Abstract:
Lubricating oil is forced and pumped into and through the first passageway through the floating ring gear and into the annulus between the gearbox housing and the floating ring gear. Lubricating oil from the annulus is pumped into and through the second passageway and through the joint between the second and third passageway, and through the third passageway into the void in the cover. Thereafter the oil passes through the fourth passageway between the void in the cover and the circumferential recess in the cover and lubricating the bearing mounted adjacent the recess in the cover/housing.

Description:
FIELD OF THE INVENTION 
     The invention is in the field of bearing lubrication systems for gearboxes used to drive earth boring machines. 
     BACKGROUND OF THE INVENTION 
     A roadheader is an earth-boring machine which experiences high axial and radial loads on and in the frame of the machine. The roadheader includes a cutter head, a gearbox and a motor (prime mover). When the gearing, most notably the ring gear, is affixed to the housing of the gearbox, the axial and radial forces imparted on the cutter head are transmitted to the ring gear through the housing and cause misalignment of the gears and other components. The misalignment causes abnormal gear wear and ultimately destruction of the gears, carriers and other components. 
     Roadheaders operate in a range of motion with respect to horizontal. In other words, the cutter head of the roadheader and the gearbox affixed thereto may be inclined with respect to horizontal and creating lubrication problems with some of the bearings within the gearbox as the bearings are lifted out of the lubricating oil. 
     In the prior art, an internal tube requires internal connections which present the potential for leaks. These leaks allow water to enter within the gearbox and cause it to fail. The potential for leaks is increased due to the extreme vibrations that exist within the gearbox as the cutter head cuts into soil and rock. The tube vibrates within the gearbox and the connections leak due to the vibrations. 
     U.S. Pat. No. 7,935,020 to Jansen et al. issued May 3, 2011, states that: “A drive train for a wind turbine is provided. The wind turbine comprises a low speed shaft connected to blades of the wind turbine and a higher speed shaft connected to a generator. The drive train also includes a bearing that substantially supports the weight of at least the low speed shaft. A compound planetary gear stage is connected to the low speed shaft and the higher speed shaft, and includes a rotating carrier, a nonrotating ring gear, a plurality of planetary gears, and a rotating sun gear. The sun gear is connected to the higher speed shaft.” 
     U.S. Pat. No. 4,873,894 to Avery et al. issued Oct. 17, 1989, states: “A balanced free-planet drive mechanism includes a reaction ring gear, an output ring gear, an input sun gear arranged along a central axis, and a plurality of floating planet elements individually having a first planet gear engaged with the sun gear, a second planet gear engaged with the output ring gear, and a third planet gear engaged with the reaction ring gear. A required first rolling ring gear resists radially inward movement of the planet elements adjacent the third planet gear, and an optional second rolling ring gear resists radially inward movement of the planet elements adjacent the first planet gears to maintain the planetary elements essentially parallel to the central axis. A plurality of ring segments are connected to the output ring gear and engage a groove in each of the planet elements to maintain the planet elements in a preselected axial position and to transmit relatively low thrust forces. The drive mechanism is easy to assemble in a ground-engaging wheel of a truck or the like, with the output ring gear being connected to rotate with the wheel. The incorporation of the drive mechanism in a wheel eliminates the usual planet carrier and planetary bearings associated with a conventional multi-stage planetary final drive, and is lighter in weight and less costly while fitting compactly within the same general space envelope.” 
     SUMMARY OF THE INVENTION 
     Floating Gearbox 
     When gears are under load, forces within a gear system align the gears and other components of the gear system so that optimum load balancing occurs, that is, the gears align themselves. External forces not generated by the gear system move the gears out of this alignment and thus adversely affect the gear position causing damage and premature wear. The floating gear system of the invention allows gears to retain their most favorable alignment position. 
     An electric motor drives an input gears via spline connections. The input gear drives an intermediate gear. The intermediate gear drives the shaft which, in turn, drives the first sun gear such that the intermediate gear and the first sun gear rotate together at the same speed. The first sun gear drives a set of first planet gears. Preferably there are three first planet gears. The planet gears are engaged with a static (fixed) ring gear. A first pair of spherical bearings is interposed between each first planet gear and each first planet shaft. The first pair of spherical bearings is separated from each other and provides support for the first planet gear. Each first planet shaft is affixed to the first planetary carrier. The first planet gear forces the first planet carrier to rotate and thus drives second sun. Second sun includes an external spline and a gear. 
     The second sun gear drives four second planet gears. The second planet gears engage static (rotationally fixed) ring gear. A second pair of spherical bearings is interposed between each second planet gear and each second planet shaft. The second pair of spherical bearings is separated from each other and provides support for the second planet gear. Each second planet shaft is rotatably affixed to the second planetary carrier. The second planet gear forces the second planet carrier to rotate and thus drive the output shaft. 
     The gears are allowed to float. Both vertical and horizontal forces act on the cutter head. These forces are transmitted through the gearbox and back to the supporting structure. In the present invention, the gears run independent of the housing, that is, they float. The ring gear floats. The ring gear is spaced apart from the housing. A small annular gap exists between the ring gear and the housing, thus deflection due to external forces in the housing doesn&#39;t affect the gear alignment because the gears aren&#39;t directly attached to the housing. The ring gear has torque passing through it and thus is anchored back (against rotation) to the housing through a spline connection between the ring gear and the cover. The cover is affixed to the housing and the spline connection acts like a hinge. The ring gear and housing deflect independently of each other. 
     Spline connections in the present invention make the gears float. Splines have small gaps in them. These gaps allow small relative movement between meshing splines and help the gears find a position that best suits them. The spline connections include the connection between ring gear and cover; the second planet carrier and the output shaft; the first carrier and the second sun; and, the first sun gear and the splined shaft, and, the intermediate gear and the splined shaft. 
     When gears are under load, the forces within the gear system align the gears so that optimum load balancing occurs, that is, the gears align themselves. In the prior art, external forces not generated by the gear system, move the gears out of alignment and thus adversely affect their positions. The present invention allows the planetary gear systems to retain their most favorable alignment positions. 
     A gearbox which includes a housing having a cover is disclosed. The cover is affixed to the housing. The cover includes an external spline located on a central portion thereof. There are two input gears driven by prime movers, for example, electric motors. The input gears drive an intermediate gear which is known as a drop down gear. The intermediate (drop down) gear includes an internal spline. The splined shaft includes a first external spline and a second exterior spline. The internal spline of the intermediate gear engages the first exterior spline of the shaft rotating the shaft with the intermediate gear. A centrally located tube resides along a first longitudinal axis of the housing. A centrally located adapter also resides along a first longitudinal axis of the housing. The centrally located adapter is affixed to the housing. The centrally located adapter and centrally located tube are stationary. There are two spherical bearings, the shaft input spherical bearing and the shaft output spherical bearing, which enable the components of the gearbox to float within the gearbox thus avoiding deformation and subsequent destruction of the components. The components include the ring gear, a splined shaft, a first planetary system, a second planetary system, and an output shaft. Each of the planetary systems includes a sun gear, a plurality of planet gears, a planet gear carrier, and a plurality of planet gear shafts. 
     A first shaft input spherical bearing is interposed between the stationary tube and the rotating input shaft. A first sun gear includes an internal spline. The second external spline of the input splined shaft engages the internal spline of the first sun gear driving the sun gear therewith. 
