Patent Publication Number: US-2023148100-A1

Title: Fixtures for testing elasticity of drug delivery members and related methods

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Priority is claimed to U.S. Provisional Patent Application No. 63/014,006, filed Apr. 22, 2020, the entire contents of which are hereby incorporated herein by reference. 
    
    
     FIELD OF DISCLOSURE 
     The present disclosure generally relates to testing drug delivery devices, and more particularly, to testing elasticity of drug delivery members, such as cannulas and/or needles. 
     BACKGROUND 
     Conventional drug delivery can be accomplished through the use of a syringe with a drug delivery member in the form of a rigid hollow cannula and/or needle, for example. For reliability and efficacy, certain standards and/or regulations may be implemented requiring that these types of cannulas/needles maintain a specific elasticity or resistance to deformation under some measure of lateral loading. It may therefore benefit manufacturers to test their cannulas/needles to ensure compliance with such standards and/or regulations. 
     SUMMARY 
     In accordance with a first example, a fixture assembly for testing the elasticity of a cannula of a drug delivery device includes a fixture block and a movable strike member. The fixture block defines a barrel receptacle and has a distal end surface. The barrel receptacle is adapted to receive the drug delivery device. The drug delivery device has a barrel and the cannula extends from a distal end of the barrel such that when the drug delivery device is received in the barrel receptacle, the cannula extends out of the fixture block and beyond the distal end surface, thereby defining the cannula as having a fulcrum point located at the distal end surface and spaced from the distal end of the barrel. The movable strike member is arranged to selectively apply a load to a distal end of the cannula spaced from the fulcrum point. 
     In accordance with a second example, a method of testing the elasticity of a cannula of a drug delivery device includes securing a barrel of the drug delivery device within a fixture such that the cannula fixed to a distal end of the barrel extends out from the fixture. The method includes applying a lateral force to a distal end of the cannula using a strike member to move the distal end of the cannula a threshold distance. The method includes removing the force from the cannula. The method includes determining a final position of the distal end of the cannula after the force has been removed. 
     In further accordance with the foregoing first and/or second examples, an apparatus and/or method may further include any one or more of the following: 
     In accordance with an example, the drug delivery device is disposed in the barrel receptacle. 
     In accordance with another example, the strike member is disposed a predetermined distance from the distal end surface and the fulcrum point of the cannula. 
     In accordance with another example, the predetermined distance is approximately 25*D 2 , where D is the outer diameter of the cannula in millimeters. 
     In accordance with another example, the fixture assembly also includes a plurality of gauge blocks for setting the predetermined distance between the strike member and the distal end surface. Each gauge block has a distinct length dimension corresponding to one of a plurality of predetermined cannula gauges. 
     In accordance with another example, each gauge block corresponds to a cannula gauge of between about a 10 gauge and about a 34 gauge. 
     In accordance with another example, the figure block includes a first fixture block and a second fixture block. 
     In accordance with another example, the first fixture block and the second fixture block are coupled in a clam-shell arrangement. 
     In accordance with another example, each fixture block has a first end, a second end, and defines a barrel groove extending between the first end and the second end and the first and second fixture blocks are adapted to be coupled together such that the barrel grooves align with each other and form the corresponding barrel receptacle. 
     In accordance with another example, the fixture assembly also includes a latch to secure the first fixture block and the second fixture block relative to one another. 
     In accordance with another example, the fixture assembly also includes a first end plate and a second end plate coupled to the second ends of the first and second fixture blocks, respectively. Each end plate defines a plunger groove. The plunger grooves collectively defines a plunger receptacle for receiving a plunger rod of the drug delivery device when the drug delivery device is disposed in the barrel receptacle. 
     In accordance with another example, the fixture block includes a support block that includes a top support surface and the distal end surface, and when the drug delivery device is received in the barrel receptacle, the cannula extends across the top support surface of the support block. 
     In accordance with another example, the fixture block is formed of a first material and the support block is formed of a second material different from the first material. 
