U.S. patent application number 15/590556 was filed with the patent office on 2017-08-24 for medical device with retractable needle and moveable plunger seal.
The applicant listed for this patent is Retractable Technologies, Inc., Thomas J. Shaw. Invention is credited to Thomas J. Shaw, Ni Zhu.
Application Number | 20170239426 15/590556 |
Document ID | / |
Family ID | 45400257 |
Filed Date | 2017-08-24 |
United States Patent
Application |
20170239426 |
Kind Code |
A1 |
Shaw; Thomas J. ; et
al. |
August 24, 2017 |
Medical Device with Retractable Needle and Moveable Plunger
Seal
Abstract
A medical device having a barrel, a retractable needle, a needle
retraction assembly and a plunger, the needle retraction assembly
including and being held inside the barrel prior to retraction at
least in part by a retainer member contacting the barrel, the
plunger comprising a plunger seal with an body having at least a
portion that is rearwardly moveable relative to the plunger and an
elastomeric web that seals a retraction cavity inside the plunger
prior to retraction of the needle, the retainer member and the
plunger seal each cooperating with an inside wall of the barrel to
provide a sealed liquid containment chamber inside the device.
Inventors: |
Shaw; Thomas J.; (Frisco,
TX) ; Zhu; Ni; (Plano, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Shaw; Thomas J.
Retractable Technologies, Inc. |
Frisco
Little Elm |
TX
TX |
US
US |
|
|
Family ID: |
45400257 |
Appl. No.: |
15/590556 |
Filed: |
May 9, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12827548 |
Jun 30, 2010 |
9642970 |
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15590556 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61M 5/508 20130101;
A61M 2005/3239 20130101; A61M 5/3234 20130101 |
International
Class: |
A61M 5/32 20060101
A61M005/32 |
Claims
1. A medical device having a retractable needle, the device
comprising: a barrel; a needle retraction assembly further
comprising a needle holder seated inside the barrel and a retainer
ring that seals against fluid leakage between the needle holder and
the barrel, wherein the retractable needle is attached to the
needle retraction assembly and projects forwardly of the barrel;
and a plunger inserted into an opening in the rear of the barrel
that slidably engages the barrel so as to allow forward movement of
the plunger inside the barrel, the plunger further comprising a
longitudinally extending sidewall defining an interiorly disposed
retraction cavity with a forwardly facing open end, an annular
shoulder facing radially outward from the plunger sidewall, and an
elastomeric plunger seal disposed at the front of the plunger; the
plunger seal further comprising an annular body disposed in
spaced-apart relation to the annular shoulder of the plunger that
is moveable rearwardly on the plunger sidewall prior to needle
retraction, and an elastomeric web that extends across the open end
of the retraction cavity and prevents liquid from leaking into the
retraction cavity prior to needle retraction.
2. The medical device of claim 1 wherein the plunger comprises at
least one surface that limits how far at the at least part of the
annular body can move on the plunger sidewall.
3. The medical device of claim 1 wherein the plunger has a blunt
forwardly facing surface surrounding the forwardly facing open
end.
4. (canceled)
5. (canceled)
6. (canceled)
7. The medical device of claim 1 wherein the elastomeric plunger
seal is molded from a rubbery material.
8. The medical device of claim 1 wherein the retainer ring is
molded from an elastomeric material.
9. (canceled)
10. The medical device of claim 8 wherein the needle holder has an
outside diameter and the sidewall of the plunger has an inside
diameter greater than the outside diameter of the needle
holder.
11. The medical device of claim 1 wherein a portion of the needle
holder projects forwardly of the barrel prior to needle
retraction.
12. The medical device of claim 1 wherein the needle holder
comprises a longitudinally extending fluid passageway and wherein
the needle is attached in fixed longitudinal relation to the fluid
passageway.
13. (canceled)
14. (canceled)
15. (canceled)
16. The medical device of claim 1 wherein a forwardly extending
part of the plunger causes the plunger seal to contact the retainer
ring prior to retraction of the needle.
17. The medical device of claim 1 wherein the retainer ring is
moved forwardly and is displaced from the needle holder by forward
movement of the plunger during retraction.
18. The medical device of claim 16 wherein the annular body of the
plunger seal is displaced rearwardly on the plunger after the
forwardly extending part of the plunger seal contacts the retainer
ring.
19. The medical device of claim 1 wherein the needle retraction
assembly comprises at least one rearwardly projecting structure
that is configured to contact and penetrate the elastomeric web
extending across the open end of the retraction cavity when the
plunger is moved forwardly inside the barrel just prior to needle
retraction.
20. The medical device of claim 1 wherein the needle retraction
assembly comprises at least one rearwardly projecting structure
that is configured to contact and displace the elastomeric web
extending across the open end of the retraction cavity when the
plunger is moved forwardly inside the barrel just prior to needle
retraction.
21. (canceled)
22. The medical device of claim 1 wherein the plunger has a
rearwardly facing thumb cap that is disposed inside or adjacent to
the opening in the rear of the barrel when the plunger is fully
depressed inside the barrel.
23. The medical device of claim 1 wherein a thumb cap disposed at
the rear of the plunger is lodged inside a substantially
cylindrical collar at the rear of the barrel so as to make the
thumb cap difficult to grasp.
24. The medical device of claim 1 wherein said device is a
syringe.
25. (canceled)
26. (canceled)
27. The medical device of claim 1 wherein the plunger is configured
to apply a forwardly directed force to the retainer ring through
the plunger seal as the plunger is moved forwardly inside the
barrel to a point where the plunger seal contacts the retainer
ring.
28. (canceled)
29. (canceled)
30. The medical device of claim 3 wherein the blunt surface is
stepped longitudinally.
31. (canceled)
32. The medical device of claim 1 wherein the plunger seal and
retainer ring are made from different elastomeric materials.
33. A medical device having a barrel, a retractable needle, a
needle retraction assembly, and a plunger that slidably engages the
barrel, wherein: the needle retraction assembly is biased to
project the needle rearwardly relative to the barrel during
retraction of the needle and is held in place relative to the
barrel prior to retraction of the needle at least in part by a
retainer member that contacts and frictionally engages the barrel;
and the plunger comprises an interior retraction cavity, an
elastomeric plunger seal disposed on the plunger, at least part of
which is rearwardly moveable on the plunger, the plunger seal
further comprising an elastomeric web that spans and seals an
opening into the retraction cavity prior to retraction of the
needle; wherein an annular body portion of the elastomeric plunger
seal is displaced and pushed rearwardly on the plunger by an
annular shoulder disposed inside the barrel as the plunger is moved
forwardly inside the barrel; and wherein the needle retraction
assembly further comprises a rearwardly extending projection that
contacts and stretches the elastomeric web as the annular body
portion of the elastomeric plunger seal is displaced and moved
rearwardly on the plunger as the plunger is moved forwardly inside
the barrel.
34. (canceled)
35. The medical device of claim 33 wherein the needle retraction
assembly comprises a plurality of rearwardly extending projections
that contact and puncture the elastomeric web as the plunger is
moved forwardly inside the barrel.
36. The medical device of claim 33 wherein the plunger contacts the
retainer member to release the retainer member from frictional
engagement with the barrel as the plunger is advanced inside the
barrel.
