Patent Publication Number: US-2011060286-A1

Title: Indwelling needle assembly

Description:
TECHNICAL FIELD 
     The present invention relates to an indwelling needle assembly to puncture and indwell in a blood vessel at the time of infusion, for example. 
     BACKGROUND ART 
     At the time of carrying out an infusion on a patient or in other similar situations, an indwelling needle connected with an infusion line is made to puncture a blood vessel of the patient and is kept indwelling there during infusion. 
     Such an indwelling needle (indwelling needle assembly) is composed of a hollow outer needle, an outer needle hub secured to the proximal end (base end) of the outer needle, an inner needle which is inserted into the outer needle and which has a sharp needle tip at its distal end, an inner needle hub secured to the proximal end (base end) of the inner needle, and a protector detachably connected to the outer needle hub. The outer needle hub is provided with a main pipe having a flow path communicating with a lumen of the outer needle and a side pipe having a branch flow path branched from the flow path in the main pipe, and the infusion line is connected to the side pipe. (See, for example, Patent Document 1.) 
     When the indwelling needle punctures the patient&#39;s blood vessel, the puncturing operation is performed in the condition where the inner needle is inserted into the outer needle and the needle tip of the inner needle protrudes from the distal end of the outer needle in an assembled state. 
     When the needle tip of the inner needle has reached the inside of the blood vessel, blood flows into the inner needle through a distal portion thereof. The blood, in its course, flows through a hole formed in a side portion of the inner needle into a flow path between the outer needle and the inner needle, flows through the flow path, then flows into the inside of the transparent outer needle hub, specifically, into the flow path in the main pipe, and further flows through the main pipe into the branch flow path in the side pipe (flashback). Consequently, it can be confirmed (visually confirmed) that the inner needle has captured (reached securely the inside of) the blood vessel. 
     After this flashback is confirmed, the outer needle is advanced using the inner needle as a guide, and the outer needle is inserted into (let puncture) the blood vessel. 
     Next, while fixing the outer needle and the outer needle hub by grasping them with one hand, the inner needle hub is grasped with the other hand and moved in the proximal direction, whereby the inner needle is pulled out of the outer needle. Then, an infusion agent is administered through the infusion line, the side pipe and the main pipe of the outer needle hub, and the outer needle which are connected to one another. 
     Meanwhile, as shown in  FIG. 15 , an outer needle hub  300  is provided with a rib  330  at its proximal portion (an end portion on the right side in  FIG. 15 ). 
     On the other hand, the protector is equipped with a V-shaped spring  920  which has a projecting piece  9240  engageable with the rib  330  of the outer needle hub  300  (see  FIG. 6 ). Incidentally, in  FIG. 15 , of the spring  920 , only a part inclusive of the projecting piece  9240  is shown. By the engagement of the projecting piece  9240  of the spring  920  with the rib  330  of the outer needle hub  300 , the protector is detachably connected to the outer needle hub  300 . 
     In addition, the spring  920  makes contact with an outer peripheral surface of the inner needle in the condition where the projecting piece  9240  thereof is engaged with the rib  330  of the outer needle hub  300  through elastic deformation thereof, whereby the engaged state is maintained. When the inner needle is pulled out of the outer needle, the spring  920  is restored by parting from the outer peripheral surface of the inner needle, and, at the time of the restoration of the spring  920 , the projecting piece  9240  is moved toward the lower side in  FIG. 15  relative to the rib  330 , whereby the projecting piece  9240  and the rib  330  are disengaged from each other. 
     However, respective opposed surfaces of the projecting piece  9240  of the spring  920  and the rib  330  of the outer needle hub  300  are substantially perpendicular to the center axis O 1  of the inner needle. Before the projecting piece  9240  and the rib  330  are disengaged, the spring  920  (protector) is pulled in the proximal direction by way of a connection member interconnecting the inner needle hub and the protector. Therefore, the projecting piece  9240  of the spring  920  is difficult to move toward the lower side in  FIG. 15 , and would be caught on the rib  330 , resulting in an increase in resistance. 
     In short, in the conventional indwelling needle assembly as above-mentioned, there is a problem that when the inner needle hub is moved in the proximal direction so as to pull the inner needle hub out of the outer needle and to release the protector from the outer needle hub  300 , at the final stage of the operation the projecting piece  9240  would be caught on the rib  330 , thereby abruptly increasing the resistance to the movement, namely, resulting in the load in the operation. This makes it necessary to abruptly increase the force for moving the inner needle hub in the proximal direction. Consequently, the outer needle hub might be moved in the proximal direction and the outer needle might be pulled out of the blood vessel, unless the outer needle hub is securely fixed. 
     Patent Document 1: U.S. Pat. No. 6,749,588 
     DISCLOSURE OF INVENTION 
     It is an object of the present invention to provide an indwelling needle assembly such that a protector can be smoothly released from an outer needle hub. 
     In order to attain the above object, the present invention provides an indwelling needle assembly including: 
     an inner needle having a sharp needle tip at a distal end; 
     an inner needle hub secured to a proximal portion of the inner needle; 
     a hollow outer needle into which the inner needle is inserted; 
     an outer needle hub which is secured to a proximal portion of the outer needle and which has a projection at a proximal portion thereof; and 
     a protector which has an elastic connection member with a projecting part engageable with the projection, and which is detachably connected to the outer needle hub by engagement of the projecting part with the projection, wherein 
     the projection of the outer needle hub includes a sliding surface which is tilted relative to an axis of the inner needle and on which the projecting part is slidingly moved, and 
     the connection member takes a first state in which the projecting part is engaged with the projection and a second state in which the projecting part is disengaged from the projection, and, when the connection member is changed from the first state to the second state, the projecting part is slidingly moved along the sliding surface of the projection. 
     According to the present invention as above, at the time of pulling the inner needle out of the outer needle and releasing the protector from the outer needle hub, the projecting part of the connection member of the protector is slidingly moved along the sliding surface of the projection of the outer needle hub, whereby resistance can be reduced. This ensures that the operation of pulling the inner needle out of the outer needle and releasing the protector from the outer needle hub can be carried out smoothly and assuredly. 
     In addition, in the indwelling needle assembly of the present invention, preferably, the connection member is held in the first state in a state of being elastically deformed by making contact with an outer peripheral surface of the inner needle, the connection member is restored by parting from the outer peripheral surface of the inner needle when the inner needle is pulled out of the outer needle, and, when the connection member is restored, the projecting part is slidingly moved along the sliding surface of the projection, resulting in the second state. 