     A plurality of first planet gears is carried by a first planet gear carrier. Each planet gear is pinned to the first planet gear carrier by a first planet gear shaft. A first pair spherical bearings is interposed between each of the first planet gear shafts and each of the first planet gears. The first sun gear drives the first planet gears. The first planet gear carrier restrains each of the first pair of spherical bearings interposed between the first planet gear and the first planet gear shaft against longitudinal movement. The first planet gear carrier restrains each of the first planet gears with respect to its respective first planet gear shaft holding them against longitudinal movement in their respective planet gear shaft. A ring gear is mounted within the housing and includes an internal spline. The internal spline of the ring gear engages the external spline of the cover affixing the ring gear against rotation with respect to the cover/housing. 
     The plurality of first planet gears engages the ring gear driving the first planet carrier. The first planet carrier includes an internal output spline. A second sun includes an external spline and a sun gear. 
     The internal output spline of the first planet carrier drives the external spline of the second sun gear. The plurality of second planet gears engages the ring gear driving the second planet carrier. The gear of the second sun drives the second planet gears which, in turn, drive the second planet carrier. The second planet gears engage the ring gear. A second pair of spherical bearings is interposed between the second planet gear shaft and the second planet gear. The second planet gear carrier restrains the second pair of spherical bearings interposed between each of the second planet gears and the second planet gear shaft against longitudinal movement. The second planet gear carrier restrains the second planet gears with respect to its respective second planet gear shaft against longitudinal movement holding each of them against longitudinal movement. The second planet carrier includes an internal output spline. 
     The output shaft includes an external spline. The housing, the cover and the output shaft have a longitudinal axis. The internal output spline of the second planet carrier drives the external spline of the output shaft. 
     A shaft output spherical bearing resides intermediate the output shaft and the cover of the gearbox supporting the output shaft. The shaft output spherical bearing permits angular displacement of the output shaft with respect to the longitudinal axis of the output shaft. The ring gear pivots with respect to the cover/housing. The shaft output spherical bearing enables the ring gear to float within the housing and not engage the housing. 
     A gearbox in combination with a roadheader is also disclosed. A prime mover, a cutter head, a gearbox are disclosed. The gearbox includes: a housing having an inner surface and an external spline; an input shaft; a first planetary gear system driven by the shaft; and, a second planetary gear system driven by the first planetary gear system. A ring gear includes an internal spline. A first pair of spherical bearings supports the first planetary gear system. A second pair of spherical bearings supports the second planetary gear system. The ring gear includes an outer surface and the outer surface is substantially cylindrically shaped. The outer surface of the ring gear is spaced apart from the inner surface of the housing forming an annular gap therebetween. The internal spline of the ring gear engages the external spline of the housing affixing the ring gear against rotation with respect to the housing. The ring gear is pivotable with respect to the housing. An output shaft is driven by the second planetary gear system. The gearbox is interposed between the prime mover and the cutter head. The prime mover delivers power to the input shaft of the gearbox and the output shaft of the gearbox drives the cutter head. 
     Lubrication 
     A bearing lubrication system is disclosed which includes a gearbox housing wherein the gearbox housing includes a planetary gear system, the planetary gear system includes planet gears, an external spline, an interior surface and an exterior surface. Lubricating oil resides in the gearbox housing and the planet gears pass through the lubricating oil in the gearbox housing. The floating ring gear resides within the gearbox housing and the floating ring gear is substantially cylindrically shaped. The floating ring gear includes an inner portion and an outer surface. The inner portion of the floating ring gear includes an internal spline and an internal gear. The internal spline of the floating ring gear engages the external spline of the gearbox housing preventing rotation of the floating ring gear with respect to the housing. The exterior surface of the floating ring gear is radially spaced apart from the interior surface of the gearbox housing forming an annulus between the gearbox housing and the floating ring gear. 
     The planet gears of the planetary gear system engage the internal gear of the floating ring gear. The internal gear of the floating ring gear includes a first passageway therein for receiving oil from the meshing of the planet gears with the internal gear of the floating ring gear. The first passageway extends through the floating ring gear. The outer surface of the floating ring gear includes first and second grooves therein. First and second O-rings reside in the first and second grooves of the outer surface of the O-rings and seal the annulus formed by the space between the exterior surface of the ring gear and the interior surface of the housing. The gearbox housing includes a second passageway in communication with the annulus. The second passageway in the gearbox housing extends to the exterior surface of the housing. A cover affixed to the housing includes a third passageway in communication with the second passageway of the gearbox. The second passageway and the third passageway are joined together at a joint and the joint is sealed with an O-ring. 
     The cover includes a void or cavity therein. The third passageway communicates between the joint and the void in the cover. The cover includes a fourth passageway and a circumferential recess. The fourth passageway communicates between the void in the cover and the circumferential recess in the cover. The shaft output spherical bearing is mounted adjacent the circumferential recess in the cover. The lubricating oil is forced and pumped into and through the first passageway through the floating ring gear and into the annulus between the gearbox housing and the floating ring gear. Lubricating oil from the annulus is pumped into and through the second passageway and through the joint between the second and third passageway. Then the oil is pumped through the third passageway into the void/cavity in the cover. Thereafter the oil passes through the fourth passageway between the void in the cover and the circumferential recess in the cover and lubricating the shaft output spherical bearing mounted adjacent the recess. 
     A bearing lubrication system is disclosed which includes a gearbox housing wherein the gearbox housing includes a planetary gear system, the planetary gear system includes planet gears, an external spline, an interior surface and an exterior surface. The gearbox includes an output shaft and the shaft output spherical bearing is interposed between the output shaft and the cover. Lubricating oil collects in the void and the gearbox tilts at an angle up to 43° with respect to horizontal during operation. A floating ring gear resides within the gearbox housing and is substantially cylindrically shaped. The floating ring gear includes an inner portion and an outer surface. The inner portion of the floating ring gear includes an internal gear. The floating ring gear engages the gearbox housing preventing rotation of the floating ring gear with respect to said housing. The exterior surface of said floating ring gear is radially spaced apart from the interior surface of the gearbox housing forming an annulus between the gearbox housing and the floating ring gear. The planet gears of the planetary gear system engage the internal gear of the floating ring gear. The internal gear of the floating ring gear meshes with the planet gears pumping oil through the floating ring gear, the annulus, the gear box housing, the cover and the shaft output spherical bearing. 
     The shaft output spherical bearing which resides between the cover/housing and the output shaft has oil pumped to it to ensure that it is lubricated at all times. When the cutter head resides horizontally with respect to the earth, oil is supplied to the shaft output spherical bearing by virtue of the oil within the housing. At this time the shaft output spherical bearing also receives oil from the pumping system of the invention. The cutter head, and thus the gearbox, can tilt substantially with respect to the horizontal axis of the gearbox. The shaft output spherical bearing when inclined is lifted up out of the oil residing in the housing. Oil, or other lubricant, normally fills the housing up to the 50% level based on height. A sight glass is provided in the window which enables the roadheader user to view the oil level in the gearbox. Ring gear and surrounding pieces act, in addition to their normal function, like a pump. In the ring gear, just above the first planet gears, there are three small holes between the teeth of the ring gear. The three holes are spaced 120° apart. As the gear teeth of the first planet gears and the ring gear mesh (engage), oil is forced up into these holes. Oil will then flow to and then through the narrow cavity that is between the ring gear and the housing. O-rings at the ends of the ring gear keep the oil from leaving the volume bounded by the exterior surface of the ring gear and the internal surface of the housing. Oil is then forced though passageways and cavities in the housing and cover so that oil reaches the shaft output spherical bearing, and thus keeps the shaft output spherical bearing lubricated. 
