Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND TO THE INVENTION
This invention relates to a drive for a saw blade. : -
ln a copending patent application filed simultaneously with the present
application, it is proposed to provide a selective non-explosive mining
apparatus in which cuts are made into the working face in a mine
working using rotating circular saw blades.
An object of the present invention is to provide a drive for the circular
saw blade which is designed for convenient replacement of the blade and
which permits the blade to operate in limited access conditions.
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SUMMARY OF THE INVENTION
According to the present invention there is provided a circular saw blade
drive comprising a motor, a gear train driven by the output shaft of the
motor, a hollow spindle driven by the gear train and lockable in a
rotationally fast manner to a hub carl~ing the saw blade so that in use
the saw blade rotates in unison with the spindle, a bolt of which the
shank passes through the hollow of the spindle and a nut having an
internally threaded recess engagable with a threaded end of the shank,
the nut bearing upon the hub and holding the hub in rotationally fast
engagement with the spindle, the head of the bolt being remote from the
blade and no part of the drive extending beyond that surface of the
blade which is remote from the head of the bolt.
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In the preferred form of the invention, the motor is an hydraulic motor
and the gear train is a reduction gear train which includes a pinion
carried by the output shaft of the motor and a gear fast with the spindle
and meshing with the pinion.
The spindle may have an out-of-round portion, typically of hexagonal
shape at the extremity of the spindle, that locates in a complemental
cavity of the hub to hold the hub in rotationally fast manner to the
spindle. Also, the nut may have a peripheral flange which bears upon an
anm~lar shoulder presented by the hub.
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BRIEF DESCRIPTION OF THE DRASiVlNGS
The invention will now be described ;n more detail, by way of example
only, with reference to the accompanying drawings in which:
Figure 1 shows a perspective view of an apparatus used in a
non-explosive mining technique, the apparatus
including a circular saw blade which is driven by a
drive of the present invention; and
Figure 2 shows a cross-sectional view through a drive of the
invention.
DESCRIPIION OF AN EMBODIMENT
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Figure 1 shows the relevant parts of a non-explosive mining apparatus
which is described in detail in the previously mentioned copending
patent application.
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The apparatus of Figure 1 includes a skid mounted module 10 having a
rail 12 on which a carriage 14 can be driven by a traverse drive 16.
Pivoted to the carriage 14 at a lateral pivot 18 is a tilt frame 20. Pivoted
to the tilt frame 20 at an upright pivot 22 is a ranging arm 24 carrying
a circular saw 26 at its end. The circular saw includes an hydraulic motor
28 supplied with pressurised hydraulic fluid from a remote power pack
(not illustraled~ through the illustrated array of hydraulic hoses. The
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circular saw also includes a gearbox drive 30 by means of which the
motor drive is applied to a diamond impregnated circular saw blade 32.
In use, hydraulic cylinders 31 and 33 respectively are used to tilt and
slew the blade 32. With the carriage moving along the rail 12 and with
the blade rotating and applied to the working face in a mine working,
a continuous cut is formed in the working face.
Referring now to 3~igure 2, the drive 30 is shown in more detail in a
position inverted with respect to the view of Figure 1. I he hydraulic
motor 28 drives a hollow splined pinion 34 which meshes at 36 with a
gear 38. The pinion 36 and gear 38 constitute a reduction gear train. The
gear 38 is mounted fast on a hollow spindle 40. The hollow splined
pinion 34, gear 38 and the majority of the spindle 40 are located in a
casing constituted by a lower cover 42 to which the motor is bolted and
an upper casing part 44 connected to the cover 42 by bolts 46.
A bearing 48 ensures that the spindle is rotatable relative to the casing
part 44 while a bearing 50 ensures that the spindle is rotatable relative
to the cover 42. The spindle projects out of the casing through the casing
~ part 44. At the extremity 52 of its projecting end, the spindle 40 is
- formed externally with a hexagonal cross-section. The internal cavity of
an annular hub 54 is complemental in shape to the extremity 52 of the
spindle 40 and receives that extremity snugly. The hub is thus engaged
~ in a rotationally fast manner by the extremity 52 and is caused to rotate
in unison with the spindle 40. The circular saw blade 32is fixed to the
hub 54 and ;s therefore caused to rotate in unison with the hub and the
spindle.
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The assembly just described is held together by a bolt which has a head
58 and a shank 60. The shank 60 passes through the spindle 40 and its
threaded end 62 is engaged in a threaded nut 64. The nut has a flange
66 that bears against an annular shoulder 68 of the hub 54 and holds the
hub in engagement with the end of the spindle. The nut has a short
hexagonal extension 71 which engages in a complemental recess in the
hub 54 to prevent rotation of the nut 64 when the bolt is tightened up.
A first important feahlre of the illustrated embodiment is the fact that
no part of the drive protrudes beyond the surface 70 of the blade 32.
Thus the surface of the flange 66 is flush with the surface 70. As a result
there is no part of the drive which can foul on an external obstruction
located axially in front of the blade when the blade is rotating.
A second important feature of the illustrated embodiment is the fact that
access is only necessary from one side to detach the blade 32. In the
orientation illustrated in Figure 2, access from the bottom is required.
To detach the blade 32, a spanner is applied to the head 5~ of the bolt
to unscrew it ~rom the nut 64. Once the bolt is detached from the nut,
the blade and nut can be lifted slightly or the saw can be lowered to
clear the extremity 52 of the spindle moved sideways away from the
spindle and casing. This is a major advantage since there will in practice
often be no room for an operator to approach the blade 32 from both
sides, particularly when the blade is close to a surface such as the
surface of a hanging wall or footwall in a mine working. For instance,
with the saw blade 32 in a low position, close to a footwall, as illustrated
in Figure 1, there is no access from beneath the blade.
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To install a new blade, the new blade and nut are slipped sideways and
then dropped onto the extremity 52 of the spindle. The threaded end 62
of the bolt is then engaged with the nut 66 to secure the assembly.
In another version of the invention, a s~ivel arrangement is incorporated
between the drive assembly 30 and the tilt frame 20 to allow the drive
assembly to be rotated through a full 180. This renders the apparatus
more flexible as one saw can now cut the footwall and the hanging wall
without having to carry out a major, time-consuming dism~ntling and
reassembling procedure. Also, should it be preferable, one saw only can
be used to create the necessary slots in a variety at mining methods.
The relative importance of factors such as mining speed and capital
expenditure will dictate ~he preferred combination of saws.
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