Railway rolling stock – Special car bodies – Dumping
Reexamination Certificate
1998-09-04
2001-02-27
Le, Mark T. (Department: 3617)
Railway rolling stock
Special car bodies
Dumping
C105S269000, C105S286000
Reexamination Certificate
active
06192804
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to railroad dump cars. In particular, the present invention is a hydraulically powered system for operating the dumping mechanism of the dump car.
2. Description of the Prior Art
Side dump railroad cars are used for carrying and unloading bulk materials. The typical car comprises a frame with wheels and a pivotally connected hopper body. The body characteristically consists of side doors that open when the body is tilted at an angle sufficient to discharge the bulk material.
These present-day side-dump railroad cars are actuated by pneumatic rams that are attached to the frame of the car. Upon actuation, a piston raises the bed on one end, discharging the material over the other side of the car through the opened side door.
The source of compressed air to drive these rams is from an air compressor inside of the locomotive. A disadvantage to the use of pneumatic rams, however, is that they are (i) large, (ii) expensive to service, (iii) because they operate by air pressure, they are difficult to control and regulate under varying load conditions, and (iv), are susceptible to condensing and freezing of water vapor in the rail air lines and system components during cold winter months, thus causing blockage.
Probably most important from a safety standpoint relates to the difficulty of precisely controlling the movement of the dump body. This is because high pressure is initially required to begin the dumping process and as the load is removed, less pressure is required to complete the dumping process. When this condition occurs, the reduced compression of the air in the pneumatic ram causes a large and rapid travel in the piston, completing the dumping in an uncontrolled manner. This inability to control the rate of dumping as the load is removed causes great stress on all components of the dump car as the dump bed is slammed to the travel stops.
Others have attempted to solve this problem by replacing the pneumatic rams with hydraulic drive rams. A major disadvantage inherent in some systems, such as that depicted in McCormick, U.S. Pat. No. 4,407,202, is the use of a hydraulic accumulator attached to each railroad car to store hydraulic fluid pressure. This accumulator poses a potential safety problem, since hydraulic fluid may be at a pressure of 3000 psi or greater, a valve failure could cause the car to dump unexpectedly, having serious consequences. Therefore, a hydraulically operated side dump railroad car having a dump mechanism that operates at approximately the same rate as a car equipped with a hydraulic accumulator would be an important advancement for railroad operators.
SUMMARY OF THE INVENTION
The present invention seeks to overcome these and other disadvantages present in the prior art by providing a side dump railroad car that is operated by hydraulic rams but does not require a hydraulic accumulator. Utilizing compressed air from the locomotive or other source, the system for generating hydraulic pressure, in its basic form, includes a pair of opposing air brake cylinders whose actuating arms are connected to a pivoting lever. This lever in turn is connected to the piston of a double-acting hydraulic pump. This hydraulic pump in turn is operatively linked to at least one hydraulic ram that is capable of lifting the dump bed.
When the pump mechanism is actuated, air travels into a first air brake actuator and causes movement of its piston outwardly. This piston is connected by a first connecting arm to a centrally located pivot arm, which moves outwardly from the first air brake actuator. The pivot arm is connected to a hydraulic ram, which in turn moves and generates hydraulic fluid pressure. When the first air brake actuator connecting arm reaches its maximum travel, a valve is actuated, allowing air to fill the second opposing air brake actuator and release air pressure from the first air brake actuator. A piston in the second air brake actuator is connected to a second connecting arm that is also connected to the pivot arm. The pivot arm is then moved in the opposite direction by the second connecting arm, causing another stroke of the hydraulic ram and generation of additional hydraulic fluid pressure. When the second air brake actuator connecting arm reaches its maximum travel, a valve is actuated, allowing air to fill the first opposing air brake actuator and release air pressure from the second air brake actuator. In this manner, air pressure is converted to hydraulic pressure to activate the car's lift system.
Operation of the dumping mechanism is commenced by a hydraulic valve that selectively causes the hydraulic fluid pressurized by the converter pump to flow into at least one hydraulic ram. The pressurized hydraulic fluid causes the hydraulic ram to move the dump bed causing removal of materials contained therein. Also, an advantage of the present system is the ability to hold a dump body in mid-position for extended periods of time, unlike pneumatically-driven systems.
Noteworthy in the present system is the lack of an oil or hydraulic accumulator tank or device. Hydraulic fluid is pumped from a hydraulic fluid reservoir directly into the hydraulic rams that lift the dump bed. The oil reservoir of the present invention serves as a supply source for the hydraulic oil and as a return vessel for oil following use in the hydraulic drive rams. A pressure relief valve maintains the pressure in the oil reservoir well below that required to move the hydraulic drive rams, and thus the oil reservoir does not serve as a hydraulic accumulator. The present invention therefore provides a safer mechanism for moving the dump body of a side dump railroad car.
In other embodiments, it is envisioned that the hydraulic pump mechanism that converts pneumatic pressure to hydraulic pressure will be a part of each individual dump car. In alternative embodiments, a larger pneumatic to hydraulic system may be placed on an auxiliary railroad car and serve to actuate the hydraulic rams of a series of side-dump railroad cars. Moreover, it is contemplated that hydraulic power from a locomotive's hydraulic pump could be used to activate the dump car's hydraulic mechanism.
The hydraulic system of the present invention further eliminates safety problems that may occur when using a hydraulic storage accumulator that holds the hydraulic fluid pressure even after the air pressure source is disconnected. For example, should the hydraulic accumulator tank become compromised, the release of high pressure oil may be dangerous to railroad workers and equipment. Moreover, a safety hazard exists with accidental movement of the hydraulic valve, which may result in an unintended dumping of the car contents.
REFERENCES:
patent: 4407202 (1983-10-01), McCormick
International Search Report dated Oct. 26, 1998 (PCT/US98/18549) (GEOE:064P).
Howrey Simon Arnold & White , LLP
Le Mark T.
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