GB2116502A - Electrical sliding contact line and current pick-up assembly, in particular for use in firedamp- endangered mine openings - Google Patents

Abstract

A universally flexible tubular casing (1) of rubber-elastic material (which is filled, in use, with pressurised protective gas) accommodates sliding contact conductors (2) and has a longitudinally extending slot (3), for a current pick-up arm of a current pick- up assembly (6). The sealing gap (3) has a cross-section which reduces in an outward direction and accommodates a resilient sealing member (4) preferably of circular annular cross-section which is flexible in all directions and which is insensitive to thrust forces. The current pick-up assembly (6) includes guide elements which lift the sealing member (4) out of the sealing gap (3) in front of the current pick-up assembly (6), guide the sealing member (4) closely on all sides over the length of the current pick-up assembly (6), and lay the sealing member (4) back into the sealing gap (3) behind the current pick-up assembly (6). <IMAGE>

Description

SPECIFICATION Electrical sliding contact line and current pickup assembly, in particular for use in firedampendangered mine openings The invention relates to an electrical sliding contact line and current pick-up assembly which is particularly though not exclusively suitable for use in firedamp-endangered mine workings.

In a previously proposed electrical sliding contact line, UK published specification 2 072 111, a tubular casing member of resilient material which is flexible in all directions accommodates sliding contact conductors and has a longitudinal slot closed by a resilient sealing means, through which slot extends a current pickup arm of a current pick-up assembly that is displaceable within the tubular casing member to pass longitudinally thereof, the tubular casing member being continuously supplied with protective gas under an increased pressure and the resilient sealing means for sealing the longitudinal slot being formed by a double-lip sealing arrangement the lips of which are pressed apart by the current pick-up arm passing therebetween. In German patent application No.

P 31 23 221.3 which is not a prior publication, anti-friction support members are proposed in the region of the lips, to reduce friction between the current pick-up arm and the lips.

This form of means for sealing the longitudinal slot requires the lips to be under a comparatively high resilient biasing force, which can be ensured only if the universally flexible tubular casing member is partially surrounded by slotted spring steel tube portions which apply the resilient sealing forces and which must therefore be in the same position everywhere, relative to the lips. It is not always possible to ensure that that is the case, with a sufficient degree of certainty, because the sliding contact line is required to be movable in all directions, particularly under rough operating conditions underground.

In addition, German published specification No. 28 08 240 discloses a sliding contact line of a different basic kind, which is composed of rigid pipe portions for accommodating sliding contact conductors, wherein the pipe portions have longitudinal slots which are covered by a continuous flat sealing member in the form of a steel strip which is held against the edges of the slot in the sealing position by permanent magnets and which can be deflected into the interior of the pipe portions by a wedge-shaped guide member on a current pick-up member. However, a sliding contact line of this kind is very unsuitable for use underground because, due to the use of the flat sealing member, the line can move only in one bending plane which extends along the longitudinal axis and normal to the plane of the flat sealing member, even if the rigid pipe portions are pivotally joined together.In comparison with that, a sliding contact line which is suitable for universal use in underground mining must be flexible in all directions so that it can adapt to the nature of galleries or workings, which is predetermined by the operating circumstances and the situation in regard to the rock to be mine.

According to the invention there is provided an electrical sliding contact line and current pick-up assembly in particular for use in firedampendangered mine openings, comprising an elongate tubular casing member of resilient material, which is flexible in all directions, accommodates sliding contact conductors and has a longitudinally extending slot therein closed by resilient sealing means, and a current pick-up assembly displaceable in the tubular casing, the current pick-up assembly including a current pickup arm extending outwardly through the longitudinally extending slot, wherein the tubular casing member can be continuously supplied with a protective gas under pressure, the longitudinally extending slot in the tubular casing member is in the form of a sealing gap with a cross-section which reduces in an outward direction, the resilient sealing means is formed by a shaped sealing member of resilient material accommodated in the sealing gap, the shaped sealing member is flexible in all directions and is insensitive to thrust forces, and the current pickup assembly includes guide elements which lift the sealing member out of the sealing gap in front of the current pick-up assembly, having regard to the direction of movement thereof, guide the sealing member closely on all sides over the length of the current pick-up assembly and lay the sealing member back into the sealing gap behind the current pick-up assembly.

In such a flexible sliding contact line, no or only slight resilient biasing forces are required for sealing the longitudinally extending slot, and the three-dimensional mobility of the sliding contact line is not detrimentally affected by the sealing means. Thus the sliding contact line can be flexible in all directions. The use of a universally flexible shaped sealing member of resilient or rubberelastic material gave rise to problems, for that use, insofar as the shaped sealing member is necessarily subjected to stretching forces by the current pick-up assembly at the trailing end thereof, such stretching forces being caused by inevitable frictional forces between the current pick-up assembly and the sealing member.Such stretching forces cause tensile stress in the sealing member as it runs off the current pick-up assembly, and thus in an increase in the length of the curve of the sealing member, where it passes over the current pick-up assembly particularly when the material used for the sealing member is a resilient or rubber-elastic material which undergoes a comparatively great increase in length. The invention can avoid such increase in the length of the curved part of the sealing member in that the sealing member is insensitive to thrust forces, is closely guided on all sides over the length of the current pick-up assembly and is fixed in the outwardly reducing sealing gap.By virtue of the co-operation of those features, the frictional forces which inevitably occur between the sealing member and the current pick-up assembly at the leading end can be compensated by thrust forces so that the above-mentioned increase in the length of the curved part of the sealing member which passes over the current pick-up assembly due to pulling forces does not occur, even when comparatively soft rubberelastic material is used for the sealing member, Another advantage of this combination of features is that differences in thermal expansion in respect of the tubular casing member and the sealing member are automatically compensated, which is an important consideration, particularly when the sliding contact line is of substantial length.

