Syringe pump, seal piece, and automatic analyzer equipped therewith

Abstract

To provide a syringe pump which reduces wear of a seal piece and lowers maintenance frequency by using a sliding material having both high wear resistance and sealing performance for the seal piece used in the syringe pump, a seal piece used therein, and an automatic analyzer using the same.SOLUTION: A syringe pump comprises a syringe tube that contains a liquid, a plunger that moves in a longitudinal direction of the syringe tube to discharge the liquid contained in the syringe tube, and a seal piece that is positioned between the plunger and the syringe tube, and slides against the plunger as the plunger moves. The seal piece is made of polyethylene having a weight-average molecular weight of 130×104 g / mol or more and a density of 0.93 g / cm3 or less. There are also provided a seal piece used in the syringe pump and an automatic analyzer equipped therewith.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a syringe pump for transferring a predetermined amount of liquid, and in particular to a syringe pump suitable for use in an automatic analyzer that performs qualitative and quantitative analysis of biological samples such as blood and urine, a seal piece used in the syringe pump, and an automatic analyzer equipped with the same. [Background technology]

[0002] The syringe pump of this invention can be applied to various devices that have the function of transporting liquids, but the following describes an example in which it is applied to an automatic analyzer. In an automatic analyzer, a biological sample such as serum or urine is reacted with a reagent to analyze its components, and the resulting changes in color and turbidity are optically measured using a photometric unit such as a spectrophotometer.

[0003] To cause a reaction between a sample and a reagent, they must be dispensed from the containers in which they are stored to the reaction containers. For this reason, automated analyzers are equipped with a dispenser that draws in and dispenses liquids such as sample or reagent from the containers in which they are stored to the reaction containers.

[0004] Various pumps can be used to generate pressure changes for the aspirating and dispensing of liquids in dispensing devices, but the "syringe pump," which generates pressure changes by inserting and removing a rod-shaped component called a plunger inside a syringe, is the most commonly used due to its response speed and accuracy. In a syringe pump, the plunger slides inside the syringe while maintaining watertightness. In particular, the sealing components that slide directly against the plunger are limited-life items (consumables), and the maintenance cycle of the plunger pump is affected by the lifespan of these sealing components.

[0005] Seals are generally made of soft materials such as resin, and seal the liquid in the syringe while experiencing sliding resistance during plunger movement. Wear and tear on the seals can lead to liquid leakage from the syringe or changes in the dispensed volume due to pressure loss, potentially resulting in inaccurate analytical results. Therefore, the wear resistance of seals is an important factor that not only affects the maintenance cycle but also the analytical accuracy. Patent Document 1 discloses a syringe that includes a cylinder for filling a drug solution and a seal member that contacts the inner surface of the cylinder and is slidable within the cylinder. The seal member has a base and an ultra-high molecular weight polyethylene film bonded to the base. The ultra-high molecular weight polyethylene film has an ultra-high molecular weight polyethylene layer and an adhesive film layer, and is bonded to the base via the adhesive film layer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-73246 Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, the processing power of automated analyzers has improved, and as the devices have become faster, they are sometimes operated continuously, resulting in longer operating times.As mentioned above, the seal parts that make up the syringe pumps in liquid dispensing units need to be replaced due to wear, which increases the frequency of replacement due to deterioration of the seal parts, and increases the maintenance burden.In order to reduce the maintenance burden, extending the lifespan of seal parts has become an issue.

[0008] Among the sealing components is a part called a seal piece that seals the liquid inside the syringe pump. To ensure performance and stable operation, seal pieces generally need to be replaced every few months.

[0009] The seal piece comes into contact with the moving plunger during dispensing, and is subjected to repeated sliding loads from the plunger during dispensing, resulting in wear. Since a seal is required to prevent leakage of the liquid inside the syringe, the seal piece must have high wear resistance and flexibility to achieve sufficient sealing performance. The rubber molded product disclosed in Patent Document 1 has enhanced wear resistance by including an ultra-high molecular weight polyethylene layer with wear resistance. However, the syringe described in Patent Document 1 is a syringe for injectors, and unlike syringe pumps in automatic analyzers that operate the plunger at high speed using a motor, the material of the ultra-high molecular weight polyethylene layer has not been considered from the perspective of wear resistance (durability).

