GB2155888A

GB2155888A - Winch drive means

Info

Publication number: GB2155888A
Application number: GB08506947A
Authority: GB
Inventors: Eric Albert Whateley
Original assignee: BROWN GEAR IND; David Brown Gear Industries Ltd
Current assignee: BROWN GEAR IND; David Brown Gear Industries Ltd
Priority date: 1984-03-22
Filing date: 1985-03-18
Publication date: 1985-10-02
Also published as: CA1227188A; GB8506947D0; GB8407523D0; GB2155888B; ZA852125B

Abstract

Winch drives for intermittently adjusting tension in conveyors must be braked when inoperative has a worm wheel drive and an enclosed disc brake 21-28 held applied by an end thrust exerted on the worm shaft 15 by the load on the winch. A double-helical driving connection 29-37 is located between the drive motor 10 and the worm drive to create an opposing axial force which exceeds the above-mentioned end thrust and releases the disc brake 21-28 automatically in both driving directions. <IMAGE>

Description

SPECIFICATION Winch drive means This invention relates to winch drive means, particularly but not exclusively for the intermittent adjustment of a continuous 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 exposed 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 wormwheel meshing with the worm, a winch drum driven by the wormwheel, and an enclosed friction brake comprising a face on a housing which contains the worm and wormwheel and a co-operating disc which is axially fixed relative to the worm shaft and is driveably connected to said shaft by a oneway 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 rotating 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 undesirable heating and wear.

The object of the present invention is to avoid the disadvantages 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 shaft provided with a worm, a wormwheel meshing with the worm, and a winch drum driven by the wormwheel, wherein a friction brake comprising a face on a housing which contains the worm and wormwheel 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-helicai 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 described, by way of example, with reference to the accompanying drawings of which: Figure 1 is a sectional side elevation of winch drive means; Figure 2 is a side elevation of a detail of said means shown in section in Fig. 1; and Figure 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 constituting 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 wormwheel 17 which drives a winch drum (not shown), said worm and wormwheel being contained within a housing 18. The driven cylindrical gear 14 is supported 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 the housing 18 and provided with a friction face 22; and a cooperating 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 automatically 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 acmethreaded zone 29 and a right-hand acme-threaded zone 30 in an axial bore through said gear, the lefthand 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 engaging 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 shaft 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 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 direction 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 lefthand 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 splined zone 42 formed in the bore of the driven cylindrical gear 14, and the zone 41 engages with a mating splined zone 43 formed in said bore, the zones 42 and 43 being shown in dotted lines. The splines in the left-hand zones 40 and 42 are staggered in relation to the splines 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 splined 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 splined zone 41 of the worm 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 embodiment and the foregoing alternative embodiment, the gears driveably connecting the motor 10 to the worm shaft 15 are other than cylindrical, for example of bevel type. In another modification applicable to both the preferred embodiment and the foregoing alternative embodiment, the gears driveably connecting the motor 10 to the worm shaft 15 are dispensed with and the driving member constitutes a coupling sleeve or the like directly connecting the motor 10 co-axially to the worm shaft 15 by way of double-helical threads or splines.

In another alternative embodiment of the invention similar in principle to said one alternative em bodiment thereof, the gears driveably 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.

Claims

1. Winch drive means comprising a reversible motor, a driving member connecting the motor to a shaft provided with a worm, a wormwheel mesh ing with the worm, and a winch drum driven by the wormwheel, wherein a friction brake compris ing a face on a housing which contains the worm and wormwheel 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 driving member and the worm shaft exert an opposing ax ial 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.

2. Winch drive means according to claim 1, wherein the driving member is the driven one'of a pair of gears, the driving one of which is connected to the motor.

3. Winch drive means according to claim 1 or claim 2, wherein the double-helical drive means comprise left-hand and right-hand threaded zones on the worm shaft engaging with mating threaded zones in a bore of the driving member.

4. Winch drive means according to claim 1 or claim 2, wherein the double-helical drive means comprise left-hand and right-hand helically-splined zones on the worm shaft engaging with mating splined zones in a bore of the driving member, the splines in the left-hand zones being staggered in relation to the splines in the right-hand zones.

5. Winch drive means according to claim 2, wherein the gears are cylindrical and the doublehelical drive means comprise left-hand and righthand 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.

6. Winch drive means constructed, arranged and adapted to operate substantially as hereinbefore described with reference to, and as illustrated by, Figs. 1 and 2 of the accompanying drawings.