A particularly advantageous embodiment of the sliding contact line is provided when the sealing member is of a generally circular, possibly annular section. By generally circular is meant shapes which approximate to a circular profile, for example an equal-sided regular polygon. Such profiles are particularly well-suited to the transmission of thrust forces and have the same or at least approximately the same resistance to bending in all bending planes.

Desirably, the tubular casing member and the sealing member comprise silicone rubber which has particularly good temperature resistance and electrical insulation value or dielectric strength.

The guide elements which guide the sealing member over the current pick-up assembly are desirably in the form of support and guide rollers.

Such an arrangement can minimise the frictional forces which inevitably occur between the sealing strip and the current pick-up assembly.

Desirably, the support and guide roller which is first at the leading end and the support and guide roller which is last at the trailing end are each of such a width that it rolls on the inside wail surface of the tubular casing member, on both sides of the sealing gap, and in this way serves at the same time as a mounting roller for the current pick-up assembly.

In order to minimise loss of the pressurised protective gas, which occurs at the location at which the current pick-up arm passes through the tubular casing member, in the region of the sealing member which is lifted out of the gap, the current pick-up arm is connected to a threedimensionally pivotal and vertically movable plate array which seals the sealing gap from the exterior.

In order in that respect to minimise friction between the plate array and the tubular casing member, sealing of the sealing gap in the region of the sealing member where it is lifted up is effected in the manner of an aerostatic bearing having pressure gas formed by the pressurised protective gas, a variable gap-forming throttle means formed by the sealing plate array that is pressed against the tubular casing member from the outside by means of springs supported on the current pick-up assembly, and a constant pre-throttle formed by a throttle member which is also connected to the current pick-up assembly and which is displaceable in the sealing gap. Such sealing members, associated with the current pick-up assembly, can have a negligibly low level of frictional resistance and also enjoy the advantage that virtually no wear occurs at the aerostatically supported member.

The invention is diagrammatically illustrated by way of example with reference to the accompanying drawings, in which: Figure 1 shows a view in cross-section taken along line I-I in Figure 2 of a sliding contact line and current pick-up assembly according to the invention; Figure 2 shows a view of the sliding contact line and the current pick-up assembly in longitudinal section taken along line Il-I I in Figure 1, only the left-hand half of the current pick-up assembly being shown; Figure 3 is a view in section taken along line Ill-Ill in Figure 2; and Figure 4 shows a detail indicated at IV in Figure 2.

Referring to the drawings, a sliding contact line comprises an elongate hose or tubular casing member 1 which is flexible in all directions and is formed of silicone rubber, sliding contact conductors 2 being disposed at the inside wall thereof. In its underside, the tubular casing member 1 has a longitudinal slot which is in the form of a sealing gap 3. The sealing gap 3 reduces in width in a downward direction and is sealed by an elongate sealing member 4.

The tubular casing member 1 is partially surrounded by a slotted steel tube portion 5 which supports and protects the tubular casing member 1. A multiplicity of such steel portions 5 (not shown) are disposed in a mutually overlapping relationship in the longitudinal direction of the sliding contact line so that, considered generally, in spite of the steel tube portions 5, the sliding contact line remains movable and flexible in all directions.

A current pick-up assembly 6 is movable within the tubular casing member 1 longitudinally thereof, being supported against the inside wall surface of the tubular casing member 1 by means of support and guide rollers 7, 8 and 9. The current pick-up assembly 6 is connected to a current pick-up arm 10, and the sealing member 4 can be lifted up out of the sealing gap 3 to permit the arm 10 to pass along the sealing gap 3. For that purpose, the current pick-up assembly 6 is provided with further support and guide rollers 11, 12, 13 and 14 which lift the sealing member 4 up out of the sealing gap 3 at the front of the current pick-up assembly 6, guide it closely on all sides over the length of the current pick-up assembly 6, and lay it back into the sealing gap 3 behind the current pick-up assembly 6. In this connection, the support and guide rollers 7 at the leading end and at the trailing end are of such a width that they roll against the inside wall surface of the tubular casing member 1 on both sides of the sealing gap 3 and in so doing press the sealing member 4 into the sealing gap 3.

