referring to fig1 , blood collection tube holder 100 satisfactorily comprises body 102 , discharge needle displacement member 104 and removable needle cap 106 . body 102 further comprises front wall sections 136 , 158 , outwardly projecting rear flange 134 , and optional textured gripping surfaces 103 , 101 ( with 101 being visible in fig4 ). discharge needle displacement member 104 desirably comprises outwardly facing textured touch surface 130 and rearwardly projecting needle retraction chamber 105 . referring to fig2 , removable needle cap 106 of fig1 is removed to reveal forward projecting venipuncture needle 108 held by needle holder 110 seated inside nose 138 of body 102 in addition to parts already mentioned in relation to fig1 . referring to fig3 , removable needle cap 106 further comprises opposed textured gripping surfaces 148 , tapered cylindrical body 156 having closed front end 152 and rear flange 150 , and rearwardly projecting , selectively releasable locking arm 154 . body 102 further comprises substantially cylindrical outside wall 132 , an elongate opening 124 disposed between longitudinally extending wings 125 , 127 , guide structures 144 , 145 disposed behind front wall 136 , and front opening 140 into interior passage 141 inside nose 138 . notch or recess 142 is provided in front wall 136 of body 102 to provide clearance for releasable locking arm 154 of removable needle cap 106 . recess or orifice 131 is optionally provided in the forwardly facing surface of flange 134 between wings 125 , 127 for use in releasably engaging and supporting rearwardly facing end 107 of needle retraction chamber 105 as further discussed below in relation to fig4 . still referring to fig3 , the front portion of discharge needle displacement member 104 further comprises front opening 128 that facilitates access into needle retraction chamber 105 , and opposed arms 124 , 126 that are slidably engageable with cooperatively sized and configured guide structures 144 , 145 disposed behind front wall 136 of body 102 . latches 115 , 117 on opposed arms 124 , 126 are configured to slide past opposed shoulders inside the front portion of body 102 during installation of discharge needle displacement member 104 inside body 102 during assembly of blood collection tube holder 100 as indicated by arrows 121 , 122 . also disposed inside body 102 of blood collection tube holder 100 are compression spring 120 ( depicted in expanded condition prior to compression ), venipuncture needle 108 having a forwardly projecting beveled end 160 and an opposed blunt end that is insertable into axial bore 162 , where it can be held in place by a uv - curable adhesive or by any other similarly effective conventional means . during assembly of blood collection tube holder 100 , spring 120 is desirably seated inside nose 138 and is disposed around venipuncture needle 108 and the shaft portion of needle holder 110 , and is constrained behind larger diameter head portion 164 of needle holder 110 . body 102 of blood collection tube holder 100 also comprises needle holder 114 for rearwardly facing fluid discharge needle 116 . needle holder 114 is desirably configured with a front portion 168 that slidably engages guide members 144 behind front wall 136 of body 102 and further comprises intermediate portion 169 , rearwardly projecting portion 172 and centrally disposed longitudinal bore 170 that is desirably coaxially aligned with needle holder 110 . forwardly facing end 174 of fluid discharge needle 116 is desirably inserted into bore 170 and is held in place by a uv - curable adhesive or another similarly effective conventional means . rearwardly facing tip 176 of needle 116 is desirably configured to penetrate the stoppered end of a conventional blood collection tube ( not shown ) when the blood collection tube is inserted through the opening defined by rear flange 134 of body 102 and into cylindrical cavity 133 inside body 102 ( visible in fig4 and 6 ) prior to use . collapsible elastomeric sheath 118 is substantially cylindrical and comprises open end 178 communicating with an internal bore and close end 182 . collar 180 is provided for use in frictionally attaching sheath 118 to rearwardly projecting portion 172 and holds collapsible sheath 118 in position behind intermediate portion 169 . collapsible sheath 118 is desirably long enough to cover rearwardly facing tip 176 of fluid discharge needle 116 prior to use and is collapsed and pushed forward around needle 116 after tip 176 penetrates closed end 182 as it is inserted into the stoppered end of a blood collection tube . referring to fig3 and 6 , compressible fluid seal 112 is substantially cylindrical and has centrally disposed bore 166 that is coaxially aligned with the fluid flow path through needle holders 110 , 114 . during assembly of body 102 of blood collection tube holder 100 , larger diameter head portion 164 is desirably pressured forwardly inside nose 138 of body 102 to compress spring 120 , and is held in nose 138 while the front end of compressible fluid seal 112 is inserted into nose 138 behind needle holder 110 . the rear end of