US2920879A - Mining apparatus utilizing two side cutting augers - Google Patents

Description

Jan. 12, 1960 H. w. DRIEHAUS MINING APPARATUS UTILIZING TWO SIDE CUTTING AUGERS Filed Oct. 18, 1956 5 Sheets-Sheet l w H. A

LzlTtruulir INVENTOR. Herman W Drlehaus BY ATTORNEY Jan. 12, 1960 H. w. DRIEHAUS MINING APPARATUS UTILIZING TWO SIDE CUTTING AUGERS Filed Oct. 18, 1956 5 Sheets-Sheet 2 3 mu w om w Q Q MM Kin R on INVENTOR. Herman W Dmehaus BY TTO/PNEV Jan. 12, 1960 H. w. DRIEHAUS 2,920,879

MINING APPARATUS UTILIZING TWO SIDE CUTTING AUGERS Filed Oct. 18. 1956 5 Sheets-Sheet 3 INVENTOR.

Fjerman W. Driehaus ATTORNEY I Jan. 12, 1960 H. w. DRIEHAUS 2,920,879

MINING APPARATUS UTILIZING TWO SIDE CUTTING AUGERS Filed Oct. 18, 1956 5 Sheets-Sheet 4 INVENTOR. Herman W. Dmehaus BY Z a. gum,

ATTORNEY Jan. 12, 1960 H. w. DRIEHAUS 2,920,879

MINING APPARATUS UTILIZING TWO SIDE CUTTING AUGERS.

Filed Oct. 1a, 1956 s Sheets-Sheet 5 I I 1 I F g 7 INVENTOR.

Herman W Driehaus ATTORNEY United States Patent-"O MINING APPARATUS-UTILIZING TWOSIDEY CUTTING AUGERS' 'Herman W. Driehaus, Chicago, Ill., assignor to Goodman Manufacturing Company, Chicago, Ill., a corporationof Illinois Application October 18, 1956, Serial No. 616,763

9 Claims (Cl..26219) This invention relates to mining apparatus and more particularly relates to improvements in mining machines of the continuous mining type.

A principal object of the invention is to provide a novel form of continuous mining and loading machine arranged to mine and load an entire coal seam while being'advanced laterally across the seam.

, A further object of the invention is to provide an improved form of continuous mining machine operating on .novel formof mining head utilizing two side cutting angers adjustable about a longitudinal axis disposed between the augers for adjusting theaugers to cut out coal seams'of varying heights and having 'a simplifiedmdrive arrangement-for reciprocably moving the angers during rotation and lateral feeding movement thereof.

A still further object of the invention is to provide an improved form ofmining machine particularly adapted for operation in low seams of coal in which an: entire seam is mined by two side cutting augers movable laterally across a coal face in an arcuatev path and in which a simple and novel form of cuttingand collecting means is provided to extend along the retreating auger and collect the cuttings for picking upby a gathering device regardless of the position of the retreating auger withrespect to the ground. g

These and other objects of the invention will appear from time to time as the following specification proceeds and with reference to the accompanying drawings 1 wherein: V

Figure l is a plan view of a continuous mining machine constructed in accordance with the principles of the present invention;

Figure 2 is a view in side elevation of the machine shown in Figure 1;

Figure 3 is a sectional view taken substantial-1y along the line III-III of Figure 2,,drawn to an enlarged scale, with certain parts removed and showing the mining head in the operation of cutting across a coal face;

Figure 4 is a fragmentary vertical sectional view taken through the pivot for the swivel or turret frame supporting the mining head for lateral movement across the main frame of the machine;

Figure 5 is a horizontal sectional view taken through one ofthe side cutting augers substantially along line V-V of Figure 2;

Figure 6 is an enlarged fragmentary plan view of the rear portion ofhthe mining head and pivotal support therefor,gon thetleveling frame for the mining head, with ice . 2 certain parts shown in horizontal section in order to illustrate-the drive mechanism for reciprocably moving the mining head during a side cutting mining operation;

Figure 7 is a fragmentary vertical sectional view taken substantially along line VII-VII of Figure 6;

Figure8 is a sectional view taken substantially along the line VIII-VIII of Figure 6 and-showing the connection for pivoting the'mining head to adjust the head to cut outseams of varying thicknesses; and

Figure :9 is an enlarged fragmentary detail view showing one of the leveling jacks and its connection between the elevating and leveling frame. v

