Electronic endoscope system with suction channel of controllable strength of suction

An electronic endoscope system equipped with a suction channel, capable of freely adusting the inhalation strength of the suction channel. The system includes a suction switch to be pressed by an operator for indicating a desired strength of inhalation through th esuction channel by an extent of depression; a sensor for dtecting the extend of depression of the suction switch; a pinching valve for adjusting a strength of inhalation through the suction channel by adjustably changing an extend of opening; and a controlling unit for controlling the strength of inhalation through the suction channel to the desired strength of inhalation through the suction channel indicated by the suction swtich, by adjusting the extend of opening of the pinching valve in accordance with the extent of depression of the suction switch detected by the sensor.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an endoscope system equipped with a 
suction channel for inhaling air from an end of a scope section of the 
endoscope system. 
2. Description of the Background Art 
A conventional electronic endoscope system equipped with a suction channel 
for inhaling air from an end of a scope section of the endoscope system 
has been that in which the turning on and off of the inhalation is 
controlled by opening and closing of an electromagnetic pinching valve, 
such that when a suction switch provided on the scope grip portion is 
pressed down by an operator, the electromagnetic pinching valve is opened 
and the inhalation at a prescribed inhalation strength is started, whereas 
when the suction switch is released, the electromagnetic pinching valve is 
closed and the inhalation stops. 
Because of this ON/OFF control at two levels, it has been impossible for a 
conventional electronic endoscope system equipped with a suction channel 
to adjust the inhalation strength freely, as had been possible for an old 
fashioned endoscope equipped with a mechanical valve structure in which 
the valve had been operated manually through a control lever. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide an electronic 
endoscope system equipped with a suction channel, capable of freely 
adjusting the inhalation strength of the suction channel. 
This object is achieved by the present invention by providing an electronic 
endoscope system, comprising: a scope section having an end portion; 
suction pump means for providing a power for inhalation; suction channel 
means for providing a path for inhalation by the suction pump means from 
the end portion of the scope section; suction switch means to be pressed 
by an operator for indicating a desired strength of inhalation through the 
suction channel means by an extent of depression; sensor means for 
detecting the extent of depression of the suction switch means; pinching 
valve means, located on the suction channel means between the end portion 
of the scope section and the suction pump means, for adjusting a strength 
of inhalation through the suction channel means by adjustably changing an 
extent of opening; and means for controlling the strength of inhalation 
through the suction channel means to the desired strength of inhalation 
through the suctuon channel means indicated by the suction switch means, 
by adjusting the extent of opening of the pinching valve means in 
accordance with the extent of depression of the suction switch means 
detected by the sensor means. 
Other features and advantages of the present invention will become apparent 
from the following description taken in conjunction with the accompanying 
drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIG. 1, there is shown one embodiment of an electronic 
endoscope system according to the present invention. 
This electronic endoscope system generally comprises a scope section 1 and 
a system body 2, connected through a joint cord 3. From an end portion 4 
of the scope section through the joint cord 3 and the system body 2 to a 
suction pump 5 annexed to the system body 5, there is provided a suction 
channel 6. 
Inside the system body 2, a pinching valve 7 is provided on the suction 
pump 6, and opening and closing of this pinching valve 7 is adjustably 
controlled by a valve controlling unit 11 connected to the pinching valve 
7 inside the system body 2. 
On the scope grip portion 8 of the scope section 1, a suction switch 9 and 
a photo interrupter 10 are provided. As shown in FIGS. 2(A) and 2(B), this 
suction switch 9 comprises a spring 9a wound around a rod 9b, where the 
rod 9b has a triangular window 9c on its lower part thrusted into the 
photo interrupter 10. Thus, according to how much the suction switch 9 is 
pressed down by an operator, a different amount of light can be 
transmitted through the photo interrupter 10, so that an extent of 
depression of the suction switch 9 can be determined from an interruption 
signal outputted by the photo interrupter 10. Such an interruption signal 
of the photo interrupter 10 is provided to the valve controlling unit 11, 
so as to control an extent of opening of the pinching valve 7 in 
accordance with an extent of depression of the suction switch 9. 
When an electromagnetic valve is employed as the pinching valve 7, the 
valve controlling unit 11 can be constructed as follows. 
Namely, as shown in FIG. 3, the valve controlling unit 11 in this case 
comprises a feed-back circuit formed by an operational amplifier 12, a 
pulse width modulator 13, a valve driver 14a, and a valve opening detector 
14b. The interruption signal and a feed-back signal from the valve opening 
detector 14b are fed into the operational amplifier 12, so that an output 
of the operational amplifier 12 is proportional to a voltage difference 
between the interruption signal and the feed-back signal. Then, the pulse 
width modifier 13 is controlled by this output of the operational 
amplifier 12, so as to voltage control the valve driver 14a to control the 
extent of opening of the electromagnetic valve 7a in accordance with an 
extent of depression of the suction switch 9. 