[0010] An object of the present invention is to provide a syringe pump in which wear of the seal piece used in the syringe pump is reduced by using a sliding material that combines high wear resistance and sealing properties, thereby reducing the frequency of maintenance, a seal piece used therein, and an automatic analyzer using the same. [Means for solving the problem]

[0011] The present invention has the following configuration to achieve the above object. The syringe includes a syringe tube containing a liquid, a plunger that moves in the longitudinal direction of the syringe tube to push out the liquid contained in the syringe tube, and a seal piece that is positioned between the plunger and the syringe tube and slides against the plunger when the plunger moves. The seal piece is a polymer having a weight average molecular weight of 130×10 4 g / mol or more and a density of 0.93 g / cm 3 A syringe pump made of polyethylene, a seal piece used in the syringe pump, and an automatic analyzer equipped with the seal piece. [Effects of the Invention]

[0012] According to the present invention, by using a sliding material that combines high wear resistance and sealing properties for the seal pieces used in a syringe pump, it is possible to provide an automatic analyzer that reduces wear on the seal pieces and reduces the frequency of maintenance. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of an automatic analyzer according to an embodiment of the present invention. [Figure 2] FIG. 1 is an external view showing an example of a syringe pump to which the present embodiment is applied. [Figure 3] 2 is a cross-sectional view of the syringe pump shown in FIG. 1 taken along the central axis of the plunger. [Figure 4] FIG. 4 is a graph showing the relationship between the wear resistance and sealing performance with respect to the weight average molecular weight (polyethylene equivalent) of the seal piece in this embodiment. [Figure 5] FIG. 4 is a diagram showing the relationship between the density of the seal piece and the wear resistance and sealing performance in this embodiment. [Figure 6] FIG. 10 is a graph showing the relationship between the wear resistance and sealing performance with respect to the crystallinity index in this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the automatic analyzer, syringe pump, and sliding member of the present invention will be described in detail with reference to the drawings. In the drawings used in this specification, identical or corresponding components are designated by the same or similar reference numerals, and repeated description of these components may be omitted. [Example]

[0015] [Automatic analyzer] First, a schematic diagram of an automatic analyzer according to an embodiment of the present invention is shown in Fig. 1. In Fig. 1, the automatic analyzer 100 includes a sample disk (specimen disk) 102 capable of mounting a plurality of blood collection tubes (specimen containers) 101 for holding samples, a first reagent disk 104 and a second reagent disk 105 capable of mounting a plurality of reagent containers 103 for holding reagents, and a reaction disk 107 having a plurality of reaction containers 106 arranged on its periphery.

[0016] The automatic analyzer also includes a probe (sample probe) 108 that dispenses a sample aspirated from a blood collection tube 101 into a reaction container 106, a first reagent probe 109 that dispenses a reagent aspirated from a reagent container 103 in a first reagent disk 104 into the reaction container 106, and a second reagent probe 110 that dispenses a reagent aspirated from a reagent container 103 in a second reagent disk 105 into the reaction container 106.

[0017] Furthermore, the automatic analyzer includes an agitator 111 that agitates the liquid in the reaction vessel 106, a vessel cleaning mechanism 112 that cleans the reaction vessel 106, a light source 113 installed near the inner circumference of the reaction disk 107, a spectroscopic detector 114, a computer 115 connected to the spectroscopic detector 114, and a controller 116 that controls the operation of the entire automatic analyzer and exchanges data with the outside.

[0018] The sample probes 108 are connected to the corresponding syringe pumps 117 through dispensing channels. Although not shown in Fig. 1, syringe pumps corresponding to the sample probe 108, first reagent probe 109, and second reagent probe 110 are connected to the automated analyzer 100 through channels.

[0019] [Syringe pump] Figure 2 shows an external view of the syringe pump of this embodiment, and Figure 3 shows an axial cross-sectional view of the central axis of the plunger. A syringe pump 117 in an automated analyzer includes a syringe tube 9 capable of storing liquid therein, a plunger 8 that can move up and down in the longitudinal direction of the syringe tube 9, an upper plunger retaining part 5 that contacts the plunger 8, a power transmission part 4 that transmits power to the plunger 8 via the upper plunger retaining part, and a lower plunger retaining part 6 that contacts the power transmission part 4. As the plunger 8 moves up and down within the syringe tube 9, the internal volume of the syringe tube 9 changes, allowing the liquid to be sucked in and discharged.

