WO2008035990A2

WO2008035990A2 - Screening apparatus

Info

Publication number: WO2008035990A2
Application number: PCT/NZ2007/000272
Authority: WO
Inventors: George Burgess; Brian Burgess
Original assignee: Power-Glides Screens Limited
Priority date: 2006-09-19
Filing date: 2007-09-19
Publication date: 2008-03-27
Also published as: WO2008035990A3; WO2008035990A9

Abstract

A screen assembly for removing unwanted material from a fluid flow comprises a rake assembly mounted on a slidable carriage which is mounted and spaced from a screen via a frame. The rake assembly have tines mounted on a shaft with a T-bar assembly which in use the tines can move from a retracted or non-operating position to an extended position and vice versa. A drive shaft mounted to the carriage and frame is operatively connected to the rake assembly whereby movement of the drive shaft causes T-bar assembly to move the tines into an extended position or non extended position which such tine movement is then followed by moving the carriage with the tines to push or remove any of materials caught on the screen, off the screen or along the screen.

Description

Screening apparatus

The invention relates to a screening apparatus for removing unwanted material from a fluid flow. The invention is directed particularly but not solely towards a screening apparatus for removing solid impurities from wastewater flow

Background of Invention

Known screening apparatus are used to remove unwanted materials from a fluid flow. Such apparatus or devices are large and unwieldy with complicated components that require intensive maintenance, are unreliable and are both expensive to purchase and maintain.

As a result of extensive development and use of existing apparatus it was found that there were problems with multiple parts, their difficulty in coordination and cost.

In this specification unless the contrary is expressly stated, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date, publicly available, known to the public, part of common general knowledge; or known to be relevant to an attempt to solve any problem with which this specification is concerned.

Object of the Invention

It is an object of the invention to provide an improved screening apparatus and method of operation that ameliorates some of the disadvantages and limitations of the known art or at least provide the public with a useful choice.

Summary of Invention

In a first aspect the invention resides in a screening apparatus for removing unwanted material from a fluid flow, that includes a screen having a length and longitudinal slots therein and a rake assembly operatively positioned along the screen by a carriage at a set distance therefrom, the rake assembly being displaceable along the screen by at least one driving means, the rake assembly including a plurality of tines movably connected to a rake one end of the screen and an operative position as the rake moves to the other end of the

-screen such that any solids or unwanted materials caught by or located on the screen or flow are removed from the screen or .moved along the screen, displacement means comprise a mechanical linkage acting between each rake assembly and the screen or apparatus dependent from the screen, the actuator comprises at least one hydraulic ram or drive shaft wherein the rake assembly is fixedly mounted on the drive shaft by a slotted block and rotatably mounted to the carriage by a T-bar assembly which operatively rotates the rake assembly from a retracted position to an extended position and vice versa, with respect to the screen to then move with the carriage to move any unwanted material thereon from the screen or along the screen.

Preferably the T-bar assembly includes at least one fan shaped member having at one end a - bar in a manner to form a T-bar and the fan shaped member having one end slidably held within the slot of the block to form the T-bar assembly and the other end rotationally mounted to a transversely mounted shaft which such shaft is supported by the carriage^" ^" -whereby movement initiated by the drive shaft can cause movement of the- bar of the T-bar assembly about an offset rotational point as provided by the square transverse shaft to the T- bar to cause the movement of the square shaft and all of the tines of-the rake assembly. "

Preferably the transverse shaft also has further tines mounted thereon.

Preferably the drive shaft has at least an upper and lower push or pull plate mounted thereon which such shaft is also mounted to the carriage

whereby movement of the drive shaft between fixed positions with the lower push plate being between a lower T-bar assembly and a lower drive shaft bearing supports on the carriage can cause movement of the rake assembly and carriage at sequenced consecutive positions on the frame when the carriage travels down the screen with a first shaft movement retracting the tines and then the carriage moves, and the upper push plate being located between an upper carriage drive shaft bearing and a middle carnage drive shaft bearing which in use extends the tines and then pushes the carriage up the screen, whereby one movement being the movement of the rake assembly and the following movement then being the movement of the carnage along the screen until it hits the end of the frame. Preferably the carriage is slidably mounted on the drive shaft and frame by carriage bearing assemblies. .. . .. . . ^■

Preferably several tines are connected to the transverse shaft which shaft is rotatably connected to the drive shaft and to the carriage which carriage is-slidably connected to the 5 drive shaft whereby movement of the drive shaft in the opposite direction after the carriage is stopped causes the tines to be extended or retracted and further movement of the drive shaft causes the carriage and tines to move up or down the screen.

