US2657028A

US2657028A - Walking jack

Info

Publication number: US2657028A
Authority: US
Inventors: Joseph F Joy
Original assignee: Joy Manufacturing Co
Current assignee: Joy Manufacturing Co
Priority date: 1949-06-15
Filing date: 1949-06-15
Publication date: 1953-10-27
Anticipated expiration: 1970-10-27

Description

J. F. JOY

WALKING JACK oct. 27, 1953 7 Sheets-Sheet l Filed June l5, 1949 7 Sheets-Sheet 2 J. F. JOY

WALKING JACK VMT...

Oct. 27, 1953 Filed June l5, 1949 J. F. JOY

WALKING JACK Oct. 27, 1953 7 Sheets-Sheet 5 Filed June l5 1949 mw, R, wm,

J. F. JOY

WALKING JACK Oct. 27, 1953 '7 Sheets-Sheet 4 Filed June l5, 1949 IQAW J. F. JOY 2,657,028

WALKING JACK Oct. 27, 1953 Filed June l5, 1949 7 Sheets-Sheet 5 hay V f5 /2 Eig. Il.

im @l \\4 v 1/34 iiiiii [Wzzfor: fos @p22 eil/oy,

Oct. 27, 1953 J. F. .JOY 2,657,028

WALKING JACK Filed June l5, 1949 7 Sheets-Sheet 6 ligJ/. 2,513.

Qs.. Ml

Illllll I 2 "N/ fofagne ,4.14.9 4 WIM/mc.

ZZorz ey.

J, F. JOY

WALKING JACK Oct. 27, 1953 'r sheets-sheet 7 Filed June 15, 1949 kwa.

Patented Oct. 27, 1953 2,5'z,ozs

WALKING JACK Joseph F. Joy, Pittsbur Manufacturing Corn gh, Pa., assignor to Joy pany, Pittsburgh, Pa., a

corporation of Pennsylvania Application June 15, 1949, Serial No. 99,292

10 Claims. (C1. 262--1) This invention relates to apparatus for mine roof control. y p

Rooi control is one of the most troublesome and expensive items in mining. This is so because of the expense oi the materials which have.`

customarily been used and because so large a percentage of the materials employed is lost as a result of roof subsidence as the Working face advances. The large amount of labor involved in building cribs, setting timbers, etc., also adds.`

to the expense. Accordingly, if there be provided an effective rapidly adjustable means for roof control-one that is relatively secure against loss of its elements and which has a comparatively long lifeit will be highly desirable, and this:

will be so whether or not such devices be employed with long or short faces. In this application, I shall disclose, describe and claim an improved roof control arrangement which marks a substantial improvement over prior devices of` this character, in that there Will be not only a roof support by devices which may yield under increased roof pressure but which shall further have the characteristic of being capable of having their pressure upon the roof diminished during repositioning without the necessity for the release oi any fluid from them.

An object of my invention is to provide an improved and dependable means resisting the closling of the gap caused in the strata of the earth by the removal of certain layers thereof, such as coal seams or the like, such resistance being maintained for the full length of time to permit the effective mining of such layers. An-

other objeet is to provide an improved roof supporting structure for yieldably sustaining the pressure of the roof and adapted to have the pressure exerted between the roof and the floor diminished when adjustment or Walking of the roof supporting structure is to be accomplished,

this without releasing any of the fluid medium4 with which the roof supporting structure may have expansible chambers thereof lied. Still another object is to provide improved mechanically actuated structures for the control of mine;`

roofs which support the roof close up to the face along the roof line, but which have the jack devices ivhich. form a part thereof spaced far enough back from the face to permit efficient operation of coal producing apparatus. object of my invention is to provide an improved method of mine roof control. It is a further object to provide an improved roof jack mechanism. Another object is to provide an improved :roof jack mechanism which shall facilitate jack` Anetherv adjustment, through a temporary reduction in the force With which the mechanism engages the mine roof, but Without the dissipation of any part of the force in such a manner that in the event of a sudden subsidence of the roof there would be an inadequate-reduced-force for sustaining the roof pressure. Still a further object of my invention is to provide an improved roof jack mechanism or the hydraulic type having incorporated therein means for providing for a limited degree of yield without venting of hydraulic iluid, and in which there may be an actual reduction in the pressure exerted by the jack mechanism on the roof Without a corresponding reduction in the force which the jack mechanism is constantly ready to exert at any given elevation. Yet a further object is to provide an improved roof control system having the advantages of resilient yielding through the concurrent use of a trapped body of gaseous fluid and a hydraulic iluid, together with the advantage of an over-riding control without the release of either the gaseous or hydraulic fluids. A further object of the invention is to provide an im- 25 proved roof jack mechanism in which mechanical i the event of even a slight subsidence of the roof the full roof supporting pressure. Another object is to provide an improved roof jack structure having an improved roof engaging and supporting skid structure fully protecting underlying working parts. Still another object is to provide an improved jack mechanism including improved means for overcoming, Without releasing, the resilient pressure exerted on the roof during roof support. Still another object is to provide an improved roof jack mechanism having a combination of toggle mechanism and pressure fluid operated mechanism arranged between upper, roofand lower, Hoor-engaging elements, with improved means for enabling the toggle mechanism to overcome the fluid operated mechanism. Still a further object is to provide an improved roof jack mechanism having improved means for adapting it to different roof heights. Still another object of the invention is to provide improved means for controlling the jacks of a. roof parture from parallelism of its roof and floor purposes of illustration l have shown one embodiment which my invention may assume in practice,

