GB2225300A - Overhead electrical current collector arrangement - Google Patents

Description

6 n r ' - 3 610 CASE 4935 overhead Electrical Current Collector

Arrangement This invention relates to an overhead electrical current collector arrangement comprising an overhead guide rail, a bus-bar and pantograph means.

overhead electrical current collector arrangements of various types are well-known and have been used for many years for electrical traction purposes. They are particularly used for supplying power to electrically driven tractors, trolley buses and trains. The general advantage of using a pantograph system to collect current from an overhead conductor rather than to use a third rail ground located system is primarily one of safety. Generally, the overhead wire is above the normal position where personnel are by a significant distance, which means that the live conductors are unable to be touched inadvertently by the personnel. This is not so with a third rail system, where there is relatively easy access to the conductor. If the transport system using the electrical traction drive is in a confined space and uses a third rail system then as long as the system is in an enclosed tunnel to which there is no access or in a remote location which is generally inaccessible no safety problems are likely to occur. In other situations the overhead conductor system is preferred although problems can arise in restricted locations when there is a limitation of height when the overhead rail becomes less attractive, since there is always the risk that the live conductor or bus-bar may be touched. It is thus necessary to take precautions wherever possible to avoid inadvertent contact with the live conductor.

Electric traction can operate on two basic systems, one is to have a single live conductor which carries current at a potential above earth and an earth return contact which completes the path for the current. The alternative system is to have two conductors, one of which may be at earth potential and the other of which is above this. The conductors may operate to transmit either direct or alternating current. Generally for traction purposes, direct current is selected because the characteristics of the electric motors used are such as to give maximum torque on the start-up, whereas with alternating current, unless compound windings are incorporated, the start-up torque is relatively small.

The present invention is able to be used with both direct and alternating current.

The use of electric traction in underground tunnels and galleries requires the siting of the live conductors to be given special consideration. As has been mentioned above, because of the low levels in many situations, there is a risk to personnel and therefore a special form of bus-bar is best used. A suitable. form of bus-bar is described in our co-pending application (reference 4933) where accidental access to the live part of the conductor is very difficult to achieve.

One of the advantages of using an overhead conductor is that 4 the vehicle which draws power from the conductor uses a pantograph engaging with the conductor and is allowed a restricted amount of wander from a path strictly defined by the path of the conductor so as to allow the vehicle to make slight deviations. As long as the pantograph remains in contact with the overhead conductor# the precise route followed by the vehicle is not important.

It is often necessary for vehicles to have a local power source such as a battery. and this enables short journeys to be made away from the defined route of the overhead conductor. When this happens the pantograph has to be removed from the overhead conductor and also replaced when the route is resumed. A suitable system for doing this is defined in our co-pending application (reference 4934).

When electric traction is used in underground workings such as coal mines or in other hazardous atmospheres such as petrol refineries, there is always the risk of explosion from incendive sparking, particularly where gases such as methane are present. A mixture of methane and air in a range of about 2% to 15% is highly explosive, and it is thus necessary to ensure that if any sparking does occur that either the spark does not have sufficient energy to cause an explosion, ie it is intrinsically safe, or the quantity of methane is such as to put it below the explosive limit. One way of dealing with this problem, which has been tried with fixed conductors, is to blow a fresh air or inert gas as a flushing medium bver the travelling pantograph. This has been particularly applied to coal cutting machinery which has picked up its current from a static bus-bar which lays in a trough along side a conveyor over which the cutting machine traverses such as is disclosed in Patent Specification NO 1508786. The bus-bar has been encased in a housing which has a flexible seal and has been purged with air or nitrogen gas. Unfortunately, this type of bus-bar has suffered from problems of the ingress of dirt and moisture, and has not always been effective. Furthermore being floor mounted, there is a risk of personnel inadvertently making contact with it, either by dropping objects through the seal or by stumbling and falling into contact with the bus-bars.

it is an object of the present invention to provide an overhead electrical current collector arrangement which is safe to use in hazardous atmospheres, which follows a defined path and which enables the pantograph always to-ensure that good electrical contact takes place with a bus-bar.

