Abstrict Blood lancet for withdrawing blood for diagnostic purposes. It
has a housing with an outlet opening for the tip of a lancet, and
a lancet drive with a drive rotor driven in a sense of rotation
by a drive spring. The drive rotor converts the relaxation movement
of the drive spring to a pricking movement, moving the lancet with
high speed in pricking direction, until the tip protrudes from the
outlet opening. The drive rotor has a pressure surface directed
radially outwardly and running around the rotation axis with varying
center distance. The pressure surface has a vertex with maximum
center distance, and a propelling section, following the vertex
against the sense of rotation and having a center distance decreasing
against the sense of rotation. The drive spring effects a pressure
on the propelling section of the pressure surface, thus driving
the drive rotor in sense of rotation, whereas the drive rotor is
coupled to the lancet holder.
Claims We claim:
1. Blood lancet device for withdrawing blood from a body part for
diagnostic purposes, comprising
a housing with an outlet opening for a tip of a lancet and a contact
surface around the outlet opening for contacting to the body part,
a lancet holder for holding the lancet and movable within the housing
along a predetermined puncturing path,
a lancet guide guiding the lancet holder along the predetermined
puncturing path,
a lancet drive with a drive rotor driven by a drive spring in a
sense of rotation, by which lancet drive a relaxation movement of
the drive spring is converted into a pricking movement during which
the lancet held by the lancet holder moves with high speed along
the predetermined puncturing path in a pricking direction, until
its tip protrudes from the outlet opening and a wound is generated
at the body part contacting the contact surface and by which lancet
drive the lancet holder is retracted to a position where the tip
of the lancet is within the housing,
wherein
the drive rotor has a pressure surface which is directed radially
outwardly and runs with varying center distance around the rotation
axis in such a manner that it has a vertex with maximum center distance,
and a propelling section following the vertex against the sense
of rotation, with a center distance decreasing against the sense
of rotation,
the drive spring is adapted for effecting in a propelling angle
section of the rotation of the drive rotor via a pressure element
a pressure with a component in radial direction to the rotation
axis onto the propelling section of the pressure surface, thus driving
the drive rotor by the pressure of the drive spring onto the pressure
surface in the propelling section in the sense of rotation, and
the drive rotor is coupled via an output-side coupling mechanism
with the lancet holder, in such a manner that the tip of the lancet
protrudes from the outlet opening at a point of time in which the
drive rotor is in the propelling angle section.
2. Blood lancet device according to claim 1 wherein the propelling
section has a convex shape in at least a partial section thereof.
3. Blood lancet device according to claim 1 wherein the pressure
surface comprises a tensioning section preceding the vertex against
the sense of rotation, and having an increasing center distance
against the sense of rotation.
4. Blood lancet device according to claim 3 wherein the tensioning
section has a convex shape in at least a partial section thereof.
5. Blood lancet device according to claim 3 wherein the pressure
surface has in its range adjacent the vertex a continuous convex
shape, so that the tensioning movement passes to the pricking movement
without a stop.
6. Blood lancet device according to claim 3 wherein the pressure
surface has a recess at the vertex, where the pressure element latches
in.
7. Blood lancet device according to claim 1 wherein the pressure
surface has at least two vertexes.
8. Blood lancet device according to claim 1 wherein the pressure
surface is a continuous surface completely surrounding the axis.
9. Blood lancet device according to claim 1 wherein the output-side
coupling mechanism includes a recess, rotatable together with the
drive rotor, and forming an operating cam, in mesh with a pivot
linked to the lancet holder, where at least a part of the pricking
and retraction movement is determined by a rotation movement of
the operating cam, where the pivot moves along the operating cam
formed by the recess, and where the maximum deflection of the lancet
holder in pricking direction is determined by a lower reverse point
in the operating cam.
10. Blood lancet device according to claim 9 wherein the recess
which forms the operating cam is formed in the drive rotor.
11. Blood lancet device according to claim 1 comprising a tensioning
lever which effects a torque in the sense of rotation onto a thrust
piece provided on the drive rotor, for the tensioning of the lancet
drive.
12. Blood lancet device according to claim 1 wherein the housing
has an end piece with the contact surface, having an elongated shape,
the main axis of which is parallel to the rotor plane, and which
is articulated to the housing on one of its shorter sides, with
a hinge.
13. Blood lancet device according to claim 12 wherein the end
piece is provided with an adjusting device at the shorter side opposite
to the hinge, for the adjustment of the distance from the housing
and thus for adjusting the pricking depth.
