Ultrasonic measuring apparatus for determining wall thickness of a workpiece

Claim 2

An ultrasonic measuring apparatus for determining the thickness of a workpiece comprising: a receive transducer probe for converting acoustic signals responsive to vibrations of a workpiece under test into electrical oscillations and supplying said oscillations as an output; a transmit transducer probe having an input for converting electrical oscillations cyclically supplied to said input into vibrations which cause when transmitted to the workpiece under test the workpiece to exhibit free resonance vibrations of decaying amplitude; electronic control means which include a forward-backwards counting means counting bidirectionally at a predetermined frequency, said control means connecting the output of said receive transducer probe to the input of said transmit transducer probe in a feedback arrangement to feedback to said transmit transducer probe, responsive to the operation of said counting means, only the free resonance vibrations in the workpiece under test, and delay means coupled in circuit with said probes for causing said free resonance vibrations to be fed back after the workpiece has ceased resonating from the vibrations previously transmitted.

Claim 3

An ultrasonic measuring apparatus for determining the thickness of a workpiece as set forth in claim 1, said delay means comprising a sound transmission path interposed between at least one of said probes and the workpiece, and means coupled in circuit with said control means and coupled to said counting means for causing said counting means to count in the forward direction and accumulate counts during the time interval in which said transmit transducer probe transmits vibrations to the workpiece and for causing said counting means to start counting backwards, diminishing said accumulated counts, responsive to a signal arising from the receipt of workpiece responsive vibrations by said receive transducer probe.

Claim 4

An ultrasonic measuring apparatus for determining the thickness of a workpiece as set forth in claim 2, and including an additional counting means coupled in circuit with said control means for counting the oscillations manifest at the output of said receive transducer probe, and means coupled to said forward-backwards counting means and said additional counting means for causing said additional counting means to be rendered operative responsive to said forward-backwards counting means attaining a predetermined count condition.

Claim 5

An ultrasonic measuring apparatus for determining the thickness of a workpiece as set forth in claim 3, and including readout means coupled to said additional counting means for indicating responsive to the frequency of said oscillations a value commensurate with the thickness of the workpiece, and said additional counting means including a gate means for causing said readout means to be rendered operative after the receipt of a predetermined quantity of oscillations by said additional counting means.

Claim 6

An ultrasonic measuring apparatus for determining the thickness of a workpiece as set forth in claim 3, and including readout means coupled to said additional counting means for indicating responsive to the frequency of said oscillations a value commensurate with the thickness of the workpiece, and said additional counting means including a gate means for causing said readout means to be rendered operative for a predetermined quantity of oscillations received by said additional counting means.

Claim 7

An ultrasonic measuring apparatus for determining the thickness of a workpiece as set forth in claim 1, and including a random noise generator; switching means coupled for selectively interrupting said feedback arrangement and coupling said noise generator to said transmit transducer probe for aligning the position of said transmit and receive transducer probes relative to the workpiece, and signal amplitude responsive indicating means coupled to said receive probe for providing an indication of such alignment as a function of the amplitude of the signal received by said receive transducer probe.

Claim 8

An ultrasonic measuring apparatus for determining the thickness of a workpiece as set forth in claim 3, and adjustable time delay means coupled between said forward-backwards counting means and said additional counting means for varying the repetition rate of the cyclically transmitted vibrations in relation to the length of said sound transmission path.

Claim 9

An ultrasonic measuring apparatus for determining the thickness of a workpiece comprising: a receive transducer probe for converting acoustic signals responsive to vibrations of a workpiece under test into electrical oscillations and supplying said oscillations as an output; a transmit transducer probe having an input for converting electrical oscillations cyclically supplied to said input into vibrations which cause when transmitted to the workpiece under test the workpiece to exhibit free resonance vibrations of decaying amplitude; electronic control means which include a counting means counting bidirectionally at a predetermined frequency, said control means connecting the output of said receive transducer probe to the input of said transmit transducer probe in a feedback arrangement to feedback to said transmit transducer probe, responsive to the operation of said counting means, only the free resonance vibrations in the workpiece under test, and delay means coupled in circuit with said probes for causing said free resonance vibrations to be fed back after the workpiece has ceased resonating from the vibrations previously transmitted.