Fig. l is a horizontal sectional view through a mine adjacent to a longwall working face, showing illustrative embodiments of the invention from its apparatus aspect in use.

Fig. 2 is an enlarged sectional view on a Vertical plane corresponding to the plane of the section line 2-2 of Fig. l.

Fig. 3 is illustrative embodiment of my improved roof jack structure.

Fig. 4 is a side elevational view of the structure of Fig. 3.

Fig. 5 is a view corresponding to Fig. Ll, showing the roof supports at the conclusion of one step of advance of the floor and roof engaging support elements.

Fig. 6 is a vertical transverse section on the plane of the line fi-t of Fig. 5, the parts being shown on a still larger scale.

Fig. 7 is a detail View, with parts broken away, showing one of the toggle mechanisms, with provision for adjustment incorporated therein.

Fig. 8 section line 8-3 of Fig. 4, parts being shown on an enlarged scale and some parts being shown in full.

Fig. 9 is a further enlarged fragmentary sectional view on the plane of the section line 9-9 35 of Fig. 8.

Fig. l0 is a plan View on a considerably enlarged scale of a control valve mechanism.

Fig. 1l is a vertical section through the control valve mechanism of Fig. 10, the section being taken on the plane of the line II-II of Fig. 10.

Fig. l2 is a vertical transverse section on the plane of the line IZ-i 2 of Fig. ll.

Fig. 13 is an elevational View of the control valve mechanism of Fig. 10, viewed from the 45 right-hand end thereof.

Fig. la is a fragmentary sectional view in the same plane as Fig. 11 showing a distributing valve forming a portion of the valve mechanism moved to a different position from the one shown 50 in Fig. 1l.

Fig. l5 is a partly diagrammatic View, with parts shown in section, illustrating the hydraulic system of the roof jack mechanism.

Referring now brieily, initially, to Fig. l, it will 65 be noted that a longitudinal face is indicated at l. This includes a portion IA which has been advanced one operation width X of a mining machine 2 beyond the portion IB which still remains to be mined out and advanced to a position in line with the portion IA. The mining machine 2 may obviously assume various forms, and as shown has suitable mechanism 3 for disintegrating the mineral, herein, coal. The vface I has at its opposite ends spaces G and 5, and roadways 6 provided for ventilation and coal removal communicate with these spaces, which are really the ends of the roadways. These roadways have been driven to the limits of the area to be mined out,

and are arranged between the ribs of a large .m unmined block of coal 'I and side walls 8. The roof is indicated at e as having been caved'for the full width of the distance between the side walls or ribs 3. A conveyor I3 herein shown as a a further enlarged plan View of an 15 is a horizontal section on the plane of forms, extends for the full width of the portion of the face which has been advanced, and its length is progressively increased by one section each time the face is extended by an amount equal to the distance between the center lines of Ithe roof jack mechanism I which provide roof support between the face and the caved portion of the roof. The conveyor I discharges onto a conveyor herein shown as a belt conveyor I2 which extends out through the roadway B. The conveyor I0 may be driven by a suitable drive mechanism I3 of conventional form and is made up of sections I4 of appropriate length, say, 8', new ones of which may be quickly attached to .the ends of the conveyor line as the disintegrating apparatus progresses along the face. Roof subsidence along the face is prevented by the improved roof jack mechanisms of this application, which are herein designated II as above noted, and these roof jack mechanisms by their construction and spacing are adapted to hold the roof from caving, except in the manner and to the extent desired.

