US3736771A - Removable bearing assembly for tunneling machine - Google Patents

Abstract

An easily replaceable bearing assembly for a tunneling machine including a housing, a rotor within the housing, radial bearings for supporting respective ends of the rotor from the housing, a thrust bearing intermediate the radial bearings and disposed between respective thrust collars on the housing and rotor so that a forward thrust on the housing can drive the rotor forward, removable means for applying a forward drive to the rearward end of the housing and a rotating drive to the rearward end of the rotor, and means for attaching a rotating cutter to the forward end of the rotor so as to be concurrently driven forwardly and in rotation.

Description

llited States Patent 11 1 Safar 51 June 5, 1973 541 REMOVABLE BEARING ASSEMBLY 2,756,036 7/1956 Mclntyre ..299 31 x FOR TUNNELING MACHINE 1,232,750 7/1917 Amess ..308/175 X [75] Inventor: Frank Saiar, Fullerton, Calif. Primary Examiner Emest R. Purser [73] Assignee: Smith International, Inc., Newport Att0rney-Beehler,Arant&Jagger Beach, Calif 22 Filed: Aug. 30, 1971 [57] ABSTRACT An easily replaceable bearing assembly for a tunneling [21] Appl' 175824 machine including a housing, a rotor within the hous Related US, A li ti D t ing, radial bearings for supporting respective ends of 62 the rotor from the housing, a thrust bearing inter- 1 Dw'slon ofser 8637810 1969' mediate the radial bearings and disposed between respective thrust collars on the housing and rotor so 2? 43 33 32 3;g figzi that a forward thrust on the housing can drive the l58l F It! 299/3; 33 59 rotor forward, removable means for applying a for- 0 174 /5 ward drive to the rearward end of the housing and a rotating drive to the rearward end of the rotor, and means for attaching a rotating cutter to the forward [56] References Cned end of the rotor so as to be concurrently driven for- UNITED STATES PATENTS wardly and in rotation- 2,991,058 7/1961 Alspaugh et al ....299/57 6 Claims, 4 Drawing Figures PATENTEDJUH 5 I975 SHEET 1 [IF 4 PATENTEDJUN 5|975 3.736.771

SHEET 2 OF 4 INVENTOR.

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SHEET U 0F 4 INVENTOR. F64/VA $454.2

% aw/M REMOVABLE BEARING ASSEMBLY FOR TUNNELING MACHINE This application is a division of my prior copending application, Ser. No. 863,783, filed Oct. 6, 1969.

BACKGROUND OF THE INVENTION The present invention relates to replaceable bearing assemblies for tunneling machines having a rotary boring head or cutter for cutting passages through hard rock and minerals. Machines of this type frequently bear stress loads of a million pounds or more. The high degree of hardness of material being cut reflects a heavy stress load on the boring head or cutter, and this stress load in turn must be carried by a bearing mechanism which permits the boring head or cutter to rotate, and must also be transmitted to other supporting portions of the machine.

It is well known in the art in a machine of this type to utilize a main support frame and a movable frame, which are longitudinally movable relative to each other, thus permitting a stepwise advance of the machine in a forwardly direction as the tunnel is being cut. The main frame typically has a set of forward shoes and a set of rearward shoes, each of which may be extended for supportive engagement with the tunnel wall. The movable frame also has a forward shoe and a rearward shoe which support both frames during the time when the main support frame is being relocated in the tunnel.

Heretofore, the machines of this general type have suffered from a very short useful life before rebuilding or major repair has been required. The primary object and purpose of the present invention is to provide a replaceable bearing assembly for a machine of the type described, which has a long useful life before rebuilding or repairs are required.

