GB2527801A

GB2527801A - Screen assembly

Info

Publication number: GB2527801A
Application number: GB1411834.3A
Authority: GB
Inventors: Kieran Mckiver
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-07-02
Filing date: 2014-07-02
Publication date: 2016-01-06
Also published as: GB201411834D0; IE20150194A1

Abstract

A screen assembly 10 features adjacent pairs of first and second transverse members 14,15 movable towards and away from each other in a common plane. Between the transverse members 14,15 are held, flexible screening mats (12, fig.2) with apertures, flexation of the mats (12, fig.2) by the reciprocating movement of the transverse members 14,15 stopping the apertures in the mats 12 from blocking with material. The screen assembly 10 may be used as the bottom of two screen assemblies, may be retrofitted to existing arrangements, and may be more compact than previous flexible screening mat assemblies.

Description

Screen Assembly This invention relates to a screen assembly and in particular to a screen assembly of the flip flow type than can be retrofitted to an existing vibrating screen.

Vibrating screens are used in a number of industries for sorting, grading and/or dewatering particulate or loose material, such as quarried stone or sand or for processing and separating materials for recycling, such as scrap metal or used building materials from demolition sites or other waste materials that need to be sorted by size. Vibrating screens are also commonly used for removing dirt and foreign matter from such materials.

A typical vibrating screen comprises a frame, defined by a pair of substantially parallel side walls, interconnected by transversely extending bridging members upon which are supported a screen, typically defined by one or more screen panels, having small openings or slots formed therein for water and/undersize particles to pass through. The screen panels are typically formed from a moulded plastic material or from wire mesh. A typical screen assembly may have two or more vertically spaced screen decks, the lowermost deck typically having a screen with a smaller aperture size than the deck thereabove, such that material passing through the apertures of the screen of the upper deck can be further screened on the lower deck.

The or each deck is vibrated at a frequency to shake out excess water and/or undersize material through the openings in the screen thereof and to convey the material across the deck to one end of the screen, whereby the dry and/or oversize material is discharged onto a conveyor or into a collection bay or hopper. The frame is typically mounted on a base via resilient supports, such as springs or rubber blocks, and the frame, and thus the deck, is typically vibrated by means of one or more eccentrically mounted rotors, driven by one or more drive motors, to impart circular or reciprocating vibratory motion to the or each deck.

Typically the frame vibrates in a reciprocating or circular motion. This motion works the undersize material through the or each screen. Typically the or each deck is mounted at an inclined angled so that material on the deck is conveyed down the or each screen thereof under the action of gravity as the screen is agitated by the vibratory motion of the deck.

A problem with such known vibrating screens is that the openings in the screen of the or each deck, particularly in a lowermost deck having the smallest openings, can easily become clogged, especially when screening wet material.

In order to overcome such clogging it is know to provide flip flow" screens having flexible screen panels, typically defined by a flexible polyurethane mat, attached at intervals to parallel screen supports which are mounted so that adjacent supports alternately approach each other and recede from each other in such a way that the screen between them is alternatively flexed and stretched to produce stationary waves as the screen is vibrated.

Screens of this kind are known from US 4600506 and US 2,980,254. The formation of stationary waves by the alternate flexing and stretching of the screen at various positions applies very high accelerations to the material being screened, assisting in separating the material and allowing particles below a certain size to pass through the screen. This effect is particularly marked when the screen vibrates locally between a strongly convex shape and a moderately convex or substantially flat shape, that is to say between a slack or flexed state and a taut or stretched state. In this vibratory movement it is important to ensure that the openings in the screen repeatedly change shape, because this tends to prevent them from becoming clogged with the material being screened and thus helps to keep them clear.

In known vibrating screens of the flip flow type, this vibration of the flexible screen is obtained by mounting the screen on supports which are alternately mounted on two separate frame systems mounted to permit linear motion with respect to each other.

At least one of the frame systems is typically provided with an oscillating or eccentrically mounted mass which is driven to impart a vibratory motion to the frame system. The frame systems are typically mounted on a base frame by means of resilient mounts so that the base frame is isolated from the vibratory motion of the frame systems.

However, the requirement for two separate frame systems in known flip flow screens makes the screen assembly of each deck more complex and larger than typical vibrating screens having rigid screens supported on fixed bridging members.