Now referring initially particularly to Figs. 3 and 4, it will be observed that the apparatus shown includes an upper, roof load-sustaining support element 2l and spaced parallel mine bottom engaging support elements or skids 22, an anchor jack mechanism 23, front and rear roof load-sustaining

jack structures

24 and 25, herein two of each, expansible chamber means 26 for effecting repositioning of the

jack structures

24 and 25 relative to the anchor jack 23 and vice versa, and means generally designated 2I for at least partially relieving the roof of the pressure of .the roof support 2| as adjustment of the roof support relative to the anchor jack 23 is effected. The roof engaging structure 2l consists of a relatively wide plate structure 3I considerably longer than its width and having a short downturned end 32, to make its advance smoother, and a considerably longer, more steep-ly downturned end or skid-like portion 33 at its rear end. This plate Structure is relatively rectangular in proj ection on a horizontal plane, save that there isa slot 35 formed in it at its rearward end of suitable width for the projection through it of the anchor jack 23 and of such length as to accommodate the relative movements between the anchor jack and the roof engaging member 2l. The plate 3i is stiifened by laterally spaced members 36 extending for substantially the full length of the plate 3l and having secured to their lower edges plate elements 3l extending longitudinally beneath and in spaced relation to the plate 3I and connected at 38 to the downwardly directed nose 32 and at 39 to the lower end of the most steeply downwardly directly skidlike portion 33.

The lower support structure 22 includes H- beamlke members 4I as it were lying on their sides and having lower horizontal ilanges 42 provided with upturned ends 43 and also provided with relatively horizontal upper flange portions 44 parallel to the portions 32. The members 4I are cross connected to each other by cross shaft portions 45 and 43, and at their front ends the members 22 each carry a forwardly projecting bracket lil, each bracket rotatably supporting a guide roller48 for a shaker conveyor trough section 49. Rigidly secured to each of the spaced sideomembers of the iloor support base portion of the walking jack structure, adjacent the opposite ends of each of the latter, are the jack devices shaker conveyor, but which may assume various 24 and 257 the former arranged near the front end of the supports and the latter near the rear ends thereof. These jack devices include fixed cylinder elements 50 in which tubular piston elements are reciprocable. Each piston element is of the trunk type, as illustrated, and the piston elements of the jack devices 24 each have a pivotal connection at 52 with a perforated ear 53 secured to the anges 3l at points approximately midway between the ends of the roof engaging support structure 2 I. The rearward jacks 25 simply have suitably domed tops 55 engaging the surfaces of the flanges 3'| near` the downwardly inclined portions 39 thereof, as at 56. The pistons 5| are packed in any suitable manner (not shown) so as to prevent the escape of fluid around them from the bores of the cylinders 50.

The anchor jack 23 includes a vertical cylinder E0 mounted on a skid 6| shown as made up of channel irons 62 having their flanges extending longitudinally of the jack mechanism. The cylinder 60 has a piston 63 reciprocable in it. This piston is a so-called trunk type piston also, and at its top engages an enlarged roof supporting plate E@ having a serrated top 65 adapted to be pressed into non-skid relation with the mine roof. Upward movement of the piston 63 in the cylinder 60 causes the anchor jack to provide a rigid abutment against which a thrust can be exerted for the purpose of advancing the floor and

roof engaging elements

22 and 2| and the

several jack devices

24 and 25. On the other hand, relief of pressure from the cylinder 50 will permit the anchor jack to be moved forward readily relative to the structure which has been previously advanced with respect to it. The walking jack 26 is supported through the piston portion thereof on a clamping sleeve 'l0 which is secured as at 1| about the upper end of the cylinder 60. The clamping' sleeve carries a socket providing lug l2, in the socket 13 of which the piston rod T4 of the walking jack piston 'l5 is fixedly secured. The cylinder 'I6 of the walking jack receives the piston 'f5 in its bore and the cylinder 'I6 is reciprocable relative to the piston 15 under the action of hydraulic fluid admitted to the opposite ends of the cylinder through conduits, respectively numbered i8 and T9, conduit 13 leading Ito the rearward end of the cylinder 16 and the conduit "is to its forward end. The cylinder 16 has forward and rearward heads, as best shown in Figs. 4, 5 and 8. The forward head 80 has projecting arms 8| between which a cross pin 82 extends, and the adjacent ends of toggle links 83 and Se are connected to the pin 82. The end of link 83 is made in the form of a fork element which is connected by a screw 85 with a tubular internally threaded element 86 carrying a sleeve ill iournaled on the cross shaft or bar 45. The