Alternatively several tines are connected to the transverse shaft which is rotatably connected to the drive shaft and to the carriage which is slidably connected to the drive shaft whereby0 movement of the drive shaft after the carriage is stopped in the same direction causes the tines to be extended or retracted and further movement of the drive shaft can cause the carriage and tines to move up or down the screen.

^"In another aspect the invention comprises a method of raking a screen with a screening

^{" ' "•}'-^'■ assembly for removing unwanted material from a fluid flow which includes a screen having5 a length and longitudinal slots therein and a rake assembly operatively positioned along the. screen by a carriage at a set distance therefrom, the rake assembly being dϊsplaceable along the screen by at least one driving means, the rake assembly including at least "one tine movably connected to a rake arm and displacement means to move the said at least one tine with respect to the rake arm, between an inoperative position as the rake moves to one end of0 the screen and an operative position as the rake^fthoves to the other end-of the screen such.

-that-any solids or unwanted materials caught by or located on the screen or flow are removed thereon/therefrom, displacement means comprise a mechanical linkage acting- between each rake assembly and the screen or apparatus dependent from the screen, the actuator comprises at least one hydraulic ram or drive shaft including an upper and lower push plates which can5 move between carriage bearings wherein the rake assembly is fixedly mounted on the drive shaft by a slotted block and rotatably mounted to the carriage by a transverse T-bar to form a

T-bar assembly -which operatively rotates the rake assembly from a retracted position to an extended position and vice versa, with respect to the screen to move any unwanted material thereon from the screen whereby the method includes the following steps of: tines are inoperative position & upper push plate abuts the carriage guide bearings;

move drive shaft in opposite direction ie now upwards;

lower push plate moves with shaft to meet carriage bearings causing T-bar assembly to move which moves the rest of the tines move/rotate^rextending downwards while 5 carriage stationary;

- drive shaft still moves and lower push plate then moves carriage up the screen;

- extended tines and carriage move debris to top of screen;

- carriage hits upper end of frame and drive shaft stops;

- lower push plate abuts carriage and tine^as extended;

10 - drive shaft then moves in opposite direction-downwards;

.-■.-, , -. as drive shaft moves carriage, assembly is stationary until the upper ^"push plate meets . . the. carriage bearings whereby the tines are retracted- by movement of the T-bar ^" - ■ _. .. ^{■ '}. . assembly; . -. . . , ^{' ' ■ "}.-

- upper push plate then abuts carriage bearing assembly;

15 -^■- - drive shaft then moves taking carriage and tines to bottom;

- carriage then hits end of frame so that the carriage and drive shaft stop;

and back to the first step to repeat all the ^"previous steps.

Brief Description

The invention is described, by way of non-limiting examples only, with reference to the 20 accompanying drawings, in which:

Figures IA to 1C are diagrammatic side elevations illustrating the raking cycle of the raking assembly of the present invention with the rakes extending from underneath the screen Figure 2 is a plan view of screen apparatus with the rakes extending from above the screen

Figure 3 is a side view of the screening apparatus of Figure 2

Figure 4 is an end view of the screening apparatus ofFigure 2

Figure 5 is an upper close up perspective view of the apparatus of Figures- 2-4

Figure 6 is an end cross sectional view of the apparatus showing the frame and screens

Figure 7 is another end view but showing the carriage

Figure 8 is a close up side view of the T-bar assembly and push plates

Figure 9 is an upper perspective view of the apparatus with the drive shaft located . underneath the frame

Figure 10 " is a close up view of a portion of the apparatus of figure 9

Figure 11 is a schematic representation of the screening apparatus in a simple form

Description of Drawings

The following description will describe the invention in relation to preferred embodiments of the invention, namely- a screening apparatus. The invention is in no way limited to these preferred embodiments as they are purely to exemplify the invention only and that possible variations and modifications would be readily apparent without departing from the scope of the invention. ^■ - ^. -^{■ ■}

As shown in the figures the tines of the rake assembly can extend from above or from below th^"e screen. Figures 1A-1C and 5-10 show the tines extending from below while figures 2-4 show the tines extending from above the screen. Any such configuration is possible.

Operation of a screening apparatus according to the invention is shown diagramniatically in Figures IA to 1C the rake assembly being operatively located underneath the screen. In those Figures, a screen 1 having screen elements 2 is shown in side elevation having a first end (or in use a lower end) being the entry end of the screen and a second end (or in use the upper end) being the discharge end. However, it will be seen that screen 1 may also be viewed in Figures IA to 1C as being plan views if the screen is arranged horizontally rather than vertically. As can be seen, individual screen elements 2 can be disposed vertically and spaced horizontally but can also be disposed horizontally and spaced vertically. Thus the screening system according to the invention can be useebvith the screen elements arranged in a vertical or horizontal disposition, or possibly one or more intermediate dispositions.

