MXPA98000659A - Mixing mixes locomot accession improvement materials - Google Patents

Abstract

The adhesion between a locomotive drive wheel and a support rail can be substantially increased by the application of a powder mixture containing a hard particle constituent preferably including alumina, a smooth particle constituent preferably including titania and an iron oxide constituent. The mixture may be in the form of a dry powder, a paste with water or an alcohol vehicle, or a metal compound including the pol

Description

MIXTURES OF LOCOMOTIVE ADHESION IMPROVING MATERIAL TECHNICAL FIELD This invention relates to mixtures of adhesion-enhancing (friction) material for use between the drive wheels of a locomotive and a support rail. More specifically, this invention relates to particulate mixtures which may be used in the form of a dry paste or powder or in a metal matrix for the above-mentioned purpose.

BACKGROUND OF THE INVENTION It has been the long-standing experience of railway engineers that there are situations in which it is desirable or necessary to increase the friction between the drive wheels of the locomotive and the support rails. Many situations can arise in the cases of train start or in situations of inclined braking or the like in which an increase in adhesion between the driving wheels of the locomotive and the rails will allow the train to better handle the situation of operation.

The pulling force of a locomotive is the pulling force it is capable of generating in order to move a train of rail cars. The traction adhesion of the locomotive is the tensile stress divided by the weight of the locomotive expressed as a percentage. The level of adhesion delivered by a locomotive is ultimately limited by the capacity of the system apparatus. However, since adhesion depends on the frictional conditions between the steel wheel of the locomotive and the steel rail, contaminants, lubricants and other operating conditions can lower the available adhesion. A higher adhesion value is of great technical and commercial significance since this means that the locomotive can pull more freight cars or passenger cars having the same rolling resistance per vehicle.

The conventional strategy that has been followed for many decades is to distribute sand particles in front of some of the wheels of the locomotives which, together with the wheel slip, increase the levels of friction by cleaning the surfaces or by diluting the pollutants.

Typical contaminants include grease, oil, water, leaves or the like that are on the rails or fall off the train. These reduce the traction by reducing the adhesion between the drive wheels and the rails. The sand was used in the form of a powder of a suitable particle size range.

The sand is stored in sandboxes of the locomotives and, when required, they are allowed to flow by gravity supply and then they are blown through a hose under air pressure, out of the flat nozzles and up to the wheel contact -rail. The description of sand typically in use requires a minimum silica content of 90 percent so that the rest of the material (which for commercially available sand, is usually clay) is not expected to be sufficient to significantly reduce the friction capacity Of the sand.

The main advantages of using sand are its low cost and the fact that it provides reasonable increases in adhesion under polluted conditions. The main disadvantages of sand are that large quantities are required, which means an important added weight to the locomotives, the damage caused to the vehicles and the rails by the abrasive characteristic of the sand, and the big capital and something expensive of the equipment facilities that are necessary in the railway yards to store and distribute the sand. In addition, sand simply does not provide optimal adhesion levels that are required in the railroad industry.

Apart from sand, other oxides such as alpha alumina and mullite, a mineral consisting of 3A1203 • 2Si02, have also been described in the literature even though they have not been used in actual practice. See "Developing a New Method for Adhesion Improvement by Replacing Traditional Sand", by K. Ohno and others, Railway Technical Research Institute, Tokyo, Japan, presented in 1994 at the International Heavy Haul International Conference, Omaha Nebraska, 5-10 June 1994. Also, see the patent of the US No. 4,431,227 issued to Howell describing a rail wheel having cermet surface pads which are described as being capable of increasing the friction between the wheel and a rail. Among the cermets which are described are the aluminum and silicon oxides, the silicon and titanium carbides, and the nitrogen and carbon borides. Industrial diamonds are also described as being useful. Similarly, U.S. Patent No. 4,310,191 issued to Halldin describes railway wheels having a peripheral wear layer made of steel or the like which has carbides, oxides, borides or nitrides embedded in the surface to increase the frictional characteristics of the wheel. In the case of these latter two patents, the friction enhancement material is embedded in the wheel and wears out and may not be available or suitable for specific situations which require temporary high adhesion or traction for acceleration or braking.

It will be apparent that the prior art does not include mixtures of dry powder, paste mixtures and rubbing on solid metal matrix compounds, formulated to maximize adhesion in traction and braking.