14. A blood lancet device comprising:
a lancet including a tip,
a housing including an outlet opening for the tip and a contact
surface around the outlet opening,
a lancet holder being movable in the housing along a path,
a lancet guide formed to guide the lancet holder along the path,
a pressure element,
a lancet drive including a rotor driven by a spring in a sense
of rotation, the rotor having a pressure surface extending about
a rotation axis and being formed to contact the pressure element,
the pressure surface running with varying center distance around
the rotation axis and having a vertex with a maximum center distance
from the rotation axis and a propelling section following the vertex
against the sense of rotation with a center distance decreasing
against the sense of rotation and the spring acting onto the pressure
element to effect a pressure against the propelling section of the
pressure surface with a component in a radial direction to the rotation
axis to drive rotation of the pressure surface about the rotation
axis, and
an output-side coupling mechanism coupling the rotor with the lancet
holder so that movement of the pressure element across the propelling
section is converted into movement of the lancet holder along the
path in a pricking direction.
15. A blood lancet device comprising:
a lancet including a tip,
a housing including an outlet opening for the tip and a contact
surface around the outlet opening,
a lancet holder being movable in the housing along a path,
a lancet guide formed to guide the lancet holder along the path,
a pressure element,
a lancet drive including a rotor driven by a spring in a sense
of rotation, the rotor having a pressure surface extending about
a rotation axis and being formed to contact the pressure element,
the pressure surface having a vertex with a maximum center distance
from the rotation axis and a propelling section following the vertex
against the sense of rotation and the spring acting onto the pressure
element to effect a pressure against the propelling section of the
pressure surface with a component in a radial direction to the rotation
axis to drive rotation of the pressure surface about the rotation
axis, the propelling section having a convex shape in at least a
partial section thereof, and
an output-side coupling mechanism coupling the rotor with the lancet
holder so that movement of the pressure element across the propelling
section is converted into movement of the lancet holder along the
path in a pricking direction.
16. A blood lancet device comprising:
a lancet including a tip,
a housing including an outlet opening for the tip and a contact
surface around the outlet opening,
a lancet holder being movable in the housing along a path,
a lancet guide formed to guide the lancet holder along the path,
a pressure element,
a lancet drive including a rotor driven by a spring in a sense
of rotation, the rotor having a pressure surface extending about
a rotation axis and being formed to contact the pressure element,
the pressure surface having a vertex with a maximum center distance
from the rotation axis and comprising a tensioning section preceding
the vertex against the sense of rotation, the tensioning section
having an increasing center distance against the sense of rotation
and a propelling section following the vertex against the sense
of rotation and the spring acting onto the pressure element to effect
a pressure against the propelling section of the pressure surface
with a component in a radial direction to the rotation axis to drive
rotation of the pressure surface about the rotation axis, and
an output-side coupling mechanism coupling the rotor with the lancet
holder so that movement of the pressure element across the propelling
section is converted into movement of the lancet holder along the
path in a pricking direction.
17. Blood lancet device according to claim 16 wherein the propelling
section has a decreasing center distance against the sense of rotation.
18. Blood lancet device according to claim 16 wherein the tensioning
section has a convex shape in at least a partial section thereof.
19. Blood lancet device according to claim 16 wherein the pressure
surface has in its range adjacent the vertex a continuous convex
shape.
20. Blood lancet device according to claim 16 wherein the pressure
surface has a recess at the vertex.
21. A blood lancet device comprising:
a lancet including a tip,
a housing including an outlet opening for the tip and a contact
surface around the outlet opening,
a lancet holder being movable in the housing along a path,
a lancet guide formed to guide the lancet holder along the path,
a pressure element,
a lancet drive including a rotor driven by a spring in a sense
of rotation, the rotor having a pressure surface extending about
a rotation axis and being formed to contact the pressure element,
the pressure surface having at least two vertexes with a maximum
center distance from the rotation axis and a propelling section
following the vertex against the sense of rotation and the spring
acting onto the pressure element to effect a pressure against the
propelling section of the pressure surface with a component in a
radial direction to the rotation axis to drive rotation of the pressure
surface about the rotation axis, and
an output-side coupling mechanism coupling the rotor with the lancet
holder so that movement of the pressure element across the propelling
section is converted into movement of the lancet holder along the
path in a pricking direction.
