Fluid handling – Systems – Sequentially progressive opening or closing of plural valves
Patent
1994-06-23
1995-10-24
Nilson, Robert G.
Fluid handling
Systems
Sequentially progressive opening or closing of plural valves
239407, 239528, B05B 712
Patent
active
054602033
DESCRIPTION:
BRIEF SUMMARY
This invention relates to an air valve more particularly for controlling the feedback air in HVLP spray guns.
An aim of the present invention is to shut off the feedback line when the spraygun is in the Off position.
According to the present invention there is provided an air valve for controlling the feedback air in spray guns comprising a valve body and a fixed valve member, a spindle slidable and sealingly passing through the valve body and valve member, the spindle having a shoulder engaging and closing a first seating in the valve member the rear of the spindle slidable in a shuttle which is itself slidable in a fixed valve spool, the spool having a second seating closed by the rear of the shuttle wherein two ports are provided one at either side of the second seating between the spool and shuttle for the passage of feedback air past the valve and two further ports are provided one at either side of the first seating between the valve member and spindle shoulder for the passage of main air through the valve so that operation of the spindle opens the first seating prior to the second seating and closes the second seating prior to the first seating.
Preferably, the spindle is returned to its closed position by a spring engaging the valve spindle. An embodiment of an air valve according to the invention will now be described by way of example only, with reference to the accompanying drawings, in which:
FIG. 1 is a cross-sectional elevation of a spray gun fitted with an air valve; and
FIGS. 2 to 5 are diagrammatic cross-sections of the air valve shown in FIG. 1 in different operational positions.
The spray gun shown in FIG. 1 comprises a main body 1, a handle 2 and an air cap 4. The paint is fed from a reservoir under the control of a regulator (not shown).
The air valve illustrated controls the feedback air sensed at the gun air cap 4 and is operated by the gun's trigger 5.
FIG. 2 illustrates the air valve in the off position with an operating spindle 6 in a released or forward position with its shoulder 7 engaging a first seating 8 of a stationary valve member 9. The spindle 6 passes through a hole in member 9 and an air valve body 10 with the interposition of a rubber or resilient plastics seal 11.
The valve member 9 is aligned with a valve spool 12 with annular ports 13 and 14. Sliding in the valve spool is a slidable shuttle 15 one end of which engages the rear of the spindle shoulder 7 and its other end is engageable with a cup 16 spring loaded by a spring 17 in the gun body 1.
A second seating 12a on valve spool 12 cooperates with a shoulder 15a on the shuttle 15 to provide a closeable passage between the inlet port 22 and the outlet port 23. The shuttle 15 and valve spool 12 are sealed between one another by O-ring seals 18 and 19 respectively and the shuttle 15 is sealed in the body 1 of the spray gun by an O-ring seal 20.
The feedback line is connected to the end of the spray gun handle 2 via pipe 21 which is connected to the air valve at port 23. The air pressure fed back from the air cap 4 is connected to the air valve at port 22. The main air enters the air valve at the main inlet 24 and leaves the air valve at the main port 25 to the atomising/spreader air circuit.
FIGS. 3 to 5 illustrate three operational positions of the trigger 5 from a slight pressure on the trigger to its fully depressed position.
It will be appreciated that the smooth operation of the trigger 5 will control the flow of the main air to the air cap 4 based on the pressure of the feedback air sensed at the gun air cap to maintain a fixed air pressure e.g. 10 psi (0.7 bar) at the air cap.
Applying a slight pressure to the trigger 5 causes a rearward movement of the operating spindle 6 opening the first seating 8 by rearward movement of the spindle shoulder 7. This allows air to pass from the main inlet 24 to the main port 25 (See FIG. 3). Further pressure on the trigger 5 moves the operating spindle 6 so that the shuttle 15 is engaged by the rear of the spindle shoulder 7.
Full pressure on the trigger 5 moves the operating
REFERENCES:
patent: 3327949 (1967-06-01), Eull
patent: 5284299 (1994-02-01), Medlock
Bate Anthony J.
Smith Rowland C.
ITW Limited
Nilson Robert G.
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