US2757515A - Tunnel breasting jumbo - Google Patents

Description

Aug. W W56 L. n. WKLBUR ETAL TUNNEL BREASTING JUMBO 7 Sheets-Sheet 1 Filed Aug. 4, 1952 INVEN TORS 0. am mm IN M. M2; Arm/Wm Aug. R958 L, m. WILBUR ET AL TUNNEL BREASTING JUMBO 7 Sheets-Sheet 2 Filed. Aug. 4, 1952 gRR/TT MZQ/l ATTUH/VEV 1956 L. D. WILBUR ETAL TUNNEL BREASTING JUMBO 7 Sheets-Sheet 3' Filed Aug. 4, 1952 INVENTORS W! L HUI? MERE/7'7 M. MASON BY, w

LYMAN 0. )6 h 8.? 9 1956 L. D. WILBUR ETAL TUNNEL BREASTING JUMBO 7 Sheets-Sheet 4 INVENTORS LYMA/V D. W/LBUH Filed Aug. 4. 1952 A 7' TORNEY II... D. WHLBUR ETAXW TUNNEL BREASTING JUMBO 7 Shee'hsSheet 7 Filed Aug. 4, 1952 mw wm d wmw mm TUNNEL BREASTING J UMBO Lyman Dwight Wilbur, Boise, Idaho, and Merritt M. Mason, Richmond, Calif; said Mason assignor to Noble (3b., 'Uairiand, Calif, a corporation of California Application August 4, 1952, Serial No. 302,550

8 Claims. (Cl. 61-85) This invention relates to improvements in a hydraulic breast boarding jumbo for use in tunnel excavation.

The invention is primarily useful in ground too heavy and rocky for a shield and not solid enough to be stable without external support. The problem in this type of situation is to support the face of the core to be removed against caving while installing permanent steel supports and blocking, prior to pouring the usual concrete lining of the tunnel.

Heretofore it has been necessary to work slowly when removing the core in this type of a bore. One method in a large tunnel has been to make a plurality of passes through the tunnel removing only a small part of the core at a time. This was costly and time consuming because of the need for careful blocking of the roof over each core; the need for hand removal of excavated material to a point where machine carrying can pick it up; and because of the difficulty of placing the permanent steel supports for the roof of the tunnel.

The invention solves this problem by allowing miners to release the forwardly applied support from small areas and to remove the dirt in that small area, while maintaining the support on the balance of the core face. Then it permits extending the support into the small excavated area. This small area excavation is repeated for each of the forward supporting means. The plurality of forward pressure applying means are rams mounted on a movable car and the invention allows the whole car or jumbo structure to be moved forward without releasing pressure from the forwardly extended rams. Thus, when the forward rams have reached their maximum extended position, the car or jumbo on which the ram cylinders are carried can be moved forward by oppositely extending rams while still maintaining adequate pressure on the forward rams as they are forcibly pushed back into their respective retracted positions. From this point on, the operation is repetitive untilthe miners have again removed sumcient of the core from in front of each of the individual rams and installed overhead permanent steel supports in the advanced position.

Another problem solved by this structure relates to the placement of the permanent steel ribs or supports for the tunnel. With this device the ribs can be hoisted onto cars operating on rails extending along the entire length of the jumbo. On these cars the ribs are carried to the face of the bore and lifted into final position by means of hydraulically operated devices permanently installed on the cars. Prior to the development of this machine, the time required to place a set of steel ribs was about two hours. After use of this machine was begun, the operation of placing a set of steel ribs was reduced to 15 to 20 minutes. This is just one place in which time and labor has been cut by the invention.

Another important problem solved by the invention is in providing a series of working platforms for the miners as the core removal progresses. Heretofore timbers and scaffold had to be built for this purpose; whereas with the extension of the supporting rams on the front of the States Patent F 2,757,515 Patented Aug. 7, 1956 r ll jumbo, a perfect support for the miners can be provided at each digging level simply by laying planks across these extended rams.

Where the height of the tunnel is sufiicient to permit the use of a core supporting structure high in the bore, it is possible to use under the jumbo a mucking machine for removal of the broken material as it is removed from the face of the core.

