Patent GB-228435-A (GB)
Title: Improvements in or relating to distance measuring apparatus for use on ships or the like
IPC: G01P5/06
Filed: 1924-07-03
Abstract: 228,435. Walker, G. July 3, 1924. Logs.-In apparatus for measuring the distance travelled by a body driven by a propeller in a fluid medium, and of the kind having an indicator controlled by means which are rotated by the propeller, compensating mechanism is provided which automatically varies the ratio between the speed of the indicator and that of the control means, in accordance with changes in the ratio between the propeller speed and the speed of the body. Means are also provided for indicating the speed of the propeller or of each propeller, and, in the case of more than one propeller, for indicating the average of the propeller speeds. Each of these speed indicators comprises two pointers which advance alternately for one minute each, then remain stationary for one minute at the end of which they are reset to zero. The Figures show an apparatus for use with two propellers, the indicators being mounted in a casing 1, and comprising propeller speed indicators 12 - - 14<1>, revolution counters 6<11>, 7<11>, 8<11>, distance and trip indicators 99, 99<1> and ahead and astern indicators 9, 9<1> for the propellers. The shafts 15, 15' of the indicators 12, 12<1> for example are provided with gears 16, 16<1> Fig. 3, meshing with a gear 16" secured to a shaft 15<11> which is driven by gearing from a synchronous motor M, Fig. 4, so as to rotate continuously at a speed proportional to that of the port propeller. To produce the intermittent movement and re-setting of the pointer 13, for example, the gear 20, which rotates loosely on the shaft 19, carries a circular magnet 27, Fig. 6, the armature 28 of which is secured to the shaft 19, so that when the magnet is energized the gear 20 is locked to the shaft and the pointer 13 is rotated. The shaft 19 also carries a disc 31 co-operating with a ball clutch 32, Fig. 11, to retain the pointer in its advanced position when the circuit of the magnet 27 is interrupted. The clutches for the pointers 12, 13, 14 are connected by bell-cranks 41 to a bar 40 adapted to be moved longitudinally by a magnet 39 to release the clutches, the pointers being then reset to zero by springs 33. Similar operating means are provided for the lower set of pointers 12', 13<1>, 14<1>. The circuits of the magnets 27, 27<1>, 39, 39<1> are controlled by clock-driven switches so as to produce the alternate advance and alternate resetting of the two sets of pointers. The shaft 19" is operated by a differential gear 26 which is driven from the shafts 15", 17<11> so that the speed of this shaft is the mean of these of the other two. The distance and trip indicators 99, 99<1> are operated by a shaft 70 geared to shafts 71, 71', Fig. 4, which are connected by gearing to shafts 74, 74' to which are secured gear segments 75, 75<1> engaging racks 76, 76<1> which are slidably mounted in guides 77 and are provided with rollers 78, 78<1> adapted to be engaged by cams 79, 79<1> on the shafts 19, 19'. By means of clutches the segments 75, 75<1> are locked to the gears 73, 73<1> when rotating counter-clockwise, but are freed from these gears when rotating clockwise. The indicators 99, 99<1> are thus operated by the two cams alternately so as to receive continuous movement in one direction. The cams are so shaped that the speed ratio between the shafts 19 or 19' and the shaft 70 is continuously varied as the cam rotates, to compensate for changes in the ratio of propeller speed to the speed of the ship &c. The revolution counters 6<11>, 7<11> are operated from shafts 50, 50<1> geared to the motors M, M'. In a modification the cams 79, 79<1> are replaced by two wheels having variably-spaced notches around their peripheries, the notches being arranged to operate make-andbreak devices in the circuits of electromagnets which operate the indicators 99, 99<1>.