GB540064A - Improvements in and relating to hobbing machines and the method of hobbing - Google Patents

Abstract

540,064. Gear-cutting. TRIGGS, W. W. (Cleveland Hobbing Machine Co.). May 31, 1940, No. 9575. [Class 83 (iii)] A gear hobbing machine, has the blank mounted on a vertical axis and fed in the same direction as the cutting thrust of the hob on the blank. Preferably both the cutting thrust and the work feed are in a downward direction Fig. 6. The machine comprises a fluid retaining base A, of rectangular form to facilitate ganging a number of machines, and a hollow frame B provided with upper and lower guides 11, 12 for the work head C. The work W is mounted on an arbor which is supported between a work spindle 22 and a tail centre 18, the latter being carried by a stock 19 movable over ways 20 by rack-and-pinion gearing operated from a handle 25. The work-spindle is driven from the main driving motor 30 through belt gearing 32 shaft 31, vertical shaft 41, shaft 49, change gearing 53 and worm gearing 60. The tool-head comprises a member 70 slidable on horizontal ways 71 and fitted with an angularly-adjustable portion 72 in which the tool-spindle is carried. The hob H is mounted on an arbor 80 driven from the shaft 31 through bevel-gearing 74 and spiral gears 78, 79. The angular setting of the hob is indicated by a scale. The member 70 has a telescopic connection with a boss-like member 35 to prevent entrance of chips into the toolhead. The hob may be adjusted transversely of the work axis by a pinion 91 engaging a rack 92. The work is carried downwards from the hob by gravity under the control of a leadscrew 100 moving in a nut 101. The lead screw is driven in timed relation with the work and tool through change gears 108, 110 and worm gearing 117. A rapid tranverse for approach and return of the work head may be obtained from a reversible motor 120 which drives a worm wheel portion of the nut 101. The frame 10 is partitioned into two compartments by a partition 51 to enclose the gears and exclude chips. A telescopic guard 124 excludes chips from the ways 12 and cutting fluid is supplied by a pump 125 driven from the motor 30. The motors are controlled by upper and lower limit switches 130, 131 and start-stop push buttons 133, 134 respectively. The switch 130 is actuated by stops 137, 138 and the switch 131 by a stop 139 all these stops being mounted on the work head. The motor connections to supply lines L1-L3 are shown in Fig. 5. In operation after positioning the work the machine is started by the button 133 which closes the circuit of a relay 147 which in turn closes the circuit of solenoid d and energizes motor 120 (leads T<SP>1</SP>1, T<SP>1</SP>3) to lower the work head. A holding circuit maintains these connections after release of the button. Prior to engagement of the work with the hob the limit switch 131 is operated to stop motor 120 and start motor 30 (leads T1-T3) which runs until the cutting operation is completed whereupon switch 130 is operated to stop motor 30. The work head remains in its lower position until the finished blank is removed after which button 133 is again pressed to energize solenoid u and start motor 120 in reverse direction to raise the work head. At the upper limit of travel the motor 120 is stopped and a fresh blank positioned. The machine may be stopped at any time by pressing the stop button 134.