Pipet cleaning apparatus

A pipet cleaning apparatus in which cleaning liquid is fed into a cleaning tank, where a pipet is accommodated, through a feeding pipe line, a liquid level in the tank is raised to the full liquid level to immerse the pipet in the cleaning liquid, then the used cleaning liquid is overflown through an overflow portion of a discharging pipe line and by repeating the same process, the pipet cleaning is carried out, characterized in that the cleaning liquid is detected by a sensor at a level lower than the full liquid level by each cleaning time, the detected signal is counted by a counter, and when a preset number of cleaning times is counted, a valve of the feeding pipe line is closed.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a pipet cleaning apparatus for use in various 
experiments such as biological testing, chemical testing and in 
laboratories. 
2. Description of the Prior Art 
Generally, the pipet cleaning is carried out after the chemical 
pretreatment in a cleaning tank, and it is conventional to use a cleaning 
apparatus constructed as shown in FIG. 12. This known cleaning apparatus 
has a structure in which a pipe line B for feeding cleaning liquid and 
another pipe line C for discharging the used cleaning liquid (hereinafter 
called "waste liquid") out of a cleaning tank A are respectively connected 
with the cleaning tank A, and an overflow portion D of the same level as 
the full liquid level L.sub.1 established in the cleaning tank A is formed 
in the discharging pipe line C. 
With respect to the cleaning operation, a liquid feeding cock E is opened 
for feeding the cleaning liquid (water) from the pipe line B to the 
cleaning tank A to fill it. At the same time, the liquid level in the 
discharging pipe line C is raised, and as the cleaning liquid overflows 
through the overflow portion D when the liquid level in the tank reaches 
the established full liquid level L.sub.1, the waste liquid flows down 
through the discharging pipe line C. Thus, by repeating the operation, the 
required number of immersion cleaning times (several or over ten times) is 
applied to the pipet. 
In this connection, when the number of pipet cleaning times is set at ten, 
for example, it is necessary to stop the feed of cleaning liquid after 
completing the established ten times of cleaning in order to save the 
cleaning liquid or solvent. For that purpose, as a control system of the 
number of cleaning times, two kinds of systems have been proposed up to 
the present, i.e., a timer count type based on cleaning time corresponding 
to the number of cleaning times and a flow quantity count type on the 
basis of the used quantity of liquid corresponding to the number of 
cleaning times. In either of these two systems, however, the liquid level 
in the tank at the time of stopping the count (or the moment of completing 
the final cleaning) is not taken into consideration, and accordingly, 
there exist disvantages described hereinafter. 
In case that the number of cleaning times is set at 10, for example, it is 
desired that at the time of completing the 10th (final) cleaning, the used 
cleaning liquid in the tank is still kept at the full liquid level without 
being discharged through the discharging pipe line C so that the pipet may 
still be kept immersed in the cleaning liquid. This is because it is 
necessary to prevent the cleaned pipet from being stuck by water spoor, 
dust or various germs in the air. 
This requirement is not satisfied by either of the aforementioned two known 
control systems, because according to these systems, at the time of 
completing final cleaning, the liquid in the tank is drawn into the 
discharging pipe line C, once the liquid level in the tank reaches the 
full liquid level L.sub.1 and the completion of cleaning comes when the 
tank becomes empty. 
Furthermore, during repeated cleaning, even when the waste liquid is drawn 
into the discharging pipe line C, the new cleaning liquid is fed from the 
feeding pipe line B to the cleaning tank A. Accordingly, the new cleaning 
liquid flows into the tank while discharging with the waste liquid drawn 
into the discharging pipe without being used for the pipet cleaning, this 
results in the cleaning liquid or solvent wastage and an increase of 
discharging time, bringing about a cost increase in cleaning and 
redundancy of cycle time from cleaning to discharge. 
SUMMARY OF THE INVENTION 
An object of this invention is, therefore, to provide a pipet cleaning 
apparatus wherein the cleaning operation is automatically stopped at the 
time of final cleaning in the established number of cleaning times without 
drawing the waste liquid in the cleaning tank to the discharging pipe line 
while keeping the liquid level in the tank almost at the full liquid 
level. 