     This ensures that at the time of pulling the inner needle out of the outer needle and releasing the protector from the outer needle hub, the resistance (resistance to release) can be reduced. Consequently, the operation of pulling the inner needle out of the outer needle and releasing the protector from the outer needle hub can be performed smoothly and assuredly. 
     Further, in the indwelling needle assembly of the present invention, preferably, 
     a direction in which the projecting part is moved by restoration of the connection member is a direction substantially perpendicular to the axis of the inner needle; and 
     when the inner needle is pulled out of the outer needle, the protector is moved in a proximal direction, whereby the projecting part is slidingly moved along the sliding surface of the projection. 
     This ensures that at the time of pulling the inner needle out of the outer needle and releasing the protector from the outer needle hub, the resistance (resistance to release) can be reduced. As a result, the operation of pulling the inner needle out of the outer needle and releasing the protector from the outer needle hub can be carried out smoothly and assuredly. 
     In addition, in the indwelling needle assembly of the present invention, preferably, the projection is formed at an outer peripheral surface of the outer needle hub along a circumferential direction of the outer needle hub. 
     This ensures that at the time of pulling the inner needle out of the outer needle and releasing the protector from the outer needle hub, the resistance (resistance to release) can be reduced. Accordingly, the operation of pulling the inner needle out of the outer needle and releasing the protector from the outer needle hub can be performed smoothly and assuredly. 
     Further, in the indwelling needle assembly of the present invention, preferably, the tilt angle θ of the sliding surface of the projection relative to the axis of the inner needle is 30° to 85°. 
     This ensures that the area (area of contact) of the region of contact between the projecting part and the sliding surface of the projection is small, and, therefore, the frictional resistance (sliding resistance) between the projecting part and the sliding surface of the projection is also small. Consequently, the projecting part can be slid (moved) along the sliding surface of the projection more smoothly. 
     In addition, in the indwelling needle assembly of the present invention, preferably, a height of the projection gradually decreases along a direction in which the projecting part is slidingly moved along the sliding surface of the projection. 
     This ensures that the connection member can be brought into the second state more smoothly and assuredly. 
     Further, in the indwelling needle assembly of the present invention, preferably, an opposed surface of the projecting part to the sliding surface of the projection is tilted relative to the axis of the inner needle. 
     This ensures that at the time of pulling the inner needle out of the outer needle and releasing the protector from the outer needle hub, the resistance generated between the projecting part and the projection can be reduced securely. Consequently, the pulling-out and releasing operation can be carried out more smoothly and assuredly. 
     In addition, in the indwelling needle assembly of the present invention, preferably, a tilt angle of the opposed surface of the projecting part relative to the axis of the inner needle is different from a tilt angle of the sliding surface of the projection relative to the axis of the inner needle. 
     This ensures that at the time of pulling the inner needle out of the outer needle and releasing the protector from the outer needle hub, the resistance generated between the projecting part and the projection can be reduced assuredly. Therefore, the pulling-out and releasing operation can be performed more easily and assuredly. 
     Further, the indwelling needle assembly of the present invention, preferably, further includes connection means for connecting the inner needle or the inner needle hub with the protector, wherein 
     when the inner needle is pulled out of the outer needle, the inner needle hub is moved in a proximal direction, whereby the protector is moved in the proximal direction so as to be released from the outer needle hub. 
     This ensures that the protector is securely prevented from slipping off the needle tip of the inner needle, and, therefore, it is possible to securely maintain the condition where the needle tip is covered by the protector. Consequently, at the time of discarding the inner needle or the like or in other similar situations, the accident that the worker or the like might stick his or her finger or the like with the needle tip by mistake can be securely prevented, and high safety is ensured. 
     In addition, in the indwelling needle assembly of the present invention, preferably, the protector covers at least the needle tip of the inner needle when the inner needle has been pulled out of the outer needle. 
     This ensures that at the time of discarding the inner needle or the like or in other similar situations, the accident that the worker or the like might stick his or her finger or the like with the needle tip can be securely prevented, and high safety is promised. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view showing a first embodiment of the indwelling needle assembly according to the present invention; 
         FIG. 2  is an exploded perspective view of the indwelling needle assembly shown in  FIG. 1 ; 
         FIG. 3  is a sectional view showing an outer needle hub, an inner needle, an inner needle hub, a protector, etc. of the indwelling needle assembly shown in  FIG. 1 ; 
         FIG. 4  is a sectional view taken along line A-A of  FIG. 3 ; 
         FIG. 5  is a sectional view showing the outer needle hub, the inner needle, the inner needle hub, the protector, etc. of the indwelling needle assembly shown in  FIG. 1 ; 
         FIG. 6  is a perspective view showing a connection member of the protector of the indwelling needle assembly shown in  FIG. 1 ; 
         FIG. 7  is a bottom view showing schematically the outer needle hub and the connection member of the protector in the indwelling needle assembly shown in  FIG. 1 ; 
         FIG. 8  is a bottom view showing schematically the outer needle hub and the connection member of the protector in the indwelling needle assembly shown in  FIG. 1 ; 
         FIG. 9  is a bottom view showing schematically an outer needle hub and a connection member of a protector in a second embodiment of the indwelling needle assembly according to the present invention; 
         FIG. 10  is an exploded perspective view showing a third embodiment of the indwelling needle assembly according to the present invention; 
         FIG. 11  is a sectional view showing an outer needle hub, an inner needle, a protector, etc. of the indwelling needle assembly shown in  FIG. 10 ; 
         FIG. 12  is a sectional view showing the outer needle hub, the inner needle, the protector, etc. of the indwelling needle assembly shown in  FIG. 10 ; 
         FIG. 13  is a perspective view showing a connection member of the protector in the indwelling needle assembly shown in  FIG. 10 ; 
         FIG. 14  is a perspective view showing a shutter member of the protector in the indwelling needle assembly shown in  FIG. 10 ; and 
         FIG. 15  is a bottom view showing schematically an outer needle hub and a connection member of a protector in a conventional indwelling needle assembly. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     The indwelling needle assembly according to the present invention will be described in detail below, based on preferred embodiments shown in the accompanying drawings. 
     First Embodiment 
       FIG. 1  is a perspective view showing a first embodiment of the indwelling needle assembly according to the present invention;  FIG. 2  is an exploded perspective view of the indwelling needle assembly shown in  FIG. 1 ;  FIG. 3  is a sectional view showing an outer needle hub, an inner needle, an inner needle hub, a protector, etc. of the indwelling needle assembly shown in  FIG. 1 ;  FIG. 4  is a sectional view taken along line A-A of  FIG. 3 ;  FIG. 5  is a sectional view showing the outer needle hub, the inner needle, the inner needle hub, the protector, etc. of the indwelling needle assembly shown in  FIG. 1 ;  FIG. 6  is a perspective view showing a connection member of the protector of the indwelling needle assembly shown in  FIG. 1 ; and  FIGS. 7 and 8  are each bottom views showing schematically the outer needle hub and the connection member of the protector in the indwelling needle assembly shown in  FIG. 1 . 