The present invention provides a replaceable bearing assembly for a tunneling machine comprising: a hollow housing having a generally cylindrical configuration and having means on its rearward end adapted for removable attachment of said housing to the forward end of a movable support frame, said housing having on its interior surface a thrust collar located intermediate to its forward and rearward ends, said interior thrust collar having a forwardly facing thrust shoulder, a rotor disposed within said housing, said rotor having on its forward end means for removably attaching a rotating cutter thereto, having on its rearward end means for coupling a drive shaft thereto, and having on its exterior surface a thrust collar with a rearwardly facing thrust shoulder, a thrust bearing disposed between said interior thrust collar of said housing and said thrust collar of said rotor, whereby forward thrust exerted against said housing may be imparted to said rotor, and a pair of radial bearings disposed between said housing and said rotor, one at the forward end and the other at the rearward end, whereby rotating thrust from said drive shaft may be concurrently imparted to said cutting wheel.

In the drawings:

FIG. 1 is a schematic diagram showing the main operative parts of the machine;

FIG. 2 is a side elevational view of a tunneling machine in accordance with the present invention, located in a cutting position within a tunnel;

FIG. 3 is a vertical cross-sectional view of the machine taken on the line 3-3 of FIG. 2;

FIG. 4 is a longitudinal cross-sectional view of the front end portion of the machine.

The tunneling machine of the present invention will first be generally described with reference to FIG. 1 of the drawings.

The tunneling machine includes a main support frame 50 having front telescoping legs 60 and rear telescoping legs 65 which are adapted for outward extension to grip the tunnel wall. Thrust cylinders carried at the forward end of main support frame 50 provide a forward thrust drive means and are expanded for driving the operative portions of the machine in a forwardly direction so as to force the cutter 300 against the end face of the tunnel.

A movable frame is disposed within the main support frame 50, and is longitudinally movable relative to the main support frame. All of the operative portions of the tunneling machine are connected or coupled, either directly or indirectly, to the movable frame 110. Thus the machine as a whole can be advanced stepwise in the forwardly direction. The procedure is that the main support frame 50 is located in a particular longitudinal position within the tunnel; the telescoping legs 60 and 65 are extended into engagement with the tunnel walls so as to rigidly support the main support frame in that location; and the thrust cylinders 80 are then expanded forwardly until a particular cutting stroke has been completed. Auxiliary shoes 160 and 165, associated with the forward and rearward ends, respectively of the movable frame 110 are then used for supporting the entire machine while the main support frame 50 is being relocated to a more forwardly advanced position. This general mode of advancing the machine is well known in the art and hence need not be described in further detail.

Although the specific mechanism is not shown in FIG. 1, the movable frame 110 is supported in a nonrotative relationship to the main support frame 50, but is free to move longitudinally relative to the main support frame 50, and is preferably supported in a longitudinal sliding relationship relative to the main frame 50.

A main drive shaft 130 is disposed inside the movable frame 110, and is advanced along the tunnel in conjunction with movement of the movable frame. A rear bearing supports the rearward end of drive shaft for rotation relative to movable frame 110. A gear box is attached to the rearward end of movable frame 110, and is also coupled to the rearward end of the main drive shaft 130. A drive motor associated with gear box 135 is operable for imparting a rotating drive to the drive shaft 130, so that the drive shaft will rotate relative to the movable frame 110. The rear auxiliary shoe 165, although it could be attached directly to the rearward end of movable frame 110, is for convenience attached underneath gear box 135.

To complete the rotating drive mechanism a pair of driving gears 150, 155 are located at the forward end of the main drive shaft 130. The drive gear is a male gear which is rigidly attached to the forward end of drive shaft 130. The driving gear is a female gear which is rigidly (but removably) attached to the rotor 220 of main bearing assembly 200. An important feature of the present invention is that the female gear 155 is free to slide longitudinally, at least to some extent, relative to the male drive gear 150. The significance of that feature of the machine will be described subsequently.

