Method for manufacturing molded articles and medical assemblies

Abstract

To prevent a groove formed on an outer peripheral surface of a protrusion from becoming an undercut.SOLUTION: A method for manufacturing a molding 30 provided with a protrusion 32 and grooves 34 having a depth of 30 μm or more and 70 μm or less formed on an outer peripheral surface of the protrusion includes steps of: moving a movable side mold 362 toward a stationary side mold 361 so that a mold cavity 363 is defined between the stationary side mold and the movable side mold; injecting a molten thermoplastic resin into the mold cavity; performing primary cooling so that the thermoplastic resin solidifies; moving the movable side mold away from the stationary side mold; performing secondary cooling for cooling the protrusion; and releasing the molding from the movable side mold.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a molded article having a groove, and a method for manufacturing a medical assembly. [Background technology]

[0002] Patent Document 1 discloses a blood pump including a pump housing and an impeller disposed inside the pump housing. The pump housing is a molded product made of a resin that is transparent to visible light wavelengths. The impeller is rotatably disposed within the pump housing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-213605 Summary of the Invention [Problem to be solved by the invention]

[0004] When manufacturing a blood pump, which is an example of a medical assembly, the pump housing of the blood pump can be manufactured by assembling multiple components. Furthermore, in this case, each component can be formed by injection molding. When forming a component with a groove, for example, a dynamic pressure groove for realizing a dynamic pressure bearing, the dynamic pressure groove may become undercut when the molded product is released from the mold. [Means for solving the problem]

[0005] A method for manufacturing a molded product according to one embodiment of the present invention is a method for manufacturing a molded product having a convex portion and a groove having a depth of 30 μm or more and 70 μm or less formed on the outer peripheral surface of the convex portion, in which the movable side mold is moved toward the fixed side mold so that a molding cavity is defined between the fixed side mold and the movable side mold, molten thermoplastic resin is injected into the molding cavity, primary cooling is performed so that the thermoplastic resin solidifies, the movable side mold is moved away from the fixed side mold, secondary cooling is performed to cool the convex portion, and the molded product is released from the movable side mold.

[0006] Furthermore, a method for manufacturing a medical assembly according to one aspect of the present invention includes manufacturing a molded product using the above-described manufacturing method, preparing a member to be mated with the molded product, heating a first mating portion of the member to expand it, mating the first mating portion with a second mating portion of the molded product, cooling the first mating portion, and welding the first mating portion and the second mating portion together.

[0007] This makes it possible to prevent the grooves formed on the outer peripheral surfaces of the convex portions from becoming undercuts. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic perspective view of a blood pump. [Figure 2] FIG. 2 is a schematic exploded perspective view of a pump housing. [Figure 3] 1 is a schematic plan view of a blood pump. [Figure 4] 1 is a schematic cross-sectional view of a blood pump according to a first embodiment. [Figure 5] Schematic cross-sectional view of an impeller. [Figure 6] Schematic cross-sectional view of a molded product. [Figure 7] FIG. 1 is an explanatory diagram of an injection mold in a closed state. [Figure 8] An explanatory diagram of secondary cooling. [Figure 9] FIG. [Figure 10] 1 is a flowchart showing a molding process. [Figure 11]FIG. 10 is a schematic cross-sectional view of a blood pump according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Exemplary embodiments for carrying out the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of components described in the following embodiments can be set arbitrarily and can be changed depending on the configuration of the device to which the present invention is applied or various conditions. Furthermore, unless otherwise specified, the scope of the present invention is not limited to the embodiments specifically described below. In this specification, when the inlet port side is defined as the upper direction, the opposite side corresponds to the lower direction.

[0010] [First embodiment] The blood pump 100 shown in FIG. 1 is an example of a medical assembly. It is a single-use centrifugal pump used in an extracorporeal circulation circuit and is driven by a drive unit (not shown). The medical assembly is an article constructed by assembling multiple components. Other examples of medical assemblies include an oxygenator, a heat exchanger, an arterial filter, and a blood reservoir. The following description will be given using the blood pump 100 as an example of a medical assembly.

[0011] As an example, an extracorporeal circulation circuit in which the blood pump 100 is used includes a flow sensor, a blood reservoir, an oxygenator, and the like. A blood removal circuit, a suction circuit, a negative pressure suction auxiliary circuit, and a fluid replacement filling circuit are connected upstream of the blood reservoir. A blood transfer circuit equipped with an arterial filter is connected downstream of the oxygenator. A gas supply circuit for supplying gas for oxygen exchange is connected to the oxygenator. The oxygenator and the blood reservoir are further connected by a blood collection circuit equipped with a stopcock. The blood transfer circuit is connected to the blood removal circuit via a recirculation circuit, but the recirculation circuit is closed during extracorporeal circulation. To start extracorporeal circulation, blood is injected into the blood reservoir, and the blood stored in the blood reservoir is introduced into the blood pump 100.

[0012] The blood pump 100 includes a pump housing 10 and an impeller 50 (FIG. 5) housed inside the pump housing 10. The pump housing 10 is configured by assembling a top case 20, which is an example of a first member, and a base case 30, which is an example of a second member. An inlet port 21 of the blood pump 100 is formed in the top case 20 and is connected to the downstream side of a blood reservoir. Furthermore, an outlet port 22 of the blood pump 100 is formed in the top case 20 and is connected to the upstream side of an oxygenator.

[0013] The top case 20 and the base case 30 are formed from a transparent thermoplastic resin, such as polycarbonate, which is transparent to the wavelength region of laser light. As an example, the absorptance of laser light in the near-infrared region of the transparent thermoplastic resin used in this embodiment is 60 percent or less. In addition, the absorptance of laser light in the near-infrared region of thermoplastic resins according to other examples is 40 percent or less, or 30 percent or less and 20 percent or more. Alternatively, the top case 20 located on the outside may be formed from a transparent thermoplastic resin, and at least the welded portion of the base case 30 located on the inside may be formed from an opaque thermoplastic resin.

