US3830070A

US3830070A - Mine roof support assemblies

Info

Publication number: US3830070A
Application number: US00293895A
Authority: US
Inventors: H Rosenberg; E Wojaczek; L Plevak; K Becker
Original assignee: Gewerkschaft Eisenhutte Westfalia GmbH
Current assignee: Gewerkschaft Eisenhutte Westfalia GmbH
Priority date: 1971-10-02
Filing date: 1972-10-02
Publication date: 1974-08-20
Anticipated expiration: 1991-08-20
Also published as: BE789390A; GB1410664A; FR2156656B1; FR2156656A1; JPS4842549A

Abstract

Mineral mining installations provided with movable roof support assemblies at the stowage side of a conveyor with shifting rams connected between the conveyor and the assemblies. Each assembly has a number of extendible hydraulic props mounted between a floor sill and a roof cap. At the stowage side of the assembly there is provided a stowage shield composed of relatively pivotable components at least one of which has a U-shaped crosssection. The shield components are connected to a system of levers which control the movement of the components when the props are extended or retracted so as to continuously screen off the stowage zone from the assembly.

Description

0 United States Patent 11 1 1111 3,830,070 Rosenberg et al. I Aug. 20, 1974 MINE ROOF SUPPORT ASSEMBLIES 3,686,874 8/1972 Bell 61 45 1) [75] Inventors: Harry E. Rosenberg, Ludinghausen; FOREIGN PATENTS OR APPLICATIONS Y Bockum'Hoveli 1,503,990 10/1967 France 61/45 D Lubomll' Pl va Aschenberg; 1,937,308 2/1971 Germany 61 45 D Kumbert Becker, Werl, all of 1,061,071 3/1967 Great Britain 61 /45 D Germany 1,815,585 4/1966 U,S.S.R......... 61/45 D [73] Assigneez Gewerkscha Eisenhutte westfalia 238,488 3/1969 U.S.S.R 61/45 D Westfaha Germany Primary Examiner-Dennis L. Taylor [22] Filed: Oct. 2, 1972 Attorney, Agent, or Firm-Sughrue, Rothwell, Mion, 21 Appl. No.: 293,895 Macpeak o [57] ABSTRACT [30] Foreign Application Priority Data O t 2 1971 G 21 9380 Mmeral mmmg installations provided w1th movable 1972 Germany 4 roof support assemblies at the stowage side of a conmany 2217830 veyor with shifting rams connected between the conveyor and the assemblies. Each assembly has a number of extendible hydraulic props mounted between a [58] Fi d 299/31 1 floor sill and a roof cap. At the stowage side of the ase 0 can 91/170 M sembly there is provided a stowage shield composed of relatively pivotable components at least one of which has a U-shaped cross-section. The shield components [56] References and are connected to a system of levers which control the UNITED STATES PATENTS movement of the components when the props are ex- 3,324,664 6/ 1967 Allen 61/45 D tended or retracted so as to continuously screen off 3,357,742 12/1967 Dommann et al. 61/45 D X the stowage zone from the assembly. 3,483,705 12/1969 Roberts 61/45 D 3,564,857 2/1971 v6 Hippel 61 45 1) 24 Claims, 8 Drawing F gu es j w I L Till? A sum 1 or 4 PATENTEBwszo 1914 Fig/1 15 PATENTEB M1820 m4 SHEET 2 OF 4 113 110 113 29 Flg. 4.

PATENTED 1112201914 SHEET 3 [IF 4 Fig.5.

F i g. 7.

MINE ROOF SUPPORT ASSEMBLIES BACKGROUND TO THE INVENTION SUMMARY OF THE INVENTION The invention provides a mine roof support assembly comprising hydraulic props mounted between a floor sill and a roof cap and a stowage shield composed of relatively pivotable components adapted in use to screen off the stowage zone from the assembly when the props are retracted or extended.

