| 摘要 |
1434488 Photographic drafting THOMSON C S F 14 Feb 1974 [16 Feb 1973] 6877/74 Heading G2A In a photographic drafting machine comprising two tables movable in mutually perpendicular directions, the upper table 101 carries three pneumatically operated clamps for accurately positioning the photographic surface of a photographic plate 200 parallel to the upper surface of table 101 during photographic exposure. The clamps comprise stop blocks 61-63 having rubber stops (8), Fig. 1, (not shown), and thrust blocks 71-73 containing plungers (17) which are spring-urged to the clamping position and are withdrawn under the action of vacuum. Plate 200 is conveyed to the exposure position on a platform 111 integral with a carriage 1 having rods 2 sliding in bearings 4 carried by table 101. Carriage I is moved first to the position (as shown) in which a screw 140 and a cam 12 carried by carriage 1 make respective contacts with a stop 13 and a pin 16 carried by table 101 and secondly, after activation of the clamps and withdrawal of screw 140, to the exposure position in which magnets 11 carried by carriage 1 make contact with stop 13. During the second movement, temporary plate-locating studs 10 (on platform 111) and roller 15 (carried by cam 12) are withdrawn from plate 1, roller 15 being removed against a spring-bias by the action of a pin 16 carried by table 101. |