37. The medical device of claim 36 wherein the plunger seal
contacts the retainer member to release the needle retraction
assembly from frictional engagement with the barrel as the plunger
is advanced inside the barrel.
38. (canceled)
39. The medical device of claim 37 wherein a portion of the
elastomeric web contacts and displaces the elastomeric retainer
member forwardly to release the needle retraction assembly from the
barrel as the plunger is advanced inside the barrel.
40. The medical device of claim 33 wherein at least part of the
elastomeric web is stretched and thinned as the annular body is
moved rearwardly on the plunger.
41. The medical device of claim 33 when configured as a
syringe.
42. The medical device of claim 33 wherein the plunger comprises a
front end that is configured to contact the retainer member so that
a force applied to the retainer member through the plunger is
concentrated on one portion of the retainer member.
43. The medical device of claim 42 wherein the front end comprises
a contact interface that is configured to contact the retainer
element so that a force applied to the retainer member through the
plunger is initially concentrated on one side of a rearwardly
facing portion of the retainer member.
44. The medical device of claim 33 wherein the plunger comprises a
front end that is configured to contact the retainer member so that
a force applied to the retainer ring through the plunger is
distributed substantially evenly around the retainer member.
45. (canceled)
48. The medical device of claim 33 wherein the needle retraction
assembly comprises a spring that biases the retractable needle
rearwardly toward the retraction cavity.
49. The medical device of claim 33 wherein the needle retraction
assembly comprises a spring that biases the retractable needle
toward the retraction cavity and wherein the rearwardly extending
projection punctures the elastomeric web in such manner that the
spring does not hang up on the elastomeric web during needle
retraction.
50. The medical device of claim 33 wherein the needle is releasably
attachable to the needle retraction assembly and can be changed
during use of the device or prior to needle retraction.
51. The medical device of claim 33 wherein the plunger is
configured to concentrate a forwardly directed force applied
through the plunger against an arcuate segment of the retainer
member.
52. The medical device of claim 33 wherein the retainer member is
elastomeric.
53. The medical device of claim 52 wherein the retainer member is
an elastomeric ring.
54. The medical device of claim 33 wherein the retainer member and
the plunger seal each cooperates with an inside wall of the barrel
to provide a sealed liquid containment chamber inside the
device.
55. A medical device comprising: a barrel; a retractable needle; a
needle retraction assembly comprising a needle holder, a retraction
spring, and a compressible retainer ring; and a plunger slidably
engaging the barrel, wherein: the needle retraction assembly is
held inside the barrel prior to needle retraction at least in part
by the retainer ring contacting the barrel; and the plunger
comprises an interior retraction cavity, a unitary elastomeric
plunger seal with an annular body coaxially disposed on the plunger
in axially spaced-apart relation to an annular shoulder projecting
outwardly from the plunger, the annular body being rearwardly
slidable on the plunger prior to engaging the annular shoulder, and
an elastomeric web that spans and seals an opening into the
retraction cavity prior to retraction of the needle; wherein the
retainer ring and the plunger seal each providing sealing
engagement with an inside wall of the barrel to provide a liquid
containment chamber inside the device so that prior to retraction
of the needle a liquid can flow into or out of the liquid
containment chamber through the needle.
56. The medical device of claim 55 wherein the retraction spring
biases the retractable needle toward the retraction cavity prior to
and during needle retraction.
57. The medical device of claim 55 wherein the needle holder
comprises at least one rearwardly extending projection that
punctures the elastomeric web in such manner that the retraction
spring does not hang up on the elastomeric web during
retraction.
58. The medical device of claim 55 wherein forward movement of the
plunger pushes the retainer ring out of sealing engagement with the
barrel without breaking or cutting any part of the needle
retraction assembly during retraction.
59. The medical device of claim 55 when configured as a
syringe.
60. The medical device of claim 55 wherein the needle is releasably
attachable to the needle retraction assembly and can be changed
during use of the device or prior to retraction.
61. The medical device of claim 55 wherein the plunger is
configured to concentrate a forwardly directed force applied
through the plunger against an arcuate segment of the retainer
ring.
62. (canceled)
63. (canceled)
64. (canceled)
65. (canceled)
66. (canceled)
67. A medical device comprising a barrel, a retractable needle
projecting forwardly of the barrel, a plunger further comprising a
retraction cavity and a plunger seal, and a needle retraction
assembly further comprising a rearwardly extending projection,
wherein the plunger seal further comprises a body surrounding a
portion of the plunger and a transverse elastomeric web that seals
the retraction cavity prior to needle retraction; whereby prior to
retraction, the body acts to reduce a force otherwise required for
the rearwardly extending projection to penetrate the elastomeric
web by sliding rearwardly on the plunger as the plunger is moved
forwardly inside the barrel past a point where the plunger seal is
contacted by an annular shoulder inside the barrel.
68. The medical device of claim 67 when configured as a
syringe.
69. The medical device of claim 67 wherein the needle is releasably
attachable to the needle retraction assembly.
70. The medical device of claim 67 wherein the needle is detachable
from the needle retraction assembly.
71. (canceled)
72. The medical device of claim 67 wherein the rearward movement of
the body stretches and thins the elastomeric web.
73. The medical device of claim 67 wherein the plunger has a
stepped front end.
74. (canceled)
Description
TECHNICAL FIELD
[0001] This invention relates to medical devices having needles
that are retractable following use to reduce the likelihood of
reuse, needle-stick injuries and accidental contamination of
healthcare workers and patients, especially by the transmission of
pathogens carried by bodily fluids. More particularly, the
invention relates to a medical device having an elastomeric
retainer ring and an elastomeric plunger seal moveable on the
plunger that cooperate to provide smoother operation and to
significantly reduce the pressure that must be applied by a user to
retract the needle.
BACKGROUND ART
[0002] In the past, clinicians have sometimes complained about the
magnitude of the thumb force (sometimes called the "retraction
force," "activation force" or "total force") that is required to
initiate needle retraction in syringes having retractable needles.
When using conventional syringes having needles that are retracted
by the expansion of a compressed spring, an additional thumb force
is typically applied axially at the back of the plunger handle
following injection to initiate needle retraction. The magnitude of
the thumb force that is required depends upon the structure and
operation of each particular syringe. One part of the required
thumb force is attributable to the force needed to break, rupture,
remove or displace the cover over the opening into a retraction
cavity inside the plunger handle. Another part of the required
thumb force is attributable to the force needed to release whatever
structure is holding the spring in compression. If the required
thumb force is too great, especially for clinicians having small
hands, it can be difficult to retract the needle after an
injection. This can cause the user to move or twist the syringe
while a needle is still inside the patient in order to gain more
leverage. Also, unless the structural elements of the device are
configured so that the thumb force can be applied smoothly so as to
open the retraction cavity and release the compressed spring
without jerks or abrupt movement prior to retraction.
[0003] Some prior art syringes have utilized a plug or
substantially rigid barrier to block the entrance to a retraction
cavity inside the plunger handle prior to retraction, but the force
required to dislodge or displace the plug, or to fracture the
substantially rigid barrier, also increased the required thumb
force. Other prior art syringes have used an axially fixed plunger
seal having a rubbery portion covering the opening to the
retraction cavity in combination with a two-part plunger handle in
which an inner member had to be moved past a detent to advance a
cutter that severed the covering portion, thereby also increasing
the required thumb force. In such cases, the force required to
dislodge a plug, fracture a barrier or move a plunger section past
a detent not only increased the thumb force required to initiate
retraction but also caused the syringe to jerk or move abruptly
prior to needle retraction.
