Spindle probe with orbital transformer

Abstract

A probe is mounted on the nose of a toolholder which fits into the spindle of a numerically controlled machine tool. An oscillator is mounted within the toolholder and is powered by a battery within the toolholder. The output of the oscillator is coupled to a primary coil on the toolholder which is inductively coupled to a ringshaped secondary coil on the spindlehead of the machine tool. Switches within the toolholder are wired to the oscillator to cause it to shift frequency when the probe stylus makes contact with a workpiece when moving along any one of the X, Y or Z axes. The ringshaped secondary coil is coupled to the machine tool's NC circuits to indicate when the probe makes contact with the workpiece.

The principles of this invention having now been fully explained in connection with the foregoing, we hereby claim as our invention: 
     
       1. A spindle probe for a machine tool having a spindlehead and having a spindle rotatably mounted on said spindlehead for rotation about a spindle axis, said spindle being adapted to receive a toolholder and said spindle probe comprising: a toolholder adapted to fit in said spindle;   a probe element on said toolholder;   an oscillator within said toolholder;   means within said toolholder for energizing said oscillator; .Iadd.   means coupled between said oscillator and said means for energizing said oscillator for providing a completed electrical circuit path between said oscillator and said means for energizing said oscillator when said toolholder is inserted into said spindle; .Iaddend.   means within said toolholder for altering the output of said oscillator when said probe element contacts a surface being measured;   a primary coil mounted on said toolholder and coupled to the output of said oscillator; and   a secondary coil mounted on said spindlehead adjacent to said toolholder to receive signals from said primary coil.   
     
     
       2. A spindle probe according to claim 1 wherein said secondary coil is ring-shaped and is mounted on said spindlehead coaxial with said spindle axis. 
     
     
       3. A spindle probe according to claim 1 and further comprising an arm projecting laterally from said toolholder, said primary coil being mounted in said arm. 
     
     
       4. A spindle probe according to claim 3 wherein said means for energizing said oscillator comprises a battery and .[.further comprising.]. .Iadd.wherein said means for providing a completed electrical circuit path between said oscillator and said means for energizing said oscillator when said toolholder is inserted in said spindle comprises .Iaddend.a pressure actuated switch on said arm and means coupling said switch in series with said battery to connect said battery to said oscillator circuit when said switch is actuated. 
     
     
       5. A spindle probe according to claim 3 wherein there is electrically conductive metal around the portions of said primary coil which are not adjacent to said secondary coil to minimize electromagnetic radiation from said primary coil. .Iadd. 6. A spindle probe for a machine tool having a spindlehead, a spindle rotatably journaled in said spindlehead for receiving a toolholder therein and a numerical control circuit for controlling the movement of said spindlehead, said spindle probe comprising: a toolholder adapted to be received in said spindle;   an oscillator disposed within said toolholder, said oscillator including at least one switch which, when actuated, causes the oscillator frequency to change discreetly;   means disposed within said toolholder for energizing said oscillator;   a probe element fastened to said toolholder so as to actuate said oscillator switch when said probe is brought into contact with a workpiece surface;   a primary coil mounted on said toolholder and coupled to said oscillator; and   a secondary coil mounted on said spindlehead adjacent to said toolholder for receiving oscillator signals from said primary coil and for transmitting said oscillator signals to said numerical control circuit to indicate that a workpiece surface has been contacted. .Iaddend.