Patent Publication Number: US-2021178078-A1

Title: Needle hub and syringe arrangement

Description:
TECHNICAL FIELD 
     The present invention relates to the field of a needle hub and syringe arrangement. 
     BACKGROUND 
     Fluids, such as liquid medicine, are often provided in a syringe and needle hub arrangement for providing a pre-determined amount of the fluid to for example a body part of a patient using a needle. Worldwide, a lot of liquid medicine is discarded without being used as it is left after use in a syringe in what is known as a dead volume. Conventional needle hubs which are arranged to be provided on syringes are often designed to a specific standard, such as an ISO standard, and are arranged to fit on a plurality of different syringes. Therefore, a perfect fit will not be achieved and a dead volume will be present between syringe and needle hub. 
     WO2014011046 discloses a needle and syringe arrangement with a frustoconical male slip fitting and a frustoconical female slip fitting. The male slip fitting is insertable into the female slip fitting establishing a press fitted connection with a small dead volume. In this needle and syringe arrangement, the barrel may be inserted into the needle. When the piston has been pressed against the needle hub, and the maximum amount of fluid has been pressed out of the arrangement, a part of the piston protrudes from the barrel. This protrusion creates a dead volume between the barrel, the piston, and the needle hub. 
     US20160008545A1 discloses a low-waste needle and syringe assembly for injecting a fluid into a patient. syringe. A syringe tip defining a substantially frusto-conical interior void extends from an end wall of the syringe frusto-conical member of the needle hub matingly engages the frusto-conical void of the syringe tip when the hub is secured to the syringe, forming a fluid-tight seal. A plunger positioned in the fluid chamber can be depressed by a user, and a piston cap attached to the plunger urges fluid in the chamber out of the chamber through the syringe tip and into the needle. The piston cap matingly engages the end wall of the syringe so that substantially all fluid is urged from the chamber to the needle. 
     SUMMARY 
     In the needle and syringe arrangement of WO2014011046, the barrel end plane is bevelled, and the abutment plane of the needle hub against which the piston is to abut is tapered towards the cannula opening. Furthermore, only a small part of the surface of the plunger end may actually contact the abutment plant of the needle hub. As such, a relatively large volume of fluid may be trapped between the plunger, barrel and needle hub. This trapped volume forms part of the residual dead volume. As a result hereof, the residual dead volume of this needle and syringe arrangement may not be zero, or even close to zero. 
     In the needle and syringe assembly of US20160008545A1, the cannula opening extends into the barrel of the syringe when the needle hub is placed over the proximal end of the barrel. Furthermore, when the piston is in the second position, and thus the dead volume is minimized, the piston does not abut the plane surrounding the cannula opening, or only a small area of the piston end plane abuts the plane surrounding the cannula opening. As a result hereof, the residual dead volume of this needle and syringe assembly may not be zero, or even close to zero. 
     The aim of the present invention is to further reduce the dead volume in a needle hub and syringe arrangement. Such a dead volume may be defined as the volume of fluid inside the syringe which cannot be pressed out of the syringe and needle hub arrangement using a piston of the syringe. The dead volume will thus remain in the arrangement after use of the arrangement. However, when using the term dead volume in the following description, only the dead volume due to a mismatch in shape of the syringe and the needle hub is implied. Reducing the dead volume in the cannula bore of the needle hub will not be considered. 
     A first aspect provides a needle hub and syringe arrangement, comprising a needle hub and a syringe comprising a barrel and a piston. The needle hub comprises an axially oriented cannula bore comprising a cannula opening, wherein the cannula opening is surrounded by an abutment plane. The barrel comprises an axially elongated hollow cylinder. A first of the needle hub and the barrel is arranged as a male part arranged to be received by a second of the needle hub and the barrel arranged as a female part. The piston comprises at a proximal end an end-plane shaped complementary to at least part of the abutment plane, and the piston is arranged to be translated axially within the barrel between a first position and a second position. In the first position, a volume arranged for holding a fluid is defined by part of an inner wall of the barrel, the end-plane of the piston, and at least part of the abutment plane. 
