US3536433A

US3536433A - Traveling prop system for a mine working face having a steep,or semi-steep,or flat orientation

Info

Publication number: US3536433A
Application number: US805565A
Authority: US
Inventors: Konrad Grebe
Original assignee: INGENIEURBUERO KONRAD GREBE
Current assignee: INGENIEURBUERO KONRAD GREBE
Priority date: 1968-03-12
Filing date: 1969-03-10
Publication date: 1970-10-27
Anticipated expiration: 1987-10-27
Also published as: FR2003695A1

Description

Oct. 27, 1970 K. GRE

TRAVELING PROP SYSTEM FOR A MINE WORKING FACE vHAVING A STEEP. SEMI-STEEP. OR FLAT ORIENTATION Filed March 1o, 1969 FIG. 1.v

Bhf h3! V32 g |-33 34-1 l 35m2 l I A v if FIG. 6. 53, y 7 1 5-.53-5-2! Si #14 t l :l L 43 46 5755'65 646352'436l4543 4l l l l l l I INVENTOR 36 z BY KONRAD GREBE I I i eww, Mfg,

ATTORNEYS.

United States Patent O U.S. Cl. 299-32 17 Clailns ABSTRACT OF THE DISCLOSURE A traveling prop system useful in connection with mining machinery comprising a multiplicity of prop containing frames driven by suitable piston cylinder means and including ladder means comprising stringers disposed in front of and behind the frames joined together by rung means suitably attached to the floor and/or roof beams. The mining machinery may be attached to the forward Stringer as a guide rail.

. A traveling prop system has been proposed for working faces, preferably those having a steep or a semi-steep orientation, which consists of a series of frames which are attached to a ladder-like member extending through the breast in such a manner as to preserve their spacing along the downgrade. During their advancement, the frames are held by the ladder-like member through connecting rods, and the stringers of the ladder extend between the rows of the props of the traveling prop system.

The use of connecting rods has the disadvantage that, during their advancement, the frames have to perform a swinging movement. This brings it about that the beams of the successive frames have to be spaced apart along the downgrade so as to permit this swinging movement. Precisely in the case of steep and semi-steep orientation, however, it is important to cover the full area of the roof as well as the floor with the beams, so as to prevent the development of pits in the floor or roof due to break-outs, thereby providing a poor basis for the proper setting of the advanced frames under pressure between the floor and the roof. But even in a level orientation, when the roof or oor are poor it may be desirable to have complete iloor and roof coverage. Under all circumstances it is desirable to advance the frames along the roof and floor, straight in the direction of advancement, while maintaining an elastic contact pressure. A swinging movemeut, however, practically requires the operator to loosen the frames from the roof and oor completely during their advancing movement.

Another disadvantage of the prior proposal consists in the fact that first all frames have to be advanced in some desired sequence by corresponding swinging movements, before the ladder-like member can be moved forward, and a simultaneous swinging movement of all connecting rods in the opposite direction is then necessary for this purpose. To make it at all possible to fetch the ladder-like member forward in they manner contemplated, all frames must previously have performed a step of the same size. In other words, a certain invariable step length must be observed; but this is difficult to accomplish when the forward step entails a swinging movement. The swinging movement of the ladder and the arrangement of its stringers inside of the rows of props excludes the possibility of using the stringers of the ladder for the guidance of a mining apparatus or for the hanging of a gob curtain.

It is the aim of the invention to overcome these disadvantages and difliculties.

The invention relates to a traveling prop system for a working face, preferably for a working face having a steep or semi-steep orientation, comprising a succession of frames which are connected, in a manner assuring their downgrade spacing from one another, to a ladderlike member extending through the breast. The invention is characterized in that the rung-like elements associated with the ladder-like members lie displaceably on the floor beams of the frames and are guided by the latter in their longitudinal displacement. The ladder-like members preferably have a restricted vertical movement with the stringers of the ladder being disposed in front of the front row of props of the traveling prop system and in back of the rear row of props. At the same time, the floor beam of each frame can be located between two successive rungs of the ladder-like member, or else it may have a recess in which only one rung associated with it is guided. Of course, the beams are guided by rungs, or the rungs are guided by the beams, in a reciprocal manner, depending on which of the two is being moved.

It is desirable that a second ladder-like member of the same kind be associated with the roof beams of the frames in order to guide them. This second ladder-like member can be replaced, when the traveling prop system is used in semi-steep and steep orientations, by other guiding means between the roof beams of the successive frames; when the traveling prop system is used in level orientations, such replacement may be required, under certain circumstances.

