US2836407A - Continuous mining machine of the boring type having adjustable cutter chains - Google Patents

Description

May 27, 1958 B. F. TRACY EIAL 2,336,407

CONTINUOUS MINING MACHINE OF THE BORING TYPE HAVING ADJUSTABLE CUTTER CHAINS Filed Sept. 24, 1953 4 Sheets-Sheet 1 IN VENTORS g} Beg mini? 71mg 'd Jame; ai'ads ATTORNEY May 27, 1958 B. F. TRACY ETAL 7 CQNTINUOUS MINING MACHINE OF THE BORING TYPE HAVING ADJUSTABLE CUTTER CHAINS 4 Sheets-Sheet 2 Filed Sept. 24, 1953 mi k-31 023 flezy'aminiffracy BY dJames afiads gm, &

ATTORNEYS H! ll May 27, 1958 B. F. TRACY ETAL 2,335,407

CONTINUOUS MINING MACHINE OF THE BORING TYPE HAVING ADJUSTABLE CUTTER CHAINS Filed Sept. 24, 1953 4 Sheets-Sheet 3 dvuw, #4404.

ATTORNEYS May 27, 1958 F. TRACY ETAL 2,836,407

CONTINUOUS ING MACHINE E BORING TYPE HAVING ADJUSTABLE C CHAINS Filed Sept. 24, 1953 4 Sheets-Sheet 4 J J 7 y. 6. 7 y.

Bey aim?! 1. Tracy James 0.1700:

INVENTORS zwwwwm ATTORNEYS United States CONTINUOUS Mina-No amounts or eon ING TYPE HAVENG ADEUSTAL-LE rren CHAINS Benjamin F. Tracy and Blames O. Ends, Point Pieasant, VJ. Va, assignors, by mesne assignments, to National Mine Service Company, a corporation of West Virginia Application September 2d, 1953, Serial No. 332,il2

4 Claims. (Cl. 262-7) Generally this invention relates to a continuous ing machine for mining frangible rocks of the nature coal, particularly in tunneling operations through coal veins. More specifically the invention relates to oer and lower cusp cutter chains on a continuous coal mining machine an adjustable mounting for such cusp cutter chains.

Through the ye; substantial advances have been made i the mechanization of coal mining, such mechanization .crning highly developed, not only for greater safety of the operating personnel in the mine, but also to subst ntially increase the productive yield of coal from the re. Thus, in both surface mining and below-ground .ining, machines have been developed for producing a ..-.ibstantially continuous mining of the coal from th vein. The hereinafter disclosed invention is particularly concerned with a continuous mining machine specifically adapted for underground mining operations. The continuous operation or" this mining machine produces an entry into which the machine moves during mining of the coal from the coal vein.

Generally, the continuous mining machine as described hereinafter utilizes a pair of rotary cutters respectively mounted on the forward ends of a pair of horizontal parallel shafts, which shafts are rotated by driving means carried on the main frame of the mining machine. These rotary cutters during forward movement of the machine into the coal vein cut kerfs in the vein and break down the intervening coal mass to produce parallel cylindrical ores through the coal vein. The bores produced by such rotary cutters overlap one another so as to leave an upper and lower cusp of coal separating the two parallel bores formed by the cutting action of the rotary cutters. To remove these two coal cusps extending downwardly and upwardly from the roof and floor, respectively, the entry, 21 pa of endless cutter chains are mounted on the mining machine adjacent but rearwardly of the face of the rotary cutters so as to produce cuts tangent to the uppermost and lowermost points on the bores proby such rotary cutters. These cuts made by the pair of cutter chains define the roof and floor of the completed tunnel or entry created by operation of the mining machine, and thus clear the entry of the two cusps of coal left by the cutting action of the two rotary cutters. As the mining machine is propelled gradually forward into the coal vein, the coal severed by the combined action of the rotary cutters and the two endless cutter chains '2 collected from the face of the vein being mined and transported rearwardly of the machine by a traveling conveyor mounted on the main frame of the mining machine.

Operation of the type of mining machine generally described above produces a substantially continuous mining action, in that as the mining machine is propelled slowly forward into the coal vein, the rotary cutters and cutter chains continuously mine away the coal in front of the n'iachine produce entry or tunnel suf- 2835,43? Patented May 27, 1958 ice ficiently large to enable the machine to move continuously forward into the vein of coal.