     The gearbox of the invention is large and deep holes in the housing for a lubrication system are costly and difficult to manufacture. Instead, the invention obviates the need for deep holes. The gap between the ring gear and the housing is adapted to transport oil. Both ends of the ring gear are sealed with the O-rings. This gap provides an oil passage for the majority of the distance—the distance up to the front of the gearbox. The first planet gear pumps the oil used for lubricating the shaft output spherical bearing instead of the second planet gear because the first planet gear rotates much faster than the second planet gear and therefore makes a much more effective pump. After the gap, oil passes through some relatively short length passageways and thereafter falls into a cast cavity/void in the cover. This cast cavity is used in the lubrication system and obviates deep holes. After the cast cavity, oil passes through another short passageway and reaches the shaft output spherical bearing. 
     Overload Protection 
     The gearbox has over-torque protection. The input shaft includes a narrowed diametrical portion which acts as a fuse. In the prior art, if excessive force is applied to the cutter head an internal gear component fails. The input shaft acts as a fuse and breaks at the narrowed diametrical portion. When the fuse breaks, the portion of the shaft that is still connected to the electric motor spins harmlessly within a bushing. The bushing prevents the spinning portion of the input shaft from entering the bore in the gear too far. A screw retains the portion of the shaft bearing the external spline. The internal spline of the bore in the input gear remains meshed together with the external spline of the shaft after breakage or fracture of the shaft. This over-torque protection system prevents damage to the ring gear as well as to components of the rest of the gearbox. The two broken portions of the input shaft can easily be replaced. 
     To prevent damage to the input gear while the outer half of the input shaft is spinning, a bushing permits spinning to occur in a controlled fashion and thus prevent damage to the input gear. In other words, the bushing acts as a shoulder and prevents the input shaft from moving inwardly toward the input gear thus damaging the gear. When the fuse is not broken and the gearbox is running in a normal, proper fashion, the bushing sees no rotation and it radially supports the input shaft. The bushing only functions when the fuse breaks. If any damage occurs to the O-ring when the fuse breaks, it can be easily replaced. The function of the O-rings along the input shaft is to retain grease at the bushing and the spline. The input shaft includes an external spline which mates with an internal spline on the input gear. 
     An overload protection device in combination with a prime mover and gearbox transmission supplying torque through said gearbox transmission to a load is disclosed. An input shaft includes a bore therethrough enabling affixation of the input shaft to an input gear. The input shaft includes a key for coupling to the prime mover and for rotation therewith. The input shaft also includes an external spline which mates with an internal spline in the bore of the input gear. The prime mover transmits torque to the input shaft which drives the input gear. The input gear includes a bore therein. An internal spline in the bore of the input gear meshes with the external spline of the input shaft. The bore of the input gear includes a shoulder therein, and the bushing resides in the bore of the gear and engages the shoulder of the bore. The input gear of the gearbox transmission drives a planetary gear system which, in turn, supplies power to the load. 
     The input shaft includes an annular groove which breaks when the load impressed upon the cutting tool of the roadheader is too large. Upon overload of the gearbox transmission, the input shaft breaks at the location of the annular groove. The input shaft includes a bore therein and the annular groove in combination with the bore through the shaft results in a thin section which acts as a fuse. The input shaft is affixed to the input gear against longitudinal movement such that the input shaft will not move longitudinally after the input shaft breaks. 
     Cooling Cavities 
     A gearbox, comprising: a housing and a floating gear means for protecting a gear mechanism from damage due to axial and radial forces applied to the gearbox is disclosed. A first cooling compartment and a second cooling compartment are disclosed. The first and second cooling compartments are isolated from the floating gear means. First and second ports supply cooling fluid to the first compartment, and, the third and fourth ports supplying cooling fluid to the second compartment. 
     It is not possible for cooling water to leak into the gearbox as the gearboxes are sealed with respect to the cooling compartments. Instead, any water leakage falls harmlessly to the ground. Water in the cavities/compartments is isolated from the gearbox by a thick, heat conductible, wall of steel. Cooling cavities/compartments exists at each end of the gearbox, behind the rear plate and the front plate. Plugs are removed from threaded holes, and hoses are attached to the threaded holes for pumping cooling water into and through the cavities/compartments. The cooling water in the cavities soaks up heat generated in the gearbox. 
     There is a tube that passes through the central portion of the gearbox. When the gearbox is installed in an earth-boring machine, a pipe carrying cooling fluid is installed which passes through this tube and feeds water to the cutter head. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a roadheader including the cutter head, gearbox and prime mover. 
         FIG. 1A  is an enlarged portion of the schematic view of  FIG. 1  illustrating the cutter head and gearbox. 
         FIG. 1B  is a perspective view of the gearbox. 
         FIG. 1C  is a front view of the gearbox. 
         FIG. 1D  is a right side view of the gearbox where power is input to the gearbox. 
         FIG. 1E  is a left side view of the gearbox where power is output from the gearbox. 
         FIG. 1F  is a cross-sectional view taken along the lines  1 F- 1 F of  FIG. 1D  illustrating the first planetary gear system, the second planetary gear system, the floating ring gear, the input to the first planetary gear system, and the output from the second planetary gear system, all of which are supported by the shaft input and output spherical bearings and connected with splines enabling the gear systems and ring gear to float within a fixed housing. 
         FIG. 1G  is an enlarged portion of the cross-sectional view of  FIG. 1F  illustrating the floating ring gear, the spline connection between the floating ring gear and the cover, and a portion of the lubrication system. 
         FIG. 1H  is an enlarged portion of the cross-sectional view of  FIG. 1F  illustrating the spline input to the first sun driving the first planetary gear set, the first planet carrier driving the second sun, the second sun driving the second planetary gear set and the second planet carrier driving the output spindle (shaft), all of which are supported by shaft input spherical bearing and the shaft output spherical bearing enabling the gear systems and ring gear to float within a fixed housing. 
         FIG. 1I  is an enlarged portion of the cross-sectional view of  FIG. 1F  illustrating the shaft input spherical bearing interposed between the centrally located support tube and the splined shaft driven by the intermediate gear. 
         FIG. 1J  is a perspective view of the floating gearbox without the ring gear and without the housing. 
         FIG. 1K  is a perspective view of the floating gearbox with the ring gear shown in an exploded position. 
         FIG. 1L  is a diagrammatic view of an angular spline. 
         FIG. 1M  is a diagrammatic view of an involute spline. 
         FIG. 2  is a cross-sectional view taken along the lines  2 - 2  of  FIG. 1D  illustrating the fused input shaft with a splined connection to the input gear which drives the intermediate gear which in turn drives the splined shaft. 
         FIG. 2A  is a front view of the input gear. 
         FIG. 2B  is a cross-sectional view of the input gear illustrating the internal spline for connection with the fused input shaft. 
         FIG. 2C  is a front view of the fused input shaft. 
         FIG. 3  is a cross-sectional view taken along the lines  3 - 3  of  FIG. 1E  illustrating the lubrication system and passageways in the ring gear, the housing, and the cover. 
         FIG. 3A  an enlargement of a portion of  FIG. 3  illustrating the lubricant passages through the cover and housing. 
         FIG. 3B  is a perspective view of a portion of the cover illustrating the lubricant pathway therethrough. 
         FIG. 3C  is a plan view of the floating ring gear illustrating one of the lubricant passageways therethrough. 
         FIG. 3D  is a cross-sectional view of the floating ring gear illustrating the lubricant passageway therethrough, the housing, the meshing gear and the gap between the ring gear and the housing. 