There may be two shield components pivotably interconnected through a joint which moves outwardly of the assembly when the props retract. One shield component may serve to cover or screen the space between the cap and the floor sill from the stowage zone when the props are fully retracted with the other shield component being contained within the first-mentioned component. When the props are extended, the shield components pivot out and combine to again screen off the aforesaid space.

A support assembly made in accordance with the invention can provide considerable supporting strength and angular rigidity.

Preferably the stowage shield components are connected to control levers pivotably connected between the roof cap and the floor sill. In one form there are three pivotably interconnected control levers, each of two levers being connected to a respective shield component and a third lever being connected to the floor sill. These levers may adopt a Z-shaped side profile when the props are fully retracted.

In a particularly advantageous construction, an upper shield component is pivotably connected at a joint to the roof cap, the control levers being such that when the props are extended or retracted the pivot joint moves along a substantially vertical line. It follows that when the props are extended or retracted there is no lateral forces which would otherwise tend to alter the inclination of the props. The control levers in this construction are each pivotably connected between said upper shield component and the floor sill. Preferably 'there are two sets of levers, one set being disposed above the other, the pivot joints of each set of levers being offset vertically and horizontally from the other, the lower set of levers having a plate constituting a lower component of the shield connected therebetween.

By making at least one of the pivot joints adjustable in a direction parallel to the floor sill, the angle of inclination of the props can be varied, typically in the range 2 to 9 from the vertical. In one constructional embodiment employing such adjustment, a shifting ram can be used to displace a common shaft forming two pivot joints.

Preferably the shield components, or at least one of these components, has a U-shaped cross-section. In this way the shield component can partly surround the stowage side props of the assembly.

The floor sill of the assembly may be connected through a shifting ram to a conveyor or a troughsupport for the conveyor. Preferably guide beams serve to guide the support assembly in relation to the conveyor.

The invention may be understood more readily and various other features of the invention may become more apparent from consideration of the following description.

BRIEF DESCRIPTION OF DRAWINGS Embodiments of the invention will now be described, by way of examples only, with reference to the accompanying drawings, wherein:

FIG. 1 is a side view of a mineral mining installation employing a roof support assembly made in accordance with the invention with the props of the assembly fully extended;

FIG. 2 is a plan view of the floor section of the assembly shown in FIG. 1;

FIG. 3 is a side view of the assembly shown in FIG. 1 with the props fully retracted;

FIG. 4 is a schematic side view of another support assembly made in accordance with the invention;

FIG. 5 is a side view of a mineral mining installation employing an assembly represented schematically in FIG. 4 with the props of the assembly fully extended;

FIG. 6 is a side view of the assembly shown in FIG. 5 with the props fully retracted;

FIG. 7 is a part-sectional plan view of the floor section of the assembly shown in FIGS. 5 and 6; and

FIG. 8 is a side view of a further installation employing a roof support assembly made in accordance with the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring initially to FIGS. 1 to 3, a roof support assembly is provided at the stowage or goaf side of a scraper chain conveyor 10 installed alongside the mineral face in a mine working. The conveyor 10 is in known manner composed of channel sections arranged end-to-end, and a number of assemblies as illustrated would be disposed alongside the conveyor 10. The assembly shown in FIGS. 1 to 3 has a floor sill in the form of a torsionally rigid base frame 11 which supports four hydraulically operated

props

12, 13 disposed in a rectangular array as depicted in FIG. 2. Each

prop

12, 13 is connected to the frame 11 via a joint 14, preferably a universal joint, which permits the prop to tilt to a limited extent. The props l2, l3 bear a roof cap 15 at their upper ends, and the cap 15 has a scrap deflector 16 at the stowage side and a forward or advance lining cap 17 at the face side. The cap 17 is pivotably connected via a joint 18 to a toggle lever 19 which in turn is pivotably connected via a joint 20 to the face end of the main cap 15. A hydraulic piston and cylinder unit 21 is pivotably connected between the lever 19 and the underside of the cap 15. The unit 21 is operated to pivot the toggle lever 19 and raise or lower the cap 17 in relation to the roof of the mine working. When the

props

12, 13 are set and the unit 21 actuated, the caps l5, 17 can contact the roof of the working over a large area. Further auxiliary caps (not shown) can be provided on the sides of the main cap 15. These auxiliary caps can be extendible and retractable laterally so that the auxiliary caps of adjacent support assemblies can more or less cover the area of the roof between the adjacent assemblies. In this way the entire roof can be supported, if desired, throughout the complete length of the working. The main cap also has guide plates 15 at its sides, and these plates 15' may guide and support an adjacent support assembly.

