Abstract: In tack seat lasting machines, variation of the tack (nail) pattern is achieved by varying the wiper inwiping movement, itself dependent upon their lengthwise movement. Such variation also alters the "back tack" position (i.e. relationship between the heel band backseam region and corresponding region of the wipers). In accordance with the invention, the nail pattern is varied by an operator-set reference potentiometer (198) by matching with its signal that of a linear potentiometer (190) which controls operation of wiper-operating motor (72, 74). The back tack position is controlled by a motor (105) according to an operator setting of a reference potentiometer (208). The combined signal from the reference potentiometers (198, 208) is compared with a control signal of a linear potentiometer (202) associated with the heel band, the motor (105) being operated until the compared signals match.

Abstract: An apparatus for applying pressure and a high frequency electric field to material, comprising a cavity for containing the electric field which encloses platens relatively movable to apply pressure to material placed between the platens. The cavity electrically communicates with the platens for supplying the contained electric field to the platens which, in turn, cooperate with each other to apply the field to the material between the platens. The cavity and the platens are also directly coupled into the means for generating the electric field as a resonant circuit. The apparatus includes a triode tube having means for preventing excessive current therethrough as voltage is first applied, and means for operating the triode under optimum conditions utilizing an automatically variable capacitor to maintain a predetermined grid current for a workpiece placed within the apparatus after full voltage has been applied.