22. A blood lancet device comprising:
a lancet including a tip,
a housing including an outlet opening for the tip and a contact
surface around the outlet opening,
a lancet holder being movable in the housing along a path,
a lancet guide formed to guide the lancet holder along the path,
a pressure element,
a lancet drive including a rotor driven by a spring in a sense
of rotation, the rotor having a pressure surface extending about
a rotation axis and being formed to contact the pressure element,
the pressure surface being a continuous surface completely surrounding
the axis and having a vertex with a maximum center distance from
the rotation axis and a propelling section following the vertex
against the sense of rotation and the spring acting onto the pressure
element to effect a pressure against the propelling section of the
pressure surface with a component in a radial direction to the rotation
axis to drive rotation of the pressure surface about the rotation
axis, and
an output-side coupling mechanism coupling the rotor with the lancet
holder so that movement of the pressure element across the propelling
section is converted into movement of the lancet holder along the
path in a pricking direction.
23. A blood lancet device comprising:
a lancet including a tip,
a housing including an outlet opening for the tip and a contact
surface around the outlet opening,
a lancet holder being movable in the housing along a path and including
a pivot,
a lancet guide formed to guide the lancet holder along the path,
a pressure element,
a lancet drive including a rotor driven by a spring in a sense
of rotation, the rotor having a pressure surface extending about
a rotation axis and being formed to contact the pressure element,
the pressure surface having a vertex with a maximum center distance
from the rotation axis and a propelling section following the vertex
against the sense of rotation and the spring acting onto the pressure
element to effect a pressure against the propelling section of the
pressure surface with a component in a radial direction to the rotation
axis to drive rotation of the pressure surface about the rotation
axis, and
an output-side coupling mechanism coupling the rotor with the lancet
holder so that movement of the pressure element across the propelling
section is converted into movement of the lancet holder along the
path in a pricking direction and including an operating cam in mesh
with the pivot, so that at least a part of the pricking and retraction
movement is determined by a rotation movement of the operating cam.
24. Blood lancet device according to claim 23 wherein the operating
cam includes a lower reverse point and a maximum deflection of the
lancet holder in the pricking direction is determined by the lower
reverse point.
25. Blood lancet device according to claim 23 wherein the operating
cam is formed in the rotor.
26. A blood lancet device comprising:
a lancet including a tip,
a housing including an outlet opening for the tip and a contact
surface around the outlet opening,
a lancet holder being movable in the housing along a path,
a lancet guide formed to guide the lancet holder along the path,
a pressure element,
a lancet drive including a rotor driven by a spring in a sense
of rotation, the rotor including a thrust piece and having a pressure
surface extending about a rotation axis and being formed to contact
the pressure element, the pressure surface having a vertex with
a maximum center distance from the rotation axis and a propelling
section following the vertex against the sense of rotation and the
spring acting onto the pressure element to effect a pressure against
the propelling section of the pressure surface with a component
in a radial direction to the rotation axis to drive rotation of
the pressure surface about the rotation axis,
a tensioning lever formed to effect a torque in the sense of rotation
onto the thrust piece, and
an output-side coupling mechanism coupling the rotor with the lancet
holder so that movement of the pressure element across the propelling
section is converted into movement of the lancet holder along the
path in a pricking direction.
27. A blood lancet device comprising:
a lancet including a tip,
a housing including an outlet opening for the tip, a contact surface
around the outlet opening, a lower end and an end piece that is
articulated to the lower end of the housing with a hinge,
a lancet holder being movable in the housing along a path,
a lancet guide formed to guide the lancet holder along the path,
a pressure element,
a lancet drive including a rotor driven by a spring in a sense
of rotation, the rotor having a pressure surface extending about
a rotation axis and being formed to contact the pressure element,
the pressure surface having a vertex with a maximum center distance
from the rotation axis and a propelling section following the vertex
against the sense of rotation and the spring acting onto the pressure
element to effect a pressure against the propelling section of the
pressure surface with a component in a radial direction to the rotation
axis to drive rotation of the pressure surface about the rotation
axis, and
an output-side coupling mechanism coupling the rotor with the lancet
holder so that movement of the pressure element across the propelling
section is converted into movement of the lancet holder along the
path in a pricking direction.
28. Blood lancet device according to claim 27 wherein the end piece
is provided with an adjusting device that is formed to move the
distance of the end piece from the lower end of the housing.