Underground coal mining operations expose the mining personnel to a wide variety of ever-present dangers within the mine. Obviously, in utilizing machines to increase the productivity of the coal mining operation, it is of primary importance that such machines be designed and developed with the safety of the operating personnel always in mind. One of the ever-present dangers encountered in underground mining stems from the possibility of settling of the roof of the entry or tunnel in the mine occurring When the machine has not been operated for a period of time, as for example, when the machine stands overnight, or when the roof of the entry falls as a result of the removal of the coal from the vein. Such a settling or roof fall will invariably result in the cutting elements or" the mining machine becoming jammed in the entry immediately adjacent the face of the coal vein being mined. Obviously, a sudden roof fall requires that the operating personnel of the mining machine abandon the machine in the interest of their own safety. Subsequently, in salvaging operations or Where a minor roof settling or floor upheaval has taken place, it is necessary that the cutting elements of the mining machine be capable of being retracted to decrease the overall dimensions of such cutting elements and thereby enable withdrawal of the mining machine from its wedged position within the mine entry.

Since it is a dangerous operation for the operator and other personnel in the mine to work adjacent the front of the machine to attempt to free the cutting elements so that the machine may be moved from its jammed location, it is extremely desirable for the safety of the operating personnel that the cutting elements be readily retractable and that such retracting may be performed at a point remote from the front of the machine which has become jammed in the entry. in addition to the salvage and recovery advantages of a mining machine wherein the overall dimensions of the mining machine cutting elements may be readily decreased, it is important that the mining machine cutting elements be capable of being retracted to enable free movement of the machine around the mine through restricted entries in transporting the machine from one point of use to another.

Accordingly, it is a principal object of this invention to provide an improved continuous mining machine suitable for mining frangible rocks of the nature of coal which will provide the highest degree of safety for the operators and other personnel in the mine.

it is also a primary object of this invention to provide a coal mining machine wherein the cutter chains which produce cuts defining the roof and floor of the mine entry may be moved from their normal operating positions to facilitate removal of the machine from the mining posi tion and permit movement of the machine through restricted entries Within the mine.

It is another object of this invention to provide a mining machine having vertically adjustable upper and/ or lower cutter chain guides to enable retraction of the cutter chains from their normal cutting plane.

It is a further object of this invention to provide a continuous mining machine having endless cusp cutter chains traveling in a substantially vertical plane with the upper and lowermost portions of the respective chains traveling in a path which is variable to change the height of entry produced upon operation of the mining machine.

It is another object of this invention to provide a mining machine having a horizontal chain guide which is hydraulically raised and lowered and is capable of being rigidly secured in the desired location for the cutting operation.

It is an additional object of this invention to provide a mining machine having cusp cutter chain guides hydraulically actuable from a point remote from the cutting face of'the machine, which utilizes improved hydraulic actuators designed to effectively preclude the entrance of coal dust thereinto, such actuators being vari- 1 able by the use of stops positioned to determine the limit of the individual actuator extension.

With the foregoing and other objects in view which will appear as the description proceeds, the invention resides in the combination and arrangement of parts and in the details of construction hereinafter. described and claimed, it being understood that changes in the precise embodiments of the invention herein disclosed may be made within the scope of the appended claims without departing from the spirit of the invention. 7

Referring'to the drawings: I

' Figure l is a partial side elevational view illustrating the forwardend of the mining machine of this invention.

Figure 2 is a view taken on line 22 of Figure 1.

Figure 3 is a detailed elevational view illustrating the 'mounting of the upper cutter chain guide.

Figure 4 is a sectional view taken on line 44.of Figure 3. i V

Figure 5 is a plan view of the upper cutter chain guide mounting and associated parts as shown in Figure 3.

4 rotary cutter are fully set forth and described in the above noted application.

The individual rotary cutters6 mounted on the forward ends of the parallel shafts 5 are synchronized through the gearing within the casing 4 so that during the cutting operation they produce the parallel overlapping bores,

the diameter of which determines the size ,of the final entry produced by the mining machine. Generally, each rotary cutter 6 is characterized by having a central pilot bit 8 and radially spaced kerf cutting bits 9. mounted on the radial arms of the rotary cutter. A swaging member 10 is carried by the pilot bit 8 so as to enterthe 'bor'e produced by such bit'and wedge the coal material outwardly to break free the frangible rock material between the bore made by the pilot bit 8 and the innermost kerf cutting bits 9. Adjacent the kerf cutting bits" .9 there is supported a breaker roller 11 mounted so as Figure 6 is a front elevational view similar to Figure 7 3 illustrating an alternative form of upper chain guide taken on line 99 of I lizing. adjustable cutting elements which cut a tunnel of suflicient size to enable the machine 'to move thereinto and further permit retraction or decreasing of the dimensions of the cutting elementsto permit withdrawal of the machinefrom a jammed position and/or facilitate the movement of the machine around the mine from the various points of use. The mining machine consists. V