As mentioned, the

props

12, 13 can tilt, and to bring the props 13 into the desired orientation these props 13 are pivotably interconnected via a yoke 22 and a hydraulic piston and cylinder unit 25 is pivotably connected to the yoke 22 and to the frame 11. Thus, the unit 25 can be used to tilt the props 13 about the joints 14.

The assembly is provided with a screen or shield for screening off and protecting the assembly from the stowage material. This shield is composed of two relatively movable components denoted 30, 32 controlled with

levers

26, 27, 28. The

levers

26, 27, 28 may be rigid plates or frames. The upper lever 26 is pivoted at its upper end to a joint 29 provided on the underside of the cap 15 between the

props

12, 13. The upper end of the intermediate lever 27 is pivotably connected to the lower end of the lever 26 by means of a joint 31. Similarly the lower lever 28, which is somewhat shorter than the

levers

26, 27, has its upper end pivotably connected to the lower end of the lever 27 via a joint 33. The lower end of the lever 28 is pivotably connected to a joint 35 provided on a plate or similar projection 34 of the base frame 11.

The upper shield component 30 is rigidly connected to the lever 26 and has a U-shaped profile with its open side directed towards the face of the working. The main wall of the component 30 has slots therein for accommodating the rear props 13 and is approximately the same width as the main cap 15. The sidewalls of the component 30 have inclined outer edges 30' and recesses 39 in their lower edges adjacent the main wall. The lower shield component 32 is rigidly connected to the lever 27 and also has a U-shaped profile with its open side directed towards the face of the working. The main wall of the components 32, designated 36, is again about the same width as the cap 15 but slightly larger than that of the component 30. The sidewalls of the component 32 have a trapezoidal configuration, and the component 30 has a narrow lower portion snugly received within the component 32 when the

props

12, 13 are set as depicted in FIG. 1 to provide a composite inclined shield in respect of the goaf or stowage material. In this position with the

props

12, 13 set, the

levers

26, 28 are inclined in relation to the axis of the

props

12, 13, whereas the lever 27 is substantially parallel to the prop axis. In the vicinity of the joint 29, the cap 15 has on its underside a bracket 37 which engages the lever 26 when the

props

12, 13 are fully extended and thereby acts as a stop member to prevent the lever 26 from pivoting to displace the joint 31 towards the mineral face. When the

props

12, 13 are retracted, the shield component 30 pivots into the component 32 as the joint 31 moves in the direction of arrow A in FIG. 1 and the joint 33 moves in the direction of arrow B. When the

props

12, 13 are fully retracted, as shown in FIG. 3, the lever 26 adops a near horizontal position and the

levers

26, 27, 28 present a Z-shaped side profile. In this position solely the wall 36 of the component 32 serves to screen off the stowage material. The space between the front and rear props 12, '13, respectively, is essentially unimpeded by the

components

30, 32. The control lever carries a stop member in the form of a pin 38 or the like which engages in the recesses 39 in the sidewalls of the shield component 30 when the

props

12, 13 are fully retracted as shown in FIG. 3.