A main bearing assembly 200 is used to support and to drive the cutter 300, and concurrently receives both the forward thrust drive from thrust cylinders 80 and the rotating drive from drive shaft 130. The main bearing assembly 200 includes a housing or stator 210 which is of a generally hollow cylindrical configuration. A rotor 220 is disposed concentrically within the housing 210, and is supported for rotation relative to the housing by means of a front end radial bearing 240 and a rear end radial bearing 250. Removable attachment means such as bolts 221 are employed for removably attaching the female drive gear 155 to the rearward end of rotor 220. Removable attachment means such as bolts 222 are used for removably attaching the cutter 300 to the forward end of rotor 220.

The rearward end of housing or stator 210 is removably attached to the forward end of movable frame 110, as by means of bolts 211. The forward thrust of the thrust cylinders 80 is applied to a thrust collar 215 formed on the housing 210, hence the forward thrust of the thrust cylinders 80 serves to pull the movable frame 110 in a forwardly direction.

Also located between the housing 210 and the rotor 220 is a thrust bearing 230, which is disposed intermediate to the forward and rearward end bearings. The

. function of the thrust bearing 230 is to impart a forward thrust drive from the housing or stator 210 into the rotor 220. The associated mechanism includes an interior thrust collar 217 on the housing 210 which has a forwardly facing thrust shoulder, and an exterior thrust collar 225 on the rotor 220 which has a rearwardly facing thrust shoulder, the thrust bearing 230 being supported between these two thrust shoulders.

The forward auxiliary shoe 160, although it could be attached directly to the forward end of movable frame 110, is for convenience attached under the housing 210.

During a cutting operation of the machine the cutter 300 receives both rotational and thrust loadings which vary over a wide range in a rather unpredictable manner, with the peak loadings being very high. In most or all of the prior art machines for tunneling in hard rock or hard minerals, the longitudinal thrust force of the machine as well as vibrational stresses are imparted through the main drive shaft into the rotating drive mechanism. According to the present invention, however, the female drive gear 155 is longitudinally slidable relative to the male drive gear 150, hence the longitudinal and vibrational stresses imparted from cutter 300 to rotor 220 are not transmitted to the drive shaft 130, except perhaps with a greatly reduced magnitude. The gear box 1135 is thus protected from any extraneous interference, and is free to perform its simple function of imparting a rotating drive to the drive shaft 130, under conditions which permit it to have a long useful life and to operate relatively free of maintenance requirements.

Another significant feature of the invention is that the main bearing assembly 200 is arranged for easy removal, in its entirety, from the tunneling machine. Thus the coupling of thrust cylinders 80 to the thrust collar 215 of housing 210 is such as to permit easy detachment of the housing 210 from the thrust cylinders. Removable bolts 211 also permit easy detachment of housing 210 from the movable frame 110. Removable bolts 221 permit easy detachment of female drive gear 155 from rotor 220, and removable bolts 222 permit easy detachment of cutting wheel 30% from the rotor. The radial bearings 240 and 250, and the thrust bearing 230, involve a large number of individual parts, and these bearing mechanisms tend to wear during operation of the machine. The easily removable nature of the attachments of housing or stator 210 and of rotor 220 to the other parts of the machine makes it possible to remove the entire main bearing assembly 200 as a unit. A new main bearing assembly may be inserted in the tunneling machine with comparatively small loss of working time. The worn or damaged main bearing assembly may then be transported away from the construction job to a shop or factory where its repair or overhaul may be conducted on a more leisurely basis.

In utilizing the tunneling machine of the present invention it may be preferred, however, to replace the main bearing assembly 200 periodically as a preventive maintenance feature. In that case, the main bearing assembly which is removed may not be significantly worn or damaged at all, but replacing the old assembly with a new one involves only a short down time for the machine and insures a long uninterrupted operating time for the machine when its usage is resumed.

The presently preferred embodiment of the invention, as illustrated in drawing FIGS. 2, 3 and 4, inclusive, will now be described in some detail.

The structure and operation of the machine has already been described with reference to FIG. 1, where the various component parts of the machine are illustrated schematically, rather than in accordance with their precise mechanical construction. The reference numbers used in FIG. 1 are also applied to the corresponding parts of the machine in FIGS. 2, 3 and 4, hence it will be understood that in FIG. I the particular reference number applies to a schematic representation of the part, whereas in FIGS. 2, 3 and 4, the same reference number indicates the actually preferred, precise form of the same part.