4end of link 34 is connected by a threaded element E33 with an internally threaded tubular element $0 which is connected to a sleeve 9| which is iournaled on a forward cross shaft 92 extending between the iianges 36. The rear head of the walking jack cylinder has projecting lateral ears i0! in which adjusting screws |02 are arranged. These are adapted to engage head elements |03 connected by threaded rods |015 to tubular internally threaded elements |05 which are pivotally supported on the cross shaft or bar 4S. The members H23 are each connected by cross pins i H5 to forked end members which are connested by threaded elements H2 with internally threaded elements H3, and the two internally threaded elements 3 are connected at their upper ends by collars ||4 to a cross shaft l|5 `extending between the flanges 36 at a point adjustability and nearer the rear ends thereof. By having the cross pin 82 directly fastened to the cylinder head B0 but having adjustment of the effective length of the adjusting screws |02 a possibility, it will be appreciated that absolute parallelism of the roof engaging member 2| and of the floor engaging member 22 is not requisite, and that if the adjusting screws |02 are screwed outwardly in their supporting ears, that is, to the left i'n Fig. 8, there may be a somewhat greater distance between the most remote surfaces of the door and roof engaging members at points in line with the axes of the yjacks 25 than exists between points in these members in line with the axes of the jacks 24. C'orrespondingly, by turning the screws |02 further forwardly through their supporting ears, there may be a convergence of the top and bottom surfaces of the jack mechanism toward the rear. Normally, however, when the arms of the toggle mechanism are parallel to each other the screws |02 will be slightly out of contact with the end members |03, with the result that, as the walking jack cylinder l5 moves forwardly in a manner hereinafter described, the pressure applied by the roof jack elements 24 will be diminished somewhat before the pressure exerted by the roof jacks 25 commences to be overcome.

Before describing the system in more detail, the modification of a toggle mechanism shown in Fig. 7 may be noted. Here it will be noted that a hand wheel controlled turnbuckle 6 is arranged between the head element |03 and pivot members Ill rotatably supported by the cross shaft A6, and a hand wheel controlled turnbuckle I8 is arranged between the forked end members Ill' and the collars H4 mounted on the cross shaft H5. Similar arrangements may be provided for the other rear toggle device, or for al1 of the toggle devices, thus providing for greater greater relative adjustability between the elements 2| and 22.

The system for the operation of the several jacks mentioned can best be understood by refi storage tank |20 through a conduit |2|.

or it could be used for erence to Figs. 8, 9 and 15, `and a principal con` trolling valve structure forming a portion of the system is shown in the several figures numbered l0, ll, l2, i3 and le. The fluid for the extension of the several roof jacks and of the anchor jack and for the effecting of relative extension and collapse of the walking `jack is supplied from the This conduit |2| communicates with a connection |23 in which a hand operated pump |24 having a built-in relief valve is provided. It will be appreciated that the hand pump |24, which is of a wellknown commercial type, may be used vto effect the pumping of fluid from the storage tank |20, pumping fluid back into the storage tank |20. The hand pump has a conduit |25 at its opposite side from the conduit |23, and this conduit enters a valve block |26 at |21, and communicates with a port |28 therein. The port |28 extends into a larger passage |29, shown in Figs. 11, l2 and 14 as extending vertically. There also communicates with the passage |29 a passage |30, this being in line with the passage |28, as illustrated, and having in communication with it a conduit |3| which constitutes a discharge connection from a motor driven pump |32 whose driving motor |33 may be mounted in any suitable position on the apparatus, as, for ex ample, on one of the door-engaging structures 22. This pump too will have a built-in adjustable relief valve (not shown). The suction line |34 el! ltl'iepump 132 Vopens into a generally U-shaped passage 135 extending transversely of the valve vblock 126 near the top of the latter, and a conduit 131, also communicating with the cross passage 135, is connected with the tank through the conduit 121. At the lower end of the vertical passage 129, previously mentioned, there is provided a transversely lextending passage 140 surrounded by a valve seat 141 on which valve seat va manually adjustable valve 142 having a controlling hand wheel 143 is adapted to seat. When the valve 1-42 is opened, rluid may pass freely between the passage 129 and a conduit 144 which is connected by a branch conduit 145 with one of the rear jacks 25, and through Va branch conduit 146 with another conduit 141 leading to one of the front jacks 24, and through Aa conduit 148 and

branch conduits

149 and 150 respectively, to the other of the rear jacks 25 and to the other of the front jacks 24. The conduits 18 and 19 open into the valve block 126, and 'are adapted, upon opening movement of

