Patent Publication Number: US-2023146037-A1

Title: A medical syringe barrel and a manufacturing method for producing the same

Description:
TECHNICAL FIELD 
     The present invention relates to a medical syringe barrel for constituting a medical syringe and a manufacturing method for producing the same. 
     BACKGROUND ART 
     In general, a medical syringe comprises a syringe barrel having a tip on which a needle is to be attached and a syringe plunger which is to be inserted into the syringe barrel from an opening on the other end for moving a piston in the axial direction. A flange is formed at the opening on the other end of the syringe barrel to project radially outward. 
     For simplifying medicine management, controlling infection, preventing errors at the time of dispensing, speeding up administration and so on, a prefilled syringe, in which an accurate dosage of medicine is previously filled, is used. Plastic syringes are widely used because they have advantages of being highly flexible in the shape, lightweight, capable of preventing cracks, easy to dispose by fire and so on, and they improve the usability at pharmaceutical companies and medical institutions. 
     In general, such plastic syringes are manufactured by injection molding of a synthetic resin material. The injection molding is a typical plastic molding method which can produce products having complicated and precise shapes in a short time and at a low cost by mass production. This is a processing method for obtaining a molded article having a desired shape by heating and melting a synthetic resin material, applying pressure to the material, injecting it into a closed mold, cooling it, opening the mold and taking the solidified article out from the mold. 
     Patent Document 1 discloses a technique of installing a gate for injecting a synthetic resin material at the shaft center to form a rotating body shaped molded article by a synthetic resin material using a mold. Patent Document 2 proposes a technique of preventing a weld line from being formed in the blood contacting area of a blood equipment cap.
     Patent Document 1: Japanese laid-open patent application 2001-121546   Patent Document 2: Japanese laid-open patent application 2019-150588   

     DISCLOSURE OF INVENTION 
     Problems to be Resolved by the Invention 
     Conventionally, as shown in Patent Document 1, when a syringe barrel is manufactured by injection molding of a synthetic resin material, a gate is installed at the shaft center, namely an injection nozzle section of a syringe barrel, because the mold can be easily manufactured. In a molded article by injection molding of a synthetic resin material, a small groove or recess known as a weld line, which extends linearly, is formed at a position where the streams of the melted resin material join together inside the mold. Because a syringe barrel is a hollow structured molded article with a hole bored in the center, an injected melted resin material divides into two streams at a position, where a hollow structured hole is formed, and the streams join together thereafter. In such a syringe barrel, a weld line is formed at a position which is close to the injection nozzle section between the injection nozzle section and the barrel section. 
     If a weld line is formed at an internal liquid filled section in which an internal-use solution is filled, a groove shaped gap is formed between the outer circumferential surface of a piston and the inner wall surface of a barrel section, and there is some possibility of running of the internal-use solution out from the internal-use solution filled section along the gap. There is also a possibility that an internal-use solution remains in the weld line at the time of using the syringe. When a minimal capacity syringe is used, it is necessary to administer a regulated amount of the internal-use solution accurately, and therefore it is necessary to prevent such a leakage of the internal-use solution or a residual internal-use solution. When the side wall of the internal-use solution filled section of a barrel is tapped by a medical worker for discharging air bubbles at the time of using a syringe, the weld line can be a cause of a breakage like a crack on the barrel. 
     It is also necessary for a medical syringe barrel for a prefilled syringe to receive a sterilization treatment, be packaged and then be transported to a pharmaceutical company without being subjected to post processing like polishing after injection molding in order to prevent contamination. 
     Means for Solving the Problems 
     (1) A medical syringe barrel according to the present invention comprises a tubular barrel section for accommodating an internal-use solution in the interior thereof, an injection nozzle section formed at one end of the barrel section, and a flange section which is formed at an opening section on the other end of the barrel section to project radially outward, The barrel section includes an internal-use solution filled section which is set to be filled with the internal-use solution and an internal-use solution unfilled section which is set not to be filled with the internal-use solution when the internal-use solution is poured into the syringe barrel from the opening section. The surface of the flange section has a recess portion, and a weld line which is potentially formed by injection molding is not formed in the internal-use solution filled section. 
