Patent Publication Number: US-2021181222-A1

Title: Autosampler

Description:
TECHNICAL FIELD 
     The present invention relates to an autosampler for a liquid chromatograph. 
     BACKGROUND OF THE INVENTION 
     Typically, an autosampler for a liquid chromatograph is configured such that a sample rack holding at least one vial containing a sample is placed in a predetermined position in a casing. In an autosampler, a needle for sucking and discharging a liquid from the tip of the needle is provided so as to be movable in a horizontal plane direction and in a vertical direction above a sample rack set in the casing. A sample is collected through the needle from a desired vial, and the collected sample is injected into an analysis flow path of a liquid chromatograph (see Patent Document 1). 
     When manufacturing, inspecting, or installing of an auto-sampler, or replacing a needle, it is necessary to perform the position calibration (so-called “teaching”) to bring the needle to the desired position. The teaching is to make the apparatus remember the drive pulse number of the needle moving motor required for the tip of the needle to reach from the reference position (home position) to the predetermined position. 
     PRIOR ART DOCUMENT 
     Patent Document 
     Patent Document 1: WO2017/037770 A1 
     Patent Document 2: WO2014/162921 A1 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     In typical teaching, the lowering position of the needle is shifted by minute intervals in the vicinity of a specified position, and the position (the number of drive pulses) of the needle when it is visually confirmed that the tip of the needle has reached the specified position is stored in the device. 
     However, according to the method in which the lowering position of the needle is shifted by minute intervals, there is a problem that teaching is time-consuming and money-consuming. In particular, in cases where the operator visually determines whether or not the tip of the needle has reached the predetermined position, there is a difference in the accuracy of the teaching for each worker. 
     The present invention aims to eliminate the need for a visual teaching operation by an operator. 
     Means for Solving the Problem 
     The auto-sampler according to the present invention includes: 
     a vial arrangement portion configured to arrange a plurality of vials thereon; 
     a needle assembly including a needle holding portion for holding a needle with a tip of the needle facing vertically downward, the needle being configured to insert the tip into a vial arranged on the vial arrangement portion from above to suck a sample in the vial from the tip, the needle assembly being configured to move the needle holding portion in a vertical direction and a horizontal plane direction to move the needle in the horizontal plane direction and the vertical direction; 
     an imaging portion configured to be movable in the horizontal plane direction and the vertical direction in a state in which a positional relationship with the needle is maintained, the imaging portion being configured to image the tip of the needle from a position obliquely above the tip of the needle so that the tip of the needle, a top surface of a vial directly below the tip, and a top surface of a nearby vial are within a visual field of the imaging portion; 
     a correlation storing portion configured to store a correlation between a position and a size of the top surface of the vial within a visual field image of the imaging portion and a distance between the imaging portion and the vial; 
     a distance measuring portion configured to measure a distance between the tip of the needle and a target position above a target vial which is a vial that the tip of the needle is to be reached, in a state in which a top surface of the target vial is within the visual field image of the imaging portion together with the tip of the needle, based on a position and a size of the top surface of the target vial within the visual field image, a positional relationship between the tip of the needle and the target position above the target vial within the visual field image, and the correlation stored in the correlation storing portion; and 
     a needle moving portion configured to control the moving mechanism to make the tip of the needle reach the target position, based on the distance measured by the distance measuring portion. 
     In the present invention, an imaging portion is provided. The imaging portion is configured to be movable in a horizontal plane direction and a vertical direction while maintaining a positional relationship with the needle. The imaging portion is configured to image the tip of the needle from a position obliquely above the tip of the needle so that the tip of the needle, a top surface of a vial directly below the tip, and a top surface of a nearby vial are within a visual field of the imaging portion. And, the distance between the tip of the needle and the target position is measured utilizing the visual field image of the imaging portion. Based on the calculated distance, the tip of the needle is made to reach the target position. Thus, it is possible to position the tip of the needle at the desired position without performing a visual teaching operation by the operator. 
     In Patent Document 2 (WO2014/162921 A1), it is disclosed to perform calibration of a needle drive by utilizing an image acquired by an imaging apparatus such as a CCD camera. In the invention disclosed in Patent Document 2, the needle is brought close to the target position while looking at the image acquired by the imaging apparatus. Then, calibration is performed using the position coordinate of the needle when it is recognized that the needle has reached the target position on the captured image. On the other hand, in the present invention, the distance between the needle and the target vial is calculated by the position and/or the size of the top surface of the target vial within the visual field image of the imaging portion, and the needle assembly is driven based on the calculated distance. In this respect, the present invention is different from Patent Document 2. 
