GB2056932A

GB2056932A - Device for feeding finely divided material

Info

Publication number: GB2056932A
Application number: GB7925637A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-07-23
Filing date: 1979-07-23
Publication date: 1981-03-25
Also published as: GB2056932B

Abstract

A device for extracting divided material capable of being moved in an air stream from a body a body of the material comprises a circular disc (2) with a central passage (4) from the upper end of which an extraction tube (16) extends. Air from a side passage (8) is directed into the central passage (4) by tube (12) so that the material is sucked into the extraction tube (16) from the lower face of the disc to agitate the material prior to extraction, air is ejected from an annular chamber (20) within the disc through a ring of smaller apertures (22) around the passage (4). To contain the agitating air a ridge (28) projects downwardly around the apertures. <IMAGE>

Description

SPECIFICATION Device for feeding finely divided material The invention relates to the feeding of divided material capable of being moved in an air stream.

The invention is particularly but not exclusively concerned with the delivery of powder of plastics material from a container to an electrostatic spray gun. Conventionally, this is done by a suction device operating on the Venturi principle which withdraws the powder in an air flow from a fluidised bed, into which the powder has been poured from the packaging containers in which it is received from the supplier. The heavy packaging container has to be lifted and its contents poured into the hopper of the feed apparatus, with some powder inevitably being lost and requiring to be cleared away. It would be advantageous to withdraw the powder directly from the packaging container but to obtain a satisfactory flow it has been found necessary to support the container on a vibrating platform to create a powder cloud in which the Venturi extractor is located, again with loss of the powder.

The present invention is accordingly concerned with the provision of a device for the extraction of divided material from a container in an air flow, the extractor device requiring no external agitation and being of simple construction.

The invention thus provides a device for extracting divided material capable of being moved in an air stream from a body of the material, the device comprising a member provided with a main aperture through which the material can be sucked, and at least one subsidiary aperture adjacent the main aperture from which air can be directed to agitate the material for extraction through the main aperture.

The device of the invention thus effects the agitation of the material needed to effect the separation required for extraction exactly where this is needed, in the vicinity of the aperture through which the material is withdrawn, and not elsewhere.

Conveniently the device comprises a platform with a plurality of the subsidiary apertures distributed in a ring around the main aperture in the lower face of the platform. The agitating air jets may be directed parallel to the axis of the main aperture. To limit the disturbance of the material, a rim or skirt can project downwardly around the air jet apertures to tend to contain the air emerging from them.

The agitating air jets tend to lift the device from the material if placed on a free surface thereof and to allow itto float on this surface. The air supply and powder feed tubes connected with the device are of course flexible and allow the device to lower itself into the container as the powder is extracted therefrom. The device will tend to burrow directly downwardly until the powder collapses onto it, with no disadvantage as the device can function as well when buried in the powder as when floating on the surface.

The invention is further explained below, by way of illustration, with reference to the accompanying drawings in which: Figure lisa sectional side view of a powder feed device embodying the invention; and Figure 2 is a partial diagrammatic electric and air circuit for an electrostatic spray gun apparatus in which the device of Figure 1 can be employed.

The powder extraction device 1 of Figure 1 comprises a main support block 2 in the general form of a thick circular disc. The block 2, which may be built up from a plurality of ring-shaped elements, has a central passage 4 which is tapped at its upper end to receive an externally screw-threaded tubular fitting 6. A side passage 8 extends radially from the central passage 4 and turns upwardly at its outer end to a port on the upper surface of the block which is also tapped and receives an externally screw-threaded fitting 10. At its inner end, the passage 8 co-axially receives one limb of a right-angled tubular element 12, the other limb of which extends co-axially upwardly within the passage 4. A hose 14 is received on the free end of the fitting 10, and a hose 16 is received on the free end of the fitting 6.

