GB2252740A

GB2252740A - Automatic spraygun

Info

Publication number: GB2252740A
Application number: GB9026542A
Authority: GB
Inventors: Neville Thomas Pettit
Original assignee: ITW Ltd
Current assignee: ITW Ltd
Priority date: 1990-12-06
Filing date: 1990-12-06
Publication date: 1992-08-19
Also published as: GB9026542D0

Abstract

An automatic spraygun operable by high volume low pressure air comprises a spraygun body (1) which includes a threaded inlet (2) receiving air from a compressor or airline and supplies high volume low pressure air to annular chambers (3 and 4) and to a nozzle (5) which is screwed into a sleeve (7) which is sealed to a rear baffle (6) by an annular seal (8). A control ring (11) is positioned between the baffle (6) and body (1) for rotation relative to the baffle to control the flow of a fluid to be sprayed and air. The control ring (11) has a series of peripheral teeth (33) which mesh with a pinion (32) rotatably mounted in the body (1) to adjust the position of the control ring (11) relative to the baffle (6). <IMAGE>

Description

AN IMPROVED AUTOMATIC SPRAYGUN This invention relates to an improved automatic spraygun and particularly to an automatic spraygun operable by high volume low pressure air.

In our co-pending patent application serial No.

2215239A there is described and claimed a spraygun operable by low presssure high volume air comprising an air cap formed with a central spraying aperture and a fluid nozzle projecting towards the spraying aperture.

The profile of the nozzle is a plain frustum of a cone terminating at a small front face bounding an orifice through which fluid is discharged. A baffle and 2 control ring cooperate with the nozzle and the air cap to divide the delivered air between the atomisation air orifice and a spreader air orifice to control the shape of the fan of fluid being sprayed.

This known automatic spraygun is normally mounted for example in a paint spraybooth or attached to an electronically controlled robot. However, when the shape of the fan of fluid being sprayed requires alteration or adjustment the spraying process has to be discontinued for manual adjustment of the fan control ring.

It is an aim of the present invention to provide an improved automatic spraygun in which the adjustment of the fan control ring and thus the shape of the fan of fluid being sprayed can be automatically or remotely controlled.

According to the present invention there is provided a spraygun comprising a body having an axis and a nozzle having a fluid orifice for discharging a fluid jet and an air cap attached to the front of the body, the air cap defining an annular orifice about the fluid nozzle for discharging atomisation air and including a pair of horns each having an orifice for discharging spreader air means for delivering a relatively high volume flow of low pressure air to the spraygun, a baffle positioned between the barrel and the air cap, the baffle cooperating with the nozzle and the air cap to divide the delivered air between the atomisation air orifice and the spreader air orifices, a control ring positioned between the baffle and the body for rotation about an axis parallel to the body axis, the control ring having a first position wherein the flow of such delivered air through the baffle to the atomisation air and spreader air orifices is unimpeded and a second position wherein the control ring obstructs the flow of the delivered air through the baffle to the spreader air orifices, and wherein the nozzle includes a threaded end attached to the body to retain the baffle and the control ring on the body, the improvement comprising a series of gear teeth on the periphery of the control ring which mesh with a pinion rotatably mounted in the spraygun body to adjust the position of the control ring relative to the baffle.

Preferably, the gear teeth are formed on a circumferential segment of the control ring.

Conveniently, the pinion is mounted on a shaft rotatably mounted in a sleeve screwed into the spraygun body.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which; Figure 1 is a fragmentary axial section of the nozzle end of an automatic spraygun according to the invention; Figure 2 is a rear view of a baffle head forming part of the spraygun of Figure 1; Figure 3 is a front view of the baffle head shown in Figure 2; and Figure 4 is a rear view of a fan control ring also forming part of the spraygun of Figure 1.

The automatic spraygun shown in Figure 1 comprises a body 1 including an inlet 2 which is supplied, via the air valve in the rear body (not shown) of the spraygun, with compressed air (typically 68-70 psi) which, when passing through the two orifices 2A into chamber 3, is reduced in pressure by the controlled sizes of these orifices to a pressure of 10 psi.

This air flows into annular chambers 3 and 4 to a fluid nozzle 5 with a surrounding rear baffle 6. The fluid nozzle is screwed into a sleeve 7 located in the body and is sealed to the rear baffle head 6 by annular seal 8.

The front end of the spraygun carries an air cap (not shown) which screws onto the threaded portion 9 of the front baffle 10. The air cap has two horns with air passages connecting with the pressurised air supply via the annular chamber 4A which is fed by the four holes 16 passing the front and rear baffles 10 and 6.

The flow of spreader air to the horns in the air cap is regulated by the rear baffle 6 and a control ring 11 (see Figure 4), which fit one behind the other in the body 1.