of a main frame 1 which carries all of the coal cutting machinery of the mining machine, including the driving means for the rotary cutters and cusp cutter chains,

and the propulsion means for the endless mining machine crawler tracks 2. The main frame 1 is supported on the crawler trackframe by four hydraulic trim jacks, one of which is shown at 3 on Figure 1. These trim jacks, positioned adjacent each of the four corners of thelmining' machine, enable the'main frame 1 to be readily adjusted with relation to the crawler tracks 2 so as to position the; cutting elements of the machine in the desired relation with respect to the crawler tracks.

Thedriving means (not shown) for the parallel shafts V which support the rotary cutters and for the cusp cutter chains is coupled to suitable gearing housed in a casing 4 mounted on the forward end of the mainframe 1.

Appropriate gearing within the casing 4 reduces the speed of the driving means and appropriately synchronizes the speed of rotation of the two shafts S which are parallel to and spaced on either side of the longitudinal axis of the mining machine. The forward end of each of the shafts 5 has mounted thereon a rotary cutter 6 which preferably is of the type disclosed and claimed in copending application Serial No. 374,910 filed August 18, 1953, now abandoned. The rotary cutter 6 secured on the shaft 5 is provided with an actuating means 7 which is manually operated to decrease the length of the rotary cutters from a point'remote from the face of the mining machine. The operation and purposes ofthis adjustable to engage the side of the annular mass of coal material remaining between the kerf cutting bits 9 to efiect breaking of this mass of coal from the face of the vein being mined. A shovel plate 12 is also mounted on each end of rotary butter 6 adjacent the kerf cutting bits 9 on the side opposite the breaker roller 11.-

To move the mass of coal which is cut and broken away from the face of the vein being mined, a traveling conveyor 15 is mounted intermediate the mining machine crawler tracks 2 to extend from a point adjacent the forward end of the machine near the floor level of the mine upwardly and rearwardly to the rear end of the mining machine. This conveyor collects the coal from the front .of the machine as deposited in its intake by shovel plates 12 on the rotary cutters 6, and transports it rearwardlyfor loading into mine cars or other means to remove the coal from the point ofmining.

The cutting action of the two overlapping rotary cutters 6, as hereinbefore described, leaves an upper and lower cusp of coal extending respectively downwardly and upwardly from the roof and floor of the mine entry. In order to enable the mining machine to completely move into the tunnel or entry which it is cutting into the coal vein, it is necessary that these two coal cusps be cut and removed from the tunnel being mined. To perform this cutting and removing action, a pair of endless cutter chains and 21 are mounted adjacentbutrear wardly of the cutting face of the rotary cutters 6. These two endless cutter chains produce cuts which define the roof and fioor of the mine entry intowhich the machine gradually moves during continuous. operation of the miner. The path of these two cutter chains generally lies in a vertical plane immediately behindthe two rotary cutters 6. The path of travel of these two chains is best illustrated by the view shown in Figure 2, wherein it will be noted that the cutting portion of the path of travel of the cutter-chains 20 and 21 is supported and guided by an upper chain guide 22 and a lower chain guide 23, respectively. p

The lower chain guide 23 is mounted to extend beneath front plates 24 positioned at each side of the entrance tothe conveyor 15. These plates 24, attached to the forward end of'the miner, function to hold or confine coal vein.

'Idler pulleys 25 are carried by the lower chain guide 23 at the opposite ends thereof around which the cutter chain 21 extends in traversing its path. upwardly across the face of the mining machine. The chain guide 23 is mounted for adjustment relative to the other mining elements carried on the main frame 1 by suitable hydraulic actuators'26. These hydraulic actuators connectedbe tween the main frame 1 and chain guide 23 may be actuated as desired by controlling the flow of hydraulic fluid thereto, through appropriate manipulation of valves on the hydraulic manifold mounted adjacent the operator of the mining machine.

