DE1564997A1 - X-ray recording device - Google Patents

Description

Applicant TJSIKES BALTEAlJ, Societe Anonyme

X-ray device

The invention relates to an X-ray recording device, consisting from a hermetically sealed housing in which an X-ray tube is arranged, which is powered by an alternating high-voltage transformer fed with high voltage rectified via semiconductor rectifiers and capacitors will. .

It is known that the X-ray tubes perform the best, that is, they hold the highest Voltage stand, show the strongest power output

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and have the longest lifespan when the power is supplied with continuous voltage. A high continuous The easiest way to get voltage is through a high voltage transformer, rectifier and filter capacitors achieved. However, these elements have the consequence that the device provided with them is large, heavy and becomes costly.

It is also known that the Höntgenröhren through a High-voltage alternating current are supplied, but the current only flows in one direction through the tube, because the X-ray tube blocks the flow of current in the other direction. This is the reason why the X-ray tube works "self-rectifying". In this case, sit down. electrostatic charges on the glass, so that the insulation of the tube during the ineffective negative The polarity of the AC supply voltage is heavily stressed. To avoid the risk of breaking the insulation, it is therefore necessary to limit the supply voltage and / or the current flowing through the tube.

This difficulty is eliminated by rectifying Power supply, even without filtering, is carried out.

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Because of this, the one communicated to the tube is high Intermittent voltage as it does not change polarity. An X-ray tube fed in this way has Performances that are approximated to those of a tube supplied with a constant voltage. Inspired by Hontgen apparatus have already been proposed for this advantage in which the supply voltage is rectified in an economical way, in particular by means of vacuum tubes and semiconductor elements. Unfortunately requested the use of semiconductors a bridge circuit to get accurate rectification and for a X-ray tube that works at a very high voltage, a very large number of rectifier elements is required, which are connected in series, since a simple rectifier element can only withstand a few tens of volts. For example, for an X-ray tube that works under a voltage of 400,000 volts and a dry rectifier is supplied with rectified voltage, about 30,000 rectifier elements are required.

The arrangement of these numerous plates in the housing presents a problem and attempts have been made to achieve one easy and economical solution to be found.

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But again and again the flat stress offers a big one Difficulty. In addition, the panels have a considerable weight, in addition to the weight of their insulation in addition, which must be particularly careful because of the high tension · These disadvantages caused by the weight and the bulkiness are given, form a major obstacle in the implementation of an X-ray imaging device, which takes up less space and is lighter in weight to be easily transported.

The object of the invention is to eliminate these disadvantages and to provide an X-ray recorder in which the X-ray tube is placed in a hermetically sealed housing with insulation and high voltage which is rectified by semiconductor rectifiers which are switched on in a circuit that have capacitors.

The X-ray recording device according to the invention is thereby characterized in that the capacitors are made from the metallic protective cover of the X-ray tube, from at least two pieces of metal, which are connected to the corresponding electrodes of the tube and made of the insulating filler of the Device exist. The capacitors so formed are like this

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designed so that they have a capacity between two specific limits, such that on the one hand the capacity is sufficiently weak that the capacitors are almost discharged at the end of the positive half-wave, while on the other hand, it must be sufficiently large so that the current in the rectifiers during the negative half-wave at the terminals of the capacitors cannot produce a voltage which at the terminals of the X-ray tube can cause the insulation of this tube could generate dangerous voltage.

In a preferred embodiment of the invention In the X-ray device, the metal pieces connected to the electrodes of the X-ray tube are replaced by the metal ones Holders or supports of the tube formed, analogous to the caps covering the ends of the tube.

The invention is explained in more detail below with reference to the drawing explained in which an embodiment of the inventive X-ray recording device with its circuit is shown schematically.

The device shown works with a supply voltage of 400,000 volts and a current of two milliamperes. The voltage at the terminals of the X-ray tube is intermittent.

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An X-ray tube 7 is arranged in a hermetically sealed housing 2, around which a protective cover 6 is placed that does not let X-rays through. This envelope, which is provided with a radiolucent window 6a is provided, is non-positively connected to a metallic supporting skeleton 11, which in turn is attached to the housing is attached. The latter lets the X-rays through at 2b. The shell is grounded as the housing 2, for example through a conductor 2a. The housing 2 is provided with handles 1 at both ends, which are used to lift and change the position of the device.

In the tube 7 electrodes 7a and 7b are arranged. the Cathode 7b consists of a wire which is heated by the current supplied by a transformer 12. The transformer is fed via the conductors 14 with a voltage of 220 volts at 50 Hz.