An object of the present invention is to provide a screen assembly of the flip flow type that has a compact and simple construction, allowing such screen assembly to be retrofitted into an existing vibrating screen by replacing one of the decks of the screen, typically the lowermost deck which is most prone to clogging, with said screen assembly.

According to a first aspect of the present invention there is provided a screen assembly for a vibrating screen comprising a pair of substantially parallel longitudinal frame members having a plurality of first and second transverse bridging members extending therebetween and lying in a common plane, said first transverse bridging members being arranged in alternating relationship with respect to said second bridging members such that each first bridging member is located adjacent to a respective second bridging member, a screen having a plurality of openings therein for passing water and/or undersize particles therethrough, said screen being supported upon said first and second bridging members, wherein each of said elongate frame members comprises an outer part adapted to be mounted to a side wall of said vibrating screen and an inner part coupled to the outer part by resilient mounting means permitting longitudinal displacement of the inner part of each longitudinal frame member with respect to the outer part thereof, said first transverse bridging members being mounted between respective outer parts of said longitudinal frame members and said second transverse bridging members being mounted between respective inner parts of said longitudinal frame members such that oscillating longitudinal displacement of said inner parts of said longitudinal frame members with respect to said outer parts thereof, caused by a rotary or reciprocating vibration of the screen assembly, causes adjacent pairs of first and second transverse members to move towards and away from each other in said common plane.

In one embodiment the outer part of each frame member may have a 1' shaped cross section defining a substantially vertically aligned outer wall, adapted to be attached to an inner face of a side wall of the vibrating screen, and a substantially centrally located horizontally extending flange extending from said outer wall towards the inner wall of the respective frame member, the inner part of each frame member having a "Li' shaped cross section defining a vertically aligned inner wall and vertically spaced upper and lower walls extending from the inner wall towards the outer part of the respective frame member such that the horizontally extending flange of the outer wall is located between said upper and lower walls of the inner part, wherein the inner part of each frame member is supported on the outer part thereof by means of longitudinally spaced pairs of rubber blocks located between the inner and outer walls of the respective frame member above and below the horizontally extending flange of the respective outer part, between said flange and respective upper and lower walls of the inner part.

Preferably said first bridging members are coupled to the outer parts of the frame members and said second bridging members are coupled to the inner parts of the frame members.

Brackets may be mounted on said outer part of each longitudinal frame member to which respective ends of said first bridging members are coupled, apertures being provided in said inner wall of the inner part of each longitudinal frame member through which said first bridging members may pass.

Respective ends of the second bridging members may be coupled to the respective inner wall of the inner parts of the longitudinal frame members.

Preferably biasing means are providing acting between the inner and outer parts of each longitudinal frame member in opposing directions in alignment with the longitudinal axis of each frame member to bias the inner part thereof towards a neutral longitudinal position with respect to the outer part thereof to control the movement of the inner and outer parts of each frame member with respect to one another.

The biasing means may comprise respective compression springs acting between opposite ends of the inner part and adjacent ends of the respective outer part of each longitudinal frame member.

Each biasing means may act between respective stops is provided on said inner and outer parts of each longitudinal frame member such that said biasing means provide a biasing force urging the inner part of the respective longitudinal member to its neutral position with respect to the outer part thereof.

The longitudinal position of at least one of said stops may be adjusted with respect to the outer part of the respective longitudinal frame member to permit adjustment of a pre-load applied to the respective biasing means, enabling adjustment of the resistance to longitudinal motion of the inner part with respect to the outer part of the respective longitudinal frame member imparted by means of said biasing means.

In one embodiment a respective threaded bolt or screw engages said adjustable stop such that the pre-load applied to the respective biasing means can be increased by screwing in the respective bolt.

Preferably said flexible screen is carried by said first and second bridging members such that the screen sags between each first and a respective second bridging member as the respective first and second bridging members approach one another and is drawn taut between respective first and second bridging members as said first and second bridging members move apart.

According to a further aspect of the present invention there is provided a vibratory screen comprising a frame comprising a pair of parallel side plates having at least one screen deck mounted therebetween, said frame being mounted on a base via resilient mountings permitting movement of the frame with respect the base and being provided with vibration generating means for imparting vibratory motion to the frame, wherein at least one of said at least one screen decks comprises a screen assembly in accordance with the first aspect of the invention.

