Fluid-pressure and analogous brake systems – Multiple fluid-receiving devices – Multiple motors
Reexamination Certificate
1999-03-03
2001-07-10
Oberterton, Robert (Department: 3613)
Fluid-pressure and analogous brake systems
Multiple fluid-receiving devices
Multiple motors
Reexamination Certificate
active
06257680
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to braking systems for railcars. More particularly, the present invention relates to an improved braking system for a lightweight railcar moving vehicle comprising a modified semi-tractor wherein the braking system of the connected railcar(s) is connected to and actuated by the compressed air braking system of the semi-tractor.
2. State of the Art
In the railroad industry, maintenance of way is a critical activity and a major expense. Frequently, when maintenance is needed at a particular location along the right-of-way and heavy equipment or materials are required, a work train and crew are sent to that location to perform the needed repairs. For example, a work train may carry a load of railroad ties and short sections of rail for repairing track, along with heavy equipment for unloading and installing these items. Often, a work train consists of a locomotive pulling a single work car, and the maintenance work can be performed by one or two workers.
However, this approach can be very cost inefficient. Because maintenance of way crews and locomotive crews are differently trained and unable to perform each other's duties, the work train will frequently employ a crew much larger than actually needed at any given time. Obviously, this is costly. Furthermore, the use of a typical locomotive—which may cost in excess of a million dollars—to transport a single car and a few workers is extremely cost inefficient. For these reasons, it would be desirable to have a railcar moving vehicle that can pull one or a few railcars along the railroad track at mainline speeds, but that is not a conventional locomotive, and thus is not as costly as a locomotive, nor requires a full locomotive crew. With such a vehicle, a work crew could transport themselves to the work site with their materials and equipment, and perform the work with far less expense.
Additionally, it would be desirable to have such a railcar moving vehicle that is operable both on rails and on roadways. Such a vehicle would be valuable for maintenance of way crews by allowing a work crew to transport themselves and their equipment by highway to a rail siding, where the crew simply transfers their materials and equipment to a waiting railcar, and uses the semi-tractor on the rails to pull the railcar to the work site.
This sort of vehicle would have additional uses, as well. For example, many railroad customers have a need to move railcars and highway trailers within a rail yard or industrial siding. However, except for the largest industries, the cost to purchase and maintain a conventional switching locomotive is prohibitive or economically unwarranted. Thus, lightweight, multipurpose railcar moving vehicles have been developed and used to perform many functions normally assigned to switching locomotives, but which may also be used off the track to move trailers and containers about a switching yard or industrial site. Such modified or hybrid vehicles are more economical for many industries because of their relatively low cost and high versatility. They allow smaller industries to take advantage of the efficiency and economy of rail transport for heavy freight where otherwise they would not be able to do so.
However, conventional railcar moving vehicles are still relatively highly specialized, limited production vehicles. The cost per horsepower of these vehicles is significantly higher than the cost of a conventional semi-tractor, for example, which enjoys the cost advantages of much greater mass production. Additionally, conventional railcar moving vehicles are not designed or configured to operate on public highways as long or short haul trucks, but are confined to the industrial site or switching yard. Many of them do not have the functional and safety equipment required to be street legal, and are designed for low speed operation only, being unable to travel at speeds beyond 15 to 20 miles per hour. Moreover, they cannot operate at top speed for extended periods of time without overheating their hydraulic systems. To address these problems, railcar moving vehicles which are constructed from mass produced vehicles such as semi-tractors have been devised to reduce the acquisition cost and versatility of these vehicles.
Normally, the brakes of railroad cars are linked through a common line to the locomotive, which provides pressurized air to operate the braking system of all attached railroad cars. However, when a lightweight railcar moving vehicle such as a modified semi-tractor is coupled to a standard railcar, braking is a major concern. Because a single loaded railcar may weigh many times more than the lightweight railcar moving vehicle, the lightweight vehicle will be able to provide only a small fraction of the braking force needed for stopping in a reasonable distance, especially in an emergency. Obviously, it is desirable to utilize the railroad car brakes in order to take advantage of the weight of the railcar in braking. Conventional railcar moving vehicles known in the art do this by providing a compressed air link to the brake pipe of the connected railcar, thus using the railcar's braking system to stop.
A schematic diagram of a conventional railroad car braking system is given in
FIG. 1
, which depicts a string of conventional railcars
10
having steel wheels
12
riding on steel rails
14
, and coupled together by couplers
16
. Each railroad car
10
has installed thereon a brake pipe
18
, piston valve
20
, reservoir
22
, and brake cylinder
24
. The brake pipe
18
is in fluid communication with the piston valve
20
through valve
26
which can be opened or closed to allow or prevent compressed air in the brake pipe
18
to pass. Under normal conditions, and as shown in
FIG. 1
, valve
26
is open. Two conduits
28
and
30
connect the piston valve
20
to the reservoir
22
, and one similar conduit
32
connects the piston valve
20
to the brake cylinder
24
. The brake cylinder
24
comprises an actuating rod
34
which extends from the cylinder and is axially reciprocally moveable depending on the pressure in the brake cylinder
24
. This actuating rod
34
is connected via a mechanical linkage
35
(not shown in its entirety) to the individual brake actuators
36
on each wheel
12
of the railcar in a manner well known in the art.
The brake pipe
18
is connected to the brake pipes
18
of both preceding and following railcars
10
, by flexible hoses
38
. It will be appreciated that any railcar
10
may be connected to a locomotive and the brake pipe of the locomotive, rather than another railcar, in the same manner.
The typical railcar braking system thus shown operates in the following manner. The locomotive provides compressed air to the brake pipe
18
which communicates along the entire length of the train. Railcar braking systems typically maintain a running pressure of 90 psi in the brake pipe and associated components. With valve
26
open, this operating pressure is maintained within piston valve
20
, conduit
28
, and reservoir
22
. In a non-braking condition, the pressure in conduit
32
is less than that in the brake pipe and other components mentioned, and is approximately equal to atmospheric pressure.
To actuate the brakes of the railcar, the locomotive engineer moves a brake actuating lever (not shown) which opens a valve to allow pressure to escape from the bake pipe
18
. Because the brake pipes of all connected railcars are in fluid communication, this action simultaneously releases the pressure in the brake pipes of all connected railcars. When pressure is released from the brake pipe
18
, the change in pressure actuates the piston valve
20
to close off its connection to the brake pipe, and simultaneously release compressed air from the cylinder
22
, through conduit
30
, thence into conduit
32
and the brake cylinder
24
. This actuation thus prevents compressed air from reservoir
22
from escaping through the brake pipe, but sends it instead to the brake cylinder
24
. Pressuri
Bartz C. T.
Oberterton Robert
Thorpe North & Western
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