Note: Descriptions are shown in the official language in which they were submitted.
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Blocking device for a locking-stressing-mechanism having
a spring-actuated output drive device
The invention relates to a blocking device by means of
which the proper use of a device equipped with a locking-
stressing mechanism and a spring-actuated output drive is
prevented after a given number of actuations. The device
may be, for example, a high pressure atomiser or a
needleless injector.
The aim of the invention is to reliably limit the period
of use of such a device and meet safety requirements.
The reasons for the limitation may be based on hygiene,
medical or technical considerations.
The locking-stressing-mechanism, which is to be blocked
after the permitted period of use, has elapsed preferably
comprises a helical thrust gear accommodated in a
manually operated device, by means of which a rotary
movement is converted into a linear movement and an
operating spring is put under tension. The operating
spring acts on a spring component of the locking-
stressing-mechanism the movement of which is initially
blocked as soon as the operating spring has reached the
tensioned state. Secured in the spring component there
may be a piston movably mounted in a cylinder. Inside
the cylinder, in front of the piston, is a liquid which
is expelled out through a nozzle as the locking mechanism
of the locking-stressing mechanism is actuated by the
piston driven by the operating spring. The number of
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actuations of the locking-stressing-mechanism and hence
of the device can be counted by a mechanical counter.
WO-93/21980 describes a metered-dose inhaler. The dose
of a substance to be inhaled is introduced, by means of a
hand-operated device, from a supply of the substance
contained in the inhaler, into a chamber from which the
dose is expelled with the current of air which the user
sucks in through the inhaler as they breathe in. The
metered-dose inhaler is fitted with a counter which
comprises a rotatable screw spindle and a rod, one end of
which engages in the form of a nose in the thread of the
screw spindle. The rod moves parallel to the screw
spindle as the rotation of the spindle increases. The
counter indicates, by means of the position of the nose-
like end of the rod, the number of doses which have
already been taken out of the supply of substance, or
those which can still be taken out. The other end of the
rod is movably held in a guide shaft into which the rod
extends more deeply as the rotation of the screw spindle
increases. As soon as the supply of substance in the
inhaler is coming to an end, the nose-like end of the rod
engaging in the screw spindle reaches that part of the
spindle which has a number of courses of thread having a
greater pitch than the rest of the screw spindle. As a
result, on each rotation of the screw spindle, the rod
moves along faster than before. The other end of the rod
meanwhile bears on a flexible lever, and further
actuation of the metered-dose inhaler is prevented.
WO-97/20590 describes a locking stressing mechanism for a
spring-actuated output drive. WO-97/24586 describes a
mechanical counter for a metering device. WO-97/12687
describes a device for generating high pressure in a
fluid in a miniature arrangement provided with a locking
stressing mechanism and a counter. The apparatus is used
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to atomise a fluid to produce an inhalable aerosol. wo-
01/64268 describes a needleless injector which contains a
locking stressing mechanism.
The pieces of equipment mentioned above by way of example
are intended for repeated use, e.g. for repeated
atomisation of a given amount of liquid to produce an
aerosol for inhalation into the lungs, or for needleless
injection of a given quantity of liquid underneath the
skin of humans or animals. The quantity of liquid
atomised or injected may contain a therapeutically active
substance.
The problem of the present invention is to provide a
device for an apparatus which will reliably, effectively
and finally prevent further use of the apparatus after a
given number of actuations if there is a compelling
reason for this. The apparatus comprises a locking-
stressing-mechanism with an operating spring and a spring
transfer member in which is accommodated a piston which
is mounted to be movable in a cylinder. The components
are housed in a two-part housing which comprises an upper
housing part and a lower housing part. The two housing
parts are mounted to be rotatable relative to each other.
The operating spring is tensioned by means of a screw
thrust gear by manually rotating the two housing parts
relative to each other. At the same time as the housing
parts are rotated relative to each other, a mechanical
counter is actuated which comprises a threaded spindle
and a slider. The threaded spindle is mounted in the
wall of the lower housing part. The slider is moved up or
down the spindle by an amount which depends on the number
of rotations of the two housing parts relative to each
other.
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This problem is solved according to the invention by a
device having the following characterising features:
= A recess is provided in the outer wall of the lower
housing part and in the inner wall of the upper
housing part. The two recesses are opposite each
other when the two housing parts are in a given
rotary position.
= In the recess in the lower housing part there is a
movable blocking element which is located only in
this recess before the blocking device is activated
and allows the two housing parts to rotate relative
to each other. After the activation of the blocking
device the blocking element is located in both
recesses and prevents the two housing parts from
rotating relative to each other.
= By means of a push-rod which co-operates with the
slider on the spindle of the counter, the blocking
element is moved out of its resting position into
the position which it occupies after activation of
the blocking device.
On the one hand, the push-rod may be mounted on the
slider to the side of the spindle of the counter. In
this embodiment of the blocking device, during normal
use of the device, the slider moves towards the upper
spindle mounting and towards the upper housing part.
The recess in the wall of the lower housing part is
mounted next to the axis of the counter spindle.
Before the slider makes contact with the upper spindle
mounting, the push-rod moves the blocking element
located in the recess in the wall of the lower housing
part out of its resting position and thereby activates
the blocking device.
The push-rod can also be constructed as an extension
of the blocking element. In this embodiment, the end
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of the push-rod projects into the path travelled by
the slider during normal use of the device before the
slider comes to abut on the upper mounting of the
counter spindle. This embodiment works in exactly the
5 same way as the embodiment described above.
