GB2191127A

GB2191127A - Grit-blasting nozzle

Info

Publication number: GB2191127A
Application number: GB08711882A
Authority: GB
Inventors: Michael Marius Byers
Original assignee: Laing & Sons Ltd James
Current assignee: Laing & Sons Ltd James
Priority date: 1986-06-02
Filing date: 1987-05-20
Publication date: 1987-12-09
Also published as: GB8711882D0

Abstract

A grit-blasting nozzle has an inlet end (4) to which is supplied grit under pressure, and a hollow outlet extent (12) having a bore (18) which is of rectangular shape in transverse section. <IMAGE>

Description

SPECIFICATION Improved grit-blasting nozzle The present invention relates to an improved gritblasting nozzle.

The principal function of grit-blasting, sometimes referred to as shot-blasting, is in the cleaning or preparation of a surface prior to subsequenttreatment such as painting. The areas to be cleaned offoreign mattersuch as dirt, scale or rust are often substantial, for example ships' hulls, large steel fabrications orstone buildings. Consequently it is desirablefor the grit-blasting equipment to be as efficient as possible.

Conventional grit-blasting equipment comprises a pressure chamber or blast kettle containing particulate abrasive or grit and to which is attached a source of compressed air the flow ofwhich is controlled by valves. In operation of the equipment, grit from the chamber isfed with thecompressed airthrough a blast hose, through a nozzle attachedtothe end of the hose and onto the surface to be treated.

The nozzle is held at various distances from the surface to be blasted depending upon the difficulty or otherwise of removing the dirt, rust or the like. In all instances, the nozzle is swept over the area to be treated and it will be appreciated that the efficiency ofthe equipment is, to a great extent, dependent upon the nature of the grit output from the nozzle.

Conventional nozzles comprise an outlet extent having a bore of circular cross-section the diameter of which increases towards the outlet end ofthe nozzle. The output from such nozzles therefore comprises a pressurised stream of grit of circular crosssection which can be directed as required acrossthe surface to be treated.

According to the present invention there is provided a grit-blasting nozzle having an inlet end adapted to be supplied with grit under pressure, and a hollow outlet extent the bore of which is of rectangulartransverse section.

It will be appreciated that the output from such a nozzle comprises a pressurised stream of grit of rectangularcross-section, such a stream being much more efficient than a stream of circular cross-section in traversing a given area, thus significantly reducing the time and effort needed to clean or prepare said surface, and consequently reducing the amount of abrasive that need be used.

Preferably the cross-sectional area ofthe bore of said outlet extent of the nozzle increases towards the outlet end of said nozzle.

Conveniently the inlet end ofthe nozzle feeds into a hollow inlet extent the bore of which is of circular transverse section, which transverse section may decrease in area from said inlet end towards the outlet extent ofthe nozzle.

By way of example only, an embodiment ofthe in vention will now be described in greater detail with reference to the accompanying drawings of which: Figure lisa central longitudinal section through a grit-blasting nozzle according to the invention; Figure 2 is an end view in the direction of arrow 11 in Figure 1; Figures 3 and 4 are transverse sections on the lines Ill-Ill and IV-IV respectively in Figure 1, and FigureS is an end view in the direction of arrow in Figure 1.

Referring to the drawings, the illustrated nozzle comprises a hollow, elongate member of generally cylindrical shape including an inlet extent 2 having an inletend 4 adapted to be connected to the end of a blast hose of grit-biasting equipment. The outer such face 6 of the inlet extent 4 is of circular cross-section and tapers from the inlet end 4 such that the diameter thereof decreases gradually towards the central re gions ofthe memben Similarly, the innerwall 8of the inlet extent 2 is of circular cross-section and defines a tapering bore 10 the diameter of which also decreases gradually from the inlet end 4towards the central regions ofthe member.