The flow of fluid to be sprayed is controlled by the fluid nozzle 5 and the fluid needle (not shown) inside the fluid nozzle 5. The rear baffle 6 may be machined out of a bar and has an annular body 12 having a hole 13 through which passes a pin (not shown) which is fitted into the front baffle 10 and passes through the rear baffle 6 and the control ring 11, and locates into a hole in the face of body 1. This pin prevents the front and rear baffles from rotating relative to body 1 and acts as a stop for the angular rotation of the control ring 11. The rear baffle has a spigot 14 within which are formed four splines 15 which fit over the sleeve 7 to define there between passages for forward flow of atomising air.

As seen in Figure 4 the central bearing region 21 which is formed in separated portions, as shown, leads via cam regions 22, 23 to a pair of diametrically opposed arculate slots 24, 25 and slot 24 having a greater angular extent. When the control ring 11 is in position on the baffle 6 the pin (not shown) locates in slot 24 to define a range of angular movements of the control ring 11. The control ring is rotatable between a first position in which the holes 16 in the baffle 6 appear in slots 24, 25 to permit the free flow of spreader air, to a second position in which the holes 16 are occluded to block off the flow of spreader air. In intermediate positions the holes 16 are gradually opened or choked off and the cam regions 24, 25 enable the extent of flow to be more finely controlled.The rotation of control ring 11 also opens or closes the outer of the two holes 2A in the body which enables the pressure in the atomising chamber 4 to be maintained at 10 psi as the air flow through the air cap reduces due to the spreader air being shut off.

The control ring 11 is rotatably supported on the spigot 14 of the rear baffle by central bearing portions 21.

The front face of baffle 6 is formed with a seating face 26 for the annular seal 8 which seals the atomising chamber 4 from the spreader feed holes 16.

The control ring 11 and baffle 6 and 10 are held to the gun body 1 by the fluid nozzle 5 which has a threaded back portion 28 that screws into the threaded region 29 of sleeve 7 until the conical ring 30 seats onto the conical seat 31 of sleeve 7 The control ring 11 is partially rotated by a pinion 32 which engages an arcuate row of gear teeth 33 covering a circumferential segment of the periphery of the control ring 11. The pinion 32 is mounted to rotate with a shaft 34 having bearing surfaces 35 which engage the innter surface of a sleeve 36 screwed into the body 1. The end of the shaft 34 can be retained in the sleeve 36 with a clearance 37 by a nut 38. In operation the control ring 11 is reciprocated clockwise or anticlockwise by rotating the pinion 32 to select the required setting of the control wheel relative to the fixed baffle 6 to align the cam regions 24, 25 of the control ring with the holes 16 in the baffle 6 providing the desired air supply for the required spray pattern width and with an even distribution of the fluid.

A seal on the shaft 34 prevents leakage from the body and also provides a slight controlled resistance to rotation so that, once set to a defined position, the control ring 11 will not move until reset.

Various modifications may be made to the automatic spraygun described, for example, the control ring may be rotated by remote control e.g. from the outside of a spray booth in which the automatic spraygun is mounted.

Claims

CLAIMS:

1. A spraygun comprising a body having an axis and a nozzle having a fluid orifice for discharging a fluid jet and an air cap attached to the front of the body, the air cap defining an annular orifice about the fluid nozzle for discharging atomisation air and including a pair of horns each having an orifice for discharging spreader air, means for delivering a relatively high volume flow of low pressure air to the spraygun, a baffle positioned between the barrel and the air cap, the baffle cooperating with the nozzle and the air cap to divide the delivered air between the atomisation air orifice and the spreader air orifices, a control ring positioned between the baffle and the body for rotation about an axis parallel to the body axis, the control ring having a first position wherein the flow of such delivered air through the baffle to the atomisation air and spreader air orifices is unimpeded and a second position wherein the control ring obstructs the flow of the delivered air through the baffle to the spreader air orifices, and wherein the nozzle includes a threaded end attached to the body to retain the baffle and the control ring on the body, the improvement comprising a series of gear teeth on the periphery of the control ring which mesh with a pinion rotatably mounted in the spraygun body to adjust the position of the control ring relative to the baffle.

2. A spraygun as claimed in Claim 1, wherein the gear teeth are formed on a circumferential segment of the control ring.

3. A spraygun as claimed in Claim 1 or 2, wherein the pinion is mounted on a shaft rotatably mounted in a sleeve screwed into the spraygun body.

4. A spraygun as claimed in Claim 3, wherein there is a clearance between the end of the shaft and a nut holding the shaft in the sleeve.

5. A spraygun as claimed in Claims 3 or 4, wherein the shaft has bearing surfaces which engage the sleeve to facilitate rotation of the shaft relative to the sleeve.

6. A spraygun as claimed in any of Claims 1 to 3, wherein the shaft is connected to a drive extending to a remote location relative to the spraygun, to permit the pinion to be remotely operated.

7. A spraygun substantially as hereinbefore described with reference to and as shown in the accompanying drawings.