Geometrical instruments – Gauge – Internal
Patent
1995-12-22
1998-05-05
Will, Thomas B.
Geometrical instruments
Gauge
Internal
33556, G01B 702
Patent
active
057460035
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a gauge for checking linear dimensions of mechanical parts comprising a support casing substantially arranged along a longitudinal direction; a transducer unit coupled to the support casing and including a movable rod, substantially movable along said longitudinal direction; a substantially ball-shaped element, movable depending on variations of said linear dimensions along a direction transverse to said longitudinal direction; an elongate element, substantially arranged along said longitudinal direction, the elongate element carrying at a first end said ball-shaped element and having a second end coupled to said movable rod; and an abutment member defining a surface portion arranged along a direction inclined with respect to said longitudinal direction and transverse direction, said ball-shaped element being into contact with said surface portion and movable on it along said inclined direction.
BACKGROUND ART
U.S. Pat. No. 4,926,559 discloses a measuring device for determining the position of workpiece faces and for similar applications by means of a single contacting feeler. The device includes a casing defining a longitudinal axis; a transducer unit; an elongate element carrying at an end a ball element; a leaf spring-arranged (in rest condition) along a determined plane-, for coupling the other end of the elongate element to the transducer unit; and a member defining a plane abutment surface, inclined to the longitudinal axis. During measurement, the elongate element and the workpiece are mutually displaced and the ball element can contact, directly or through other elements, a point of the workpiece. Due to the contact of the ball element with the inclined surface and the bending of the leaf spring, the transversal deviations of the workpiece dimension from a nominal dimension cause displacement of a movable member of the transducer unit along the longitudinal axis.
In this device, the use of a flat abutment surface and of a leaf spring can give rise to drawbacks. For example, the accuracy and repeatability of the measurements can be jeopardized by torsional forces possibly acting on the leaf spring.
U.S. Pat. No. 2,842,858 discloses a gauge comprising a casing and two feeler balls coupled to the casing through flexible stems for performing mutual movements towards and away from each other. The balls are into contact with symmetrical inclined surfaces of a central prismatic element coupled to a rod that can perform longitudinal translations.
This gauge, as other conventional gauges having a similar structure, cannot be easily used for checking small and deep holes, owing to the not negligible transversal dimensions of the two movable balls and of the central prismatic element.
Moreover, the transmission of movement between the prismatic element and the balls, and the associated slidings on the inclined surfaces can cause inaccuracy and poor repeatability of the gauge. It is also necessary, when assembling the gauge, to fix with great care the position of the balls, in order to guarantee the proper cooperation between the prismatic element and the balls.
The symmetrical arrangement required for the movable balls involves a correct centering between the axis of the hole to be checked and the gauge axis.
DISCLOSURE OF THE INVENTION
Object of the present invention is to provide an accurate and reliable gauge having a particularly simple, compact and inexpensive structure.
This and other objects are achieved by a gauge for checking linear dimensions, comprising a support casing substantially arranged along a longitudinal direction; a transducer unit coupled to the support casing and including a movable rod, substantially movable along said longitudinal direction; a substantially ball-shaped element, movable depending on variations of said linear dimensions along a direction transverse to said longitudinal direction; an elongate element, substantially arranged along said longitudinal direction, the elongate element carrying at a first end said ball-sha
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Hirshfeld Andrew
Marposs Societa ' per Azioni
Will Thomas B.
LandOfFree
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