Work article handling system in surface treatment apparatus

Claim 1

In a surface treatment apparatus wherein a work article is immersed successively in a plurality of treatment tanks arranged in a sequence and containing respective treatment liquors thereby to subject the article to successive surface treatments, the combination therewith of a work handling system comprising: a crane traveling way laid out along said sequence of tanks; a traveling crane adapted to travel along the crane traveling way and having a hoist mechanism for raising and lowering the article out of and into each of the tanks, a travel motor for driving the crane along the traveling way, at least one hoist motor for driving the hoist mechanism, and a motor control device operating in response to command signals to controllable operate each motor; and a control system for controlling said travel and hoist motors in a manner such that the crane is driven to undergo a travel with a repeated horizontal speed pattern comprising, in sequence, a specific period of steady acceleration starting from the center of each tank to a high speed, a specific period of travel at the high speed, and a period of steady deceleration terminating at zero speed at the center of the succeeding tank, and in a manner such that the hoist mechanism is driven to lower the article with a vertical speed pattern comprising, in sequence, an initial period of low speed, a period of high speed until the lower end of the article approaches the surface of the treatment liquor in said tank, a period of low speed until the lower end of the article has entered the liquor, a period of high speed until the lower limit of descent of the article is approached, and then a period of low speed until said lower limit is reached and to raise the article with a vertical speed pattern comprising at least an initial period of low speed, a period of high speed until the upper limit of ascent of the article is approached, and then a period of low speed until said upper limit is reached.