[0014] The top case 20 shown in FIG. 2 has a substantially cylindrical internal space formed therein so as to be covered by the base case 30. The top case 20 has an annular thin-walled portion 24 (FIG. 4) as an example of a first fitting portion. The thin-walled portion 24 defines an opening 23 of the top case 20. The base case 30 also has a substantially cylindrical protrusion 32 formed to form a recess that opens downward. The protrusion 32 is inserted into the internal space of the base case 30. A central protrusion 33 is formed in the center of the top surface of the protrusion 32. Furthermore, a plurality of substantially spiral dynamic pressure grooves 34 that realize a dynamic pressure bearing are formed on the outer circumferential surface of the protrusion 32.

[0015] A substantially doughnut-shaped peripheral recess 35 is formed around the protrusion 32 so as to surround the protrusion 32. Furthermore, the base case 30 has a raised portion 36 as an example of a second fitting portion. The raised portion 36 protrudes from the peripheral recess 35 between the outer peripheral edge of the base case 30 and the peripheral recess 35. Furthermore, the raised portion 36 faces the thin-walled portion 24 after fitting. That is, the outer surface of the raised portion 36 faces the inner surface of the thin-walled portion 24 of the top case 20 when the top case 20 and the base case 30 are fitted together. In other words, the outer peripheral surface of the raised portion 36 in the radial direction of the base case 30 faces the inner peripheral surface of the thin-walled portion 24 of the top case 20 in the radial direction.

[0016] 3 is a schematic plan view of the blood pump 100 as viewed from the inlet port 21 side. As shown in FIG. 3, the base case 30 has a substantially circular outer shape when viewed from the inlet port 21 side. The inlet port 21 is formed to protrude from the top surface of the pump housing 10. The outlet port 22 is formed to protrude from the outer peripheral surface of the pump housing 10.

[0017] Fig. 4 is a schematic cross-sectional view showing a cross section taken along the dashed line IV-IV in Fig. 3 that passes through the center of the blood pump 100. For ease of explanation, the impeller 50 housed inside the pump housing 10 is shown by a dashed line in Fig. 4. Fig. 5 is a schematic cross-sectional view showing a cross section passing through the center of the impeller 50. The cross section shown in Fig. 5 corresponds to the cross section shown in Fig. 4, and the IV-IV cross section is a cross section passing through the center of the impeller 50.

[0018] As shown in FIG. 5 , a central recess 51 that opens downward is formed in the center of the lower part of the impeller 50. A donut-shaped sealed space 52 that is liquid-tightly sealed is formed outside the central recess 51. A plurality of magnetic elements 53 are housed inside the sealed space 52 at predetermined intervals in the circumferential direction. As an example, the plurality of magnetic elements 53 are housed inside the sealed space 52. The magnetic elements 53 are, for example, permanent magnets. Alternatively, the magnetic elements 53 may be formed of iron pieces, and the drive unit (described later) may have a permanent magnet or an electromagnet that has a magnetic force that attracts the iron pieces.

[0019] The impeller 50 has a plurality of blades (not shown) that push out blood. An inlet flow passage 54 through which blood flows is formed in the center of the impeller 50 along the rotation axis CL of the impeller 50. The plurality of blades are disposed in the space between a pair of end plates 55A and 55B that extend in a direction intersecting the rotation axis CL of the impeller 50, and extend in the radial direction of the impeller 50. A through-hole 56 communicating with the inlet flow passage 54 is formed in the center of the impeller 50 coaxially with the rotation axis CL. The through-hole 56 communicates with the inlet port 21 via the inlet flow passage 54. The inlet flow passage 54 communicates with a flow path 11 (FIG. 4) inside the pump housing 10 (described later) via a plurality of flow passages 57 formed in the space between the end plates 55A and 55B. A plurality of arc-shaped dynamic pressure grooves are formed in an impeller top surface 58 of the impeller 50. Furthermore, a plurality of dynamic pressure grooves curved in an arc shape are also formed in the impeller bottom surface 59 of the impeller 50. Furthermore, a plurality of dynamic pressure grooves curved in an arc shape are formed in the upper surface 51A of the central recess 51. These dynamic pressure grooves extend, for example, from the periphery of the impeller 50 toward the rotation axis CL of the impeller 50.

[0020] Inlet flow path 54 is formed coaxially with rotation axis CL of impeller 50. Blood flowing in from inlet port 21 is guided through inlet flow path 54 to flow path 57 between end plates 55A and 55B of impeller 50. A plurality of blades are provided to separate each flow path 57. As impeller 50 rotates about rotation axis CL, the blood guided to flow path 57 is transported to the outer periphery of impeller 50 by centrifugal force. The transported blood flows through flow path 11 along the inner circumferential surface of pump housing 10 and is successively discharged from outlet port 22.

[0021] As shown in FIG. 4, the base case 30 is disposed on the bottom side of the pump housing 10. The base case 30 and the top case 20 that covers the base case 30 are joined together in a liquid-tight manner. A donut-shaped flow path 11 is formed between the base case 30 and the top case 20 so as to surround the periphery of the impeller 50. The flow path 11 is connected to an outlet port 22. A central protrusion 33 that protrudes from the top surface of a protrusion 32 formed in the center of the base case 30 has a substantially conical shape.

[0022] The inlet port 21 is formed to extend coaxially with the rotation axis CL of the impeller 50. The inlet port 21 is connected to a tube (not shown) that forms part of the upstream flow path of the blood pump 100. The tip opening of the inlet port 21 functions as a blood suction port. The outlet port 22 is formed to extend in a direction approximately tangential to the rotation direction of the impeller 50. The outlet port 22 is connected to a tube (not shown) that forms part of the downstream flow path of the blood pump 100. The tip opening of the outlet port 22 functions as a blood discharge port.

[0023] The protrusion 32 is inserted into the central recess 51 of the impeller 50. An internal space is formed in the protrusion 32, forming a recess that opens downward. A drive section (not shown) of a drive unit is disposed in the internal space of the protrusion 32. The drive unit rotates the impeller 50 via a magnetic element 53. As an example, the drive unit has a motor. The drive section is attached to an output shaft connected to the motor and rotates together with the output shaft. The drive section also has the same number of drive magnetic elements as the magnetic elements 53 of the impeller 50, arranged at regular intervals in the circumferential direction. The orientations of the drive magnetic elements and the magnetic elements 53 are adjusted so that they are attracted to each other. As a result, the drive section attracts the magnetic elements 53 by magnetic force. When the motor is driven and the output shaft rotates, the drive section fixed to the output shaft rotates. When the drive section rotates, the impeller 50 rotates together with the magnetic elements 53.

