US 4,377,911 AGranted

Contour measuring instrument

AssigneeMitutoyo Mfg. Co., Ltd.

InventorsJynichi Iida, Seiji Sakagami

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Abstract

A measuring instrument for measuring the contour of the outer surface of a workpiece. This measuring instrument is of such an arrangement that the tip end of a stylus solidly secured at one end of an arm adapted for rotational movement is brought into contact with the outer surface of the workpiece by a slight pressing force, the arm in this condition is moved in the axial direction thereof, and the displacement of the stylus tracing the irregularities of the outer surface of the workpiece to vertically move due to the abovedescribed movement is converted into the rotational movement of the arm, which is measured by measuring means such as a differential transformer, whereby the contour of the outer surface of the workpiece is measured from the vertical movement of the stylus and the axial (or horizontal) movement of the arm. The arm of the measuring instrument of this type has a dual construction adapted to be held in place by means of springs, wherein a mechanism for detecting the relative movement between these dual arms is provided, whereby a force exceeding a predetermined value applied to the stylus is detected, so that the breakage of the stylus, damages of the object to be measured and the like can be prevented.

Claims12

Dependent claims

A contour measuring instrument for measuring the contour of an object, said instrument comprising:

an arm support member movable in a predetermined direction, an arm assembly having one end portion rotatably supported on said arm support member and provided at the other end thereof with a stylus, contour signal detecting means for measuring displacement of said arm assembly due to abutment of the stylus against an object to be measured while said arm support member is being fed in said predetermined direction, circular arc error correcting means for correcting errors in measured value caused to the stylus due to shifts in position in the feeding direction of the arm support member when said stylus is displaced following the contour of the object to be measured, said correcting means including a fulcrum of rotation for rotatably supporting the arm assembly in relation to the arm support member which fulcrum is movable in a direction along said predetermined direction of feeding of the arm support member, a connecting link having one end rotatably supported by said arm assembly and the other end rotatably supported by a fixed fulcrum on the arm support member and, with the tip end of said stylus positioned on a reference plane incorporating therein said arm assembly fulcrum and said fixed fulcrum of said connecting link, at least the length axis of the arm assembly portion between the fulcrum of rotation of the arm and the fixed fulcrum of the connecting link is substantially aligned with said reference plane, said connecting link having a through-hole or an extended groove through which the arm assembly can be extended, and the arm assembly is extended through and outwardly from said through-hole or extended groove, said fulcrum of rotation of the arm assembly being adapted to move in said predetermined direction of the arm support member while being abutted against a straightened guide surface provided on the arm support member.

In a contour measuring instrument comprising a Y-direction detecting mechanism including an arm assembly carrying a stylus wherein a Y-direction detecting mechanism and an object to be measured are movable relative to each other in a predetermined feeding direction other than said Y-direction so that a configuration of the object to be measured can be measured by displacement in the Y-direction of the arm assembly due to abutment of the stylus against the object to be measured and subsequent movement in the feeding direction of the stylus relative to the object to be measured,

said Y-direction detecting mechanism comprising:
an arm support member rotatably supporting said arm assembly;
a circular arc error correcting means having a guide means provided on said arm support member for linearly movably guiding a fulcrum of rotation of said arm assembly in a direction parallel to said predetermined direction, and a connecting link, one end of which is rotatably supported by said arm assembly and the other end of which is rotatably supported by a fixed fulcrum on said arm support member so that the circular arc error of said arm assembly can be corrected through causing a linear movement in said predetermined direction of said fulcrum of rotation of the arm assembly in accordance with rotating angle of the arm assembly due to a displacement of said stylus;
and
contour signal detecting means for detecting a movement value in the Y-direction of said stylus in response to a displacement of said arm assembly.

2 more elements

Dependencies are inferred from the claim text.