WO1996030132A1

WO1996030132A1 - Screen cleaning means

Info

Publication number: WO1996030132A1
Application number: PCT/AU1996/000169
Authority: WO
Inventors: Steven James Mciver
Original assignee: Steven James Mciver
Priority date: 1995-03-29
Filing date: 1996-03-26
Publication date: 1996-10-03

Abstract

A screen cleaning means for use with a vibrating screen (11) comprising a plurality of flexible elongate members (15) which are each supported at one end in the region of the upper end portion of the screen (11), the flexible elongate members (15) being located at spaced intervals across the screen (11) and being mounted to extend downwardly over the surface of the screen (11) for at least a portion of the length of the screen (11), and where the flexible elongate members (15) are provided along their length with a linear discontinuous surface to provide spaced portions of reduced surface area which will impact on the screen deck (12) with vibration of the screen deck (12).

Description

TITLE: SCREEN CLEANING MEANS

This invention relates to a screen cleaning means.

In many areas of industrial activity including the mineral processing industry, it is necessary to screen particulate materials according to size. In most cases this is effected by utilisation of a screen having an inclined screen deck which is provided with a set of apertures of predetermined size over which the particulate material is caused to flow under the influence of gravity from the upper end of the screen deck to its lower end whereby material having dimensions equal to or less than the dimensions of the apertures in the screen deck or will flow through the screen deck and the oversized material will flow from the lower end of the screen deck.

It has been found however that in circumstances where such screens are used with wet or moist material, the screen decks can block up which requires the screen to be regularly shut down in order to effect clearance of the apertures provided in the screen deck. This is a particularly time consuming activity and can be a very expensive activity since in many cases the processing plant with which the screen is associated is required to be shutdown until such cleaning action has been completed.

In the past, there have been several proposals for the clearing of screen decks. One of these proposals has been to provide a secondary deck below the screen deck and locating a plurality of resilient ball-like members between the screen deck and the secondary deck which are caused to impact upon the underneath of the screen deck when in use for the purpose of clearing the holes. Other similar arrangements are exemplified in AU-B-59120/73, US-4,288,320 and US- 3,070.230 where ball-like elements are caused to impact on the undersurface of the screen deck. The difficulty with each of these arrangements however, relates to the wear which such an arrangement causes to the underneath of the screen deck, the ball-like elements and the ancilliary support for the ball-like elements which necessitates the regular replacement of the the ball-like elements as well as the main screen deck. This can be difficult and requires the complete shutdown of the screen.

Other prior art arrangements to the invention are disclosed in US-1 , 397,906, US-2,617,533 and SU-A-1 ,031 ,538 which each disclose the use of flexible elongate members which extend across the surface of the screen deck. In the case of US-1 ,397,906 and US-2,617,533 the flexible elongate members extend across the underneath of the screen deck and are fixed to opposite sides of the deck or to each other and impact the underneath of the deck as a result of the relative movement of the deck. In the case of SU-A-1,031 ,538 the flexible elongate members overlie the screen deck and are fixed to opposite sides of the deck whereby the vibration of the deck causes the members to impact with the deck. Each of these arrangements are unsatisfactory since at least they cannot be readily decommissioned without significant downtime of the screening means as well. In addition the action of the flexible elongate members are severely restricted as a result of them being fixed to opposite sides of the screen deck and/or to each other.

It is an object of this invention to provide an effective screen cleaning means which does not necessarily require the shutdown of the screen for the purposes of maintenance or decommissioning of the screen cleaning means and which is effective in its screen cleaning action.

Accordingly, the invention resides in a screen cleaning means for use with a vibrating screen comprising a plurality of flexible elongate members which are each supported at one end in the region of the upper end portion of the screen, said flexible elongate members being located at spaced intervals across the screen and being mounted to extend downwardly over the surface of the screen for at least a portion of the length of the screen, wherein the flexible elongate members are provided along their length with a linear discontinuous surface to provide spaced portions of reduced surface area which will impact on the screen deck with vibration of the screen deck. According to one form of the invention some of the flexible elongate members extend over the full length of the screen deck. According to an alternative form of the invention the flexible elongate members are of differing lengths with at least one extending substantially the full length of the screen deck.

