GB2230211A - A wet abrasive blasting machine - Google Patents

Abstract

A wet abrasive blasting machine comprises a pressure vessel (1) having upper and lower dished ends (2) and an internal fixed funnel (6) dividing the vessel into upper and lower chambers (A, B). An abrasive/liquid mixture is introduced into the upper chamber (A) and clean water into the lower chamber (B). A tortuous passage or labyrinth between the bottom (7) of funnel (6) and an upstanding tubular member (8) enables some abrasive material to enter the labyrinth but prevents the flow of further abrasive material into the clean water chamber (B). The vessel (1) and a blast hose (23) are pressurised. Valves (10, 12) control the supply of abrasive/ liquid mixture and liquid respectively to blast hose (23) whilst an operator's handle (25) controls a pinch valve (22) to enable the machine to be used by a single operator. <IMAGE>

Description

A WET ABRASIVE BLASTING MACHINE THIS INVENTION relates to abrasive blasting machinery in which a liquid/abrasive mixture is fed from a pressurised vessel into an entrainment delivery line to an outlet nozzle controlled by an operator.

It is an object of the present invention to provide a wet abrasive blasting machine which is so constructed and arranged that it may be used by a single operator, does not require a separate pump unit for delivering additional liquid into a delivery pipe along with the liquid/abrasive mixture, and wherein the mixture and the liquid are contained within separate chambers which communicate via means substantially preventing the flow of abrasive material into the liquid chamber.

According to the present invention there is provided a wet abrasive blasting machine comprising a pressure vessel having therein separate chambers adapted to contain respectively a liquid/abrasive mixture and a liquid, at least one inlet for the introduction of an abrasive material and the liquid, an outlet for the mixture and a separate outlet for the liquid, a delivery pipe having valved connections to the two outlets, and means for delivering pressurised fluid to the delivery pipe to entrain the mixture therealong and also to the interior of the vessel to effect and maintain a pressure balance between the latter and the delivery pipe to facilitate the egress of mixture out of the vessel into the delivery pipe; the machine being characterised by a labyrinth interconnection between the chambers so disposed as substantially to prevent the passage of abrasive material into the liquid chamber.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawing which is a vertical sectional view of a wet abrasive blasting machine made in accordance with the invention.

The machine comprises a pressure vessel consisting of an outer cylindrical shell 1 with dished upper and lower ends 2. An orifice plate 3 is centrally disposed within upper dished end 2 and houses a rubber sealing ring 4 against which an inverted dished air lock valve 5 seals when the vessel is pressurised. The valve 5 sits loosely over the open end of a pipe 19 delivering pressurised fluid as will be described.

A funnel 6 of inverted conical form is rigidly fixed within the cylindrical shell 1 essentially to divide the vessel into upper and lower chambers A and B. The bottom of the funnel terminates in a straight cylindrical section 7 having an open lower end positioned centrally above a bottom outlet plate 9. Surrounding the cylindrical section 7 and upstanding from a rigid connection to bottom plate 9 is a short length of tube 8 open at its upper end and of a diameter just greater than that of cylindrical section 7, so that the latter together with tube 8 forms a labyrinth interconnection between chambers A and B.

Attached to the bottom of plate 9 is a valve 10 to control the flow of liquid/abrasive mixture from the vessel. Thus plate 9 and valve 10 form an outlet for the mixture immediately beneath the cylindrical section 7 at the bottom of funnel 6.

An additional outlet 11 for chamber B is provided in the bottom dished end 2 outside of the tube 8 and includes a valve 12 to control the flow of liquid, as will be described, from this chamber.

A pressure equalising pipe 13 is attached to the upper region of funnel 6 and forms a communication between the upper regions of chambers A and B.

Liquid, in this case water, is fed to the vessel via a T-piece 14 which is connected to a water supply pipe via a valve 15. An adapter 16 is attached to the T-piece 14 and carries a pipe 17 having an open end into chamber A and positioned within the T-piece 14. Pipe 17 and adapter 16 communicate with an overflow pipe having a control valve 18.

With this arrangement, water may flow into the vessel via valve 15 and T-piece 14 and when the level in the vessel reaches the pipe 17 it may overflow via adapter 16 and valve 18. The supply/overflow system just described provides a single physical connection to the interior of the vessel.

Pressurised air fed into the vessel via supply pipe 19 is adapted to lift air lock valve 5 into contact with sealing ring 4. Once valve 5 is closed in this way pressurised air may continue to flow from beneath valve 5 into the remainder of the vessel.

Mounted below control valve 10 is a mixing chamber 21 designed to ensure correct entry of a liquid/abrasive mixture into an air stream supplied to the chamber 21 via a non-return valve 20. After leaving the chamber 21 the mixture entrained in the air stream passes via a pinch valve 22 to a blast hose 23 having an outlet nozzle 24 and operators handle 25 (shown schematically) of conventional form.

The machine is operated in the following manner.

With the vessel depressurised and all valves in a fully closed position, water inlet valve 15 and overflow valve 18 are both opened. Thus water flows into chamber A and via the labyrinth interconnection 7/8, also into chamber B.

The pressure equalising pipe 13 permits both chambers to fill until the level reaches overflow pipe 17 whereupon the operator seeing water flowing from the overflow pipe then closes valves 15 and 18.

Thereafter, an abrasive material which may be sand, granules, pellets or beads, is introduced into chamber A through orifice plate 3 with air lock valve 5 open. When a predetermined quantity of abrasive material has been introduced into the vessel, pressurised air is fed through pipe 19 to close vessel 5.