According to the present invention, an overhead electrical current collector arrangement ccmprises an overhead guide rail, a bus-bar and pantograph means, wherein the overhead guide rail is of a generally square cross section and is arranged in use to be secured to an overhead support in such a manner as to have its diagonals disposed substantially horizontally and vertically, the pantograph means including a substantially enclosed housing having externally mounted roller means arranged in operation to engage the guide rail on either side of the horizontal diagonal.

The pantograph means preferably includes within a housing, an!lectrical pick up means adapted to engage with the bus-bar passing through the housing. The pick up means is preferably a spring-loaded carbon brush.

The bus-bar may comprise a solid electrical conductor 1 suspended from brackets secured to the lower side of the overhead guide rail, the brackets passing through a slot in the housing of the arrangement.

In order to enable some degree of movement of the arrangement the guide rail is preferably suspended by flexible mountings from suitable suspension points.

The roller means mounted externally of the housing may include rollers having recessed faces so as to receive the horizontal diagonals of the guide rail between them, and to rest on the inclined faces of the guide rails. The roller means are preferably spring biased towards the guide rail, to hold the rollers in firm engagement therewith.

Means may be provided on the housing to enable an electrical flexible conductor to be secured through the housing to connect with the pick up means. There may also be inlet means on the housing to allow the supply of a purging gas to the housing through a flexible hose.

In order that the invention may be readily understood, one example of an overhead electrical current collector arrangement in accordance therewith, for use in an underground coal mine, is now to be described by way of example only, with reference to the three figures of the accompanying drawings. These figures all show different views of the same collector arrangement. Figure 1 shows a top plan view of the arrangement with part of the housing cut away.

Figure 2 is a side view of Figure 1. taken in the direction of the arrow II, and Figure 3 is a sectional side view of Figure 1 including a cross section on the lines III-III. Figure 1 itself is showing the section of Figure 3 along the lines I-I of Figure 3.

Referring now to the drawings, these show a guide rail (1) which is of a square cross section and which is disposed in a mine passageway such that it presents a diamond shaped appearance in cross section with a vertical diagonal and a horizontal diagonal. The apex of the guide rail has secured to it, at intervals along its length, suspension elements (2) which are connected through shackles (3) to the overhead arches of the mine.

The collector arrangement itself comprises a metal housing (4) which has a longitudinal slot (5) in the centre of its upper surface. As can be seen the lower diagonal point of the guide rail (1) projects into this slot (5) and has depending from it and attached to it a bracket (6). The bracket (6), as shown, is one of a number of brackets secured along the length of the conductor and supports two bus-bars (7) on either side of the bracket (6). In Figure 3 only one bus-bar is shown. The other lies in housing (4) on the other side of the bracket (6). The bus-bars and their particular arrangement are more fully described in our co-pending application (reference 4933).

The housing has four sets of rollers (8) situated on top of it and these rollers are joined in pairs on either side of the guide rail (1) by a strap (9). The rollers engage closely with the sides of the guide rail, and the construction of the roller -can be properly seen in Figure 3. The rollers are made in two parts, an upper and lower part (11), (12) respectively, each mounted on bearings (13) and secured together by bolts (14) which also pass through a distance spacer (15). A cable gland (16) on the underside of the housing (2) enables an electric cable to be connected through a terminal arrangement (17) to a carbon brush (18) engaging with the conductive element of the bus-bars (7). There are two cables which pass through the gland (16), one connecting with each of the bus-bars and separated electrically from each other.

The housing (2) also has a further inlet (19) which is connected to a flexible hose (not shown). through which purging air is forced under pressure into the body of the housing (2).