Another advantage of the invention is that it has made possible speeding up the mining operation by the use of light shots of explosive to loosen material in the core. On the particular tunnel on which this invention was first used, the soft nature of the materials had made it exceedingly dangerous theretofore to use any explosive to speed up the work because it was impossible to control the caving and settlement of the ground above.

With the present invention the individual rams maintained a support on the face of the tunnel while these shots were exploded, thus preventing undue caving. The jacks held the loosened material until the miners were ready to remove it.

All of the foregoing advantages, plus the fact that the miners feel safe and have a nice place in which to work, has meant that the first tunneling operation on which the invention was used was speeded up approximately 400 percent. Whereas the bore was progressing at about 4 feet a day it increased to about 16 feet a day when the machine was placed in use.

Another advantage of the invention is the provision of means for mechanically locking all the rams in a position to maintain pressure on the face of the core independently of maintenance of hydraulic pressure in the rams, thus removing dangers incident to a shut down from a power failure, holidays, or from any other causes. The machine can be left indefinitely in a bore without any attendants as it would be in case of a strike.

It is therefore the object of this invention to provide a tunnel breasting jumbo having a plurality of individual forwardly extending pressure applying rams; to provide a movable unitary support for said rams; to provide a control system for said rams so they can be extended individually as the loosened core under each is removed; to provide a control system for said rams so they can be yieldably supported to maintain a predetermined sup porting force against the core face while the movable support is moved toward the core face thereby forcing said rams into their retracted position ready for another cycle of core removal; to provide a control system for said rams so each will move inwardly whenever the forward pressure medium is released; to provide means for positively locking said rams in any desired position independently of the maintenance of hydraulic pressure on the rams; to provide a support for each ram so that when extended it can serve as a horizontal support for floor planks for the miners as they loosen the core ahead of the rams; and to provide cars with lifting means atop the jumbo mounted on tracks running parallel with the tunnel bore and having extensible track means capable of projecting forwardly out over the extended pressure applying rams for lifting into place the permanent steel support Where the core has just been removed and of projecting rearwardly out over the rear end of the jumbo for receiving from the tunnel floor the steel support preparatory to carrying it forward on the jumbo for placement.

In summary, What the invention includes is a large unitary movable support means A, with a ram housing unit B having a plurality of individually movable forwardly extending pressure applying rams B on its front end, with a fluid pressure producing means C and a control system D for the rams on a platform usually amidship, with two or more individually movable rearwardly extending pressure applying rams E on each side for advancing the jumbo forwardly in the bore, and with cars F movable fore and aft along the top of the support A.

While, for the purpose of compliance with the Statute, the invention is shown in a'form proven to be practicable, it is not intended hereby to limit the invention to embodiment in this one form, except as may be required by the language of the appended Claims. Each element comprising the combination is capable of variation to express the choice of different engineers and some variation may be dictated by'the size of the tunnel in which it is to be used.

Reference will now be had to the illustrative embodiment called for by U. 8. Revised Statute 4888 and shown in the drawings which are mainly diagrammatic and in which Fig. l is a vertical longitudinal cross-sectional view of a tunnel bore taken on a 'line just inside the steel supporting beams on the side wall and showing in vertical elevation the tunnel jumbo with the forwardly extending pressure rams partly extended, and the beam carrying car carrying a steel beam toward the forward end of the jumbo;

Fig. 2 is a horizontal longitudinal cross-sectional view of a tunnel bore as if the top of the here were lifted off at about the line IIII-in Fig. 3, leaving the jumbo exposed in plan view;

'Fig. 3 is a cross-sectional view of the upper portion of the tunnel bore taken about on the line Illlll in 1, showing the frame in which the forwardly and rearwardly extending pressure rams are mounted on the front end of the jumbo;

Fig. 4 'isa view in plan of one of the forwardly extending pressure rams with the mechanical locking means in place as it would 'be if the jumbo were left unattended;

Fig. 5 is a cross-section view in vertical elevation showing the ram partially extended and the protective housing around it which also-serves as the arms for the scaffold to support the miners while digging;

Fig. 6 is a view in vertical elevation of the device of Fig. 4 showing the sockets to receive the mechanical locking means;

Fig. 7 is a view in cross section taken on the line VII--VII of Fig. -6;

Fig. 8 is a view in end elevation of the tote car showing the several tracks and the frame of the cantilever car in cross section;

Fig. 9 is a planview of the tote car showing it on the cantilever car; and

Fig. 10 is a diagrammatic layout of the control system for the pressure applying rams.

