X-Ray photograph unit

In an X-ray photograph unit of the type which controls an X-ray projection on the basis of a tube voltage, a tube current and an exposure time, this invention relates to an X-ray photograph unit including photograph portion switches disposed so as to correspond to portions of the human body to be photographed and which set primarily and automatically the tube voltage and the tube current, and thickness switches disposed so as to correspond to the thickness of the portions to be photographed and setting automatically the exposure time in combination with said photograph portion switches, wherein the selection of said photograph portion switches and said thickness switches along makes it possible to carry out the X-ray projection.

BACKGROUND OF THE INVENTION 
This invention relates to an X-ray photograph unit which simplifies 
photograph control procedures. 
In an X-ray photograph unit, a tube voltage and tube current of the X-ray 
tube and the exposure time must be suitably set in accordance with an 
object to be photographed. 
Heretofore, the X-ray photograph unit has been set to the optimum 
photographing conditions and actuated by operating a tube voltage 
regulator, a tube current regulator and an exposure time adjuster 
(hereinafter called "timer") with reference to a photograph table which 
exclusively illustrates the conditions for the X-ray photograph for the 
portion to be photographed such as the tube voltage and tube current of 
the X-ray tube and the exposure time. 
In other words, the optimum photographing conditions must be selected by 
sorting out the three kinds of factors on the photograph table. This 
procedure is not only time-consuming but also involves a high possibility 
of selecting the wrong conditions. In the latter case, the photograph 
itself must be taken again and this is extremely undesirable in the aspect 
of the exposure of the subject to the radioactive rays. 
In the conventional X-ray photograph unit, the X-ray projection time is 
controlled by means of the timer. If the timer gets out of order, 
therefore, it sometimes happens that the X-ray irradiation does not stop, 
thus leading to a remarkable increase in the dose of exposure of the 
subject to the X-rays and hence, is extremely undesirable from the 
viewpoint of medical safety. As for the X-ray photograph unit, on the 
other hand, the X-rays are continuously irradiated in such a case, though 
the photograph must be originally taken within a short period of time 
under the rated state. Accordingly, the X-ray tube becomes overloaded and 
overheated and is eventually damaged and broken. 
The present invention is directed to provide an X-ray photograph unit which 
eliminates the abovementioned drawbacks of the prior art, enables to 
simplify and accurately carry out the photograph control procedures and 
prevents the continuation of the X-ray irradiation at the time of 
accident. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, there is provided an X-ray 
photograph unit including photograph portion switches disposed so as to 
correspond to portions of the human body to be photographed and which set 
primarily and automatically the tube voltage and the tube current, and 
thickness switches disposed so as to correspond to the thickness of the 
portions to be photographed in combination with said photograph portion 
switches, wherein the selection of said photograph portion switches and 
said thickness switches alone makes it possible to carry out the X-ray 
projection without using a photograph table. 
Furthermore, in accordance with the present invention, protective timers 
for providing the upper limits of the exposure time for the portions to be 
photographed are controlled by means of the above-said portion switches.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Hereinafter, an embodiment of the present invention will be explained by 
referring to the accompanying drawings. 
FIG. 1 shows an operation board of the X-ray photograph unit in accordance 
with the present invention. The illustration 1 depicting the human body is 
divided into three portions, e.g., the limbs, the chest and the 
head-and-trunk, and these portions are designated by three different 
shadings. The limbs, the chest abd the head-and-trunk correspond to 
portion switches S.sub.1, S.sub.2 and S.sub.3, respectively. Thickness 
switches represent the thickness of portions of the subject and consist of 
twelve switches S.sub.11 -S.sub.22, for example. The range of thickness of 
each portion is represented in the cm graduation below each thickness 
switch. Hence, S.sub.15 represents 16 cm-17 cm, for example. 
The portion switches S.sub.1 -S.sub.3 and the thickness switches S.sub.11 
-S.sub.22 are of a so-called multi-throw push switch type and are so 
constructed that when the portion switch S.sub.3 is depressed while 
S.sub.1 is in the depressed state, for example, S.sub.3 is turned ON while 
S.sub.1 is turned OFF automatically. In other words, the switch which is 
finally depressed is turned ON with the others being automatically turned 
OFF. Auxiliary contacts for each switch are incorporated below the control 
board. In FIG. 1, the groups of the auxiliary contacts 2, 2' for the 
portion switches and the thickness switches are represented by 
dot-and-chain lines, respectively. The control circuit of the X-ray 
photograph unit in accordance with the present invention such as shown in 
FIGS. 2 through 4 is constructed by suitably combining the connections of 
these auxiliary contacts. 