As can be seen from the other figures 2-8 the screen elements 2 have gaps or slots between adjacent elements. The gaps can be formed by the individual screen elements 2 simply comprising bars or the screen could be manufactured in another manner, for example having slots cut out of a sheet material, or could alternatively be moulded or cast. In one embodiment, the screen is constructed from steel, but those skilled in the art will appreciate that other materials could be used, forexample suitable plastics materials. The screen slots and elements are shaped such that in when fluid enters from above the screen at any angle, to exit below or through the screen there. is created a pressure differential from entry to exit ; . thereby causing a general sucking or forcing of fluid flow through and past the screen elements.

Screen 1 is sized and operates by allowing liquid which includes water and solids to allow the fluid to pass through the slots in between the screen elements, but impeding suspended solids." Therefore, the spacing between adjacent screen ^"elements^' 2 is selected so as to provide an appropriate degree of filtering. Accordingly, only suspended solids which^" have a dimension which is greater than the gap between adjacent screen elements will be trapped on the screen. ^{" ~ *} " ^" "

It is desirable to remove solids that have collected on the screen (referred to generally in this document as "screenings") in order to allow the screen to function properly. If the solids are- not regularly removed from the screen, then the passage of liquid through the screen is impeded. , . . .

The screen face is best oriented at angle to any fluid flow to enable a general screening of unwanted debris to occur. In one example when disposed in a non-horizontal position, is usually disposed at an angle of approximately 50-60 degrees from the vertical, sloping backwardly in the downstream direction relative to the flow of water through the screen. However any orientation for the screen 1 is also possible. Typically, the screen 1 is placed in a channel such as a, water, sewerage or treatment channel. However, screen 1 may also be placed across an exit from a pool or other reservoir, such as the intake for a hydroelectric power station for example or_be located in a vertical flow...

The rake assemblies for the present invention can be provided at the underneath or rear of the screen, or on top of/above the screen and the tines of each rake assembly may be arranged to

- project through the slots in the screen between the screen elements. However, a person skilled in the art to which the invention relates will realise that the rake assemblies for the present invention may be suspended above a front surface of the screen and be extended to move the screening up the screen and also be retracted by moving rake(s) away from the front.surface of the screen. -

Referring again to Figure IA, o^'he_; rake assembly is generally referenced as 4 is shown including rake tines or teeth 8 in the extended operable position with the tines 8 projecting through slots in the screen 1. In this position, the tines 8 interdigitate with the screen elements 2. Rake assembly 4 is mounted on a sub-assembly which includes a carriage 10 which is slidably supported by a frame 20.

Carriage 10 is capable of being moved relative to the screen 1 in a direction substantially parallel to the screen 1. Therefore, if the carriage 10 is moved from the position shown in Figure. IA from the first end of the screen, up the screen in a direction shown by arrow 12 then the solids 14 will be collected and or pushed by the tines 8 of ra_ke assembly 4. The result. of movement in the direction' shown by arrow 12 is illustrated in Figure IB where the screenings that were collected by rake assembly 4 have been moved by that rake assembly off the top end or second end of the screen 1. In practice, a bin (not shown) or similar disposal area is- provided at or below the top end of the screen. 1 so that screenings which have been collected by rake assembly 4 may and 5-10 be disposed of. ^~ ■ -

The next step in the screening process is retraction of the tine(s) 8 of rakes assembly 4 which can be referred to as the inoperative position. This is shown in Figure 1C. Referring to that Figure, it can be seen that the tine(s) 8 have been moved to a retracted inoperable position where they are disposed in such a way that they do not interfere with the screenings 16, or any other solid matter (not shown) which may be deposited on the screen while the retraction operation occurs. Figure 1C shows that and freshly collected screenings 16 remain in position on the screen. This occurs because the angle of the screen is such that screenings do not tend to fall down the screen. Also, the flow of liquid through the screen, as represented - by arrow 3, maintains a force against the screenings which- maintains the screenings in place on the -screen.

The next step is to extend the tines 8 of the. rake assembly 4 so that they assume the orientation shown in Figure IA. In this orientation, the screenings 16 will be collected by the tines of rake assembly 4 ready for removal, from the screen by being pushed off the -• screen 1. -

It will be seen that the effect of the operation is to enable each rake assembly 4 to be moved in a single operation a distance which is at least equal to the length of the screen 1 on which the rake 4 operates from the first end to the second end without any staged removal being necessary. However in another variation the apparatus can also be operated in a staged removal system whereby any debris is moved up the screen in stages by successive waves of

^■ rake assemblies travelling a portion of the screen length.