     Incidentally, in the following, the left side in  FIGS. 2 ,  3  and  5  will be referred to as a “proximal” side and the right side as a “distal” side. In addition, the right side in  FIGS. 7 and 8  will be referred to as a “proximal” side and the left side as a “distal” side. Further, in  FIGS. 7  and  8 , of the connection member of the protector, only a first part and a projecting piece are drawn. 
     An indwelling needle assembly  1  shown in the drawings includes a hollow outer needle  2 , an outer needle hub  3  secured to a proximal portion of the outer needle  2 , an inner needle  4  inserted into the outer needle  2 , an inner needle hub  5  secured to a proximal portion of the inner needle  4 , and a tube  7  connected to a side portion (or a proximal portion) of the outer needle hub  3  so that its lumen  71  communicates with a lumen  21  of the outer needle  2 . Configurations of the parts will be described below. 
     As the outer needle  2 , one having a certain degree of flexibility is preferably used. The material constituting the outer needle  2  is preferably a resin material, particularly a flexible resin material. Examples of the material include fluoro-resins such as PTFE, ETFE, PFA, etc., olefin resins such as polyethylene, polypropylene, etc. and mixtures thereof, polyurethane, polyesters, polyamides, polyether nylon resins, and mixtures of the olefin resins with ethylene-vinyl acetate copolymer. 
     The outer needle  2  as above-mentioned may, wholly or partly, have inside visibility. Further, the material constituting the outer needle  2  may be admixed with a radiopaque material such as barium sulfate, barium carbonate, bismuth carbonate, tungstic acid, etc. so as to be radiopaque. 
     The outer needle hub  3  is secured (fixed) to the proximal portion of the outer needle  2  in a liquid-tight fashion by such a method as caulking, fusing (heat fusing, microwave fusing, etc.), adhesion with an adhesive, etc. 
     The outer needle hub  3  has a substantially tubular main pipe  36 , and a side pipe (branch pipe)  37  which has a branch flow path  32  branched from a flow path  31  in the main pipe  36  and which is substantially tubular. 
     As has been described above, a proximal portion of the outer needle  2  is secured to the distal side of the main pipe  36 , and the flow path  31  communicates with the lumen  21  of the outer needle  2  on its distal side. The flow path  31  (main pipe  36 ) is disposed such that its axis (center axis) substantially coincides with the center axis of the outer needle  2 . 
     On the other hand, the branch flow path  32  (side pipe  37 ) is disposed such that its axis (center axis) is inclined at a predetermined angle relative to the center axis of the outer needle  2 , that is, the axis of the flow path  31  (main pipe  36 ). In this case, the branch flow path  32  is so inclined that the proximal side of the branch flow path  32  is located on the left side in  FIG. 2 . Incidentally, the axis of the branch flow path  32  (side pipe  37 ) may be perpendicular to the axis of the flow path  31  (main pipe  36 ) (may be non-inclined). 
     In addition, a distal portion (one end portion) of the tube  7  is connected to the side pipe  37  of the outer needle hub  3 . This ensures that a liquid such as a medicinal liquid (infusion liquid) can be supplied into the outer needle  2  (outer needle hub  3 ) by way of the tube  7 . 
     Further, the outer needle hub  3  is formed with a rib  33  at a proximal portion thereof. The rib  33  will be detailed later. 
     In addition, on lateral sides of the outer needle hub  3 , a pair of wings  12   a  and  12   b  are formed integrally with the outer needle hub  3 . At the time of causing the outer needle  2  and the inner needle  4  to puncture a blood vessel or the like, puncturing is conducted by pinching the inner needle hub  5  by a thumb and a middle finger, and, when the distal end of the outer needle  2  has reached the inside of the blood vessel, a finger holder part  916  which will be described later is pushed by an index finger to advance the outer needle hub  3 , whereby only the outer needle  2  can be advanced into the blood vessel. At the time of leaving the outer needle  2  indwelling, the wings  12   a  and  12   b  are fixed to a skin by a pressure sensitive adhesive tape or the like. 
     The inner needle  4  having a sharp needle tip  41  at the distal end thereof is inserted into the outer needle  2 . The indwelling needle assembly  1  is used in the state wherein the inner needle  4  is inserted into the outer needle  2  and the needle tip  41  is protruded from a tip opening  22  of the outer needle  2 , that is, in the state as shown in  FIGS. 1 ,  3 ,  4  and  7 . Hereinafter, this state will be referred to as the “assembled state.” 
     The length of the inner needle  4  is set such that at least the needle tip  41  protrudes from the tip opening  22  of the outer needle  2  in the assembled state. 
     The inner needle  4  may be a hollow needle or may be a solid needle. Where the inner needle  4  is a solid needle, a sufficient strength can be secured while letting the outside diameter small. In addition, where the inner needle  4  is a solid needle, it is ensured that at the time of discarding the inner needle  4  after an operation is over, there is no risk that blood might remain inside the inner needle  4  or the blood might flow out, and, therefore, high safety is secured. 
     Further, where the inner needle  4  is a hollow needle, upon puncture of a blood vessel by the inner needle  4 , blood flows into the hollow portion of the inner needle  4 , permitting flashback of blood to be confirmed. Where the inner needle  4  is a solid needle, the flashback of blood can be confirmed earlier, since the blood flows into a gap between the inner needle  4  and the outer needle  2 . 
     In the configurations shown in the drawings, the inner needle  4  is a hollow needle, and is formed with a hole (side hole) (not shown) in a side portion of an intermediate part thereof. This ensures that upon puncture of a blood vessel by the inner needle  4 , blood flows into the hollow portion of the inner needle  4 , and the blood, in its course, flows through the hole formed in the side portion of the inner needle  4  into the gap between the inner needle  4  and the outer needle  2 , whereby the flashback of blood can be confirmed earlier. 
     Incidentally, while the inner needle  4  can have a configuration in which both a hollow portion and a solid portion are present (for example, a configuration in which a part of the lumen of a hollow needle is filled up so that the needle is hollow on the distal side and solid on the proximal side), composing the inner needle  4  wholly of a single member promises a reduction in the cost of the inner needle  4 . 
