Patent Publication Number: US-2016220766-A1

Title: Safety needle assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application filed under 25 U.S.C. 111(a) claiming the benefit under 35 U.S.C. §§120 and 365(c) of PCT International Application No. PCT/JP2015/065040 filed on May 26, 2015, which claims priority to Japanese Patent Application No. 2014-137253, filed on Jul. 2, 2014. The contents of these applications are hereby incorporated by reference in their entireties. 
    
    
     BACKGROUND 
     The present disclosure relates to a safety needle assembly that is used in subcutaneous injection of a high viscosity formulation, and more particularly, to a safety needle assembly that ensures safety in subcutaneous injection of a high viscosity formulation. 
     Conventionally, injection has been employed as a method for delivering therapeutic agents into the body of a patient. Examples of the injection include intradermal injection, subcutaneous injection, intramuscular injection, intravenous injection, arterial injection, intraarticular injection, and epidural injection. Among these injections, for example, subcutaneous injection is used in diseases such as diabetes and rheumatism. JP 2012-509749 A (“Patent Literature 1”) proposes a subcutaneous infusion system as a system that performs subcutaneous injection. The subcutaneous infusion system is provided with a needle of 24 to 27 gauge or 18 gauge and a medication dispensing device. The needle includes a shaft having an internal duct of unvarying diameter defining a fluid pathway between openings at distal and proximal ends of the needle. A hub in fluid communication with the duct is disposed at the distal end of the needle, and the needle length from the hub to the proximal end is approximately 4 to 6 mm. The medication dispensing device is in detachable fluid communication with the needle duct and contains approximately 3 to 100 mls of a highly viscous therapeutic fluid composition. The subcutaneous infusion system of Patent Literature 1 is configured for subcutaneous delivery of the therapeutic fluid composition at a flow rate of approximately 1 to 20 ml per minute. 
     SUMMARY 
     Health care workers have to safely handle subcutaneous injection needles. For example, if a health care worker erroneously sticks a subcutaneous injection needle used for a patient or the like into the own body (finger, for example), the health care worker may be infected with a disease. However, the system of Patent Literature 1 has no means for preventing such a sting accident and thus cannot be perfectly safe. There may be a method, as safety measure, that covers a used subcutaneous injection needle with a cylindrical cap. However, even in this method, a health care worker may erroneously stick the needle into his finger holding the cap. Therefore, this method also cannot be perfectly safe. 
     It is an object of the present invention to solve the above problem associated with conventional techniques and provide a safety needle assembly that ensures safety in subcutaneous injection of a high viscosity formulation. 
     In order to solve the above issue, one embodiment of the present invention is directed to a safety needle assembly including: a hub including a proximal end connected to a syringe and a distal end; a cannula including a proximal end connected to the distal end of the hub, a lumen extending in a longitudinal direction of the cannula, and a distal end, the cannula having a thickness of 18 to 24 gauge and a length between the hub and the distal end of 8 to 22 mm; a collar attached to the hub and including a sheath attachment part; a protector configured to cover the distal end of the cannula by being attached to the hub or the collar, the protector being detachable for exposing the distal end of the cannula; and a sheath including an opening extending along at least a part of the sheath in a longitudinal direction, the opening being capable of housing the cannula, the sheath further including: a cannula fixing part configured to fix the cannula, the cannula fixing part extending along at least a part of the sheath in the longitudinal direction; an attachment part configured to rotatably support the sheath in a direction of housing the cannula in the opening when the protector is detached to expose the distal end of the cannula, the attachment part being attached to the sheath attachment part of the collar; a projecting stopper for restricting movement, toward a distal end of the sheath, of a finger of a user pushing the sheath for housing the cannula into the opening, the stopper being disposed near a central part of the sheath in a longitudinal direction or at a position between the central part and the distal end of the sheath at an opposite side of an opening face of the opening; and a guide rib including a locking protrusion for locking the cannula inside the opening with an angle, in a side view, between a line passing through an end face of the opening of the sheath and a line passing through a surface of the cannula of 0° or more with respect to the housing direction of the cannula. 