[0004] U.S. Pat. No. 5,053,010 (McGary) discloses a syringe having
a retractable needle and a plunger with an axially slidable plunger
seal having a transverse web portion that seals the opening into
the plunger retraction cavity prior to retraction. That syringe has
a cutting tool disposed on the forwardly extending tip of the
plunger that cuts through both the transverse web across the
opening to the retraction cavity and another circumferentially
extending tab that secures the needle retainer to the barrel wall.
Because of the cutter positioned behind the transverse web, there
is a risk of premature rupture of the web during injection, which
is not desirable because the remaining portion of medicine in the
syringe could flow back into the retraction cavity rather than into
the patient.
[0005] U.S. Pat. No. 5,064,419 (Gaarde) discloses a syringe having
a retractable needle and a piston with a piston packing that is
confined to prevent axial movement relative to the piston. FIG. 3
discloses a thin membrane attached to the piston packing. The thin
membrane seals off a cavity inside the piston until the flat head
of the needle holder punctures or destroys the membrane for
retraction. The needle holder is held in place by the closed bottom
end of a barrel section that is disposed inside the spring
retainer.
[0006] U.S. Pat. No. 5,180,369 (Dysarz) discloses a syringe having
a retractable needle and a gasket disposed between the plunger and
the barrel that is axially slidable on the plunger. That syringe
has a shatter plate that seals the opening into the retraction
cavity inside the plunger prior to retraction. The needle holder is
held in place prior to retraction by a shatter plate and shatter
ring, each of which requires an additional gasket to provide a
fluid seal.
[0007] U.S. Pat. No. 5,180,370 (Gillespie) discloses a syringe
having a retractable needle and an annular seal ring that provides
a fluid seal between the plunger and barrel. The annular seal ring
does not appear to be confined to prevent axial movement relative
to the plunger but does not appear to slide axially relative to the
plunger during use. The plunger has a hollow chamber that is sealed
from the interior of the barrel by a resilient rupturable
cover.
[0008] U.S. Pat. No. 5,201,710 (Caselli) discloses a syringe having
a retractable needle held by a needle holder having a head with a
sharp part shaped like a crown with a sharp edge that first bends
and then breaks a diaphragm connected to a plunger seal element
that is confined to prevent axial sliding relative to the plunger
cylinder.
[0009] U.S. Pat. No. 5,578,011 (Shaw) discloses a syringe having a
retractable needle and an elastomeric friction ring to hold the
needle holder inside the barrel and to provide a fluid seal between
the barrel wall and the needle holder. That syringe has a plunger
seal that is confined from sliding axially along the plunger, and
an elastomeric plug that provides a releasable seal inside the
front opening to the retraction cavity inside the plunger.
[0010] U.S. Pat. No. 6,015,438 (Shaw) discloses a syringe having a
retractable needle, an annular retainer member to hold the needle
holder inside the barrel and an a plunger seal disposed between the
plunger and the barrel that is axially slidable along the plunger
for retraction. That syringe has a separate, removable stopper that
seals the opening into the retraction cavity inside the plunger
prior to retraction.
[0011] U.S. Pat. No. 6,994,690 (Kiehne) and U.S. Pat. No. 7,544,182
(Kiehne) disclose syringes having a retractable needle and a
tapered extension on the inner part of the head of the needle
holder that projects rearwardly to burst or pierce a frangible
portion of a fixed plunger seal as the plunger is advanced against
the needle holder. However, in those syringes the plunger seal is
axially confined and cannot slide rearwardly in relation to the
front of the plunger to stretch the frangible portion tautly from
the barrel side as the plunger contacts the needle holder.
[0012] A medical device having a retractable needle is therefore
needed that can be operated smoothly to initiate needle retraction
and that reduces the thumb force required to initiate
retraction
SUMMARY OF THE INVENTION
[0013] The medical devices of the invention desirably comprise a
barrel, a plunger slidably engaging the barrel, and a needle
retraction assembly that can be selectively activated to retract
the needle by moving the plunger forward relative to the barrel.
The needle retraction assembly can desirably comprise an
elastomeric retainer ring that contacts an inside wall of the
barrel to help create a liquid seal between a needle holder and the
inside wall of the barrel, and that helps hold a needle retraction
spring in compression prior to needle retraction. The plunger
desirably comprises an elastomeric seal with an annular body
portion and a transverse elastomeric web portion. The annular body
can function as a liquid seal between the plunger and barrel, and
the transverse web portion can seal off an opening into a
retraction cavity disposed inside the plunger prior to
retraction.
[0014] The annular body portion of the plunger seal can be mounted
on the front portion of the plunger in such manner that the body
portion is axially moveable relative to the outside wall of the
plunger to stretch and thin the transverse web across the opening
into the retraction cavity without prematurely rupturing the
transverse web portion prior to initiating needle retraction. The
forwardly facing annular end of the plunger, disposed behind the
transverse elastomeric web, is preferably configured so as not to
cut the elastomeric web when the web is stretched across the
opening into the retraction cavity prior to retraction, but can be
configured to exert a force that is either evenly or unevenly
distributed around the circumference of the retainer ring as
desired. An unevenly distributed force can reduce the force
required to initiate movement of the retainer ring relative to the
barrel prior to retraction. The force of the plunger is typically
applied to the retainer ring through that portion of the plunger
seal that covers the front tip end of the plunger handle, although,
a portion of the plunger handle can contact the retainer ring
directly in some cases such as, for example, if the elastomeric web
ruptures prior to contacting the retainer ring.
[0015] Prior to retraction, the needle and needle holder portions
of the needle retraction assembly can be biased rearwardly by a
compressed spring. The biasing force is desirably slightly less
than a holding force exerted on the needle holder portion by a
retainer member that establishes a liquid seal between the inside
of the barrel and the needle holder, and that maintains the front
tip of the needle holder in a forwardly projecting position
relative to the barrel until retraction. As the plunger is fully
depressed inside the barrel, the body portion of the elastomeric
plunger seal can be pushed rearwardly relative to the plunger and
the transverse web portion of the elastomeric plunger seal can be
stretched, thinned, and eventually penetrated, pierced or ruptured
by a rearwardly projecting portion of the needle holder as the
retainer member is displaced by the plunger to release the holding
force exerted on the needle holder by the retainer member and the
inside wall of the barrel. This in turn can allow the biasing force
of the compressed spring to propel the needle holder, spring and
needle rearwardly through the ruptured web of the elastomeric
plunger seal and into the retraction cavity. As the plunger is
fully depressed into the barrel, a thumb cap at the rear of the
plunger can be lodged inside a cylindrical collar at the rear of
the barrel so as to render the thumb cap substantially ungraspable
for reuse.
