This drillhead unit includes a sealed housing mounting a bevel gear assembly and a bevel drive pinion assembly. The bevel gear assembly includes a hollow shaft providing a chuck for receiving a hollow drill bit and the bevel pinion assembly includes a shaft providing a connection for a hydraulic drive motor. The hollow shaft is connected to a cavity within the housing, which is connected to exhaust passages connected to a vacuum source. A vacuum sealing assembly is provided within the housing between the bevel gear assembly and the housing to eliminate bearing lubrication loss. The unit can also be used for reverse flow positive water pressure in lieu of a vacuum.

BACKGROUND OF THE INVENTION 
This invention relates generally to drillhead units and particularly to a 
drillhead unit used in conjunction with a hollow drill bit to provide 
holes for the insertion of roof bolts in coal mines. 
There are several problems connected with the drilling of holes in coal 
mine roofs for the insertion of roof bolts, particularly when drillhead 
units are used of the type which rely on a vacuum pulled through a hollow 
drill bit. 
One of these problems is the relatively short life of the drillhead unit 
resulting from the fact that the vacuum used to remove cuttings from the 
hollow drill bit tends to suck the lubricant out of the unit which results 
in failure of the bearings and pinions. 
Another problem is that when the hydraulic motors, which are used to drive 
the pinions, are changed due to malfunction dirt enters the drillhead unit 
and can cause premature failure. In general, drillhead units provide a 
beveled pinion mounted to the motor shaft, and when the motor is inserted 
into the pinion housing it automatically positions the pinion. This 
arrangement tends to lead to sealing problems and, in addition, in some 
cases, only the tips of the cooperating pinions in the drillhead are 
engaged due to an improperly located motor pinion and this can also result 
in wear and premature failure. 
Still another problem is that the chuck depth for the hollow drill bit must 
be sufficient to provide a secure connection for the drill bit, so that it 
cannot be thrown out of the chuck during rotation, and this can result in 
the chuck extending a substantial distance above the drillhead unit. 
Yet another problem with known drillhead units resides in the fact that the 
top surface of the housing is normally covered with dirt which migrates 
into the top seals because of inadequate sealing of the gear assembly of 
the unit operating in powdered coal and rock which is very destructive to 
the mechanism. 
This drillhead unit solves the above and other problems in a manner not 
disclosed in the known prior art. 
SUMMARY OF THE INVENTION 
This drillhead unit is provided with a seal assembly between the 
bit-receiving gear assembly and the housing interior which virtually 
eliminates loss of bearing lubrication resulting from the application of a 
vacuum to the drill bit through the interior of the housing. 
A drive pinion assembly is provided which is accurately mounted within the 
housing rather than to the end of the drive motor shaft so that the motor 
shaft can be removed without loss of lubrication and admission of dirt. 
The drive pinion assembly is mounted independently of the motor so that it 
need not be disturbed when the motor is replaced and a more effective seal 
is achieved. 
The structural arrangement of the drill bit gear assembly shaft provides a 
deep chuck passage extending into the interior of the housing which tends 
to hold the drill bit in place and reduce the possibility of the bit being 
thrown out from the chuck during rotation. 
A dust cover and seal assembly is provided between the housing and the 
drillhead gear assembly to protect the upper portion of the housing from 
the ingress of dust and dirt from the mine roof and into contact with the 
gear assembly. 
The housing is provided with dual vacuum exhaust passages so that one 
drillhead unit will accommodate either position on a twin bolter unit and 
eliminate the need for providing left and right hand drillhead units. 
This drillhead unit includes a housing having an inner passage portion. A 
gear assembly is received by the housing having a longitudinal axis of 
rotation and including a shaft, said shaft having an outer bit-receiving 
end, an inner end remote from said outer end, and an axial passage 
extending between said inner and outer ends and connected to the inner 
passage portion of the housing, said assembly also including a gear 
disposed between the inner and outer ends of the shaft and being connected 
to said shaft for rotation therewith. 
Mounting means are provided for the gear assembly including bearing means 
disposed in coaxial relation between the gear assembly and the housing and 
pressure sealing means is disposed between the gear assembly and housing 
for separating the bearing means for the inner passage portion of the 
housing. 