SYNTHESIS OF THE INVENTION This invention uses a particulate mixture of two or three different types of constituents. The composition, hardness and particle size of the respective constituent particles is such that they co-operate to promote adhesion between a locomotive wheel and its support surface, thereby allowing a given locomotive to exert a greater pull force or a braking force on the wagons of the train.

In a preferred embodiment of the invention, a suitably prepared and ground member of the mineral bauxite group is employed. In its useful form, the calcined and crushed bauxite material, typically dried, includes alumina (Al203) as the main constituent with small amounts of titania (Ti203), iron oxide (Fe203), and silica particles (Si02). Alumina typically constitutes 85 percent by weight or more of the mixture. The particle sizes of the tensile increase material are in the range of 30 to 100 standard mesh sizes or about 150 to 600 microns.

In this embodiment of the invention, compositions containing aluminum oxide predominantly with relatively small amounts of titanium dioxide and iron oxides with some permissible silica are available from the bauxite mineral precursors. Of course, bauxite is a mineral that is located in many parts of the world and is known to be rich in an aluminum oxide content with small amounts of other metal oxides such as titanium oxide, iron oxides and silicon oxide among others. Some of these materials are not particularly preferred for the production of aluminum metal and are cleaned, calcined or otherwise processed to provide a source of aluminum oxide containing material that can be variously known as brown alumina or calcined bauxite. It has been found that in the practice of the present invention, such materials especially those containing more than about 80 percent alumina with a few percent each of titanium oxide and iron oxide, are suitable for the purposes of Improvement of adhesion of the locomotive to the rail. In the use of these materials, there are combined oxide particles, not individual oxide particles, suitably such particles in the range of 30 to 100 mesh can be used in the practice of this invention. Alternatively, the particles of the same composition having different mesh size ranges such as, for example, a group of particles of mesh size 30 to 100 and another group that could be essentially thinner in the mesh size can be used to form the Adherent traction layers between the locomotive wheel and the underlying rails.

In a somewhat broader embodiment of the invention, the mixture may be formed of a suitable synthetic blend of the above-identified oxides having specific particle sizes. The mixture, in percentage by weight of alumina from 40 percent to 96 percent, of titania and / or iron oxide of 4 percent to 60 percent, and optionally silica from 0 percent to 20 percent have been effective where the mesh size of the alumina is suitably in the range of 30 to 100 meshes, from 150 to 600 μm, to the size mesh size of titania and / or iron oxide particles is in the range of 200 to 325 meshes, from 45 to 75 μm and the mesh size of the silica, (if present) is 100 to 200 meshes 75 to 150 μm.

Particle mixtures containing two or three types of constituent mentioned above provide a significant improvement in the coefficient of friction, in adhesion or in traction between a driven locomotive wheel and the underlying rail due to the respective hardness values in its capacity to intermix so as to provide an adherent traction layer between the wheel and the rail.

The alumina constituent has a high hardness value, for example, a value of 9 on the Mohs scale. The titania has a hardness value of only 6 on the Mohs scale and serves to flatten and form complementary particle forms between the harder alumina particles. The iron oxide particles, either hematite (Fe203) or magnetite (Fe304) have hardness values of about 6 to 6.5 on the Mohs scale and are chemically compatible with the oxides that can form on the surface of the wheels and rails of steel. Silica particles with a Mohs hardness of 7 are seen as optional filler particles not required in the blends of the present invention.

Thus in a more general statement of the invention, provided that the mixtures include particles of different hardness properties and particle sizes as specified herein.

With respect to the hard particle constituent, chromium oxide (Cr203) with a Mohs of hardness of 8.5; diamond with a Mohs hardness of 10; Silicon carbide with a Mohs hardness of 9 and / or titanium carbide with a Mohs hardness of 9 are suitable. Such particles can be used in place of Al203. The amount of hard particles is from 40 percent to 97 percent by weight of the mixture. The particle size is 30 to 100 meshes.

Solutions have also been made for the titanium paste and iron oxide forming particles.

