Method and system for the production of a plastic needle

Abstract

A method and a system is provided for producing a needle of plastic, as well as a needle of plastic, in particular a needle for medical purposes. The method produces a needle having at least the outer diameter of one end being less than 0.50 mm using a moulding system having an assembly comprising a feed system and a mould cavity. The method includes introducing a melt of plastic into the feed system, increasing the melt pressure gradually during melt passage through the feed system, passing the melt into the mould cavity whereby the melt substantially fills the mould cavity, cooling the melt in the mould cavity whereby the melt solidifies to a needle, and removing the needle from the mould cavity.

What is claimed:  
     
         1 . A method for producing a plastic needle, the needle having two ends, and having at least the outer diameter of one end being less than 0.50 mm, the needle having a longitudinal lumen extending between two openings of the needle, said method using a moulding system having an assembly comprising a feed system, a mould cavity, and an insert corresponding to and for forming the lumen in the needle, said method comprising the following steps: 
 introducing a melt of plastic into the feed system;    increasing the melt pressure gradually during melt passage through the feed system;    passing the melt into the mould cavity whereby the melt substantially fills the mould cavity;    cooling the melt in the mould cavity whereby the melt solidifies to form a needle; and    removing the needle from the mould cavity.    
     
     
         2 . The method according to  claim 1 , wherein the mould cavity is substantially filled in a period of time from 0.1 to 10 msec.  
     
     
         3 . The method according to  claim 2 , wherein the mould cavity is substantially filled in a period of time from 1 to 2 msec.  
     
     
         4 . The method according to  claim 1 , wherein the melt is introduced into the feed system with a rate of from 0.10 to 100 ccm/sec.  
     
     
         5 . The method according to  claim 1 , wherein the melt is introduced into the feed system with a rate of from 1 to 10 ccm/sec.  
     
     
         6 . The method according to  claim 1 , wherein the mould temperature is from 50 to 350° C.  
     
     
         7 . The method according to  claim 6 , wherein the mould is from 120° C. to 140° C.  
     
     
         8 . A system for producing a plastic needle, said plastic needle having an outer diameter of one end being less than 0.5 mm and having a longitudinal lumen extending between two openings of the needle, said system comprising: 
 an assembly comprising a feed system, a mould cavity, and an insert corresponding to and forming the lumen in the needle, said feed system being arranged for increasing the melt pressure gradually during melt passage through the feed system; and    means for passing the melt into the mould cavity, so that the melt substantially fills the mould cavity.    
     
     
         9 . The system according to  claim 8 , wherein the feed system is at least partly conical shaped with the narrow part being downstream of the melt flow passage.  
     
     
         10 . The system according to  claim 8 , wherein the feed system comprises cylindrical parts having a respective cylindrical flow passage of different diameters separated by conical parts.  
     
     
         11 . The system according to  claim 8 , wherein a ring gate is arranged in front of the mould cavity, whereby melt is introduced into the ring gate before entering the mould cavity.  
     
     
         12 . The system according to  claim 11 , wherein the ring gate is of conical shape.  
     
     
         13 . The system according to  claim 11 , wherein the melt of plastic is introduced radially into the ring gate.  
     
     
         14 . The system according to  claim 8 , wherein the feed system and the mould cavity are adapted to exhibit a temperature in the range of 50-350° C.  
     
     
         15 . The system according to  claim 8 , wherein the feed system and the mould cavity are adapted to exhibit a temperature in the range of 120-140° C.  
     
     
         16 . The system according to  claim 8 , wherein the insert is a wire substantially centered in the mould cavity.  
     
     
         17 . The system according to  claim 16 , further comprising means for removing the wire after moulding is arranged.  
     
     
         18 . The system according to  claim 8  wherein said means for passing the melt into the mould cavity is adopted to fill the mould cavity in a period of time from 0.1 to 10 msec.  
     
     
         19 . The system according to  claim 18 , wherein said means for passing the melt into the mould cavity is adapted to substantially fills the mould cavity in a period of time from 1 to 2 msec.  
     
