Patent GB-593865-A (GB)
Title: Improvements in or relating to instruments for recording surface roughness
IPC: G01B5/28
Filed: 1945-06-18
Abstract: 593,865. Gauging surface roughness. BLOXAM, H. P. [Representative of TOMLINSON, G. A.]. June 18, 1945, No. 15424. [Class 106 (ii)] An instrument for recording the roughness of a curved surface has a flexible sole which can adapt itself to the surface and thus constitutes a reference surface for a probe which moves normally to the sole and projects through it into contact with the test surface. The sole 6 comprises a strip of thin steel and vertical arms 10, 11, having handles 17, are secured to its ends. A strut 14 extends between the vertical arms, the upper ends of which are linked by a spring to maintain the sole under tension. A base-plate 18 is secured, by means of a shoe piece, transversely to the sole and carries at one end a'channel piece, to the ends of which are secured two spring leaves 20, 21. The other ends of the spring leaves are secured to metal blocks and connected by a bracket 25, the probe 26 being held in the blocks by setscrews and projecting through holes in the base plate, shoe piece and sole. A bridge piece 28, also secured to the base-plate, carries a strip 29, which may be of phosphor bronze, on which is mounted a bearing bracket 30, the vertical position of which may be adjusted by a screw 35. The upper probe-carrying block is connected by a flexible steel strip 34 to a block pivoted in the bearing bracket 30 and carried by a transverse lever 33 which is thereby rotated by vertical movement of the probe in its spring mounting. An arched resilient recording arm 37 is pivoted to one end of the lever 33 and an adjusting screw 38 enables the angular position of the arm relative to the lever to be adjusted against a spring. A recording needle is held in the outer end of the recording arm, which is bent into U-shape, and the needle co-operates with a piece of smoked glass in a holder 47, its pressure being adjustable by means of a screw 41 in'the lever 33 which bears on the recording arm. The needle may be retracted by means of a control arm 48 frictionally pivoted to the base-plate 18. The holder 47 is secured to a tube carrying at its other end a notched plate 46, the tube running on a slide rod and the notched plate engaging a guide rod 44, both of which are carried by the bridge piece 28. An arm 54 engages the notched plate and traverses it, and thereby the smoked glass holder, against the pull of a spring as a screw, on which it is mounted, rotates. The screw is rotated as the instrument is moved over the test surface by means of rubber-tyred rollers 52 mounted in a bracket 49. When used to test concave surfaces, the base-plate, and so the sole, may be urged outwardly by means , of a pivoted bifurcated pressure-plate 56, pressure being applied by means of a compression spring 61, centred by a spigot. When this pressure is not required, a retaining pin may be passed through the upper end of the spigot to retain the spring in compressed form. The instrument may be used with a thin steel track (not shown) provided with cross-pieces so that it may be held stretched over the test surface by hand or by means of cords. The track is slotted to enable the probe to contact the test.surface and may be provided with a longitudinal scale which co-operates with a pointer 5 secured to the base-plate 18. The track and sole are preferably chromium-plated. Specification 568,509 is referred to.