         FIG. 4  is a top view of the gearbox illustrating cooling water plugs. 
         FIG. 4A  is a right end view of the gearbox with the cooling water plate removed illustrating the water cavity, the water inlet, the water outlet, and a wall separating the water cavity from the gear systems. 
         FIG. 4B  is the left end view of the gearbox with the cooling water plate removed illustrating the water cavity, the water inlet, the water outlet, and a wall separating the water cavity from the gear systems. 
     
    
    
     DESCRIPTION OF THE INVENTION 
       FIG. 1  is a schematic view  100  of a roadheader  7 R including the cutter head  3 , gearbox  9  and prime mover  7 .  FIG. 1A  is an enlarged portion  100 A of the schematic view of  FIG. 1  illustrating the cutter head  3  and gearbox  9  in more detail. As illustrated in  FIGS. 1 and 1A , electric motors  7  drive input gears  2 B which in turn drive, via spline connections, input gears  2 A. Input gears  2 A drive intermediate gear  3 A. 
     Still referring to  FIGS. 1 and 1A , a horizontal or axial force  4  is imparted on the cutter head  3  in earth boring operations. The roadheader (earth boring machine) is forced into earthen material which may be very hard. The cutter head  3  includes spikes thereon (not shown) which forcibly cut into the earthen material. All of the axial forces  4  are transmitted through the frame of the cutter head  3 , the coupling frame  6 A, the housing  1  of the gearbox  9 , the cover  2  of the gearbox  9 , and the motor frame  7 A. Similarly, the cutter head is subject to radial force  5  as illustrated in  FIGS. 1 and 1A . All of the radial forces are transmitted through the frame of the cutter head  3 , the coupling frame  6 A, the housing  1  of the gearbox  9 , the cover  2  of the gearbox  9 , and the motor frame  7 A. The vertical and horizontal forces are not transmitted to the ring gear, and, therefore, not transmitted to the first and second planetary gear systems. The planetary gear systems within the gearbox are supported by a shaft input spherical bearing and a shaft output spherical bearing enabling the planetary gear systems to float, that is, to self-center and align and to avoid deformation and misalignment caused by forces normally transmitted (in the prior art) to the gear systems by the frame of the gearbox. The shaft input and output spherical bearings, a plurality of meshing internal and external splines, and a plurality of meshing gears permit the planetary gear systems to float, that is, to self-center and align. Tolerance stack up of the components, namely, the various gears, splines, carriers etc. cause the components of a gearbox to find a natural orientation and alignment within the gearbox. 
     The gears are allowed to float. Vertical and horizontal forces act on the cutter head. These forces are transmitted through the gearbox and back to the supporting structure. In the prior art, the ring gear is fixed to the housing and forces transmitted to the housing cause misalignment of the ring gear and other components of the planetary gear system. This misalignment will cause abnormal alignment, gear wear and damage to the planetary gear system. 
     In the instant invention the gears run independent of the housing; that is, they float. Ring gear  22  floats as it is separate from the housing  1 . A small annular gap  22 G exists between the ring gear  22  and housing  1 , and, thus forces in the housing  1  do not affect alignment of the gears within the housing. 
     The ring gear  22  has torque passing through it and is anchored to the housing  1 . This is done through a spline connection  59 ,  60  between the ring gear  22  and the cover  2  which acts like a hinge and pivots as indicated by reference numeral  99 . Cover  2  is affixed to housing  1 . Ring gear  22  and housing  1  deflect independently of each other. 
     Still referring to  FIGS. 1 and 1A , the drive shaft  6 A in the roadheader is coupled to the output shaft  28  through a coupling  6 B. Coupling  6 B further isolates and prevents any force from transmission to the output shaft  28 . Coupling  8  couples the input of the electric motor to the input shaft  2 B. Channel  6 C functions as a water conduit through the roadheader to cool the cutter head  3  during operation. 
       FIG. 1B  is a perspective view  100 B of the gearbox  9  illustrating input shafts  2 B,  2 B and bearing retention plates  10 ,  10 . Housing  1 , cover  2  and an unnumbered sight glass are illustrated in  FIG. 1B . Receptacles  2 R,  2 R of input gears  2 A,  2 A receive input shafts  2 B,  2 B. Referring to  FIGS. 1B and 1F , adapter  13  is bolted to housing  1  with screws  13 A as illustrated in  FIG. 1F . Further, the rear cooler cap  12  is bolted to housing  1  with screws  12 S. Front cooler cap  25  is affixed to the cover  2  as illustrated in  FIG. 1E  by screws  11 . Tube  21  is affixed to adapter against rotation by dowel pin  26  as illustrated in  FIGS. 1F and 1I . 
       FIG. 1E  is a left side view  100 E of the gearbox  9  where power is output from the gearbox  9  by output shaft  28  and through spline connection  28 S.  FIG. 1E  further illustrates bearing cover  30 , retainer  36 , and tube  21 . 
     Referring to  FIGS. 1E and 1F , bearing cover  30  is affixed to the cover  2  by screws  30 S and retains the shaft output spherical bearing  27 . Dowel pins  41  are used to correctly orient the cover  2  with respective receptacles in housing  1 . Screws  2 X secure the cover  2  to the housing  1 . Lip seal  31  is interposed between bearing cover  30  and output shaft  28 . 
     Referring to  FIGS. 1F and 1H , the shaft output spherical bearing  27  includes an inner race  271 , and outer race  270 , and rollers  27 R. Shaft output spherical bearing  27  is interposed between output shaft  28  and cover  2  and is longitudinally held in place by bearing cover  30 , a shoulder  28 L on shaft  28 , and a shoulder  2 S of cover  2 . Tube  21  is stationary and affixed to adapter  13  proximate the rear end of the gearbox by dowel  26  and is supported by retainer  36  proximate the front end of the gearbox  9 . Retainer  36  is affixed to output shaft  28  by a screw in a different plane which is not shown. Retainer  36  rotates with output shaft  28 . 
     Referring to  FIG. 1F , bearing  34  is interposed between tube  21  and retainer  36  enabling rotation of the retainer  36  while supporting second planet carrier  5 A. Lip seal  33  is interposed between retainer  36  and tube  21  retaining lubricant for bearing  34  and other components. Retainer  36  retains shaft  28  from extraction. O-ring  61  is retained axially between shaft output spherical bearing  27  and second planet carrier  5 A. 
       FIG. 1C  is a front view  100 C of the gearbox  9  illustrating most of the same principal elements illustrated in  FIG. 1B .  FIG. 1C  illustrates output shaft  28  having an external spline  28 S for mating with coupling  6 B.  FIG. 1C  further illustrates bearing cover  30  for retention of shaft output spherical bearing  27  which supports output shaft  28  as illustrated in  FIG. 1F . Cooling cover plate  12  is also illustrated in  FIG. 1D . 
       FIG. 1D  is a right side view  100 D of the gearbox  9  where power is input to the gearbox  9  via input shafts  2 B. Receptacles  2 R receive the input shafts  2 B which are keyed. Bearing covers  10  retain bearings as illustrated in  FIG. 2 . Input shafts  2 B include external splines  2 P which mesh with internal splines  2 I in receptacles  2 R.  FIG. 3  is a cross-sectional view taken along the lines  3 - 3  of  FIG. 1E  illustrating the input shaft  2 B and the input gear  2 A. 
