US2452760A - Mining machine - Google Patents

Description

R. K- JEFFREY MINING MACHINE Nov. 2, 1948.

11 Sheets-Sheet 1 Filed Aug. 10, 1943 II I III E E R QF T E WKDH. [m E E C B o a Exacu'rRlx,

Nov. 2, 1948. R. K. JEFFREY 2,452,760

I MINING MACHINE Filed Aug. 10, 21.943 Y 11 Sheets-Sheet 2 ROBERT K.JEFFREY,

DECEASED,

,s m m. mm,

ATTY

R. K. JEFFREY MINING MACHINE Nov. 2, 1948.

Filed Aug. 10, 1943 11 Sheets-Sheet 4 R. K. JEFFREY MINING mama Nov. 2, 1948.

'11 Sheets-Sheet 7 Filed Aug 10, 1943 A I48 4 HI An 1W ATT'Y Y1 mi? 7 "w s F m N m: E EJ N D B W H M E m M N om m H 5 Y a B l, H 3 4 5 F 5 5 8 5 I M 4 B A 6 a h, 4 q. x //|.lr.l|.'l| WISH VI Y. .5 a 7 5 w B l Nov. 2, 1948. JEFFREY 2,452,760

MINING MACHINE Filed Aug. 10, 1943 11 Sheets-Sheet 8 /NVENTOE EoBEie-r KJEFFREY,

DECEASED,

BY FLORENCE H.C. JEFFREY) EXECUTRI x,

ATT'Y Nov. 2, 1948. R. K. JEFFREY ,4 ,7

' MINING. MACHINE Filed Aug. 10, 1943 11- Sheets-Sheet 1o EQBEE'T K.JEFFEEY,

DECEASED,

BY FLORENCE HCJEFFEEY,

ExEcuTEnx,

BY 72m,

HTT'Y I NOV. 2, 1 948. JEFFREY 2,452,760 w MINING MACHINE Filed Aug. 10, 194:

11 Sheets-Sheet l1 l/YVENTOE ROBERT K.JEF'FREY,'

I DECEASED) j, 1 5 50251402 H.C.JEFFREY, EXECUTEIX,

H 2% 300 219.30 BY Patented Nov. 2, 1948 MINING MAiDHIN'E Robert iLJefl'rey, deceased, ,late of Be xley, hio,

by FlorenceH. 'C. Jeffrey, executrix, Bexley, Ohio, assignor, by mesne assignments, to The .lefirey Manufacturing Company, a corporation of Ohio Application August .10, 1943, :SerialNo. 498,087-

28 Claims. Cl; '2'6230') This invention relates to a mining machine of the type which rests on and slides over the mine bottom and includes rope feeding mechanism, and one of the objects of the invention is the provision of improved and eificient fluid pressure apparatus for controlling the operations of such type of mining machine.

Another object of the invention is the provision of means entirely dependent upon a fluid pressure system for controlling the operations of a-mining machine.

A further object of the invention is the provision of means for automatically regulating the feed of a mining machine in accordance With the load thereon by slowing down the feed thereof when hard cutting is encountered and automatically speeding up the feed when normal cutting is resumed.

Another object of the invention is the provision of fluid pressure operated controlling means for a minin machine embodying means for automatically slowing down the feed of the ma.-

chine When the fluid pressure in the controlling.

system exceeds a predetermined maximum until such fluid has been reduced and then automatically resuming normal feed.

A further object of the invention is the provision of an electro-magnet in circuit with the electric driving motor of a mining machine and combining with such electro-magnet a fiuid pressure control system to effect automatically av slowing down of the feed of the machine when such electric motor is overloaded and then upon the overload being spent restoring the feed. to such normal as has been predetermined by the manual setting of a controlling valve.

.2 oombinedwith automatic means for varying the volume of delivery of said .pump in compliance with requirements and then restoring the volume ofdelivery to normal as predetermined by the manual setting of said valve.

Another object of the invention is the provision of an improved hydraulic system of control of the feeding of cutting mechanism =of-a mining machine wherein a variable volume pump is acted on to establish a normal output as predetermined by the manual setting ofya valve and wherein such output is varied in accordance with the load on the cuttingmechanism while the feeding "of the machine :is not interrupted A further object of the invention is the provision of fluid pressure controlling means fora variable volume pump to enable the volume of Another object of the invention is the provision of a supercharging pump of relatively low fluid pressure in a mining machine controlling system embodying a pump of relatively high fluid pressure so as to keep such system filled with oil and displace oil heated during operation of the mac M- and thereby effect radiation of the heat from the oil and render more uniform the temperature of the oil used in the controlling system. V

A further object of the invention is the provi sion vof a variable volume pump and means for controlling the volume of delivery of said pump in accordance with the manual setting of a valve delivery to be predetermined by the manual setting of a valve combined'with automatic means for varying the volume of delivery from said pump and then restoring such delivery volume to that predetermined by such manual setting.

Another object of the invention is the provision of hydraulically operated motor means :for continuouslyieeding a mining machine irrespective of varying loads thereon, combined with automatic means for supplying variable volumes of hydraulicliquid to said motor means in accord ance with such varying'loads, without interrupting the feed of the machine,

A further object of the invention is the provision of an improved automatic suction selector in an automatic hydraulic system of controlyof' a mining machine to adapt the latter for operation on steeply pitched mine veins.

More particularly. it is the object of the present invention to provide in that type of mining. machine adapted to rest on and slide over a mine.

bottom, a hydraulic system of control of the feeding of the machine that shall automaticallyvary the rate of feed of the machine in accordance with the hardness of the material being cut so that when relatively hard material is encounteredthe feed will slow down automatically and pick up again automatically after normal conditions of operation are resumed, the feeding operation being carried on continuously without stalling the machine.

Other objects of the invention will appear 3 hereinafter, the novel features and combinations being set forth in the appended claims.

The mining machine shown in the accompanying drawings includes the structure disclosed in applicants co-pending application, Serial No. 468,398, filed Dec. 9, 1942, for an improvementin Mechanism for removing cuttings from the kerf cutter of a mining machine, now Patent No. 2,359,422, dated October 3, 1944.

