Protective circuit for x-ray tube and method of operation

Claim 2

In an X-ray apparatus a protective circuit for limiting the value of a signal applied to an X-ray tube and comprising: signal generating means for generating a limit signal which varies in value as a function of elapsed exposure time in accordance with the value of a maximum tube rating signal; programming circuit means for developing a program signal having a value representative of the value of a preselected signal to be applied to said X-ray tube; comparator means for monitoring the limit and program signals for developing an output signal when the value of a said limit signal attains a predetermined value with respect to the value of a said program signal; and, actuatable circuit means coupled to a said comparator circuit means for, upon receipt of a said output signal, interrupting a signal which is applied to said X-ray tube.

Claim 3

An apparatus as defined in claim 1 wherein said programming means includes variable circuit means for altering the value of a said program signal in accordance with the value of the voltage to be applied to said X-ray tube.

Claim 4

An apparatus as defined in claim 1 wherein said signal generating means includes circuit means for generating a said limit signal which decreases in value with respect to time in accordance with the value of a decreasing maximum power rating with respect to exposure time of said X-ray tube.

Claim 5

An apparatus as defined in claim 3 wherein said signal generating circuit means includes variable control means for varying the rate at which a said limit signal decreases with respect to time.

Claim 6

An apparatus as defined in claim 4 wherein said programming means includes variable circuit means for altering the value of a said program signal in accordance with the value of the voltage to be applied to said X-ray tube.

Claim 7

An apparatus as defined in claim 4 wherein said programming means includes variable circuit means for altering the value of a said program signal in accordance with the value of the current to be applied to said X-ray tube.

Claim 8

An apparatus as defined in claim 4 wherein said programming means includes first variable circuit means for altering the value of a said program signal in accordance with the value of the voltage to be applied to said X-ray tube; and, second variable means for altering the value of a said program signal in accordance with the value of the current to be applied to said X-ray tube.

Claim 9

An apparatus as defined in claim 1 wherein said signal generating means includes circuit means for generating a said limit signal which decreases in value with respEct to time and which varies in the rate of decrease in value with respect to time.

Claim 10

An apparatus as defined in claim 8 wherein said programming means includes first variable circuit means for altering the value of a said program signal in accordance with the value of the voltage to be applied to said X-ray tube; and, second variable means for altering the value of a said program signal in accordance with the value of the current to be applied to said X-ray tube.

Claim 11

An apparatus as defined in claim 1 wherein said signal generating means includes circuit means for generating a said limit signal which decreases in amplitude by a predetermined amount for N intervals of time where N is equal or greater than five.

Claim 12

An apparatus as defined in claim 1 wherein said signal generating means includes circuit means for generating a said limit signal having a plurality of timed portions each being of a different amplitude.

Claim 13

An apparatus as defined in claim 11 wherein said programming means includes variable circuit means for altering the value of a said program signal in accordance with the value of the current to be applied to said X-ray tube.

Claim 14

An apparatus as defined in claim 11 wherein said programming means includes first variable circuit means for altering the value of a said program signal in accordance with the value of the voltage to be applied to said X-ray tube; and, second variable means for altering the value of a said program signal in accordance with the value of the current to be applied to said X-ray tube.

Claim 15

An apparatus as defined in claim 1 wherein said signal generating means includes a plurality of circuit means each for generating a said limit signal which varies in value with respect to time in accordance with one of a plurality of different predetermined tube rating signals; actuatable switch means for selectively developing a pattern of control signals representative of a desired one of said plurality of predetermined tube rating signals; and, second actuatable circuit means coupled to said actuatable switch means for, upon receipt of a pattern of control signals, actuating a signal generating circuit means corresponding to said received pattern of control signals to thereby generate a said limit signal which varies in accordance with a selected one of said plurality of predetermined tube rating signals.

Claim 16

An apparatus as defined in claim 14 wherein said programming means includes variable circuit means for altering the value of a said program signal in accordance with the value of the current to be applied to said X-ray tube.

Claim 17

An apparatus as defined in claim 14 wherein said programming means includes first variable circuit means for altering the value of a said program signal in accordance with the value of the voltage to be applied to said X-ray tube; and, second variable means for altering the value of a said program signal in accordance with the value of the current to be applied to said X-ray tube.

