GB409476A - Improvements in or relating to x-ray installations - Google Patents

Abstract

409,476. R÷ntgen-ray apparatus. MULLER AKT.-GES., C. H. F., 24, R÷ntgenstrasse, Hamburg, Germany. Feb. 6, 1933, No. 3603. Convention date, Feb. 8, 1932. [Class 39 (i).] In installations for making short photographic exposures and having control devices for adjusting the voltage across the X-ray tube and the time of the exposure, the current through the tube is controlled so that the average current during an exposure is greater if the time is adjusted to a smaller value at a definite voltage adjustment and if the voltage is adjusted to a lower value at a definite time adjustment. The power supplied to the tube is made independent of the particular voltage used and the tube may always be loaded up to the limit of its power and the exposure made in the shortest time. In one arrangement in which a time switch 24, Fig. 1, controls through a relay 25<1> the closure of the supply circuit to the high-tension transformer 4 for the X-ray tube 1, a short 25<11> across a resistance 26 in the cathode-heating circuit is removed, or the heating circuit is broken, when the transformer 4 is energized at the beginning of an exposure. The resulting decrease in cathode-heating current causes the cathode to cool and the current through the tube 1 to decrease during the exposure, the average current being thus less if the exposure is larger. The voltage applied to the transformer 4 is controlled by an autotransformer 7 with tappings selected by a control drum A. On this drum, or on a drum coupled thereto, are contacts controlling the amount of a resistance 22 in the cathodeheating circuit and so decreasing the current through the tube 1 as the voltage is increased. In a modification in which the current through the tube 1 is constant during the exposure, the coupled voltage and current controls A, 22 are retained and the adjusting shaft 29, Fig. 3, of a time-switch is coupled to a control 27 for an autotransformer determining the cathode-heating voltage so that the cathode current is decreased if the time of exposure is increased. The shaft 29 carries a pin 30 bearing against a pin 32 to turn the control 27. During the exposure, the pin 30 turns to the left but the control 27 is held stationary by a catch 33, the control 27 being returned to its normal position by a spring 35 when the catch 33 is released at the end of the exposure.