[0016] The use of an elastomeric retainer ring in combination with
a plunger seal having a body portion that is axially moveable
rearwardly along the barrel and an elastomeric web portion that can
be stretched and thinned by such rearward axial movement of the
body portion prior to retraction is believed to provide smoother
retraction and to substantially reduce the thumb force that must be
applied by a user to initiate needle retraction. Smoother operation
and a lower required thumb force are in turn believed to reduce
motion of the needle tip either forwardly or laterally inside a
patient prior to retraction, to promote the usage of devices having
retractable needles by clinicians, and to thereby reduce the
incidence of unwanted needle stick injuries and the associated
spread of blood-borne pathogens due to inadvertent contamination by
contact.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The apparatus of the invention is further described and
explained in relation to the following drawings wherein:
[0018] FIG. 1 is a perspective view of one embodiment of the
medical device of the invention;
[0019] FIG. 2 is an exploded perspective view of the medical device
of FIG. 1; FIG. 3 is an enlarged, cross-sectional vertical
elevation view taken along line 3-3 of FIG. 1 wherein the needle is
in a forwardly projecting use position;
[0020] FIG. 4 is an enlarged detail view taken from FIG. 3 but
showing the elastomeric seal across the front of the retraction
cavity being distended by the rearwardly projecting head of the
needle holder as the plunger tip moves forwardly inside the
barrel;
[0021] FIG. 5 is a cross-sectional elevation view of the medical
device of FIG. 3 wherein the needle is in its fully retracted
position;
[0022] FIG. 6 is an enlarged cross-sectional detail view of the
front portion of a plunger as shown in FIG. 3, with the elastomeric
seal disposed in the position shown in FIG. 3;
[0023] FIG. 7 is an enlarged cross-sectional detail view of the
front portion of a plunger as shown in FIG. 5, with the elastomeric
plunger seal displaced rearwardly from the position shown in FIGS.
3 and 6, with the portion of the plunger seal that previously
extended across the end of the plunger having ruptured and
contracted to the sides of the forwardly extending end of the
plunger;
[0024] FIG. 8 is a bottom plan view of the medical device of FIG.
1;
[0025] FIG. 9 is a top plan view of the medical device of FIG.
1;
[0026] FIG. 10 is an enlarged cross-sectional horizontal view,
partially broken away, of another embodiment of the medical device
of the invention wherein the needle is in a forwardly projecting
use position;
[0027] FIG. 11 is an enlarged detail view taken as indicated in
FIG. 10;
[0028] FIG. 12 is an enlarged cross-sectional horizontal view of
the medical device of FIG. 10 but rotated 90 degrees around the
longitudinal axis of the device, wherein the plunger is fully
depressed into the barrel and wherein the needle is fully
retracted;
[0029] FIG. 13 is an inclined elevation view of another embodiment
of the medical device of the invention;
[0030] FIG. 14 is an exploded perspective view of the medical
device of FIG. 13;
[0031] FIG. 15 is an enlarged, cross-sectional horizontal elevation
view taken along line 3-3 of FIG. 1 wherein the needle is in a
forwardly projecting use position and is covered by a protective
cap;
[0032] FIG. 16 is a cross-sectional left side elevation view taken
along line 16-16 of FIG. 15;
[0033] FIG. 17 is an enlarged, cross-sectional horizontal elevation
view wherein the plunger is fully depressed inside the barrel and
wherein the needle is fully retracted;
[0034] FIG. 18 is a cross-sectional elevation view of another
embodiment of the medical device of the invention when disposed in
a horizontal position, wherein the plunger handle has a
stepped-front;
[0035] FIG. 19 is a left side elevation view of the entire (not in
cross-section) medical device of FIG. 18;
[0036] FIG. 20 is a right side elevation view of the entire (not in
cross-section) medical device of FIG. 18;
[0037] FIG. 21 is a cross-sectional elevation view of the
embodiment of FIG. 21 wherein the rearwardly projecting head of the
needle holder has engaged and stretched or distended the
elastomeric web of the plunger seal rearwardly, and wherein the
most forwardly extending portion of the plunger handle, covered by
the elastomeric web of the plunger seal, is contacting the retainer
member prior to needle retraction;
[0038] FIG. 22 is a cross-sectional elevation view of the
embodiment of FIG. 21 following needle retraction; and
[0039] FIG. 23 is an enlarged detail view taken from FIG. 18 that
better illustrates the stepped-front of the plunger portion of the
subject medical device.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0040] One embodiment of the medical device of the invention is
described and explained in relation to FIGS. 1-9, wherein syringe
10 comprises as its principal parts barrel 24, a needle retraction
assembly installed in the front portion of barrel 24, and plunger
assembly 12 that slidably engages an opening in the rear of the
barrel. The needle retraction assembly comprises needle holder 18,
needle 20, compression spring 22 and retainer member 16. A
removable needle cover that protects the tip of needle 20 during
packaging, shipment and storage is not shown in FIGS. 1-9, but a
suitable needle cover is shown, for example, in relation to another
embodiment of the invention as molded plastic needle cover 206 in
FIGS. 13-14.
[0041] Barrel 24 comprises tubular body 26 with opposed radially
extending flanges 28 providing contact surfaces for the index and
middle fingers of a user, a larger diameter collar 30 disposed
behind flanges 28, a smaller diameter front collar optionally
comprising a plurality of arcuately spaced, longitudinally directed
ribs 98 that provide a seating surface for a removable needle
cover, and a tapered, forwardly extending nose 76 having an open
end through which forward tip 70 of needle holder 18 desirably
projects when the needle retraction assembly is seated inside
barrel 24. Referring to FIG. 2, collar 30 is optionally provided
with one or more notches 29 so that collar 30 can expand slightly
if needed in order for collar 30 to receive end cap 34 of plunger
assembly 12. The provision of notches 29 allows the use of closer
tolerances between the inside diameter of collar 30 and the outside
diameter of end cap 34 to insure a close fit between the two parts
and make plunger end cap 34 less graspable following injection and
retraction to help prevent reuse of syringe 10.
[0042] Plunger assembly 12 includes tubular body 38 with a larger
diameter end cap 34, a plurality of optional, arcuately spaced,
longitudinally extending ribs 60 disposed around body 38, annular
land 42, annular positioning ring 44, front tip 94, and elastomeric
plunger seal 14. Plunger seal 14 is preferably unitarily molded
from a compressible, rubbery material and comprises an annular body
portion and a transverse web portion. The annular body portion of
plunger seal 14 desirably comprises outwardly facing, axially
spaced annular ridges 48, 50, 52 separated by annular recesses 54,
47, respectively, and an inwardly facing annular recess 46. It will
be appreciated by those of skill in the art upon reading this
disclosure that the forwardly disposed annular ridge or flange, as
exemplified for example by annular ridge 48 in FIG. 6, performs the
primary sealing function, while the second, spaced-apart annular
flange such as ridge 50 in FIG. 6 primarily serves to align the
plunger seal inside the barrel.
