Patent GB-946951-A (GB)
Title: Improvements in or relating to chart position indicating apparatus
Inventor: HOLDEN ALFRED THOMAS
IPC: G01C21/14
Filed: 1961-06-08
Abstract: 946,951. Course recording apparatus; indicating apparatus. DECCA Ltd. June 1, 1962 [June 8, 1961],No 20820/61. Headings G1F and G1J. Apparatus having a chart 10 in the form of a strip carried on spools 11, 12, which chart is traversed past an indicating or marking stylus 13, is provided with a first rotatable member 31 frictionally engaging the chart to be driven by it as the chart moves, means for turning a second rotatable member e.g. an arm 30 in accordance with the required movement of the chart, spool drive means including a clutch 22, which when engaged causes the chart to be traversed at a speed greater than the required speed, and comparator means to disengage the clutch when they rotational movement of the member 31 exceeds that of the member 30 so that the actual chart movement corresponds to that of the member 30. The members 30, 31, are driven from a reversible constant speed motor 14 through an adjustable variable gear 15 e.g. a double cone gear system. The member 30 is rotated by a shaft 34 at an adjusted speed corresponding to the required speed of the chart 10. The chart is held in engagement with the member 31 by pressure from a roller 35 and a spring arm 36. Each of the spools 11,12 is driven from the gear 15 through its arm clutch 22, which is perferably electromagnetically operated. Alternatively each clutch may be driven direct from the motor 14,the speed of rotation of the shaft 34 and being adjustable by the gear 15. Only one clutch 22 is engageable at any one time depending on the direction of rotation of the motor 14. The member 31 has six segmental metal contacts 32, which can engage with a contact 33 on the arm 30. The arm 30 is connected to a negative supply and alternate contacts 32 on the member 31 are connected in circuits 39,40, in turn connected through slip rings 43 to two separate relay coils 43 supplied from a positive supply terminal 49. Thus, as the member 31 is rotated it overtakes the contact 33, and with this contact in engagement with one of the contacts 32, one of the coils 43 will be energized and the associated relay will energize one of two coils 38 which in turn energizes one of the clutches 22. As the chart 10, and thus the member 31 is moved at a higher speed than the required speed as set by rotation of the arm 30, the contact 33 will become disengaged from the contact 32, and thus the clutch 22 will also be disengaged and the chart 10 will be stopped until the contact 33 has rotated to remake the contact. Thus the chart 10 moves at the speed dictated by rotation of the arm 30 in either direction depending on which relay coil 43 is energized. In an alternative arrangement the making of the contacts 32 and 33 may disengage the respective clutches 22. The stylus 13 may be fixed and may mark the chart 10, or, as in Fig. 1, the stylus may be a mark or an endless strip 54 driven by a reversible motor 51 from a Doppler navigation equipment 50 in an aircraft. This equipment controls both the movement of the chart 10 and the movement of the strip 54 so that the stylus 13 indicates the portion of the aircraft at any particular time. The chart 10 may be moved rapidly manually for setting the apparatus by spring-loaded or ratchet-controlled pull cards (not shown), one card being provided for each direction of movement of the chart 10. These pull cards may have switches 47,48 incorporated in them to break the circuit to the clutches 22 as soon as either of the cards is pulled.