     In accordance with another example, the method also includes determining an initial position of the distal end of the cannula prior to applying the force to the distal end of the cannula by moving the strike member into contact with the distal end of the cannula. 
     In accordance with another example, the method also includes determining a change between the final position and the initial position by moving the strike member into contact with the distal end of the cannula. 
     In accordance with another example, the method also includes determining a change in an angle of the cannula between the final position and the initial position. 
     In accordance with another example, the method includes defining a fulcrum point of the cannula a spaced distance from the distal end of the barrel. 
     In accordance with another example, defining the fulcrum point includes providing the fixture with a pair of fixture blocks and a support block that extends from the fixture blocks. The support block defines a top support surface supporting the cannula and a distal end surface spaced away from the distal end of the barrel of the drug delivery device and beyond which the distal end of the cannula extends, the fulcrum point of the cannula thereby being disposed at the distal end surface of the support block. 
     In accordance with another example, the method includes positioning the strike member a predetermined distance from the fulcrum point of the cannula prior to applying the lateral force to the distal end of the cannula. 
     In accordance with another example, positioning the strike member includes positioning the strike member a distance of approximately 25*D 2 , where D is the outer diameter of the cannula in millimeters, from the fulcrum point of the cannula. 
     In accordance with another example, positioning the strike member includes selecting a gauge block from a plurality of gauge blocks based on the outer diameter of the cannula, positioning the selected gauge block against the fixture adjacent to the cannula, and moving the strike member into contact with the selected gauge block. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       It is believed that the disclosure will be more fully understood from the following description taken in conjunction with the accompanying drawings. Some of the drawings may have been simplified by the omission of selected elements for the purpose of more clearly showing other elements. Such omissions of elements in some drawings are not necessarily indicative of the presence or absence of particular elements in any of the exemplary embodiments, except as may be explicitly delineated in the corresponding written description. Also, none of the drawings is necessarily to scale. 
         FIG.  1    is a schematic illustration of one embodiment of a fixture assembly constructed in accordance with a first example of the present disclosure. 
         FIG.  2    is an expanded view of the fixture assembly of  FIG.  1   . 
         FIG.  3    is an isometric view of the fixture assembly of  FIG.  1    secured to a base plate of a compression testing machine including a strike member. 
         FIG.  4    is an isometric side view of a portion of the fixture assembly securing the barrel of the drug delivery device and the strike member engaging the cannula to allow an initial position of the cannula to be determined. 
         FIG.  5    is an isometric side view of the portion of the fixture assembly shown in  FIG.  4    with the strike member applying a force to the cannula to move the cannula a threshold distance. 
         FIG.  6    is an isometric view of the portion of the fixture assembly shown in  FIG.  4    with the force from the strike member removed. 
         FIG.  7    is an isometric view of the portion of the fixture assembly shown in  FIG.  4    with the strike member determining a final position of the cannula after the force has been removed. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure generally relates to testing fixtures used to determine the elasticity of drug delivery members, such as cannulas and/or needles (hereinafter referred to as “cannulas”). During an example elasticity test, the cannula may be bent a threshold distance for a threshold amount of time and then released. The example fixtures may be used to secure the drug delivery devices during these elasticity tests in a repeatable manner. Positioning the cannula in substantially the same location during each test allows a strike member used to move the cannula to contact substantially the same portion of the cannula. As a result, the tests can be performed substantially in the same way regardless of who or where the test is performed. 
     Each of the foregoing components of the drug delivery devices will now be described in more detail. 
