Patent GB-561171-A (GB)
Title: Improvements in mechanical copying machines
IPC: B23Q35/128
Filed: 1941-09-13
Abstract: 561,171. Photo-electric automatic control systems for contour reproduction. LINDE AIR PRODUCTS CO. Sept. 13, 1941, No. 11739. Convention date, Sept. 21, 1940. [Class 38 (iv)] [Also in Groups XXXVII and XL] Work 80 is moved in relation to a machine tool 11 so that the contour of an opaque templet 90 or of a transparent line templet 50 is reproduced to the same or a different scale. Two electric motors 19, 20 drive a work support in two directions at right angles and are controlled by a rotating switch 27 periodically reversing them in turn in overlapping phases, while light passing the templet and through a rotating shutter on to a photo-electric cell determines the direction of the resultant motion. The templet and. work table are coupled and the templet edge is maintained at a predetermined average distance from the axis of the shutter by the movement. Fig. 5a shows a plan of the shutter 48 and switch contacts 44 ... 47 in relation to a transparent templet line 50 and Fig. 4 shows the circuit connections. The motor armatures 56, 57 are supplied each by a generator 53, 54 which has opposed field windings connected through opposite quadrantal switch segments contacted in turn by a rotating shoe 43 extending over 45 degrees of arc so that, with a relay contact 74 closed, the work would be moved during one rotation of the switch in eight directions differing successively by 45 degrees. When the line 50 has been made tangential to the circular opening in the shutter 48, which rotates with the shoe 43, the relay will close each time the photo-cell 33 is energized sufficiently by light passing through the line 50 and a notch 49 in the opening. Each duration of closure depends upon the degree of overlap of notch and line, and the instant of closure depends on the angular position of the notch when overlap occurs. The resulting feed motion is such as to maintain a constant degree of overlap and to feed the templet and work in the direction of the line. To eliminate the effect of time lag in the relay and in the motor circuits and to cause correct action of the overlap control, the switch segments are skewed to an angle x in relation to the longitudinal axis of the machine. No feeding motion can take place if the templet does not occupy a position such that light can fall on the photo-cell or if the position be such that the cell is continuously illuminated. The diameter of the shutter is correlated with the diameter of a rotary cutting tool so that the dimensions of the article produced agree with those of the template. A male or female copy will be produced according as the outer or inner edge of the templet is made tangential with the shutter opening. A die may be cut from a solid templet such as 90 and the die used as templet for producing a matched punch. The clearance between these may be determined or adjusted (1) by varying the relative size of shutter opening and cutter, or (2) the shutter may be mounted on an adjustable eccentric, or (3) its distance from the templet may be changed, or (4) the sensitivity of the amplifier 79 may be altered as by grid bias variation. A multiplying (e.g. pantograph) coupling between templet and work may be used to increase accuracy in the product. For work with sharp concave corners a shallow notch is used in the shutter. A portion of the shutter hole may be covered by a shield to produce a positive interruption of light in each cycle, to compensate excessive backlash in the feeding mechanism and to facilitate operation with reverse movement of the shutter.