GB757847A - - Google Patents

Abstract

757,847. Profile gauges. ANCIENS ETABLISSEMENTS AUBERT & DUVAL, A.R.J. DUVAL SUCCESSEURS. July 27,1954 [Aug. 7, 1953; June 28, 1954], No. 21932/54. Class 106 (2). [Also in Group XX] In pantographic apparatus for tracing the contour of an object the follower engaging the object is a roller of finite diameter and the tracing device is arranged to draw circles of a diameter greater than that of the roller in the enlargement ratio. As shown, Fig. 3, the object of which the profile is required to be traced is coupled to a table 11 for rotation therewith about an axis 12. The roller follower 13 is pivoted on an arm 14 adjustable in height on a shaft 15, of prismatic section, to the required part of the object. The shaft 15 is coupled to a shaft 19 by arms 16, 17 connected by a link 18 and a spring 24 by the action of which pressure is applied by the roller 13 on to the object. An arm 1 pivoted about a horizontal axis to the shaft 19 carries a tracing device 21 comprising a pair of wheels 3, 4, Fig. 1, on an axle 2 carried on a vertical shaft 5 rotated by a motor 7 to trace a circle 9, the size of which is greater than that of the roller 13 in the ratio of the enlargement provided by the linkage 1, 14, 16, 17, 18. The table 11 is driven by friction of a wheel 26 on the shaft of a motor 27 at the end of an arm 28 pivoted by a pin 31 to a link 29 also pivoted at 32, the pin 31 being connected by a spring 30 to a fixed point 33. The link and spring have a toggle action by which the wheel is held either in contact with the periphery of the table 11 or out of engagement. It is moved to this latter position at the end of a tracing operation by a ramp 43 on the table periphery. In this position the end of the arm 28 opens a switch 42 to switch off the whole mechanism. The arm 28 is guided between two pre-loaded spring plungers 34, 35. Any undue drag on the table 11 causes a reaction on the motor 27 and actuation of one of the plungers depending on the direction of motor rotation, to actuate one of the switches 40, 41. Such a condition occurs if the roller 13 encounters a portion of the surface of the object normal to the line joining the roller to the axis of the shaft 15. In this case the motor 27 is switched off and the shaft 19 coupled by an electromagnetic clutch, not shown, to a slowly running motor which continues the tracing and moves the roller over the object until the switch 40 or 41 is allowed to re-set. The shaft 19, however, is coupled to the arm 17 by a coupling which, if the transmitted torque exceeds a certain value, opens a switch to free the electromagnetic clutch. Such a condition will occur if the roller 13 enters a part of the object which is concave so that reversal of the table 11 is necessary for the tracing to continue, such reversal being effected manually through the electrical control of the motor 27. If the roller 13 engages a steep portion of the object such as would produce rapid movement of the tracing mechanism the speed of the motor 27 is reduced, say to one quarter, electromagnetically.