Patent GB-371987-A (GB)
Title: Improvements in gear grinder and the like
IPC: B23F5/02
Filed: 1931-02-16
Abstract: 371,987. Gear-cutting. TRIGGS, W. W., 57, Lincoln's Inn Fields, London.-(Pratt & Whitney Co. ; Hartford, Connecticut, U.S.A.) Feb. 16, 1931, No. 4892. [Class 83 (iii).] A gear grinder of the kind in which the gear blank is mounted on an arbor associated with a master gear element the arbor being mounted on a transversely moving carriage while a grinding wheel is reciprocated axially of the blank, is provided with primary and secondary hydraulic motors for traversing the carriage and with another hydraulic motor which effects indexing of the blank on completion of each reciprocation of the carriage. The ram 4 carrying the grinding wheel 5 is reciprocated by means of a hydraulic cylinder 29 supplied by a pump 6 driven by an electric motor 8. The pipe 12 from the pump conducts fluid past a valve 14 and thence through passage 17 and reversing- valve 19, to the cylinder 29, the discharge being through passages 27, 24 to reservoir 10. The valve 14, Fig. 8, includes a byepass valve 34 seated by a spring 35 which is adjustable by a nut 38. When a predetermined pressure is exceeded oil is byepassed from the passage 17 to the drain connection 22. The valve 14 is manually operated for starting and stopping the machine by a lever 15 connected to the valve through shaft 15a, Fig. 21, arms 15b, shaft 16, and link 16b. When the machine is stopped and the valve 14 is closed, fluid from the pressure line is permitted to flow directly into the drain. The reversing valve 19 is operated by means of lever arms 39, 40, coacting with adjustable dogs 41 mounted on the ram 4. The knee 75 carries a work carriage 76 and the work arbor 78 carries a number of blanks A which are aligned by means of a support 94, Fig. 3, mounted on an adjustable base. A plurality of locating- fingers 97 are supported in a housing 94a, the fingers being normally extended by springs 98 but being retractable independently by the stems 99. The fingers may be withdrawn collectively by a lever 100 connected to an eccentric 103 so that when the lever is operated the housing 94a is drawn back to withdraw all the locating-fingers from the blanks. The blank supporting sleeve 79 carries a master gear 104 coacting with a master rack 108 supported on a forked arm pivoted on an adjustable bracket 111. During the transverse movement of the work table the master gear rolls on the rack so that the work is given the correct generating motion past the reciprocating grinding wheel which has a profile of rack tooth form. The movement of the work table is produced by a rack and pinion gearing 115 driven from a shaft 117 rotated by a hydraulic motor 65a, Fig. 17. Means are provided for manually operating the shaft 117 from a hand-wheel 118. A hub on a sleeve mounted on the shaft 117 is provided with spaced rings 121 fitted with pins 126 which project into the space between the rings. A double pawl 127, Fig. 2, coacts alternately with notches 125 in the rings and a pivoted trip finger 129 extends between the rings and coacts with the pins. The double pawl is normally retained in a neutral position by spring pins 131. As the motor 65a operates, the work table is moved transversely, and at the end of the travel one of the notches 125 is engaged by the pawl 127 to stop the motor and the work carriage. At the other end of the travel the opposite notch is effective. By adjustment of the two rings the circumferential spacing of the notches 125 and pins 126 and thus the travel of the table may be regulated according to the size of the gears to be ground. The pawl 127 is integral with a cam 132 coacting with a follower on a crank 134 associated with the right hand motor 65b, this follower serving to disengage the pawl from the rings 121 for reversing the work carriage. A split link 135 is connected from the crank 134 to the master rack 108 which is thus moved out of engagement with its gear. The motors 65a, 65b each have a rotatable piston 119a coacting with a fixed wall 119b, the piston and the wall being provided with expansible sealing devices 119c of rubber or similar material to prevent leakage. Check valves are arranged at 119f in the fixed wall and at 119e in the piston. When pressure fluid is admitted for instance against one side of the piston, one of the check valves opens and the other closes, and the pressure within the piston cavity causes expansion of the piston into contact with the shaft and the internal cylindrical wall of the motor. Liquid is admitted to the motors from line 11a into a chamber 173 through valve 176 and passage 177 to both motors. In the other position of the valve fluid is admitted to both motors through passages 179. The exhaust of the motors passes through a valve 169 which is provided with a stem 169a having axial grooves 169b of unequal length so that as the stem is moved axially a variable resistance is imposed on the fluid leaving the motors. The valve stem is controlled by a link 166 operated by a cam 182 on a shaft 183 so that the speed of the motors is varied during operation. Thus the motors may be rotated slowly to give a variable slow feed during the grinding and may be accelerated to increase the speed of the work movement when the work has moved clear of the grinding wheel. For indexing the blanks, the master gear coacts with a rack 139 having two rack teeth 140 which are adjustably spaced apart the rack being supported on an arm 141 connected to the piston-rod 142 of hydraulic motor 143. This motor is supplied with fluid passing through a piston valve operated by a projection 149 on the arm 109. When the indexing mechanism is in the position shown in Fig. 13 the piston valve is moved upward as the arm 109 is raised and fluid is admitted to the cylinder 146. In operation, when the work table has reached the right hand end of its movement, Fig. 13, then on lowering the master rack and reversing the motors 65a, 65b the work table is moved to the left hand end of its travel where the left hand indexing tooth engages the master gear. The master rack is now again withdrawn and the motor 143 is operated to index the blank one tooth. On re-engaging the master rack the work table again moved to the right and the rack 139 is retracted as the master gear moves out of engagement with the left hand indexing tooth knees are provided for stopping the machine on completion of one revolution of the blanks. For this purpose the crank 134 is arranged to operate a ratchet wheel 151 mounted on a shaft carrying a trip pawl 158, Fig. 21, which releases a shaft 16 which is thereupon actuated by spring pressure to cut off fluid supply at the valve 14. Means for stopping the machine manually are also provided. When the drop mechanism is actuated, the interlccking arms 159, 160 are disengaged and the link 166 controlling the operation of the motors 65a, 65b is thus allowed to fall. Chucks.-The arbor 78, Fig. 19, is supported in a roller bearing sleeve 79, 79a fitted at opposite ends with collets 80, 81. The gear A to be ground is integral with the arbor 78. A tapered sleeve 82 receives a draw-bar 83 screwing into the arbor and the tightening of the blank against the collet 80a is effected by means of a hand-wheel 85 which is unscrewed from a nut 93 on the sleeve and acts through a thrust bearing 89 on the draw-bar 83. In a modification, a series of blanks A are mounted on an extension of the arbor, the draw-bar being moved axially to tighten the blanks by means of a hand-wheel acting against a thrust bearing.