According to a further preferred feature of the invention, the one end of the flexible elongate members are rotatably supported for the flexible elongate members to be rotatable about their longitudinal axis

According to a further preferred feature of the invention, the flexible elongate members are supported to be capable of transverse movement across the upper end of the screen and a drive means is provided to effect reciprocation of the one end of the flexible elongate members across the screen. According to one embodiment the flexible elongate members comprise a number of sets of differing length which are arranged such that on reciprocation of the support substantially the full width of the screen is swept jointly by some of the members of each set.

According to a further preferred feature of the invention one or more further flexible elongate members are supported from the support and extend underneath the screen to lie within the chute which conveys screened material away from the screen and which serve in clearing deposits which can build up within the chutes. According to this arrangement the further flexible elongate members are caused to reciprocate across the surface of the chute.

According to a further preferred feature of the invention, the flexible elongate members are supported from their one end by a support which is mounted proximate the upper end of the screen and either the support or the mounting for the members on the support is pivotable about a transverse axis to enable the mounting to be movable between a first position closely adjacent the upper end of the screen and a second position spaced from the upper end of the screen. If desired, a storage means is provided to receive the flexible elongate members when the mounting is in its second position. According to a further preferred feature of the invention, the flexible elongate members comprise a plurality of interconnected segments. One form of such a member can comprise a length of chain.

According to a further preferred feature of the invention, the flexible elongate members comprise an elongate member supporting a plurality of beads mounted along the length of the member. In one form the beads can be formed integrally with the member or may be threaded over the member. Furthermore the member can comprise a length of cable, rope, chain or the like. In one form the beads comprise elements have a generally cylindrical configuration with a discontinuous outer surface. According to one embodiment the external surface is formed with a plurality of axially spaced annular ribs. In another embodiment the external surface is formed with a plurality of angularly spaced substantially axial ribs. In yet another embodiment the external surface is formed with a plurality of axially and angularly spaced radial protrusions and if desired the protrusions have an outer end dimensioned to be receivable in the apertures of the screen

The invention will be more fully understood in the light of the following of several specific embodiments. The description is made with reference to the accompanying drawings of which:

Figure 1 is a side elevation of the first embodiment with the support in the first position;

Figure 2 is a sectional side elevation of the first embodiment with the support in the second position;

Figure 3 is a plan view of the first embodiment with the support in the first position;

Figure 4 is a plan view of the first embodiment with the support in the second position; Figure 5 is a part sectional side elevation of a screen with a second embodiment of the invention located therein;

Figure 6 is a sectional side elevation of the support of the second embodiment;

Figure 7 is a side elevation of a portion of the flexible elongate members of the second embodiment;

Figure 8 is a side elevation of a portion of a second alternative form of the flexible elongate member of the second embodiment;

Figure 9 is a side elevation of a portion of a third alternative form of the flexible elongate member of the second embodiment; and

Figure 10 is a cross-section of the beads of the third alternative form of third alternative form of the flexible elongate member of Figure 9.

The first embodiment is directed towards a screen cleaning device which is to be used in cleaning the screen deck of a vibrating screen. As shown in the drawings, the first embodiment comprises a sαeening apparatus 11 which is provided with an inclined substantially planar screen deck 12. The screen is associated with an imput chute 13 from which particulate material is delivered onto the screen to be distributed over the screen deck 12 in order to be screened.

The screen cleaning apparatus according to the embodiment comprises a support arrangement 14 provided proximate the upper end of the screen deck 12 which supports a set of flexible elongate members which comprise lengths of chain 15 and which, when the support arrangement 14 is in its active position as shown at Figure 1 will extend downwardly over the screen deck 12 to lie on the screen deck 12. The chains 15 are of differing lengths with at least some extending substantially the full length of the screen deck. The chains are fixed at their upper ends to an elongate support 16 at spaced intervals along the support 16. The connection of each chain to the elongate support 16 is effected by means of a swivel connection in order that the chain is rotatable about its longitudinal axis with respect to the support 16 The support 16, is in turn supported within a support housing 17 by two opposed sets of V-shaped rollers 18 where by the elongate support is capable of transverse displacement within the housing 17 with respect to the upper end of the screen deck. As a result of the support provide by the elongate support 16 the chains are spaced substantially equidistant across the screen deck 12. Joint t-ansverse movement of the chains 15 is effected by means of a drive motor 19 and associated gear box 20 which causes the elongate support to reciprocate within the housing 17