In the embodiment shown on the drawings, hydraulic actuators 26 serve as the mounting for the lower chain guide 23 and idler pulleys 25 to enable adjustment of the lower chain guide relative to the floor of the mine entry. However, as previously described, the main frame 1 is mounted on four hydraul c trim jacks 3 by means of which such main frame may be suitably positioned with relation to the crawler tracks 2 of the mining machine. Therefore, if desired, the hydraulic actuators 26 may be omitted and the chain guide 23, which carries the pulleys 25, rigidly mounted, as by bolting, on the forward end of the mining machine. Then the trim jacks 3 will be used to adjust the lower chain guide relative to the mine floor. By such rigid mounting of the chain guide 23, as by bolting or welding it to the front of the miner, the necessary adiustment of the level of the lower chain guide 23 may be secured by using the hydraulic trim jacks 3 to raise or lower the main frame 1 with respect to the crawler tracks 2.

The lower cutter chain 21 extends upwardly from its horizontal cutting path across the front face of the mining machine to drivingly engage a driving sprocket 34 which is suitably secured on the outer end of a shaft 31 extending through the front of the gear casing 4 and driven at an appropriate speed by the main driving means coupled through the gearing in the casing A tensioning sprocket 32 is journaled on the outer end of a stub shaft 33 mounted on a support 34 which in turn is pivotally supported behind the driving sprocket 3% so as to be movable about the axis of the shaft 31. The sr port 34, which carries the tensioning sprocket 32 on the stub shaft 33, is continuously urged about its support axis by a tensioning device 35 secured to the front of casing so that the tensioning sprocket will be urged into engagement with the cutter 21 to continuously maintain such chain taut about the driving sprocket 3i idler pulleys 25 and chain guide 23.

it will be readily recognized that rotation of the shaft 31 through the a, ropriate gearing in the casing will cause the cutter chain 21 to move along the path, as outlined on figure 2, with the portion of such path extending betwee the idler pulleys 25 forming the cutting portion of the chain to remove the lower coal cusp during operation of the fililil'lg machine in a coal mine. The tensioning device 35 at all times urges sprocket 32 to wrap the cutter chain 21 further around the driving sprocket 35} to keep such cutter chain taut and driving engagement w 'ocket The upper cutter chain 29 travels in a path lying in a vertical plane similar to the path traversed by the lower cutter chain 21. "e upper cutter chain 2i? is supported and guided dur'ng the portion of its path wherein cutting is performed by the upper chain guide 22. The opposite e ds of the uper chain guide 22 have journaled thereon i dler pulleys 4% similar to the idler pulleys 25 adjacent the ends of the lower chain guide 23. The path of the cutter extends down aro" id a driving sprocke ll mounted on a shaft 42 extending from the casing 4 wherein it is suitably coupled to the main driving means of the mining machine so as to be driven thereby. A tens oning sprocket 4 3 is ournaled on a stub shaft carried by a support 45 pivotally mounted so as to be movable about the axis of the sh= ft 42, and a tensioning device 46 is secured to the front face of the casing 4 to continuously urge the tensioning sprocket 43 against the cutter chain 20 to maintain such chain taut and in driving engagement with the driving sprocket 41. Thus the operation of the upper cutter chain 2b is substantially identical to that of the lower cutter chain 23 in being driven by the sprocket 41 coupled to the shaft .2 which 3 rotated t the proper speed by the gearing within the rising To support the upper chain guide 22, a pair of hydraulic actuators 5d are secured between lugs 51 on the ends of the guide 22 and brackets 52 mounted on the front face of the casing 4 adjacent the bearings for the shafts 5 on each side of the mining machine. These hydraulic actuators 50 are pivotally interconnected at their respective ends with the lugs 51 and brackets 52 so that when hydraulic fluid pressure is applied to such actuators, it will cause raising or lowering of the upper chain guide as may be desired during appropriate manipulation of the mining machine.

Cooperating with the hydraulic actuators 50 to guide the movement of the upper chain guide 22 during raising and lowering thereof by the supporting hydraulic actuators 59, there are provided guide arms 55, bolted to the underside of each end of the chain guide 22, with the guiding surfaces thereof extending vertically with respect to the normally horizontal chain guide. A guide rail 56 having a mating surface to engage the vertical guide surface of the guide arm 55 is bolted to the front face of the casing 4 at each side thereof and a notched positioning plate 59 bolted to the top of the casing 4 to extend outwardly over the edge thereof and maintain the rail 56 with its guide engaging surface substantially vertical to cooperate with the guide arm 55.

