GB2146396A

GB2146396A - Self adjusting brake mechanism

Info

Publication number: GB2146396A
Application number: GB08324037A
Authority: GB
Inventors: Reginald Frank Warry
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-09-08
Filing date: 1983-09-08
Publication date: 1985-04-17
Also published as: GB8324037D0; GB2146396B

Abstract

The mechanism is e.g. and specifically fitted to a hoist winch unit with a drum 10 and includes a ratchet lever 26 held in contact with a straight toothed gear wheel 18 which has a thread screwed onto a threaded rod 17 between two posts 31, the lever 26 being operable to turn wheel 18 to slide rod 17 to compensate for brake lining wear. As shown, the mechanism includes a brake band 12 acting on drum 10 and with a rope 14 therearound whose ends are connected to the rod 17 and to a brake lever 19 by means of an adjustable threaded hook 15. Lever 19 also connects with ratchet lever 26 whose length is adjustable. Turning of the gear wheel 18 shortens rope 14. <IMAGE>

Description

SPECIFICATION Self adjusting brake This invention relates to a self-adjusting brake mechanism intended primarily but not necessarily exclusively for application to the cable winding drums of hoists such as are employed on building sites.

In this type of hoist it is the practice to effect the lifting and lowering of a load platform through the medium of a hoist rope or cable which is wound on to and off a drum, the latter being driven by a suitable prime mover through the intermediary of a clutch.

Commonly the operation of such hoists is controlled buy a manually operable control lever fitted with a weight which is movable between one limited position in which the clutch is disengaged and the brake is effectively applied to the drum and a secondary limiting position in which the brake is released and the clutch is applied.

The arrangement is such that the load platform is raised when the control lever is lifted and held in the clutch engaged position. The moving platform is stopped when the control lever is moved to the brake engaged position. The platform is lowered when the control lever is moved to a position in which the clutch is fully disengaged and the brake is slightly released.

The smoothest, safest and most efficient operation of the hoist is achieved when the brake is kept adjusted to give the smallest possible movement of the control lever between the following positions: brake fully engaged for holding the raised load platform brake slightly released for lowering the platform brake fully released and clutch fully engaged for raising the platform.

If the required adjustment to compensate for brake wear is not from time to time carried out the movement of the control lever can get so large that a loaded platform can fall a considerable distance during the time taken for the control lever to pass from the clutch engaged position to the brake engaged position.

It is the chief object of the present invention to evolve a mechanism which will automatically adjust the brake as the brake lining wears. The arrangement is such that the seif-adjusting brake mechanism is set in relation to the position of the hoist control lever when the hoist winch unit is installed in the hoist framework. No further setting or adjustment will be needed until the brake lining is worn out.

In accordance with the invention it is proposed to provide self-adjusting brake mechanism to be actuated by the up and down movement of the hoist control lever comprising of: An extension arm welded to the brake lever on which is mounted for pivotable movement an adjustable rachet lever, the free end of the said rachet lever has a foot which is shaped to fit under a tooth of a gear wheel.

A straight toothed gear wheel which has an internal thread in the centre bore hole for mounting on to an external threaded rod.

An external threaded rod mounted for sliding movement in the bore holes of two posts welded to the winch unit framework, one end of the said rod is coupled to a length of wire rope.

The gear wheel is mounted on the threaded rod and is situated between the two posts welded to the winch unit frame.

The wire rope attached to the end of the threaded rod is wrapped round the outside of the winch brake band and connected to the brake lever by means of an adjustable threaded hook, adjusting nut and lock nut.

The arrangement being such that the position of the hoist control lever is preset in relation to the band brake by means of the gearwheel mounted on the sliding threaded rod and the adjustable threaded hook adjusting nut and lock nut.

The rachet lever is set when the brake is fully applied by means of an adjusting slot and lock bolt so that the top of the foot on the rachet lever does not engage under a tooth on the gear wheel with sufficient depth to turn the gear wheel when the hoist control lever is moved from the brake engaged position to the clutch engaged position.

As the lining of the brake wears the position of the end of the hoist control lever and weight will get lower when the brake is fully applied, at the same time the foot on the rachet lever will move lower down on the gearwheel. In this case the foot of the rachet lever will fully engage under a tooth of the gear wheel.

When the hoist control lever and weight is raised to release the brake and engage the clutch the first part of the upward movement will take the pressure applied by weight off the brake and off the gear wheel. If the foot of the rachet lever is fully engaged under a tooth in the gear wheel continued upward movement of the control lever will cause the gear wheel to turn and advance one tooth. This in turn will pull in the sliding threaded rod and wire rope and automatically adjust the mechanism to compensate for wear on the brake lining.

Four a better understanding of the invention reference will now be made to the accompanying perspective drawing wherein: Figure 1 shows a self-adjusting brake mechanism in the brake engaged position.

Referring now to the drawing, 10 denotes the wire rope drum and brake section of a hoist winch unit. 11 denotes the shaft on which the drum revolves. 12 denotes the steel section and lining of a brake band which prevents the wire rope drum from revolving when the hoist control lever is placed in the brake engaged position. One end of the brake band steel section 12 is welded to a substantiai lug and is mounted on the fixed post 13 welded to the winch unit base frame. The other end of the band after being wrapped round the brake section of the wire rope drum 10 is left free to take up its own position.

The wire backing rope 14 runs round the outside of the steel band, small lugs (not shown) are welded to the steel band and so positioned to keep the wire rope in the centre of the band.

