Patent GB-442339-A (GB)
Title: Improvements in or relating to machines for milling screw propellers
IPC: B23C3/16
Filed: 1935-05-08
Abstract: 442,339. Milling screw propellers. ENGINEERING & RESEARCH CORPORATION, 6100, Sligo Mill Road, Washington, U.S.A. May 18, 1935, No. 13506. Convention date, June 26, 1934. [Class 83 (iii)] In a machine for milling screw propellers, the tool is reciprocated transversely of the longitudinally moving work and is controlled by a pattern which is rotatable on an axis at right angles to the work support. The base 10 is fitted with a work supporting table 14 provided with a slide 16 fed by a rack 17 and carrying the headstock 18 and tailstock 20. The headstock, Fig. 3, comprises a member 22 fitted with a cylindrical block 24 terminating in a tapered work-engaging arbor 26 and slotted to receive a pin 32 which also engages one of a pair of opposite holes 30 in the root of the blade 28 to locate the blade relative to the block In order that the work may be rotated accurately through 180‹ for machining opposite sides, the member 22 is provided with holes 38, 40 which may be aligned with holes spaced 180‹ apart in the block 24 by means of a pin 36. The blade is finally secured by a clamp 42 engaging the flange thereof. The tailstock is provided with a centring pin engaging a hole in the blade tip. While the upper surface is being machined the blade is supported on a number of supports each comprising a base secured to the bed and fitted with adjustable slotted legs engageable with the work. In a modification, the work supports comprise base members carrying adjustable plates 56, Fig. 5, shaped to fit a finished blade surface. The plates are located by pins 60 and may be turned over to support a blade of reverse pitch. A weighted arm 64 carries rollers 66 which bear on the top of the blade to provide additional steadying means. The cutter support comprises a bed 72 secured to a pivot rod 74 rotatably mounted in the frame the bed being fitted with a slide 76 carrying an electric motor 78. The motor is connected through belt gearing 80 and worm gearing 82, adjustable crank arm 90 and link 94 to a member 98 adjustably secured to the member 74 so that a reciprocating movement transverse to the blade is imparted to the cutter slide. By adjusting the bolt 96 along its slot a quick return motion of the cutter slide in either direction may be obtained. The rotary cutter 104 is mounted on the cutter slide and is driven from the motor through a belt. The copying movement is controlled by a cam 112 engaged by a roller 114 on a rotatable shaft on the cutter slide. This shaft is vertically adjustable to vary the depth of cut by a screw 120. In operation the work carriage is fed longitudinally while the cutter is reciprocated across the face of the blade, the control cam . 112 being slowly rotated in unison with the longitudinal work feed. For this purpose a rod 122 carrying stops 124 and actuated by a member 126 on the cutter carriage is connected to a bar 138 which operates a pair of pawls 142. The direction of engagement of these pawls with their wheels 172, 174 may be determined by vertical movement of a bar 156 effected from a handle 170 through gears 166, shaft 162, and rack pinion 160. Since the pawls act in opposite directions on intermeshing wheels 172, 174, a double acting feed is imparted to a shaft 176 connected by gearing 180 to the rack 17 of the work slide. The direction of motion of the feed may be reversed by means of the handle 170. The control cam 112 is rotated intermittently from the same mechanism through gearing 186, bevel gearing 190 and worm gearing 192, provision being made for inserting an idler in this train to reverse the movement of the cam. In operation, in order first to form the control cam, a finished blade is mounted in the work slide and a cam blank mounted at 112. The positions of the cutter and copy roller are then interchanged and the cam is cut to the contour of the blade. The edge of the blade is preferably sheathed. At each stroke of the cutter slide the blade is fed longitudinally and the cam blank rotated by one feed step by the above described pawl mechanism. In some cases instead of cutting the cam directly, a wooden pattern which afterwards serves as a pattern for casting a cam may be cut. A separate cam may be cut for each face of the blade. After completing the cam, the cutter and roller are placed in the positions shown in Fig. 1 and blades corresponding to the master blade may then be cut. A switch 204 may be operated by a pin 208 on the bed to stop the motor when the cutter reaches the end of the blade. A pedal 210 is connected by linkage to the member 98 to lift the tool away from the work when required. In order to profile the edge of the blade a second motor 222 is arranged at the axis of a pivoted frame 224 which carries a roller 228 engaging an edge templet 234 to control a cutter 226 which shapes the edge of the blade and is driven by a belt from the motor 222. The templet 234 has two operative edges, one for each side of the blade, and it may be formed in the machine by interchanging the cutter 226 and roller 228 and shifting the belt 230 to drive the cutter at the lower part of the frame.