Inthe embodiment of the invention illustrated in the drawings, I.have shown aminingmachine- 10 of a continuous mining type adapted to cut'and load an entire coal seam by arcuate feeding movementof a mining head 11 across the front of a main frame 12 for the machine abouttheiaxis of a pivot 'pin 13, pivotally connecting a turret 15 to said main frame adjacent the forward end thereof-3(see Figure 4). I

The'main'frame 12 is shown as being mounted on a pair'oflaterally spaced continuous traction tread devices 16, for propelling the machine from working place to working place and advancing the machineinto aworking face. The continuous traction tread devices 16 are driven from individual motors'17, disposed adjacent the rear end of the main frame atopposite sides thereof, and each h'avingdrivingconnection; with an associated continuous traction tread device through a-suitable speed reducer, which maygbe-ofany well known'form, so need not herein be shownror described further; r v

A conveyor 19 is shown as extending alongthe main framef121from a'position adjacent the forward .end of said main frame-to a position beyond the rear end of said main frame forvdischarging the mined material into a As herein shown, the elevating conveyor is pivotally connected to spaced support members 25 of the turret 15 on pivot pins 26;. The support members 25 of the turret 15 and the pivot pins 26 connecting the conveyor 22 to said turret, space the discharge end of the conveyor 22 in cascade "relation with respect to' the receiving end of the conveyor 19, for arcuate movement acrossthe receiving endiof; said conveyor and for vertical movement about the axes of the pivot pins 26. The conveyor 22 is provided with gathering devices 27 at its forward end for pickingzup the mined coal from the ground and progressing the mined coal onto said elevating conveyor'22 during the mining operation and in cooperation with a cutting confining shield 29'on the mining head 11 and "extending along a retreating 'side cutting auger 30 of said mining I head;- i

The mining head 11 also includes an advance'side cutting auger 31 extending in parallel relation with respect to the side cutting anger 30 andexactly like the side cutting auger 30, except the side cutting auger 31 rotates in an opposite direction from the direction of rotation of the side cutting auger 30, so that each auger .will progress the mined material in the space therebetween, :torbe progressed by scrolls'or spirals 32and 33 ofzthei augers 30 and 31,irespectively", toward the gatheralong opposite sides of the conveyor 19.

ing mechanism 27 during the operation of cutting across a mine face The side cutting augers 30 and 31 extend forwardly of shells 35 and 36 of motors 39 and 40, respectively, for driving the respective side cutting augers 30 and 31 in opposite directions in a manner which will hereinafter be more clearly described as this specification proceeds.

The motor shells 35 and 36 extend along opposite sides of a roll-over frame 41 and are suitably supported thereon. The roll-over frame 41 is journaled in a leveling frame 43 for rotation about an axis extending longitudinally of'the motors 39 and 40, and spaced therebetween, on spaced bearings 44 and 45 mounted in a forward boss 46 and a rear wall 47, respectively, of said roll-o er frame. Adjustable movement of said roll-over frame..- will thus adjust the mining head 11 about a longitudinal axis disposed intermediate the side cutting augers 30 and 31, to adjust the mining head for cutting in coal seams of various desired thicknesses.

The .leveling frame 43 has spaced cars 48 extending rearwardly therefrom adjacent opposite sides thereof and pivotally connected between the furcations of bifurcated arms 49 of an elevating frame 50, .on pivot pins 51. The

leveling frame 43 is vertically adjusted about the axes of the pivot pins 51 by operation of laterally spaced leveling jacks 53 trunnioned on said leveling frame adjacent opposite ends thereof. Each leveling jack 53 has a piston rod 54 pivotally connected with a depending arm portion 55 of the elevating frame 50, extending in advance of the arm 49. The leveling jacks 53 thus serve to adjust the leveling frame 43 with respect to the elevating frame 50 and to adjust the side cutting augers 30 and 31 into parallel relation with respect to the ground, as said side cutting augers are elevated or lowered by the elevating frame 50. I

The elevating frame 50 is pivotally connected adjacent itsrearward end to supports 58 extending forwardly of the support portions 25 of the turret 15. As herein shown, the supports 58 extend between the bifurcations of bifurcated rear end portions. 56 of the elevating frame 50 and are pivotally connected thereto as by pivot pins 57.