     According to a medical syringe barrel which is configured as described above, a weld line by injection molding of a synthetic resin material is formed at a position which is close to the flange section between the flange section and the barrel section, where melted resin streams join together on the circumference. However, no weld line is formed at the internal-use solution filled section, namely the portion which is close to the injection nozzle section in the barrel section. Therefore, it is possible to prevent formation of a gap by the weld line between the outer circumferential surface of the piston and the inner wall surface of the syringe barrel, and therefore it is possible to provide a syringe barrel in which a predetermined amount of the internal-use solution can be filled and administered accurately, when the internal-use solution is filled in the syringe barrel. 
     (2) In a medical syringe barrel according to the present invention described in (1), the height of a gate rest which is potentially formed by injection molding is smaller than the depth of the recess portion of the flange section, and the gate rest fits inside the recess portion. It becomes unnecessary to conduct post processing like polishing by configuring the recess portion which is formed in the flange section as described above, because the gate rest fits inside the recess portion certainly, although the projection by the gate rest may cause an injury at the time of use by a medical worker and it may cause improper mounting of a finger grip. Therefore, it is possible to provide a medical syringe barrel which is suitable for a hygienic full-automatic manufacturing and packaging process which can prevent contamination by foreign substances. 
     (3) A manufacturing method for producing a medical syringe barrel according to the present invention is a method for manufacturing a medical syringe barrel which comprises a tubular barrel section for accommodating an internal-use solution in the interior thereof, an injection nozzle section formed at one end of the barrel section, and a flange section which is formed at an opening section on the other end of the barrel section to project radially outward, In the present invention, injection molding of a thermoplastic resin material is conducted by preparing a mold so that a recess portion is formed on the surface of the flange section and installing a gate at a position where the recess portion is to be formed. 
     By configuring a medical syringe barrel in this way, a weld line by injection molding of a synthetic resin material is potentially formed at a position which is close to the flange section between the flange section and the barrel position, where the streams of a melted resin material join together on the circumference. However, no weld line is formed in the internal-use solution filled section, namely at the position which is close to the injection nozzle section in the barrel section. Therefore, it is possible to manufacture a syringe barrel which can prevent a gap by a weld line from forming between the outer circumference surface of the piston and the inner wall surface of the syringe barrel, and therefore can fill and administer a predetermined amount of the internal-use solution accurately, when the internal-use solution is filled in the syringe barrel. It is also possible to complete a syringe barrel without requiring any post processing like polishing for removing gate rests because the surface of the flange section is formed so as to have a recess portion. 
     Effect of Invention 
     In a medical syringe barrel and a manufacturing method for producing the same according to the present invention, it is possible to provide a syringe barrel which can be completed as a molded article by injection molding of a synthetic resin material without requiring post processing like polishing and can fill and administer a predetermined amount of the internal-use solution accurately. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1 (A)  shows a perspective view of a schematic configuration of a syringe barrel according to one embodiment of the present invention, and (B) shows a perspective view of a configuration example of a medical syringe made by assembling a syringe barrel shown in (A), in which an internal-use solution is filled, together with a piston, a plunger and a finger grip. 
         FIG.  2 (A)  shows an axial cross-sectional view of a syringe barrel according to one embodiment of the present invention, (B) shows a side view observed from the arrow B in (A), and (C) shows an enlarged view of the portion C surrounded by the dotted line in (A). 
         FIG.  3    shows a schematic cross-sectional view of a mold and a gate for explaining a manufacturing method for producing the syringe barrel shown in  FIG.  2   , (A) shows an axial cross-sectional view of the mold, (B) shows a B-B′ cross sectional view of the mold shown in (A), (C) shows an enlarged cross-sectional view of the portion F of the mold in (A), and (D) shows a D-D′ cross sectional view of the mold shown in (A). 