valve members

152 and 153, which respectively have

hand wheels

154 and 155, to communicate with passages 156 and 151 which open into

annular grooves

158 and 159 which are arranged at the opposite sides of an annular groove 150 with which the passage 129 communicates and from Vwhich another passage 151 in line with the passage 129 opens out. A valve 162 having a controlling hand wheel 163 controls the communication of the passage 161 with a conduit 164, which last conduit communicates with a tube 165 extending through the cylinder 16, and a bore 156 inthe piston 15 and the piston rod '14, and the bore 166 is in communication with a conduit 151 opening into the bottom of the anchor jack Two other annular grooves 111 and 112 are arranged co-axially with the

grooves

153, 159 and 160 and respectively at the sides more remote from the groove 160 of the

grooves

159 and 150. The grooves 111 and 112 communicate respec- -tively with the passages or arm portions 113 and v114 of the transverse passage 135. Above the passage 161 and the valve 162 there is a further extension of the passage 161, this extension being numbered 111 and being surrounded by valve seat v118 on which a valve 1.19 is adapted to seat. The valve 119 has a stem 100 with which an O-ring seal 181 cooperates, and has a pivoted control lever 1182 having one end pivoted at 183 by means of ears 184 cn the valve block 126 and a cross pin 185, and having an operating handle H at its opposite end.

The

several grooves

158, 159, 160, 111 and 112 surround aperforated sleeve element S containing a valve receiving bore 186 in which a twospool piston valve 181 is reciprocable. The valve sleeve is traversed by five circumferentially arranged sets of ports, each set arranged in one of the annular grooves. The ports of these sets are numbered:

With respect to the groove |58: 188 With respect to the groove 159: 189

'With respect to the groove 160: 1 90 With respect to the groove 111 :191,'and With respect to the groove 1121192.

The spools 193 and 194 of the valve member are Vspaced by an annular groove 195 whose length is .in lthe oppositely disposed end positions of the valvemember 1181, When the valve is pushed in one direction from the centralposition shown in Fig. ll, to the right in that figure, the passage 1.29: is connected with the passage 151 and the pas-- sage 1515 is connected with the passage 114. In theoppositely disposed position of the valve y181, the passage 129 is connected with the passage 156,. while the passage 151 is connected with the passage 113. The valve has enlarged

end portions

195 and 191. These, in the central position of the valve, are adapted to be simultaneously con-- tacted, or at least almost contacted, by

tubular follower thimbles

193 and 199 which are spring-- pressed toward

shoulders

200 and 201 in

enlarged bores

202 and 203 in the valve

sleeve S. Springs

204 and 205 are provided to press the thimbles toward their shoulders and to center the valve 181 normally.

Suitable packings

206 and 201 are arranged outside the springs to cooperate with extension stems 208 and 209 on the valve 181. The stem 208 has an operating lever 210 having a grasping portion 21 1 and a pivotal support at one end 212.

It will be evident that, whether iiuid be supplied from the tank by the hand operated pump through the passage 128 or by the motor operated pump 132 through the passage 130, the fluid so supplied will pass freely through the passage 129, the annular groove 160, the passage 161, around the stem of the valve 162, through the passage 111, past the valve 119, if this be open, through the passage 135, the connection 131 and the conduit 121 back to the tank 120. In other words, there will simply be, Whenever the valve 11s is open, a circulation of fluid Without the development of any substantial pressure. When the lever H is used to press the valve 119 onto the seat 118, this free return of fluid will be prevented, and a pressure will build up within the passage 129, the annular groove and the passage 161 which will be determined by the setting of the relief valve associated with Whichever one of the

pumps

124 or 132 is the source of the pressure. Of course, separate external connections, each with a suitable relief valve, could be connected between the

conduits

123 and 125 and the

conduits

131 and 134. So long as all of the

valves

142, 152, 153 and 162 are closed and the valve 181 is in the central position thereof shown in Fig. ll, no fluid will be delivered to any of the operating devices. If the valve 142 is opened, however, fluid will be delivered to the roof jacks 24 and 25 through the

conduits

144, 145, 145, 141, 143, 149 and 150. The pressure which will be built up within these roof jacks will be determined by the relief valves mentioned, but, as shown in Fig. 8, an accumulator is arranged in communication with the conduit 149 through a conduit 215. This accumulator is of a well known construction, and includes a metallic walled chamber 216 in which there is arranged a collapsible Huid-tight bag 211 carrying a valve element 218 on the end thereof towards the point of communication of the conduit 215 with the casing 216. It will be noted in Fig. 8 that an annular valve seat 210 surrounds the passage 220 through which the conduit 215 communicates with the interior of the casing 215. The collapsible bag 211 will be prefilled with a gaseous fluid under a considerable pressure on the order of a number of hundreds of pounds per square inch, and nitrogen may conveniently be used as this gaseous uid. This accumulator provides for .the maintenance of a yielding pressure by the

hydraulic jacks

24 and 25 forcing the roof engaging plate structure 21 and the base structure 22 apart and maintaining a desired pressure on the roof. This may be on the order of 371/2 tons per jack for a roof support 2| on the order of 20 long and 6 wide.