The high voltage imparted to the tube 7 is supplied by two sets of dry rectifiers 4a and 4b connected to two high voltage transformers 3a and 3b which in turn are supplied with low voltage by the conductors 13 and 15 respectively. The two

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Transformers 3a and Jb and the two groups of rectifiers 4a and 4b are on either side of the tube 7 in Arranged in a row.

The sealed housing 2 is completely filled with an insulating gas consisting of sulfur hexafluoride, which is under a pressure of 2.5 atm «.

The X-ray tube 7 is provided at both ends with metal holders or metal caps 5a and 5b, which are attached to corresponding Electrodes 7a and 7b are connected. The metal holders 5a and 5b are attached to insulating arms 10, which in turn are connected to a metallic supporting skeleton 11 attached to the housing 2. the The capacitance of the capacitors formed by the metal holders 5a and 5b and the protective cover 6 has a certain value, since the elements forming the capacitors are applied values that are determined by their size given are. In the case of the device described, which contains a 400,000 volt tube, the pieces of metal 5a and 5b have a diameter of about 100 mm and a length of 100 mm, while the protective cover 6 has an inner diameter of 200 mm. In this way, the surfaces of the protective cover 6 and the two metal holders form 5a and 5b two capacitors, their respective capacitances

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BATH ORIGINAL

respond to the state evoked according to the invention. In fact, the calculated capacities are 8 picofarads. On the one hand, during the pole change of the positive high voltage supplied to the tube 7, the tube 7 emits a current of 2 milliamps and the capacitors charged with 200 KV discharge in 0.5 milliseconds, whereas the decreasing positive voltage lasts about 5 milliseconds. In this way it can be determined that the capacitance discharges sufficiently quickly and that when the tube no longer lets any current through, the metal holders or caps 5a and 5t> are approximately at ground potential and the capacitors' from the holders together with the protective cover 6 are almost discharged. On the other hand, the X-ray tube 7 does not supply any current during the polarity change of the negative high voltage. The rectifiers 4 ·, which are never completely blocked, allow a leakage current of about 30 microamps through which charges each capacitor up to a maximum electrical charge of 30 microamps Σ 5 milliseconds equal to 150 nanocoulombs. In this way, the potential of the metal holders 5a and 5b with respect to the earth does not exceed 150.10 = 18,000 volts.

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It is obvious that these values are only approximate represent the tenth part of the maximum voltage of an electrode. It is concluded that during the The tube only carries about a tenth of the maximum voltage and the voltage remains so during the negative wave negative voltage wave never reaches a voltage that is dangerous for the X-ray tube.

It should be noted that if the capacitance of the capacitors were well below 8 picofarads, the Rectifiers remained completely at the potential of the transformers and therefore the full voltage during the negative half-wave of the tube would be delivered. This effect is detrimental to the quality and behavior of the tube would be avoided by the invention.

In practice, the X-ray tube stops supplying current before the polarity of the positive high voltage does not change has reached zero, in such a way that during the negative pole change the tube has a slightly positive or almost zero voltage holds. For this reason, the behavior Tube and, accordingly, its service life under high voltage is greatly increased.

A surprising but extremely beneficial and useful one The effect is that each rectifier group only has one

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Maximum voltage of 200 KV, from which the extraordinary the practical fact is that the number of rectifier base plates is halved. The device described above contains about 15,000 plates, while the known gate directions are around 30,000.

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Claims (5)

Λ, X-ray recorder, consisting of a housing having an insulation, an X-ray tube which is fed by a high voltage, which is rectified by semiconductor rectifiers, which in turn are enclosed in a circuit having capacitors, characterized in that the capacitors are through the metallic Protective cover (6) of the X-ray tube (7) »at least two metal pieces (5a, 5b) connected to the corresponding electrodes (7a, 7b) of the tube (7) and formed by the insulating filling of the device and having a capacitance which is selected in this way that it is sufficiently weak on the one hand that the capacitors are almost discharged at the end of the positive pole change and, on the other hand, that it is sufficiently large so that during the negative pole change the leakage current of the rectifier cannot charge the capacitors to such an extent that a voltage occurs at their terminals that on the clamps of the X-ray tube one for the insulation of the tube transmits dangerous voltage. 909851/1080 2. X-ray recording device according to claim 1, characterized in that that with the electrodes (7a, 7b) of the X-ray tube (7) connected metal pieces (5a, 5b) at the same time . the support members or brackets for the ends of the Tube are. 3. X-ray recording device according to claim 2, characterized in that the metal brackets (5a, 5b) for the X-ray tube (7) are caps which at least partially enclose the ends of this tube. 4 ·. X-ray recording device according to claims 2 and 3, characterized in that that the brackets for the ends of the X-ray tube are in place. 5. X-ray recording device according to claim 2 and 3 »characterized in that that the holders for the ends of the X-ray tube are made with the tube. 909851/1080