GB2065514A - Improvements in or relating to blast apparatus - Google Patents

Abstract

A blast gun 1 for discharging a pressurised mixture of abrasive material (in slurry form) and air, comprises a body 2 having an internal mixing chamber 3 of elongated form, internal passageways 4 and 5 for introducing separate flows of the abrasive material and air into a common end of the mixture chamber 3, and a mixture discharge nozzle 6 demountably disposed within the chamber 3. The body 2 preferably comprises a one-piece moulding of tough but resilient plastics material which allows the nozzle 6 to be replaced, when necessary, by distortion of the body. <IMAGE>

Description

SPECIFICATION Improvements in or relating to blast apparatus BACKGROUND TO THE INVENTION This invention relates to blast apparatus.

The invention is concerned with blast guns for discharging a mixture of abrasive material and fluid, for example, air, whereby surfaces may be polished, scoured or mechanically plated.

As used herein, the term "abrasive material" includes slurrys.

SUMMARY OF THE INVENTION According to the invention, a blast gun for discharging a mixture of abrasive material and fluid comprises a body having an internal mixing chamber of elongated form, duct means for introducing separate flows of the abrasive material and fluid into a common end of the mixing chamber, and a mixture discharge nozzle demountably disposed within the mixing chamber.

At least the inlet portions of the duct means may be disposed in substantially parallel array and at an angle to the longitudinal axis of the mixing chamber.

The body is preferably of resilient form whereby it can be distorted to allow removal and replacement of the mixture discharge nozzle.

The body preferably comprises a moulding of plastics material and preferably has substantially flat side surfaces.

The duct means for introducing a separate flow of fluid to the mixing chamber may be provided with non-return valve means.

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein: Figure 1 is a side view, in medial section, of a blast gun, Figure 2 is a plan view of the gun, but with flexible hoses 10 and 11 removed therefrom, Figure 3 is a front end view of the gun, and Figure 4 is a fragmental side view in medial section of a modified gun.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to Figs. 1, 2 and 3, blasting apparatus in the form of a blast gun 1 for discharging a pressurised mixture of abrasive material (in slurry form) and air, comprises a body 2 having an internal mixing chamber 3 of elongated form, duct means comprising internal passageways 4 and 5 for introducing separate flows of the abrasive material and air into a common end of the mixing chamber 3, and a mixture discharge nozzle 6 demountably disposed within the mixing chamber.

The body 2 comprises a one-piece moulding of ADIPRENE (Registered Trade Mark) or similar tough (100 Shore) but resilient plastics material. As shown by Fig. 3, the body 2 has substantially flat side surfaces. In fact, all the external surfaces of the body 2 are substantially flat.

The whole of passage 4, and the inlet portion of the passageway 5, are disposed in substantially parallel array and at an angle, (in this example 60o), to the longitudinal axis 7 of the mixing chamber 3.

Flexible hoses 10 and 11 are coupled to the inlet ends of the passageways 4 and 5 by way of tubular connections 1 2 and 1 3 screwed into the body 2. The connections 1 2 and 13, and the portions of flexible hose attached thereto, are disposed on axes 14, 1 5.

The outermost portion 5a of passageway 5 is disposed at an angle to the inlet portion thereof, and extends into the adjacent end of the chamber 3, in substantial alignment with axis 7. The outlet portion 5a of the passageway 5 is of smaller cross-sectional area than the inlet portion thereof, which is smaller in turn than that of passageway 4.

A disc 20 with a central hole in it is disposed between the lower end of tubular connection 1 3 and an adjacent land formed in the body 2. The disc cooperates with a ball 21 to form nonreturn valve means whereby backflow of abrasive material into flexible hose 11 is prevented.

The ball 21 is of too large a diameter to enter the mixing chamber 3. In addition, stop means in the form of a resilient retaining clip 35 is provided. The clip 35 is "V, '-shaped and is formed so as to allow free passage of fluid through the passageway 5 whilst preventing the ball 21 from entering the outlet portion 5a of the passageway.

The mixture discharge nozzle 6 is of tubular form and has a convergent entry portion 22 merging with a substantially parallel outlet portion 23. The nozzle 6 is prevented from being blown out of the chamber 3 by stop means comprising a land formed by an inwardly extending flange portion 24 of the body 2.

The body 2, being resilient and therefore deformable, allows the nozzle 6 to be replaced, when necessary, by distortion of the body, whereby a nozzle can be removed from, or inserted into, the chamber via the hole bounded by the flange portion 24.

The substantially flat sides of the body 2 allow several such blast guns to be stacked side by side, (in substantial contact with each other), to form a group or "battery" of the guns. A hole 30 extending laterally through the body 2 of a gun allows the guns of the "battery" to be clamped together by a bolt or the like.

The mixture discharge nozzle 6 is preferably of a hard plastics material such as "ADIPRENE" (100 Shore). Alternatively, it may be metallic, for example, it may be of boron carbide.

The inclined hoses 10, 11, where they connect to the body 2 of the gun 1, conveniently serve as a supporting handle for the gun.

