OPERATION


In rope hauled raking machine, the raking skip is supported by wire ropes wound onto hoisting drums above deck level. Two hoisting ropes are used for lowering and hoisting the skip, whilst a third rope moves the raking teeth in and out of mesh with the screening bars.

As the hoisting ropes are unwound the skip descends under its own weight and the central rope is tightened by moving pulley in the head frame, thus holding the rake teeth away from the screen bars.

The skip is then raised to deck level where a wiper blade scrapes off the collected debris of the rake into the discharge chute.

Guide rollers on the skip carriage hold it in position during lowering and raising.

The raking machine can be operated manually or fully automatically. During automatic operation wherever the level difference between up and down stream of screen bars exceeds a present value a signal will be transmitted from the differential level switch to control panel and machine will start automatically.

THE HOIST MECHANISM

The hoisting equipment is mounted in a head frame at deck level and all three ropes are wound onto drum mounted on a common shaft. The control of the central rope is by means of a snub pulley which is moved by an electric ram,bringing the rake in and out of mesh with the screen bars.

Power to the drum shaft is provided by a heavy duty drive mechanism.

Where the width of the screen permits, the hoisting equipment may be mounted in a fixed head frame at deck level.

Screened discharge may be taken to one point through debris conveyors. Fixed raking machines are recommended for heavy debris areas needing continuous cleaning.

MOBILE RAKING MACHINE

On very wide screens, or where a number of screening channels exist side by side, a mobile raking machine can be installed thus obviating the need for a separate machine at each screening position.

This runs on rails set on the deck and can be accurately positioned to rake at any one of a number of similar screens.

A special control unit is mounted on the Travelling Raking Machine and ensures that the head can only be moved with the rake fully raised and that raking only takes place at a specific position.

Debris is normally discharged into a floor channel or a wheeled trolley which can be internally mounted in the travelling head to travel with the machine. Belt conveyors can also be offered for removal of debris.

1. Suitable for Deep Channel : Rope length and control switches can be set for depth up to 20m. Deeper options can be offered on request.

2. Pivoted Rake Head : The raking skip pivots within the raking carriage, which in turn is fitted with guide rollers which run on tracks set in the channel. This arrangement provides alignment with screen bars at all times.

3. Skip Rake Drive : The skip rake drive mechanism can be arranged to provide a lowering speed twice that of the hoisting speed.

4. Safety Device : If the downrun of the skip is obstructed the hoist rope slackens and a slack rope safety device is automatically actuated. This stops further descend of skip. Triping mechanism is also provided to prevent over tensioning of rope while hoisting the skip.

5. Mobile Machine for Multi-Screen Raking : The mobile raking machine can be installed to rake multiple bar screens installed side by side,in both a manual or fully automatic mode. Powered travers gives positive location at each screening position.