     In the second position, the end-plane of the piston abuts the abutment plane and the fluid volume left in the arrangement is reduced to the dead volume. This dead volume may be defined by part of an inner wall of the barrel, the end-plane of the piston, and at least part of the abutment plane. Alternatively, it may be defined by the end-plane of the piston, and at least part of the abutment plane—such may be in particular the case if there is a mismatch in some way between the end-plane of the piston, and at least part of the abutment plane, for example due to manufacturing issues. 
     The needle hub and syringe arrangement is typically used as follows: the needle hub and syringe are press-fitted together such that a watertight seal is provided between the needle hub and syringe. Preferably, a distal end of the syringe, at which the end-plane of the piston is located in the second position, abuts to the abutment plane. 
     A needle may be provided to the needle hub, and a fluid is sucked into the barrel of the syringe through a cannula bore of the needle hub by moving the piston inside the barrel away from the needle hub, creating a low pressure inside the barrel towards which a fluid will flow. Using volume indicators for example provided on the outside of a transparent barrel, the user may suck up a desired volume of fluid. Next, the user will press the piston back again towards the needle hub until a small drop emerges from the needle or the cannula bore of the needle hub. The drop will indicate to the user that the dead volume has been totally filled with the fluid and that the needle hub and syringe arrangement is ready for use. 
     In an alternative use of the needle hub and syringe arrangement, first a filter needle is fitted on the syringe. Fluid is sucked into the barrel through the filter needle, wherein the filter needle is arranged to filter out possible contaminants which might be present in the fluid and are undesired. Filter needles often comprise a larger diameter needle, wherein the larger diameter reduces the risk of unwanted air bubbles being sucked into the barrel. Furthermore, filter needles may comprise a longer needle which may reach the bottom of an ampule out of which the fluid will be sucked. After the fluid has been sucked into the syringe, the filter needle may be removed and the needle hub may be press-fitted on the barrel. 
     Different complementary shapes of the barrel and the piston next to being cylindrical are envisioned as well. Any hollow barrel shape and corresponding piston shape that will fit into the hollow barrel may be used in the arrangement. 
     The complementary shapes of the end-plane of the piston and the abutment plane provide that a small or even absent residual volume is left between the barrel and the needle when the piston has been moved to the second position. 
     Typically, the arrangement according to the present invention may reduce wasted fluid by 0.05 mL compared to conventional syringe and needle hub arrangement. Considering the costs of medical fluids and the amount of syringe and needle hub arrangement used worldwide the invention presents a considerable advantage over the arrangements known in the art. 
     It is noted that with the wording “piston” actually pistons as well as plungers are meant or any other body performing such function in the barrel of the syringe. 
     In an embodiment of the arrangement, the end-plane of the piston and the abutment plane are substantially planar and/or parallel. In such embodiments, it may be at least partially prevented that fluid is trapped between the piston and the barrel and cannot leave the arrangement. As such, dead volume or residual volume may be reduced or preferably even prevented. 
     In embodiments of the arrangement, when the piston is in the second position, the end-plane of the piston, the abutment plane and the cannula opening are substantially parallel and aligned. In such embodiments, it may be at least partially prevented that fluid is trapped between the piston and the barrel and cannot leave the arrangement. As such, dead volume or residual volume may be reduced or preferably even prevented. 
     In an embodiment of the arrangement, the volume constrained between the end-plane of the piston, the abutment plane and a part of the inner wall of the barrel is smaller than 0.005 mL and preferably zero. 
     In a preferred embodiment of the arrangement, the abutment plane comprised by the needle hub is oriented substantially perpendicular to the axial direction. The complementary shape of the end-plane of the piston is also oriented substantially perpendicular to the axial direction. When both shapes are flat, the embodiment has the advantage that the syringe and needle hub may be arranged regardless of the angular orientation of barrel relative to the needle hub. 
     The needle hub may comprise a second opening opposite to the cannula opening for receiving a needle. 
     In a further preferred embodiment of the arrangement, the needle hub is arranged as the female part and the needle hub comprises a cavity for receiving at least part of or with provided therein at least part of the barrel arranged as the male part such that part of an outer wall of the barrel is press-fitted against at least part of an inner wall of the cavity of the needle hub. 