The device 1 as so far described is capable of acting a convention Venturi extractor if air under pressure is fed through the hose 14. The air flow is carried by the side passage 8 and the tubular element 12 axially upwardly in the fitting 6 and the hose 16, and induces a low pressure region in the lower part of the passage 4. If the device 1 is placed upon a body of powder or other finely divided material, this will be sucked up into the passage 4 and conveyed along the hose 16 by the air flow. The flow of powder along the hose 16 however will be smooth and continuous only if the powder beneath the device is well separated. If the powder is caked or compacted the powder flow will be irregular or may even be interrupted. The device 1 is accordingly provided with agitating means ensuring a steady flow of the powder.

As shown, the block 1 includes an annular distribution chamber 20 centered on the axis of the passage 4. A plurality of equi-angularly spaced restricted outlet passages 22 communicate the chamber 20 with the lower surface of the block 2, and a single passage 24 extends upwardly from the chamber to the upper surface of the block. The upper end of the passage 24 is tapped to receive a screw-threaded fitting 25 to which an air supply hose 26 is connected. At the outer edge of the lower face of the block 2, a downwardly facing skirt or ridge 28 of square crosssection is provided.

In use, the device can be placed within a container containing powder, which container may be of any shape and may but need not be open topped. Air is supplied through the hose 26 as well as through the hose 14, so as to reach the annular distribution chamber 20 through the passage 24 and to create air jets from the passages 22, in a ring around the passage 4. The effect of these air jets is to agitate the material in the vicinity of the lower face of the block 2, so that the powder beneath the passage 4 is well separated. The powder can accordingly be sucked into the passage 4 and transmitted smoothly and continuously through the hose 16. The ridge 28 serves to limit the outward flow of the agitator air from the jets to within the region within it is required.

The device 1 described can be employed for feed ing any material in a finely-divided form, for any purpose. The material for example can be flock to be sprayed onto an article by an applicator, or insecti cide to be sprayed onto plants and depending on the application, the device can be modified in various ways. The number and spacing of the passages 22 can be selected according to the density and fineness of division of the material to be moved, and the passages 22 need not extend parallel to the main passage 4 but can for example be directed so as to converge to this axis.The air supply to the hose 26 need not be at the same pressure as that supplied to the hose 14, but where equal pressures are applied, the device can be modified by omission of the passage 24, and inclusion of a passage 30 between the side passage 8 and the chamber 20, so that air supply through the hose 14 operates the Venturi as well as the agitator jets. The agitator jets are then necessarily operated simultaneously with the suction feed supply. The agitator air can instead be supplied continuously, or intermittently under control separate from that of the suction feed air supply. It can in any event be advantageous to supply the agitator air in pulses at a predetermined or selectively variable rate.

Figure 2 schematically indicates a typical use of the device of Figure 1, in an electrostatic spray powder apparatus. Air under pressure is supplied from a source (not shown) through a tube 31 which branches toward two selectively adjustable pressures reducing valves 32,34 associated with respective pressure gauges 35,36. The branch tubes continue from the valves 32,34 to respective solenoid operated valves 39,40 from which connection is made to the hoses 26, 14. The solenoid valves 39,40 have their parallel connected coils in series with a pair of contacts of a relay 41 and an electrical supply source 42 conveniently at mains voltage.A transformer primary 44 in this circuit feeds a secondary 45 in series with the coil of the relay 41 and a trigger switch 50 provided on an electrostatic spray gun to which powder is supplied from the device 1 through the hose 16. The circuit including the trigger switch 50 operates at a lower voltage for example 12 volts for safety reasons.

When a mains switch 51 is closed, closure ofthe spray gun trigger switch 50 energises the relay 41 to open the solenoid valves 39,40. The air then supplied through the hoses 26, 14 to the device 1 provides a smooth and continuous supply of powder through the device 1 from a container in which it is placed to the spray gun, the smoothness and continuity of the supply being ensured by the agitator air supplied through the passages 22. The valves 32,34 are preset to desired pressures which can be read from the gauges 35, 36; for example, the suction air can be at about twice the pressure of the agitator air.

