U.S. patent application number 10/790866 was filed with the patent office on 2005-02-10 for drive mechanisms suitable for use in drug delivery devices.
Invention is credited to Perkins, Robert, Plumptre, David Aubrey, Veasey, Robert Frederick.
Application Number | 20050033244 10/790866 |
Document ID | / |
Family ID | 9954010 |
Filed Date | 2005-02-10 |
United States Patent
Application |
20050033244 |
Kind Code |
A1 |
Veasey, Robert Frederick ;
et al. |
February 10, 2005 |
Drive mechanisms suitable for use in drug delivery devices
Abstract
A drive mechanism suitable for use in drug delivery devices is
disclosed. The drive mechanism may be used with injector-type drug
delivery devices, such as those permitting a user to set the
delivery dose. The drive mechanism may include a housing, a dose
dial sleeve, and a drive sleeve. A clutch is configured to permit
rotation of the drive sleeve and the dose dial sleeve with respect
to the housing when the dose dial sleeve and drive sleeve are
coupled through the clutch. Conversely, when the dose dial sleeve
and drive sleeve are in a de-coupled state, rotation of the dose
dial sleeve with respect to the housing is permitted and rotation
of the drive sleeve with respect to the housing is prevented. In
the de-coupled state, axial movement of the drive sleeve transfers
force in a longitudinal direction for actuation of a drug delivery
device.
Inventors: |
Veasey, Robert Frederick;
(Leamington Spa, GB) ; Perkins, Robert;
(Leamington Spa, GB) ; Plumptre, David Aubrey;
(Droitwich, GB) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER
LLP
1300 I STREET, NW
WASHINGTON
DC
20005
US
|
Family ID: |
9954010 |
Appl. No.: |
10/790866 |
Filed: |
March 3, 2004 |
Current U.S.
Class: |
604/211 |
Current CPC
Class: |
A61M 5/31535 20130101;
A61M 5/31578 20130101; A61M 5/32 20130101; A61M 5/31563 20130101;
A61M 5/31575 20130101; A61M 5/31593 20130101; A61M 2005/2407
20130101; A61M 5/31546 20130101; A61M 5/31565 20130101; A61M
2005/3126 20130101; A61M 5/24 20130101; A61M 5/31541 20130101; A61M
2205/582 20130101; A61M 2205/581 20130101; A61M 5/3156 20130101;
A61M 5/31568 20130101; A61M 5/3157 20130101; A61M 5/31551 20130101;
A61M 5/31585 20130101; A61M 5/31533 20130101; A61M 5/31536
20130101; A61M 5/31528 20130101 |
Class at
Publication: |
604/211 |
International
Class: |
A61M 005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 3, 2003 |
GB |
0304822.0 |
Claims
1. A drive mechanism for use in a drug delivery device comprising:
a housing having an internal helical thread; a dose dial sleeve
having a helical thread engaged with the helical thread of the
housing; a drive sleeve releasably connected to the dose dial
sleeve; and a clutch means located between the dose dial sleeve and
the drive sleeve; the clutch means configured such that, a) when
the dose dial sleeve and the drive sleeve are coupled, both are
allowed to rotate with respect to the housing; and b) when the dose
dial sleeve and the drive sleeve are de-coupled, rotation of the
dose dial sleeve with respect to the housing is allowed, while
rotation of the drive sleeve with respect to the housing is
prevented, whereby axial movement of the drive sleeve is allowed so
that a force is transferred in the longitudinal direction to a
proximal end of the drug delivery device.
2. A drive mechanism according to claim 1, further comprising a
piston rod adapted to operate through the housing and transfer the
force in the longitudinal direction to the proximal end of the drug
delivery device.
3. The drive mechanism according to claim 1, wherein said dose dial
sleeve further comprises a helical thread, which has the same lead
as the lead of the helical thread of the drive sleeve.
4. The drive mechanism according to claim 2, wherein the piston rod
is designed to have attached a toothed gear designed to mesh with
the threads of the drive sleeve and the teeth of a toothed rack,
whereby the toothed rack is fixed to the housing.
5. An assembly for use in a drug delivery device comprising the
drive mechanism of claim 1.
6. A drug delivery device comprising the drive mechanism of claim
1.
7. The drug delivery device according to claim 6, wherein the
delivery device is a pen-type device.
8. The drug delivery device according to claim 6 wherein the
delivery device is an injector-type device.
9. The drug delivery device according to claim 6, wherein the
delivery device further comprises a needle.
10. The drug delivery device according to claim 6, which wherein
the delivery device is a needle-free device.
11. (Canceled)
12. The method of claim 22, wherein dispensing a medicinal product
includes dispensing a pharmaceutical formulation comprising an
active compound selected from the group consisting of insulin,
growth hormone, low molecular weight heparin, analogues thereof,
and derivatives thereof.
13. The method of manufacturing or assembling a drug delivery
device, comprising the step of providing the drive mechanism of
claims 1.
14. A drug delivery device comprising the assembly of claim 5.
15. The drug delivery device of claim 14, wherein the device is a
pen-type device.
16. The drug delivery device of claim 14, wherein the device is an
injector-type device.
17. The drug delivery device of claim 14, further comprising a
needle.
18. The drug delivery device of claim 14, wherein the device is a
needle-free device.
19. A method of delivering a drug, comprising: providing the device
of claim 14, dispensing a medicinal product with the device.
20. The method of claim 19, wherein dispensing a medicinal product
includes dispensing a pharmaceutical formulation from the device,
wherein the pharmaceutical formulation comprises an active compound
selected from the group consisting of insulin, growth hormone, low
molecular weight heparin, analogues thereof, and derivatives
thereof.
21. A method of manufacturing or assembling a drug delivery device,
comprising providing the assembly of claim 5.
22. A method of delivering a drug, comprising: providing the device
of claim 6, dispensing a medicinal product with the device.
Description
THE TECHNICAL FIELD OF THE INVENTION
[0001] The present invention relates to drive mechanisms suitable
for use in drug delivery devices, in particular pen-type injectors,
having dosage setting means, enabling the administration of
medicinal products from a multi-dose cartridge. In particular, the
X present invention relates to such drug delivery devices where a
user may set the dose.
DESCRIPTION OF RELATED ART
[0002] Such drug delivery devices have application where regular
injection by persons without formal medical training occurs, i.e.,
patients. This is increasingly common amongst those having diabetes
where self-treatment enables such persons to conduct effective
management of their diabetes.
[0003] These circumstances set a number of requirements for drug
delivery devices of this kind. The device must be robust in
construction, yet easy to use in terms of the manipulation of the
parts, understanding by a user of its operation and the delivery of
the required dose of medicament. Dose setting must be easy and
unambiguous. In the case of those with diabetes, many users will be
physically infirm and may also have impaired vision requiring the
drive mechanism to have low dispensing force and an easy to read
dose setting display. Where the device is to be disposable rather
than reusable, the device should be cheap to manufacture and easy
to dispose of (preferably being suitable for recycling). To meet
these requirements the number of parts required to assemble the
device and the number of material types the device is made from
need to be kept to a minimum.
[0004] User operated drug delivery devices are well known within
the medical field.