[0024] The rotation axis CL of the impeller 50 is set coaxially with the output shaft of the motor. That is, the impeller 50 is disposed in the pump housing 10 so as to be rotatable about the rotation axis CL, with the rotation axis CL positioned coaxially with the output shaft of the motor. When the impeller 50 rotates, blood flows into the pump housing 10 through the inlet port 21. The blood that has flowed into the pump housing 10 flows into the introduction flow path 54 of the impeller 50. The blood that has flowed into the introduction flow path 54 is then forced into the flow path 11 by the rotating blades. The blood that has flowed into the flow path 11 is then sent from the flow path 11 to the outside of the blood pump 100 through the outlet port 22.

[0025] The thin-walled portion 24 of the top case 20 is thinner than other portions so as to form a step at the end of the top case 20 on the base case 30 side. When the base case 30 and the top case 20 are fitted together, the inner dimension of the thin-walled portion 24 approximately matches the outer dimension of the raised portion 36. The thickness of the raised portion 36 also approximately matches the width of the step in the radial direction of the top case 20. Furthermore, the height of the raised portion 36 in the direction along the rotation axis CL of the impeller 50 approximately matches the height of the step. This prevents a step from being formed at the boundary between the thin-walled portion 24 and the raised portion 36 on the inner surface of the pump housing 10 when the base case 30 and the top case 20 are fitted together.

[0026] [Dynamic bearing] A relatively narrow gap is formed between the inner surface of the pump housing 10 and the impeller top surface 58 of the impeller 50 to form a hydrodynamic bearing DB1 that rotatably supports the impeller 50. A relatively narrow gap is also formed between the inner surface of the pump housing 10 and the impeller bottom surface 59 of the impeller 50 to form a hydrodynamic bearing DB2 that rotatably supports the impeller 50. Hydrodynamic grooves are formed in the impeller bottom surface 59, and as the impeller 50 rotates, hydrodynamic pressure is generated, causing the impeller 50 to float from the hydrodynamic bearing DB2. Furthermore, a relatively narrow gap is formed between the outer peripheral surface of the protrusion 32 and the inner peripheral surface of the central recess 51 of the impeller 50 to form a hydrodynamic bearing DB3 that rotatably supports the impeller 50. Additionally, a relatively narrow gap is formed between the upper surface 51A of the central recess 51 and the protrusion top surface of the protrusion 32 to form a hydrodynamic bearing DB4 that rotatably supports the impeller 50. Through holes 56 in impeller 50 allow blood to move between flow path 57 between end plates 55A and 55B and hydrodynamic bearings DB2, DB3, and DB4.

[0027] When blood is introduced into the pump housing 10, some of the introduced blood flows into the dynamic pressure bearings DB1, DB2, DB3, and DB4. As a result, the blood introduced into the pump housing 10 flows into the gap between the pump housing 10 and the impeller 50. When the impeller 50 rotates with blood flowing in, the blood pressure in the dynamic pressure bearings DB1, DB2, DB3, and DB4 increases. This creates a support effect in the dynamic pressure bearings DB1, DB2, DB3, and DB4, rotatably supporting the impeller 50. In other words, the impeller 50 rotates without contacting the pump housing 10 due to the action of the liquid pressure (dynamic pressure) generated by the rotation of the impeller 50. The support provided by the dynamic pressure bearings DB1, DB2, and DB4 acts in the direction of the rotation axis of the impeller 50. In other words, the dynamic pressure bearings DB1, DB2, and DB4 function as a type of thrust bearing. Furthermore, the support provided by the dynamic pressure bearing DB3 acts in the radial direction of the impeller 50. In other words, the hydrodynamic bearing DB3 functions as a type of radial bearing.

[0028] As a modified example, the hydrodynamic grooves may be formed on the inner surface of the top case 20 facing the impeller top surface 58 of the impeller 50. Alternatively, the hydrodynamic grooves may be formed on the inner surface of the base case 30 facing the impeller bottom surface 59 of the impeller 50, or on the convex top surface of the convex portion 32 facing the upper surface 51A of the central recess 51. Furthermore, the hydrodynamic grooves may be formed on the inner circumferential surface of the central recess 51 of the impeller 50. A thrust bearing may also be realized by magnetic coupling between the drive unit and the impeller 50. For example, magnetic coupling is formed between the magnetic element 53 and the driving magnetic element to constrain the impeller 50 in the direction along the rotation axis CL. This allows the impeller 50 to be supported without contacting the pump housing 10. Alternatively, a thrust bearing may be realized by disposing a magnetic element that levitates the impeller 50 below the impeller 50.

[0029] [Assembly manufacturing method] First, the top case 20, the base case 30, and the impeller 50 are prepared. The top case 20 and the base case 30 are formed from a transparent thermoplastic resin. One example of the transparent thermoplastic resin is polycarbonate, and the top case 20 and the base case 30 can be formed by injection molding. Alternatively, the top case 20 may be formed by other methods such as cast molding and 3D printing. The impeller 50 can be formed by a known method.

[0030] Fig. 6 is a schematic cross-sectional view showing a cross section passing through the center of base case 30. As shown in Fig. 6, base case 30, which is an example of a molded product, has a substantially cylindrical protrusion 32 formed to form a recess that opens downward. A plurality of spiral dynamic pressure grooves 34, which are an example of a groove, are formed on the outer peripheral surface of protrusion 32. As shown in enlarged view B surrounded by a dashed line in Fig. 6, the depth DP of dynamic pressure groove 34 is 30 µm or more and 70 µm or less. In addition, a peripheral recess 35 is formed around protrusion 32 so as to surround protrusion 32.