       FIG.  1    is a schematic illustration of one embodiment of a fixture assembly  100  constructed in accordance with a first example of the present disclosure. The fixture assembly  100  is used for testing a drug delivery device  102 , such as the syringe shown. However, the fixture assembly  100  may alternatively be configured to test a free cannula. The drug delivery device  102  includes a barrel  104 , a flange  106 , and a drug delivery member such as a cannula  108  coupled with the barrel  104 . The drug delivery device  102  also includes a plunger rod  110  movably disposed within the barrel  104 . A plunger (not shown) may be coupled to the plunger rod  110  and slidably disposed within the barrel  104 . However, the tests disclosed herein may be performed using the fixture assembly  100  with the plunger rod  110  not disposed within the barrel  104 . The cannula  108  may be a rigid cannula such as a hollow needle or in some version, the cannula could be a flexible soft cannula. Generally, during an elasticity test, the drug delivery device  102  is clamped or otherwise received within and/or secured relative to the fixture assembly  100  and a force is applied to and removed from the cannula  102 . Thereafter, the cannula  102  is measured to determine if the cannula  102  plastically deformed as a result of the force applied. 
     Referring now to the fixture assembly  100 , the fixture assembly  100  includes a fixture block  111  including a first fixture block  112 , a second fixture block  114 , and a support  116 . The first fixture block  112  may be referred to as an upper fixture block and the second fixture block  114  may be referred to as a lower fixture block. Each of the fixture blocks  112 ,  114  has first and second ends  118 ,  120  and define a barrel groove  122  (more clearly shown in  FIG.  2   ) that extends between the ends  118 ,  120 . The barrel grooves  122  are adapted to mate to form a barrel receptacle  124 . 
     The support  116  is coupled to and extends from the first end  118  of the second fixture block  114 . The barrel grooves  122  are adapted to receive the barrel  104  to allow the cannula  108  to lay over the support  116  and for a fulcrum point  126  (see,  FIG.  5   ) of the cannula  108  to be spaced from a distal end  127  of the barrel  104  when the cannula  108  is bent during the elasticity test. The fulcrum point  126  may be positioned adjacent a distal end surface  128  of the support  116 . The distal end surface  128  is spaced away from the first end  118  of the second fixture block  114  and forms a fulcrum for the cannula  108 . In another example, the fixture block  111  may not include the first and second fixture blocks  112 ,  114  but may define the barrel receptacle  124  and includes the support  116 . In such an example, the drug delivery device  102  may be loaded within the fixture block  111  from the second end  120  to allow the cannula  108  to extend beyond the distal end surface  128 . An end cap may be included that is used to secure the drug delivery device  102  within the fixture block  111 . 
     Because the fulcrum point  126  is spaced from the distal end  127  of the barrel  104 , during the elasticity test, the cannula  108  itself is being flexed or bent. However, if the fulcrum point  126  were at the coupling between the cannula  108  and the barrel  104 , the adhesive or coupling between the barrel  104  and the cannula  108  may be flexed/bent instead. Flexing the adhesive coupling may result in inaccurate test results and/or the elasticity of the cannula  108  itself not being tested. 
     Referring still to  FIG.  1   , the support  116  is a support block  130 . The support block  130  has a top support surface  132  that may be substantially planer with an upper facing surface  134  of the second fixture block  114 . The cannula  108  lays over the top support surface  132  when the drug delivery device  102  is secured within the fixture assembly  100 . 
     The first fixture block  112  and the second fixture block  114  may be coupled in a clam-shell arrangement, as shown. Thus, the fixture blocks  112 ,  114  may be rotatably coupled. 
     A latch  135  is used to secure the first fixture block  112  and the second fixture block  114  relative to one another. The latch  135  may be referred to as a clamp. The latch  135  includes a male portion  136  that is rotatably coupled to the second fixture block  114  and a female portion  138  that is coupled to the first fixture block  112 . The male portion  136  and the female portion  138  are shown coupled to the fixture blocks  112 ,  114  using fasteners (e.g., bolts). However, the male and/or female portions  136 ,  138  may be coupled to the fixture blocks  112 ,  114  in different ways. For example, the male and/or female portions  136 ,  138  may be brazed to the corresponding fixture blocks  112 ,  114  and/or adhesive may be used. 
     In the example shown, the male portion  136  includes an elongated fastener  140  having a threaded end that extends through a slot  142  of the female portion  138 . A nut  144  is threaded onto the male portion  136  and is driven against a face  146  of the female portion  138  to secure the fixture blocks  112 ,  114  together. However, in another example, the fixture blocks  112 ,  114  may be coupled in a different way. For example, a plurality of fasteners may be used to couple the first fixture block  112  and the second fixture block  114  together. Other methods may prove suitable. 
