GB1217674A - Improvements in and relating to means for generating involute and non-involute gears - Google Patents

Abstract

1,217,674. Gear-grinding; grinding wheels. PRECISION KINEMATICS (GEARS & MECHANISMS) Ltd. 4 Jan., 1968 [6 Jan., 1967], No. 843/67. Headings B3D and B3K. A machine for generating involute or non- involute straight or helical external or internal gear teeth on a workgear, comprising means for indexing a work-table 2 about an axis, a powerdriven spindle carrying a finishing wheel 30 having an operative face defining a generatrix, a two-part swing frame 25, 27 angularly movable on a swivel frame 22 about a pair of main pivots 26 whose common axis is always normal to the wheel generatrix and either parallel or inclined at the workgear helix angle to the work-table axis, means for movably connecting the spindle to the frame so as to allow movement of the spindle relative to the swing frame in a plane at right angles to the common main pivot axis, a main feed slide 13 movable on a column 12 in a direction parallel to the work-table axis, the main swivel frame being angularly adjustable and then clampable to the main feed slide, and, finally, means for correlating the movement of the swing frame and of the wheel so that the generatrix (if a straight line) sweeps out as a line curve an involute tooth profile on a workgear in accordance with the fundamental kinematic equation: wherein x is the instantaneous perpendicular distance of the generatrix from the common main pivot axis; a 0 is the perpendicular distance between the main pivot axis and the base cylinder of the workgear; R 0 is the base cylinder radius of the workgear; and # is the angle of oscillation of the swing frame relative to the swivel frame. The gear is indexed by a motor 6 and a clutch 8 which may be associated with diffractiongrating; a decade-counter or tape control. The column 12 is adjustable to and from the table 2 and carries the slide 13 reciprocated vertically by a screw 14 rotated by the motor 6 through a clutch 16 and a differential 17. The swivel-frame 22 is carried on the slide 13 by a pivot 23 and is locked by bolts 24. The extension 27 of the frame 25 is adjustable radially of the table 2 and carries links 32, 33 attached to a carrier 28 which supports the wheel 30 with its motor 29 and dressing and compensating means 31. A guide bar 38 on the carrier 28 is parallel to the rectilinear generatrix of the wheel and is engaged by a follower 39 pivoted to an arm 41 of a bell-crank lever 42, 44 mounted by a pivot 43 on the frame 25, the distance 40-43 being adjustable and equal to a 0 . The arm 44 carries a pivot 45 and is adjustable as regards the length 45-43 and the perpendicular distance of its centre-line from the axis of the pivot 43. The involute can be generated from the point A* k , Fig. 2 (not shown), instead of the point A 0 , a 0 then becoming a k . The pivot 45 is integral with a pivot 56 on an adjustable lever assembly (52), 55. The arm 55 is slidable through a pivot block 48 carried on an adjustable plate 47 which also carries adjustable guide waves 50 carrying a sliding pivot block 54 connected to the arm (52). The latter correlator mechanism provides nine independently adjustable variables px, py, #, p1, p2, p3, p4, p5 and p6. It can be replaced by other fourlink or by six-link, mechanisms. In a modified correlator mechanism for non- involute gears, the pivot 45 is connected to a lever 57, Fig. 5, connected by a pivot 58 to the frame 22 and a pivoted block 59 connects the follower 39 to the slotted arm 41 of the bellcrank 42, 44. The block 59 is moved in timed relation to the movements of the frame 25 by a slider-crank mechanism having adjustable parameters (q1 to q4). The tooth profiles produced may be modified by modifying the apparatus to impose a non-circular movement on the pivot 45. Grinding wheel sections.-Grinding wheels may be used of the forms shown in Fig. 4 and may have a cone angle of 150 degrees.