[0005] In U.S. Pat. No. 5,304,152 a dispensing device is disclosed
which has a body length to plunger length ratio of about 1:1 in
order to allow the dispensing of relatively large doses. Whilst
this device provides many improvements over the prior art the easy
correction of a set overdose remains unresolved without either
dispensing the set amount of fluid or dismantling the
cartridge.
[0006] WO 9938554 A2 teaches an injection syringe for apportioning
set doses of a medicine from a cartridge wherein a drive mechanism
comprising a unidirectional coupling (i.e., a ratchet) is disclosed
which allows correction of a set overdose without dispensing the
set amount of fluid or requiring the dismantling of the
cartridge.
[0007] Surprisingly it was found that the drive mechanism according
to instant invention Without having a unidirectional coupling
provides a valuable technical alternative for drive mechanisms,
wherein reduced force is needed to actuate the mechanism. This is
achieved by the introduction of a clutch means as defined by
instant invention. The Drive mechanism according to instant
invention further provides the advantage of intuitive and easy to
use correction of a set dose.
DESCRIPTION OF THE INVENTION
[0008] According to a first aspect of the present invention, a
drive mechanism for use in a drug delivery device is provided
comprising:
[0009] a housing having a helical thread;
[0010] a dose dial sleeve having a helical thread engaged with the
helical thread of the said housing;
[0011] a drive sleeve releasibly connected to the said dose dial
sleeve;
[0012] and a clutch means located between the dose dial sleeve and
the drive sleeve;
[0013] characterized in that,
[0014] a) when the dose dial sleeve and the drive sleeve are
coupled, the dose dial sleeve and the drive sleeve are allowed to
rotate with respect to the housing; and
[0015] b) when the dose dial sleeve and the drive sleeve are
de-coupled, rotation of the dose dial sleeve with respect to the
housing is allowed, whilst rotation of the drive sleeve with
respect to the housing is not allowed, whereby axial movement of
the drive sleeve is allowed so that a force is transferred in the
longitudinal direction to the proximal end of the drug delivery
device.
[0016] In a preferred embodiment of the drive mechanism of instant
invention the said drive mechanism further comprises a piston rod
adapted to operate through the housing and transfer the said force
in the said longitudinal direction to the proximal end of the drug
delivery device.
[0017] In another preferred embodiment of the drive mechanism of
instant invention the said dose dial sleeve further comprises a
helical thread, which has the same lead as the lead of the helical
thread of the said drive sleeve.
[0018] In a more specific embodiment of instant invention, the
drive mechanism further comprises a nut, which is rotatable with
respect to the drive sleeve and axially displaceable but not
rotatable with respect to the housing.
[0019] The term "drug delivery device" according to instant
invention shall mean a single-dose or multi-dose, disposable or
re-useable device designed to dispense a selected dose of a
medicinal product, preferably multiple selected doses, e.g.
insulin, growth hormones, low molecular weight heparins, and their
analogues and/or derivatives etc. Said device may be of any shape,
e.g. compact or pen-type. Dose delivery may be provided through a
mechanical (optionally manual) or electrical drive mechanism or
stored energy drive mechanism, such as a spring, etc. Dose
selection may be provided through a manual mechanism or electronic
mechanism. Additionally, said device may contain components
designed to monitor physiological properties such as blood glucose
levels, etc. Furthermore, the said device may comprise a needle or
may be needle-free. In particular, the term "drug delivery device"
shall mean a disposable multi-dose pen-type device having
mechanical and manual dose delivery and dose selection mechanisms,
which is designed for regular use by persons without formal medical
training such as patients. Preferably, the drug delivery device is
of the injector-type.
[0020] The term "housing" according to instant invention shall
preferably mean any exterior housing ("main housing", "body",
"shell") or interior housing ("insert", "inner body") having a
helical thread. The housing may be designed to enable the safe,
correct, and comfortable handling of the drug delivery device or
any of its mechanism. Usually, it is designed to house, fix,
protect, guide, and/or engage with any of the inner components of
the drug delivery device (e.g., the drive mechanism, cartridge,
plunger, piston rod) by limiting the exposure to contaminants, such
as liquid, dust, dirt etc. In general, the housing may be unitary
or a multipart component of tubular or non-tubular shape. Usually,
the exterior housing serves to house a cartridge from which a
number of doses of a medicinal product may by dispensed.
[0021] In a more specific embodiment of instant invention, the
exterior housing is provided with a plurality of maximum dose stops
adapted to be abutted by a radial stop provided on the dose dial
sleeve. Preferably, at least one of the maximum dose stops
comprises a radial stop located between a helical thread and spline
means provided at a second end of the housing. Alternatively, at
least one of the maximum dose stops comprises a part of a raised
window portion provided at a second end of the housing.
[0022] The term "engaged" according to instant invention shall
particularly mean the interlocking of two or more components of the
drive mechanism/drug delivery device, e.g. a spline, thread, or
meshed teeth connection, preferably the interlocking of helical
threads of components ("threadedly engaged").
[0023] The term "helical thread" according to instant invention
shall preferably mean a full or part thread, e.g., a cylindrical
spiral rib/groove, located on the internal and/or external surface
of a component of the drug delivery device, having an essentially
triangular or square or rounded section designed to allow
continuous free rotational and/or axial movement between
components. Optionally, a thread may be further designed to prevent
rotational or axial movement of certain components in one
direction.
[0024] The term "dose dial sleeve" according to instant invention
shall mean an essentially tubular component of essentially circular
cross-section having either:
[0025] a) both an internal and external thread, or
[0026] b) an internal thread, or
[0027] c) an external thread.
[0028] Preferably, the dose dial sleeve according to instant
invention comprises a helical thread having a lead, which is
similar to, preferably the same as the lead of the helical thread
of the drive sleeve. In yet another preferred embodiment the dose
dial sleeve is designed to indicate a selected dose of a
dispensable product. This may be achieved by use of markings,
symbols, numerals, etc., e.g. printed on the external surface of
the dose dial sleeve or an odometer, or the like.
[0029] In a more specific embodiment of instant invention, the dose
dial sleeve is provided with a plurality of radially extending
members adapted to abut a corresponding plurality of radial stops
provided at a second end of the housing.
[0030] The term "lead" according to instant invention shall
preferably mean the axial distance a nut would advance in one
complete revolution; preferably "lead" shall mean the axial
distance through which a component having a helical thread, i.e.
dose dial sleeve, drive sleeve, piston rod, etc., of the drive
mechanism travels during one rotation. Therefore lead is a function
of the pitch of the thread of the relevant component.
[0031] The term "pitch" according to instant invention shall
preferably mean the distance between consecutive contours on a
helical thread, measured parallel to the axis of the helical
thread.
[0032] The term "drive sleeve" according to instant invention shall
mean any essentially tubular component of essentially circular
cross-section and which is further releasibly connected to the dose
dial sleeve. In a preferred embodiment the drive sleeve is further
engaged with the piston rod.
[0033] In a more particular embodiment of instant invention, the
drive sleeve is provided at a first end with first and second
flanges with an intermediate helical thread between the first and
second flanges, having a nut disposed between the first and second
flanges and keyed to the housing by spline means. Optionally, a
first radial stop may be provided on a second face of the nut and a
second radial stop may be provided on a first face of the second
flange.