The schematic representation of the machine in FIG. I ignores the fact that in addition to the cutter which may take the form of a circular main cutting wheel 300 the machine also includes a center drill 400. The detailed drawings illustrate a drive mechanism and a bearing support assembly for the center drill, which are concentrically arranged relative to the main drive shaft and main bearing assembly. Before going into a detailed description of the center drill and its associated bearing assembly and drive mechanism, however, it will be advantageous to describe in detail the main portions of the machine which have already been discussed in connection with FIG. ll.

Thus the main support frame 50 has a square crosssectional configuration and is formed of two separate frame halves 52, 5d which are joined together by bolts 58 (FIG. 35). Each of the telescoping front legs 60 has a leg base 62 onto which ribs 56 are attached for purposes of structural reinforcement. Similar rib structures are also associated with the leg bases 67 of the rear telescoping legs 65. Wear bars 70 are attached to the interior corners of the housing structure 52-54 and provide surfaces within which the guide tube 115 may slide longitudinally. The wear bars 70 are preferably made of machined brass material.

The actual physical structure of movable frame includes a guide tube whose cross-sectional configuratiois in the form of a hollow square (FIG. 3) and which extends throughout the greater part of the length of the machine. The exterior corner surfaces of guide tube 115 slide within the wear bars 70, the wear bars being located at both the forward and the rearward ends of housing 50. A circular ring 117 is welded onto the forward end of guide tube 115 (FIG. 4) and forms the forward end portion of movable frame 110. A circular ring 119 is welded to the rearward end of guide tube 115 and forms the rearward end portion of mov able configuration 110.

A front bellows 75 and a rear bellows 77 constitute, in a sense, extensions of the main support frame 50 (FIG. 2). The purpose of these bellows is to prevent dirt and other foreign materials from entering into the interior spaces between housing 50 and guide tube 1 15, in which a precisely controlled longitudinal sliding action of the movable frame 110 needs to be achieved. The front bellows 75 therefore has its rearward end attached to the front end of housing 50 and its forward end attached to the guide tube forward ring 117 (FIG. 4). The rear bellows 77 has its forward end attached to the rearward end of housing 50 while its rearward end is attached to the gear box 135 (FIG. 2).

There are four of the thrust cylinders 80 located at the top, bottom, and sides of main support frame 50 (FIG. 3). Each thrust cylinder has an associated cylinder rod 83 which is extendable in the forward'direction for imparting the thrust force. A removable thrust collar 85 slides over the rearward portion of housing 210 of the main bearing assembly (FIG. 2) and has circumferentially spaced ears 86 in which pins 87 are carried, each pin 87 being pivotally connected to the forward end of the associated rod 83. Removable bolts are used to attach to forward end of thrust collar 85 to the thrust collar 215 of housing 210.

The main drive motor 140 which is schematically illustrated in FIG. 1 by a single-block is in fact a group of six separate motors disposed about the periphery of gear-box 135 (FIG. 2). Each of these motors drives a bull gear 137 (not shown) which is attached to the rearward end of drive shaft 130. During cutting operations of the machine the forward end of drive shaft 130 is supported by the gears 150, 155. When the main bearing assembly 200 is removed from the machine, however, it becomes necessary to indiepndently support the front end of the drive shaft, and for this purpose a support ring 127 is provided within the forward end of guide tube 115.

In the main bearing assembly the front radial bearing 240 has an inner ring or raceway 242, an outer ring or raceway 246, and cylindrical bearings 244 which are retained between the two raceways. A front bearing retainer 260 is attached both to the housing 210 and to the rotor 220 for shielding the bearing 240 from dirt.