     In the present invention, it is possible to automatically perform teaching using the visual field image of the imaging portion. In other words, the target vial may be a vial arranged at a predetermined position of the vial arrangement portion at the time of the teaching mode performed based on the user input. In this case, the distance measuring portion is configured to measure, during the teaching mode, the distance between the tip of the needle and the target position. The needle moving portion is configured to control the moving mechanism based on the distance measured by the distance measuring portion until the moving mechanism makes the tip of the needle reach the target position during the teaching mode. A teaching information storage portion is further provided. The teaching information storage portion is configured to store, as teaching information, the drive amount of the needle assembly for making the needle reach the target position from the preset reference position during the teaching mode. 
     It is preferable that the auto-sample further include a vial determination portion. The vial determination portion is configured to determine whether or not a sample vial is present directly below the needle based on the visual field image of the imaging portion when the needle has been moved to the target position. With this configuration, it is possible to determine whether or not a vial is arranged at the target position by using the visual field image of the imaging portion. 
     Further, the auto-sampler may be provided with a normal image storage portion configured to store, as a needle normal image, the visual field image of the imaging portion when the needle is in a normal condition, and a needle determination portion configured to determine whether or not the needle is normal by comparing the visual field image of the imaging portion with the needle normal image stored in the normal image storage portion. With this configuration, it becomes possible to detect abnormalities, such as, e.g., misalignment and/or bending of the needle, based on the visual field image of the imaging portion. 
     Effects of the Invention 
     In the auto-sampler according to the present invention, an imaging portion is provided. The imaging portion is configured to be movable in a horizontal plane direction and in a vertical direction while maintaining a positional relationship with the needle. The imaging portion is configured to image the tip of the needle from a position obliquely above the tip of the needle so that the tip of the needle, a top surface of a vial directly below the tip, and a top surface of a nearby vial are within a visual field of the imaging portion. And, it is configured such that the distance between the tip of the needle and the target position is measured utilizing the visual field image of the imaging portion and the tip of the needle is made to reach the target position based on the calculated distance. Thus, it is possible to position the tip of the needle at the desired position without performing a visual teaching operation by the operator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram schematically showing an example of an autosampler. 
         FIG. 2  is an example of a visual field image of an imaging portion of the example. 
         FIG. 3  is a flowchart showing an example of a needle positioning operation of the example. 
         FIG. 4  is a block diagram schematically showing another example of an autosampler. 
         FIG. 5  is a flowchart showing an example of an operation during the teaching mode of the example. 
     
    
    
     EMBODIMENTS FOR CARRYING OUT THE INVENTION 
     Hereinafter, a preferable embodiment of an autosampler according to the present invention will be described with reference to the drawings. 
     An example of an autosampler will be described with reference to  FIG. 1 . 
     The autosampler of this example is provided with a vial arrangement portion  2  for arranging vials  6  each containing a sample, a needle assembly  8  having a needle  12  for sucking a sample from a desired vial  6 , and a controller  20  for controlling the operation of the needle assembly  8 . 
     A sample rack  4  for holding a plurality of vials  6  arranged in a matrix is placed at a predetermined position on the vial arrangement portion  2 . The needle assembly  8  is configured to be movable in two directions (the left-right direction and a direction perpendicular to the paper plane in the drawing) perpendicular to each other in the horizontal plane above the vial arrangement portion  2 . The needle assembly  8  has a needle holding portion  14  for holding the needle  12  and is configured to move the needle holding portion  14  in the vertical direction. The needle  12  is fixed to the needle holding portion  14  with the tip of the needle  12  facing vertically downward. 
     An imaging portion  18  is fixed to the needle holding portion  14  of the needle assembly  8  via an arm  16 . The imaging portion  18  moves in the horizontal plane direction and the vertical direction with the needle  12 . The imaging portion  18  is, for example, a CCD camera. The imaging portion  18  is provided to image the tip of the needle  12  with the tip of the needle  12  from a position obliquely above the tip of the needle  12  so that the top surface of the vial  6  directly below the tip of the needle  12  and the top surface of a nearby vial  6  fall within the visual field image of view together. 
     The controller  20  is realized by a computer circuit provided in the autosampler or a dedicated or general-purpose computer connected to the auto-sampler. The controller  20  is provided with a distance measuring portion  22 , a needle moving portion  24 , a correlation storing portion  26 , a vial determination portion  28 , a needle determination portion  30 , and a normal image storage portion  32 . The distance measuring portion  22 , the needle moving portion  24 , the vial determination portion  28 , and the needle determination portion  30  are functions obtained by executing programs by arithmetic elements such as a microcomputer provided in the controller  20 . The correlation storing portion  26  and the normal image storage portion  32  are functions realized by a part of the storage area of the storage device provided in the controller  20 . 
     The distance measuring portion  22  is configured to measure the distance between the vial  6  (hereinafter referred to as “target vial  6 ”) to which the needle  12  is to be accessed and the tip of the needle  12  based on the visual field image of the imaging portion  18 . 
