GB1598130A - Apparatus for clearing screens - Google Patents

Description

(54) APPARATUS FOR CLEARING SCREENS (71) We, LONGWOOD ENGINEERING COMPANY LIMITED, a British Company of Parkwood Mills, Longwood, Huddersfield, HD3 4TP, do hereby declare this invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to apparatus for clearing screens, such as deep channel screens, such as those used in sewage installations, or pumping stations and whose function it is to stop debris and other solid objects and material referred to herein collectively as debris being carried along in a flow of liquid, from passing the screen, which in effect filters out the debris from the flow. The invention also relates to plants comprising the said apparatus and a screen to be cleared thereby.

The known screen clearing apparatus of the type to which the invention relates usually comprises a rake which moves across or up the screen to remove collected debris from the screen and suitably discharge it.

The rake is usually carried by a rake gear and may be swept in a linear path over a flat screen or in a curved path over a curved screen. The screen conventionally is a plurality of bars arranged parallel and the rake has teeth or tines which pass between the parallel screen bars.

It sometimes happens that a piece of debris, such as a branch of a tree, will become wedged in the screen bars so firmly as not to be displaceable by the rake, at least not by a single pass of the rake. To avoid damage to the rake and to the drive thereof in such circumstances it is known to arrange for the rake to retract from the screen as a result of engagement with such piece of debris.

A disadvantage of this arrangement, is that whilst and when the rake gear retracts from the screen, the whole width of the screen is not cleaned, and if the rake retracts repeatedly at each pass of the screen will continue not to be cleaned across its width in the region of said piece of debris, until the obstruction is otherwise removed.

The present invention aims to overcome this difficulty and in accordance with the invention there is provided an apparatus for cleaning a screen of debris filtered by the screen from a flow of liquid which passes through the screen, comprising rake gear having an elongated rake for sweeping over the screen in an operative raking position to clear debris from the screen, said rake being in two or more aligned sections which are maintained in the raking position under the action of gravity and are individually displaceable from the raking position to a non-raking position against gravity in the event of any of the sections meeting an obstruction on the screen which offers greater resistance than the gravitational force.

It will be appreciated that with such arrangement if there is an obstruction which causes displacement of one of the rake sections, the other rake section or sections can continue sweeping the other portion or portions of the screen, as the whole of the rake is not retracted.

The rake is preferably in three sections, and each of said sections preferably is mounted on a pivotal sub-frame for movement between said positions, the gravitational force including the weight of the sub-frame. The sub-frames preferably are pivoted around common pivot axis.

The apparatus may comprise an intermediate frame on which the sub-frames are pivotally mounted, and a main frame on which the intermediate frame is mounted for back and forth linear movement. Also according to the invention there is provided plant comprising apparatus as aforesaid and a screen arranged to be swept clear of debris by said rake. The said main frame may also carry the said screen. Such arrangement is for positioning in a flow channel with the screen upright (not usually vertical) so that the intermediate frame can be moved up and down, the rake effecting raking of the screen as it moves upwardly and being held clear of the screen as it moves downwardly, the rake sections being held in the raking position by gravity during said upwards movement.Each of the sub-frames may be provided with a counterweight of appropriate mass related to the normal loads to be experienced in the particular application of the invention.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, wherein: Fig. 1 is a sectional side view of apparatus according to the embodiment of the invention; Fig. 2 is a sectional side view to an enlarged scale of the intermediate frame and raking gear assembly shown in Fig. 1; and Fig. 3 is an end view of the assembly shown in Fig. 2 looking from the left, the left hand half of the figure being a sectional view.

Referring to the drawings, in Fig. 1, there is shown the apparatus according to the embodiment of the invention, when located in a channel which normally carries sewage or effluent to be screened. The flow of sewage along the channel is indicated by arrow 10 and it will be seen that the apparatus according to the invention, indicated generally by numeral 12, comprises a main frame 14 which extends from the base of the channel upwardly and rearwardly relative to the flow direction. The main frame 14 is provided with guide rails 16 and support rails 18 which carry a screen 20 comprising a plurality of spaced parallel bars. At the top of the screen support rails 18 is a weir 22 over which screenings moved upwardly by raking gear 24 are tipped into a discharge channel 26 from whence they are removed.

