GB2046116A

GB2046116A - Bar screen cleaner

Info

Publication number: GB2046116A
Application number: GB8008755A
Authority: GB
Original assignee: Passavant Werke AG and Co KG; Passavant Werke Michelbacher Hutte
Current assignee: Aqseptence Group GmbH
Priority date: 1979-04-14
Filing date: 1980-03-14
Publication date: 1980-11-12
Also published as: SE8002372L; GB2046116B; DE2915341C2; DE2915341B1; FR2453687A1; SE432068B; JPS55142808A

Abstract

A screen cleaner for a bar screen has at least one cleaning carriage 5, 8 for ascending and descending a bar screen in a respective guide 1 on the bar screen and arranged parallel to the bar screen. A cleaning rake 12 is articulated to the carriage by two guide arms 10 and 20 pivotally mounted at a distance from each other. One of the guide arms 10 is shorter than the other 20 and is designed to have a greater pivoting angle than the longer guide arm whereby the rake is brought into a steeply inclined discharge position between its cleaning position and its return position, the discharge position lying outside the plane of the bar screen. In Fig. 1 the rake tips forwards to drop solids on to chute 3'. <IMAGE>

Description

SPECIFICATION Bar screen cleaners This invention relates to bar screen cleaners.

German Offenlegungsschrift 2 623 269 describes a screen cleaner for bar screens having a cleaning carriage ascending and descending in guides on the bar screen, which guides are arranged parallel to the bar screen, a cleaning rake articulated to the cleaning carriage by two guide arms pivotally mounted at a distance from each other, which rake is the coupling member for said arms, and a drive control engaging with at least one of the guide arms or the rake, whereby the cleaning rake can be pivoted between a cleaning position and a return position. In the case of this known screen cleaner both guide arms are of the same length and are arranged in parallel. Through the motion in the form of a parallelogram caused thereby, the cleaning rake can be moved only paralled to itself.

If the rake is moved in an essentially horizontal position along the bar screen, the material removed from the bar screen continues to cling to the cleaning rake. A special wiper is, therefore, necessary to remove the material from the cleaning rake. In the case of a fixed cleaning rake the wiper blade must be moved over the rake, or in the case of a fixed wiper blade the rake must be moved below the wiper blade. This wiper and the hydraulic drive necessary for the relative motion between the wiper blade and the cleaning rake considerably increase the cost of the screen.

According to the invention there is provided a screen cleaner for bar screens comprising at least one cleaning carriage for ascending and descending the bar screen in a respective guide arranged on the bar screen and parallel thereto, a cleaning rake articulated to the or each carriage by two guide arms pivotally mounted at a distance from each other, which rake is a coupling member for said guide arms, and a drive control associated with at least one of said guide arms or the rake, whereby the rake is pivotable between a cleaning position and a return position, one of the two guide arms being shorter than the other and being designed to have a greater pivoting angle than the longer guide arm whereby the rake between its cleaning position and its return position is brought into a steeply inclined discharge position lying outside the plane of the bar screen.

Because the guide arms of different lengths, the cleaning rake can be moved not only parallel to itself, but also tipped. On the other hand, the cleaning rake can also be brought into a discharge position lying beyond the plane of the bar screen; for example, this discharge position can lie behind the bar screen above a chute. If the cleaning rake is brought into the inclined discharge position at this position, the debris removed by the cleaning rake from the bar screen falls under the effect of gravity into the chute. The fact that the guide arms are of different lengths also results in the cleaning rake having an accelerated motion with a basically uniform drive. If as a result of this the cleaning rake carries out an accelerated rearward movement when it is in the inclined discharge position, the discharging of the collected material is further facilitated.

It is, however, also possible to provide the discharge position in front of the bar screen. In this case, the cleaning rake would have to carry out a more pronounced swinging motion in which it would discharge, for example, the collected material beyond and behind itself to a chute or other material-collecting apparatus located there.

