Patent Grant
12071732
Railroader sleepers represent one of the various components of a railroad network and, in conjunction with the ballast and other fastening elements, promote correct anchorage (fixation) of the rails on which the coaches travel. Conventionally, the great majority of the elements are made of wood (about 90%), the rest being steel, concrete or recycled-plastic sleepers.
A wooden sleeper has a useful life estimated to be a few decades; after this period, it is necessary to replace it. It is estimated that over 30 million wooden sleepers are replaced each year in the world, and there are the legal restrictions relating to the use of determined types of raw materials, causing the sector to look for alternatives to wooden sleepers. Generally, alternatives have concentrated on sleepers made of wood, steel, concrete, reforestation-wood, plastic (be it recycled or virgin).
The use of sleepers made of virgin plastic have exhibited good behavior. However, the use of this type of sleeper is restricted to passenger-transportation railroads, of narrow gauge, subject to efforts other than those resulting from a load system.
Recycled plastic sleepers were used in a few railroad networks and showed structural problems, such as endemic dissemination of cracks, warping and fixation problems. In particular, with a recycled sleeper it becomes difficult to obtain homogeneity in the material forming the sleeper.
Concrete sleepers, in spite of being widespread in railroad networks around the world, have not proved to be the best solution for the characteristics of the railroad beds and ballasts of the lines existing in some countries (such as Brazil and the United States), due to the great inertia and rigidity of the commercial models that are most commonly available. This tends to cause high breakage of ballasts, which increases the railroad-maintenance costs and enables the occurrence of accidents. Furthermore, installation of concrete sleepers in countries with high humidity weather is difficult due to the material's inherent water absorption characteristics.
Classified according to their shape, concrete sleepers may be of the mono-block type, formed by a single rigid and continuous piece, and are subjected to great bending moments, which appear at different sections of the sleeper. There are also concrete sleepers of the bi-block type (mixed sleepers), composed of two rigid blocks of reinforced concrete arranged under each rail and joined by a flexible steel bar. Due to the elasticity of the beam, the two blocks of concrete will be immune to most stresses of static bending and alternating bending, which sleepers made of pre-stressed concrete hardly resist.
Among concrete sleepers, there are also bi-block sleepers, wherein two reinforced-concrete blocks are arranged at the ends in conjunction of an intermediate piece, also made from concrete. The blocks of the sides, as well as the intermediate one, are joined by steel means of rods having high elastic limit, stressed and anchored at the ends.
On the other hand, the use of concrete sleepers presents a few disadvantages, such as higher transportation cost, due to the greater weight of this sleeper as compared with wood ones, as well as the questionable re-use of the sleeper after the occurrence of derailment. Additionally, using concrete sleepers, the fastening systems are not adjustable to the rail wear and to the widening of the railroad. Further, there is the need for expensive equipment for installing and maintaining the railroads, and in some situations, damage may be caused to the ballast due to the great weight of the sleeper.
As already mentioned, in addition to concrete and plastic sleepers, some sleepers are also made of steel. Steel sleepers exhibit satisfactory behavior when in use. However, they may have high and uncertain costs, since their cost depends directly on the price of the steel, which is extremely instable. Further, the fastening of this type of sleeper is usually made by means of screws and chestnuts and needs permanent maintenance. Further, the fastening by means of screw ends up weakening the sleeper due to the bores made therein.
Advantages of steel sleepers include the possibility of recycling, long useful life (about 60 years), being inert and non-toxic, low installation cost, simple transportation, and it is non-combustible by virtue of its manufacture material. Its disadvantages include that the use of steel sleepers requires a greater number of interventions and change in the tamping area. Further, this type of sleeper may entail the interruption of the trip, due to the isolation jeopardy and still may undergo corrosion problems.
With regard to wooden sleepers, these should be previously treated (chemically) in order to be suitable for use. Such a chemical treatment is harmful to the environment. Chemical treatment stations are responsible for storing the sleepers and for applying preservatives, with a view to prolong the useful life of the sleeper and preventing the proliferation of fungi and insects. In addition to being a long process comprising a number of steps, the process of treating sleepers may cause various environmental problems, such as air pollution, due to the breaking of storage tanks, treatment cylinders and tubing that contain the preserving agents. Additionally, it is not rare that employees may accidentally absorb, inhale, and ingest chemical products. Further, the use of herbicides and pesticides may contaminate the soil and the streams, causing changes in the behavior of the fauna and the possibility of extinction of species.
