Patent GB-189850-A (GB)
Title: Improvements in mechanical relays
IPC: G05D3/12
Filed: 1921-09-02
Abstract: 189,850. Barr & Stroud, Ltd., Barr, A., and Stroud, W. Sept. 2, 1921. Tell-tale apparatus.-A mechanical relay comprises hunting mechanism for causing a highpower output shaft M to copy the low-power rotations of an input shaft K controlled, for example, by a distant gyro-compass, the additional power being derived from the shaft. C of a servomotor such as that described with reference to Fig. 7 of Specification 16480/10, [Class 97 (i), Optical systems &c.]; The input shaft K, on receiving a rotary movement from the distant station, carries with it the jockey j of the differential d. The bevel-wheel e of this differential, being geared to the output shaft M at 17, 18, shown as if disconnected, offers so much resistance that all the motion is taken up by the bevel-wheel e<1> and the jockey J of a differential D similar to that described with reference to Figs. 8, 9, and 10. of Specification 126,798, [Class 106 (i), Calculating &c.]. The motion of the jockey J causes the bevel-wheel E to move through a small angle backwards or forwards, and thereby to set the servomotor in action through gearing Rand H, X or H<1>, Y as described below. The remainder of the jockey's motion is taken up by the bevelwheel E', relative motion of the wheels E, E<1> being controlled by scroll-plates F, F<1>, which are attached to them and which co-operate with pins P, P<1> on arms L, L<1> of a lever pivoted at L<2>. When the pin P lies in either of the radial portions, Fig. 2, of the groove G, the plate F is locked against rotation, but when the. device is at rest, the pin P lies in the fiducial position in the central oblique portion of the groove, so that a slight rotation of the bevel wheel E and plate F raises or lowers the lever L. The pin P<1>, Fig. 3, when such rotation occurs, is consequently moved from the central radial stop portion S into the outer or the inner spiral of the groove in the plate F<1>. The rotation of this plate, in taking up the balance of the motion of the jockey J, as described above, moves the lever L, L<1 >still further away from its mean position, and so prevents the wheel E from being returned until the whole of the motion has been wiped out by the hunting action described below. The slight movement of the bevel-wheel E is communicated to a pair of arms H, H<1>, one or other of which stops a fly X or Y forming part of the servomotor. The latter comprises a power-driven shaft C which carries round the jockey 7 and so normally turns the bevel-wheels 8, 9. These bevel-wheels are geared respectively to the flies X, Y and to the bevel-wheels 14, 16 in such a way that normally the wheels 14. 16 are driven at equal speeds in opposite directions. When, however, one of the flies X, Y is stopped by its arm H or H', the corresponding bevel-wheel 14 or 16 is also stopped, and the shaft M is caused to rotate. The shaft M is geared at 17, 18 to the bevel-wheel e of the differential d. so that, as the shaft M turns, the disturbance imparted to the differential D is gradually wiped out, and when the shaft M has reproduced the motion of the shaft K, the parts of the differential are restored to the fiducial position of Figs. 2 and 3. In a modification, the scroll-plates F, F' may be replaced by two cylinders having parallel or coincident axes. Specification 128,236, [Class 118 (ii), Signals], is also referred to..