     Further, certain embodiments of the present invention are preferably used for a high viscosity formulation. Further, a silicone film is preferably formed on the surface of the cannula within a range of 60% to 85% of the length from the distal end. 
     Further, the sheath preferably includes, as a finger guiding region with which a finger of a user operating the sheath comes into contact, a circular recess and a slope formed between the circuit recess and the stopper, the slope having a plurality of protrusions and recesses, the circular recess and the slope being located between the stopper and a proximal end of the sheath at the opposite side of the opening face of the opening. 
     Embodiments of the present invention make it possible to safely house the cannula in the sheath and reliably prevent a sting accident. Further, the silicone film formed on the cannula enables the cannula to be more reliably and safely housed in the sheath. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of a safety needle assembly in an embodiment of the present invention. 
         FIG. 2  is a perspective view of a hub of the safety needle assembly of  FIG. 1 . 
         FIG. 3A  is a perspective view of a collar of the safety needle assembly of  FIG. 1 . 
         FIG. 3B  is a perspective view of the collar of  FIG. 3A  viewed from a back side thereof. 
         FIG. 4A  is a perspective view of a sheath of the safety needle assembly of  FIG. 1 . 
         FIG. 4B  is a perspective view of the sheath of  FIG. 4A  viewed from a bottom side thereof. 
         FIG. 5A  is a perspective view illustrating a state in which a cannula is housed in the sheath of the safety needle assembly of  FIG. 1 . 
         FIG. 5B  is a sectional view taken along line A-A of  FIG. 5A . 
         FIG. 5C  is a sectional view taken along line B-B of  FIG. 5B . 
         FIG. 6  is a perspective view of the safety needle assembly in the embodiment of of  FIG. 1 . 
         FIG. 7  is a perspective view of the safety needle assembly in a state ready to be used. 
         FIG. 8  is a perspective view illustrating a state just before the cannula is housed in the sheath in the safety needle assembly of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Hereinbelow, an example of safety needle assembly of the present invention will be described in detail on the basis of an embodiment illustrated in the accompanying drawings. 
       FIG. 1  is an exploded perspective view of the safety needle assembly in one embodiment of the present invention. 
     The safety needle assembly  10  in the present embodiment is connected to a fluid transfer device such as a syringe (hereinafter, merely referred to as “syringe”) to be used. 
     The safety needle assembly  10  is used in subcutaneous injection of a high viscosity formulation. The high viscosity of the high viscosity formulation indicates a viscosity of 30 cP or more. 
     The safety needle assembly  10  is packaged, for example, in a blister packaging which is formed by extending a plastic sheet material and connected to a syringe by a user such as a health care worker when used. Alternatively, the safety needle assembly  10  may be packaged after connected to a syringe. 
     Note that when each component is described, a “direction” described therein is defined by the respective directions of “UP” and “DOWN”, “FRONT” (distal end side) and “BACK” (proximal end side), and “LEFT” and “RIGHT” illustrated in  FIG. 1 . In the other drawings, the directions are similarly described to those in  FIG. 1 . Further, it should be noted that the “proximal end” and the “distal end” may include not only the “end”, but also a peripheral portion of the “end”. 
     The safety needle assembly  10  illustrated in  FIG. 1  includes a hub  12 , a cannula  14 , a collar  16 , a protector  18 , and a sheath  20 . Note that an assembly having no protector  18  is also referred to as a “safety needle assembly  10 ”.  FIG. 6  illustrates an assembled state (described below) of the safety needle assembly  10  illustrated in  FIG. 1 . 
     The cannula  14  is connected to the hub  12  by a general method, for example, using an epoxy resin. The cannula  14  includes a proximal end  52  which is connected to a distal end  30  of the hub  12  and a distal end  54  which has a blade surface  50 . The distal end  54  includes a needle point  14   a.    
