Liquid Distributing Device for Use in Chemical Analyzer

This invention relates to a liquid distributing device for use in an automatic analyzing apparatus, for delivering a given amount of a liquid such as a sample liquid from a sample cup into a reaction vessel comprising a probe to be immersed into the sample liquid contained in the sample cup, pumping means such as a syringe connected to said probe for sucking and discharging a given amount of the sample liquid through said probe and means for driving said syringe.

In automatic analyzing apparatuses, various distributing devices are used to deliver various kinds of liquid such as samples, reagents and diluents by means of one probe. Such distributing devices perform a sucking operation even if a liquid level of the liquid contained in a vessel descends below a tip of a probe and thus air is sucked in the probe. Therefore, the amount of the liquid sucked in the probe is smaller than a given amount to be delivered. This results in that the predetermined amount of the liquid could not be delivered and erroneous measurement might be introduced. In order to avoid the above mentioned drawback, it has been proposed to detect a liquid level of the liquid during the aspiration. This can be effected by providing a photoelectric detecting means having an elongated detecting region extending in an axial direction of the vessel, because the liquid level descends in accordance with the aspiration. Therefore, the photoelectric detecting means is liable to be large in size and complicated in construction. It has also been proposed to descend the probe in accordance with the progress of aspiration. However, such a case, a very complicated probe driving mechanism must be provided.

The present invention has for its object to provide a novel and useful distributing device which can obviate the above mentioned delivery error causing an erroneous measurement by means of a simple construction.

To fulfill the object, the present invention provides a distributing device for delivering a given amount of a liquid from a first vessel into a second vessel comprising a probe to be immersed into the liquid contained in the first vessel, pumping means connected to said probe for sucking and discharging a given amount of the liquid through said probe and means for driving said pumping means, the improvement comprises

means for detecting whether or not the liquid is present in the first vessel up to a predetermined level to produce a liquid detection signal;

means for receiving said liquid detection signal to produce a first signal representing an actual amount of the liquid sucked through the probe;

means for storing a second signal representing said given amount of liquid to be delivered; and

means for comparing said first and second signals with each other to produce a discrimination signal denoting that the actual amount of the sucked liquid is not equal to the given amount to be delivered into the second vessel.

FIG. 1 is a schematic diagram showing one embodiment of the distributing device according to the invention;

FIG. 2 is a schematic diagram illustrating another embodiment of the distributing device according to the invention; and

FIG. 3 is a schematic diagram depicting still another embodiment of the distributing device according to the invention.

In FIG. 1, a sample vessel 1 for containing a sample solution is mounted on, for instance, a turntable of a sampler of an automatic analyzing apparatus (not shown). A probe 2 is arranged movably in vertical and horizontal directions and is first immersed in the sample solution to suck the sample. Then the probe 2 is moved upwards and is fed horizontally into a position above a reaction vessel (not shown). Then the sucked sample solution is discharged into the reaction vessel. This probe 2 is connected to a syringe 3 by means of a connecting tube 4. The syringe 3 operates as pumping means for sucking and discharging the sample and comprises a cylinder 3A, a piston 3B movably arranged inside the cylinder and a rod 3C having one end connected to the piston and the other end coupled to a pulse motor 5 by means of a suitable link mechanism 5A. By rotating the pulse motor 5, the rod 3C and thus the piston 3B are moved up and down. The syringe 3 is further connected to a washing liquid vessel 8 through a valve 6 and a washing pump 7 so as to discharge a washing liquid through the probe 2 to wash the probe. To the pulse motor 5 are supplied a given number of driving pulses from a driver 9 under control of a controlling circuit such as a microcomputer. The number of pulses supplied from the driver 9 to the pulse motor 5 are counted by a counter 10. A light source 11 and a light detector 12 are arranged at opposite positions with respect to the sample vessel 1. They are so arranged that an optical axis OP is set slightly lower than a tip position of the probe 2 when the probe 2 is immersed in the liquid to suck the liquid in the sample vessel 1. Then, a light emitted from the light source 11 is transmitted through the liquid in the sample vessel 1 and is received by the light detector 12. The light detector 12 is connected to one input of a comparator 1 13 having the other input connected to a variable voltage source 14. When an output from the light detector 12 becomes larger than a reference voltage produced by the variable voltage source 14 due to the fact that a liquid level descends lower than the optical axis OP, a count stop signal is supplied from the comparator 13 to the counter 10 so as to stop counting the driving pulses from the driver 9. The counter 10 is connected to a discriminator 15 to supply a count value to the discriminator 15. It should be noted that the count value represents an actual amount of the liquid 1 sucked through the probe 2. Moreover, a memory 16 is connected to the discriminator 15. The number of driving pulses necessary for sucking the given amount of the liquid to be delivered has been stored in the memory 16 by means of the controlling circuit. The number thus stored in this memory 16 is supplied to the discriminator 15. In the discriminator 15, the count value from the counter 10 is compared with the desired value stored in the memory 16. If the count value is smaller than the desired number, the discriminator 15 supplies a signal to an alarm unit 17 so as to activate an alarm.

