Patent GB-675488-A (GB)
Title: Improvements in or relating to apparatus for measuring or indicating the roughness or undulations of a surface
IPC: G01B7/34
Filed: 1949-04-04
Abstract: 675,488. Gauging surface roughness. REASON, R. E., ADAMS, J. R., and KAPELLA, Ltd. June 14, 1950 [April 4, 1949], No. 9111/49. Class 106 (ii). [Also in Group XXIV] In a surface roughness gauge having means for constraining a traversing member to which the pick-up head is connected to move along an approximately straight line, the constraining means comprise a pair of normally parallel main links B, B<SP>1</SP> pivoted to a framework A, a pair of levers C, C<SP>1</SP> respectively fulcrumed on the free ends of the links, a pair of short links E, E2 each acting to constrain the end of the longer arm of one lever to move along an arcuate path, and pivotal connections between the ends of the shorter arms of the two levers and the traversing member D, the two short links normally lying between and approximately parallel to the main links. The pickup head is preferably of the electrical variableinductance type and may be rigid with a spigot to be engaged in a bore D<SP>2</SP> of the traversing member. Alternatively, the pick-up head may be pivoted to the spigot and guided over the test surface as described in Specifications 577,139, 579,003 and 587,127. The links B, B<SP>1</SP>, levers C, C<SP>1</SP> and the member D are of plate form and are pivoted together by spring ligaments. The short links E, E<SP>2</SP> are adjustable in length and engage in ball-and-socket fashion with the plates C, C<SP>1</SP> and with adjustable bearing members F, F<SP>1</SP>, the plates C, C<SP>1</SP> being urged upwardly by springs C<SP>6</SP>, C<SP>7</SP>, which also reduce the elastic stiffness of the linkage. The member D is traversed by rotation of a shaft H having a buttress screw-thread engaged by a half-nut K on a rod K<SP>2</SP> and urged into engagement with the thread by a spring K<SP>4</SP> acting on the rod K<SP>2</SP> and by two springs L acting on the member D. The rod K<SP>2</SP> is pivoted at an adjustable height in a post K<SP>1</SP> carried by the member D and passing through a hole in the plate C. In order to reset the member D, a hand-lever (not shown) is operated to cause an arm M<SP>2</SP> to rock the plate B, the half-nut K sliding over the ratchet teeth on the shaft H. Graduations on a frame plate G and on a plate D<SP>4</SP> secured to the member D indicate the extent of the re-setting movement. The member D is driven by an electric motor J at either of three speeds as determined by the position of a cam shaft Q<SP>1</SP> set by a knob (not shown). In one position, a cam co-operates with an arm N<SP>4</SP> to allow a gear H<SP>1</SP>, rotatable on the shaft H and driven by the motor to be clutched to a gear H<SP>2</SP> fast on that shaft by the engagement of a spring-loaded pin H<SP>3</SP> in the gear H<SP>2</SP> with a slot in the gear H<SP>1</SP>. In the other positions, a shaft carrying a pair of gears O<SP>1</SP>, O<SP>2</SP>, driven at different speeds by the motor, is moved longitudinally by an arm O<SP>4</SP> to engage one or the other of the gears O<SP>1</SP>, O<SP>2</SP> with the gear H2. The motor is started by the closing of contacts T on return of the hand-operated re-setting arm M<SP>2</SP> and continues until a further switch is operated by a stop (not shown) adjustably carried by the plate B. During the traversing movement, stops U<SP>1</SP>, U<SP>2</SP>, U<SP>3</SP> on a bar U carried by the plates B, B<SP>1</SP> operate contacts T<SP>1</SP>, T<SP>2</SP> and T<SP>3</SP> associated with an integrating circuit used, when employing the greatest speed of traverse, to determine the average roughness as described in Specifications 539,272, [Group XXXVIII], and 539,273. The contacts T<SP>2</SP>, T3 are carried by a block T<SP>4</SP> adjustable by a cam T<SP>8</SP> set by a hand knob (not shown). A bar T' carried by the block T4 co-operates with a stop U' on the bar U to determine the extent to which the plate B can initially be rocked by the arm M<SP>2</SP>. Specification 577,980 also is referred to.