The elevating frame 50 is raised and lowered about the axes of the pivot pins 57 and is maintained in various de sired positions of' adjustment with respect to the ground by hydraulic lift jacks, herein shown as comprising cylinders 59 pivotally connected at their head ends to the turret on support cars 60 extending upwardly therefrom, and having piston rods 61 extending therefrom. The piston rods 61 are pivotally connected at their free ends to a cross frame member 62 of the elevating frame 50 between connecting ears 63, projecting rearwardly therefrom.

' The gathering mechanism 27 and elevating conveyor 22 are raised and lowered about the axis of the pivot pins 26 by operation of hydraulic lift jacks comprising cylinders 64 pivotally connected to opposite sides of the elevating frame 50 and piston rods 65 extensible therefrom and pivotally connected to opposite sides of said elevating conveyor (Figure l).

The mining head 11 is pivotally moved across the forward end of the main frame 12 by hydraulic swing jacks comprising cylinders '67 trunnioned to the main frame 12 for movement about vertical axes .on trunnion supports 70 projecting laterally from side ,plates 73 extending Piston rods 75 extensible from the cylinders 67 are pivotally connected with the support members 25 on vertical pivot pins 76.

Referring now in particular to the roll-over frame 41 and leveling frame 43 and the means for adjustably moving said roll-over frame with respect to said leveling frame and for holding said roll-over frame in position, as

well as the means for reciprocably moving the roll-overframe 41 and side cutting augers 30 and 31 with respect to the elevating frame 43 during the mining operation,

the roll-over frame 41 has spaced shaft portions 77 and 79, respectively journaled in the bearings 44 and 45 and has an intermediate splined portion 80 between said shaft portions and of a larger diameter than said shaft portions. engaged by the splines of an internally splined collar 81 extending about said splined portion and having an car 83 extending radially therefrom through a slot 85 in an arcuate bottom wall portion 86 of the leveling frame 43. The ear 83 extends between the furcations of a bifurcated connector 87 on the outer end of a piston rod 88, and is pivotally connected thereto as by a pivot pin 89. The piston rod 88 is extensible from a cylinder 90 pivot ally connected at its outer end to spaced ears 91 on a pivot pin 93 extending through connecting ears 94 extending outwardly from the head of the cylinder 90.

A motor 95 is shown in Figures 6 and 7 as being mounted on the rear wall of the leveling frame 43 for reciprocably moving the roll-over frame 41 and mining head 11 with respect to the leveling frame 43. The motor 95 may be a fluid pressure operated motor and is provided with a motor pinion 96 driving a worm 97 through an intermediate spacer gear 99 meshing with a gear 100 on a shaft 101 for the worm. The shaft 101 is journaled at its ends in opposite side walls of a gear housing 103,

extending along opposite sides of and connected with one end of a lever 111 by a pivot pin 112. The lever 111'is connected at its opposite end to the rear wall of the leveling frame 43 on the opposite side of the pivotal axis of the roll-over frame 41 from the connecting link by a link 113. The link 113 is pivotally connected to the leveling frame 43 at one end by a pivot pin 114, and pivotally connected to the level 111 at its opposite end by a pivot pin 115.

A connector 116 extends rearwardly of a shaft 117 which is mounted in the shaft portion 79 of the roll-over frame 41 in a cavity 119 extending axially along said shaft portion. A pivot pin 120 is provided to connect 'the lever 111 to the connector 116 and shaft 117 intermediate the ends of said lever.

The shaft 117 is mounted within the cavity 119 on spaced collars 121 and 122, spaced apart by an intermediate collar 123 and connected together by a sleeve 124. The intermediate collar 123 abuts a shoulder 125 on the shaft 117 and is maintained in engagement there- 79 on its flange and as extending inwardly along the cavity 119 into engagement with the outer end of the collar 122. The collar 121 abuts a shouldered portion 129 of the cavity 119. Thus, upon operation of the motor 95 and oscillating movement of the lever 111, the roll-overframe 41 and side cutting augers 30 and 31 will be reciprocably moved with respect to the leveling frame 43 along the bearings 44 and 45, to free the side cutting angers 30 and 31 during rotation thereof and during feeding movement thereof across a coal face.

Referring now to Figures 1, 3 and 5 and the side cutting augers 30 and 31 and the drive thereto, each side cutting auger is of a similar construction, as has previously been mentioned, so the side cutting auger 30 only need herein be shown and described in detail.

