GB2170422A

GB2170422A - Bar screen

Info

Publication number: GB2170422A
Application number: GB08601400A
Authority: GB
Inventors: John Darcy
Original assignee: Longwood Engineering Co Ltd
Current assignee: Longwood Engineering Co Ltd
Priority date: 1985-02-01
Filing date: 1986-01-21
Publication date: 1986-08-06
Also published as: GB8601400D0; GB2170422B

Abstract

A bar screen 12 in an effluent channel is cleaned by a rake 32 which is raised and lowered along a frame 22 by a drive motor 34 carried by the frame. Frame 22 is also pivotted about axis 24 by a ram, so that the frame is in position A while the rake is lifted and position B when the rake is lowered. Motor 34 drives a sprocket wheel 40 on a shaft 42, parallel to but spaced from pivot axis 24. A chain 36 is entrained over the sprocket wheel and connected to fixed framework 26 at one end and rake 32 at the other. The motor current is monitored, and the ram is controlled to withdraw the rake from the screen if it encounters an obstruction. <IMAGE>

Description

SPECIFICATION Improvements relating to rake bar screens This invention relates to rake bar screens for use in effluent chambers, and is of the type comprising a screen disposed in the channel, such screen comprising a plurality of bars which extend upright so that the water of the effluent can pass through the bars whilst debris and water borne solids can be caught by the bars and filtered from the water. A rake having fingers which engage between the bars is adapted to be moved upwardly of the bars thereby to sweep away the collected solid material up the bars and out of the channel. The discharged solid material is collected and disposed of clear of the channel.The present invention is concerned with the mounting arrangement for the rake, such mounting arrangement being designed so that the rake can be lowered into the channel when it is held spaced from the screen, and then moved towards the screen so that the rake fingers engage between the screen bars at the lower end of the screen, and underneath the collected solid material to be discharged from the screen. The rake is then moved upwardly as explained above so as to sweep the collected material from the screen, out of the channel and to the point of discharge.

In accordance with the present invention, the rake is mounted on a movable frame so as to be movable thereon as described above, the movable frame also mounting a drive motor for driving a transmission which effects the raising of the rake on the frame, said movable frame being pivotally mounted on a stationary frame located above the channel, and wherein the drive mechanism for raising the rake comprises a drive shaft drivingly connected to a cord or chain or the like which is connected to the rake, and said pivotal connection between the movable and stationary frames are parallel to but offset relative to said drive shaft.

This arrangement provides the advantage that the movable frame and the drive assembly can be fabricated and assembled under factory conditions, and it is only necessary to mount the movable frame on the stationary frame by establishing the said pivotal connection when on site. This simplifies erection on site which in advantageous as the site location being in an effluent environment may be unpleasant and may present difficult working conditions.

The means for moving the movable frame on the stationary frame between a rake lowering position and a rake raising position may comprise a ram, which for example could be hydraulically, electrically or pneumatically operated, connected between the frames, said ram serving to maintain the movable frame in position whilst the rake is being raised to clear the screen. The movable frame may comprise a generally flat frame with side rails in which the rake runs via suitable rollers, and in use the flat frame may lie in a plane which is at a slight angle to the vertical, as it is usual to arrange the screen at such a slight angle.

The drive assembly may comprise a motor and gear box operatively connected to the said drive shaft, the motor and gear box being supported by a suitable casing which has mountings enabling the casing to be pivotally mounted to the stationary frame.

The rake may be of conventional construction comprising a plurality of parallel fingers for engagement between the screen bars. The screen may also be of conventional construction.

The drive assembly for moving the rake on the movable frame may be adapted to drive the drive shaft which is provided with a sprocket around which a chain is trained, one end of the chain being fixed to the stationary frame, whilst the other end is connected to the rake. When the motor is driven in a first direction with the mounting frame pivoted away from the screen, the rake is lowered on the mounting frame to a lowermost position. When it reaches such position the motor is stopped which stops the movement of the rake, the mounting frame is then swung into the screen engaging position by means of the ram, and is held in such a position by the ram whilst the motor is driven in the reverse direction in order to raise the rake through the medium of the chain.The raising of the rake effects clearing of the screen as above described and the loose chain between the point of connection with the stationary frame and where the chain engages a sprocket simply hangs loose in a catenary curve. During the upward travel of the rake towards the top of its stroke it engages a rake clearing#device which sweeps the debris discharged by the rake out of the effluent channel and above the screen, into a collecting container of conventional type. the mounting frame is then pivoted to the position clear of the screen ready for the next cycle of operations. The rake may be arranged to enter the screen, between the bars thereof from either side of the screen.

It is usual to construct the various parts of frames rake and screen in metal such as steel, but the invention is not to be limited as regards the materials used.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, wherein: Figure l is a side view illustrating the apparatus according to the embodiment of the invention; and Figure 2 is also a side view of the apparatus to a larger scale and showing only an upper portion of the apparatus.

Referring to the drawings, in Figure 1 there is shown a U-section effluent channel 10 in which is contained a screen 12 lying at the angle X in the channel base as shown. At the lower end of the screen 12 are parallel screen bars 14 which trap effluent carried debris as the effluent passes between the bars and along the channel as indicated by arrow 16. A rake arrangement, to be described, sweeps the collected debris from the bars 14 up the screen 12 and over a discharging edge 18 into a collecting trough 20 or other similar receptacle from whence it is disposed of in any convenient manner.