It is further possible to use sleepers made from reforestation wood, this type of sleeper exhibiting resistance significantly lower than that of hard wood. Additionally, the impossibility (in some countries) of treating sleepers with some products (such as creosote) that are strongly aggressive to the environment enables the sleeper to be attached by biological agents, such as bacteria and white ants, resulting in an extremely short life time (on the order of three to four years), which is much shorter than the useful life of sleepers made from hard wood.
This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.
In one aspect, embodiments disclosed herein relate to a railroad sleeper for fixation of at least one pair of rails of a railroad network, where the railroad sleeper includes a contact surface, wherein each rail of the pair of rails is fixed thereto and spaced apart from each other; anchorage walls extending downward from the contact surface and having a support point at a bottom surface thereof, the anchorage walls having at least one aperture formed therein; and a void delimited by the contact surface and anchorage walls.
In another aspect, embodiments disclosed herein relate to a fastening block for use with a railroad sleeper to fix at least one pair of rails of a railroad network, where the fastening block includes at least one aperture or void spaced formed therein.
In yet another aspect, embodiments disclosed herein relate to a railroad structure assembly that includes a railroad sleeper for fixation of at least one pair of rails of a railroad network, the railroad sleeper comprising: a contact surface, wherein each rail of the pair of rails is fixed to the contact surface and spaced apart from each other; anchorage walls extending downward from the contact surface; and a void space delimited by the contact surface and anchorage walls; and at least one fastening block present within the void space at a portion of the railroad sleeper corresponding to a location of a rail, wherein at least one of the anchorage walls or the at least one fastening block as apertures formed therein or the at least one fastening block has a void space formed therein.
Other aspects and advantages of the claimed subject matter will be apparent from the following description and the appended claims.
In one aspect, embodiments disclosed herein relate to components of a railroad network, specifically railway sleepers (also referred to in some locations as a railroad tie or crosstie) and fastening blocks that may, in conjunction with the ballast and other fixing elements, promote correct anchorage (fixation) of the rails on which the coaches travel. Railway sleepers are the rectangular supports for the rails in railroad tracks, which are generally laid perpendicular to the rails. They serve to transfer loads to the track ballast and subgrade, hold the rails upright and keep them spaced to the correct gauge. As discussed above, there are concerns with different types of materials conventionally used in railway sleepers, some of which limit the useful life of the sleepers and others of which limit the types of railroad lines in which the materials may be used. Embodiments disclosed herein relate to the use of a railway components that may be used on railroad lines in both construction and operation, for transporting loads and/or passengers.
Plastic composite-engineered sleepers (either virgin or recycled) known from the prior art do not exhibit optimized combinations between weight of the piece and elasticity modulus. Most known plastic proposals for sleeper exactly imitate the shape of a wooden sleeper, making the piece heavier and consuming not only more raw material, but also significant man-hours and machine-hours to make the pieces. Such factors make the production process slow and increase the final price of the sleepers.
However, embodiments disclosed herein are directed to a railroad sleeper, made of a polyolefin material, such as for example polypropylene with fiberglass, manufactured from a high-productivity process, preferably extrusion, and further having a structural shape that enables one to achieve rigidity close to those of the hard-wood sleepers, as well as competitive costs. Embodiments disclosed herein are also directed to a process for manufacturing a railroad sleeper by an extrusion process that enables compaction of the composition used in making the sleeper within the calibrator of the extruding machine, as well as homogeneous cooling of the whole thickness of the sleeper that is being produced.
Advantageously, the sleeper of the present disclosure may have a reduced final price, which facilitates transportation and installation of the piece. The presently described sleepers also enable the use of standard fixing devices used on wooden sleepers, use standard machines employed for installation and maintenance of sleepers and, due to their manufacture material, enable one to recycle the product at the end of the useful life of the sleeper.
