Patent Application
20090032607
A railroad tie, cross tie, or railway sleeper is a rectangular object used as a bottom section for railroad tracks. Railroad ties are members generally laid transverse to the rails and on which the rails are supported and fixed, to transfer the loads from rails to the ballast and sub grade below, and to hold the rails to the correct gauge. Synthetic, i.e., plastic, railroad ties that are used to couple the rails of a train track are known in the art. Known synthetic railroad ties include U.S. Pat. Nos. 4,083,491; 6,021,958; and 7,204,430. These ties are said to outlast the classic wooden tie, being resistant to environmental stress, while otherwise exhibiting properties similar to their wooden counterparts in terms of damping impact loads, lateral stability, and sound absorption. Regrettably, these ties suffer from one or more disadvantages such as high cost, instability during installation, and difficult installation on a grade. Therefore, there is a need for a reinforced railroad tie that is lower cost, has greater stability during installation, and is easier to install on a grade.
According to the present invention, there is provided a tie for use on a railway that satisfies the above-identified needs for a reinforced railroad tie. The railway tie according to the present invention is formed at least partially of polymeric material and may be manufactured at a lower cost than other known polymeric railway ties. The tie according to the present invention is weighted such that it has greater stability during installation and is easier to install on a grade.
In one embodiment of the present invention, a tie having a substantially rectangular prismatic body formed at least partially of polymeric material is provided. The body has a horizontal axis, a vertical axis, a top surface, and a bottom surface, and preferably, has substantially no external apertures. Encapsulated within the body is an elongated reinforcement. The reinforcement has a horizontal axis, a vertical axis, a top section having a top surface, a bottom section having a bottom surface, and a support section connecting the top section and the bottom section. The bottom section of the reinforcement has a greater weight, and cross-sectional area, than the top section of the reinforcement. Preferably, the reinforcement is centrally encapsulated within the body such that the vertical axis of the reinforcement is substantially parallel with the vertical axis of the body, and the horizontal axis of the reinforcement is substantially parallel with the horizontal axis of the body. Also preferably, the bottom surface of the bottom section of the reinforcement has a substantially flat planar surface.
In another embodiment according to the present invention, there is provided a track for a vehicle. In one embodiment the track comprises at least one rail, a plurality of elongated ties supporting the rail, and a fastener for holding the rail to the ties. According to this embodiment, at least one tie a body formed at least partially of a polymeric material and an elongated reinforcement encapsulated within the body as described herein. In one preferred embodiment, the track is on a bridge, in another preferred embodiment, the track is on a grade.
These and other features, aspects and advantages of the present invention will become better understood from the following description, appended claims, and accompanying figures where:
Most conventional ties are made of very strong hardwood timbers, which are very scarce, expensive to produce, and susceptible to decay. Degradation of a railway tie, also known as a “sleeper”, can lead to instability of the railway system which they support, and in turn lead to decreased safety of the rails. The present invention provides a railway tie that is strong, easily installed, and more durable than a traditional wooden tie and is particularly adapted for use as a bridge tie or installed on a grade. The railway ties according to the present invention in general have a body formed at least partially of polymeric material which has substantially no external apertures and a reinforcement which is totally encapsulated within the body. The ties are configured to provide sufficient strength to withstand the tensile, compression, shear, and torsion forces and bending moments that are exerted by a heavy load.
The encapsulation of the reinforcement structure within the polymeric body in accordance with the present invention contributes to the longevity of the ties by protecting the metal from corrosive intrusions. The reinforcement structure provides at least a substantial portion of the structural strength, integrity, and stability. In other words, the reinforcement structure functions to provide the structural core to resist bending and shear loads. The polymeric body casing provides the bulk of the mass needed to which other members can be affixed, non-limiting example of which are rails and spikes, to allow the encapsulated structure to function as tie. The casing also provides a non-conductive mass to prevent an electrical current from passing from one steel rail to another (prevents cross circuiting), if the tie is used in as a railway cross tie. It is an industry standard practice to use the steel rails on a railway to send electrical signal to traffic control systems.
