WO2002034403A1

WO2002034403A1 - Autogenous brush

Info

Publication number: WO2002034403A1
Application number: PCT/US2000/041585
Authority: WO
Inventors: John Vilinskis; Brian W. Packer; Michael J. Mankosa
Original assignee: Eriez Manufacturing Co.
Priority date: 2000-10-26
Filing date: 2000-10-26
Publication date: 2002-05-02
Also published as: AU2001237903A1

Abstract

A mechanical device (5) for cleaning the surface of a roll-type electrostatic separator (8) that does not use a conventional fibrous brushing system. A novel feature of this device is the autogenous nature of the mechanism. This approach offers an improvement in surface cleaning beyond that, which is currently available using existing techniques. The improved surface conditions allow the separator (8) to continuously operate at peak efficiency. Furthermore, maintenance time currently associated with existing practices is dramatically reduced. This disclosure describes several distinctive features of the device including the innovative approach of using the process material to clean the surface of the separator (8).

Description

AUTOGENOUS BRUSH

REFERENCE TO RELATED APPLICATIONS

Not applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT Not applicable

FIELD OF THE INVENTION

This invention relates to the use of a mechanical brushing system utilized intermittently and a tray containing a bed of non-conductive sand particles to continuously clean a roll surface in an electrostatic or other separator. The devices use the material being processed as an abrasive agent to remove hardened coating on the separator surface .

BACKGROUND OF THE INVENTION Electrostatic separators were first used near the turn of the century for separation of gold and sulfides from non-conductive siliceous gangue . One of the earliest recorded inventions was a device for concentrating gold ore that was patented by Thomas A. Ediso in 1892. The interest quickly dissipated/ however, with the advent of froth flotation. Renewed interest developed in the 1940 ' s due to a titanium shortage as a result of World War II.

Titanium naturally exists as ilmenite or rutile and most often occurs as alluvial or beach sand deposits in association with other heavy minerals such as zircon and various alumino-silicates . The primary contaminant is silica sand. Many of these heavy minerals have similar density, magnetic and surface chemical characteristics. As a result existing processing techniques were not feasible. Rutile and ilmenite, however, are conductive minerals. Therefore, the increased demand for these materials led to a new era of electrostatic separator development that provided improvements in separator design and high voltage power supplies. Currently, electrostatic separation is applied almost exclusively for the recovery of beach/mineral sands containing titanium. Other mineral applications have included cassiterite and iron ore. Applications outside of mineral processing include recycling of chopped wire and cable and processing of food products such as grains and cereals .

Electrostatic separation is the selective sorting of conductive from non-conductive solid species by means of forces acting on charged or polarized bodies in an electric field. The "high-tension" separator uses the mechanism of ion bombardment in an electrostatic field that is produced by a fine wire positioned parallel to a grounded rotor. Ion bombardment is the result of a corona discharge produced whenever the wire is raised to an electrical potential such that the electric field in the immediate vicinity exceeds the electrical breakdown strength of the ambient air.

A typical electrostatic separator consists of a feed hopper, rotor/drum, ionizing electrode, product discharge splitters and a brush for removing non-conductive material. The feed hopper discharges a consistent layer of particles onto the surface of the grounded, rotating drum. Particle charging is achieved as the solids pass through the intense corona discharge produced by the electrode . Conductive particles quickly share their charge with the grounded rotor and discharge from the drum in a trajectory determined by centrifugal force and gravity. The