A drive pinion assembly is received by the housing having an axis of 
rotation disposed transversely of the axis of rotation of the gear 
assembly and including a shaft, said shaft having an outer end connected 
to the motor and an inner end remote from said outer end, said assembly 
also including a pinion disposed at the inner end of the shaft and 
connected to said shaft for rotation therewith, said pinion being drive 
engageable with the gear assembly. 
Mounting means are provided for the drive pinion assembly including bearing 
means disposed between the pinion assembly and the housing. The bearings 
of the pinion assemblies include spaced inner and outer taper bearings 
having radial and thrust bearing capability. 
The gear assembly shaft inner end includes an annular recess having a 
transverse bearing face and spaced cylindrical walls and the pressure 
sealing means includes a coaxial cylindrical element attached to the base 
and having a transverse bearing face, said element being spaced from said 
recess walls and transverse bearing face, and a resilient combination seal 
mounted between said recess walls and said cylindrical element. 
The pressure sealing means includes an annular metallic ring having opposed 
bearing faces, one of which is engageable in bearing relation with said 
recess bearing face; a spring mounted to said cylindrical element and 
engageable with said cylindrical transverse bearing face; an annular 
friction seal having opposed bearing faces one of which is engageable in 
bearing relation with the spring and is urged away from the cylindrical 
transverse bearing face; and a carbon ring disposed between the annular 
seal and the other face of the annular ring in sliding relation to said 
other face. The pressure sealing means also includes an O-ring means 
disposed between the annular ring and one of said cylindrical recess walls 
in frictional relation with said parts to provide that they rotate 
together; and an O-ring means between said cylindrical element and the 
other of said recess walls to seal said parts. 
The housing includes a base and a removable cover for the second pinion 
assembly carrying at least part of the drive pinion assembly and shim 
means are provided between the cover and the base for axial adjustment of 
said cover relative to said base to locate the drive pinion relative to 
the axis of the gear assembly 
The drive pinion assembly shaft includes a threaded end and the mounting 
means for the drive pinion assembly includes a collar threadedly received 
by the thread end and the bearing means cooperate with the collar to hold 
the pinion assembly to said cover. 
The housing also includes a removable cover for the gear assembly carrying 
at least part of said assembly and shim means is provided between the base 
and the cover for axial adjustment of the cover relative to the base to 
locate the gear relative to the axis of the pinion assembly. 
The gear assembly shaft includes an outer portion, extending both outwardly 
and inwardly of the cover, an inner portion disposed entirely within the 
housing and a thrust plate disposed between said inner and outer portions, 
said thrust plate being engageable by the drill bit. 
The drive pinion assembly shaft is recessed to receive the motor shaft and 
sealing means is provided between said collar and said removable cover. 
The gear assembly includes a dust cover rotatable with the gear assembly 
shaft. 
The housing inner passage portion includes a cavity connecting the shaft 
passage to a pair of transversely extending exhaust passages disposed 
within the housing and connected to the pressure source which is a vacuum. 
The drillhead unit is adapted for use with reverse flow positive pressure 
water in lieu of a vacuum source.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now by reference numerals to the drawings and first to FIG. 1, it 
will be understood that the drillhead unit generally indicated by numeral 
10 is used in conjunction with a roof bolter unit 12 and is shown 
operatively mounted to said unit. The roof bolter 12 includes a frame 14 
having a mast 16 extending between upper and lower frame members 18 and 
10, respectively, which provides a guide for a vertically movable carriage 
member 22 having a mounting plate 24 to which the drillhead unit 10 is 
operatively attached. The mounting blade 24, and therefore the drillhead 
unit 10, is raised and lowered toward and away from the roof 30 by means 
of a chain drive system generally indicated by numeral 26. Power is 
supplied to the unit 10 by a motor 20. 