Another object of this invention is to provide a pipet cleaning apparatus 
wherein, after completion of each cleaning, the feed of new cleaning 
liquid (containing cleaning solvent) to the cleaning tank is automatically 
stopped during the period of discharging the waste liquid from the tank to 
the discharging pipe line. 
In order to accomplish the foregoing objects, the pipet cleaning apparatus 
of this invention is characterized by comprising a cleaning tank for 
accommodating a pipet, a pipe line for feeding cleaning liquid to the 
cleaning tank, a siphon-shaped pipe line for discharging used cleaning 
liquid out of the cleaning tank having an overflow portion at the same 
level as a full liquid level established in the cleaning tank, a sensor 
for detecting existence of the cleaning liquid immediately before the 
cleaning liquid reaches the full liquid level, a counter for counting 
signals detected by the sensor, and a valve on the feeding, pipe line to 
be closed by the signal which is output by the sensor when a specified 
number of cleaning times is counted. 
According to the aforementioned pipet cleaning apparatus, since the sensor 
detects the completion of immersion of the pipet immediately before 
reaching the full liquid level and the number of cleaning times at the 
moment of such detection is counted, the liquid level in the tank does not 
reach the full liquid level as the valve is closed by the detection of the 
final cleaning. As a consequence, after the completion of the final 
cleaning, the waste liquid is not drawn out of the tank to the discharging 
pipe, the pipet is still kept immersed in the liquid, and therefore, there 
no longer exists the disadvantage that the cleaned pipet is stuck by water 
spoor, dust, various germs, etc. 
The pipet cleaning apparatus of this invention is further characterized by 
comprising a cleaning tank for accommodating a pipet, a pipe line for 
feeding cleaning liquid to the cleaning tank, a siphone-shaped pipe line 
for discharging used cleaning liquid out of the cleaning tank having an 
overflow portion at the same level as a full liquid level established in 
the cleaning tank, a first sensor for detecting existence of the cleaning 
liquid immediately before the cleaning liquid reaches the full liquid 
level, a counter for counting signals detected by the first sensor, a 
second sensor for detecting the starting of overflow of the cleaning 
liquid, and a valve on the feeding pipe line to be closed by the signal 
which is output when a specified number of cleaning time is counted and by 
the signal which is detected by the second sensor respectively. 
According to the aforementioned pipet cleaning apparatus, the second sensor 
detects that the waste liquid is discharged out of the tank to the 
discharging pipe line through the overflow portion after completion of 
each cleaning, and the valve in the feeding pipe line is closed using the 
detected signal so as to stop the feed of new cleaning liquid during the 
discharge of the waste liquid from the tank. Thus, the waste of the 
cleaning liquid or solvent is prevented and the cycle time from cleaning 
to discharge can be shortened. 
Other features and advantages of this invention will become apparent in the 
course of the following description of the preferred embodiment with the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The pipet cleaning apparatus of which the outline shown in FIG. 1 is 
equipped with a cleaning tank 1. A supporting plate 2 made of a perforated 
plate or a mesh member bridges the cleaning tank by extending across the 
tank a little above the inner bottom of the cleaning tank 1. A basket 3 is 
placed on the supporting plate 2. 
A full liquid level L.sub.1 is established near the opening of the cleaning 
tank 1 at a position a little above the top of the basket 3. The pipet 
accommodated in the basket 3 is immersed in the liquid when the liquid 
rises up to the full liquid level L.sub.1. A liquid detection level 
L.sub.2 is established at a position a little lower than the full liquid 
level L.sub.1 in the cleaning tank, and a sensor 4 for detecting the 
cleaning liquid (hereinafter called "the first sensor") is mounted at the 
position of the detection level L.sub.2. In this case, the sensor 4 is 
fixed as shown in FIG. 2, to a clip-shaped hanger 5 beforehand, and 
thereby the sensor 4 is easily mounted and demounted by only hanging the 
hanger 5 on the opening edge of the cleaning tank 1. 
The sensor 4 is connected with a counter 6 by way of cord 7 as shown in 
FIGS. 1 and 3. Thus, the sensor 4 outputs a liquid level detection signal 
each time the liquid in the tank reaches the liquid detection level 
L.sub.2, and the detected signal is transmitted to the counter 6 to be 
stored therein. 