In a further aspect there is provided a method of upgrading a vibratory screen comprising removing a screen deck from a vibratory screen and replacing it with a screen assembly as claimed in the first aspect of the invention.

The screen assembly may comprise a plurality of vertically spaced screen decks, said screen deck removed from the vibratory screen comprising a lower screen deck.

A screen assembly in accordance with an embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:-Figure 1 is a perspective view of a vibrating screen incorporating a screen assembly in accordance with an embodiment of the present invention; Figure 2 is a perspective view of the screen assembly of Figure 1 in isolation; Figure 3 is a perspective view of the screen assembly of Figure 2 with the screen panels removed for clarity; Figure 4 is a detailed perspective view of the discharge end of the screen assembly of Figure 2; Figure 5 is a detailed perspective view of the feed end of the screen assembly of Figure 2; Figure 6 is a sectional perspective view of the screen assembly of Figure 2; Figure 7 is a transverse sectional perspective view of the screen assembly of Figure 2; Figure 8 is a transverse sectional end view of the screen assembly of Figure 2; Figure 9 is a detailed sectional side view of the discharge end of the screen assembly of Figure 2; and Figure 10 is an end view of the screen assembly of Figure 2 viewed from the discharge end.

Figure 1 illustrates a twin deck vibrating screen 1 incorporating a screen assembly in accordance with an embodiment of the present invention. The vibrating screen 1 may be a conventional screen having twin decks both of the rigid or fixed screen panel type, wherein the screen panels are supported on fixed transverse bridging members arranged parallel on one another. The screen assembly 10 in accordance with an embodiment of the present invention may be retrofitted to such vibrating screen 1, here replacing the existing lower deck, such that the screen may be modified to be used to screen wet material, which might generally lead to clogging of the conventional fixed screen panels, particularly those of the lower deck having smaller openings than the screen panels of the upper deck.

As shown in Figure 1, the vibrating screen 1 comprises a screen frame 2 defined by a pair of parallel side plates 3,4 between which the upper and lower decks 5,10 are mounted. The upper deck 5 comprises a conventional screen, having parallel bridging members 6 extending between and connected to the side plates 3,4 at opposite ends thereof. A plurality of apertured screen panels 7 are supported on the bridging members 6.

A motor driven eccentrically mounted rotor 8 is mounted on one of the support plates for imparting circular motion to the screen. Springs 9 are mounted on the side plates 3,4 of the screen frame 2 for supporting the screen frame 2 on a base frame (not shown). The screen frame 2 is mounted on the base frame such that the decks are downwardly inclined from a feed end to a discharge end thereof such that material is conveyed over the screen panels of each deck from the feed end to the discharge end thereof The screen assembly 10 in accordance with an embodiment of the present invention defines a lower deck of the vibrating screen 1, such screen assembly 10 comprising a flip flow type screen, wherein the screen panels 12 are formed from a flexible material, for example flexible polyurethane mats, supported on transverse bridging members 14,15 wherein adjacent bridging members are adapted to alternately approach each other and move away from each other, such that the screen panels 12 between them are alternately flexed and stretched, as the screen assembly 10 is vibrated by means of the eccentrically mounted rotor 8.

The screen assembly 10 comprises a pair of longitudinally extending frame members 16,18 adapted to be mounted on inner sides of the respective side plates 3,4, of the screen frame 2, the frame members 16,18 being bridged by a plurality of mutually spaced apart first and second bridging members 14,15 to which the screen panels 12 are connected to be supported thereby.

As shown in Figures 4 and 5, each longitudinally extending frame member 16,18 is formed from an outer part 20 and an inner part 22, the inner part 22 of each frame member being resiliently mounted on the outer part 20 to permit limited longitudinal displacement of the inner part 22 with respect to the outer part 20, as will be described below in more detail.

As best shown in Figure 7, the outer part 20 of each frame member 16,18 has al" shaped cross section defining a vertically aligned planar outer wall 23 which may be bolted or otherwise attached to an inner face of a respective side plate 3,4 of the screen frame 2, and a substantially central inwardly extending horizontal flange 24 extending from the outer wall 23.

"U" shaped mounting brackets 25 are affixed to a respective inner side of the outer part 20 of each frame member 16,18 at spaced locations for mounting the ends of respective first bridging members 14 thereto, such that the first bridging members 14 are supported between the outer parts 20 of the longitudinally extending frame members 16,18.