[0034] The term "releasibly connected" according to instant
invention shall preferably mean that two components of instant
mechanism or device are reversibly joined to each other, which
allows coupling and decoupling, e.g. by means of a clutch.
[0035] The term "piston rod" according to instant invention shall
mean a component adapted to operate through/within the housing,
designed to translate axial movement through/within the drug
delivery device, preferably from the drive sleeve to the piston,
for the purpose of discharging/dispensing an injectable product.
Said piston rod may be flexible or not. It may be a simple rod, a
lead-screw, a rack and pinion system, a worm gear system, or the
like. The "piston rod" shall further mean a component having a
circular or non-circular cross-section. It may be made of any
suitable material known by a person skilled in the art.
[0036] In a preferred embodiment, the piston rod comprises at least
one, more preferably two, external and/or internal helical threads.
In another preferred embodiment of the piston rod according to
instant invention, a first helical thread is located at a first end
and a second helical thread is located at a second end of the said
piston rod, whereby the said threads may have the same or,
preferably, opposite dispositions. In another preferred embodiment
the piston rod of instant invention comprises threads having the
same leads at the first and the second end.
[0037] In yet another preferred embodiment of instant invention the
lead of the first helical thread of the piston rod shall be greater
than the lead of the second helical thread. More preferred, the
ratio of the leads of the helical threads of the said first and the
second helical threads is 1:1,01 to 1:20, even more preferred 1:1,1
to 1:10. Preferably, one of the said threads is designed to engage
with the drive sleeve.
[0038] Alternatively, in another preferred embodiment of the piston
rod of instant invention, the piston rod is designed to have
attached, optionally by means of a journal bearing, a toothed gear,
and wherein said toothed gear is designed to mesh with the threads
of the drive sleeve and the teeth of a toothed rack, whereby said
toothed rack is fixed to the housing.
[0039] The term "first end" according to instant invention shall
mean the proximal end. The proximal end of the device or a
component of the device shall mean the end, which is closest to the
dispensing end of the device.
[0040] The term "second end" according to instant invention shall
mean the distal end. The distal end of the device or a component of
the device shall mean the end, which is furthest away from the
dispensing end of the device.
[0041] The term "clutch means" according to instant invention shall
mean any means, which releasibly connects the dose dial sleeve and
the drive sleeve and which is designed to allow rotation of the
dose dial sleeve and the drive sleeve with respect to the housing
when the dose dial sleeve and the drive sleeve are coupled and,
when both are de-coupled, allows rotation of the dose dial sleeve
with respect to the housing, but does not allow rotation of the
drive sleeve with respect to the housing and allows axial movement
of the drive sleeve. Preferably, the clutch means releasibly
connects the drive sleeve to the housing. Accordingly, the term
clutch means is any clutch engaging for the purpose of reversibly
locking two components in rotation, e.g., by use of axial forces to
engage a set of face teeth (saw teeth, dog teeth, crown teeth) or
any other suitable frictional faces.
[0042] In a more specific embodiment of instant invention, a second
end of the clutch means is provided with a plurality of dog teeth
adapted to engage with a second end of the dose dial sleeve.
[0043] In an alternative embodiment, the clutch means of instant
invention is a locking spring, operable, e.g., by means of a dose
dial button, between a first, relaxed position, in which the dose
dial sleeve is locked with respect to rotation with the drive
sleeve and a second, deformed position, in which the dose dial
sleeve is locked with respect to rotation with the housing.
[0044] In still another embodiment of instant invention, the drive
mechanism further comprises a clicker means, optionally disposed
between the clutch means and spline means provided on the
housing.
[0045] Optionally, the clicker means comprises a sleeve provided at
a first end with a helically extending arm, a free end of the arm
having a toothed member, and at a second end with a plurality of
circumferentially directed saw teeth adapted to engage a
corresponding plurality of circumferentially saw teeth provided on
the clutch means. Alternatively, the clicker means comprises a
sleeve provided at a first end with at least one helically
extending arm and at least one spring member, a free end of the arm
having a toothed member, and at a second end with a plurality of
circumferentially directed saw teeth adapted to engage a
corresponding plurality of circumferentially directed saw teeth
provided on the clutch means.
[0046] In still another embodiment of the drive mechanism of the
invention, the drive mechanism is provided with a first stop means,
preferably in the form of an external flange on the dose dial
sleeve, adapted to engage limiting means associated with the
housing, preferably in the form of an internal flange in the
housing, to limit the maximum dose which can be dialed. In yet
another embodiment of the drive mechanism of the invention, the
drive mechanism is further provided with a second stop means,
preferably in the form of an external flange on the drive sleeve,
adapted to engage limiting means, preferably in the form of a
limiting nut keyed to the housing and mounted for rotation on an
external threaded section of the drive sleeve, to provide an end of
life stop.
[0047] A second aspect of instant invention provides an assembly
for use in a drug delivery device comprising the drive mechanism
according to instant invention.
[0048] A third aspect of the present invention provides a drug
delivery device comprising the drive mechanism or the assembly
according to instant invention.
[0049] A fourth aspect of the present invention provides a method
of assembling a drug delivery device comprising the step of
providing a drive mechanism or an assembly according to instant
invention.
[0050] A fifth aspect of instant invention is the use of a drug
delivery device according to instant invention for dispensing a
medicinal product preferably dispensing a pharmaceutical
formulation (e.g. solution, suspension etc.) comprising an active
compound selected from the group consisting of insulin, growth
hormone, low molecular weight heparin, their analogues and their
derivatives.
BRIEF DESCRIPTION OF THE DRAWINGS
[0051] Without any limitation, the instant invention will be
explained in greater detail below in connection with a preferred
embodiment and with reference to the drawings in which:
[0052] FIG. 1 shows a sectional view of a first embodiment of the
drug delivery device in accordance with the present invention in a
first, cartridge full, position;
[0053] FIG. 2 shows a sectional view of the drug delivery device of
FIG. 1 in a second, maximum first dose dialed, position;
[0054] FIG. 3 shows a sectional view of the drug delivery device of
FIG. 1 in a third, maximum first dose dispensed, position;
[0055] FIG. 4 shows a sectional view of the drug delivery device of
FIG. 1 in a fourth, final dose dialed, position;
[0056] FIG. 5 shows a sectional view of the drug delivery device of
FIG. 1 in a fifth, final dose dispensed, position;
[0057] FIG. 6 shows a cut-away view of a first detail of the drug
delivery device of FIG. 1;
[0058] FIG. 7 shows a partially cut-away view of a second detail of
the drug delivery device of FIG. 1;
[0059] FIG. 8 shows a partially cut-away view of a third detail of
the drug delivery device of FIG. 1;
[0060] FIG. 9 shows the relative movement of parts of the drug
delivery device shown in FIG. 1 during dialing up of a dose;
[0061] FIG. 10 shows the relative movement of parts of the drug
delivery device shown in FIG. 1 during dialing down of a dose;
[0062] FIG. 11 shows the relative movement of parts of the drug
delivery device shown in FIG. 1 during dispensing of a dose;
[0063] FIG. 12 shows a partially cut-away view of the drug delivery
device of FIG. 1 in the second, maximum first dose dialed,
position;
[0064] FIG. 13 shows a partially cut-away view of the drug delivery
device of FIG. 1 in the fourth, final dose dialed, position; FIG.