     
    
    
     A MODE FOR IMPLEMENTING THE INVENTION 
     A configuration of a medical syringe barrel according to one embodiment of the present invention will be described below referring to the drawings. In  FIG.  1 (A) , a syringe barrel  20  is a molded article by injection molding of a synthetic resin material like a polyolefin resin material, and comprises a tubular barrel section  21  for accommodating an internal-use solution in the interior thereof, a Lure Lock type injection nozzle section  22  which is formed at one end of the barrel section  21  and to which a needle as an example is to be attached, and a flange section  23  which is formed at an opening section on the other end of the barrel section  21  to project radially outward. The syringe barrel  20  is a transparent molded article, however only the outer shape is shown in  FIG.  1 (A) . 
       FIG.  1 (B)  shows a perspective view of a configuration example of a medical syringe which is assembled by a syringe barrel  20  according to one embodiment of the present invention in which an internal-use solution is filled, together with a piston, a plunger and a finger grip. This medical syringe is a prefilled syringe with a minimal capacity for ophthalmic use as an example, and a disposable syringe for which a single time use is assumed. In  FIG.  1 (B) , a syringe  10  is an assembly which is made of a syringe barrel  20 , a finger grip  30 , a syringe plunger  40  and a piston  50 . An internal-use solution  60  is accommodated in a hollow barrel section of the tubular syringe barrel  20 , the internal-use solution  60  is pushed out from the tip of the syringe barrel  20  by pushing the piston  50  with the tip of the syringe plunger  40 . As shown in  FIG.  1 (B) , the syringe barrel  20  is a transparent barrel of a molded article made of a polyolefin resin material as an example, and it is possible to visually recognize the internal-use solution  60 , the piston  50  and a part of the syringe plunger  40  which are inside the hollow barrel section. 
       FIG.  2    is an axial cross-sectional view which shows a configuration of the syringe barrel  20  according to one embodiment of the present invention. The syringe barrel  20  is a molded article by injection molding of a synthetic resin material like a polyolefin resin material, and comprises a tubular barrel section  21  for accommodating an internal-use solution in the interior thereof, an injection nozzle section  22  which is formed at one end of the barrel section  21  and to which a needle as an example is to be attached, and a flange section  23  which is formed at an opening section on the other end of the barrel section  21  to project radially outward. In this embodiment, as shown in  FIG.  1 (B) , when the internal-use solution is poured into the syringe barrel  20 , a portion of the syringe barrel  20 , which is filled by an internal-use solution  60 , is called as an internal-use solution filled section  20 F, and a portion which is not filled by the internal-use solution  60  is called as an internal-use solution unfilled section  20 N. 
     In  FIG.  2   , the injection nozzle section  22  is formed as a Lure Lock type, wherein a screw tube part is connected to the outer side of a cylindrical nozzle part, the cylindrical nozzle part has a tapered surface, which is formed to be thinner toward the tip, on the outer circumference, and the screw tube part has a male screw on the inner wall surface. In this structure, by fitting an injection needle to the injection nozzle section  22  firmly, it is possible to certainly prevent the attached injection needle from becoming loose or being dislocated from the nozzle section, when it is used in a medical field or the like. Such a syringe barrel  20  may be used for mixed injection to a drip infusion portion, a two-liquid blending syringe between syringes or the like. 
     The syringe barrel  20  comprises an internal-use solution filled section  20 F corresponding to the portion which is closer to the injection nozzle section  22  than a piston tip position  20 P and an internal-use solution unfilled section  20 N corresponding to the portion which is closer to the flange section  23  than the piston tip position  20 P, when a predetermined amount of the internal-use solution is put into the interior thereof. 
     As shown in  FIG.  1 (A)  and  FIG.  2 (A) , a portion of the barrel section  21 , which is close to the flange section  23 , constitutes a large outer diameter barrel section  24 , which has an outer diameter lager than the outer diameter of the intermediate body part  21 M, and is formed between the flange section  23  and the intermediate body part  21 M. It is considered that the relationship between the outer diameter D22 of the injection nozzle section  22 , the outer diameter D21 of the intermediate body part  21 M and the outer diameter D24 of the large outer diameter barrel section  24  may be D24=D22&gt;D21, D24&gt;D22&gt;D21 or D22&gt;D24&gt;D21, however the relationship of D24≥D22&gt;D21 is preferable. 
