Patent GB-738578-A (GB)
Title: Apparatus for use in the production of objects of predetermined arbitrary forms in three dimensions
Inventor: MARWOOD WILLIAM JOHN
IPC: B23Q35/10
Filed: 1952-05-23
Abstract: 738,578. Copy-milling; making propellers. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Aug. 21, 1953 [May 23, 1952], No. 13177/52. Class 83 (3). [Also in Group XXIII] Apparatus for three-dimensional copying comprises a set of flat templets 32, a rotary tool 44 of near-point form and means for guiding a follower 23 over the templets and the tool over the blank in a series of positions corresponding to the templets, the only movements of the blank relative to the tool being one corresponding to the length of the templet and one directly controlled by the ordinates of the templet. The curved templets 32 correspond to a series of sections of a blade of a propeller, and are clamped between blocks 31 by a screw 29. The templets are positioned by a key 27 on a plate 25 which may be indexed on a disc 24 for the machining of a set of grooves on each blade of the blank 33. The follower 23 is carried on a slide 19 adjustable by a screw 21 on a slide 18 mounted for vertical movement on a slideway 17. The tool 44 is driven by beltgearing or an air-motor and is carried on an arm 42 supported by a roller 43. The arm is set at the correct height by slip gauges, such as 45, and is clamped in a holder 41 on a disc 36 which can be rotated to allow raked blades to be machined. The holder 41 itself can be rotated to position the tool in an advantageous position to be as nearly at right-angles as possible to the surface during the cutting, the point of the tool lying on the axis of adjustment of the holder. The follower-slide may be linked to the arm for simultaneous adjustment but is preferably adjusted independently. One templet may have an arcuate notch to engage the follower and enable the cutter to make a centre mark at the extreme tip of the blade. Several cuts may be taken at each section by rotating the shaft 16 several times and adjusting the screw 21 between each revolution, according to the depth of cut required, until a predetermined zero setting is reached. To machine the opposite sides of the blades the holder 41 is rotated through 180 degrees and a different set of templets fitted to the disc 24. Alternatively, the propeller blank may be reversed on the shaft 16, or a separate cutter arm may be fitted. Feed may be by hand, spring, hydraulic or pneumatic means. The blank may be linked with the follower instead of with the templets. Instead of indexing the blank, a number of spaced tools may be used. When all the grooves have been cut, the remainder of the blade surfaces is machined to size using the groove bases as references. The templets may be cut by a grinding-wheel and pantograph mechanism directly from drawings. The grinding-wheel is conveniently of the same radius as the follower so that no allowance need be made for the difference in radii of follower and wheel. The templets may represent unequally-spaced sections of the blades and may be arranged in any order and in any positions on the plate 25 provided that the appropriate allowances have been made in machining the templets.