Abstract:
An auto-disable safety syringe including a needle, a needle seat, a plunger, and a barrel. A cover of a needle seat chamber formed in the needle seat is provided with a splined hole having teeth and grooves. The needle seat has a ring block and an outer wall with splined teeth capable of passing through the grooves. A locking groove is formed in an inner cavity of the ring block and a locking head is formed on a connecting head to form a locking mechanism. Spiral grooves on the inner cavity engage with protrusions on the connecting head. When the locking head and the locking groove are interlocked and the plunger is retracted, the needle seat and the needle are retracted inside the barrel together. The syringe protects both patient and medical staff, is simple in structure, convenient to use and destructible.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention generally relates to a syringe, and more particularly, to an auto-disable safety syringe having a barrel and a needle seat, in which the needle seat of the syringe can be not only engaged securely with the barrel but also released easily from the barrel of the syringe so as to allow a needle being fully retracted inside the barrel by a plunger, so that the needle is prevented from pricking, scratching or other harmful exposure to medical staffs during subsequent handling of the self-destructed syringe, thus achieving a dual protection of patients and medical staffs. 
   2. Background of the Related Art 
   Medically, a disposable syringe is widely used in order to avoid cross contaminations. Conventionally, a medical staff breaks a plunger of the disposable syringe after an injection so as to achieve the disposable purpose. However, the auto-disable syringe still tends to prick or scratch the medical staff during its subsequent handling, this may cause a further contamination, so that the conventional disposable syringe could not achieve a “dual protection”, that is, the conventional syringe could not protect both medical staffs and patients simultaneously. 
   Recently, for protecting both medical staffs and patients, there have been proposed safety syringes, some of which have been filed for patents, such syringes employ a structure with a manually retractable needle. With the structure, a plunger and a needle seat are connected and interlocked with each other after an injection of syringe, then both the needle seat and the needle are retracted inside the barrel by the plunger when the plunger is manually drawn back. This structure could prevent the used needle from pricking the medical staff. However, the above safety syringe with a manually retractable needle has a problem in connection between the needle seat and the barrel. Conventionally, the needle seat is connected to the barrel by a rubber ring, or an interference fit between a convex ring, a boss or a convex hoop formed integrally on a needle assembly or the needle seat and a certain portion of the barrel. The above connection should be firm and could not be too firm, if the connection is too firm, the needle seat may not be pulled inside the barrel after injection and during destruction, if the connection is not sufficient firm, the injectant may be leaked out and the needle may be automatically retracted during injection, the automatic retraction of the needle will cause that the injection could not be performed. In the prior art, there is provided a syringe in which the needle seat is provided with thread, the needle seat is securely connected to a barrel of the syringe through threaded engagement therebetween, however, in order to release the needle seat from the barrel, the threaded engagement must be manually released directly or indirectly, so that the releasing operation depends on the subjective consciousness of an operator, then there may be a hidden trouble that the syringe is not destructed after use, that is, the syringe is not disposable. Meanwhile, the needle provided with thread is not a standard needle, thus causing the medical staff inconvenient to change needles during use. 
   In a word, it is in urgent need of providing a safety syringe which can protect both medical staffs and patients simultaneously. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide an auto-disable safety syringe to mitigate or obviate the aforementioned problems, the auto-disable syringe of the present invention has a simple structure, is convenient to use and destructive, in which a needle seat of the syringe can be not only connected securely to a barrel of the syringe but also released easily from the barrel to allow a needle being fully retracted inside the barrel by a plunger, thus achieving dual-protection of the medical staffs and patients simultaneously. 
   The above object of the present invention is achieved by providing an auto-disable safety syringe, comprising a needle; a needle seat connected to the needle; a seal; a plunger; a piston connected to one end of the plunger; a barrel, the plunger and the piston being capable of fitting and reciprocating inside the barrel, the barrel being formed at a bottom end thereof with an ellipse-shape finger grip, a needle seat chamber being formed in front of a large top cover provided at a top end of the barrel, a small top cover formed at a top end of the needle seat chamber being provided with a splined hole, the splined hole being provided with plural protruding teeth on an inner wall thereof, and grooves of the splined hole being formed between adjacent protruding teeth respectively; and a plunger positioning plate capable of fitting over the finger grip of the barrel, the needle seat is formed with a conical fitting and a ring block at a front end and a rear end thereof respectively, the needle seat is formed on an outer wall thereof with splined teeth capable of passing through the grooves, and a neck for embedding the seal is formed between the splined teeth and the ring block. 