The drillhead unit 10 is used to rotate a hollow drill bit generally 
indicated by numeral 28, which drills vertical holes in the mine roof 30 
preparatory to the insertion of an anchored roof bolt such as that 
generally indicated by numeral 32. The hollow drill bit 28 receives the 
drill cuttings which are drawn through the drillhead unit 10 by a vacuum 
which is applied to said unit through a vacuum hose 204 by a vacuum source 
such as a blower B by way of a dust collector D, as shown in FIG. 1, at a 
pressure of between 15-20 inches of mercury. 
The drillhead unit 10 will now be described with particular reference to 
FIGS. 2 through 5. As shown in FIG. 2, the drillhead unit 10 includes a 
housing having a base 42, an upper cover plate 44 removably connected to 
the base 42 as by fasteners 45 and a side cover plate 46 removably 
connected to the base 412 as by fasteners 47. 
The cover plate 44 is apertured to receive a gear assembly generally 
indicated by numeral 48, which includes an outer bit-receiving shaft end 
portion 50 having a deep interior passage 52 adapted to receive the end of 
the hollow bit 28, and a shaft inner end portion 54 having an enlarged 
coaxial passage portion 56 receiving the outer portion 50, said shaft 
portions constituting a shaft. The passage 56 includes an end wall 58 
providing an abutment for a thrust plate 60 disposed between the upper and 
lower shaft portions. The inner shaft portion 54 also includes a reduced 
passage 62 extending between the passage 52 at one end and communicating 
at the other end with a cavity 64 provided in a hub-like seating portion 
66 of the housing base 42, said cavity being provided with a sealed 
removable clean-out plug 65. The cavity 64 receives cuttings from the 
drill bit 28 via passages 52 and 62 and communicates with a vacuum source 
as will be discussed below. A gear 68 is mounted to the shaft upper and 
lower portions 50 and 54 by means of splines 70 so that said shaft 
portions rotate with said gear 68. The gear assembly 48 is rotatively 
mounted to the housing 40 by tapered roller cone bearings 72 and 74. 
Bearing 72 is disposed between the gear 68 and the housing cover plate 44 
and includes shoulders 76 which provide the bearing with both radial and 
thrust bearing capability. A seal ring 78 of rubber or similar material is 
disposed in sealing relation between the stationary cover plate 44 and the 
rotating gear 68. The gear assembly 48 also includes a dust cover 80 which 
is attached to said gear as by fasteners 82 for rotation with said gear, a 
teflon ring 84 being provided between the relatively movable dust cover 80 
and the stationary housing cover plate 44, said dust cover and said cover 
plate being suitably grooved at 85 and 87 to receive said ring in spaced 
and fitted relation respectively. The dust cover 80 is provided with a 
grease fitting 84, having a protective shroud 86, and supplying grease to 
the labyrinth between seals 78 and 84 including groove 85. 
The inner roller bearing 74 also includes shoulders 88 which provide the 
bearing with radial and thrust bearing capability. A face seal assembly is 
provided between the inner shaft portion 54 and the housing base 42, 
generally indicated by numeral 90 which constitutes a pressure sealing 
means and is best understood by reference to FIG. 5. As shown in FIG. 5, 
the inner shaft portion 54 includes a deep annular socket 92 having 
oppositely disposed generally cylindrical sidewalls 94 and 96 and endwall 
98 which receives the seal assembly 90, which provides a resilient 
combination seal. 
The seal assembly 90, which is capable of resisting positive or negative 
pressure and is used as a vacuum seal in the embodiment described, 
includes a cylindrical element 100 which is threadedly engageable with an 
annular rim 102 formed on the seating portion 66 of the housing base 42. 
The cylindrical element 100 includes an annular ledge 104, and an O-ring 
seal 106 is disposed between said ledge 104 and said rim 102. This seal 
assembly 90 also includes a stainless steel ring 108 which rotates with 
the shaft 54. This stainless steel ring 108 is engageable with the socket 
endwall 98, which constitutes a transverse bearing face, and an O-ring 
seal 110 is disposed between said ring 108 and said cylinder wall 94 and 
provides sufficient friction to ensure that said ring 108 and said shaft 
54 rotate together. A resiliently mounted seal 112 of rubber or the like 
is mounted to the cylindrical element 100 and is urged outwardly by means 
of a compression spring 114 extending between said ring and the annular 
ledge 104, said ledge providing a transverse bearing fall for said spring. 