     In such an embodiment, an inner wall of the cavity of the needle hub may comprise one or more recesses wherein at the one or more recesses the outer wall of the barrel when the barrel is inserted into the cavity does not touch the inner wall of the cavity. The recesses decrease the contact surface between the cavity and the outer wall allowing an easier insertion of the barrel into the cavity. 
     In embodiments of the arrangement, the needle hub does not extend into the syringe. For example, when the needle hub is the female part and the barrel is the male part, the barrel extends into the needle hub but no part of the needle hub protrudes into the barrel. Hence, the volume available for fluid in the barrel is not decrease due to any part of the needle hub protruding into the barrel. For providing the fit between the barrel and the needle hub, some part of the needle hub may extend outside the barrel, and for example engage an outer surface of the barrel or any structure provided at the outer surface of the barrel. This may for example result in a higher accuracy of fluid volume that is to be dispensed from the arrangement. 
     To provide a better lock between the syringe and the needle hub than just friction between the two parts, a first of the outer wall of the barrel and the inner wall of the cavity may comprise a protruding section and a second of the outer wall of the barrel and the inner wall of the cavity may comprise a receding section corresponding to the protruding section such that when the barrel is inserted into the cavity the protruding section may engage with the receding section forming a locking engagement. 
     In embodiments of the arrangement, the barrel end-plane may constitute the furthest point of the syringe reaching towards the needle hub. In such embodiments, and optionally also in other embodiments, the cannula opening does not reach within the syringe. In other words, at the proximal end of syringe, the syringe does not extend beyond the abutment plane of the needle hub. In such embodiments, a residual volume is the piston is in the second position may be decreased up to a zero volume, next to other embodiments in which this may be possible. 
     In embodiments of the arrangement, when the piston is in the second position, at least 20%, preferably at least 30%, even more preferably at least 40% or at least 50%, and even more preferably at least 60%, at least 70%, at least 80% or even more preferably at least 90% of the surface area of the piston end-plane contacts the abutment plane. As such, the volume of fluid that may be trapped between the piston and the barrel, which residual volume cannot be pressed out of the syringe, may be reduced to a volume smaller than 0.005 mL or even to zero. 
     A second aspect provides a needle hub, comprising a cavity arranged for receiving a barrel, an axially oriented cannula bore comprising a cannula opening. The cannula opening is in fluid connection with the cavity, and the cannula opening is surrounded by a substantially flat abutment plane. Further more, the abutment plane is oriented substantially perpendicular to the axial direction. The orientation allows the piston to align with a substantially flat end-plane of a piston which is also oriented substantially perpendicular to the axials direction. 
     The needle hub may be used in arrangements with syringes other than the syringes that will be discussed here. Any syringe which is compliance with ISO 594-1 may be used in an arrangement in the needle hub. Although in such arrangements the dead volume is not reduced as much as with the arrangement according to the present invention, still a reduction in dead volume may be achieved due to the substantially perpendicular to the axial direction oriented abutment plane. 
     A third aspect provides a syringe, comprising a barrel, comprising an axially elongated hollow cylinder, arranged to at least partly be inserted into a cavity of a needle hub. The syringe further comprises an axially elongated piston, arranged to be translated axially within the barrel. The piston comprises a substantially flat end-plane oriented substantially perpendicular to the axial direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The various aspects and embodiments thereof will now be discussed in conjunction with drawings. In the drawings: 
         FIG. 1  shows a needle hub and syringe arrangement; 
         FIG. 2A  shows a detailed view of a part of the arrangement; 
         FIG. 2B  shows a detailed view of a part of another embodiment of the arrangement; 
         FIG. 2C  shows an exploded view of a part of an embodiment of the arrangement; and 
         FIG. 3  shows another embodiment with a Luer Lock coupling. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  shows an embodiment of a needle hub and syringe arrangement  100 , comprising a needle hub  102  and a syringe  104  comprising a barrel  106  and a piston  108 . The needle hub  102  comprises an axially oriented cannula bore  110  comprising a cannula opening  112 , which is surrounded by an abutment plane  114 . The barrel  106  comprises an axially elongated hollow cylinder. 