[0043] Referring to FIGS. 2-3 and 6, annular recess 46 is deep
enough to receive cooperatively sized and shaped annular
positioning ring 44 when plunger seal 14 is mounted on tubular body
38 of plunger assembly 12 and has an inclined front wall and a
square back wall. When elastomeric plunger seal 14 is mounted on
the front end of tubular body 38, the open rear end is pressed over
front tip 94 and annular positioning ring 44 so that the inwardly
facing portion of plunger seal 14 at the rear end of annular recess
46 slides upwardly over the inclined front face of annular
positioning ring 44 and along the top of annular ring 44 until the
forwardly facing square shoulder at the rear of annular ring 46
drops over the rearwardly facing square shoulder of positioning
ring 44. As the body portion of plunger seal 14 reaches the
position shown in FIGS. 3 and 6, the transverse web portion 58 of
plunger seal 14 blocks and seals the opening in the front end of
tubular body 38 that is defined by the blunt annular surface of
front tip 94. As used herein, the term "blunt surface" is intended
to differentiate a surface having edges that do not cut from a
surface having edges that can cut, and it should be appreciated by
those of skill in the art upon reading this disclosure that an
injection molded plunger body or handle will have a front tip with
a small radius on each edge that will prevent the plunger tip from
cutting the transverse elastomeric web, particularly when the shear
force exerted on the web by the tip is spread evenly around the
circumference of the web as the web is stretched and thinned by
rearward movement of the tubular body on the plunger.
[0044] Referring to FIG. 2, front tip 94 of tubular body 38 can
define a single plane that is perpendicular to longitudinal axis 55
through syringe 10 or can be otherwise configured so that at least
a portion of front tip 94 advances ahead of the remainder of front
tip 94 as plunger 12 is advanced into barrel 24 to facilitate
retraction as has previously been disclosed, for example, in U.S.
Pat. No. 6,572,584. It will be appreciated whenever plunger 12 is
advanced inside barrel 24 to facilitate retraction that front tip
94 of plunger 12 is desirably covered by plunger seal 14, thereby
causing front tip 94 to contact retainer member 16 indirectly
through plunger seal 14, or directly if transverse web portion 58
ruptures first.
[0045] Annular recess 46 of the annular body can have an axial
length sufficient to permit plunger seal 14 to slide rearwardly on
the outside of tubular body 38 and provide a predetermined range of
travel between the position as shown in FIGS. 3 and 6, and the
position as shown in FIGS. 5 and 7. When the body portion of
plunger seal 14 is in its rearmost position relative to tubular
body 38, annular surface 86 at the rear of plunger seal 14 can abut
against forwardly facing annular shoulder 88 of tubular body 38 and
the inclined front wall of annular recess 46 can likewise abut
against the inclined front surface of annular positioning ring
44.
[0046] Referring to FIGS. 2 and 3, the needle retraction assembly
can be assembled by applying retainer member 16 to larger-diameter
section 62 of needle holder 18, inserting forward tip 70 and
elongated tubular body portion 74 through compression spring 22,
and then inserting retainer member 16, needle holder 18 and spring
22 into the rear of barrel 24 and advancing them forwardly inside
barrel 24 until forward tip 70 extends through narrow opening 63 in
the front of barrel 24 and forwardly facing annular shoulder 68 of
needle holder 18 is blocked by a cooperating rearwardly facing
annular shoulder 65 inside the front end of nose 76 of barrel 24.
At the same time, spring 22 is compressed between the underside of
larger-diameter section 62 of needle holder 18 and annular shoulder
65 inside nose 76. When the needle retraction assembly is in the
position shown in FIG. 3, inside surface 80 of retainer member 16
provides a liquid seal between retainer member 16 and the outwardly
facing surface of larger-diameter section 62 of needle holder 18,
and outside surface 82 of retainer member 16 provides a liquid seal
against the inside of tubular body 26 of barrel 24. The blunt,
rearwardly facing end of needle 20 can then be inserted into the
forwardly extending tip 70 of needle holder 18 and glued into place
or otherwise attached by similarly effective known methods, thereby
protecting the tip from insertion through the rear of barrel 24.
When syringe 10 is assembled in this manner, fluid communication is
established from the beveled, forwardly extending tip of needle 20,
through axially extending chamber 84 and transversely extending
pathways 65 of needle holder 18, and into fluid chamber 90 of
barrel 24.
[0047] As plunger assembly 12 is advanced into barrel 24 during an
injection, typically by pressing a thumb against thumb cap 36 of
end cap 34 while simultaneously exerting rearward pressure against
ridges 42 disposed around the front-facing surfaces of opposed
flanges 28, plunger assembly 12 reaches a point where transverse
web 58 contacts and flexes around the rounded, rearwardly
projecting tip 64 of needle holder 18 as seen in FIG. 4. This
causes fluid remaining inside chamber 90 of syringe 10 to be forced
into fluid pathways 65 as annular front surface 100 of the body
portion of elastomeric plunger seal 14 continues downwardly to a
point where annular surface 100 is seated against inclined surface
102. As this happens, the pressure exerted rearwardly by inclined
surface 102 against annular surface 100 causes the annular body
portion of elastomeric seal 14 to move, slide, displace or stretch
rearwardly relative to annular positioning ring 44 of tubular body
38. As the annular body portion of elastomeric seal 14 moves
rearwardly relative to tubular body 38 of plunger 12, transverse
web portion 58, preferably being integrally formed with the annular
body portion, is stretched tautly over front tip 94 and is then
distended rearwardly by rearwardly projecting tip 64 of needle
holder 18. In this embodiment of the invention, neither front tip
94 nor rearwardly projecting tip 64 of the needle holder 18 is
sharp enough to function as a cutter prior to the time that
projecting tip 64 pierces or punctures stretched transverse web
58.
[0048] The continued application of thumb force to thumb cap 36 of
plunger assembly 12, which in practice occurs as one smooth,
continuous motion, causes rearwardly projecting tip 64 of needle
holder 18 to rupture transverse web 58 and allows front tip 94 of
plunger body 38 to contact, either directly or indirectly (if
transverse web portion 58 ruptures before contact is made), and
push retainer member 16 forwardly off of large-diameter section 62
of needle holder 18, thereby allowing compressed spring 22 to push
needle holder 18 and at least part of needle 20 rearwardly into
retraction cavity 40 inside plunger body 38, with the beveled front
tip of needle 20 also being drawn inside and confined within barrel
24. Referring to FIGS. 4, 5 and 7, because the ruptured transverse
web portion 58 is desirably elastomeric and because it was tightly
stretched across the opening defined by front tip 94 of plunger
body 38 prior to rupturing, remnants of the transverse web can
contract out of the path of front tip 94 as it contacts retainer
member 16, and also out of the path of needle holder 18 and needle
20 as they are projected rearwardly by spring 22 to avoid hang-up
during retraction. As a result, referring to FIGS. 5 and 7, needle
20 is retracted into barrel 24, the bottom of relaxed spring 22
remains seated on annular shoulder 65 inside nose 76, and annular
rear surface 86 of the annular body portion of elastomeric plunger
seal 14 moves toward annular shoulder 88 of tubular body 38 of
plunger assembly 12. After retraction, the forwardly extending end
of spring 22 does not necessarily have to remain seated on annular
shoulder 65 inside nose 76.
[0049] FIGS. 10-12 depict another embodiment of the invention in
which syringe 110 is made similarly to but slightly different than
syringe 10 as discussed above. One readily noticeable difference in
syringe 110 is the vent hole 116 that is provided through the wall
of tubular body 114 of the plunger assembly to vent retraction
cavity 150 as needle holder 118 and needle 122 are propelled
rearwardly during retraction. Another readily noticeable difference
in syringe 110 is the configuration of needle holder 118. Unlike
needle holder 18, needle holder 118 has two opposed, relatively
pointed cusps 140, 142 that cooperate to pierce the transverse web
portion 148 of slidable elastomeric plunger seal 144. Because the
cusps are opposed and do not extend circumferentially around the
rearwardly extending head of needle holder 118, medicine can enter
the centrally disposed bore 166 of needle holder 118 and no
transverse liquid flow paths such as fluid pathways 65 of needle
holder 118 are needed to reduce the amount of ullage or "dead
space" that could otherwise be present. Except for these noted
differences, the structure, assembly and operation of syringe 110
of the invention are substantially the same as disclosed in
relation to syringe 10.
