GB2196279A

GB2196279A - Pressurized blasting machine

Info

Publication number: GB2196279A
Application number: GB08624987A
Authority: GB
Inventors: Rhoderick Jonathan Spenc Baker
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-10-17
Filing date: 1986-10-17
Publication date: 1988-04-27
Anticipated expiration: 2006-10-17
Also published as: GB2196279B; GB8624987D0

Abstract

In a pressurized abrasive blasting machine for blasting surfaces to be cleaned with abrasive, a container (12) for abrasive delivers abrasive through its outlet (13) into a delivery hose (17) carrying pressurized air. A pump (21) delivers water at a higher pressure than the air to direct a stream of water towards the outlet (13). This introduces water at a desirable position and enables wet abrasive, which conventionally will not flow properly through the outlet, to be used in the container. The water issues from a nozzle (27) coaxial with the outlet (13) and from a sprinkler head (32). <IMAGE>

Description

SPECIFICATION Pressurized blasting machine This invention relates to a pressurized abrasive blasting machine for blasting surfaces to be cleaned with abrasive.

Blasting machines are known which comprise a container for abrasive, the container having an outlet at its base controlled by a metering valve and the outlet opening into a delivery hose through which pressurized air, normally at about 100 p.s.i., is passed. The pressurized air picks up the abrasive leaving the container and directs it through a nozzle on to the surface to be cleaned. Pressurized air, also at about 100 p.s.i. is introduced into the top of the container to urge the abrasive out of the outlet.

All such known blasting machines rely on having dry, free flowing, abrasive passing through the metering valve into the air stream in the delivery blast hose. Should the abrasive become wet it will not flow and the machine becomes inoperative and, due to the nature of its assembly, time consuming measures have to be taken to clear it.

Dry abrasive emitted from the machine causes a considerable dust hazard. In order to combat this dust problem it is common to introduce water into the delivery system normally downstream of the container outlet. The introduction of water produced the danger of back flow of water into the container thus clogging up the flow through the metering valve. In addition, the abrasive cannot be recovered and re-used since it is wet.

In one known form of blasting machine the water is introduced into the delivery nozzle.

This produces an undesirable slurry like mix of water, air and abrasive which makes it difficult for the operator to see what is happening, and leaves the surface which has been sprayed needing to be washed in addition to the abrasive cleaning. In addition the operator has to handle two separate hoses, one for air and abrasive and one for water, both leading to the nozzle and to operate two separate on/off switches. He has to be trained to ensure that the water supply is turned off before the air supply and that he never sprays water near the container. These machines are tiring to use and therefore unpopular with operators.

Another known form of machine introduces water into the delivery hose upstream of the nozzle and only a short way downstream of the container outlet. This eliminates the need for the operator to carry two separate hoses and produces a more desirable mixture. However, in order to ensure prevention of flowback of water into the container these machines incorporate elaborate and very expensive valve and control mechanisms between the water inlet and the container outlet.

The present invention provides a pressurized abrasive blasting machine including means for introducing water under pressure into the abrasive container in a manner to enable flow of wet abrasive through the container outlet.

In its preferred form the present invention provides a pressurized abrasive blasting machine comprising a container for abrasive having an outlet controlled by a metering valve, a delivery hose for receiving abrasive from the outlet, first pressurized air supply means for supplying pressurized air through the delivery hose, further pressurized supply means for supplying pressurized fluid, preferably water, into the interior of the container at a pressure greater than the air pressure such that the fluid is directed in a stream towards and substantially coaxially with the outlet.

Preferably the pressure of the water is at least twice that of the air and with advantage is in the range of 400 to 600 psi., preferably 500 p.s.i. The water outlet is preferably located directly above the metering valve preferably substantially at a level at which the container starts to taper. Normally pressurized air will additionally be supplied to the upper part of the container as in conventional machines.

We have found that introducing water in this manner into the receiver causes a good flow of abrasive through the outlet/metering valve even when the abrasive is wet. By allowing the use of wet abrasive, cheaper abrasive can be used and abrasive already used can be recovered and re-used. No expensive water control valves are required since there is no harm done by water entering the container. In addition the air/water/abrasive mixture discharged through the delivery nozzle is of a form improved over that of either known blasting machine as described above.

With advantage a single switch adjacent the nozzle is arranged to automatically shut off both the air and water supplies together. The machine can be operated without a water supply where dry abrasive blasting is required.

One embodiment of pressurized abrasive blasting machine will now be described, by way of example only with reference to the accompanying sketch which shows diagrammatically a blasting machine.

In the drawing a container in the form of a hopper 12 with a tapered lower end having an outlet 13 controlled by a metering valve 14 is arranged to be filled with abrasive. A pressurized air supply 15 is connected via an on/off valve 16 to a delivery hose 17 ending in a delivery nozzle 18. The outlet 13 connects into this delivery hose. A second air supply pipe 19 ending in an upwardly facing outlet 20 and pop up valve 33 extending from the valve 16 into the upper part of the container on demand sealing the abrasive filling hole 31 and therefore pressurising the container.

A pump 21 connected to a water supply 22 is arranged to deliver water via a regulator 23 and on/off valve 24 to a pipe 25 extending into the container and having a downwardly extending leg 26 ending in a sprinkler head 32 which allows fine water jets to fan the sides of the chamber to keep the grit flowing smoothly and an outlet nozzle 27. The sprin kler is substantially at a level at which the container starts to taper. This downwardly extending leg and nozzle 27 are arranged coaxially with the outlet and the nozzle 27 ends a short distance above the outlet.

A pressurized air supply line 28 connects the pressurized supply 15 via the valve 16 to the pump to drive the pump, which could of course be driven by alternative means. The air supply 28 does not have to come from 16 it could come direct from or any other supply. A control switch 29 on the nozzle 18 is connected by an air control line 30 to both the valves 16 and 24 to simultaneously switch off and on the water supply and air supply. In use air under pressure is supplied to the delivery hose and the interior of the upper part of the container for example at a pressure of substantially 100 p.s.i. and water is supplied through the pipe 25 at a pressure more than the internal air pressure, for example at 500 p.s.i. The introduction of water immediately above the metering valve allows the flow of wet abrasive through the valve at the same time as serving to introduce water into the delivery hose.

Claims

1. The present invention provides a pressurized abrasive blasting machine including means for introducing water under pressure into the abrasive container in a manner to enable flow of wet abrasive through the container outlet.

2. A pressurized abrasive blasting machine comprising a container for abrasive having an outlet controlled by a metering valve, a delivery hose for receiving abrasive from the outlet, first pressurized air supply means for supplying pressurized air through the delivery hose, further pressurized supply means for supplying pressurized fluid, preferably water, into the interior of the container at a pressure greater than the air pressure such that the fluid is directed in a stream towards and substantially coaxially with the outlet.

3. A machine according to Claim 2 including means for introducing pressurized air into the upper part of the container.

4. A machine according to Claim 2 or Claim 3 including a switch adjacent the nozzle arranged to automatically shut off both water and air supplies substantially together.

5. A machine according to any of Claims 2 to 4 arranged to supply water at at least twice the pressure of the air supply.

6. A machine according to Claim 5 arranged to supply water at a pressure in the range 400 to 600 p.s.i.

7. A machine according to any of Claims 2 to 6 in which an outlet of the water supply means is located substantially at the level at which the lower end of the container starts to taper towards the container outlet.

8. A pressurized abrasive blasting machine substantially as described herein with reference to or as illustrated in the accompanying drawing.

9. A method of abrasive blasting substantially as described herein with reference to the accompanying drawing.