[0031] Furthermore, a raised portion 36 protrudes from the peripheral recess 35 between the outer peripheral edge of the base case 30 and the peripheral recess 35. The height H of the raised portion 36, which corresponds to the depth of the peripheral recess 35, is set to a height that allows the base case 30 to be released from the mold even if it shrinks inward due to secondary cooling, which will be described later. Furthermore, the height H is set to a length that ensures an area for welding to the thin-walled portion 24. As an example, the height H is 1.1 mm or more and 1.3 mm or less. Furthermore, the inner side surface of the raised portion 36, which is the edge of the peripheral recess 35, is slightly inclined outward.

[0032] Here, when the base case 30 is molded using a conventional method, the hydrodynamic grooves 34 become undercut when the base case 30 is released from the movable mold. As a result, the hydrodynamic grooves 34 get caught in the mold during release. To address this issue, the movable mold can be configured to be separable or can be rotated to enable release. However, if the movable mold is configured to be separable, a parting line that overlaps with the hydrodynamic grooves 34 is created. Furthermore, if the movable mold is rotated, the hydrodynamic grooves 34 may be rubbed against the mold and scratched. Therefore, the parting line or scratch may interfere with the hydrodynamic bearing configuration, potentially causing problems such as eccentricity of the rotating impeller 50. Furthermore, if the movable mold is configured to be separable or if the movable mold is rotated, the cost of mold production increases.

[0033] Therefore, in this embodiment, the molded product is released from the mold by performing secondary cooling to cool the protrusions 32 as follows. That is, the protrusions 32 are contracted by secondary cooling, and the surfaces of the dynamic pressure grooves 34 are separated from the movable mold. As a result, the dynamic pressure grooves 34 do not become undercut, and the molded product can be released from the mold simply by moving it linearly away from the mold. Below, with reference to FIGS. 7 to 10, a molding method according to this embodiment will be described as a method for manufacturing a base case 30, which is an example of a molded product. Note that FIGS. 7 to 9 are explanatory diagrams illustrating the operation of a fixed mold 361 and a movable mold 362. Also, FIG. 10 is a flowchart showing the molding process.

[0034] [Molding process] Specifically, injection molding of the base case 30, which is an example of a molded product, is performed as follows using an injection mold 300 including a fixed mold 361 and a movable mold 362. The fixed mold 361 has a core 364 for forming the recesses in the protrusions 32. The fixed mold 361 also has a pin gate 366. In the example of FIG. 7, the fixed mold 361 has three pin gates, including a pin gate not shown. The movable mold 362 also has a stripper 365 for releasing the base case 30 from the movable mold 362.

[0035] First, as shown in FIG. 7, the movable mold 362 is moved toward the fixed mold 361 so that a molding cavity 363 is defined between the fixed mold 361 (cavity mold) and the movable mold 362 (core mold), and the injection molding die 300 is closed (S110 in FIG. 10). Next, molten thermoplastic resin is injected into the molding cavity 363 through the pin gate 366 (S111 in FIG. 10). As an example, the injection time is 2 seconds. Subsequently, primary cooling is performed so that the thermoplastic resin solidifies (S112 in FIG. 10). In the primary cooling, as an example, the mold temperature, which is the cooling temperature, is lowered to 75°C or higher and 90°C or lower to cool the base case 30. The cooling time is 25 seconds or higher and 30 seconds or lower.

[0036] Next, as shown in FIG. 8, the movable mold 362 is moved away from the fixed mold 361, and the injection mold 300 is opened (S113 in FIG. 10). When the injection mold 300 is opened, the runner 367 is cut off from the base case 30. Furthermore, before the secondary cooling, the core 364 is extracted from the protrusion 32 of the base case 30 (S114 in FIG. 10). That is, when the movable mold 362 is moved away from the fixed mold 361, the core 364 is extracted from the protrusion 32 of the base case 30. Then, with the core 364 extracted, secondary cooling is performed (S115 in FIG. 10). The base case 30, which is a molded product, is cooled and contracted by the secondary cooling process. The core 364 can be extracted simultaneously with, before, or after the movement of the movable mold 362.

[0037] In this way, the core 364 is extracted from the convex portion 32 before the secondary cooling. Therefore, the outer peripheral surface of the convex portion 32, which shrinks due to the secondary cooling, shrinks toward the center of the concave portion of the convex portion 32. In other words, the outer peripheral surface of the convex portion 32 is not obstructed by the core 364 and displaces inward toward the central axis of the base case 30. As a result, the dynamic pressure grooves 34 are displaced in a direction away from the movable-side mold 362. A gap is then formed between the dynamic pressure grooves 34 and the movable-side mold 362. This allows the base case 30 to be released from the movable-side mold 362 simply by moving the base case 30 in a direction away from the movable-side mold 362. Alternatively, if sufficient shrinkage of the convex portion 32 can be achieved, the core 364 may be extracted simultaneously with or after the secondary cooling.

[0038] The secondary cooling is intended to cause the protrusions 32 to shrink by cooling. Therefore, the cooling time for the secondary cooling is shorter than that for the primary cooling. For example, the cooling time for the secondary cooling is 6 seconds or more and 10 seconds or less. The cooling temperature for the secondary cooling is lower than that for the primary cooling. For example, the mold temperature, which is the cooling temperature for the secondary cooling, is 75°C or less. Furthermore, during the secondary cooling, a low-temperature fluid (for example, cooled gas) may be sprayed onto the protrusions 32. For example, the temperature of the low-temperature fluid at this time is 75°C or less.

[0039] Thereafter, as shown in FIG. 9, the base case 30 is released from the movable mold 362 (S116 in FIG. 10). Specifically, during release, the stripper 365 holding the base case 30 is moved away from the movable mold 362. That is, the stripper 365 lifts the shrunk base case 30 from the movable mold 362. This releases the base case 30. The top case 20 is also injection molded in the same manner, except for the secondary cooling step.