Referring now to the drawings the several units will be described in order.

The movable support means A The movable support means A is shown best in Figs. 1 and 2 and comprises the frame or support for all the parts which together constitute thetunnel breasting jumbo.

The support means itself is made up of a braced framework having the longitudinal members 10, 11 secured together by vertical upright members 12 and diagonal braces 13 with lateral bracing and floor supporting beams (not shown). Near its four corners are the legs 14 each having a wheel truck 15 secured at its lower end with flanged wheels 16 engaging the track rail 17 laid along each edge of the tunnel bore. The front of the support means has a vertical frame 18 with braces 19 to provide the anchor plate for the forwardly extending pressure applying jack assembly'B.

On top of the longitudinal members 11 are secured suitable floor joists 20 which in turn support a top flooring 21 and the rails 22 for the cantilever cars F. There are two such cars therefore ,four rails 22, as shown in Fig. 2. The rails 22 terminate at the front end of the frame B.

On the lower .of the longitudinal members 16 are secured floor joists (notashown which suport a floor for the 4 hydraulic power unit C, the control section D, and other miscellaneous equipment.

The ram housing Unit B This assembly is preferably made up as a separate unit and is hung on the front end of the support frame A, where it is bolted in place. The forwardly and rearwardly extending rams are preferably secured to this assembly so it can be made as rugged as needed Without being dependent on the support frame A for strength.

The ram housing unit B has provision for as many rams as the particular tunnel job requires. The one on which this invention was first used has 18 forwardly extending rearwardly extending rams. As shown in Figs. 1, 2, and 3, the frame of the ram housing unit B is made up of two sets of spaced apart horizontal channel members 23 joined together by like vertical members 24. Where each adjacent pair cross they form a rectangular space 25 on the vertical inside face of which a fore and aft extending channel 2.6 is secured with its legs facing out. These chan nels 26 extend between the forward and rear sets of channel members 23, 24. Cross braces '27 strengthen the ram housing frame so it can stand the pressures exerted by the rams when-in use. When viewed from the front, the frame has somewhat the appearance of a honeycomb with the rectangular spaces formed between the adjacent flat faces of each pair of channels 26 comprising a cell 28. A plate 2.9 closes the back side'of each cell and has legs 30 with a hole 31 adapted to receive a bolt (not shown) by which the ram unit B is secured to the front of the support means A. (See Fig. 4 and broken away portion in Fig. 1.) To add strength to the ram housing unit in the region where the rearwardly acting rams exert their force several I beams 33 may be secured.

All of the forward rams are identical and one is shown in detail in Figs. 4 to 7. The housings for the top two rams are pivoted at 34 to the frame B and are adjustably supported at 35 in the extensions 36. The housings are like the rigid ones which will now be described and which were referred to earlier as the cells 28.

The sliding ram housings 37 In each cell 28 is slidably mounted a sliding ram housing 37 which has several important functions. It provides for the ram rod 38 and ram cylinder 39 a protection from injury by .grit, .or boulders which are ever present. It provides a horizontal support 40 right at the work zone on which the miners can place temporary flooring 41, and the guide plates 42 and 43 extending out over the side channels 26 keep all strain from being put on the ram rod 38, as the plates support the back end of the sliding ram housing and .its forward end is supported on the lower channel 23 of the cell opening 28. It also provides a member having a plurality of bayonet openings 44 to receive the lug 45 on the jack flange 46 for the mechanical looking screw jack 47 with its tightening nut 48. It also provides a rugged mounting for the toggle fitting 49 by which the pressure plate 50 is secured to the ram. The inside end 51 of the toggle fitting is pinned at 52 to the end of the ram rod 38. The ram cylinder is pinned at 53 to afiange 54 on .the back plate 2? of each cell 28. The ram cylinder has an inlet 55 at one end and an inlet 56 at the other end so the piston 57 can be moved in either direction. .A suitable packing is provided around the .ram rod 38 at the end 3% of the cylinder.