By constructing the traveling prop system according to the invention, it is possible to guide, one or the other all of the frames of a traveling prop system extending over the entire length of the breast, by means of the ladder-like members, in a manner which has hitherto been possible only in the case of the reciprocal guidance of two frames combined in a single chock. The frames can move straight forward, always in the direction of their beams, and the beams can follow one another without any appreciable amount of space in between them, and consequently a virtually complete coverage of the roof and oor can be achieved in the direction of both dip and strike, to a far greater extent than'has hitherto been possible. It is possible to advance the frames While they are applying an elastic tension between the roof and the floor, and no longer is a separate period required for the advancement of the ladder-like member.

Instead, it is desirable for an advancing cylinder extending lengthwise of the beam to be associated with each beam of each frame. The pistons are fastened to elements of the ladder (rungs or stringers) and the cylinder is fastened to the beam, or vice versa. If the successive frames are now alternately set and released, and if they are alternately set forward and backward in relation to one another, it is desirable to perform the advancement of the traveling prop system so that, while the forward frames are set under pressure between the roof and the door, the ladder rungs associated with the roof beams of said forward frames are displaced along the beams of these frames towards the working face, the ladders with the relieved rear frames associated with the rest of their rungs are pulled along by the same amount and the rear frames are again advanced along their rungs by the same amount. The set frames located at the leading end of the rungs at the beginning of the advancing period are now at their trailing end, and the released frames originally located at the trailing end of the rungs are now at the leading end of the advanced rungs. Now, when these frames are set and the other frames are released, it is possible to continue the advancement of the traveling prop system in a virtually continuous manner.

The breast-side Stringer of the ladder can be constructed as a guiding rail for a winning apparatus, and

the gob-side stringer can be constructed as a rail for hanging a gobl curtain or mat. It is desirable for these rails to have individual sections which can flex against one another at least upwardly, because it cannot be expected that the floor and the roof of the seam will have an entirely uniform inclination over their entire length, or for that matter, even an uniform inclination through the entire advancing cycle. If the changes in the course of the seam that occur in the area of the roof differ from the simultaneous changes in the area of the floor, the correct position of the frames in relation to the bedding might be adversley influenced by the fact that the distance of the roof beams from one another and the distance of the floor beams from one another are kept constantly invariable by the stringers, even though the position which the succeeding beams assume in relation to one another as regards height is different in the area of the roof from what it is in the area of the lloor. In order nevertheless to permit an always correct position of the frames in relation to the bedding, the stringers of the ladder associated with the roof beams have telescoping rail sections whose length is variable by the operation of adjusting devices.

The manner in which the rungs are joined to the stringers of the ladder must always provide a certain amount of play, as must also the manner in which the guiding surfaces of the beams are joined to the stringers. The ladder will hang from the set frames, and each of the released frames will hang from the ladder. That is, in the case of the set frames, play will occur between the beams and the rungs and between the rungs and the stringers in the downhill direction of the breast (below the beams), and in the case of the released and advancing frames, there will be play in the upward direction of the breast (above the beams). If the advanced frames are then set in this position, the ladder, after the release of the other frames, will shift with these frames downhill in the breast, i.e., upon each setting and releasing action, the prop system will drift downhill by a certain amount.

No matter how slight this amount might be, it can, on account of the constant repetition of the process, prove to be intolerable, even if an attempt is made to compensate the drift by angling the frames to some extent in respect to the direction of advancement. It is, therefore proposed to provide elastic elements between cooperating contact surfaces associated with the stringers on the one hand and with the beams on the other. These elastic elements -urge the beams and rungs uphill to such an extent that play exists between beams and rungs and between rungs and stringers only in the downhill direction. That is, the elastic elements must be strong enough to hold the individual frame that has been released in the plane of the ladder at the height at which it was previously located in relation to the ladder.

The same applies accordingly in the vertical plane of the frames as regards the play which the rungs of the ladder have in relation to the beams. It is desirable for this play to be compensated for by elastic elements which tend to displace the rungs associated with the roof beams in the direction of the roof (the ladder associated with the floor beams is urged towards the floor by its own fweight). The elevation of the ladders thus varies only when such variation is required by irregularities in the course of the roof and/ or floor. While it is always only one of the two groups of frames that is set, while the other is tensed elastically between the roof and the floor, the stringers of the ladders are always urged only to a certain extent elastically towards the roof or floor, as the case may be, by the springs in the case of the roof and by the weight of the ladders in the case of the floor, and the total strength of these springs must be suflicient to bear the weight of the ladder associated with the roof beams. 'Ihe pressure of the ladders against the roof can be augmented by making the springs stronger, and the bearing contact of the other ladder against the floor can be augmented by additional springs at the iloor beams.