In the accompanying drawings,

Fig. 1 is a side elevation of a short wall kerfcutting mining machine to which my improvements are particularly adapted;

Fig. 2 is a rear end elevational view of the mining machine shown in Fig. 1;

Fig. 3 is a plan view of the mining machine shown in Fig. 1;

Fig. 4 is an enlarged sectional elevation of the mining machine kerf-cutting and feeding mechanism shown in Fig. 3;

Fig. 5 is a sectional elevation of one of the rope drums shown in plan in Fig. 3;

Fig. 6 is a sectional elevational view taken on the line 66 of Fig. 5, looking in the direction of the arrows;

Fig. 7 is an enlarged plan view of the rear end of the mining machine with the cover removed to show the apparatus enclosed in the main frame;

Fig. 8 is a sectional elevation taken on the line 8--8 of Fig. '7, looking in the direction of the arrows;

Fig. 9 is a sectional elevation of a variable volume hydraulic pump with a manually set hydraulically actuated volume control device and balance cylinder connected thereto;

,, Fig. 10 is an elevation of the left-hand end of the unit illustrated in section in Fig. 9;

Fig. 11 is a sectional plan view taken of that portion of Fig. 9 back of the central horizontal shaft;

Fig. 12 is a sectional elevation of the upper right-hand portion of Fig. 10;

Fig. 13 is an elevational view of the right-hand upper portion of Fig. 10;

Fig. 14 is a sectional elevation taken in a plane at right angles to the upper central portion of Fig. 12;

Fig. 15 is a sectional elevation of an electromagnetic valve for use in a hydraulic system for automatically controlling the variable volume pump when the electric motor for driving the kerf-cutter is overloaded;

Fig. 16 is a sectional elevation of the left-hand four-way directional control valve;

Fig. 16a is a sectional elevation of the lefthand four-way directional control valve;

Fig. 17 is a sectional elevation of the automatic suction selector valve mechanism;

Fig.. 18 is a sectional elevation of a 3-core differential pressure control valve mechanism;

Fig. 19 is an enlarged sectional elevation of the manually set hydraulically actuated volume control device and balance cylinder shown in Fig. 9;

Fig. 19a is a development of a portion of the interior of a valve sleeve and cooperatin valve post;

double check valve for use in supercharging the hydraulic system;

Fig. 21 is a sectional elevation taken on the line 2l2l of Fig. 9, looking in the direction of the arrows;

Fig. 22 is a sectional elevation taken on the Fig. 20 is an enlarged sectional elevation of a 4 line 2222 of Fig. 9, looking in the direction of the arrows;

Fig. 23 is a sectional bottom plan view taken on the line 2323 of Fig. 21, looking upwardly in the direction of the arrows;

Figs. 24 and 25 are left-hand and ight-hand sectional views of the supercharging check valve and emergency relief valve combination;

Fig. 26 is a sectional elevation of the tramming relief valve;

Fig. 27 is a plan, view of a shortwall kerfcutting mining machine mounted on a truck and operatively connected to truck propelling mechanism to transport the machine from one place to another;

Fig. 28 is a sectional elevational view of the power transmission mechanism driven by one of the rotary hydraulic motors and adapted to be connected to the truck propelling mechanism as illustrated in Fig. 2'7;

Fig.v 29 is an enlarged plan View of the rear end portion of the mining machine with the cover removed to show the hydraulic apparatus used in the operation of the power transmission mechanism shown in Fig. 28 when connected to the truck propelling mechanism illustrated in Fig. 27;

Fig. 30 is a rear end view of the structure shown in Fig. 29, with the rear end cover of the main frame removed;

Fig. 31 illustrates diagrammatically the complete hydraulic system of hydraulic circuits and connections for a shortwall kerf-cutting mining machine including provision for transportation truck drive as shown in Fig. 27 and Fig. 32 is a piping diagram for a shortwall kerf-cutting mining machine without any provision for transportation truck drive.

As shown in Figs. 1 and 3, the chain kerfcutter 12 comprises a cutter bar l6 which is provided with the conventional endless cutter chain I7 carrying picks or bits l8. The cutter chain I! is driven from an electric motor carried by the main frame I l of the mining machine under the cover plate l9 shown in Fig. 3. As indicated in this View and in Fig. 7, the armature shaft of the electric motor is connected to the pinion 20 which meshes with the gear 2| secured to the shaft 31 carrying the worm 22.

The worm 22 meshes with a worm gear 23 as shown in Figs. 3, 4 and '7. This worm gear is mounted on the roller bearing 24 concentric with the vertical shaft 25 to the upper end of which is secured the clutch gear element 26.

Secured to the upper side of the worm gear 23 are splines 2? which mesh with splines on the vertically sliding clutch element 28; the latter has an annular groove 29 to which is connected the shipper 32. By means of the shipper 39 the splines on the clutch element 28 may be slid upwardly into mesh with the gear element 26 and when this occurs the worm gear 23 will be brought into driving relation with the vertical shaft 25, the lower end of which carries the sprocket 3! meshing with the cutter chain ll.

As shown in Fig. 4, the vertical shaft 25 is journaled by means of the opposing roller thrust bearings 32 and 33 to the tubular support 34 which is secured to the frame 1 i of the mining machine by means of the cap screws 35, 35. A retaining ring 36 is'secured to the tubular support 3 3 by means of cap screws to hold the thrust bearings 32, 33 in adjusted positions.

The shaft 3? (Fig. 7) which carries the worm 22 is connected to the hydraulic variable volume pump 64 for supplying hydraulic pressure to the hydraulic motors '65 and 66. The hydraulic motor is connected to a shaft 4i carrying a worm 42 which meshes with a worm wheel 43. as shown in Fig. 4. The worm wheel 43 is keyed to a shaft 44 mounted in journal bearings and secured to a pinion 45 which meshes with an inner annular gear 45 of a rope drum il. In a similar manner, the rope drum G8 on the opposite side of the machine as shown in Figs. 3 and 7 connected through worm gearing 9 to the hydraulic motor 66 for operation thereby. The helix angles of the gears 42 and 33 and of the gearing 49 are such that their drives are reversible, that is, gears 42 may drive gears 43 or gears l3 may be caused to drive gears 12..

As best seen in Figs. 5 and 6, secured to the lower edge of a plate I l of frame H is a bracket 230 for carrying the sleeve -23! which has an enlarged cylindrical head 232 fitting into a cir-.

cular opening at the lower end of the plate 233 and serving to pivot the latter for tilting adjustment. The rope drum t? is journaled on the stub shaft 234 which is supported by the plate 233.

The upper left-hand portion of the plate 233 is provided with an arm 233 carrying a cupshaped sleeve 235 in which is slidable a latch 236 adapted to fit into recesses 23?, 238 in the plate H. The latch 236 is urged against the plate II and into the recesses .237, 238 by the spring 239 in the cup 235. A stem 24 connects the latch 236 to the knob or handle 24!.

