GB798092A - Improvements in on-off recorders - Google Patents

Abstract

798,092. Recording-apparatus. ROBINSON & PARTNERS, Ltd., F. C., and ROBINSON, F. C. Dec. 18, 1956 [Oct. 3, 1955], No. 28134/55. Class 106 (4). [Also in Group XV] An on-off recorder for a machine in which a pen 15 is supported in contact with the metal coating of a chart 14 traversed therepast has a switch 26 controlled by the machine to apply voltage between the pen 15 and metal coating over periods determined by the operation of the machine. The recorder of Specification 729,663 is modified to use as its heat-sensitive chart, a backing material coated with a metal which will be removed by volatilization upon the application of a voltage of the order of 10-50 volts, e.g. cadmium or aluminium, the coating having a thickness of the order of 10-150 millimicrons. The chart is drawn from a supply roll 16 by a motor-driven roller 18 passing under a contact roller 27 receiving current through a brush 23 from a rectifier 22 fed from the secondary of a mains transformer 21. A series of pens 15 are arranged transversely of the chart and when a switch 26 under the control of a machine to be monitored is closed the associated pen will produce on the chart a trace e.g. <SP>1</SP>/ 16 inch wide. Screws are provided for varying the spring pressure of each pen against the chart and the pens may take the form of flat metal strips, brushes formed of a number of fine wires or preferably wheels which reduce the tendency for metal oxide to accumulate. During recording the metal is burnt away in advance of the pen which thus intermittently encounters non- conducting spots. At these times a capacitor 29 charges and serves to reduce the current required and also reduces electrical interference with radio equipment.