     In addition, the inner needle  4  may be constant in outside diameter, or may have a plurality of parts differing in outside diameter. 
     The material constituting the inner needle  4  as described above may be a metallic material such as, for example, stainless steel, aluminum or aluminum alloys, titanium or titanium alloys, etc. 
     The inner needle hub  5  is secured (fixed) to a proximal portion of the inner needle  4 . The inner needle hub  5  is provided with a protector insertion section (connection member containing section)  51  at its distal portion. In the protector insertion section  51 , a proximal portion of a protector  9  to be described later is inserted (disposed) and a connection member  20  to be described later is contained (disposed), in the assembled state. The protector  9  and the connection member  20  can each be moved relative to the protector insertion section  51 . 
     Examples of the method for fixing the inner needle  4  to the inner needle hub  5  include such methods as fitting, caulking, fusing, adhesion with an adhesive, etc. and combinations of some of these methods. Incidentally, in the configuration shown in the figures, the inner needle  4  is hollow, and, therefore, a proximal portion of the inner needle hub  5  is sealed so that the blood flowing back upon puncture of a blood vessel would not fly out from the proximal portion of the inner needle hub  5 . 
     The inner needle hub  5  as just-mentioned and the outer needle hub  3  described above are each preferably formed from a transparent (colorless transparent), colored transparent or semi-transparent resin, whereby inside visibility is secured. This ensures that when the outer needle  2  has captured (has reached the inside of) a blood vessel, flashback of the blood flowing in through the inner needle  4  mentioned above can be visually confirmed. 
     Materials constituting the outer needle hub  3 , the inner needle hub  5 , and the wings  12   a  and  12   b  are not particularly limited. Examples of the materials include various resin materials such as polyolefins such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, etc., polyurethane, polyamides, polyesters, polycarbonate, polybutadiene, polyvinyl chloride, polyacetal, etc. 
     The tube  7  is flexible, and its distal (end) portion is connected to the side pipe  37  of the outer needle hub  3 , as above-mentioned. A connector  72  is attached to a proximal portion (other end portion) of the tube  7 . The connector  72  is connected with, for example, a connector attached to an end portion of an infusion line for supplying an infusion liquid (medicinal liquid) to be administered, a mouth portion (tip portion) of a syringe in which a medicinal liquid is contained, or the like. 
     Incidentally, the material constituting the tube  7  is not particularly limited; examples of the material include polyolefins such as polyethylene, polypropylene, ethylenevinyl acetate copolymer, etc., polyvinyl chloride, polybutadiene, polyamides, polyurethane, polyesters, etc. 
     In addition, the indwelling needle assembly  1  is provided with a cylindrical (block-shaped) seal member (not shown) as sealing means for sealing the flow path  31 , in the flow path  31  of the outer needle hub  3 . The seal member is disposed (fixed) in the flow path  31  of the main pipe  36  on the proximal side relative to the branch flow path  32 . In this embodiment, the seal member is disposed in the vicinity of the branch flow path  32 . 
     The seal member is formed with a hole or slit into which the inner needle  4  can be inserted and which is closed when the inner needle  4  inserted thereinto is pulled out. In this embodiment, the seal member is provided with a slit (not shown) piercing the seal member along the longitudinal direction thereof, substantially in its center. 
     The slit is in the shape of a straight line segment. This permits the slit in a closed state to be easily brought into an open state. Therefore, the inner needle  4  can be smoothly inserted through the seal member (slit); specifically, at the time of advancing the outer needle  2  using the inner needle  4  as a guide as will be described later, frictional resistance between an outer surface of the inner needle  4  and an inner surface of the slit can be reduced. Accordingly, operability at the time of a puncturing operation of the indwelling needle assembly  1  is enhanced more. 
     The seal member has a self-closing property such that the inner needle  4  can be inserted into the slit in the assembled state and, when the inner needle  4  thus inserted is pulled out, the slit is closed by an elastic force (restoring force) of the seal member itself. This ensures that when the inner needle  4  is pulled out, leakage of liquid from the proximal end of the outer needle hub  3  can be prevented, and asepsis of the inside of the outer needle hub  3  can be maintained. 
     Examples of the material constituting the seal member as described above include various elastic materials such as various rubber materials (particularly, vulcanized ones) such as natural rubber, isoprene rubber, butyl rubber, butadiene rubber, styrene-butadiene rubber, urethane rubber, nitrile rubber, acrylic rubber, fluoro-rubber, silicone rubber, etc., various thermoplastic elastomers based on urethane, polyester, polyamide, olefin, styrene or the like, and mixtures thereof. 
     Further, the indwelling needle assembly  1 , preferably, has been subjected to a friction reducing treatment for reducing the frictional resistance between the inner surface of the slit and the outer surface of the inner needle  4 . 
     Examples of the friction reducing treatment include a treatment in which a lubricant is applied to at least one of the inner surface of the slit and the outer surface (outer peripheral surface) of the inner needle  4 , and a treatment in which a layer composed of a low-friction material (low-friction layer) is formed on the inner surface of the slit. 
     Such a friction reducing treatment enables an assured reduction in the frictional resistance between the inner needle  4  and the seal member when the outer needle  2  is advanced using the inner needle  4  as a guide. This ensures that the outer needle  2  can be moved smoothly, and the indwelling needle assembly  1  is made to be excellent in operability at the time of a puncturing operation. 
     In addition, the indwelling needle assembly  1  has the protector  9  which covers at least the needle tip  41  of the inner needle  4  when the inner needle  4  has been pulled out of the outer needle  2 . The protector  9  will be described below. 
     The protector  9  is inserted (disposed) in the protector insertion section  51  of the inner needle hub  5  in the assembled state. 
     The protector  9  is detachably connected to the outer needle hub  3 . As shown in  FIGS. 2 ,  3  and  5 , the protector  9  has a protector body  91  and a connection member  92  provided inside the protector body  91 . 
     The protector body  91  is provided with a bottomed hole  911  in its distal portion. Into the bottomed hole  911 , a proximal portion of the outer needle hub  3  is inserted in the assembled state. 
     The material constituting the protector body  91  is not particularly limited; for example, materials identical or similar to those mentioned above as materials for the outer needle hub  3  and the inner needle hub  5  can be used. 
     Further, in the hole  911  in the protector body  91 , the connection member  92  is contained on the proximal side. Specifically, the protector body  91  is formed with a wall section  912  constituting a bottom wall of the hole  911 , and a wall section  913  disposed on the proximal side of the wall section  912 , with the connection member  92  being disposed between the wall section  912  and the wall section  913 . 