[0020] As shown in FIG. 3, the power transmission unit 4, which transmits the rotational force from the motor 2, and the upper holding part 5 of the plunger 8, which transmits the force when the plunger 8 moves upward, are in point contact at a single point, a contact part 5a. Also, as shown in FIG. 3, the power transmission unit 4 and the lower holding part 6 of the plunger 8, which transmits the force when the plunger 8 moves downward, are in point contact at a single point, a contact part 6a. Furthermore, the contact part 5a and the contact part 6a are provided on the movement axis of the plunger 8. The upper holding part 5 of the plunger 8 and the lower holding part 6 of the plunger 8 are fixed via a connecting part 7.

[0021] A seal piece 10 is attached to the syringe pump 117 between the plunger 8 and the syringe tube 9 to prevent leakage of the internal liquid due to the operation of the plunger 8. When the plunger 8 operates, it slides against the seal piece 10. The seal piece wears as the plunger operates, and the operating speed (sliding speed) of the plunger affects the wear of the seal piece. A faster operating speed is desirable because it speeds up dispensing and increases the device throughput. However, it places strict conditions on the seal piece wear. For this reason, the operating speed must be appropriately controlled; it is generally between 0.01 m / s and 0.5 m / s, and a speed between 0.01 m / s and 0.3 m / s is preferable to prioritize wear suppression (maintenance).

[0022] On the other hand, the contact pressure between the plunger 8 and the seal piece 10 affects wear, so the contact pressure must also be appropriately controlled. Generally, excessive wear can be suppressed by keeping the pressure at 10 MPa or less, and more preferably at 7 MPa or less. Furthermore, the plunger 8 is generally made of a material such as stainless steel or ceramics to prevent deterioration due to the liquid being dispensed.

[0023] The seal piece 10 is generally made of a soft material such as resin. In particular, in the present invention, a weight average molecular weight (polyethylene equivalent) of 130×10 4 g / mol or more and a density of 0.93 g / cm 3By using polyethylene having the following properties, it is possible to achieve both wear resistance and sealing performance, and the timing for replacing the seal piece can be delayed.

[0024] The present invention will be specifically explained below by showing examples and comparative examples, but the present invention is not limited to the following examples.

[0025] [Evaluation of sliding materials for seal pieces in examples and comparative examples] The evaluation of the sliding materials in the examples and comparative examples is described below. The sliding materials of the present invention were polyethylenes with different molecular weights. The wear resistance, sealing performance, molecular weight, and crystallinity of the sliding materials in the examples and comparative examples were evaluated using the following procedures. The wear resistance of each sliding material was measured by a block-on-ring test. The block was the sliding material, and the ring was made of stainless steel and acted as the mating material, simulating the plunger. The sliding conditions were a sliding speed of 0.22 m / s, a load of 129 N, and a sliding time of 240 minutes. The wear amount was calculated using the dry weight of the sliding material before and after sliding, and then calculated as a volume from the wear weight and density (Equation 1). Furthermore, the wear amount was normalized by the sliding speed, load, and sliding time to calculate the specific wear amount, which was used as an index of wear resistance (Equation 2).

[0026] Wear amount (mm 3 ) = ((dry weight before sliding (mg) - dry weight after sliding (mg)) × density (mg / mm 3 )(Formula 1) Specific wear rate (mm 3 / N·m) = wear amount (mm 3 ) / load (N) / sliding speed (m / s) / sliding time (s) (Equation 2) The sealing performance was evaluated by measuring the hardness using a durometer. In the present invention, it is assumed that the lower the hardness, the higher the flexibility of the sliding material, which increases the adhesion with the plunger and improves the sealing performance, and the sealing performance was evaluated as the reciprocal of the hardness (Equation 3). The hardness was measured in accordance with JIS K 7215 using a Mitsutoyo rebound-type portable altimeter. The needle at the tip of the instrument was pressed into the sample, and the hardness was measured 15 seconds later.