In another embodiment of the blocking device the push
rod may be constructed as an extension of the counter
spindle and may project beyond the upper spindle
mounting. In this case the counter spindle is mounted
to be axially moveable. The recess in the wall of the
lower housing part is preferably provided on the axis
of the counter spindle. Before the blocking device is
activated the counter spindle is pressed against the
lower spindle mounting by a spring, e.g. a helical
spring. In this embodiment of the blocking device the
slider moves towards the lower spindle mounting during
normal use of the device. As soon as the slider comes
to abut on the lower spindle mounting, the counter
spindle moves axially towards the upper housing part
as it continues to rotate. The extension of the
counter spindle in the form of a push rod moves the
blocking element located in the recess in the wall of
the lower housing part out of its resting position,
thereby activating the blocking device.
In a reversal of the embodiments described, the
blocking element may be pulled out of its resting
position by the slider.
The blocking element located in the wall of the lower
housing part may be axially or radially moveable. The
blocking element may be a leaf spring, preferably a
pre-stressed leaf spring with two legs preferably made
of metal.
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The blocking device according to the invention has the
following advantages:
= It is suitable for miniaturised equipment.
= It is arranged between the housing parts which
overlap one another and in its position of use in
a device it is inaccessible to the user.
= It is easy to assemble.
= A blocking element in the form of a pre-stressed
leaf spring with two legs is secured against
movement in its resting position without any
additional effort.
= A pre-stressed leaf spring can be pushed into or
pulled out of its resting position with
relatively little force.
= A pre-stressed leaf spring with two legs jumps
abruptly from its resting position into the
position it occupies when the blocking device is
activated, as soon as it has been moved a certain
distance by means of a push rod. Thus the
response point of the blocking device is
precisely fixed.
= The rotation of the two housing parts relative to
one another is blocked directly as soon as the
blocking element, which was originally located in
the recess in the wall of the lower housing part,
is situated in both recesses at the same time.
= The activated blocking device which contains a
pre-stressed metal leaf spring can only be
overcome by a force moment amounting to several
Newton metres, which will destroy the blocked
device.
The blocking device according to the invention is used
for example in a high pressure atomiser or in a
needleless injector. A medical liquid administered
using such a device may contain a drug dissolved in a
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solvent. Suitable solvents include, for example,
water, ethanol or mixture thereof. The drugs in
question may be, for example, Berotec (fenoterol
hydrobromide; 1-(3,5-dihydroxy-phenyl)-2-[[1-(4-
hydroxy-benzyl)-ethyl]-amino]-ethanol-hydrobromide),
Atrovent (ipratropium bromide), Berodual (combination
of fenoterol hydrobromide and ipratropium bromide),
salbutamol (or albuterol), Combivent, Oxivent
(oxitropium bromide), Ba 679 (tiotropium bromide), BEA
2108 (tropenol di-(2-thienyl glycolate), flunisolide,
budesonide "=and others.
A preferred embodiment of the blocking device
according to the invention will be explained in more
detail with reference to the figures. Figures 1 and 2
show partial longitudinal sections through the wall of
the lower and upper housing part as well as a leaf
spring as a blocking element and a push rod level with
the recesses in the walls. The longitudinal section
runs parallel to the axis of the lower and upper
housing parts.
Figures 3 and 4 show a longitudinal elevation of a
device cut open in the region of the counter and the
blocking device.
In Figures 1 and 3 the blocking device is shown in the
resting position. The blocking element is in its
resting position and is located only in the recess in
the wall of the lower housing part. Figures 2 and 4
show the blocking device activated. The blocking
element has been moved out of its resting position and
is located in both recesses in the walls of the two
housing parts.
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The upper housing part (1) overlaps the lower housing
part (2). The gap (3) between the two housing parts,
mounted to be rotatable relative to each other, is
exaggerated in the drawing. In the upper housing part
there is the recess (4) and in the lower housing part
the recess (5). The recess (5) contains an undercut
projection (6) which is connected to the lower housing
part at the side walls of the recess (5). The push
rod (8a, 8b) projects into the recess in the wall of
the lower housing part. The push rod is mounted on
the slider (not shown in Figures 1 and 2) which is
located on the spindle (not shown in Figures 1 and 2)
of the counter. The blocking element is a leaf spring
with two legs. In its resting position the leaf
spring (7a) is jammed between the base of the recess
(5) and the undercut projection (6). The push rod
(8a) is shown in a position which it occupies shortly
before making contact with the leaf spring (7a). As
the device is further actuated the push rod moves
towards the leaf spring and pushes it out of its
resting position, until the end of the leaf spring
jumps forward behind the projection (6). If the two
recesses (4) and (5) are not yet located opposite each
other at this moment the end of the leaf spring which
has jumped forward behind the projection (6) first
makes contact with the inner wall of the upper housing
part. As soon as the two recesses (4) and (5) are
located opposite one another, as the rotation of the
two housing parts relative to each other continues,
the end of the leaf spring jumps into the recess (4).
The leaf spring (7b) is thus located in both recesses
and the blocking device is activated.
Figure 3 shows the spindle (10) of the counter on
which the slider (9) is located in its (lower)
starting position before the device is used for the
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first time. The push rod (8a) is at some distance
from the leaf spring (7a).
In Figure 4 the slider on the spindle is in its (top)
end position in which it has made contact with the end
of the leaf spring (8b) and pushed the leaf spring out
of its resting position, as a result of which the
blocking device has been activated.
The pre-stressed leaf spring (7a; 7b) shown in the
figures as a blocking element consists for example of
spring steel about 0.2 mm thick and is about 3.5 mm
wide. The two recesses in the walls of the two
housing parts are about 4 mm wide and about 1 mm deep.
Once the blocking device has been activated the two
housing parts can only be rotated relative to one
another by the application of considerable force
(force moment about 3 Newton metres), but this
destroys the device and makes it unusable.
