US3503302A - Mine roof supports - Google Patents

Description

March 31, 1970 3,503,302

HERMANN-JOSEF SCHULZE-HEIMING ErAL MINE ROOF SUPPORTS Filed May 10, 1967 INVENTOR 5 HERMANN-JOSET ScHuLze-PnMms Herman SCHULZE-PEIWNG A r m v8 g2, jmr tzm.

United States Patent K 59,2 Int. Cl. FOl b 25/26; F15b 11/08, F16k 31/44 US. Cl. 911 2 Claims ABSTRACT OF THE DISCLOSURE A self-advancing mine roof support having a hydraulic ram for holding a beam against a roof support in which a pump pressurizes the ram and hydraulic pressure fluid is released from the ram by a device having an expansible chamber communicating with the ram and which has means for releasing fluid from such chamber, there being controllable means for enlarging such chamber so that it can accommodate a greater volume of pressure fluid to lower the pressure on the ram. A manually adjustable setting nut is associated with a scale so that the enlargement of the chamber as well as the release of fluid can be predetermined.

The present invention relates to the operation of mine roof support arrangements and more particularly to the depressurisation of hydraulic rams of self-advancing longwall support units, each such unit comprising a roof-engaging beam and at least one hydraulic ram.

The generally accepted practice is to depressurize such rams as quickly as possible preparatory to advancing. As a result the beam or roof bar of the unit is jerked. The reason for this rapid depressurisation is to enable the dangerous interval in which the roof is not supported by the unit to be reduced to a minimum. The jerking or dynamic effect on the roof is commonly quite significant since a ram may apply a force of 40 tons against the roof and complete depressurisation may take place in a fraction of a second. Large forces will therefore occur which would not arise if the depressurisation were carried out slowly.

The diflerence between sudden and gradual depressurisation is particularly significant in the case of roof supports having a beam or root bar with three or more rams, since if one ram is suddenly depressurized there will be a resilient flicking action of the roof beam against the roof while if depressurizing takes place slowly, there will be no such flicking action.

Although safety measures are clearly to remain of paramount importance, one aim of the present invention is to provide for the avoidance of such jerks or dynamic stresses in the roof, so that damage to the roof is prevented: that is to say, a roof which is sufficiently sound not to collapse spontaneously when one or more of the rams of the self-advancing units are depressurized slowly should not be damaged by a rapid depressurisation so that collapse occurs, or is likely to occur if for one reason or another there is a delay in advancing and repressurisation.

The present invention consists in a self-advancing roof support unit comprising a beam, at least one hydraulic ram for holding the beam against the mine roof, a pump for pressurizing the ram, means for releasing hydraulic fluid from the ram, and means for controlling the releases of the fluid.

Preferably the means for releasing hydraulic fiuid from the ram and the means for controlling the release of the fluid include a piston in a chamber, means for moving the piston, and means for setting the stroke of the piston.

The stroke setting means can be in the form of an abutment or alternatively, in a preferred embodiment of the invention, the means are in the form of a scale.

Preferably the arrangement comprises a valve placed at the opposite end of a chamber whose other end is defined by the piston, and means which provide for lost motion and cause the valve to be opened when the piston has moved to allow a certain amount of hydraulic fluid to escape from the ram into the chamber.

One embodiment of the invention is now described with reference to the accompanying drawings.

FIG. 1 is a section through a preferred embodiment of the invention, an associated pump and self-advancing mine roof support unit being shown diagrammatically.

FIG. 2 is a surface view of the right-hand end of the control arrangement shown in FIG. 1.

As shown more particularly in FIG. 1 the arrangement for releasing hydraulic liquid from a hydraulic ram .comprises a housing 1 with an end portion 2, an O-ring 3 being placed between them to effect a sealing joint. In the housing there is a valve element 4 which prevents hydraulic fluid under pressure from escaping over a seating 5 from a chamber 20 inside the housing 1. The chamber is connected by a union 6 with a ram R of a selfadvancing mine roof support unit SU. This ram R can be extended, that is to say pressurized, by a pump P. As a result of the connections, therefore, ignoring any effects due to viscosity of the liquid, the pressure inside the ram R equals the pressure inside the chamber 20. In the housing 1 there is a spindle 7 with an O-ring between it and the valve elements 4. The spindle carries a cap 10 which is attached by means of a screw 11. The spindle can move in direction of its axis but carries a part of a rectangular cross-section 12 which prevents the spindle rotating. The right-hand end of the spindle carries a screw thread 13 with a setting nut 14 with a scale 15 so as to indicate. the position of the spindle. The piston 7' carries an O-ring 8 and defines the right-hand end of chamber 20 while the valve element 4 defines the left-hand end. Between the piston 7' and the right-hand end of the housing 1 there is a spring 17 while there is a similar spring 18 between the piston 7' and the valve element 4. The last-named spring presses the valve element 4 against its seating 5 on the portion 2.

When the ram R is being maintained in the pressurized, i.a. roof supporting condition, the chamber 20 holds fluid under pressure at the same pressure as in the ram and the valve element 4 is pressed against the portion 2 so that no hydraulic liquid can escape from the chamber 20.

If the ram is now to be depressurized, the setting nut 14 is turned so as to move the piston 7' to the right, the amount of movement being controlled by reading the scale 15 at an index mark 21. Consequently the chamber 20 is increased in size so that hydraulic liquid flows from the ram R. T o depressurize the ram R completely the nut 14 is turned until the cap 10 pulls the valve element 4 away from its seat so that hydraulic liquid rapidly escapes from the ram R. When the nut 14 is turned in the opposite direction the valve element 4 is closed again by the spring 18.

Preferably the operation is so carried out that depressurisation of the ram occurs within a period of not less than about 5 seconds and not more than about 15 seconds.

What we claim is:

1. In a self-advancing mine roof support unit having at least one hydraulic ram for holding a beam against a roof support and a pump for pressurizing the ram, the improvement which comprises a device for controlling the release of hydraulic pressure fluid from the ram, said device having an expansible hydraulic fluid containing chamber communicating with said ram, means for releasing fluid from said chamber, and controllable means for en larging the volume of said chamber, thereby to accommodate a greater volume of pressure fluid from said ram to lower the pressure thereof, said controllable means comprising a manually operated member for effecting an alteration in the size of said chamber, said manually operated member comprising a shiftable spindle, a piston on said spindle, a setting nut on said spindle for predetermining the position of said piston, and a scale associated with said nut for determining the position of said piston.

2. In a self-advancing mine roof support unit as claimed in claim 1, in which said fluid releasing means comprises a valve, and means including a lost motion connection between said spindle and said valve for opening the latter upon predetermined adjustment of said setting nut. 1

References Cited UNITED STATES PATENTS 2,657,028 10/1953 Joy 61-45 2,748,799 6/1956 Rath 25177X 2,783,773- 3/1957 'Rasch= 2'51-77 X 901,712 10/1908 Kenevel 236-100 974,189 1 1/1910 Ritter.

2,585,389 2/1952 Kehrl 6054.5 5 2,825,240 3/1958 Gray 6054.5 X 3,216,201 11/1965 Kibble et a1. 911,X

' FOREIGN PATENTS V i Y 982,978 2/1965 vGreat Britain.

10 MARTIN P. SCHWADRON, Primary Examiner CL COHEN, Assistant Examiner

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