Claim 18

An apparatus as defined in claim 1 wherein said signal generating means includes a timer means for developing a plurality of patterns of signals each representative of the elapsed time; a plurality of circuit means each for generating a limit signal which varies in accordance with one of a plurality of predetermined time functions; and, second actuatable circuit means coupled to said timer means for, upon receipt of one of a said plurality of patterns of signals, actuating a signal generating circuit means corresponding to a said received pattern of signals to thereby generate a limit signal which varies in accordance with a selected one of said plurality of time functions.

Claim 19

An apparatus as defined in claim 17 wherein said programming means includes variable circuit means for altering the value of a said program signal in accordance with the value of the current to be applied to said X-ray tube.

Claim 20

An apparatus as defined in claim 18 wherein said prOgramming means includes first variable circuit means for altering the value of a said program signal in accordance with the value of the voltage to be applied to said X-ray tube; and, second variable means for altering the value of a said program signal in accordance with the value of the current to be applied to said X-ray tube.

Claim 21

A control system for indicating that the input power which is applied to an X-ray tube has exceeded a level defined by a maximum tube power rating which varies in value with respect to time and comprising; tube limit signal generating means for developing a limit signal which varies in value as a function of elapsed exposure time in accordance with variations in a said maximum power rating of the tube with respect to time; variable programming circuit means for developing a program signal having a value representative of the value of voltage and current signals applied to said X-ray tube; comparator means for monitoring the limit and program signals for developing an output signal when the value of a said limit signal attains a predetermined value with respect to the value of a said program signal; and indicator circuit means coupled to a said comparator circuit means for, upon receipt of a said output signal, developing an output indication that the tube input power has exceeded the maximum power rating.

Claim 22

A control system for indicating that the input power which is applied to an X-ray tube has exceeded a level defined by a maximum tube power rating which varies in value with respect to time and comprising; tube limit signal generating means for developing a limit signal which varies in value as a function of elapsed exposure time in accordance with variations in a said maximum power rating of the tube with respect to time; variable programming circuit means for developing a program signal having a value representative of the value of voltage and current signals applied to said X-ray tube; comparator means for monitoring the limit and program signals for developing an output signal when the value of a said limit signal attains a predetermined value with respect to the value of a said program signal; and indicator circuit means coupled to a said comparator circuit means for, upon receipt of a said output signal, developing an output indication that the tube input power has exceeded the maximum power rating.

Claim 23

An apparatus as defined in claim 20 wherein said variable program circuit means includes first variable circuit means for developing a first signal having a value representative of the value of a voltage potential to be applied to said X-ray tube; second variable circuit means for developing a second signal having a value representative of the value of a current to be applied to said X-ray tube; and, resolving circuit means coupled to said first and second circuit means for developing a said program signal having a value representative of the values of said voltage potential and said current to be applied to said X-ray tube.

Claim 24

An apparatus as defined in claim 20 wherein said variable program circuit means includes first variable circuit means for developing a first signal having a value representative of the value of a current to be applied to said X-ray tube; second variable circuit means for developing a second signal having a value representative of the value of a current to be applied to said X-ray tube; and, resolving circuit means coupled to said first and second circuit means for developing a said program signal having a value representative of the values of said current to be applied to said X-ray tube.

Claim 25

An apparatus as defined in claim 20 wherein said tube limit signal generating means includes timer means for developing a plurality of patterns of control signals each representative of the elapsed exposure time; a plurality of signal generating circuits each for developing a limit signal which decreases in value at a different predetermined rate; actuator circuit means coupled to said timer means for, upon receipt of said plurality of predetermined patterns of signals, actuating a corresponding one of said plurality of signal generating circuits to thereby develop a limit signal which decreases in value at a corresponding predetermined rate.

Claim 26

An apparatus as defined in claim 23 wherein said timer means includes time accumulator means for developing a plurality of patterns of signals each of which take the form of binary coded decimal signals; and matrix circuit means for converting said binary coded decimal signals to a plurality of patterns of signals each of which takes the form of analog signals.

Claim 27

In an X-ray apparatus a protective circuit for indicating that the value of a signal applied to an X-ray tube has reached a time-varying maximum tube limit rating and comprising: an X-ray tube; a voltage supply source coupled to said X-ray tube for applying an operating signal to said X-ray tube; meanS for varying the value of a said operating signal applied to said X-ray tube; waveform generating means for developing a limit signal having a value which decreases as a predetermined function with respect to elapsed exposure time for a preselected period of time; monitor circuit means for developing a signal having a value representative of a said operating signal applied to said X-ray tube; comparator means coupled to said waveform generating means and said circuit means for developing an output signal when the value of the limit signal decreases to a predetermined level relative to the monitor signal; and, indicator circuit means coupled to said comparator circuit means for, upon receipt of a said output signal, developing an output indication that the operating signal has reached a maximum limit value.

