US 4,363,971 A · Method of and apparatus for controlling the electric power applied to a rotary-anode X-ray tube

Abstract

The temperature of the anode disc of a rotary-anode X-ray tube is continuously determined by means of the method apparatus in accordance with the invention. When the temperature exceeds a first limit value, the power of the X-ray tube is reduced to a fraction (for example, 80%) of the otherwise permissible power. When a second limit value of the anode disc temperature is exceeded, exposures are completely inhibited. In the case of exposures which are performed in rapid succession with a comparatively low power, it may occur that the anode disc temperature does not reach the second limit value, but that the mean value of the applied electric power is so high that the bearing of the rotary anode, and possibly also the joint between the anode shaft and the rotor, is overloaded. Overloading is prevented by generating a bearing-temperature signal indicative of the rotary anode bearing temperature and comparing it with a third limit value.

Claims16

Dependent claims

A method of controlling the electric power applied to a rotary anode X-ray tube in an X-ray generator in dependency of the anode temperature of the X-ray tube which includes the steps of continuously determining the anode disc temperature, comparing said temperature with a first limit value and automatically reducing the electric power applied to the X-ray tube when the anode disc temperature exceeds the first limit value, the improvement comprising automatically reducing the power fed to the X-ray tube to a permissible predetermined constant fraction of the power each time, wherein the power reduction takes place during intervals between exposures;

comparing the anode disc temperature with a second limit value which is higher than the first limit value (T.sub.g1) and reducing the tube power to a second predetermined constant fraction, when the anode disc temperature exceeds the second limit value (T.sub.g2) during an interval between exposures;
continuously determining the temperature of the rotary anode bearings to monitor the mean value in time of the applied electric power;
comparing said bearing temperature with a third limit value (T.sub.1g), and inhibiting the start of an exposure for as long as the bearing temperature determined exceeds the third limit value.

Apparatus for controlling the electric load of an X-ray tube having a rotary anode disc with a bearing comprising:

generator means which supply a high voltage to the X-ray tube;
input means which supply input signals selecting a use of the X-ray tube;
control means which control the generator means in dependency of the input signals;
means which generate an anode temperature signal indicative of the temperature of the rotary anode disc of the X-ray tube;
comparator means which compare the anode temperature signal with a first limit value and which generate a reduction signal, which is applied to the control means, said reduction signal in cooperation with the input signals determining the load of the X-raty tube;
means which generate a bearing-temperature signal indicative of the temperature of the rotary anode bearing;
and
further comparator means which compare the anode-temperature signal with a second limit value which is larger than the first limit value, and which compare the bearing temperature signal with a third limit value, thereby generating a second and a third reduction signal respectively, said second and third reduction signal being applied to the control means for further reducing the X-ray tube load to a predetermined level or to inhibit any load respectively.

5 more elements

An apparatus for controlling the electric load of an X-ray tube comprising:

generator means for supplying a high voltage to the X-ray tube,
input means for supplying input signals which determine the use of the X-ray tube,
control means for controlling the generator means in dependency of the input signals,
processing means for generating an anode temperature signal indicative of the temperature of the rotary anode disc of the X-ray tube,
for generating a bearing temperature signal indicative of the temperature of the rotary anode bearing of the X-ray tube,
for comparing the anode temperature signal with a first limit value to generate a first reduction signal,
for comparing the anode temperature signal with a second limit value, which is larger than the first iimit value, to generate a second reduction signal,
for comparing the bearing temperature signal with a third limit value to generate a third reduction signal,
for generating a power factor signal from said reduction signal,
for multiplying the X-ray tube load determined by the input signals by said power factor signal to obtain a permissible load to the X-ray tube and
for supplying control signals to the control means for activating the X-ray tube with said permissible load.

8 more elements

Dependencies are inferred from the claim text.

Method of and apparatus for controlling the electric power applied to a rotary-anode X-ray tube

Life of this patent

Method of and apparatus for controlling the electric power applied to a rotary-anode X-ray tube

Life of this patent

Abstract

Claims16