The side cutting auger 30 is shown as comprising a drum 130 having the conveying scroll or spiral 32 extending' along the periphery thereof for advancing the cut The intermediate splined portion 80 is slidably Rand broken down coal toward the gathering devices 27.

The conveying spiral 32 has spacedcutterbits131 extending outwardly therefrom andcarried thereby and pitched to cut upon rotation of the auger in a direction, which is having a central pilot bit 137 for cutting at the inner end of the auger and accommodating the auger to advance endwise into the coal face at the initiation of the mining operation.

The drum 130 is shown as being journaled adjacent its rear end on a bearing 139 mounted on a cylindrical housing 140 extending outwardly of an end plate 141 of the motor 39, adjacent said end plate. The drum 1'30 is supported adjacent its forward end on a drive member 144 keyed or otherwise secured to a drive shaft 145 journaled intermediate its ends in an end wall 146 of the housing 140 and projecting forwardly therefrom. The drive member 144 hassupporting and driving engagement with an annular ring 147 extending inwardly of the periphery of the drum 130 adjacent the forward end thereof.

The drive from the motor 39 to the shaft 145 includes a clutch 150, herein shown as being a friction disk clutch having a driving member 151 keyed or otherwise secured to the rear end of a hollow motor shaft 153 and driving a driven member 154 keyed or otherwise secured to a longitudinal shaft 155 through friction disks 156 in a manner well known to those skilled in the art so not herein shown or described further.

The drive shaft 155 is coaxial with and extends through the center of the hollow motor shaft 153 beyond the forward end of said hollow motor shaft and has a pinion 157 on its forward end having driving connection with the drive shaft 145, through a geared reduction train 159.

The cuttings confining shield 29 is shown in Figures 3 and 5 as comprising an inner cuttings confining plate 160 generally conforming to the path of travel of the cutter bits 131, and having a bar 161 extending along the lower end thereof and slid ably engageable with the ground. The plate 160 is reinforced by an outer plate 163 extending downwardly from the plate 160 from a position adjacent the center thereof for a portion of the length thereof and then angularly inwardly to the bar 161 and spaced from the plate 160 by areinforcing spacer 164. The plate 160 is shown in Figure 5 as having spaced arms 165 and 166 extending inwardly therefrom. The arm l65 is bolted or othelwise secured to a ring 167 rotatably carried on the rear end portion of the motor shell 35. In a like manner the arm 166 is bolted or otherwise secured to a ring 169 rotatably carried at the opposite end of the motor 1 shell 35 at the rear end portion of the drum 130. The

cuttings confining shield 29 is thus pivotally mounted on the motor 35 to freely engage and slide along the ground as the mining head 11 is adjustably moved, by adjustable movement of the roll-over frame 41 to confine the cuttings to be conveyed bythe conveying spiral or scroll 32 to the gathering devices 27, to be picked up thereby.

. lowered by operation of the hydraulic cylinders 59 and the mining head may be leveled with respect to the ground by operation of the cylinders 53.

6 When the mining head'isadjusted to the height of the coal seam and is inthe proper relation with respect to the ground, the turret 15 :maybe'swung to the extreme right hand positionshown by broken lines in Figure 1, by the admission of fluid underpressure to the head end of the left hand cylinder 67 and the piston rod end of the .right hand cylinder 67. Themotors 39 and 40 may then be started and the continuous traction tread devices 16 may also be put into operation to sump the augers 30 and 31 into the coal face tothe required depth, it being understood that the side cutting auger 30 is sumped along the right hand rib of the working place.

Fluid under pressure may then be admitted to the head end of the right hand cylinder 67 and the piston rod end of the left hand cylinder 67 to laterally feed the mining head across the coal face to the left hand rib thereof, in substantially the broken line position shown in Figure 1, at which time the entire machine may be withdrawn by operation of the continuous traction tread devices 16, to mine and clean up the left hand rib of the working place.

During the mining operation, the top side cutting auger 31 will make a generally arcuate cut in the coal face, advancing from the top to substantially the center of the face and will advance the cuttings and broken down coal to be picked up and carried away by the side cutting auger 32, cutting from the mine floor up to substantially the center of the coal face, as shown in Figure 3. It should here be understood that the coal'in the space between the bits of the side cutting augers 30 and 31-1 breaks away as the lateral cutting operation progresses across the coal face.

While I have herein shown and" described one form in which my invention may be embodied, it should be understood that modifications and variations of the invention may be effected without departing from the spirit and scope of the novel concepts thereof.