14 shows a partially cut-away view of the drug delivery device of
FIG. 1 in one of the first, third or fifth positions;
[0065] FIG. 15 shows a cut-away view of a first part of a main
housing of the drug delivery device of FIG. 1; and
[0066] FIG. 16 shows a cut-away view of a second part of the main
housing of the drug delivery device of FIG. 1;
[0067] FIG. 17 shows a sectional view of a second embodiment of the
drive mechanism according to instant invention in a first,
cartridge full, position.
[0068] FIG. 18 shows a sectional side view of a third embodiment of
the drug delivery device in accordance with the present invention
in a first, cartridge full, position;
[0069] FIG. 19 shows a sectional side view of the drug delivery
device of FIG. 18 in a second, maximum first dose dialed,
position;
[0070] FIG. 20 shows a sectional side view of the drug delivery
device of FIG. 18 in a third, maximum first dose dispensed,
position;
[0071] FIG. 21 shows a sectional side view of the drug delivery
device of FIG. 18 in a fourth, final dose dialed, position;
[0072] FIG. 22 shows a sectional side view of the drug delivery
device of FIG. 18 in a fifth, final dose dispensed, position;
[0073] FIG. 23 shows a fragment of the drug delivery device of FIG.
18 in a larger scale and
[0074] FIG. 24 shows a further fragment of the drug delivery device
of FIG. 18 in a larger scale.
DETAILED DESCRIPTION OF THE EMBODIMENTS
EXAMPLE 1
[0075] Referring first to FIGS. 1 to 5, there is shown a drug
delivery device in accordance with the present invention in a
number of positions.
[0076] The drug delivery device comprises a housing having a first
cartridge retaining part 2, and second main (exterior) housing part
4. A first end of the cartridge retaining means 2 and a second end
of the main housing 4 are secured together by retaining features 6.
In the illustrated embodiment, the cartridge retaining means 2 is
secured within the second end of the main housing 4.
[0077] A cartridge 8 from which a number of doses of a medicinal
product may be dispensed is provided in the cartridge retaining
part 2. A piston 10 is retained in a first end of the cartridge
8.
[0078] A removable cap 12 is releasably retained over a second end
of the cartridge retaining part 2. In use the removable cap 12 can
be replaced by a user with a suitable needle unit (not shown). A
replacable cap 14 is used to cover the cartridge retaining part 2
extending from the main housing 4. Preferably, the outer dimensions
of the replaceable cap 14 are similar or identical to the outer
dimensions of the main housing to provide the impression of a
unitary whole when the replaceable cap 14 is in position covering
the cartridge retaining part 2.
[0079] In the illustrated embodiment, an insert 16 is provided at a
first end of the main housing 4. The insert 16 is secured against
rotational or longitudinal motion. The insert 16 is provided with a
threaded circular opening 18 extending therethrough. Alternatively,
the insert may be formed integrally with the main housing 4 having
the form of a radially inwardly directed flange having an internal
thread.
[0080] A first thread 19 extends from a first end of a piston rod
20. The piston rod 20 is of generally circular section. The first
end of the piston rod 20 extends through the threaded opening 18 in
the insert 16. A pressure foot 22 is located at the first end of
the piston rod 20. The pressure foot 22 is disposed to abut a
second end of the cartridge piston 10. A second thread 24 extends
from a second end of the piston rod 20. In the illustrated
embodiment the second thread 24 comprises a series of part threads
rather than a complete thread. The illustrated embodiment is easier
to manufacture and helps to reduce the overall force required for a
user to actuate the device when dispensing the medicinal
product.
[0081] The first thread 19 and the second thread 24 are oppositely
disposed. The second end of the piston rod 20 is provided with a
receiving recess 26.
[0082] A drive sleeve 30 extends about the piston rod 20. The drive
sleeve 30 is generally cylindrical. The drive sleeve 30 is provided
at a first end with a first radially extending flange 32. A second
radially extending flange 34 is provided spaced a distance along
the drive sleeve 30 from the first flange 32. An intermediate
thread 36 is provided on an outer part of the drive sleeve 30
extending between the first flange 32 and the second flange 34. A
helical groove (thread) 38 extends along the internal surface of
the drive sleeve 30. The second thread 24 of the piston rod 20 is
adapted to work within the helical groove 38.
[0083] A first end of the first flange 32 is adapted to conform to
a second side of the insert 16.
[0084] A nut 40 is located between the drive sleeve 30 and the main
housing 2, disposed between the first flange 32 and the second
flange 34. In the illustrated embodiment the nut 40 is a half-nut.
This assists in the assembly of the device. The nut 40 has an
internal thread matching the intermediate thread 36. The outer
surface of the nut 40 and an internal surface of the main housing 4
are keyed together by splines 42 (FIGS. 10, 11, 15 and 16) to
prevent relative rotation between the nut 40 and the main housing
4, while allowing relative longitudinal movement therebetween.
[0085] A shoulder 37 is formed between a second end of the drive
sleeve 30 and an extension 38 provided at the second end of the
drive sleeve 30. The extension 38 has reduced inner and outer
diameters in comparison to the remainder of the drive sleeve 30. A
second end of the extension 38 is provided with a radially
outwardly directed flange 39.
[0086] A clicker 50 and a clutch 60 are disposed about the drive
sleeve 30, between the drive sleeve 30 and a dose dial sleeve 70
(described below).
[0087] The clicker 50 is located adjacent the second flange 34 of
the drive sleeve 30. The clicker 50 is generally cylindrical and is
provided at a first end with a flexible helically extending arm 52
(FIG. 6). A free end of the arm 52 is provided with a radially
directed toothed member 54. A second end of the clicker 50 is
provided with a series of circumferentially directed saw teeth 56
(FIG. 7). Each saw tooth comprises a longitudinally directed
surface and an inclined surface.
[0088] In an alternative embodiment (not shown) the clicker further
includes at least one spring member. The at least one spring member
assists in the resetting of the clutch 60 following dispense.
[0089] The clutch 60 is located adjacent the second end of the
drive sleeve 30. The clutch 60 is generally cylindrical and is
provided at a first end with a series of circumferentially directed
saw teeth 66 (FIG. 7). Each saw tooth comprises a longitudinally
directed surface and an inclined surface. Towards the second end 64
of the clutch 60 there is located a radially inwardly directed
flange 62. The flange 62 of the clutch 60 is disposed between the
shoulder 37 of the drive sleeve 30 and the radially outwardly
directed flange 39 of the extension 38. The second end of the
clutch 60 is provided with a plurality of dog teeth 65 (FIG. 8).
The clutch 60 is keyed to the drive sleeve 30 by way of splines
(not shown) to prevent relative rotation between the clutch 60 and
the drive sleeve 30.
[0090] In the illustrated embodiment, the clicker 50 and the clutch
60 each extend approximately half the length of the drive sleeve
30. However, it will be understood that other arrangements
regarding the relative lengths of these parts are possible.
[0091] The clicker 50 and the clutch 60 are engaged as shown in
FIG. 7.
[0092] A dose dial sleeve 70 is provided outside of the clicker 50
and clutch 60 and radially inward of the main housing 4. A helical
groove 74 is provided about an outer surface of the dose dial
sleeve 70.
