US2147424A

US2147424A - Roentgen tube control

Info

Publication number: US2147424A
Application number: US71063A
Authority: US
Inventors: Bischoff Kurt
Original assignee: Siemens Reiniger Werke AG
Current assignee: Siemens Reiniger Werke AG
Priority date: 1935-03-29
Filing date: 1936-03-26
Publication date: 1939-02-14
Anticipated expiration: 1956-02-14

Description

K. BISCHOFF ROENTGEN TUBE CONTROL Feb. 14, 1939.

Filed March 26, 1936 Patented Feb. 14, 1939 ROENTGEN TUBE CONTROL Kurt Bischoff, near Erlangen, Germany, assignor to the firm Siemens-Reiniger-Werke Aktiengesellschaft, Berlin, Germany Application March 26,

1936, Serial No. 71,063

In Germany March 29, 1935 9 Claims.

The present invention relates, broadly speaking, to the art of controlling high tension apparatus and is particularly concerned with a new method and with novel and improved means for controlling Roentgen tubes in such a manner as to protect them against overloads.

It will be advisable to refer briefly to the prior art in order to furnish a basis for a better understanding of the detailed description of my invention which is. yet to follow. However, in the course of the following discussion, I will describe in detail only those parts and their functions which are new; what may be considered old and known in the art will be explained only to such 5 extent as is necessary for supporting the understanding of my invention.

In prior arrangements for protecting Roentgen tubes against overloads, the control means for the operating factors such as tube tension or voltage e, tube current i, and load-time t-(or the control means for the resulting or derived factors such as work input and milliampere/second product) are coupled with one another and are actuated in such a manner that the tube is always operated with the maximum permissible load. The disadvantage of such an arrangement resides in the fact that the tube is operated up to its load limit even in cases where the full utilization of its maximum load capacity is not required, and accordingly, the useful life of the tube is thereby greatly shortened. In another known arrangement of this class, the control means for the previously mentioned operating factors are not coupled with one another but with the adjustable maximum current or cut-out switch, in such a manner, that the switch releases or disconnects when that load I limit is exceeded which is permissible for the Roentgen tube in use. In this latter case, we are faced with the disadvantage that a Roentgen exposure might'fail due to wrong setting or adjustment of the control means and consequent premature release of the cut-out switch provided for protecting the tube.

These disadvantages may be avoided and Roentgen tubes may be protected to some extent,

after determining the individually adjustable load range'which is dependent on the third factor, thus preventing an overload adjustment or control prior to subjecting the tube to the load, and indicating such overload adjustment by means of a device adapted to show simultaneously all three load determining factors or values derived therefrom. The indicating device may be so constructed as to show the margin between the adjusted load value and the load capacity or load. limit of the tube.

The above intimated prior development is based on the fact that the load of a Roentgen tube is determined by the three variables mentioned previously, namely, the tube tension or voltage 6 (kV), the tube current 1 (mA), and the load time 25 (sec). The limit loads which are permissible for any given Roentgen tube may be represented in a coordinate system in the form of curves, wherein two of the three variables are used as coordinates, while the third value serves as a parameter. For example, the limit loads which are admissible in a Roentgen tube may be expressed in a curve system wherein t=const., that is, a coordinate system with the coordinates (2 (kV) and 2' (mA), wherein the individual curves correspond to different constant values of t. It is similarly possible to express the limit loads in a system with the coordinatesi (mA) and 15 (sec), wherein e=const. The values 2' and t are preferably plotted in such a coordinate system on a logarithmic scale because in that case the curves e=const. will assume an almost linear form.

As previously suggested, such a load diagram may be employed in connection with the control board of the Roentgen equipment, and pointers or fingers may be provided for indicating upon the respective diagram axes the values of the corresponding operating factors. The pointers may also be suitably coupled with the respective control means in such a manner that they indicate the operating values adjusted or set by these. Such an arrangement furnishes a certain safeguard against overloads, inasmuch as it affords an indication of the various values and factors involved in the operation of Roentgen tubes.

My present invention represents an improvement over the prior developments mentioned above and avoids the drawbacks and disadvantages noted previously in connection with the customary control arrangements for and mode of operation of Roentgen tubes. It is understood, of course, that the instant invention is explained and described herein in conjunction with Roentgen apparatus chiefly for the-purpose of guiding others in applying the novel features in practice, but not to indicate any limitations outside of those that are imposed by the prior art. Some of the salient objects are noted below.

A specific object of the present invention, in an arrangement of the class generally defined above and including the device for preventing and indicating an overload adjustment or overload condition, resides in the provision of a movable member, e, g., a pointer or finger, the adjusted operative position of which corresponds at any time to. the work input of the tube, and means for cooperative actuation of such movable member with a timing switch, in such a manner that the maximum permissible load time corresponding to any given work input or the maximum permissible work input corresponding to a given load time are indicated, whereby the over-stepping of this load value or load limit is prevented.

