In the operation of the conventional parison molding portion of an IS machine, baffle mechanism, such as that shown in Mumford, U.S. Pat. No. 3,586,494 issued June 22, 1971, requires the operation of a motor with a piston rod-guiding arrangement so that the piston rod will be rotatably oscillated about its vertical axis in a repetitive cycle which may occur as frequently as twenty times a minute. Thus, the design of the mechanism and the motor which moves the baffle arm up and down and turns the arm so that the baffles are moved into and out of mold-closing position must be of a rugged character capable of operation over long periods of time without significant break-downs.