   Preferably, a limit boss is provided on each protruding teeth for limiting a rotation angle of the needle seat, and a slope having a locking angle is formed at a bottom portion of each splined tooth. 
   Further, a locking groove is provided at a top end of an inner cavity of the ring block, the inner cavity is formed with spiral grooves in an inner wall thereof, a connecting head of the plunger is formed at a top end thereof with a locking head which forms a locking mechanism together with the locking groove, and the connecting head is provided on a side wall thereof with protrusions for engaging with the spiral grooves respectively. 
   In addition, two plunger positioning plates of semi-ellipse shape are fit over the finger grip of the barrel, the plunger positioning plates are each provided with T-shape grooves respectively, a cross groove is formed by the T-shape grooves when the two plunger positioning plates match each other to fit over the finger grip, and the cross groove limits the plunger to only move linearly inside the barrel. 
   Preferably, the piston is formed in the form of a seal plate of the plunger or combination of a piston head with a piston ring of the plunger, and one or more piston grooves, in which the piston ring is embedded, are formed in a side wall of the piston head. 
   Moreover, the rotation angle of the needle seat is set within a limit of 90° by the limit boss, the locking angle of the slope is within a range of 0–25°. Further, the splined hole is provided with one or more grooves, the needle seat is provided on the outer wall thereof with one or more splined teeth which are capable of passing through the grooves and whose shapes are consistent with that of the grooves, and axial shapes of the grooves and the splined teeth are one selected from a group consisted of triangle, rectangle, oblong, trapezoid, sector and semicircle. 
   In addition, the inner cavity of the ring block is provided at the inner wall thereof with one or more spiral grooves, the connecting head is provided at the side wall thereof with one or more protrusions, and cross sections of the spiral grooves and the protrusions have one shape selected from a group consisted of triangle, rectangle, oblong, trapezoid, sector and semicircle. 
   Preferably, a stop sheet capable of being torn is formed at a rear portion of the plunger. 
   In the present invention, since the small top cover of the needle seat chamber is provided with a splined hole, protruding teeth, and grooves, the needle seat is provided at the outer wall thereof with splined teeth capable of passing through the grooves, the neck in which the seal is embedded is formed between the splined teeth and the ring block, and the protruding teeth are each provided with a limit boss thereon, after the needle seat is slid into the needle seat chamber of the barrel, the splined teeth are passed through the grooves of the spline hole, then the needle seat is rotated rightward until it is stopped by the limit boss, at this time, the respectively, and the splined teeth are engaged circumferentially with the limit boss respectively, in addition, the splined teeth are each provided at the bottom portion thereof with a slope having a locking angle, so that the slope at the bottom portion of the splined teeth tightens the engagement between the small top cover of the needle seat chamber, the seal and the needle seat as the rotation angle of the needle seat increases, thus achieving both sealing of the barrel and secure engagement of the needle seat with the barrel. In addition, the ring block at the rear end of the needle seat is fitted in the barrel with a clearance therebetween, so that the needle seat can enter and retreat from the splined hole easily, therefore, it is easy to assemble the syringe and to retract the needle seat. 
   According to the present invention, the ring block is provided at the inner wall thereof with spiral grooves, the connecting head of the piston is provided at the side wall thereof with protrusions for engaging with the spiral grooves, the spiral grooves and the protrusions form a spiral mechanism which employs a single thread or multiplex thread structure, when the plunger is moved linearly, the protrusions enter the spiral grooves, thus causing the needle seat to rotate in the reverse direction, the splined teeth on the needle seat return to their positions where the splined teeth and the protruding teeth of the splined hole formed on the small top cover of the needle seat chamber are not offset from each other, at this time, the splined teeth can pass through the grooves of the splined hole. While the needle seat is rotated in the reverse direction to its designated position, the locking head of the plunger reaches its designated position and is inserted into the locking groove of the needle seat, thus being interlocked integrally with each other, the locking head and the locking groove form a locking mechanism, when the plunger is retracted, the needle seat and the needle will be drawn to retract inside the barrel together. Then, the plunger is pushed back toward the top of the barrel, so that the needle is pressed into a spiral shape and destroyed. Finally, the plunger is broken, so that the syringe is destroyed and not reusable, therefore, the syringe of the present invention can provide protection of both patient and medical staff. 
