GB2227989A

GB2227989A - Particulate solids feeder

Info

Publication number: GB2227989A
Application number: GB8902735A
Authority: GB
Inventors: Ronald John
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-02-08
Filing date: 1989-02-08
Publication date: 1990-08-15
Anticipated expiration: 2009-02-08
Also published as: GB2227989B; GB8902735D0

Abstract

A particulate solids feeder, for e.g. spherical particulate solids, has a flexible, textured or roughened belt (3) which is deformed by a shaped roller (6) to form a depression. The depression retains free flowing spherical particles to a depth determined by the position of an adjustable tube (2). A spool shaped front roller (4) assists retention of the flow to the point of discharge, the belt being supported (8) over the load carrying length. The discharge of the particulate material is then controlled by the speed of the conveyor, through a variable speed motor (9). The depth of material on the conveyor is changed by adjusting the feed tube (2) to increase or decrease the range of feed rates with respect to the speed range. Therefore, the discharge rate of material from the belt is directly proportional to the speed of the belt, and the amount of material discharged per revolution of the drive roller (5) is proportional to the depth of material on the belt. <IMAGE>

Description

Patent Application.

PATENT APPL ICAT ION.

Bsprnvesents in or relating to a Voluietric feeder of particulate solids.

I Ronald John, a British subject resident at 10 Piddington Lane, Piddington, JR. High Wycombe, Buckinghamshire, HP14 3BD. do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed to be particularly described in and by the following statement.

The present invention concerns a means of controlling the volumetric dispensation of particulate materials.

Some particulate materials, particularly those that are spherically shaped are free flowing and have some of the characteristics of a liquid and are difficult to dispense in a controlled manner.

The control of the flow of particulate materials from a storage vessel into the -material conveying system is particularly important on precision shot peening or abrasive blasting machines. Hitherto the amount of solids transferred to the air stream has been strongly influenced by the quantity, pressure and velocity of the conveying air. In such a system the air flow characteristics have an affect on the amount of material transferred to the conveying system, and conversely, the amount of material added to the system affects the air flow characteristics, this makes the system difficult to accurately control.

Such control is also important on a diverse number of applications where the flow rate of a particulate material is important to the process on which the plant is used.

In accordance with the present invention there is provided a means of controlling the flow of particulate material such that the material nay be transferred from the device to another part of the system or discharged from the device in a controlled manner and feed rate. The material is prevented from moving in any direction whilst the system is inactive or stationary by the shaping of the conveyor and the natural attributes of the material.

With reference to figure 1, the particulate material is transferred from a storage hopper or container to the feeder device through a fixed tube (1).

Attached to the fixed tube is an adjustable tube (2) by which the distance between the end of the adjustable tube and the surface of the conveyor belt may be varied. The lower part of the adjustable tube may be shaped to assist the deposition of material onto the belt.

The adjustable supply tube (2) is positioned just forward of the puddle roller (6). The height of the tube, relative to the belt, is adjusted to allow the depositing of a quantity of material in the depression created by the puddle roller (6). The amount of material deposited in the depression will depend upon the relative height of the tube < 2) and the natural repose angle of the material. (The repose angle of a particulate material is the angle between the horizontal and the sloping surface of a quantity of the material at repose on a flat smooth surface). The puddle roller (6) presses downward in the middle of the belt thereby causing a depression to be created between the sides of the belt, the rear roller (5), and the forward roller (4).The belt is of a flexible nature to permit the deformation without damage or excessive strain, the surface of the belt is textured or Continued: Patent Application.

roughened to ensure material is carried up the shallow angle of the forward slope when the conveyor is caused to move Vith reference to figure 2, the conveyor belt (3) is of a very flexible material with a textured or roughened surface and passes over a forward roller (4) which is of a concave or spool shape and a rear roller (5) which is of a convex or barrel shape. Between these two rollers is set a third roller (6), this roller is narrow in relation to the belt, and is arranged to depress the flexible conveyor belt between the forward and rear rollers so that a shape (8) is generated that would form a puddle if a liquid were poured upon the belt.This shape is a 'particulate material retaining shape' which prevents excess material being loaded to the belt by blocking the down flow of material from the feed tube once the desired depth of material on the belt is attained.