Structurally, the proposed railroad sleeper forms an inverted U shape (bored-through sector), which acts as an important differential for the function and characteristic of anchoring on the ballast. Due to its proposed shape, the ballast used on the railroad will penetrate the sleeper, thus becoming an integral body. Further, with the compaction of the ballast inside the sleeper, greater rigidity for the ballast/sleeper system will be generated, and the final inertia moment will be the sum of the inertia moment of the sleeper and the ballast layer arranged inside it.
Additionally, due to the proposed shape of the railroad sleeper, embodiments are directed to a light sleeper that is easy to install and maintain, easy to be carried by two workers, and suitable for being transported by engaging one piece to another (one sleeper to another), thus resulting in many logistic advantages, particularly as compared to the conventional sleepers which have high rigidity and weight in concrete sleepers, which damage the ballast layers, which have a short useful life for sleepers of poor-quality wood, which have electric conductivity in steel sleepers, and which have reliability problems in sleepers using recycled resins.
As mentioned above, embodiments of the present disclosure are directed to high-performance railroad structures (sleepers and/or fastening blocks), produced from a polyolefin composition including, for example, polypropylene and fiberglass, wherein the fiberglass content in the composition may range from 5 to 40% by weight of the composition, and which may be advantageously manufactured by an extrusion process. In one or more embodiments, the sleepers may comprise an outer layer of polypropylene (i.e., without other major polymer species or fiberglass, but including common additives such as antioxidants, anti-UV agents, etc.) as an envelope around a layer of a composition of polypropylene and fiberglass, applied by a co-extrusion process. In one or more embodiments, the railroad structures of the present disclosure may be formed with one or more apertures or structural gaps contained therein. The inclusion of such apertures or structural gaps may be without sacrificing the mechanical properties of the components, despite being formed with less material than designs without the apertures. The presently described railroad sleeper may exhibit a high elastic modulus and performance close to that of wood, thus enabling application on railroads for transporting load and passengers.
Turning to the included figures,
Referring now to
Referring now to
Upon installation, void 4 may be filled with ballast (not shown). The lower portions of the anchorage walls 5, 5′, that is, the portion that supports the sleeper 1 on the soil, are called support points 7, 7′, such support points 7, 7′ being opposite the points of association between the contact surface 3 and the anchorage walls 5, 5′. Within anchorage walls 5, 5′ (which may also be referred to as sidewalls), there may be one or more apertures 6 formed. Apertures 6 may reflect a structural gap or absence of material in the anchorage walls 5, 5′ and may be numbered, sized, and of a geometric shape to maintain the mechanical properties of anchorage walls 5, 5′ though forming anchorage walls 5, 5′ with a reduced quantity of a propylene-based material. As shown, there is a pair of apertures 6 in each anchorage wall 5, 5′, each having a semi-elliptic cylinder shape. However, other geometric shapes are envisioned such as circular, elliptical, rectangular, and the like. Further, the sizing of the shape may be selected so that the quantity of material forming anchorage walls 5, 5′ may be reduced without negatively impacting the mechanical properties of the sleeper 1 (or only to an extent that is acceptable for the sleeper in use in a railway network).
With reference to
On the other hand, the embodiment shown in
Referring now to
As illustrated, support protrusion 9 may protrude through the whole height of the void 4 (i.e., terminating at the same distance as anchorage walls 5, 5′), as illustrated in the embodiments shown in
As illustrated in
Referring now to
Referring now to
Referring now to
In the embodiments in which the railroad sleeper 1 comprises laterally extending support feet 8, 8′, such feet 8, 8′ may protrude away from void 4 (as shown in
In the above described embodiments (and with specific reference to
For any of the embodiments described herein for the railroad sleeper 1, the first width L1 may range from 18 to 30 cm. In embodiments using laterally extended support feet 8,8′ may have a second preferred width L2 ranging from 19 to 48, provided that obviously the second width L2 (extended support feet) is larger than the first width L1 (simple support points). In the embodiments in which the support feet 8, 8′ protrude only into the void 4, the second width L2 will assume a value equal to the first width L1.
