GB2253384A

GB2253384A - Controlled descent device

Info

Publication number: GB2253384A
Application number: GB9021495A
Authority: GB
Inventors: Reginald Frank Warry
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-10-03
Filing date: 1990-10-03
Publication date: 1992-09-09
Also published as: GB9021495D0

Abstract

A controlled descent device which will automatically control the lowering of loads on a winch drum 1 by means of a band brake 13 applied through pivoted operating levers 10, 11 which mount rollers 7, 9 engageable respectively with the outside and inside of a flat ring 2 mounted on the end of the member 1 through lugs 3 permitting the ring to centrifuge into an eccentric position relative to the member 1 upon the latter reaching a preset minimum speed. <IMAGE>

Description

CONTROLLED DESCENT DEVICE This invention relates to a controlled descent device intedded primarily but not necessarily exclusively for application to cable winding drums of hoists such as are employed on building sites.

In mobile hoists, such for example of the kind described in prior patent specification 'o.905928 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 from a suitable prime mover through the intermediary of a clutch. Commonly the operation of such hoists is controlled by a manually operable control lever which is moveable between one limiting position wherein the clutch is disengaged and a brake is effectively applied to the drum and a secondary limiting position wherein the brake is released and the clutch is engaged.At an intermediate position between the aforesaid limiting positions of the control lever there is a neutral position wherein the braKe is released and the clutch is not engaged. With non-skilled labour often employed on building sites it can happen that when the load platform is in an elevated position and the operator moves the lever to release tne brake and to allow lowering of the said platform, he will move said lever into the neutral position so that the platform will be free to descend under the action of gravity. If the operator is not sufficiently skilled in the use of hoists to control the speed of the descending platform by means of the brake the load platform could rush down at high speed which could be the cause of accident and damage.

Some makes of hoists employ tuo sets of gearing, one set runs from the engine to the drum via a clutch and is used vor lifting the platform, the other set runs from the druni to the engine via a "spring" clutch and is used when the platform is being lowered. A centrifugal brake is also fitted to the engine crankshaft to prevent overspeed of the engine when the hoist is being used for lowering materials. This arrangement often called a "drive up and drive down winch unit" is a relatively expensive unit.

It is the chief object of the present invention to evolve a low cost mechanism which would effectively control the descending speeds of loads.

A preferred embodiment in accordance with the invention comprises a flat ring mounted for slideable movement on a rotating member to be actuated by a pivotable centrifugal operated lever when said rotating member exceeds a predetermined speed, the said lever is slideably connected to the said flat ring; the position of the centrifugally operated lever on said rotating member is such that when held against a fixed stop on the said rotating member the said flat ring will run true and concentric with the axis of said rotating member; a adjustable retaining element effective to maintaining said centrifugally operated lever in a inoperative position against a fixed stop during such times as said rotating member is rotating at or below the predetermined maximum speed; the arrangement being such that when the speed of said rotating member exceeds the maximum the centrifugal force acting on said centrifugally operated lever will overcome the power of the adjustable restraining element and cause said centrifugally operated lever to move outwards this in turn will cause said flat ring to move outwards and run eccantric to the axis of said rotating member; a pivotable lever mounted on the side of the winch unit frame, one end of said pivotable lever is fitted with a roller which runs on the inside of said flat ring the other end is pivotably connected to a bfake,when said flat ring revolves eccentrical in relation to the axis of said rotating member the inside part of said flat ringnearest the axis of said rotating member pushes the end of said pivotable lever fitted with the roller down, the other end of said lever in turn moves up and applies a brake; the above described arrangement when operated applies the brake in a on and off manner once per revolution of the said rotating member this is generally suitable for smali hoists and light loads; for larger hoists and heavy loads a second lever is mounted on the side of the winch unit frame, one end of the said second lever is hingedly connected to said mounting, the other end via a adjustable threaded rod and short length of chain or tension spring is connected to a brake, a roller which runs on the outside of said flat ring is fitted to the said second hinged lever approximately half way along its length. When said flat r;ng revolves eccentrically in relation to the axis of said rotating member the part of said flat ring furthest from the axis of said rotating member pushes said second hinged lever upwards and applies a brake, the pressure applied to the brake by said second hinged lever can be adjusted by means of the adjustable threaded rod; means are provided to minimise the sound emitted by the moving parts.

For a better understanding of the invention reference will now be made to the accompanying drawings wherein; Figure 1 shows a perspective drawing of a controlled descent device fitted with the first and second brake operating levers in the inoperative position.

Figure 2 A diagrammatic drawing of a controlled descent device fitted with only the first brake operating lever in the operating position.

Figure 3 A diagrammaticdrawing of a controlled descent device fitted with both first and second brake operating levers in the operating position.