       FIG. 1F  is a cross-sectional view  100 F taken along the lines  1 F- 1 F of  FIG. 1D  illustrating the first planetary gear system, the second planetary gear system, the floating ring gear  22 , the input to the first planetary gear system, and the output from the second planetary gear system  28 , all of which are supported by shaft input and output spherical bearings and connected with splines enabling the gear systems and ring gear to float within the fixed housing. A pair of first spherical bearings  4 C,  4 C is interposed between the first planet gears  4 B and the first planet shaft  4 D supporting the first planet gears  4 B with respect to first planet shaft  4 D. A pair of second spherical bearings  5 C,  5 C is interposed between the second planet gears  5 B and the second planet shaft  5 D supporting the second planet gears  5 D with respect to first planet shaft  5 D. Shaft input spherical bearing  3 C is interposed between tube  21  and splined shaft  3 B supporting the splined shaft with respect to the tube  21 . Tube  21  is affixed to adapter  13 , and adapter is affixed to the housing  1 . Seal  14  is an O-ring seal interposed between the adapter and the housing  1 . Shaft output spherical bearing  27  is interposed between the cover  2  and the output shaft  28  supporting said output shaft with respect to the cover  2 . Cover  2  is affixed to housing  1  by screws  2 X shown in  FIG. 1E . 
     Referring to  FIGS. 1F and 1G , each of the pair of spherical bearings  5 C includes an inner race  71 , outer race  73 , and rollers  72 . Referring to  FIGS. 1F and 1I , shaft input spherical bearing  3 C includes inner race  77 , outer race  79 , and rollers  78 . Referring to  FIGS. 1F and 1H , each of the pair of spherical bearings  4 C includes inner race  74 , outer race  76 , and rollers  75 . 
       FIG. 1G  is an enlarged portion  1000  of the cross-sectional view of  FIG. 1F  illustrating the floating ring gear  22 , the spline connection  59 ,  60  between the floating ring gear  22  and the cover  2 , and a portion of the lubrication system. 
     Referring to  FIGS. 1F and 1G , cover  2  includes an external spline  59  and ring gear  22  includes an internal spline  60 . External spline  59  loosely engages internal spline  60  permitting ring gear  22  to pivot with respect to external spline  59 . Ring gear  22  does not rotate with respect to cover  2 . However, ring gear  22  may pivot or rotate slightly as indicated by arrow  99 . Gap  22 G is an annular gap between the interior surface of the housing  1  and the exterior surface  22 Z of the ring gear  22 . The ring gear is viewable in  FIGS. 3B and 3C . 
     Referring to  FIGS. 1F and 1G , ring gear  20  includes teeth  57  which mesh with teeth  58  of the second planet gears  5 B, and, ring gear  20  includes teeth  56  which mesh with teeth  55  of the first planet gears  4 B. Although the teeth mesh as described, there is sufficient play between the teeth to permit the relative rotational movement between the ring gear  20  and the planet gears so as to enable ring gear  20  to pivot as indicated by reference numeral  99 . The amount of pivoting or rotation of the ring gear will, of course, depend on the size of the annular gap  22 G. Further, there may be relative rotational movement between the planet gears  4 B,  5 B and the internal ring gear  20  depending upon the dynamics and loading of the planetary gear systems within the gearbox. 
       FIG. 1H  is an enlarged portion  100 H of the cross-sectional view of  FIG. 1F  illustrating the spline shaft  3 B input to the first sun  3 E driving the first planetary gear set  4 B, the first planet carrier  4 A driving the second sun  20 , the second sun  20  driving the second planetary gear set  5 B and the second planet carrier  5 A driving the floating output spindle  28 , all of which are supported by shaft input and output spherical bearings  3 C,  27  enabling the gear sets, carriers, suns and ring gear to float within a fixed housing  1 . 
     Referring to  FIGS. 1F and 1H , second sun  20  includes a first external gear  69  having teeth  69 A and an external spline  68 . External spline  68  of second sun  20  meshes with internal spline  67  of first planet carrier  4 A. Teeth  69 A of second sun gear  69  mesh with teeth  70  of planet gear  5 B. Further, second carrier  5 A includes an internal spline  66  which meshes with external spline  65  of output shaft  28 . Internal spline  66  meshes with external spline  65  and there may be some relative rotational movement between the meshed splines. Although the teeth and spline mesh as described, there is sufficient play between the teeth to permit the relative rotational movement between the second sun  20 , the first carrier  4 A, and the second planet gears  5 B so as to enable pivoting as indicated by reference numeral  99 A. 
     Still referring to  FIGS. 1F and 1H , second carrier  5 A includes an internal spline  66  and output shaft  28  includes external spline  65 . Internal spline  66  meshes with output spline  65 . Although the spline meshes as described, there is sufficient play between and in the spline connection to permit relative rotational movement between the second sun  20 , the first carrier  4 A, and the second planet gears  5 B so as to enable pivoting as indicated by reference numeral  99 A. 
       FIG. 1I  is an enlarged portion  100 I of the cross-sectional view of  FIG. 1F  illustrating shaft input spherical bearing  3 C interposed between the centrally located support tube  21  and the splined shaft  3 B driven by the intermediate gear  3 A.  FIG. 1I  illustrates retaining rings  3 F holding first sun gear  3 A in place. Shaft input spherical bearing  3 C is positioned between the adaptor  13  and a shoulder on tube  21 . Additionally, bearing  3 C is positioned between the spline shaft  3 B and the retaining rings residing partially in a groove of the splined shaft  3 B. Referring to  FIGS. 1F ,  1 H, and  1 I, splined shaft  3 B includes external spline  53  meshing with internal spline  54  of intermediate gear  3 A. Splined shaft  3 B includes external spline  51  meshing with internal spline  52  of sun  3 E. Although the spline meshes as described, there is sufficient play therebetween to permit the relative rotational movement between the splined shaft  3 E, first sun  3 E, and intermediate gear  3 A so as to enable pivoting as indicated by reference numerals  99 B and  99 C. 
       FIG. 1J  is a perspective view  100 J of the floating gearbox without the ring gear  20  and without the housing  1  shown.  FIG. 1K  is a perspective view  100 K of the floating gearbox with the ring gear  20  shown in an exploded position and without the input gears shown. Passageway  22 Z is for lubricant to flow from the interior side of the ring gear and, more specifically, from the interior teeth  56  to the outer surface  22 S. There are three passageways  22 P in the ring gear. Also illustrated well in  FIG. 1K  is the interior gear  58  of the ring gear  22  and the internal spline  60 . Internal spline  60  meshes with the external spline  59  of cover  2 . Cover  2  is fixed to the housing  1  and prevents rotation of the ring gear  22  with respect to cover  2  and housing  1 . 
     Referring to  FIG. 1J , the input drive shafts  2 B drive input gears  2 A which, in turn, drive intermediate gear  3 A. Intermediate gear  3 A includes an internal spline  53  meshed with spline  54  of shaft  3 B such that spline shaft  3 B rotates with intermediate gear  3 A. Input gears  2 A include teeth  84  which mesh with teeth  85  of intermediate gear  3 A. 
     The first planetary gear system illustrated in  FIGS. 1F ,  1 J and  1 K includes a plurality of planet gears  4 B, a first planet carrier  4 A, and, a first sun gear  3 E. Preferably there are three planet gears  4 B and they are retained in place by shaft retainers  17 . The second planetary gear system illustrated in  FIGS. 1F ,  1 J and  1 K includes a plurality of planet gears  5 B, a second planet carrier  5 A, and a second sun  20 . Preferably there are four planet gears  5 B and they are retained in place by shaft retainers  17 . Second sun  30  is self-centering and is spaced about tube  20 . Washers  20 R,  20 L position second sun  20  between retainer  36  and spline shaft  3 B. 