     The controller  20  can grasp the approximate position of the target vial  6  and also can move the tip of the needle  12  to the position above the target vial  6 . When the tip of the needle  12  is arranged above the target vial  6 , as shown in  FIG. 2 , the top surface of the target vial  6  is imaged by the imaging portion  18  together with the tip of the needle  12 . From the position and the size of the top surface (septum portion) of the target vial  6  within the visual field image of the imaging portion  18 , the distance in the height direction between the imaging portion  18  and the top surface of the target vial  6  can be obtained. The correlation between the position and the size of the top surface of the vial  6  within the visual field image of the imaging portion  18  and the distance in the height direction between the imaging portion  18  (or the tip of the needle  12 ) and the top surface of the target vial  6  has been obtained in advance and held by the correlation storing portion  26 . Further, it is possible to determine the distance between the tip of the needle  12  and the center of the top surface of the target vial  6  within the visual field image of the imaging portion  18  from the relative positional relationship between the tip of the needle  12  and the center of the top surface of the target vial  6 . 
     The distance measuring portion  22  is configured to measure the distance between the tip of the needle  12  and the center of the top surface of the target vial  6  in the horizontal plane direction and the vertical direction, based on: the position and the size of the top surface of the target vial  6  within the visual field image captured by the imaging portion  18  when the tip of the needle  12  has moved to the position above the target vial  6 ; and the relative positional relationship between the tip of the needle  12  and the center of the top surface of the target vial  6 . 
     The needle moving portion  24  is configured to perform the drive control of the needle assembly  8  based on the distance measured by the distance measuring portion  22  such that the needle  12  approaches the target position. 
     The vial determination portion  28  is configured to determine the presence or absence of the target vial  6  depending on whether or not the target vial  6  is present within the visual field image of imaging portion  18  when, for example, the needle  12  has been moved to the position where the target vial  6  is arranged. The vial determination portion  28  may be configured to emit a warning when no target vial  6  to be placed is present within the visual field image of the imaging portion  18 . The warning may be performed by displaying an image or by emitting a sound. Note that the vial determination portion  28  is not an essential component. 
     The needle determination portion  30  is configured to determine whether or not there is an abnormality in the needle  12  by comparing the needle  12  within the visual field image of the imaging portion  18  with the needle within the visual field image of the imaging portion  18  when the needle  12  is normal (hereinafter referred to as “normal image”). The normal image captured in advance is stored in the normal image storage portion  32 . When the state of the needle  12  within the visual field image of the imaging portion  18  does not coincide with the state of the needle  12  within the normal image, the needle determination portion  30  determines that the needle  12  is abnormal. The determination of whether or not the needle  12  is abnormal can be made, for example, by determining whether or not the difference (the number of pixels) in the position of the tip of the needle  12  is within a preset tolerance. When there is an abnormality in the needle  12 , the needle determination portion  30  may be configured to emit a warning. The warning may be performed by displaying an image or by emitting a sound. Note that the needle determination portion  30  is not an essential element. 
     Next, an exemplary positioning operation of the tip of the needle  12  will be described with reference to the flowchart of  FIG. 3  together with  FIG. 1  and  FIG. 2 . 
     First, the needle  12  is moved to the approximate position above the target vial  6  (Step S 1 ). At this time, as shown in  FIG. 2 , the top surface of the target vial  6  is within the visual field image of the imaging portion  18  together with the tip of the needle  12 . The distance measuring portion  22  detects the position of the tip  12   a  of the needle  12  within the visual field image of the imaging portion  18  (Step S 2 ) and then detects the position of the center  6   a  of the top surface of the target vial  6  (Step S 3 ). Then, the distance measuring portion  22  obtains the distance between the tip  12   a  of the needle  12  and the center  6   a  of the top surface of the target vial  6  from the position and the size (area value) of the top surface of the target vial  6  of the imaging portion  18  and the relative positional relationship between the tip  12   a  of the needle  12  and the center  6   a  of the top surface of the target vial  6  within the visual field image (Step S 4 ). 
     When the distance between the tip  12   a  of the needle  12  and the center  6   a  of the top surface of the target vial  6  is measured by the distance measuring portion  22 , the needle moving portion  24  drives the needle assembly  8  based on the distance measured by the distance measuring portion  22  so as to bring the tip of the needle  12  closer to the target position set directly above the target vial  6  (e.g., 2 mm directly above the center  6   a ) (Step S 5 ). After driving the needle assembly  8 , it is determined whether or not the tip  12   a  of the needle  12  has reached the target position based on the visual field image of the imaging portion  18  (Step S 6 ). When the tip  12   a  of the needle  12  has reached the target position, the positioning of the needle  12  is completed. 