A carbon ring 116 is disposed between the seal 112 and the stainless steel 
ring 108 and, by virtue of the friction between the rubber seal 112 and 
the carbon ring 116, the latter is maintained in a substantially 
stationary condition to provide a bearing face for the relatively smooth 
rotating stainless steel ring 108. An O-ring 118 is disposed between the 
cylindrical element 94 and the socket wall 96. The drillhead housing is 
supplied with lubricant by means of an oil fill plug 218 and the seal 
assembly 90, by virtue of the cooperation between the O-rings 110 and 118 
together with the seal 114 and O-ring 106, provides an effective seal 
which prevents the escape of lubricant into the cavity 64 when a vacuum is 
applied to said cavity. The vacuum is applied to the housing cavity 64, 
the shaft passages 62 and 52 and the bit 28 by the blower vacuum source B 
through the medium of one of two exhaust passages 122 and 124 connected to 
said vacuum source and said cavity 64. As shown in FIG. 3, two exhaust 
passages are provided so that the drillhead unit 10 can be used in 
alternative positions in conjunction with a twin head bolting unit thereby 
obviating the need for left and right hand drillhead units. In the 
embodiment shown the exhaust passage 124 is connected to the vacuum source 
by way of fitting 128 and hose 204, and a closure plug fitting 126 is 
provided for exhaust passage 122. It will be understood that the exhaust 
passages are formed, as by boring, in a thickened portion of the housing 
base 42 extending between the cavity 64 and the fittings 126 and 128, and 
indicated by numeral 130. It will also be understood that said cavity and 
exhaust passages cooperate to define a housing inner passage portion 
connecting the vacuum hose 204 to the shaft passage 62 and the hollow 
drill bit 28 and separated from the outer portion of the housing 
containing the lubrication by the seal assembly 90. 
The gear 68 is driven by a drive pinion assembly generally indicated by 
numeral 140. This assembly includes a shaft portion 142 having a drive 
pinion 144 integrally formed on the end thereof and having a socketed 
remote end portion 146 which receives the splined shaft 202 of the drive 
motor 200. The cover plate 46 is apertured to receive the drive pinion 
assembly 140 and includes an outer flange 148, which is connected to the 
relatively thick housing sidewall 150 by means of fasteners 47, and a 
reduced inner portion 151, which is received within an opening 152 
provided in said relatively thick housing sidewall. 
The pinion assembly 140 is rotatively mounted to the housing 40 by means of 
a pair of tapered roller bearings 154 and 156 received within grooves 158 
and 160 respectively provided on the cover plate 46. The roller bearings 
154 and 156 each include shoulders such as those indicated by numerals 162 
and 164 respectively which provide the tapered roller bearings with radial 
and end thrust bearing capability and the pinion shaft 142 is provided 
with a threaded end portion 160 which receives a compatibly threaded 
adjustable collar 168. The collar 168 is tightened into thrust bearing 
relation with bearing 156 and secured in the adjusted position by means of 
a key 170 as shown in FIG. 4. This key 170 is attached by means of 
fasteners 172 to the collar 168 which includes a plurality of spaced 
threaded openings 174 for this purpose, and said key is received within a 
spline groove 176 provided in the threaded end 166 of the drive shaft 142 
to prevent loosening of the collar. A sealing ring 180 is disposed between 
the cylindrical wall 182 of the socketed end portion of the cover plate 46 
and the collar 160. 
The longitudinal disposition of the gear assembly 48 is accurately 
determind by the provision of shims 184 of selected thickness disposed 
between the cover plate 44 and the housing base 42. In the same manner, 
the longitudinal disposition of the drive pinion assembly 140 is 
accurately determined by the provision of shims 186 between the side cover 
46 and the housing sidewall 150. 
The housing of the motor 200 includes a flange 206 which is attached to the 
drillhead unit 10, as by fasteners 208 received within threaded openings 
210 provided in the drillhead unit cover plate 46. The drillhead unit 10 
is attached to the roof bolter carriage 24 as by fasteners 212 received 
within threaded openings 214 provided in the housing base 42. 