Alternatively, a stepping motor driven valve such as that shown in FIG. 4 
may be employed as the pinching valve 7. In this stepping motor driven 
valve 7b of FIG. 4, the suction channel 6 is attached to an outer frame 
7d, and inside the outer frame 7d, an inner frame 7e with a spring 7f 
attached is slidably placed, such that when the inner frame is at the 
highest position, the sucton channel 6 is completely closed, whereas when 
the inner frame is at the lowest position, the suction channel 6 is fully 
open. The inner frame 7e slides inside the outer frame 7d as a stepping 
motor 7c engaging to the inner frame 7e rotates. The stepping motor 7c is 
capable of rotating a prescribed amount of angle in either direction each 
time. 
Now, when such a stepping motor driven valve 7b is employed as the pinching 
valve 7, the valve controlling unit 11 can be constructed as follows. 
Namely, as shown in FIG. 5, the valve controlling unit 11 in this case 
comprises a circuit including an operational amplifier 15 to which the 
interruption signal from the photo interrupter 10 is fed and compared with 
a signal indicating a current setting of the stepping motor 7c, a 
direction of rotation determining unit 16 for determining a direction of 
rotation of the stepping motor 7c from an output of the operational 
amplifier 15, an absolute value calculator 17 for obtaining an absolute 
value of the output of the operatonal amplifier 15, voltage/frequency 
converter 18 to convert a voltage representing the absolute value obtained 
by the absolute value calculator 17 to a frequency, a valve driving unit 
19 for adjusting the pinching valve 7 by driving the stepping motor 7c in 
the direction of rotation determined by the direction of rotation 
determining unit 16 at the frequency obtained by the voltage/frequency 
converter 18, an up/down counter 20 for counting a number of increments in 
up or down direction into which the stepping motor 7c has been rotated, a 
D/A converter for converting a digital information of the number of 
increments counted by the up/down counter 20 into an analog information to 
be fed back to the operational amplifier 15 as the signal indicating the 
current setting of the stepping motor 7c, and a reset signal generator 22 
for generating a reset signal to be supplied to the valve driving unit 19 
and the up/down counter 20 in response to the interruption signal due to 
the suction switch 9 at an undepressed position. 
Here, the valve driving unit 19 adjusts the amount of rotational angle of 
the stepping motor 7c by driving the stepping motor 7c at the higher 
frequency when the absolute value of the difference between the 
interruption signal and the signal indicating the current setting of the 
stepping motor 7c is large, in which case the stepping motor 7c rotates by 
a large angle, or at a lower frequency when the absolute value of the 
difference between the interruption signal and the signal indicating the 
current setting of the stepping motor 7c is small, in which case the 
stepping motor 7c rotates by a small angle. 
Thus, in this case, as in the previous case, an extent of opening of the 
pinching valve 7 is controlled in accordance with an extent of depression 
of the suction switch 9. 
Referring now to FIG. 6, there is shown another embodiment of an electronic 
endoscope system according to the present invention. In the following, 
those parts of the system which are equivalent to the previous embodiment 
will be given the same reference numerals in the figures, and their 
explanation will be omitted. 
In this embodiment, the electronic endoscope system of the previous 
embodiment is further equipped with a flux or pressure sensor 23 placed 
between the joint cord 3 and the pinching valve 7 inside the system body 
2, whose detection signal is utilized as a feed back for the valve 
controlling unit 11, so to stabilize the flux or pressure in the suction 
channel 6 by controlling the extent of opening of the pinching valve 7 in 
accordance with the flux or pressure in the suction channel 6 as well as 
in accordance with an extent of depression of the suction switch 9. 
In this case, if the stepping motor driven valve 7b is employed as the 
pinching valve 7, the valve controlling unit 11 can be constructed as 
follows. 
Namely, as shown in FIG. 7, the valve controlling unit 11 of FIG. 5 can be 
modified by removing the up/down counter 20 and the D/A converter 21, and 
providing the flux or pressure sensor 23 for detecting the flux or 
pressure in the suction channel 6, a sensor driving unit 24 for activating 
the sensor 23, and an amplifier 25 for amplifying an output of the sensor 
23. The amplified output of the sensor 23 from the amplifier 25 is fed to 
the operational amplifier 15 as the signal indicating the current setting 
of the stepping motor 7c. 
Thus, acccording to this embodiment, the flux or pressure in the suction 
channel 6 can be stabilized by controlling the extent of opening of the 
pinching valve 7 in accordance with the flux or pressure in the suction 
channel 6 as well as in accordance with an extent of depression of the 
suction switch 9. 
Such an additional feature is useful in removing a fluctuation in the 
relationship between the extent of depression of the suction switch 9 and 
the flux or pressure in the suction channel 6 due to structural 
limitations, a differrence of inner diameter of the suction channel 6, an 
initial instability resulting from a limited capacity of the suction pump 
5, and other causes. 
It is to be noted that the electromagnetic valve 7b can equally be applied 
to this embodiment, utilizing the output of the sensor 23 as the feed back 
to control the valve driver 14a in the configuration of the valve 
controlling unit 11 shown in FIG. 3. 
It is also to be noted that the pinching valve 7 can be of any electrically 
driven type other than the electromagnetic one and the stepping motor 
driven one used in the above description of the preferred embodiments. 
Besides these, many modifications and variations of the above embodiments 
may be made without departing from the novel and advantageous features of 
the present invention. Accordingly, all such modifications and variations 
are intended to be included within the scope of the appended claims.