Claim 10

An ultrasonic measuring apparatus for determining the thickness of a workpiece comprising: a receive transducer probe for converting acoustic signals responsive to vibrations of a workpiece under test into electrical oscillations and supplying said oscillations as an output; a transmit transducer probe having an input for converting electrical oscillations cyclically supplied to said input into vibrations which cause when transmitted to the workpiece under test the workpiece to exhibit free resonance vibrations of decaying amplitude; electronic control means which include a counting means counting bidirectionally at a predetermined frequency, said control means connecting the output of said receive transducer probe to the input of said transmit transducer probe in a feedback arrangement to feedback to said transmit transducer probe, responsive to the operation of said counting means, only the free resonance vibrations in the workpiece under test, and delay means coupled in circuit with said probes for causing said free resonance vibrations to be fed back after the workpiece has ceased resonating from the vibrations previously transmitted.

Claim 11

An ultrasonic measuring apparatus for determining the thickness of a workpiece by means of utilizing for measurement the decaying free resonant vibrations produced by the workpiece which apparatus includes a feedback circuit for causing the vibrations produced by the workpiece to be sensed by an ultrasonic receive transducer probe and fed back to an ultrasonic transmit transducer probe for causing said transmit transducer probe to transmit the vibrations only after the decaying free resonant vibrations of the workpiece resulting from a preceding operation of the transmit transducer probe have ceased, and including control means for controlling the feedback circuit for causing said transmit transducer probe to be rendered operative for transmitting vibrations upon the receipt of the decaying free resonant portion of the vibrations, the improvement comprising: a forward-backwards counting means counting at a predetermined frequency; means for causing said counting means to accumulate counts during the interval in which said transmit transducer probe transmits vibrations and for causing said counting means to decrease the accumulated counts responsive to a signal which is responsive to the workpiece responsive vibrations received by said receive transducer probe; a further counter coupled to said forward-backwards counting means; means actuating said further counter when said forward-backwards counting means attains a predetermined status, and means for causing said further counter responsive to its actuation and subsequent to the passage of a predetermined first quantity of counts of vibrations from said receive transducer probe to count a predetermined second quantity of such counts of vibrations, the time span for counting said second quantity of counts being a measure of the thickness of the workpiece.

Claim 12

An ultrasonic measuring apparatus for determining the thickness of a workpiece by means of utilizing for measurement the decaying free resonant vibrations produced by the workpiece which apparatus includes a feedback circuit for causing the vibrations produced by the workpiece to be sensed by an ultrasonic receive transducer probe and fed back to an ultrasonic transmit transducer probe for causing said transmit transducer probe to transmit the vibrations only after the decaying free resonant vibrations of the workpiece resulting from a preceding operation of the transmit transducer probe have ceased, and including control means for controlling the feedback circuit for causing said transmit transducer probe to be rendered operative for transmitting vibrations upon the receipt of the decaying free resonant portion of the vibrations, the improvement comprising: a forward-backwards counting means counting at a predetermined frequency; means for causing said counting means to accumulate counts during the interval in which said transmit transducer probe transmits vibrations and for causing said counting means to decrease the accumulated counts responsive to a signal which is responsive to the workpiece responsive vibrations received by said receive transducer probe; a further counter coupled to said forward-backwards counting means; means actuating said further counter when said forward-backwards counting means attains a predetermined status, and means for causing said further counter responsive to its actuation and subsequent to the passage of a predetermined first quantity of counts of vibrations from said receive transducer probe to count a predetermined second quantity of such counts of vibrations, the time span for counting said second quantity of counts being a measure of the thickness of the workpiece.