     The cannula  14  has a thickness of  18  to  24  gauge and a length L between the hub  12  and the distal end  54  of 8 to 22 mm. The length L indicates the length between the distal end  54  of the cannula  14 , that is, the needle point  14   a  and the hub  12  (refer to  FIG. 5B ). 
     The thickness of 18 to 24 gauge of the cannula is suitable for injection of a high viscosity formulation. When the thickness of the cannula falls out of this value range, defective conditions occur. Specifically, when the thickness of the cannula is larger than this value range, a range of damaging tissues is expanded. On the other hand, when the thickness of the cannula is smaller than this value range, it is difficult to inject a high viscosity formulation. Further, the length L between the hub  12  and the distal end  54  of 8 to 22 mm is suitable for subcutaneous injection performed at an angle of approximately 45° with respect to a skin surface. From the above viewpoints, the thickness of the cannula is more desirably 18 to 19 gauge, and the length L is more desirably 12 mm to 16 mm. 
     The surface of the cannula  14  is silicone-treated to form a silicone film  55  thereon. The silicone film  55  is formed within a range of 60% to 85% of the length L between the needle point  14   a  and the hub  12 . For example, when the length L is 13 mm, the silicone film  55  is formed up to a position that is 8 mm to 11 mm from the needle point  14   a.  The silicone film  55  is formed by, for example, dipping. 
     The silicone film  55  enables a patient to feel less pain during injection. As described below, the cannula  14  is locked by a guide rib  106  (refer to  FIG. 5C ). In this locking, the silicone film  55  enables the cannula  14  to be more reliably and safely locked. When the silicone film  55  is formed within the range of 60% to 85% of the length L between the hub  12  and the distal end  54  as described above, it is possible to reduce pain during injection, and more reliably and safely lock the cannula  14  inside the sheath  20  by the guide rib  106 . 
     It is preferred to mold the hub  12 , the collar  16 , the protector  18 , and the sheath  20  as one-piece parts. However, the present embodiment is not limited to this configuration. 
     The collar  16  is attached to the hub  12  at a predetermined position. The protector  18  is guided by the hub  12  and attached to at least either the collar  16  or the hub  12  to thereby cover the cannula  14 . The sheath  20  is pivotably attached to the collar  16 . These components will be described in detail below. 
     As illustrated in  FIG. 2 , the hub  12  includes the distal end  30  and a proximal end  32  which is connected to a syringe (not illustrated). A through hole  34  extends along the entire length of the hub  12  in a longitudinal direction (front-back direction) thereof. The through hole  34  is open at both the distal end  30  and the proximal end  32  of the hub  12 . The proximal end  52  of the cannula  14  illustrated in  FIG. 1  is fitted and fixed to the inside of the through hole  34  at the distal end  30  of the hub  12  by, for example, using an epoxy resin. Accordingly, a lumen extending along the entire length of the cannula  14  communicates with the through hole  34  inside the hub  12 . 
     The distal end  30  of the hub  12  includes a plurality of stepped ribs  36  extending in the longitudinal direction. The ribs  36  facilitate coaxial attachment (in a central axis c) of the collar  16  to the hub  12 . 
     An outer surface of the hub  12  includes a plurality of protrusions  38  extending outward in the radial direction from an outer circumferential surface of the hub  12 . 
     A ring-shaped recessed region  40  is located at a distal side of the protrusions  38 . Accordingly, step parts  42  and  44  which are adjacent to the ring-shaped recessed region  40  have larger outside diameters than the ring-shaped recessed region  40 . 
     The proximal end  32  of the hub  12  includes a flange  46  which projects outward in the radial direction. The flange  46  is engaged with, for example, a distal end of a syringe body (not illustrated). The engagement allows the hub  12  to be connected to the syringe body (not illustrated). This connection may be performed by a known method, for example, by engaging the flange  46  with a screw (female screw) located at the distal end of the syringe body (not illustrated). 