Another object is realized in the provision of means for mechanically or electrically coupling the above noted movable member with the tubecurrent or heating-current control means and with the means for controlling the tube voltage.

A further object receives expression in an arrangement wherein the tube-current or heatingcurrent control means and the control provisions for the tube tension each govern an auxiliary circuit in such a manner that the currents flowing in these circuits are proportional to the adjusted values of the tube current and tube tension and are fed to the movable member which is constructed in the form of a wattmeter system.

Still another object refers to the provision of means for governing or adjusting the current in the corresponding previously noted auxiliary circuits and mechanically or electrically coupling said means with the tube-current or filament heating-current control and with the control for the tube tension.

A further object of the invention is concerned with an arrangement as previously intimated, wherein the adjustment of the movable member and of the timing means are directly indicated on, and readable from, a common dial or scale.

Another object has to do with the provision of means whereby an overload adjustment of the tube is prevented by a movable stop member which is mechanically or electrically coupled with the previously noted movable means or pointer, and controls or limits the adjustment or setting of the timing switch.

Still another object is realized by the provision of means whereby an overload adjustment of the tube is prevented by a movable stop member which is mechanically or electrically coupled with the timing means and controls or limits the adjustment or setting of the previously intimated movable member or pointer.

Other objects and features will appear from the following detailed description which is rendered with reference to the drawing. In the drawing:

Figure 1 illustrates a circuit diagram of a new system embodying the features of my invention, and specifically a system wherein the control means for the operating values of the tube are coordinated with the timing device; and

Figure 2 represents a modification of my new system wherein auxiliary circuits are employed for control and indication together with a coordinate control of the timing device.

It will be recalled from the foregoing discussion that the load capacity of a Roentgen tube may be characterized accurately by a single curve whichindicates theload capacity at a given voltage 6 as a function of the current i and as a function of the load time t. On this fact is also based the use of a movable member, for example, a pointer for preventing or indicating an overload adjustment, the setting of the pointer corresponding at any time to the input in kilowatts which is supplied to the tube at such setting, and the movable member cooperating with a time switch in such a manner that the maximum permissible load time at a given input or the maximum permissible input at a given load time can be recognized and the overstepping of this load value made impossible.

The present invention will now be described in detail with reference to the Figures 1 and 2 which show schematic circuit diagrams and the related control and indicating devices.

Referring now particularly to Figure 1, the

Roentgen tube I I is supplied with current from g the high tension transformer I2 and the filament or heating current transformer I3. These transformers are connected to the commercial current supply I4. The connection and disconnection of the high tension transformer I2 takes place by means of a protecting switch I5 which is controlled by the timing device I6. The Roentgen voltage or tension is controlled in the usual manner by means of the control device I! and the tube current and filament current, respectively, by means of the control device It in such a manner that the tube tension and the tube current will change proportionally with the adjustment or setting of the control devices I1 and I8. The function of these control devices will be readily understood, as the device I! is a potentiometer, while the device I8 is a variable resistance.

The control knobs or handles I1 and I8 for operating the control devices I! and I8 actuate the multiplication gears I9, causing a multiplication of the values of the tube current i and the tube tension e and actuating a pointer 22 by means of the roller 20 and the rack 2|. The setting of the pointer 22, therefore, corresponds to or indicates the power input which is supplied to the tube. The multiplication gear will be presently described more in detail. Upon the rack 2I is secured an intermediate member 23 which may be exchanged when a Roentgen tube is used which has a different load degree or capacity.

The pointer or indicator 22 and the adjusting or setting pointer 24 of the timing switch I6 operate over a common scale in such a manner that it can be directly read from the scale whether the tube is overloaded at the adjusted values, namely,

at the determined tube input indicated by the pointer 22 and at the determined load time t indicated by the pointer 24. Overloading may be prevented, if desired, by equipping the pointer 22 or the finger 24, or both, with stops 41, thereby limiting the adjustment of the input or the load time.

The multiplication gear arrangement I9 is shown only in sufficient detail so that its operation may be understood. When the tube current is to be adjusted, the handle I8 on shaft 40 is depressed against the tension of spring 45 and is rotated until the pin 46 enters a slot in the head of the tubular shaft 4!. At the same time the gear 42 on the lower end of shaft 40 meshes with gear 43. Rotation of the handle I8 will now rotate the shaft 4| to raise or lower the control device I8, depending on the direction of rotation, and will also rotate shaft 44 by means of gears 42 and 43. The adjustment of the tube tension is carried out in a similar manner by means of handle ll', depression and rotation of which raises or lowers the control device I! and simultaneously rotates the shaft 44. The arrangement is such that the eifects of the current and tension adjustment on" shaft 44 are cumulative. That is, an adjustment to increase the current, and also an adjustment to increase the tension, should rotate the shaft 44 in the same direction, and this direction, moreover, should be such as to advance the roller 20 to the left.