     An upper end plate  152  and a lower end plate  154  may be included that are coupled to the second end  120  of the corresponding fixture block  112 ,  114 . The end plates  152 ,  154  are shown being coupled to the fixture blocks  112 ,  114  using fasteners. Other methods of coupling the end plates  152 ,  154  and the fixture blocks  112 ,  114  may prove suitable. In the example shown, each of the end plates  152 ,  154  define a plunger groove  156  that mate with one another and form a plunger receptacle  158 . When the drug delivery device  102  is secured in the fixture assembly  100 , the plunger rod  110  of the drug delivery device  102  may extend through the plunger receptacle  158 . 
     The fixture blocks  112 ,  114  may be formed of a first material and the support  116  may be formed of a second material. In an example, the fixture blocks  112 ,  114  are formed of metal such as Aluminum and the support  116  is formed of plastic such as polyether ether ketone PEEK. Using PEEK for the support  116  may reduce abrasion of the cannula  108 . However, other materials may prove suitable to form the fixture blocks  112 ,  114 , and/or the support  116  and the fixture blocks  112 ,  114 , and/or the support  116  may be formed of the same or different materials. 
       FIG.  2    is an expanded view of the fixture assembly  100  of  FIG.  1   . The fixture blocks  112 ,  114  include lateral sides  159 ,  160  and, in the example shown, are rotatably coupled at the lateral side  159  by a hinge  162 . While two hinges  162  are shown, any number of hinges may be included instead. The latch  135  is used to selectively couple the fixture blocks  112 ,  114  at the second lateral side  160 . 
     In the example shown, the support  116  includes a barrel seat  164  that is adapted to receive an end of the barrel  104  of the drug delivery device  102 . During the elasticity test, the distal end  127  of the barrel  104  may bear against the barrel seat  164 . The barrel seat  164  may be referred to as a cut out. The barrel seat  164  may be formed by a semi-circular groove or may otherwise have a cross-section that corresponds to at least a portion of the cross-section of the drug delivery device  102 . In other implementations and based on the length of the drug delivery device  102  being tested (e.g., the length of the barrel  104 ), the barrel seat  164  may be modified in shape, dimension, etc., and/or may be omitted. Moreover, additional or alternative changes to the fixture assembly  100  may occur to accommodate different styles and/or brands of drug delivery devices produced by the same or different manufactures. For example, in some implementations, centering pieces (e.g., strips, o-rings, or other constructs) may be used in conjunction with the fixture blocks  112 ,  114  to account for syringe barrels, for example, having different physical shapes and/or dimensions. In one contemplated version, for example, the fixture blocks  112 ,  114  may define opposing grooves that are connected to and outwardly extending from the corresponding barrel grooves  122 , transvers to the longitudinal dimension of the barrel grooves  122 . These opposing grooves may receive an elastomer material in the form of a rubber strip, for example, that is used to center and/or secure the drug delivery device  102 , the barrel  104 , and/or the cannula  108  relative to the fixture assembly  100 . Other configurations are possible. 
     The fixture blocks  112 ,  114  also each define a flange groove  165  adjacent the second end  120 . The flange grooves  165  are adapted to mate and receive the flange  106  of the drug delivery device  102 . The flange grooves  165  enable the drug delivery device  102  to be positioned in substantially the same fixed location during the elasticity tests performed on the different drug delivery devices. The end plates  152 ,  154  also form a portion of the flange grooves  165  when they are coupled to the fixture blocks  112 ,  114 . 
       FIGS.  3 - 6    depict a process of using the fixture assembly  100  during an elasticity test. 
       FIG.  3    is an isometric view of the fixture assembly  100  of  FIG.  1    secured to a base plate  166  of a compression testing machine  168 . The compression testing machine  168  includes a strike member  170  shown as a strike pin. The compression testing machine  168  may be a force testing machine. 
     In the example shown, a gauge  172  is positioned on the support  116 . The gauge  172  may be referred to as a gauge block. The gauge  172  is L-shaped and includes an upper leg  174  and a lower leg  176 . 
     In practice, the gauge  172  is used to define a distance  178  between a face  180  (see,  FIG.  1   ) of the support  116  and the strike member  170 . In some examples, the distance  178  is defined by Equation 1, where D corresponds to the distance  178  and the diameter corresponds to an outer diameter of the cannula  108 . The diameter of the cannula  108  may be in millimeters and the distance  178  may be in millimeters. It is noted that the distance, D, is a length measurement even though the Diameter 2  is an area measurement. In an example, the outer diameter of the cannula  108  is about 1.0 millimeter. 
         D= 25(Diameter 2 )  Equation 1:
 