In order to clear the screen 12 as described, there is provided a screen clearing arrangement comprising a movable mounting frame 22 which is pivotally mounted at pivot point 24 on a stationary frame 26 located above the channel at ground level 28. The mounting frame 22 carries a rake 30 which has rake fingers 32 which in this example project in the direction of arrow 16 and can as shown in full lines engage between the bars 14. The rake is displaceable along the mounting frame 22 by means of a drive motor 34 and an elongated flexible member such as a chain 36 of which one end is connected to the rake 30, the other end is connected to the stationary frame 26 at location 38, and the drive member is trained round a sprocket or other pulley type wheel 40 for the displacing of same by the motor 34.A sprocket 40 is mounted on a shaft 42 which is drivingly connected to the motor 34 through a suitable transmission 44, and it will be noticed that the pivot axis 24 is separated from shaft 42 but is parallel thereto. A power operated ram 46 is operatively connected between the stationary frame 26 and the mounting frame 22 to move the mounting frame 22 between the full line position shown at A in Figure 1 and the dotted line position shown at B in Figure 1.

If reference is made to Figure 2, it will be seen that the drive shaft 42 is shown in greater detail, and is supported in bearings 48. The motor 34 and transmission 44 are supported on the mounting frame 22 so as to swing with the same when the mounting frame is pivoted about the axis 24.

The operation of the apparatus is essentially simple in that assuming the mounting frame 22 is held in the dotted line position B shown in Figure 1, when there is an accumulation of debris on the screen bars 14, the mounting frame 22 is swung to the full line position A shown in Figure 1 by means of the ram 46 which causes the fingers 32 of the rake 32 to enter between the rake bars 14 at the lower ends thereof. When the mounting frame 22 is in position, the motor 34 is driven in order to wind up the chain 36, surplus chain being allowed to hang in a natural catenary as shown in Figure 2, until the rake 30 reaches a position where its fin gers are engaged by a rake clearing device 50 to displace the debris into the collecting trough 20.

When the rake has been thus cleared, the ram 46 is operated to swing the mounting frame once more to the dotted line position B. The motor is reversed to lower the rake back to the position shown in Figure 1 in which it is ready to be moved forwards towards the screen to enable the fingers 32 once more to enter the spaces between the screen bars 14. The ram 46 will be arranged to hold the frame 22 in the correct position in relation to the screen 12 whilst the rake moves upwardly thereof. The rake may be of conventional construction and may be provided with rollers which run in rails defined in the mounting frame 22.

There may be a current sensing device or similar device mounted in the control panel which will sense current surge to the motor giving an indica tion that an obstruction has been encountered.

This causes retraction of the actuator ram causing the current to drop. Dropping of the current causes the actuator ram to re-extend and re-engage the rake with the grid, giving a profiling action of the rake around the obstruction.

Claims

1. A rake bar screen comprising a rake mounted on a movable frame, said rake being movable on the frame so as to be capable of being raised and lowered thereon, the movable frame also mounting a drive motor for driving a transmission which effects the raising of the rake on the frame, said movable frame being pivotally mounted on a stationary frame located above the channel, and wherein the drive mechanism for raising the rake comprises a drive shaft drivingly connected to a cord or chain or the like which is connected to the rake, and said pivotal connection between the movable and stationery frames are parallel to but offset relative to said drive shaft.

2. A rake bar screen according to Claim 1, wherein the means for moving the movable frame on the stationary frame between a rake lowering position and a rake raising position comprising a ram connected between the frames, said ram serving to maintain the movable frame in position whilst the rake is being raised to clear the screen.

3. A rake bar screen according to Claim 1 or 2, wherein the movable frame comprises a generally flat frame with side rails in which the rake runs via suitable rollers.

4. A rake bar assembly according to Claim 1, 2 or 3, wherein the drive assembly comprises a motor and gear box operatively connected to the said drive shaft, the motor and gear box being supported by a casing which has mountings enabling the casing to be pivotally mounted on the stationary frame.

5. A rake bar screen according to any preceding Claim, wherein the drive assembly for moving the rake on the movable frame is adapted to drive the drive shaft which is provided with a sprocket around which a chain is trained, one end of the chain being fixed to the stationary frame, whilst the other end is connected to the rake.

6. A rake bar screen according to Claim 1, including a current sensing device for sensing a current surge to the motor indicating the presence of an obstruction to the rake, and means for causing retracting of the rake upon such sensing, with automatic return of the rake when it has passed the obstruction.

7. A rake bar screen comprising a rake mounted on a movable frame, said rake being movable on the frame so as to be capable of being raised and lowered thereon, the movable frame also mounting a drive motor for driving a trans mission which effects the raising of the rake on the frame, said movable frame being pivotally mounted on a stationary frame located above the channel, and a current surge to the motor indicat ing the presence of an obstruction to the rake, and means for causing retracting of the rake upon such sensing, with automatic return of the rake when it has passed the obstruction.

8. A rake bar screen substantially as hereinbefore described with reference to the accompanying drawings.