     As shown in  FIGS. 3 ,  5  and  6 , the connection member  92  has a plate-like projecting piece (projecting part)  924  which is elastic and which is engageable with the rib  33  of the outer needle hub  3 . In the assembled state, the protector  9  is detachably connected to the outer needle hub  3  by the engagement of the projecting piece  924  of the connection member  92  with the rib  33  of the outer needle hub  3  in the condition where a proximal portion of the outer needle hub  3  is inserted into the hole  911  of the protector  9 . 
     In this embodiment, the connection member  92  is a member (plate spring) which is substantially V-shaped in general shape and which is formed by bending an elastic belt-like plate member into the substantially V shape (being elastically deformable). Specifically, the connection member  92  includes a first part  921 , a second part  922  which is connected to the upper side in  FIG. 6  of the first part  921  and which forms the substantially V shape together with the first part  921 , a third part  923  disposed on the lower side in  FIG. 6  of the first part  921 , the projecting piece  924  projecting toward the upper side in  FIG. 6  from the proximal end of the third part  923 , and a shutter part  925  disposed at an intermediate portion of the first part  921  and on the proximal side. In addition, a portion of the second part  922  which is on the lower side in  FIG. 6  is curved or bent toward the upper side. Further, an opposed surface  926  of the projecting piece  924  opposed to a sliding surface  331  of the rib  33  to be described later is substantially perpendicular to the center axis O 1  of the inner needle  4 . 
     The connection member  92  can take (can be deformed into) a first state (first shape) in which the projecting piece  924  and the rib  33  are engaged with each other and a second state (second shape) in which the projecting piece  924  and the rib  33  are disengaged from each other, through a change in the opening angle between (mutual opening/closing of) the first part  921  and the second part  922 . 
     Specifically, in the assembled state, as shown in  FIGS. 3 ,  4  and  7 , the connection member  92  is contained in the state of being folded to reduce the opening angle (in an elastically deformed state), and the first part  921  makes contact with an outer peripheral surface of the inner needle  4 , whereby the connection member  92  is held in the first state. In this state, the protector  9  is connected to the outer needle hub  3 . In addition, the protector  9  and the outer needle hub  3  are movable relative to the inner needle  4  and the inner needle hub  5  along the longitudinal direction of the inner needle  4 . 
     When, starting from this state, the inner needle hub  5  is moved in the proximal direction relative to the protector  9  and the needle tip  41  of the inner needle  4  reaches the proximal side of the first part  921  of the connection member  92 , the connection member  92  is opened (restored) by its own elastic force (restoring force), and is moved by being pulled in the proximal direction through the connection member  20  (described later), resulting in the second state, as shown in  FIGS. 5 and 8 . The direction in which the projecting piece  924  is moved by the restoring of the connection member  92  is a direction substantially perpendicular to the center axis O 1  of the inner needle  4 . In this state, the protector  9  and the outer needle hub  3  are disconnected. In addition, the shutter part  925  of the connection member  92  is located on the distal side of the needle tip  41  on the center axis O 1  of the inner needle  4 , whereby the needle tip  41  is inhibited from moving (passing) in the distal direction past (beyond) the connection member  92 . Incidentally, when the inner needle hub  5  is moved further in the proximal direction, the protector  9  is moved by being pulled in the proximal direction through the connection member  20  (described later), thereby being released from the outer needle hub  3 . 
     The material constituting the connection member  92  is not particularly limited. Examples of the material which can be used here include various resin materials identical or similar to those mentioned above as materials for the outer needle hub  3  and the inner needle hub  5 , and various metallic materials such as, for example, stainless steel, aluminum or aluminum alloys, titanium or titanium alloys, copper or copper alloys, etc. 
     Incidentally, a part of the connection member  92  may be secured to the protector body  91  by such a method as caulking, embedding, fusing, adhesion with an adhesive, etc. Further, the connection member  92  is not limited to the configuration shown in the drawings but may have other shapes or configurations. 
     In addition, at a distal portion of the protector body  91 , the finger holder part (tab)  916  is projectingly formed (is provided). The protector body  91  and the finger holder part  916  are formed integrally with each other. Further, the finger holder part  916  is projecting upward. With the finger holder part  916  pushed in the distal direction by a finger, the outer needle  2  can be moved in the distal direction relative to the inner needle  4 . 
     Incidentally, the protector body  91  and the finger holder part  916  may be formed as separate members and they may be joined to each other. In this case, the material constituting the finger holder part  916  is not particularly limited; for example, materials identical or similar to those mentioned above as materials for the outer needle hub  3  and the inner needle hub  5  can be used. In addition, the finger holder part  916  may be projectingly formed on other part (member), for instance, the outer needle hub  3 . 
     Further, as shown in  FIGS. 2 ,  3  and  5 , the indwelling needle assembly  1  has the connection member  20  which has both a function of slip-off preventive means for preventing the protector  9  from slipping off the needle tip  41  of the inner needle  4  when the needle tip  41  is covered by the protector  9  and a function of connection means for connecting the protector  9  with the inner needle hub  5 . 
     The connection member  20  is configured so as to connect the protector body  91  of the protector  9  with the inner needle hub  5 . This ensures that when the inner needle hub  5  is moved in the proximal direction, the protector  9  is pulled (moved) in the proximal direction through the connection member  20 . 
     In addition, the connection member  20  is bellows-like in shape and, therefore, can be contracted and expanded. The connection member  20  has such a length that in its maximally expanded state (fully expanded state), the needle tip  41  of the inner needle  4  is located on the proximal side relative to the shutter part  925  of the connection member  92  and the needle tip  41  is stored inside the protector body  91  (is prevented from slipping off the protector body  91 ). 
     Thus, the connection member  20  connects the protector body  91  with the inner needle hub  5 , and has such a length that in its maximally expanded state the needle tip  41  is contained in the protector body  91 . Therefore, the protector  9  is securely prevented from slipping off the needle tip  41  of the inner needle  4 , so that the condition where the needle tip  41  is covered by the protector  9  can be maintained assuredly. Accordingly, at the time of discarding the inner needle  4  or the like or in other similar situations, an accident that a worker or the like might stick his or her finger or the like with the needle tip  41  by mistake can be securely prevented from occurring, and high safety is ensured. 
     Further, the connection member  20  is contracted, or folded, in the assembled state, and is expanded, or spread, in the condition where the inner needle  4  is pulled out of the outer needle  2  and the needle tip  41  is covered by the protector  9 . 