:By rasping the knob 25! and pulling the same outwardly the latch 235 may be released and the plate 233 tilted on its cylindrical pivot 232 to throw the pinion 45 into or out of mesh with the inner annular gear 4%. The latch 236 may'initially be in the recess 23! but when the gears 45, 45 are to be thrown out of mesh with each other to enable a manual pull on the rope 5G to rotate the rope drum er freely, the latch is adjusted to the recess 238.

The gears should not be moved too far out of mesh rith each other. however, and this is prevented by the screws 24.2, 243, 244 and 24.5 each of which extends through a slot in the plate 233 and is screwed into the supporting plate I I, The slots for the screws 2 2 i and 245 are shown at 256, 2A1 and this view illustrates the slot 246 for the screw 2A2 and the slot 2 3? for the screw 243.

A wire 2&8 may be extended through holes in the heads of the screws 242, 2 33 and a wire 249 may be extended through holes in the heads of the screws 24 3, 2 .5. The ends of the wires may be twisted together as shown in Fig. 5. By soldering these twisted ends the arrangement will be sealed and tampering with the proper support of the rope drum prevented. v

In the bearing block 232 is located a brake shoe 258 which is pressed against the rope drum 4! by means of the sprin 25! as shown at the lower end of Fig. 6. The stem 252 of the brake shoe extends through the spring 225i and is provided with a transverse slot 253 through which extends a limiting or locking rivet 254 to prevent the brake shoe from dropping out when the plate 233 is removed for repairs or replacements.

It should be understood that when the gears st, 45 are thrown out of mesh, too free rotation of the rope drum is prevented by the brake shoe 25. 3 .frictionally engaging the peripheral portion of the rope drum 41', as shownin Fig. 6.

For normal feeding operation of the kerficutter horizontally transversely of itself, a rope 50 and 58.

6 is connected to "and wound on the drum 1 to extend therefrom around theguldepulley'li l, and the rope 52 is connected to and wound on'the drum A3 to extend therefrom over the direction pulleys 53, 54. The ends of the ropes are connected to'anchora'gcs in the mine and as rope :52 is wound up the other rope 5B is paid out, under control of the hydraulicmotors '65 and 56. For haulage purposes when the mining machine is to be moved from place to place in the mine without efiecti'ng any feeding operation, the rope. 55% may be extended around the direction pulleys =55 and 55 and its free end anchored in the mine distant from the machine. When the pulley 56 is not in use, its supporting arm -may be moved to the vertical position shown in full lines in Fig. anclheld there by a pivoted latch.

It will thus be seen that when the electric motor drives the chain cutter l2, it .at the same time drives the shaft .3? which is connected to the variable volume pump 5 This variable volume pump 64 is shownin detail in Figs. 9, .21, 22 and 23. Theshaft .58 of this pump is adapted to have its outer extensions? connected to the shaft 31 (Figs'S, '2 so as tobe'inalinement therewith. It should be understood that when the Keri-cutter driving motor operates, the variable volume'pump 54 will be driven but the volume of liquid delivered by this pump will vary from zero to a maximum according to the adjusted positic'n of the swash plate 59. When the latter is adjusted to the position shown in Fig. 9, it may be said that it is centered, in which position :the pump has zero capacity. The .angle of the inclination of the swash plate 69 relative to the axis of rotation of the shaft 68 will determine the capacity of the pump or the volume of its delivery, as hereinafter more fully explained.

While the variable volume pump 64 and the two constant volume fluid pressureimotors 65 and 66 areconnected in series, these motors are operable singly or in series and each is reversible independently of the other. Therefore, the rope drum 4'! may be rotated in either direction by means of its rotary hydraulic motor 65 and the rope drum 48 may be rotated in either direction by means of its hydraulic motor fifi. Fig. 16 when considered as a sectional plan view represents a left-hand four-way valve for controlling the rotary hydraulic motor 66 and the same View when considered as a sectional bottom plan view represents a right-liandsfour way valve for contro1- ling the rotary hydraulic motor 55 shown in Fig. 3.

A handle lll connected to the left-hand zfourway valve for the motor o5 may be located at the rear end of the machineas shownin Fig. 2. A similar handle 55 may be located as shown in' the same view and connected to the right-hand fourway valve for the motor 55.

If the coal to be cut is relatively soft the variable volume pump as may be adjusted for maximum delivery which will effect relatively high speeds of rotation of the rope drum motors 65 But if as the machine is cutting, the feed is set so high as to cause excessive pull on the feed cable 52 there will result a hydraulic pressure overload in the hydraulic system. Or if the Keri-cutter after cutting along through relatively soft coal encounters a hard spot, the

cutting motor :may be overloaded. in which event the hydraulic system of control illustrated in the accompanying drawings comes into play automatically to decrease the volume of the variable volume pump untilthe relatively hard magreased '7 terial has been cut through whereupon the desired rate of feed of the kerf-cutter is automatically resumed.

Within the supporting frame ll back of the electric chain cutter driving motor are two compartments covered by the plate 12 and entirely closed to form a sump (Fig. 8) for the oil used in the hydraulic control system. There may be two compartments divided by the partition 13 through openings 13' in which the oil may be free to flow from one compartment to the other as shown in Fig. 8 but the enclosure of such compartments is such that the oil can not escape therefrom during normal operation of the mining machine.

The worm gearing 22, 23, 32 and 49 may run in oil in one compartment and the other compartment may serve as the sump or source of supply for the automatic suction selector valve 14 shown in section in Figs. '7, 8 and 17 and diagrammatically in Figs. 31 and 32 in the hydraulic control system. This automatic suction selector valve is so arranged that, regardless of the tilt of the mining machine including the frame H, oil will be drawn into the pipe 15 by the supercharging pump El. This supercharging pump is a gear pump designed so that the suction and pressure ports will. respectively be the same irrespective of the direction of rotation of the pump.

From the supercharging pump ill the oil flows through the pipe it (see Fig. 32) to and through primary filter Ti into the pipe 18 and from the latter into the lower left-hand port 19 of the double valve 26 shown in detail in Fig. 20.

The pipe E8 has connected thereto the branch pipe 85 which leads to a secondary filter 82. The latter may be provided with a relief valve therein. After passing through the secondary filter 82 the oil flows through the pipe 83 to the top of the gurnmer shaft 25 (Fig. 32) and thence back to the gear case and oil sump. The quantity of oil flowing to the shaft 25 should be small and is regulated by a restricted orifice in the secondary filter 82.

Another pipe as may be connected to the pipe 18 to branch therefrom through the low pressure relief valve 86 into the pipe 37 and thence into the gear case or into the sump.

When the mining machine is cutting from right to left while feed rope 52 is being reeled in and rope 59 paid out, the variable volume pump 64 will be running in a counter-clockwise direction so that pipe 95 is connected to the suction port of the pump and the pressure port of the latter is connected to the supply pipe 97.

