GB789081A - An improved machine for hobbing the teeth of gear wheels - Google Patents

Abstract

789,081. Gear-cutting. BROWN MACHINE TOOLS, Ltd., D. Feb. 27, 1956 [Nov. 25, 1954], No. 34142/54. Class 83 (3). A gear-hobbing-machine comprises a bed 1 carrying work-driving-means, and a hob 13 angularly adjustable on a slide 9 movable on the face of a cradle 8, the cradle being angularlyadjustable on a head 7 movable to-and-from the work. The hob is rotated through changegearing by a reversible main motor in the machine-bed, which also rotates two oppositelyrotating bevel gears 45, 46, which rotate a faceplate 5 in one or other direction according to the setting of a clutch-lever 48, through changegears 49-52. The slide 9 is traversed by an hydraulic-piston 62, movement of the slide causing a rack to rotate a pinion connected to two adjustable cam-discs, one of which operates a switch 70 to reverse the slide-movement when cutting is complete, and the other operates a switch 71 to stop the slide in its initial position. The head 7 is adjusted to-and-from the work by a screw. The hob is fed into the work at the beginning of a cut by a piston 78 to which the screw is attached, the stroke of the piston being determined by adjustment during setting-up according to a depth-of-cut dial 87. In operation, a valve-lever 151 is moved manually to clamp the work against the face-plate 5 by a ram 97, and to extend a tailstock 6 by a ram 99, the valve returning automatically to neutral when clamping is complete. A button is then pressed to start the main motor and to operate a valve 103 causing the piston 78 to advance the head 7 to cutting-position at a rate determined by a valve 107. Pressure then builds up to operate hydraulic means 90 to clamp the head to the bed. After a time delay, the piston 62 is actuated to traverse the hob along the work at a speed determined by a valve 115. When hobbing is complete the switch 70 is operated to actuate the valve 103, causing the clamps 90 to be released and the head 7 to be withdrawn. In its rearward position, the head actuates a switch 119 to stop the main motor. Pressure build-up then causes a valve 117 to pass fluid to the piston 62 and return the hob-slide 9. Finally, the valve 94 is actuated manually to release the work. If the valve 94 is accidentally operated during cutting, a switch 121 stops the machine. To ensure even wear of the hob, the hob is carried on a slide 123 which is movable by small increments between cuts, and is clamped during cutting by hydraulic-means. To advance the slide, a rotary member is oscillated by surges of pressure each time the valve 94 is actuated. The oscillation in one or other direction drives, through a reversible roller-clutch, a nut engaging a screw which moves the slide 123. At the limit of the slide-travel, a switch is actuated to illuminate a warning-light and prevent further operation of the machine.