     In the arrangement  100 , a first of the needle hub  102  and the barrel  106  is arranged as a male part arranged to be received by a second of the needle hub  102  and the barrel  106  arranged as a female part. In the embodiment as shown in  FIG. 1 , the needle hub  102  is arranged as the female part arranged to receive the barrel  106  as the male part. 
     The piston  108  comprises an end-plane  116  at a proximal end, which is shaped complementary to the abutment plane  114  of the needle hub  102 . The piston  108  is arranged to be translated axially within the barrel  106  between a first position and a second position. In the first position, a fill volume  118  arranged for holding a fluid is defined by part of an inner wall  120  of the barrel, the end-plane  116  of the piston, and at least part of the abutment plane  114 . In the second position, the fill volume  118  is reduced to zero and only the dead volume is left in the arrangement  100  because in the second position the end-plane  116  of the piston abuts the abutment plane  114 . 
     On a distal end of the piston  108 , opposite to the end-plane  116 , the piston may be provided with a handle  117  arranged for allowing easy control of the axial position of the piston  108  inside the barrel  106  to a user. 
     By translating the piston  108  within the barrel  106  from the second position to the first position, a fluid may be sucked into the volume  118  through the cannula opening  112 . With the opposite movement from the first position to the second position, the fluid present in the volume  118  may be ejected out of the volume  118  through the cannula opening  112 . 
     When the syringe is provided  104  without the needle hub  102 , the barrel  106  itself may be placed in contact with a fluid that is to be sucked into the barrel  106 , and by moving the piston  108  inside the barrel  106  the fluid may be sucked into the barrel  106 . Alternatively, another needle like a filter needle arrangement may be used. After a desired amount of fluid is present in the barrel  106 , the needle hub  102  may be provided to the syringe  104  to form the arrangement  100 . 
     In an embodiment of the needle hub  102 , the needle hub  102  comprises a second opening  136  opposite to the cannula opening  112  for receiving a needle. The cannula bore  110  may be tapered away from the cannula opening  112  such that the needle may be inserted more easily. After the needle has been inserted, it may be glued to the cannula bore  110 . The second opening  136  may additionally or alternatively be arranged to be connected to another device arranged to receive or provide fluid respectively from or to the assembly  100 , for example medical tubing, a bag or a catheter. 
     The shape of the end-plane  116  of the piston  108  is complementary to the shape of the abutment plane  114 . Hence, the volume  118  constrained between the end-plane  116  of the piston  108 , the abutment plane  114  and the part of the inner wall  120  of the barrel  106  between the end-plane  116  and the abutment plane  114  will be very small when the piston  108  is in the second position. Preferably, the volume  118  is smaller than 0.01 mL, even more preferably smaller than 0.005 mL when the piston  108  is in the second position. 
     In a preferred embodiment of the arrangement  100 , the end-plane  116  of the piston  108  is a substantially flat surface provided perpendicular to the axial direction of the piston  108 . The complementary shape of the abutment plane  114  to this embodiment of the piston  108  is a substantially flat shaped abutment plane  114  provided perpendicular to the axial direction of the needle hub  102 . 
     Different complementary shapes of the end-plane  116  of the piston  108  and the abutment plane  114  are envisioned as well, for example a tapered end-plane  116  and a similarly tapered abutment plane  114 , or a substantially flat end-plane provided at an angle relative to the axial direction of the piston  108 , and a abutment plane  114  provided substantially flat at the same angle. 
     A further advantage of the small or even absent residual volume  118  may be an increase in accuracy of the amount of fluid inside the syringe  104  as the amount of fluid inside the syringe  104  substantially equals the volume  118 . The volume of a dead volume is often unknown or only known to a certain degree of accuracy. Syringes such as the syringe  104  in the arrangement  100  of the present invention are often used for very small volumes of liquid, typically smaller than 1 mL, or even as small as 0.5 mL, or even more as small as 0.3 mL. With these small volumes, the dead volume is preferred to be as small as possible, especially small compared to the fluid volume that is to be ejected from the arrangement  100 . 
     Because the sizes of the syringe may differ per application, the dead volume may also be specified as a percentage of the maximum fluid capacity of the barrel. For example, an embodiment of the barrel holds a maximum fluid volume of 0.3 mL. A preferred dead volume of less then 0.01 mL results in a dead volume percentage of 3.33%. Even more preferred is a dead volume percentage smaller than 3%, even more preferably a dead volume percentage smaller than 2%, and still even more preferably a dead volume percentage smaller than 1%. 