Although only one carriage with one rake assembly is shown-per screen, many more carriage and screen assemblies may be mounted, depending upon the overall size of the screen and

-the . distance over which the actuation device that moves the .carriage 10 is capable of

: extending. More rakes assemblies can be provided on a single carriage or further carriages

. can be designed to be attached to an existing carriage with one or more rakes. Also, carriages can be provided across parts of the screen in a. side by side relationship/ Thus carriages may be operated in- unison across^" a screen, or .could be operated independently across a screen.

Turning now to Figures 2 to 4, the rake assembly 4 is .shown operatiyely supported above the screen 1 though it is equally possible to have the rake assembly below the screen. In Figure 2, a partial side elevation of a screening system is shown. The reference numerals used in Figures IA to 1C are used in the remaining drawings to illustrate features which are similar or the same.

The screening system of Figure 2 is supported on a frame 20 to which the screening elements

2 are connected. As shown in figure 4 there is a space between the lower part or rear part of the frame 20 and the screening elements. It is in this space that carriage 10 is provided or located. In another example in a vertically disposed screen, the screening elements 2 are provided down the front face of the assembly and are mounted and fastened at the top and bottom of the frame. The screening elements can be post-tensioned.. ^■ — , ..

Each carriage 10 shown can have at least one rake assembly 4 mounted thereon per screen.

In another option there can be several .-carriages 10 each supporting at least one rake assembly 4 per screen but all coordinated or not as required. The carriage 10 includes a

- carriage frame 21 slidably supported by frame 20. Each rake assembly 4 includes" at least one tine 8 movably supported by a transverse shaft 22. Transverse shaft 22 spans across the width of screen 1 and is spaced from one side of the screen elements 2 to the other and said shaft 22 is connected -to at least one fan-shaped -arm 22a which intύrn is located in a bearing assembly 23 or block which itself is operatively connected to longitudinal extending shaft

24. Shaft 24 can be located above or below the screen and is operatively supported by the frame 20 and is connected to the carriage 10 without obstructing the sliding movement of the carriage on the frame.

In figure 3, shaft 22 is shown as being above the screen element even though other orientations spacing such as being above the screen is or are equally possible^ In this example shaft 22 is has a square cross section and is end supported by slidable bearings 23 at " each side of the screen on the frame 20.

In general there will be several tines 8 movably connected to a common transverse shaft 22. At least one tine-8 Js connectively and movably supported-to drive shaft -24 - by a driving : block 25. This is shown in'figures 8 and 9. Block 25 is fixedly connected to drive shaft 24. with a push pull bracket 26 whereby movement in the longitudinal direction i.e. along the length of the screen or parallel to the flow of liquid 3, by the drive shaft 24 causes the block 25 to longitudinally move thereby causing the square shaft 22 to rotate arid move-all tines in the same rotational direction from either retracted or extended position.

The actuator or means that initiates movement of the tines begins with the movement of the shaft 24. Shaft 24 is supported by several bearing supports to the carriage and frame with at least one spacer inbetween. The spacer can merely be a ringed member fixedly adjustably attachable to the shaft 24. The driver block 25 is fixed to the drive shaft which in turn is slotted with a bearing assembly to rotatably house a T-bar member. The T-bar member is operationally joined to the rake assembly by the transverse shaft 22. The T-bar member and slotted block form a T-bar assembly. As shown in the drawings the driving block 25 is slotted and can be orientated differently

= -depending on whether the drive shaft 24 is mounted on top of the screen or below it. If

^■ mounted above (see figures 2-4) then the slotted block with its opening facing downwards has a stopping portion to keep the T-bar member from falling out. If mounted below then the opening can face upwards without any stopping portion being required.

Drive shaft 24 is operatively connected to an assembly can also have several, push/pull plates

27 and 27a, -support bearings 31 connected to the carriage/frame and push pull brackets 28

^" whereby movement of the drive shaft 24 via any operating means such as hydraulics, causes

. the longitudinal movement needed via the push/pύll plates to move the rake assembly 4 as -described and also move the carriage 10 after the rake assembly has been moved. Drive shaft 24 can be moved directly with or without an outer receiving tubular- shaft portion. As at least one tine per rafe^" assembly 4 has the driving block 25 which is connected to one end of a tine via another transverse shaft 22b and as the tine is also rotatably connected to square shaft 22 movement by the drive shaft 24 only allows the tines to rotate about the square shaft .22 thereby allowing the tines to move from an inoperative position to an operative position (or from a retracted position to a retracted position) and visa-versa.

