Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to winch drive means, particularly
but not exclusively for the intermittent adjustment of a con-
tenuous load, for example for intermittently adjusting the
tension in conveyor systems in coal mines and the like. Such
means require to be braked when inoperative.
One known arrangement of winch drive means has a band brake
around the periphery of the winch drum, but as the brake is ox-
posed it is prone to physical damage and to contamination by
dirt and possibly oil.
Another known arrangement of winch drive means comprises a
reversible motor connected to a shaft provided with a worm, a
warmly meshing with the worm, a winch drum driven by the
warmly, and an enclosed friction brake comprising a face on a
housing which contains the worm and warmly and a co-operating
disc which is axially fixed relative to the worm shaft and is
drivable connected to said shaft by a one-way clutch. The
brake is applied automatically when the winch is not operating
by an end thrust exerted on the worm shaft in the brake-applying
direction by the load on the winch. When the motor is rotating
in one direction, the one-way clutch overruns and the worm shaft
can be driven without hindrance even though the brake is still
held applied by the load on the winch, but when the motor is no-
toting in the other direction the one-way clutch is locked and,
as the brake is still held applied by the load on the winch, the
motor has to overcome the action of the brake in order to drive
the worm shaft. The resulting frictional drag causes undesir-
able heating and wear.
The object of the present invention is to avoid the disk
advantages of both of the aforementioned known arrangements.
According to the invention, winch drive means comprise a
reversible motor, a driving member connecting the motor to a
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shaft provided with a worm, a warmly meshing with the worm,
and a winch drum driven by the warmly, wherein a friction
brake comprising a face on a housing which contains the worm and
warmly and a co-operating disc rigidly secured on the worm
shaft is applied automatically when the winch is not operating
by an end thrust exerted on the worm shaft in the brake-applying
direction by the load on the winch and wherein double-helical
drive means between the drive member and the worm shaft exert an
opposing force which exceeds said end thrust so as to release
the brake automatically when the winch is operating whatever the
direction of rotation of the motor.
A preferred embodiment of the invention will now be desk
cried, by way of example, with reference to the accompanying
drawings of which:-
Fig. 1 is a sectional side elevation of winch drive means;
Fig. 2 is a side elevation of a detail of said means shown
in section in Fig. l; and
Fig. 3 shows diagrammatically a detail of an alternative
embodiment of the invention.
Referring now to Figs. 1 and 2, winch drive means comprise
a reversible electric motor 10 having a driving cylindrical gear
11 rigidly secured by means including a key 12 on its shaft 13.
The gear 11 meshes with a driven cylindrical gear 14 constitute
in a driving member connected by double-helical drive means
hereinafter described to one end of a shaft 15 provided with a
worm 16. The worm 16 meshes with a warmly 17 which drives a
winch drum (not shown), said worm and warmly being contained
within a housing 18. The driven cylindrical gear 14 is support-
Ed by a thrust bearing 19 carried by an end casing 20 secured
between the housing 18 and the motor 10. A friction brake for
the winch drive means comprises an annular member 21 secured to
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the housing 18 and provided with a friction face 22; and a co-
operating disc 23 rigidly secured by means comprising a key 24,
a castle nut 25 and a tab-washer 26 on the other end of the worm
shaft 15 and having bonded to it a ring 27 of friction material,
the arrangement being such that the brake is applied automatic
gaily when the winch is not operating by an end thrust indicated
by the arrow A exerted on the worm shaft 15 in the brake-
applying direction by the load on the winch. The brake is
enclosed by a cover 28 secured to the housing 18. The double-
helical drive means for connecting the driven cylindrical gear
14 to the worm shaft 15 comprise a left-hand acme-threaded zone
29 and a right-hand acme-threaded zone 30 in an axial bore
through said gear, the left-hand zone 29 engaging with a mating
thread on a first collar 31 rigidly secured by means including
a key 32 to the worm shaft 15 and the right-hand zone 30 engage
in with a mating thread on a second collar 33 rigidly secured
by means including a key 34 to said shaft. Shims 35 may be
inserted as required between the two collars 31 and 33 to enable
their respective key-ways to be aligned with the associated
keys 32 and 34 during assembly, and additional means for rigidly
securing both of said collars to the worm Swift 15 comprise a
castle nut 36 and a tab-washer 37.
In operation, with particular reference to Fig. 2, when the
motor 10 operates the winch by rotating the driven cylindrical
gear 14 in the direction of the arrow B, the axial component
indicated by the arrow C of the force exerted by said gear on
the first collar 31 opposes and exceeds the end thrust indicated
by the arrow A exerted on the worm shaft 15 by the load on the
winch so as to release the brake automatically. Similarly, when
the motor 10 is run in reverse to operate the winch by rotating
the gear 14 in the direction of the arrow D, the axial component
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also indicated by the arrow C of the force exerted by said gear
on the second collar 33 opposes and exceeds the aforesaid end
thrust A so as again to release the brake automatically. Thus
there are provided winch drive means with an enclosed brake
which are not subjected to frictional drag whatever the direct
lion of rotation of the motor 10.
In one alternative embodiment of the invention a detail of
which is shown diagrammatically in Fig. 3, the double-helical
drive means comprise a left-hand helically-splined zone 40 and a
right-hand helically-splined zone 41 formed on the worm shaft
15, said zones being shown in full lines. The zone 40 engages
with a mating splinted zone 42 formed in the bore of the driven
cylindrical gear 14, and the zone 41 engages with a mating
splinted zone 43 formed in said bore, the zones 42 and 43 being
shown in dotted lines. The splints in the left-hand zones 40
and 42 are staggered in relation to the splints in the right-
hand zones 41 and 43. In operation, when the gear 14 is driven
in the direction of the arrow E, the axial component indicated
by the arrow F of the force exerted by said gear on the splinted
zone 40 of the worm shaft 15 opposes and exceeds the end thrust
indicated by the arrow A exerted on said shaft by the load on
the winch so as to release the brake automatically. Similarly,
when the gear 14 is driven in the direction of the arrow G, the
axial component also indicated by the arrow F of the force
exerted by said gear on the splinted zone 41 of the worn shaft 15
opposes and exceeds the aforesaid end thrust A so as again to
release the brake automatically.
In one modification applicable to both the preferred embody
immunity and the foregoing alternative embodiment, the gears drive-
ably connecting the motor 10 to the worm shaft 15 are other than
cylindrical, for example of bevel type. In another modification
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applicable to both the preferred embodiment and the foregoing
alternative embodiment, the gears drivable connecting the motor
lo to the worm shaft 15 are dispensed with and the driving
member constitutes a coupling sleeve or the like directly con-
nectir.g the motor 10 co-axially to the worm shaft 15 by way of
double-helical threads or splints.
In another alternative embodiment of the invention similar
in principle to said one alternative embodiment thereof, the
gears drivable connecting the motor 10 to the worm shaft 15 are
cylindrical and the double-helical drive means comprise left-
hand and right-hand helically-toothed zones on the driving gear
meshing with mating toothed zones on the driven gear, the teeth
in the left-hand zones being staggered in relation to the teeth
in the right-hand zones.
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