     The connection member  20  as described above is contracted in the assembled state; in the contracted state, the connection member  20  is contained (disposed) in the protector insertion section  51  of the inner needle hub  5  on the proximal side relative to the protector. This ensures that at the time of a puncturing operation, the connection member  20  would not obstruct the operation, so that operability of the indwelling needle assembly  1  is enhanced. Further, there is a merit that a reduction in size of the indwelling needle assembly  1  can be contrived. 
     In addition, in the contracted state and in the expanded state of the connection member  20 , the inner needle  4  is penetrating the connection member  20 . This ensures that the inner needle  4  functions as a guide for the connection member  20  at the times of contraction and expansion of the connection member  20 . Therefore, for example when the indwelling needle assembly  1  is put into the assembled state (is manufactured), the connection member  20  can be securely prevented from being contracted in an unintended state, specifically, from being contracted without being contained in the inner needle hub  5 . 
     Further, the connection member  20  has a self-restoring property (restoring property) with which it tends to return into its natural state. In the state of being contracted to be shorter than in the natural state, the connection member  20  functions as biasing means for biasing in the expanding direction by its restoring force; on the other hand, in the state of being expanded to be longer than in the natural state, the connection member  20  functions as biasing means for biasing in the contracting direction by its restoring force. Here, the term “natural state” means the state of the connection member  20  in which no external force is exerted on the connection member  20 . 
     Incidentally, the connection member  20  may be configured so as to interconnect the protector  9  and the inner needle  4 . 
     Meanwhile, as shown in  FIGS. 2 ,  3 ,  5 ,  7  and  8 , the outer needle hub  3  of the indwelling needle assembly  1  is provided with the rib (linear projection)  33  at its proximal portion as a projection engageable with the projecting piece  924  of the connection member  92  of the protector  9 . 
     The rib  33  is formed on the outer peripheral surface of the proximal portion of the outer needle hub  3  along the circumferential direction, and is ring-like in shape in the configuration shown in the figures. 
     The rib  33  has the sliding surface  331  which is tilted relative to the center axis (axis) O 1  of the inner needle  4  and on which the projecting piece  924  is slidingly moved. When the connection member  92  is changed from the first state shown in  FIGS. 3 ,  4  and  7  to the second state shown in  FIGS. 5 and 8 , the projecting piece  924  of the connection member  92  is slidingly moved along the sliding surface  331 . Specifically, when the inner needle  4  is pulled out of the outer needle  2 , the connection member  92  is restored, with its first part  921  released from the outer peripheral surface of the inner needle  4 , and, during the restoration of the connection member  92 , the projecting piece  924  is slidingly moved along the sliding surface  331  of the rib  33 , resulting in the second state. 
     This ensures that when the inner needle  4  is pulled out of the outer needle  2  and the protector  9  is thereby released from the outer needle hub  3 , the resistance (resistance to release) can be reduced. Consequently, the operation of pulling the inner needle  4  out of the outer needle  2  and releasing the protector  9  from the outer needle hub  3  can be carried out smoothly and assuredly. 
     In addition, since the sliding surface  331  is inclined, the area (area of contact) of the region of contact between the projecting piece  924  and the sliding surface  331  of the rib  33  is small, so that the frictional resistance (sliding resistance) between the projecting piece  924  and the sliding surface  331  of the rib  33  is small. Accordingly, the projecting piece  924  can be slid (moved) along the sliding surface  331  of the rib  33  more smoothly. 
     The tilt angle of the sliding surface  331  of the rib  33  relative to the center axis O 1  of the inner needle  4  (the angle formed between the sliding surface  331  and the center axis O 1 ) θ is less than 90°, and is preferably about 30° to 85°, more preferably about 45° to 80°. 
     This ensures that the protector  9  can be released from the outer needle hub  3  more smoothly. 
     Here, the tilt angle θ is preferably set so as to satisfy the following condition, where F 1  is a force necessary when the connection member  92  is in the first state, in the process in which starting from the assembled state the inner needle hub  5  is gradually moved in the proximal direction relative to the protector  9  so as to pull the inner needle  4  out of the outer needle  2 , and F 2  is a force necessary after the moment the needle tip  41  of the inner needle  4  has been moved to the proximal side of the connection member  92  until the projecting piece  924  of the connection member  92  and the rib  33  are disengaged, in other words, when the connection member  92  is shifted from the first state to the second state. 
     A preferable condition is F 2 ≦2×F 1 , and a more preferable condition is F 2 ≦1.5×F 1 , and a further preferable condition is that F 2  is equal to or lower than F 1 . 
     Further, it is preferable to set the tilt angle θ so that F 2  and F 1  are approximately equal to each other. 
     This permits the protector  9  to be released from the outer needle hub  3  more smoothly. 
     Incidentally, most part of F 1  is a force for opposing the frictional resistance between the outer peripheral surface of the inner needle  4  and the first part  921  of the connection member  92 . In addition, most part of F 2  is a force for opposing the frictional resistance between the projecting piece  924  of the connection member  92  and the sliding surface  331  of the rib  33 . 
     In addition, while the height of the rib  33  is constant in this embodiment, the height may gradually decrease in the moving direction at the time of sliding movement of the projecting piece  924  along the sliding surface  331  of the rib  33 . In the case where the height of the rib  33  gradually decreases, the connection member  92  can be brought into the second state more smoothly and assuredly. 
     Incidentally, it is preferable that a lubricant such as a silicone oil, a surfactant, etc. is given (applied) to either one or both of the sliding surface  331  of the rib  33  of the outer needle hub  3  and the opposed surface  926  of the projecting piece  924  of the connection member  92 . This ensures that the frictional resistance (sliding resistance) between the projecting piece  924  and the sliding surface  331  of the rib  33  is reduced, so that the projecting piece  924  of the connection member  92  can be slid (moved) along the sliding surface  331  of the rib  33  more smoothly. 
     Further, the lubricant is preferably given (applied) also to that region of the first part  921  of the connection member  92  which makes contact with the outer peripheral surface of the inner needle  4 . This ensures that the frictional resistance between the outer peripheral surface of the inner needle  4  and the first part  921  is reduced, so that the inner needle  4  can be moved relative to the protector  9  more smoothly. 
     One example of the method of using the indwelling needle assembly  1  (in the case of puncturing a blood vessel) (operation) will be described in detail below. 
     [1] The indwelling needle assembly  1  is put into the assembled state (see  FIGS. 1 ,  3 ,  4  and  7 ), and a connector attached to an end portion of an infusion line is preliminarily connected to the connector  72  so that an infusion liquid from the infusion line can be supplied. 
     Incidentally, in this case, a predetermined part on the tube  7  or the infusion line is pinched, for example, by a clamp (an example of flow path opening/closing means) so as to close the lumen of the tube  7  or the infusion line. 