Claims

dielectrics or nonconductors lose their charge slowly and are held to the surface of the grounded rotor. Residual non-conductive particles that do not discharge are removed by mechanical brushing. Historically, brushing techniques have included natural or metallic, static fiber brushes. This approach is often ineffective and has led to the development of rotary-type brushes for improved surface cleaning. In many instances, however, extremely fine particles (<50 microns) are present in the feed material. These fine particles are resistant to current brushing techniques since they are much finer than the brush fiber. In time, these particles tend to accumulate on the roll creating a non-conductive surface. Since electrostatic separation depends upon good electrical conductance between the particles and roll surface, the efficiency of the process quickly deteriorates. As a result, it is often necessary to stop the process and mechanically scour the roll to remove the surface coating. This inherent problem with electrostatic roll-type separators demonstrates the need for an improved device for cleaning the roll surface.BRIEF SUMMARY OF THE INVENTIONFrom the discussion presented above, it is apparent that modifications should be incorporated into new devices to correct the inefficiencies associated with existing electrostatic separator brushing systems. Since the nature of the feed material cannot be modified, the presence of fine particles will be a persistent problem in these systems. Therefore, a different approach must be considered. The most obvious approach is to build upon the abrasive, scouring technique currently used to remove the particle coatings. This process, however, requires equipment downtime and often removal of the roll from the separator, thus resulting in reduced productivity. A distinctive feature of the present invention is use of the non-conductive particulate species as a cleaning medium. Additionally, the device can be incorporated into existing machine housings and either manually or automatically actuated without interruption of the separation process. The mechanism consists of a sufficiently rigid, lined plate that spans the roll adjacent to and in a position ahead of the existing fiber brushing system. The plate incorporates a spring or pnuematic cylinder tensioning system that applies an even pressure across the roll surface. Positioning of the plate is such that it rotates into position and traps the non- conductive material between the plate and roll surface prior to brushing. The non-conductive particulates that have not discharged the roll accumulate at the intersection of the plate and roll surfaces. This action basically retards the advance of the non-conductive material such that the roll continues to move past the pinned particles. Since the non-conductive particles(silica and zircon) are typically quite abrasive, a scouring action takes place between the surface of the roll and the applied plate. This action works to abrade the coating on the roll surface.Another embodiment utilizes a tray located at the underside of the separator roll which contains a bed of the no -conductive particulate species of sand which is being separated. The bed of sand is in constant contact with the roll as it rotates, thereby providing a constant scouring action to abrade the coating from the surface of the roll. An advantage of this constant contact is that the coating of fine particles has a very short time in which to build up, basically only part of one revolution of the roll.Additional advantages of the devices include retrofit into existing equipment, automation and remote actuation. Since respirable dust is a major concern in any industry, electrostatic separators are often fully enclosed to allow for efficient dust extraction. Furthermore, machine access is usually restricted to maintain good housekeeping practices with regard to dust contamination. Safety issues are also critical due to the presence of rotating machinery and the use of high-voltage, direct current power. Therefore, remote actuation is critical to the success of any ancillary device. The autogenous brush has been designed to allow for remote actuation (manual or automatic) to ensure operator safety.Based on the above description, it is obvious that the autogenous brush and sand tray have potential applications exceeding those presented. Furthermore, the simplicity of the devices lends themselves to varied design approaches that may accomplish the same goal.It is the intent of this patent to disclose the procedure of removing build-up and/or contamination on surfaces by using the particulates that are being processed on the device. Other objects and applications of this device will become apparent from the following detailed description. It is an object of the present invention to provide an autogenous brush that uses non-conductive particulate material as a cleaning medium. It is another object of the present invention to provide an autogenous brush that uses non-conductive particulate material as the scouring agent to abrade the coating on the roll surface. It is another object of the present invention to provide a sand tray arrangement to provide continuous abrading of the coating on the roll surface.It is another object of the present invention to provide an autogenous brush and sand tray that is simple in construction, economical to manufacture and simple and efficient to use.With the above and other objects in view, the present invention consists of the combination and arrangement of parts hereinafter more fully described, illustrated in the accompanying drawing and more particularly pointed out in the appended claims, it being understood that changes may be made in the form, size, proportions and minor details of construction without departing from the spirit or sacrificing any of the