Another functionperformed by the sliding ram housing 37 is in providing a stop to limit its outward movement. This is performed in the device described by the plate 42 whose edge 58 will engage the upper frame member 23 when the full ram stroke is reached.

As shown in Fig. 7, the sliding ram housing 37 is made up of two channels 59, .60 with the longitudinally extending plates 61, 62 welded to the channel legs to form a rectangular box-like housing. Its inner end at 63 is open and its outer end is closed by the plate 64.

The advancing and holding rams E The functions performed by these rams, of which there are preferably two on each side of the machine, are several. They provide the backing up or holding support needed for the ram housing unit B with the individual forwardly extending rams as the core removal goes on. They must have a capacity so that when all the forward rams have been extended as the core is removed from in front of each ram, they can advance the whole jumbo forward on its tracks 17 and cause the forward rams 37 (which are still supporting the core) to be pushed back into their respective cylinders without letting up on the core supporting pressure. The hydraulic system for the forward rams has a relief valve set at a lower pressure than the pressure in the advancing rams E so that when the push from the latter exceeds the relief valve setting, the hydraulic fluid will be forced out from behind each piston 57 and the jumbo will move up to the core to start another core removal cycle. By having at least a pair of the advancing and holding rams E on each side of the jumbo, the load can be taken by one ram while the other is drawn in and takes a new purchase on the Whalers 65 supported along the steel ribs 66 of the tunnel.

As shown in Figs. 1 and 2, the upper rams 67 of the advancing and holding rains E are pivotally secured at 63, while the lower rams 69 are similarly secured at 70 both to the back side of the ram housing unit B. Brackets '71 and 72 extend outwardly from the forward legs 14 on the frame A to support the ram E in a generally horizontal position. These rams differ from those previously described in that here the cylinder is pivoted to the support and the ram rod 73 has a blunt nose 74 which engages directly with the whaler 65'. A boot 75 keeps dirt from the ram rod. Fluid pressure is introduced either at 76 or 77 in each cylinder. A working platform 97 is provided for the operator working with these rams.

The rate and cantilever track cars F One of the time saving advantages from this invention arises from the provision for picking up sections of the steel crown rib 73 at the back end of the jumbo and being able to carry it beyond the forward end of the jumbo (Where the support rams 3'7 are holding the core until the crown rib can be put into place), and then lifting the crown rib into place. On a jumbo of the size shown, it is preferable to have twin tote cars 79 and that necessitates a cantilever track car 00 for each. They are identical in construction except that when set on their tracks one has its jack set opposite to the other. Only one will be described in reference especially to Figs. 8 and 9.

The tote cars 79 These cars have a frame 81 supported on four flanged wheels 82 journaled along the side of frame 81 and adapted to run on the flanged cantilever track 83 on the cantilever car 50. A lifting arm 34 has a suitable crown rib support 855 at one end and it is pivoted at its other end 86 to the side frame member 87. The arm 84 is lifted and lowered by the hydraulic jack 88 pivoted at 89 to the arm and at 90 to the other side frame member. The tote cars are moved along the cantilever tracks 83 by the workman as they roll easily even when the crown rib is being carried by the two tote cars.

The cantilever cars 80 These cars provide an extended cantilever track 83 for the tote cars when at the core end of the jumbo and preferably when at the rear end of the jumbo, because the track 22 terminates at the rear end of the main support frame A and extends only to the forward end of the frame B. With the cantilever track 83, the tote car can be wheeled up close enough to the core that the crown rib can be lifted into place with a minimum of physical exertion by the operators.

The cantilever car 80 has a frame 91, 92 with the flanged wheels 93 journaled therein at a gauge to fit the rails 22 secured along the top of the jumbo support frames A and B. The upper frame 92 extends beyond each of the cross members 94 and on its inside has the rails or cantilever track 83 on which the tote car runs. The length of the cantilever track is determined by the distance the tote car has to travel beyond the end of the rails 22 to receive the crown rib from the hoist, and at the other end to carry the crown rib into position at the roof of the bore. The under side of the cantilever car frame 92 has near each end a cross member 95 with arms 96 and pads 97a which extend under the flange of each rail 22 so that when the tote car runs out on the rails 03 the arms 96 will support the rails in a substantially horizontal position.