   In the present invention, the needle seat, the needle seat chamber and the seal are universal, the needle seat assembly consisted of the above three elements has two types, i.e. Luer needle seat and Luer-Lock needle seat, the syringe can be constructed as central needle syringe and eccentric needle syringe by mounting the needle seat such that the central line of the needle seat is coincided with or offset from that of the barrel, respectively. The syringe can be also constructed as two-part syringe and three-part syringe by using different pistons. 
   The present invention has the following advantages: 
   1. The structure of the syringe is simple, the sealing is secured, and the needle seat may be connected securely to the barrel. 
   2. The needle is standard so that the syringe is convenient to use. 
   3. The medical staff can release the needle seat from the barrel through conventional operation without additional operations, and retract the needle seat together with the needle inside the barrel so as to destroy the syringe, thus achieving the disposableness of the syringe. 
   4. The present invention may be constructed as two-part or three part, central or eccentric, Luer or Luer-Lock needle seat auto-disable safety syringe. 
   Therefore, the syringe of the present invention can protect both medical staffs and patients simultaneously, avoid cross contaminations, and prevent the used needle from pricking or scratching, thereby infecting the medical staff, so that the present invention provides a novel safety syringe. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings of which: 
       FIG. 1  is a schematic structural view of a two-part type auto-disable safety syringe with a central needle and a threaded Joint of a needle seat according to the first embodiment of the present invention; 
       FIG. 2  is a schematic structural view of the barrel of the auto-disable safety syringe according to the first embodiment of the present invention; 
       FIG. 3  is a plane view of  FIG. 2 ; 
       FIG. 4  is a sectional view of the needle seat having the Luer-lock conical fitting according to the first embodiment of the present invention; 
       FIG. 5  is a right view of  FIG. 4 ; 
       FIG. 6  is a left view of  FIG. 4 ; 
       FIG. 7  is a view of a splined tooth in direction A; 
       FIG. 8  is a structural view of a plunger according to the first embodiment of the present invention; 
       FIG. 9  is a plane of  FIG. 8 ; 
       FIG. 10  is a schematic structural view of two plunger positioning plates in a matching state according to the first embodiment of the present invention; 
       FIG. 11  is a half section view of one of the two positioning plates; 
       FIG. 12  is a schematic state view of a two-part type auto-disable safety syringe with a central needle and a Luer-lock conical fitting of a needle seat after it finishes an injection; 
       FIG. 13  is a schematic structural view of a three-part type auto-disable safety syringe with an eccentric needle and a Luer conical fitting of a needle seat according to the second embodiment of the present invention; 
       FIG. 14  is a schematic structural view of a barrel of the auto-disable safety syringe according to the second embodiment of the present invention; 
       FIG. 15  is a plane view of  FIG. 14 ; 
       FIG. 16  is a sectional view of a needle seat having a Luer conical fitting according to the second embodiment of the present invention; 
       FIG. 17  is a right view of  FIG. 16 ; 
       FIG. 18  is a left view of  FIG. 16 ; 
       FIG. 19  is a structural view of a plunger according to the second embodiment of the present invention; 
       FIG. 20  is a plane of  FIG. 19 ; 
       FIG. 21  is a schematic state view of a three-part type auto-disable safety syringe with an eccentric needle and a Luer conical fitting of a needle seat after it finishes an injection. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The preferred embodiment of the present invention will be described in detail with reference to the drawings, examples of which are illustrated in the drawings, wherein like reference numerals refer to like elements throughout. 