The base frame 11 has lugs 40 on the side facing the a conveyor 10. The lugs 40 bear pins pivotably locating projections 41 connected to the lower part of the associated channel section of the conveyor 10. The projections 41 may be, alternatively, resiliently connected to the frame 11. The conveyor 10 rests on a trough-like support 42. The conveyor 10 may move to a limited extent on the support 42, or a locking device may clamp the conveyor channel sections to the support 42. In known manner the support 42 carries a guide 43 on its face side for a plough or the like. The conveyor 10 is not itself directly subjected to shifting forces and accordingly the sections of the conveyor 10 can be lightweight components. Barrier plates 44 are attached to the stowage side of the conveyor 10 as well as guides 45 again for the plough or the like. The support 42 has beams 46 rigidly secured thereto. Each beam 46, as shown in FIG. 2, extends between two adjacent support assemblies and acts as a guide means to mutually align the assemblies and the supports 42. The frame 11 has a bracket 51 which is pivotably connected, at joint 50, to the piston rod 49 of a shifting ram 47. The ram 47 has its cylinder connected, via a vertically movable connection 48 to the support 42. The ram 47 can thus effect relative movement between the support assembly and the support 42 with its associated section or sections of the conveyor 10. The rams 47 would be used to advance the conveyor 10 or the support assem blies towards the mineral face. The support assemblies can be shifted under load with their caps 15 only partly lowered. The aforesaid beams 46 and guide plates 15' serve to align the assemblies and the conveyor 10 during shifting.

Referring now to FIGS. 4-7 a roof support assembly has a floor sill and four props 112 each connected to the sill 110 with a ball and socket joint 113. A roof cap 111 is similarly connected to the props 112 with ball and socket joints 114. A forward lining cap 115 is pivotably connected to the front end of the cap 111 and a piston and cylinder unit 116 is connected between the

caps

111, 115 to enable the cap 115 to be raised and lowered in relation to the roof. A goaf screen or shield 118 is pivotably connected via joints 119 to the stowage end 111 of the cap 111. The shield 118, which has a U-shaped cross-section with a main wall facing the stowage zone and two sidewalls, surrounds the stowage-side props 112. Two sets of

control levers

120, 121 are operably connected to the shield 118. The upper levers 120 are pivotably connected to the shield 118 via joints 123 and to side panels 129 of the floor sill 110 via joints 122. The lower levers 121 are pivotably connected to the shield 118 via joints and to the panels 129 of the floor sill 110 via joints 124. With the props 112 fully extended as illustrated in FIG. 4, the sets of

levers

120, 121 converge towards the roof above the stowage zone and extend at an angle in the region of 50 70 in relation to the floor of the working. The

joints

122, 123 are disposed above the

joints

124, 125, respectively. The

joints

119, 123 and 125 lie on a common line X. The main stowage wall of the shield 118 is formed of a lower portion co-planar with the outside of the levers 121 and an upper portion inclined in relation to the lower portion. The juncture between the portions of the stowage wall is denoted 118.

When the props 112 are retracted the

levers

120, 121 pivot so that the

joints

123, 125 move towards the stowage zone. The control levers 120, 121 and associated joints form a lemniscale" guide system since each of the joints 119 moves along an almost planar vertical curve y. This ensures that the inclination of the props 112 denoted Z does not alter when the props are retracted or extended. The shield 118 and the

levers

120, 121 provide angular rigidity to the assembly to ensure that the assembly will not tilt when subjected to forces from the stowage zone or roof. The angular position of the props 1 12, i.e., Z, can be varied by adjusting the position of the joints 122 in a direction parallel to the floor. To this end the levers 120 are connected to a common shaft constituting the joints 122, and this shaft is displaceable in slots 129 in the panels 129 by means of an adjusting device 122 which may be a mechanical screw type device or a hydraulic device. The slots 129' are of such length as to enable the props 112 to form an inclined Z of from 2 to 9 in relation to the vertical V.