[0093] The main housing 4 is provided with a window 44 through
which a part of the outer surface of the dose dial sleeve may be
seen. The main housing 4 is further provided with a helical rib
(thread) 46, adapted to be seated in the helical groove (thread) 74
on the outer surface of the dose dial sleeve 70. The helical rib 46
extends for a single sweep of the inner surface of the main housing
4. A first stop 100 is provided between the splines 42 and the
helical rib 46 (FIG. 15). A second stop 102, disposed at an angle
of 180.degree. to the first stop 100 is formed by a frame
surrounding the window 44 in the main housing 4 (FIG. 16).
[0094] Conveniently, a visual indication of the dose that may be
dialed, for example reference numerals (not shown), is provided on
the outer surface of the dose dial sleeve 70. The window 44
conveniently only allows to be viewed a visual indication of the
dose currently dialed.
[0095] A second end of the dose dial sleeve 70 is provided with an
inwardly directed flange in the form of a number of radially
extending members 75. A dose dial grip 76 is disposed about an
outer surface of the second end of the dose dial sleeve 70. An
outer diameter of the dose dial grip 76 preferably corresponds to
the outer diameter of the main housing 4. The dose dial grip 76 is
secured to the dose dial sleeve 70 to prevent relative movement
therebetween. The dose dial grip 76 is provided with a central
opening 78. An annular recess 80 located in the second end of the
dose dial grip 76 extends around the opening 78.
[0096] A button 82 of generally `T` section is provided at a second
end of the device. A stem 84 of the button 82 may extend through
the opening 78 in the dose dial grip 76, through the inner diameter
of the extension 38 of the drive sleeve 30 and into the receiving
recess 26 of the piston rod 20. The stem 84 is retained for limited
axial movement in the drive sleeve 30 and against rotation with
respect thereto. A head 85 of the button 82 is generally circular.
A skirt 86 depends from a periphery of the head 85. The skirt 86 is
adapted to be seated in the annular recess 80 of the dose dial grip
76.
[0097] Operation of the drug delivery device in accordance with the
present invention will now be described. In FIGS. 9, 10 and 11
arrows A, B, C, D, E, F and G represent the respective movements of
the button 82, the dose dial grip 76, the dose dial sleeve 70, the
drive sleeve 30, the clutch 60, the clicker 50 and the nut 40.
[0098] To dial a dose (FIG. 9) a user rotates the dose dial grip 76
(arrow B). With the clicker 50 and clutch 60 engaged, the drive
sleeve 30, the clicker 50, the clutch 60 and the dose dial sleeve
70 rotate with the dose dial grip 76.
[0099] Audible and tactile feedback of the dose being dialed is
provided by the clicker 50 and the clutch 60. Torque is transmitted
through the saw teeth 56,66 between the clicker 50 and the clutch
60. The flexible arm 52 deforms and drags the toothed member 54
over the splines 42 to produce a click. Preferably, the splines 42
are disposed such that each click corresponds to a conventional
unit dose, or the like.
[0100] The helical groove 74 on the dose dial sleeve 70 and the
helical groove 38 in the drive sleeve 30 have the same lead. This
allows the dose dial sleeve 70 (arrow C) to extend from the main
housing 4 and the drive sleeve 30 (arrow D) to climb the piston rod
20 at the same rate. At the limit of travel, a radial stop 104
(FIG. 12) on the dose dial sleeve 70 engages either the first stop
100 or the second stop 102 provided on the main housing 4 to
prevent further movement. Rotation of the piston rod 20 is
prevented due to the opposing directions of the overhauled and
driven threads on the piston rod 20.
[0101] The nut 40, keyed to the main housing 4, is advanced along
the intermediate thread 36 by the rotation of the drive sleeve 30
(arrow D). When the final dose dispensed position (FIGS. 4, 5 and
13) is reached, a radial stop 106 formed on a second surface of the
nut 40 abuts a radial stop 108 on a first surface of the second
flange 34 of the drive sleeve 30, preventing both the nut 40 and
the drive sleeve 30 from rotating further.
[0102] In an alternative embodiment (not shown) a first surface of
the nut 40 is provided with a radial stop for abutment with a
radial stop provided on a second surface of the first flange 32.
This aids location of the nut 40 at the cartridge full position
during assembly of the drug delivery device.
[0103] Should a user inadvertently dial beyond the desired dosage,
the drug delivery device allows the dosage to be dialed down
without dispense of medicinal product from the cartridge (FIG. 10).
The dose dial grip 76 is counter rotated (arrow B). This causes the
system to act in reverse. The flexible arm 52 preventing the
clicker 50 from rotating. The torque transmitted through the clutch
60 causes the saw teeth 56,66 to ride over one another to create
the clicks corresponding to dialed dose reduction. Preferably the
saw teeth 56,66 are so disposed that the circumferential extent of
each saw tooth corresponds to a unit dose.
[0104] When the desired dose has been dialed, the user may then
dispense this dose by depressing the button 82 (FIG. 11). This
displaces the clutch 60 axially with respect to the dose dial
sleeve 70 causing the dog teeth 65 to disengage. However the clutch
60 remains keyed in rotation to the drive sleeve 30. The dose dial
sleeve 70 and associated dose dial grip 76 are now free to rotate
(guided by the helical rib 46 located in helical groove 74).
[0105] The axial movement deforms the flexible arm 52 of the
clicker 50 to ensure the saw teeth 56,66 cannot be overhauled
during dispense. This prevents the drive sleeve 30 from rotating
with respect to the main housing 4 though it is still free to move
axially with respect thereto. This deformation is subsequently used
to urge the clicker 50, and the clutch 60, back along the drive
sleeve 30 to restore the connection between the clutch 60 and the
dose dial sleeve 70 when pressure is removed from the button
82.
[0106] The longitudinal axial movement of the drive sleeve 30
causes the piston rod 20 to rotate though the opening 18 in the
insert 16, thereby to advance the piston 10 in the cartridge 8.
Once the dialed dose has been dispensed, the dose dial sleeve 70 is
prevented from further rotation by contact of a plurality of
members 110 (FIG. 14) extending from the dose dial grip 76 with a
corresponding plurality of stops 112 formed in the main housing 4
(FIGS. 15 and 16). In the illustrated embodiment, the members 110
extend axially from the dose dial grip 76 and have an inclined end
surface. The zero dose position is determined by the abutment of
one of the axially extending edges of the members 110 with a
corresponding stop 112.
EXAMPLE 2
[0107] In another embodiment of the invention (FIG. 17) there is
seen a drive mechanism comprising a second main housing 4' having a
first end and a second end. A cartridge, containing medicinal
product, can be mounted to the first end of the second main housing
4' and retained by any suitable means. The cartridge and its
retaining means are not shown in the illustrated embodiment. The
cartridge may contain a number of doses of a medicinal product and
also typically contains a displaceable piston. Displacement of the
piston causes the medicinal product to be expelled from the
cartridge via a needle (also not shown).
[0108] In the illustrated embodiment, an insert 16' is provided
within the main housing 4'. The insert 16' is secured against
rotational and axial motion with respect to the second main housing
4'. The insert 16' is provided with a threaded circular opening
extending therethrough. Alternatively, the insert may be formed
integrally with the second main housing 4'.
