GB2193745A

GB2193745A - Adjustment cylinder for mine roof support roof bars

Info

Publication number: GB2193745A
Application number: GB08717324A
Authority: GB
Inventors: Willy Watermann; Heinz-Gerd Schlutz
Original assignee: Kloeckner Becorit GmbH
Current assignee: Kloeckner Becorit GmbH
Priority date: 1986-08-08
Filing date: 1987-07-22
Publication date: 1988-02-17
Anticipated expiration: 2007-07-22
Also published as: GB2193745B; GB8717324D0; DE3626951C1

Abstract

A mine roof support includes a roof bar arrangement comprising a main bar (41 Fig. 2) supported by a prop and an adjustable bar (42 Fig. 2) pivotally connected to the main bar. An adjustment cylinder 44 is pivotally connected to both the main bar and the adjustable bar. The adjustment cylinder comprises a housing 1, a pair of pistons 2, 3, bores 18, 39 for the supply and discharge of pressure medium, and a pressure intensifier formed from a differential piston 27, a return valve 34, 35 operated by piston 27, and a control valve 23, 24 operated by a control piston 21. When pressure medium is supplied to bore 39 at a normal operating pressure, return valve 34, 35 is open and the pressure medium flows through bores 38, 32, 37 into chambers 31 thereby causing piston rods 4, 5 to move outwards. If pressure medium is now supplied to bore 39 at an elevated operating pressure, control valve 23, 24 opens and differential piston 26 is brought into operation thereby closing return valve 34, 35 and greatly increasing the pressure in chambers 31. Consequently, the adjustable bar (42) engages the roof with increased force. <IMAGE>

Description

SPECIFICATION Adjustment cylinder for a coalface support structure The invention relates to an adjustment cylinder a for coalface support structure. Such a support structure includes a roof bar arrangement comprising a main bar supported by a prop and an adjustable bar, the main bar and the adjustable bar being pivotally connected to each other by a common adjustable bar joint, and number of adjustment cylinder pivotally connected on the stowing side to the main bar and on the coalface side to the adjustable bar and having two connections for the supply and discharge of pressure medium.

A known adjustment cylinder comprises a cylinder and, displaceably arranged therein, a piston having a piston rod, two pressure-medium connections being provided respectively for the cylindrical chamber and the annular chamber. The known adjustment cylinder is acted on by a pressure medium at normal operating pressure so that three such adjustment cylinders must be provided between the main bar and the adjustable bar distributed over their width, in order that the tip of the adjustable bar can be pressed with the required force against the roof. In this case, the space taken up by the adjustment cylinders is unavailable for other components, especially control elements.

The object of the invention is to provide an adjustment cylinder of the type mentioned in the introduction in such a manner that less than three adjustment cylinders are required under the roof bar arrangement in order to - ensure the necessary force to press the tip of the adjustment bar against the roof.

According to the invntion, there is provided a coalface support structure including a roof bar arrangement comprising a main bar supported by a prop and an adjustable bar, the main bar and the adjustable bar being pivotally connected to each other by a common adjustable bar joint, at least one adjustment cylinder, the or each adjustment cylinder being pivotally connected both on the stowing side to the main bar and on the coalface side to the adjustable bar and having two connections for the supply and discharge of pressure medium, the or each adjustment cylinder being arranged to be operated upon by pressure medium at a normal operating pressure and at an elevated operating pressure, and a pressure-controlled pressure intensifier associated with the or each adjustment cylinder, the response pressure of the pressure intensifier being slightly below the increased operating pressure.

In this manner, an adjustment cylinder is obtained which is to be operated upon by an elevated operating pressure and therefore introduces a correspondingly high pressure into the tip of the adjustable bar. In addition, a comparatively small lever arm is sufficient between the adjustable bar joint and the working point of the adjustment cylinders on the adjustable bar in order to adjust and secure the adjustable bar. As a result, the roof bar arrangement is of a relatively shallow construction and no components of the adjustment cylinders project downwards below the main bar and the adjustable bar.

Advantageously, the adjustment cylinders are arranged as at least one group of adjustment cylinders. Thus, only one cylinder housing is required for several pistons and piston rods.

There may be an individual pressure-controlled pressure intensifier for the or each group of adjustment cylinders. Consequently one pressure intensifier is sufficient for several pistons and piston rods.

The pressure intensifier may be arranged integrally with the adjustment cylinder or cylinders in the cylinder housing so that a compact unit is obtained comprising cylinder housing, piston, pistons and piston rod or rods, and pressure intensifier.

Alternatively the pressure intensifier may be formed separately from the adjustment cylinder or cylinders as a separate functional group outside the cylinder housing. This is especially advantageous where there is insufficient space for the entire unit comprising cylinder housing, pistons and pressure intensifier.

In a particular embodiment of the invention, the pressure intensifier comprises an adjustable, hydraulically operated control valve, a control piston cooperating with the control valve, a differential piston and a return valve.

The valves and the pressure intensifier are advantageously so adjusted that, above a certain pressure which is slightly below said elevated operating pressure, the differential piston comes into operation, the control valve opens and the return valve closes.

