An apparatus for mining a mineral seam, comprising a motor, and a cutting drum carried on the frame for winning aggregate material from the mineral seam. The cutting drum encloses the motor, and a gear case drivingly connected between the motor and the cutting drum transmits power from the motor to the cutting drum. The gear case is also enclosed within the cutting drum.

BACKGROUND 
     This disclosure relates to a cutter head for a mining machine, and more particularly, to a mechanism for delivering power to the cutter head of a mining apparatus, such as a continuous miner. 
     As shown in  FIGS. 1 and 2 , a conventional mining machine  10  includes a main frame  12  supported for movement or propulsion relative to the ground by means of crawler or caterpillar assemblies  14 , one on each side of the mining machine. The crawler assemblies  14  are powered by electric or hydraulic motors (not shown) carried on the frame  12  in a manner well known in the art. 
     The mining machine  10  also includes a means, generally designated by reference numeral  16 , for cutting an opening in and winning aggregate material from the mineral seam. More particularly, the cutting and winning means  16  is carried on the forward end of a boom  20  that is pivotally mounted to the frame  12 . The cutting drum assembly  18  includes a series of picks  19  for ripping, breaking or cutting aggregate material from the mineral seam for subsequent recovery. 
     The boom  20  includes a bulkhead  21  that interconnects a pair of spaced, lateral arms  22 , each arm being pivotally mounted to the frame through a trunnion (not shown). A pair of hydraulic actuators  24  allows the selective angular positioning of the boom  20  relative to the frame  12 . Thus, the boom  20  and, therefore, the cutting drum assembly  18  may be raised and lowered as the mining machine  10  is advanced into the mineral seam so that aggregate material is cut from the full vertical dimension of the seam. This material is collected in an underlying loading shovel  26  and delivered into a twin chain conveyor  28  for subsequent recovery in a manner known in the art. Each arm  22  carries one motor  30  and a cooperating gear case  32  (see  FIG. 2 ) to drive the cutting drum assembly  18 . The gear case  32  includes webs  34  that connect the cutting drum assembly  18  to the bulkhead of the boom  20 . The webs  34  are the portion of the gear case  32  that connects the actual cutting drums to the cutting boom and therefore to the rest of the machine. 
     One common mode of failure of the above conventional continuous miner is crushing of the webs. Not only do these webs have to handle large forces from the cutting of materials, they traditionally need to provide for a means of transmitting mechanical power from cutting motors to the cutting drum. This power transmission is usually accomplished through a complex set of gears and shafts that run through the web, as shown in  FIG. 2 . To allow for this power transmission, the webs  34  must have much of their material machined away, thereby greatly reducing the overall strength of the web. In certain circumstances, when a piece of material or broken cutter bit gets jammed against these webs, it can cause the webs to crush in. When this occurs, the web material may come into contact with the shafts or gears that are running through the web, causing failure of the machine. 
     SUMMARY 
     The object of this disclosure is to eliminate the need to transmit mechanical power through the webs. 
     This disclosure thus provides an apparatus for mining a mineral seam, comprising a motor, and a cutting drum carried on the frame for winning aggregate material from the mineral seam. The cutting drum encloses the motor, and a gear case drivingly connected between the motor and the cutting drum transmits power from the motor to the cutting drum. The gear case is also enclosed within the cutting drum. 
     The cutter head of this disclosure is the first continuous miner cylindrical cutter head with one or more (typically two) cutting motors contained in the cutting drums. It is also the first double planetary gear train utilizing a compound planetary gear set located inside the cutter head. 
     The cutter head of this disclosure eliminates several problems that occur with the current design of cutter heads. The cutter head of this disclosure also reduces the number of parts and complexity of the cutting system. 
     The cutter head employs a rigid gear case in the cutting drum assemblies that not only houses the cutting motors and gear train, but also provides greater torsional strength over existing models of continuous miners. The cutter head of this disclosure also makes the cutting head more easily expandable by using a modular design to simply increase its width to allow room for a larger motor, thereby greatly enhancing the machines overall capabilities and productivity. The cutter head of this disclosure also costs less to produce than a conventional current cutter head because of its reduced complexity. The cutter head of this disclosure also affords a lower cost cutter boom and enables the cutter boom to be narrower, to accommodate roof-bolting drills, for example. Another added benefit is that the cutter motor mass now moves forward, where it will add to the cutting efficiency of the machine. The cutter head of this disclosure also utilizes a simpler gear train than that used in conventional miners. The new gear train also has fewer unique individual parts, which reduce manufacturing costs and required spare parts inventory. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a prior art mining apparatus. 
         FIG. 2  is a partially cross-sectional view of the mining apparatus shown in  FIG. 1 , illustrating the boom, cutter drum assembly and cutter drum transmission. 
         FIG. 3  is a perspective view of a mining apparatus including a boom and a cutter head according to this disclosure, with the center and left cutting drum's removed. Only some cutting bits are visible. 
         FIG. 4  is a perspective view of a gear train inside the web of the mining apparatus of  FIG. 3 . 
         FIG. 5  is a left side perspective view of the gear train inside the main gear case housing of the mining apparatus of  FIG. 3 . 
         FIG. 6  is a right side perspective view of the gear train inside the main gear case housing of the mining apparatus of  FIG. 3 . 
     