Hereinafter, an operation of the distributing device according to the invention will be further explained. When the driving pulses are supplied from the driver 9 to the pulse motor 5 by means of the controlling circuit, the rod 3C is moved downward so that the sample solution in the sample vessel 1 is sucked into the probe 2. For the time being, it should be noted that the valve 6 is closed. After sucking a predetermined amount of the sample solution, the probe 2 is moved above the reaction vessel and the pulse motor 5 is driven again to deliver the sample solution into the reaction vessel. Next, the probe 2 is moved to a washing position (not shown) so as to discharge the washing liquid from the washing liquid vessel 8 by means of the washing pump 7 through the valve 6, which is now opened, and the probe 2, so that the syringe 3, the probe 2, and the connecting tube 4 are washed.

When the liquid level of the sample solution in the sample vessel 1 is still located above the optical axis OP near the tip of the probe 2 after the aspiration, all of the driving pulses supplied to the motor 5 for aspiration are counted by the counter 10, because the count stop signal is not supplied from the comparator 13 to the counter 10. In this case, since the count value of the counter 10 is the same as the desired value stored in the memory 16 so that an alarm is not activated. Contrary to this, when the liquid level of the sample solution drops below the optical axis OP during the aspiration, the subsequent driving pulses supplied from the driver 9 to the pulse motor 5 are not counted by the counter 10, because the comparator 13 supplies the count stop signal to the counter 10 during the aspiration. Therefore, the count value of the counter 10 becomes smaller than the desired value stored in the memory 16 and a signal is supplied from the discriminator 15 to the alarm unit 17 so as to raise an alarm.

As mentioned above, according to the invention the alarm is produced before discharging the sucked liquid. Whenever the aspirated amount is smaller than the predetermined amount, any erroneous measurement can be effectively prevented and abnormal analysis results can be identified by alarm marks on analysis reports. Moreover, in case of delivering the sample solution sucked at one time into a plurality of reaction vessels by means of the probe 2, if a required amount of the sample solution is not sucked, the amount of the sample solution which is sucked in the syringe 3 can be determined from the count value of the counter 10. Therefore, by previously providing a priority for test items, it is possible to deliver selectively the sample solution into reaction vessels beginning from the one of highest priority and to give the alarm only for items wherein the distribution cannot be performed. In such a case, it is also possible to cancel the sample delivering operation for the test items for which the given amounts of sample could not be delivered under control of the controlling circuit.

Furthermore, in regard to as for the means for detecting the liquid level of the sample solution, various known systems such as systems for measuring an electric resistance between electrodes reflection of light or ultrasonic wave, and an electrostatic capacity between an electrode and a liquid surface may be utilized instead of the photoelectric measuring system mentioned above.

FIG. 2 is a schematic diagram illustrating another embodiment of the distributing device according to the invention. For the sake of simplicity, the same numerals are used for denoting the same portions as those in FIG. 1. In this embodiment, a general AC or DC motor 20 is used for driving the syringe 3 instead of the pulse motor 5. Therefore, a driving electric current is supplied to the motor 20 for a time interval during which the predetermined amount of the sample solution can be sucked under the control of the controlling circuit (not shown). Further, in this embodiment, a clock pulse generator 21 is connected to the counter 10 through a gate 22, and also an output of the comparator 13 is supplied to the gate 22. The gate 22 is made OFF when the count stop signal is supplied from the comparator 13, and made ON when a signal is not supplied. The clock pulse generator 21 generates the pulses continuously which are counted by the counter 10 only for a time interval when the driving electric current is supplied from the driver 9 to the motor 20. Furthermore, in the memory 16 is stored a desired count value which is equal to the number of pulses generated from the clock pulse generator 21 for a time interval during which the driving electric current is supplied to the motor 20 for aspirating the predetermined amount of the liquid.