FIGS. 5 to 7 depict a mining installation employing roof support assemblies of the type generally described in connection with FIG. 4 and like reference numerals denote like parts in FIGS. 4-7. As shown the props 112 each have two extendible parts or stands 112", 112'. It is advisable to make the props 112 on the stowage side retractable hydraulically, i.e., the so-called robbing aid. Thus when the props 112 retract the cap 111 pivots about the joints 114 of the face side props 112. If the

cap

111 or 115 fails to find adequate contact with the roof, where for example fractures occur, the rear or stowage side props 112 can be relieved hydraulically to tilt the front end of the cap 111 upwardly to provide a better supporting contact. When the props 112 are retracted to lower the cap 111, the

levers

120, 121 pivot with the shield 118 so that the joints 119 move along an almost vertical path while the

joints

123, 125 move along intersecting arcuate paths K, K2 in FIG. 5. When the props 112 are fully retracted, the shield 118 and the

levers

120, 121 take the position shown in FIG. 6 with the shield 118 covering the entire space between the cap 111 and the floor sill 110. The levers 121 are interconnected via a shield plate 128 at the stowage side which is substantially co-planar with the lower portion 118' of the shield 118 to screen off the stowage space when the props 112 are fully extended. The side panels 129 of the floor sill 110 extend upwardly to about the upper end of the base part of the props 112 and lie within the sidewalls of the shield 118 so as to form a substantially continuous side cover with these sidewalls when the props 112 are set.

A shifting ram 117 has a piston rod 130 with a bifurcated end pivotably connected at a joint 134 to a plate 131 in turn connected to the centre of a shaft 126. The shaft 126, which also forms the joints 122, is supported in slots in brackets 127 of the floor sill 110 to form a thrust bearing for the ram 117. The shaft 126 is displaceable parallel to the floor to vary the inclination of the props 112. The actual displacement of the shaft 126 can be effected by means of the ram 117 and detachable clamping means, such as wedges or bolts, can be used to secure the shaft 126 in any desired position commensurate with some inclination of the props. The clamping means would be operated to release the shaft 126 so that it can be moved by the ram 117 whenever the inclination of the props 112 is to be altered.

The cylinder of the ram 117 is connected via a shackle with a pivot pin 132 to a connecting piece 133 having a slidable bushing 135 located on a rail 136. The rail 136 is connected to the stowage face side of the associated channel section or sections of a conveyor 137. At either side of the connection between the rail 136 and the ram 117 there is provided a tapered guide beam projecting at one side of the associated support assembly. The beams 140 are connected to the rail 136 via similar connections to that of the ram 117, the pivot pins being denoted 138 and the slidable bushing 139. The beams 140 serve to guide the support assemblies.

Hydraulic piston and cylinder units 141 used to tilt the conveyor 137 are connected between the rail 136 and a floor support. The conveyor 137 has guide ramp l44 at the mineral face side which supports and guides a plough 142. By operating the units 141 the conveyor 137 can be tilted about the floorengaging edge 143 of the ramp 144 to adjust the cutting path of the plough 142.

Another installation employing a further type of roof support assembly is depicted in FIG. 8 and like reference numerals denote like parts to those shown in FIGS. 4 to 7 and described above. In the construction shown in FIG. 8, the props 112 have a single extendible stand. As before the control levers 120 are connected to the joints 122 provided on side panels 129 of the floor sill 110, but the corresponding joints 124 for the levers 121 are provided on brackets extending upwardly from the floor sill 110. The means for adjusting the position of the joints 120 is not illustrated. The floor sill 110 has projections directed towards the mineral face which are slidably guided on their inner faces by two parallel guide beams 156. These beams 156, which extend beneath the conveyor 161, are rigidly interconnected with a baseplate 157 which carries two

hollow bars

158, 159, in turn interconnected by a web 160 extending parallel to the baseplate 157. The web 160 and the

bars

158, 159 form a trough support into which the associated channel section or sections of the conveyor 16] is received. The sections of the conveyor 161 can, as is known, be lightweight components. The conveyor section or sections may move in relation to the

trough support

160, 158, 159 or be clamped thereto. To this

end cover plates

162, 163 are secured with screws onto the

bars

158, 159 to engage over the sides of the channel section(s) and form guides for the scrapers of the conveyor. A mineral cutting machine 164 can be supported on the

plates

162, 163 and a plough can be supported on a guide ramp 165 and the bar 162. The shifting ram 117 has its piston rod 130 pivotably attached, at a joint 166, to the bar 159 and the cylinder of the ram is connected to the floor sill 110. By extending the rod 130 the components l56-l65 can be moved towards the face and guided by the projections 1 55, and by retracting the rod 130 the floor sill 110 and the remainder of the support assembly can be drawn up and guided on the beams 156.

