Railway draft appliances – Cushioned – Combined spring and friction
Reexamination Certificate
1998-01-20
2001-08-28
Butler, Douglas C. (Department: 3613)
Railway draft appliances
Cushioned
Combined spring and friction
C213S029000, C213S043000, C213S223000, C267S201000, C267S207000, C267S204000, C267S202000, C188S269000
Reexamination Certificate
active
06279765
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to railway car cushioning devices of the type having a hydraulic shock absorber which is moved from a neutral position for absorbing both buff and draft impacts.
BACKGROUND OF THE INVENTION
Cushioning devices are used to protect railcars and lading from impacts during coupling and train action events. To absorb the high forces caused by these impacts, cushioning devices are employed between the frame of the railcar and couplers.
Impacts applied to railcars result in high forces applied to the coupler in both the buff direction and the draft direction. “Buff” is a term in the rail industry used to describe the movement experienced by the coupler when it is moved towards its associated railcar. “Draft” is a term in the rail industry used to describe the movement experienced by the coupler when it is moved away from its associated railcar. A buff impact moves the coupler towards its associated railcar. A draft impact moves the coupler away from its associated railcar.
Conventionally railcar impacts are cushioned by hydraulic cylinders. In one type of hydraulic cylinder, pressurized gas in hydraulic fluid in the cylinder biases the piston to a fully extended position. If a draft impact occurs while the piston is fully extended, the device is unable to cushion the impact because the piston cannot move further in draft. In another type of gas charged hydraulic cushioning device, an externally mounted spring prevents the pressurized hydraulic fluid from fully extending the piston and holds the piston in a neutral position. The piston can move from the neutral position in response to either buff or draft impacts. The external spring increases the size of the cushioning device and makes installation difficult. The external spring is exposed to dirt and other environmental contaminants that can adversely affect operation of the cushioning device. The restoring force generated by the external spring acts along a line of force eccentric with the line of action of the cylinder itself, and may cause uneven or accelerated wear of moving components.
Thus, there is a need for an improved gas charged hydraulic railcar cushioning device that can cushion both buff impacts and draft impacts without an external spring device, and has forces applied along the line of action of the cushioning device itself.
SUMMARY OF THE INVENTION
The present invention is an improved railcar cushioning device that is responsive from a neutral position for absorbing buff and draft impacts. The cushioning device includes a hydraulic cylinder charged with pressurized hydraulic fluid. A piston in the cylinder is connected to a piston rod extending out of the cylinder through a front head. The hydraulic fluid urges the piston towards the front head of the cylinder. A spring assembly in the cylinder includes a spring confined between the piston and the front head of the cylinder. The spring surrounds the piston rod. The pressurized fluid holds the piston against the spring in a neutral position spaced inwardly from the front head of the cylinder.
In the preferred embodiment of the present invention, the spring is a friction or ring spring having a plurality of interfitted circular rings with engaged conical friction surfaces. During a draft impact, the rings are stressed and slide against one another. Impact energy is stored and dissipated. The improved railcar cushioning device allows hydraulic cushioning of buff impacts and combined hydraulic and mechanical cushioning of draft impacts.
Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings illustrating three embodiments of the invention, of which there are five sheets.
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ASF-Keystone, Inc.
Brosius Edward J.
Butler Douglas C.
Manich Stephen J.
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