[0027] Sealing ability = 1 / durometer hardness (Equation 3) The weight average molecular weight was evaluated by high temperature gel permeation chromatography. The equipment used was a GPC-IR type high temperature PGC (PolymerChar), the solvent was o-dichlorobenzene, and molecular weight calibration was performed in polyethylene equivalent. Note that for sliding materials that remained partially dissolved in the solvent, the molecular weight values ​​disclosed by the manufacturer were used, and an estimated value was calculated by correlating the manufacturer's disclosed values ​​with the measurement results.

[0028] The crystallinity was calculated based on the absorbance ratio of the CH2 peak in the Fourier transform infrared spectroscopy (FT-IR) spectrum. Specifically, CH2 contained in polyethylene is separated by crystallization. In the present invention, the ratio of the crystalline CH2 peak to the amorphous CH2 peak was calculated and used as the crystallinity index (Equation 4). Crystallinity index=1473cm -1 Peak intensity / 1463cm -1 Peak intensity (Eq. 4) The molecular weight evaluation results for Examples 1 to 5 and Comparative Examples 1 to 3 are shown in Table 1.

[0029] [Table 1]

[0030] As shown in Table 1, the weight-average molecular weight of the sliding materials used in Examples 1 to 5 was 1,580,000 to 3,420,000. On the other hand, the molecular weight of the sliding materials used in Comparative Examples was 180,000 to 1,240,000.

[0031] FIG. 4 shows the relationship between the weight average molecular weight and the sealability evaluated in the examples and comparative examples. As shown in Figure 4, it was confirmed that the specific wear rate tends to decrease with an increase in weight-average molecular weight, that is, the specific wear rate tends to improve. The approximate line for the results of the investigations of Examples 1 to 5 is shown by a dashed line. This approximate line and the specific wear rate of 8.0 x 10 required to prevent seal piece wear from becoming a rate-limiting component that increases the frequency of maintenance, that is, to prevent the frequency of maintenance from increasing due to the deterioration of other components, are -7 mm 3The molecular weight that satisfies / N·m was calculated.

[0032] As a result, it was determined that a polyethylene weight-average molecular weight of 1.3 million or more is a sliding material with sufficiently high wear resistance. It was also confirmed that sealing performance also tends to improve as the weight-average molecular weight increases. It is believed that the higher the sealing performance, the more likely it is to reduce the risk of liquid leakage, and it has been confirmed that, under the currently required dispensing liquid and dispensing conditions, a weight-average molecular weight of 0.015 or more will prevent liquid leakage. Therefore, by using polyethylene with a weight-average molecular weight of 1.3 million or more for the seal piece, it is believed that it will be possible to achieve both wear resistance that sufficiently reduces maintenance and sealing performance that prevents liquid leakage.

[0033] FIG. 5 shows the relationship between the specific wear rate and sealing performance with respect to density evaluated in the examples and comparative examples. As shown in Figures 5 and 6, we confirmed that both wear resistance and sealing performance tend to decrease as density increases. Density and crystallinity are correlated, and as density (crystallinity) increases, hardness increases, which has the effect of improving wear resistance, but crystallinity above a certain level is thought to make the material brittle and reduce wear resistance. On the other hand, as explained using Figure 4, molecular weight affects wear resistance.

[0034] This is thought to be because the longer the molecular chains and the more entangled they are, the less likely they are to fall off due to friction, resulting in higher wear resistance. On the other hand, the sealing performance is thought to decrease because the hardness increases with increasing density. As mentioned above, the required specific wear rate is 8.0 x 10 -7 mm 3 / N·m, and the required sealing performance is 0.015, so the density required to achieve both wear resistance and sealing performance is 0.93g / cm 3 The crystallinity index was 0.98.

[0035] Furthermore, durability tests were conducted using syringe pumps using sheath pieces made from the polyethylenes described in Examples 1 to 5 and Comparative Examples 1 to 3. As shown in Figures 4 and 5, it was confirmed that the polyethylenes described in the Examples did not wear even after long-term operation and could operate without leaking liquid, demonstrating high durability, compared to the seal pieces of the Comparative Examples. It was found that the use of the polyethylenes described in the Examples of the present invention contributed to reduced maintenance of syringe pumps and automatic analyzers due to the high wear resistance and sealing properties of the seal pieces.