Advantageously, the effective length of the shorter arm is smaller than the effective length of the cleaning rake. The term effective length means the distance of the pivotal mounting points in the coupled "square" which is formed by the connecting lines between the mounting points of both guide arms, by both guide arms themselves and by the cleaning rake. In this manner, a complete 3600 rotation of the rocker arm can be achieved. It is, however, not absolutely necessary for the shorter arm to actuaily have a shorter length than the cleaning rake. By such a rotating motion the problems which otherwise exist connected with each reciprocated movement can be avoided.

By way of example, specific embodiments in accordance with the invention will be described with reference to the accompanying drawings in which Figure 1 is a perspective illustration of a bar screen showing the cleaning rake and the elements connected therewith, whereby the desired movements of the cleaning rake are achieved; Figure 2 is a schematic illustration of the course of motion carried out by the cleaning rake, in side view and partly in sectional view in the direction of the vertical centre line of the bar screen; Figure 3 is a view similar to that of Figure 2 showing the movement of the cleaning rake at the lower end of the bar screen; and Figures 4 and 5 show further arrangements in the direction of the transverse axis of the cleaning rake.

Referring to Figure 1, a bar screen cleaner is arranged to slide vertically in lateral guide rails 1.

These guide rails 1, of which one is shown in Figure 1, extend in a vertical direction parallel to the bar screen 2 which stands vertically. At the top end the screen 2 becomes a chute 3, on the top edge of which and on the side remote from the screen cleaner there is a downwardly inclined slide plate 3', the material removed from the bar screen being intended to slide down over this plate.

The screen cleaner is supported in the guide rails 1 by means of rollers 4, two of which are provided on each side of the screen cleaner. These rollers are located at a distance from each other at each end of a respective vertical carriage support 5. Adjacent the upper ends of the carriage supports 5 projections 6 are provided on which hoisting or draw cables 7 engage, whereby the screen cleaner can be moved vertically.

Approximately in the centre of the carriage supports 5 there are rearwardly extending platetype support components 8 rigidly fixed to the supports. On the ends of the components 8 rocker arms 10 are pivotally mounted at 9. A shaft 11 rigidly connects the rocker arms 10 at their ends remote from the mounting points 9. The rear part of a cleaning rake 12 is pivotally mounted on this shaft 11. In addition, a control cable 13 engages on the shaft 11. This control cable, like the draw cables 7, extends upwardly.

Adjacent the mounting points 9, there are provided control discs or cams 10' which are rigidly connected with the rocker arms 1 0. Pins 14 extending outwardly are fixed to these control discs 10'. In addition, the control discs 10' have locking piojections 1 5 which cooperate with pawls 1 6 which at 1 7 are pivotally mounted on the support components 8. The pawls 1 6 at their ends remote from the control discs 10' are provided with pins 1 8 which cooperate with stops formed by the lower ends of projections 1 9 which are fixed to the guide rails 1.

Guide arms 20 are pivotally mounted to the upper ends of the carriage supports 5. These arms 20 are longer than the rocker arms 10 and will be designated by swinging arms. At the lower ends of the swinging arms 20 the cleaning rake 12 is hinged in the vicinity of its front edge. In this way a coupled "square" is formed through one corner of which the shaft 11 passes, the second corner of which is formed by the pivot point 25 of the cleaning rake at the swinging arm, the third corner of which is formed by the pivot point of the swinging arm at the carriage support and the fourth corner of which is the pivot point 9 of the rocker arm on the support component 8.

The pins 14 provided on the control discs 10' can cooperate with guide tracks which extend horizontally and are bounded at the top by a rail 21 and at the bottom in the rear part by a strip 22.

The front part of the strip 22 passes into catch 24 pivotable about an axis 23. When pivoted down this catch forms a flat lower slide surface with the strip 22 for the pin 14. The pin 14 can, however, press the catch 24 upwards so that it can pass between the strip 22 and the catch 24 into the guide track.

The mode of operation of the bar screen cleaner according to the invention will now be described in connection with Figure 2. As the draw cables 7 and the control cable 13 are pulled upwards at same time, the cleaning carriage with the cleaning rake 12 lying in an almost horizontal position is drawn upwards. By appropriate location of the centre of gravity of the rake, which can optionally be altered by metal or concrete weights, and by corresponding location of the engagement points of the cables, it is ensured that a torque is applied to the cleaning rake under the influence of its weight so that it is urged towards the bar screen 2. The movement in this direction is, however, limited by the pawls 1 6 which engage with the locking projections 1 5 of the control discs 1 0'.