Reverting to the conditions when the valve |42 is open, it will be noted that iiuid will be supplied to the

jacks

24 and 25 if the Valve |19 is closed, but will drain back out of the jacks if the valve Vis is open. Fluid may be admitted to the anchor jack 23 by opening the valve |62 and closing the valve |19. Because the accumulator 2|6 will have communication with the anchor jack 23 through the conduits 2|5, |49, |48, |46 and |44 and passages |29, groove |60, passage |6|, conduit |64, tube 65 and conduits |66 and |61, the anchor jack may also exert a yielding pressure on the roof so long as the valve |42 is open. If the operator releases the handle H, however, all the iluid supplied to these jacks will commence to escape, and accordingly, the valves i42 and |62 will normally be closed when such pressure has been built up in the jacks which they respectively control, as may be desired. By opening the valves |2 and |53, it will be possible respectively to advance the anchor jack relative to the roof jacks and to advance the roof jacks and the upper and lower support devices 2| and 22 relative to the anchor jack. Ordinarily, there will be no occasion for maintaining pressure on the anchor jack except when it is desired to move the roof jacks forwardly, but if it is desired to provide the cumulative pressures of the roof jacks and the anchor jack on the mine roof, this is possible through proper control of the various valves.

When it is desired to advance the roof load sustaining support 2l and the mine bottom engaging skids 22, normally fluid will be entrapped in each of the four roof jacks and in the anchor jack. Each of the five jacks will exert a force on the order of 371/2 tons with the construction and in an apparatus of the size mentioned, or, a total of 1871/2 tons. To this could be added, it may be noted in passing, a further large amount of pressure if the toggle devices which can have force exerted through them by the horizontal jack cylinder have the latter employed to tend to straighten them. It Will be clear that with the four roof jacks cumulatively exerting 150 tons pressure on the mine roof, the anchor jack, with but 371/2 tons of roof pressure, would perhaps slip first, notwithstanding its special serrated roof surface engaging construction, if the action of iiuid admitted between the piston 'l5 and the cylinder head 8|] simply exerted opposite longitudinal thrusts on the anchor jack and on the skid and roof support forced apart by the roof jacks. However, the frictional resistance to sliding the skids and roof support plate is much less than that of the base and top of the anchor jack, and the mechanical advantage with the toggle connections shown is very great, and the forward thrust of the walking cylinder first greatly reduces the `pressure exerted by the jacks 24 on the roof, and then, as the screws |02 engage the elements |03, also the pressure exerted by the jacks 25, and as the hydraulically applied pressures maintained by the action of the accumulator (whose presence permits any slight displacement of liquid desirable to facilitate advance of the roof support) is greatly offset by the forces transmitted through the toggles, there is an advance of the roof support as desired. It may be noted that if the roof should suddenly lower enough to tend to collapse the roof jacks beyond the points to which the toggles might have brought them the full force of the jacks would be instantly available to sustain the roof, assuming there was not a continued admission of liquid to the walking jack in such manner as to cause the toggles to reexert their counter force. Release cf the handle I-I would in any event instantly make the full roof supporting force available.

The general mode of operation is clear from what has already been explained, but it may be noted that as rapidly as the mining apparatus moves beyond the line of advance of a unit, the latter will be advanced until its end 32 is closely adjacent the newly formed face, and the iull pressures of both the roof jacks 24 and 25 and of the anchor jack 23 may be made use of in supporting the roof. The iront toggle mechanism even can be used, by admitting fluid to eifect a retracting force on the cylinder of the walking jack 26, to augment the roof supporting pressure. The shaker pan section of each unit will be connected to the pan line as soon as the section has been moved into line with the previously connected and operating pan line.

The apparatus of the invention is strong, is very readily controlled, does not require a potentially dangerous relief of roof supporting pressure for its advance, and has a control system which, by the closure of the lines to the energized roof and anchor jacks, produces a condition in which the mere release of the handle H will result in an instantaneous reapplication of the full roof supporting pressure.