       FIG. 1L  is a diagrammatic view  100 L of an angular internal spline and an angular external spline with vertical gaps  95 A,  96 A between the internal and external spline teeth. Further,  FIG. 1L  illustrates a horizontal gap  97 A between the internal and external spline teeth. Sometimes horizontal gap  97 A is called the backlash between the teeth of the mated spline. SW is the space width and TT is the tooth thickness as used in  FIGS. 1L and 1M . 
       FIG. 1M  is a diagrammatic view  100 M similar to  FIG. 1L  using an involute spline tooth profile with vertical spline gaps  95 I,  96 I between the involute internal and external spline teeth. Further,  FIG. 1M  illustrates a horizontal gap  97 I between the involute internal and external spline teeth. Sometimes horizontal gap  97 I is called the backlash between the teeth of the mated spline. 
     The gaps just described and illustrated are demonstrative of all of the spline interconnections described herein and enable relative rotational movement between components. Relative rotational movement also occurs between gears. For instance, rotational movement may take place between ring gear  22  and cover  2 , second planet gear  5 B and ring gear  22 , second planet gear  5 B and second sun  20 , second planet carrier  5 A and output shaft  28 , first planet gear  4 B and ring gear  22 , first planet gear  4 B and first sun gear  3 E, first planet carrier  4 A and second sun  20 , first sun gear  3 E and splined shaft  3 B, and, intermediate gear  3 A and splined shaft  3 B. 
       FIG. 2  is a cross-sectional view  200  taken along the lines  2 - 2  of  FIG. 1D  illustrating the fused input shaft  2 B with a splined connection  2 I,  2 P to the input gear  2 A which drives the intermediate gear  3 A. Intermediate gear  3 A includes an internal spline  54  which is meshed with external spine  53  of spline shaft  3 B. Splined shaft  3 B rotates with intermediate gear  3 A. 
     Still referring to  FIG. 2 , input gear  2 A is supported by cylindrical bearings  48 ,  49  in housing  1 . Seal  40  resides between bearing cover  10  and receptacle  2 R. Bearing cover  10  and input gear shoulder  48 S secure cylindrical bearing  48  in place between the housing and the input gear. Housing shoulder  49 S and shoulder  49 B in input gear  2 A secure cylindrical bearing  49  in place between the housing  1  and the input gear  2 A.  FIG. 2A  is a front view  200 A of the input gear  2 A illustrating gear teeth  84  and the receptacle portion  2 R.  FIG. 2B  is a cross-sectional view  200 B of the input gear  2 A illustrating the internal spline  2 I for connection with the fused input shaft.  FIG. 2C  is a front view  200 C of the fused input shaft  2 B illustrating a fuse portion  82 F, an external spline  2 P, an outer shaft portion  82 C, an inner shaft portion  82 D, and a stepped bore  81  therethrough. A keyway  82 K is illustrated in the shaft portion  82 C. Keyway  82 K mates with a corresponding key of the coupling  8  which transfers power from the electric drive motor  7  to the input shaft  2 B. 
     Gearbox  9  has over-torque protection. Input shaft  2 B includes a diametrically reduced portion  82 F. The shaft thickness in the region  82 R between the stepped bore  81  and the diametrically reduced portion  82 F is considerably smaller than in other shaft locations  82 C,  82 D. O-rings  2 E,  2 G seal input shaft  2 B against the unwanted intrusion of dirt and for the retention of grease between the seals. Should excessive force be applied to the cutter head  3 , input shaft  2 B functions as a fuse and fractures at the diametrically reduced portion  82 F. When this fracture occurs, a portion of input shaft  2 B is still connected to the coupling  8  and spins harmlessly within bushing  2 C. 
     Input gear  2 A includes a stepped bore  86  having a first shoulder  86 A and a second shoulder  86 B therein. Bushing  2 C resides in the bore  86  of the receptacle  2 R and engages second shoulder  86 B therein. Input shaft  2 B includes outer shoulder  82 H thereon. Outer shoulder  82 H of input shaft  2 B engages first shoulder  86 A in the bore  86  of receptacle  2 R when the fuse  82 F breaks. It will be noticed that outer shoulder  82 H includes a chamfer  82 Z which matches a corresponding surface on first shoulder  86 A of bore  86  of receptacle  2 R. In the normal condition without the fuse broken, outer shoulder  82 H does not engage first shoulder  86 A in the bore  86 . Bore  81  of the input shaft  2 A is a stepped bore which includes a first shoulder  81 A and a second shoulder  81 B. 
     Bushing  2 C and shoulders  86 A,  86 B in bore  86  of receptacle portion  2 R of input gear  2 A prevent the diametrically reduced portion  82 F (once broken) from moving inwardly toward the central portion of gear  2 A preventing damage to gear  2 A and/or the internal spline  2 I of the receptacle portion  2 R of gear  2 A. Screw  2 F retains the inner portion  82 D of the shaft  2 B within the receptacle portion  2 R of input gear  2 A. This over-torque protection system prevents damage occurring to ring gear  2 A as well as to the other components of the gearbox. The two broken shaft portions  82 C,  82 D of shaft  2 B are easily replaced. 
     To prevent damage to gear  2 A while the outer fuse half is spinning, bushing  2 C permits spinning to occur in a controlled fashion and thus prevents damage to the receptacle  2 R of gear  2 A. When fuse  82 F is not broken and the gearbox is running in a normal, proper fashion, bushing  2 C supports shaft  2 B. Bushing  2 C only functions when fuse  82 F breaks or opens. If any damage occurs to the O-ring  2 G when fuse  2 C breaks, it can be easily replaced. The function of the O-rings  2 G,  2 E is to retain grease at the bushing  2 C and the spline  2 P. 
       FIG. 3  is a cross-sectional view  300  taken along the lines  3 - 3  of  FIG. 1E  illustrating the lubrication system and passageways in the ring gear  22 , the housing  1 , and the cover  2 .  FIG. 3A  is an enlargement  300 A of a portion of  FIG. 3  illustrating the lubricant passageways through the cover  2 . Gap  22 G is formed as an annulus between ring gear  22  and the interior surface of housing  1 . The geometry of gap  22 G changes with operation of the gearbox, that is, with the pivoting action of the ring gear  22  with respect to cover  2 . 
       FIG. 3B  is a perspective view  300 B of a portion of the cover  2  illustrating the lubricant pathway therethrough by the unnumbered arrows. The arrows with dashed lines indicate the lubricant flow within and through cover  2 . 
       FIG. 3C  is a plan view  300 C of the floating ring gear  22  illustrating the lubricant passageway  22 P therethrough.  FIG. 1K  illustrates  3  oil passageways  22 P which are separated 120° apart meaning that at least two passageways  22 P may be oriented below the oil line if the housing  1  is filled half full of lubricant.  FIG. 3D  is a cross-sectional view  300 C of the floating ring gear  22  illustrating the lubricant passageway  22 P, housing  1 , and annular gap  22 G between the ring gear and the housing  1 . Planet gear  4 B is illustrated meshed with ring gear  4 B wherein pumping action of the planet gear forces lubricant into and through passageway  22 P. 
