Patent Application
20140261066
This disclosure relates to the field of vehicles for use on railway tracks and conventional roads and highways, and in particular a mechanism for raising and lowering the front rail wheels.
It is known to adapt vehicles such as conventional highway tractors for use on rails by providing retractable rail wheels which are lowered to maintain the position of the vehicles on the railway tracks and are raised for road use of the vehicle.
For example U.S. Pat. No. 5,103,740 to Masse and U.S. Pat. No. 5,868,078 to Madison disclose road/rail vehicles. U.S. Pat. No. 5,016,544 to Woollam discloses a convertible road/rail power vehicle with road wheels and retractable front, middle, and rear rail wheels for moving rail cars. Drive is provided by a set of retractable solid rubber rail wheels near the longitudinal center of gravity near the middle of the vehicle.
U.S. Pat. No. 6,976,432 to Jacob discloses a railcar moving vehicle with retractable rail wheels for guiding the vehicle on rails, and rubber-tired drive wheels that provide drive for both road and rail use. The rubber-tired drive wheels are configured to support the vehicle on a roadway in highway mode, and to contact the rails in rail mode such that the same road wheels drive the vehicle in both the rail and road modes.
Brandt Road Rail Corporation of Regina, Canada manufactures road/rail vehicle with front and rear rubber road wheels and front and rear retractable steel rail wheels where, like the Jacob vehicle described above, the rubber rear wheels provide drive for both road and rail use. With the Jacob and Brandt vehicles, the front and rear rail wheels are mounted on pivot arms that are pivotally attached to the vehicle frame. In rail mode the front rail wheels are lowered and the front road wheels raised above the rails. The rear rail wheels are lowered to engage the rails to keep the vehicle on the rails, but a significant portion of the weight of the rear end of the vehicle remains on the rubber rear wheels to provide traction to move the vehicle and rail cars attached to it. An air bag suspension system raises and lowers the front and rear rail wheels and also controls the proportion of vehicle weight that is carried by the rear rail wheels and the rear drive wheels.
The rear wheels only move down to engage the wheels and the rear rubber wheels remain in contact with the rails. The front rail wheels however must move downward farther in order to raise the front road wheels above the rails. The longer range of travel required by the front pivot arm causes significant deformation of the airbag which inflates and deflates to move the front pivot arm, causing wear. In some vehicles the range of travel required to raise the front road wheels above the rails cannot be obtained with the airbag alone.
When the front rail wheels are raised in the road travel position, the weight of the front end of the vehicle is carried on the front wheels through a spring suspension that bends in response to the weight. As the front rail wheels move down into the rail travel position, the frame moves upward however the springs must unbend before the front wheels move above the rails as required. To reduce the required range of travel of the front rail wheels, the spring suspension may be pinned to the frame when the front rail wheels are raised and the springs are bent, such that the front road wheels move upward directly with the frame. Pinning the front road wheels and/or spring suspension is inconvenient and time consuming.
The present disclosure provides a retractable rail wheel apparatus for a road/rail vehicle that overcomes problems in the prior art.
In a first embodiment the present disclosure provides a road/rail vehicle apparatus comprising a vehicle frame, and a rail axle with right and left rail wheels rotatably attached to corresponding right and left ends of the rail axle. At least one parallel link assembly comprises a lower arm pivotally attached at a first end thereof to the vehicle frame about a lower frame pivot axis and extending in a direction substantially parallel to an operating travel direction of the vehicle frame, and attached at an opposite second end thereof the rail axle, an upper arm pivotally attached at a first end thereof to the vehicle frame about an upper frame pivot axis above the lower frame pivot axis, and a link arm pivotally attached at a lower end thereof to the lower arm at a lower link pivot axis and pivotally attached at an upper end thereof to a second end of the upper arm at an upper link pivot axis. A distance between the upper and lower link pivot axes is substantially equal to a distance between the upper and lower frame pivot axes, and a distance between the lower link and lower frame pivot axes is substantially equal to a distance between the upper link and upper frame pivot axes. An airbag mounting plate is fixed to the link arm, and an airbag is attached at a lower end thereof to the airbag mounting plate and attached at an upper end thereof to the vehicle frame. An airbag control is operative to vary air pressure inside the airbag.