Shortly after the rake in the cleaning position A, shown in Figure 2 in solid lines, has reached the upper edge of the chute 3, the pins 1 8 come inXo contact with the stops on the projections 1 9, whereby the pawls 1 6 are released from the locking projections 1 5 so that the cleaning rake can move to the right as viewed in Figure 2 over the edge of the chute 3. In this way any material picked up by the cleaning rake is prevented from falling back behind the bar screen. As the rake continues to move upwardly, the pin 14 of each control disc 10' passes into the respective guide track formed by the elements 21,22 and 24, the catch 24 being lifted. On still further upward movement of the rake, the pin 14 slides to the left in the guide track.Whereby the rocker arm 10 rotates the rake in an anticlockwise direction.

Thereby the cleaning rake is pushed forward and at the same time tipped to the right about the pivot points 25 of the swinging arms 20 on the cleaning rake. Thus, the control cable must be taken up more quickly than the draw cables. This may take place in known manner through variable drives for the control cable and the draw cables or, in the case of a synchronous drive of the draw cables and control cable, by shortening the control cable or lengthening the draw cables. In known manner, one reversing position for either the control cable or the draw cables can be displaced laterally. Such a device is known from German Auslegeschrift 2 544 586.

The front edge of the cleaning rake 12 thus moves along the path 26 indicated in Figure 2 by dashes and dots. Should the front edge of the rake be approximately at the furthest position forward on this path, each pin 14 has reached its left-hand reversing position in the respective guide track; it slides from there over the closed catch 24 to the right and draws the rake, as it continues to tip upwards, to the left as far as the discharge position B, indicated in chain line. In this position, all drives are stopped by limit switches or are reversed.

As it descends, the cleaning rake passes through the curve 26 up to the point 27 in the reverse direction. From there the front edge of the rake follows a new path 28, since each pin cannot leave its guide track at the point at which it entered the guide track, but must move over the catch 24. At the moment when each pin 14 moves past its catch 24 at the end nearer to the screen, i.e. leaves its guide track, the engagement point of the control cable 13, i.e. the shaft 11, has already passed to the left of the pivot point 9 of the rocker arm. A braking force is now exerted on the control cable 13 by the drive, whereby the rocker arm 10 is rotated further clockwise and the rake 12, as it tips, is drawn further to the left until it has reached its steepest position C. Since, as a result of the braking force acting on the control cable 13, the rake 12 would continue to be pivoted until the shaft 11 and with it the point of engagement of the control cable 13, as well as the control cable itself, would lie in a line above the joint 9, the rotation is ended by the upper stops 29 on the rocker arms 10 resting against the swinging arms 20. Subsequently, the control cable and the draw cables are lowered together down to the base of the screen.

At this point the braking force on the control cable 13 is ended, for example by a slack-cable lever operated by the draw cables, i.e. the control cable 13 is relieved. Subsequently, the rake 12 can swing to the right, as the rocker arms turn to the left, under the influence of its weight, if necessary increased by metal or concrete weights.

Shortly before the rake would otherwise contact the screen, the pawls 1 6 pass over the locking projections 1 5 and prevent the rake edge from colliding with the screen grating. By corresponding dimensioning of the above-mentioned coupled square, it is possible to ensure that the front edge of the rake moves inwardly approximately in a straight line towards the base of the bar screen, whereby material lying at the foot of the bar screen is also collected. This part of the motion is illustrated in Figure 3.

By means of the slack-cable control it is possible for the cleaning rake 12 to move also into any intermediate position should jammed screenings lie in the way as the rake descends and the draw cables 7 become slack through this. One of the pawls 1 6 or the locking members 1 5 can be used as a sensor for the switching over to cleaning travel.