     As illustrated in  FIGS. 3A and 3B , the collar  16  has an outline in a ring shape, and has a proximal end  74  and a distal end  66 . The collar  16  further includes a through hole  76  for attaching the collar  16  to the hub  12 . An inside surface of the collar  16  has a plurality of protrusions  78 a projecting inward. The protrusions  78 a projecting inward are engaged with the protrusions  38  (refer to  FIG. 2 ) of the hub  12 . This engagement unrotatably fixes the collar  16  to the hub  12 . 
     The collar  16  includes a ring-shaped ridge  78   b  projecting inward on an inner surface thereof. The ring-shaped ridge  78   b  extends over the whole circumference of the inner peripheral part of the through hole  76 . When the collar  16  is attached to the hub  12 , the ring-shaped ridge  78   b  is seated onto the ring-shaped recessed region  40  (refer to  FIG. 2 ) of the hub  12 . Therefore, the ring-shaped ridge  78   b  has an inside diameter that is smaller than the outside diameters of the two step parts  42  and  44  which are directly adjacent to the ring-shaped recessed region  40  of the hub  12  and substantially equal to the outside diameter of the ring-shaped recessed region  40  of the hub  12 . The ring-shaped ridge  78   b  projecting inward in the radial direction is illustrated as a continuous ring-shaped ridge. However, the ring-shaped ridge  78   b  may be formed as a plurality of separate segments, each of which extends along a part of the inner circumference of the collar  16 . 
     The collar  16  includes a pair of ear-shaped projections  60  (sheath attachment part) projecting outward in the radial direction. Each of the projections  60  includes a circular through hole  64  which houses therein a pin  126  of the sheath  20  (described below, refer to  FIGS. 4A and 4B ), and a chamfer  62 . The chamfer  62  is formed in an upper part of the projection  60  at the inner side thereof as illustrated in  FIGS. 3A and 3B . The pin  126  of the sheath  20  passes the chamfer  62 , and is then housed in the through hole  64 . 
     That is, the pair of projections  60  enables the sheath  20  to be rotatably attached to the collar  16 . More specifically, the chamfers  62  facilitate the attachment of a pair of the pins  126  of the sheath  20  to the respective projections  60  of the collar  16 . When the pair of pins  126  is attached to the pair of projections  60 , the projections  60  slightly bend in directions away from each other. The thickness of each of the projections  60  may be appropriately determined taking into consideration the strength for resistance to damage and the flexibility for easier attachment of the sheath  20 . 
     The collar  16  includes a ring-shaped ridge  70  projecting outward in the radial direction. The ring-shaped ridge  70  is a component for seating the protector  18 . 
     The collar  16  further includes a pair of sheath fixing protrusions  68 . Each of the sheath fixing protrusions  68  has a substantially triangular shape, and is disposed at the opposite side of the projections  60 . The sheath fixing protrusion  68  further includes a groove  72  which is engaged with a wing wall  96  (cannula fixing part) (refer to  FIGS. 4A and 4B ) of the sheath  20 . 
     As illustrated in  FIG. 1 , the protector  18  is formed as a hollow member having an elongated cylindrical shape, including a distal end  80  and a proximal end  82 . Preferably, the protector  18  is open at the proximal end  82  and closed at the distal end  80 . A plurality of ribs  84  extending in the longitudinal direction are formed on the outer surface of the protector  18  in an middle part thereof so that a health care worker can easily hold the protector  18 . 
     The protector  18  is attached at the position to cover the cannula  14  to thereby cover up the distal end of the cannula  14 . At this time, the protector  18  is fixed to at least either the collar  16  or the hub  12 . The protector  18  is detachable so as to expose the distal end  54  of the cannula  14 . A seating face (not illustrated) for the collar  16  may be provided inside the protector  18  at the proximal end  82  thereof. 
