RAIL POINT SWITCHING SYSTEM

FIELD OF THE INVENTION

The invention relates to the filed of railway track engineering. In particular, the invention relates to an improved design for railway switching points or turn outs. BACKGROUND OF THE INVENTION

The route of locomotives on modern multi-track railway transport systems is controlled mainly by track switching devices which are capable of re-routing the locomotive onto a different line. These devices typically involve the reversible sliding of a set of switching, or 'swing', rails from a first position in alignment with a first track to a second position in alignment with a second track.

However, problems relating to design and maintenance with where such a sliding mechanism is expected to operate reliably over thousands of switching events, in all weather conditions, particularly considering that the sliding mechanism is expected to bear the weight of locomotives as they pass over the swing rails.

The primary sliding bearing members tend to be flat, smooth steel wear plates. However, given the very substantial weight which is borne by these bearings, there is a very large frictional force which must be overcome in order for the swing tracks to slide into the desired position.

The contact surface between the tracks and the wear plates, or between a pair of wear plates, is typically lubricated using a graphite powder material or a grease. The disadvantage this poses is that it has a tendency to be washed or blown away over time due to weather conditions. This also presents a health risk as dangerous fumes are formed when graphite powder comes in contact with some solvents. In addition, there are relatively high labour costs incurred in continuously monitoring and re-lubricating these surfaces.

In spite of the above measures, it is unfortunately common for these wear surfaces to seize due to loss or lack of lubricating material. This in turn may lead to overloading of the linear actuator (that is used to move the track), resulting in mechanical failure and attendant costs in labour and parts.

An alternative design for wear surfaces of this type is to fit a plurality of nylon rollers between the moving parts of the switching system. However, these also have been found to require continual maintenance, due to rapid wearing of the nylon parts, leading to failure. Accordingly, it is an object of the invention to provide a bearing for moveable tracks in a railway point switching system which overcomes at least some of the disadvantages of the prior art. SUMMARY OF THE INVENTION

A bearing for a railway point switching system, said system including at least: two connected rails supported by sleepers which are moved in unison from a first position to a second position; and a slidable support bearing for said rails which bears said rails as they are moved horizontally from said first position to said second position; said bearing including upper and lower engagement plates or the like which are capable of sliding horizontally relative to one another and which tend to be forced toward one another by the weight of said rails on said sleepers, and wherein the upper engagement plate is operatively connected to said rails; wherein said engagement plates incorporate, are attached to or are formed from high strength magnets, such as permanent rare earth magnets, said magnets being arranged such that, in operation, like poles are located directly opposite one another thereby to cause the engagement plates to tend to repel one another.

The invention thereby provides that the action of the repelling magnetic fields of the like poles (North-North or South-South) of the magnets assist in providing an upward 'lifting' force to the upper engagement plate. This partially counteracts the downward force of gravity acting to pull the upper engagement plate down toward the lower engagement plate.

As the frictional force tending to prevent the sliding of the upper engagement plate across the lower engagement plate is proportional to the sum of forces acting to push the plates together, any reduction in the net downward force acting on the upper engagement ^, plate will proportionally reduce the frictional force resisting the sliding movement of the plates.

Any magnet of suitable magnetic flux strength, and mechanical strength, may be used in this application, including electromagnets. Preferred are rare earth magnets for their magnetic and physical strength and low required maintenance. Rare earth magnets are called so because they are manufactured using materials located in the rare earth section of the Periodic Table of Elements. They include Neodymium-lron-Boron (Nd ₂ Fe- _I4 B) magnets and Samarium-Cobalt (SmCo ₅ ), among others.

Preferably, the rare earth magnets are inserted into the engagement plates so as to form a plurality of matched pairs of opposing magnets. If so, it is particularly advantageous that the plurality of opposing magnets are arranged so that, while the upper plate is travelling between first and second positions associated with the first and second positions of the rails, there is provided a substantially continual juxtaposition of individual opposing magnets. This arrangement provides the most efficient use of the rare earth magnets when employed in the manner described above.

The bearing may be positioned on a mounting bracket suspended between two adjacent sleepers, upon which the lower engagement plate is mounted. This arrangement allows retrofitting of the bearing to an existing rail switch point without necessarily disturbing the sleepers.

Alternatively, the lower engagement plate is mounted directly on top of, or recessed into the top surface of, a sleeper. This has the advantage that the bearing structure has greater overall strength and the need to provide a separate mounting bracket sized to fit between two adjacent sleepers is obviated. Advantageously, for the above described mounting, it is preferred that the magnets in the lower engagement plate is mounted in a groove cut in the lower engagement plate, and wherein the magnet in the upper engagement plate is arranged to slide in said groove when travelling between said first and second positions. This provides greater stability to the overall arrangement. Alternatives to this arrangement occur where the lower engagement plate is mounted within a sleeper, or where the lower engagement plate is formed integrally with a sleeper. i

According to another aspect of the invention, there is provided the use of a bearing as defined in any preceding claim in a railway point switching system.