advantages of the invention. BRIEF DESCRIPTION OF THE DRAWINGSFIGURE 1 is an end view of the mechanical brushing system according to the invention.FIGURE 2 is an isometric view of a second embodiment of the mechanical brushing system according to the invention.FIGURE 3 is a top view of a third embodiment of the sand brush assembly according to the invention.FIGURE 4 is an end view of the friction pad and support structure as shown in Figure 3. FIGURE 5 is an end view of an fourth embodiment utilizing a sand tray to providing continuous scrubbing action according to the invention. FIGURE 6 is an isometric view of the sand tray embodiment .DESCRIPTION OF THE PREFERRED EMBODIMENTS Now with more particular reference to the drawings, shown is a mechanical device for cleaning the surface of a roll-type electrostatic separator consisting of air- actuated spring cylinder 1 that is anchored to main support structure 2. The opposite end of spring cylinder 1 is attached via swivel connection 3 to lever arm 4. Lever arm 4 is used to apply force directly onto sand brush assembly 5. Sand brush assembly 5 consists of curved support backing 6 with lined surface 7. The action of sand brush assembly 5 is against separator roll 8 located on cantilever support arm 9. Sand brush assembly 5 is located on the lower right hand portion of separator roll 8 beneath conventional fiber brush 10.The method of the invention consists of gathering non-conductive particles that have been pinned to the roll surface in such a manner as to develop a bed of sand between sand brush assembly 5 and the roll surface. The accumulated sand acts to scour the surface of the roll thus removing any residual build-up on the roll surface. The intent of this device is to intermittently brush the roll surface. Sand brush assembly 5 can be either manually or automatically actuated on a regular service interval.Under typical conditions air actuated spring cylinder 1 will hold sand brush assembly 5 in a disengaged position via the spring action. Compressed air will be used to actuate cylinder 1, thus forcing the face of sand brush assembly 5 against the roll surface. As shown in Figure 2, a mechanical device for cleaning the surface of a roll-type electrostatic separator consists of sand brush assembly 15 consisting of support backing 16 with lined surface 17. Lined surface 17 may be a pad of rubber or other suitable material. Drum or roll 8 rotates about shaft 19. Sand brush assembly 15 is supported on sand brush support 20. There may be one or more sand brush supports provided. Adjacent the upper end of sand brush support 20 is sand brush pivot 21. Sand brush pivots 21 rotatably supports sand brush levers 22 attached thereto. Each sand brush lever 22 has sand brush assembly 15 adjacent its first end, is rotatably attached to a sand brush pivot 21 adjacent its midpoint and has a tension spring 23 affixed adjacent its second end. Tension springs 23 are attached at their second ends to fixed point 24 to fix them in place. Tension springs 23 pull downwardly on sand brush levers 22 which forces sand assembly 15 against roll 8 to scour the surface of the roll . The method of the invention remaining as discussed above consists of gathering no -conductive particles and developing a bed of sand between sand brush assembly 15 and surface of drum 18. The accumulated sand acts to scour the surface of the drum thus removing any residual build up of material from the roll surface.Figures 3 and 4 show a third embodiment of the sand brush assembly 30. Sand brush assembly 30 is used for cleaning the surface of a roll-type electrostatic separator. Sand brush assembly 30 consists of sand brush drive rod 31 , which is rotatably supported adjacent roll 8 and extends along the length thereof. Spacers 32 may be supported on sand brush drive rod 31 to position friction pad support 34 there along. A friction pad 35 is mounted on the friction pad support 34. Angle supports 33 are spaced along the length of sand brush drive rod 31. Sand brush drive rod 31 extends through holes 37 in angle supports 33. Angle 36 is secured to angle supports 33 along first side 38 and supports straight friction pad support 34 along second side 39 thereof. Friction pad 35 is supported on friction pad support 34. Sand brush assembly 30 is rotated by sand brush drive rod 31 against roll 8.It is recognized that alternate means, either manual or automatic, can be used to engage the brushing system.Figures 5&6 show a fourth embodiment for the removal of surface coatings from the separator roll 45. Sand tray assembly 40 comprised of sand tray 41 and support structure 42 is mounted at the underside 47 of separator roll 45, which is supported by cantilever support arm 46 mounted on base 48. Contained in sand tray 41 is a sufficient quantity of the non-conductive particles portion of the processed sand 44 so that the sand is in contact with underside 47 of the separator roll's 48 outer surface 49. The sand 44 is in continuous contact with the outer surface 49 of separator roll 45 thereby scouring the surface of small particles which otherwise would tend to build up.The foregoing specification sets forth the invention in its preferred, practical forms but, the structure shown is capable of modification within a range of equivalents without departing from the invention which is to be understood is broadly novel as is commensurate with the appended claims. The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An abrasive scouring device to remove particle coatings from electrostatic separator rolls without interruption of the separation process comprising: a sufficiently rigid plate supported adjacent to and extending generally across a separator roll having a surface; a tensioning system operatively attached to said plate to apply an even plate pressure across said surface of said separator roll.