[0109] An internal housing 154 is also provided within the second
main housing 4'. The internal housing 154 is secured against
rotational and axial motion with respect to the second main housing
4'. The internal housing 154 is provided with a circular opening
extending through its length in which a series of longitudinally
directed splines are formed. A helical thread 150 extends along the
outer cylindrical surface of the internal housing 154.
Alternatively, the internal housing may be formed integrally with
the second main housing 4' and/or with the insert 16'.
[0110] A first thread 19' extends from a first end of a piston rod
20'. The piston rod 20' is of generally circular section. The first
end of the piston rod 20' extends through the threaded opening in
the insert 16' and the first thread 19' of the piston rod 20' is
engaged with the thread of the insert 16'. A pressure foot 22' is
located at the first end of the piston rod 20'. The pressure foot
22' is disposed to abut a cartridge piston (not shown). A second
thread 24' extends from a second end of the piston rod 20'. The
first thread 19' and the second thread 24' are oppositely
disposed.
[0111] A drive sleeve 30' extends about the piston rod 20'. The
drive sleeve 30' is generally cylindrical. The drive sleeve 30' is
provided at a first end with a first radially extending flange 32'.
A second radially extending flange 34' is provided, spaced a
distance along the drive sleeve 30' from the first flange 32'. An
external helical thread (not shown) is provided on the outer part
of the drive sleeve 30' extending between the first flange 32' and
the second flange 34'. An internal helical thread extends along the
internal surface of the drive sleeve 30'. The second thread 24' of
the piston rod 20' is engaged with the internal helical thread of
the drive sleeve 30'.
[0112] A nut 40' is located between the drive sleeve 30' and the
internal housing 154, disposed between the first flange 32' and the
second flange 34' of the drive sleeve 30'. The nut 40' can be
either a `half-nut` or a `full-nut`. The nut 40' has an internal
thread that is engaged with the external helical thread of the
drive sleeve 30'. The outer surface of the nut 40' and an internal
surface of the internal housing 154 are keyed together by means of
longitudinally directed splines to prevent relative rotation
between the nut 40' and the internal housing 154, while allowing
relative longitudinal movement therebetween.
[0113] A clicker 50' and a clutch 60' are disposed about the drive
sleeve 30', between the drive sleeve 30' and the internal housing
154.
[0114] The clicker 50' is located adjacent the second flange 34' of
the drive sleeve 30'. The clicker 50' includes at least one spring
member (not shown). The clicker 50' also includes a set of teeth
(not shown) having a triangular profile disposed towards the second
end of the drive mechanism. When compressed, the at least one
spring member of the clicker 50' applies an axial force between the
flange 34' of the drive sleeve 30' and the clutch 60'. The outer
surface of the clicker 50' and an internal surface of the internal
housing 154 are keyed together by means of longitudinally directed
splines to prevent relative rotation between the clicker 50' and
the internal housing 154, while allowing relative longitudinal
movement therebetween.
[0115] The clutch 60' is located adjacent the second end of the
drive sleeve 30'. The clutch 60' is generally cylindrical and is
provided at its' first end with a plurality of teeth of triangular
profile disposed about the circumference (not shown), that act upon
the teeth of the clicker 50'. Towards the second end of the clutch
60' there is located a shoulder 158. The shoulder 158 of the clutch
60' is disposed between the internal housing 154 and a radially
inwardly directed flange of the dose dial grip 76' (described
below). The shoulder 158 of the clutch 60' is provided with a
plurality of dog teeth (not shown) extending in the direction of
the second end of the drive mechanism. The clutch 60' is keyed to
the drive sleeve 30' by way of splines (not shown) to prevent
relative rotation between the clutch 60' and the drive sleeve
30'.
[0116] A dose dial sleeve 70' is provided outside of the internal
housing 154 and radially inward from the second main housing 4'. A
helical thread is provided on an inner surface of the dose dial
sleeve 70'. The helical thread of the dose dial sleeve 70' is
engaged with the helical thread 150 of the internal housing
154.
[0117] The second main housing 4' is provided with a window (not
shown) through which part of the outer surface of the dose dial
sleeve 70' may be viewed. Conveniently, a visual indication of the
dose that may be dialed, for example reference numerals (not
shown), is provided on the outer surface of the dose dial sleeve
70'. Conveniently, the window of the second main housing 4' allows
only the dose that is currently dialed to be viewed.
[0118] A dose dial grip 76' is located towards the second end of
the drive mechanism. The dose dial grip 76' is secured against
rotational and axial motion within respect to the dose dial sleeve
70'. The dose dial grip 76' is provided with a radially inwardly
directed flange 160. The radially inwardly directed flange 160 of
the dose dial grip 76' is provided with a plurality of dog teeth
(not shown) extending in the direction of the first end of the
drive mechanism to abut the dog teeth of the clutch 60'. Coupling
and decoupling of the dog teeth of the dose dial grip 76' with the
dog teeth of the clutch 60' provides a releasable clutch between
the dose dial grip 76' and the clutch 60'.
[0119] A button 82' of generally `T` shaped cross-section is
provided at a second end of the drive mechanism. A cylindrical
feature of the button 82' extends towards the first end of the
drive mechanism, through an opening in the dose dial grip 76' and
into a recess in the drive sleeve 30'. The cylindrical feature of
the button 82' is retained for limited axial movement in the drive
sleeve 30' and against rotation with respect thereto. The
cylindrical feature of the button 82' has lugs extending radially
(not shown) that abut the second surface of the shoulder 158 of the
clutch 60'. The second end of the button 82' is generally circular
and has a cylindrical skirt about its' periphery that descends
towards the first end of the drive mechanism. The skirt of the
button 82' is located radially inward from the dose dial grip
76'.
[0120] Operation of the drive mechanism in accordance with the
present invention will now be described.
[0121] To dial a dose, a user rotates the dose dial grip 76'. The
spring member of the clicker 50' applies an axial force to the
clutch 60' in the direction of the second end of the drive
mechanism. The force exerted by the spring member of the clicker
50' couples the dog teeth of the clutch 60' to the dog teeth of the
dose dial grip 76' for rotation. As the dose dial grip 76' is
rotated, the associated dose dial sleeve 70', the drive sleeve 30'
and the clutch 60' all rotate in unison.
[0122] Audible and tactile feedback of the dose being dialed is
provided by the clicker 50' and the clutch 60'. As the clutch 60'
is rotated, torque is transmitted from the teeth at the first end
of the clutch 60' and the teeth of the clicker 50'. The clicker 50'
cannot rotate with respect to the internal housing 154, so the at
least one spring member of the clicker 50' deforms allowing the
teeth of the clutch 60' to jump over the teeth of the clicker 50'
producing an audible and tactile `click`. Preferably, the teeth of
the clicker 50' and the teeth of the clutch 60' are disposed such
that each `click` corresponds to a conventional unit of the
medicinal product, or the like.
[0123] The helical thread of the dose dial sleeve 70' and the
internal helical thread of the drive sleeve 30' have the same lead.