[0040] During injection molding of the base case 30, the base case 30 is formed so that the dynamic pressure grooves 34 have a predetermined depth, for example, a depth of 30 μm to 70 μm. By forming the dynamic pressure grooves 34 to a depth of 30 μm or more, it is possible to prevent the pressure between the inner circumferential surface of the central recess 51 of the impeller 50 and the outer circumferential surface of the protrusion 32 of the base case 30 from decreasing below a desired value. This prevents the impeller 50 from becoming eccentric during rotation, and prevents contact between the base case 30 and the impeller 50. Furthermore, by forming the dynamic pressure grooves 34 to a depth of 70 μm or less, it is possible to prevent hemolysis. Furthermore, since the dynamic pressure grooves 34 have a small depth, the dynamic pressure grooves 34 that have shrunk during secondary cooling can be separated from the movable mold 362.

[0041] As shown in FIG. 6 , the base case 30 has a raised portion 36 between the protrusion 32 and the outer peripheral edge. The height of the raised portion 36 is set to a level that allows the base case 30 to be released from the movable mold 362 even if it shrinks due to secondary cooling. Specifically, the height of the raised portion 36 is 1.1 mm or more and 1.3 mm or less. This reduces the contact area between the raised portion 36 displaced inward due to shrinkage and the movable mold 362 when the base case 30 shrinks. This prevents the raised portion 36 from becoming an undercut. Furthermore, the inner side surface of the raised portion 36, which is the edge of the peripheral recess 35, is slightly inclined outward. This further prevents the raised portion 36 from getting caught on the movable mold 362 during release.

[0042] [Assembly process] Before fitting the thin-walled portion 24 of the top case 20 and the raised portion 36 of the base case 30 together, the impeller 50 is placed so that it is accommodated within the space defined by the top case 20 and the base case 30. Specifically, after preparing the top case 20, the base case 30, and the impeller 50, the impeller 50 is placed on the base case 30 so that the protrusion 32 of the base case 30 is inserted into the central recess 51 of the impeller 50. Note that the placement of the impeller 50 may be performed after or simultaneously with the heating process of the thin-walled portion 24. For example, the impeller 50 may be placed inside the top case 20 in a heated and expanded state. In this case, the base case 30 is fitted into the held top case 20 so that the protrusion 32 of the base case 30 is inserted into the central recess 51 of the impeller 50.

[0043] Next, in the heating process, the thin-walled portion 24 of the top case 20 is heated to expand it. Before heating, the inner dimension of the thin-walled portion 24 is smaller than the outer dimension of the raised portion 36. That is, if the inner diameter of the thin-walled portion 24 in the radial direction of the top case 20 is defined as ID and the outer diameter of the raised portion 36 in the radial direction of the base case 30 is defined as OD, then the relationship OD > ID holds. Therefore, in the heating process, the thin-walled portion 24 is heated to expand it, thereby making the inner dimension of the thin-walled portion 24 larger than the outer dimension of the raised portion 36. Note that the outer dimension of the raised portion 36 is set to be smaller than the inner dimension of the thin-walled portion 24 that expands upon heating. In other words, the inner dimension of the thin-walled portion 24 is set to be larger than the outer dimension of the raised portion 36 when the size of the expansion upon heating is added.

[0044] Specifically, in the heating step, the thin-walled portion 24 is heated to expand. To this end, the top case 20 is placed in a high-temperature bath and heated for 15 to 30 minutes in an air atmosphere at 40°C to 60°C. The top case 20 is then removed from the high-temperature bath and fitted to the base case 30 in a held state in an air atmosphere at room temperature. Alternatively, the base case 30 may be fitted to the top case 20 in a held state. The thin-walled portion 24 may also be heated by bringing a heating device (e.g., a heater) into contact with the thin-walled portion 24 or by spraying a high-temperature fluid (e.g., heated gas) onto the thin-walled portion 24.

[0045] When fitting the thin-walled portion 24 and the raised portion 36 together, the lower end of the thin-walled portion 24 abuts against the base case 30. Specifically, the lower end of the thin-walled portion 24 abuts against the plane between the raised portion 36 and the periphery of the base case 30. This allows the thin-walled portion 24 to be positioned in the height direction. This prevents the welding positions of the thin-walled portion 24 and the raised portion 36 from becoming misaligned. In contrast, when fitting by press-fitting, the top case 20 and the base case 30 are fitted together with the thin-walled portion 24 abutting against the raised portion 36. This creates resistance during fitting, which may result in the top case 20 being fixed in an inclined position. Furthermore, the thin-walled portion 24 and the raised portion 36 may be deformed or damaged during press-fitting.

[0046] Next, in the cooling step, the thin-walled portions 24 are cooled. To do this, the top case 20 and the base case 30 are cooled in an air atmosphere at room temperature for 10 to 20 seconds. This causes the thin-walled portions 24 to shrink, fixing the thin-walled portions 24 and the protruding portions 36 together. Furthermore, the contracted thin-walled portions 24 press the protruding portions 36 inward, so that the thin-walled portions 24 and the protruding portions 36 come into tight contact with each other. Alternatively, the thin-walled portions 24 may be cooled by spraying a low-temperature fluid (e.g., a cooled gas) onto the thin-walled portions 24.

[0047] [Welding process] Next, in the welding process, the thin-walled portion 24 and the raised portion 36 are welded together. If the thin-walled portion 24 and the raised portion 36 are not in close contact at this time, the heat conduction efficiency of the heated thermoplastic resin will decrease, resulting in a decrease in bond strength. In this regard, with the assembled body fitted together as described above, the contracted thin-walled portion 24 presses the raised portion 36 inward. This allows the thin-walled portion 24 and the raised portion 36 to be in close contact, preventing a decrease in bond strength. Furthermore, bonding by welding is more suitable for medical assemblies than bonding using adhesives, which may be thermally altered or may have an adverse effect on the human body.

[0048] In the welding process, the thin portion 24 and the raised portion 36 are welded to each other by irradiating a laser onto the interface between the thin portion 24 and the raised portion 36. Alternatively, the top case 20 and the base case 30 may be welded to each other by a method other than laser welding, such as ultrasonic welding or high-frequency welding. In this case, at least one of the top case 20 and the base case 30 may be formed from an opaque thermoplastic resin. However, in medical assemblies, using a transparent resin has the advantage of allowing the interior of the assembly to be seen.