According to the present invention, the reinforcement is proportioned such that the bottom section of the reinforcement has a greater weight than the top section of the reinforcement, and is generally proportioned such that the reinforcement stands upright without support, i.e., is freestanding. Preferably, the bottom section of the reinforcement has a substantially flat bottom. The proportions of the reinforcement lead to greater stability of the reinforced tie during installation, and ease of installation of the reinforced tie on a grade. Preferably the reinforcement is a recycled or “scrap” railway section. This substantially lowers the cost of producing the reinforced railway tie.
In one embodiment, the present invention is a tie for use on a railway. Referring now to
The tie 10 comprises a body 12 formed at least partially of polymeric material. The body 10 has a horizontal axis 14, a vertical axis 16, a top surface 18, and a bottom surface 20. Preferably, the body has substantially no external apertures.
As shown in
As shown in
The reinforcement 22 according to the present invention has a horizontal length 38 from about 6 feet to about 14 feet and a vertical height 40 from about 5 inches to about 8 inches. However, the length of the reinforcement 22 will vary depending on the length of the tie. Preferably, there is at least about two inches of body 12 encapsulating the reinforcement 22 on each side.
Preferably, the reinforcement 22 is a rail section, and more preferably a scrap rail section. The use of scrap rails as the reinforcement 22 in the tie 10 of the present invention lowers the cost of producing the ties. Rail sections, 115 RE; 119 RE; 132 RE; 133 RE; 136 RE; 140 RE and 141 RE, as designated in the AREMA Manual for Railway Engineering, American Railway Engineering and Maintenance-of-Way Association, copyright 2006, Part 1, Design, may be used in the present invention.
Referring now to
1AREMA Manual for Railway Engineering, American Railway Engineering and Maintenance-of-Way Association, copyright 2006, Part 1.
The tie according to the present invention may be prepared by placing a reinforcement 22 inside a mold to be encapsulated within the body 12 using injection-molding techniques. The interior chamber of the mold may be configured to be commensurate with the required parameters of a typical tie. The reinforcement 22 is intentionally placed in the mold cavity to allow extruded material to evenly be distributed on all sides of the reinforcement 22. As illustrated in
The body 12 of the tie 10 is formed from a polymeric material using an injection molding technique and equipment similar to that for die casting, in that a precision mold of desired shape is clamped shut, and melted material (for example, from palletized plastics) is forced into the cavity between the mold and the reinforcement 22 that is placed inside the mold. The exemplary palletized plastic material is fed into a heated chamber, or barrel, by a large, slowly rotating mechanism, and is melted. When a sufficient quantity to fill the mold cavity has been prepared, the rotating mechanism is moved axially under high pressure to extrude the melted material into the mold cavity. Some molds may have channels through which coolant is circulated to remove heat and to chill the plastics. When the plastic has cooled sufficiently, the mold is unclamped (or opened), and the molding is either forced out by strategically located ejectors or simply forcefully removed (depending on the type of mold being used.) During cooling and removal, material for the next part is plasticized within the barrel, ready for the cycle to be repeated. For further details of this process and suitable materials for the polymeric body, see U.S. Pat. Nos. 6,244,014 and 6,412,431, all to Barmakian, the entire disclosures of which are incorporated herein by reference. A preferred plastic material for the body 12 is recycled polyethylene that contains at least 96% to 98% polyethylene film for lubricity and flexibility.
In general, the rails 54a and 54b are laid transverse to the ties and held to the tie with one or more fasteners 60, such as a cleat, a bolt, a rail spike, a rail clip, or a screwed rail attachment, or a combination thereof. The tie 10 acts as an anchor and spacer for the rails, and the tie transfers the load from the rails 54a and 54b to the underlying girders 52a and 52b or ballast. Under heavy load conditions, the tie 10 according to the present invention can withstand tensile, compression, shear, and torsion forces and bending moments.
Although the present invention has been discussed in considerable detail with reference to certain preferred embodiments, other embodiments are possible. Therefore, the scope of the appended claims should not be limited to the description of preferred embodiments contained herein.