The support housing 17 is mounted to an upstanding frame member 21 which is positioned adjacent the upper end of the screen deck 12 and the support for the screen housing 17 from the frame 21 is effected by means of a pivot shaft 22 whereby the support housing 17 is movable from the first position (active position) as shown at Figures 1 and 3 at which the supports 16 are closely adjacent the upper end of the screen to a second position (inactive position) as shown at Figures 2 and 4 at which position the supports 16 are positioned clear of the upper end of the screen deck 12 to provide access to the upper end of the screen deck 12.

In order to effect pivotal movement of the support housing 17, a suitable hand operated drive mechanism and gear box 23 is provided between the frame 21 and the support housing 17. By operation of the handle associated with the drive mechanism 23, the support housing can be control lably moved from the active position as shown at Figures 1 and 3 to the inactive position as shown at Figures 2 and 4 and from the inactive position to the active position as required

The support housing 17 is associated with a storage receptacle 24 which has a length corresponding to the length of the support housing 17 and which is located underneath the support housing 17 when the latter is in its inactive position as shown at Figures 2 and 4 When the support housing 17 is in its active position, the chains will extend from the support 16 over the upper end of the screen deck 12 to overlie at least the upper portion of the screen deck 12. On vibration of the screen deck 12 the chain is caused to vibrate on the screen deck. Because of the linked nature of the chain, each link will vibrate somewhat independently of the other chain links and as a result each will independently impact upon the screen deck and in so impacting upon the screen deck will effect a concentrated impact loading at the point of impact. Such regular impact by each of the links of the chain serves to facilitate clearance of any material which may otherwise be deposited on the surtace of the screen deck and the apertures of the screen deck. During the operation of the screen, the elongate support 16 is caused to reciprocate within the housing 17 by the first drive means 20 to reciprocate cross the upper end of the screen. The degree of reciprocation corresponds substantially to the spacing between the chains 15 whereby the complete surface of the screen deck is traversed jointly by the chains 15 as a result of the reciprocating movement of the elongate support 16.

When it is necessary to either service the cleaning apparatus or the screen deck, the support housing 17 is pivoted to the inactive position as shown at Figures 2 and 4 and the chains 15 can then be withdrawn from over the screen deck to be deposited into the storage receptacle 24. Once the chains are clear of the screen deck, the screen can be serviced as required and the cleaning apparatus can be serviced as is necessary. In order to reinstate the action of the cleaning apparatus, the chains are reintroduced onto the screen deck from the storage receptacle and the support housing is pivoted to the active position

It is a characteristic of the first embodiment that the movement of the support housing 17 between the active and inactive position and withdrawal and reinsertion of the chains 15 as required can be effected without shutting down the screen. Therefore, servicing of the cleaning apparatus can be effected without the need to close down the screen and the plant associated with the screen. This represents a significant saving in plant and a significant reduction in downtime of the plant. Furthermore, when the screen is being used with material which is unlikely to cause blockage of the screen deck, the cleaning means can be withdrawn from service to reduce the wear on the screen deck. Alternatively, if the screen is being used with material which is likely to cause blockages, the cleaning apparatus can be periodically brought into and out of service where the length of the period during which the cleaning apparatus is in service and out of service can be varied according to the nature of the material being screened and the frequency of blockage.

