Patent GB-736167-A (GB)
Title: Improvements in apparatus for recording periods of electric current flow
IPC: G07C1/08
Filed: 1953-05-08
Abstract: 736,167. Recording-apparatus. ARNOLD, J. C. (Service Recorder Co.). May 8, 1953, No. 12957/53. Class 106 (4). [Also in Group XXXVI] Apparatus for recording periods of electric current flow in a circuit, comprises time-controlled means operative to move a recording sheet continuously, a stylus adapted to bear against the sheet, an electric motor reciprocating the stylus continuously transversely to the direction of movement of the sheet and means responsive to current flow in the circuit operative to start and stop the motor. The particular embodiment described is for recording periods of operation of an electrically operated machine. As shown, the apparatus comprises a record disc 5 clamped by fingers 6, 7 to a support plate 4 driven by clookwork C and a stylus 11 carried by an arm 10 pivoted, preferably in needle bearings, on one arm of a member 9 itself pivoted on a boss 8 with another arm thereof formed with a rack 15 moved outwardly to cause a spiral record by the fingers 6, 7 engaging an actuator 14. A wear plate 12 near the middle of the stylus arm 10 is urged by a spring S into contact with an eccentric 13 driven through reduction gearing by an electric motor 16 of the type used to operate electric clocks. The record disc is preferably dark in colour and covered with a thin layer of wax which is scraped away by the stylus 11 leaving a narrow line when the eccentric is not turning and a broad solid line when the eccentric is being driven by the motor 16 at a suitable speed. Control mechanism for the motor 16 in a ventilated housing 19, 20, Fig. 6, comprises an electromagnet 21 adapted when energized to attract a clapper 22 " floating " in a cage 23 to operate a loaded microswitch 24 in the motor circuit. The coils 29 of the electromagnet 21 may be in the power circuit of the machine being checked and the motor 16 may be operated from the same power source or from a different source. The coils 29 may be in circuit with the secondary of a transformer whose primary is in circuit with the source of power for the machine. A variable resistance may be inserted in the transformer circuit to render the magnet 21 ineffective to operate the micro-switch 24 until a predetermined current is drawn as e.g. in recording actual welding in an electric arc welding machine. To record slight currents below the limit of sensitivity of the solenoid controlled micro-switch, a current may be imposed on the solenoid circuit just insufficient to operate the switch so that a slight additional current will be adequate. When a transformer is used it is advantageous to use a magnet of a type designed to become saturated under the influence of relatively low exciting current as the same transformer can then be used for a wide range of loads since the impedance afforded by such a magnet operates to prevent undue rise of current in the secondary under increased loads. The magnet 21 is of modified horseshoe type having a core of laminated silicon steel and magnetizes under relatively light current, has a low hysteresis loss and low residual magnetism. One pole face is recessed slightly to reduce magnetic coupling of the clapper and ensure release when current ceases. Specification 388,139 is referred to.