In the case of the screen cleaner of this embodiment, the discharge of material collected by the cleaning rake on to the slide surface 3' is firstly accomplished as the front edge of the rake moves upwardly along the path 26 (Figure 2) the rake tipping into a steep position, whereby the material collected can fall out of the rake. At the top end of the path 26 the front edge of the rake secondly effects an accelerated backward return motion, whereby discharge of the material into the chute is facilitated. The material will discharge even more easily if the cleaning rake is provided with a non-stick covering (for example, coverings which are marketed under the trade names "Perlon" or "Teflon").

In the case of the embodiment described, the shorter guide arms, namely the rocker arms 10, carry out a reciprocating motion. It would, however, also be possible to provide these guide arms with a rotary motion. If the rocker arms carry out complete rotations, the path 26 is described by the front edge of the rake only in the upward direction, the path then continuing to the rear. In this case it is only necessary to ensure that each pin 14 at the top reversing point of the screen cleaner has already passed the dead centre in its guide track to the right so that it can be moved further to the right at the beginning of the downward travel and out of the guide track. For such a procedure it is useful, if not also essential,.

to make to effective length of the coupling element formed by the cleaning rake greater than that of the rocker arms so that the pivot points 25 remain to the right of the pivot points 9.

The pins 14 can be provided with guide tracks of other types. It is not necessary for each guide track to be so defined by the rail 21 and the strip 22, as well as the catch 24, that it is straight.

Inclined, curved and step-type guides are also possible for the pins 14 which can also be fixed directly to the rocker arms 10.

As already mentioned, the pressing force of the rake in the direction of the screen can be increased by providing the rake with metal or concrete weights. To increase this force, provision can also be made for one of the two guide arms to be extended beyond its pivot point on the carriage support and for the carriage drive to engage the extended portion. - The screen cleaner need not be retained by pawls 1 6. Slides or rollers may also be provided supported on rails located at the sides of the screen.

In Figure 4 an arrangement is shown in which the rake is retained by a pawl 20 in the essentially vertical reverse position until the screen cleaner reaches the bottom. A slack-cable lever 31 then enters into action, which can turn to the left as far as the stop 32 and then releases the pawl 30 via the cable 33. In the case of the arrangement according to Figure 5 the slack-cable lever is combined with the pawl, the draw cable being directly fixed to the counter-arm of the pawl and retaining this in the stop location, as long as a hoisting force acts on the cable. An additional weight 35 provides for opening of the pawl 34.

The pawl has limit stops for both positions.

It is also possible to drive the rocker arm direct.

The direct drive may be fixed to the screen cleaner so that the control cable, guide tracks for the pins 14, and the pawls 1 6, 30 or 34 can then be omitted. Only stops or switches are necessary for initiating the further rotation of the motor into the next position. As drive units, hydraulic motors in particular may be considered, such motors being particularly suitable for submerged operation.

A zero-stop motor can also be used as drive unit. This has the advantage that is is controlled by electromagnetically operated intermediate stops, but can itself remain continually switched on.

The cleaning rake 1 2 is suitably fixed to the carriages 5, 8 in such a way that because of the resistance and weight of the material that is to be conveyed upwardly along the bar screen, the cleaning rake 1 2 is additionally pressed in the direction of the bar screen 2.

Claims

1. A screen cleaner for bar screens comprising at least one cleaning carriage for ascending and descending the bar screen in a respective guide on the bar screen and arranged parallel thereto, a cleaning rake articulated to the or each carriage by two guide arms pivotally mounted at a distance from each other, which rake is a coupling member for said guide arms, and a drive control associated with at least one of said guide arms or the rake, whereby the rake is pivotable between a cleaning position and a return position, one of the two guide arms being shorter than the other and being designed to have a greater pivoting angle than the longer guide arm whereby the rake between its cleaning position is brought into a steeply inclined discharge position lying outside the plane of the bar screen.

2. A screen cleaner according to claim 1, wherein the effective length of the shorter guide arm is smaller than the effective length of the cleaning rake.

3. A screen cleaner according to claim 1 or claim 2, wherein the shorter guide arm is pivotally mounted towards the edge of the cleaning rake remote from the bar screen.

