GB2230485A

GB2230485A - Pressurized blasting machine

Info

Publication number: GB2230485A
Application number: GB8908542A
Authority: GB
Inventors: Rhoderick Jonathan Spenc Baker
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-04-14
Filing date: 1989-04-14
Publication date: 1990-10-24
Anticipated expiration: 2009-04-14
Also published as: GB2230485B; GB8908542D0

Abstract

In an abrasive blasting machine for cleaning buildings comprising a container (12) for abrasives, the container having an air supply line (18) from a pressurized air supply via an isolator valve (59) arranged to be turned on and off by a pilot air pressure supply line (54), and having an outlet (15) controlled by a motoring valve (16) and opening into a delivery hose (21) supplied with pressurized air via the isolator valve, the isolater valve (59), preferably a ball valve, is selected so that when fully open it does not substantially restrict the air flow to the container and hose. The container includes an exhaust outlet (64) controlled by an exhaust valve comprising a length of flexible hose squeezed by a piston actuated by pilot air pressure. The metering valve (16) comprises an unflanged length of grit blasting hose (81) located in a gate valve. Preferably all of the isolator (20), exhaust (65), choke (66) and air pressure control (19) valves are controllable by pilot air pressure supplied by a common line (53) to control means (50, 51, 52) adjacent the outlet (22) of the hose (21). <IMAGE>

Description

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 abrasives, 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.

Conventionally, a source of pressurized air is connected to the hose and container via an isolator valve which can be turned on or off remotely using the pilot air pressure. Conventional isolator valves are of the double piston type serving to supply air to or cut off air from the container and hose and simultaneously to close or open respectively the exhaust outlet from the container. Thus in the on position the pilot air pressure is applied to a first piston to open a passage to the hose and container and to a second piston to close the exhaust passage; in the off position when the pilot pressure is removed the first piston is forced by the pressure of air in the supply line to close the passage to the hose and container and the second piston is forced to open the exhaust by the -pressure of air remaining in the container.Such valves severely restrict the flow of air therethrough to the hose and container and additionally suffer from the abrasive entrained in the exhaust air, which abrasive damages the material of the valve body and the seals.

It is well known for blasting machines to have additionally a choke valve downstream of the isolator valve and in the hose line, whereby the hose line can be closed or restricted thus directing more air into the container to help clear blockages in the supply of abrasive from the container.

Conventionally such valves are all manually operated and thus cannot be controlled by an operator at the nozzle end of the machine.

Additionally, with conventional machines it is not possible for the operator who is at the nozzle end to control the pressure of the air supply.

The pressurized blasting machine of the present invention has a number of novel features which may be claimed independently or together: According to one feature, the isolator valve for switching on and off the pressurised air supply to the container and hose is selected so that it does not substantially restrict the air flow when fully open.

Preferably, the isolator valve is a rotary actuated valve and preferably is a ball valve. Other known valves which fall within the selected category comprise disc valves and pinch valves but the rotary actuated ball valve is preferred since it has the best flow rate for its body size. The exhaust valve is separate from this isolator valve but controlled by the same pilot air pressure supply line.

According to a further inventive feature the exhaust valve comprises a length of flexible hose connected to the exhaust outlet of the container and a piston connected to receive the pilot air pressure supply controlling the isolator valve and arranged such that the pressure applied to the piston by the pilot air pressure acts to close the flexible hose by squeezing it and is sufficient to hold it closed against the pressure in the container. The piston carries a mandrel which sqeeezes the hose against a backing member. The hose is easily and cheaply replaceable and no exhaust air carrying abrasive contacts a valve body or its seals.

A conventional metering valve has a flexible sleeve with flanged ends which goes inside a flanged valve body and is expensive.

In another aspect of the invention the metering valve (normally manually operable although it could be remotely controllable by air pressure) uses only a simple unflanged length of ordinary gritblasting hose held in place by two standard reducing nipples in a conventional gate valve By another feature the choke valve is arranged to be remotely operable from the nozzle end of the hose.

Preferably an air pressure control valve is connected between the air pressure supply and the isolator valve and is adjustable from the nozzle end of the hoze to vary the air pressure. The isolator and air pressure control valve may be a common valve. Preferably, all the isolator, exhaust, choke and air pressure control valves are controllable by pilot air pressure and the same supply line supplies pilot air to the operating means at the nozzle to control all four valves.

