Measuring and testing – Dynamometers – Responsive to torque
Patent
1985-07-01
1987-04-14
Ruehl, Charles A.
Measuring and testing
Dynamometers
Responsive to torque
73 1R, 73 1C, 7386249, G01L 310, G01L 2500
Patent
active
046568751
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of measuring the deformation of a rotating shaft in which calibration means are used for calibrating the measured deformation value.
Such a method is known from U.S. Pat. No. 3,134,279, in which the calibration means are formed by a resistor of known value connected parallel to a strain gauge. These calibration means are temperature sensitive and by this circuitry only the proportionality error of the measuring system is detected.
The invention has for its object to obviate said disadvantage. In the aforesaid patent, a resistor 55 is connected in parallel with the strain gauge 18 through the relay A1. When thus connected, the resistor unbalances the strain gauge bridge by a predetermined amount corresponding to the apparent transmission of a predetermined torque. Consequently, this unbalanced condition is used to calibrate the bridge. As noted, however, the resistor 55 will be temperature sensitive and its predetermined value will thus change, giving a false calibration value. This invention overcomes this disadvantage, in the broadest sense, by measuring the values of three signals, one of which is the indicated signal of the deformation of the shaft, another of which is an approximation of what the indicated signal would be in the absence of deformation of the shaft (hereinafter the signal produced by the zero calibration means) and the third of which is an approximation of what the indicated signal would be if it were unbalanced as in the above patent (hereinafter the signal produced by the proportionality calibration means). A linear plot of these three values allows the calibrated value of the indicated signal to be calculated with great accuracy. When proportionality calibration and zero calibration means pick up signals by means of proportionality calibration and zero calibration bridges arranged on an annular metal carrier connected with the shaft and having the same temperature as the measuring bridge, the measuring value originating from the deformation measuring bridge is compensated for temperature, whilst a calibration signal of the same order of magnitude as the measuring signal is obtained. Moreover, by the zero calibration signal picked up by means of a zero calibration bridge a satisfactory interpolation of the proportionality error between zero calibration and calibration value is possible. Finally, owing to the accurate zero calibration value it is possible to measure a propulsion value in the direction of length, which differs only little from the zero calibration value and which is a measure for the propulsion of, for example, a vessel. The propulsion (propelling pressure) is a very interesting datum for a ship for setting optimum operational conditions of a vessel. The number of revolutions and/or the blade of adjustable propellers can be set in dependence on the measured propelling pressure for different navigation conditions.
The invention will be described more fully hereinafter with reference to a drawing.
The drawing shows schematically in
FIGS. 1 and 4 are similar views but illustrating different embodiments of the invention,
FIG. 2 a graph of the deformation measured by the device of FIGS. 1 and 4,
FIGS. 3 and 5 a block diagram of the device of FIGS. 1 and 4 respectively,
FIG. 6 a perspective view of the device of FIG. 4.
The rotating shaft 1 is provided with pick-up means 3 formed by a measuring bridge of strain gauges known per se. Furthermore, calibration means are rigidly connected with the shaft 1 so that they rotate together with the shaft 1, said calibration means 7 consisting of a carrying ring 8 having zero calibration means 9 not affected by the deformation of the shaft 1 and proportionality calibration means 10 consisting each of a bridge of strain gauges arranged at such a place in the carrying ring 8 that they have the same temperature as the shaft 1. Finally a first alternating switch 4, amplifying means 20, modulation means 5, transmitted means 6, an oscillator 21 and a secondary feed circuit 24 for the electric feed are rigidly
REFERENCES:
patent: 3134279 (1964-05-01), Sims et al.
patent: 3234787 (1966-02-01), Ruge
patent: 3535637 (1970-10-01), Guransson
patent: 3759093 (1973-09-01), Farr
patent: 3797305 (1974-03-01), Haskell
patent: 3850030 (1974-11-01), Adler
patent: 3877300 (1975-04-01), Ginns
patent: 4535854 (1985-08-01), Gard et al.
Suzuki et al., "Measuring Shaft Torque During . . . Pump Turbines", Water Power, vol. 23, No. 1, Jun. 1971, pp. 20-25.
Ruehl Charles A.
Snyder John P.
Techno Diagnosis B.V.
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