   Embodiment 1: Two-part Type Auto-disable Safety Syringe with a Central Needle and a Luer-lock Conical Fitting of a Needle Seat 
   With reference to  FIG. 1  to  FIG. 12 ,  FIG. 1  is a schematic structural view of a two-part type auto-disable safety syringe with a central needle and a Luer-lock conical fitting of a needle seat according to the first embodiment of the present invention, the auto-disable safety syringe comprises a needle  1 , a needle seat  2 , a seal  3 , a piston  4 , a plunger  5 , a barrel  6 , and plunger positioning plates  7 , a finger grip  69  is integrally formed at a rear end (bottom end in  FIG. 1  and  FIG. 2 ) of the barrel  6 . 
     FIG. 2  is a schematic structural view of the barrel of the auto-disable safety syringe according to the first embodiment of the present invention, and  FIG. 3  is a plane view of  FIG. 2 , a cylindrical needle seat chamber  62  is formed in front of a large top cover  61  provided at a front end (top end in  FIG. 2 ) of the barrel  6 , the central line of the needle seat chamber  62  is coincided with that of the barrel  6 , that is, the barrel  6  is coaxial with the needle seat chamber  62 . A small top cover  63  is formed integrally at a top end of the needle seat chamber  62 , the small top cover  63  is formed centrally with a splined hole  64 , as shown in  FIG. 3 , plural protruding teeth  65  of the splined hole  64  are provided on the inner wall of the splined hole  64 . There is provided a limit boss  66  on each protruding teeth  65  for limiting the rotation angle of the needle seat  2 , grooves  67  of the splined hole  64  are formed between adjacent protruding teeth  65 , in the present embodiment, there are provided four grooves  671 ,  672 ,  673  and  674 . The needle seat  2  is formed integrally at a front end thereof with a Luer-Lock conical fitting  26 , and with a ring block  22  at a rear end thereof, the Luer-Lock conical fitting  26  can pass through the splined hole  64 . The needle seat  2  are formed integrally on an outer wall thereof with splined teeth  21  which can pass through the grooves  67 , a neck  25  is formed between the splined teeth  21  and the ring block  22  so as to be embedded with the seal  3 . The number of the splined teeth  21  is identical with that of the grooves  67  of the splined hole  64 , that is, there are four splined teeth  211 ,  212 ,  213  and  214  in the present embodiment, preferably, a slope having a locking angle  28  is formed at the bottom portion of each splined tooth  21 , as shown in  FIG. 5 . 
   As shown in  FIGS. 4 and 5 , a locking groove  23  is provided in front of the top end of an inner cavity  27  of the ring block  22 , and the inner cavity  27  is provided with spiral grooves  24  in the inner wall thereof, the piston  4  is formed in the form of a sealing plate  55  of the plunger  5 , a locking head  51  is formed at a top end of a connecting head  56  of the plunger  5 , the locking head  51  and the locking groove  23  form a locking mechanism, the connecting head  56  is provided on the side wall thereof with protrusions  52  for engaging with the spiral grooves  24  respectively. The spiral grooves  24  are formed in the form of four-head dextral female thread grooves  241 ,  242 ,  243  and  244 , the protrusions  52  are formed in the form of four-head male thread columns  521 ,  522 ,  523  and  524 , as shown in  FIG. 9 . 
   A square stop sheet  54  is formed at a rear portion of one of body pieces  53  of the plunger  5 , the stop sheet  54  could be torn off from the plunger  5  by hand. 
   As shown in  FIGS. 1 ,  10  and  11 , two plunger positioning plates  7  of semi-ellipse shape are fit over the finger grip  69 , the plunger positioning plates  7  are each provided with T-shape grooves respectively, a cross groove is formed by the T-shape grooves when the two plunger positioning plates  7  match each other to fit over the finger grip  69 , the cross groove is used to limit the plunger to be only moved linearly inside the barrel  6 . 
   The rotation angle of the needle seat  2  is set within the limit of 90° by the limit bosses  66 , the splined teeth  21  are each formed with a slope at the bottom portion thereof, the locking angle  28  of the slope is within the range of 0–25°. 