The pressure blasting machine is preferably of the type described in my co-pending Patent Application No: 8624987 (published No: 2196279) in which the abrasive can be used either wet or dry, with water, when used, being supplied into the container. Alternatively the water can be supplied directly into the hose at any convenient point.

When used with this type of machine, preferably the water and air supplies can be cut off together using a single control adjacent the nozzle end of the hose.

The container and metering valve normally have a greater height than horizontal dimensions and it is convenient when transporting the machine in a vehicle to turn it through approximately 900 onto its side so that its longest dimension is substantially horizontal. According to another feature of the present invention, the container is provided with wheels or other rolling or sliding members on which it can be easily transported on its side. This assists loading of the container into and out of a vehicle.

One embodiment of blasting machine, incorporating the various features of the invention, will now be described by way of example only, with reference to the accompanying drawings of which: Figure 1 is a diagramatic view of a blasting machine showing a container, air and water supply lines, control valves and a hose, Figure 2 is a diagramatic view taken at right angles to the view of Figure 1 and showing the interior of the container but omitting some of the control and supply lines and valves or showing these diagrammatically, Figures 3a and 3b show, in section, one form of isolator valve, respectively in closed and open positions, Figure 4a and 4b show, in section, one form of metering valve, respectively in open and closed positions, and Figures 5a and 5b show, in section, one form of exhaust valve, respectively in open and closed positions In the drawings, a container in the form of a hopper 12 has a tapered lower end 14 ending in an outlet 15 controlled by a metering valve 16 having a control mechanism 17 for varying the passage through the valve. The internal surface of the container is coated with a layer of plastics material e.g. Nylon by spraying with plastics powder and baking the coating. The container is arranged to be filled with abrasive. A pressurized air supply line 18 is connected via an air pressure control valve 19 and an isolator valve 20 to a delivery hose 21 ending in a delivery nozzle 22. A choke valve 23 is located in the hose downstream of the isolator valve, and the hose upstream of the choke valve is connected into the container via a line 24 having an upwardly facing outlet 25 housing a poppet valve 26. Pressure in this line 24 acts to raise the poppet valve 26 thus closing an abrasive filling opening 27 in the top 28 of the container and allowing the container to become pressurized.

A pump 31 connectable to a water supply via line 32 and quick release coupling 29 is arranged to deliver water via a remote controlled on/off water valve 33 and a manual on/off water valve 34 to a pipe 35 extending into the container and having a water distribution nozzle 37 located substantially at the height of the top of the conical part of the container. The water distribution nozzle 37 has first water outlet means 38 to distribute a substantially horizontal or horizontal and downwardly directed spray to wash the walls of the conical part of the container and a second pencil nozzle outlet 40 directing a stream of water downwardly coaxially with the container outlet 13. As shown in Figure 1 the pump is driven by pressurized air supplied from an always live pilot air supply line 39 through line 42 and a regulator and filter 43, but clearly could be driven by other means.The water pressure should be greater than the air pressure in the hose, preferably 400 to 600 p.s.i. In the alternative shown in Figure 2, a water outlet hose 44 is connected to the outlet of a pump 45, which hose can be introduced into the blast hose 21 at any convenient point.

The isolator valve 20 is a ball valve 59, controlled by a rotary actuator 60 operable by pressure in a pilot air control line 61 itself connected through a shuttle valve 62 with the pilot air supply line 39. The ball valve is shown in greater detail in Figure 3 and as seen in the fully open position does not produce any substantial restriction in the flow passage through the valve.

The choke valve 23 is also a rotary actuated ball valve having a ball valve 66, a rotary actuator 67, and a shuttle valve 68 controlling the connection 69 between the rotary actuator and the supply line 39. The ball valve 66 again produces no substantial restriction into the hose line when in its fully open position and the shuttle valve is controllable from adjacent the nozzle end of the hose.