As more clearly illustrated in Figure 4, the guide surface of the arm 55 is provided with a ridge 57 which cooperates with a groove 58 in the surface of the guide rail 56. This cooperating ridge and groove construction between the arm 55 and the rail 56 provides a support construction for the upper chain guide 22 which in cooperation with the supporting hydraulic actuators 50 will resist the rearward thrust applied to the chain guide during operation of the mining machine when the cutter chain 2% is cutting into the upper coal cusp.

The arms 55 and rails 56 are provided with a series of apertures 66 which, upon relative movement between the respective arms and rails, become aligned to enable the insertion of locating bolts 61 to rigidly secure the upper chain guide in its desired location with respect to the parts of the mining machine. Obviously, however, during raising and lowering of the upper chain guide 22 by the supporting hydraulic actuators 50, the bolts 61 wi 1 not be in place, so that the arms 55 will slide relative to the rails 56 mounted on the front face of the casing Likewise, during various other conditions of use, locating bolts 61 need not be employed, at which time the arms 1'5, by cooperation with the rails 56, will serve to effectively guide and maintain the upper chain guide 2?. horizontal during raising, lowering, and/or While in use.

To provide additional support to resist the thrust encountered during cutting with the chain 20, the upper chain guide 22 is further provided with lugs 65 at each 7 end which carry pins 66 extending from each side thereof. Brackets 67' are secured to the top face of the casing 4 to pivotally support diagonal struts 68 which each carry a yoke 69 at the opposite end thereof to engage the respective pins 66 and lugs 65 on the upper cutter chain guide 22. The length of the diagonal strut 68 is variable by means of a nut 70 threaded onto the rod which carries the yoke 69 and adapted to engage the end of the sleeve into which such rod slides and which is pivotally carried by the bracket67. Thus, it will be seen that once the chain guide 22 has been positioned at its desired height, the additional thrust resisting support provided by the diagonal struts 68 may be brought into use by threading the nut 7% down into engagement with the end of the sleeve of the strut so that the diagonal struts will provide thrust resistance for the cutter chain in addition to the thrust resistance offered by the engaging relationship between the arms 55 and rails 56.

With tie hereinabove described structure, it can readily be appreciated that the upper path of travel of the cutter chain 26 may be lowered or raised by suitably With'the rails 56.. The'engagement' of these two latter; members provides a thrust resisting support for the cutter chain to which is' added the support of the diagonal .struts 68 which are adjustable in length to accommodate the varying diagonal distances encountered when the Chain guide 22 is at the'various levelsof adjustment.-

Generally, it is contemplated that the upper chain .guide will be u'sedat a particular location correlated with the specific location of'the lower'chain guide 23 and the length of the rotary cutters 6. This location is determined by the height at which the cutter chain 2%? will make a cut in the frangible rock material which is tangent to the circles scribed by the two overlapping rotary cutters,6. Thus when'the hydraulic actuators 50 are fully extended the chain guide 22 is at its proper heightto guide the chain 20 in cutting 'the'roof line of the entry,

V the rotary cutters 6 will be retracted by manipulation'of the individual actuating. means 7 for each rotary cutter.

This combined action will reduce the overall'dimensions:

our

serves to admit the hydraulic fluid into the plunger. 81 to eifect actuation of the hydraulic actuator as hereinafter described. 7 2 Q The ,plunger- 81 is telescopedinto a cylinder 84 which :is connected 'to' the underside of the chain guide 22 by a pin .en ga'ging-a'bracket 86 bolted to the underside of suchchain guide adjacent theend thereof. The cylinder 84. is provided with a suitable packing gland. 87' to pre.-'