For example, one or more of magnesium (MgO) with a Mohs hardness of 4, calcite (calcium carbonate) with a Mohs hardness of 3, zinc oxide (ZnO) with a Mohs hardness of 4.5, manganese oxide (MnO) ) with a Mohs hardness of 5.5, gypsum (CaS04 • 2H2) with a Mohs hardness of 2 or hydraulic cement (A1203 • Si02) with a Mohs hardness of 4 can be used instead of, or in combination with titanium or iron oxide. As suggested above, hematite or magnetite can be used together or interchangeably. Other paste-forming oxides and minerals are dissolved below. The mild and suitable paste forming additives constitute from 4 percent to 60 percent by weight of the present adhesion mixtures and have particle sizes in the range of 200 to 325 mesh.

As stated above, the mixture of alumina, titania and iron oxide with or without substitutions (or other hard particles and mixtures of paste-forming particles) can be used as a dry powder and applied to the interface between the driving wheel and the rail when improved adhesion is required. In another form of the invention, however, the powder mixture can be used in the form of a paste using for example, water and water mixed with isopropyl alcohol as the carrier for the paste. Neither soil nor isopropyl alcohol are harmful to the environment. Where necessary, the isopropyl alcohol provides a shorter evaporation time to the vehicle mixture and significantly reduces its freezing point.

In yet another embodiment of the invention, the powder mixture is uniformly suitably embedded in a metal matrix. For example, it can be sintered with forged or cast, soft iron or aluminum or otherwise appropriately imbedded in an iron, copper or aluminum matrix. In the metal matrix composite form of the invention, the material is suitably processed in the form of a shoe which sometimes has to be displaced against the rail in front of the drive wheel and erode to form and drive the particles friction between the wheel and a rail. Alternatively, the shoe can be pressed against the drive wheel above the wheel-rail interface for a similar purpose.

Therefore, even when the invention has been briefly summarized, other objects and advantages will be appreciated from a more detailed description that follows.

DESCRIPTION OF THE PREFERRED MODALITIES In accordance with this invention, the families of adhesion promoting materials for use between a locomotive wheel and an underlying support surface are described. A preferred family of materials uses particles that contain aluminum oxide, titanium oxide and iron oxide, either as individual oxide particles or specified particle sizes or as oxide mixtures within particles. Such oxide compositions have been tested both on commercial locomotive apparatuses in real-world situations as well as in laboratory tests. In both test modes, these particles have been shown to provide improved traction and improved braking adhesion (on sand, alumina or mullite) between the locomotive wheels and the underlying rails in dry conditions, in wet conditions and in rail conditions. with oil and other contaminants.

For testing purposes, the locomotive's tractive effort is the pull force measured on a pull bar that links the locomotive to a test vehicle. This force divided by the measured weight of the locomotive, expressed as a percentage, is recorded as the measured adhesion of the locomotive. Additionally, on a single axis of the locomotive, the measurements of the electrical parameters on the motor that drives the wheels are used to calculate the frictional force on an axis (connected to a pair of wheels). The proportion of the vertical load that comes on a particular axis was determined experimentally by means of an analysis of the weight change measurements, and the adhesion for that axis was calculated by dividing the frictional force by the vertical load, expressed as a percentage.

Many adhesion tests were run on both an operating locomotive and laboratory friction test devices. In general, the materials declared herein as suitable for use in the present invention were found to consistently exhibit superior adhesion than the others similar for sand alone, for pure alumina alone or for the data reported by K. Ohno and others in 1994 with respect to mullite, a mineral consisting of A1203 • 2Si02. The Ohno data reported adhesion ranges of 0.15 to 0.25 for wet conditions, but the adhesion levels for alumina / titania / iron oxide and optionally the silica formulas tested were in the range of 0.24 to 0.38 at slow speeds under wet conditions and even higher under dry conditions. In addition, the present formulas demonstrated good adhesion under oily conditions that were not reported in article 1. Therefore, the current conditions under which the locomotives operate, this is where the rails can be dry, oiled, dirty or wet, Present compositions consistently provide durable adhesion layers that were better than sand or silicas alone or alumina or mullite and offer better traction to start and stop trains. The following Table 1 summarizes the specific oxides and minerals to be used in the practice of the present invention.