A feeding pipe line 8 for feeding cleaning liquid includes a feed water 
cock 9, and an electromagnetic valve 10 mounted on the outlet of the feed 
water cock 9. The electromagnetic valve 10 is connected with the counter 6 
by way of a cord 11, and is switched off (closed) by the output signal 
from the counter 6 when the counter 6 counts a specified number of 
cleaning times. In this connection, it is preferred that a hole 13 is 
formed on a frame 12 of the counter 6 in order to hang the counter 6 in an 
adequate place as a wall as shown in FIG. 3. Further, a dial 14 for 
setting the number of the cleaning time and a stater 15 are provided on 
the counter 6 respectively. 
An inlet of a siphon-shaped discharging pipe line 16 is connected with the 
bottom of the cleaning tank 1, and an outlet 17 of the discharging pipe 
line 16 is positioned lower than the inner bottom of the cleaning tank 1. 
An overflow portion 18 formed on the discharging pipe line 16 is 
positioned at the same level as the full liquid level L.sub.1. 
With regard to the operation of the foregoing pipet cleaning apparatus, in 
the first place the basket 3 for accommodating a pipet therein is placed 
on the supporting plate 2, and the number of cleaning times is set by 
means of the dial 14 of the counter 6. 
When the starter 15 is switched "ON" and the feed water cock 9 is opened, 
the cleaning liquid runs through the electromagnetic valve 10 to flow into 
the cleaning tank 1 by way of the feeding pipe line 8. Then the liquid 
level in the tank increases so that the pipet may be immersed in the 
cleaning liquid thereby carrying out the cleaning thereof. When the liquid 
in the tank reaches the liquid detection level Lz, the sensor 4 outputs a 
detection signal so that a counter 6 counts one time of cleaning. When the 
liquid in the tank further rises and reaches the full liquid level 
L.sub.1, the cleaning liquid overflows the overflow portion 18 of the 
discharging pipe line 16, and the air in the discharging pipe line 16 is 
discharged out of the outlet 17 with the overflowing waste liquid. Thus, 
the waste liquid is completely drawn into the discharging pipe line 16 by 
the difference in level (or height) between the full liquid level L.sub.1 
in the cleaning tank 1 and the outlet 17 of the discharging pipe line 16, 
thereby the liquid level in the tank becomes zero. 
However, since the cleaning liquid is successively fed from the feeding 
pipe line 8, the liquid level in the tank begins to rise again. The 
above-described process is repeated thereafter in the same way. 
In this manner, each time the liquid level in the tank rises (corresponding 
to one time of pipet cleaning), the counter 6 counts the signal detected 
by the sensor 4. When reaching the established number of cleaning times, 
the electromagnetic valve 10 is closed to shut off the feeding pipe line 
8. 
Since the liquid detection level L.sub.2 of the sensor 4 is lower than the 
full liquid level L.sub.1, the liquid does not rise over the level L.sub.2 
by the actuation of the electromagnetic valve 10, i.e., the cleaning 
liquid does not overflow the overflow portion 18, and accordingly the 
cleaning liquid is kept at the level near the full liquid level L.sub.1 to 
automatically stop the pipet cleaning operation at this state. 
Since the required number of pipet cleaning is freely selected (or preset) 
by the dial 14 of the counter 6, the number of cleaning times is variable. 
Even when using the conventional pipet cleaning tank, it is possible that 
the above-described automatic cleaning is achieved by mounting the sensor 
4 and the counter 6 thereon. In such a case, it is also preferred that the 
sensor 4 be fixed to the clip-shaped hanger 5 and that the hole 13 be 
provided on the counter 6 as shown in FIG. 2 and FIG. 3 respectively so as 
to easily mount these members on the conventional pipet cleaning tank. 
In addition, it is possible to attach an annuciator or indicator as a 
buzzer, or lamp to provide a signal at the time of closing the 
electromagnetic valve 10, i.e., when completing a specified number of 
cleaning times. 
FIGS. 4 to 6 show another embodiment of this invention, in which a valve 
unit comprising a diaphram valve 19 and a pilot valve 20 are used in place 
of the electromagnetic valve 10. 