     As shown in  FIG.  1 (A)  and  FIG.  2 (A) , (B). the flange section  23  has two recess portions  23 R, each has an approximately semielliptical notched shape and is formed at one of two positions on the outer periphery, respectively. When the flange section  23  is observed from the direction shown by the arrow B in  FIG.  2 (A) , as shown in  FIG.  2 (B) , the inner wall surface  24 N of the large outer diameter barrel section  24 , the inner wall surface  21 N of the intermediate body part  21 M and the inner wall surface  22 N of the nozzle part of the injection nozzle section  22  are viewed in this order concentrically from the outer surface. 
     Next, a manufacturing method for producing the syringe barrel  20  shown in  FIG.  2    will be explained referring to  FIG.  3   . As shown in  FIG.  3   , a mold  300  is prepared for molding the syringe barrel  20 . The mold  300  has a structure which can be divided appropriately for molding complicated shapes like the shapes of the injection nozzle section  22 , the flange section  23  and the like. Although the mold  300  is shown as a mold for molding a single syringe barrel  20 , it is possible to use a mold for molding plural syringe barrels  20  simultaneously. An injection molding machine, which is not shown in the drawings, has a mold closing mechanism to which a mold is installed and an injection equipment for filling a melted resin material. 
     The injection molding method comprises a mold closing step for closing an open mold by a mold closing mechanism, a melted resin filling step for filling a melted resin material into a closed mold by an injection molding machine, a molded article cooling step for cooling the resin material in the mold for a predetermined time after the melted resin filling step, and a molded article extracting step for extracting the molded article by opening the mold after the molded article cooling step is completed. 
     For example, a female die of the mold is installed to the injection equipment side (the fixed side) and a male die of the mold is installed to the mold closing mechanism side (the movable side). A melted resin material is injected into the cavity which is formed by engaging the male die of the mold with the female die of the mold. The injected melted resin material flows into the cavity through a gate from a spool in the mold. A molded article is released from the mold after cooling and solidifying the resin material which is filled in the mold. 
     As shown in  FIG.  3 (A) , a cavity  320 , in which the syringe barrel  20  is to be molded, is formed by a mold  300 . The cavity  320  comprises a cavity  322  corresponding to the injection nozzle section in which two cylindrical cavities are connected, a cylindrical cavity  321 M corresponding to the intermediate body part, a cylindrical cavity  324  corresponding to the large outer diameter barrel section, and a cavity  323  corresponding to the flat plate shaped flange section. Also, the mold  300  has a shape for forming the recess portions  23 R in the flange section  23 . 
     In  FIG.  3 (B) , the mold for surrounding the outside of the cavity  323  corresponding to the flange section is omitted, and the cavity  323  corresponding to the flange section is a flat plate shaped cavity in which a portion corresponding to the inner wall surface  24 N of the large outer diameter barrel section  24  is partitioned by the mold. Two convex portions  323 C which project inwardly are formed on the inner wall surface of the mold  300  so that the two convex portions  323 C penetrate the cavity  323  corresponding to the flange section at the two positions on the outer periphery. 
     As shown in  FIG.  3 (C) , the shape of the convex portions  323 C which are formed at the two positions on the outer periphery of the cavity  323  corresponding to the flange section corresponds to the shape of the recess portions  23 R. The gates  310  of the injection molding machine are installed at the positions where the recess portions  23 R are formed, and the melted resin material is delivered into the cavity  320  in the mold  300  from the injection molding machine through the gates  310 . 