     The cutter head  3 , and thus the gearbox  9 , can tilt up to a maximum of 43°22′ with respect to horizontal as illustrated by arrow  99 Z in  FIG. 1 . The tilt in a downward arc may occur to a minor extent but it will not affect bearing lubrication When gearbox  9  is tilted up it will lifted out of the lubricant (oil). This in turn will cause the bearing to overheat, scorch, and then fail. Ring gear  22  and surrounding pieces, in addition to their normal function, function as an oil pump. In the ring gear  22 , just above planet gear  4 B is a small passageway between the teeth of the ring gear. As the gear teeth mesh, lubricating oil is forced up into this passageway  22 P. First planet gears  4 B were chosen to pump oil instead of second planet gears  5 B because planet gears  4 B spin much faster than second planet gears  5 B and therefore make a much more effective pump. Lubricating oil then flows to and then through the annulus  22 G that is between the ring gear  22  and the housing  1 . O-rings  24  at each end of the ring gear keeps the lubricant under pressure from spilling out. Lubricating oil is then forced though a series of passageways of holes and cavities so that oil reaches shaft output bearing  27 , and thus keeps the shaft output bearing  27  lubricated. 
     Referring to  FIGS. 1G ,  3  and  3 A, lubricant is pumped by gear teeth  55  of first planetary gears  4 B through passageways  22 P. There are three passageways  22 P spaced 120° apart as illustrated in  FIG. 1K . The lubricant exits passageways  22 P supplying a volume as defined by generally annularly shaped gap  22 G and O-rings  24 ,  24  as illustrated in  FIG. 1G . When the oil is in the volume as defined it is under pressure and it enters vertical passageway  22 A in housing  1  which, in turn, communicates with horizontal passageway  22 B in housing  1 . Seal  22 S resides in a recess  2 Z in cover  2 . Recess  2 Z is aligned with passageway  22 B in the housing and communicates, horizontally, with a short passageway  2 Y in cover  2  which, in turn, communicates with a vertical passageway  22 C in cover  2 . Vertical passageway  22 C communicates with volume  22 V which is enclosed by front cooler plate  25 . Cooler plate  25  is affixed to cover  2  with screws  11 . As lubricant collects and resides in volume  22 V, it passes into and through necked-down area  22 D where it is communicated to horizontal passageway  22 H. Horizontal passageway  22 H communicates opening  22 R which provides lubricant to shaft output spherical bearing  27 . Lubrication is provided despite the orientation of the gearbox, in other words, if the gear box in inclined, lubrication will continue by virtue of the just-described pumping system. 
     Referring to  FIGS. 4 ,  4 A and  4 B, a gearbox, comprising a housing and a floating gear means for protecting a gear mechanism from damage due to axial and radial forces applied to the gearbox is disclosed. A first cooling compartment and a second cooling compartment are disclosed. The first and second cooling compartments are isolated from the floating gear means. First and second ports supply cooling fluid to the first compartment, and, the third and fourth ports supplying cooling fluid to the second compartment. The ports are all identified with the reference numeral  38  in  FIG. 4 . 
     It is not possible for cooling water to leak into the gearbox as the gearboxes are sealed with respect to the cooling compartments. Water in the cooling cavities/compartments  12 C,  25 C is isolated from the gearbox by a thick, heat conductible, wall of steel  12 W,  25 W, respectively. Cooling cavities/compartments  12 C,  25 C exist at each end of the gearbox, behind the rear plate  12  and the front plate  25 . 
       FIG. 4  is a top view  400  of the gearbox  9  illustrating cooling water plugs  38 ,  38  for the supply of cooling water at the ends of the gearbox.  FIG. 4  also illustrates the input shafts  2 B,  2 B, cover plate  12 , cover plate  25 , and the output shaft spline  28 S.  FIG. 4A  is the right end view  400 A of the gearbox with the cooling water plate removed illustrating the water cavity  12 C, the water inlet  121 , the water outlet  120 , and the wall  12 W separating the water cavity  12 C from the gear systems. Wall  12 W is highly thermally conductive.  FIG. 4B  is the left end view  400 B of the gearbox  9  with the cooling water plate  25  removed illustrating the water cavity  25 C, the water inlet  251 , the water outlet  250 , and a wall  25 W separating the water cavity  25 C from the gear systems. Wall  25 W is also highly thermally conductive. Large amounts of power flow through the gearbox and heat is generated through friction of the gear systems. Referring to  FIG. 4 , plugs  37 ,  37  are illustrated sealing the oil lubrication drill holes created in the manufacturing process. Plugs  37 ,  37  are also illustrated in  FIGS. 3 and 3A . 
     Cooling cavities  12 C,  25 C exist at each end of the gearbox, behind plate  12  and plate  25 , respectively. A portion of cavity  25 C is viewable in  FIG. 1F .  FIG. 4  is a top view  400  of gearbox  9 . Plugs  38  are illustrated and they are removed from threaded holes, and hoses are attached to those holes in order that cooling water be pumped into the cavities. The cooling water within the cavities  12 C,  25 C removes heat generated in the gearbox. Cavities  12 C,  25 C are completely sealed from the gear systems which reside behind walls  12 W,  25 W, respectively. 
     There is a water conduit that passes through the central portion of the gearbox. When the gearbox is installed in an earth-boring machine, the water conduit  6 C carrying cooling fluid is installed which passes through this tube and feeds water to the cutter head. In  FIGS. 1 and 1A , reference numeral  6 C is used to denote the water conduit  6 C through the gearbox  9  and the cutter head  3 . Water conduit  6 C resides within tube  21  as illustrated in  FIG. 1F . 
     REFERENCE NUMERALS 
     
         
           1 —housing 
           2 —cover 
           2 A—input gear 
           2 B—input shaft 
           2 C—cylindrical bushing 
           2 E,  2 G,  14 ,  24 —O-ring 
           2 F—screw/connector affixing input shaft  2   b  to input gear  2 A 
           2 I—internal spline of input gear  2 A 
           2 P—external spline of input shaft  2 B 
           2 R—receptacle for input shaft  2 B 
           2 S—shoulder for retaining bearing 
           2 X—plurality of screws affixing cover  2  to housing  1   
           2 Z—recess in cover in which seal  22 S resides 
           3 —cutter head 
           3 A—intermediate gear 
           3 B—splined shaft 
           3 C—shaft input spherical bearing between tube  21  and shaft  3 B 
           3 E—sun gear 
           3 F—retaining ring 
           4 —horizontal force acting on the cutter head  3   
           4 A—first planet carrier 
           4 B—first planet gears 
           4 C—first pair of spherical bearings between first planet shaft  4 D and first planet gear  4 B 
           4 D—first planet shafts 
           5 —vertical force acting on the cutter head  3   
           5 A—second planet carrier 
           5 B—second planet gears 
           5 C—second pair of spherical bearings 
           5 D—second planet shafts 
           6 A—coupling frame 
           6 B—coupling 
           6 C—water conduit for cooling and lubricating cutting head 
           7 —electric motor, prime mover, one of two 
           7 A—motor frame 
           7 R—roadheader assembly 
           8 —coupling between motor and input gear 
           9 —gearbox 
           10 —bearing cover 
           11 —headed screw 
           12 —rear cooler plate/cap 
           12 S—connector for cooler plate/cap  12   
           13 —adapter 
           13 A—connector/screw 
           17 —planet shaft retainer 
           20 —second sun having a gear and an external spline 
           21 —tube 
           22 —ring gear 
           22 B—horizontal passageway in housing  1   
           22 C—vertical passageway in cover  2   
           22 D—necked down area in cover  2   
           22 G—gap between ring gear  22  and housing  1   
           22 H—horizontal passageway in cover  2  in communication with opening  22   r    
           22 P—port leading to vertical passageway  22 A 
           22 R—opening in cover  2  providing lubricant to shaft output spherical bearing  27   
           22 V—volume in cover  2  in which lubricant resides 
           22 Y—short horizontal passageway in cover  2   
           22 Z—exterior surface of ring gear  22   