The pipe 18 is connected to the chamber 19 in the double check valve 20 shown in Fig. 20. Since the high pressure pipe 98 is connected to the supply pipe 9'! and leads to the chamber 88 in the double check valve 26; as shown in Fig. 20, the check valve 89 will be held closed. The supercharged oil enters by way of the chamber 79. This supercharged oil is at a lower pressure than the high pressure oil in the pipe 98 and consequently it is not able to open the valve 59 which remains closed. But the supercharged oil in the chamber "it; has sufiicient pressure to ope the check valve 92 and flow into the chamber ill and thence into pipe at. In this manner the supercharged oil enters the system by way of the suction pipe to the variable volume pump 64,

since pipe as is connected to the pipe-95 as shown in Fig. 32.

High pressure oil in the supply pipe 91 flows nw n.

to the right-hand four way valve I 0|. When this valve is in its neutral position shown in Fig. 16 the oil under pressure will extend from port 9? to port 902 and thence through the hole 103 to the interior of the hollow valve HM and along the latter to and through the hole Hi5 into the pgt Hit and out from the latter into the pipe The left-hand valve It! is illustrated in Fig. 16a. The oil enters the valve is! from pipe I06 to port 166 and fiows through ports 562, I93, Illa and 05 and finds its Way back to the pump through the return pipe H4. The right-hand four-way valve is connected by means of the ports H18, H39 and the pipes HE), Ill to the rotary hydraulic motor as shown in Figs. 16 and 32. The left-hand four-way valve is connected by similar ports and the pipes l l2, l 93 to the rotary hydraulic motor 6%. It is evident from Fig. 16

that when the valve H15 is in neutral position the supply pressure is exerted at both ports of the motor 65 and therefore the latter does not operate. In a similar manner when the valve iii! is in neutral position supply pressures will be exerted in the pipes H2, H3 connected to this valve and therefore the latter will not be rotated. Consequently when both the right-hand four-way valve and the left-hand four-way valve are in their neutral positions neither the motor -35 nor the motor as will be operated, but a noload by-pass will be established between the pressure and suction ports of the variable volume hydraulic pump 64.

Under these conditions the cutter chain I1 may be driven by the motor located under the plate l9. At the same time the supercharging pump Bl may be driven by sprocket chain gearing 332 including the sprocket H5 on the shaft 3"! and the sprocket H6 connected to the pump 6'7 as illustrated in dotted lines in Fig. 3 and in full lines in Fig, 7. That is to say, whenever the mining machine electric motor is operating, both pumps 6 and 6'! will be driven, but so long as the valves Hll and Iii! remain in their neutral positions the mining machine will not be given any feeding movement because the rotary hydraulic motors 65, 86 will not be driven.

Feeding of the machine may be eifected by manually actuating the rods H5, N6 of the valves lill, Nil. By moving the rod H5 to the right as viewed in Figs. 30, 31 and 32, high pressure oil is delivered through the port I99 and the pipe Hi to the motor 65 to efiect operation of the latter to drive the rope drum A8 to reel in the cable 52. At the same time the rod H6 may be moved to the right to cause supply pressure to be exerted in the pipe I I2 and return through the pipe 1 E3 to operate the motor 66 to effect paying out of the retarding rope 50. Inasmuch as the motors 65 and 66 may each be controlled independently of the other, the machine may be retarded by the rope 50 as desired and further more the machine may be hauled about in the mine by exerting a pull on the rope 59 particularly when the latter is extending from the pulley 56 and anchored extraneous to the machine.

Branching from the pipe 98 adjacent the valve N36 is a pipe H! which leads to the central core valve N8 of the three-core dilferential pressure control He shown in Fig. 18. It should therefore be understood that when the mining machine is cutting a kerf from right to left, the core valve H8 is held up since the pipe H1 is being supplied with high pressure oil from the supply port of the pump 64. When the core exceeds that on the lower side the spool 9. Valve H8 is thus held up, high pressure oil is delivered through the passagew y I29 tothe core. Valve I2I.

Thepipe II! is connected to the annular port 222 which is connected through'the annular chan-. nel 2,23 to the annular port 224. Ports 225 connect the channel 223; to the bore 225 which extends upwardly to the port22'l. When thepres sure in the pipe II'I is sufficiently low the 13,8 5- sageway 228 will let the core I I8, drop into the recess, I I;8'. The port I29 isthen cut; off from the channel 223 but the por-t22lis connected by the dropping of the core II8, tov the port I23.

It should also be noted that the core valve H8 is. connected by the pipe I22 to the pipe Il 4 (see Fig 32) near the Valve I91, which pipe H4. in turn communicates with the suction pipe 94. When the valve H9 is up, the pipe I22 is. con-. nected through the channel 229 and the passageway I :23,to the low pressure relief valve I24. When the valve H8 drops, the connection between the- I12. The Supply pipe II'I' will thenbe connected to both the pipes I59 and I59. The connection to the pipe 159 results in the opening of the check valve IlIl shown in Fig. 19 with the consequent tilting of" the swash plate 69 toward central position thereby reducing the output from the variable volume pump 64 and the reduction in hydraulic pressure in the supply line.

When the hydraulic pressure overload has been spent, the valve I2I is pushed down by the spring I'I'2 as permitted by the restricted passageway I I3. The swash plate is then automatically restoredto its normal position as predetermined by the setting of the manual valve I38. During this automatic restoration the hydraulic motor 125' predominates while liquid is drained from the volume control device I39 through pipe I59, channels I58, I59 into the pipe-I51 and thence into the sump.

It should be particularly noted that if the pres-.

sure in the supply line I I1 falls unduly, the float-,- ing spool I I 8 will drop down from its position shown in Fig. 18 because of the. hydraulic pressure exerted from the supercharging pump 61 through the pipe 122 into channel-229 and thence along the passageway 228 to the closed upper end of the floating spool valve II;8. If the pres-1 sures on the ends of the valve H8 are approximately the same, the latter acts as a floating valve but when the pressure on the upper end H8 moves down and becomes a differential valve.

When in its lowermost position the valve I I8 cuts off the supply pipe I I? from the passage.- way I-Elil and the channel port I69, and the valve charging pump 61 past the check valve 89 in Fig.