     As illustrated in  FIG. 4A , the sheath  20  includes a proximal end  114  and a distal end  120 , and is formed as an elongated member in the whole body. The sheath  20  includes an opening  101  which extends along at least a part of the sheath  20  in the longitudinal direction. The opening  101  is an internal space of the sheath  20 . The cannula  14  is housed inside the opening  101 . In the present embodiment, the opening  101  of the sheath  20  extends along the entire length in the longitudinal direction of the sheath  20 . The proximal end  114  is open in the longitudinal direction of the sheath  20 , while the distal end  120  is closed in the longitudinal direction of the sheath  20 . 
     The sheath  20  includes a finger guiding part  90 , a finger guiding part  92 , and a distal part  94 , each of which includes a pair of side walls and a back wall. A circular recess  112  is formed on the back wall of the finger guiding part  90 . The circular recess  112  is used as a finger guiding region with which a finger of a user such as a health care worker operating the sheath  20  comes into contact. 
     The back wall of the finger guiding part  92  is formed as a stepped slope inclined downward toward the front side. On the slope, protrusions  116  and recesses  118  are repeatedly formed so as to increase the friction against a finger of a health care worker. 
     The back wall of the distal part  94  includes a projecting stopper  100  which prevents a finger of a health care worker pushing the sheath  20  from further moving toward the distal end  120  of the sheath  20 . The stopper  100  is formed near a central part in the longitudinal direction of the sheath  20  or at a position between the central part and the distal end  120  of the sheath  20  so that a larger moment is generated to smoothly pivot the sheath  20  when a health care worker pushes the sheath  20  with the finger. 
     The sheath  20  includes a collar connection mechanism  98  (attachment part) which has a pair of cylindrical pins  126 . The pins  126  are attached to the respective through holes  64  of the projections  60  of the collar  16  so as to rotatably connect the sheath  20  to the collar  16 . Each of the pins  126  is chamfered so as to facilitate the above connection. 
     As illustrated in  FIG. 4A , a pair of wing walls  96  is disposed at the proximal end  114  side of the finger guiding part  90 . Inside each of the wing walls  96 , a slope  122  is formed in the direction toward the proximal end  114 . The slopes  122  enables the sheath  20  to be easily attached to the collar  16  (that is, with a relatively small force). A groove  124  (cannula fixing part) which is fitted with the corresponding sheath fixing protrusion  68  of the collar  16  is formed at the front side of the wing wall  96 . When the sheath fixing protrusions  68  (refer to  FIG. 3A ) of the collar  16  are fitted with the respective grooves  124 , the wing walls  96  are expanded outward just before the fitting. 
     As illustrated in  FIG. 4B , a recess  102 , a rib  104 , and the guide rib  106  are formed in the opening  101  of the sheath  20 . The recess  102 , the rib  104 , and the guide rib  106  are arranged in this order from the finger guiding part  90  toward the distal part  94 . 
     The recess  102  holds the distal end  30  (refer to  FIG. 2 ) of the hub  12 . The rib  104  is used for maintaining a space of the opening  101  of the sheath  20 . 
     The guide rib  106  is used for holding the cannula  14  inside the sheath  20 . The guide rib  106  includes a groove  107 . A locking protrusion  108  is disposed to partially close an opening of the groove  107 . The locking protrusion  108  is bendable. The guide rib  106  is, for example, integrally molded with the rib  104 . 
       FIGS. 5A to 5C  illustrate the state in which the cannula  14  is housed and locked in the sheath  20  of the safety needle assembly  10 . 