     [2] Next, the closure of the tube  7  or the infusion line with the clamp or the like is released, and the infusion liquid from the infusion line is introduced through the tube  7  into the outer needle hub  3 . 
     The infusion liquid introduced into the outer needle hub  3  fills up the branch flow path  32  and the flow path  31  on the distal side relative to the seal member, and is introduced into the lumen  21  of the outer needle  2 , whereby the lumen  21  of the outer needle  2  is primed with the infusion liquid. In this instance, part of the infusion liquid flows out via the tip opening  22  of the outer needle  2 . 
     [3] After the priming is completed in this manner, the tube  7  or the infusion line is again closed with a clamp or the like, then the inner needle hub  5  is grasped, and the outer needle  2  and the inner needle  4  integrated to each other are caused to puncture a blood vessel (a vein or an artery) of a patient. 
     When the blood vessel is captured by the outer needle  2 , the internal pressure in the blood vessel (blood pressure) causes blood to flow back in the proximal direction through the inner needle  4  and then through the lumen  21  of the outer needle  2 , so that this blood flow can be confirmed by at least one part of the outer needle  2 , the outer needle hub  3 , the inner needle hub  5  and the tube  7  that has inside visibility. 
     After the confirmation of the blood flow, the outer needle  2  is advanced by a very short distance in the distal direction along the inner needle  4 , using the inner needle  4  as a guide. 
     In addition, at the time of puncturing the blood vessel in this manner, the lumen  21  of the outer needle  2  has already been primed with the infusion liquid, so that erroneous penetration of a bubble or bubbles into the blood vessel is securely prevented, and safety is extremely high. 
     [4] When the blood vessel has been captured by the outer needle  2  (when the outer needle  2  has been moved to a target position), the outer needle  2  or the outer needle hub  3  is fixed by one hand, and the inner needle hub  5  is gripped by the other hand and pulled in the proximal direction. By this, operations (motions) ranging from a motion of pulling the inner needle  4  out of the outer needle  2  to the release of the protector  9  from the outer needle hub  3  are carried out sequentially and continuously. Specifically, first, the inner needle  4  is moved in the proximal direction and pulled out of the outer needle  2 . 
     [5] When the inner needle  4  has been moved further in the proximal direction and the needle tip  41  has passed through the slit, the seal member having the self-closing property closes the slit by its own elastic force. This ensures that leakage of liquid through the slit is prevented from occurring, and asepsis of the inside of the outer needle hub  3  and the infusion line is secured. 
     [6] When the inner needle  4  is moved further in the proximal direction and the needle tip  41  reaches the proximal side of the first part  921  of the connection member  92 , the connection member  92  is opened (restored) by its own elastic force (restoring force), and is moved by being pulled in the proximal direction through the connection member  20 , resulting in the second state, as shown in  FIGS. 5 and 8 . 
     In this case, as above-mentioned, the direction in which the projecting piece  924  is moved by restoration of the connection member  92  is a direction substantially perpendicular to the center axis O 1  of the inner needle  4 . In this connection, since the protector  9  is moved by being pulled in the proximal direction through the connection member  20 , the connection member  92  is also moved in the proximal direction together therewith, whereby the projecting piece  924  is slidingly moved along the sliding surface  331  of the rib  33 , and the connection member  92  is put into the second state. After the connection member  92  is thus put into the second state, even if the needle tip  41  of the inner needle  4  tends to move so as to return in the distal direction again, the needle tip  41  abuts on the shutter part  925  of the connection member  92  and, therefore, cannot return. 
     [7] The inner needle hub  5  is moved further in the proximal direction, whereby the protector  9  is moved by being pulled in the proximal direction through the connection member  20 , and is separated (released) from the outer needle hub  3 . 
     The connection member  20  has such a length that, in its maximally expanded state, the needle tip  41  is contained in the protector body  91 . Therefore, the protector  9  can be securely prevented from slipping off the needle tip  41 . Accordingly, the condition where the needle tip  41  is covered with the protector  9  can be maintained assuredly. 
     After the inner needle  4  is pulled out of the outer needle  2  in this manner, the inner needle  4  and the inner needle hub  5  are useless, and, therefore, they are put to a discarding procedure. 
     Of the inner needle  4 , the needle tip  41  is covered by the protector  9 . Particularly, the needle tip  41  is prevented from moving toward the distal side beyond the shutter part  925  of the connection member  92  to protrude from the distal end of the protector  9 . Therefore, an accident that a person in charge of the discarding treatment or the like might pierce his or her finger or the like with the needle tip  41  by mistake is prevented from occurring. 
     [8] Subsequently, the wings  12   a  and  12   b  are fixed to a skin with a pressure sensitive adhesive tape or the like, the closure of the tube  7  or the infusion line with the clamp or the like is released, and supply of the infusion liquid is started. 
     The infusion liquid supplied from the infusion line is injected into the patient&#39;s blood vessel via the respective lumens or inner cavities of the connector  72 , the tube  7 , the outer needle hub  3  and the outer needle  2 . 
     As has been described above, according to the present indwelling needle assembly  1 , at the time of pulling the inner needle  4  out of the outer needle  2  and releasing the protector  9  from the outer needle hub  3 , the resistance can be reduced. Consequently, the operation of pulling the inner needle  4  out of the outer needle  2  and releasing the protector  9  from the outer needle hub  3  can be carried out smoothly and assuredly. 
     Second Embodiment 
       FIG. 9  is a bottom view showing schematically an outer needle hub and a connection member of a protector in a second embodiment of the indwelling needle assembly according to the present invention. 
     Incidentally, in the following description, the right side in  FIG. 9  will be referred to as a “proximal” side and the left side as a “distal” side. Further, in  FIG. 9 , of the connection member of the protector, only a first part and a projecting piece are drawn. 
     The second embodiment will be described below, referring mainly to differences from the above-described first embodiment, and descriptions of the same items as mentioned above will be omitted. 
     As shown in  FIG. 9 , in the indwelling needle assembly  1  according to the second embodiment, an opposed surface  926  of the projecting piece  924  of a connection member  92  which is opposed to a sliding surface  331  of a rib  33  is tilted relative to the center axis O 1  of an inner needle  4 . 
     Further, the tilt angle of the opposed surface  926  of the projecting piece  924  relative to the center axis O 1  of the inner needle  4  and the tilt angle of the sliding surface  331  of the rib  33  relative to the center axis O 1  of the inner needle  4  are different from each other. 
     According to this indwelling needle assembly  1 , effects equivalent to those of the indwelling needle assembly  1  in the first embodiment described above can be obtained. 
