GB2083432A - Device for guiding a meter over and levelling a moving layer of loose material - Google Patents

Abstract

A device for guiding a meter over and levelling a moving layer of loose material is provided with a meter 8 and a levelling skid 9, mounted on a movable frame 4 pivotally suspended over the layer of the loose material from an immovable supporting structure 3 on pairs of parallel rocker arms 5 and 6 of identical length. The weight of said movable frame 4, the meter 8, and the levelling skid 9 is counterbalanced by spring elements 10 connecting the rocker arms 6 with the supporting structure 3. Outriggers (14) are mounted to the sides of the movable frame 4, and are provided with rubber buffers (15) whereunder stops (16) are located, said stops being mounted on vertical beams of the supporting structure 3. One said stop is provided with a limit switch (17). The levelling skid 9 is slidably connected to the movable frame 4 by means of guides 11. The described device finds its application for continuous measurements of physical and chemical properties of materials, such as humidity using a microwave method, or ash content in coal using a radiometric method. <IMAGE>

Description

SPECIFICATION Device for guiding a meter over a moving layer of loose material This invention relates to a device to be used for guiding a meter at a constant distance from the surface of loose material layer transported on a conveyor.

The device according to the invention finds its application for continuous measurements of physical and chemical properties of materials, such as humidity, using a microwave method, or for determination of the content of ash in coal, using a radiometric method.

The accuracy of measurements of physical and chemical properties of materials is dependent to a large extent on maintaining a precisely definite constant distance between the measuring element and the surface of the material being investigated.

Even quite insignificant variations in said distance lead immediately to changed indications and, in consequence, to erroneous readings of the characteristic being measured.

There are known (from the Report of the Conference ICAMC 4, Vol. C, pp. 118-136, Bulgaria, Varna 1973) various types of scraper arranged above the conveyor, appropriate to secure a uniform layer thickness and an even surface of the loose material being inspected.

However, these scrapers operate satisfactorily in a very limited range, only at insignificant fluctuations of the stream depth.

Also known are devices wherein a constant distance of the measuring element from the surface to be measured is maintained by the use of special sample-formers having the shape of a tube with a worm conveyor, or a vessel mounted on a rotary disk (Polish Patent Specifications Nos.

66 224 and 83 010).

It is a substantial disadvantage of devices employed hitherto that their use is limited to coal streams showing relatively little and slowly varying depth of the layer resting on the belt conveyor. It should also be noted that the scrapertype designs require that the amount of the coal stream might be dosed, whereby the measuring system fitted with a sample-former makes it practically impossible to perform the measurement of the whole stream moving on the conveyor.

Still another device is known, from Polish Patent Specification No. 65 530/, to be appropriate for guiding a meter. This device consists of a horizontal frame suspended, together with the meter, over the conveyor on tilting arms.

In said frame there is also mounted a rotary roll rolling on the surface of the material. The rotary toll guarantees the constant distance of the meter from the material surface, but is does not level said surface.

Accordingly the present invention provides a device for guiding a meter over a moving layer of loose material, provided with a movable levelling skid, wherein the meter and the levelling skid are mounted on a counterbalanced movable frame pivotally suspended from an immovable supporting structure on pairs of parallel identical length rocker arms. The movable frame is thus suspended in such a way that both the measuring instrument and the levelling skid perform a translatory motion in the plane of symmetry of the conveyor transporting the material being measured.

The counterbalancing may be effected by spring biassing elements. The biassing spring elements may be disposed between the rear rocker arms and the supporting structure so that they counterbalance the weight of the movable frame, the meter, and the levelling skid.

To the side surfaces of said movable frame outriggers are mounted, fitted with rubber buffers over stops mounted on vertical beams of the supporting structure, the stops being provided with limit switches.

The levelling skid is slidably connected with said movable frame by means of guides, whereas the rocker arms are inclined to the horizontal beams of the supporting structure at an angle of no greater than 450. The device according to the invention guarantees the maintenance of a constant distance between the measuring instrument and the surface of the material being measured.

During the measurement, the skid slides on the material thus evening up and smoothing its surface. The varying depth of the layer being measured causes the skid and the instrument mounted thereto to perform a translatory motion.

Owing thereto, the measuring instrument does not change its distance from the layer of the material, and ensures a correct and accurate measurement.

In the described device, owing to the eveningup skid, the measuring instrument is mounted just behind the evening-up skid which minimizes the variations of the distance of the meter from the surface being measured, produced by the forces of inertia of the system. Moreover, the shape of said evening-up skid is so chosen as to ensure an accurate evening-up of the surface of the material.

The present invention will be now explained in particular by means of an exemplary embodiment.

