Maag Gear-wheel & Machine Company Limited

Nikolaus Berchtold

The measuring system of the gear measuring feeler contains, as a Hall-effect sensor, two Hall-effect sensor elements which are arranged in opposing relationship to each other in the magnetic field. The differential output signal of this dual Hall-effect sensor is processed in a matching circuit which is designed as a differential amplifier circuit, to yield a measuring voltage with respect to zero volt. This measuring voltage is twice as high as in the case where only one Hall-effect sensor element is used as the Hall-effect sensor. Furthermore, the matching circuit is of a simpler structure and the measurement is substantially more precise since there is not required any reference voltage source in the matching circuit.

Differential Hall-effect gear measure feeler

The gear tooth test feeler contains a sensing lever pivotally journalled in a carrier member by means of a cross-spring joint. The cross-spring joint generates a counter-force which increases in proportion to the angular deflection of the sensing lever. Two rocking levers are arranged on opposite sides of the sensing lever. The two rocking levers are positioned between the carrier member and the sensing lever by further pivot bearings and stop members such that the rocking levers maintain the sensing lever in a central position and such that the sensing lever entrains one of the rocking levers whenever the sensing lever deflects while the other rocking lever retains its initial position and vice-versa. Two permanent magnets fastened to the sensing lever exert a magnetic force of attraction upon each of the ferrous rocking levers. When the sensing lever deflects, one of the permanent magnets moves away from its associated rocking lever, so that the magnetic force of attraction exerted upon the rocking lever diminishes. The algebraic addition of this diminishing magnetic force of attraction and the increasing counter-force of the cross-spring joint produces a constant contact pressure of a feeler tip of the sensing lever against a gear tooth flank being sensed throughout its deflection displacement path. The sensing lever is deflectable out of its central position in both directions without requiring a switching operation for selectively sensing right hand and left hand gear tooth flanks.

Gear tooth test feeler

The feeler in the tooth flank profile measuring apparatus for determining the roughness of the tooth flank surface comprises a Hall-effect sensor placed in a static magnetic field between two permanent magnets instead of the otherwise conventional piezo-electric or inductive measuring system. One of the two permanent magnets is adjustably mounted at one end of a feeler rod or arm which carries at its other end a feeler tip for scanning the tooth flank surface. A conventional cross-spring joint serves to rotationally mount the feeler rod or arm. The cross-spring joint need not be distorted or loaded for adjusting the bearing load of the feeler tip because there is provided for this purpose a magnetic bearing load adjustment device. The magnetic bearing load adjustment device not only compensates for the biasing force of the two permanent magnets of the measuring system, but generates a selectable bearing load for the feeler tip by overcompensating for the biasing force of the permanent magnets of the measuring system. This selectable bearing load for the feeler tip can be already measured during the adjusting operation. Since this bearing load is generated by the magnetic fields and since the cross-spring joint need not be distorted, the feeler has a substantially greater mobility and a substantially wider frequency response compared to known feelers. The feeler additionally has a simpler mechanical structure and the circuitry in the evaluation circuit is substantially less complicated in comparison to known feeler arrangements.

Tooth flank profile measuring apparatus containing a feeler for

The measuring system of a gear measuring feeler in a gear measuring or testing machine comprises two oppositely arranged permanent magnets mounted at an end of a feeler rod located opposite to its end provided with a feeler probe. The measuring system further comprises a Hall-effect generator or sensor fixedly connected to a housing and arranged between the two permanent magnets and spaced therefrom. The Hall-effect generator or sensor is connected to a stationary electronic circuit containing a null point or zero compensation circuit and operational amplifiers. The measuring system supplies an output signal free of any residual or remaining carrier signal and having an extended frequency response range of up to 100 kHz. The output impedance of the measuring system is low and amounts to approximately 1 ohm. The zero point and the amplification or gain can be electrically adjusted without a change in the output impedance. The measuring system has a substantially simpler structure than known inductive measuring systems, consists of a substantially smaller number of individual members, enables a longer measuring path and provides a greater run-out distance after the feeler rod has been moved into contact with a stop.

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Zurich, Switzerland

Nikolaus Berchtold