The inclined angle of funnel 6 is designed to be greater than the natural angle of repose of the abrasive material so that the latter may descend into cylindrical section 7, and a small quantity enters the annular passage, or labyrinth connection, between section 7 and tube 8 and rises therein to a level approximately a quarter to a third of the height of tube 8. In this way, the abrasive material is mixed with water in chamber A whilst chamber B contains clean water alone. The pressurised air fed to the vessel via pipe 19 maintains equilibrium between chambers A and B and so the system is then ready for operation once control valve 10 is opened and a pressurised air stream is fed to chamber 21.

With valve 12 closed, control valve 10 is opened to the required setting as determined by the operator. The flow of liquid/abrasive mixture may then be instantaneously started and stopped from the operator's handle 25 close to the outlet nozzle 24.

During the blasting operation additional water may be introduced into the mixture through the clean water valve 12 in order to dilute the liquid/abrasive mixture if required.

Also, at any time before or during the operation the surface to be blasted may be washed down with clean water by closing valve 10 and opening valve 12.

The machine presents several advantages when compared with convention equipment of this kind. For example, the labyrinth interconnection between chambers A and B is so formed as to ensure a continuous smooth and surge-free flow of the liquid/abrasive mixture into the outlet. The labyrinth also eliminates any possibility of contamination of the water in chamber B by the abrasive which resides within the labyrinth as a filter.

The height of the tube 8 within vessel B ensures that there always remains a reservoir of clean water in the bottom of the chamber whilst valve 12 is closed. This water may be used, for example, to wash down a work surface after a blasting operation.

The combined water fill and overflow connection comprising T-piece 14 and adapter 16 with pipe 17 and valves 15 and 18, provides a single connection to the vessel.

Furthermore, the funnel shaped dividing wall between chambers A and B within the vessel eliminates the possibility of abrasive retension whilst minimising overall vessel height to facilitate the abrasive filling.

The equalising pipe 13 is of such a diameter as to ensure the integrity of the filter system within the labyrinth when wash down valve 12 is fully open and abrasive control valve 10 is closed.

Still further, a combination of pinch valve 22 non-return valve 20 and the blast hose with an operator's handle is so arranged as to provide an instantaneous stop and start system without the need to depressurise or repressurise the vessel. This minimises consumption of compressed air. Also, the combination just described eliminates the need to close or open the abrasive control valve 10 or the wash down water valve 12 when stopping or starting during the process, thus enabling the machine to be used by a single operator.

Whilst the pressure vessel is preferably constructed of mild steel or other metal, in certain applications where relatively low pressures are imposed within the vessel, it may be made of a rigid and durable plastics material or of glass reinforced plastic.

In a simplified form of the machine, the air lock valve 5 may be replaced by a manually screwed plug.

Claims (11)

1. A wet abrasive blasting machine comprising a pressure vessel having therein separate chambers adapted to contain respectively a liquid/abrasive mixture and a liquid, at least one inlet for the introduction of an abrasive material and the liquid, an outlet for the liquid/abrasive mixture and a separate outlet for the liquid, a delivery pipe having valved connections to the two outlets, and means for delivering pressurised fluid to the delivery pipe to entrain the mixture therealong and also to the interior of the vessel to effect and maintain a pressure balance between the latter and the delivery pipe to facilitate the egress of mixture out of the vessel into the delivery pipe; the machine being characterised in that the two chambers are interconnected in the region of the mixture outlet by a tortuous passage so disposed as substantially to prevent the passage of abrasive material into the liquid chamber.

2. A wet abrasive blasting machine according to Claim 1, wherein said pressure vessel comprises an outer cylindrical shell with dished upper and lower ends, the upper dished end having the inlet for introduction of the abrasive material, said lower dished end having the separate outlets for the mixture and the liquid, and a funnel rigidly fixed within the cylindrical shell to divide the vessel into upper and lower chambers.

3. A wet abrasive blasting machine according to Claim 2, wherein said funnel terminates at its lower end in a straight cylindrical section having an open lower end positioned centrally above the outlet for said mixture-.

4. A wet abrasive blasting machine according to Claim 3, wherein, upstanding from the outlet for said mixture is a tubular member open at its upper end and of a diameter just greater than that of the cylindrical section of said funnel so that the latter, together with the tubular member forms the interconnection between said two chambers in the manner of a labyrinth.

5. A wet abrasive blasting machine according to any preceding claim, including a liquid inlet connected to the chamber adapted to contain the liquid/abrasive mixture, said liquid inlet being combined with an overflow duct such that when the pressure vessel is filled to the level of said liquid inlet, overflowing liquid provides an indication to the operator that the vessel is filled with liquid to the required level.

6. A wet abrasive blasting machine according to any one of Claims 2 to 4, including a pressure equalising pipe passing through the funnel wall between the upper and lower chambers.

7. A wet abrasive blasting machine according to any preceding claim, wherein a pressurised fluid delivery pipe is connected to the chamber adapted to contain the liquid/abrasive mixture.

8. A wet abrasive blasting machine according to any one of Claims 2 to 4, wherein the inlet for the introduction of the abrasive material is adapted to be closed by a valve which rises to seal an associated aperture upon pressurisation of the interior of the pressure vessel.

9. A wet abrasive blasting machine according to any preceding claim, wherein said delivery pipe terminates in an outlet nozzle with an operator's handle to enable the operator to open and close the delivery pipe at a position remote from the valved connection thereof to the outlets of the pressure vessel.

10. A wet abrasive blasting machine according to Claim 2, wherein the angle of inclination of the funnel wall is designed to be greater tnan the natural angle of repose of the abrasive material so that the latter may descend into the lower region of the funnel whereby a small quantity of said material may enter the tortuous passage between the chambers.

11. A wet abrasive blasting machine substantially as hereinbefore described with reference to and illustrated in the accompanying drawing.