GB590788A - Impeller vane milling machine - Google Patents

Abstract

590,788. Milling machines. VLIEG, C. 13. DE. July 14, 1944, No. 13502. [Class 83 (iii)] [Also in Group XXXVII] In a machine and method for producing vaned articles such as impellers for engine superchargers from solid disc-shaped blanks, a blank A, Fig. 23, indexably mounted on a work holder 85 rotatable about an axis 12 inclined to the work axis B, is first gashed by being fed horizontally and simultaneously rotated about axis 12 against a milling cutter 14 and is subsequently moved in a similar manner against successive cutters which shape the straight and curved portions of the vanes 1, the combined movements producing the helical formation of the vanes. The machine comprises a base 26, Fig. 11, having horizontal ways 27 for a headstock 28 carrying a rotary spindle 64, Fig. 14, to which the holder 85 is secured by a split clamp 85a, the axis of spindle 64 constituting the axis 12. The headstock 28 is traversed by a lead screw 31, Fig. 13, rotated through gearing 44 from a shaft 48 rotatable in the base 26 and having splined thereon a clutch 56 engageable with a worm-wheel 51 or a chain sprocket 54 whereof the former is driven by a two-speed reversible feeding motor and the latter by a single speed reversible fast-traverse motor. A spring-actuated brake 46 on the gear 44 prevents overrun of the headstock after a rapid traverse, and the screw 31 may be hand rotated at 31a after a cover 166 has been swung aside to engage a switch and cut out the feeding and traversing motors. During a feeding stroke of the headstock, cam bars 83 on the base 26 engage rollers 72 on two plungers 74 in the headstock, each of which carries a grooved sleeve 74a engaging an elongated gear on the spindle 64 which will thereby be rotated during the feeding movement. The plungers 74 are slidable laterally in bushes 76 in the headstock and one carries a spring 79 to maintain the rollers in contact with the cams. Work gripping and mounting.-The work A is mounted on the holder 85, Fig. 17, by a central post 87 secured thereto by a flange 89 and screws 90 and having a cylindrical portion 88 fitting the bore of the work. A clamping ring 92 actuated by a nut 93 has a spherical seat engaging a similar surface on the nut and has splines engaging a splined portion 91 on the post 87 to prevent its rotation. The vane 1 which is being milled is supported by a centre 96 engaging a conical depression in a spigot 13 on the end of the vane, a uniform pressure being applied to the centre by a spring 97. The centre 96 is formed on a member 95 movable in slots in the holder 85 and capable of being withdrawn to allow indexing of the work by a cam 104 on a transverse hand-operated spindle. A nut on the end of the spindle operates a clamp through a convex surface thereon to secure the member 95 to the holder after engagement of the centre 96 with the work. The strength of the spring 97 is selected according to the type of work. Cutter arbors and mountings ; headstocks; lathe &c. centres.-The cylindrical cutters 14 for/gashing the work and the cutter 22, Fig. 9, for producing the straight-sectioned trailing portion 6 of the vanes, the latter being of smaller diameter so as to approach near the hub 2, are supported and driven at each end by spindles 129 rotatably mounted in a head 107, Fig. 20, adjustable vertically at 114 on a slide 108 horizontally adjustable on the base 26. The spindle 129 shown in Fig. 20 is rotated by an electric motor through a chain or belt drive 121a and gearing 123, 126 and the other spindle 129, which replaces the dead centre spindle 138, is driven by similar gearing and a transverse shaft 124. When operating on the leading surface 5 of a vane, as shown in Fig. 10, the cutter is supported by a dead-centre 134 which is offset as shown to clear the curved edge of the vane. The centre is mounted in a spindle 138 slidable within a sleeve 139 screwed in the headstock 107 and secured by screws 147, the spindle 138 being adjusted or removed by means of a screwed rod 137 hand-operated at 145. Rotation of spindle 138 is prevented, and axial motion thereof is limited, by a key 149 and the spindle is pressed towards the cutter 24 by a spring 139a. The centre 134 is cooled and lubricated by oil supplied from a pump 133 driven by shaft 124 and passing by pipe 155 and a central bore 152 to an inclined passage 152a in the centre. Lubricating and cooling cutting tools and work.-Cutting oil is supplied to the cutter by a pump drawing from a sump in the machine base, and the pump 133 supplying oil to centre 134 draws from the outlet of this pump. A byepass valve allows excess output from pump 133 to mix with the oil supplied to the cutter. Operation. A disc-shaped blank with bosses 13 on its periphery opposite the required positions of the vanes is mounted on the holder 85 and the centre 96 applied to one of the bosses. The operator then actuates a starting button to energize the fast traverse motor and the clutch 56 is automatically moved to the right in Fig. 13, thus causing the head 28 to be fed rapidly towards the cutter head until a dog 161, Fig. 11, on head 28 engages a switch in a stationary casing 163. This stops the rapid traverse motor, starts the cutter driving and coolant pump motors, and also moves clutch 56 to the left and starts the feed motor at its higher speed. The work is then fed against the gashing cutter and simultaneously rotated about axis 12 until a dog 160 on head 28 changes the feed motor control to slow speed to enable the cutter to clear itself when approaching the roots of the vanes. A dog 159 on head 28 then reverses the feed motor and subsequently dog 160 speeds up the motor for rapid reverse feed, this being succeeded by rapid reverse traverse initiated by a dog 162. The traverse is stopped by a limit switch and the work may be indexed for a further gashing cut. When the work has been completely gashed, the flat surfaces 5, 6 of the vanes are roughed out by cylindrical cutters 22, 24, Figs. 9 and 10, either in the same or a different machine, the curved surfaces 7, 8 are machined by formed cutters 18, 20, Figs. 7 and 8, and finally all the surfaces are finished by similar cylindrical and formed cutters. The order in which the cylindrical and formed cutters are used may be varied. A diagram of the automatic electrical control of the machine is described in the Specification and a switch is provided for allowing the machine to be controlled manually.