In the accompanying drawings:- Figure 1 is a side view of the device for guiding the meter: Figure 2 is the front view of the same device; and Figure 3 is a fragmentary view of the design of rubber buffers for protection against stroke of the movable part against the supporting structure.

On the supporting frame 1 of the belt conveyor 2 there is mounted a rigid supporting structure 3 constituting, above the conveyor, a suspension of a movable unit consisting of a movable frame 4 and two pairs of parallel rocker arms 5 and 6 of identical length. The meter 8 is installed on said movable frame 4 just above the surface of the material 7 being measured. The movable frame 4 is also provided with a skid 9 for levelling the surface of the material 7 being measured.

The rocker arms 5 and 6 have their upper parts pivotally mounted on the supporting structure 3 and their lower ends connected to the movable frame 4. Thus they represent a tilting equilateral linkage which abuts the surface of the material 7 being measured through mediation of the levelling skid 9.

Parallel rocker arms 5 and 6 are inclined relative to the horizontal beams of the supporting structure 3 at an angle which is preferably no greater than 450 and as a result the falling speed of said movable part is large enough to ensure an adequate accuracy of measurements should the layer thickness decrease abruptly, which can occur particularly in the event of a considerable speed of the conveyor.

The weight of the meter 8 and the entire movable structure can be partly counterbalanced by a suitable counterweight, or by means of spring elements 10 fixed with one end in mid-length of the rear rocker arms 6, and with the opposite end to the supporting structure 3. The adjustment of the tension of the springs 10 makes possible the adjustment of the pressure of the skid 9 against the surface of the material 7 being transported on the conveyor 2. This counterbalancing obtained due to the action of the springs 10 does not lead to an increased mass of the movable part of the device. This is of importance since the smaller are the forces of inertia of the movable part, the greater is the accuracy of following the variable thickness layer of material 7.

The levelling skid 9 is slidably connected with the movable frame 4 by means of guides 11 inclined to the horizontal. The levelling skid can be set in the required position in a continuous (i.e.

infinitely variable regulation) way by means of the screw 12 and the nut 13 fastened to said levelling skid 9. By regulating the position of the levelling skid 9 relative to the movable frame 4 it is possible to change the distance between the meter 8 and the surface of the layer of material 7, to enable an optimum distance (from the point of view of the accuracy of measurement) to be chosen. On both sides of the movable frame 4 there are mounted outriggers 14 provided with rubber buffers 1 5.

Under said rubber buffers 1 5 stops 1 6 are mounted to the vertical beams of the supporting structure 1 6. One of said rubber buffers includes a limit switch 1 7. Limit switches could, if desired, be mounted on both of the buffers 1 5.

Due to the use of the rubber buffers 1 5 which serve as shock absorbers, the mechanical part of the supporting structure 3 is protected against shocks at the moment when the layer of material decays, and the individual units of the device, and particularly the meter 8, are thus protected against premature wear and tear.

The stops 1 6 together with the limit switch 1 7 serve for signalling of an excessive decrease of the layer depth below the value necessary for correct measurement. Apart from this, they also serve for switching off the measuring system during any time when the layer thickness of the material being measured has dropped below the permissible minimum value.

In the case of an insufficient depth of the layer of material 7 on the conveyor, the movable frame 4 rests through rubber buffers 15 on stops 16, and the measuring system of the meter 8 is simultaneously switched off by the limit switch 1 7.

During the measurement, the surface of the material 7 being transported by the conveyor 2 becomes levelied and the levelling skid 9, together with the meter 8, is deflected depending upon the depth of the layer in such a way that the distance of said meter 8 from the levelled surface does not change.

Claims (6)

1. A device for guiding a meter over a moving layer of loose material, provided with a movable levelling skid, wherein the meter and the levelling skid are mounted on a counterbalanced movable frame pivotally suspended from an immovable supporting structure on pairs of parallel identical length rocker arms.

2. A device as defined in Claim 1, wherein said counterbalancing is effected by means of springs between said rocker arms and said supporting structure.

3. A device as defined in Claim 1 or 2, wherein outriggers are mounted on the frame sides of the movable frame, said outriggers being provided with rubber buffers co-operating with stops which are fixed to vertical beams of said supporting structure, at least one said stop being provided with a limit switch.

4. A device as defined in Claim 1, 2 or 3, wherein the levelling skid is slidably connected with said movable frame by means of guides.

5. A device as defined in any one of Claims 1 to 4, wherein said rocker arms are inclined in relation to horizontal beams of said supporting structure at an angle of no more than 450.

6. A device for guiding a meter over a moving layer of loose material, such device being constructed and adapted to operate substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.