4. A screen cleaner according to any one of claims 1 to 3, wherein the drive control comprises a stationary track and a pin or the like fixed to the shorter guide arm, which cooperate during the movement of the cleaning rake from its cleaning position through it discharge position into its return.

5. A screen cleaner according to claim 4, wherein the pin is provided on an extension of the shorter guide arm extending beyond the pivotal connection of the shorter guide arm on the cleaning carriage.

6. A screen cleaner according to claim 4 or claim 5, wherein the track is a horizontal guide rail for the pin.

7. A screen cleaner according to claim 6, wherein a lower strip is associated with the guide rail and lies parallel thereto in which strip an opening accessible only from below via a catch for the pin is provided, and the space between the guide rail and the strip being open in the direction of the bar screen.

8. A screen cleaner according to any one of claims 1 to 7, wherein the guide arms are pivotally connected to the cleaning rake so that in the position at the centre of gravity, in which the cleaning rake is free to oscillate, the front edge of the rake lies behind the bar screen or an upper extension of the screen designed in the form of a chute.

9. A screen cleaner according to any one of claims 1 to 8, wherein the drive for the screen cleaner is associated with one component of the coupled square formed by the connecting line between the mounting points of both guide arms, by both guide arms themselves and by the cleaning rake in such a way that the cleaning rake is urged towards the bar screen by the torque applied to the cleaning rake.

10. A screen cleaner according to claim 9, including a drive in the form of a cable or chain, one of the two guide arms being extended beyond its pivot point by the cleaning carriage and the drive engaging there.

11. A screen cleaner according to claim 7, wherein the cleaning rake is held at a short distance from the bar screen or a chute by means of a locking device during its cleaning motion, the locking device being released by a stationary stop at that moment when the front edge of the cleaning rake passes the upper end of the bar screen or the chute.

12. A screen cleaner according to claim 11, wherein the locking device comprises a pawl pivotally mounted on the cleaning carriage and a projection provided on the extension of the shorter guide arm.

1 3. A screen cleaner according to any one of claims 1 to 12, including a hoisting mechanism (e.g. a cable) engaging on the cleaning carriage and serving as drive means, and a control hoisting mechanism (e.g. another cable) engaging on the cleaning rake or one of its pivoting parts and serving as a control drive, wherein in the case of separate drives for both hoisting mechanisms one the drives, and in the case of a common drive, an additional drive is capable of effecting a relative motion between the two hoisting mechanisms for moving the cleaning rake into its return position.

14. A screen cleaner according to claim 13, wherein both guide arms in the return position of the cleaning rake are arrested by steps or the like to prevent further pivotal movement relative to one another.

1 5. A screen cleaner according to claim 13, wherein the hoisting mechanism is provided with a slack-cable sensor or the like which is connected with the drive of the control hoisting mechanism or with the additional drive in such a way that when the slack-cable sensor is tripped, relative motion between the two hoisting mechanisms is prevented.

1 6. A screen cleaner according to any one of claims 1 to 15, wherein the cleaning rake is retained by a pawl or the like in the return position and the slack-cable sensor is operatively connected with this pawl so as to release the pawl when it is tripped.

1 7. A screen cleaner according to claim 16, wherein the hoisting mechanism itself engages on the pawl in such a way that when the hoisting mechanism becomes slack, the pawl is released.

18. A screen cleaner according to any one of claims 1 to 1 7, wherein the length of the members of the coupled square are so adjusted to one another and the pivotal points of the guide arms on the cleaning carriage are so arranged that the front edge of the rake, as it swings in towards the bar screen, describes a straight path of motion normal to the bar screen.

19. A screen cleaner according to any one of claims 1 to 18, wherein the shorter guide arm is driven in rotary motion with angular positions determined by stops or the like.

20. A screen cleaner according to claim 15, wherein the rotary drive is in the form of a zerostopping motor

21. A screen cleaner according to any one of claims 1 to 20, wherein the top side of the cleaning rake is provided with a non-stick covering.

22. A screen cleaner for bar screens substantially as hereinbefore described with reference to and as shown in the accompanying drawings.