With respect to the structure of the diaphram valve 19, a mouth ring 21 is 
fixed to a faucet 9a of the cock 9 by a set screw 22. A joint sleeve 23 is 
screwed in the mouth piece 21 from below for engagement therewith, and the 
periphery of the end of the faucet is sealed by a rubber packing 24 
mounted inside of the joint sleeve 23. A cylindrical valve box 25 is 
further screwed in the joint sleeve 23 from below for engagement 
therewith. A valve chest 26 is formed in the valve box 25 so as to expand 
outwardly at a level approximately the middle of the overall height of the 
valve box 25; a diaphram valve plug 27 is vertically mounted on said valve 
chest 26. In addition, a transverse wall or bulkhead 28 facing the 
diaphram valve plug 27 is projectingly provided from the opposite wall. 
The cleaning liquid passes through a liquid passage 29 formed inside of 
the joint sleeve 25, flows into the valve chest 26 from the inlet 30 above 
the bulkhead, and pushes or presses the diaphram plug 27 by water pressure 
so that the outlet 31 under the bulkhead 28 is opened. An aperture 32 is 
provided on the diaphram plug 27 at the part corresponding to the inlet 
30, so that a back pressure chamber 33 at the back side of the valve 
member is communicated with the inlet 30. The aperture 32 is sufficiently 
smaller in diameter than the liquid passage 29. 
The pilot valve 20, which is closed by the signal output from a counter 34, 
is incorporated in a control box 35 together with the counter 34, as shown 
in FIG. 5. The back pressure chamber 33 is connected with an inflow port 
20a of the pilot valve 20 by way of a pilot passage 36 comprising a tube, 
for example. Further, an outflow port 20b of the pilot valve 20 is 
connected with the feeding pipe line 8 by way of a drain passage 37 
comprising a tube, for example, and both the passages 36, 37 are 
communicated or shut off from each other by means of the pilot valve 20. 
Each diameter of the said passages 36, 37 is sufficiently smaller than 
that of the feeding pipe line 8. 
A hanger 39 for mounting a sensor 38 and the control box 35 on the cleaning 
tank 1 is made of a bar member which is bent in the shape of a clip, being 
different from the hanger 5 of FIG. 2. The control box 35 is hung on one 
leg portion 39a of the hanger 39, while the sensor 38 is mounted on the 
other leg portion 39b so as to be slidable up and down. Thus the liquid 
detection level L.sub.2 is varied by sliding the sensor 38. In this 
connection, numeral 40 is a belt for fastening the control box to the 
cleaning tank 1. 
In FIG. 6, when the pilot valve 20 is open, the cleaning liquid flows 
sequentially through the inlet 30, the aperture 32, the back pressure 
chamber 33, the pilot passage 36, the pilot valve 20, the drain passage 37 
thus reaching the feeding pipe line 8, while pushing the diaphram valve 
plug 27 to be opened, as indicated by the solid line of FIG. 6, and 
reaching the cleaning tank 1 through the outlet 31. 
When final cleaning is completed and the pilot valve 20 is closed by the 
signal output from the counter 34, the flow of cleaning liquid through the 
pilot passage 36, and the pilot valve 20 reaching the drain passage 37 is 
shut off. Accordingly, the back pressure in the back pressure chamber 33 
rises, the diaphram valve plug 27 is pushed against the liquid pressure to 
close the outlet 31 as indicated by broken line of FIG. 6., thus shutting 
off the feeding pipe line 8. 
In FIGS. 7 to 9, a further embodiment is illustrated, including a sensor 38 
for detecting the liquid level in the cleaning tank 1 to be a first 
sensor. Another sensor is mounted on the outlet 17 of the discharging pipe 
line 16 as a second sensor 41 which detects the overflown waste liquid. 
In addition to the counter 34, to which the signal detected by the first 
sensor 38 is input, and the pilot valve 20, a control circuit 45 is 
accommodated in the control box 42. To the control circuit 45, on-off 
signals of the starter 44, the output signal of the counter 34 and the 
detected signal of the second sensor 41 are input respectively. 
FIG. 9 shows one mode of the control circuit 45 having therein an OR gate 
element 46 to which respective signals of the counter 34 and the second 
sensor 41 are input, a NOT gate element 47 for inverting the output of the 
element 46, and an AND gate element 48 to which respective outputs of the 
NOT gate element and the starter 44 are input. 