The relay 41 includes further contact pairs by which an electrostatic generator for the spray gun is energised.

Cleaning of the device 1 can be very readily effected by placing it on a clean level surface, and applying suction and agitator air. Surplus powder is displaced by the agitator air and extracted through the tube 16.

The device can be employed not only to withdraw powder or otherfinely-divided material from a sup ply container for use, but alsaforthe reclamation and recirculation of oversprayed powder in a spraying booth for example. This application can be facilitated if the booth itself is designed to function as a hopper, so that the surplus powdertends to collect in a region from which it can be conveniently withdrawn by means of the device. The powder supply to the gun can comprise a mixture of reclaimed powder from the booth and fresh powder from the supply container, powder from both sources being fed buy a device according to the invention.

Claims

1. An apparatus for extracting divided material capable of being moved in an air stream from a body of the material, the apparatus comprising a device having an end for presentation to the body of the material, a main aperture in the end through which the material can be drawn by suction, and means around the main aperture for spacing the main aper ture from the adjacent surface of the body ofthe material.

2. An apparatus as claimed in claim 1 wherein the means around the main aperture comprises a plurality of subsidiary apertures in the surface from which air can be directed against the body of the material.

3. An apparatus as claimed in claim 1 wherein the means around the main aperture comprises projecting wall means around the main aperture.

4. An apparatus for extracting divided material capable of being moved in an air stream from a body of the material, the apparatus comprising a device having an end for presentation to the body of the material, a main aperture in the end through which the material can be drawn by suction, and a plurality of subsidiary apertures positioned around the main aperture from which air can be directed to agitate the material for extraction through the main aperture.

5. An apparatus as claimed in claim 4 having projecting wall means around the apertures to restrict lateral flow df air directed through the subsidiary apertures.

6. An apparatus for extracting divided material capable of being moved in an air stream from a body of the material, the apparatus comprising a device having an end for presentation to the body ofthe material, a main aperture in the end through which the material can be drawn by suction, and wall means projecting from the end around the aperture.

7. An apparatus as claimed in claim 6 having at least one subsidiary aperture in the end from which air can be directed to agitate the material forextrac- tion through the main aperture.

8. An apparatus as claimed inclairn? having a plurality of the subsidiary apertures between the wall means and the main aperture.

9. An apparatus as claimed in claim 5 or8 wherein the subsidiary apertures are located in a ring concentric with the main aperture.

10. An apparatus as claimed in any one of claims 2, 4, 5,7,8 and 9 having first and second air supplies thereto for creating the suction at the main aperture and for supply to the or each subsidiary aperture.

11. An apparatus as claimed in any one of claims 2,4,5,7,8 and 9 having a single air supply thereto for creating the suction at the main aperture and for supplyto the or each subsidiary aperture.

12. An apparatus as claimed in claim 5,8 or 9 wherein the device comprises a circular disc having a central axial passage providing the main aperture, a concentric annular chamber within the disc and subsidiary passages extending from the chamber to one face of the disc to provide the subsidiary apertures, the wall means being constituted by a rim around the one face.

13. An apparatus as claimed in claim 12 having at the other face of the disc an extraction line connection communicating with the central passage and an air supply line connection for creating the suction therein.

14. An apparatus as claimed in claim 13 having a restricted connection between the air supply line and the annular chamber.

15. An apparatus as claimed in claim 13 having a second air supply line communication with the annular chamber whereby the air supply to the subsidiary apertures can be controlled independently of the suction.

16. An apparatus as claimed in claim 15 having means supplying air to the second line in pulses.

17. An apparatus as claimed in any one of claims 12 to 16 wherein the subsidiary passage are parallel to the central passage.

18. An apparatus for extracting divided material capable of being moved in an air stream from a body of the material subsidiary as herein described with reference to the accompanying drawings.