The second embodiment of the invention is illustrated at Figures 5 and 6 and the same numerals have been used for corresponding components. In the case of the second embodiment the support housing 17 is fixed and accommodates the elongate support 16 through a track 30 which is accommodated within the housing 17 while the elongate support 16 comprises a carriage having a set of rollers 32 which are received in the track 30 to facilitate the reciprocation of the elongate support within the housing 17. The flexible elongate members 15 are each mounted to the elongate support housing by an upstanding arm 34 which are supported at spaced intervals along the length of the elongate support 16. The upper end of each arm 34 supports the one end of each flexible elongate member by a radial arm 36 which is pivotally mounted at one end to the upstanding arm for movement about a transverse axis and is mounted at its other end to the one end of the flexible elongate member through a swivel connection 38. The pivotable movement of the radial arm enables the one end of the flexible elongate members to be moved between a position adjacent the upper end of the screen 12 and a position rearward of the upper edge of the screen to enable the flexible elongate members to be moved between their active and inactive positions respectively. The upper end of the upstanding arms 34 are provided with a part circular plate 40 where the one end of the radial arm 36 is supported from the centre of the plate. The plate is provided around its perimeter with a plurality of apertures 42 which are in alignment with a further aperture provided in the radial arm (not shown) and a pin 43 is provided which is receivable through one of the apertures 42 and the further aperture to retain the radial arm in one of a range of desired positions. The mounting of the

SUBSTITUTE SHEET (Rule 26; flexible elongate member to the upstanding arms by means of the radial arms facilitates the transposition of the flexible elongate members between the active and inactive positions as required.

The elongate support 16 also supports a second set of flexible elongate members 44 which are located below the screen 12 and extend into the chute 46 which is located below the screen. The flexible elongate members comprise several lengths of chain which are spaced transversely across the chute 48. The chains are positioned to lie over the surface 46 of the chute 48 below the screen and will reciprocate over the surface on reciprocation of the elongate support 16. The function of the chains 44 is to prevent the accumulation of deposits of screened material on the contact surfaces 46 of the chute 48. The mounting of the chains to the elongate support is effected through a pivot 50 which will enable the chains to be pulled from the chute 48 when they are not required.

The flexible elongate members 15 of the second embodiment and as shown at Figures 5 and 6 comprise lengths of chain which support a plurality of beadlike members 52 along their length. As further shown at Figure 7 the beadlike members are formed of polyurethane or a like synthetic composition and each have a generally cylindrical configuration with the cylindrical surface formed with a plurality of annular ribs 54 in order to provide a discontinuous surface. The mass of the beadlike members serves to increase the impact forces exerted on the screen when they are caused to vibrate as a result of the vibration of the screen deck. In addition the discontinuous nature of the surface of the beadlike members serves to concentrate the impact forces. Furthermore the generally nonabrasive nature of the material of which the beadlike members are formed serves to resist undue wear of the screen deck.

A second form of the beadlike members which can be used with the flexible elongate members is shown at Figure 8. The second form comprises a generally cylindrical member which is formed with a plurality of angularly spaced longitudinal ribs 56 in order to provide the discontinuous surface. A third form of the beadlike members which can be used with the flexible elongate members is shown at Figures 9 and 10. The third form comprises a generally cylindrical member which is formed with a plurality of angularly and longitudinally spaced radial protrusions 58 in order to provide the discontinuous surface. The protrusions have an outer end which is generally of the same size or less than the apertures in the screen deck in order that it is possible for them to penetrate the apertures on vibration of the flexible elongate members to facilitate the clearing of the apertures.

According to a further embodiment a screen cleaning means of a similar form to both the first and second embodiment can be utilised with a multilayer screen which comprises a number of screen decks located one above the other in order to provide a number of grades of screened particulate material.. The third embodiment comprises a set of flexible elongate members for each deck which are supported from a suitable support at the upper end of each deck and which are caused to reciprocate cross their respective deck through a common drive means.

It should be appreciated that the scope of the present invention need not be limited to the particular scope of the embodiment described above. In particular, the flexible elongate members can take alternative forms other than those described in relation to the embodiments. For example, the flexible elongate members may comprise lengths of cable or like elongate members with moulded rubber, polyurethane or beadlike members or segments mounted at spaced intervals along their length ,or a set of interconnected moulded segments formed of rubber polyurethane or like material. Each of these arrangements being intended provide a concentrated impact loading on the screen with vibration of the screen to facilitate effective cleaning.