According to another aspect of the invention, there is provided a railway point switching system incorporating a bearing according to any described above. Now will be described, by way of specific, non-limiting examples, preferred embodiments of the invention with reference to the figures. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic plan view of a part of a rail point switching assembly, incorporating a bearing according to one embodiment of the invention. Figure 2 is a schematic, side view of the assembly of figure 1.

Figure 3 is a schematic plan view of a support plate for a base magnet bracket as shown in the assembly of figure 1.

Figure 4 is a schematic elevation and end elevation of a mounting bracket suitable for attaching a magnetized upper engagement plate to a swing rail, as per the assembly of figure 1.

Figure 5 is a schematic elevation and end elevation of a mounting bracket suitable for attaching a magnetized lower engagement plate to a base magnet bracket, as per the assembly of figure 1.

Figure 6 is a schematic plan view of a part of a rail point switching assembly, incorporating a bearing according to an alternative embodiment of the invention.

Figure 7 is a schematic side view of ithe assembly of figure 6.

Figure 8 is a schematic elevation of the engagement plate assembly of included in the overall assembly of figure 6. Figure 9 is a schematic plan view of the engagement plate assembly of figure 8. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The bearing for a railway point switching system, in accordance with the present invention, utilises magnets arranged in operation to produce a repulsive force between the swing rails and their supports, which reduces the overall contact force between the swing track and said support, particularly at the point of sliding contact, thereby to reduce the frictional force required to cause the sliding movement for the swing tracks from a first position to a second position.

This results in a reduction in maintenance and cost of downtime and materials required to maintain prior art systems in working order. The invention may also allow smaller and cheaper linear transducers to be specified for the operation of actuating movement of the switching track. This is accomplished in the invention, broadly, by arranging said magnets such that the surfaces of like poles of the magnets (North-North or South-South) are always positioned adjacent one another: there natural tendency to repel is used to tend to force the wear surfaces away from one another, partly counteracting the gravitational forces which tend to push the sliding or wearing surfaces together.

Rare earth magnets are preferred for this purpose, but other types of magnets may be employed.

Rare earth magnets are so called because they are manufactured using materials located in the rare earth section of the Periodic Table of Elements. They include Neodymium-lron-Boron (Nd ₂ Fe- _I4 B) magnets and Samarium-Cobalt (SmCo ₅ ), among others.

A single pair, or a number of sets, of opposing magnets may be provided at each switching point. The magnet that is attached to the switching or 'swing' track may vary in size but should be of sufficient length such that the (upper) magnet attached to the swing track can traverse its intended swing distance and still remain in direct juxtaposition with the (lower) base magnet, thereby retaining the repulsive force for the entire travel distance. In order to achieve this, the base magnet should preferably be relatively elongate: optionally consisting of more than one individual magnet, while the swing track magnet may be smaller in surface area.

There are a number of alternative ways in which the magnets may be mounted to achieve the aim of the invention.

One alternative is that the lower magnets will be located between two adjacent track sleepers, supported by a bracket that is attached to the fixed track ad effectively suspended between said sleepers. The upper swing track magnets are mounted in a bracket that is attached to said track. Both brackets may be bolt mounted to the supporting structures for ease of maintenance and possible component replacement. This type of assembly may most readily be retrofitted to

an existing switch point, since disturbance of the mounting of the rail on the sleeper is minimised.

A second alternative design would be to have the lower magnet embedded within the wear plate metal on the sleeper mount. The wear plate sheet metal that sits on the sleeper would preferably be machined such that the upper and lower magnets could be located in a machined groove within the wear plate.

A third alternative assembly design would be, where the sleepers are made of concrete, wood or other suitable material, to have the lower magnet recessed into the sleeper itself. It will be understood by those skilled in the art that many other mounting assemblies for the magnet are possible and that the above are merely particularly useful examples of same.

The exposed surface area dimensions of both the swing track magnet and the lower or base magnet can, be modified accommodate different installations. To reduce the likelihood of the magnets being damaged by vibration or impacting, a sacrificial wear element can optionally be placed between the two magnets. Ideally, this element would work to maintain an air gap of approximately one eighth of an inch between the magnets. It may also be possible to recess the magnets slightly into the wear plates. The material used for directly mounting the magnets in the assembly can be selected from wood, aluminium, mild steel or stainless steel, or other suitable material.

The magnets may be additionally secured to the bracket structure by the use of an adhesive compound. This will assist to eliminate the likelihood of the magnets dislodging themselves from their seating.

As one of the effects of the invention is to reduce the force required to overcome friction between the sliding parts during track switching, it may be possible to downsize the linear actuators installed to effect this movement. This would assist in reducing the overall cost of the installation. An important role for the linear actuator in an assembly incorporating the invention is in limiting the travel distance of the swing track. For example, it is typical for the travel of the swing track to be approximately perpendicular at 90° to the length of the track and for a distance of approximately 150mm. This traversing

distance is important as, if the magnet on the switching track goes past the edge of the base magnet, there will be a tendency for the magnets to attract rather than produce a repulsion force.

The invention may be better understood with reference to the figures. Turning first to figures 1 and 2, there is shown part of a rail track switching assembly which incorporates a bearing according to the invention.