If the greatest possible coverage of the roof and floor area is to be achieved, care must be taken to see that the widths of the beams correspond approximately to the spacing of the rungs, if only one rung is associated with each beam, or to the spacing of the pairs of rungs if two rungs are associated with each beam, etc. Care must also be taken to see that the advancing cylinders associated with the beams have only a very short stroke. In the case of complete coverage of the roof and oor, and in the case of the maintenance of an elastic contact pressure during the advancing of the frames, there is no objection to breaking down long steps of the frames into a number of short steps performed alternately by frames A and B. On the contrary, in this manner it is possible always to sustain an especially favorable prop resistance per square meter of covered surface. The steps of the frames can furthermore be made so short that it is not only possible to advance all frames A simultaneously and then to advance all frames B simultaneously, but also it is possible first to advance the series of frames A successively and then advance, one after the other, the frames B situated alternately between them.

The new traveling prop system is especially suited for use in conjunction with a mining method in which a kerfing and ripping chain is carried on controllable and lixable rails laid along the floor and roof. To understand the advantages `which the construction according to the invention offers for this method of mining, it is necessary at this point rst to present an explanation of the process itself and of the diiculties which have hitherto caused problems in its application.

With the kerfng and ripping chain there are associated elements which cut kerfs and elements that rip, the kerling elements producing kerfs that are made progressively deeper into theseam along the roof and lloor, and after the kerf has reached the proper depth, a ripping tool mounted on the same chain rips away the working face between the kerfs, advancing it by a corresponding amount.

For example, seven kering groups, each cutting the kerf S mm. deeper, are followed in each case by a ripper which advances the working face by 56 mm. A working face is thus produced which is of a sawtooth shape, the ripper forming in each case the tip of such a sawtooth. It takes away the undercut part of the working face, and it is followed by another set of kerf cutters which again undercut the new Working face, which, on account of the sawtooth shape of the face, runs somewhat at an angle to the kerng and ripping chain guide rails, until the next ripper again advances the working face, and so on. The kerng elements are fastened to Scrapers which keep the kerf and the space between the chain and the working face free of the lines produced by the kerfng. Since the space between the guiding rail and kerng and ripping chain, on the one hand, and the working face on the other, becomes progressively narrower due to the sawtooth shape of the working face, the Scrapers arranged in succession along the chain must become progressively thinner in that portion of them that extends between the chain and the working face. As the mining progresses, the prop system on which the mining apparatus is supported by the rail or channel guiding the kerfing and ripping chain is continuously advanced. Assuming that the successive ripping tools, each of which advances the working face by 56 millimeters, are spaced 56 meters apart from one another, then in the same time in which the chain moves forward l meter in its guide, the traveling prop system would have to be advanced one millimeter, in order that the working face might always have the same sawtooth shape and that the ripping tools might always rip to the same depth. Hitherto it has been possible to achieve this only by letting the front side of the Scrapers lie ilat against the working face and constantly urging the set of frames A, on which the guide rail of the kerling and ripping chain was fastened, against the working face by means of feed cylinders supported by the set frames B. When these feed cylinders reached the end of their excursion, the mining had to be interrupted for the purpose of bringing up (advancing) frames B. Another disadvantage resides in the fact that the constant contact pressure of the scraping tools against the coal face produced a constant friction, and the friction losses involved, which only served for controlling purposes, substantially impaired the efficiency of the kerling and ripping chain drive.

Now, if the same mining apparatus is associated with the traveling prop system according to the invention, a double advantage is achieved. In the first place, the interruptions for the purpose of advancing frames B are eliminated, since the stringers of the ladder-like members, which are constructed as guide rails for the kerng and ripping chain, are now joined both to frames A and to frames B, and they are advanced continuously and with complete uniformity both during the advancement of frames A (B) and during the bringing up and pushing forward of frames B (A). In the second place, however, there is no longer any need to lay the Scrapers at against the working face in order to provide for the correct depth of penetration of the keriing and ripping tools, because the proper control can also be assured by a precise metering of the feed of the frame being advanced in each case.

Assuming that the kerng and ripping chain is moved forward at a speed of 1 m./s., provision must be made according to the above example for a metering of the feed so that the stringers of the ladder are pushed forward at a rate of 1 mm. per second.