In a second embodiment the present disclosure provides a road/rail vehicle apparatus comprising a vehicle frame and front road wheels mounted under a front end portion of the vehicle frame and supporting the front end portion of the vehicle for travel on roads in a road mode. A front rail axle with right and left front rail wheels rotatably attached to corresponding right and left ends of the front rail axle supports the front end portion of the vehicle for travel on rails in a rail mode. Right and left parallel link assemblies are attached to corresponding right and left sides of the vehicle frame and to corresponding right and left end potions of the front rail axle. Each parallel link assembly comprises a lower arm pivotally attached at a rear end thereof to the vehicle frame about a lower frame pivot axis and extending forward to an opposite front end thereof attached to the front rail axle; an upper arm pivotally attached at a rear end thereof to the vehicle frame about an upper frame pivot axis above the lower frame pivot axis and extending forward from the upper frame pivot axis to a front end thereof; a link arm pivotally attached at a lower end thereof to the lower arm at a lower link pivot axis and pivotally attached at an upper end thereof to the front end of the upper arm at an upper link pivot axis; wherein a distance between the upper and lower link pivot axes is substantially equal to a distance between the upper and lower frame pivot axes, and a distance between the lower link and lower frame pivot axes is substantially equal to a distance between the upper link and upper frame pivot axes, and an airbag mounting plate fixed to the link arm. An airbag is attached at a lower end thereof to the airbag mounting plate and is attached at an upper end thereof to the vehicle frame, and an airbag control is operative to increase air pressure inside the airbag to expand the airbag and move the rail axle down such that the front road wheels are raised above the rails when in the rail mode.
The parallel link assembly provides an increased range of travel and reduces lateral stresses on the airbag.
While the invention is claimed in the concluding portions hereof, preferred embodiments are provided in the accompanying detailed description which may be best understood in conjunction with the accompanying diagrams where like parts in each of the several diagrams are labeled with like numbers, and where:
In the prior art vehicle 1 the front rail axle 7 is moved down by directing pressurized air into an airbag 13 that is attached at an upper end thereof to the vehicle frame 3 and is attached at a lower end thereof to a pivot arm 15. The pressurized air expands the airbag 13 and pushes the front rail axle 7 and wheels 9 downward to raise the front road wheels 5 above the rails 11.
It can be seen that the top and bottom end plates 13A, 13B of the airbag 13 are not parallel but are oriented at an angle to each other in both the road and rail modes. This non-parallel orientation causes lateral stresses on the airbag 13 as it expands and contracts, and also limits the range of movement. It thus may be necessary to pin the front road wheels 5 to the vehicle frame 3 in order to raise the wheels 5 above the rails as illustrated in
Each parallel link assembly 120 comprises a lower arm 121 pivotally attached at a rear end thereof to a bracket 123 fixed to the vehicle frame 103 about a lower frame pivot axis LF and extending forward to an opposite front end thereof attached to the front rail axle 107. An upper arm 125 is pivotally attached at a rear end thereof to the bracket 123 fixed to the vehicle frame 103 about an upper frame pivot axis UF above the lower frame pivot axis LF and extends forward from the upper frame pivot axis UF to a front end thereof. A link arm 127 is pivotally attached at a lower end thereof to the lower arm 121 at a lower link pivot axis LL and is pivotally attached at an upper end thereof to the front end of the upper arm 125 at an upper link pivot axis UL. The distance between the upper and lower link pivot axes UL, LL is substantially equal to a distance between the upper and lower frame pivot axes UF, LF, and the distance between the lower link and lower frame pivot axes LL, LF is substantially equal to the distance between the upper link and upper frame pivot axes UL, UF such that the upper and lower arms 121, 125, the link arm 127 and the pivot axes UF, LF on the bracket 123 form a parallelogram.
In such a parallel link assembly 120, the link arm 127 remains in the same orientation as it moves up and down. An airbag mounting plate 129 is fixed to the link arm such that same is oriented horizontally and the airbag mounting plate 129 will therefore also remain horizontal at it moves up and down. Front and rear airbags 113F, 113R are attached at lower end plates 113B thereof to the airbag mounting plate 129 and are attached at upper end plates 113A thereof to an frame mounting plate 131 that is fixed to the vehicle frame 103 parallel to the airbag mounting plate 129. In
Thus as the parallel link assembly 120 moves between the rail mode of
An airbag control 133 located in the vehicle operator station 135 is operative to increase air pressure inside the airbags 113 to expand the airbags and move the rail axle 107 down such that the front road wheels 105 are raised above the rails 111 when in the rail mode illustrated in
The parallel link assembly 120 thus provides a mechanism for moving the rail axle 107 between the road and rail modes with an increased range of travel, and reduced lateral stresses on the airbags.
The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous changes and modifications will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all such suitable changes or modifications in structure or operation which may be resorted to are intended to fall within the scope of the claimed invention.