Description BACKGROUND AND SUMMARY OF THE INVENTION
The invention applies to a blood lancet device for withdrawing
blood for diagnostic purposes. It comprises a housing with an outlet
opening for the lancet tip, a lancet holder for holding the lancet
and movable along a predetermined, straight puncturing path within
the housing, and a lancet guide, guiding the lancet holder along
the predetermined puncturing path.
In order to obtain a drop of blood, the blood lancet device must
be pressed with a contact surface located around the outlet opening,
against the skin (in particular against the finger tip or the earlobe).
Subsequently, a pricking process is performed. During the pricking
process, the lancet holder and the lancet held by it are moved along
the predetermined puncturing path with high speed, driven by a lancet
drive located in the blood lancet device, until the lancet tip comes
out of the outlet opening and generates the wound necessary for
obtaining the blood drop. After that, the lancet holder is driven
back, by the lancet drive, into a position with the lancet tip inside
the housing.
Lancet devices of this type are already known in many designs.
In most cases, the lancet drive is a simple mechanism driving the
lancet holder directly by a linear spring, being stopped by a thrust
block at the point of the longest protrusion of the lancet tip.
This stops the lancet abruptly; the spring action returns the lancet
into its initial position. Such a blood lancet device can be produced
simply. It is, however, not optimal with respect to its function,
in particular as the pain caused by the prick is relatively high.
However, reduction of the pain caused by wound generation is of
high medical importance. This is particularly true for diabetics,
who must control their glucose level frequently and regularly, in
order to adapt the necessary insulin injections to their requirements
(depending on factors as e.g. food ingestion, physical activity
and others), thus, if possible, always keeping the glucose level
within defined target limits. This is of highest importance for
the health of those patients, especially for the avoidance of serious
late injuries, as e.g. amaurosis. Comprehensive investigations have
shown that a tight glucose level control can dramatically reduce
serious late injuries caused by diabetes mellitus.
Blood lancet devices which convert the relaxation movement of the
drive spring by means of a rotatable drive rotor into the prick
movement allow blood withdrawal with little pain. The vibration
caused by the impact of the lancet holder onto a thrust block can
be avoided.
U.S. Pat. No. 4924879 describes a blood lancet device with a
rotor drive of that type, driving the rotor by a coaxial coil spring.
The rotation movement of the rotor is converted to the linear movement
of the lancet by means of a push rod system.
In the lancet device described in U.S. Pat. No. 5318584 the
drive rotor has a rotation axis parallel to the prick direction.
Here, it is also driven by a coaxial coil spring. The conversion
of the rotational movement into the necessary linear movement of
the lancet holder is performed by a rotary drive, preferably realized
by a cam control. In this mechanism, a pivot of the lancet holder
meshes with a corresponding recess in the rotor. This design allows
a very good pricking behavior with low vibrations and a precisely
reproducible pricking depth. This makes the pain, occurring with
the wound generation, very small. However, a disadvantage of this
system is the necessity of components with relatively complex shape
which have to interact in a very precise way. Thus, their production
is expensive. A precise manufacturing is the condition for a reliable
function.
Based on this, the invention addresses the problem to provide a
blood lancet device which achieves a pricking behavior which is
low in vibrations and precise, and which can be produced with less
manufacturing expense, thus reducing production costs.
With a blood lancet device of the type described above, with a
rotor driven lancet holder, this task is obtained in the following
way: The drive rotor has a pressure surface which is directed radially
outwardly and runs with varying center distance around the rotation
axis in such a manner that it has a vertex with maximum center distance,
and a propelling section following the vertex against the sense
of rotation, with a center distance decreasing against the sense
of rotation. The drive spring is adapted for effecting in a propelling
angle section of the rotation of the drive rotor via a pressure
element a pressure with a component in radial direction to the rotation
axis onto the propelling section of the pressure surface, thus driving
the drive rotor by the pressure of the drive spring onto the pressure
surface in the propelling section in the sense of rotation. The
drive rotor is coupled via an output-side coupling mechanism with
the lancet holder, in such a manner that the tip of the lancet protrudes
from the outlet opening at a point of time in which the drive rotor
is in the propelling angle section.
The drive rotor having a pressure surface which is directed in
radially outward direction (away from the rotation axis) can be
easily produced as a plastic part. The power transmission from the
drive spring to the rotation movement of the drive rotor (subsequently
called "drive-side coupling mechanism of the lancet drive")
is determined by the form of the drive section of the pressure surface.