Assuming that advancing cylinders are associated with the beams of frames A and the beams of frames B, whose pistons have a stroke of 50 mm., that the props of the set frames A are disposed 5() mm. ahead of the props of the released frames B and that the advancing cylinders both of frames A and of frames B are fed by metering cylinders, the pressure chamber of each advancing cylinder is times the size of the pressure chambers of the associated metering cylinders, then, according to our example, the metering cylinders would have to be cycled every 5 seconds;'they would then produce a piston movement of 5 mm. in the advancing cylinder for each cycle, and, after ten cycles of metering cylinder operation, i.e., after 50 seconds, the pistons of all of the advancing cylinders would be in their end position, the ladder would have advanced 50 mm., and frames B would have passed from a position 50 mm. behind frames A, over a distance of 100 mm. into a position 50 mm. ahead of frames A. Then, by reversing the hydraulic pressure in the lines feeding the props of frames A and B, frames B would have to be set and frames A would have to be released, and the advancement of the traveling prop system would thus continue uniformly and at the same tempo. The progression of mining in this manner is more uniform than in the case of a flat support of the Scrapers against the working face, since the working face can still be ripped out, and the friction losses produced by the Scrapers on the breast are avoided.

Needless to say, the Scrapers must still be constructed so that their upper edge is in contact with the working face. Otherwise they could not keep the space between the chain and the working face clear of nes. Above or below this edge, however, there is no longer any need for a surface extending all the way to the floor and to the root` and resting against the working face. Instead, the edges can project beyond the actual body of the Scrapers and can be provided with a clearance angle, so that the scraper can cut freely at all times.

If it is assumed that the excursion of the advancing cylinders corresponds to the active width of the ripping device associated with the mining system, the above considerations relating to the rate of feed of the advancing cylinders can be expressed by saying that, if the ripping apparatus associated with a kerng and ripping chain are equally spaced apart, the rate of excursion of the advancing cylinder is regulated by metering cylinders, which are to be cycled preferably in uniform sequence, in such a manner that a full stroke of the advancing cylinder, which corresponds to n full strokes of the metering cylinder, takes place in the same period of time in which the kertng and ripping chain covers a distance corresponding to the distance between two ripping members on the kerng and ripping chain.

The prop system according lto the invention is thus, on the one hand, especially suitable for the performance of the mining process just described, while on the other hand, this method of mining, which constantly clears a small but uniform alleyway ahead of the traveling prop system, offers a particularly good opportunity for the use of the prop system according to the invention.

If a breast, in which the prop system and the mining proceed in this manner, has to be slowed, an adjustable apparatus can be associated with each advancing cylinder, by which the excursion of its piston can be limited. The advancing cylinders associated with the wing that has to turn are in each case fully extended; at the other end of the breast the advancing cylinder is blocked, and at the frames between them the system that limits the stroke is so adjusted that, starting from the pivot point, the stroke is slightly larger in each succeeding advancing cylinder. As soon as this stroke has been completed, the advancing cylinder and the metering cylinder feeding it are automatically blocked, so that the keriing tools and ripping tools associated with the kerng and ripping chain no longer attack the working face at these points.

The annexed drawings show embodiments of the traveling prop system according to the invention. Understanding of this invention will be facilitated by reference to the drawing, wherein:

FIG. 1 is a plan view, partially in section along line I-I of FIG, 3 of a portion of an apparatus in accord with this invention;

FIG. 2 is a side elevation of the same apparatus;

FIG. 3 is a front elevation (as seen from the breast), partially in section along linev III- III of FIG. 1 of the apparatus of this invention;

FIG. 4 shows, on a reduced scale, a schematic view of the advancement of the prop system of this invention and the shape of the working face when the stringers associated with the traveling prop system according to the invntion are used for the guidance of a kerfing and ripping c am;

FIGS. 5 and 6 are supplementary to FIG. 4, showing how the kerf in the working face is produced when the kerng tools arranged between the rippers are set close together, and when they are uniformly spread out, respectively.

According to FIGS, 1, 2 and 3, prop frames A and prop frames B are disposed alternately in the downhill direction along the breast. In the period of operation shown in the drawing, frames A are set and frames B are relieved. In the lower half of the igure, the prop system is represented in its position at the beginning of the advancing cycle, and in the upper half of the gure it is represented at the end of the advancing cycle. Frames A as Well as frames B have roof beams 1 and 'oor beams 1. Beneath the roof beams 1 and above the oor beams 1 there are disposed on either side thereof, a web 2 (2'), and rungs 11 (11') of a ladder Whose breast-side stringers are formed by guide bars 12 (12') of a mining apparatus which is not shown, and whose gob-side stringers 13 (13') serve for the hanging of a gob curtain 21. The props of frames A are marked 3 and those of frames B are marked 4.