     Another cause of the dead volume may be manufacturing tolerances of the end-plane  116 , the distal end of the barrel  106  and the abutment plane  114 , which causes a mismatch in correspondence between said two planes. It is therefor preferred to manufacture the piston  108  and the needle hub  102  to a very high degree of manufacturing accuracy. 
     In order to achieve such a high degree of manufacturing accuracy, the needle hub and the barrel may be injection moulded. As injection moulding still results in some inaccuracies, moulds may be used that provide a plurality of at least one of the needle hubs and barrels. A best match may then be searched between the plurality of combinations of needle hubs and barrels which results in the smaller dead volume 
       FIG. 2A  shows a detailed view of a part of the arrangement  100  comprising the needle hub  102  and syringe  104  comprising the barrel  106  and inserted into the barrel  106  the piston  108 . In the arrangement  100  as shown in  FIG. 2A , the barrel  106  is arranged as the male part, which is arranged to be inserted in to a cavity  103  comprised by the needle hub  102  as the female part. The barrel  106  may be press-fitted into the cavity  103  of the needle hub  102  such that a watertight seal is provided between an outer surface  124  of the barrel  106  and an inner surface  126  of the cavity  103  of the needle hub  102 . 
     The press-fit fitting of the barrel  106  into the cavity  103 , a Luer-slip connection may be used. In such a case, the barrel  106  and the cavity  103  may be tapered according to, for example, the ISO 80369-7:2016 standards, or at an angle on approximately 6%. 
     Alternatively, a Luer-Lock connection as an example of a threaded connection between barrel  106  and needle hub  102  may be used,  FIG. 3  shows part of an embodiment of the needle hub and syringe arrangement  100 , wherein the barrel  106  is provided with a threaded section  302  arranged to receive the needle hub  102 . The threaded section  302  may be designed according to the ISO 80369-7:2016 standard. The threaded section  302  in  FIG. 3  is arranged as a skirt part protruding from the outer wall  124  of the barrel  106 . 
     The needle hub  102  as shown in  FIG. 3  is provided with a protrusion  304  as an example of a protrusion arranged to engage with the threaded section such that an axial connection may be achieved between the barrel  106  as a part of the syringe  104  and the needle hub  102 . Alternatively, the protrusion  304  may be arranged as a thread, shaped complementary to the thread of the threaded section  302  of the barrel  106 . For achieving the axial connection, the needle hub  102  may be screwed into the threaded part of the syringe  104 . 
     The needle hub  102  as shown in  FIG. 2A  comprises a skirt part  302 . The skirt part  302  surrounds the cavity  103 , and may be arranged to engage the outer surface  124  of the barrel  106 , for example to form a fluid-tight fit. The cannula opening  112  is not provided in the cavity  103 , and is hence not surrounded by the skirt part  302 . As such, when a needle is inserted into the cannula  110 , the needle may not extend into the cavity  103 . Then, when the barrel  106  is partially inserted at its proximal end into the cavity  103 , the cannula opening  112  does not extend into the barrel  106 , and a needle may also not extend into the barrel  106 . This leaves all the inner volume of the barrel  106  at its proximal end available for fluid, which may contribute to the accuracy of fluid dosage. 
     The barrel  106  comprises a barrel end-plane  122 , which, when the barrel  106  is inserted into the needle hub  102  may abut the abutment plane  114 . In the second position of the piston, the barrel end-plane  122  and the end-plane  116  are preferably substantially at the same level, i.e. in the same plane. With such an abutment, a volume constrained between the barrel end-plane  122 , the abutment plane  114 , the piston  108  in the second position and, optionally, the inner wall of the barrel  106 , is substantially negligible. 
     When the barrel end-plane  122  abuts the abutment plane  114 , the cannula opening  112  does not extend within the barrel  106  or in the syringe  104 . In the embodiment of  FIG. 2A , the barrel end-plane  122  is the further extending point of the barrel  106  at the proximal end, and also of the syringe  104 . 