     When the cannula  14  is inserted into the opening  101  so as to be housed in the sheath  20 , the locking protrusion  108  of the guide rib  106  is bent, which allows the cannula  14  to enter the groove  107  of the guide rib  106 . At this time, since the silicone film  55  is formed on the cannula  14 , the resistance against the locking protrusion  108  is small. Thus, the cannula  14  can smoothly enter the groove  107 . As illustrated in  FIG. 5C , after the cannula  14  has passed the locking protrusion  108 , the guide rib  106  holds the cannula  14  by the locking protrusion  108  and permanently locks the cannula  14  inside the opening  101 . This locking automatically occurs when the cannula  14  passes the locking protrusion  108  of the guide rib  106  and enters the groove  107 . That is, this permanent locking of the cannula  14  inside the sheath  20  can be achieved merely by allowing the cannula  14  to move into the opening  101  of the sheath  20  and enter the groove  107  of the guide rib  106 . The groove  107  plays a role of positioning the cannula  14  in the right-left direction thereof when the cannula  14  is introduced into the opening  101 . In this case, the distal end  30  of the hub  12  is held in the recess  102 . 
     The cannula  14  is locked inside the sheath  20  by the locking protrusion  108 . In this case, when, in a side view of  FIG. 5B , an angle between a line C 1  passing through an end face  101   a  of the opening  101  of the sheath  20  and a line C 2  passing through the surface of the cannula  14  is denoted by θ, the cannula  14  can be locked with an angle θ of 0° or more with respect to a direction of housing the cannula into the sheath. As the angle θ increases, the cannula  14  is tilted toward the inside of the opening  101 , and the tip of the cannula  14  is located at the deeper side inside the opening  101 . Thus, the cannula  14  can be more reliably housed inside the opening  101 . A value of the angle θ is appropriately set in accordance with the length of the cannula  14  and the shape of the inside of the sheath  20  within a range that prevents the tip of the cannula  14  from coming out of the internal space (cannula housing space) of the sheath  20  and from abutting against the inner surface of the sheath  20  or the rib  104 . The range of the angle θ is desirably 0°≦θ≦4.4°. More preferably, the range of the angle θ is desirably 0.19°≦θ≦4.4°. 
     The cannula  14  having a thickness of  18  gauge to  24  gauge and a length L of 8 to 22 mm can be reliably locked by the guide rib  106  by increasing a distance D between the cannula  14  and the rib  104  illustrated in  FIG. 5C . 
     As described above, the silicone film  55  is formed on the cannula  14 . Thus, when the cannula  14  comes into contact with the locking protrusion  108  and enters the groove  107 , it is possible to reduce the resistance of the cannula  14 , and more reliably and safely lock the cannula  14  inside the sheath  20 . 
     The components described above are arranged as illustrated in  FIG. 1  and assembled to obtain the safety needle assembly  10  illustrated in  FIG. 6 . The assembled safety needle assembly  10  illustrated in  FIG. 6  may be packaged in a blister packaging or the like in the state illustrated in  FIG. 6 , or may be packaged after connected to a syringe (not illustrated). 
     Next, a method for using the safety needle assembly  10  will be described with reference to  FIGS. 6 to 8 . 
     As illustrated in  FIG. 6 , in the safety needle assembly  10 , the protector  18  is attached to the cannula  14  (not illustrated in  FIG. 6 ). When the safety needle assembly  10  is used in subcutaneous injection of a high viscosity formulation, a health care worker detaches the protector  18  to expose the cannula  14 . Thus, the health care worker first pivots the sheath  20  in a direction R L  so as to be apart from the protector  18 . 
     After the sheath  20  is pivoted, the health care worker removes the protector  18  to expose the cannula  14  as illustrated in  FIG. 7 . In this state of the safety needle assembly  10  illustrated in  FIG. 7 , the health care worker can use the cannula  14 , for example, for subcutaneously injecting a high viscosity formulation to a patient. In this case, the silicone film  55  enables the patient to feel less pain during the injection. 
     After finishing the use of the cannula  14 , the health care worker first pivots the sheath  20  in a direction Rc toward the cannula  14  so that the safety needle assembly  10  becomes a state illustrated in  FIG. 8  to house the cannula  14  inside the sheath  20 . 