- As shown in figures 2-10 transverse shaft 22 has several tines 8 fixedly affixed either directly as shown in figure 5 or indirectly to shaft 22 by at least one T-bar- assembly. This T- bar assembly is shown in figures 5- 10 which such T-bar assembly comprises at least one fan shaped member 22a to a block 25 via a movable bearing assembly. The movable bearing assembly comprises a vertically oriented aperture or slot 25a in a substantially rectangular shape having a slidable bearing surface within for short the shaft 22b. Fan-shaped member 22a comprises an elongate planar member with one end being connected to square shaft 22 via a square aperture and at the other end to short shaft 22b. Short shaft 22b comprises a rotatable member which can be in this example a rod member connected transversely to the planar member.to formjhe T-bar assembly where by in use the rod member is able to move vertically within the aperture when shaft 24 is moved. The T-bar assembly acts in use as the actuator for initiating movement of all the tines of the rake assemblies, as the rest of the tines are also connected to the same square transverse shaft 22. The tines which are directly connected to the shaft 22 do not have a separate fan shaped member at one end but are just formed with an aperture to accept the shaft 22 directly therethrough. As the rake assembly is located above the screen the aperture of the driving block 25 which -=-^■ can be U-shaped needs to have a stop portion to not allow the rake assembly to drop out but - - still move within. However for the rakes assembly being located underneath the screen, the aperture need only be U shaped. -

5 As shown in figure 3 push plate 27 is affixed to drive shaft 24 at a suitable position with . respect to the start end of screen 2. Another push plate 27a is also fixed -to shaft 24 at a

: suitable distance X from the first push plate which can for. example comprise a first ring portion being larger than a second co-joined ring portion. The distance X. is determined by

.. the degree of.rota.tion required in_the tines in light of its rotational connection to the squareO-- shaft 22 and to the drive shaft 24. Within distance X there is the carriage .slidably: located

-thereon via carriage bearings 23. Outside distance-X in the forward direction at a distance Y is fixedly located On drive shaft 24, is. block 25, so that when in the upwards direction or debris removing direction first . push plate is. abutting carriage shaft bearings movement of shaft 24 moves push-plate to push carriage bearings and block 25. 5 As shown in figure 5 there is a close up perspective view of the rake assembly being above the carriage 10 and screen 1. There are two positions for the tines 8 being shown in that the solid lines represent or show the tines being in an extended or operative position while dotted - lines show the tines 8 in a retracted or inoperative position. A push plate 27 is shown which

^■ is fixedly attached to shaft 24 and spaced a certain amount from the bearing- supports of the0 shaft to carriage. ^This positioning of the tines can be adjusted depending on what is required or is necessary.

Figures 6-10 show the carriage and rake assembly 4 being positioned underneath the screen

- 1. This variation in positioned uses the same apparatus as for the above position as shown in figures 1-5 except that the block 25 does not need to have a stopping means to hold the T-5 assembly in place or stop if from falling out. Other variations include the use of spacers in combination with the push pull plates 27 as fixed on drive shaft 24.

As shown in figure 6 the structure of the frame 20 with part of the carriage and rake assembly is shown. The tines 8 are shown as being in an operative position while in figure 7 this cross section shows more of the carriage 10 with the tines being retracted. Figure 80 shows the tines in two sequences with one ^"tine for example being shown, whereby the tine orientation on the left shows a retracted or inoperative position while the right hand portion shows one tine extended or in operation where as figures 9 and 10 show the rake assembly

- - . ;^■- with' the T-bar assembly being clearly shown in a 'revealed portion' whereby movement by the drive shaft or output shaft 24 which can or not have an outer ram portion 26,(see Figure 7 which shows ram 26) through the push plates between stops pushes/moves at least one T-bar

5 assembly which by virtue of theroffset rotation as provided by connection to the square shaft

22, moves the other linked tines of the rake assembly 4 from a retracted to extended positions (or vice versa) as well. The dotted lines show the tines in a retracted position (or non operating position) while the solid lines for the tine indicates an extended or operating position.

10 ^TJie steps of operation using an upper and lower push orpull plate movable between carriage 'V bearings can be: ^■• - - . . - - ..

- have rake assembly (tines & carriage) at base (start) of screen;

- rakes are inoperative position & upper push plate abuts the carnage guide bearings;

- move drive shaft in opposite direction i.e. now upwards;

15 - lower push plate moves with shaft to meet carriage bearings causing the tines move/rotate extending downwards while carriage stationary;

- lower push plate ^"moves carriage up the screeh;

_ .- -■ ^■ extended tines and carriage move .debris to top of screen;

carriage hits upper end of frame and drive shaft stops;

20 - lower push plate abuts carriage and tines extended;

- - - drive shaft then moves in opposite direction-downwards; -

- as shaft moves carriage assembly is stationary until the upper push plate meets the carriage bearings whereby the tines are retracted;

- upper push plate then abuts carriage bearing assembly;

25 - drive shaft then moves taking carriage and tines to bottom; - -carriage then hits end of frame so that the carriage and drive shaft stop;

and back to the first step to repeat all the previous steps.

