Patent GB-567549-A (GB)
Title: Improvements in or relating to machines for producing convex surfaces
IPC: B23D3/04
Filed: 1943-05-25
Abstract: 567,549. Shaping curved surfaces. BRISTOL AEROPLANE CO., Ltd., BOLAS, J. T., EDWARDS, R. W., and LATTY, W. J. May 25, 1943, No. 8283. [Class 83 (iii)] In a machine for producing a convex surface having a curved axis, a section of the surface normal to the axis being part-circular about the axis, a cutter is oscillated about the axis by a fluid motor and is fed relatively to the work along the axis by a second fluid motor, the supply of pressure fluid to the two motors being controlled so that they are operated in timed relationship to cause the cutter to generate the convex surface. As applied to the formation of the edges f, Figs. 1 and 2, on the inner rim of a centrifugal impeller 4, which are arcuate in section as well as in length, an arcuate cutter 5 is made to oscillate about an axis 6 concentric with the surface f, the impeller being fed about its centre i whilst the cutter is in the withdrawn position shown and being indexed to cause the cutter to act on each pocket d in succession, thus causing each surface f to merge into the radial webs c of the impeller. The work is mounted on an index plate 104, Fig. 4, mounted on a central boss i on a plate 7 which is rotatable about an axis h on a support 107 laterally slidable under control of a cam 81 on a table 8 carried by horizontal pivots 9 on the machine frame. The plate 104 is indexed by a plunger 18 in a fluidpressure cylinder 14 carried by the plate 7, the plunger being raised when a valve 17, Fig. 3a, is actuated by a handle 16 to engage one of the index holes 105 spaced at the same pitch as the pockets d in the work. Release of the plunger allows the work to be indexed manually. The cutter is oscillated by a hydraulic motor 27 having a radial vane 26. A constant delivery pump 10 supplies oil to a twin-pressure valve 11 having high- and low-pressure lines 49, 65 respectively, 55 being a return line. In operation, the cutter commences at a point g<1>, Fig. 1, and is oscillated continuously, with rotary feed of the work until the point g<2> is reached, and on the next rearward oscillation of the cutter the oil supply to the cutter motor 27 and the feed cylinder 42 are cut off, to allow indexing or removal of the work. As shown, the cutter is completing its last rearward oscillation in a clockwise direction and highpressure oil is proceeding from supply line 49 by valves 50, 24, 35 and pipe 48 to a reversing valve assembly 53 in which it is directed by valve 58 and pipe 54 to the left-hand side of motor vane 26. A ring 28 is connected with the cutter by a pawl and ratchet 31, such that the ring will make a partial clockwise revolution from a starting position whilst the cutter is making the oscillations required to shape the work from g<1> to g<2>. When the cutter completes its last withdrawal oscillation a notch 33 on the ring 28 comes under a plunger 34 on valve 35, thus allowing the low-pressure fluid proceeding from the supply line 45 and valve 44 to the right-hand side of the valve to move it to the left to shut off the high-pressure supply to the motor 27 and admit high-pressure fluid by pipe 79 to a cylinder 40 whose piston carries a pawl 37 engaging ratchet teeth 36 on the plate 7. The pawl 37 also withdraws an indexing pawl 38 from the plate 7, through a tail 41, thus allowing the plunger of a cylinder 43 constantly supplied with low-pressure fluid to rotate the work anti-clockwise to starting position. The operator then indexes the work by rotating a valve 44<1> through 90 degrees, allowing low-pressure fluid from pipe 45 to proceed by pipe 81 to a cutter interlock valve 82 which is then in position to allow the fluid to pass by pipe 83 to valve 50. This moves the valve to the left and admits high-pressure fluid from pipe 49 to pipe 85 and plunger 24 to withdraw a projection 23 thereon from a recess 21 on the table 8 to allow the table to be lowered about the axis 9. A valve 17 may then be lowered by a handle 16 to admit lowpressure fluid above the plunger 18 which is thus withdrawn from the index notch of the table, this action also admitting low-pressure fluid above a piston 15 to lower the table clear of the cutter. The table may then be indexed by hand to bring the next pocket d of the work under the cutter, after which raising of the valve 17 lifts the table to operative position and re-inserts the index plunger 18, the arrangement being such that the table cannot be raised unless the plunger 18 has entered its index notch. To start the next cutting operation, valve 44<1> is rotated anti-clockwise to cause fluid to pass by pipe 86 and move valve 50 to the right and actuate plunger 23 to lock the table in operative position, and valve 44 is moved manually to the right to admit fluid by pipe 47 to valve 35, thus withdrawing plunger 34 and pawl 32 from the ring 28 which is then rotated anti-clockwise to starting position by a spring to set the motor 27 ready for cutter operation. The valve 44 is next moved to the left-hand position shown, whereupon fluid proceeds by pipe 46 to move valve 35 to the left, with the plunger 34 against the periphery of ring 28, and admitting fluid from pipe 49 by valve 50, pipe 51, valve 24, pipe 52, valve 35, and pipe 48 to the reversing valve 58, from which it is directed by pipe 55 to motor 27 to oscillate the cutter on a cutting stroke. On completion of the cutting stroke, further movement of the vane 26 is prevented by its cylinder and the pressure in .the supply line rises and is transmitted by pipe 77 to a pilot valve 64 which is normally held raised by a low-pressure supply 65 acting on a differential piston of the valve. This lowers the valve and admits high-pressure fluid to valve 61, moving it to the right as shown and connecting the high-pressure channel 67 by passage 71 to valve 62, which is thereby also moved to the right. Fluid from channel 67 is thus admitted by pipe 72 to cylinder 42, drawing the pawl 38 downwards ready for a rotational feed of the plate 7 and work, and is also admitted by pipe 78 to pilot valve 60 which is thereby raised against the constant low pressure to move valve 57 to the right. This admits highpressure fluid by channel 69 to reversing valve 58, moving it to the right and connecting the supply channel 68 with pipe 54, whereby the cutter is oscillated on a return stroke. At the end of this stroke the pressure rise due to inability of the motor vane 26 to move further, causes pilot valve 63 to be lowered, moving valves 61, 62 to the left and allowing fluid to proceed by pipe 74, valve 35 and pipe 75 to cylinder 42, raising pawl 38 to impart rotational feed to the work whilst the cutter is withdrawn therefrom. Pilot valve 59 is also raised by fluid from pipe 76 to move valves 57, 58 to the left to reverse the supply to motor 27 and institute the next anti-clockwise cutting stroke. These operations continue until the cutter reaches the point g<2>, and on the next withdrawal oscillation of the cutter the plunger 34 enters the recess 33 of the ring 28 to allow valve 35 to break the circuits to the cutter motor 27 and feed cylinder 42 so that the work may be indexed. Rotation of the plate 7 by the pawl 38 causes a roller 8<11> on the table 8 to ride along the cam 81 on the plate 7 so that the support 107 will be moved laterally and cause the rotational feed of the'work to take place about the axis i instead of about the axis h of the plate 7.