     An end  182  of the strike member  170  is adapted to engage and move a distal end  171  of the cannula  108  during the elasticity test, for example. The distal end  171  of the cannula  108  extends from the fixture assembly  100 . The strike member  170  may be pointed or rounded. 
     To position the strike member  170  to engage the gauge  172  and define the distance  178 , the fixture assembly  100  and the gauge  172  may be moved toward the strike member  170 . After the gauge  172  engages the strike member  170  and the gauge  172  and the fixture assembly  100  are unable to be further moved toward the strike member  170 , the fixture assembly  100  is secured to the base plate  166 . In the example shown, the fixture assembly  100  includes slots  184  through which fasteners  186  extend and couple the fixture assembly  100  to the compression testing machine  168 . An interaction between the fasteners  186  and the slots  184  allows the fixture assembly  100  to move in a direction generally indicated by arrow  188 . 
     While the gauge  172  is shown in  FIG.  3   , different gauge blocks may be used. For example, a plurality of gauge blocks may be provided where each of the gauge blocks has a distinct length dimension (e.g., a width) associated with a different cannula gauge (e.g., needle gauge). The gauge blocks including the gauge  172  may be used with a cannula gauge of between about a 10 gauge and about a 34 gauge. In an example, the gauge  172  is associated with a cannula having a 20 gauge, a 21 gauge, a 22 gauge, a 23 gauge, a 25 gauge, a 29 gauge, a 30 gauge, or a 31 gauge. 
     Prior to determining the elasticity of the cannula  108 , the strike member  170  may also be zeroed by touching the strike member  170  to the fixture assembly  100  and/or the support  116  until a force of between about 1 Newton (N) and about 5 N is recorded. The axial height may be defined as “zero.” When and/or before the elasticity test begins, the strike member  170  may be moved above the fixture assembly  100  to allow the drug delivery device  102  to be secured within the fixture assembly  100 . 
       FIG.  4    is an isometric side view of a portion of the fixture assembly  100  securing the barrel  104  of the drug delivery device  102  and the strike member  170  engaging the cannula  108  to allow an initial position of the cannula  108  to be determined. With the drug delivery device  102  secured within the fixture assembly  100 , the cannula  108  staked to the barrel  104  is allowed to extend from the fixture assembly  100 . The cannula  108  is shown overlaying the support  116  and extending beyond the distal end surface  128  of the support block  116 . In the example shown, the strike member  170  is shown touching the cannula  108  to allow the compression testing machine  168  to determine an initial position of the cannula  108  prior to the strike member  170  bending/moving the cannula  108  during the elasticity test. 
     In an example, when the strike member  170  initially contacts the cannula  108 , the strike member  170  approaches the cannula  108  at a speed of about 5 millimeters (mm)/minute. However, the strike member  170  may approach the cannula  108  at a speed of about 0.1 mm/min to about 500 mm/min or another speed. The strike member  170  may contact the cannula  108  at a portion  189  on the cannula  108  that is defined by the distance  178  set by the gauge  172 . The strike member  170  may stop moving for approximately one second after a force of about 0.15 N is recorded. The axial distance of the strike member  170  may be recorded as the initial position of the cannula  108  and represented by P i . 
       FIG.  5    is an isometric side view of the portion of the fixture assembly  100  shown in  FIG.  4    with the strike member  170  applying a force to the cannula  108  to move the cannula  108  a threshold distance  190 . The threshold distance  190  may be referred to as a test condition or a threshold amount. During the elasticity test, the strike member  170  may bend the cannula  108  a given bend angle in degrees, a given axial distance, and/or with a particular amount of force for a threshold amount of time. The fulcrum point  126  is shown being spaced a distance  192  from the distal end  127  of the barrel  104  of the drug delivery device  102  and being formed over the support  116 . 
     In an example, during the elasticity test, the strike member  170  applies a lateral force to the cannula  108  in the direction indicated by arrow  193  and toward the base plate  166  at a speed of approximately 5 mm/min. In another example, the strike member  170  may be moved toward the base plate  166  at a speed of about 0.1 mm/min to about 500 mm/min until the threshold distance is met. As an example, some elasticity tests require that the cannula  108  be bent to an angle of 12 degrees from the initial position and held at 12 degrees for 60 seconds. However, the elasticity tests of different countries may have different requirements. 
       FIG.  6    is an isometric view of the portion of the fixture assembly  100  shown in  FIG.  4    with the force from the strike member  170  removed. Thus, the cannula  108  has been allowed to move to its natural state and/or to its final position after being moved by the strike member  170 . In an example, after the threshold distance  190  is satisfied, the strike member  170  may be moved away from the cannula  108  at a speed of approximately 500 mm/min. In another example, the strike member  170  may be moved away from the cannula  108  at any speed of between about 0.1 mm/min to about 2000 mm/min. Other speeds of moving the strike member  170  may prove suitable. 
       FIG.  7    is an isometric view of the portion of the fixture assembly  100  shown in  FIG.  4    with the strike member  170  determining a final position of the cannula  108  after the force has been removed. The cannula  108  may be inspected to determine if the cannula  108  has returned to its initial position or if plastic deformation has occurred while the cannula  108  was under load. Thus, using the disclosed examples, plastic deformation (if any) of the cannula  108  can be quantified by measuring a change between an initial position of the cannula  108  and a final position of the cannula  108 . The change between the initial and final positions may be defined in millimeters or a deflection angle in degrees. 
     An output on the results of the elasticity test may be generated by the compressible testing machine  108 . The results may be displayed using different methods such as displaying the results on a user interface, providing access to the results at a different device, printing the results, etc. 
     In an example, to determine the final position of the cannula  108 , the strike member  170  may approach the cannula  108  at a speed of about 5 mm/min. In another example, the strike member  170  may move toward the cannula  108  at a speed of between about 0.1 mm/min to about 500 mm/min. The strike member  170  may contact the cannula  108  at the portion  189  of the cannula  108  and stop moving for approximately 1 second after a force of approximately 0.15 N is recorded. The axial distance of the strike member  170  may be recorded as the final position of the cannula  108  and represented by P f . 
     Equation 2 may be used to determine the change in the position (bend) of the cannula  108 , where P i  is the initial position of the cannula  108  in millimeters, P f , is the final position of the cannula  108  in millimeters, D is the nominal outer diameter of the cannula  108  in millimeters, and the deflection angle is the angle formed by the initial position and the final position of the cannula  108  after having the force applied at the portion  189  of the cannula  108 . 
     