With regard to the width of the support feet 8, 8′, referred to as third width L3 (
As to the height of the railroad sleeper 1 disclosed herein, it is referred to as a first height H which may range, for example, from 14 to 20 cm. In the embodiments that make use of the support protrusions 9, such an element protrudes from the contact surface 3 at values in the range from 0.5 to 19 cm, with the maximum being the height of the anchorage walls. The width of the anchorage protrusion 9, protruding from anchorage walls, referred to as L4, may range from 0.5 to 3.0 cm.
The transition between the anchorage walls 5, 5′ and the contact surface 3 and/or the support feet 8, 8′ may be carried out orthogonally or angled, as shown in previous figures, alternatively it may be carried out by segments in curvature or with a radiused transition, as in the embodiment shown in
In one or more embodiments, apertures 6 may have a width (measured at the widest point thereof) up to 50% of the thickness E or 40% of the thickness E, and a total length (as the sum of the lengths of all apertures) up to 80% of the height H or 70% of the height H. In particular, in one or more embodiments, apertures 6 may have a width ranging from 20 to 40% of thickness E and a total length ranging from 50 to 70% of height H.
As mentioned above, in order for the sleeper 1 to be capable of standing the stresses of its application field, it may be made of a material having a high elastic modulus (high rigidity), having also high resistance to impact, resistance to fatigue and high market availability. More specifically, in one or more embodiments, a sleeper may be formed from a singular material, however, in other embodiments, a sleeper may be a multi-layer product having an inner wall 13 (represented by dashed line) and an outer wall 14 (represented by a solid line), as shown in
In other embodiments having a multilayer structure, the inner wall 13 and the outer wall 14 may be manufactured with a composition comprising polyolefins such as polypropylene (being the same or different from the inner layer polypropylene), and the intermediate layer 15 may be manufactured from a second material. For example, polypropylene may be used in the outer surface layer and a composition comprising polypropylene and fiberglass may be used in in the intermediate layer of the sleepers.
It is noted that use of the composition of polypropylene with fiberglass as the single material or in the intermediate layer 15 is one embodiment of the present disclosure, and that in other embodiments any material or composition having a bending modulus, as determined according to the ISO 178 standard, higher than or equal to 5000 MPa might be used.
Referring now to
It is further noted in
Such fastening blocks 10 may be manufactured by different processes, such as extrusion molding, pultrusion, injection molding and machining processes that use massive blocks to obtain the final shape of the piece. Further, in one or more particular embodiments, fastening blocks, like in the sleepers described herein, may include one or more apertures 16 or structural gaps that reduce the amount of material needed to form fastening block 10 without negatively impacting the mechanical properties of fastening block 10, or with an impact on the mechanical properties that still allows the use of those blocks in the sleeper structure, as shown in
For better fixation of the blocks 10 to the sleeper 1, fixing elements, preferably configured as hexagonal screws 26 might be arranged transversely to the sleeper 1, as preferably represented in
The embodiments illustrated in
Thus, the rib structures 27 combine resistance and lightness and establish a new possibility of arranging the fastening blocks 10. Further, blocks 10 may further comprises orifices 28 designed for arrangement of appropriate screws. It should be pointed out that the arrangement and the shape of the structures 27 should not be limited to the embodiments shown in
As shown in
In one or more embodiments, the fastening blocks 10 described in
In one or more embodiments, any of the fastening blocks 10 discussed in the present disclosure and disclosed in
In one or more embodiments, as an alternative to using fastening blocks with sleepers, it is also envisioned that the sleepers 1 of the present disclosure may be fixed by means of the already existing cast-iron plates 25 and still by means of the metallic plates 22 (preferably made of steel) fixed to the existing plates (plate 25) by means of conventional fixing element 23, such as screws, press washers and nuts, which is inserted through orifices (shown in
Such fastening form is illustrated in
Referring now to
The structural forms of the railroad sleeper 1, 1′ described herein may be obtained preferably by an extrusion/co-extrusion process. Such a process is carried out by means of a conventional extruding machine, provided, for example, with a feed point, thread cannon, matrix, calibrator and velocity reducer.