[0049] When laser welding is performed, the top case 20 and the base case 30 are formed from the same thermoplastic resin that transmits laser light. Alternatively, the top case 20 and the base case 30 may have different laser light transmittances. Then, a laser is irradiated from the outer surface side of the thin-walled portion 24 in the direction indicated by arrow D in FIG. 4 , which is perpendicular to the rotation axis CL of the impeller 50, with the focal point set at the interface between the thin-walled portion 24 and the raised portion 36. For example, the laser is a near-infrared laser, e.g., a laser with a wavelength in the range of 800 nm to 2500 nm, preferably a laser with a center wavelength of 1940 nm. Alternatively, the laser may be irradiated from an oblique direction intersecting the rotation axis CL, with the focal point set at the interface between the thin-walled portion 24 and the raised portion 36.

[0050] When the laser is applied, heat is generated on at least one of the inner circumferential surface of the thin portion 24 and the outer circumferential surface of the raised portion 36 at the interface between the top case 20 and the base case 30, causing the thermoplastic resin to melt. The heat is then conducted to the other of the inner circumferential surface of the thin portion 24 and the outer circumferential surface of the raised portion 36, causing the thermoplastic resin in the other to also melt. The melted thermoplastic resin then re-solidifies when the application is stopped and the heat generation subsides. This welds the inner circumferential surface of the thin portion 24 and the outer circumferential surface of the raised portion 36 together, resulting in a liquid-tight bond between the thin portion 24 and the raised portion 36. Alternatively, the laser may be applied to the interface between the top surface of the raised portion 36 and the surface of the top case 20 facing the top surface.

[0051] Then, while the laser is being irradiated, the blood pump 100 is rotated at a uniform speed around the rotation axis CL. This allows the laser to scan the outer periphery of the blood pump 100, welding the entire circumference of the blood pump 100. Alternatively, the laser emission part may move around the blood pump 100 to weld the entire circumference of the blood pump 100. The laser may be irradiated intermittently or continuously. However, continuous irradiation can prevent distortion of the shape of the welded portion. This more reliably joins the top case 20 and the base case 30 in a liquid-tight manner.

[0052] Furthermore, when irradiating with a laser, the laser is irradiated onto the interface between the thin-walled portion 24 and the raised portion 36 so as to avoid the space defined by the top case 20 and the base case 30. In other words, the laser may be irradiated so as to avoid the space in which the impeller 50 is housed. Specifically, in the example of FIG. 4 , the laser is irradiated at a height lower than the bottom of the peripheral recess 35. This prevents the impeller 50 from being irradiated with the laser that has passed through the top case 20 and the base case 30. However, if laser irradiation does not pose a problem, the laser may be irradiated onto the space defined by the top case 20 and the base case 30.

[0053] According to the method for manufacturing a molded product according to the first embodiment described above, it is possible to prevent the grooves 34 formed on the outer peripheral surface of the convex portions 32 from becoming undercut. That is, the convex portions 32 are contracted by secondary cooling, and the surfaces of the dynamic pressure grooves 34 can be separated from the movable mold 362. As a result, the dynamic pressure grooves 34 do not become undercut, and the molded product can be released from the mold simply by moving it linearly away from the mold.

[0054] Furthermore, the manufacturing method of the medical assembly described above allows for stable joining of the components constituting the medical assembly. Furthermore, since press-fitting is not required, design constraints on the components to be fitted together can be reduced. That is, one of the components to be fitted together is heated and expanded, and the two components are fitted together in the expanded state and then cooled. This allows the contracted one component to pressurize the other component, easily achieving a tight fit between the two components. Therefore, the two components can be stably welded together without press-fitting, and the welded portion can also provide a seal. Furthermore, while a press-fitting device is required for press-fitting, this is not necessary because the components can be fitted together simply by heating them.

[0055] [Second embodiment] The second embodiment will be described with reference to FIG. 11 . The second embodiment differs from the first embodiment in the positions at which the thin-walled portion 224 and the raised portion 236 are formed. Furthermore, in the second embodiment, the base case 230 is molded in the same manner as in the first embodiment, but the height of the raised portion 236 is greater than that of the first embodiment. Furthermore, the raised portion 236, which is an example of a first mating portion, and the thin-walled portion 224, which is an example of a second mating portion, both have an annular shape. However, the second embodiment differs from the first embodiment in that, before heating, the inner dimension of the raised portion 236 is smaller than the outer dimension of the thin-walled portion 224. In the description of the second embodiment, differences from the first embodiment will be described, and components already described will be denoted by the same reference numerals and their description will be omitted. Unless otherwise specified, components denoted by the same reference numerals perform substantially the same operations and functions, and their effects are also substantially the same.

[0056] FIG. 11 is a schematic cross-sectional view showing a cross section passing through the center of the blood pump 200. For ease of explanation, the impeller 50 housed inside the pump housing 210 is shown by a dashed line in FIG. 11. In FIG. 11, a base case 230, which is an example of a first member, and a top case 220, which is an example of a second member, are joined liquid-tightly. A substantially cylindrical internal space is formed in the top case 220 so as to be covered by the base case 230. The top case 220 has an annular thin-walled portion 224 as an example of a second fitting portion. The base case 230 has a substantially cylindrical protrusion 232 formed so as to form a recess that opens downward. The protrusion 232 is inserted into the internal space of the base case 230.

[0057] Furthermore, a substantially doughnut-shaped peripheral recess 235 is formed around the periphery of the protrusion 232 so as to surround the protrusion 232. Furthermore, the base case 230 has a raised portion 236 as an example of a first fitting portion. The raised portion 236 protrudes from the outer peripheral edge of the base case 230 between the outer peripheral edge of the base case 230 and the peripheral recess 235. Furthermore, the inner surface of the raised portion 236 faces the outer surface of the thin portion 224 of the top case 220 when the top case 220 and the base case 230 are fitted together. In other words, the inner peripheral surface of the raised portion 236 in the radial direction of the base case 230 faces the outer peripheral surface of the thin portion 224 of the top case 220 in the radial direction.