   The axial shape of the grooves  67  and the splined teeth  21  is one selected from a group consisted of triangle, rectangle, oblong, trapezoid, sector and semicircle, respectively. The cross section of the spiral grooves  24  and the protrusions  52  has one shape selected from a group consisted of triangle, rectangle, oblong, trapezoid, sector and semicircle, respectively. 
   The assembling of the syringe of the present embodiment is described as follows. 
   Firstly, the seal  3  is fit over the neck  25  of the needle seat  2 , the needle seat  2  is slid into the needle seat chamber  62  of the barrel  6 , the splined teeth  21  are passed through the grooves  67  of the splined hole  64 , then the needle seat  2  is rotated rightward until the splined teeth  21  touch the limit bosses  66 , so that the needle seat  2  could not be rotated further, at this time, the splined teeth  21  are offset from and overlap the protruding teeth  65  of the splined hole  64 , so as to engage circumferentially with the limit bosses  66 , respectively. The splined teeth  21  are each provided at the bottom portion thereof with a slope having the locking angle  28  of 0–25°, therefore, as the rotation angle of needle seat  2  increases, the engagement between the small top cover  63  of the needle seat chamber  62 , the seal  3  and needle seat  2  will become tighter and tighter, so that the needle seat  2  is engaged securely with the barrel  6 . Sequentially, the two-part type plunger  5  is mounted, any one of the body pieces  53  of the plunger  5  is kept in a direction corresponding to the direction of a short axis  68  of the finger grip  69  of the barrel  6 , and the stop member  54  formed at the rear portion of the plunger is outside of the finger grip  69  of the barrel  6 , the two plunger positioning plates  7  are fit over the finger grip  69 , the plunger  5  is pushed until the stop member  54  just touches the plunger positioning plates  7 . 
   In use, the stop sheet  54  is first torn off by hand, so that the syringe could be used in a conventional manner. During the whole injection, the plunger  5  is limited to only move linearly parallel to the central line of the barrel  6  due to the plunger positioning plates  7 , when the injection approaches finishing, the four columns  521 ,  522 ,  523  and  524  on the plunger  5  will be engaged with the four spiral grooves  241 ,  242 ,  243  of the needle seat  2 , respectively. As the plunger  5  is pushed, the protrusions  52  of the plunger  5  will cause the needle seat  2  to rotate in a reverse direction, the splined teeth  21  and the protruding teeth  65  of the splined hole  64  will return to a non-offset state, while the needle seat  2  is rotated in the reverse direction to its designated position, the locking groove  23  of the needle seat  2  and the locking head  51  of the plunger  5  will reach its designated positions and interlocked integrally with each other respectively, when the plunger  5  is retracted, the needle seat  2  and the needle will be drawn to retract inside the barrel  6  together, As shown in  FIG. 12 . Then, the plunger  5  is pushed back toward the top of the barrel, so that the needle  1  is pressed into spiral shape. Finally, the plunger  5  is broken, so that the syringe is destroyed and not reusable. 
   Embodiment 2: Three-part Type Auto-disable Safety Syringe with an Eccentric Needle and a Luer Conical Fitting of a Needle Seat 
   The needle  1 , the needle seat  2 , the seal  3 , the plunger  5 , the barrel  6 , and the plunger positioning plates  7  in the embodiment 2 are identical with that in the embodiment 1, so that the detail descriptions thereof are omitted here, the embodiment 2 is different from the embodiment 1 in the following. 
   In the embodiment 2, as shown in FIG.  13 – FIG. 21 , the barrel  6  of the syringe has an eccentric head portion, the central line of the needle seat chamber  62  of the barrel  6  is parallel to that of the barrel  6  and positioned on the short axis  68  of the finger grip  69  of the barrel  6 . 
   The fitting  26  formed at front end of the needle seat  2  is a Luer conical fitting. 
   The piston  4  is formed by combination of a piston head  58  with piston rings  59  of the plunger  5 , two piston grooves  57  are formed in the side wall of the piston head  58 , in which the piston rings  59  are embedded respectively. 
   The assembling and use of the syringe according to the embodiment 2 are identical with that according to the embodiment 1. 
   Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.