Patent GB-343241-A (GB)
Title: Improvements in or relating to method of and apparatus for cutting spiral gears
IPC: B23F5/12
Filed: 1929-12-17
Abstract: 343,241. Gear-cutting. WHITE, A. E., 5, Quality Court, Chancery Lane, London.-(Perkins Machine & Gear Co. ; Circuit Avenue, West Springfield, Massachusetts, U.S.A.) Dec. 17, 1929, No. 38667. [Class 83 (iii).] In a process for generating helical gears a cutting tool representing one tooth of the basic involute rack is reciprocated in a rectilinear path while the blank, mounted with its axis inclined to the tool path, is rolled past the tool to generate the tooth profiles. The bed of the machine is provided with two horizontal work carriages 4, one on either side of a central vertical column 2. Each carriage carries a bed 5 which is adjustable by a screw 7. The column is fitted with a pair of tool-holding rams 13 which are reciprocated in opposite directions and are balanced by connecting them together by a chain 131 passing over a pulley 132. The rams carry broach-like tools 17 secured in position by bolts 16, 136, the teeth of the tool being of straight sided section corresponding with a tooth of an involute generating rack. The rams are also fitted with vertical cam plates 18 having an inclined surface 18<11> merging into a more steeply inclined upper surface 18<1>, these cams serving to impart tangential generating movement to the blanks. Racks 22 secured to the rams are engaged by a pinion 21 mounted on a shaft 20 which is driven alternately in opposite directions to reciprocate the rams by gears 37, 24 operated from the reversing belt-driven pulleys 30, 31. The pulleys are selectively clutched to the shaft 28 by means of a friction clutch member 42 controlled by a sliding rod 43 operated by a yoke 48. This yoke is actuated through the lever mechanism shown in Fig. 2 from a rock-shaft 58 carrying an arm 62 having a lostmotion connection with a pivoted arm 61. The arm 61 is actuated to control the reversal by a dog wheel 39 driven from the shaft 20 and carrying adjustable dogs 40. 41. The reversing-mechanism is interconnected with lever mechanism, Fig. 4, for moving the work to and from the tools. Thus when the lever 61 is moved to the left, Fig. 4, by the dog 41, a link 79 rocks the bell-crank 75 to break a toggle device consisting of links 67, 69 whereupon a spring 72 withdraws the carriage. Similarly when the lever 61 is moved to the right, the parts are restored to the position shown in Fig. 4 and the work mounted on the left hand carriage is moved up to the tools. On account of the lost-motion device 63, the carriage movements are effected before the reversal of the ram takes place. The withdrawal of the right hand carriage is effected during the advance of the left hand carriage and vice versa. Each bed 5 carries an upper bed 84 whose upper surface is inclined at the spiral angle of the gears to be cut and carries a slide 85 actuated by the cam 18 in conjunction with a roll 93 to reciprocate the slide 85 on its bed. A stud 99 on the slide 85 carries a pivoted detent 101 and is mounted in an extension 124 of a loose gear segment 123 of the same pitch diameter as the blanks. The detent also carries a pivoted pawl 102, and a lug 104 coacting with a dog 107 pivoted on the slide 85. A number of blanks 129 are secured to an arbor 115 mounted in the slide 85 by means of a shroud 130 and nut 117. A completed supporting gear 128 similar to those to be cut is mounted below the blanks, this gear serving to prevent the tool from breaking away the teeth of the lowest blank. The gear 128 is bolted to the index wheel 126 coacting with the teeth on the detent 101. In operation, when the tool is moving downwards on its cutting stroke the cam 18 imparts tangential movement to the blanks and at the same time a pinion 96 rolls on a fixed rack 94 and actuates the segmental gear 123 which through the detent 101 rotates the index wheel and the blanks to give correct rolling movement thereto. Towards the end of the stroke the part 18<1> of the cam accelerates the movement and causes the lug 104 to be carried past the dog 107. On the return stroke, the segment 123 is. moved back by a spring 98 and the lug 104 engages the dog 107 to withdraw the detent 101 from the index wheel and engage the pawl 102 therewith, the movement of this pawl against a spring 106 serving to index the blank through one tooth. After the lug 104 has passed the dog 107, the detent 101 is re-engaged by a spring to lock the index wheel and the return roll of the blanks continues until the tool reaches its upper position whereupon the carriage is again moved up to the tool and the ram reversed for a fresh cutting stroke on another tooth. One tooth is completed at each stroke and the operation is continued until all the teeth of the blanks are cut.