The hydraulic drive shaft 24 includes at one end to an output shaft 24 of a ram such as a pneumatic or hydraulic ram! The shaft 24 is also connected to carriage 10 by a pin. Although only a single ram is shown, a dual hydraulic cylinder arrangement, or even further hydraulic cylinders or rams may be provided depending upon the size of the installation.

^~ The most preferred form of actuation is hydraulic, but a pneumatic power source may also ^"be used, as may a worm device or a rack and pinion arrangement. Hydraulic actuation has the

. advantages of simplicity, reliability and the ability to exert a considerable force which may be required in large installations.

In another variation of the screening apparatus of the previous assembly can be simplified by having a single carriage slidably on top of the frame but with say two rake assemblies being

- movably fixed to the carriage. This can be seen in schematic plan view of figure 11. This is a mainly plan view but with the end part -of frame 10 being shown protruding upwards to show that the frame has an upper portion above carriage to support the drive shaft 24 which is also above and rotatably support the carriage. This uses the principles of the tine movement as previously disclosed but only uses one push plate which can move between bearing supports but still uses the drive shaft to cause consecutive movement of the tines followed by the carriage which such tine movement is initiated by a central actuator using a T-bar assembly. _. : ^" ,_{. .}._ ^■

As shown in figure 11 the carriage 20 can have say fojr example a lower frame 2OA made up of two main transverse members and longitudinal member supported by the frame 10 by slidable end bearings 23 and further upwards the carriage includes an upper frame 2OB comprising three transverse supports all interconnected to form rectangular frames. As shown there are three carriage drive shaft bearings 31 ie an upper 3 IA, middle 3 IB and lower one 31C. For each rake there is an upper T-bar assembly 25 D which is located upwards and beyond the upper carriage bearings 31 and lower T-bar assembly located between the middle bearings and lower bearings 31. Lower push plate 27B is located between the lower bearing and lower T-bar assembly.

"^{' " " • "} In terms of a forward movement of the carriage 20, the- upper rake assembly 4A is attached to the front of the reaF-transverse frame member and the other rake assembly 4B can be attached to the very front carriage transverse member and also being in front thereof: The carriage 20 is also slidably support and or connected to the drive shaft 24 as centrally located thereon. At each point on. the shaft where the rake assembly is located, there is an actuator or

T-bar assembly. Also there are sliding bearing supports on the upper frame- with a fixed stop or push/pull plate 27 on-shaft 24 (as shown roughly in the middle) so that the shaft 24 only can move from the stop to the end of the frame which then actuates the T-bar assembly 25D and then, is followed by the whole carriage 20 moving with tines 8 extended or retracted as required. In another variation the T-bar assembly can be formed as having the short bar joined to a fan shaped member or web member whereby the web member can be fixedly attached to a transverse top cover member which then has all the tines extending therefrom with or without the transverse -square cross sectional shaft. The carriage 20 is prevented by going any further by the end stopes provided by the frame 10 which also includes an upper portion which can also support the drive shaft. .

In general with the carriage at the bottom or start of the screen, the drive shaft then moves upwards to -cause the first movement of the tines to an extended position until it hits the uppercarriage drive shaft bearings which then means the upper push plate 27A pushes the carriage and tines up the screen to move any debris thereon.

Once the top of the screen is reached the drive shaft 24 then stops and then changes direction to move downwards. This first movement, pushes the lower push plate 27B to retract, the tines and then when the lower push plate hits the lower carriage member it then pushes the carriage back down the screen with the tines up or retracted.

In an example of extra features the screen of the screen apparatus can also have a separate transverse bar with fins 22D (see figure 11) there-attached which can protrude upwardly without blocking the movement of the tines 8 or rake assemblies through and past the screen elements. In use the rake assemblies can push any unwanted debris on the screens up or along the screen until they reach ^"the fins which then in use hold or present the debris from sliding backwards. These fins include a planar structure similar in dimensions to the tines having rounded edges and can also be provided at any position of and on the screen as required like for example to be directly fixed to the top of each screen element in any desired

- spacing.

Although not clearly identified in the drawings, internal surfaces of the driving blocks or shoes or any abutting co-acting surfaces are coated with friction reducing materials, such as a suitable plastics material or lubricant, in order to reduce friction therebetween.

A roller can be provided mounted on carriage 10 and in use contacts the rear or lower edges - of the screen elements 2. -Therefore; the carriage 10 is mounted within frame 20 and screen 1 ' by being supported at its lower edges on rails and being guided and supported relative to the screen at its upper extremity by roller.

