238,237. Uhlich, F. Aug. 5, 1924, [Convention date]. Gear-cutting.-Bevel gears, spur gears, or racks having teeth which are curved in the longitudinal direction are planed by means of a pair of tools which have a rocking movement about centres which are displaced from one another so that two different tooth faces may be cut simultaneously to the same radius of curvature. In the application to bevel gears, Fig. 1, the cutting-edges 1, 2 of the tools 3, 4 represent a crown wheel and the axes 6, 6, of the respective rocking movements are displaced by half a pitch (or a multiple, thereof) along the circle 10. The teeth formed are of crescent shape as shown at 9 and the size of the circle 10 may be varied according to the obliquity of tooth required. Spur wheels and racks may be produced in a similar way, the centres of the tool movements being in these cases displaced along a. straight line by half a pitch or a multiple thereof. In the machine for carrying out the invention, the blank 70 is mounted on a spindle carried on a headstock 72 supported on a slide which is radially adjustable on a support 74 carried by a plate 75 which may move on circular guides to adjust the blank in relation to the tool-head. The latter is actuated from a vertical shaft 12 which is pivoted to the frame and drives a horizontal shaft 15 which through spur gears 16, crank disc 17 and connecting-rod 18, actuates a link 21 secured through a sleeve to a shaft 23 which thus receives an oscillatory movement. The shaft 23 may be adjusted relatively to its driving link by gearing 24 and carries at its forward end a. tool head 28 having two tool-holders 29, 35, provided with cutting tools 30, 26 respectively. The tools may be composed of sections of ring-shaped members and are supported on inclined surfaces to give. relief to the cutting-edges. The tool-holders are pivoted at 42. 43, to permit withdrawal of the tools from the work on the idle strokes. This movement is effected from the shaft 15 which imparts rocking movement to a shaft 53 provided with pinions which reciprocate cam plates 54, 55, having projections 56 which engage plates 57, 58, on the rear of the tool-holders. In Fig. 11 the tools cut in opposite directions and the tool 36 is in the cutting, and tool 30 in the non- cutting position. The tool-holder 30 rocks about the axis of the shaft 23 but the pivot 34 of the second tool holder is carried on a bracket 33 which is adjustable in the tool-head in order to obtain the required distance between the centres of oscillation of the tools. Rocking movement is imparted to the tool - holder 35 by means of a bolt 38. In a modification which is used in cases where cutting cannot be effected in a direction away from the blank cone apex, the two tool holders are arranged as shown in Fig. 12 and both tools cut simultaneously towards the blank apex. In this modification the two tools may cut faces of two different teeth, the rocking axes of the tool holders being correspondingly displaced on the circle 10. In a further modification more than two tools may be employed. The tool mechanism is carried on a drum 60 which is rotated in a bearing 59 by a worm gear 61, the drum having a radial slide 62 to enable the tools to be set according to the size of the circle 10. The rotation of the drum constitutes generating movement of the tool-head, and the blank is rotated in unison with the tool-head. The Specification as open to inspection under Sect. 91 (3) (a) states also that the tools 3, 4 may be replaced by grinding segments. The gearing shown diagramatically in Fig. 12 (Cancelled) for operating the various motions is also described. The main driving pulley 65 drives the shaft 12 through change speed gear 80 and bevel gearing, thus effecting the rocking movement of the tools. Further gears 84, change wheels 68, bevel gears 86, reversing clutch 88, reversing bevel gearing 87 and gearing 89. 90, actuate the generating rotation of the tool head. A quick reverse movement is obtained by engaging the clutch 88 with gearing 71<1>, and by means of the gearing 87, the slow generating movement may be effected in either direction. The work is drawn from the gearing 89 through the gear train shown in Fig. 12. The indexing mechanism 100 is driven from a pulley 97 on the main shaft through gears 99 and is released by link mechanism actuated by stops 104, 105, on the tool head through a rod 106. The shaft 101 of the indexing mechanism indexes the blank through half a pitch or a multiple thereof by means of gearing 102 and differential gear 92. During indexing, the blank is withdrawn from the tools by means of a connecting rod 110 actuated from the shaft 101 and connected to a, segment 111 to move the base plate 74 to withdraw the work. In operation, at the end of the generating rotation of the blank and tool-head the work is withdrawn from the tools and indexed through half a pitch. At the end of the quick return movement the blank is again indexed half a pitch and then returned to the tools whereupon another cycle of operations is performed. This subject-matter does not appear in the Specification as accepted.