In FIG. 2, the a.c. power source 3 is connected via a power switch 4 to a 
series circuit consisting of a normally-open contact of the portion switch 
S.sub.1, a coil of an auxiliary relay Y.sub.1 of the portion switch 
S.sub.1 and normally-closed contacts of the portion switches S.sub.2, 
S.sub.3, to a series circuit consisting of a normally-open contact of the 
portion switch S.sub.2, a coil of an auxiliary relay Y.sub.2 of the 
portion switch S.sub.2 and normally-closed contacts of the portion 
switches S.sub.3, S.sub.1 and to a series circuit consisting of a 
normally-open contact of the portion switch S.sub.3, a coil of an 
auxiliary relay Y.sub.3 of the portion switch S.sub.3 and normally-closed 
contacts of the portion switches S.sub.1, S.sub.2 whereby these three 
series circuits are parallel to each other. The a.c. power source 3 is 
also connected to an autotransformer T.sub.1. Three output taps of this 
autotransformer T.sub.1 are connected to one end of a high-voltage 
transformer T.sub.2 on its primary side through the respective contacts of 
the relays Y.sub.3, Y.sub.2, Y.sub.1 and also through a CT contact. The 
other end of the high-voltage transformer T.sub.2 on its primary side is 
connected to the other output tap of the autotransformer T.sub.1. The 
secondary side of the high-voltage transformer T.sub.2 is connected via a 
rectification circuit 5 to the cathode and anode target 7 of the X-ray 
tube 6 and impresses a high voltage upon the same. When each portion 
switch S.sub.1, S.sub.2, S.sub.3 is turned ON, the tube voltage is 
primarily and automatically determined as tabulated in Table 1. 
TABLE 1 
______________________________________ 
Tube voltage 
Tube current 
______________________________________ 
S.sub.1 70 KV 20 mA 
S.sub.2 70 KV 50 mA 
S.sub.3 100 KV 20 mA 
______________________________________ 
The power switch 4 is also connected to a d.c. constant voltage source 8. 
The output circuit of the d.c. constant voltage source 8 is connected to a 
series circuit consisting of an X-ray projective switch Sx, a CT coil, a 
protective timer 9 and a timer 10, and sets the X-ray projection time in 
combination with the portion switches and the thickness switches as will 
be explained later in further detail. 
The power switch 4 is also connected to an a.c. constant voltage source 
(AVR) 11, the output of which is connected to the primary side of a 
filament transformer T.sub.3 via three series circuits Y.sub.3 -R.sub.3, 
Y.sub.2 -R.sub.2, Y.sub.1 -R.sub.1 consisting of the contacts of the three 
auxiliary relays Y.sub.3, Y.sub.2, Y.sub.1 and three resistors R.sub.3, 
R.sub.2, R.sub.1, respectively, the three series circuits being wired in 
parallel with one another. The secondary side of the filament transformer 
T.sub.3 is connected to a heater filament 12. According to this circuit 
arrangement, the tube currents as tabulated in Table 1 are primarily and 
automatically determined as each portion switch is turned ON. 
FIG. 3 shows the detailed circuit construction of the timer 10. The d.c. 
constant voltage source 8 is connected to the portion switches S.sub.1, 
S.sub.2 and S.sub.3 that are in parallel with one another, and the portion 
switch S.sub.1 is in turn connected to the thickness switches S.sub.11 
-S.sub.22 that are in parallel with one another. These thickness switches 
S.sub.11 -S.sub.22 are connected to a timer set value circuit t.sub.1 
which has in advance determined the X-ray projection times in view of the 
respective portion and thickness. In the same way, timer set value 
circuits t.sub.2 and t.sub.3 are connected to the contacts of the 
thickness switches S.sub.11 -S.sub.22 of the portion switches S.sub.2 and 
S.sub.3, respectively. The relationship between the timer set values 
versus the portion switches S.sub.1 -S.sub.3 and thickness switches 
S.sub.11 -S.sub.22 is tabulated in Table 2 below. 