    
    
     Before one embodiment of the disclosure is explained in detail, it is to be understood that the disclosure is not limited in its application to the details of the construction and the arrangements of components set forth in the following description or illustrated in the drawings. The disclosure is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. Use of “including” and “comprising” and variations thereof as used herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Use of “consisting of” and variations thereof as used herein is meant to encompass only the items listed thereafter and equivalents thereof. Further, it is to be understood that such terms as “forward”, “rearward”, “left”, “right”, “upward” and “downward”, etc., are words of convenience and are not to be construed as limiting terms. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIGS. 3 through 6  illustrate a boom and cutter head assembly  100  for a continuous miner. The boom and cutter head assembly replace the means, generally designated by reference numeral  16 , for cutting an opening in and winning aggregate material from the mineral seam, shown in  FIGS. 1 and 2 . 
       FIG. 3  is a perspective view of a mining apparatus including a boom  124  and a cutter head  120  according to this disclosure, with the center and left cutting drum's removed. Only some cutting bits  188  are visible. More particularly, the boom and cutter head assembly  100  includes cutting motors  104  and a gearbox  108  entirely within a cutting drum  112 . The assembly  100  further includes two spaced apart webs  116  that connect the cutter head  120  to the boom  124 . The webs  116  are made from steel plates, and are each attached by bolts  128  to a respective side of the boom  124 . 
     The webs  116  include openings (not shown) to allow for electric and wire lines to power and cool the motors as well as provide a supply of water for water sprays to control dust wall mining. These openings are smaller than in a conventional web, where the openings provide space for gearing to connect the cutter head gearing for rotation to a remote drive. 
     Electric power is transmitted through the webs  116  and into the electric motors  104  where it is transformed into mechanical rotating power, which needs to go through a speed reduction and torque amplification process before it can effectively be used for mining purposes. As illustrated in  FIGS. 4 ,  5  and  6 , this rotational power exits the motor  104  via a shaft  130  that connects to a sun or central gear  134  of a primary planetary gear set. This sun gear  134  then transmits the power to planet gears  140 . These planet gears  140  mesh with an internal annulus gear  148  that provides the output of the primary gear set. Power is then transmitted from the annulus gear  148  to a sun gear  152  (see  FIG. 5 ) of a secondary compound planetary set via another shaft  160 . It is important to note that the secondary sun gear  152  is the output for the primary planetary set, as well as the input for the secondary planetary set. The rotational power is transmitted from this sun gear  152  to a set of large, non-orbiting planet gears  164 . These planet gears  164  are not meshing with an annulus at their full diameter, as would be the case in a normal planetary set. Instead, there is a spur gear  168  attached to each side of every planetary gear  164 . These spur gears  168  share the same axis of rotation as the large planet gears  164 . These spur gears  168  protrude through openings  172  in a main gear case housing  176 , permitting them to transfer power outside of the main housing  176 . Two such spur gear and planetary gear combinations are shown in each of  FIGS. 5 and 6 . 
     On the outside of the housing  176 , the spur gears  168  mesh with large ring gears  180 . These ring gears  180  are then attached either directly to the cutting drum  112 , or through an intermediate inner drum (not shown) that is then attached to the cutting drum  112 . The cutting drum rotate relative to ribs  198  on the main gear case housing  176 . Appropriate bearings (not shown) are between the ribs  198  and the cutting drum  112 , and between the various gears and their supports. Power is transmitted from the cutting drum  112  into actual cutting forces to mine material through the use of the cutting bits  188 . 
     The axes of all of the above gears are fixed relative to the main gear case housing  176 . Each gear can spin, but it does not otherwise rotate around another gear. For example, none of the planetary gears revolve around a sun gear. In  FIG. 6 , one of the supports  192  for fixing of the primary planetary gears to the main gear case housing is shown. Further, the supports  196  for the secondary sun gear, as well as the supports  197  for the spur gears  168 , are also shown in  FIGS. 5 and 6 . 
     In the illustrated embodiment, a gear reduction is provided between the motor shaft and the secondary sun gear. In other embodiments (not shown), if no reduction were needed, the motor shaft could directly drive the sun gear  152 . 
     Various other features and advantages of the disclosure are apparent from the following claims.