Torque measuring apparatus

Claim 2

A torque measuring apparatus comprising: a torque shaft having a plurality of circumferentially spaced apart teeth disposed about the surface thereof with adjacent teeth in fixed axially displaced connection to the shaft such that the application of torque to the shaft operates to twist the shaft and change the spacing between adjacent teeth; a sensor stationed in fixed spaced apart relation to the shaft to proviDe an output signal waveform indicative of each time one of the teeth rotate past the sensor; a comparator which receives the output signal from the sensor and provides a primary output pulse train, each primary pulse of which corresponds to the rotation of a tooth past the sensor; a bi-stable multivibrator which receives the primary pulse train from the comparator and changes state between a high and low output signal upon receipt of each primary pulse from the primary pulse train; a DC filter which receives the output signal from the multivibrator and provides an average DC output signal which is an analog indication of the actual torque applied to the shaft; and a presetting comparator which receives the output signal from the DC filter and provides a preset input signal back to the multivibrator interrupting the primary pulse train to the multivibrator and causing the multivibrator to change to a predetermined state so as to assure that the average DC output signal from the DC filter remains at a predetermined polarity regardless of the state of the multivibrator upon initiation of shaft rotation.

Claim 3

The torque measuring apparatus of claim 1 including a switch in serial connection between the multivibrator and DC filter wherein a change in state of the output signal from the multivibrator operates to switch the output signal from the switch to the DC filter between a reference supply potential and open circuit.

Claim 4

The torque measuring apparatus of claim 2 wherein the output signal waveform from the sensor generates a secondary pulse each time one of the teeth rotate past the sensor and each secondary pulse includes a negative extending portion and a positive extending portion together with a zero potential crossover point therebetween corresponding to direct alignment between a tooth and the sensor, and the comparator includes an operational amplifier having two input erminals, the first of which receives the input signal from the sensor and the second of which is biased slightly negative through positive feedback resistors to prevent a false triggering of the comparator, wherein a dip in the level of the input signal from the sensor below the negative bias operates to switch the level of the output signal from the comparator and bias the first input terminal to the operational amplifier at the zero potential baseline such that a return in the level of the input signal from the sensor back to the zero potential baseline operates to again switch the level of the output signal from the comparator back to its initial value, said instant of comparator switch back to its initial value being indicative of direct alignment between the sensor and a tooth, and further triggering a change of state in the multivibrator.

Claim 5

The torque measuring apparatus of claim 2 wherein: the DC filter is of the low pass type and includes a DC operational amplifier with a long time constant determined by a double break filter and wherein one input terminal to the DC operational amplifier is biased from the reference supply potential, the value of which determines the effective torque sensitivity of the low pass DC filter without offsetting the analog indication for zero torque.

Claim 6

The torque measuring apparatus of claim 2 wherein: the presetting comparator includes an operational amplifier having positive feedback together with a low pass filter limiting the voltage ripple input to the operational amplifier.

Claim 7

The torque measuring system of claim 2 including a low voltage reference supply which receives a variable input voltage representative of a changing temperature of the shaft and thereafter furnishes the reference supply potential which varies as a function of the variable input voltage and adjusts the effective torque sensitivity of the DC filter without offsetting the zero torque output signal so as to compensate for changes in the shaft spring constant with variations in temperature.

Claim 8

The torque measuring system of claim 6 wherein the low voltage reference supply receives the variable input voltage representative of changing temperature from a thermocouple stationed in proximity to the shaft; and the low voltage reference supply includes an operational amplifier connected to a reference compensated zenor diode and an output drive transistor, further including a filter capacitor together with a feedback resistor.

Claim 9

A torque measuring apparatus comprising: a torque shaft having a plurality of circumferentially spaced apart teeth disposed about the surface thereof with adjacent teeth in fixed axially displaced connection to the shaft, such that the application of torque to the shaft operates to twist the shaft and change the spacing between adjacent teeth; a variable reluctance type pickup sensor stationed in spaced apart relation to the shaft to provide an output signal waveform indicative of each time one of the teeth rotates past the sensor wherein the sensor includes a core with a pole piece together with an outer casing therearound having a magnetic polarity opposed to that of the pole piece so as to shield the sensor in order that only one tooth can be sensed at a time with the output signal waveform returning to a zero potential baseline for a limited period between adjacent teeth; and conversion means for converting the output signal from the pickup sensor to an analog representation of the actual torque applied to the shaft wherein the conversion means include: a comparator which receives the output signal from the sensor and provides an output pulse train, each pulse of which corresponds to the rotation of a tooth past the sensor; a bi-stable multivibrator which receives the output pulse train from the comparator and changes state between a high and low output signal upon receipt of each pulse from the pulse train; a DC filter which receives the output signal from the multivibrator and provides an average DC output signal which is an analog indication of the actual torque applied to the shaft, and a presetting comparator which receives the output signal from the DC filter and provides a preset input signal back to the multivibrator interrupting the pulse train to the multivibrator and causing the multivibrator to change to a predetermined state so as to assure that the average DC output signal from the DC filter remains at a predetermined polarity regardless of the state of the multivibrator upon initiation of shaft rotation.

Claim 10

A torque measuring apparatus comprising: a torque shaft having a plurality of circumferentially spaced apart teeth disposed about the surface thereof with adjacent teeth in fixed axially displaced connection to the shaft, such that the application of torque to the shaft operates to twist the shaft and change the spacing between adjacent teeth; a variable reluctance type pickup sensor stationed in spaced apart relation to the shaft to provide an output signal waveform indicative of each time one of the teeth rotates past the sensor wherein the sensor includes a core with a pole piece together with an outer casing therearound having a magnetic polarity opposed to that of the pole piece so as to shield the sensor in order that only one tooth can be sensed at a time with the output signal waveform returning to a zero potential baseline for a limited period between adjacent teeth; and conversion means for converting the output signal from the pickup sensor to an analog representation of the actual torque applied to the shaft wherein the conversion means include: a comparator which receives the output signal from the sensor and provides an output pulse train, each pulse of which corresponds to the rotation of a tooth past the sensor; a bi-stable multivibrator which receives the output pulse train from the comparator and changes state between a high and low output signal upon receipt of each pulse from the pulse train; a DC filter which receives the output signal from the multivibrator and provides an average DC output signal which is an analog indication of the actual torque applied to the shaft, and a presetting comparator which receives the output signal from the DC filter and provides a preset input signal back to the multivibrator interrupting the pulse train to the multivibrator and causing the multivibrator to change to a predetermined state so as to assure that the average DC output signal from the DC filter remains at a predetermined polarity regardless of the state of the multivibrator upon initiation of shaft rotation.

Claim 11

The torque measuring apparatus of claim 8 wherein the spacing between adjacent teeth is sufficient so that only one tooth is sensed at a time with the output signal waveform returning to the zero potential baseline for a limited period between adjacent teeth regardless of the amount of shaft twist received through the application of torque to the shaft.

Claim 12

The torque measuring system of claim 9 including a low voltage reference supply which receives a variable input voltage representative of a changing temperature of the shaft and thereafter furnishes a reference supply potential to the conversion means wherein the reference supply potential varies as a function of the variable input voltage and adjusts the gain of the conversion means without offsetting the zero torque output signal so as to compensate for changes in the shaft spring constant with variations in temperature.