The assembly is shown mounted on two adjacent sleepers (5, 10). A fixed rail 15 is mounted directly on to each of the sleepers (5, 10) by mountings (20, 25) and runs transversely across them. The switching or 'swing' rail 30, which has a distinctive tapered profile, is mounted alongside the fixed rail 15 and shown supported by the bearing according to the invention 35.

The bearing is supported underneath by a relatively flat U-profile bracket 40 which is suspended between the sleepers (5, 10). This bracket is shown in greater detail and in an unassembled state in figure 3.

Bolted to the fixed rail 15 and effectively suspended from same is a mounting bracket 44 for the lower engagement plate 45. This bracket 44 is shown in greater detail and in an unassembled state in figure 5. The engagement plate 45 incorporates a wear surface 50 which features a flush mounted rare earth magnet 55 which is oriented to match the path of travel of the swing rail 30. It is also oriented such that its 'North' pole is uppermost/outermost. The magnet 55 is recessed in to the wear surface 50.

Resting directly on the lower engagement plate 45 is a mounting bracket 60 for the upper engagement plate 65. This bracket is shown in greater detail and in an unassembled state in figure 4. The engagement plate 65 features a flush mounted rare earth magnet 70, which is noticeably smaller than the magnet 55 of the lower engagement plate, and a wear surface 75. The magnet 70 is oriented such that its 'North' pole is lowermost/outermost

In the assembly, the upper and lower engagement plates (45, 65) are arranged so that their wear surfaces are in direct contact, an in particular so that the rare earth magnets (55, 70) are in direct abutment.

The mounting bracket 60 for the upper engagement plate 65 is in turn bolted to, and thereby suspended from, the swing rail 30.

The magnets (55, 70) are secured in their respective engagement plates (45, 65) by a suitable adhesive compound.

It will be noted that, when the swing rail 30 traverses a path moving it either toward or away from the fixed rail 15 during a switching operation, the magnets (55, 70) remain in direct abutment throughout, thereby allowing the like North magnetic fields to continuously repel one another. This tends to force the engagement plates (45, 65) apart and thereby counteract the gravitational force pulling the swing rail 30 toward the lower engagement plate 45.

This in turn reduces the frictional force required to move the swing rail 30. Turning to figures 6 and 7, there is. shown part of a rail track switching assembly which incorporates a bearing according to the invention, but where an alternative mounting assembly has been employed.

The assembly is shown mounted on two adjacent sleepers (105, 110). A fixed rail 115 is mounted directly on to each of the sleepers (105, 110) by mountings (120, 125) and runs transversely across them.

The switching or 'swing' rail 130, which has a distinctive tapered profile, is mounted alongside the fixed rail 115 and shown supported by two bearings (135, 140) according to the invention. Both of said bearings are mounted directly on to the respective sleepers (105, 110) and are recessed into same. For each of the bearings (135, 140), the lower engagement plate 145 is recessed directly into the sleepers. The lower engagement plate is shown in greater detail in figures 8 and 9. A slot 150 is provided in the engagement plate, said slot 150 being oriented to match the ¹ travel path of the fixed rail 130 during switching. A the bottom of the slot is a flush mounted a rare earth magnet 155 which is oriented to match the path of travel of the swing rail 130. It is also oriented such that its 'North' pole is uppermost.

As shown more clearly in figure 9, a moveable slide 160 is also positioned in the slot 150. This slide 160 effectively provides the upper engagement plate, and features a flush-mounted rare earth magnet 170, which is the same width as, but noticeably shorter than, the magnet 155 of the lower engagement plate. The magnet 170 is oriented such that its 'North' pole is lowermost.

The swing rail 130 is mounted directly on to the slide 160, which supports it as it traverses a path moving it either toward or away from the fixed rail 115

during a switching operation. The magnets (155, 170) remain in direct abutment throughout, thereby allowing the like North magnetic fields to continuously repel one another. This tends to force the engagement plates (145, 160) apart and thereby counteract the gravitational force pulling the swing rail 130 toward the lower engagement plate 145.

This in turn reduces the frictional force required to move the swing rail 130. As can be seen in figure 8, a physical barrier 175 is provided that restricts the magnets (155, 170) from rotating, sliding or flipping out of position.

A further variation on the construction shown in figure 6 may be obtained where the sleepers are constructed from suitable material, such as concrete or wood, and where the lower magnet is mounted within a moulded recess in the sleeper itself, rather than in a separately inserted wear plate. The moulded recess in the sleeper would be of a similar profile to the recess machined in the lower engagement plate as shown in figures 7, 8 and 9. In this variation, the engagement plates would be designed such that one side of the wear plate will be capable of being bolted to the fixed track, while the other side would be open along the centreline to allow the upper swing track magnet to hover over the base magnet. Each corner of the wear plate would preferably be bolted to the sleeper. It will be well understood by the skilled addressee that the above description merely outlines some of the many ways in which the invention can be put into useful effect. Many variations in the mounting of the rails and magnets are conceivable which may vary in detail from those described herein, but which nevertheless remain within the spirit and scope of the invention.