We claim:

1. In a mine roof support assembly comprising hydraulically extendible props mounted between a floor sill and a roof cap, the improvement comprising a novel stowage shield composed of relatively pivotable components for screening off the assembly from the stowage zone whether the props are extended or retracted, said novel stowage shield comprising:

l. a first shield component pivotably connected to the roof cap at first points thereon for rotational movement in the longitudinal direction of the assembly;

2. a first pair of parallel control levers pivotably connected to said first shield component at second points thereon and to the floor sill at third points thereon in a manner permitting said first pair of parallel control levers to rotate about said third points in the longitudinal direction of the assembly;

3. a second pair of parallel control levers disposed beneath said first pair of parallel control levers, said second pair of parallel control levers being pivotably connected to said first shield component at fourth points thereon which are offset vertically and longitudinally from said second points and to the floor sill at fifth points thereon which are offset vertically and longitudinally from said third points in a manner permitting said second pair of parallel control levers to rotate about said fifth points in the longitudinal direction of the assembly; and

4. a second shield component connected between said second pair of parallel control levers.

2. A mine roof support assembly as claimed in claim 1 wherein the hydraulically extendible props are mounted at an angle to the vertical, but the relation of said first shield component to said first and second pairs of parallel control levers is such that said first points move along a near vertical line as the props extend or retract.

3. A mine roof support assembly as claimed in claim 1 wherein said first points, said second points, and said fourth points lie on common lines in side view when the props are fully extended.

4. A mine roof support assembly as claimed in claim 1 wherein at least one of said third and said fifth points is adjustable longitudinally of the assembly to vary the inclination of the props.

5. A mine roof support assembly as claimed in claim 1 wherein at least one of said third and said fifth points is joined by a common shaft displaceable in a direction substantially parallel to the floor sill to vary the inclination of the props.

6. A mine roof support assembly as claimed in claim 5 and further comprising means for adjusting the position of said common shaft to vary the inclination of the p 7. A mine roof support assembly as claimed in claim 1 wherein said fourth points move outwardly of the assembly when the props retract.

8. A mine roof support assembly as claimed in claim 1 wherein at least one of said first and second shield components is of U-shaped cross-section with its open side facing inwardly of the assembly.

9. A mine roof support assembly as claimed in claim 1 and further comprising at least one hydraulic piston and cylinder unit for varying the inclination of at least one of the props.

10. A mine roof support assembly as claimed in claim 1 and further comprising:

1. an advance lining cap pivotably connected to the roof cap and 2. means for raising and lowering said advance cap.

11. A mine roof support assembly as claimed in claim 1 wherein said first and second pairs of parallel control levers converge towards the roof of the stowage zone.

12. A mine roof support assembly as claimed in claim 11 wherein said first and second pairs of parallel control levers extend at an angle in the region of 5070 in relation to the floor sill when the propsar e fully extended.

13. A mine roof support assembly as claimed in claim 1 wherein said first and second pairs of parallel control levers extend at an angle in the region of 50-70 in relation to the floor sill when the props are fully extended.

14. In a mine roof support assembly comprising hydraulically extendible props mounted between a floor sill and a roof cap, the improvement comprising a novel stowage shield composed of relatively pivotable components for screening off the assembly from the stowage zone whether the props are extended or retracted, said novel shield comprising:

1. a first shield component pivotably connected to the roof cap at first points thereon for rotational movement in the longitudinal direction of the assembly;

2. first and second pairs of parallel control levers pivotably connected to said first shield component at second and fourth points thereon, respectively, and

to the floor sill at third and fifth points thereon, re-

spectively, in a manner permitting said first and second pairs of parallel control levers to rotate about said third and fifth points, respectively, in the longitudinal direction of the assembly;

3. a second shield component connected between said second pair of parallel control levers; and

4. means for adjusting at least one of said third and said fifth points longitudinally to vary the inclination of the props.