       
         
           
             
               
                 
                   
                     Deflection 
                     ⁢ 
                         
                     Angle 
                   
                   = 
                   
                     
                       tan 
                       
                         - 
                         1 
                       
                     
                     [ 
                     
                       
                         
                           P 
                           f 
                         
                         - 
                         
                           P 
                           i 
                         
                       
                       
                         25 
                         ⁢ 
                         
                           D 
                           2 
                         
                       
                     
                     ] 
                   
                 
               
               
                 
                   Equation 
                   : 
                       
                   2 
                 
               
             
           
         
       
     
     The deflection may also be reported as the distance, P f −P i    
     While the present disclosure has been described in connection with various embodiments, it will be understood that the present disclosure is capable of further modifications. The present disclosure is intended to cover any variations, uses, or adaptations of the disclosed subject matter following, in general, the principles of the present disclosure, and including such departures from the present disclosure as, within the known and customary practice within the art to which the present disclosure pertains. 
     It is noted that the construction and arrangement of the drug delivery device and its various components and assemblies as shown in the various exemplary embodiments is illustrative only. Although only a few embodiments of the subject matter at issue have been described in detail in the present disclosure, those skilled in the art who review the present disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter disclosed herein. For example, elements shown as integrally formed may be constructed of multiple parts or elements, and vice versa. Also, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present disclosure as defined in the appended claims. Furthermore, the order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present disclosure.