[0058] A doughnut-shaped flow path 11 is formed between the base case 230 and the top case 220 so as to surround the periphery of the impeller 50. An outlet port 222 is connected to the flow path 11. The inlet port 221 is formed to extend coaxially with the rotation axis CL of the impeller 50. The outlet port 222 is formed to extend generally tangentially to the rotation direction of the impeller 50. The protrusion 232 of the base case 230 is inserted into the central recess 51 of the impeller 50. An internal space is formed in the protrusion 232, constituting a recess that opens downward. The central protrusion 233 that protrudes from the top surface of the protrusion 232 of the base case 230 has a substantially conical shape.

[0059] A drive part (not shown) of the drive unit is disposed in the internal space of the protrusion 232. When the impeller 50 rotates, blood flows into the pump housing 210 via the inlet port 221. The blood that has flowed into the pump housing 210 flows into the introduction flow path 54 of the impeller 50. The blood that has flowed into the introduction flow path 54 is then forced into the flow path 11 by the rotating blades. The blood that has flowed into the flow path 11 is then sent from the flow path 11 to the outside of the blood pump 200 via the outlet port 222.

[0060] A relatively narrow gap is formed between the inner surface of the pump housing 210 and the impeller top surface 58 of the impeller 50 to form a dynamic pressure bearing DB1 that rotatably supports the impeller 50. Also, a relatively narrow gap is formed between the inner surface of the pump housing 210 and the impeller bottom surface 59 of the impeller 50 to form a dynamic pressure bearing DB2 that rotatably supports the impeller 50. Furthermore, a relatively narrow gap is formed between the outer circumferential surface of the protrusion 232 and the inner circumferential surface of the central recess 51 of the impeller 50 to form a dynamic pressure bearing DB3 that rotatably supports the impeller 50. In addition, a relatively narrow gap is formed between the upper surface 51A of the central recess 51 and the protrusion top surface of the protrusion 232 to form a dynamic pressure bearing DB4 that rotatably supports the impeller 50.

[0061] When blood is introduced into pump housing 210, some of the introduced blood flows into dynamic pressure bearings DB1, DB2, DB3, and DB4. As a result, the blood introduced into pump housing 210 flows into the gap between pump housing 210 and impeller 50. When impeller 50 rotates with blood flowing in, the pressure of the blood increases in dynamic pressure bearings DB1, DB2, DB3, and DB4. As a result, a supporting effect is generated in dynamic pressure bearings DB1, DB2, DB3, and DB4, and impeller 50 is rotatably supported.

[0062] In the second embodiment, before heating, when comparing the outer dimension of the thin portion 224 with the inner dimension of the raised portion 236, the inner dimension of the raised portion 236 is smaller than the outer dimension of the thin portion 224. That is, when the outer diameter of the thin portion 224 in the radial direction of the top case 220 is OD and the inner diameter of the raised portion 236 in the radial direction of the base case 230 is ID, the relationship OD > ID holds. Therefore, in the heating process, the raised portion 236 of the base case 230 is heated and expanded. Note that the outer dimension of the thin portion 224 is set to be smaller than the inner dimension of the raised portion 236 expanded by heating. In other words, the inner dimension of the raised portion 236 is set to be larger than the outer dimension of the thin portion 224 when the size of expansion due to heating is added.

[0063] [Assembly manufacturing method] First, the top case 220, the base case 230, and the impeller 50 are prepared. The top case 220 and the base case 230 are made of a transparent thermoplastic resin. An example of the transparent thermoplastic resin is polycarbonate, and the top case 220 and the base case 230 can be formed by injection molding.

[0064] The base case 230 is injection molded in the same manner as in the first embodiment. That is, the injection mold 300 is closed so that a molding cavity 363 is defined between the fixed mold 361 and the movable mold 362. Next, molten thermoplastic resin is injected into the molding cavity 363 through the pin gate 366. Subsequently, primary cooling is performed so that the thermoplastic resin solidifies. Then, the movable mold 362 is moved away from the fixed mold 361, and the injection mold 300 is opened. Furthermore, before secondary cooling, the core 364 is removed from the protrusion 232 of the base case 230. Then, secondary cooling is performed with the core 364 removed. Thereafter, the base case 230 is released from the movable mold 362. The top case 220 is injection molded in the same manner, except for the secondary cooling step. In this manner, the top case 220 and the base case 230 are prepared.

[0065] Then, before fitting the thin-walled portion 224 of the top case 220 with the raised portion 236 of the base case 230, the impeller 50 is positioned so that the impeller 50 is accommodated within the space defined by the top case 220 and the base case 230. Specifically, after preparing the top case 220, the base case 230, and the impeller 50, the top case 220 is turned upside down and the impeller 50 is inserted into the top case 220 with the inlet port 221 facing downward.

[0066] Next, in a heating step, the raised portion 236 of the base case 230 is heated and expanded. Thereafter, the base case 230 is fitted to the top case 220 in a held state in an air atmosphere at room temperature. Alternatively, the top case 220 may be fitted to the base case 230 in a held state. The raised portion 236 may also be heated by bringing a heating device into contact with the raised portion 236 or by spraying a high-temperature fluid onto the raised portion 236.

[0067] When fitting the top case 220 and the base case 230 together, the top surface of the raised portion 236 is abutted against the top case 220. Specifically, the top surface of the raised portion 236 is abutted against the plane between the thin portion 224 and the periphery of the top case 220. This allows the raised portion 236 to be positioned in the height direction. Therefore, it is possible to prevent the welding position from shifting.

[0068] Subsequently, in the cooling step, the raised portion 236 is cooled. To this end, the top case 220 and the base case 230 are cooled in an air atmosphere at room temperature. This causes the raised portion 236 to contract, fixing the thin-walled portion 224 to the raised portion 236. Furthermore, the contracted raised portion 236 presses the thin-walled portion 224 inward, causing the thin-walled portion 224 and the raised portion 236 to tightly adhere to each other. Alternatively, the raised portion 236 may be cooled by spraying a cryogenic fluid onto the raised portion 236. Note that the impeller 50 may be positioned after or simultaneously with the heating step of the raised portion 236. For example, the impeller 50 may be placed on the heated and expanded base case 230. In this case, the protrusion 232 of the base case 230 is inserted into the central recess 51 of the impeller 50. The top case 220 is then fitted to the held base case 230.