20 will replenish the liquid in the pipes 98, 9'I

" and III, the outlet for the flowing liquid being past the low pressure relief valve 524 in Fig. 18. This flow from the superoharging pump is in addition to the delivery from the main pump 64 and therefore the pressure in: pipe 99 soon builds up, until the check valve 89 closes and the check valve 2 99 opens, whereupon the supercharging pump 6! delivers the fluid into the suction pipe. 95. It is during the period when the pumps 64 andlil are in parallel that normal pressure in the supply pipe H1 is restored so that by the time these pumps are again connected in series, the pressure on the lower end of the valve H8 is sufiicient to lift the latter to its position shown in Fig. 18. The pipe I22 will then be again connected to the low pressure relief valve I24 and the port 221 will again be closed. During normal operation the supercharging pump 61 is connected in series with the pump 64 through pipe 91, the pipes I I4, I22 serving as a. by-pass through the low pressure relief valve I24 to the sump.

I 2! remains in its lowermost position shown in Fig. 13. The dropping of the valve II8 also cuts off the pipe I 22 from the relief valve !24 while the pipe II! will be connected through the tubular chamber 226 and the lateral port'22l to the low pressure relief valve I24.

It will'thus be seen that when the pressure in the supply pipe II! falls below a predetermined minimum, the valve II9 will drop to cut oifpipe II! from the pipe I59 and at-the same However, there takes place a constant draining of the liquid pressure medium into the sump in order to keep down the temperature of such liquid pressure medium. This may be understood by considering the valves m1 and IIlI in their,

neutral positions. The flow will then be through the no-load by-passes in the valves I'9I and H11. In Fig. 32 the flow .may be traced from pump 64 through pipe 91, valve Illl, pipe I96, valve I91, to pipe I22 and thence through the low pressure reliefvalve I24 to the sump. When this flow as traced reaches the pipe II4 someliquid may go back to the pipe depending upon the pressure exerted by the supercharging pump 61 in the pipes 94 and 95.

When the valve II 8 is in its lowermost posi-.

tion the closure of the ports I29 and I69 locksthe liquid in the pipe I59 thereby preventing operation of the hydraulic motor regulating means shown in Fig. 19, until normal pressure has been restored in the supply line In and the differential valve II8 has been moved back to its uppermost position shown in Fig. 18.

The three core differential pressure control shown in Figs. 18 and 32 determines the supercharging pressure of the circuit. The supercharger circuit extends from pipe I8 through port I9,

passageway 92, check valve 99, passageway 9I,

pipes 94, H4, I22, channel 229, port I23 through channel 93 abeverelief valve I24 to pipe I25. All supercharging oil in excess of that lost through use or leakage in the system is discharged through pipe I25 as a lubricant over the sprocket shaft '25. (Figs. 18,. 31 and 32).

In the event of the pressure in pipe 91 droppressure produced by the supercharging pump 61 in the pipe I8.

The volume of oil delivered by the variable volume pump 64 is regulated by adjusting the angle of tilt of the swash plate "69 (Fig. 9). A hydraulic motor I26 comprising a cylinder I21 and a plunger I28 is mounted in position to act on the roller !29 as shown in Fig. 9. The hydraulic motor I 29 acts as a balancing motor and is always connected'to the high pressure side of the circuit as will hereinafter more fully appear.

To the port I30 at the left-hand end of the cylinder I21 is connected a pipe I3I. A pipe I32 branches to the left from pipe I'3I as shown in Fig. 32. The pipe I32 is connected to the port I32 of the manually set hydraulically actuated volume control device I33 which is shown in sectional elevation in Fig. 19.

The volume control device I33 comprises a casing I34 which is rigidly secured to the base plate I35 to which is also rigidly secured the casing I36 of the pump 64. (Fig. 9). To the outer end of the casing I34 is secured the bearing block I3'I in which is journaled the core valve I38. To the outer end of the valve I38 is secured a handle I39 (Fig. 9). By means of the handle I39 the valve I38 may be rotated to various positions to 1 secure adjustment of the tilt of the swash plate 69.

The casing I34 in reality constitutes a hydraulic cylinder because within the same is a piston I40. Extending to the right from the central portion of the piston I40, as viewed in Fig. 9, is a cylinder I4I closed at its right-hand end by the block I42. Extending to the right from the central portion of the casing I34 is a cylinder I43 adapted to act as a tubular guide for the plunger I44 the outer end of which is in. engagement with the roller I29 mounted on the swash plate 69 diametrically opposite the roller I29.

The valve I38 is provided with two parallel longitudinal bores I45 and I46, each closed at its ends but each in communication with a pair of spaced lateral ports or passageway I45 and I55, each pair of which is connected by a groove or channel as seen in Figs. 9 and 19. A port I32 communicates with an annular groove I41 in the end block I31. The port I48 at one end of the bore I45 is always in communication with this annular groove I41, as shown in Fig. 19.

High pressure oil delivered to the core valve I2I flows from port I49 through the pipe I50 to the port I30 at the left-hand end of the hydraulic motor I26, as viewed in Fig. 9. The pressure in the cylinder I21 on the plunger I28 tends to tilt the swash plate 69 away from central position, thus increasing the volume of flow from the pump 64. The flow will be at a minimum when the parts occupy the positions shown in Figs. 9 and 19 because the piston I40 is then in its extreme right-hand position where it is locked by the oil confined in chambers II and I53 of the volume control device I33. The piston I40 is confined to a rectilinear movement by a spline or key I52 between the cylinder MI and the tubular guide I43.

Within the cylinder I4I is a spiral groove I53 which extends substantially the full length thereof making one complete convolution and connects the chambers I5I and I54. The separate ports I45 and I55 for the bores I45 and I46, respectively, normally straddle this groove I53 and may selectively be brought into communication with the spiral groove I53 by opposite relative rectilinear or axial movements between sleeve I4! and post I38. When the core valve I 38 is turned by means of the handle I39 until the port I55 communicates with the spiral groove I53, the charm bers I5i and I54 will be in communication with the port I55 through spiral groove I53 and will be 1 toward its full-off position.

thatwhen high pressure oil enters chambers 14:

vented through the bore I46, annular groove I55, pipe I50, ports I58, I59 and pipe I5! to the gear case or oil sump. The hydraulic motor I25 then acts to move its plunger I28 outwardly and at the same time due to the Venting of the oil through the spiral groove I53 the plunger I44 will be retracted. The tilt of the swash plate 59 will thus be increased to effect an increase in the volume of liquid pumped by the pump 54.

When motor I 26 acting through swash plate 59 moves cylinder I to such extent that the spiral groove I53 is no longer in communication with the port I55 the pump 84 attains the output volume predetermined by the setting of the core valve I35. That is to say, as the piston I49 moves into the chamber I5I, the port I55 moves away from the spiral groove I53 and the flow through the latter is discontinued. The oil in the chambers I 54 and I5I again becomes trapped because the vent connections of the chambers which are through spiral groove I53 and ports I55 to the sump are sealed. The swash plate 69 is held at its adjusted angle because plunger I44 can recede no further and motor I 26 is always acting to rotate swash plate 69 to apply pressure upon it. Thu the pump is confined to the volume predetermined by the setting of the core valve I 38.

