Patent GB-213320-A (GB)
Title: Improvements in or connected with relays and the like
IPC: F16H3/66
Filed: 1922-12-20
Abstract: 213,320. Barr & Stroud, Ltd., Stroud, W., and French, J. W. Dec. 20, 1922. Hunting switches; switches, actuating. - Relates to relay devices for gunnery and other purposes of the hunting-switch or follow-up type, in which the movements of a low-powered member are followed by those of a, member which may be high powered, the speed of following up being so controlled as to prevent over-running or oscillation due to inertia. According to the invention a power driven shaft drives a follow-up shaft through a change-speed gear and a change-direction gear in series, these gears being controlled by a device of the hunting-switch type. In the example shown the movement of the low powered member 22, Fig. 2, selectively closes the circuits of magnetic clutches 10, 10', Fig. 1, which determine the speed of the following or output shaft 18, and selectively closes also the circuits of magnetic clutches 21, which determine the direction of that shaft, power being supplied locally through the input shaft 1 which is constantly driven in one direction. The clutches control the operation of differential, epicyclic, or other gears. Variable speed gear. The shaft 1 drives directly a shaft 2<1> carrying the jockey 2 of a differential gear, and thereby the intermediate shaft 8 is driven at a speed which depends on whether the side wheel 3 or the side wheel 4 of the differential has been locked by the appropriate clutch 10 or 10' ; for these side wheels are geared, in different ratios, with the side wheels 5, 6, of a second differential whose jockey 7 is mounted on the shaft 8. If neither clutch is operative, the shaft 8 is driven at some intermediate speed depending on the load, a ratchet or like mechanism 34 being provided to ensure that the wheels 3, 5, on the high gear side shall not reverse their motion under a heavy load. In a modification a further intermediate shaft may be interposed between the shafts 1 and 8 and connected to each of these by pairs of differentials similar to 2, 3, 4 and 5, 6, 7. In this case there will be four clutches similar to 10, 10', and by energizing or releasing these singly or in pairs it is possible to obtain nine variations of gearing. Where the load on the shaft 18 is heavy it is possible to dispense with the clutch 10 leaving the high gear free except for the ratchet 34. For the magnetic brakes or clutches may be substituted band brakes, pawl and ratchet devices or the like, or the oil brake described below. Reversing gear. The motion of the shaft. 8 is communicated to the output shaft 18 through a pair of differentials 12, 13, 14, and 15, 16, 17, of which the jockeys 12, 17, are carried by the respective shafts, the side wheels 13, 15, being directly engaged while the side wheels 14. 16 are engaged through a reversing pinion 19. Thus the shaft 18 will be driven in a direction similar or opposite to that of the shaft 8, according to the clutch 21 which is operative. The shaft 18 is locked, when the follow-up motion has been completed, by the release of the armature 42 of magnet 43 as described below. Follow-up action. The contact 22, Fig. 2, whose motions are to be repeated by the shaft 18, Fig. 1, controls the direction of motion of this shaft by closing the circuit of one or other of the clutches 21, through the appropriate contact 27 or 28, whereupon the shaft 18 while turning against the load as required also moves the contact carrier 25 until the contact 22 once more lies in the fiducial or insulated region between the contacts 27, 28. To prevent over-runninn. due to inertia., the low gear 4, 6, is brought into play through contact 31 and clutch 10<1> during the final approach to the fiducial position; but when the contact 22 lies on either of the contacts 29. 30, it brings the high gear 3, 5, into play through clutch 10, while in the intermediate position neither clutch is energized and the gear ratio, owing to the differential action, assumes some intermediate value depending on the load, the ratchet 34 preventing reversal due to the load of the motion of the high gear elements 3, 5. The electromagnet 43 is energized at the same time as the clutches 21, so that when these are released the armature 42 locks the shaft 18. Oil pressure brake. Instead of the magnetic clutches or brakes 10, 10<1>, 21, the means for preventing the rotation of a shaft may comprise a crank pin 46 fixed to the shaft and operating one or more pistons 47 connected by oil-filled passages 51 with a reservoir 55. The shaft can then be stopped by closing the passages 51 by means of a valve 52 operated electromagnetically or mechanically. Specification 15760/10, [Class 38 (iii), Electric motor control systems &c.], is referred to.