The blast gun 1 has several advantages over existing blast guns, namely: (a) Cheapness and ease of manufacture.

(b) Simplicity.

(c) Nozzle 6 is cheaply and easily replaced.

(d) No nozzle at the outlet end of passageway 5, where it would become eroded externally, by abrasive material flowing out of passageway 4.

(e) Similarly-shaped guns can be stacked together to form a "battery".

(f) The body 2 of the gun can be a one-piece moulding.

(g) The gun does not require a separate handle.

(h) Slurry flow through the gun is substantially straight and is unobstructed.

The rate of discharge of mixture from the gun is best controlled by regulating the flow of air through passageway 5. This adjustment can be achieved by a foot-operated flow control valve.

In the case of the modified gun 1 a illustrated by Fig. 4, the inwardly flanged portion 24a of the gun is shaped so as to provide the gun with a divergent outlet portion. This shaping also assists replacement of a nozzle 6.

Further details of the example of blast gun described and illustrated herein are as follows: Body 2 Overall length-138 mm Width-40 mm Overall height-80 mm Passageway 4 Diameter-19 mm Passageway 5 Inlet portion15 mm diameter Outlet portion-5.5 mm diameter Chamber 3 Diameter-22 mm Length-68 mm Nozzle 6 External diameter-22 mm Diameter of central bore-l0 mm Flange portions 24 8 24a Diameter of hole defined in each case-16 mm Typical air supply pressure 80 p.s.i.

Typical content of abrasive particles in a slurry 30% (by volume).

Use of the tough material "ADRIPENE" for the body 2 provides the body with a good degree of abrasion resistance by "overspray" from adjacent guns when a battery of guns 1 is employed. The material has been found to be superior in this respect to metals such as steel and aluminium.

Although tough, the "ADRIPENE" material is sufficiently resilient to avoid accidental damage to components by contact with the body 2.

The outlet of passage 5a, which, like the passageway, is an integral part of the body 2, does not extend into the flow of abrasive material passing into the mixing chamber 3 and is thus not subject to damage by erosion.

The gun 1 may be used with a blast cabinet of the form disclosed by British Registered Design No. 988,338, which cabinet comprises a body supported on legs. The cabinet body is provided with a window and a pair of arm-access ports.

Access to the cabinet interior, for gun maintenance and/or for insertion or removal of workpieces, is by-way of a slidable door.

In a modification of the invention, a venturi system is used whereby abrasive slurry is drawn from a sump by means of vacuum created by an air jet in a divergent nozzle.

In another modification, the flow of air through passageway 5 is controlled automatically by a suitable regulating valve.

In yet a further modification, the gun 1 is formed with a convex side and a concave side, whereby when a plurality of similarly-shaped guns are stacked together to form a battery, the convex side of one gun nests within the concave side of an adjacent gun to provide substantial contact with each other.

Claims (14)

1. A blast gun for discharging a mixture of abrasive material and fluid comprising a body having an internal mixing chamber of elongated form, duct means for introducing separate flows of the abrasive material and fluid into a common end of the mixing chamber and a mixture discharge nozzle demountably disposed within the mixing chamber.

2. A blast gun as claimed in Claim 1, wherein at least the inlet portions of the duct means are disposed in substantially parallel array and at an angle to the longitudinal axis of the mixing chamber.

3. A blast gun as claimed in Claim 1 or 2, wherein the body is of resilient form whereby it can be distorted to allow replacement of the mixture discharge nozzle.

4. A blast gun as claimed in Claim 1, 2 or 3, wherein the body comprises a moulding of plastics material.

5. A blast gun as claimed in any one of Claims 1 to 4, wherein the body has substantially flat side surfaces.

6. A blast gun as claimed in any one of Claims 1 to 5, wherein the duct means for introducing a separate flow of fluid to the mixture chamber is provided with non-return valve means.

7. A blast gun as claimed in any one of Claims 1 to 6, wherein the mixture discharge nozzle has a convergent entry portion merging with a substantially parallel outlet portion.

8. A blast gun as claimed in any one of Claims 1 to 6 wherein the mixture discharge nozzle has a divergent outlet portion.

9. A blast gun as claimed in any one of Claims 1 to 8, wherein the mixture discharge nozzle is disposed in the internal mixing chamber and is prevented from being blown out of said chamber by stop means comprising a land formed by an inwardly-extending flange portion of the body.

10. A blast gun as claimed in any one of Claims 1 to 9, wherein the flow of fluid into said common end of the mixing chamber is by way of a passageway terminating in an outlet which is an integral part of the body.

11. A blast gun as claimed in Claim 10, wherein said outlet does not extend into the flow of abrasive material.

1 2. A blast gun as claimed in any one of Claims 1 to 11, wherein the sides of the body are formed so that, when similarly-shaped guns are stacked together to form a group, the sides of adjacent guns are in substantial contact with each other.

1 3. A blast gun substantially as hereinbefore described with reference to Figs. 1 to 3 of the accompanying drawings.

14. A blast gun substantially as hereinbefore described with reference to Figs. 1 to 3 of the accompanying drawings, modified substantially as herein before described with reference to Fig.

4 thereof.