In this embodiment, as is the same as the aforementioned embodiment, when the liquid level of the sample solution in the sample vessel 1 does not descent to the optical axis OP of the photoelectric detector 11, 12, the count stop signal is not supplied from the comparator 13 to the gate 22. Therefore, the gate 22 is made ON and the count value of the counter 10 becomes the same as the desired value stored in the memory 16 so that the alarm unit 17 does not produce an alarm. Contrary to this when the liquid level of the sample solution descends below the optical axis OP during the aspiration the count stop signal is generated so as to make the gate 22 OFF. Therefore, the count value of the counter 10 becomes smaller than the desired value in the memory 16 and the discriminator 15 sends to the alarm unit 17 an alarm signal indicating that the given amount of sample has not been sucked.

FIG. 3 is a schematic diagram depicting still another embodiment of the distributing device according to the invention. In this embodiment, the optical axis OP of the photometric device 11, 12 is located slightly above the tip position of the probe 2 so as to prevent the syringe 3 from sucking air when the liquid level of the sample solution becomes below the tip position of the probe 2. Then, after detecting the liquid level of the sample solution at this optical axis OP, the sucking operation is carried out by the syringe 3 for a given short time interval until the surface of the sample solution reaches near the tip position of the probe 2 and after that the sucking operation of the syringe is stopped. To this end, in this embodiment, the signal generated from the comparator 13 is supplied to a stop signal generating circuit 24 through a delay circuit 23. After that, the stop signal generating circuit 24 supplies a stop signal to the driver 9 so as to stop supply of the driving pulse from the driver 9 to the pulse motor 5 and at the same time the counter 10 stops its counting operation.

In this embodiment, in case of sucking the sample solution utilizing the syringe 3, if the surface of the sample solution does not reach the optical axis OP, the alarm unit 17 does not operate as it operated in the previous embodiments. On the contrary, when the surface of the sample solution reaches the optical axis OP, the signal is supplied from the comparator 13 to the delay circuit 23 and after the given time the delay circuit 23 supplies the signal to the stop signal generating circuit 24. During this delay time the sample solution existing between the optical axis OP and the tip position of the probe 2 is sucked by the syringe 3. Then, the stop signal generating circuit 24 supplies the stop signal to the driver 9 so as to stop the supply of the driving pulse to the pulse motor 5, so that a driving of the pulse motor 5 and a sucking of the syringe 3 are ceased. Moreover, since the supply of the driving pulse from the driver 9 to the pulse motor 5 is stopped, the count value of the counter 10 is not same as the stored value of the memory 16 so that the signal is supplied to the alarm unit 17 to raise an alarm.

In the embodiment shown in FIG. 3, it is possible to stop the aspirating operation of the syringe 3 before the liquid level of the sample solution becomes a threshold level at which point the aspiration could not be effected and then an alarm is produced by the alarm unit 17. Moreover, the distributing device illustrated in FIG. 3 is formed by modifying the embodiment shown in FIG. 1. It is possible to apply such a modification to the embodiment shown in FIG. 2. Furthermore, in the embodiment shown in FIG. 3, it is necessary to set up the photometric position defined by the optical axis OP at such a position that an amount of the sample solution between the tip position of the probe and the photometric position does not exceed a total amount of sample solution to be sucked by the syringe 3.

By the distributing device according to the invention, it is possible to prevent an erroneous measurement due to inaccurate delivery of the liquid such as the sample, reagent and diluent even if the amount of the liquid is smaller than necessary.

The present invention is not limited to the embodiments mentioned above, but many modifications may be conceived within the scope of the invention. For example, in the embodiments mentioned above, a detection of the sample shortage is carried out by comparing the count value of the pulses with the predetermined value, but it is possible to compare them in an analogue manner. For instance, an amount of electric charge stored in a capacitor during the aspiration time may be compared with a predetermined voltage.