I claim as my invention:

1. In a mining apparatus, a main frame, a mining head including a pair of laterally spaced side cutting augers, a turret pivotally mounted on said main frame and forming a support for said augers, means laterally swinging ,said turret for feeding said augers across a working place,

a supporting connection between said turret and said side cutting augers comprising an elevating frame pivotally connected to said turret, a roll-over frame supporting said augers for adjustable movement about an axis extending longitudinally thereof, a leveling frame rotatably supporting said roll-over frame on said elevating frame and maintaining saidaugers in parallel relation with respect to the ground, fluid pressure operating devices interposed between said turret and elevating frame for lifting and lowering said frame, fluid pressure operating devices interposed between said elevating frame and leveling frame for leveling said augers with respect to the ground, a fluid pressure operating device interposed between said leveling frameand said roll-over frame for pivoting said roll-over frame and augers in accordance with the thickness of the seam to be mined and cuttings confining means adjustably mounted'on the retreating of said side cutting augers for engagement with the ground by gravity upon adjustable movement of said side cutting augers with respect to the ground for confining the cuttings to be conveyed toward said frame by the retreating of said side cutting augers.

2. In a mining apparatus, a mobile main frame, a side cutting mining head having two laterally spaced side cutting mining augers, means for rotatably driving said augers, a support for said augers on said main frame including a turret, means for laterally moving said turret across the front of said main frame for feeding said augers across a working place, means for supporting said augers on said turret including a roll-over frame supporting said augers for adjustable movement about an axis extending longitudinally thereof and spaced therebetween, means selectively operable for rotatably moving tion of said roll-over frame comprising a motor, a crank I driven by said motor, a lever arm oscillatably driven by said crank, and a drive connection between said lever arm and said roll-over frame concentric with the axis of rotation thereof.

3. In a mining apparatus, a mobile main frame, a side cutting mining head having two laterally spaced side cutting mining angers, means for rotatably driving said augers, a support for said angers on said main frame including a turret mounted on said main frame for movement across the front thereof, means for pivotally moving said turret and feeding said angers across said main frame, an elevating frame mounted on said turret, means for raising and lowering said elevating frame, a leveling frame mounted on said elevating frame and extending in advance thereof, means for adjustably moving said leveling frame with respect to said elevating frame, a roll-over frame pivotally mounted on said leveling frame for movement with respect thereto about an axis extending longitudinally of said angers and spaced therebetween, and for movement along the axis of said roll-over frame, said roll-over frame having said angers mounted on opposite sides thereof, means for adjustably moving said roll-over frame with respect to said leveling frame for selectively adjusting said angers to the seam to be mined, and means for reciprocably moving said angers during operation thereof comprising a motor on said leveling frame, a crank driven by said motor, a lever pivoted to said leveling frame at one end and oscillatably driven by said crank at its opposite end, and a drive connection between said lever and said roll-over frame concentric with the axis of rotation thereof.

4. In a mining apparatus, a mobile main frame, a side cutting mining head having two laterally spaced side cutting mining angers, means for rotatably driving said augers, a support for said angers on said main frame including a turret mounted on said main frame for movement across the front thereof, means for pivotally moving said turret and feeding said angers across said main frame, an elevating frame mounted on said turret, means for raising and lowering said elevating frame, a leveling frame mounted on said elevating frame and extending in advance thereof, means for adjustably moving said leveling frame with respect to said elevating frame, a rollover frame pivotally mounted on said leveling frame for movement with respect thereto about an axis extending longitudinally of said angers and spaced therebetween, and for movement along the axis of said roll-over frame, said roll-over frame having said angers mounted on opposite sides thereof, means for adjustably moving said roll-over frame with respect to said leveling frame for selectively adjusting said angers to the seam to be mined, means for reciprocably moving said angers during operation thereof comprising a motor on said leveling frame, a crank driven by said motor, a lever pivoted to said leveling frame at one end and oscillatibly driven by said crank at its opposite end, and a drive connection between said lever and said roll-over frame concentric with the axis of rotation thereof comprising a shaft mounted in said over-roll frame for rotation with respect thereto about the axis of rotation thereof, means restraining axial movement of said shaft with respect to said roll-over frame, and an operative connection between said shaft and lever, intermediate the ends thereof.

