Patent GB-646773-A (GB)
Title: Improvements in or relating to the grinding of gear wheels
IPC: B23F5/04
Filed: 1945-08-30
Abstract: 646,773. Gear-cutting. RICKENMANN, A. Aug. 30, 1945, No. 22400. [Class 83 (iii)] In a machine for finishing toothed gears by means of a helically-ribbed grinding hob, the hob and the work are driven by synchronous electric motors and the work-driving motor and work slide are mounted on an angularly adjustable drum which also carries spur gear trains rotating on parallel axes for connecting the motor to the work. The machine comprises a base 1, Fig. 2, having a headstock 8 in which the work-carrying drum 9 is rotatably adjustable (for treating helical gears 12), by means of a hand-operated worm 15 and an arcuate scale, the drum being locked in adjusted position. The work 12 is mounted between head and tailstocks 36, 37 on a slide 10 movable on diametrical guides on the drum by a hydraulic cylinder 79 and a stationary piston 81. The workdriving motor 20 rotates the headstock spindle 35 through a spur differential train 22 ... 25, change-speed gears A ... D for determining the number of teeth on the work, an elongated pinion 30 and further spur gears 31 ...34. When finishing straight toothed gears the casing 40 of the differential gear is held stationary by a fluid-pressure plunger 122, Fig. 5a, but for spiral gears the casing is rotated to impart an additional rotation to the work by change gears E ... H driven by a pinion 46 meshing with a rack 45 attached to the work slide 10. Fluid supply to the plunger 122 is controlled by a hand-operated valve 111 having two positions for " spiral " and " straight '' teeth. In the former position pressure is cut off from plunger 122 and is supplied to a hydraulic motor 116 which applies a torque to the differential casing 40 sufficient to take up backlash in the gear train from the rack 45 to the easing in either direction of movement of the rack, this torque being regulated according to the velocity ratio of the train by a relief valve 120 and pressure gauge 127. For straight teeth the valve 111 shuts off motor 116 and admits fluid to plunger 122. Fluid-pressure work feed.-A pump 520, whose delivery pressure is controlled by an automatic .valve 590 and indicated by a gauge 60, delivers fluid by pipe 550 through the bore of a valve 61 and passage 71 to a speed control valve 72 which is set as shown in Fig. 6, for slow working feed, whereby fluid flows by pipe 82 to a pump 83 and is supplied to feed cylinder 79 through the hollow piston rod 81. The output of pump 83 is controlled by a manuallyadjustable cam 87 and the pump is driven from pinion 30 at a speed proportionate to the rotational speed of the work. The fluid raises the slide 10 on its working stroke at the end of which a dog 64 on the slide oscillates a lever 88 to close a switch 95 and energize a solenoid 99 to swing a lever 66 and move valve 61 to the left and cut off fluid to cylinder 79. The slide 10 will then return on its downward stroke under gravity, fluid from cylinder 79 passing by pipe 76, valve 72 and passage 108 of valve 61 to the sump. At the end of the downward stroke a dog 65 on slide 10 again actuates switch 95 to energize a solenoid 67 and reverse the valve 61. For rapid upward feed of the slide 10, valve 72 is moved by hand to the right and fluid proceeds by pipe 76 to cylinder 79 without passing through pump 83, and when valve 72 is in its extreme left-hand position the cylinder 79 is cut off from both supply and exhaust to bring the slide 10 to rest in its upper position. Cutter-slide feed.-The grinding worm 7, Fig. 2, is mounted on a shaft 6 driven directly during grinding by an electric motor 3, Fig. 5, and carried by a slide 2, Fig. 2, movable to and from the work 12. The slide 2 is fed by a rod 130, Fig. 5, screwing at one end in a nut 131 on the slide and carrying at its other end a piston 135 working in a cylinder 149 in the base 1. A spring 157 normally presses the slide to the withdrawn position and a bevel gear 133 operated by a handle 136 enables the rod to be rotated in the nut 131 for adjustment. Fluid to cylinder 149 is controlled by a valve 139, Fig. 6, operable by a hand-lever 142 into " forward," " stop " and " return " positions. In the first position, if valve 61 is in operative position, fluid proceeds therefrom by passage 141 and pipe 145 to space 147 of cylinder 149 and thence through the piston to feed the latter forward at a relatively rapid rate. When a shoulder 1351 on piston 135 closes the inlet 145, fluid proceeds by a needle valve 152 behind the piston and feeds the slide 2 at a slower rate until the piston meets a pivoted stop 154 resting against an adjustable rod 153. When the valve 61 is operated by solenoid 99 to stop the work slide 10 at the top of its stroke, and before the downwards stroke commences, the valve 61 shuts off fluid supply to pipe 145 and connects return pipe 150 to an annular groove 158 of valve 61, whereupon an amount of fluid is forced by the spring 157 into the groove sufficient to fill the groove. This allows a slight withdrawal of the grinding worm from the work for the return stroke of the latter, and the slide is again fed to the work when the valve 61 is actuated for the next upward working stroke of the work slide 10. The stop rod 153 is retracted before each working stroke of slide 10 to apply cutting feed, this being effected by a plunger 177, Figs. 5 and 19, pressed to the left (Fig. 19), by a spring 179 against an adjustable stop 180. A rack on the plunger meshes with a toothed segment 165 carrying a pawl 168 engaging a ratchet 166 attached to the rod 153. When the valve 61 is actuated for a working stroke of slide 10, fluid is admitted by pipe 163 to the cylinder 176, thereby forcing plunger 177 to the right and rotating rod 153 through the pawl and ratchet. On the return stroke of the work, valve 61 exhausts cylinder 176 and the spring 179 returns the plunger and pawl, the ratchet 166 being held by a non-return spring pawl. When the required number of feeding steps have been imparted to the slide 2, a stop 173 on the ratchet 166 engages a fixed abutment and simultaneously operates a switch 175, Fig. 6, to prevent the solenoid 67 from being operated at the end of the next downward stroke of the work. The machine then comes to rest and an alarm light 194 is illuminated. If the work is not yet to size, the slide 2 is fed in the required amount by means of handle 136 and a push button 192 is actuated to short-circuit the switch 175 and energize solenoid 67, whereupon the work slide performs a working and return stroke and then comes to rest with the alarm 194 again illuminated. During this cycle the automatic feed is inoperative as stop 173 still rests against its abutment. When grinding has been completed valve 72 is moved into the '' stop " position to cut off fluid from the workslide cylinder 79 and valve 139 is moved to " return " position for return of slide 2, and the motors 3 and 20 stopped. In the middle position of valve 139 the cylinder 149 is cut off from supply and exhaust and the slide 2 is stopped in its momentary position. A sprocket wheel 164 keyed to rod 153 has a chain 169 and weight 171 attached thereto so that the weight is raised during the feed steps of the rod 153. To restore the parts to starting position the non-return pawl is lifted by a handle and the weight rotates the rod until the stop 173 arrives at its initial position, the switch 175 being released to allow solenoids 67, 99 to function again. The machine may be stopped at any time by moving valve 139, Fig. 5a, to stop motors 3, 20, but to prevent the work being damaged by stoppage of the motors before the slide 2 has been withdrawn a solenoid 190 is arranged in circuit with a switch 193 so that it is de-energized when the circuit is broken and allows a spring 195 to move the valve to " return " position. This action also takes place if the current supply fails, thus ensuring that the work is never in contact with the cutter when the motors are slowing down.