Rotary transformer shunt calibration

#This invention relates generally to rotary transformer systems and, more particularly, to an improved shunt calibration system for a rotary transformer transducer system.

#Rotating shaft torque transducers often utilize the maintenance advantages of rotary transformers for signal transfer. Rotating transformers differ from conventional transformers only in that either the primary or secondary winding is rotating. Such rotary transformers are generally described in U.S. Pat. No. 3,611,230 entitled Rotary Transformer Structure. One transformer is used only to transmit the AC bridge supply voltage to the strain gage bridge, and a second transformer is used to pick off the output voltage. Thus, there is no direct contact between the rotating and stationary elements of the sensor. Due to this isolation, an external or dummy bridge or a Ground Reference Network, as disclosed in U.S. Pat. No. 3,790,811 must be used on the instrument side of the transformers to provide a current return path for the AC carrier instruments used.

#When a rotary transformer system is utilized in conjunction with a strain gage bridge transducer to measure the torque on the shaft, it is desirable to calibrate the strain gage bridge relative to the electrical instrumentation. Such calibration is necessary because of normal variations in the electrical equipment which provides the multiple functions of supplying the signal to the strain gage bridge and which receives the output signal from the strain gage bridge. In addition, it is sometimes desirable to calibrate the equipment while the shaft is rotating.

#The various objects and advantages of the present invention will become more apparent upon reading the following detailed description of the invention taken in conjunction with the drawings. In the drawings, wherein like reference numerals identify corresponding components:

#FIG. 1 is an electrical representation of the present invention in a rotary transformer system illustrating both the electrical coupling and the mechanical isolation of the system;

#FIG. 2 is a front elevation of a first embodiment of the magnetic switches and ring assembly of the present invention;

#For a full understanding of the present invention, reference will be made to an environment in which the invention has a particular utility. That environment is a rotary transformer transducer system. It must be appreciated that once the broad principles of the present invention are understood, the invention may be utilized in other environments.

#A rotary transformer transducer system is illustrated in FIG. 4 for measuring the torque of a rotatable shaft 10. The input signal is coupled to the shaft by a transformer 12 having a stationary winding 14 which enters a connecting block 16, and a rotatable winding 18 connected to a strain gage bridge transducer 20. The output is taken from the bridge by a second transformer 22 having a rotatable winding 24 coupled to the transducer and a stationary winding 26 which is also coupled to the connector block 16.

#Transformers 12 and 22 are of the rotary type such as those manufactured by Lebow Associates, Inc., of Troy, Michigan, and generally disclosed in the aforementioned U.S. Pat. No. 3,611,230. Both rotary transformers are mounted within a stationary housing 28.