     As shown in  FIG.  3 (B) , the cavity  323  corresponding to the flange section of the cavity  320  has a same shape as the flange section  23 . When a melted resin material is injected from the outer periphery of the flat plate shaped cavity  323  corresponding to the flange section through the two gates  310 , the flat plate shaped cavity  323  corresponding to the flange section will be filled with the melted resin material from the outer periphery toward the inner periphery, and the streams of the melted resin material will join together in the vicinity of the center line portion  323 M which is shown by the dotted line. The filling balance is improved by installing the two gates  310  when the mold is filled with the melted resin material. For manufacturing a minimal capacity syringe barrel according to the present embodiment, it is possible to fill the mold with the melted resin material by installing one gate to four gates. If one gate is installed, it becomes difficult to keep the filling balance because the filling port is unbalanced. If three or more gates are installed, although the filling speed becomes higher, it requires a larger amount of melted resin material because the number of runners will increase. Therefore, it is preferable to install two gates in the present embodiment. 
     The melted resin material flows into the cavity  323  corresponding to the flange section first, and then flows into the cavity  324  corresponding to the large outer diameter barrel section. As shown in  FIG.  3 (D) , there is also a possibility that the streams of the melted resin material join together in the vicinity of the center line portion  324 M of the cavity  324  corresponding to the large outer diameter barrel section which is shown by the dotted line. In  FIG.  3 (D) , the outer and inner molds for the cavity  324  corresponding to the large outer diameter barrel section are omitted, the molds are installed at the inner circular portion and the outer portion which is not shown in the drawings. 
     After the cavity  320  is filled completely in the circumferential direction with the melted resin material, the streams of the melted resin material no longer join together in the circumferential direction, the melted resin material flows cylindrically toward the side of the cavity  322  corresponding to the injection nozzle section, and the melted resin filling step is completed by filling the cavity  322  corresponding to the injection nozzle section. Subsequently, a syringe barrel as a molded article shown in  FIG.  2    is obtained by conducting the molded article cooling step and the molded article extracting step. 
     In this embodiment, when the syringe barrel  20  is formed by injection molding of a synthetic resin material, as shown in  FIG.  3 (B) , the streams of the melted resin material, which are injected from the two gates  310 , join together in the vicinity of the center line portion  323 M shown by the dotted line, by flowing around the circumference of the cylindrical male die of the mold while being cooled on the surface of the male die inside the inner wall  324 N of the cavity  324  corresponding to the large outer diameter barrel section. 
     A linear pattern called as a weld line is formed at the merging part of the two streams of the resin material, wherein the weld line may cause occurrence of failure on its appearance and insufficient mechanical strength. The weld line is a phenomenon occurred by a slightly solidified resin material surface. 
     For creating a condition in which the surface of the merged melted resin material hardly solidifies, it is considered to delay the solidification by increasing the mold temperature, make the solidified layer on the surface thinner by increasing the injection speed, set the resin material temperature higher, set the resin material pressure higher and so on, however it is impossible to prevent occurrence of the weld line by these treatments. 
     In this manner, when the flange section  23  is formed, a weld line is formed in the vicinity of the center line  323 M where the streams of the melted resin material join together. Next, there is also a possibility that a weld line is formed in the large outer diameter barrel section  24  when the melted resin material flows into the cavity  324  corresponding to the large outer diameter barrel section after filling the cavity  323  corresponding to the flange section and then the streams of the melted resin material join together in the vicinity of the center line  324 M. 
     When the melted resin material fills the cavity  324  corresponding to the large outer diameter barrel section and extends through the entire circumference, the streams of the melted resin material no longer join together on the circumference at the time of flowing into the cavity  321 M corresponding to the intermediate body part. Therefore, no weld line will be formed in the intermediate body part  21 M. 
     Depending on the injection molding condition, there is also a possibility that the streams of the melted resin material join together on the circumference in a part of the cavity  321 M corresponding to the intermediate body part which is close to the cavity  324  corresponding to the large outer diameter barrel section, and a weld line is potentially formed. However, no weld line is formed in a part of the cavity  321 M corresponding to the intermediate body part which is close to the cavity  322  corresponding to the injection nozzle section because the streams of the melted resin material do not join together on the circumference. 