compressible fluid seal 112 , which extends rearwardly from nose 138 , is then desirably compressed sufficiently to enable needle holder 114 to be slidably inserted into body 102 behind compressible fluid seal 112 to establish fluid - tight engagement between compressible fluid seal 112 and each of needle holders 110 , 118 . the relative positions of nose 138 , needle holders 110 , 114 compressible fluid seal 112 as assembled inside body 102 are better seen in fig6 . referring to fig4 , like reference numerals are used to identify parts of blood collection tube holder 100 already discussed above in relation to fig3 . additional structural elements not visible in fig3 include inside bore 153 of removable needle cap 106 , textured gripping surface 101 ( visible in fig5 opposite textured gripping surface 103 ), and optional rearwardly facing projection 119 of discharge needle displacement member 104 that is aligned with aperture 131 when discharge needle displacement member 104 is installed inside body 102 as shown in fig6 . it should be understood that projection 119 and aperture 131 are merely illustrative of other similarly effective structures that can optionally provide releasable frictional engagement between the closed rear end of discharge needle displacement member 104 and outwardly projecting rear flange 134 . where present , projection 119 and aperture 131 are desirably cooperatively sized and aligned to form a releasable frictional engagement mechanism that provides additional support to the rear end of discharge needle displacement member 104 prior to and during use of blood collection tube holder 100 to collect a blood sample . projection 119 desirably remains in releasable engagement with aperture 131 until discharge needle displacement member 104 is moved into contact with needle holder 114 inside body 102 following withdrawal of a blood collection tube from cylindrical cavity 133 ( fig6 ) inside body 102 . referring to fig5 and 6 , blood collection tube holder 100 of the invention as described in relation to fig1 and 4 is shown in fully assembled form with removable needle cap 106 installed as shown in fig1 , and with releasable locking arm 154 inserted into body 102 . when disposed in the position shown , releasable locking arm 154 supports and prevents the front portion of discharge needle displacement member 104 from being inadvertently moved further inwardly into body 102 during shipping and storage , and prior to removal of needle cap 102 prior to use . as depicted in fig6 , a continuous fluid flow path extends from venipuncture needle 108 thorough needle holder 110 , compressible fluid seal 112 and needle holder 114 to fluid discharge needle 116 , all of which are desirably coaxially aligned for use in drawing a blood sample after removal of needle cap 106 and insertion of a blood collection tube into blood collection tube holder 100 . referring to fig3 , 7 and 8 , structures are disclosed that are exemplary of a variety of different structures that can be used by one of ordinary skill in the art upon reading this disclosure to position and support discharge needle displacement member 104 relative to body 102 ( as viewed from the rear through the opening defined by flange 134 ) even after releasable locking arm 154 is withdrawn from its locking position beneath discharge needle displacement member 104 following removal of needle cap 106 . looking first at fig4 and 7 , rearwardly facing projection 119 of needle retraction chamber 105 is aligned with and releasably inserted into a recess or aperture 131 of flange 134 . looking next at detail view of fig8 with reference to fig3 and 7 , as discharge needle displacement member 104 is inserted into body 102 , free ends 194 , 196 of arms 124 , 126 , respectively , slide past inwardly facing tapered shoulders 190 , 192 of guide members 144 , 145 behind front portion 168 and beside intermediate portion 169 of needle holder 114 ( fig3 and 4 ) until the tapered portions of shoulders 135 , 137 of arms 124 , 126 , respectively , contact and rest against inwardly facing tapered shoulders 190 , 192 . fig7 and 8 indicate the resting position of discharge needle displacement member 104 relative to body 102 prior to and during use of the device to draw a blood sample . referring to fig9 and 10 , a transverse cross - sectional view is taken behind front wall 136 of body 102 to better illustrate the positions of discharge needle displacement member 104 and opening 128 into needle retraction chamber 105 relative to body 102 prior to and during use of the device but prior to retraction of the venipuncture needle . as best seen in fig1 , when support arms 109 , 111 of discharge needle displacement member 104 are installed in body 102 , hook members 115 , 117 disposed at the lower ends of support arms 111 , 109 , respectively , are initially flexed inwardly and then pass opposing square shoulders in walls 202 , 204 of guide structures 144 , 145 , respectively , that permit movement in the direction of arrows 198 , 200 ( which movement is still restricted by the resistance imposed by tapered shoulders 190 , 192 as discussed