Now in order to decrease the volume of the pump 64, that is, to expand the volume control de vice I 33 and to retract the piston I28 of the motor I26, the core Valve I38 is rotated until the high pressure 011 port I45 is in communication with the spiral groove I53. Then oil under pressure flows through the spiral groove I53 into the chambers I5I and I54 to act on the piston I40 and closure I42. At the same time high pressure oil acts on the plunger I28 of the motor I26, but the combined areas of the piston I40 and closure I42 are greater than the cross-sectional area of the plunger I28. Consequently the plunger I44 will be extended and the plunger I28 will be retracted,

thereby effecting tilting of the swash plate 59 toward central position to decrease the volume of the pump 64.

'As the piston I40 moves toward the plunger I44, the port I45 will be moved away from the spiral groove I53 and the flow of oil into the chambers I5I and I54 cut off, whereupon the oil in the chambers I5I and I54 will be locked to block the piston I40 against further relative movement in the cylinder I 34. The swash plate will thus be locked in adjusted position in accordance with the manual setting of the core valve I39.

. Under normal or balanced conditions, as illustrated in Fig. 19a, the ports I55 and M5 straddle spiral groove I53 with ports I55 and I45 so located that as post I38 is rotated from its full-on position toward the full-off position to decrease the normal pump output, the pressure port I45 moves toward the spiral groove I53 and the exhaust port I55 moves away from said spiral groove.

It will be seen that when the pressure port I45 opens into the spiral groove I53 as a result of such movement, high pressure oil will flow into the chambers I5I and I54 to cause the piston I40 to move upwardly until the sleeve I4I closes the port I41. Thus the piston I48 will move upwardly as the post I38 is rotated from its full-on (position It will also be seen and I54 through check valve I10, the piston !49 will be moved upwardly even though the port M I' "be closed. When this occurs the exhaust port,

tion with the spiral groove I53 but because the assatzeo passage I l-t is also subjected to the pressure of the oil entering the chambers lfil and lfi l from pipe 15% it i e fectively sealed. When the overload condition in the hydraulic system has been re lieved, and consequently the high pressure in pip? E9 removed, th oil in chambers l5! and Iii i will flow or be ex rausted through the spiral groove 553 and port 555 to the ltd and to the sump, as previously dcsiirribed, to permit the piston It'll to move downwardly until the spiral groove I53 is again straddled by the ports I55 and M5. A single exception to the above description relating to the communication between the exhaust port 555 and the spiral groove is when the post is set to the full-off position. In this setting of the post the exhaust port as viewed in Fig. 18a, is positioned too far to the left and does not meet the spiral groove. This because it is desired to lock the piston in the full-oi? position by closing the exhaust port I55. The maximum angle through which post I33 can be rotated from the full-on to the full-off or mini-mumpositions is preferably not over 189 degrees. The spiral groove I53 extends preferably through an angle of 360 degrees but not more. As viewed in Fig. 19a, th

pressure port H5 will be just below and near the top of the groove I53 when the post I38 is in the full-on position.

It should be particularly noted that Fig. 18 is a sectional elevation of three core differential pres sure control valve mechanism for use in the hydraulic systems of Figs. 31 and 32 in controlling the maximum pressure oil of the supercharging and high. pressure circuits.

valve mechanism shown. in Fig. '18 is so located in Figs. 31 and 32 in the hydraulic circuits that it will be possible to separate the low pressure supercharging oil from that of the high pressure oil.

In Fig. 18 the center core valve l 58 be considered floating spool which. is controlled by the h gh pressure oil being delivered through the pipe i El and the low pressure oil being delivered through. the p'pe i22. When high pressure oil is being delivered through. pipe ill into port 222, it passes by ports into the core 22 of the valve 5 8.

The low pressure oil flows from pipe I22 into the annular channel 229 and thence through the tubular passageway to the upper end ofthe valve H8. Since high pressure oil is exerting its pressure on the underside of the valve H8 and low pressure oil is exerting its pressure on the upper side of the valve M8, the latter will be held in its uppermost position as shown in Fig. 18. If the pressures in the pipes ill and I22 were reversed, the greater oil pressure would be on the upper side of the valve H8, and the valve Iii! would be forced down to its lowermost position.

The right-hand core valve I25 of the three core valve mechanism shown in Fig. 18, is the high pressure relief valve and the left-hand core valve IZ Z is the low pressure relief valve. So long as the central core valve i i3 is held in its uppermost position shown in Fig. 18, high pressure oil will always be delivered to the high pressure relief valve I2 I through the port :25 while low pressure oil is being delivered to the low pressure relief valve 32 through the port I23.

The high pressureoil that is delivered'to the high pressure relief valve 525 may flow from the annular hannel I into the lower chamber Isl. From the chainber $9? the oil may flow through the .vertical-re- I of the annular channel and sec through the radial ports ward action of the spring .to the top of the sprocket shaft 25.

stricted passageway H3 into thebored, recess I98 in which the restoring spring I12 is located..

Since the oil pressure extends to both ends, of the core valve I2l the pressure on the latter will be equalized thereby permitting the spring H2 to hold the valve IZI in its lowermost position as shown in Fig. 18. This spring 572 is of just'sufficient strength to hold the valve I2I in its lowermost position so lon as the hydraulic pressure in pipe ill does not exceed a predetermined normal maximum.

Excessive pull on the feed cable 52 may take place, whereby a pressure overload may occur.

For instance, if during cutting, harder coal than usual is encountered, the motor 86 will be called upon to do more work. The volume from the pump. 64 remains constant for a given setting of the valve I38 of the volume control device I33, but the heavier duty thrown on the motor 56 increases the pressure in the system.

In case of such high pressure overload due to excessive cable pull, the spring loaded ball check valve I65 (Fig. 18) will be opened to effect by-passing of the oil from upper side of the valve 7 I2! faster than it can enter through the restricted orifice H3 in the center of the valve I2I, causing a pressure differential between the top area and the bottom area of the valve I2! of sufficient magnitude to lift the valve I25 against the downil2. It should be understood that the port I58 in Fig. 18 affords free communication between the chamber It? and the port or passageway 455. It should also be noted that when such high pressure overload takes :place, it is extended to the pipe Ill and to the chamber It at the lower end of the valve IZI and that when the check valve I55 opens as above explained, escape of oil through the pipe I94 is cut on by the closure at this time of the ,port I96 by the valve I as illustrated in Fig. 15

and as more fully explained hereinafter.