[0050] Referring to FIG. 10, syringe 110 comprises barrel 112 into
which plunger 114 is inserted in sealing engagement, which sealing
engagement is provided by a unitarily molded, rubbery plunger seal
comprising an annular body 144 and a transverse elastomeric web
148. When annular body 144 contacts inclined shoulder 155 as
plunger 114 is advanced inside barrel 112 prior to needle
retraction, annular body 144 can move rearwardly along annular
surface 146 of plunger 114, thereby stretching elastomeric web 148.
Retraction cavity 150 disposed inside plunger 114 has an open front
end that is sealed by elastomeric web 148 and a closed rear end
that is blocked by end cap 162. As plunger 114 is fully depressed
inside barrel 112 during and following an injection, end cap 162 is
desirably lodged into annular recess 164 of the barrel collar,
making end cap 162 less graspable for subsequent withdrawal of
plunger 114 from barrel 112.
[0051] In the front portion of barrel 112, needle holder 118 is
seated in a position where annular shoulder 156 engages the inside
of barrel 112 as front tip 158 of needle holder 118 extends
forwardly out an opening at the front end of barrel 112. Referring
to FIGS. 10 and 11, needle 122 is attached to needle holder 118
inside the centrally disposed bore 166 of elongated front section
120. The forwardly extending end of retraction spring 124 is also
seated against an annular shoulder at the front of barrel tip 112,
and the rearwardly facing end of compressed spring 124 is
contacting and exerting a biasing force against a forwardly facing
annular shoulder 128 of a larger-diameter section 126 of need
holder 118. Needle holder 118 is held in place prior to retraction
by compressed elastomeric retainer ring 130 that also provides a
fluid-tight seal between needle holder 118 and the inside wall of
barrel 112. Annular space 154 is desirably provided forwardly of
retainer ring 130 to facilitate retraction as discussed below in
relation to FIG. 12. Referring again to FIG. 10, a sealed liquid
containment chamber 147 is thereby provided inside barrel 112
between retainer ring 130 and the annular body 144 and elastomeric
web 148 of the plunger seal, with the only remaining fluid pathway
being through the bore of needle holder 118 and needle 122.
[0052] Referring to FIGS. 10 and, by comparison, 12, as plunger 114
is advanced fully into barrel 112 by thumb pressure from the user
following in injection, rearwardly projecting structures 140, 142,
best seen in FIG. 11, contact and rearwardly distend or displace
elastomeric web 148. As this occurs, the annular body of plunger
114 advances against the opposed annular shoulder 155 inside barrel
112, which causes annular body 144 to move rearwardly, stretching
elastomeric web 148 more tautly as plunger 114 continues to move
forward relative to barrel 112. When the front end of the plunger,
acting through the plunger seal, contacts and pushes retainer ring
130 forwardly into space 154, projections 140, 142 rupture
elastomeric web 148 and retainer ring 130 releases needle holder
118 to effect retraction of needle 122 into barrel 112 as needle
holder 118 is pushed into retraction cavity 150. Following
retraction, as seen in FIG. 12 in comparison to FIG. 11, annular
body 144 of the plunger seal is displaced toward annular wall 145
of plunger 114. Retainer ring 130 remains in annular space 154,
spring 124 is relaxed, and needle holder 118 and needle 122 are all
disposed inside the retraction cavity of plunger 114. As depicted
in FIG. 12, needle holder 118 and needle 122 are rotated 90 degrees
from the position shown in FIGS. 10 and 11 to better illustrate
flanges 164 and projection 140.
[0053] Another embodiment of the invention is described and
explained in relation to syringe 200 as shown in FIGS. 13-17. FIG.
13 depicts syringe 200 as it might be packaged, shipped and stored.
Syringe 200 preferably comprises barrel 202, plunger 204 inserted
into and slidably engaging the inside wall of barrel 202, and
protective cover 206 covering needle 236 as seen in FIG. 14. As
previously noted in relation to syringe 10, needle cover 206 is
shown in FIGS. 13-15 to illustrate how such a cover can be
constructed and releasably attached to the front end of barrel 202
to protect needle 236 from being accidentally dulled or bent prior
to use. Needle cover 206 is desirably releasably attached to the
front of barrel 202 by frictional engagement, although it will be
appreciated that such frictional engagement can be implemented in
various ways known to those of skill in the art. For example, the
frictional engagement can be achieved by using an annular snap
ring, cooperatively tapered conical or ribbed surfaces, threads, or
the like, that are disposed either inside the cap, or on the nose
portion of barrel 202, or both. By providing a cap that has a wider
opening at the end facing barrel 202, it is possible to use the cap
as a guide during assembly. According to one preferred embodiment
of the invention, the front tip of needle cover 206 is open to
allow the cap to breathe and to permit mold core pins to be pulled
from each end. When used with syringes 202 having detachable
needles, the cap can even be used as a wrench to help secure a
threaded needle tip to the front end of a needle holder, or to
assemble a front-end attachment comprising a needle to the
barrel.
[0054] Referring next to FIG. 14, plunger 204 of syringe 200
further comprises a molded end cap 210 having a removable insert
208; a plurality of circumferentially spaced, axially extending
ribs 212 to provide rigidity to plunger 204 and to minimize
possible frictional contact between plunger 204 and barrel 202; a
plunger seal having an annular body portion 220 that can be seated
around the tip of plunger 204 over annular boss 214 and can slide
rearwardly across recess 218 toward shoulder 216 of plunger 204 to
facilitate retraction. The plunger seal also has a transverse
elastomeric web portion 242 (FIG. 15) that provides a seal over the
forwardly facing open end of plunger 204 prior to retraction.
Annular boss 214 on the outside of plunger 204 is received inside
cooperating annular recess 240 of annular body 220 and provides
sufficient holding force to prevent plunger 204 from pulling out of
the plunger seal as plunger 204 is pulled rearwardly inside barrel
202 during aspiration.
[0055] The needle retraction assembly of syringe 200 as shown in
FIG. 14 comprises a needle holder having two parts that are
threaded together to facilitate changing needles if needed. Needle
base 234 has a male threaded section that is releasably engageable
with the female threaded front end portion 228 of elongated body
section 226 below larger-diameter head section 224 that further
comprises at least one rearwardly facing projection 246 as
described in more detail in relation to FIG. 15. During assembly of
syringe 200, elastomeric retainer ring 222 is stretched slightly so
that it can be applied over head portion 224 of the needle holder.
Front end portion 228 of the needle holder is inserted into spring
256, which is compressed around body section 226 and inserted into
barrel 202 until both body section 226 and spring 256 are seated
inside barrel 202 and retainer ring 222 is compressed sufficiently
against the inside of barrel 202 to prevent spring 256 from
expanding and to establish a liquid seal between head portion 224
of the needle holder and inside wall of barrel 202. In the
embodiment shown (FIG. 15), a small annular bump 272 is also
provided on the inside wall of barrel 202 to provide additional
frictional support and engagement between retainer ring 222 and the
inside wall of barrel 202. Following installation of the needle
retraction assembly, the assembled plunger, with plunger seal 220
attached, can then be inserted into open collar at the rear of
barrel 202 to slidably engage the inside wall.