[0036] From the above, in the present invention, the inventors have made extensive studies and have found that, while the molecular structure has a complex effect on wear resistance, the molecular weight and density are within the ranges of the present invention (weight average molecular weight of 1.3 million or more, density of 0.93 g / cm 3 By using a material with a high hardness (see below), it was possible to achieve high levels of both high wear resistance and high sealing performance (low hardness), and it was found that this range would enable the realization of reduced maintenance for syringe pumps and automatic analyzers.

[0037] On the other hand, in Example 6, the mating material was changed to ceramics and tested. In Example 6, the same sliding material as in Example 5 was used. Table 2 shows the wear resistance and sealing performance when the mating material was different. When the molecular weight and density of the ultra-high molecular weight polyethylene, which were evident in Examples 1 to 5 and Comparative Examples 1 to 3, were within the ranges, high wear resistance and high sealing performance were achieved, and it was found that the effects of the present invention could be obtained even when the mating material was changed.

[0038] [Table 2]

[0039] The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0040] <Additional Notes> The wear mode varies greatly depending on the combination of sliding materials, sliding speed, and surface pressure, and it is a technical field in which it is ultimately necessary to confirm the optimum combination conditions through experiments. The inventors conducted sliding experiments at sliding speeds and surface pressures expected when the sliding material is applied to a syringe pump of an automatic analyzer to find the optimum material composition for use in combination with hard materials such as stainless steel and ceramics. The materials suitable for a member that slides against a soft material at low speed and low surface pressure, such as the syringe syringe described in Patent Document 1, are naturally different from the materials suitable for a member that slides against a hard material at high speed and relatively high surface pressure, which is the subject of the present invention, and the optimum material is found through experiments. [Explanation of symbols]

[0041] 2: motor, 2a: motor rotating shaft, 3: rotation transmission part, 4: power transmission part, 4a: tip of power transmission part, 5: upper pressing part of plunger, 5a: contact part between upper pressing part of plunger and power transmission part, 6: lower pressing part of plunger, 6a: contact point between lower pressing part of plunger and power transmission part, 7: connecting part of plunger pressing part, 8: plunger, 8a: contact part between plunger and power transmission part, 9: syringe tube, 10: seal piece, 11: elastic body, 12: lowest pressing part, 13: Magnetic material, 100: automatic analyzer, 101: blood collection tube (sample container), 102: sample disk (specimen disk), 103: reagent container, 104: first reagent disk, 105: second reagent disk, 106: reaction container, 107: reaction disk, 108: dispensing probe (sample probe), 109: first reagent probe, 110: second reagent probe, 111: stirring device, 112: container cleaning mechanism, 113: light source, 114: spectroscopic detector, 115: computer, 116: controller, 117: syringe pump.

Claims

1. a syringe tube containing a liquid; a plunger that moves in the longitudinal direction of the syringe tube to push out the liquid contained in the syringe tube; a seal piece located between the plunger and the syringe tube, the seal piece sliding against the plunger when the plunger moves; The seal piece has a weight average molecular weight of 130×10 ４ g / mol or more and a density of 0.93 g / cm ３ A syringe pump characterized by being made of polyethylene, which is:

2. 2. The syringe pump according to claim 1, A syringe pump characterized in that the polyethylene has a durometer hardness of 67 or less.

3. 3. The syringe pump according to claim 2, The syringe pump is characterized in that the crystallinity index of the polyethylene determined from an FT-IR spectrum is 0.98 or less.

4. 2. The syringe pump according to claim 1, The syringe pump is characterized in that the plunger is made of either stainless steel or ceramics.

5. In an automatic analyzer equipped with a dispensing unit that aspirates and dispenses liquid, An automatic analyzer, wherein a syringe pump for delivering and sucking liquid to the dispensing unit is the syringe pump according to any one of claims 1 to 4.

6. A seal piece used in a syringe pump that delivers and aspirates liquid to a dispensing unit of an automatic analyzer equipped with the dispensing unit that aspirates and discharges liquid, characterized in that the seal piece is made of the polyethylene according to any one of claims 1 to 3.

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