Patent GB-1437539-A (GB)
Title: Micrometer with digital reading
IPC: G01D5/04
Filed: 1973-08-07
Abstract: 1437539 Digital micrometer TESA SA 7 Aug 1973 [24 Sept 1972 25 June 1973] 37432/73 Heading G1M A digital micrometer comprises a fixed support constituted by tubes 1, 5, a micrometer screw 2 threadably engaging the fixed support through a tolerance compensation device 3, a body 7 axially fixed relative to the screw 2 and angularly fixed relative to the fixed support, a tube 19 rotatably mounted in and axially fixed relative to the body 7, either the tube 19 having a pair of helical grooves 28, 29 in its inner surface and the tubes 5 having a pair of pins 30 fixed therein, or vice versa, the pins 30 engaging the grooves 28, 29, whereby as the screw is rotated, and the screw, the body 7 and the tube 19 move axially relative to the fixed support, the tube 19 is caused to rotate and figures 25 on the peripheral portion 20 of tube 19 indicate in a window 23 the units or the units and tenths of the measurement. Pins 30 are mounted on a spring ring 31. The tube 19 is rotatably mounted in body 7 by means of bearings 20, 21. The screw 2 is extended rearwardly by a shaft 4 which may be rotated by means of a ratchet 18 or a drive ring 15 coupled to shaft 4 by a hub 16 and screw 17. Body 7 is rotatably connected and axially fixed to the hub 16 by a ball bearing 14, and the front end 6 of body 7 slides on the tube 5, rotation of body 7 being prevented by a shoe 8 engaging a groove 9 in tube 5. The pitch of the grooves 28, 29 may be equal to or greater than the measuring range of the instrument. The micrometer is also provided with a digital or analogue means for displaying the fractions of a unit of a measurement result. In the digital system of Figs. 1, 4, a member 32 is rotatably mounted on the hub 16 and is rotated as the screw rotates by means of a pinion 36 meshing with teeth 35 on the member 32 and teeth 12 on the part 11 of body 7. Member 32 has a series of lateral legs 37 to which are pivoted prisms 39 about axes 38, the prisms having figures on their faces. The prisms are rotated about their axes 38 as the member 32 rotates about the screw by means of a cam 46 prevented from rotation by an arm 48 engaging a stop member 49. As shown in Fig. 4, the faces of the prisms indicate the tenths and hundreds of a unit, and the thousandths are indicated by a scale 42 on the member 32. Alternatively Fig. 3 (not shown) the faces of the prisms may indicate the tenths, and the scale on member 32, the hundreds and thousandths. In the analogue system of Fig. 5, the fractions are indicated by a scale 54 on the body 7. The portion 22 of member 19 exhibits a marking alongside the figure 25. This marking may take the form of sawteeth Fig. 2 (not shown), each sawtooth occupying an interval around the periphery corresponding to one unit of measurement. In Figs. 4 and 5, the marking 50 consists of alternate black and white zones 51, 52 each corresponding to half a unit and the faces of the prisms or the portions of the scale 54 are marked in black or white according to whether they correspond to a black or white zone. Each interval corresponding to a unit of measurement may be split up into more than two zones e.g. four zones: the zones may be of unequeal lengths and different colours may be used for the zones, the faces of the prisms or the portions of scale 54 being correspondingly coloured. Specification 1437540 is referred to.