Patent GB-465447-A (GB)
Title: Improvements in and relating to automatically acting copying milling machines
IPC: B23Q35/122
Filed: 1936-07-21
Abstract: 465,447. Copying by scanning. SIEMENSSCHUCKERTWERKE AKT.-GES. July 21, 1936, No. 20209. Convention date, July 31, 1935. [Class 40 (iii)] [Also in Group XXII] In an automatic copying milling-machine having an electric tracer, particularly for making aircraft propellers &c., the work and pattern are rotated in synchronism about parallel axes and the milling tool, in addition to being moved to and from the work axis under tracer control, is moved axially along the work together with axial movement of the tracer along the pattern. The pattern 1 and work 2 are mounted between centres 4, 6, Fig. 1, which are driven by an electric motor 8, an electromagnetic clutch 9 and a chain 14. The motor 8 may be reversible or may drive through reversing gearing. A saddle 15 is slidable longitudinally by means of a screw 16 driven by a reversible motor 17 and carries a transverse slide 21 carrying the cutter 3 driven by a motor 20. A slide 35 on the saddle is linked at 36 to the slide 21 so as to move transversely therewith and supports the tracer 37 which is pivoted and axially slidable at 371. The screw 22 for feeding the slides 35, 21 is driven by a motor 23 and one of the reversely rotating drives 31, 34, which is selected by the electromagnetic couplings 26, 27. The rear end of the tracer 37 engages the lever 38 pivoted at 59 which carries a contact 39 engageable with either of the contacts 40, 41 on levers 42, 43 pivoted on the slide 35 at 44 and 45 respectively. Contacts 46, 47 on the levers 42, 43 are normally maintained by springs 48 in contact with a conductor 50. In operation, with the motors 8, 17, 20 and 23 rotating, the clutch 9 energized and the clutches 26, 27 inactive, the work and pattern are rotated slowly and the saddle 15 is slowly fed axially. A spring 51 tends to rock the lever 38 to close the contacts 39, 41 so that if the tracer is out of contact with the pattern, current will be supplied to a grid transformer 57, thus actuating a valve 54 and energizing clutch 27 so as to feed the slide 21, together with the tracer and cutter, towards the pattern and work. Pressure of the pattern on the tracer rocks the lever 38 to open contacts 39, 41 and close contacts 39, 40, thereby energizing transformer 56, valve 53 and clutch 26 to withdraw the cutter and tracer. If the tracer deflections are so great as to rock either of the levers 42, 43 and open the contacts 46, 50, 47, a transformer 55 will be cut out and the energizing current of the clutch 9, which passes through a valve 52, will be stopped, thereby throwing out the clutch and stopping rotation of the work and pattern until the pressure on the tracer has been relieved. This relieves the cutting pressure on the cutter when surmounting abrupt portions of the work. In order to maintain the axis of the cutter perpendicular to a tangent to the work at the point being cut, the cutter and motor 20 may be mounted on an angularlyadjustable table 60, Fig. 2, which is adjusted by a worm 61 driven in either direction from a motor 62 and one of the reversely driven trains 67, 71 selected by one of the electromagnetic clutches 63, 64. The clutches are actuated by grid-controlled valves 72, 73 operated by grid transformers 74, 75 energized by photo-electric cells 77, 78. A beam of light is directed from a source 76 onto the pattern 1 and is reflected on a screen 79. When the cutter axis is perpendicular to the work neither of the cells is energized, but as the pattern is rotated the beam will be reflected on one of the cells through a slot 80 or 81 in the screen, thereby actuating one of the clutches 63, 64 and rotating the table 60 to maintain the cutter perpendicular to the work. Electromagnetic clutches 86, 87 for controlling forward or backward movement of the screen 79 by means of a motor 89 and screw 83, are connected in parallel with the clutches 63, 64 so that the screen will be displaced as soon as the table 60 is rotated, thereby preventing further rotation of the table unless the transverse curvature of the pattern continues to change. The source of light 76 and‹photo-electric cells may move axially along the pattern together with the tracer 37, or may be stationary and co-operate with one portion only of the pattern, such as the zone 97, Fig. 1. If the surface of the pattern is not a sufficiently good reflector it may be treated, such as by the application of a band of tinfoil &c., at the zone 97, so as to reflect the beam of light on the screen 79, and when the source of light 76 moves axially with the tracer, the whole surface of the pattern must be so treated. The copying feed to and from the work axis may be controlled by a beam of light and photo-electric cells instead of by the tracer 37.