As shown in FIG. 3 a breather fitting 220 is provided for the fill plug 218 
which is threadedly connected to the cover plate 44 to prevent oil 
pressure build-up within the drillhead unit 10 due to expansion and 
contraction of the oil resulting from heat change when the unit is 
operating. The plug 218 includes a dip stick (not shown) and a drain plug 
120 is provided to drain oil from the unit during repair. 
In the embodiment described above, the cuttings are removed from the hollow 
drill bit 28 by vacuum, i.e., negative pressure. However, the structural 
arrangement of parts of the face seal assembly 90 is such that it can 
resist positive pressure resulting from reverse fluid flow. Because of 
this, it is possible to apply positive water pressure to the drillhead 
unit 10 in lieu of neagtive air pressure. The use of water pressure 
requires the substitution of the blower B (FIG. 1) by a pump P or similar 
pressurized water source, the elimination of the dust collector D and the 
replacement of the vacuum hose 204 by a water pressure hose 230. When 
water pressure is used the direction of the fluid flow is reversed as 
compared with flow when air is used as follows. Water is applied to 
drillhead unit 10 through the pressure hose 230 which is connected to 
passage 124. This passage is now a supply passage and conveys water under 
pressure, at about 200 psi, through the cavity 64 and the passages 62 and 
into the hollow drill bit 28. The water issuing from the drill bit 28 
flushes away the cuttings down the side of the drill bit and, in addition, 
tends to cool the bit and thereby keep it sharp longer. The combination 
seal 90 can operate under pressure and thereby prevents the ingress of 
water into the drillhead unit 10. The water pressure system described is 
particularly useful in conditions where hard roof conditions are 
experienced. 
It is thought that the structural features and functional advantages of 
this drillhead unit have become fully apparent from the foregoing 
description of parts, but for completeness of disclosure, the installation 
and operation of the device will be briefly described with respect to the 
drillhead unit used in a vacuum system. 
The housing base 42 is fitted with the portion of the seal assembly 90 
comprising the cylindrical element 100 having the sealing ring 112, the 
spring 114 and the carbon ring 116 in position. The preassembled gear 
assembly having the bearings 72 and 74 and stainless stell ring 108 fitted 
is emplaced coaxially within the housing so that the stainless steel ring 
108 is disposed above the resiliently mounted carbon ring 116. The cover 
plate 44 including the seal 78 is attached to the housing base 42 by means 
of fasteners 45 with shims 184 and the dust cover 80 is attached to the 
gear 68 by means of fasteners 82. The drive pinion assembly 140 is 
preassembled within the housing cover 46 and the cover is attached to the 
housing sidewall 150 by means of fasteners 47 taking care that the desired 
shims 186 are in position to insure that the drive pinion 144 accurately 
engages the gear 68 correctly meshed. The hydraulic motor 200 is connected 
to the drillhead unit 10 by means of the motor flange 206 and the 
drillhead unit 10 and the motor 200 are mounted together to the frame 14 
of the roof bolter unit 12. The vacuum connection is made to fitting 128 
and the other fitting 126 is closed with the plug, the fitting used 
depending on the proximity to the vacuum supply from the blower B. 
In operation, as shown in FIG. 1, the hollow drill bit is fitted into the 
hexagonal socket 52 and raised upwardly by the carriage into its drilling 
position. As will be readily understood, the vacuum applid to fitting 128 
is applied to the vacuum cavity 64 and removes cuttings from within the 
hollow drill bit 28 by the negative pressure produced. The sealing system 
provided by the seal assembly 90, in particular, provides that no negative 
pressure is applied to the interior of the housing to cause lubricant to 
be drawn from the bearings. 
As will be readily understood, the use of the drillhead unit in a water 
pressure system simply requirs the substitution of the blower B by a water 
pressure system, which can be provided by a pump P or by a gravity feed 
system, the elimination of the dust collector D and the substitution of 
the vacuum hose 204 with a water hose 230.