Patent GB-373851-A (GB)
Title: Improvements in and relating to bevel gears and to apparatus for cutting the same
IPC: B23F9/08
Filed: 1931-07-30
Abstract: 373,851. Toothed wheels. KLINGELNBERG, G. A., KLINGELNBERG, M., KLINGELNBERG, R. G., KLINGELNBERG, W. H., and KLINGELNBERG, H. W., (trading as KLINGELNBERG, SÍHNE, W. F.), Remscheid, Berghausen, Germany. July 30, 1931, No. 21805. Convention date, Aug. 28, 1930. Addition to 365,744. [Class 80 (i).] The process of cutting bevel gears with longitudinally curved teeth the thickness of which decreases from the centre towards either end, by swing- ing and simultaneously rotating about its axis a concave conical hob in the tangent plane of the imaginary basic crown wheel across the face of the bevel blank rotating in timed relation, is modified for the production of a bevel gear of large pitch cone angle such as a crown wheel by omitting the swinging motion of the hob. The blank and hob are caused to rotate continuously about their respective axes whilst the hob is fed to the full tooth depth perpendicular to the conical surface of the blank. The crown wheel blank 90 is cut in the machine shown in Figs. 3 and 4, being mounted on a headstock 95 axially slidable on a table 96 rotatable about a vertical axis through the pitch cone vertex. The cutter headstock 97 is longitudinally slidable in the direction of the arrows 101, 103 to regulate the depth of cut, this movement being performed by a double-acting hydraulic piston 98 under oil pressure controlled by a valve 100. A fixed stop 102 and an adjustable stop 104 are provided, the stop 104 being first screwed up against the headstock 97 with the interposition of gauge block 105 whilst the cutter is just in contact with the blank. The block 105 corresponds to the depth of teeth to be out and is removed after the positioning of the stop 104. The valve 100 may be automatically controlled so that the cutter moves rapidly up to the blank and slows to feeding rate before touching it. The tooth profiles of the crown wheel differ but little from the trapezoidal teeth of the basic crown wheel. The concavity of the hob is slightly greater than that corresponding to a hyperbolic section taken through the axis of the hob and crown wheel at the point of engagement. The Specification as open to inspection under Sect. 91 (3) (a) describes also means for compensating for the increase in pressure angle of the teeth from the inner to the outer diameter of the hob. For this purpose the flank angle of the teeth of the hob 11, Fig. 7 (Cancelled), increases from 30‹ at its larger to 44‹ at its smaller diameter, giving a uniform pressure angle of 23‹ over the whole length of the crown wheel teeth. This continuous variation in flank angle of the hob teeth is obtained by causing a milling finger, Fig. 8 (Cancelled), or turning tool, grinding wheel &c. cutting the thread of the hob to take up a progressively increasing inclination about the pitch line point 106 as it traverses the length of the hob 11. A slide 21 carrying the tool holder is mounted in a circular guide centred at the point 106 and is connected through worm gearing 108, universally jointed telescopic shaft 111 and change gears 110, with a rack 32 on the traversing table 14 carrying the hob 11. A crown wheel having teeth with their pressure angle varying from 16‹ at the smaller to 23‹ at the larger diameter, cut by a hob of constant 30‹ flank angle is also shown. This subjectmatter does not appear in the Specification as accepted.