[0056] Needle base 234, with or without needle 236 already
attached, is then threaded into engagement with front end 228 of
body section 226 of the needle holder seated inside barrel 202.
Depending upon the internal configuration of need cover 206, it can
possibly be used as a wrench to turn needle base 234 to engage the
threads with those of body section 226. At the same time,
rearwardly facing open end 261 of needle cover 206 can be placed
around the forwardly extending nose of barrel 202 to help align
needle base 234 and threaded end 228 of body section 226 for
achieving proper threaded engagement. If desired, it will be
appreciated that needle base 234 can likewise be attached prior to
inserting plunger 204 inside barrel 202.
[0057] FIGS. 15-16 further depict in more detail the internal
structure of assembled syringe 200. Barrel 202 comprises opposed
flanges 232 near the rear end that provide gripping surfaces for
the user's fingers and prevent syringe 200 from rolling off a
support surface. Rearwardly extending collar 230 is desirably
provided behind flanges 232 and comprises recess 238 adjacent to
the open rear end of barrel 202. Recess 238 is desirably sized and
positioned so that the perimeter of plunger end cap 210 is disposed
in close association with, and preferably nested inside, collar 230
following needle retraction. Insert 208 is provided with vent 209
for retraction cavity 244, and also facilitates the insertion and
removal of a core pin during molding.
[0058] In the embodiment shown in FIG. 15, a small annular snap
ring 258 comprising a cooperatively sized and aligned boss and
recess disposed inside front section 260 of needle cover 206 near
the front of needle base 234 is provided to provide frictional
engagement between needle cover 206 and syringe 200. This allows
the sidewall of cover 206 to be spaced slightly apart from nose 268
of barrel 202. Opening 262 is desirably provided at the front end
of front section 260, but sterility is not adversely affected
because syringe 200 is stored inside a sterile wrapper until the
time of use, when cover 206 is removed in any case.
[0059] Needle 236 is desirably attached to needle base 234 by glue
(or by another similarly effective attachment method) disposed
inside annular recess 254, and needle base 234 is releasably
attached to the inside of needle holder body 226 by cooperating
threads 264, 266. Retraction spring 256 is compressed inside the
annular space between nose 268 and needle holder body 226. Spring
256 is held in compression by retainer ring 222 disposed around
needle holder head 224. Rearwardly facing, projection 246 at the
rear of the needle holder is centrally disposed and comprises a
plurality of circumferentially spaced inclined buttresses providing
lateral support. Rounding the tip of projection 246 allows
elastomeric web 242 to be distended rearwardly a greater distance
than would otherwise be possible prior to rupturing during
retraction. Transverse flow channel 248 desirably provides fluid
communication with bore 250 of the needle holder to allow fluid to
flow into or out of liquid containment chamber 270 of barrel 202
through needle 236. The projection 246, elastomeric web 242 and
transverse flow channel 248 cooperate to provide greater
utilization of the volume inside liquid containment chamber
270.
[0060] Referring now to FIG. 15 in relation to FIG. 17, as plunger
204 advances forwardly toward projection 246, the projection
contacts elastomeric web 242, causing it to distend rearwardly into
the retraction cavity, while the front portion of annular body 220
of the plunger seal contacts inclined annular shoulder 274 of
barrel 202. As the plunger advance continues, annular body 220
slides rearwardly until it abuts against annular shoulder 216 of
plunger 204, which also stretches and thins elastomeric web 242 to
the point of rupture by projection 246. It should be appreciated
upon reading this disclosure that the use of a rearwardly facing
projection, even one that does not form a sharp point or edge, is
likely to rupture the elastomeric web at the region of contact
between the projection and the web prior to separation of the web
from the annular body around the circumference of the plunger tip.
This is believed to be because the stretching force exerted on the
web by the annular body is spread evenly around the circumference,
whereas the force exerted on the web by the projection is
concentrated within a much smaller area.
[0061] As the plunger seal moves rearwardly on plunger 204, the
front end of the plunger, acting through the plunger seal, contacts
retainer ring 222 either directly or indirectly and begins to push
it forwardly into annular space 252. Elastomeric web 242 desirably
ruptures just before the needle holder is released by retainer ring
222. When the needle holder is released, spring 256 drives the
needle holder rearwardly through the opening at the front of
retraction cavity 244 of plunger 204 that is formed as the annular
skirt that was previously elastomeric web 242 can snap back after
elastomeric web 242 is ruptured by projection 246. Once elastomeric
web 242 snaps back following penetration by projection 246,
remnants of the web can in some cases remain disposed between the
front tip of the plunger and retainer ring 222. In other cases, the
front tip of the plunger can directly contact retainer ring 222
following needle retraction. In FIG. 17, needle holder body 226,
needle base 234, needle 236 and all but the front end of spring 256
have been forced into retraction cavity 244 by the expanding
spring. Although the length and diameter and post-retraction
position of relaxed spring 256 can vary, needle 236 should remain
inside barrel 202 following retraction for protection against
accidental needle sticks.
[0062] Another embodiment of the medical device of the invention is
disclosed in relation to FIGS. 18-23 of the drawings. Referring to
these figures, medical device 300, which can be, for example, a
hypodermic syringe, comprises barrel 302, a retractable needle
assembly seated in the forward portion of barrel 302, and plunger
304 that is slidably inserted into an opening defined by
substantially tubular collar 342 at the rear of barrel 302. Barrel
302 further comprises a pair of oppositely projecting, transverse
flanges 326, 328 and a smaller-diameter nose section 336.
[0063] The retractable needle assembly is supported inside the
front portion of barrel 302 and further comprises needle holder
308, elastomeric retainer member 310, compressed spring 312.
Retainer member 310 provides a fluid seal between needle holder 308
and the inside wall of barrel 302. The forwardly extending end of
compressed spring 312 is impeded from forward movement relative to
barrel 302 by a rearwardly facing annular shoulder 331 of nose
section 336 that also engages a forwardly facing annular shoulder
disposed near the front of needle holder 308. Fluid flow path
through needle holder 308 is 334 preferably disposed between the
bore of needle 314 and transverse fluid flow path 332, which is
disposed just forwardly of rear tip 348 of needle holder 308.
[0064] Plunger 304 preferably comprises a substantially tubular
wall defining a retraction cavity 330, the tubular wall having at
least two circumferentially spaced, axially extending ribs 305
projecting radially outward to help maintain proper alignment
between plunger 304 and barrel 302, leaving a smaller diameter
section 318 of ribs 305. A larger diameter section 340 is desirably
disposed at the rear of plunger 304 that is receivable inside, or
into close association with the inside of, rear collar 342 of
medical device 300. The tubular wall of plunger 304 defines a
longitudinally extending retraction cavity 330 that is closed at
its rear end by end cap 338 and at its front end by generally
transverse elastomeric web 317 of plunger seal 316. Plunger seal
316 is seated on small outside diameter section 318 of plunger 304.