verit'leakage of hydraulic fluid from the interior of the cylinder e i'and plunger 8l during use of the hydraulic actuator. I i i Cooperating with the hydraulic actuators to guide movement of the upper chain guide 22 there are'p rovided guidemembers 90 each having a slot'91 to receive one the cylinders dtherein and secured as by welding to front face of the casing 4. Each cylinder34 has wings which extend along'a portion of the lengthof the tal. The guiding action of guide members 90, together withtheir support by the hydraulic actuators oftersfan of the cutting elements of the mining machine to enable its a free withdrawal from the face of the vein being mined and/or permit the machine to be moved aboutthe mine through restricted entriestherein. To insure that the lower chain guide 23 and its cutter chain 21 are free of obstructions on the mine floor, the lower chain guide'and idler pulleys 25 carried thereby may also be raised by appropriate control of hydraulic fluid pressure to the hydraulic actuators 2&5. This will efiect a further reduction in the overall dimensions of the cutting elements of the miner. f When the chain guide 23 is bolted to the forward end of the miner with the hydraulic cylinders omitted, the trim jacks 3 which support the main frame 1 on the crawler tricks 2'may beused to raise the lower a is supported by a pair o f hydraulic actuators and guided by'a guide means cooperating with the hydraulic actuators as in ;the previously described embodiment; As will'be apparent from the description that follows, these. hydraulic actuatorsare of an improved construction and so related to the upper chain guide 22' as to efiectively preclude the entrance of'coal dust or other foreign materialinto the moving parts of the actuator. Figure .6 illustrates one of such supporting hydraulic actuators in its relationship to the chain guide 22 and the front of the casing 4 on which it is mounted. It will be understo od that as in the previously described embodiment, there are two supporting actuators for-the chain' guide 22,. one at each end thereof. T I 7 V In this modified form, a supporting shelf is suitably secured to the front face of the casing 4 as by welding, .to p'rovide an abutment to be engaged. by the end of a plunger-81, the lower end of which rests on the shelf 80 and is suitably retained in positionthereon to provide a pocket forthe end of the plunger 8L The lower end of the plungenSl is suitably tapped to receive a fitting to which is coupled the hydraulic fiuidline 83 which extremely strong and rigid mounting means for the upper chain guide, similar to the mounting described with regard to the 'first'embodiment. V V

The flanges on strips 93 extend into slot 91 sons to engage the outer side of the wings 92 as shown most clearly in Figure 8. Howevena portion of these flanges adjacent the top of guide member 99 extends'further into slot 91 to form limiting abutments 97 for the upper ends of Wings 92 to engage and prevent the cylinder 84 from unduly raising the chain guide-.22; Thus these ab utments' V limit for raising the upper shown in Figures 6 through 10, there is provided'stops' 95 which fit into the spacein the slidepocket provided for the wings 92. These stops aresecured below the limiting abutments 97 by screws 96, and when so" posi tioned and engaged by the upper ends of wings 92, de-

termine the upper limit of the cylinder 84 in raising the upper chain guide 22. a A plurality of tapped bores are provided along the strips 93 as shown on Figureo to accommodate the screws 96 and permit the stops '95 v to be secured in the pocket for wings 92 at any one of a number of positions depending on the desired upper limit for the chain guide 22.

In the use of the hydraulic actuators of the modifical- I 7 tion shown in Figures 6 through 10, the hydraulic fluid admitted through 'line 83 causes the cylinder 84 to move to its extended position limited by engagementof the wings 92 with abutments 97 at the upper ends o f the strips 93, or, if present, stops 95. "In operation of the miner with this modified chain'guide mounting, the cut-' ting elements are. retracted similarly to the operation of the previously described embodiment. The hydraulic actuators support the chain guide, and. the wings 92 on the sides of the cylinders 84 cooperate with guide members to properly guide the raising and lowering of the chain guide. Thus hydraulic pressure applied through line 83 will propel the hydraulic actuators to their limit of travel to position the upper Cutter'chain for use. Likewise on release of the hydraulic fluid by proper manipulation ofthe manifold valves adjacent the mining machine operator the cutter chain'will be -lowered.

The rotary cutters will also be retracted .by actuating.

means .7 so that the cutting elements of the miner be contracted to enable the miner to be readily moved from miuing position and/or be transported through the mine entries. It will be appreciated that the lower chain guide 23 may be raised by employing hydraulic cylinders 26, if present, or by utilizing the trim jacks 3 to clear the cutter chain 21 above the mine floor.

In addition to the increased safety to mine personnel offered by the mining machine of the hereinabove-dcscribed invention, the flexibility of use is substantially increased. The ability to contract the cutting elements of the mining machine with the retracting operation being performed at a point remote from the cutting face of the mining machine promites safe mine operating procedures, since the operator or other mine personnel need not subject themselves to the hazards of working adjacent the cutting face where roof settling may have occurred or may occur while they are working on the machine. Likewise, the adjustability of the relationship between the various cutting elements of the mining machine permits the machine to be readily adjusted to produce a variety of different size entries, depending on the settings of the cutting elements. Thus the stops 95 may be employed to vary the upper limit of the chain guide 22 and the rotary cutters 6 adjusted to correspond to the diameter necessary to cooperate with the plane of the upper cutter chain at its limit. By the same token the lower cutter chain may be adjusted by hydraulic cylinders 26 to be tangent with the bores produced by the new setting of the rotary cutters 6 or be adjusted by relocating the chain guide 23 as bolted on the forward end of the miner in the absence of hydraulic cylinders 26.