Props

3 and 4 are mounted in prop sockets 5 and 5' which are associated with the beams 1 1') and are provided with lateral gussets 6 and 6' having apertures in which the rungs 11 and 11' are carried in a vertically displaceable manner. The rungs 11, 11', which are associated with the same beam, are in turn fastened together by

crossbars

14, 14. These crossbars 14 14', are engaged by the piston rods 15, of advancing cylinders whose

jackets

7, 7, marked 8, 8', in the case of frames B) are in turn fastened to the webs 2, 2', of the beams.

In the advancing period represented in FIG. 1, the props 3 of the frames A are set and pressure is delivered to the gob-side chambers of cylinder 7, 7', associated therewith. Props 4 of frames B, however, are either relieved of pressure or are held by light elastic pressure between the roof and the floor, and hydraulic pressure is delivered to the breast-side chambers of their associated cylinders 8, 8'. At the beginning and at the end of the advancing cycle, therefore, the frames A are in the same place, but the ladder Stringing together frames A and B has, by the end of the cycle, advanced one step laterally along the rungs of this ladder. In the next cycle, therefore, the frames B, which are now ahead of the frames A, are set, and pressure is delivered to the gob-side chambers of their associated cylinders 8, and to the breast-side chambers of cylinders 7 associated with the now release frames A. At the same time, each full stroke of the pressure cylinder 7 (8) can correspond to n strokes of a preceding metering cylinder, which is not shown, so that the tempo of the advancement of all frames A and B and the tempo of the advancement of the ladder can be made completely uniform.

If the roof beams of the ladder are provided with a vertical articulation, the associated rungs can also have an articulation. Besides, between the rungs of the ladder and the breast-side stringers 12, 12', of the ladder, it is desirable to provide a vertical articulation 16, 16', so as to make it possible to bring the guide bars 12, 12', provided for the mining apparatus, into the desired position for the advancement of the working face, using for that purpose a controlling means 17, which in the drawing appears only in the area of the roof beams. Similar articulations can be provided for joining the rungs to the gob-side ladder stringers 13, 13'. Also represented in the drawing is a coal shield 22 cooperating with a chute 23.

The breast-side stringers 12, 12', of the ladder are preferably in the form of a channel in which a winning apparatus can be guided. This channel is divided into sections 18, 18', which are joined together by vertical articulations 20. At the roof, these channel sections have portions 19 telescoping inside of them so that they can be lengthened and shortened to some extent. It is desirable not to leave the length of each such rail section 18-19 to arbitrary movement of the section in relation to one another, but to adjust such in a predetermined manner. Accordingly, the gob-side stringers 13, 13', are formed of extensible sections at the roof and of sections of constant length on the floor, which are joined together by vertical articulations. The cross-section of the breastside stringers, however, does not have to be that of a channel.

The individual channel or guide-bar sections have bearing surfaces against which springs 24, 25, rest, which in turn act upon bearing surfaces on the roof and floor beams 1, 1', so that they seek to displace the beams, and consequently the prop frames A or B with which they are associated, in an uphill direction along the breast. These springs are represented only diagrammatically, as are also the additional springs 26 which act 0n the rungs 11 of the ladder and urge such against the roof.

FIG. 4 shows, on a greatly reduced scale, longitudinally of the breast, in a purely diagrammatic manner, how the powered prop system advances when its breast-side stringers are used to guide a kerng and ripping chain. The solid line 31 shows the position of the guide bar 12 (i.e., its rear edge) at the beginning of the advancing cycle; the broken line 32 shows the position of the guide bar after it has been advanced one half step; solid line 33 shows the shape of the coal working face produced by the rippers at the beginning of the advancing 8 cycle, and broken line 34 shows the position of this working face after the prop system has been advanced by the amount stated.

While the prop system is advancing continuously and uniformly under the effect of the metering cylinder from line 31 to line 32, the rippers guided in channel 12 move continuously and uniformly in the direction of the arrow. At the beginning of the advancing cycle they are at

points

35 and 36, where the line 33 breaks to form a sawtooth. It is assumed that the depth of cut of each ripper (i.e., the height of each sawtooth) corresponds to a full step of the power prop system, as shown in FIG. l; it is furthermore assumed that there is such a coordination between the advancement of the power prop system and the movement of the rippers that the rippers, during one full step of the prop system, cover a distance that is the same as the distance between them, i.e., the distance between

points

35 and 36. After a half step of the power prop system, therefore, the rippers have covered half of this distance and have moved from point 35 to point 37 and from point 36 to point 38, while maintaining their distance from the channel 12 that is guiding them, so that the working face now has the shape indicated by the broken line 34.