Claim 28

In an X-ray apparatus a protective circuit for indicating that the value of a signal applied to an X-ray tube has reached a time-varying maximum tube limit rating and comprising: an X-ray tube; a voltage supply source coupled to said X-ray tube for applying an operating signal to said X-ray tube; meanS for varying the value of a said operating signal applied to said X-ray tube; waveform generating means for developing a limit signal having a value which decreases as a predetermined function with respect to elapsed exposure time for a preselected period of time; monitor circuit means for developing a signal having a value representative of a said operating signal applied to said X-ray tube; comparator means coupled to said waveform generating means and said circuit means for developing an output signal when the value of the limit signal decreases to a predetermined level relative to the monitor signal; and, indicator circuit means coupled to said comparator circuit means for, upon receipt of a said output signal, developing an output indication that the operating signal has reached a maximum limit value.

Claim 29

An apparatus as defined in claim 25 wherein said waveform generating means includes circuit means for generating a said limit signal which decreases in value with respect to time and which varies in the rate of decrease in value with respect to time.

Claim 30

An apparatus as defined in claim 25 wherein said waveform generating means includes a plurality of circuit means each for generating a said limit signal which varies in value with respect to time in accordance with one of a plurality of different predetermined tube rating signals; actuatable switch means for selectively developing a pattern of control signals representative of a desired one of said plurality of predetermined tube rating signals; and, second actuatable circuit means coupled to said actuatable switch means for, upon receipt of a pattern of control signals, actuating a signal generating circuit means corresponding to said received pattern of control signals to thereby generate a said limit signal which varies in accordance with a selected one of said plurality of predetermined tube rating signals.

Claim 31

In an X-ray apparatus a protective circuit for monitoring the value of a signal applied to an X-ray tube from exceeding a time-varying maximum tube limit rating and comprising: signal generating means for generating a limit signal which decreases in value as a predetermined, non-linear function with respect to elapsed exposure time in accordance with the value of a time-varying maximum tube rating; programming circuit means for developing a program signal having a value representative of the value of a preselected signal applied to a said X-ray tube; comparator means for monitoring the limit and program signals for developing an output signal when the value of a said limit signal decreases to a predetermined value relative to the value of a said program signal; and, indicator circuit means coupled to said comparator circuit means for, upon receipt of a said output signal, developing an output indication that the operating signal has reached a maximum limit value.

Claim 32

In an X-ray apparatus a protective circuit for monitoring the value of a signal applied to an X-ray tube from exceeding a time-varying maximum tube limit rating and comprising: signal generating means for generating a limit signal which decreases in value as a predetermined, non-linear function with respect to elapsed exposure time in accordance with the value of a time-varying maximum tube rating; programming circuit means for developing a program signal having a value representative of the value of a preselected signal applied to a said X-ray tube; comparator means for monitoring the limit and program signals for developing an output signal when the value of a said limit signal decreases to a predetermined value relative to the value of a said program signal; and, indicator circuit means coupled to said comparator circuit means for, upon receipt of a said output signal, developing an output indication that the operating signal has reached a maximum limit value.

Claim 33

An apparatus as defined in claim 28 wherein said signal generating means includes a timer means for developing a plurality of patterns of signals each representative of the elapsed time; a plurality of circuit means each for generating a limit signal which varies in accordance with one of a plurality of predetermined time functions; and, second actuatable circuit means coupled to said timer means for, upon receipt of one of a said plurality of patterns of signals, actuating a signal generating circuit means corresponding to a said received pattern of signals to thereby generate a limit signal which varies in accordance with a selected one of said plurality of time functions.

Claim 34

An apparatus as defined in claim 28 wherein said signal generating means includes a plurality of circuit means each for generating a said limit signal which varies in value with respect to time in accordance with one of a plurality of different predetermined tube rating signals; actuatable switch means for selectively developing a pattern of control signals representative of a desiRed one of said plurality of predetermined tube rating signals; and, second actuatable circuit means coupled to said actuatable switch means for, upon receipt of a pattern of control signals, actuating a signal generating circuit means corresponding to said received pattern of control signals to thereby generate a said limit signal which varies in accordance with a selected one of said plurality of predetermined tube rating signals.