The circuit 45 of FIG. 9 is operated as described below. When switched "ON" 
the starter 44 for starting the cleaning, one input terminal of the AND 
gate element 48 comes to a level "H". Since the outputs of the counter 34 
and the second sensor 41 are at level "L" respectively, the output of the 
OR gate element is also at the level "L", while the output of the NOT gate 
element 47 is at the level "H". Accordingly, the other input terminal of 
the AND gate element 48 comes to the level "H", and the output of the 
control circuit 45 is also at the level "H", thereby the pilot valve 20 is 
kept at the open state. When the liquid level in the tank reaches the full 
liquid level L.sub.1 and the waste liquid is drawn into the discharging 
pipe line 16, the second sensor 41 detects the beginning of overflow and 
the output thereof comes to the level "H", and the output of the control 
circuit 45 comes to the level "L", thereby the pilot valve 20 is closed. 
Accordingly, the flow of cleaning liquid through the pilot passage 36 and 
the pilot valve 20 reaching the drain passage 37 is stopped, the diaphram 
valve member 19 is closed, and the feed of new cleaning liquid is stopped, 
is thereby liquid level in the tank being rapidly lowered. 
When the tank becomes empty, the output of the second sensor 41 returns to 
the level "L" to open the pilot valve 20, and as a result thereof the new 
cleaning liquid is fed to the cleaning tank 1 by way of the feeding pipe 
line 8. 
In this manner, the counter 34 counts the detected signal everytime the 
liquid level in the tank rises (corresponding to one time of the pipet 
cleaning), and when completing the final cleaning and the output of the 
counter 34 comes to the level "H", the output of the control circuit 45 
turns to level "L" so that the pilot valve 20 is closed to shut off the 
feeding pipe line 8. 
As is obvious by the foregoing description, when the waste liquid in the 
cleaning tank 1 begins to overflow to the discharging pipe line 16, the 
feed of new cleaning liquid to the tank 1 is stopped, and such a state 
continues up to the completion of discharge. Therefore, there is no longer 
any wastage such as discharging new cleaning liquid without being used in 
the pipet cleaning. Furthermore, the time necessary for discharging the 
waste liquid is exclusively decided by the liquid quantity in the tank at 
the time of starting the discharge and the discharging speed, resulting in 
shortening the discharging time. 
Referring now to FIG. 10 which shows a further modification, a basket 50 
accommodated in the cleaning tank 49 is rotated by the force of the 
cleaning liquid flowing into the cleaning tank 49. To be more specific, a 
supporting pin 52 is projectingly provided on the upper side of a 
supporting plate 51 of the cleaning tank 49, while an engaging pin 54 is 
projectingly provided on the lower side of a cover 53 for covering the 
cleaning tank 49. Thus, the basket 50 is supported by the supporting pin 
52 at the bottom part thereof, and is rotatable by engaging the pin 54 
with an aperture (not shown) provided on the handle 55 of the basket 50. 
The cleaning liquid is fed from the feeding pipe line 8 to the cleaning 
tank 49 in a tangential direction, and the basket 50 is forcibly rotated 
by eddy current produced in the cleaning tank, thereby greatly improving 
the cleaning effect. The cleaning effect is far more improved when the 
cleaning tank 49 is placed on an ultrasonic vibrating device 56 to add 
ultrasonic vibration to the cleaning liquid. 
Since there is a possibility that the basket 50 will come in contact with 
the first sensor and stop the rotation of the basket, when using the 
rotatable basket 50 as shown in FIG. 10.sub.1 it is preferred that the 
first sensor be constructed to be thin as shown in FIG. 11. For example, a 
stainless steel plate of 0.5-1.0 mm in thickness is bent to be a 
clip-shaped hanger 58. Then an electro-conductive film 50 is adhered onto 
the hanger 58, and an insulating and water-resistant coating is applied 
thereto. The insulating and water-resistant coating is then torn off at 
two optional parts to use the exposed parts of the electro-conductive film 
as contact points for switching. Thus, being constructed a sensor 57 is 
constructed which outputs a detected signal when both contact points are 
short-circuited by the cleaning liquid. 
As many apparently widely different embodiments of this invention may be 
made without departing from the spirit and scope thereof, it is to be 
understood that this invention is not limited to the specific examples 
thereof except as defined in the appended claims.