List of reference numtars with part names 1 Rotating Member 2 Flat Ring 3 Retaining lugs 4 Pivot point 5 Pivotable centrifugally operated lever 6 Fixed stop 7 Top roller 8 Lifting lug 9 Inside roller 10 First pivotable brake operating lever 11 Second pivotable brake operating lever 12 Adjustable tension spring 13 First brake lever mounting post 14 Anchor point section of band brake 15 Adjustable rod and chain 16 Link bar 17 Operating section of band brake 18 Section of winch unit frame 19 Section of winch unit frame 20 Second brake lever post 1 denotes a rotating member; it will be assumed that the member is incorporated in a hoist and that when it is rotating in the direction of the arrow the cable will be unwound from the member thereby to effect a lowering of the load; 2 denotes a flat ring, the said flat ring is mounted for slideable movement on the said rotating member 1 by means of the retaining lugs 3 welded to the said flat ring; the said flat ring 2 is actuated and moved outwards in relation to the axis of the said rotating member 1 by the pivotable centrifugally operated lever 5 when said rotating member 1 exceeds a maximum preset speed; the said flat ring 2 is slideably connected to said pivotable centrifugally operated lever 5 by the lifting lug 8 which is welded to the said flat ring 2; the said flat ring 2 is held in a inoperative position against the fixed stop 6 mounted on said rotating member 1 by the adjustable tension spring 12 during such times as the said rotating member 1 is rotating below the maximum preset speed; the first pivotable brake operating lever 10 is mounted on the post 13 which is in turn rigidly bolted to the side of the winch unit frame 18; one end of the said first pivotable brake operating lever 10 is fitted with the inside roller 9 which runs on the inside of the said flat ring 2 the other end is pivotly connected to the link bar 16 which is in turn pivotly connected to the end of the band brake 17; when the said rotating member 1 revolves at a speed in excess of the maximum preset speed the centrifugal force acting on the said pivotable centrifugally operated lever 5 causes the said centrifugally operated lever 5 to move outwards around the pivot point 4 this in turn moves said flat ring 2 outwards in relation to the axis of said rotating member 1 this in turn causes said flat ring 2 to run eccentrically to the axis of said rotating member 1; when the said rotating member 1 is revolving with ttBe said flat ring 2 in the eccentric position the inside Fart of the said flat ring 2 ;;zarest the axis of said rotating member 1 pushes the end of the said first pivotable brake operating lever 10 fitted with the inside roller 9 down the other end in turn moves up and applies the band brake 17 via the link bar 16 to the said rotating member 1 in a on and off manner, this has the effect of controlling the speed of the descending load; the above described arrangement when operated applies the band brake 17 in an on and off manner to the said rotating member 1, once per revolution, this is generally suitable for small hoists and light loads; for larger hoists and heavy loads a second brake operating lever 11 is mounted on the post 20 which in turn is rigidly bolted to the side of the winch unit frame 19; one end of the said second brake operating lever 11 is pivotly connected to said post 20-the other end via a adjustable threaded hooked rod and short length of chain or tension spring 15 is connected to said band brake 17; the top outside roller 7 which runs on the outside of said flat rilg 2 is fitted to the said second brake operating lever 11 approximately half way awl it its length; when the said flat ring 2 revolves eccentrically in relation to the axis of said rotating member 1 the part of the said flat ring 2 farthest from the axis of said rotating member 1 pushes the said second pivotable brake lever 11 upwards this applies the said band brake 17 to said rotating member 1; the pressure applied to the said rotating member 1 by the said band brake 17 can be adjusted by means of the said adjustable threaded rod and chain or tension spring 15 means are provided to minimise the sound emitted by the moving parts; the combination of the first and second brake operating levers 10 and 11 gives two applications of the said brake 17 per revolution of the said rotating member 1 in an on and off manner; this arrangement allows for smoother and greater control over both light and heavy descending loads.

Claims

CONTROLLED DESCENT DEVICE 1. A controlling descent device for automatically lowering a load at preset speeds without using a running Electric Motor, Diesel Engine, Petrol Motor or other running mechanism for retarding purposes comprising of pivotable levers running by means of rollers on the inside and outside of a flat ring mounted for slideable movement on the side of a rotatable winch unit winding drum; the first pivotable lever mounted on the rigid Post 13; the first pivotable brake operating lever 10 fitted with a roller 9 which runs on the inside of said flat ring 2; the second pivotable lever 11 mounted on the rigid post 20; fitted with a roller 7 which runs on the outside of said flat ring 2; a adjustable rod and chain or tension spring 15 connected to the first brake operating lever 10; means provided to minimise the sound emitted by the moving parts.