The cantilever cars may be moved along the rails 22 by manpower or by motor power.

The control system From the foregoing description it should be clear that the core supporting rams 39 and the advancing and holding rams 67, 69 must be controlled in a particular relationship in order to gain the advantages possible with this invention. Reviewed briefly, this relationship calls for the following:

1. Controls on the hydraulic circuit to each of the sup porting rams 39 so each can be moved independently by hydraulic pressure in either direction;

2. A control on the hydraulic circuit to the supporting rams 39 which will permit the rams to be pushed back into their cells 28 while they retain their full supporting pressure on the core face, as the advancing rams 6'7, 69 move the jumbo toward the core face; and

3. Controls for moving the advancing rams 67, 69.

One form which such controls might take is shown diagrammatically in Fig. 10 where for the purpose of clarity only four core supporting rams 39 are shown and only two of the advancing rams 67, 69 are shown. Also, only one control valve circuit is shown to one ram 39 and one control valve circuit to one advancing ram 67. These are suflicient to give a clear idea of how the complete device is controlled.

The low pressure system This system operates at about 150# pressure and is continuouslyconnected to the fitting 56 on the ram end of each supporting ram 39 and the fitting 77 on each advancing ram 67, 69, so these rams are floating on the line. The only control is the relief valve 109 set at about 175# and located between the low pressure manifold 101 and the return line 102 which brings the oil back to the reservoir 103. The low pressure oil system is kept supplied by the line 104 which bleeds off the high pres sure line 105 through the pressure regulator 106. In the control system the low pressure maintained on the ram end of each ram 39, 67, 69 effects an inward movement of the ram whenever its control valve 107, 101i is placed in its open position so the high pressure fluid is disconnected from the piston end 55, 76 of the ram and the fluid in the ram is released so it flows through pipe 109, back to the oil reservoir 103. This means great simplification because no separate control valve is needed to return each ram inwardly. The low pressure fluid is always there waiting to act when the operator places either lever 107a or 108a in the open position for the valve 107 or 108.

The high pressure system This system operates preferably at about 1200# pressure and is supplied from suitable compressors 111, 112 and reservoir 103 with accumulators 113,. 114, 115 to make up for any leaks and to absorb any shocks in the line 105. Suitable check valves 116 and needle valves 117 are provided where needed. The high pressure mani fold 105 leads to the fitting 55 on the piston end of each supporting ram 39, with a valve 107 interposed between the manifold 105 and each ram 39. Only one of these valves is shown in Fig. 10. In each pipe 118 between each valve 107 and each ram 39 is a relief valve 119 set at about 700# pressure, with its outlet 120 connected back to the reservoir 103. The high pressure line 105 also leads to the fitting 76 on the piston end of each advancing ram 67, 69, with a valve 108 interposed between the manifold 105 and each ram 67, 69. There is no relief valve in these lines 121 to the rams 67, 69 because it is necessary to introduce suflicient fluid pressure in these rams to move the whole jumbo toward the core face against the resistance of the 700$; pressure in the supporting rams 39.

The valves 107, 108 each have a lever 107a, 108a respectively in convenient reach of the operator on the con trol panel D, so the valve can be moved into either of its three positions. In the up position the valve 107 connects the high pressure manifold 105 with the line 118 leading to the piston end of the ram 39. It is in this position that the operator places the valve when the miners have completed the core removal in the area ahead of a particular supporting ram 39. This causes the ram to move forward against the new core face, simultaneously emptying fluid from the ram side of the ram cylinder through the relief valve 100 set at 17'5#. The operator may leave the valve 107 in this position until it is time to advance the jumbo toward the core face, when it is preferable to move it to its middle position.

In the middle position (full line in Fig. 10), the valve closes the connection between the :high pressure manifold 105 and the ram 39. This leaves the ram 39 still under pressure at or near the pressure in the manifold 105, but no longer connected to the manifold. When the jumbo is advanced by the rams 67, 69, the pressure fluid escapes from the relief valves 119 at about 700.# pressure, thus maintaining a full supporting pressure on the core face as the rams 38 are pushed back into their cylinders 39. The better practice is not to advance the jumbo so close to the core face that the supporting rams are pushed completely to the bottoms of their respective cylinders.