Generally speaking, during the extrusion process, compaction of the composition (structure that forms the sleeper 1,1′) that happens when the melted polymer passes through the die plate and within the calibrator with a homogenous cooling and vacuum by the whole profile of the piece is permitted.
The process described herein comprises an initial step of adding the composition used (preferably polypropylene with fiberglass) to the feeder of the extruding machine and then regulate the temperatures of all melting zones of the extruder and in the die plate to meet the characteristics of the material.
In embodiments using a multi-layer sleeper, concomitantly with the above step, the first polymeric material (polypropylene with fiberglass) may be added to an extruding machine, and in a co-extrusion connected before the die plate, other resins such as pure polypropylene, polypropylene with black master batch, or polypropylene with additives may be added together with the composition of polypropylene and fiberglass.
Thus, the composition of polypropylene with fiberglass may be coated with polypropylene (without fiberglass, such as pure polypropylene or polypropylene with other additives), thus establishing a structure with the arrangement of the inner 13 and outer 14 walls in polypropylene (without fiberglass) and the intermediate layer 15 in polypropylene and fiberglass. Thus a structure similar to the extrusion process known as ABA is formed, in which the first layer (layer A) consists of a determined material (in this case, polypropylene), the intermediate layer (layer B) consists of another material (in this case a composition of polypropylene with fiberglass), and the third layer consists again of the material A (polypropylene). It is also envisioned that only an inner 13 or an outer 14 layer is coextruded with the intermediate layer 15, therefore forming and AB or a BA multilayer structure.
It should be pointed out that the manufacture of the inner 13 and outer 14 walls from the same material used in making the intermediate layer 15 (in this case, polypropylene without fiberglass) is just an example embodiment. Thus, the walls 13 and 14 might be made from a material other than that used in the layer 15, as long as obviously it provides the necessary adherence to the piece. It is also envisioned that only a composition comprising polypropylene and fiberglass may be added to the extruder for embodiments using a single material structure.
Following the description of the above-mentioned steps, after melting the structure within the cannon and the screw of the extruding machine, the molten structure is extruded within the matrix, said matrix having the main function of shaping the structure to a desired shape.
Subsequently, the structure, upon coming out of the matrix, passes through calibrator provided with a water-based cooling system. Said cooling system aims at keeping the molten structure in its final shape, besides aiding in cooling the piece.
Upon coming out of the calibrator, the piece gets into a system for controlling the velocity of the extruding machine, thus limiting the flowrate of the process and enabling compaction of the structure within the calibrator, thus preventing bubbles and loss of material. Finally, the molten structure is cut into a desired size.
Depending on the desired shape for the railroad sleeper 1, 1′, the calibrator of the extruder may be configured as a calibrator with or without vacuum. On calibrators without vacuum, an example length may range from 0.3 to 0.5 meters, while on a calibrator with vacuum, a length may range between 1 and 4 meters and vacuum of the cooling chamber from 0 to 0.4 bar.
It is pointed out that a calibrator without vacuum may be particularly desirable for shaping the railroad sleeper 1 containing an open void (shown in
Additionally, the following preferred parameters for the extruding machine may be used:
Although the process of shaping the railroad sleeper 1, 1′ has been referred to as an extrusion process, one should understand that such a characteristic is just a preferred embodiment, so that other processes might be used for structural shaping of the proposes sleeper 1, such as an intrusion, injection molding or pultrusion process.
In one or more embodiments, the composition comprising polypropylene and fiberglass contains fiberglass in the range from 5 wt % to 40 wt % of the composition, and more particularly from 33 wt % to 37 wt % of the composition.
A sleeper (S1) of the type shown in
The studies carried out for the design of S2 revealed low levels of stress in the central region of the sleeper section, as shown in
As the stiffness of S1 is less than S2, the effect of this stiffness in the railroad track gauge was tested. Applying a characteristic load (vertical and horizontal) in a regular railroad, as shown in
Advantageously, the railroad sleepers described in the present disclosure may have one or more of the following:
Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. § 112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function.
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| Entry |
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| Number | Date | Country | |
|---|---|---|---|
| 20200370247 A1 | Nov 2020 | US |
| Number | Date | Country | |
|---|---|---|---|
| 62852873 | May 2019 | US |