The raking gear is adapted to be moved up and down the guide rails 16 in a manner indicated by arrow 28 in Fig. 1, and to this end the raking gear 24 is suspended by a link chain 30 connected to suitable raising and lowering means (not shown) of conventional form. The raking gear 24 is shown in two positions in Fig. 1, namely an upward position indicated by the letter x and a lower position indicated by the letter y. In position x, the raking gear 24 is in the course of moving upwardly on the rails 16 and it will be seen that a rake 32 of the raking gear has spaced parallel fingers 34 of the rake 32 located between the bars of screen 20, and therefore the rake is in the process of lifting screenings up the screen 20 to the discharge weir 22.

In the position shown at y in Fig. 1 the raking gear 24 is in the course of moving downwardly, and it will be seen that the raking gear 24 is tilted in position y relative to the position shown at x such that the rake 32 and the teeth 34 are held clear of the screen 20. This is achieved in that spaced guide rollers of the raking gear locate in a guide channel 36 defined by rails 16 while the raking gear moves upwardly, keeping the rake 32 in the position in which the teeth 34 engage between the rake bars of the screen 20, whilst in the downwardly travelling position of the rake gear, one of said guide rollers is located outside the channel 36, which maintains the rake in the relatively inclined position shown at y in Fig. 1.When the raking gear reaches the bottom of its travel, the said guide rollers can then become aligned with the channel 36 and will remain so aligned as the raking gear travels up the screen 20.

When the raking gear reaches an upper position, not shown in the drawings, it is forced by camming action to tilt to the disposition shown at y in Fig. 1., for the return lowering movement of the raking gear. This arrangement gives the operation that as the raking gear moves up the rake screen 20 the fingers 34 are engaged between the bars of the screen, whilst when the raking gear moves downwardly, the fingers 34 are maintained out of engagement with the screen bars until the raking gear reaches the bottom of its travel. This is to ensure that screenings are not forced downwards into the channel by the raking gear moving downwardly.

If reference is now made to Figs. 2 and 3, it will be seen that the raking gear is essentially symmetrical in end view about a centre line, and the various components illustrated in Fig. 1 are duplicated at each side of the apparatus. Thus, two chains 30 are illustrated in Fig. 3 and the two pairs of the said guide rollers are indicated by numerals 38 and 40.

The raking gear comprises an intermediate frame 42 comprising four spaced plates 44, 46 (two), and 50 of the configuration shown clearly in Fig. 2, and these plates 44, 46 and 50 are held spaced by being rigidly connected to two parallel tubes 52 and 54.

The plates 44, 46 and 50 carry three subframes 56, 60 and 62, each comprising a pair of arms 64 and 66 which support a tion of angle iron 68 at the lower ends thereof.

Each section of angle iron 68 supports a section 32A, 32B or 32C of the rake 32, the arrangement being that the sub-frames 56, 60 and 62 are independently swingable about a common axis 70 defined by a pivotal connections of the sub-frames to the plates 44, 46 and 50 of the intermediate frame. The sections of rake 32A, 32B and 32C are aligned, and the teeth of the repective sections are pitched so that there will be even pitching of teeth throughout the entire length of the rake 32.

In Fig. 2, the rake 32 is shown in the x position of Fig. 1, and it will be seen that the arms 64 (and 66) rest against the tube 54 which serves as a stop for said arms limiting the extent to which the teeth of the rake penetrate between the bars of the screen 20 when the raking gear is being moved up the screen, The sub-frame 56, 60 and 62 are positioned by gravity in the x position shown in Fig. 1, and to this end may be provided with weights as indicated y numeral 72 in Fig. 1.

