Abstract: A spray gun with an automatic valve opening control means which enables remote and stepless control of a paint spraying operation has atomizing means provided at the front end thereof, a paint valve member which enables adjustment of the amount of paint jetted out from the atomizing means, and a spray pattern adjusting valve member adapted to adjust the spray pattern by controlling the amount of compressed air jetted out from the atomizing means. A threaded slider mechanism is provided on the proximal portion of a valve body of either the paint valve member or the spray pattern adjusting valve member (or both). A servo motor and an encoder are connected to a drive screw member of the threaded slider mechanism. The encoder is adapted to detect the rotational position of the servo motor and output a controlled variable of the motor, and the servo motor is controlled in response to an external signal.

Abstract: An automatic spraying method wherein the amount of displacement of a valve member is calculated from data representing a particular spray distance by means of a microcomputer, and the valve member is activated on the basis of the displacement amount thus obtained. A curve which represents the relationship between the valve member displacement and the amount of a fluid which is to be jetted out is experimentally obtained in advance, and this curve is approximated by a plurality of straight lines or parabolas. The slopes or average slopes of these lines or curves are obtained, and the ratio between the respective slopes of the sections which are adjacent to each other is calculated. Trial spraying is carried out at two different spray distances within a range of valve member displacement amounts so as to provide a desired coating, and the relationship between the spray distance and the valve member displacement amount which provides similar coatings is obtained at two points.