Rear radial bearing 250 includes an inner ring or raceway 252, an outer ring or raceway 256, and cylindrical bearings 254 which are disposed between and retained by the two raceways. There are two separate retainers for the rear bearing, the outer one being designated as 270 and the inner one as 280 (FIG. 4). A rotary seal 275 is located between retainers 270, 280.

Thrust bearing 230 includes a rear thrust plate or ring 231 which is supported from the thrust collar 217 of housing 210. A bearing cage 233 (FIG. 4) has radial legs, and on each radial leg there are three cylindrical bearing members 234 disposed for rotation. The thrust ring or plate 231 lies in a plane that is transverse to the longitudinal axis of rotor 220, and the outer circumferential surface of ring 231 firmly engages the interior wall surface of housing 210 while its inner circumferential surface is spaced away from the rotor 220. The cylindrical bearing members 234 ride on the forward flat surface of the rear pressure plate 231, and also ride on the rear flat surface of the rear pressure plate 231, and also ride on the rear flat surface of a forward pressure plate 235. Pressure plate 235 is disposed parallel to the pressure plate 231, having its interior circumferential surface in firm engagement with the exterior surface of rotor 220 to rotate therewith while its outer circumferential surface is spaced away from housing 210. The forward flat surface of pressure ring 235 bears against a spacer ring 225.

It will be noted that in FIG. 1 the reference numeral 225 applies to a part which is schematically illustrated as a thrust collar formed on the exterior surface of rotor 220. In the preferred embodiment of the invention, however, the member 225 is in fact a spacer ring which is slid over the exterior surface of rotor 220, the forward edge of the spacer ring being lodged against inner raceway 242 of the front radial bearing 240. The raceway 242 is, in turn, lodged against a shoulder 226 of rotor 220. Hence, the spacer ring 225 is supported against forward motion relative to the rotor 220, and forward thrust bearing 230 is operative to impart forward thrust from housing 210 into the rotor 220 in the manner which is schematically illustrated in FIG. 1.

The tunneling machine of the present invention is designed for a forward loading on the cutting wheel of approximately one million pounds, and this forward loading is also carried by the thrust bearing 230, thus involving the possibility of a substantial deformation of the component parts of the thrust bearing and associated mechanism. Before placing the machine in operation the parts are aligned in such a way that the rear thrust plate 231 of thrust bearing 230 is spaced a predetermined amount, such as 0.030 inches, from the thrust collar 217 of housing 210. A plurality of recesses 218 are formed in the thrust collar 217, and a separate com pression spring 232 is places within each of the recesses 218 so as to provide a forward pressure against the thrust plate 231. Associated peep holes 212 are formed in the housing 210 so that the initial spacing between thrust plate 231 and thrust collar 217 can be observed, measured, and hence established at its proper value.

The main cutting sheel 300 includes a central hub portion 310 which is machined so as to fit precisely over the forward end of rotor 220. The outer or main part of the cutting wheel and the hub portion are welded together to form an integral structure. A number of bolts pass through corresponding openings in hub portion 310 and into appropriately located threaded openings of the rotor 220. Cutters 320 are mounted about the circumference and face of the cutting wheel 300, as shown in FIG. 2. In the preferred embodiment of the invention there may typically be 31 of these cutters.

The thrust cylinders which are used to drive the machine forward during its cutting stroke may also be used for retracting the cutting wheel 300 away from the tunnel face. Bolts connecting thrust collar 215 to thrust collar provide a positive coupling to the main bearing housing 210 so that it may be withdrawn in the rearward direction. Thrust bearing 230 is effective for thrusting the rotor 220 forward but is not effective in retracting the rotor. However, rear bearing 250 in conjunction with the inner bearing retainer 200 is effective to impart a withdrawing motion from the housing 210 to the rotor 220. The rearward motion of housing 210 is imparted through radial bearing 250 to the outer circumferential portion of bearing retainer 280. The inner circumferential portion of bearing retainer 280 is fastened to rotor 220 by means of bolts 281 (FIG. 1) and is therefore effective to withdraw the rotor 220. Thus a withdrawing action of the thrust cylinders 80 is effective to withdraw cutting wheel 300 from the tunnel face.