Claims

The claims defining the invention are as follows:

1. A screen cleaning means for use with a vibrating screen comprising a plurality of flexible elongate members which are each supported at one end in the region of the upper end portion of the screen, said flexible elongate members being located at spaced intervals across the screen and being mounted to extend downwardly over the surface of the screen for at least a portion of the length of the screen, wherein the flexible elongate members are provided along their length with a linear discontinuous surface to provide spaced portions of reduced surface area which will impact on the screen deck with vibration of the screen deck.

2. A screen cleaning means as claimed at claim 1 wherein some of the flexible elongate members extend over the full length of the screen deck.

3. A screen cleaning means as claimed at claim 1 wherein the flexible elongate members are of differing lengths with at least one extending substantially the full length of the screen deck.

4. A screen cleaning means as claimed at claim 1 , 2, or 3 wherein the one end of the flexible elongate members are rotatably supported for the flexible elongate members to be rotatable about their longitudinal axis

5. A screen cleaning means as claimed at claim 1 , 2, 3, or 4 wherein the flexible elongate members are supported to be capable of transverse movement across the upper end of the screen and a drive means is provided to effect reciprocation of the one end of the flexible elongate members across the screen.

6. A screen cleaning means as claimed at claim 5 wherein the flexible elongate members comprise a number of sets of differing lengths which are arranged such that on reciprocation of the support substantially the full width of the screen is swept jointly by some of the members of each set.

7. A screen cleaning means as claimed at any one of the preceding claims wherein one or more further flexible elongate members are supported to extend underneath the screen to lie within a chute which conveys screened material away from the screen.

8. A screen cleaning means as claimed at claim 7 wherein the further flexible elongate members are caused to reciprocate across the surface of the chute

9. A screen cleaning means as claimed at any one of the preceding claims wherein the flexible elongate members are supported from their one end by a support which is mounted proximate the upper end of the screen and the support is pivotable about a transverse axis to enable the mounting to be movable between a first position closely adjacent the upper end of the screen and a second position spaced from the upper end of the screen.

10.A screen cleaning means as claimed at any one of claims 1 to 8 wherein the flexible elongate members are supported from their one end by a support which is mounted proximate the upper end of the screen and the mounting for the members on the support is pivotable about a transverse axis to enable the mounting to be movable between a first position closely adjacent the upper end of the screen and a second position spaced from the upper end of the screen.

11. A screen cleaning means as claimed at claim 9 or 10 wherein a storage means is provided to receive the flexible elongate members when the mounting is in its second position.

12. A screen cleaning means as claimed at any one of the preceding claims wherein the flexible elongate members comprise a plurality of interconnected segments.

13.A screen cleaning means as claimed at any one of the preceding claims wherein the flexible elongate member comprises a length of chain.

14. A screen cleaning means as claimed at any one of the preceding claims wherein the flexible elongate members comprise an elongate member supporting a plurality of beadlike members mounted along the length of the member.

15.A screen cleaning means as claimed at claim 14 in which the beadlike members are formed to be integral with the flexible elongate, member or may be threaded over the member.

16. A screen cleaning means as claimed at claim 14 in which the beadiike members are threaded over the flexible elongate, member.

17.A screen cleaning means as claimed at claim 14, 15 or 16 wherein the member comprises a length of cable, rope, chain or like elongate member.

18. A screen cleaning means as claimed at claim 14, 15, 16 or 17 wherein the beadlike members comprise elements having a generally cylindrical configuration where the outer surface is formed to be discontinuous

19. A screen cleaning means as claimed at claim 18 wherein the outer surface is formed with a plurality of axially spaced annular ribs.

20.A screen cleaning means as claimed at claim 18 wherein the outer surface is formed with a plurality of angularly spaced substantially axial ribs.

21. A screen cleaning means as claimed at claim 18 wherein the outer surtace is formed with a plurality of axially and angularly spaced radial protrusions.

22.A screen cleaning means as claimed at claim 20 wherein the protrusions have an outer end dimensioned to be receivable in the apertures of the screen.

23. A screen cleaning means substantially as herein described.

24.A vibrating screen having an inclined screen deck and a sαeen cleaning means associated with the deck of the form as claimed at any one of the preceding claims.