The down position of the valve 107 closes off the high pressure manifold 105 from the ram inlet 55 and connects the piston end of the ram with the fluid return line 109 in which there is no pressure to speak of. This allows the pressure fluid (about 150#) acting on the ram end of the ram 38 to move the ram into its full depth in the cylinder 39, thereby withdrawing the ram supporting face 50 from the cor face directly before it, so the miners can remove the core in that localarea. As soon as the core in that area is removed for a depth at which the extended ram 38 will be able to reach conveniently, the miners get out of the way and the operator moves the valve lever 107a into its upper position. This puts the high vpressure on the piston side of the ram which moves the ram 38 outwardly against the resistance of the 1504i pressure on the ram side of the cylinder. This latter fluid escapes through the relief valve 100 and gives the ram 38 a smooth deliberate stroke as it moves toward and into contact with the new core face. The operator manipulates the valves 107 oneat a time until the.. I iners out front have removed the .core face around each supporting ram face 50.

A valve 108 is provided for controlling each advancing ram 67, 69 and this valve is similar to the ones just described. When the jumbo is ready to be advanced, the operator actuates the valves 108 to introduce the high pressure fluid medium to the piston end 76 of the rams 67, 69. When the jumbo'has moved forward, as explained above, these rams 67,69 stilli'have a holding function to perform so sufiicient pressure is kept in at least one ram 67, 69 on each side to resist the thrust ofthe supporting rams 39 Which-if not resisted-will push the jumbo back away from the core-face. The operator needs to prepare the advancing rams;.67, 69,forthe ne xt forward movement of the jumbo and he does this on one ram at a time by moving its valve handle 108a into its lower position where the high pressure fluid is cut off and the low pressure fluid on the ram side of the cylinder 67, 69 moves the ram 73 into the cylinder. The operator places the end 74 of the ram against the nearest Whaler 65 and then actuates the valve 108 to introduce enough pressure on the ram 67, 69 to bring it into holding strength, but not so much pressure as to overcome the supporting rams 39 and advance the urnbo prematurely.

Globe valves 123 may be provided to close the fluid lines to each ram, but they play no part in the normal operating cycle above described.

Any suitable method may be used for obtaining an adequate source of fluid under pressure. In Fig. 10, the pump 111 is a high volume low pressure pump with an unloader 124 which cuts off this pump when it gets the fluid up to 500# pressure. The pump 112 is a low volume high pressure pump which maintains about 1200# pressure on the high pressure line. It is equipped with a relief pilot unloader 125 to unload the pump motor when the pressure gets up to 1200#. These are well known pieces of equipment and require no further description.

When it is necessary for the work to stop, whether because of a holiday, a strike, or other reason, the crew puts in place the screw jacks 47 (see Fig. 4) on each of the rams 38 and adjacent the rams 67, 69 so that there is no fluid pressure being employed to maintain the status quo. This means no attendant need be left on duty which is a substantial economy for the contractor.

To those skilled in the art to which this invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the spirit and scope of the invention. The disclosures and the description herein are purely illustrative and are not intended to be in any sense limiting.

We claim:

1. In a tunnel breasting jumbo for supporting the core face during boring of a tunnel the combination of a frame movable horizontally in relation to the tunnel bore; a plurality of spaced apart forwardly extending individually extensible and retractable pressure rams secured on the forward end of said frame, adapted to engage the core to be removed from the tunnel; a plurality of rearwardly extending pressure rams secured to said frame, adapted to engage the walls of said tunnel to hold and to advance said frame horizontally in said tunnel; control means for moving all of said rams selectively in either direction, said means including pressure release mechanism associated with each of the forwardly extended rams and actuated by a rise in fluid pressure when the forward movement of said frame is produced by said rearwardly extending pressure rams, whereby the pressure on the forwardly extending rams on the core face will be preserved during forward movement of said jumbo.

said pressure applyingmeans to move each one forward independently of the others; return means operative on all of said forward pressure applying means to move each one backward whenever its forward movement control means is inactivated; a pressure sensitive control on said forward control means whereby said forward pressure applying means will retain a supporting pressure on the bore as they are pushed into a retracted position as said frame is moved forwardly; and a plurality of rearward pressure applying means, projecting rearwardly from said frame, and means for energizing said last named means to apply a holding and a moving pressure on said frame.