Thus, different required drive rotor movement characteristics (rotation
speed depending on rotation angle) can be adjusted by different
designs of the pressure surface. A form with a propelling section
which is, at least in parts of the propelling section, convex, has
proven advantageous.
For tensioning, the drive rotor must be moved into a position where
the pressure element is in contact with the pressure surface at
the vertex. This can be obtained with different tensioning mechanisms.
Preferably, not only the prick movement drive, but also the tensioning
of the lancet drive is realized by an interaction of the spring
and the pressure surface. To this end the pressure surface has a
tensioning section with a center distance from the rotor center
which increases against the sense of rotation. The tensioning section,
too, has a convex shape, at least in a partial section thereof.
According to another preferred design, the output-side coupling
mechanism, which converts the rotation movement of the drive rotor
to the pricking and retraction movement of the lancet holder, is
formed by a recess rotatable with the drive rotor, forming an operating
cam and meshing with a pivot connected to the lancet holder. This
design allows a variation of the output-side coupling mechanism,
according to the desired pricking behavior, a corresponding variation
of the form of the operating cam. This results in comprehensive
possibilities for optimization of the speed profile of the pricking
movement (dependence of current speed from lancet holder position)
with respect to a pain which is as low as possible. A particularly
simple design is obtained if the recess forming the operating cam
is located in the drive rotor.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will subsequently be further explained with the design
examples represented in the figures. The details described therein
can be applied individually or in combination with each other in
order to obtain preferred embodiments of this invention.
FIG. 1 shows a longitudinal section through a blood lancet device
according to the invention in a position in which a lancet is inserted
into the lancet holder;
FIG. 2 shows a longitudinal section through the device according
to FIG. 1 in the rest position of the lancet drive;
FIG. 3 shows a longitudinal section through the device according
to FIG. 1 in the tensioned position of the lancet drive;
FIG. 4 shows a longitudinal section through an alternative design
of a blood lancet device in rest position;
FIG. 5 shows a longitudinal section through the device according
to FIG. 4 in the tensioned position of the lancet drive;
FIG. 6 shows a lateral view of the drive rotor of the device according
to FIG. 4 and
FIG. 7 shows a lateral view of the tensioning lever of the device
according to FIG. 4.
DETAILED DESCRIPTION OF THE INVENTION
In the housing 1 of the blood lancet device 2 represented in FIGS.
1 to 3 a lancet holder 3 is driven by a lancet drive, in its entirety
designated with 5 in a way that a lancet 6 fixed in the lancet
holder 3 performs a pricking movement during which the tip 7 protrudes
out of an outlet opening 8 of the housing 1 in order to generate
a wound at a body part 9 which is in contact with the outlet opening
8 (FIG. 3). The surface surrounding the outlet opening, designed
for contacting the body part 9 is designated as the contact surface
10. In the case represented, the pricking and retraction movement
of the lancet holder 3 is precisely guided by a lancet guide 13
formed by plastic bridges 12 on a linear and straight puncturing
path, such that practically no vibrations with movement components
vertical to the pricking direction, which is symbolized in FIG.
1 by arrow 14 can arise.
The lancet drive 5 consists essentially of a drive rotor 16 rotating
on an axis 15 and a drive spring 17 designed in the represented
case as a coil spring with two legs 20 21 and coiled around a fixing
post 19.
The drive rotor 16 presents a radially outwardly directed pressure
surface 23 which runs around the rotation axis 15 in varying distance
therefrom. The first leg 20 of the drive spring 17 effects a force,
via a pressure element 24 with a component in radial direction
towards the rotation axis 15 onto the pressure surface 23. This
pressure transmission should be as low friction as possible. Therefore,
the pressure element 24 is designed as a wheel 25 fixed at the
end of the first leg 20 running on the pressure surface 23. The
second leg 21 is fixed outside the rotation range 26 of the drive
rotor 16.
The drive rotor 16 is triple-symmetric with axis 15 as center of
symmetry, so that its shape elements are repeated every 120.degree..
In the drawing plane of FIGS. 1 to 3 which corresponds to the
rotation plane of drive rotor 16 the pressure surface 23 is approximately
triangular. The (slightly rounded) corners form vertexes 27 delimiting
the maximum distance of pressure surface 23 from the rotation axis
15. The vertexes are followed, against the sense of rotation (marked
by arrow 28) of the drive rotor 16 by a section with decreasing
center distance, called propelling section 30. In front of the vertexes
27 (referring to the sense of rotation 28) there are respective
sections of the pressure surface 23 the center distance of which
decreases in sense of rotation (thus increasing against the sense
of rotation), and which are called tensioning sections 31. As a
whole, the pressure surface 23 has a slight convex curvature in
the rotation plane between the vertexes 27.
