Method and apparatus for supporting the roofs in underground excavations

Claim 3

A method as defined in claim 1, wherein said measuring step comprises monitoring the pressure in the region of at least one end of the strip and said adjusting step comprises automatically adjusting the variable force in accordance with the result of measurement at said one end of the strip.

Claim 4

A method as defined in claim 1, wherein said measuring step comprises monitoring the pressure at least in the region of that end of the strip which is adjacent to the mine face and said adjusting step comprises reducing the force at the other end of the strip when the pressure at the first mentioned end of the strip increases.

Claim 5

A method as defined in claim 3, further comprising the step of terminating the application of force to the other end of the strip and increasing the force which acts against the first mentioned end of the strip.

Claim 6

A method as defined in claim 1, wherein said adjusting step comprises maintaining the force acting against the end of the strip which is remote from the mine face at a constant value and increasing the force acting against the remainder of the strip when the result of the measurement indicates an increase in the pressure exerted by the strip.

Claim 7

A method as defined in claim 1, wherein the variable force is transmitted by way of a roof engaging assembly which is subject to bending stresses and wherein said adjusting step comprises changing the force in the region of that end of the strip which is remote from the mine face when the pressure transmitted to the roof engaging assembly generates a bending stress which exceeds a predetermined value.

Claim 8

A method as defined in claim 1, further comprising the step of supporting from below with a variable force at least one additional strip of the roof adjacent to the first mentioned strip, measuring the pressure which the additional strip exerts in a downward direction, and adjusting the variable force which acts on said first mentioned strip in accordance with the result of measurement of the pressure transmitted by the additional strip.

Claim 9

A mobile mine roof supporting apparatus, particularly for use in longwall mining, comprising a support arranged to rest on the floor of an underground excavation; an elongated roof engaging assembly having front and rear portions and arranged to engage the roof in the excavation; at least one adjustable variable-lEngth propping device mounted on said support and connected with said assembly between said rear and front portions whereby the assembly is respectively urged against and moves away from the roof in response to lengthening and shortening of said device; at least one adjustable balancing device connected with and operative to apply to the rear portion of said assembly a force in line with the load upon said rear portion; and a control system comprising at least one signal generating load monitoring member responsive to changes in load upon said assembly and adjusting means for adjusting at least one of said devices in response to signals from said monitoring member.

Claim 10

A mobile mine roof supporting apparatus, particularly for use in longwall mining, comprising a support arranged to rest on the floor of an underground excavation; an elongated roof engaging assembly having front and rear portions and arranged to engage the roof in the excavation; at least one adjustable variable-lEngth propping device mounted on said support and connected with said assembly between said rear and front portions whereby the assembly is respectively urged against and moves away from the roof in response to lengthening and shortening of said device; at least one adjustable balancing device connected with and operative to apply to the rear portion of said assembly a force in line with the load upon said rear portion; and a control system comprising at least one signal generating load monitoring member responsive to changes in load upon said assembly and adjusting means for adjusting at least one of said devices in response to signals from said monitoring member.

Claim 11

Apparatus as defined in claim 8, wherein said balancing device is connected with said support and is adjustable to exert a thrust or a pull on the rear portion of said assembly.

Claim 12

Apparatus as defined in claim 9, wherein said balancing device comprises at least one hydraulically operated ram having a first portion coupled to the rear portion of said assembly and a second portion coupled to said support behind said propping device, one of said portions of said ram being movable lengthwise of the ram relative to the other portion of said ram and said adjusting means comprising means for moving said one portion of said ram in response to said signals.

Claim 13

Apparatus as defined in claim 8, wherein said monitoring member comprises a pressure gauge mounted in the front portion of said assembly so as to be subjected to the pressure of the roof and conduit means for transmitting signals from said gauge to said adjusting means.

Claim 14

Apparatus as defined in claim 8, wherein said monitoring member comprises a pressure gauge mounted on the rear portion of said assembly so as to be subjected to the pressure of the roof and conduit means for transmitting signals from said gauge to said adjusting means.

Claim 15

Apparatus as defined in claim 12, wherein said one device is said balancing device and wherein said signals from said pressure gauge are indicative of maximum permissible bending stresses upon said assembly.

Claim 16

Apparatus as defined in claim 8, wherein said balancing device comprises at least one hydraulically operated cylinder and piston unit of variable length and wherein said one device is said balancing device.

Claim 17

Apparatus as defined in claim 14, wherein the cylinder of said unit is a double-acting cylinder.

Claim 18

Apparatus as defined in claim 14, wherein said unit is a multi-stage cylinder and piston unit.

Claim 19

Apparatus as defined in claim 8, wherein the front portion of said assembly comprises a cover plate which yieldably engages the roof and said monitoring member comprises a pressure gauge mounted in said front portion below said cover plate to produce signals in response to displacement of the cover plate by the roof.

Claim 20

Apparatus as defined in claim 8, wherein the rear portion of said assembly has a downwardly and rearwardly inclined roof-engaging upper side and said balancing device comprises at least one hydraulically operated ram coupled to said rear portion and to said support and extending substantially at right angles to said upper side.

Claim 21

Apparatus as defined in claim 8, further comprising means for pivotally connecting said assembly to the upper end of said propping device.

Claim 22

Apparatus as defined in claim 8, further comprising a link connected to said support behind said devices and to the front portion of said assembly.

Claim 23

Apparatus as defined in claim 20, wherein said support comprises a transversely extending rear wall having an upper portion located substantially midway between the upper side of said assembly and the underside of said support, and means articulately connecting the ends of said link to said front and upper portions.

Claim 24

Apparatus as defined in claim 20, further comprising a second mine roof supporting apparatus having a floor-engaging support laterally adjacent to and connected with said first mentioned supporT said link being disposed in a vertical plane between said two apparatus and being further connected to the front portion of the roof engaging assembly of said second apparatus.

Claim 25

Apparatus as defined in claim 8, wherein said roof engaging assembly comprises an elongated beam, means for pivotally connecting said beam to the upper end of said propping device, and at least one roof engaging cap reciprocably supported by said beam.

Claim 26

Apparatus as defined in claim 23, wherein said cap is pivotable in a vertical plane with reference to said beam.

Claim 27

Apparatus as defined in claim 23, wherein said balancing device comprises at least one ram mounted on the rear portion of said cap and having a portion movable upwardly against the roof.

Claim 28

Apparatus as defined in claim 25, further comprising means for coupling said ram to said support.

Claim 29

Apparatus as defined in claim 25, wherein the portion of said ram is shorter than said cap and is slidable along the roof.

Claim 30

Apparatus as defined in claim 25, further comprising means for articulately connecting said portion of said ram to said cap.

Claim 31

Apparatus as defined in claim 8, wherein said roof engaging assembly comprises an elongated beam connected to the upper end of said propping device and a pair of interconnected elongated roof engaging caps reciprocably by said beam.

Claim 32

Apparatus as defined in claim 29, wherein said caps have front end portions connected to each other and wherein said monitoring member is supported by the front end portions of said caps.

Claim 33

Apparatus as defined in claim 29, wherein said balancing device comprises two hydraulically operated rams each connected with the rear portion of one of said caps.

Claim 34

Apparatus as defined in claim 8, wherein said roof engaging assembly comprises a pair of parallel elongated beams mounted on the upper end of said propping device and an elongated roof engaging cap disposed between and reciprocably supported by said beams.

Claim 35

Apparatus as defined in claim 32, wherein said cap is pivotable in a vertical plane with reference to said beams.

Claim 36

Apparatus as defined in claim 32, wherein said balancing device comprises a hydraulically operated ram connected with the rear portion of said cap.