Patent GB-617331-A (GB)
Title: Improvements in and relating to pneumatic spray guns and the like
IPC: B05B7/12
Filed: 1945-07-03
Abstract: 617,331. Spraying-machines; relief valves. AEROSTYLE, Ltd., and DIXON, R. B. July 3, 1945, No. 16972. [Classes 69 (iii) and 135] [Also in Group XXI] A spray head 1 is attached to a cylinder 3 in which a piston 2 is located, in axial alignment with the air needle valve 4 of the spray head, which enters the head at one end, and at the other end terminates in an enlargement intermediately of the ends of a rigid tube 5 extending from the piston and passing through an opening in the end of the cylinder 3a which is screwed into the top of the cylinder 3. Springs 7 and 10 within the tube 5 tend to urge the needle in opposite directions, while a compression spring 12 surrounding the tube 5 urges the piston towards the head of the cylinder 3. The spray head is pivoted at 13 to a frame 14, while a radius rod 15 is pivoted at 16 to a rigid extension of the cylinder body. The radius rod is hinged at 20 to a connecting rod 19 which is fixed to the frame at 21 by an adjustable pin-and-slot joint. A portion of the compressed air entering the spray head through the nipple 23 passes through the duct 24 and lifts the piston and the attached tube 5 against the spring 12 until the spring 7 is compressed, the spring 10 relaxed, and the needle 4 is unseated, allowing a spray to be produced by the gun. Further movement of the needle is prevented by the adjustable stop 26, while the tube 5 is pressed against the radius rod 15, moving the gun about the pivot 13 until the piston 2 abuts against the bottom of the cylinder 3a. On completion of a stroke, the air supply to the gun is cut off either by hand or by a valve mechanically coupled to the rod 19, the spring 12 returns the piston to the bottom of the cylinder, the needle 4 reseats, and owing to its eccentric mounting the gun returns under gravity to its original position. The amplitude of movement of the gun is controlled by adjustment of the pin 21 and the stop 27. Fig. 3 shows a modification in which the spray head 1 is pivoted at 13 and is oscillated by a double-acting pneumatic motor 42, the cylinder of which is pivoted at 44 to a bracket 41. The piston-rod 45 is hinged to the cylinder 3 of the spray head at 47, and the reversing valve 48 of the motor is actuated by an over-centre trip 49, operated by adjustable stops on arms fixed to the top of the cylinder 3. Air enters the reversing valve at 52, part operating the motor and part passing to the nipple 23 through the non-return valves 54, while the trip device ensures quick action of the valve 48, and consequent seating and unseating of the needle 4 at the ends of the strokes. A quick action valve, Fig. 4, may be provided in the air line to the nipple 23, instead of or in addition to the trip device for operating the valve 48. A jumper 55, fitting loosely in a valve body 57 is pressed by a spring 60 on to the lower of two seats 56, so as to close the input port 58. Air at sufficient pressure to overcome the spring 60, snaps the jumper to the upper seat and holds it there, since once the jumper is raised, the air pressure acts on an increased area. Immediately the air pressure falls sufficiently for the spring to unseat the jumper, the pressure on the latter is balanced, and it is snapped. to the lower seat, rapidly closing the valve. Means for altering the rate of oscillation of the spray head are described,