As shown each tine^" 8 is shown as having an arm portion with a distal end having a hook

- portion. Proximal end of tine arm is joined to driving block 25 via moving rod portion which

- is captured within a recess portion of block 25. At a set distance along the tine ami there is a rotating portion whereby shaft 22 is connected such that translational movement of driving block 25 causes rotation of the shaft 22 and in turn all tines connected thereto.

It is also apparent that a number of carriages may be provided side by side or underneath each other and linked together for example. Also, a number, for example three, carriages cqμld be provided, each with its own driveshaft 24 and ram 26 to operate various sections of the screen independently or together as required or sequentially.

Screen elements can be provided in different forms, shapes and sizes depending upon the application for which they are required. The screen elements are provided as ah arm or web which has an end thereon that is exposed to the incoming fluid or water flow. The web can be typically 50-75mm deep and lies substantially parallel to the liquid flow path. The width of the front face of the elements that is exposed to the flow path is approximately 10-30mm depending upon the application. -

Screen elements may be made of various materials. The most desirable is stainless steel, but plastics materials, GRP, aluminium, or mild steel which has been suitable treated, for example by a galvanic process, may also be used. As previously stated the tines are rotatably connected to a central block 25 via a transverse shaft which is end supported by the carriage which block 25 is removably fixed to drive shaft 24 and is located as shown in figure 3 on one side of one of the push plates. The carriage is slidably connected to drive shaft 24 between the two push plates and is also slidably end supported on the screen framer

Alternatively to the arrangement where the tines change from operation to being in non operational mode. only after the drive shaft changes direction there is another arrangement- where this only happens when the carriage hits the end of the screen i.e. the several tines are connected to the transverse shaft which is rotatably connected to the drive shaft and to the

V carriage which is slidably connected to the drive shaft whereby movement of the drive shaft after the carriage is stopped in the same direction causes the tines to be extended or retracted and further movement of the drive shaft can cause the carriage and tines to move up or down

. the screen. . ■ ^■ . .

Throughout the description and claims of this specification the word "comprise", and , variations of that word, such as "comprises", and "comprising", are not intended to exclude other additives, components, integers or steps.

This invention may also broadly be said to consist in the parts, elements and features referred I? to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of the parts, elements or features, and where specific integers are mentioned herein which have known equivalents such equivalents are deemed to be incorporated herein as if individually set forth.

Advantages . .^■■ -- . a) Single or multiple rake assemblies. - b) Single T-bar actuating assembly for each rake assembly. c) Few moving parts. d) Economical construction costs. e) Reliable and efficient operation. f) Rapid operation. Variations

Throughout the description of this specification, the word "comprise" and variations of that word such as "comprising" and "comprises", are not intended to exclude other additives, components, integers or steps.

It will of course be realised that while the foregoing has been given by way of illustrative example of this invention, all such and other modifications and variations thereto as would be apparent to- persons skilled in the art are deemed to fall within the broad scope and ambit of this inventioivas is hereinbefore described/ .

To those skilled in the art to which the invention relates, many changes inxonstruction and widely differing embodiments and applications of the invention will suggest themselves^* &; without departing from the scope of the invention as defined in the appended claims. The . disclosures and the description herein are purely illustrative and are not intended to be in any sense limiting.

Claims

WHAT WE CLAIM IS:

Claim 1:- _ - A screening apparatus for removing unwanted material from a fluid flow, that

- includes a screen having a length and longitudinal slots therein and a rake assembly

5 operatively positioned along the screen by a carriage at a set distance therefrom, the rake assembly being displaceable along the screen by at least one driving means, the rake assembly including a plurality of tines movably connected to a rake arm and displacement means to move at least one tine with respect to the, rake arm to cause movement of alj_rthe tines, between - an. inoperative position as the rake assembly moves to one end of the screen

, 10 and an. operative position as the rake moves to. the other end of the. screen such that any solids .or unwanted materials caught by or Iocate4 on the screen or flow are removed from the screen or moved along the screen, displacement means comprise a mechanical linkage acting between: each_, rake assembly and the- screen or apparatus dependent from, the screen,

. , the actuator comprises at least one hydraulic ram or drive shaft wherein the rake assembly is

-15 _— fixedly mounted on the drive shaft by a slotted block and rotatably mounted to the carriage by a T-bar assembly which operatively rotates the rake assembly from a retracted position to an extended position and vice versa^", with respect to the screen to then move with the carriage to move any unwanted material thereon from the screen or alόhg the screen.

20 Claim 2: A screening ^"apparatus as claimed in claim 1 wherein the T-bar assembly, includes at least one fan shaped member having at one end a bar in a manner to form a T^bar and the fan shaped member having one end slidably held within the slot of the block to form the T-bar assembly and the other end rotationally mounted to a transversely mounted shaft which such shaft ^"is supported by the carriage whereby movement initiated by the drive shaft

25 can cause movement of the. bar of the T-bar assembly about an offset rotational point as provided by the square transverse shaft to the T-bar, to cause the movement of the square shaft and all of the tines of the rake assembly.