     On the other hand, when the tip  12   a  of the needle  12  has not reached the target position, a series of operations of the detection of the center  6   a  of the top surface of the target vial  6  within the visual field image of the imaging portion  18  by the distance measuring portion  22  (Step S 3 ), the measurement of the distance between the tip  12   a  of the needle  12  and the center  6   a  of the top surface of the target vial  6  by the distance measuring portion  22  (Step S 4 ), and the driving of the needle assembly  8  by the needle moving portion  24  (Step S 5 ) are performed until the tip  12   a  of the needle  12  reaches the target position (Step S 6 ). 
     In the above example, the embodiment is described in which the direct positioning of the needle  12  with respect to the target vial  6  is performed using the visual field image of the imaging portion  18 . However, the present invention is not limited to this. The functions of the distance measuring portion  22  and the needle moving portion  24  may be used for the position calibration (teaching) of the needle  12 . By acquiring the drive amount of the needle assembly  8  required to reach the predetermined teaching position on the vial arrangement portion  2  from the reference position of the needle  12  and storing it in the apparatus, it is possible to correctly make the needle  12  access the desired vial  6  by using the relative positional relationship between the teaching position and the position where each vial  6  is arranged. 
     An example of the autosampler that executes teaching using the visual field image of the imaging portion  18  will be described with reference to  FIG. 4 . 
     The example of  FIG. 4  has the same basic configuration as that of the example described with reference to  FIG. 1 . The controller  20 ′ in this example is provided with a teaching information storage portion  34  in addition to the function of the controller  20  of the example of  FIG. 1 . The distance measuring portion  22  and the needle moving portion  24  of the controller  20 ′ are functions that are enabled during the teaching mode executed based on the user input. The teaching information storage portion  34  is configured to store, as teaching information, the drive amount of the needle assembly  8  required to make the tip of the needle  12  reach the target position on the target vial  6  arranged at a predetermined teaching position using the functions of the distance measuring portion  22  and the needle moving portion  24 . The teaching information storage portion  34  is a function realized by a part of the storage area of the storage device provided in the controller  20 ′. 
     The operation during the teaching performed in the autosampler of this example will be described with reference to the flowchart of  FIG. 5 . 
     First, the user arranges a vial  6  at a predetermined teaching position (Step S 11 ). In the teaching mode, the vial  6  arranged at the teaching position is a target vial. The needle  12  is moved from the home position to the teaching position (approximate position above the target vial  6 ) (Step S 12 ). 
     The distance measuring portion  22  detects the position of the tip  12   a  of the needle  12  within the visual field image of the imaging portion  18  (Step S 13 ) and then detects the position of the center  6   a  of the top surface of the target vial  6  (Step S 14 ). The distance measuring portion  22  determines the distance between the tip  12   a  of the needle  12  and the center  6   a  of the top surface of the target vial  6  from the position and the size (area value) of the top surface of the target vial  6  within the visual field image of the imaging portion  18 , and the relative positional relationship between the tip  12   a  of the needle  12  and the center  6   a  of the top surface of the target vial  6  within the visual field image of the imaging portion (Step S 15 ). 
     When the distance between the tip  12   a  of the needle  12  and the center  6   a  of the top surface of the target vial  6  is measured by the distance measuring portion  22 , the needle moving portion  24  drives the needle assembly  8  by the distance measuring portion  22  based on the distance measured to bring the tip of the needle  12  closer to the target position set directly above the target vial  6  (Step S 16 ). After the needle assembly  8  is driven, it is determined whether or not the tip  12   a  of the needle  12  has reached the target position based on the visual field image of the imaging portion  18  (Step S 17 ). When the tip  12   a  of the needle  12  has reached the target position, the drive amount of the needle assembly  8  required to make the needle  12  reach the target position from the home position is stored in the teaching information storage portion  34  as the teaching information (Step S 18 ). 
     On the other hand, when the tip  12   a  of the needle  12  has not reached the target position, the operations of the above-described Steps S 14  to S 16  are repeated. In cases where a plurality of teaching positions are set, the above operations are repeated in each teaching position (Step S 19 ). 
     The controller  20 ′ has a function of positioning the needle  12  to a desired vial  6  in normal operation by using the teaching information acquired by the above operations. 
     As described above, the autosampler provided with the imaging portion  18  can make the needle  12  access the desired vial  6  without the need for a visual teaching operation. 
     DESCRIPTION OF SYMBOLS 
     
         
           2 : Vial arrangement portion 
           4 : Sample rack 
           6 : Vial
         6   a : Center of a top surface of a vial     
           8 : Needle assembly 
           12 : Needle
         12   a : Needle tip     
           14 : Needle holding portion 
           16 : Arm 
           18 : Imaging portion 
           20 ,  20 ′: Controller 
           22 : Distance measuring portion 
           24 : Needle moving portion 
           26 : Correlation storing portion 
           28 ; Vial determination portion 
           30 : Needle determination portion 
           32 : Normal image storage portion 
           34 : Teaching information storage portion