As best shown in Figure 8, the inner part 22 of each frame member has a "U" shaped cross section having a vertically aligned inner wall 19 to which may be bolted or otherwise attached the ends of respective second bridging members 15, such that the second bridging members 15 are supported between the inner parts 22 of the longitudinally extending frame members 16,18, wherein the first bridging members 14 are interposed in alternating relationship between the second bridging members 15. Openings 17 are formed in the inner wall 19 of the inner parts 22 of each frame member 16,18 to permit passage of the respective ends of the first bridging members 14 therethrough.

As shown in Figure 6, the inner part 22 of each frame member 16,18 is supported on the outer part 20 thereof by means of longitudinally spaced pairs of rubber blocks 26,27 located above and below the inwardly extending horizontal flange 24 of the respective outer part 20, between the horizontal flange 24 and respective upper and lower walls 28,29 of the "U" cross section inner part 22. Such rubber blocks 26,27 permit longitudinal displacement of the inner part 22 with respect to the outer part 20 of the respective frame member 16,18.

As shown in Figure 7, the dimensions of the "U" shaped inner part 22 of each frame member 16,18 are such that the "U" shaped mounting brackets 25 of the outer part fit within the "U" shaped inner part 20 of each frame member 16,18.

As shown in Figure 2, the flexible screen panels 12 are affixed to the first and second bridging members 14,15 such that the screen panels 12 are alternately flexed and stretched to produce stationary waves when adjacent pairs of the first and second bridging members 14,15 approach and move away from one another due to longitudinal displacement of the inner part 22 of each frame member 16,18 with respect to the outer part 20 thereof during vibratory motion of the screen frame 2.

As illustrated in Figure 9, the movement of the inner and outer parts of each frame member 16,18 with respect to one another is controlled by springs 30 acting between opposite ends of the inner part 22 and adjacent ends of the respective outer part 20. A stop 32 is provided adjacent each end of the inner part 22 of each frame member 16,18 against which a respective spring 30 acts. An outer end of each spring 30 acts against an adjustable stop 34. A respective threaded bolt 35 engages each adjustable stop 34 such that the respective spring 30 can be preloaded by screwing in the respective bolt 35 to control longitudinal displacement of the inner part 22 with respect to the outer part 20 of the respective frame member 16,18, thus enabling the magnitude of the movement of the first and second bridging members 14,15 with respect to one another to be adjusted without requiring adjustment of the speed of the eccentrically mounted rotor 8.

In use, vibratory motion of the screen frame 2 by virtue of the eccentrically mounted rotor 8 imparts a circular or oscillatory motion to the screen assembly 10. This motion is transmitted to the outer parts 20 of the frame member 16,18 by virtue of their connection to the side plates 3,4 of the screen frame 2. The inner part 22 of each frame member 16,18 is resiliently mounted on the outer pad 20 of the respective frame member 16,18 via the rubber blocks 26,27. As such, the inertia of the inner parts 22 of the frame members 16,18 and the second bridging members connected thereto tends to cause longitudinal displacement of the inner parts 22 with respect to the outer parts 20 of the frame members 16,18 during such circular or oscillatory motion of the screen assembly 10, causing adjacent first and second bridging members 14,15 to be displaced towards and away from each other, cyclically relaxing and stretching the screen panels 12 mounted thereon.

The longitudinal motion of the inner parts 22 of the frame members 16,18 with respect to the respective outer parts 20 thereof is resisted by the springs 30 located at the ends of the frame members 16,18. Thus the amount of longitudinal motion of the inner and outer parts 20,22 of the frame member 16,18 can be adjusted by adjusting the pre-load applied to the springs 30 via the bolts 35.

The invention is not limited to the embodiment(s) described herein but can be amended or modified without departing from the scope of the present invention.

