Steel railroad sleepers

Details Steel railroad sleepers Steel railroad sleepers

1999-06-11

2001-05-15

Morano, S. Joseph (Department: 3617)

Railways: surface track

Ties

Cross section

C238S060000

Reexamination Certificate

active

06230981

ABSTRACT:

This invention relates to steel railroad or railway sleepers and to methods of producing such sleepers.
Sleepers are integral parts of flexible support systems used for guiding trains. Their key functions are to retain the gauge and inclination of the rails which they support and to assist to maintain both lateral and vertical tolerances placed on the track. They also transmit loads to a supporting bed of ballast over a surface area which is significantly greater than that applied by a wheel of a train and are required to do so in such a manner as to enable the ballast to spread the transmitted load onto the subsoil below the ballast bed without deformation of that subsoil. Sleepers are required to maintain rail track stability during the passage of trains and to maintain this stability notwithstanding temperature changes, this latter feature being more important when continuously welded track is employed.
A minor proportion of sleepers currently employed are produced from steel, these providing lower installation costs than more conventional sleepers of concrete or timber. Steel sleepers are generally of box or inverted channel section and are relatively easy to transport having a higher stacking density, require less expensive equipment to instal, have no need for re-ballasting and require less ballast depth because of their shape. Their use results in shorter and predictable track possession times, and their relatively light weight makes them easier to handle and instal than the more conventional solid concrete or timber sleepers. Also, they are less susceptible to gauge spread and derailment damage and can be repaired; they also have a scrap value.
Conventional steel sleepers are produced by hot forming which results in relatively high manufacturing costs. Increased initial tamping is required to achieve consolidation.
Although a desirably high resistance to lateral movement is achieved, steel sleepered track is more difficult to move during realignment schemes.
A steel box-section sleeper is disclosed by DE-A-2951272. The open ends of this sleeper are closed by welded steel plates or mouldings of reinforced concrete or plastics. The hollow interior of the box-section is filled with an insulating material, for example a mix of cement and water or a rubber elastomer.
WO 89/10450 discloses a steel railroad sleeper of inverted channel section which includes restraining elements attached to and dependent from the underside of the upper supporting surface of the sleeper. These elements include downwardly oriented branches which, in use of the sleeper, provide lateral stability for the sleeper.
Both of the disclosed sleepers suffer from the disadvantages discussed above.
The present invention sets out to provide a sleeper which overcomes, or at least alleviates, some of the disadvantages referred to above.
According to the present invention in one aspect there is provided a steel railroad sleeper of inverted channel section and end plates for selectively closing the open ends thereof, substantially vertically downward movement of the end plates being detachably connectable one to each open end of the sleeper and the sides of the sleeper inclining downwardly and outwardly from an upper rail supporting surface of the sleeper, the sleeper being produced by cold forming strip steel.
The end plates may be latchable into position.
The sleeper may be produced by cold pressing or cold rolling. The end plates may also be produced by cold forming steel strip.
The depth of each end plate may exceed the depth of each side of the sleeper.
The sleeper and/or end plates may be produced from mild or stainless or HSLA steel. If produced from stainless steel, shot peening or anti-corrosion coatings may be effected or provided, to counter any stress corrosion.
The free end of each side of the sleeper may be turned outwardly and upwardly to define a lip.
An opening may be provided in the top of each end plate through which ballast can pass. Alternatively or additionally, the sleeper may be formed at or adjacent one or each end with an opening through which ballast can pass.
The sleeper may have a waisted section of reduced width. This waisted section may be positioned generally midway along the length of the sleeper.
The central section of the sleeper interior may be filled with a material to prevent the ingress of ballast to this central region. The material may be a sound deadening material and may comprise expanded polyurethane foam. Alternatively or additionally, the internal walls of the sleeper may be at least partially coated with a sound deadening material.
In a further aspect, the invention provides a method of producing a steel railroad sleeper of open-ended inverted channel section and end plates therefor, the method comprising the steps of cold forming steel strip to the required inverted channel section and to the required end plate dimensions, and providing on each end plate and/or each open end of the sleeper fittings for securing the end plates to close the open ends of the sleeper, said fittings enabling substantially vertically downward attachment of the end plate to the sleeper.
In another aspect, the invention provides a railroad sleeper of inverted channel section produced by cold forming steel strip, end plates detachably secured one to each open end of the sleeper to close the same, a rail supported by the upper surface of the sleeper and a spring steel clip which secures the rail to the sleeper, the clip including a first bearing surface for engagement with the upper surface of the sleeper, a second bearing surface for engagement with the underside of the rail supporting surface of the sleeper, and a loop section intermediate the first and second bearing surfaces which, in use, engages the upper surface of a foot flange of the rail, and including tool means for applying a force to the internal surfaces of the loop section of the clip to increase the separation thereof whereby the required engagement of the bearing surfaces with the rail and the loop section of the clip with the rail flange is facilitated after the insertion of insulation material between the opposed surfaces of the loop and the rail flange and relaxation of the force applied by the tool.
The insulation material is preferably preformed to complement the upper surface of the rail flange.
In a still further aspect, the invention provides a method of attaching a rail to a sleeper of inverted channel section produced by cold forming steel strip and including detachable endplates using a spring steel clip, the method comprising the steps of positioning a shoulder of the clip in engagement with the sleeper with a bearing surface of the shoulder in contact with the underside of the rail bearing surface of the sleeper adjacent to the edge, positioning a second bearing surface of the clip in contact with the upper surface of the sleeper, positioning a loop section of the clip intermediate the shoulder and second bearing surface with its underside above a foot flange of the rail, inserting into the loop a spreading tool and operating the same to increase the mouth of the loop thereby increasing the separation between the loop and the rail flange, inserting between the loop and the rail flange a preformed insulator, and relaxing the spreader tool to cause the two bearing surfaces firmly to engage the sleeper and the loop firmly to engage the rail flange.
The clip may be generally “U” shaped in plan with each leg of the “U” defining the first mentioned bearing surfaces and a loop section and with the central section of the “U” defining second bearing surfaces.


REFERENCES:
patent: 2841338 (1958-07-01), Fairbert
patent: K09351 (1910-09-01), None
patent: 333 761 (1930-09-01), None
patent: WO 94 28245 (1994-12-01), None
Patent Abstracts of Japan, vol. 12, No. 347 (M-743), Sep. 19, 1988 & JP 63 108920 A (Takayoshi, May 13, 1988.
Patent Abstracts of Japan, vol. 7, No. 79 (M-204) (Kawasaki Seitetsu KK), Jan. 14, 1983.

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