GB888748A - Goniometer - Google Patents

Abstract

888,748. Measuring angles. ZEISS-SHIFTUNG, CARL, [trading as ZEISS, CARL. [Firm of]]. June 24, 1959 [June 25, 1958], No. 21653/59. Class 97(3). An instrument for accurately measuring the angle of a workpiece comprises two arms 8, 12, Fig. 1, which rotate about a common axis 30, arm 8 being coarsely adjusted, e.g. in intervals of a degree, by a gear clutch, and the arm 12 being finely adjusted by means of a step-down gearing mounted in the housing 1 below the gear clutch. The arm 8 is carried by a disc 4 having 360 radial teeth on its lower face to mesh with similar teeth on the upper face of a fixed disc 2. To disengage discs 2, 4, an arm 11 is moved by its handle 11a about axis 30 whereupon due to the threaded engagement of a shaft 7, rigid with arm 11, with a fixed sleeve, the shaft 7 is raised so that disc 4 may rotate freely about shaft 7. The angular position of arm 8 is indicated by a pointer 29 on housing 1 co-operating with a scale 28 on disc 4. For fine adjustment, a disc 14 carrying a gear 18 is rotated about a pin 15, the angular setting being read by means of index mark 17 on housing 1 against a scale 16 on disc 14. The gear 18 meshes with a gear 20 which rolls by means of pin 22 along a curved rail 21, the rolling being controlled by a pair of tapes 24 which are attached at one end to fixed sectors 25a, 25b, pass partly around their curved surfaces and the curved surface,of a roller 23, carried by gear 20, and are fixed to the roller 23 at their other end. Another tape 26 is similarly connected both to roller 23 and a sector 27, Fig. 4, so that the latter is rotated about axis 30 causing flexing of its spring pivot 13. The arm 12 is carried by sector 27. In a modification, Fig. 9, the disc 14 has a spiral scale 16a co-operating with an index 41 slidably mounted in a holder 43. On adjusting the holder 43 so that index 41 is moved through an angle u compensation may be effected for variations in the stepdown gearing caused for instance by variable tape thickness. The teeth on gear disc 4 may be undercut so as to render them somewhat elastic to compensate for inaccuracies in the position of one or more teeth.