2. The abrasive scouring device recited in Claim 1 further comprising no -conductive particulate material.

3. The abrasive scouring device recited in Claim 1 wherein said tensioning system further comprises a spring.

. The abrasive scouring device recited in Claim 1 further comprising a lined surface on said rigid plate to engage said roll surface.

5. The abrasive scouring device recited in Claim 4 wherein said lined surface comprises a pad made of rubber.

6. The abrasive scouring device recited in Claim 1 wherein said abrasive scouring device is placed adjacent to and upstream from a fiber brush.

7. The abrasive scouring device recited in Claim 1 wherein said tensioning system is rotatably supported by said plate and means for rotating said plate into and out of engagement with said roll.

8. The abrasive scouring device recited in Claim 7 wherein said means for rotating said plate comprises a biased spring to hold said plate in an unengaged position and an air cylinder to force said plate into an engaged position on said roll.

9. The abrasive scouring device recited in Claim 7 wherein said means for rotating said plate comprises a spring biased to hold said plate in an engaged position on said roll .

10. The abrasive scouring device recited in Claim 7 wherein said means for rotating said plate comprises a lever attached to said plate and extending outwardly therefrom; a support rotatably affixed adjacent a midpoint of said lever and a spring attached at the outer end of said lever biased to hold said plate in an engaged position on said roll.

11. An abrasive scouring device to remove particle coatings from electrostatic separator rolls without interruption of the separation process comprising: a friction pad supported adjacent to and extending generally across said roll; non-conductive particulate material disposed between said roll and said friction pad; means for moving said friction pad into scouring engagement with said roll and said non-conductive particulate material .

12. The abrasive scouring device recited in Claim 11 further comprising a tensioning system operatively attached to apply an even pressure across said roll surface .

13. The abrasive scouring device recited in Claim 11 further comprising a friction pad support adjacent to and extending generally across said roll.

14. The abrasive scouring device recited in Claim 11 wherein said means for moving said friction pad into scouring engagement comprises a drive rod and a friction pad support holding said friction pad; and, said drive rod being rotatable to move said friction pad into scouring engagement with said roll.

15. The abrasive scouring device recited in Claim 11 wherein said friction pad is curved along its scouring surface generally conforming to the shape of said roll.

16. The abrasive scouring device recited in Claim 11 wherein said friction pad is flat along its scouring surface .

17. A method for cleaning an electrostatic separator roll comprising: collecting non-conductive particulate material from the material flow being separated; scouring the roll surface with the no -conductive particulate material.

18. The method of Claim 17 further comprising developing a bed of said non-conductive material.

19. The method of Claim 17 further comprising rotating said electrostatic separator roll.

20. The method of Claim 19 further providing that all steps are conducted at the same time.

21. The method of Claim 18 further providing that all steps are conducted at the same time.

22. An apparatus for cleaning rotating electrostatic separator rolls without interruption of the separation process comprising; means for collecting non-conductive particulate material from the material flow being separated; means for scouring the roll surface with the non- conductive particulate material.

23. The apparatus of Claim 22 wherein said collection means is comprised of a tray located and mounted adjacent to and below said electrostatic separator roll so as to capture and hold a bed of said particulate matter.

24. The apparatus of Claim 23 wherein said scouring means is comprised of said bed of said particulate matter being held in continuous contact with said rotating separator roll by said tray.

25. The apparatus of claim 24 wherein said tray has a bottom and four sides.

26. The apparatus of claim 25 wherein said tray bottom is of a width and length slightly larger than the diameter and length of said electrostatic separator roll; said tray having two longitudinal sides being of a length approximately equal to the length of said bottom; said tray having one of said two longitudinal sides being of a height approximately equal to one half of the diameter of said roll; said tray having the second of said two longitudinal sides being of a height approximately equal to one quarter of the diameter of said roll; said tray having two lateral sides of a length approximately equal to the width of the bottom; said two lateral sides having a height at one end approximately equal to the height of said first longitudinal side and tapering to a height approximately equal to the height of said second longitudinal side.