FIGS. 5 and 6 offer a visualization of how the kerf preceding the working face is produced, from which the rippers supported at the roof and iloor by the flanges of

rails

12 and 12 respectively win the coal and advance the working face. There is shown a leading edge 41 of a guide rail or channel 12; the

rippers

45 and 46 carried on the guide rail; a working face 43 produced by these rippers; and kerfers 51 to 57 and 51' to 57' are disposed between the rippers. These kerfers are set, according to FIG. 5, immediately in front of ripper 46, and, according to FIG. 6, between the

rippers

45 and 46, 58 represents the depth of the kerf made by the kerfers, 59 designates the depth of the kerf after the power prop has advanced one full step and the kerfers have been moved on in the direction of the arrow by an amount corresponding to the space between the rippers. There are shown Scrapers 61 to 67 and 61' to 67 to which the kerfers 51 to 57 and 51 to 57', respectively, are fastened. The proiile of these Scrapers is designed in each case so as to cover the distance from the front edge of the rail 12, represented by line 41, to the working face represented by line 43. The system represented in FIG. 6 is somewhat different from the one shown in FIG. 5.

What is claimed is:

1. A traveling prop system for use with a mine working face comprising a succession of interconnected spaced prop containing frames, ladder means interconnecting such frames, loor beams under said frames, roof beams over said frames, rung means of said ladder means displaceably disposed on said floor beams and guided by said floor beams with respect to longitudinal displacement, and Stringer means of said ladder means disposed both in front of the front row of props and in back of the back row of props of said prop system.

2. A traveling prop system as claimed in claim 1 for use with a graded mine working face including predetermined down grade spacing of said frames.

3. A traveling prop system as claimed in claim 1, wherein said rung members have limited vertical displaceability.

4. A traveling prop system as claimed in claim 1 including second rung means operatively associated with said roof beams.

5. A traveling prop system as claimed in claim 1 including cylinder-piston drive means associated with each frame, wherein said cylinder is attached to said floor or room beams and said piston is attached to said ladder means.

6. A travelling prop system as claimed in claim 1 including cylinder-piston drive means associated with each frame, wherein said cylinder is attached to said ladder means and said piston is attached to said floor or roof beams.

7. A traveling prop system as claimed in claim 1, wherein said Stringer means of said ladder means disposed in front of the front row of props is a guide rail for mining apparatus.

8. A traveling prop system as claimed in claim 1, wherein said Stringer means of said ladder disposed behind the back row ofthe props is a gob curtain hanging rail.

9. A traveling prop system as claimed in claim 1, wherein said Stringer means are upwardly pivotable.

10. A traveling prop system as claimed in claim 4, wherein said second rung means have second stringer means associated therewith which are adjustable telescoping members. I

11. A traveling prop system as claimed in claim 4 including elastic members disposed between said second rung means and said roof beams.

12'. A traveling prop system as claimed in claim 4, wherein said roof beam width is substantially the same as the distance between adjacent rung means.

13, A traveling prop system as claimed in claim 1, including a kei-ling and ripping chain mining apparatus guided by said forward Stringer means.

14. A traveling prop system as claimed in claim 13, wherein the eiective width of said ripping apparatus is substantially equal to the stroke of cylinders associated with said frames.

15. A traveling prop system as claimed in claim 13, including substantially equally spaced ripper members on said chain.

16. A traveling prop system as claimed in claim 15, including metering means controlling the rate of extension of said cylinders and means for cycling said cylinder in substantially uniform time sequence, whereby a full stroke of said cylinder corresponding to n strokes of a cylinder in said metering means takes substantially the same time as the time it takes for said kerng and ripping apparatus to cover the distance between adjacent ripper members on said chain.

17. A traveling prop system as claimed in claim 14, including adjustable means adapted to limit the length of the excursion of a piston associated with said frames.

References Cited UNITED STATES PATENTS 3,362,169 1/ 1968 Groetschel 61--45 FOREIGN PATENTS 999,943 7/ 1965 Great Britain.

ERNEST R. PURSER, Primary Examiner U.S. Cl. X.R. 299--33; 61-45