The main drive shaft 130 is hollow (FIGS. 3 and 4) thus permitting a center drill drive shaft 410 to pass through its entire length. A separate drive motor 420 mounted on gear box 135 (FIG. 2) drives the center drill drive shaft 410 relative to the movable frame 1 10. A center drill bearing assembly 450 (FIG. 4), which is generally similar to the main bearing assembly 200, supports the center drill 400 to be driven by the center drill drive shaft 410.

More specifically, the center drill bearing assembly 450 includes a rotor 460 having on its rearward end the male portion 461 of a splined coupling. The female portion 411 is attached to the forward end of the drive shaft 410. The splined coupling permits a longitudinal sliding relationship between drive shaft 410 and rotor 460. The forward end of rotor 460 projects beyond the hub 310 of the main cutting wheel and provides a hub or base for attachment of the center drill 400.

Center drill bearing assembly 450 also includes a housing 470 that is received within a forward recess 227 formed in the rotor 220, and rotates with the rotor 220. Lugs 471 (FIG. 4) attached to the forward end of housing 470 are received in small circumferentially spaced recesses in the hub 310. Bolts 472 which pass through the lugs 471 permit housing 470 to slide longitudinally relative to rotor 220. Thus the housing 470 of the center drill bearing assembly rotates with rotor 220 of the main bearing assembly, while the rotor 460 is directly driven by shaft 410.

Rotor 460 is supported for rotation relative to housing 470 by a front radial bearing 480 and a rear radial bearing 490, and while the structure of these radial bearings is not identical to the structure of radial bearings 240 and 250 their operation is nevertheless very much the same. A front bearing retianer 482 is attached around hub 462 and extends to the forward end of housing 470 so as to protect radial bearing 480 from dirt. A thrust bearing 485 is located intermediate to the radial bearings 480 and 490, and its structure and function are very much like that of the thrust bearing 230 which was previously described. That is, forward thrust received from the housing 470 is imparted through thrust bearing 485 into rotor 460 and hence into the center drill 400.

In accordance with the preferred usage of the machine the main cutting wheel 300 is driven at a relatively slow rate, such as revolutions per minute, while the center drill 400 is driven at a more rapid rate, such as 30 revolutions per minute. By reversing motor 420 the center drill 400 may, if desired, be rotated opposite to the main cutting wheel.

The center drill bearing assembly 450 also includes a preloading mechanism which has no counterpart in the main bearing assembly 200. The rotor 220 has a cylindrical recess 227 formed in its forward end (FIG. 4), and the depth of the recess 227 is considerably greater than what is necessary to accommodate the housing 470 of the center drill bearing assembly. The preloading assembly generally designated as 500 includes a forward plate 501 which is of generally circular configuration, but having a central opening through which the female coupling 411 extends. The preloading assembly 500 also includes a generally circular rear plate 502. A plurality of bolts 503 are spaced about the circumferences of the two plates 501, 502 and are utilized to retain these plates in proximity to each other. The plate 502 has a central opening which surrounds the drive shaft 410, but not in direct engagement with it, so that drive shaft 410 is permitted to rotate relative to the plate 502. To the rear of recess 227 the rotor 220 is further recessed, with a smaller diameter opening, in order to permit the pilot drill drive shaft 410 to be received therein. Thus the recess 227 forms a circumferential shoulder which faces in a forwardly direction within the rotor 220. The outer circumferential edge of plate 502 bears against this circumferential shoulder and thus provides the basis for supporting center drill 400 for forward thrust. The inner circumferential portion of plate 502 is recessed on its front side so as to receive a'set of Belleville disc springs 504. The springs 504 push the plate 501 forward relative to the plate 502, but the total displacement is limited by the bolts 503. The forward surface of plate 501 bears tight against the rearward end of housing 470 (except for a bearing retainer therebetween). Y

The entire housing 470 of the center drill bearing assembly 450 is free to slide longitudinally, to some extent, relative to the rotor 220 and hub 310. Lugs 471 are welded to the housing 470 and hence move with the housing. Bolts 472 are firmly retained in threaded openings in the rotor 220 and in the hub 310, but the openings through which they pass in the lugs 471 are not threaded, hence the lugs 471 may slide rearwardly a limited distance relative to the bolts 472.