     Then, the health care worker pushes the back wall of the finger guiding part  92  (refer to  FIG. 4A ) with a finger against the sheath  20 . This allows the sheath  20  to further pivot toward the cannula  14 . The cannula  14  bends the locking protrusion  108  of the guide rib  106  and enters the groove  107 . Accordingly, the cannula  14  is locked by the locking protrusion  108  (refer to  FIG. 5C ). At this time, the distal end  30  of the hub  12  is held in the recess  102  (refer to  FIG. 5B ). Further, the sheath fixing protrusions  68  of the collar  16  are engaged with the respective grooves  124  of the sheath  20 . Accordingly, the cannula  14  is locked with respect to the sheath  20  (refer to  FIG. 5A ). That is, at this time, the cannula  14  is covered with the sheath  20 , and further locked inside the sheath  20 . 
     As described above, in the safety needle assembly  10  in the present embodiment, the cannula  14  is covered with the sheath  20  and locked by the guide rib  106 . Thus, it is possible to prevent a sting accident such that a health care worker erroneously sticks the cannula  14  into the body after using the cannula  14  and thus obtain a high safety. The guide rib  106  is easily integrally molded with the rib  104 . Thus, the fixing part of the cannula  14  can be achieved at a low cost. 
     Further, a high operability can be achieved due to the structure of the sheath  20  which has the projecting stopper  100  (refer to  FIG. 4A ) near the central part in the longitudinal direction of the sheath  20  or at the position between the central part and the distal end of the sheath  20 . In other words, the above positioning of the stopper  100  enables a health care worker to push the sheath  20  with a finger at a position away from the fulcrum (the position of the pins  126  of the sheath  20 ), resulting in generation of a larger moment which enables the sheath  20  to be pivoted with a relatively smaller force. 
     Further, the pair of wing walls  96  (refer to  FIG. 4B ) each having the groove  124  (refer to  FIG. 4B ) and the slope  122  (refer to  FIG. 4B ) in the sheath  20  enables a high operability to be achieved. That is, the wing walls  96  projecting from the body of the sheath  20  are easily bent outward, and the slopes  122  facilitate introduction of the sheath fixing protrusions  68  (refer to  FIG. 3A ) of the collar  16  into the grooves  124 . Further, the sheath fixing protrusions  68  can be fixed by the grooves  124 . These configurations enable the sheath fixing protrusions  68  of the collar  16  to be fitted and fixed to the grooves  124  of the wing walls  96  of the sheath  20  with a relatively small force when a user such as a health care worker pushes the sheath  20  with a finger. 
     Further, a health care worker can push the sheath  20  not only at the slope provided with the plurality of protrusions  116  (refer to  FIG. 4A ) and recesses  118  (refer to  FIG. 4A ) having a large friction, but also at the circular recess  112  (refer to  FIG. 4A ) to which the finger easily fits. Accordingly, a high operability can be achieved. 
     Further, the projections  60  (refer to  FIG. 3A ) of the collar  16  (refer to  FIG. 3A ) have the chamfers  62  (refer to  FIG. 3A ) inside thereof. The sheath  20  is attached to the collar  16  through the chamfers  62 , which results in a relatively small force required for the attachment. 
     Further, each of the sheath fixing protrusions  68  (refer to  FIG. 3A ) of the collar  16  can be achieved with a simple structure that is formed in a substantially triangle having the groove  72 . 
     For example, if there are a plurality of cannulas  14  having different lengths, different sheaths  20  corresponding to the respective lengths may be used. 
     The present invention is essentially configured in the above manner. Hereinabove, an embodiment of the safety needle assembly of the present invention has been described in detail. However, the present invention is not limited to the above embodiment. It is needless to say that various improvements and modifications may be made without departing from the scope of the invention. 
     REFERENCE SIGNS LIST 
     
         
           10  safety needle assembly 
           12  hub 
           14  cannula 
           16  collar 
           18  protector 
           20  sheath 
           104  rib 
           106  guide rib 
           107  groove