Patent GB-1117252-A (GB)
Title: Improvements in or relating to time measuring and indicating instruments
Inventor: KIRCHEL ALLEN ARTHUR
IPC: G04F7/00
Filed: 1965-06-18
Abstract: 1,117,252. Indicating - apparatus. INSTRUMENT RESEARCH LABORATORIES Ltd. June 20, 1966 [June 18, 1965], No.25851/65. Heading G1J. [ Also in Division G3] The time measuring and indicating parts of mechanical time-measuring mechanism are equipoised in a liquid filling a sealed body (i.e. each part displaces its own mass of liquid) in order to provide a more consistent performance under conditions of high acceleration or vibration. When the parts include a pallet and escape wheel driven through a gear train by a spring or other motive power source fewer gears will be needed due to the damping effect of the liquid. Compatible solids and liquids include plastics such as acetal copolymers and carbon tetrachloride, suitable adjustments to the parts can be made by adding small amounts of metal or to the liquid by diluting with oil. Two devices Figs. 3 and 4 for signalling the elapse of a predetermined time interval are described wherein an equipoised wheel 21(30) is given an angular acceleration relative to a sealed body 19(28) by fluid friction induced when the body is angularly accelerated. The body 19 Fig. 3 is accelerated about an axis parallel to the axis of rotation of the flywheel 21. By making the flywheel a hollow cylinder its moment of inertia can be increased relative to its diameter in order to reduce the angular acceleration imparted to the flywheel by the torque induced by the differential effect of the fluid friction thereon. The flywheel 21 drives a wheel 24 a few revolutions to indicate the time interval, the wheel 24 and an interposed gear 23 also being equipoised. The cylindrical body 28, Fig. 4 and piston style flywheel 30 have internal and external screw threads formed therein which co-operate through the medium of the fluid there between so that under the influence of the small relative angular acceleration induced by the low friction of the fluid the flywheel 30 moves axially relative to the body 28 while making several turns until a pin 32 on the flywheel 30 strikes an indicator 33 on the body 28. Any linear accelerations superimposed do not affect the time indication. Three devices Figs. 5, 6 and 7 for indicating intervals of time are described wherein an inertia weight 39(53), (69) is moved a defined distance relative to a sealed body 34, (45), (56) under the influence of a linear acceleration applied to the body to apply a predetermined velocity to a flywheel equipoised in liquid in the body, the flywheel then driving indicating mechanism through equipoised parts. The inertia weight 39 Fig. 5 carries a rack 38 which meshes with a pinion 37 on the shaft 35 of the flywheel and disengages immediately before the inertia weight engages the body 34. The inertia weight (53) Fig. 6 (not shown) is mounted outside the body (45) by a shaft (48) carried in sealed bearings (54) and driving the co-axial flywheel (47) through two tines (49) on the shaft (48) engaging an internal thread (48) in the flywheel (47) and the shaft (48) being held against rotation by the weight (53) being square in a suitable cavity. The inertia weight (69) Fig. 7 (not shown) is threaded inside a hollow flywheel .(58) equipoised in liquid (57) and held by a catch (70) against rotation in one direction relative to the body (56) until the linear acceleration applied to the body (56) causes the weight (69) to progress inside the flywheel (58) until it strikes the end and causes the flywheel to rotate in the direction in which it is not restrained. When the equipoised flywheel has been set in motion in any of these devices it is independent of external acceleration forces.