Having thus described our invention, what we claim is:

l. A mining machine comprising a main frame, a crawler track frame having a pair of propelling crawler tracks, means supporting said main frame on said crawler track frame to permit relative adjustment therebetween, a pair of parallel horizontal shafts carried by said main frame, rotary cutters respectively mounted on the forward ends of said shafts to cut parallel horizontal bores during operation of said mining machine, a cutter chain having an effective cutting portion normally extending tangent to said parallel bores, a chain guide engaging and supporting the effective cutting portion of said cutter chain, a pair of elongatable hydraulic actuators each having a cylinder and a plunger telescopically engaging said cylinder, said cylinders being secured to the opposite ends of said chain guide respectively to move therewith during raising and lowering of said chain guide and the plungers cooperating respectively with said cylinders being supportingly engaged with said main frame to be stationary with respect thereto, means for coupling a controlling hydraulic fluid to said cylinders to effect raising and lowering of said chain grn'de relative to said main frame, and guide members secured to said main frame each having a slot extending longitudinally thereof, one of said cylinders being slidably received in each of said guide members, said guide members guiding the movement of said cylinders in positioning said chain guide relative to said main frame to restrain said chain guide to move in a vertical plane during raising and lowering thereof under control of said actuators and resist rearward thrusts imparted to said chain guide in use of the mining machine.

2. in a mining machine of the type having rotary cutters mounted on the forward end of the machine rotatable in a vertical plane to cut parallel overlapping cylindrical bores in the material being mined, a cutter chain having an effective cutting portion thereof normally extending substantially tangentially to the parallel cylindrical bores, an elongated chain guide supporting said effective cutting portion, a first elongatable hydraulic actuator having a pair of slidably telescoping members with one of said members connected to and movable with one end of said chain guide and the other member supported on the forward end of the mining machine to be stationary with respect thereto, a second elongatable hydraulic actuator having a pair of slidably telescoping members with one of said members connected to and movable with the other end of said chain guide and the other member thereof supported on the forward end of the mining machine to be stationary with respect thereto, a pair of spaced parallel guide members rigidly mounted on the forward end of the mining machine beneath the opposite ends of said chain guide respectively, each of said guide members having a vertically extending longitudinally grooved guide surface, each of the members of said first and second elongated hydraulic actuators which are connected to and movable with said chain guide being slidably engaged with the vertically extending guide surface of one of said guide members to restrain said chain guide to move in a vertical plane during raising and lowering thereof under control of said actuators and resist rearward thrusts imparted to said chain guide in use of the mining machine, and means cooperating with the engaging guide members and members of said hydraulic actuators movable with said chain guide to limit upward movement of said chain guide, said means being selectively adjustable to alter the upper position of said chain guide.

3. In a mining machine as recited in claim 2 further comprising a second cutter chain having an effective cutting portion thereof normally extending substantially tangent to the cylindrical bores on the side thereof diametrically opposite the points of tangency of the first cutter chain, a second chain guide engaging and guiding the effective cutting portion of said second cutter chain, and hydraulic actuators mounting said second chain guide to permit limited movement of said cutting portion of said second cutter chain away from its normal position.

4. In a mining machine as recited in claim 2 wherein the members of said hydraulic actuators movable with said chain guide have longitudinal wings on the sides thereof slidably engaged in the longitudinal grooves of said guide members, and abutments are provided at the ends of the grooves in said guide members to be engaged by the ends of said wings to limit movement of said chain guide.

References Cited in the file of this patent UNITED STATES PATENTS 229,882 Gordon July 13, 1880 571,348 Dorsey Nov. 17, 1896 1,603,621 McKinlay Oct. 19, 1920 1,726,963 McKinley Sept. 3, 1929 2,093,448 Joy Sept. 21, 1937 2,461,877 Brereton Feb. 15, 1949 2,705,624 Robbins Apr. 5, 1955 2,734,731 Cartlidge et al. Feb. 14, 1956 OTHER REFERENCES Mechanization, April 1951, page 97.

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