GB1437540A - Micrometer with digital reading - Google Patents

Abstract

1437540 Digital micrometer TESA SA 7 Aug 1973 [24 Sept 1972] 37435/73 Heading G1M A digital micrometer comprises a micrometer screw 2, a series of prisms 39 carrying indicating figures on their faces and arranged to rotate about the screw axis as the screw rotates, and a cam 46 arranged to rotate each prism about an individual axis 38 as the prisms rotate about the screw axis. Screw 2 engages a fixed support comprising tubes 1 and 5 by means of a tolerance compensation system 3 (not described). The screw is extended rearwardly by means of a shaft 4 to a ratchet drive 18, and a drive ring 15 is coupled to the shaft 4 by means of a hub 16 rigidly connected to the shaft 4 by a screw 17. The prisms, which may be 4, 5 or 6 sided, are arranged between arms 37 of a member 32 rotatably mounted on hub 16 by a ball bearing 33. As shown in Fig. 1, member 32 is rotationally coupled to screw 2 by means of hub 16, and a pinion 36 rotatably mounted thereon, pinion 36 meshing with teeth 35 on the member 32 and teeth 12 on a part 11 of the non-rotatable body 7 of the micrometer. Alternatively, a direct drive may be used to drive member 32 from hub 16. The cam 46 is arranged rotatably on the hub 16 so as to have both radial and axial float and is prevented from rotation with the hub 16 by means of an arm 48 engaging a stop member 49 on the body 7. The body 7 is mounted slidably at 6 on the tube 5 of the fixed support, and rotatably on the hub 16 by means of a ball bearing 14, a shoe 8 engaging a groove 9 in the tube 5 preventing rotation of the body 7. The body 7 includes a window 40 for reading the faces of the prisms and a scale on the member 32. As shown in Fig. 2, the faces of the prisms indicate tenths and hundreds of a unit and the calibration marks 42 on the member 32 indicate thousandths. In an alternative arrangement Fig. 3 (not shown), the faces of the prisms indicate tenths of a unit, and the member 32 is marked to indicate hundreds and thousandths. The micrometer may also include an arrangement for indicating the units digitally in a further window 23 of the body 7. The arrangement includes a tube 19 rotatably mounted in the body 7 and fixed axially relative to the body 7 by the bearing 21 and by the ball bearing 20. The inner wall of tube 19 has a pair of helical grooves 28, 29 each having a pitch equal to the measuring range of the micrometer and each being engaged by a pin 30 fixed to the tube 5 of the fixed support. As the screw 2 rotates and moves axially, body 7 and tube 19 also move axially, and the tube 19 is caused to rotate by the pins 30 engaging the helical grooves. Portion 22 of tube 19 carries a units scale visible in window 23. Specification 1437539 is referred to.