The purpose of the preloading assembly 500 is to permit the center drill 400 to retract under excessive load. For example, when the machine is built with a cutting wheel diameter of thirteen feet and is designed for a total thrust of one million pounds against the tunnel face, for cutting material which has a compressive strength of 30,000 pounds per square inch, the design load for the center drill 400 is then 90,000 pounds of forward thrust. The preload assembly 500 is then set to this load value of 90,000 pounds, and in the event the center drill receives a load in excess of that amount it will move rearwardly a small distance relative to the main cutting wheel 300, thus minimizing the shock on the center drill and protecting it against damage.

The preloading is accomplished by placing the springs 504 under a compressive stress of 90,000 pounds and then tightening the bolts 503 so that the plates 501, 502 will retain the springs in their compressed condition. A gap 505 between plates 501, 502 would permit further compression of the springs 504. However, under normal operating conditions the thrust load on the center drill is 90,000 pounds or less, hence the springs 504 are not required to accept any additional compression and the gap 505 does not close even partially. But if an overload for the center drill is encountered then that overload will be picked up by the springs 504, and the center drill together with its bearing assembly 450 will be permitted to retract relative to the main cutting wheel. Lugs 471 will move rearwardly relative to hub 310 and the gap 505 will commence to close.

For purpose of moving the machine into and out of a tunnel, and transporting it, it is necessary to disassemble the main cutting wheel 300. With reference to FIG. 4, there is illustrated a removable spoke 330 of the main cutting wheel, which can be detached from the central portion of the cutting wheel simply by removing a number of bolts. This illustrated detail is typical of the cutting wheel construction and indicates the manner in which the entire cutting wheel may be disassembled for convenience in transportation.

It is possible to remove and replace both the main bearing assembly 200 and the center drill bearing as sembly 450 in a very limited time, such as two or or three hours where an overload crane and other shop equipment are available, or perhaps two or three days under conditions which prevail inside a tunnel. The procedure for removing and replacing these two bearings will now be briefly described.

First the entire machine is retracted from the tunnel face, a distance of about ten feet. Then the center drill 400 and its bearing assembly 450 are removed. This is accomplished simply by removing the nuts from the bolts 472, and the entire housing 470 together with the associated preload assembly 500 slides out of recess 227 of the rotor 220. The splined coupling 461, 411 simply separates.

The next step is to remove the main cutting wheel 300. This is done by removing the bolts connecting the wheel and rotor 220. The hub 310 then simply slips off the forward of rotor 220. The next step is to expand the thrust cylinders 80 so as to move the movable frame 1 10 about 2 feet forward from its most rearwardly position. Access can then be obtained to the bolts 211, of which in the presently preferred form of the machine there are 48 spaced about the periphery of the front guide tube ring 117.

Thereafter, the bolts 88 are removed and the thrust cylinders 80 are retracted so as to draw the thrust collar 85 rearwardly. It is then possible to pull the main bearing assembly 200 in a forwardly direction and remove it from contact both with the guide tube flange 117 and with the thrust collar 85. The female gear 155 may then be detached from rotor 220 by removing the bolts 221.

As a convenience in performing these operations it is desirable to provide a small rearward extension (not shown in the present drawings) on thrust collar 85. This extension serves to support the thrust collar 85 from the guide tube ring 117 both during and after the time when the bolts 211 are removed. Another desirable convenience is a platform which can be positioned in front of the machine to receive the main bearing assembly 200 when it is removed.