Claims

Claims 1. A screen assembly for a vibrating screen comprising a pair of substantially parallel longitudinal frame members having a plurality of first and second transverse bridging members extending therebetween and lying in a common plane, said first transverse bridging members being arranged in alternating relationship with respect to said second bridging members such that each first bridging member is located adjacent to a respective second bridging member, a screen having a plurality of openings therein for passing water and/or undersize particles therethrough, said screen being supported upon said first and second bridging members, wherein each of said elongate frame members comprises an outer part adapted to be mounted to a side wall of said vibrating screen and an inner part coupled to the outer part by resilient mounting means permitting longitudinal displacement of the inner part of each longitudinal frame member with respect to the outer pad thereof, said first transverse bridging members being mounted between respective outer parts of said longitudinal frame members and said second transverse bridging members being mounted between respective inner pads of said longitudinal frame members such that oscillating longitudinal displacement of said inner pads of said longitudinal frame members with respect to said outer parts thereof, caused by a rotary or reciprocating vibration of the screen assembly, causes adjacent pairs of first and second transverse members to move towards and away from each other in said common plane.
2. A screen assembly as claimed in claim 1, wherein the outer part of each frame member has a "T" shaped cross section defining a substantially vertically aligned outer wall, adapted to be attached to an inner face of a side wall of the vibrating screen, and a substantially centrally located horizontally extending flange extending from said outer wall towards the inner wall of the respective frame member, the inner part of each frame member having a "U" shaped cross section defining a vertically aligned inner wall and vertically spaced upper and lower walls extending from the inner wall towards the outer part of the respective frame member such that the horizontally extending flange of the outer wall is located between said upper and lower walls of the inner part, wherein the inner part of each frame member is supported on the outer part thereof by means of longitudinally spaced pairs of rubber blocks located between the inner and outer walls of the respective frame member above and below the horizontally extending flange of the respective outer part, between said flange and respective upper and lower walls of the inner part.
3. A screen assembly as claimed in claim 2, wherein said first bridging members are coupled to the outer parts of the frame members and said second bridging members are coupled to the inner parts of the frame members.
4. A screen assembly as claimed in claim 3, wherein brackets are mounted on said outer part of each longitudinal frame member to which respective ends of said first bridging members are coupled, apertures being provided in said inner wall of the inner part of each longitudinal frame member through which said first bridging members may pass.
5. A screen assembly as claimed in claim 3 or claim 4, wherein respective ends of the second bridging members are coupled to the respective inner wall of the inner parts of the longitudinal frame members.
6. A screen assembly as claimed in any preceding claim, wherein biasing means are providing acting between the inner and outer parts of each longitudinal frame member in opposing directions in alignment with the longitudinal axis of each frame member to bias the inner part thereof towards a neutral longitudinal position with respect to the outer part thereof to control the movement of the inner and outer parts of each frame member with respect to one another.
7. A screen assembly as claimed in claim 6, wherein said biasing means comprise respective compression springs acting between opposite ends of the inner part and adjacent ends of the respective outer part of each longitudinal frame member.
8. A screen assembly as claimed in claim 6 or claim 7, wherein each biasing means acts between respective stops is provided on said inner and outer parts of each longitudinal frame member such that said biasing means provide a biasing force urging the inner part of the respective longitudinal member to its neutral position with respect to the outer part thereof.
9. A screen assembly as claimed in claim 8, wherein the longitudinal position of at least one of said stops can be adjusted with respect to the outer pad of the respective longitudinal frame member to permit adjustment of a pre-load applied to the respective biasing means, enabling adjustment of the resistance to longitudinal motion of the inner part with respect to the outer part of the respective longitudinal frame member imparted by means of said biasing means.
10. A screen assembly as claimed in claim 9, wherein a respective threaded bolt or screw engages said adjustable stop such that the pre-load applied to the respective biasing means can be increased by screwing in the respective bolt.
11. A screen assembly as claimed in any preceding claim, wherein said flexible screen is carried by said first and second bridging members such that the screen sags between each first and a respective second bridging member as the respective first and second bridging members approach one another and is drawn taut between respective first and second bridging members as said first and second bridging members move apart.
12. A vibratory screen comprising a frame comprising a pair of parallel side plates having at least one screen deck mounted therebetween, said frame being mounted on a base via resilient mountings permitting movement of the frame with respect the base and being provided with vibration generating means for imparting vibratory motion to the frame, wherein at least one of said at least one screen decks comprises a screen assembly as claimed in any preceding claim.
13. A method of upgrading a vibratory screen comprising removing a screen deck from a vibratory screen and replacing it with a screen assembly as claimed in any preceding claim.
14. A method as claimed in claim 13, wherein the screen assembly comprises a plurality of vertically spaced screen decks, said screen deck removed from the vibratory screen comprising a lower screen deck.
15. A screen assembly for a vibratory screen substantially as herein described with reference to the accompanying drawings.