T A B L A 1 Mixtures / Alternative Oxides Conversion Table - Micrometer Mesh Mixtures of Bauxite Origin Material Melting Adhesion The term bauxite is generally applied to rocks that contain significant amounts of a precursor material of aluminum hydroxide. It is a primary mineral for the production of aluminum. Bauxite exists in many varieties of compositions and is found in virtually every continent of the earth. Bauxites contain varying amounts of aluminum oxide, silica and iron oxides, as well as small amounts of other materials such as titanium oxide. In the processing of bauxite such as the Bayer process to form aluminum hydroxide, several commercial products are available other than those that are used in the production of aluminum or aluminum oxide.

Among such materials which are useful as friction promoters for the locomotives are the various materials known as calcined bauxite or brown alumina and which nominally contain 85 percent by weight or more of aluminum oxide and a few hundred by weight each of titanium oxide, iron oxide and silica. Such materials are relatively inexpensive and can be crushed to a particle size of from about 30 to 100 mesh (150 to 600 micrometers) and according to this invention is found to provide excellent adhesion as dry particles when applied under the wheels of a locomotive and the support rail. Also, such bauxite-derived materials which predominantly contain aluminum oxide with small amounts of iron oxide and titanium oxide can be used in the form of a water or a water isopropanol paste or in the form of a composite in which are embedded in a soft metal matrix. In each of these embodiments, the bauxite-derived material is applied to the surface of the rail and adheres tenaciously to this providing an improved start or braking traction with the wheels of a locomotive or train carriage.

In a particularly preferred embodiment, the additional bauxite-derived material can be pulverized to a finer grain size such as 250 to 325 meshes and mixed with the bauxite-derived material of larger grains to provide a more adherent layer on the rail .

Mixtures of Synthetic Particles for M? R > t-Mi? H? mto Friction As indicated in the text given above and in Table 1, mixtures of suitable oxides and minerals can also be prepared for use as adhesion promoters.

A major constituent of the mixture is a hard oxide or carbide particles having a hardness value Mohs in the range of 8.5 to 10 and having a particle size of 150 to 600 micrometers. It is preferred but not necessary that the alumina particles, whether the alpha alumina or the alumina particle, are the main ingredient of this constituent. In a preferred embodiment, the high hardness abrasive material may consist entirely of alumina or this may contain mixtures of alumina and chromium oxide, silicon carbide, diamond or the like. It is preferred that the high hardness abrasive material constitutes 40 percent to 96 percent by weight of the adhesive mixture. It is further preferred that the abrasive particles are the largest particles in the mixture, having a size range of 30 to 100 mesh or 150 to 600 micrometer.

Critical to the function of the adhesion mixture is the presence of a paste-forming constituent. The paste-forming constituent constitutes 4 percent to 60 percent by weight of the general adhesive composition. These particles are softer than abrasive particles of high hardness. These paste-forming agents, whether metal oxides or other minerals of comparable hardness, suitably have a hardness in the range of 3.5 to about 6.5 on the Mohs hardness scale. As described in Table 1, a number of other oxides and minerals will serve the purpose of the paste forming agent. However, it is preferred that titania and iron oxides are present and constitute a major part of this ingredient. The paste forming agents are of smaller particle size so that they tend to fit within the larger abrasive particles. The paste-forming agents suitably range in size from 200 to 325 meshes, from 45 to 75 microns in particle diameter. " In some formulas, it has been found that intermediate hardness fillers increase the adhesive properties of the mixture. Examples of suitable intermediate hardness fillers are silica and zirconia. These have hardness values of the order of 6.5 to 8 on the Mohs hardness scale. Its particle size may be slightly larger than that of the paste-forming agents but smaller than that of the rougher abrasive particles. A suitable range for the particle sizes of the intermediate fillers is 100 to 200 mesh or around 75 to 150 micrometer. When these materials are used, they can be used in amounts of up to about 20 percent by weight of the general formula.

Following are examples of three synthetic mixtures of alumina, titania, iron oxide and silica that have demonstrated an excellent coefficient of friction values under a variety of wet and dry test conditions.

The aforementioned bauxite-derived materials or synthetic blends of varying hardness and particle size can be used in the form of dry powder and dispersed on the rails in front of the drive wheels of a locomotive using essentially the same or similar equipment as It is used in the distribution of sand particles on the rails. However, the blends of this invention are found to more easily form an adherent layer that sticks to the rails and provides additional braking or pulling properties.