     
         20 . A system for producing a hollow plastic needle, the needle having two ends and at least the outer diameter of one end being less than 0.50 mm, the needle having a longitudinal lumen extending between two openings of the needle, said system comprising: 
 a feed system;    a mould cavity;    an insert corresponding to and forming the lumen in the needle;    means for introducing a melt of plastic into the feed system, said feed system being arranged for increasing the melt pressure gradually during melt passage through the feed system; and    means for passing the melt into the mould cavity, so that the melt substantially fills the mould cavity in a period of time from 0.1 to 10 msec.    
     
     
         21 . The system of  claim 20 , wherein said means for passing the melt into the mould cavity substantially fills the mould cavity in a period of time from 1 to 2 msec.  
     
     
         22 . A system for producing a hollow plastic needle, the needle having two ends and at least the outer diameter of one end being less than 0.50 mm, the needle having a longitudinal lumen extending between two openings of the needle, said system comprising: 
 a feed system, said feed system being arranged for increasing the melt pressure gradually during melt passage through the feed system;    a mould cavity;    an insert corresponding to and forming the lumen in the needle;    a thermal conduit associated with the feed system for introducing a melt of plastic into the feed system; and    a mould cavity fill conduit connecting the feed system with the mould cavity, said mould cavity fill conduit adapted to provide the melt to substantially fill the mould cavity in a period of time from 0.1 to 10 msec.    
     
     
         23 . The system of  claim 22  wherein the mould cavity fill conduit is adapted to permit the melt to substantially fill the mould cavity in a period of time from 1 to 2 msec.  
     
     
         24 . A plastic needle having two ends, said needle being produced by injection moulding from a plastic melt, wherein the outer diameter of the moulded needle in at least one end of the needle is less than 0.50 mm, said needle comprising a lumen, said needle having an inner diameter corresponding to the diameter of the lumen which is no greater than 60% of the outer diameter of the needle.  
     
     
         25 . The plastic needle according to  claim 24 , wherein the inner diameter of the needle in the range of from 20% to 50% of the outer diameter.  
     
     
         26 . The plastic needle according to  claim 24 , wherein the at least one end of the needle is less than 0.45 mm.  
     
     
         27 . The plastic needle according to  claim 24 , wherein said needle is composed from an injection moulded liquid crystalline polymer melt.  
     
     
         28 . The plastic needle according to  claim 27 , wherein the liquid crystalline polymer is a polymer comprising monomer units selected the group consisting of hydroxybenzoic acid, hydroxynaphtoic acid, terephtalic acid, p-aminophenol and p-biphenol alone or in combination.  
     
     
         29 . The plastic needle according to  claim 28 , wherein the polymer is a random copolymer comprising 70-80% hydroxybenzoic acid and 20-30% hydroxynaphtoic acid.  
     
     
         30 . The plastic needle according to  claim 24 , wherein the plastic melt comprises fiber reinforcement.  
     
     
         31 . The plastic needle according to  claim 30 , wherein the reinforcement is selected from the group consisting of glass fiber or carbon fiber and aramid fiber.  
     
     
         32 . The plastic needle according to  claim 30 , wherein the reinforcement fibers constitute from 15 to 40% by weight of the solid plastic.  
     
     
         33 . A plastic needle having two ends, said needle being produced by injection moulding from a plastic polymer melt, said polymer being a random copolymer comprising 70-80% hydroxybenzoic acid and 20-30% hydroxynaphtoic acid, said needle having an outer diameter in at least one end of the needle being less than 0.50 mm and comprising a lumen.  
     
     
         34 . A plastic needle according to  claim 31 , wherein the at least one end of the needle is less than 0.45 mm.  
     
     
         35 . The plastic needle according to claims  31 , wherein the plastic melt comprises fiber reinforcement.  
     
     
         36 . The plastic needle according to  claim 35 , wherein the reinforcement is selected from the group consisting of glass fiber, carbon fiber and aramid fiber.  
     
     
         37 . The plastic needle according to  claim 36 , wherein the reinforcement fibers constitute from 15 to 40% by weight of the solid plastic.