While there is in this application specically disclosed one form, and a modification thereof, which the invention may assume in practice, it will be understood that these are shown for purposes of illustration and that the invention may be further modified and embodied in various other forms without departing from its spirit or the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent is:

l. In combination, a mine oor engaging support, a mine roof engaging frame, forwardly and rearwardly disposed jack devices yieldingly pressing said support and frame apart and causing said frame to exert a yielding supporting pressure on the roof, traction elements extending 'between said support and frame and connected at their opposite ends respectively to said support and frame, an abutment jack, and feeding means reacting upon said abutment jack and acting upon said traction elements at points intermediate their connections to said frame and said support for forcing said points, in the direction of feed, away from a straight line extending through the connections of said elements with said frame and support, to cause the exertion of a traction towards each other between said frame and support and of a longitudinal feeding force upon ,both of them.

2. In a roof control apparatus, mine floor engaging supporting means, mine roof engaging and supporting means, jack means extending between said mine floor engaging supporting means and said mine roof engaging and supporting means, said jack means including means for yieldingly pressing said first two means apart, anchor jack means engageable with the mine anchor jack means engageable with the mine floor and mine roof, walking jack means connected at one end with said anchor jack means, and an operative connection between said walking jack flflY Y means andsaid .mine iioor engaging supporting means and said mine roof engaging and supporting `means including devices connected to said rst two means forcausing a major component of the force exerted 'by said walking jack means to Vbe transitted to said nrst two means in such a di-- rection as to subtract from the separative forces exerted by said first mentioned jack means, said operative connection including elements having their opposite ends connected for relative movement; as said supporting means undergo relative movement and engaged `between their ends by said walking jack means in such a direction that extension of said walking jack means tends to cause AVa vreduction in distance between said opposite ends. n

3. Ina roof control apparatus, mine floor enfgaging supporting means, mine root `engaging andvsupporting means, jack means extending be-- tween said `mine floor engaging supportingmeans and said mine roof engaging and supporting means, said jack lmeans including Ameans for yieldingly pressing said rst 4twoumea'ns apart, anchor jack means engageable with the mine floor and mine roof, vrwalking vjack means "connected at one end with said Aanchor jack means, and lan Yoperative connection'between said walk ing jack means and Vsaidinine floor 'engaging supporting meansand said mine roof engaging and supporting means including means for causing a major component of the force exerted by said walking jack means to be transmitted to said first two means in such a direction as at least to `tend to cause approach of vthe second 'to the first while said first 'mentioned jack means are acting to press them apart, said last recited means including toggle devices having upp'er and lower ends connected respectively to said mine roof engaging and supporting means and to said mine idoor engaging supporting means and having their central portions pressed b'y 'said walking `jack means, as the latter is extended, in a direction to effect mutual approach of 'their ends. l

4, In a .roof control apparatus, 'mine floor engaging supporting means, mine roof engaging and supporting means, jack means extending between said mine floor engaging supporting means and said mine roof engaging and supporting means, Vsaid jack means including 'forwardly and rearwardly disposed ljack devices for yieldingly pressing said first two means apart, anchor 'jack means engageable with the mine floor and mine roof, walking jack means connected at 'one end with said anchor jack means, and an operative connection between said walking jack means Vand said rst two means including forwardly and rearwardly disposed toggle devices connected with said first two means 4'for causing a major component of the force exerted by said walking jack means tobe transmitted to said first two means in a directionto cause approach of the second to the iirst.

'5. 'In a roof control apparatus, mine door engaging supporting means, mine roof engaging and supportingmeans, jack means, respectively adjacent the forward and rearward ends of said floor engaging means, extending between said mine iioor engaging supporting means and said m-ine roof engaging and supporting means, said jack means including means for yieldingly pressingsaidirst two means apart, anchor jack means engageable with the mine floor and mine roof, walking jack means connected rat one end with said anchoi` jack means, and an operative con- 12 nectionfbetween lsaid walking jack fm said mine roof Mengaging v and supporting means and said mine fioo'r engaging supporting means including toggle means, respectively adjacent the forward end andadjacent the center of saidffloor engaging supporting means, and means forwren-- dering said toggle Vmeans sequentially effective for causing, a maior Component of the force 'x- -erted`by Vsaid 'walking Yjack means to be 'trans- -V -ter wherein there is provided roof Supporting means including mine ioor engaging supporting means and mine roof engaging and supporting means and jack means, including a forward jack and a rearward jack at either side, yield'ably forcing apart Vthe mine floor engaging supporting means and the'inine roof engaging andisu'pporting means, and wherein there is provided'an abutment jack'expansible into vfirm vcontact with the floor and roof, 'and in which 'there is further provided a cylinder and piston 'mechanism Vconnected 'at one end to said abutment jack vand operatively connected 'at its other end with 'said roof engaging and supporting means and 'oor engaging supporting means and which is 'selec'- tively operable to advance said abutment jack,