An exhaust outlet 64 of the container is connected via a flexible hose 65 to the atmosphere via an on/off exhaust valve 49, seen in Figure 5 and separate from the isolator valve 20. The exhaust valve comprises a cylinder 75 in which a piston carrying a mandrel 77 is slidable. The cylinder is secured to the hose 21 and the hose 65 passes between the mandrel 77 and a backing plate 78 also secured to hose 21. The cylinder is connected to a pilot air supply line via line 80 so that pressure in this line is sufficient to squeeze the hose 65 between the mandrel 77 and plate 78 to a closed position. When pressure in line 54 is released the pressure in the container is sufficient to open the hose 65 to exhaust the pressure in the container. The hose 65, or the relevant section thereof, is easily and cheaply replaced and the grit in the exhaust air does not contact any other valve part.

The metering valve 16, seen in Figure 4, similarly uses a flexible hose 81 cut from a length of grit blasting hose and located by two standard reducing nipples 82 as the only valve parts contacted by the abrasive. In this case the flexible hose 81 is in a conventional gate valve closed by a mandrel 83 operated by a rotatable member 17.

The nozzle end of the hose is provided with three separate control operating members 50, 51 and 52, each of which is an air pressure control, the operating means each being connected to a common pilot air inlet line 53 connecting to the line 39 for always supplying air under pressure. When operating lever 50 is depressed to close an exhaust hole in the supply line it connects supply line 53 to supply air under pressure via line 54 to the shuttle valve 62 of isolator valve 20 and to the water control valve 33 to act as an on/off switch simultaneously for the water and air supply and an off/on switch to the exhaust valve. The operating means 51 is connected by line 49 to the air pressure control valve 18 and is adjustable to vary the air pressure supplied to the hose. The operator means 52 is connected by choke control line 48 to the shuttle valve 68 of the choke valve 23 to vary the restriction of the choke

Claims

CLAIMS 1. An abrasive blasting machine comprising a container for abrasives, the container having an air supply line adapted to supply air under pressure from a pressurized air supply via an isolator valve, the isolator valve being arranged to be turned on and off by use of the pressure in a pilot air pressure supply line, the container having an outlet at its base controlled by a metering valve, the outlet opening into a delivery hose adapted to be supplied with pressurized air via the isolator valve and in which the isolator valve is selected so that when fully open it does not substantially restrict the air flow from the pressurized air supply to the container and hose.
2. A machine according to Claim 1 in which the isolator valve is a rotary actuated valve.
3. A machine according to Claim 2 in which the isolator valve is a ball valve.
4. A machine according to any of Claims 1 to 3 in which the container includes an exhaust outlet controlled by an exhaust valve, and in which the exhaust valve comprises a length of flexible hose connected to the exhaust outlet and a piston connected to receive the pilot air pressure supply controlling the isolator valve and arranged such that the pressure supplied to the piston by the pilot air pressure acts to close the flexible hose by squeezing it and is sufficient to hold it closed against the pressure in the container in operation.
5. A machine according to Claim 4 in which the piston carries a mandrel which squeezes the hose against a backing member, preferably carried by the delivery hose.
6. A machine according to any of Claims 1 to 5 in which the metering valve comprises an unflanged length of grit blasting hose located in a gate valve so that it can be squeezed to reduce the flow.
7. A machine according to any of Claims 1 to 6 including a choke valve located in the delivery hose downstream of the isolator valve and supply line to the container, and including control means adjacent the outlet end of the delivery hose for operating the choke valve.
8. A machine according to any of Claims 1 to 7 including an air pressure control valve for controlling the air pressure supply to the container and delivery hose and including control means adjacent the outlet end of the delivery hose for varying the air pressure control valve to vary the air pressure supplied to the delivery hose and container.
9. A machine according to any of Claims 1 to 8 in which all of the isolator, exhaust, choke, and air pressure control valves are controllable by pilot air pressure supplied by a common line to control means adjacent the outlet end of the delivery hose.
10. A machine according to any of Claims 1 to 9 in which the container and metering valve together have a greater height than the horizontal dimensions of the container and in which the container is provided with wheels or other rolling or sliding members on which it can be easily transported when it is turned through 900 so that its major dimension extends substantially horizontally for conveyance.
11. A pressurized abrasive blasting machine substantially as described herein with reference to or as illustrated in the accompanying drawings.