GB2138706A

GB2138706A - Spray gun having an air control valve

Info

Publication number: GB2138706A
Application number: GB08408727A
Authority: GB
Inventors: A T Watkins
Original assignee: Commonwealth Industrial Gases Ltd
Current assignee: Commonwealth Industrial Gases Ltd
Priority date: 1983-04-08
Filing date: 1984-04-05
Publication date: 1984-10-31
Also published as: GB2138706B; IT1180689B; GB8408727D0; JPS59196770A; ES8503260A1; IT8448003A1; AU1325483A; ES531369A0; ZA842114B; IT8448003A0

Abstract

Manually operable valve 20 is provided in a spray gun in addition to conventional trigger operated valves 5, 7, to control precisely flow of atomising air. The valve comprises a sleeve 21 having a cam-shaped outer surface which varies the size of the output from an air supply duct 4 on rotation of the valve by means of a knob 18. <IMAGE>

Description

SPECIFICATION Air control valve This invention relates to air control valves for the purpose of providing precise control of air to nozzles of spray guns used to spray paint or other liquids.

Air supply to a spray gun nozzle can be regulated in a variety of ways. One example is a simple on or off valve controlled by a trigger in the handle of the gun and manipulated by the operator.

It is desirable to adjust the rate of air flow whilst the spray gun is in operation. It is even more desirable that this be accomplished by the operator during the spraying operation.

An object of this invention is to provide a device which permits the operator to make precise adjustments to the volume of air supplied to the spray gun nozzle during its operation. A change in the total volume of air supplied to the spray gun nozzle is advantageous in many instances, for example when it is desired to paint in a restricted area and also when limiting the overspray.

One way of adjusting the total volume of air is by fitting a separate control valve in the air supply line. This increases the cost of the spray gun and is inconvenient in that the control valve is beyond the reach of the operator's hand during the spraying operation.

The invention consists in a spray gun of the kind comprising: a gun body consisting of a barrel portion having a spray nozzle assembly at one end and a hand piece joined by one of its ends to the other end of the barrel portion, a flow-control duct which extends longitudinally of said barrel portion and opens into the spray nozzle assembly, an air supply union on the distal end of the hand-piece which opens into one end of an air supply duct the other end of which opens into the flow-control duct, a liquid supply union feeding said nozzle assembly, a manually operable liquid-flow control valve to control liquid-flow to said nozzle assembly, an on-off valve in said air supply duct, and a manually operable trigger, so arranged that upon being depressed it opens said on-off valve and said liquid flow control valve, said spray gun being characterised in that:: a control valve varying the amount of air passing into the flow-control duct is axially co incident with said control duct, said control valve comprising a sleeve whose longitudinal axis is parallel to the longitudinal axis of said duct and whose outer radial surface fits closely within said duct, one end of said sleeve being connected to a control knob for rotating said sleeve, the other end of said sleeve being formed in the shape of a cam whose one side restricts or closes the opening of said air supply duct into said flow control duct and whose other side progressively permits air flow therebetween.

The control valve can vary the amount of air passing to the spray nozzle from a minimum value which may be zero to full flow as the operator conveniently turns the knob connected to it. The control is effected smoothly due to the cam action which progressively opens or closes the orifice through which the air flows.

By way of example, an embodiment of the above described invention is described hereinafter with reference to the accompanying drawings: Fig. 1 is a medial cross-sectional elevation of a spray gun incorporating a preferred form of the invention.

Figure 2 is a cross-section along the line 2-2 during full-flow.

Figure 3 is a cross-section along the line 2-2 when flow is stopped or reduced to a minimum value.

With reference to Figure 1 , the gun body consists of a barrel portion 1 having a spray nozzle assembly 11 and a hand-piece 2. Air Supply duct 3 opens into the flow-control duct 1 2 through valve 5 and passage 4. On-off valve 5 is operated by trigger 6 as is the liquid-flow control valve 7, obviously, the trigger 6 opens both valves to operate the spraying function. Flow-control duct 1 2 extends longitudinally of the barrel portion and opens into the spray nozzle assembly 11 through channels 13 and 14 to orifices 15 and 1 6 respectively. In the spray-gun shown in Figure 1 an optional fan-spread control is achieved by rod 17 in flow-control duct 12.Rod 17 is movable longitudinally by the rotation of knob 18 which acts on screw thread 1 9 to change the ratio of air flow passing through orifices 1 5 and 1 6. Such a device is well-known in the art.

What is wholly new is the control valve 20 which consists of a cylindrical sleeve 21 fitted closely within the flow-control duct 1 2 and mounted co-axially with the fan-spread control rod 17. Control valve 20 varies the total amount of air supplied to the nozzle assembly 11. Neither the main air valve 5 nor the fan-spreader control rod 17 accomplish this. The control valve 20 is responsive to knob 22 which rotates sleeve 21 to vary the flow of air by progressively uncovering passage 4 by means of its cam-shaped periphery.

An extremely compact arrangement is achieved with both control elements 1 8 and 22 convenient to the hand of the operator. It will be obvious to those skilled in the art that the control valve 20 can be fitted and operated in the flow-control duct without the pressence of the fan-spread control rod 17.

As shown in Figures 2 and 3, the outer surface of sleeve 21 is cam-shaped so that when rotated with the cam surface away from air supply passage 4 the full flow from the air compressor is supplied to flow-control duct 1 2 and when rotated 1800 the flow may be stopped as shown in Figure 3.

Smoothness of operation is enhanced by having the cam surface shaped to provide a tapered opening 25.

The preferred embodiment shown in Figure 1 shows knob 22 loaded by spring tension 23 against a stationary part 24 with the mating faces being provided with corresponding serrations. By this means knob 22 can be rotated in discrete angular increments, each of which provides a finite change in the air supply. This provides the operator with a ready means of selecting his air supply for a given job by counting the number of "clicks" or steps the knob is advanced or retarded.

Claims

1. A spray gun of the kind comprising: a gun body consisting of a barrel portion having a spray nozzle assembly at one end and a handpiece joined by one of its ends to the other end of the barrel portion, a flow-control duct which extends longitudinally of said barrel portion and opens into the spray nozzle assembly, an air supply union on the distal end of the hand-piece which opens into one end of an air supply duct the other end of which opens into the flow-control duct, a liquid supply union feeding said nozzle assembly, a manually operable liquid-flow control valve to control liquid-flow to said nozzle assembly, an on-off valve in said air supply duct, and a manually operable trigger, so arranged that upon being depressed it opens said on-off valve and said liquid flow control valve, said spray gun being characterised in that: : a control valve varying the amount of air passing into the flow-control duct is axially coincident with said control duct, said control valve comprising a sleeve whose longitudinal axis is parallel to the longitudinal axis of said duct and whose outer radial surface fits closely within said duct, one end of said sleeve being connected to a control knob for rotating said sleeve, the other end of said sleeve being formed in the shape of a cam whose one side restricts the opening of said air supply duct into said flow control duct and whose other side progressively permits air flow therebetween.

2. A spray gun as defined in claim 1 wherein said knob is held in position by a spring-loaded ratchet to permit step-wise rotation of said knob and connected sleeve.