GB884381A - Improved method and apparatus for angular division and/or measurement - Google Patents

Abstract

884,381. Indexing means for gear gauging apparatus. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Jan. 5, 1959 [Oct. 4, 1957], No. 31112/57. Class 106 (2). [Also in Group XX] Apparatus for measuring the angular motion of a body about a fixed axis passing therethrough, or for dividing said motion into determined angular steps comprises a light wedge formed by two plane light reflecting surfaces relatively inclined at an acute angle and one or more light-reflecting surfaces arranged to have rotation imparted to it or them in accordance with the rotation of said body and to reflect a beam of light on to the wedge so that the beam is returned by the wedge in its plane of incidence. As shown in Fig. 4 a light wedge of angle # is open at its apex and light from a source 3 is passed through the apex to a reflector 4 carried by a rotating body so that, each time the reflec- # tor completes a rotation through an angle -, 2 the light beam returns along its incident path. The rotating reflector may be mounted on a body to which is attached a toothed wheel to be checked (Fig. 12, not shown). The returning ray may be viewed by an auto-collimator the indication of each successive step of angular movement of the body being obtained by the successive presentations of an image of the auto-collimator slit in the field of view. Alternatively the image of a graticule projected on to the moving mirror may appear on a scale. To cover more than 90 degrees of movement, several mirrors 4 may be provided in the form of a cube or polygon or the incident path of the light beam may coincide with the axis of rotation of the body carrying a prism having one or two reflecting surfaces. When the prism has only one reflecting surface, two light wedges may be provided as shown in Fig. 8. The direction of the light ray from the source may be inclined to the plane of Fig. 9 so that the ray ultimately reflected from the light wedge may fall on the viewing surface 7 and a scale 8. To allow for continuous indication of angular position there may be provided as shown in Fig. 10 two mirror cubes which turn simultaneously about a common axis but are relatively displaced by the angle #/4. In this case there are two light wedges and two scales are provided so that at the commencement of one increment and the completion of another an image appears at the opposite ends of the respective scales. This may also be achieved by use of a single wedge and a single mirror cube.