[0069] Next, in the welding process, the thin portion 224 and the raised portion 236 are welded together. If the thin portion 224 and the raised portion 236 are not in close contact with each other, the heat conduction efficiency of the heated thermoplastic resin will decrease, resulting in a decrease in the strength of the joint. In this regard, with the assembled body fitted together as described above, the contracted raised portion 236 presses the thin portion 224 inward. As a result, the thin portion 224 and the raised portion 236 are in close contact with each other, preventing a decrease in the strength of the joint. In the welding process, the thin portion 224 and the raised portion 236 are laser-welded by irradiating a laser onto the interface between the thin portion 224 and the raised portion 236.

[0070] When performing laser welding, the top case 220 and the base case 230 are formed from the same thermoplastic resin that transmits laser light. Then, a laser is irradiated from the outer surface of the raised portion 236 in the direction indicated by arrow D in FIG. 11 , which is perpendicular to the rotation axis CL of the impeller 50, with the focal point set at the interface between the thin-walled portion 224 and the raised portion 236. When the laser is irradiated, heat is generated on one of the inner circumferential surface of the raised portion 236 and the outer circumferential surface of the thin-walled portion 224 at the interface between the top case 220 and the base case 230, melting the thermoplastic resin. Subsequently, the thermoplastic resin on the other of the inner circumferential surface of the raised portion 236 and the outer circumferential surface of the thin-walled portion 224 also melts. The melted thermoplastic resin resolidifies when the irradiation is stopped and the heat generation subsides. This results in the outer circumferential surface of the thin-walled portion 224 and the inner circumferential surface of the raised portion 236 being welded together, resulting in a liquid-tight bond between the thin-walled portion 224 and the raised portion 236.

[0071] Then, while the laser is being irradiated, the blood pump 200 is rotated at a uniform speed around the rotation axis CL. This allows the laser to scan the outer periphery of the blood pump 200, thereby welding the entire circumference of the blood pump 200. Furthermore, when irradiating with the laser, the laser is irradiated onto the interface between the thin-walled portion 224 and the raised portion 236, avoiding the space defined by the top case 220 and the base case 230. Specifically, in the example of FIG. 11 , the laser is irradiated at a height lower than the bottom of the peripheral recess 235. This prevents the impeller 50 from being irradiated with the laser that has passed through the top case 220 and the base case 230. However, if laser irradiation does not pose a problem, the laser may be irradiated onto the space defined by the top case 220 and the base case 230.

[0072] The second embodiment described above also prevents the groove 34 formed on the outer peripheral surface of the protrusion 232 from becoming an undercut. Furthermore, the manufacturing method for a medical assembly described above also allows for stable joining of components constituting the medical assembly. Furthermore, because press-fitting is not required, design constraints on the components to be fitted together are reduced. That is, one of the mating components is heated and expanded, and the two components are fitted together in the expanded state and cooled. This allows the contracted component to pressurize the other component, easily achieving a tight fit between the two components. Therefore, the two components can be stably welded together without press-fitting, and the welded portion can also provide a seal. Furthermore, while a press-fitting device is required for press-fitting, this is not necessary because the components can be fitted together simply by heating them.

[0073] Although the present invention has been described above with reference to each embodiment, the present invention is not limited to the above-described embodiments. The present invention also includes inventions that have been modified without departing from the scope of the present invention, and inventions equivalent to the present invention. Furthermore, each embodiment and each modified form can be combined as appropriate without departing from the scope of the present invention.

[0074] For example, the top case 20, 220 does not have to have the thin portion 24, 224. Specifically, the thickness of the portion of the top case 20, 220 facing the raised portion 36, 236 may be the same as or thicker than the thickness of the other portions of the top case 20, 220. However, by providing the thin portion 24, 224 and welding with a laser that has passed through the thin portion 24, 224, the proportion of laser light absorbed by the resin can be reduced. [Explanation of symbols]

[0075] 20: Top case (component) 24: Thin part (first mating part) 30: Base case (molded product) 32: Convex part 34: Dynamic pressure groove (groove) 36: Raised part (second mating part) 100: Blood pump (medical assembly) 200: Blood pump (medical assembly) 236: Raised part 361: Fixed side mold 362: Movable mold 363: Molding cavity 364 :Nakako 365: Stripper

Claims

1. A method for manufacturing a molded product that is a base case of a blood pump, the base case including a convex portion, a dynamic pressure groove formed on an outer peripheral surface of the convex portion, and a raised portion formed between the convex portion and an outer peripheral edge portion so as to surround the convex portion, moving the movable mold toward the fixed mold so that a molding cavity is defined between the fixed mold and the movable mold; Injecting molten thermoplastic resin into the molding cavity; Primary cooling is performed so that the thermoplastic resin is solidified, moving the movable mold away from the fixed mold; a secondary cooling step for cooling the protrusion while the protruding portion is in contact with the movable mold, thereby shrinking the molded product; The molded product is released from the movable mold.

2. Before the secondary cooling, the core is removed from the convex portion of the molded product, The method for producing a molded product according to claim 1 , wherein the secondary cooling is carried out in a state where the core is removed.

3. The method for manufacturing a molded product according to claim 1 or 2, wherein a stripper holding the molded product is moved away from the movable mold when the molded product is released from the movable mold.

4. The method for producing a molded article according to claim 1 , wherein the cooling time of the secondary cooling is shorter than that of the primary cooling.

5. 5. The method for manufacturing a molded product according to claim 1, wherein the height of the raised portion is set to a height that allows the molded product to be released from the movable mold even if the molded product shrinks due to the secondary cooling.

6. A molded article is produced by the production method according to any one of claims 1 to 5, preparing a member to be fitted with the molded product; Heating a first mating portion of the member to expand it; The first fitting portion is fitted to a second fitting portion of the molded product, Cooling the first mating portion; The method for manufacturing a medical assembly includes welding the first mating portion and the second mating portion.

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