The nozzlefurthercomprises an outlet extent 1 2 the outer surface 14 of which isofcircularcross- section and tapers outwardly such that the diameter thereof increases gradually from the central regions ofthe member towards the outlet end of the outlet extent 12. The inner surface 16 of the outlet extent 12 defines a hollow interior 18 to said extent of re ctangular cross-section, said interior 18 tapering outwardly ofthe member whereby the cross-sectional area ofthe interior increases from the central regions ofthe membertowards the outlet end thereof.

Althoughthe interior 18 ofthe outletextent 12is shown as rectangular with the majorand minoraxes thereof of different lengths, said interior may be of, for example, square section, whilethe outer surface 14 may be otherthan circular in transverse section, for example rectangularconforming with the shape ofthe inner surface 16. Similarly said surfaces 14,16 may or may not taper.

In use, the inlet end 4 ofthe described nozzle is attached to the end of the blast hose of grit-blasting equipmentand, in a conventional manner,gritor abrasive under pressure is forced through the nozzle to emanate from the outlet end thereof and is directed onto a surface to be cleaned or prepared, typic- ally large flat areas of steel plate such as ships' hulls or tanks. The cross-sectional area ofthe stream of abrasive from the nozzle is determined by the shape ofthe interior 18 ofthe outlet extent 12 ofthe nozzle, and is therefore of a rectangul r configuration.

Compared with streams of ci ocularsection prov- ided by conventional nozzles, the rectangularsection streams produced by nozzles according to the invention enable much more efficient cleaning or preparing of a surface, in that said surface can be swept completely much more easily and quickly by said re ctangularstreamswhilst at the sametime using less abrasive material and therefore reducing the costs involved.

As with conventional nozzles, the grit used may be expendible and may be discarded after a single gritblasting operation, or, when used in, for example, factory-type blasting chambers, the grit may be of a higherqualityand may be collected after initial use and then recycled.

Claims

1. A grit-blasting nozzle having an inlet end adapted to be supplied with grit under pressure, and a hollow outlet extent the bore of which is of rectangulartransverse section.

2. A grit-blasting nozzle as claimed in claim 1 in which the cross-sectional area of the bore of said outlet extent increases towards the outlet end of said nozzle.

3. A grit-blasting nozzle as claimed in claim 1 or claim 2 in which the bore ofthe hollow outlet extent is of square transverse section.

4. A grit-blasting nozzle as claimed in any one of claims 1 to 3 in which the outer surface ofthe hollow outlet extent is circular in transverse section.

5. A grit-blasting nozzle as claimed in any one of claims 1 to 3 in which the outer surface ofthe hollow outlet extent is rectangular in transverse section.

6. A grit-blasting nozzle as claimed in any one of claims 1 to 5 in which the outer surface of the hollow outletextenttapers outwardlytowardsthe outlet end ofthe nozzle.

7. A grit-blasting nozzle as claimed in any one of claims 1 to 6 in which the inlet end ofthe nozzle feeds into a hollow inlet extent the bore of which is of circulartransverse section.

8. A grit-blasting nozzle as claimed in claim 7 in which the cross-sectional area of the bore of the inlet extent decreasesfrom the inletendtowardstheout- let extent ofthe nozzle.

9. A grit-nozzle as claimed in claim 7 or claim 8 in which the outersurface ofthe hollow inlet extent is circular in transverse section.

10. A grit-blasting nozzle as claimed in claim 9 in which the outer surface of the hollow inlet extent tapers inwardly from the inlet end thereoftowards the outlet extent of the nozzle.

11. A grit-blasting nozzle substantially as described with reference to and as illustrated by the accompanying drawings.

Amendments to the claims have been filed, and have the following effect: (a) Claims 1 and 2 above have been deleted or textually amended.

(b) New ortextually amended claims have been filed asfollows:- (c) Claims 3 to 11 above have been re-numbered as 2 to 10 and their appendancies corrected.

1. A grit blasting nozzle having an inlet end adapted to be supplied with grit under pressure, and a hollow outlet extent the bore of which is of rectangular cross-section, the length ofthe x andy axes of said bore increasing towards the outlet end ofthe nozzlewherebythe cross-sectional area of the bore ofthe outlet extent increases towards said outlet end ofthe nozzle.