Note: Descriptions are shown in the official language in which they were submitted.
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GEARBOX
This invention relates to a gearbox, of the single
speed or change speed type.
Gearboxes are often employed in service conditions
S where loading;1s erratic and on occasion in excess of design
limits, e.g. when driving an underground mineral carrying
convenor. Furthermore, if such a convey~r is of the scraper
chain type and located along a mineral, e.g. coal face, it is
not uncommon for the conveyor to~jam for one reason or another,
possibly resulting in damage to the gearbox and/or any
intermediate transmission between the gearbox and the conveyor.
The invention pertains to a gearbox which includes a
housing, a main reduction stage contained within the housing,
and a preliminary reduction stage preceding~the~main reductlon
stage and also contained within the housing. The prelimlnary
reductlon stage comprises an input shaft rotatable about an axis
; and connectable to a prime mover, a gear carried by the lnput
shaft, a lay shaft, a gear mounted in bearings on the lay shaft
and constantly~ln mesh w1th the input shaft gear, and a clutch
to drivably connect or disconnect the lay shaft gear to the lay
shaft, the latter being rotatable about an axis spaced from, a~d
parallel to, the~input shaft;axis. ~ flexible gear type
coupli~g i~ provided at one termlnal end of the lay shaft to
n~@~ ~h~ la~ shaft to the main reduction stage. The main
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reduction stage comprises a first gear rotatable about an axis,
a second gear xotatable about a parallel axis and in mesh with
the first gear, and a carrier pivotable about the axis of the
second gear, the first gear being mounted in the carrier with a
torque sensing device connected between the carrier and the
housing.
When drive is applied to the gearbox and one of the
clutches is engaged so as to transmit the drive through the
- gearbox, the reaction torque on the carrier is continuously
monitored by the torque sensing device, which provides for
overload protection, e.g. by activating a switch controlling
current to the electric motor, and hence obviating damage to
the gearbox etc., upon a predetermined torque being exceeded.
The gearbox may comprise basically a preliminary
reduction stage preceding the first mentioned reduction stage.
In detail, the gearbox may comprise an input shaft connectable
to a prime mover and carrying a gear constantly in mesh with a
gear mounted in bearings on a lay shaft, a clutch to drivahly
connect or disconnect the gear to the lay shaft, the latter
being rotatable about an axis spaced from, and parallel to,
the axis of the input shaft, terminating in a flexible gear
type coupling to the first mentioned reduction stage. In a
change speed form, the gearbox may be provided with a connecting
gear fixed to the lay shaft and permanently in mesh with a
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gear mounted in bearings on the input
- shaft, with a further clutch to drlvably
interconnect or dlsconnect~the connecting
gear to the input~shaft.
P~eferably, the carrier also
carries the second gear as well as the
first gear of the first mentioned reduction
stage. The input shaft may incorporate~ an
internally splined or geared socket~to
receive a male, externally splined spigot
of the prime mover. ~ ~
If still further speed reduction~is
~ required, the output shaft of the first
- ~ mentioned r~eduction stage may be connected~
to~the input shaft of a further reduction
stage. The requirements for particular
speed reductions will of course depend on ;
whether the gearbox is intended for transmitting
; power to a conveyor, where further speed
~ reduction would be required.
In detail, the torque sensing device
may be connected electrically to an electric
motor constltuting the prime mover, to switch
off the motor upon a predetermined torque
being exceeded.
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The invention will now be
~described in greater detailj by way of
:example, with reference to the accompanying
drawings, in~whiah:-
: Figure 1 is:an axial sectional
,
~ view through a ~speed change gearbox in
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accordance with the invention;
Figure 2 is a section Qn the line
II-II of Figure 1.
In the drawings, the gearbox,
indicated at l, comprises a housing 2
rotatably supporting an input shaft 3
rotatable about an axis 4, and having a
female, internally splined socket 5 ta
15. receive a male, externally splined spigot
6 from an electric motor ~not shown) to which :
the gearbox 1 is bolted. ~he input shaft 3 :
has external teeth 7 constantly in mesh with
. a gear 8 mounted in bearings 9 on a lay shaft
lO~rotatablè about an axis 11 spaced from, and
para~llel to, the axis 4. The gear 8 is
connected by bolts 12 to first e`lements 13 of
.
a hydraulically operable alutah~14 with seaond
ele`ments 15 aarried by the lay shaft lO, the
25 . la`tter terminàting in a flexible gear type:
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coupling compri-sing a female, internally
splined socket 16 to receive a male,
externally splined splgot 17 of a final
reduction stage 18.
The final redaction stage 18
comprises a first gear 19 drivable by
the spigot 17 about an axis~20, and in mesh
with a secon'd gear~21'rotatable about à
Parallel 'axi5 22, both gears being mounted
within a pivotable carrier 23. The carrier
23 is pivotable about the~axis 22 by being
mounted for pivotal movement about bearing
faces 24 and shoulders 25 of the housing 2.
However, pivotal movement of the carrier 23
is cons~rained by a torque senslng device 26
connected between the carrier 23 and the housing ¦ ~,
2, wit~ the torque sensing device electrically I ;'
connected to the electric motor. Thus,
pivotal movement of the carrier 23 about axis
~ 22 is constrained by the torque sensing device
:
26 and henca the torque sensing device 26 can be
pre-set~to allow a predetermined strain to occur
and hence a pr~edetermined torque le'vel to be~
attained which level, when exceeded, e.g. by an
unusual load belng~imposed on the conveyor or by
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the conveyor becoming jammed, triggers
the torque sensing device 26 to switch
off the electric motor to avoid
unnecessary damage to the electric motor,
the gearbox 1, and the subsequent transmission -
to the conveyor.
The input shaft 3 also carries ~
first elements 27 of a further hydraulicalIy 1.
operable clutch 28, with second elements 29 ~ .
bolted to a gear 3O, mounted in bearings 31
on the input shaft 3. The gear 30 is
constantly in mesh with a connecting gear 32
fixed to the lay shaft lO. Thus, selective
operation of a clutch 14 or 28 drives the
: 15 lay shaft lO respectively either through the
gear 8, as a preliminary reduction stage, or
- through the gear 32, as an alternative
preliminary reduction stage, while oil for
the~clutches is provided by a pump 33 driven
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by a gear 34 permanently in mesh with the
teeth 7 of the input shaft 3.
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