This allows the dose dial sleeve 70' to advance along the thread
150 of the internal housing 154 at the same rate as the drive
sleeve 30' advances along the second thread 24' of the piston rod
20'. Rotation of the piston rod 20' is prevented due to the
opposing direction of the first thread 19' and the second thread
24' of the piston rod 20'. The first thread 19' of the piston rod
20' is engaged with the thread of the insert 16' and so the piston
rod 20' does not move with respect to the second main housing 4'
while a dose is dialed.
[0124] The nut 40', keyed to the internal housing 154, is advanced
along the external thread of the drive sleeve 30' by the rotation
of the drive sleeve 30'. When a user has dialed a quantity of
medicinal product that is equivalent to the deliverable volume of
the cartridge, the nut 40' reaches a position where it abuts the
second flange 34' of the drive sleeve 30'. A radial stop formed on
the second surface of the nut 40' contacts a radial stop on the
first surface of the second flange 34' of the drive sleeve 30',
preventing both the nut 40' and the drive sleeve 30' from being
rotated further.
[0125] Should a user inadvertently dial a quantity greater than the
desired dosage, the drive mechanism allows the dosage to be
corrected without dispense of medicinal product from the cartridge.
The dose dial grip 76' is counter-rotated. This causes the system
to act in reverse. The torque transmitted through the clutch 60'
causes the teeth at the first end of the clutch 60' to ride over
the teeth of the clicker 50' to create the clicks corresponding to
the dialed dose reduction.
[0126] When the desired dose has been dialed, the user may then
dispense this dose by depressing the button 82' in the direction of
the first end of the drive mechanism. The lugs of the button 82'
apply pressure to the second surface of the shoulder 158 of the
clutch 60', displacing the clutch 60' axially with respect to the
dose dial grip 76'. This causes the dog teeth on the shoulder 158
of the clutch 60' to disengage from the dog teeth of the dose dial
grip 76'. However, the clutch 60' remains keyed in rotation to the
drive sleeve 30'. The dose dial grip 76' and associated dose dial
sleeve 70' are now free to rotate (guided by the helical thread 150
of the internal housing 154).
[0127] The axial movement of the clutch 60' deforms the spring
member of the clicker 50' and couples the teeth at the first end of
the clutch 60' to the teeth of the clicker 50' preventing relative
rotation therebetween. This prevents the drive sleeve 30' from
rotating with respect to the internal housing 154, though it is
still free to move axially ith respect thereto.
[0128] Pressure applied to the button 82' thus causes the dose dial
grip 76' and the associated dose dial sleeve 70' to rotate into the
second main housing 4'. Under this pressure the clutch 60', the
clicker 50' and the drive sleeve 30' are moved axially in the
direction of the first end of the drive mechanism, but they do not
rotate. The axial movement of the drive sleeve 30' causes the
piston rod 20' to rotate though the threaded opening in the insert
16', thereby to advance the pressure foot 22'. This applies force
to the piston, causing the medicinal product to be expelled from
the cartridge. The selected dose is delivered when the dose dial
grip 76' returns to a position where it abuts the second main
housing 4'.
[0129] When pressure is removed from the button 82', the
deformation of the spring member of the clicker 50' is used to urge
the clutch 60' back along the drive sleeve 30' to re-couple the dog
teeth on the shoulder 158 of the clutch 60' with the dog teeth on
the dose dial grip 76'. The drive mechanism is thus reset in
preparation to dial a subsequent dose.
EXAMPLE 3
[0130] Referring to FIGS. 18 to 22 there may be seen a drug
delivery device in accordance with the present invention. The drug
delivery device comprises a two-part housing 2" within which are
located a cartridge 4" containing a medicinal product, means for
setting or selecting the dose of medicinal product to be expelled
and means for expelling the selected dose of medicinal product. The
housing 2" is generally cylindrical in shape and houses a rack 6"
to be described in more detail below. The cartridge 4" is located
within a first part 8" of the housing 2". The dose setting means
and the means for expelling the selected dose of medicinal product
are retained, that is held, within a second part 10" of the housing
2". The first part 8" of the housing 2" and the second part 10" of
the housing 2" may be secured together by any suitable means.
[0131] The cartridge 4" may be secured in position in the first
part 8" of the housing 2" by any suitable means. A needle unit may
be secured to a first end of the cartridge 4". A temporary covering
12" is shown in this position in the Figures. The cartridge 4"
further comprises a displaceable piston 14". Advancing the piston
10" towards the first end of the cartridge 4" causes the medicinal
product to be expelled from the cartridge 4" through the needle
unit. A cap 16" is provided to cover the needle unit when the drug
delivery device is not in use. The cap 16" may be releasably
secured to the housing 2" by any suitable means.
[0132] The dose setting means and the means for expelling the
selected dose of medicinal product will now be described in more
detail. The rack 6" is located within a drive sleeve 18" located
within the housing 2" and is fixed both axially and rotationally
with respect to the housing 2" by any suitable means. The drive
sleeve 18" comprises an internally threaded portion 20", which
extends along substantially the entire internal surface of the
sleeve. An internal toothed gear 22" is located within the drive
sleeve 18" and has helical teeth which match the pitch of the
internal thread of the drive sleeve 18". The internal thread of the
drive sleeve 18" is a multistart thread with a lead which is the
same as the lead of the helical thread of the dose dial sleeve,
which will be described later. The drive sleeve 18" terminates in
an externally threaded section 24" which extends from an end of the
sleeve as far as an external circumferential flange 26" which
projects from the drive sleeve 18". A limiting nut 28" is mounted
for rotation on the externally threaded section 24" of the sleeve
14". The limiting nut 28" is keyed to the housing 2" by means of a
plurality of longitudinally extending splines 30" which extend
along the internal surface of the first portion 8" of the housing
2". In the illustrated embodiment, the limiting nut 28" is shown as
a half-nut, but a full nut could be used.
[0133] A piston rod 32" is provided extending along the length of
the rack 6" and through a hole in the end of the rack 6". The
piston rod 32" is generally elongate and is provided ith a pressure
foot 34". In use the pressure foot 34" is disposed to abut the
cartridge piston 14". The toothed gear 22" is mounted on the end of
the piston rod 32" remote from the pressure foot 34" in a journal
bearing (not shown).
[0134] A dose dial sleeve 36" of generally cylindrical form
comprises a first section 38" of first diameter and a second
section 40" of larger second diameter. The first section is located
within the housing 2".
[0135] The second section 40" of the dose dial sleeve 36" is
preferably of the same outer diameter as the housing 2". The second
part 10" of the housing 2" comprises an external sleeve portion 42"
surrounding a coaxial internal sleeve portion 44". The external
sleeve portion 42" is closed to the internal sleeve portion 44" at
a circular internal flange portion 46". The first section 38" of
the dose dial sleeve 36" is located within the second part 10" of
the housing 2", between the external sleeve portion 42" and the
internal sleeve portion 44". An inner surface of the first section
38" and the outer surface of the internal sleeve portion 44" are
provided with interengaging features to provide a helical thread
48" between the internal sleeve portion 44" of the second part 10"
of the housing 2" and the dose dial sleeve 36". This helical thread
48" has the same lead as the internal thread of the drive sleeve
18", as noted above. Within the helical track, a helical rib
provided on the inner surface of the dose dial sleeve 36" may run.
This enables the dose dial sleeve 36" to rotate about and along the
housing 2".