The oil that flows past the check valve I65 escapes through the port I65 and the low pressure relief valve we to the pipe I25 and then t will thus be seen that since escape through the pipe IM is cut off and the pressure'at the bottom of the valve I2I is sufiicient to overcome the spring I12, the valve i2! is moved up and such upward movement-forces the oil out of the chamber I6! through the port I68 into the passageway I95, producing enough hydraulic pressure in the latter to'efl'ect opening of the check valve I55.

When the valve IZI is in its raised position, the port I69 is in communication with the port I58. High pressure oil from the pipe Ill will then. be delivered to the pipe I153. Consequently, as shown in Fig. 19, oil will flow from the annular channel I 56 past the check valve I'Hi and through the passageway I II into the chamber I5l. From the chamber iii! the oil will flow through the spiral groove I53 into the chamber Ilia.

Consequently, 'hydraulic'pressure will be exerted on both the bottom of the closure block I 42 and the bottom of the piston I iii. Th s will cause tilting of the swash plate 63 toward its central or full-ofi postion, thereby decreasing the output volume of the pump 5 Under these conditions, port I55 will communicate with groove 53 regardless of the manual setting of post I38,-

except in case it is also in the full-oil position. Consequently when normal conditions are restored in the hydraulic circuit and the pressure in pipe I59 is reduced or released the pump :will automatically return to its normal predeby efiect a gradual increase in flow into the chambers I5I and I54 of the volume control device shown in Fig. 19. The V-slots 288 will thus prevent chattering in the structure shown in Figs. 9 and 19.

After the pressure overload has been spent, the spring I72 is able again to restore the valve I2! to its lowermost position. the oil flowing upwardly through the orifice I'I3 to fill the chamber III? while the check valve I65 remains closed. The port I69 will be cut oif from port I58 and the latter will be connected to the port I59 as shown in Fig. 18.

It is therefore evident that when the valve I2I is restored to its lowermost position, as shown in Fig. 18, the pipe I58 will be vented through pipe I51 for flow of oil from the pipe I58 to the oil sump. The hydraulic pressures on the block I42 and the piston I40 are therefore relieved while the hydraulic pressure on the plunger I 28 is retained.

When a high pressure overload due to excessive cable pull occurs, the tilting of the swash plate to its central position shown in Figs. 9 and 19 is entirely automatic. Since the port I55 may not be in communication with the spiral groove I58 when the volume of delivery of the pump 64 should be automatically reduced, the automatic by-pass with the check valve I'II) therein, is provided.

It will be evident that during normal control whether the valve I38 is rotated in one direction or the other, when swash plate has been adjusted to the desired position for a predetermined output volume of the pump 84, the swash plate will be automatically locked in adjusted position and held in locked position hydraulically until automatic reduction in volume output is effected by pressure overload after which any desired readjustment of the volume output of the pump may be effected by manually rotating the valve I38.

In the event that the electric cutting motor under the cover plate I9 is overloaded, provision is included in the system illustrated in the accompanying drawings to effect automatic decrease in the volume of oil delivered by the variable volume pump 84. When electrical overload occurs, the electro-magnetic valve I18 will be operated to efiect automatically a decrease in the volume of oil delivered by the pump 84. The solenoid I19 is connected in the motor armature circuit so that when the electrical overload occurs the increased electric current through the motor armature will energize this solenoid sufliciently to cause it to pull down its plunger I 88 against the action of the spring I8I which is located within the protective cap I82. This downward movement is relatively slow because of valve I84 connected to the chamber I83 in which the lower end of the plunger-I88 is movable. When the solenoid is sufficiently de-energized the plunger I88 will be moved upwardly at a relatively rapid rate because then oil may be drawn into the chamber I 83 freely past the check valve I84 as more fully hereinafter described.

Secured to the upper end of the plunger I88 are Valves I88 and I8'I connected by the rod I9I. The valve I88 controls the connection between the ports I89 and I98. The rod I8I is of reduced diameter so that when the plunger I89 is in its upper position as shown in Fig. 15, the port I99 will be closed. When the plunger I89 is in its lower position, the valve I88 is in open position so that ports I89 and I98 will be in communication with each other.

A pipe I98 connects the port I98 of the electromagnetic valve IIS to the port I95 of the threecore differential pressure control H9. Another pipe I92 connects the port I89 to the oil sump.

In the event of an electric overload on the electric driving motor, passageway I95 is vented and the hydraulic pressure on the lower side of the valve IZI in Fig. 18 will overcome the action of the spring [772. The hydraulic pressure will move the valve I2I to its uppermost position. When the plunger I88 of the electro-magnetic device is moved down in response to said electric overload the ports I89 and I98 are connected thereby venting the passageway I95 through the pipe I94 and the ports I89, I98 to the pipe I92 which leads to the oil sump.

When the electrical overload is spent, the plunger I 89 will be moved by the spring I8I to its upper position shown in Fig. 15. This will move the valves I and I8! to their upper positions, cutting off communication of port I from port I89. This cuts off the venting from pipe I94 into pipe I 92 but the latter will still be connected to the oil sump.

The electro-magnetic valve H8 is so arranged that electrical surges, such as may occur when starting the electric motor for driving the chain kerf-cutter, do not afiect the control of the pump 64. This is accomplished by the differential action of the spring loaded ball I89 in the solenoid bleed-01f valve mechanism shown in Fig. 15, this ball I84 being held slightly off its seat by an adjustable pin 282. The upper end of this pin 292 is provided with a screw-threaded enlargement 298 which is threaded into a screwthreaded opening in the upper side of the valve block 204. By inserting a screw driver in the slot 205 at the upper end of the enlargement 283 the pin 292 may be adjusted in elevation and thus the restricted opening at the ball I84 may be varied. Screw-threaded nuts 206 and 28? may be relied on to lock the pin 292 in adjusted position.

When the plunger I89 is moved down due to an electrical overload, the fluid, such as oil, displaced from beneath the plunger, flows through the restricted passageway between the ball I84 and its seat, thus slowing down the descending movement of the plunger I89. When the spring I8I moves the plunger I88 upwardly the fluid above the latter moves along the passageways 288, 289 and 2I9 and freely past the ball I84 into the passageways 2I I, M2 and 2I3, the spring 2M being compressed sumciently to permit such free flow. This operation will permit the plunger I88 to be quickly restored to its upper position when the solenoid H9 is sufiiciently de-energized.

