GB2196877A - Nozzles - Google Patents

Abstract

A nozzle for spraying abrasive particulate material comprises a flanged body (10), made of a hard but resilient material such as rubber or plastics, and a liner (20) made of a durable ceramic material, e.g. zirconia. The liner has a conical in portion 23 and may be a friction fit in the body. <IMAGE>

Description

SPECIFICATION Nozzles Description of the Invention This invention relates to nozzles of the kind used in sand blasting and other similar apparatus which requires the production of a jet of particulate material by blowing such material through a nozzle by means of a compressed gas, usually air.

Conventionally, such nozzles are formed of a ceramic material such as alumina which may be formed to the required shape by casting.

Such nozzles are of generally tubular form, having internally a conical lead-in portion into which the particulate material and compressed gas are introduced, and a parallel-sided bore leading from the conical portion to the opposite end of the nozzle from which the required jet of material issues.

At a position between the two ends, the nozzle includes an external flange which is provided to co-operate with a screw-threaded cap nut-whereby the nozzle is mounted within a supporting tube or collar.

During use, the abrasive particles wear away the material of which the nozzle is formed, so that the diameter of the bore gradually increases. To ensure that the material is sprayed at its correct velocity, the diameter of the bore must be maintained within quite well defined limits, and as soon as it wears to an unacceptable extent, the nozzle must be replaced.

In practice, such alumina nozzles normally require replacing after only one days use. Each apparatus may have 10 or more such nozzles, and to replace each nozzle it is necessary to remove the cap nut, remove the worn nozzle, insert a new nozzle, transfer a sealing ring from the worn nozzle to the new nozzle and replace the cap screw.

In accordance with the invention such a nozzle is constructed as a body which affords said flange and a replaceable inner liner of hard, durable ceramic material, such as zirconia, which defines the lead-in portion and the bore of nozzle.

The body preferably includes a liner-receiving bore which has an internal diameter substantially equal to the maximum useful bore diameter of the nozzle, and the liner is so dimensioned as to be a friction-fit therin, the wall thickness of the liner being such as to afford an internal diameter corresponding to the minimum required for the nozzle.

Thus, the liner requires the minimum possible quantity of zirconia, so as to minimise material costs, and by making the liner of a more durable material than the alumina which is usually employed, the liner lasts several times longer than an alumina nozzle, typically for some 4 or 5 working days. The replacement need thus be carried out only once a week instead of every day, with consequent savings in maintenance, time and costs, and without any significant increase in material costs.

Instead of replacing the complete nozzle, it would normally be sufficient to replace only the worn zirconia liner, although if desired the used nozzle as a whole could be- returned-to the supplier for re-lining and returned for further use.

In accordance with a particularly preferred feature of the invention, the body of the nozzle may be formed from a suitable rubber or plastics material. This has a number of advantages over the use of a body of more rigid material such as metal or a ceramic. In particular, the liner will bed down into the body under the force of the air and sand applied to the lead-in portion of the liner, and thereby form a reliable seal between the liner and the body to pervent air escaping around the outside of the liner and consequent reduction in the performance of the nozzle and/or damage to the body. Secondly, the somewhat resilient nature of the material ensures that the flange on the body will seal effectively with the cap nut without requiring sealing washer to be interposed, thereby simplifying the replacement procedure.

A preferred embodiment of nozzle in accordance with the invention is illustrated in the accompanying drawings, wherein: Figure 1 is a perspective view showing the components of the nozzle in "exploded" relation; and Figure 2 is a diametral section through the nozzle.

As shown in the accompanying drawings, a nozzle in accordance with the invention comprises a body 10 and liner 20. The bodyl0 is formed as a moulding of rubber or other suitable hard but resilient material having a cylindrical outer surface and intermediate its ends a flange defined by a circumferential rib 11. A through-bore 12 extends centrally through the body, with a frusto-conical lead-in portion 13 at the inlet end thereof.

The bore 12 and lead-in portion 13 receive a complementary liner 20 which is made of a hard, durable ceramic material, such as zirconia or other like material. The liner 20 includes a tubular portion 22 which is a frictionfit within the bore 12, and a frusto-conical entry portion 23 which fits within the lead-in portion 13 of the body 10.

The external diameter of the tubular portion 22 of the liner is made substantially equal to the maximum permissible diameter of the bore which can be afforded by the nozzle for it to operate in accordance with its design requirements. Similarly, the wall thickness of the tubular portion 22 is such that the internal diameter is substantially equal to the minimum value which will meet the design requirements of the nozzle.

In use, the liner 20 is inserted within the body 10 as a friction fit. The complete nozzle is then mounted within a supporting tube (not shown) with the flange 11 engaging against the end of the tube. A cap nut (not shown) is then passed over the nozzle to engage the other side of the flange 11 and screwed onto the tube to hold the nozzle in place, whilst at the same time effecting an air-tight seal between the body 10 and the tube.

Whilst the body 10 is preferably formed from a material such as rubber, it may alternatively be formed from a rigid material, for example a suitable metal or ceramic, and in that case it would be necessary to employ a resilient sealing ring in association with the flange 11, and the dimensional tolerances applicable to the internal diameter of the bore 12 and external diameter of the tubular part 22 of the liner 20 would need to be maintained to relatively higher standards to ensure the required closeness of fit.

The features disclosed in the foregoing description, or the accompanying drawing, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, may, separately or in any com- bination of such features, be utilised for realising the invention in diverse forms thereof.

Claims (9)

1. A nozzle comprising a generally tubular body which affords an external flange and a replaceable inner liner of a hard durable ceramic material which defines a generally conical lead-in portion and a bore extending from the lead-in portion centrally through the body to an outlet.

2. A nozzle according to Claim 1 wherein a liner is formed from zirconia.

3. A nozzle according to Claim 1 or Claim 2 wherein the body is formed with a bore to receive the liner and the internal dimensions of said liner-receiving bore are substantially equal to the external dimensions of the liner so that the latter is a friction fit within the body.

4. A nozzle according to Claim 3 wherein the internal dimensions of said liner-receiving bore are substantially equal to the maximum permissible internal dimensions of the bore which the nozzle requires to operate in accordance with its design parameters.

5. A nozzle according to Claim 4 wherein the wall thickness of the liner is such that its internal dimensions are substantially equal to the minimum permissible internal dimensions of the bore which the nozzle requires to operate in accordance with its design parameters.

6. A nozzle according to any one of the preceding claims wherein the body is formed from a rubber or plastics material.

7. Sand blasting apparatus or the like incorporatng one ore more nozzles as claimed in any one of the preceding claims.

8. A nozzle substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

9. Any novel feature or novel combination of features disclosed herein and/or shown in the accompanying drawing.