5. In a mining apparatus, a mobile main frame, a side cutting mining head including two connected and laterally spaced side cutting mining augers, means for rotatably driving said angers in opposite directions, a support for said angers on said main frame including a turret pivoted I to said main frame for movement across the front thereof, an elevating frame mounted on said turret, a leveling frame mounted on said elevating frame and extending in advance thereto, a roll-over frame pivotally mounted ;on said elevating frame for movement with respect thereto about an axis extending longitudinally of said angers and spaced therebetween and for movement along the axis of rotation of said roll-over frame, said angers extending along opposite sides of said roll-over frame beyond the forward end thereof, means for reciprocably moving said angers during rotation thereof comprising a motor on said leveling frame, a crank rotatably driven thereby, a lever pivotally mounted on said leveling frame, a drive connection from said crank to said lever for oscillatably driving said lever, a drive connection from said lever to said roll-over frame concentric with the axis of rotation thereof, means for adjustably moving said rollover frame andretaining said roll-over frame in various desired positions of adjustment comprising a collar having splined driving engagement with said roll-over frame and accommodating axial movement of said roll-over frame with respect to said collar, and a fluid operated jack pivotally mounted on said elevating frame and having operative connection with said collar for adjustably moving said collar and roll-over frame.

6. In a mining apparatus, a side cutting mining head having two laterally spaced side cutting mining augers, support means for said angers comprising a roll-over frame disposed between said angers and having supporting engagement therewith, means supporting said rollover frame for movement about an axis extending longitudinally of said angers and spaced therebetween, fluid pressure operated means selectively operable to adjustably move said roll-over frame and angers about the longitudinal axis thereof, means for driving said angers comprising an individual motor for each anger forming a rearward continuation thereof, and a geared drive connection from each motor to an associated anger.

7. In a mining apparatus of the class described, a mobile main frame, a side cutting mining head supported on said main frame in advance thereof for lateral movement across the forward end thereof and for vertical adjustable movement about an axis extending longitudinally of said frame, a conveyor extending along said frame, gathering mechanism for picking up loose material from the ground and depositing it onto said conveyor, said side cutting mining head comprising laterally spaced advance and retreating side cutting angers and power means for driving said angers, and a cuttings confining shield movably mounted on said mining head for adjustable movement with respect thereto by gravity to maintain said shield in engagement with the ground upon vertical movement of said anger with respect to the ground and extending along the retreating of said angers and confining the material mined thereby to the path of the spiral of said auger, to be conveyed by said auger to said gathering mechanism.

8. In a mining apparatus of the class described, a mobile main frame, a side cutting mining head supported on said main frame in advance thereof, for lateral movement with respect thereto and for vertical adjustable movement about an axis extending longitudinally of said mining head, a conveyor extending along said main .frame, gathering mechanism for picking up loose material from the ground and depositing it onto said conveyor, said side cutting mining head comprising laterally spaced parallel advance and retreating side cutting angers and power means for driving said augers, a cuttings confining shield extending along the retreating side of the retreating of said angers for confining the cuttings thereto to be conveyed thereby to said gathering mechanism, and means pivotally mounting said confining shield on said mining head to engage the ground by gravity upon vertical movement of said mining head with respect to the ground.

9. In a mining apparatus of the class described, a mobile main frame, a side cutting mining head supported on said main frame in advance thereof for lateral movement across the forward end thereof and for vertical adjustable movement with respect thereto about an axis extending longitudinally of said frame, a conveyor extending along said frame, gathering mechanism for picking up loose material from the ground and depositing it onto said conveyor, said side cutting mining head comprising laterally spaced parallel advance and retreating side cutting augers having individual motors for driving the same and conveying spirals extending therealong for advancing the cuttings toward said gathering mechanism, a cuttings confining shield carried by said mining head and extending along the retreating of said augers, and means pivotally mounting said cuttings confining shield on said mining head for pivotal movement about an axis coaxial with the axis of rotation of the retreating of said augers and accommodating said cuttings confining shield to have free engagement with the ground upon vertical adjustment of said mining head with respect to the ground.

UNITED STATES PATENTS Moreau Jan. 17, 1888 OToole Apr. 13, 1920 Osgood Aug. 24, 1943 McCarthy Mar. 27, 1951 Bergmann Nov. 1, 1955 Barrett Jan. 8, 1957 FOREIGN PATENTS France July 19, 1923 Germany Oct. 5, 1923 Great Britain Apr. 13, 1922 Great Britain Aug. 3, 1955 OTHER REFERENCES

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