High capacity multiple-stage railway switching yard

Details High capacity multiple-stage railway switching yard High capacity multiple-stage railway switching yard

2001-07-31

2003-02-11

Morano, S. Joseph (Department: 3617)

Railways

Car yard

C246S16700M, C246S1820AA

Reexamination Certificate

active

06516727

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to railroads, particularly to methods of sorting cars in railroad yards.
DESCRIPTION OF THE RELATED ART
Copending utility patent application Priority Car Soiling In Railroad Classification Yards Using a Continuous Multi-Stage Method by Edwin R. Kraft, Ser. No. 09/716,300 (hereinafter referred to as the “parent application”) describes new methods of multiple stage sorting in railroad classification yards. It also suggests several new yard designs to maximize the effectiveness of those methods. An extensive review of prior art is also included in the parent application. Further refinements to those operating methods and yard designs are disclosed herein.
Copending U.S. application Ser. No. 09/716,300 is incorporated by reference into this application, as provided by Manual of Patent Examining Procedure, Section 608.01(p). However, some repetition of material already covered in the parent application is necessary. In cases where drawing figures or tables from the parent application are referenced, they keep their same figure numbers (1-22), labels and reference numbers herein. Therefore, any repetitive material which does need to be included herein can easily be identified and cross referenced with the parent application.
Prior art designs for large railway classification yards dedicate specific tracks to distinct functions of receiving inbound trains, classification (sorting) of cars, and to assembly of outbound trains. Cars always move in a predetermined sequence from the receiving yard through the classification yard, and finally into the departure yard. Hump yards are modeled after an assembly line. The problem is that it is a rigid Henry Ford, 1920's-style assembly line, rather than adapting yard design to current just-in-time manufacturing paradigms—which emphasize flexibility, short setup times and rapid response to changing and always unpredictable customer needs. This lack of flexibility inherent in current yard designs translates into an inability to:
(a) make connections as scheduled,
(b) protect capacity on outbound trains needed for higher priority cars,
(c) accommodate “block swapping” or
(d) benefit from switching already done at a previous yard.
Accordingly, major changes in design philosophy are needed to make hump yards effective in today's truck-competitive environment. Currently, hump yards generally use single stage sorting, where each car is classified only once. Single stage sorting is very restrictive, since it limits the number of classifications or “blocks” that can be built to no more than the number of tracks in the yard, and once cars are classified, affords no “second chance” to adjust the arrangement of cars. Even if a yard is built with many short tracks, single stage yards often cannot create as many blocks as are needed. Since classification tracks are usually too short to assemble outbound trains, cars have to be pulled out of the opposite end of the yard, called the “trim” end and moved into a separate departure yard having longer tracks. Usually this “flat” switching operation, and not the sorting capacity of the hump, limits maximum throughput of the yard.
In a multiple stage yard, each car may be classified more than once allowing cars to be sorted into many more blocks (distinct classifications) than the number of tracks available. As shown in the parent application if classification tracks are of sufficient length, trains of more than one block can be built “ready to go” on a single track in proper order for departure, without needing flat switching at the trim end of the yard. The second sorting stage at the hump replaces flat switching for outbound train assembly, resulting in no net increase in switching workload.
Having eliminated the flat switching bottleneck at the “trim” end of the yard, the capacity of a multiple stage yard is clearly constrained by the hump processing rate. A high processing rate is needed since each car must be classified two or three times in a multiple stage yard, as compared to only once in a single stage yard. This need for high capacity has been recognized for a long time, in fact, a lack of sufficient capacity using traditional gravity sorting has been thought to render multiple stage switching infeasible. In The Folded Two Stage Railway Classification Yard, (hereinafter referred to as Davis, 1967) on p. 55 the two-fold yard was characterized as “a new concept in yard design. It may never have been proposed before because it would be inoperative using the sorting techniques presently employed by railroads. The yard uses neither an engine nor gravity to separate the cars.” Instead, Davis proposed use of a mechanical car accelerator to boost sorting capacity.
Although some U.S. yards have classified over 3,000 cars per day across a single gravity hump, with the increasing weight and length of modern cars, yard capacity has been slowly reduced. A typical hump yard today classifies 2,000-2,500 cars per day. A multiple stage yard of the same capacity would need a humping capability of 5,000-7,500 cars per day. This invention shows how the capacity needed to enable practical multiple stage sorting can be attained within the proven capability of conventional gravity switching, without needing to resort to any exotic or untested mechanical devices for accelerating or controlling the speed of railcars.
Shortcomings of Previous Designs
FIG. 10 of the parent application shows a design for a multiple stage classification yard. This yard consists of a single body of long classification tracks
55
, which should have a slight descending gradient throughout their entire length, so cars will roll all the way to the ends of the tracks. With such a gradient, car speed can be adequately controlled using only retarder units, avoiding the necessity for more expensive booster units. FIG. 22 of the parent application shows how “Dowty” car retarders may be distributed throughout the entire length of each track to maintain continuous speed control of cars, and to stop the cars upon reaching the end of each track.
The design of FIG. 10 of the parent application permits maximum flexibility in use of classification tracks for receiving inbound trains, sorting of cars and for final assembly of outbound trains. Cart roads
60
between every pair of tracks allow convenient access by mechanical personnel for performing car inspection and repairs, and for maintaining tracks, switches and car retarder systems.
Means for accelerating cars
90
into the classification tracks (generally assumed to be a gravity hump) are provided at one end of the yard. Switches at the opposite end of the yard, called the arrival/departure end
80
, allow trains to arrive and depart the yard onto the mainline
30
without interfering with hump
90
activities. Flat switching can also be performed at the arrival/departure end
80
, permitting “swapping” blocks of preclassified cars directly from one train to another, avoiding the need for those cars to be processed over the hump.
The main weakness of the yard shown in FIG. 10 of the parent application is that it only allows one train to be processed at a time. This severely constrains its capacity. FIGS. 14 and 15, also from the parent application, suggest placing a hump on both ends of the yard to increase its sorting capacity. However, such “double ended” designs can be problematical for the following reasons:
(a) It becomes necessary to coordinate processing activities of two humps at both ends of the yard, since cars cannot be safely humped into a track from both directions simultaneously.
(b) Double ended designs cause difficulties in establishing proper gradients throughout the length of the yard. Cars would tend to collect at the low point of the yard in the middle, rather than rolling all the way to the ends of the tracks. This problem could be overcome, at some cost, by employing booster units (an optional feature of the “Dowty” retarder system) to keep the cars rolling.
(c) Humps
90
a
and
90
b
on both ends of the yard block access to classifi

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