Conveniently, the adjustment cylinder is connected to the main bar at a position spaced from the tip of the main bar and to the stowing side of the adjustable bar, there is provided on the coalface side of the main bar a bearing recess which is open towards the top and is contracted at the top to form a throat, and there is provided on the stowing side of the adjustable bar a matching bearing pin having a narrowed portion which corresponds to the throat and which is inclined at an acute angle with respect to the longitudinal direction of the adjustable bar.

In this manner, a roof bar arrangement for a coalface support structure is obtained in which the main bar and adjustable bar are built flat.

In addition, the adjustment cylinders do not take up any additional space under the adjustable bar joint so that no components project downwards below the main bar and the adjustable bar.

Advantageously, there are provided, on the coalface side of the main bar, at least one bearing extension, the or each bearing extension having a bearing recess provided with a throat.

In addition, there may be provided, on the stowing side of the adjustable bar, at least one recess, each of which is bounded, on the stowing side, by a bearing pin.

The throat of the or each bearing recess may- be oriented upwards.

Advantageously the or each bearing pin is provided, for the formation of its narrowed portion, with facing flattened portions which are inclined fowards and downwards at an acute angle with respect to the longitudinal direction of the bar.

The invention will now be described in more detail, by way of example, with reference to the drawings in which: Figure 1 shows a cross-section through an adjustment cylinder designed according to the invention, Figure 2 shows a side view of an adjustable bar joint together with the adjustable bar and the coalface-side part of the main bar, Figure 3 shows a plan view of Figure 2, Figure 4 shows a side view of the coalfaceside part of the main bar, and Figure 5 shows a side view of the stowingside part of the adjusting bar.

The adjustment cylinder shown in Figure 1 comprises a housing 1 and two pistons 2, 3 displaceably arranged in the housing 1 and having piston rods 4, 5. The piston 2, 3 and the piston rods 4, 5 are sealed with respect to the housing 1 by seals 6, 8, 10, 12. From the two annular chambers 15, 16 connected to each other by a cross-connection 14, bores -17, 18 lead to the exterior. The bore 18 communicates through a further bore 19 with a cylindrical chamber 20 in which a control piston 21 is mounted so that it can move longitudinally. The cylindrical chamber 20 communicates with a further cylindrical chamber 22 in which there is provided a valve member 24 biased by a spring 23. The spring 23 engages a hydraulically actuated piston. The valve member 24 forms, together with the spring 23, an adjustable control valve.From the cylindrical chamber 22 a cross-bore 25 leads to a further cylindrical chamber 26 in which there is arranged a differential piston 27 having a piston rod 27a. The differential piston 27 divides the cylindrical chamber 26 into a piston chamber 26a and an annular chamber 26b. In the base 28 of the housing 1, two bores 29, 30 lead from the cylindrical chamber 26 to the cylindrical chambers 31 between the base 28 and the pistons 2, 3.

Additionally, a bore 32 leads from the cylindrical chamber 26 to a chamber 33 in which there is provided a valve member 35 biased by a spring 34, valve member 35 and spring 34 together forming a return valve. The valve member 35 is to be actuated by a ram 36 of the differential piston 27. From the chamber 33 a further bore 37 leads into the cylindrical chambers 31 between the base 28 and the piston 2, 3. In addition, bores 38 and 39 lead out of the cylindrical chamber 26 to the exterior.

When the bore 39 is supplied with a pressure medium at a normal operating pressure, the return valve 34, 35 is opened and the adjustable control valve 23, 24 is closed. The differential piston 27 is not in operation. In this case, the pressure medium flows through the bore 39 and 38, the cylindrical chamber 26, the bore 32, the cylindrical chamber 33 and the bore 37 into the piston chambers 31, whereby the piston rods 4, 5 are pushed outwards. The pressure medium thereby displaced out of the annular chambers 15, 16 flows through the bores 17 and 18 to the exterior.

The individual valves are so adjusted in the embodiment shown that at an elevated operating pressure of more than 230 bar the differential piston 27 comes into operation, the adjustable control valve 23, 24 opens, and the return valve 34, 35 closes. With the valves in these positions, the pressure medium in the annular chamber 26 can flow through the bore 25, through the control valve 23, 24, the cylindrical chamber 20, the bore 19 and the bore 18 to the exterior. In this case, the differential piston 27 having the piston rod 27a moves upwards in the drawing, thus causing a considerable increase in pressure in the piston chamber 31. Thus, the adjustable control valve 23, 24, the control piston 21, the differential piston 27, and the return valve 34, 35 together form a pressure intensifier.

Figures 2 to 5 show the coalface-side part of a roof bar arrangement 40 of the coalface support structure. The roof bar arrangement 40 comprises a main bar 41 supported by a prop and an adjustable bar 42, the main bar 41 and the adjustable bar 42 being pivotally connected to each other by a common adjustable bar joint 43. The adjustable bar joint 43 is spanned by an adjustment cylinder 44 pivotally connected to both the main bar 41 and the adjustable bar 42.