` 0r, When vSaid abutil'ent jack iS in 'flll Contact with the iioor and roof, lto advance said roof supporting mea'ri's,'the arrangement in 'which said operative connections. include toggle 1links'piv'-V otally connected together and `at their mutually opposite ends pivotally connected with said mine door engaging supporting means and said mine roof engaging and supporting means 'and said cylinder and piston mechanism acts on -said togggle links in a direction to decrease the included angle between said links upon extension-of said cylinder and 'piston mechanism in the direction of feed. y

'7. In a roof control apparatus of the character wherein roof supporting means is provided including mine floor engaging supporting means andmine roof engaging and supporting means and four jack means yieldably forcing Vapart the mine iioor engaging supporting means 'and the mine roof engaging and supporting means, and in which an abutment jack is provided which is at will expansible into firm contact with the floor and roof, and there is `provided a cylinder and piston mechanism connected at one end to said abutment jack and operatively Vconnected 'at its other end with said roof supporting means V'and which is selectively `operable to advance 'said abutment jack, or, when said abutment jack `is in 'firm Ycontact with the floor vand roof, to advance said roof supporting means, the provision of toggle connections lpivotally connected to said mine oo'r engaging supporting means and 'to vsaid mine roof engaging and supporting means and engaged by said cylinder and piston mechanism` and transmitting longitudinal thrust to said rot'f supporting means and, when the thrust necessary to advance said roof supporting means exceeds a predetermined value, reducing the Veffective pressure which said 'four jack means cause 'to be exerted on the mine roof and floor. Y

8. In a roof control apparatus of the character wherein roof supporting means isprovided including mine floor engaging supporting vmeans and mine roof engaging and supporting means and jack means, which jack means yieldably force apart the mine floor and mine roof engageans vand ing supporting means, and in which an abutment jack is provided which is at will expansible into rm contact with the oor and roof, and there is provided a cylinder and piston mechanism connected at one end to said abutment jack and operatively connected at its other end with said roof supporting means and which is selectively operable to advance said abutment jack, or, when said abutment jack is in rm contact with the floor and roof, to advance said roof supporting means, the provision of operative connections between said cylinder and piston mechanism and said roof supporting means which not only transmit longitudinal thrust to the latter, but are operative when the thrust necessary to advance said roof supporting means exceeds a predetermined value to reduce the effective pressure which said jack means cause to be exerted on the mine roof and floor, said operative connections including toggle mechanisms spaced apart longitudinally of said apparatus and connected between the mine floor engaging supporting means and said mine roof engaging and supporting means and each having its joint engaged by said cylinder and piston mechanism and arranged to be collapsed on the extension of the latter.

9. In a mobile roof jack mechanism for mines, a base engageable with a floor surface, a roof engaging top overlying said base, power operated devices operatively connected to said base and said top for yieldingly forcing the same apart into roof supporting relation, an anchor device engageable with extraneous means, a horizontal feeding device operatively connected to said anchor device for moving said base and top horizontally relative to the floor and roof, and an operative connection between said feeding device and said base and top including means for causing a major component of the force exerted by said feeding device to be transmitted to said base and top in a direction to reduce the force which urges said base and said top apart, said operative connection including devices having opposite ends moved apart upon separative movement between said base and top, and connected between their ends with said feeding device and pressed by said feeding device in a direction to form a decreasing angle between their opposite end portions as feeding takes place.

10. In a portable mine roof jack, a base adapted to rest on the oor of a mine, roof engaging and supporting means for engaging and supporting the mine roof, power operated devices operatively connected between said base and said roof engaging and supporting means for yieldingly forcing said roof engaging and supporting means upwardly into roof supporting position re1- ative to said base, an anchor device engageable with extraneous means, toggle devices operatively connected between said base and said roof engaging and supporting means, and a horizontal feeding device operatively connected to said anchor device and to said toggle devices: for moving said base and said roof engaging and supporting means horizontally relative to the floor and roof, said feeding device acting on said toggle devices in a direction to decrease the included angles of said toggle devices whereby, when a predetermined feeding force is applied to said toggle devices, they reduce the force which serves to press said roof engaging and supporting means against the roof.

JOSEPH F. JOY.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,116,357 Morgan Nov. 3, 1914 1,480,733 Morgan Jan. 15, 1924 1,481,875 Morgan Jan. 29, 1924 1,639,050 Morgan Aug. 16, 1927 1,704,866 Morgan Mar. 12, 1929