Gear-measuring Instruments

apparatus for measuring gear drives. The group sometimes includes apparatus for measuring a gear-cutting tool and the equipment mounted on gear-working machines.

Gear-measuring instruments measure spur gears (straight-cut and helical gears, as well as gears with external and internal gearing), bevel gears, worms, and hob cutters. Instruments for small gears (with moduli of less than 1 mm) make up a separate group. Instruments for monitoring spur gears with external gearing are often equipped with devices for monitoring other gears or elements of the gearing or the gear-cutting tool. Gear-measuring instruments can reveal particular operational properties of gears, such as their kinematic precision, smoothness of operation, completeness of contact, and side play. Multipurpose instruments can be used to check several parameters of a wheel or a single parameter within a particular range of measurements without using special extra attachments (for example, a general-purpose involute gear gauge).

Gear-measuring instruments may be stationary, in which case the gear being tested is mounted on the instrument; they may be placed on the gear for measurement; or they may be attachable, in which case the gear and the instrument are mounted from a single base on the test plate or on the machine. The most widespread stationary gear-measuring installations are of four sizes, depending on the diameter of the pitch circles of the gears being checked: 5-120, 20-320, 200-800, and 500-1,250 mm. Gear-measuring instruments are used for acceptance (final) inspection and technological testing. For acceptance inspection the instruments rate the parameters that characterize the precision of the gear as an element of a future gearing. Such instruments are used for a multiple testing method, in which the errors in a group of interrelated elements of a gear are revealed—for example, when such a group is meshed with a measuring gear whose error is disregarded. In technological testing, gear-measuring instruments determine the individual parameters of gears (pitch, profile, and so on), which are unambiguously related to some element of the technological production process (such as the cutting tool or the machine). In practice, instruments for technological testing are often used as acceptance instruments.

Gear-measuring instruments for spur gears with moduli of more than 1 mm are intended for monitoring kinematic error, accumulated error, and difference in circular pitch, radial wobble of the gear rim (wobble meter), the center distance (center-distance meter), waviness of the surface (wave meter), tooth pitch (pitch meter), the shape and location of the overhead line (contact meter), the direction of the tooth (worm gauge), the profile (involute gear gauge), tooth thickness (tooth gauge), the length of the common normal (normal meter), and the position of the initial contour.

The diversity of gear-measuring instruments is caused by the variety of geometric shapes of gears, the variety of manufacturing methods, and the possibility of revealing the same operational properties of a gear by checks on various parameters. The specific parameters that must be checked are determined by factory and industry specifications for the manufacture of gear drives and by the recommendations for standardization RS 373-65, Instruments for Checking of Spur Gears.

A system for standardized evaluation of the performance qualities of gears based on the perfection of instruments for checking kinematic errors (instruments for multiple single-profile testing) is promising. The results of such tests are in the form of a complex periodic function which can undergo harmonic analysis (for example, on a computer). The development of such means of processing the results of measurements makes it possible to avoid to a great extent the standardization of all elements of a gear, thus leading to a decrease in the number of instruments. Such a type of testing more fully characterizes the operating properties of the gear being tested and makes possible the analysis of errors in the technological process.