15. A mine roof support assembly as claimed in claim 14 wherein the hydraulically extendible props are mounted at an angle to the vertical, but the relation of said first shield component to said first and second pairs of parallel control levers is such that said first points move along a near vertical line as the props extend or retract.

16. A mine roof support assembly as claimed in claim 14 wherein said first points, said second points, and said fourth points lie on common lines in side view when the props are fully extended.

17. A mine roof support assembly as claimed in claim 14 wherein said means for adjusting at least one of said third and said fifth points longitudinally to vary the inclination of the props comprises a common shaft displaceable in a direction substantially parallel to the floor sill.

18. A mine roof support assembly as claimed in claim 17 and further comprising means for adjusting the position of said common shaft.

19. A mine roof support assembly as claimed in claim 14 wherein at least one of said second and fourth points moves outwardly of the assembly when the props retract.

20. A mine roof support assembly as claimed in claim 14 wherein at least one of said first and second shield components is of U-shaped cross-section with its open side facing inwardly of the assembly.

21. A mine roof support assembly as claimed in claim 14 and further comprising:

22. A mine roof support assembly as claimed in claim 14 wherein said first and second pairs of parallel control levers converge towards the roof of the stowage zone.

23. A mine roof support assembly as claimed in claim 22 wherein said first and second pairs of parallel contended.

Claims

1. In a mine roof support assembly comprising hydraulically extendible props mounted between a floor sill and a roof cap, the improvement comprising a novel stowage shield composed of relatively pivotable components for screening off the assembly from the stowage zone whether the props are extended or retracted, said novel stowage shield comprising: 1. a first shield component pivotably connected to the roof cap at first points thereon for rotational movement in the longitudinal direction of the assembly; 2. a first pair of parallel control levers pivotably connected to said first shield component at second points thereon and to the floor sill at third points thereon in a manner permitting said first pair of parallel control levers to rotate about said third points in the longitudinal direction of the assembly; 3. a second pair of parallel control levers disposed beneath said first pair of parallel control levers, said second pair of parallel control levers being pivotably connected to said first shield component at fourth points thereon which are offset vertically and longitudinally from said second points and to the floor sill at fifth points thereon which are offset vertically and longitudinally from said third points in a manner permitting said second pair of parallel control levers to rotate about said fifth points in the longitudinal direction of the assembly; and 4. a second shield component connected between said second pair of parallel control levers.

2. means for raising and lowering said advance cap.

2. first and second pairs of parallel control levers pivotably connected to said first shield component at second and fourth points thereon, respectively, and to the floor sill at third and fifth points thereon, respectively, in a manner permitting said first and second pairs of parallel control levers to rotate about said third and fifth points, respectively, in the longitudinal direction of the assembly;

2. means for raising and lowering said advance cap.

6. A mine roof support assembly as claimed in claim 5 and further comprising means for adjusting the position of said common shaft to vary the inclination of the props.

7. A mine roof support assembly as claimed in claim 1 wherein said fourth points move outwardly of the assembly when the props retract.

10. A mine roof support assembly as claimed in claim 1 and further comprising:

12. A mine roof support assembly as claimed in claim 11 wherein said first and second pairs of parallel control levers extend at an angle in the region of 50*-70* in relation to the floor sill when the props are fully extended.

13. A mine roof support assembly as claimed in claim 1 wherein said first and second pairs of parallel control levers extend at an angle in the region of 50*-70* in relation to the floor sill when the props are fully extended.

21. A mine roof support assembly as claimed in claim 14 and further comprising:

23. A mine roof support assembly as claimed in claim 22 wherein said first and second pairs of parallel control levers extend at an angle in the region of 50*-70* in relation to the floor sill when the props are fully extended.

24. A mine roof support assembly as claimed in claim 14 wherein said first and second pairs of parallel control levers extend at an angle in the region of 50*-70* in relation to the floor sill when the props are fully extended.