GB707256A - Improvements in or relating to the machining of impeller wheels - Google Patents

Abstract

707,256. Copy-milling. THOMPSON PRODUCTS, Inc. Nov. 12, 1951, No. 26427/51. Class 83 (3) A method of milling the space between the adjacent vanes of an impeller wheel W consists in oscillating the work so that the cutter T traverses the whole width of the recess while the cutter and work are moved relatively to generate the required profile of the recess. A machine for carrying out the method comprises a milling tool T rotated by a motor 34 and mounted on a vertically movable slide 15, a cross slide 14 on a pedestal 11, and a motor 20 for rotating a screw 22 for feeding a work-carriage 12 carrying the impeller blank W. As the carriage 12 is fed, the work W is rotated by a cam follower 23a, a rack-bar 23 and a gear 24 on the work-spindle: The follower is held in contact with a cam B, and back-lash is taken up, by a hydraulic force applied to a rack-bar 26. For obtaining greater accuracy, the cam B is elongated and is traversed over a longer path than the slide 12 by a screw 21. The motor 20 also moves the cutter-slide 15 through shafts 28, 29 and a cam A, and traverses the slide 14 through a cam C and a follower 31a which are held in contact by a hydraulic piston 32b. The machine thus far described is similar to that described in Specification 655,207. The oscillation of the work to generate the root surface between adjacent vanes is imparted by a motor 83 through an adjustable crank 85, a lever 80 pivoted to a member 76 carrying a slideblock 78, a bell-crank 79, 71 and a slide-block 75 engaging a plate 54 to which the work is secured. The pivot 73 of the bell-crank 79, 81 is journalled in a ring member 52 secured to the spindle 13. Thus, as the impeller is moved angularly, the degree of oscillation becomes less. The work is indexed by a peg 62 which is inserted in an appropriate recess, 59a in a plate 59 fast with the plate 54.