The position of the main bar 41 and the adjustable bar 42 shown by the unbroken line in Figure 2 represents the customary operatinig position in which the main bar 41 and the adjustable bar 42 are in line with each other.

On the coalface side of the main bar 41, there are arranged bearing recesses 45, each of which is open towards the top and has a throat 46 at the top. On the stowing side of the adjustable bar 42 there are provided matching bearing pins 47, each of which has a narrowed portion 48 matching a throat 46.

The narrowed portion 48 is formed by two opposed flattened portions 49, 50, the nar rowed portion 48 or the flattened portions 49, 50 being inclined at an angle c of approximately 30 with respect to the longitudinal direction to the bar.

On the coalface side of the main bar there are provided two bearing extensions 41a having the bearing recesses 45 each of which has a throat 46. On the stowing side, there are provided on the adjustable bar 42 recesses 42a which are boundedd on the stowing side by the bearing pins 47.

In Figure 2, the insertion position of the adjustable bar is shown by the dashed line. In this insertion position, the adjustable bar 42 is inclined with respect to the vertical 51 by the angle c of approximately 30 and with respect to the adjusting bar 42 by the angle d approximately 60". In this insertion position, the adjustable bar 42 is lowered perpendicularly so that the narrowed portions 48 are guided through the throats 46. Subsequently, the adjustable bar 42 is pivoted upwards out of the insertion position into the working region. In the working position of the adjustable bar, the narrowed portions 48 are pivoted so far with respect to the insertion position that the bearing pins 47 can no longer move upwards out through the throats 46 of the bearing recesses.

The working region has, in the embodiment shown, a pivoting range of approximately 60 , namely a pivoting range e of approximately 30 upwards and a pivoting range f of approximately 30 downwards. The total pivoting range e and f is limited by the two extreme positions 42b and 42c of the adjustable bar 42.

The adjustment cylinder 44 is connected to the main bar 41 by a joint 52 and to the stowing side of the adjustable bar by a joint 53. The joint 53 is spaced at approximately half the height of the main bar below the adjusting bar joint 43, in such a manner that no parts project downwards from the adjustment cylinder 44.

Claims

1. A coalface support structure including a roof bar arrangement comprising a main bar supported by a prop and an adjustable bar, the main bar and the adjustable bar being pivotally connected to each other by a common adjustable bar joint, at least one adjustment cylinder, the or each adjustment cylinder being pivotally connected both on the stowing side to the main bar and on the coalface side to the adjustable bar and having two connections for the supply and discharge of pressure medium, the or each adjustment cylinder being arranged to be operated upon by pressure medium at a normal operating pressure and at an elevated operating pressure, and a pressure-controlled pressure intensifier associated with the or each adjustment cylinder, the response pressure of the pressure intensifier being slightly below the increased operating pressure.

2. A coalface support structure as claimed in claim 1, in which the adjustment cylinders are arranged as at least one group of adjustment cylinders.

3. A coalface support structure as claimed in claim 2, in which there is an individual pressure intensifier for the or each group of adjustment cylinders.

4. A coalface support structure as claimed in any one of the preceding claims in which the pressure intensifies is formed integrally with the adjustment cylinder or cylinders with which it is associated.

5. A coalface support structure as claimed in any one of claims 1 to 3 in which the pressure intensifier is formed separately from the adjustment cylinder or cylinders with which it is associated.

6. A coalface support structure as claimed in any one of the preceding claims, in which the pressure intensifier comprises an adjustable, hydraulically operated control valve, a control piston cooperating with the control valve, a differential piston and a return valve.

7. A coalface support structure as claimed in claim 6, in which, above a certain pressure which is slightly below said elevated operating pressure, the differential piston comes into operation, the control valve opens, and the return valve closes.

8. A coalface support structure as claimed in any one of the preceding claims, in which the adjustment cylinder is connected to the main bar at a position spaced from the tip of the main bar and to the stowing side of the adjustable bar, there is provided on the coalface side of the main bar a bearing recess which is open towards the top and is contracted at the top to form a throat, and there is provided on the stowing side of the adjustable bar a matching bearing pin having a narrowed portion which corresponds to the throat and which is inclined at an actuate angle with respect to the longitudinal direction of the adjustable bar.

9. A coalface support structure as claimed in claim 8, in which, on the coalface side of the main bar, there is provided at least one bearing extension, the or each extension having a bearing recess provided with a throat.

10. A coalface support structure as claimed in claim 8 or claim 9, in which, on the stowing side of the adjustable bar, there is provided at least one recess, each of which is bounded, on the stowing side, by a bearing pin.

11. A coalface support structure as claimed in any one of claims 8 to 10, in which the throat of the or each bearing recess is oriented upwards.

12. A coalface support structure as claimed in any one of claims 8 to 11, in which the or each bearing pin is provided, for the formation of its narrowed portions, with facing flattened portions which are inclined forwards and downwards at an acute angle with respect to the longitudinal direction of the bar.

13. A coalface support structure substantially as hereinbefore described with reference to and as shown in the accompanying drawings.