With this arrangement, should the rake meet an obstruction which offers greater resistance than the gravitational force exercised by the sub-frame and any weight carried thereby, the sub-frame will swing awayfromthe obstruction but of course the other sub-frames unless they meet similar obstructions, will carry on raking the screen, and only a portion of the screen will therefore remain uncleared.

It will be appreciated that modifications of the invention may be made without departing from the scope thereof, and also that the apparatus described can be used in different dispositions. The invention can be applied to installations using curved screens and the number of rake sections may be varied as desired.

WHAT WE CLAIM IS: 1. An apparatus for clearing a screen of debris filtered by the screen from a flow of liquid which passes through the screen, comprising rake gear having an elongated rake for sweeping over the screen in an operative raking position to clear debris from the screen, said rake being in two or more aligned sections which are maintained in the raking position under the action of gravity and are individually displaceable from the raking position to a non-raking position against gravity in the event of any of the sections meeting an obstruction on the screen which offers greater resistance than the gravitational force.

2. Apparatus according to Claim 1, wherein each of said sections is mounted on its own sub-frame, this sub-frame being mounted for pivotal movement to enable the said section to move between the said positions.

3. Apparatus according to Claim 2, including an intermediate frame on which the sub-frames are pivotally mounted, and a main frame on which the intermediate frame is mounted for back and forth linear movement.

4. Apparatus according to claim 1, 2 or 3, wherein each of the sub-frames includes a counterweight of appropriate mass related to the normal loads to be experienced in the particular use of the apparatus.

5. Apparatus according to any of claims 1 to 4, and substantially as hereinbefore described with reference to the accompanying drawings.

6. Plant comprising apparatus accordingto any of claims 1 to 4 including a screen arranged to be swept clear of debris by said rake.

7. Plant according to claim 6, when dependent upon claim 3, wherein said main frame carries said screen.

8. Plant substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. the raking gear is being moved up the screen, The sub-frame 56, 60 and 62 are positioned by gravity in the x position shown in Fig. 1, and to this end may be provided with weights as indicated y numeral 72 in Fig. 1. With this arrangement, should the rake meet an obstruction which offers greater resistance than the gravitational force exercised by the sub-frame and any weight carried thereby, the sub-frame will swing awayfromthe obstruction but of course the other sub-frames unless they meet similar obstructions, will carry on raking the screen, and only a portion of the screen will therefore remain uncleared. It will be appreciated that modifications of the invention may be made without departing from the scope thereof, and also that the apparatus described can be used in different dispositions. The invention can be applied to installations using curved screens and the number of rake sections may be varied as desired. WHAT WE CLAIM IS:

1. An apparatus for clearing a screen of debris filtered by the screen from a flow of liquid which passes through the screen, comprising rake gear having an elongated rake for sweeping over the screen in an operative raking position to clear debris from the screen, said rake being in two or more aligned sections which are maintained in the raking position under the action of gravity and are individually displaceable from the raking position to a non-raking position against gravity in the event of any of the sections meeting an obstruction on the screen which offers greater resistance than the gravitational force.

2. Apparatus according to Claim 1, wherein each of said sections is mounted on its own sub-frame, this sub-frame being mounted for pivotal movement to enable the said section to move between the said positions.

3. Apparatus according to Claim 2, including an intermediate frame on which the sub-frames are pivotally mounted, and a main frame on which the intermediate frame is mounted for back and forth linear movement.

4. Apparatus according to claim 1, 2 or 3, wherein each of the sub-frames includes a counterweight of appropriate mass related to the normal loads to be experienced in the particular use of the apparatus.

5. Apparatus according to any of claims 1 to 4, and substantially as hereinbefore described with reference to the accompanying drawings.

6. Plant comprising apparatus accordingto any of claims 1 to 4 including a screen arranged to be swept clear of debris by said rake.

7. Plant according to claim 6, when dependent upon claim 3, wherein said main frame carries said screen.

8. Plant substantially as hereinbefore described with reference to the accompanying drawings.