TABLE 2 
______________________________________ 
S.sub.1 S.sub.2 
S.sub.3 (sec) 
______________________________________ 
S.sub.11 
0.02 0.02 0.04 
(-4) 
S.sub.12 
0.05 0.02 0.04 
(5-7) 
S.sub.13 
0.08 0.04 0.05 
(8-12) 
S.sub.14 
0.15 0.04 0.10 
(13-15) 
S.sub.15 
0.25 0.05 0.20 
(16-17) 
S.sub.16 
0.30 0.08 0.30 
(18-19) Timer set 
S.sub.17 
0.40 0.10 0.40 value 
(20-21) 
S.sub.18 
0.50 0.12 0.80 
(22-23) 
S.sub.19 
0.80 0.16 1.20 
(24-25) 
S.sub.20 
1.00 0.30 1.50 
(26-29) 
S.sub.21 
1.00 0.40 1.80 
(30-34) 
S.sub.22 
1.00 0.50 2.00 
(35-) 
1.50 1.00 2.50 Set value of 
protection timer 
______________________________________ 
FIG. 4 shows the detailed circuit of the protective timer 9. The d.c. 
constant voltage source 8 is connected via a parallel circuit of the 
portion switches S.sub.1, S.sub.2, S.sub.3 to protective timer set value 
circuits t.sub.11, t.sub.21, t.sub.31, respectively. The relationship 
between the portion switches S.sub.1, S.sub.2, S.sub.3 and the protective 
timer set values is shown in Table 2. Incidentally, the timer set value 
circuits t.sub.1 -t.sub.3 shown in FIG. 3 are constructed independently of 
those t.sub.11 -t.sub.31 shown in FIG. 4 in order to minimize the 
possibility that they will simultaneously malfunction. 
Next, an example of the operation of the present invention will be 
explained. In taking an X-ray photograph of the head, by way of example, 
the head portion switch S.sub.3 is first turned ON, whereby the auxiliary 
relay Y.sub.3 for the head-and-trunk portion turns ON. Since the 
normally-closed contacts of the portion switches S.sub.1 and S.sub.2 are 
wired in series with the portion switch S.sub.3 in this instance, the 
autotransformer T.sub.1 is prevented from being burnt out. In other words, 
a situation in which two of S.sub.1, S.sub.2 and S.sub.3 are 
simultaneously turned ON can never occur. As the contact of the auxiliary 
relay Y.sub.3 is turned ON, the output of the high-voltage transformer 
T.sub.2 is set to 100 KV as illustrated in Table 1 as CT is subsequently 
closed. Since the contact of the auxiliary relay Y.sub.3 is turned ON, 
further, the output voltage of the filament transformer T.sub.3 passes a 
current of 20 mA to the filament 12 of the X-ray tube 6 in accordance with 
Table 1 by means of an a.c. constant voltage source (AVR) 11. 
It is now assumed that the thickness of the head portion in the 
photographing direction is found to be 16 cm by measurement. The thickness 
switch S.sub.15 corresponds to this thickness as shown in Table 2. When 
the thickness switch S.sub.15 is turned ON, therefore, the portion switch 
S.sub.3 as well as the thickness switch S.sub.15 are turned ON in FIG. 3 
so that the timer set value is automatically set to 0.20 sec. 
Simultaneously, in FIG. 4, the portion switch S.sub.3 is turned ON and the 
protective timer value is set to 2.50 sec. in accordance with Table 2. The 
protective timer 9 opens after the passage of a predetermined time even 
when the timer 10 is out of order and turns OFF the coil of CT to stop the 
projection of the X-rays, thereby ensuring the safety both of the patient 
and the X-ray unit. 
It can be understood from the above explanation that the conditions are set 
to a tube voltage of 100 KV, a tube current of 20 mA, a timer setting of 
0.20 sec. and a protective timer setting of 2.50 sec. 
When the X-ray irradiation switch Sx is turned ON under these conditions, 
CT is closed and the X-ray tube 6 is actuated by the output of the 
high-voltage transformer T.sub.2 and generates the X-rays. After the timer 
set value of 0.20 sec., the timer 10 opens whereby CT opens and the X-ray 
irradiation stops. If the timer is out of order, the X-ray irradiation is 
stopped by the protective timer after the passage of 2.50 sec. 
As explained in the foregoing paragraph, it is possible in accordance with 
the present invention to set and actuate the X-ray tube to and in the 
optimum condition for X-ray photography in a simple and accurate manner by 
merely depressing the portion switch and the thickness switch without 
using the photograph table. Hence, the present invention makes it possible 
to simplify the operation of the X-ray photograph and to minimize 
erroneous operation.