JPS5813000B2 - Shikayou X Sensouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to dental x-rays, and more particularly to protection circuits for x-ray tubes.

X-rays have a strong penetrating power through materials, and the penetrating power increases as the wavelength becomes shorter, and it also changes depending on the type and thickness of the material.

Recently, attention has been paid to such characteristics of X-rays, and X-ray apparatuses have recently come to be used in various medical and industrial fields.

This X-ray device is generally used in combination with a timer circuit,
The structure is such that X-rays are generated by applying power to the X-ray tube for a certain period of time determined by a timer.

However, in this case, only about 1% of the input is extracted from the X-ray tube as X-ray output, and most of the rest is converted into heat.

Therefore, in conventional X-ray equipment, measures are taken to prevent the temperature of the X-ray tube itself from rising due to the heat described above, such as making the anode of the X-ray tube rotatable or cooling the X-ray tube with oil. , once the X-ray tube starts operating in an abnormal state,
No measures have been taken to deal with the abnormal situation.

SUMMARY OF THE INVENTION Therefore, the main object of the present invention is to provide an X-ray apparatus which prevents abnormal current from being supplied to the X-ray tube.

Another object of the present invention is to provide an X-ray apparatus that can supply power to the cathode even when abnormal current is prevented from being supplied to the X-ray tube, thereby preparing for the next operation. is to provide.

In order to achieve such an objective, the present invention detects when an abnormal current is supplied to the X-ray tube and is inserted in series in the line on the primary side of a transformer that supplies power to the X-ray tube. This device is designed to make the thyristor non-conductive, and will be explained below using an example.

The drawing shows an embodiment of a dental X-ray device according to the invention,
In the figure, 10 is an alternating current (AC) power source, 11 is a main switch, and 12 is a lamp indicating that the main switch 11 is closed and the power source is connected to the apparatus.

13 is a fuse, 15 is a timer circuit, and 17 is a transformer that supplies alternating current input from the AC power supply 10 to the timer circuit 15 via the fuse 13.

Further, 18 is a resistor, 19 is a diode, and 20 is a capacitor, which constitutes a circuit that half-wave rectifies and smoothes the AC input supplied via the transformer 17.

Further, 21 is a resistor, 22 is a Zener diode, and constitutes a constant voltage circuit.

Further, 24 is a unijunction transistor, 25 is a capacitor, 26 and 27 are variable resistors, 29 to 32 are resistors,
33 is an NPN transistor, 35 is a coil of relay A,
36 is a diode, and these constitute a timer circuit that changes the set time until the unijunction transistor 24 becomes conductive by changing the resistance value of the variable resistor 26, and when the unijunction transistor 24 becomes conductive, Transistor 33 conducts and energizes coil 35 of relay A, switching the contacts of relay A.

Movable contacts a1 and a2 of relay A are in contact with fixed contacts a3a4 when transistor 33 is non-conductive, and are in contact with fixed contacts a5 and a6 when transistor 33 is conductive.

Further, 38 is a switch interlocked with the variable resistor 26, and 39 is a manually operated start switch.

Further, 41 is a coil of power relay B, b1 is a movable contact of power relay B, b3 and b5 are fixed contacts of this power relay B, 42 is a buzzer, and 43 is a lamp. The coil 41 of the head is energized to supply power, and the operator is notified by sounding a buzzer 42 and lighting a lamp 43 that power is being supplied to the head.

50 is a head of a dental X-ray apparatus characterized by the present invention.

This head 50 has an X-ray tube 51 and a step-up transformer 52, which are enclosed in an oil tank 53, as in the conventional case.

In this case, the step-up transformer 52 has a primary winding 521 and secondary windings 522, 523, and the secondary winding 521 has an intermediate tap.

One end of the primary winding 521 is directly connected to the AC power supply 10 via the main switch 11, and the other end is connected via a silicon-controlled rectifier (thyristor) 54 to the contact b5 of the relay B of the main device described above. .

Further, one end of the intermediate tapped secondary winding 522 and the intermediate tap are connected to the cathode of the X-ray tube 51, and the other end of this secondary winding 522 is connected to the coil 56 of the overcurrent detection relay C.

Further, one end of the secondary winding 523 is grounded, and the other end is connected to the anode of the X-ray tube 51.

The other end of the coil 56 of the relay C is grounded, and a capacitor 58 and a sensitivity adjustment resistor 59 of the relay C are connected in parallel to both ends of the coil 56, respectively.

Further, the anode of the thyristor 54 is connected to one end of the primary winding 521 of the transformer 52.

Furthermore, the trigger electrode of this thyristor 54 is connected to the thyristor 5 through a resistor 61 and contacts C1 and C2 of a relay C.
A series body of a capacitor 62 and a resistor 63 is connected between the connection point of the resistor 61 and the contact C1 and the anode.

Further, a resistor 65 is connected between the anode and cathode of the thyristor 54.