     Therefore, it is possible to obtain the internal-use solution filled section  20 F where no weld line is formed by setting the part of the intermediate body part  21 M, which is close to the large outer diameter barrel section  24 , to the internal-use solution unfilled section  20 N and the part of the intermediate body part  21 M, which is close to the injection nozzle section  22 , to the internal-use solution filled section  20 F. 
     According to this embodiment, because no weld line is formed in the internal-use solution filled section  20 F, no gap is formed between the outer circumferential surface of the piston  50  and the inner wall surface of the syringe barrel  20 , and thus no internal-use solution will leak out. Hereby, it is possible to obtain a syringe barrel which can fill and administer a predetermined amount of the internal-use solution accurately and is manufactured by injection molding of a synthetic resin material. 
     In the molded article extracting step, gate rests are formed when the gates are separated from the molded article. The gate rests are formed by leaving the solidified resin material at the portions of the molded article which correspond to the positions of the gates. When the portions of the molded article corresponding to the gates are not solidified, the positions of separating the gates become unstable and solidified resin material will remain at the portions of the separated molded article corresponding to the positions of the gates. Although it is considered that the gate rests can be made smaller by adjusting the gate shape, the injection time, the mold opening speed and the pressure applied to the vicinity of the gates and so on, it is practically unavoidable to form a certain size of gate rests. 
     In general, the gate rests are removed by a treatment like polishing because the projections by the gate rests may cause injury at the time of use by a medical worker and a failure in mounting a finger grip. However, it is not preferable to conduct such post processing for preventing foreign matter contamination and treating in a hygienical full-automatic production process. 
     In this embodiment, as shown in  FIG.  3 (C) . a convex portion  323 C is formed in the cavity  323  corresponding to the flange section of the mold  300 , and a gate  310  is positioned so that it corresponds to the convex portion  323 C. When a medical syringe barrel of a capacity of 0.25 mL is used as an example of the syringe barrel  20 , the thickness of the flange section is set to 2 mm, the length in the radial direction of the recess portion  23 R is set to 4 mm, and the depth of the recess portion  23 R is set to 1 mm. In this example, as shown in  FIG.  2 (C) , because the width and the height of a gate rest  25  fits inside the recess portion  23 R even though the gate rest  25  is formed inside the recess portion  23 R of the flange section  23  after the injection molding step, a medical worker will not be injured at the time of operation, and no inconvenience will occur at the time of attaching a finger grip. Therefore, it is not necessary to conduct a post processing treatment like polishing which is inconvenient for manufacturing a medical equipment. 
     According to the above-described embodiment, it is possible to provide a medical syringe as a molded article by injection molding of a synthetic resin material and a manufacturing method for producing the same, wherein it is possible to be completed without requiring a post processing treatment like polishing and therefore possible to fill and administer a predetermined amount of an internal-use solution accurately. A syringe barrel according to the present embodiment is suitable for a prefilled syringe, wherein a medical solution is filled in a syringe barrel and the syringe is assembled in advance. A syringe barrel according to this embodiment is also suitable for a disposable syringe which is assumed to be used a single time. 
     EXPLANATION OF REFERENCES 
     
         
           10  syringe 
           20  syringe barrel 
           20 F internal-use solution filled section 
           20 N internal-use solution unfilled section 
           20 P piston tip position 
           21  barrel section 
           21 M intermediate body part 
           21 N inner wall surface of the intermediate body part  21 M 
           22  injection nozzle section 
           22 N inner wall surface of the nozzle part of the injection nozzle section  22   
           23  flange section 
           23 R recess portion 
           24  large outer diameter barrel section 
           24 N inner wall surface of the large outer diameter barrel section  24   
           25  gate rest 
           30  finger grip 
           300  mold 
           310  gate 
           320  cavity 
           321 M cavity corresponding to the intermediate body part 
           322  cavity corresponding to the injection nozzle section 
           323  cavity corresponding to the flange section 
           323 C convex portion 
           324  cavity corresponding to the large outer diameter barrel section 
           324 N inner wall of the cavity corresponding to the large outer diameter barrel section 
           40  syringe plunger 
           50  piston 
           60  internal-use solution