A radially extending annular projection 322 having a sloped front
shoulder and a relatively square back shoulder, or another
similarly effective structure, is preferably provided to prevent
plunger seal 316 from sliding off the front of plunger 304 during
when plunger 304 is pulled rearwardly inside barrel 302 as can
occur, for example, during aspiration of medical device 300.
[0065] The forwardly extending end 320 of the tubular wall of
plunger 304 can have one portion that extends more forwardly than
the other, thereby causing at least a portion of elastomeric web
317 to be canted slightly out of the transverse plane that is
perpendicular to the common longitudinal axis of medical device
300. This also causes the portion of the forwardly facing surface
of elastomeric web 317 that covers the most forwardly extending
portion of stepped front end 320 to contact retainer member 310 of
the retractable needle assembly first, thereby initially
concentrating the user's thumb force on one side of retainer member
310 to initiate movement of retainer member 310 relative to needle
holder 308 and the inside wall of barrel 302.
[0066] Referring to FIG. 18 in conjunction with FIG. 21, as plunger
304 is moved forwardly inside barrel 300, elastomeric web 317
eventually contacts projection 348 of needle holder 308, causing
elastomeric web 317 to be stretched over the rearwardly extending
portion of the needle holder and distended rearwardly a slight
distance into retraction cavity 330. As plunger 304 continues to
move forwardly, the forwardly facing annular shoulder of plunger
seal 316 contacts the inwardly tapering shoulder 323 of barrel 302
adjacent nose 336, thereby causing plunger seal 316 to slide
rearwardly on small diameter section 318 of plunger 304 to the
position shown in FIG. 22. As this occurs, front end 320 of plunger
304 causes retainer 310 to be pushed forwardly into space 311 (FIG.
21) to the position shown FIG. 22. As this occurs, elastomeric web
317 ruptures, and needle holder 308 is no longer constrained
against the force exerted rearwardly by compressed spring 312. As
depicted in FIG. 22 with reference also to FIG. 21, as spring 312
expands, needle holder 308 and needle 314 are driven rearwardly
into the retraction cavity inside plunger 304. When medical device
300 is in the fully retracted position as shown in FIG. 22, all
portions of the retractable needle assembly are disposed inside of
barrel 302.
[0067] The barrel of the medical device of the invention can be
made of plastic, glass or any other material suitable for the
intended use. As used herein, the term "plastic" refers primarily
to moldable thermoplastic polymers such as, for example,
polyethylene and polypropylene, that can also contain other
ingredients such as curatives, filler, reinforcing agents,
colorants, and/or plasticizers, etc., and that can be formed or
molded under heat and pressure. Where the subject device is
intended for use in applications where the barrel can be in
prolonged direct contact with therapeutic liquids that can interact
with plastic or that can be degraded by substituents that can
otherwise enter the liquid from plastic, plastic should not be
used. The tubular body or handle of the plunger of the invention is
also preferably made of plastic, and will not typically come into
contact with a therapeutic liquid prior to retraction.
[0068] In the past, the elastomeric materials used to make plunger
seals have often included crosslinked thermosetting rubbery
polymers that are easily deformable but that are approved for use
with pharmaceutical grade fluids and are not readily susceptible to
leaching or gas migration. It has now been appreciated that the
plunger seal of the present invention can be made of an injection
moldable elastomeric material approved for use with the therapeutic
fluids of interest that, when molded into the annular body portion
that, is sufficiently rigid to provide a reliable liquid seal
between the plunger handle and the barrel and to resist
disengagement of the plunger handle from the plunger seal when the
plunger is withdrawn, for example, during aspiration. Also, because
the plunger seal is ideally unitarily molded from a single
elastomeric material, the material used should be of sufficient
thickness and toughness that it can be stretched and thinned prior
to retraction, but not prematurely, and will also tear readily when
penetrated by a rearwardly facing projection on the needle
retraction assembly to permit retraction. An elastomer suitable for
such use can be Uniprene.RTM. rubber having a Shore A hardness of
about 45. The material used to make the retainer ring is preferably
a crosslinked thermosetting rubber polymer that is more easily
deformable than plastic and that is approved for use with
pharmaceutical grade fluids and are not readily susceptible to
leaching or gas migration.
[0069] The needle holder portion of the needle retraction assembly
can also be made of plastic or glass, and the use of plastic is
preferred. The needle holder can be made, for example, from
polycarbonate or acrylonitrile-butadiene-styrene ("ABS"). Such
polymeric resins and adhesives suitable for securing a needle to
the needle holder (or the needle tip in case of a device having an
attachable, detachable and/or changeable needle are commercially
available. Similarly, compression springs, typically made of metal,
that can be used in devices having retractable needles, are also
known to those skilled in the art and are commercially
available.
[0070] As used herein, the term "fluid" refers primarily to
liquids, but can also include suspensions of solids dispersed in
liquids, and gases dissolved in or otherwise present together
within liquids inside the fluid-containing portions of the devices
of the invention. Conventional, commercially available lubricants
suitable for use with plunger seals can be used to further improve
sealing and lower the force that must be applied through the
plunger to use the devices of the invention and to effect
retraction.
[0071] One advantage of the present invention is that when the
thinned and tautly stretched elastomeric web 148 is ruptured, the
rubbery material snaps back with sufficient speed and force that
the resultant opening is sufficiently large for needle holder 118
and the front end of spring 124 to pass through without hang-up
that could otherwise impede complete retraction of needle 122 into
body 112. Another advantage of the present invention is that the
thumb force required to initiate retraction is substantially lower
than has previously been achievable in conventional, commercially
available syringes having retractable needles. This is at least
partly because the present invention has no plug that must be
dislodged to gain access to the plunger cavity, partly because
there is no cutting or breaking of plastic parts that is required
to initiate retraction, and partly because there is no need for a
two-piece plunger that must be operated to initiate cutting or
breaking. Based upon preliminary testing, it is believed that the
mean thumb force required to retract the needle is reduced by more
than thirty percent (30%) through use of the structures and
materials disclosed herein. It is believed that the sliding and
stretching of the elastomeric web of the plunger seal at the moment
of penetration by the needle holder contributes to a reduction in
the thumb force required to initiate retraction.
[0072] Another advantage of the present invention is that the use
of a moveable plunger seal with an annular body unitarily formed
together with a transverse elastomeric web permits the use of
manufacturing tolerances that are greater and more forgiving than
those previously required to produce medical devices with plungers
having internal retraction cavities that are sealed by a removable
plug prior to retraction. Also, with the devices of the present
invention, premature blowout because of pressure exerted on the
plug by a fluid contained in the device is not a constraint.
[0073] Another operational advantage of the present invention is
the smooth forward movement of the plunger to initiate retraction.
This smooth release is directly attributable to the combined use of
a slidable, rupturable plunger seal and an elastomeric retainer
ring that is pushed into the release position by the continuous
forward motion of the plunger without the bumps or jolts resulting
from breaking plastic parts, dislodging plunger plugs, or the
audible "click"s previously experienced in the use of syringes
having retractable needles.
[0074] Other alterations and modifications of the invention will
likewise become apparent to those of ordinary skill in the art upon
reading this specification in view of the accompanying drawings,
and it is intended that the scope of the invention disclosed herein
be limited only by the broadest interpretation of the appended
claims to which the inventors are legally entitled.
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