as to bias the stabilizing wheel downwardly, thereby restoring the stabilizing wheel from the less tractive position back to the more tractive position.
Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment of the invention, with reference to the accompanying drawings, in which:
Referring to
With further reference to FIGS. 4 to 6, the front wheel stabilizing device of this embodiment is shown to comprise a mount 30, a support rod 40, an axle 50, a wheel mounting member 60, a stabilizing wheel 70, two torsion springs 80, and a coupling member 90. In use, two sets of the front wheel stabilizing devices of this embodiment are preferably assembled to the wheeled vehicle 20, and are juxtaposed in the transverse direction.
The mount 30 has two side plates 32, 33 which are spaced apart from each other in the transverse direction to define a receiving space 31 therebetween, and a back plate 34 which is interposed between and which is disposed rearwardly of the sideplates 32, 33. The sideplates 32, 33 have a plurality of pairs of first mounting holes 321, 331, each pair of which are aligned with each other in the transverse direction, and a plurality of pairs of second mounting holes 322, 332, each pair of which are aligned with each other in the transverse direction.
The support rod 40 is disposed in the receiving space 31. In this embodiment, the support rod 40 is in the form of a threaded rod, and extends through a selected one pair of the first mounting holes 321, 331 to be engaged threadedly with a screw nut 41 so as to be secured to the mount 30. The axle 50 is disposed in the receiving space 31, and extends upwardly and rearwardly of the support rod 40. In this embodiment, the axle 50 is in the form of a threaded rod, and extends along a pivot axis in the transverse direction through a selected one pair of the second mounting holes 322, 332 to be engaged threadedly with a screw nut 51 so as to be secured to the mount 30.
The wheel mounting member 60 has a tubular head 61 which is sleeved on and which is rotatable relative to the axle 50 about the pivot axis, a cantilever arm 62 which extends from the tubular head 61 forwardly to terminate at a wheel-carrying end 621, and a pair of stems 63 which are disposed on and which extend from the cantilever arm 62. The cantilever arm 62 is disposed above and is supported by the support rod 40 so as to restrain excess downward movement of the stabilizing wheel 70.
The stabilizing wheel 70 is rollably mounted on the wheel-carrying end 621 to be rollable about a stabilizing wheel axis parallel to the pivot axis, and can yield under a jolting force that arises as a result of movement of the stabilizing wheel 70 over an uneven ground surface so as to displace from a more tractive position, where the stabilizing wheel 70 travels with more traction, to a less tractive position.
Each of the torsion springs 80 has a coiled segment 81 which is wound on the tubular head 61 about the pivot axis, and two urging ends 82, 83 which are connected to opposite sides of the coiled segment 81. The urging end 83 has a concave portion 84 which is configured for mounting on and abutting against the stem 63. The urging end 82 is disposed to abut against the back plate 34 so as to bias the stabilizing wheel 70 downwardly, thereby restoring the stabilizing wheel 70 from the less tractive position back to the more tractive position.
The coupling member 90 includes an upright post 91 which is mounted securely on the back plate 34 and which is adapted to be secured on one of the crossbars 213, e.g., by soldering, a crossbar 92 which is connected to and which extends from the upright post 91 in the transverse direction, and a lock seat 93 which is disposed on an end edge of the crossbar 92 and which extends laterally of the side plate 32 or 33, and a fastener 94 which is disposed to secure the lock seat 93 on the respective front upright post 211. By means of the coupling member 90, the mount 30 can be assembled to the front side of the main frame 21 conveniently without weakening the structure of the main frame 21.
In use, the angular position of the wheel mounting member 60 is adjustable.
By means of the torsion springs 80 which can bias the cantilever arm 62 and the stabilizing wheel 70 downwardly, the stabilizing wheel 70 can yield under a jolting force to displace to a more or less tractive position, thereby providing an anti-tipping effect. Hence, as shown in
It is noted that the torsion springs 80, unlike the compression or tension springs used in prior art, can provide a steady and even biasing force to the cantilever arm 62 during traveling of the wheeled vehicle 20, thereby improving the anti-tipping effect of the stabilizing wheel 70. Moreover, the number of the torsion springs 80 can be varied, i.e., the front wheel stabilizing device of this invention can include only one torsion spring 80.
According to this invention, the mount 30 can be assembled onto the main frame 21 of the wheeled vehicle 20 through the coupling member 90. Therefore, the assembling operation is convenient to conduct and will not adversely affect the structure of the main frame 21. Moreover, as the torsion springs 80 and the tubular head 61 are accommodated within the shell 25, they are not liable to be damaged.
While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretations and equivalent arrangements.
