Spray coating control system

Abstract

A spray-coating control system for automatically spraying articles moved through a spray-coating region by a conveyor is disclosed. A pulse generating means such as a shaft encoder, which is connected to the conveyor, generates conveyor movement pulses in response to movement of the conveyor. These pulses are processed by a timing signal generating circuit to produce timing signals at a fraction of the frequency of the conveyor movement pulses and in synchronism therewith. The timing signals are used to control the operation of the sprayer synchronously with the movement of the articles through the spray-coating region. Hangers for suspending the articles from the conveyor are nominally equally spaced along the conveyor. These hangers can, however, be positioned at varying distances from one another along the conveyor due to stretching of local sections of the conveyor. In order for the timing signals to be generated at a frequency representative of the true movement of the hangers, and therefore the true movement of the articles to be sprayed, even when the distance between hangers varies, the hangers serve as signal elements and are sensed by a hanger detector which generates a hanger detection signal generated every time a hanger is sensed. Each of these hanger detection signals resets the timing signal generating circuit which then begins to operate in response to pulses from the pulse generating means and generates a timing signal each time a first predetermined number of pulses from the pulse generating means has been received, until a second predetermined number of timing signals has been received.