[0136] The second section 40" of the dose dial sleeve 36" is
provided with an end wall 50" adjacent its free end, which defines
a central receiving area 52" between the end wall 50" and the free
end of the dose dial sleeve 36". A through hole 54" is provided in
the end wall 50". A dose button 56" of generally "T" shaped
configuration is provided, the head 58" of which is retained within
the receiving area 52" and the stem 60" of which is sized to pass
through the through hole 54". The stem 60" of the button 56" is
provided ith a plurality of fingers 62" that are deformable to pass
through the through hole 54" of the end wall 50" only in the
direction away from the free end of the dose dial sleeve 36".
[0137] The drive sleeve 18" is closed at its end remote from the
externally threaded section 24" by an apertured end wall 64" from
which a plurality of engagement features 66" project external to
the drive sleeve 18".
[0138] A substantially U-shaped locking spring 68" comprising first
and second legs 70", 72" joined by a link portion 74" is provided
for longitudinal mounting on the exterior of the rive sleeve 18".
The link portion 74" is of a length which is substantially equal to
the external diameter of the drive sleeve 18". Each of the legs
70", 72" of the locking spring 68" terminates in a latch portion
76", the function of which will be described later.
[0139] When the device is assembled, the locking spring 68" urges
the dose button 56" axially away from the piston rod 32" and drive
sleeve 18", towards the inside of the end wall 50" of the dose dial
sleeve 36". In this position, the dose button 56" is locked with
respect to rotation with the dose dial sleeve 36". The dose button
56" is also permanently locked with respect to rotation with the
drive sleeve 18".
[0140] An outer surface of the first section of the dose dial
sleeve 36" is provided with graphics 82". The graphics are
typically a sequence of reference numerals. The housing 2" is
provided with an aperture or window 84" through which a portion of
the graphics, representing a dosage value selected by the user, may
be viewed.
[0141] The graphics 82" may be applied to the dose dial sleeve 36"
by any suitable means. The graphics 82" may be printed directly on
the dose dial sleeve 36" or may be provided in the form of a
printed label encircling the dose dial sleeve 36". Alternatively
the graphics may take the form of a marked sleeve clipped to the
dose dial sleeve 36". The graphics may be marked in any suitable
manner, for example by laser marking.
[0142] The external circumferential flange 26" which projects from
the drive sleeve 18" is provided with a pair of diametrically
opposed through apertures 78" sized to receive the corresponding
latch portions 76" of the locking spring 68". A clicker projection
80" from the outer edge of the flange 26" is associated with each
through aperture 78".
[0143] In FIG. 18, the drug delivery device is provided with a
filled cartridge 4". To operate the drug delivery device a user
must first select a dose. To set a dose the dose dial sleeve 36" is
rotated with respect to the housing 2" until the desired dose value
is visible through the window 84". The drive sleeve 18" is linked
to the dose dial sleeve 36" and spirals out at the same rate during
dialling. During the dialling of a dose, the locking spring 68 is
straight and urges the dose button 56" axially away from the piston
rod 32" and drive sleeve 18", towards the inside of the end wall
50" of the dose dial sleeve 36", thereby providing a clutch
mechanism. The drive sleeve 18" therefore rotates over the toothed
gear 22" that is located inside it. The relative rotation between
the drive sleeve 18" and the housing 2" causes an audible
confirmation of the dose being dialed by engagement of the two
clicker projections 80" with the splines 30" which extend along the
internal surface of the first portion 8" of the housing 2".
[0144] The limiting nut 28" climbs up the drive sleeve 18" in
proportion to the dose dialed. The position of the limiting nut
28", which only moves along the external thread of the drive sleeve
18" when there is relative rotation between the drive sleeve 18"
and the housing 2", corresponds to the amount of medicinal product
remaining in the cartridge 4".
[0145] Once a desired dose has been set (as shown for example in
FIG. 19), to deliver the dose the user depresses the dose button
56" to urge the button 56" against the locking spring 68". As the
dose button 56" pushes down on the spring 68", the clutch between
the dose button 56" and the dose dial sleeve 36" is disengaged. The
axial force applied from the dose button 56" onto the dose dial
sleeve 36" causes the dose dial sleeve 36" to spin into the housing
2" on the helical thread between the dose dial sleeve 36" and the
housing 2". The locking spring 68" deforms and the legs of the
spring move axially down the drive sleeve 18". The latch portions
76" of the locking spring 68" engage in the through apertures 78"
on the external flange 26" which projects from the drive sleeve 18"
and maintain engagement between the clicker projections 80" of the
flange 26" with the grooves between the splines 30", locking the
drive sleeve to the housing 2" and preventing the drive sleeve 18"
from rotation relative to the housing 2" during dispensing of the
dose. The drive sleeve 18" is thus prevented from spinning and
moves axially in, causing the toothed gear 22" to rotate against
the fixed rack 6". The toothed gear 22", together with the piston
rod 32" on which it is mounted, move along the rack 6" a distance
corresponding to one half of the distance by which the drive sleeve
18" moves axially, creating a 2:1 mechanical advantage. This has
the two-fold benefit of allowing the display on the dose dial
sleeve 36" to be larger for a given amount of travel of the piston
14" within the cartridge 4", that is for a given amount of
medicament to be dispensed and secondly of halving the force
required to dispense the dose.
[0146] The piston rod 32" is driven through the drive sleeve 18"
towards the first end of the drug delivery device, thereby to
advance the cartridge piston 14" and expel the desired dose of
medicinal product. The piston rod 32" continues to advance until
the drive sleeve 18" and dose dial sleeve 36" have returned to
their initial positions (FIG. 20).
[0147] It can be seen that the dose selecting means and the dose
expelling means extend beyond a second end of the housing 2" as the
dose is selected and are returned within the housing 2" as the
selected dose is expelled.
[0148] Further dosages may be delivered as required. FIG. 21 shows
an example of a subsequently selected dosage. As noted above, the
position of the limiting nut 28" along the external thread of the
drive sleeve 18" corresponds to the amount of medicinal product
remaining in the cartridge 4", such that when the nut 28" reaches
the external flange 26" and can rotate no further this corresponds
to no medicinal product remaining in the cartridge 4". It will be
seen that if a user seeks to select a quantity of medical product
greater than that remaining in the cartridge 4", this cannot be
done since when the nut 28" stops rotating against the drive sleeve
18", the drive sleeve 18" and the housing 2" will become locked
together preventing rotation of the drive sleeve 18" and hence the
dose dial sleeve 36". This prevents the setting of a larger dose
than the amount of medical product remaining within the cartridge
4". FIG. 22 shows a drug delivery device according to the present
invention in which the entire medicinal product within the
cartridge 4" has been expelled.
[0149] The illustrated embodiment of the device according to the
invention further comprises a maximum dosage dial end stop. When
the dose dial sleeve 36" is dialed fully out, the external flange
26" on the drive sleeve 18" engages the internal flange 46" in the
housing 2". It will be seen that if the user tries to dial beyond
the maximum dosage, his cannot be done. When the drive sleeve 18"
stops rotating against the housing 2", the dose dial sleeve is also
prevented from rotating. The reaction between the external flange
44" and the internal flange 86" indicates to the user that the
maximum dose has been dialed.
* * * * *