The sealing member 4 is also formed of resilient silicone rubber, is of round annular crosssection and is accordingly insensitive lo thrust forces, and can therefore carry and transmit thrust forces. Accordingly, the sealing member 4 can compensate for the frictional forces which occur when the current pick-up assembly 6 is moved, between the sealing member 4 and the guide rollers 11, 12, 13 and 14, at the leading or entry end, by means of thrust forces, without the curved portion of the sealing member 4 which is guided over the current pick-up assembly 6 experiencing an increase in length.The above-mentioned reduction in the width of the sealing gap 3 is formed by oppositely disposed inclined side portions 3a and 3b against which the sealing member 4 bears, the sealing member 4 being pressed in between the side portions 3a and 3b by gas pressure in the tubular casing member 1. That arrangement can ensure that the sealing member 4 is excellently sealed and fixed in position. The sealing member 4 is further secured in position by projections 3c and 3d on the tubular casing member 1 which project inwardly into the sealing gap 3 and which prevent the inserted sealing member 4 from jumping up out of the sealing gap 3.

For the purposes of sealing the gap 3 in the region where the sealing member 4 is lifted out, there is a sealing plate array 1 5 which comprises a plurality of sealing plates 1 spa and 1 sub which are three-dimensionally pivotally (see Figure 4) interconnected and which are disposed vertically displaceably on the current pick-up arm 10 and which are pressed from below into the gap 3 by means of springs 1 6. The springs 1 6 are supported on a cantilever arm or bracket 1 7 which is fixedly connected to the current pick-up arm 1 0.

The sealing plates 1 spa and 1 sub are provided at their longitudinal edges with movable sealing apron members 18, Figure 3, and, at their leading and trailing ends, with a sealing block 19 which is displaceable vertically relative to the sealing plates 15 and which is supported on the sealing plates 1 5 by means of springs 20.

The movable sealing plate array 15 with the sealing apron members 18 and the sealing block 1 9 forms a variable, gap-forming throttle means of an aerostatic bearing, whose pressure gas is the protective gas that is under pressure in the interior of the tubular casing member 1, while the constant pre-throttle of the aerostatic bearing is formed by a throttle member 21 which is rigidly connected to the current pick-up arm 10 and which is displaceable therewith in the gap 3, without touching same. This kind of sealing arrangement, in the manner of an aerostatic bearing, can give minimum pressure gas losses with minimum friction between the sliding contact line and the movable members.

Only one end, the left-hand end, of the current pick-up assembly 6 is shown in Figure 2, the righthand end which is not shown corresponds in mirror image relationship thereto.

Claims (8)

1. An electrical sliding contact line and current pick-up assembly in particular for use in firedampendangered mine openings, comprising an elongate tubular casing member of resilient material, which is flexible in all directions, accommodates sliding contact conductors and has a longitudinally extending slot therein closed by resilient sealing means, and a current pick-up assembly displaceable in the tubular casing, the current pick-up assembly including a current pick-up arm extending outwardly through the longitudinally extending slot, wherein the tubular casing member can be continuously supplied with a protective gas under pressure, the longitudinally extending slot in the tubular casing member is in the form of a sealing gap with a cross-section which reduces in an outward direction, the resilient sealing means is formed by a shaped sealing member of resilient material accommodated in the sealing gap, the shaped sealing member is flexible in all directions and is insensitive to thrust forces, and the current pick-up assembly includes guide elements which lift the sealing member out of the sealing gap in front of the current pick-up assembly, having regard to the direction of movement thereof, guide the sealing member closely on all sides over the length of the current pick-up assembly and lay the sealing member back into the sealing gap behind the current pick-up assembly.

2. An electrical sliding contact line and current pick-up assembly according to claim 1, in which the sealing member is of generally circular, possible annular, section.

3. An electrical sliding contact line and current pick-up assembly according to claim 1 or claim 2, in which the tubular casing member and the sealing member are formed of silicone rubber.

4. An electrical sliding contact line and current pick-up assembly according to any one of claims 1 to 3, in which the guide elements are in the form of support and guide rollers.

5. An electrical sliding contact line and current pick-up assembly according to claim 4, in which the support and guide roller which is first at the leading end and the guide and support roller which is last at the trailing end are each of such a width that it rolls on the inside wall surface of the tubular casing member on both sides of the sealing gap and in this manner serves at the same time as a mounting roller for the current pick-up assembly.

6. An electrical sliding contact line and current pick-up assembly according to claims 1 to 5, in which in the region of the sealing member where it is lifted out, the current pick-up arm is connected to a three-dimensionally pivotal and vertically movable sealing plate array which seals the sealing gap from the exterior.

7. An electrical sliding contact line and current pick-up assembly according to claim 6, in which sealing of the sealing gap in the region of the lifted-out sealing member is performed in the manner of an aerostatic bearing, having pressure gas formed by the pressurised protective gas, a variable gap-forming throttle means formed by the sealing plate array which is pressed from the outside against the tubular casing member by means of springs bearing against the current pick-up assembly, and a constant pre-throttle means formed by a throttle member which is also connected to the current pick-up assembly and which is displaceable in the sealing gap.

8. An electrical sliding contact line and current pick-up assembly substantially as hereinbefore described and illustrated with reference to the accompanying drawings.