Patent GB-756036-A (GB)
Title: Improvements in or relating to indicators for determining the relationship between independently moving elements
IPC: G01P3/56
Filed: 1953-08-16
Abstract: 756,036. Speedometers. PHILLIPS, C. S. Sept. 9, 1954 [Aug. 16, 1953], No. 4301/53. Class 106 (3). As applied to means for determining whether a vehicle is maintaining a predetermined rate along a course, the indicator comprises a member e.g. a pointer 11, Fig. 1, driven from the road wheel transmission so as to be displaced by an amount proportional to the distance travelled and to a preselected scale, a second member, e.g. a concentric pointer 13, Fig. 1, driven by an adjustable speed motor at a speed proportional to a predetermined speed of the vehicle to the same scale as the first member and means for indicating the relative displacement of the two members in either sense, e.g. a drum 15 showing the amount the pointer 11 is ahead of or behind the pointer 13. The scale is calibrated in miles and the distance between the two pointers indicates how many miles the vehicle is ahead of or behind a schedule set by the adjustable gearing for the motor driving the pointer 13. The predetermined speed for this schedule is indicated by a moving drum 14. A mileometer 19 may also be provided which is initially set to the total mileage to be run and thereafter indicates the mileage outstanding. A shaft 24, Fig. 2, from the transmission drives through a worm 29 two.worm wheels 30, 31. The wheel 30 oscillates a pawl driving the ratchet of the mileometer unit and the other wheel 31 drives through gearing, not shown, a worm 38 engaging a wheel 39 connected by a friction clutch to a hollow spindle 40 to which the first pointer 11 is fixed. The clock mechanism has a two-part winding shaft 42, 43 connected by a slipping clutch 44, and the shaft 42 is driven from the main driving shaft 24 so that the clock is maintained automatically wound. One of the pinions of the clock movement driving gearing opens and closes cam-controlled contacts every four seconds, the contacts controlling the energization of a solenoid coil 55, Fig. 6, whose armature 56 has pivotally mounted on it two pawl members 57, 58 straddling a ratchet wheel 59 and drawn together by a spring 60 so that the ratchet wheel is rotated in the same direction for opposite strokes of the armature. The length of the stroke may be adjusted by an abutment 61 pivoted to a bracket 62 and provided with an extension 63 engaged by a bar 64. The drum 14 is mounted on a spindle 65 bearing a cam 66 engaging a rocking lever 67 pivoted to the frame at 68 and to the bar 64 at 69. On adjusting the clock to the predetermined rate the drum is set to indicate that rate and the stroke of the solenoid altered thereby to adjust the rate of rotation of the ratchet 59. The ratchet 59 is secured to a spindle 70 having fixed thereon gearing which drives a pinion 73 on a spindle 74 on which is secured the second pointer 13. A further pinion 75 on the same shaft 74 drives a pinion 76, Fig. 8, and through pinion 78, a long pinion 79 at a rate proportional to the rate of rotation of the pointer 13. A pinion 41 on the same differential unit, driven from the spindle 24, rotates a lead screw 82 at a rate proportional to that of the first pointer 12. The screw 82 bears a nut 83 having a pinion 84 engaging the long pinion 79. If the rates of the two pointers 11, 13 vary the nut 83 travels along the screw in one direction or the other and any such movement is transmitted by a fork mounted in a groove 85 of the nut 83 to a rack member 87 driving a pinion 88 on the spindle of the differential indicating drum 15. The differential gear may actuate switch mechanism for differently coloured lamps to indicate the. relative positions of the two pointers.