           24 R—recess for O—ring 
           25 —front cooler plate/cap 
           26 —dowel pin 
           27 —shaft output spherical bearing 
           271 —inner race 
           270 —outer race 
           27 R—rollers 
           28 —output shaft 
           28 L—shoulder on shaft  28   
           28 S—spline on the output shaft 
           30 —bearing cover 
           30 S—connector/screw 
           31 —lip seal 
           33 —lip seal 
           34 ,  48 ,  49 —bearing 
           36 —retainer 
           37 —plug in housing 
           38 —port plug in housing which is removed for cooling water connections 
           38 T—threaded connection for cooling water 
           39 —port plug in housing for the addition of oil to the gearbox  9   
           40 —seal 
           41 —dowel pins aligning cover  2  with respect to housing  1   
           48 B—shoulder 
           48 S—input gear shoulder 
           49 S—housing shoulder 
           51 —external spline of spline shaft  3   b  meshing with spline  52  of first sun  3 E 
           52 —internal spline of first sun  3 E 
           53 —external spline meshing with internal spline  54  of intermediate gear  3 A 
           54 —internal spline of intermediate gear  3 A 
           55 —first planet gear teeth 
           56 —internal ring gear mating with planet gear teeth  55  of first planet gear  4 B 
           57 —internal ring gear mating with planet teeth  58  of second planet gear  5 B 
           58 —second planet gear teeth 
           59 —external spline of the cover  2   
           60 —internal spline of the ring gear  20   
           61 —retaining ring which retains output shaft  28   
           65 —external spline of output shaft  28   
           66 —internal spline of second planet carrier  5 A 
           67 —internal spline of first planet carrier  4 A 
           68 —external spline of second sun  20   
           69 —external gear of second sun  20   
           69 A—output teeth of the second sun  20   
           70 —teeth of second planet gear  5 B 
           71 —inner race of spherical bearing  5 C 
           72 —roller bearings of spherical bearing  5 C 
           73 —outer race of spherical bearing  5 C 
           74 —inner race of spherical bearing  4 C 
           75 —roller of spherical bearing  4 C 
           76 —outer race of spherical bearing  4 C 
           77 —inner race of shaft input spherical bearing  3 C 
           78 —roller of shaft input spherical bearing  3 C 
           79 —outer race of shaft input spherical bearing  3 C 
           80 —shaft seal between second carrier  5 A and cover  2   
           81 —stepped bore in input shaft  2 B 
           81 A—first shoulder in bore of input shaft  2 B 
           81 B—second shoulder in bore of input shaft  2 B 
           82 C—outer portion of the input shaft  2 B 
           82 D—inner portion of the input shaft  2 B 
           82 H—outer shoulder on input shaft  2 A 
           82 F—annular groove, fused portion 
           82 R—thin section between annular groove and the stepped bore  81  in input shaft  2 B 
           82 Z—chamfer on shoulder  82 H 
           84 —teeth of input gear  2 A 
           85 —teeth of intermediate gear  3 A 
           86 —bore in receptacle portion  2 R of input gear  2 A 
           86 A—first shoulder in bore  86  engaging shoulder  82 H of input shaft  2 B 
           86 B—second shoulder in bore  85  engaging bushing  2 C 
           95 A—gap between internal angular spline and external angular spline 
           96 A—gap between internal angular spline and external angular spline 
           97 A—gap, backlash, between internal angular spline and external angular spline 
           95 I—gap between internal involute spline and external involute spline 
           96 I—gap between internal involute spline and external involute spline 
           97 I—gap, backlash, between internal involute spline and external involute spline 
           99 —arrow indicating relative rotation of ring gear  22 , housing  1 , and second planet gears  5 B 
           99 A—arrow indicating relative rotation of second planet gear  5 B and second sun  20   
           99 B—arrow indicating relative rotation of first sun gear  3 E and splined shaft  3 B 
           99 C—arrow indicating relative rotation of intermediate gear  3 A and spline shaft  3 B 
           99 D—arrow indicating relative rotation of second carrier  5 A and output shaft  28   
           99 E—arrow indicating relative rotation of first planet gear  4 B, ring gear  20  and housing  1   
           99 Z—arrow indicating rotation of the roadheader 
           100 —schematic view of a roadheader including the cutter head, gearbox and prime mover 
           100 A—enlarged portion of the schematic view of  FIG. 1  illustrating the cutter head and gearbox 
           100 B—perspective view of the gearbox 
           100 C—front view of the gearbox 
           100 D—right side view of the gearbox where power is input to the gearbox 
           100 E—left side view of the gearbox where power is output from the gearbox. 
           100 E—cross-sectional view taken along the lines  1 F- 1 F of  FIG. 1D  illustrating the first planetary gear system, the second planetary gear system, the floating ring gear, the input to the first planetary gear system, and the output from the second planetary gear system, all of which are supported by shaft input and output spherical bearings enabling the gear systems and ring gear to float within a fixed housing 
           100 G—enlarged portion of the cross-sectional view of  FIG. 1F  illustrating the floating ring gear, the spline connection between the floating ring gear and the cover, and a portion of the lubrication system 
           100 H—enlarged portion of the cross-sectional view of  FIG. 1F  illustrating the spline input to the first sun driving the first planetary gear set, the first planet carrier driving the second sun, the second sun driving the second planetary gear set and the second planet carrier driving the output spindle, all of which are supported by the shaft input and output spherical bearings enabling the gear systems and ring gear to float within a fixed housing 
           100 I—enlarged portion of the cross-sectional view of  FIG. 1F  illustrating a shaft input spherical bearing interposed between the centrally located support tube and the splined shaft driven by the intermediate gear 
           100 J—perspective view of the floating gearbox without the ring gear and without the housing 
           100 K—perspective view of the floating gearbox with the ring gear shown in an exploded position 
           100 L—diagrammatic view of an angular spline 
           100 M—diagrammatic view of an involute spline 
           200 —cross-sectional view taken along the lines  2 - 2  of  FIG. 1D  illustrating the fused input shaft with a splined connection to the input gear which drives the intermediate gear which in turn drives the splined shaft 
           200 A—a front view of the input gear 
           200 B—cross-sectional view of the input gear illustrating the internal spline for connection with the fused input shaft 
           200 C—front view of the fused input shaft 
           300 —cross-section taken along the lines  3 - 3  of  FIG. 1E  illustrating the lubrication system and passageways in the ring gear, the housing, and the cover 
           300 A—enlargement of a portion of  FIG. 3  illustrating the lubricant passages through the cover and housing. 
           300 B—perspective view of a portion of the cover illustrating the lubricant passages through the cover 
           300 C—plan view of the floating ring gear illustrating the lubricant passageway therethrough 
           300 D—cross-sectional view of the floating ring gear illustrating the lubricant passageway therethrough 
           400 —top view of the gearbox illustrating cooling water plugs 
           400 A—right end view of the gearbox with the cooling water plate removed illustrating the water cavity, the water inlet, the water outlet, and a wall separating the water cavity from the gear systems 
           400 B—left end view of the gearbox with the cooling water plate removed illustrating the water cavity, the water inlet, the water outlet, and a wall separating the water cavity from the gear systems 
         TT—tooth thickness 
         SW—space width 
       
    
     The invention has been set forth by way of example only and those skilled in the art will recognize that changes may be made to the examples provided herein without departing from the spirit and the scope of the appended claims.