The female drive gear may be attached to the replacement main bearing unit, which can then be inserted into the machine by following the reverse of the procedure described above. After the main bearing assembly has been replaced a new pilot drill bearing assembly is inserted, again by following the reverse of the described procedure.

I claim:

1. A replaceable bearing assembly for a tunneling machine comprising: a hollow housing having a generally cylindrical configuration and having means on its rearward end adapted for removable attachment of said housing to the forward end of a movable support frame; said housing having on its interior surface a thrust collar located intermediate to its forward and rearward ends, said interior thrust collar having a forwardly facing thrust shoulder; a rotor disposed within said housing, said rotor having on its forward end means for removably attaching a rotating cutter thereto, having on its rearward end means for coupling a drive shaft thereto, and having on its exterior surface a thrust collar with a rearwardly facing thrust shoulder; a thrust bearing disposed between said interior thrust collar of said housing'and said thrust collar of said rotor, whereby forward thrust exerted against said housing may be imparted to said rotor; and a pair of radial bearings disposed between said housing and said rotor, one at the forward end and the other at the rearward end, whereby rotating thrust from said drive shaft may be concurrently imparted to said cutting wheel; the forward and rearward ends of said housing and said rotor being essentially coterminous whereby said assembly may be conveniently removed and replaced as a unit.

2. The bearing assembly of claim 1 wherein said rotor has a cylindrical recess centrally located in its forward end, and a smaller diameter opening extending from said recess to the rearward end of said rotor.

3'. A bearing assembly as claimed in claim 1 wherein said movable support frame is a pre-loaded assembly including a forward plate, a rearward plate, spring means compressed between said plates, and retaining means limiting the separation of said plates.

4. The bearing assembly of claim 1 wherein said drive shaft coupling means includes intermeshed gears which are slidable relative to each other along the longitudinal axis of said rotor.

5. The bearing assembly of claim 1, wherein said housing also has on its exterior surface a thrust collar having a rearwardly facing thrust shoulder.

6. The bearing assembly of claim 2 wherein said interior thrust shoulder of said housing is located forwardly of said exterior thrust shoulder thereof.

l t I t t

Claims (6)

1. A replaceable bearing assembly for a tunneling machine comprising: a hollow housing having a generally cylindrical configuration and having means on its rearward end adapted for removable attachment of said housing to the forward end of a movable support frame; said housing having on its interior surface a thrust collar located intermediate to its forward and rearward ends, said interior thrust collar having a forwardly facing thrust shoulder; a rotor disposed within said housing, said rotor having on its forward end means for removably attaching a rotating cutter thereto, having on its rearward end means for coupling a drive shaft thereto, and having on its exterior surface a thrust collar with a rearwardly facing thrust shoulder; a thrust bearing disposed between said interior thrust collar of said housing and said thrust collar of said rotor, whereby forward thrust exerted against said housing may be imparted to said rotor; and a pair of radial bearings disposed between said housing and said rotor, one at the forward end and the other at the rearward end, whereby rotating thrust from said drive shaft may be concurrently imparted to said cutting wheel; the forward and rearward ends of said housing and said rotor being essentially coterminous whereby said assembly may be conveniently removed and replaced as a unit.

2. The bearing assembly of claim 1 wherein said rotor has a cylindrical recess centrally located in its forward end, and a smaller diameter opening extending from said recess to the rearward end of said rotor.

3. A bearing assembly as claimed in claim 1 wherein said movable support frame is a pre-loaded assembly including a forward plate, a rearward plate, spring means compressed between said plates, and retaining means limiting the separation of said plates.

4. The bearing assembly of claim 1 wherein said drive shaft coupling means includes intermeshed gears which are slidable relative to each other along the longitudinal axis of said rotor.

5. The bearing assembly of claim 1, wherein said housing also has on its exterior surface a thrust collar having a rearwardly facing thrust shoulder.

6. The bearing assembly of claim 2 wherein said interior thrust shoulder of said housing is located forwardly of said exterior thrust shoulder thereof.

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