The shape of the belt changes between the third (puddle) roller (6) and the forward roller S43 into a shape that corresponds to the shape of the forward roller (4). The belt is supported during this transition by the belt support (8). At the particle holding shape generated by the roller (6) the sides of the depression are at a relatively steep angle rising to the sides of the belt and to the rear roller, but have a relatively shallow angle to the forward roller.

The drive to the mechanism is by a variable speed motor (9). If the rear roller is the driven roller then the other two rollers are free to rotate with the movement of the belt. The preferred drive is via the rear roller because this places the lower part of the belt in tension and makes it easier to deform the upper length of the belt.

The lower end of the material supply tube terminates within the depression created by the puddle roller (6). The material that is falling down the supply tube will form a 'puddle' within the depression and the depth of this puddle is proportional to the distance between the lower end of the supply tube and the surface of the conveyor belt. This puddle of material is constrained by (a) the rising sides of the belt, (b) the steeply rising slope to the rear and (c) the more gentle slope to the forward roller. Vhen the conveyor belt is stationary the material remains substantially in the manner and position it held at the time the conveyor was stopped.When the conveyor moves the material is caused to stream out to the forward roller at a depth of layer which is controlled by the relative height of the supply tube, and as the material is removed from below the supply tube it is replenished by new material passing down the tube.

The transport of the particulate material from the depression up the shallow angle to the forward roller is assisted by the texturing or roughness of the belt. The texturing of the conveyor belt assists the conveyance of spherical particles up the forward leading slope by providing minute pockets or ridges that prevent the particles rolling backwards. The layer of particles in contact with the belt then provide the restraint for other particles which allows the accumulation of particles to a much greater depth for conveying to the discharge point.

The normal method of changing the discharge rate of material from the belt is to change the belt speed. Because the depth of material on the belt is controlled by the relative height of the supply tube, then the discharge rate of the material from the end of the conveyor is proportional to the speed of the conveyor.

Because the depth of the layer of material may be changed by adjusting the relative height of the supply tube, then the discharge rate may be Continued: Patent Application.

changed in relation to the conveyor speed range. If the height of the tube is increased then the depth of material on the belt will be increased and if the speed of the conveyor is the same then the discharge material will be increased, and cznversely; if the supply tube is lowered then the depth of material on the belt will be reduced and for the same speed the discharge rate will be decreased. The discharge rate may be changed for a given conveyor speed by changing the depth of material upon the belt and this is accomplished by adjusting the height of the supply tube.The adjustment of the supply tube is to set a condition wherein the normal method of altering the discharge rate, which is to control the speed of the conveyor whilst keeping the depth of material on the belt the same, is the preferred method of control. The conveyor may be driven by any means that will facilitate changes in the belt speed thereby changing the discharge.

One such method is where the drive is by a variable speed electric motor and the control voltage of the motor may be displayed by digital or analogue means. The display may then be interpreted, by virtue of the relationship between the belt speed and the discharge rate, as the discharge rate of the particulate material.

An addition to this method of control is to monitor the discharge by detecting the flow of material from the belt and using the signal so generated to control the speed of the belt until the discharge rate is comparable with a set-feed rate. By this means a desired feed rate may be set and the belt speed is then automatically adjusted to provide that feed rate.

Claims

WHAT I CLAIM IS

1. A method of deforming a flexible conveyor belt so that free flowing spherical particles are restrained in their freedom to move outside the confines of the deformation

2. 2. A method of conveying spherical particles from a depression to a point of discharge using a textured or roughened flexible belt.

3. A method according to claim 1 wherein any particulate material may be constrained by the shaping of the conveyor belt.

4. A method according to claim 2 wherein any particulate material may be conveyed up a slope on a textured or roughened surface.

5. A method according to the previous claims wherein the particulate material is a powder.

6. A method according to the previous claims wherein the discharge of particulate materials from the conveyor may be controlled to provide a required feed or discharge rate.

7. A method for controlling the feed rate or discharge rate of particulate materials substantially as herein described with reference to the accompanying drawings.