Although mixtures can be used in dry form, it is also useful to apply them in the form of a paste. In this case, the dry materials are simply mixed with sufficient water or solutions of water-isopropanol or similar mixtures so that these can be extruded in paste form on the rail in front of the drive wheel. In these wet forms, they easily form a tensile film which remains adherent even after drying. In this way, the materials that provide adhesion remain on the rail and provide an adhesion improvement for several driving wheels following the locomotives.

It is also appropriate to distribute the present bauxite-derived materials and the synthetic materials in a metal matrix of a soft metal. This can be done by pouring the melted metal into a form containing the particulate mixture so that the infiltrates of molten metal around the particles and with the solidification form a shoe suitable for rubbing against a locomotive wheel to distribute the adhesion promotion particles on the rail. In another embodiment, the powder can be mixed with forged iron or molten soft iron or aluminum particles to form a sintered shoe.

Although the invention has been described in terms of a few specific embodiments, it will be appreciated that other forms may readily be adapted for those skilled in the art. Therefore, the scope of the invention should be limited only by the following claims.

Claims (8)

R E I V I ND I C A C I O N S

1. A method for increasing the adhesion between a locomotive wheel and an underlying rail comprising applying to the track between the wheel and rail a powder mixture comprising at least one of (a) particles containing aluminum oxide, iron and titanium oxide produced from bauxite ore or (b) a particulate mixture comprising from 40 percent to 96 percent by weight of the particles having a Mohs hardness of 8.5 or greater and a particle size of 150 to 600 microns and 4 percent to 60 percent by weight of particles having a Mohs hardness in the range of 3.5 to 6 and having a particle size in the range of about 45 to 75 microns.

2. A method for increasing the adhesion between a locomotive wheel and an underlying rail comprising applying to the tread between the wheel and the rail a powder mixture comprising at least one of (a) particles containing aluminum oxide, iron and titanium oxide produced from the bauxite ore or (b) a particulate mixture comprising 40 percent to 96 percent by weight of particles having a Mohs hardness of 8.5 or higher, a particle size of 150 to 600 microns and including alumina particles as a main constituent and 4 percent to 60 percent by weight of particles having a Mohs hardness in the range of 3.5 to 6, having a particle size in the range of about 45 to 75 micrometers and containing oxide of titanium and / or iron oxide.

3. A method for increasing the adhesion between a locomotive wheel and an underlying rail as claimed in clauses 1 or 2 characterized in that in said method the applied powder mixture consists essentially of particles derived from bauxite having a grain size in the range of about 45 to 600 micrometers and comprises at least 80 percent by weight of aluminum oxide, as well as titania and iron oxide.

4. A method for increasing the adhesion between a locomotive wheel and an underlying rail as claimed in clause 2, characterized in that the powder mixture applied to said track is a mixture comprising 40 to 96 percent by weight of particles of alumina, 4 percent to 60 percent by weight of titania and / or iron oxide particles.

5. A method as claimed in any of clauses 3 or 4 characterized in that the applied powder mixture also contains silica and / or zirconia.

A method as claimed in any of clauses 1 to 5, characterized in that the powder mixture is applied to said interface in the form of a paste containing liquid.

7. A method as claimed in any one of Clauses 1 to 5, characterized in that the mixture of traction increase powder is applied to the interface by abrading a metal matrix composed of the powder mixture against the wheel or the rail for abrading particles of said powder mixture of said compound and driving the mixture between the wheel and said rail.

8. A powder mix adapted for application between a locomotive wheel and an underlying support surface for the purpose of increasing traction or braking adhesion between the wheel and the support surface, said mixture comprising 40 percent to 96 percent by weight of particles having a Mohs hardness of 8.5 or higher, a particle size in the range of 150 to 600 microns, and 4 percent to 60 percent by weight of particles having a Mohs hardness in the range of 3.5 to 6.5, and a particle size in the range of about 45 to 75 micrometers. SUMMARY The adhesion between a locomotive drive wheel and a support rail can be substantially increased by the application of a powder mixture containing a hard particle constituent preferably including alumina, a smooth particle constituent preferably including titania and an oxide constituent. iron. The mixture may be in the form of a dry powder, a paste with water or an alcohol vehicle, or a metal compound including the powder.