Patent GB-631622-A (GB)
Title: Method and machine for planing complementary toothed rotors
IPC: B23D3/04
Filed: 1947-08-01
Abstract: 631,622. Planing. WHITFIELD, J. E. Aug. 1, 1947, No. 20951. Convention date, Jan. 12, 1943. [Class 83 (iii)] [Also in Group XXIV] The intermeshing rotors 80, 81 of a rotary compressor are formed by a tool having cutting points spaced apart correspondingly to the crest edges. 82, 83 of a rotor tooth complementary to the one to be generated, the tool and blank being mounted on axes spaced apart according to the normal disposition of the complementary rotors, relatively reciprocated to give a planing cut, and rotated in timed relation corresponding to the normal ratio of the corresponding rotors in order to generate the tooth shape; the reciprocation may be straight, helical or part-straight and parthelical. The blank 30 is mounted on a shaft 26 on a reciprocable table 12, and is connected to a splined shaft 22 also supported on the table and passing through a splined nut 31 attached by a universal mounting 32 to a hollow shaft 33 in a stationary housing 16. The nut has two splined liners 42, 46 which are. relatively angularly adjustable so that one may bear on one side of the splines of the shaft 22, while the other bears on the other side of the splines, thus taking up backlash due to wear. The cutting tool 60 is secured to a shaft 61 journalled in a tool head 62 which is vertically slidable on a cross-rail 13, the cross-rail being vertically adjustable on columns 10, 11. As shown in Fig. 13, the shaft 61 has a conical surface 96 engaging a corresponding surface in the bearing on the cross-slide, and, during the cutting stroke, these surfaces are forced into engagement and lock the shaft, but are jumped free as the tool leaves the blank at the end of the cutting stroke; a clearance is left between the lock-nuts 98 and the tool head 62 to allow for this forward movement. An extension of the shaft 61 connects it through flexible couplings 63 that allow limited vertical and horizontal movement, and through gearing in the housing 16 to the hollow shaft 33. The rotary feed for the generation of the tooth shape is applied at the end of each cutting stroke by adjustable dogs 57 on a rod 55 carried by the table, the dogs acting through a lever on a reversible pawl 53 and ratchet 52 which rotate a worm-wheel 48 on the shaft 33. When cutting the female rotor, Fig. 1, having four teeth and normally engaged by a male rotor having two teeth, as shown in Figs. 17 and 18, the relative rotation of the female and male rotors is in the ratio of 1: 2, and so the feed applied to the shaft 33 and, therefore, to the blank is also imparted to the shaft 61 through the step-up gears 87 and 90, the gear 87 being clamped to the shaft 33 by means of the clutch ring 88. When cutting a male rotor, the interconnecting drive is taken through the reduction gears 94 and 91 so that the male rotor blank is advanced twice as much as the tool, the clutch ring 92 being tightened to clamp the gear 91 to the shaft 61. Figs. 17 and 18 illustrate intermediate and final steps in forming one space in a female rotor 81, and show the correspondence between the action of the tool 60 and the corresponding male rotor 80. Cutter releasing.-The tool is raised from the work for the return stroke by a wedge 75 which is pushed along a track 74 on a fixed bracket 72 by an adjustable dog 78 on the right-hand end of a rod 76 attached to the table. The wedge acts on a rod 70 and tilts a lever 66 pivoted on the tool head and on a roller 67 on the cross-rail, thus raising the tool head until, at the end of the return stroke, it is again moved from under the rod 70 by the left-hand dog 78. Tools. The tools may have integral cutting edges 82a, 83a corresponding to the crest edges 82 or 83 of the rotors; the tool 60 shown in Fig. 6 is for cutting a female rotor and those shown in Figs. 8 and 10 are for cutting a male rotor. Alternatively, a pair of bits 99, 100, spaced apart the same distance as the crest edges of a rotor, may be attached to the tool 60, Figs. 17 and 18, and one bit may have a greater rake than the other, as shown in Figs. 14 and 15, in order to provide sufficient cutting clearance from the helix of the tooth space on the side on which it cuts. Specification 558,740, [Group XXVI], is referred to.