In use, a guide rail (1) is suspended along the length of the passageway in a mine by shackles (3) at appropriate distances. The electrical collector arrangement is raised by means as described in our co-pending patent application (reference 4934) to ensure that the rollers (8) engage correctly with the guide rail (1) and that the carbon brushes (18) are entered into contact with the conductors of the bus-bars (7) within housing (7) and a towing link is attached to the housing (4) via a towing point (20). The current is then supplied via the carbon brushes (18) and through the cable to the tractor of the vehicle. The tractor pulls the vehicle attached to it along a path under the guide rail and tows the collector arrangement along the guide rail (1) as it does so. The rollers (8) run tightly against the profile of the guide rail, and because of the diamond shaped nature of the profile, they do not run any risk of moving away frem the guide rail and allowing the collector arrangement to jump from the bus-bars. As travel takes place, the purging air is blown from a blower (not shown) on the tractor through inlet (19) into the housing and escapes via the slot (5) and through the ends of the housing (4). A large quantity of air is used and this effectively purges the collector arrangement and ensures that if any sparking does take place between the carbon brushes and the bus-bars then there is not an incendive gas mixture which could explode. Because the purging air is only supplied to the housing itself and not as in previous constructions over the whole length of the bus-bars, there is not the same requirement for sealing and the risk of a build-up of methane in remote areas along the bus-bar is reduced. Thus the invention is more safe than previous installations and is cheaper to run, since the quantity of purging air or gas required is less.

The guide rail (1) itself is provided with a good surface finish and made to reasonably close tolerances, so that the arrangement may travel along it at a high speed. Since the guide rail is set with its diagonals, horizontally and vertically, sloping upper surfaces are presented to a mine roof so that if any debris or moisture which is shed frem the roof falls on to the guide rail it is more likely to be shed easily from it and not accumulate and cause problems of agglomeration or corrosion.

In practice the guide rail is made up in sections, preferably of a length of 5 metres each. such that it can easily be handled by two people for easy erection. Adjacent sections of the rail can be connected by using internal connector elements so as to give a relatively smooth joint without any jolting taking place C-e the rollers pass over the joints.

A further advantage of using the diagonal disposition of the guide rail is that the stiffness of the rail is high and it is not liable to bending since the resistance is the same in both the 1 11.7 k vertical and the horizontal plane as far as bending loads are concerned and no torsional distortion will take place. The rail itself will not bend easily on long lengths and thus where a bend is encountered this will take a smooth curve and there will be no 5 tendency for kinking at the joints.

Claims (13)

CLAIMS: CASE 4935

1. An overhead electrical current collector arrangement canprising an overhead guide rail, a bus-bar and pantograph means, in which the overhead guide rail is of a generally square cross section and is arranged in use to be secured to an overhead support in such a manner as to have its.diagonals disposed substantially horizontally and vertically, the pantograph means including a substantially enclosed housing having externally mounted roller means arranged in operation to engage the guide rail on either side of the horizontal diagonal and to enclose part of the bus-bar.

2. An overhead electrical current collector arrangement as claimed in claim 1, wherein the pantograph means includes insulated electrical pick-up means adapted to engage with the bus-bar passing through the housing of the pantograph means.

3. An arrangement as claimed in claim 2, wherein the pick-up means is a carbon brush.

4. An arrangement as claimed in claim 2 or claim 3, wherein the pick-up means is spring-loaded.

5. An arrangement as claimed in any preceding claim, wherein the bus-bar is suspended by brackets from the lower side of the guide rail and the brackets extend into the housing.

6. An arrangement as claimed in claim 5, wherein the bus-bar passing through the housing is substantially enclosed by the housing.

7. An arrangement as claimed in any preceding claim and including bracket means suspending the guide rail, the bracket means being attached to the upper diagonal of the guide rail and to an overhead support means.

8. An arrangement as claimed in claim 7 wherein the guide rail is flexibly mounted.

9. An arrangement as claimed in any preceding claim in which the externally mounted roller means include rollers disposed in operation to engage on each face of the guide rail each roller being profiled to engage with a respective face of the guide rail.

10. An arrangement as claimed in any preceding claim and including on the housing electrical input glands for electrical conductors.

11. An arrangement as claimed in any preceding claim and including on the housing means for supplying purging gas to the housing.

12. An arrangement as claimed in any preceding claim and including a towing point for the housing.

13. An overhead electrical current collector arrangement substantially as hereinbefore described with reference to Figures 1, 2 and 3 of the accompanying drawings.

Published 1990 atThe Patent Office. State House, 6671 High Holborn, London WC1R4TP. Further copies maybe obtained from The Patent OfflceSales Branch, St Mary Cray, Orpington. Kent BR5 3RD- Printed by Multiplex techniques ltd. St Mary Cray, Kent, Con. 1/87