above in relation to fig8 ) but prevent movement in the opposite direction to disengage discharge needle displacement member 104 from body 102 . fig1 and 12 disclose two additional orthogonal views of blood collection tube holder 100 with venipuncture needle 116 projecting forwardly from needle holder 110 and nose 138 , and with discharge needle displacement member installed in the use position relative to body 102 . other reference numerals used in fig1 and 12 are consistent with those previously described in relation to other drawing figures . following use of blood collection tube holder 100 , as manual pressure is applied to textured touch surface 130 ( fig7 ), free ends 194 , 196 are squeezed together by the tapered surfaces of shoulders 135 , 137 sliding downwardly past inwardly facing shoulders 190 , 192 of guide structures 144 , 145 , respectively . once shoulders 135 , 137 move past shoulders 190 , 192 , the front portion of discharge needle displacement member 104 is no longer constrained in the pre - use and use position . the same manual force applied to textured touch surface 130 is desirably sufficient to overcome the frictional holding force between projection 119 and aperture 131 . this causes projection 119 to disengage from aperture 131 and allows both the front and rear portions of discharge needle displacement member 104 to move inwardly relative to body 102 . as this movement occurs , the front portion of discharge needle displacement member 104 contacts needle holder 114 ( fig4 ) and displaces needle holder 114 and fluid discharge needle 116 laterally away from compressible fluid seal 112 , simultaneously disrupting the continuous fluid flow path that existed between venipuncture needle 108 and fluid discharge needle 116 ( fig6 ) prior to the contact and displacement . fig1 and 14 depict cross - sectional views similar to those previously described in relation to fig9 and 10 except that the section is taken through front portion 168 of needle holder 114 and the needle retraction process has been initiated . as shown , discharge needle displacement member 104 is moved out of engagement with aperture 131 in flange 134 of body 102 , and the front portion of discharge needle displacement member 104 is moved into contacting and abutting relation with the top of front portion 168 of needle holder 114 . from this position , continued application of manual pressure to textured touch surface 130 will force discharge needle displacement member 104 into the position shown in fig1 - 18 , wherein venipuncture needle 108 is fully retracted inside body 102 of blood tube collection holder 100 , front portion 168 of needle holder 114 is disengaged from the rear end of compressible fluid seal 112 , and needle holder 114 and fluid discharge needle 116 are forced into the position best shown and further described below in relation to fig1 and 20 . referring to fig1 and 20 , when discharge needle displacement member 104 is moved to the position shown , needle retraction chamber 105 becomes coaxially aligned with collapsible fluid seal 112 , needle holder 110 and venipuncture needle 108 , all of which are then propelled by expanding compression spring 120 into needle retraction chamber 105 . when disposed in this position , venipuncture needle 108 is no long exposed in a position where accidental needle stick injuries and related contamination by blood - borne pathogens can occur . this is particularly true if venipuncture needle 108 is retracted directly from the body of a patient as recommended . at the same time , needle holder 114 and fluid discharge needle 116 , together with any fluid remaining inside them , are confined between the back side of front wall 136 and the closed rear end 182 of collapsible elastomeric sheath 118 that is preferably substantially impermeable to any blood remaining inside fluid discharge needle 116 . other alterations and modifications of the invention disclosed here will likewise become apparent to those of ordinary skill in the art upon reading this specification and claims in relation to the accompanying drawings , and the inventors intend that the scope of the invention be limited only by the broadest interpretation of the appended claims to which the inventors are legally entitled .
a medical device configured as a blood collection tube holder , the device having a body with two spaced - apart , oppositely facing , coaxially aligned needles including a forwardly facing venipuncture needle and a rearwardly facing fluid discharge needle , the two needles being held by first and second needle holders separated by a compressible fluid seal defining part of a fluid path between the two needles and the two needle holders . the body also includes a discharge needle displacement member that is manually repositioned following removal of the last blood tube holder so that the discharge needle displacement member contacts the second needle holder and displaces the second needle holder and the fluid discharge needle laterally inside the body to initiate retraction of the venipuncture needle into a rearwardly projecting needle retraction chamber .