Inasmuch as the solenoid I18 is always in the electric motor circuit, it is always energized but the electro-magnetic valve is so arranged that only when the electrical current through the sole noid I19 exceeds a certain predetermined number of amperes, will it have sufiicient strength to pull down the plunger I88 against the action of the spring I8I.

amass The electrical overload at which the electrorna'gnetic valve 118" will act may be" predetermined by adjustment of the initial com ression or the spring iill'. For this purp'ose'a nut 2I51rn'ay be screw-threaded ontothe'upper end ofthe valve rod lei and provided with locking mechanism for holding the nut in adjusted position relative to the rod.

If desired, the lo'Wer'end of the its 191 maybecomprise split halves fittingln the upper e'ndof theplunger or core opening" in theb lo'ck 219 of non-magnetic material. 7

The coupling? arrangement betw en the plunger 58% and the rod Isl facilitate's'alinement' 0f the valves E88 and I8! in their bores which prevents binding. Furthermore, the'nut head 220' at the upper end of the screw 221 maybe" relied on to turnthe latter in the nut 215 whileth'e latter is held against turning. In'this way the tension of the spring l8! maybe adjusted'arid consequently the amperage necessary to; cause thesole'n'oid 119' to pull down its plunger I80 may be varied. The overload on the electric motor that will effect an automatic decrease in'the deliveryof oil from the pump 64 may thus-be predetermined.

While the tendency is for the oil from the super-charging pump 6? tube Icy-passed through the branch pipes 8|- and"8-4- (Fig. 32), the relief valve in the filter 82 and-the-r'elief valve 86 may be so set that such lay-passing Will not occur. Moreover, the closed circuit of the variable volume pump B l-handles a g'reat deal-more oil than the volume delivered by the superc harging pump 6's.- Consequently, under normal conditions of operation the entire volume from the supercharging pump is taken into the closed-circuit of the pump 64 WithOlli? any by -passing through the branch pipes Hand 84' (Fig. 32). In the event of a pressure overload in'the closed circuit of the pump 54'; no oil may be needed from the' super: charging pump and therefore the relief valve in the filter 8-2 and the relief valve 86' may be set to open automatically to by-pass the superchar'g ing pump oil in co-operation with the" automatic decrease of the volume of oil delivered iritothe closed circuit by the pump 64;

The hydraulic pressure fromthe supercharging pump 6? may be as low as 25 to 50 lbs. per square inch and the hydraulic pressure from the pump 6 may be as high as 750 to 1500 lbs; per square inch; but these figures are given merely by way of example and maybe varied according to conditions of mining operations.

By referring to Figs. 3 and 4 it will be seen that whenever the electric driving motor under the plate I9 is operated; the shaft 31 will be rotated to drive the pump 54" but by releasing the clutch 28 no power need betransmitted to the cutter chain while on the'transporting truck as shown in Fig. 2'7.

By actuating the rod H6" of the valve I01 the hydraulic motor 66 will bedriven 'fromthe pump 64. The shaft of'them otor fifi 'is'splined' to the shaft 29! as shown in Fig. 28'. This shaft is. the

one which carriestheworm 49'as' shown in full lines in Fig. '7. g p

The shaft 29! is journaled to the" support 292' by means of ball bearings'as shown in Fig; 28. The support 292 is rigidly secured byweldingj to the 'topofthe partition plate"1-3".'"

18 Keyed to the shaft 29! is a pinion 293w ii meshes with" the spur gear 294'. This spur'lg'e'a is keyed toth'e inner end of theshaftZSS. un shaft is journaled by means of the jball'bearings 2st and 291, Theball bearing'iilfi i's'lriountegd on a cylindrical support 298" which is securedgtq the partition plate 13. The ball bearing mounted in the tubular support ZQETsecured to one of the side plates of tlimairi name" of the mining machine. A tubular corin'ecoi @110 is Welded at its ends to tne'supp'orts get" an 259 and" co-op'erates with the latter to form an 911- closure for'th'e shaft-295; W a

The outer portion of the" support 299 flares outwardly as shown s Fig. 28, to'rdeive within the sam'eone' element 30! ofa coupling, theot'hr element of which is located at 3112" on thetruk 280 shown injFig. 27, When these coupling elemerits 38!, 3'62 arec dnhectedby movin tl'i' ing machine onto the truck 290 into the p s1 showh'iri Fig 27, thestartin'gof the'eltfiii diilfe in}; motor of the miningmachine will transmit power through the j reduction gearing in' the: cas mg 363 to the truck propelling mechanism 3M. I

By reversing the electric driving motor tli truck may be driven in' either" direction.

the truck is transported away from the place where'the mining operations have been carries on, thecable reel 305 is driven in proper-duet; tion' by the power transmission mechanism 3Q6 to wind up the electric cable which eonne'ctsth'e electric driving motor on theminingmacliine' to the distant'source of electric power.

When the mining machine shown'lin theaccoinpariying drawings is' supplied with thetrukdriv'fe connections shown in Fig. 28, the piping diagram of Fig. 32 is modified" by the insertion" of the trarnming relief valve 36'! shown'iiisctioh in Fig. 2e and by the substitution orthe" relief-"valve mechanism 398showri in Figs. 24 ancestor the doub-l'e'check valve device shown in Fig, 20'. piping diagram as thus modified is shown iii Fig: 31

Figsj arena 25 are left-hand andright hand sectional views of what may be termed reapercharging check valve" and eiri'e'rgiicy'reli e'f valve corrlbiriat'io'n. As stated above; this valve coinbination is useful in mining machines provided with the truck transportation drivingni'echa'iiism showninFig; 28. 7

Under normal operations of t'h e minin machine the'fiow of oil fromthe supercharging pump' throughpip'e i8 will be into thepas sageways 79' and 309; past theclfe ck valve il and thrbugh the passageway 31 cand' o'rt 3] Fin'to'the pipe'94. I

Passageways' 312; 3 I 3 connect pipers with the chamber 3M". Hydraulic pressure may thus be exerted'on the right-hand end- 0f the piston 315- asview'edin Fig. 24'.

V Achamber 3 l6; a passageways: l and a charnher 318' arranged in series; connect the pipe" 9 1 to the space 319 back of'the piston" 32c which isin alirrementwith the piston 3151' Suirlcie'nt sydr'aulic pressure either in chamber 314" or in chamber slhg'will moveone o' r'b'ot iiof'thepis tons-315; azc'a'gainst the valve ears; the left as viewed" iriFig. 24', thereby compressing' the spring 322 and connecting the chambers 32-3' by moving' the piston 324 out of the hole in whi'c'n'it fits. It will thus'b'e' seenjthatfir-t ir liydrau1ic"p1essure in either" pipe 94 o'rllfiipe 93 becomessufficiently great, the pu se 6t will-"be sliortf-cirouited by the" pipes 9E" and 98,;

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