Claim 3. A screening apparatus as claimed in claim 2 wherein the transverse shaft also has further tines mounted thereon.

30 Claim 4. A screening apparatus as claimed in claim 3 wherein the drive shaft has at least an upper and lower push or pull plate mounted thereon which such shaft is also mounted to the- carriage and frame whereby movement of the drive shaft between fixed positions with the lower push plate being between a lower T-bar assembly and a lower drive

_ shaft hearing supports on the carriage can cause movement of each rake .assembly and

-_;- carriage at sequenced consecutive positions on the frame when the carriage travels down the . screen with a first shaft movement retracting the tines and then the carriage moves, and the upper push plate being located between an upper carriage drive shaft bearing and a middle carriage, drive shaft bearing which in use extends the tines and then pushes the carriage up the screen, whereby one movement being the movement of the rake assembly and the

... following movement then being the movement of the carriage along the screen:until it hits. ... the end of the frame..

Claim 5. A screening apparatus as claimed in claim 4 wherein the screen slots are shaped to cause a pressure differential from above to below thereby causing a general drawing of fluid down and through the screen.

^' . - Claim 6.- A screening apparatus as claimed in claim 5 wherein the carriage is slϊdably- '.- mounted on the drive shaft and frame by carriage bearing assemblies.

Claim 7. A screening apparatus as claimed in claim 6 wherein several tines are

- connected to the transverse shaft which shaft is rotatably connected to the drive shaft and to the carriage which carriage is slidably connected to the drive shaft whereby movement of the drive shaft in the opposite direction after the carriage is stopped causes the tines to be extended or retracted and further movement of the drive shaft causes the carriage anff tines to

- move up or down the screen.

. Claim 8. - A screening apparatus as claimed in claim 6 wherein several tines are connected to. the transverse shaft which is rotatably connected to the drive shaft and to the carriage which is slidably connected to the drive shaft whereby movement of the drive shaft after the carriage is stopped in the same direction causes the tines to be extended or retracted and further movement of the drive shaft can cause the carriage and tines to move up or down the screen.

Claim 9. A method of raking a screen with a screening assembly for removing unwanted material from a fluid flow which includes a screen having a length and longitudinal slots therein and^" a rake assembly operatively positioned along the screen by a carriage at a set distance therefrom, the rake assembly being displaceable along -the screen by -.- at least one driving means, the rake assembly including at least one tine movably connected -.to .a rake..arm- and displacement means to move the said" at least one tine with respect to the - rake arm₅ between an inoperative position as the rake moves to one end of the screen and an .-.-aoperative position as the rake moves to the other end of the screen such that any solids or _ "unwanted -materials caught by or located on the screen or flow, are removed - thereon/therefrom, displacement means comprise a mechanical linkage acting between each ; rake assembly and the screen or apparatus dependent from the screen, the actuator comprises : at least one hydraulic: ram or drive shaft including an upper and lower pusfrplates which can_j -: move; between carriage bearings wherein the rake assembly is fixedly mounted on the drive; . shaft by a slotted block and rotatably mounted to the carriage by a transverse T-bar to form a T-bar assembly which operatively rotates the rake assembly from a retracted position to an. extended position and vice versa, with respect to the screen to move any unwanted material ; thereon from the screen -whereby the method includes the following steps of:

- have rake assembly (tines & carriage) at base (start) of screen;

- tines are inoperative position & upper push plate abuts the carriage guide bearings;

- move drive shaft in opposite direction ie now upwards;

- lower, push plate moves with shaft to meet the carriage bearings causing T-bar -_; assembly to move which moves the rest of the tines move/rotatg extending downwards while carriage stationary;

.-- extended tines and carriage move debris to top of screen; -

- carriage hits upper end of frame and drive shaft stops;

- lower push plate abuts carriage and tines extended;

- drive shaft then moves in opposite direction-downwards; as drive shaft moves carriage assembly is stationary until the upper push plate meets the carriage hearings whereby the tines are retracted by movement, of the T-bar . assembly; " .^'

- upper push plate then abuts carriage bearing assembly; ^: - drive shaft then moves taking carriage and tihes to bottom;

- carriage then hits end of frame so that the carriage and drive shaft stop; .

and back to the first step to repeat all the previous steps.

Claim 10. A screening apparatus substantially as herein described with reference, to the accompanying drawings.

Claim 11. A method of operating the screening apparatus substantially as herein described with reference to the accompanying drawings.