     Incidentally, the tilt angle of the opposed surface  926  of the projecting piece  924  relative to the center axis O 1  of the inner needle  4  and the tilt angle of the sliding surface  331  of the rib  33  relative to the center axis O 1  of the inner needle  4  may be equal. 
     In addition, the second embodiment may be applied also to a third embodiment which will be described later. 
     Third Embodiment 
       FIG. 10  is an exploded perspective view showing a third embodiment of the indwelling needle assembly according to the present invention;  FIGS. 11 and 12  are each sectional views showing an outer needle hub, an inner needle, a protector, etc. of the indwelling needle assembly shown in  FIG. 10 ;  FIG. 13  is a perspective view showing a connection member of the protector in the indwelling needle assembly shown in  FIG. 10 ; and  FIG. 14  is a perspective view showing a shutter member of the protector in the indwelling needle assembly shown in  FIG. 10 . 
     Incidentally, in the following description, the left side in  FIGS. 10 ,  11  and  12  will be referred to as a “proximal” side and the right side as a “distal” side. 
     The third embodiment will be described below, referring mainly to differences from the above-described first embodiment, and descriptions of the same items as above will be omitted. 
     As shown in  FIGS. 10 to 14 , in the indwelling needle assembly  1  according to the third embodiment, a protector  9  has a protector body  91 , and a connection member  92  and a shutter member  93  and a ring  94  which are provided inside the protector body  91 . In addition, an inner needle  4  is provided with a large diameter part (enlarged diameter part)  42  on the distal side thereof. The large diameter part  42  is large in outside diameter (enlarged in outside diameter). Further, the connection member  92  is not provided with any shutter part  925 , and a connection member  20  is omitted. 
     Specifically, as shown in  FIGS. 11 and 12 , a wall section  914  is formed on the proximal side of a wall section  913  of the protector body  91 , and the shutter member  93  is provided on the proximal side of the wall section  914 . 
     As shown in  FIG. 14 , the shutter member  93  is composed of an elastic plate member, and is provided in its central portion with a hole  931  into which the inner needle  4  is inserted in the assembled state. In addition, the shutter member  93  is formed with a plurality of cutouts, which permits the shutter member  93  to be deformed easily. 
     The diameter of the hole  931  when the shutter member  93  is in a natural state is set to be smaller than the diameter of the large diameter part  42  of the inner needle  4  and be larger than the diameter of the other parts of the inner needle  4 . This ensures that when the shutter member  93  is in the natural state, the large diameter part  42  cannot pass through the hole  931 . 
     In addition, the shutter member  93  is configured such that when the inner needle  4  is moved in the proximal direction and the large diameter part  42  of the inner needle  4  is about to pass through the hole  931 , starting from the assembled state in which the large diameter part  42  of the inner needle  4  is located on the distal side of the shutter member  93 , the shutter member  93  is deformed so that the diameter of the hole  931  becomes greater than the diameter of the large diameter part  42 . This permits the large diameter part  42  to pass through the hole  931 . 
     On the other hand, when the inner needle  4  is moved in the distal direction and the large diameter part  42  of the inner needle  4  is about to pass through the hole  931 , starting from the condition in which the large diameter part  42  is located on the proximal side of the shutter member  93 , the shutter member  93  is inhibited from deformation (is maintained in the natural state) by the wall section  914 . This prevents the large diameter part  42  from passing through the hole  931 . 
     Consequently, the needle tip  41  is inhibited from protruding from the distal end of the protector  9 . 
     Further, the ring  94  is disposed on the proximal side of the protector body  91  (on the proximal side relative to the shutter member  93 ). The diameter of the hole in the ring  94  is set to be smaller than the diameter of the large diameter part  42  of the inner needle  4  and be greater than the diameter of the other parts of the inner needle  4 . This prevents the large diameter part  42  to pass through the hole of the ring  94 . As a result, the protector  9  is securely prevented from slipping off the needle tip  41  of the inner needle  4 , and the protector  9  and the inner needle  4  are connected with each other. 
     Thus, the ring  94  has both a function of slip-off preventive means for preventing the protector  9  from slipping off the needle tip  41  of the inner needle  4  when the needle tip  41  is covered by the protector  9  and a function of connection means for connecting the protector  9  and the inner needle  4  to each other. 
     According to the present indwelling needle assembly  1 , effects equivalent to those of the indwelling needle assembly  1  in the first embodiment described above can be obtained. 
     While the indwelling needle assembly according to the present invention has been described above based on the embodiments shown in the drawings, the invention is not limited to the embodiments, and the parts constituting the indwelling needle assembly can be replaced by parts of arbitrary configurations which can exhibit functions equivalent to the original. Further, arbitrary components or structures may be added. 
     In addition, the present invention may be embodied by a combination of arbitrary two or more configurations (features) of the above-described embodiments. 
     Further, the indwelling needle assembly according to the present invention is not limited to those for used in the state of being inserted in a blood vessel; for example, the indwelling needle assembly of the invention is also applicable to those for use in the state of being inserted in an abdominal cavity, a thoracic cavity, a lymph vessel, a vertebral canal or the like. 
     In addition, in the present invention, the shape of the slit in the seal member is not limited to the shape of a straight line segment; for example, the shapes of a cross, capital Y, capital T, capital H, etc. may also be adopted. 
     Further, in the present invention, the protector is not limited to those of the configurations shown in the drawings, and may be any one that can be detachably connected to the outer needle hub. Particularly, protectors of various configurations can be used insofar as they cover at least the needle tip of the inner needle when the inner needle has been pulled out of the outer needle. 
     INDUSTRIAL APPLICABILITY 
     The indwelling needle assembly according to the present invention includes: an inner needle having a sharp needle tip at a distal end; an inner needle hub secured to a proximal portion of the inner needle; a hollow outer needle into which the inner needle is inserted; an outer needle hub which is secured to a proximal portion of the outer needle and which has a projection at a proximal portion thereof; and a protector which has an elastic connection member with a projecting part engageable with the projection, and which is detachably connected to the outer needle hub by engagement of the projecting part with the projection, wherein the projection of the outer needle hub includes a sliding surface which is tilted relative to an axis of the inner needle and on which the projecting part is slidingly moved, and the connection member takes a first state in which the projecting part is engaged with the projection and a second state in which the projecting part is disengaged from the projection, and, when the connection member is changed from the first state to the second state, the projecting part is slidingly moved along the sliding surface of the projection. Therefore, the protector can be released from the outer needle hub smoothly. Accordingly, the indwelling needle assembly according to the present invention has industrial applicability.