3. The device of claim 2 it: which each of said forward pressure applying means includes a ram, a supporting housing surrounding said ram and secured to its forward movable part for movement therewith, and a guide in said frame in which said housing slides.

4. In a tunnel-digging support mechanism, the combination of a frame slidable in a horizontal plane; a plurality of forward pressure-applying means, secured to and projecting forwardly from said frame, each said means comprising a ram having a cylinder, a piston movable therein, and a rod secured to said piston, a supporting housing surrounding said ram and secured to said rod for movement therewith, and a guide in said frame in which said housing slides; a pressure-sensitive control on said forward pressure-applying means whereby said forward pressure-applying means will exert a substantially uniform forward pressure while being pushed into a retracted position as said frame is moved forwardly; a plurality of rearward pressure-applying means secured to and projecting rearwardly from said frame and adapted to move said frame forwardly; and means for energizing each of said rearward pressure-applying means i11- dependently of each other.

5. In a tunnel breastboard jumbo, the combination of a main frame, slidable in a horizontal fore-and-aft plane; a plurality of forwardly projecting hydraulic rams secured to the forward end of said frame, each ram having a housing enclosing and supporting the working end of its associated ram, and a second frame in which the housing is slidably supported and to which the non-working end of each ram is connected; pressure-sensitive control means for separately energizing each of said rams and for deenergizing each of said rams to a predetermined pressure when said main frame is being moved forward; rearwardly projecting hydraulic rams secured to said main frame; and control means for energizing said rearwardly projecting rams to move said frame forward while simultaneously forcing said forwardly projecting rams into a retracted position.

6. In a tunnel breastboard jumbo for supporting the core face, the combination of a frame, slidable in a horizontal fore and aft plane; a plurality of forwardly projecting hydraulic rams secured to the forward end of said frame; control means for separately energizing each of said rams and moving it forward relative to said frame against the core face; control means permitting backward movement of said rams relative to said frame while maintaining a predetermined pressure in each ram, to support said core face when said frame is being moved forward; rearwardly projecting hydraulic rams secured to said frame; and control means for energizing said rearwardly projecting rams to move said frame forward while simultaneously forcing said forwardly projecting rams into their retracted position without. loss of support for the core face.

7. In a tunnel breastboard jumbo, the combination of a movable frame; a plurality of forwardly projecting hydraulic rams secured to the forward end of said frame; rearward-ly projecting hydraulic rams secured to said frame; first pressure-sensitive control means for separately energizing each of said forwardly projecting rams; second pressure-sensitive control means energizing said rearwardly projecting rams at a greater pressure than that to which said first means energize said forwardly projecting rams; and pressure-sensitive control means for relieving said forwardly projecting rams of pressure exceeding a predetermined amount, so as to move said frame forward while simultaneously forcing said forwardly projecting rams into a retracted position without decreasing their outward supporting thrust.

8. In a tunnel-digging support mechanism, the combination of a frame slidable in a horizontal plane; a plurality of forward pressure-applying means, secured to and projecting forwardly from said frame; pressure-sensitive control means on said forward pressure-applying means for holding said forward pressure-applying means at a substantially uniform forward pressure while they are retracted relative to said frame as said frame is moved forwardly; a plurality of rearward pressure-applying means secured to and projecting rearwardly from said frame and adapted to move said frame forwardly; and

means for energizing said rearward pressure-applying means to a pressure level greater than the holding pressure of said forward pressure-applying rams.

References Cited in the file of this patent UNITED STATES PATENTS 724,666 Cooper Apr. 7, 1903 1,355,290 Updegrafif Oct. 12, 1920 FOREIGN PATENTS 12,575 Great Britain 1894 79,592 Germany Apr. 2, 1895 810,151 Germany Aug. 6, 1951 658,998 Great Britain Oct. 17, 1951

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