One end of the wire backing rope 14 is connected by means of a flexible clip to the adjustable threaded hook 15, this in turn is connected to the brake lever 19 by means of the adjusting nut and lock nut 16. The other end of the wire backing rope 14 is flexibly connected to the end of the threaded rod 17.

Thethreaded rod 17 is mounted for slidable movement through the holes in the two posts 31 which are welded to the winch unit base frame.

The straight toothed gear wheel 18 which has an internal thread in its centre bore-hole is screwed on to the threaded rod 17 during assembly and is positioned between the two posts 31. The inside of the post nearest the drum acts as an anchor post for the gearwheel.

The gearwheel 18when turned in the direction of arrow A slides the threaded rod 17 in the direction of arrow B. This movement has the effect of shortening the wire backing rope 14 which runs round the outside of the steel section and lining of the brake band 12 and is used to re-adjust the brake lever 19 and the position of the control lever 22 as the brake lining wears. Means (not shown) are provided to prevent the rod 17 from being turned by the gear wheel 18.

The adjustable rachet lever 26 is connected for pivotable movement to the extension arm 25 which is welded two the brake lever 19. The length of lye said lever can be adjusted by means of the adjusting slot 27 and the lock bolt 28. The foot of the said lever is shaped so that the underside will slide over the teeth on the gear wheel 18, the top side is shaped to engage in the teeth of the gearwheel.

The adjustable rachet lever 26 is held in contact with the gearwheel by the pull of the tension spring 30, one end of the spring is attached to the said lever the other end is secured to a fixed block welded to the rachet lever stop arm 29 which in turn is welded to the brake post 20. The stop arm 29 limits the inward movement of the adjustable rachet lever 26.

The hoist control lever 22 with the brake weight 23 is preset in relation to the band brake as follows: After general assembly the control lever 22 which the brake weight 23 is temporarily held or propped up in a neutral position in which neither the clutch or brake is engaged, in this position the drum will be free to turn by hand.

The gear wheel 18 is turned clockwise or anticlockwise until about 11/2 inches of the threaded rod 17 protrudes from the face of the fixed post 31 nearest to the drum.

The control lever 22 is then lowered to the brake engaged position, the end of the brake lever 19 will come to rest on the adjusting nut and lock nut 16 this will tighten the wire backing rope 14 and close the steel section and lining of the brake band 12 round the brake section of the drum 10. The weight 23 welded to the end of the control lever 22 will apply the required pressure to the brake.

The correct setting of the control lever 22 is when the end with the weight is 3 inches lower than the end connected to the link bar 21 when the brake is in the fully applied position. Adjustment is made by screwing up or down the adjusting nut and lock nut 16 on the threaded hook 15. The control lever should be slightly raised when the adjusting nut 16 is being turned, this will rellieve the considerable pressure applied by the brake weight on the nut.

It will be appreciated that although the described and shown self-adjusting brake mechanism is cou pled to a band brake it could be arranged to suit many different types of braking systems.

Claims

1. A self adjusting brake mechanism comprising, A adjustable rachet lever mounted for pivotable movement on the brake lever of a hoist winch unit, one end of the rachet lever has a foot shaped to fit under a tooth of a gearwheel.

A straight toothed gearwheel with an internal thread for mounting on a threaded rod.

Athreaded rod mounted for slideable movement in the bore holes of two posts welded to the winch unit framework.

A wire rope attached to one end of the threaded rod then wrapped round the outside of the winch unit brake band and connected by means of an adjustable threaded hook and nut to the winch unit brake lever.

2. A self adjusting brake mechanism as claimed in claim 1 wherein the position of the rachet lever mounted on the winch unit brake lever is such that the foot of the rachet lever can slide over the tops of the teeth on the gear wheel when the hoist control lever is being moved to the brake engaged position.

The rachet lever is set when the brake is fully applied by means of an adjusting slot and lock bolt so that the top of the foot on the rachet lever does not engage under a tooth on the gearwheel with sufficient depth to turn the gear wheel when the hoist control lever is moved from the brake engaged position to the clutch engaged position. As the brake lining wears the foot of the rachet will move down and fully engage under a tooth of the gearwheel, in this case the upward movement of the rachet lever will turn the gear wheel and adjust the brake to its original set position.

3. A self adjusting brake mechanism as claimed in claims 1 - 2 wherein a straight toothed gear wheel with an internal thread is mounted on a threaded rod and positioned betweenthetwo posts welded to the winch unit framework, the post nearest the brake band acts as an abutment for the gearwheel.

4. A self adjusting brake mechanism as claimed in claims 1 - 3 wherein a threaded rod fitted with an internal threaded gear wheel is mounted for slide able movement in the bore holes of the two posts welded to the winch unit framework.

5. Aselfadjusting brake mechanism as claimed in claims 1 - 4 wherein a wire rope is attached to one end of the threaded rod then wrapped round the outside of the brake band and connected by means of an adjustable threaded hook and nut to the brake lever. the wire rope is pulled tight when the hoist control lever is placed in the brake "on" position.

The brake is automatically adjusted for wear by means of the rachet lever which turns the gear wheel thereby sliding the screwed rod in the post holes and taking up the slack in the wire rope. The initial setting of the position of the hoist control lever and the brake lever is effected by means of the gearwheel and threaded hook and nut.

6. A self adjusting brake mechanism substantially as described herein with reference to Figure 1 of the accompanying drawing.