In the embodiment shown in Fig. the Roentgen tube ll, transformers I2 and I3, and switch I 5 are the same as the correspondingly numbered parts in Fig. 1, but the multiplication gear is replaced by an electrical arrangement. Two handles may be employed, similar to I1 and [8 of Fig. 1, and hence not shown in the drawing. These handles may be mounted on threaded shafts and are used to raise and lower the control devices 26 and 21, respectively. The control devices 26' and 21' not only cooperate with the resistances 28 and 29 to regulate the tube tension and current, but also cooperate with the resistances 2'6 and 21 which are included in auxiliary circuits. The arrangement is such, as can be seen from the drawing, that an adjustment of control device 26, for example, which is effective to increase the tube tension, is also effective to increase the current in the corresponding auxiliary circuit. That is, the currents in the auxiliary circuits, respectively, are proportioned to the tube tension and tube current. The auxiliary circuits include the windings of a meter 3|], the indicator or needle 3| of which shows upon the scale 32 a value corresponding to the input supplied to the Roentgen tube. The predetermined load time t, which is adjusted or set by means of the timing device 34, will also be indicated on the scale 32 by means of the pointer 33, the latter being mechanically coupled with the time switch 34 by means of the exchangeable intermediate control member 35 and a flexible band, as shown. The control member 35 may be constructed in the form of a cam so shaped as to produce a non-linear movement of the pointer 33 with respect to the setting of the timing device.

The embodiment shown in Fig. 2 has an advantage over the one shown in Fig. 1, in that the indicator or pointer 3| (unlike the pointer 22 in Fig. 1) indicates the input supplied to the tube with substantial accuracy, even though the voltage of the commercial current source may fluctuate. This is true because the voltage fluctuations not only affect the tube tension and current, but also affect the current in the auxiliary circuits.

Changes will suggest themselves to those experienced in the art, and may be made as far as detail parts or the structure thereof or placement in the total arrangement are concerned if conditions make it desirable or necessary. Certain structures have been shown and described and others that may take their place have been indicated sufficiently to enable those who are versed in the art to carry out the invention in all its features and embodiments. Details which I have not specifically described are of such a character that they will be readily understood by those to whom the invention is addressed. It is understood, therefore, that any structure or mode of operation or both will be considered as my invention if carried out within the scope and spirit of the following claims, wherein I have defined what I believe is my invention and what I desire to have protected by Letters Patent.

I claim as my invention:

1. The combination, with a Roentgen tube, of means for adjusting the voltage applied between the anode and cathode, means for independently adjusting the current flow between the cathode and the anode, and a power indicator jointly controlled by said adjusting means.

2'. The combination, with a Roentgen tube, of means for adjusting the voltage applied between the anode and cathode, means for independently adjusting the current flow between the cathode and the anode, an indicator, and means whereby the voltage adjusting means and current adjusting means jointly control said indicator to show a value corresponding to the product of the adjusted voltage and current.

3. The combination, with a Roentgen tube, of means for adjusting the voltage applied between the anode and cathode, means for adjusting the current flow between the cathode and the anode, an indicator, mechanism whereby the said adjusting means jointly control said indicator, and a cam included in said .mechanism whose curvature depends on the characteristics of the tube, the said cam serving to determine the ratio of indicator change to voltage and current change.

4. The combination, with a Roentgen tube, of movable means for adjusting the voltage applied between the anode and cathode, movable means for adjusting the current flow between the cathode and the anode, an indicator, apparatus whereby the said adjusting means jointly move said indicator, and means for introducing a predetermined variation in the rate at which the indicator movement follows the movement of said adjusting means.

5. The combination, with a Roentgen tube, of means for adjusting the voltage applied between the anode and cathode of the tube, means for adjusting the current flow between the cathode and the anode, a time switch for stopping the operation of the tube after a predetermined time, a pointer and scale for indicating the setting of said time switch, a second pointer cooperating with said scale, and means whereby the said adjusting means jointly control said second pointer.

6. The combination, with a Roentgen tube, of means for adjusting the voltage applied between the anode and cathode of the tube, means for adjusting the current flow between the cathode and the anode, a time switch for stopping the operation of the tube'after a predetermined time, and means including a common scale for indicating the setting of said switch and the power input to the tube as determined by the adjusted values of voltage and current.

7. The combination, with a Roentgen tube, of circuits for supplying power to said tube, means for adjusting the voltage applied between the anode and cathode of the tube, means for adjusting the current flow between the cathode and the anode, two circuits separate from and in addition to said power circuits, means for causing current flow in said additional circuits, respectively, proportional to the tube voltage and current, and a meter common to said additional circuits.

8. The combination, with a Roentgen tube, of circuits for supplying power to said tube, means for adjusting the voltage applied between the anode and cathode of the tube, means for adjusting the current flow between the cathode and the anode, two circuits separate from and the voltage applied to the cathode anode circuit, means for adjusting the cathode heating current to vary the cathode anode current independent of the voltage, a time switch for predetermining the load time, and means for directly comparing the setting of said switch with the power input to said tube as determined by the adjusted value of anode voltage and cathode heating current.

KURT BISCHOFF.