Next, the operation of this X-ray apparatus will be explained.

First, when the main switch 11 is closed, the lamp 12 is turned on.

Then, the switch 38 linked to the variable resistor 26 is closed.

Other circuits do not operate at this time.

When the start switch 39 is closed in this state, the transformer 1
AC input is supplied to the primary winding of 7, and at the same time, AC input is supplied to the coil 41 of relay B, and its contacts b1 and b
Close the 5-space.

Therefore, the AC power source 10 is connected to the head 50 via the contacts b1 and b5, the buzzer 42 sounds, and the lamp 43
lights up.

On the head 50 side, the overcurrent detection relay C is not driven at this time, so its contacts c22c1 are closed.
AC power supply 10 - main switch 11 - transformer 52 - contacts c2, c1 - resistor 61 - trigger electrode of thyristor 54 - cathode of thyristor 54 - contacts b5 and b of relay B -
The thyristor 54 is triggered by the path from the main switch 11 to the AC power source 10 and becomes conductive.

Therefore, when the thyristor 54 is in the forward direction with respect to AC input, high voltage is generated on the secondary side of the transformer, current is supplied to the cathode of the X-ray tube 51, and X-rays are emitted from the X-ray tube 51. Ru.

Also, when the start switch 39 is closed, the transformer 1
AC input is also supplied to the secondary side of 7.

This AC input is rectified and smoothed by a resistor 18, a diode 19, and a capacitor 20, and converted to DC, and a DC voltage is generated across the capacitor 20.

Furthermore, a constant DC voltage is generated across the Zener diode 22.

Therefore, the capacitor 25 placed on the gate side of the unijunction transistor 24 begins to be charged via the resistor 29 and the variable resistor 26.

Then, at a set time set according to the resistance value of the variable resistor 26, the unijunction transistor 24 becomes conductive.

Therefore, the base potential of transistor 33 rises, making transistor 33 conductive.

When this transistor 33 becomes conductive, a current flows through the coil 35 of the relay A, and when this coil 35 is energized, its contacts are switched, and the movable contact a1 comes into contact with the contact a5 and is self-held.

Also, at this time, since the movable contact a2 separates from the contact a4,
The coil 41 of the power relay B is deenergized, power supply to the head 50 is stopped, and the operation of emitting X-rays from the X-ray tube 51 is ended.

During the operation of the above-mentioned X-ray apparatus, for example, when the X-ray tube 51 is abnormally heated, the windings of the transformer 52 are short-circuited, or the voltage of the AC power supply 10 is abnormally increased and an abnormal current flows through the X-ray tube. The operation of the protection circuit characterized by the present invention will now be described.

When an abnormal current flows through the X-ray tube 51, the coil 56 of the abnormal current detection relay C connected between one end of the secondary winding 522 of the transformer 52 and the ground is energized.

The operating sensitivity of this relay C is adjusted by a sensitivity adjustment resistor 59.

When the coil 56 of this relay C is energized, its contacts c27c1 open.

Therefore, the thyristor 54 becomes non-conductive, and even if a forward AC input is supplied to the thyristor 54, the thyristor 54 remains non-conductive.

Note that the resistor 63 and capacitor 62 absorb the arc that occurs between the contacts when the contacts c1 and c2 are opened. At this time, the resistor 65 supplies a current (in the forward direction with respect to the thyristor) to the cathode of the A current below the rated value of the X-ray tube (for example, this resistance is 10Ω), which is considerably smaller than the current flowing through the thyristor when an AC input of It acts on

Note that the present invention is not limited to the above-described embodiments, and various modifications and variations are possible.

As described above, according to the dental X-ray apparatus according to the present invention, when an abnormal current flows through the X-ray tube, this is detected and the power source is disconnected from the X-ray tube. It can sufficiently protect against abnormal current.

Further, according to the present invention, by connecting a resistor in parallel with the thyristor, even when the thyristor is in a non-conducting state, a current below the rated value is passed through the X-ray tube, especially the cathode, so that stable operation can be continued.

[Brief explanation of the drawing]

The drawing is a circuit diagram showing an embodiment of the dental X-ray apparatus according to the present invention. 10... AC power supply, 51... Transformer, 54... Silicon controlled rectifier (thyristor)
, 56... Coil of abnormal current detection relay C,
C1, C2... Contacts of relay C, 65...
··resistance.

Claims (1)

[Claims] 1. In a dental X-ray device that drives an X-ray tube via a transformer, the primary winding of the transformer is connected to an AC power source via a switch that works with a silicon-controlled rectifier and a timer circuit, and the X-ray tube is The secondary winding of the transformer connected to the cathode side of the transformer is also connected to an abnormal current detector whose output energizes a circuit that renders the silicon-controlled rectifier non-conducting. A dental X-ray device characterized in that a resistor connected in parallel with the rectifier supplies a current below the rated value to the X-ray tube when the silicon-controlled rectifier is in a non-conducting state.