     In another embodiment of the arrangement  100 , when the barrel  106  is inserted into the needle  102 , the barrel end-plane  120  does not abut the abutment plane  114  but is positioned at a small distance away from the abutment plane  114 . In such an embodiment, a press-fit between the barrel  106  and the needle hub  102  is ensured as a maximum axial depth by which the barrel  106  may be inserted in the needle hub  102  is defined by the diameter of the inner surface  126  of the cavity  103  and the outer surface  124  of the barrel  108 , as opposed to the abutting of the abutment plane  114  by the barrel end-plane  122 . 
     As shown in  FIG. 2A , the barrel  106 , or at least one end thereof, may be embodied substantially as a tube, wherein the barrel end-plane  120  is a donut-shaped plane, with an inner radius and an outer radius. 
       FIG. 2B  shows an embodiment of the arrangement  100  with the needle hub  102  as the male part partially inserted into the barrel  106  as the female part. In this embodiment, the needle hub  102  is press-fitted into the barrel  106 , such that a watertight seal is provided between the needle hub  102  and the barrel  106  to prevent fluid and liquid in particular from leaking between the needle hub  102  and the barrel  106  when fluid is present in the volume  118 , and especially when the piston  108  is moved towards the second position and fluid is pressed out of the volume  118  through the cannula bore  110 . 
     Now returning to  FIG. 2A , in an embodiment of the needle hub  102 , the inner wall  126  of the cavity  103  comprises one or more recesses  128 . The one or more recesses  128  are arranged such that when the barrel  106  is inserted into the cavity  103  a part of the outer wall of the barrel  124  does not touch the inner wall  126  of the cavity  103  at the one or more recesses  128 . The recesses  128  are provided concentrically around an axis of the needle hub  102 , passing through the cannula bore  110 . These recesses allow for an easier insertion of the barrel  106  into the cavity  103 . 
     Additionally or optionally, to further ease the insertion of the barrel  106  into the cavity  103 , the cavity  103  may be tapered towards the cannula bore  110 . An outer circumference  124  of the barrel  106  may also be tapered corresponding to the taper of the cavity  103 . 
       FIG. 2C  shows an exploded view of part of an embodiment of the arrangement  100  with the syringe  104  comprising the barrel  106 , and the needle hub  102 . In this embodiment, the inner wall  126  of the cavity  103  of the needle hub  102  comprises a receding section  134  corresponding to a protruding section  132  provided on the outer wall of the barrel  124 . When the barrel  106  is inserted into the cavity  103 , the protruding section  132  engages the receding section  134  and the barrel  106  is harder to remove again from the cavity  103 . Preferably, the protruding section  132  and the receding section  134  are provided circumferentially. Furthermore, a plurality of at least one of the protruding sections and receding section may be provided to provide a plurality of points of engagement between the barrel  106  and the needle hub  102 . 
     In another embodiment of the arrangement  100 , the inner wall  126  of the cavity  103  comprises the protruding section and the outer wall of the barrel  124  comprises the protruding section. 
     In embodiments of the arrangement  100 , a first of the barrel  106  and the cavity of the needle hub  103  comprises a resilient material with a stiffness lower than a stiffness of a second of the cavity of the needle hub  103  and the barrel  106 . A stiffness of a material may be defined as the amount of force required to deform the material elastically and may be expressed for example in N/mm. Such a difference in stiffness between the male part and the female part allows either the outer circumference of the male part or the inner circumference of the female part to elastically deform when the male part is inserted into the female part. This elastic deformation may provide a watertight press-fit between the male part and the female part. 
     In summary, the total volume of fluid in a syringe may not be equal to the total volume of fluid that can be pressed out of the syringe: a dead volume may be left in an arrangement of the syringe and a needle hub provided with the syringe. To reduce the dead volume, a needle hub and syringe arrangement is provided which are shaped complementary to each other. More specifically, a shape of an end-plane of a piston comprised by the syringe is complementary to a shape of a plane in which an opening of a cannula bore of the needle hub is provided. The shapes are such that the volume inside the syringe once occupied by the fluid may be occupied by the piston after fully pressing down on the piston, or only a substantially small volume of fluid may be left between the cannula opening and the syringe.