Area comparison gage

In a comparison gage for directly measuring the deviation in cross-sectional area of a passage from a nominal value, the gage having

• means for forming an enclosed hydraulic fluid chamber,
• at least a first and a second sensor piston slidably received in said chamber for displacing fluids therein according to the algebraic sum of the individual displacement of said pistons, said sensor pistons arranged for linear displacement in response to deviations from nominal values of respective dimensions of said passage along measurement axes, the ratio of the cross-sectional areas of said respective pistons being at least approximately equal to the inverse ratio of corresponding nominal dimensions of said passage along said measurement axes respectively,
• an output piston in fluid flow communication with said chamber for linear displacement in proportion to the displacement of fluid by said sensor pistons,
• a plurality of finger means, at least one finger means being movable along each of said measurement axes,
• means for supporting first and second groups of at least one each of said finger means so that each movable finger means is in driving relation with first and second groups of at least one each of said sensor pistons respectively, and
• said first and second groups of finger means being arranged to interiorly engage boundaries of a passage for substantially linear displacement along substantially perpendicular first and second groups of parallel measurement axes respectively,
• wherein the improvement comprises
• a plurality of stop positioning means, said stop means being arranged for engagement with said passage at a stable boundary thereof, and
• said second group of finger means comprises a finger means pair for engaging said passage along associated second group measurement axes at predetermined distances from said engaged passage boundary.

In a comparison gage for directly measuring the deviation in cross-sectional area of a passage from a nominal value, the gage having

• means for forming an enclosed hydraulic fluid chamber,
• at least a first and a second sensor piston slidably received in said chamber for displacing fluids therein according to the algebraic sum of the individual displacement of said pistons, said sensor pistons arranged for linear displacement in response to deviations from nominal values of respective dimensions of said passage along measurement axes, the ratio of the cross-sectional areas of said respective pistons being at least approximately equal to the inverse ratio of corresponding nominal dimensions of said passage along said measurement axes respectively,
• an output piston in fluid flow communication with said chamber for linear displacement in proportion to the displacement of fluid by said sensor pistons,
• a plurality of finger means, at least one finger means being movable along each of said measurement axes,
• means for supporting first and second groups of at least one each of said finger means so that each movable finger means is in driving relation with first and second groups of at least one each of said sensor pistons respectively, and
• said first and second groups of finger means being arranged to interiorly engage boundaries of a passage for substantially linear displacement along substantially perpendicular first and second groups of parallel measurement axes respectively,
• wherein the improvement comprises
• at least one movable finger means of said first group of finger means comprising
• a rotating section, said rotating section being mounted for rotational movement about a section rotation axis substantially perpendicular to a measurement axis associated with said movable finger means, and each said rotating section has
• a supporting, cylindrically arranged, shouldered element, said shouldered element having arranged at a shouldered portion thereof a transversely extending groove for receiving a measurement member therein,
• the measurement member comprises a precision machined rod element, said rod element being secured in said groove of said shouldered element for defining a measurement surface and said measurement surface extending substantially normal to said rotation axis, and
• said measurement surface being aligned with and substantially intersecting said section rotation axis, whereby a center point of said measurement surface is substantially stationary as said shouldered element rotates,
• a plurality of first fixed finger elements arranged in juxtaposition to movable finger means, said finger elements being arranged for engagement with said passage at a boundary of said passage juxtaposed to the passage boundary in contact with said rotating measurement surfaces, and
• said second group of finger means comprising a fixed and a movable finger element for engaging said passage along associated second group measurement axes at selected distances from said respective first fixed finger elements.