In order to tension the lancet drive 5 the lancet rotor 16 must
be rotated, in the sense of rotation 28 from the rest position
shown in FIG. 2 to the tensioned position shown in FIG. 3. This
can be effected, e.g., by an electric rotor drive. However, a mechanic
tensioning device is preferred. In the represented case, the tensioning
device has a tensioning lever 33 which effects a torque, in sense
of rotation 28 onto a thrust piece 34 (in the represented case
formed by a cylindrical pin) mounted on the drive rotor and protruding
from the front surface of the rotor 16. The tensioning lever 33
consists on an actuator key 35 protruding in rest position (FIG.
2) laterally from the housing 1 and a swiveling arm 36 located
inside the housing 1. Between the actuator key 35 and the swiveling
arm 36 there is a pivot bearing 37 the axis of which is parallel
to the rotation axis 15 of the drive rotor 16. For tensioning the
lancet drive 5 the actuator key 35 must be pressed into the housing
in direction of arrow 39. This makes the swiveling arm swivel upwards,
and a hook 40 located at the end of the swiveling arm 36 catches
one of the thrust pieces 34 thus rotating the rotor 16 in sense
of rotation 28. Thereby pressure element 24 moves along a tensioning
section 31 of the pressure surface 23. The distance of the pressure
element 24 from the rotation axis 15 increases, whereas the drive
spring 17 is increasingly tensioned, until its first leg 20 reaches
a position (represented in dotted line in FIG. 2) with maximum distance
from rotation axis 15. Once the lancet drive 5 is completely tensioned,
the drive rotor 16 is located in the position represented in FIG.
3 where the pressure element 24 is pressing against a vertex 27
of pressure surface 23.
As soon as the lancet rotor 16 is further rotated in sense of rotation
28 the pressure element 24 enters into the propelling section 30
of the pressure surface 23. With this, an angle section of the movement
of the drive rotor begins, in which the pressure of drive spring
17 (generally directed towards rotation axis 15 at least having
a component in that direction) is converted to a torque driving
the drive rotor 16 in sense of rotation 28. This angle section,
where the pressure element 24 is in contact with the propelling
section 30 is called propelling angle section.
Drive spring 17 with pressure element 24 and pressure surface 23
form a drive-side coupling mechanism, which generates a rotation
movement of the drive rotor 16 which takes place with high speed
and automatically in the propelling angle section (in this movement
phase it is neither possible nor necessary for the user to intervene).
In order to convert this rotation movement into the necessary linear
movement of the lancet holder with lancet 6 an output coupling
mechanism is necessary, which can be realized in different ways.
E.g. a push rod mechanism, as shown in U.S. Pat. No. 4924879
is appropriate.
However, the design shown in the figures is preferred. It features
an operating cam 42 formed by a recess 41 preferably integrated
into the drive rotor 16 rotating commonly with the drive rotor
16. A pivot 43 connected to the lancet holder 3 meshes with the
operating cam in a way that at least a part of the pricking and
retraction movement is controlled by the rotation of the operating
cam 42 in relation to the pivot. To this end, the pivot moves along
the operating cam 42. The maximum deflection of the lancet holder
3 in pricking direction is determined by a lower reverse point 44
of the operating cam 42 located in such a position that the pivot
43 moves through the lower reverse point within the propelling angle
section of the rotor movement. The pivot is preferably fixed directly
to the lancet holder 3 (at the end opposite to the lancet tip 7).
In order to facilitate the insertion of a lancet 6 into the lancet
holder 3 there is an end piece 46 provided at the lower end of
the housing 1 having an oblong form with a main axis parallel to
the rotor level (i.e. in the drawing plane of FIGS. 1 to 3). It
is fixed to the housing and can be swiveled to one side about one
of its short sides 46a (by means of a hinge 47 with swiveling axis
parallel to the rotor axis). For lancet insertion, the lower end
of the housing (1) must be opened by swiveling the end piece 46
(FIG. 1) aside, so that the lancet holder becomes accessible. The
lancet is taken by its protection cap 48 covering its tip 7 and
pushed into the lancet holder 3. Further details about appropriate
lancet holders can be taken from the U.S. Pat. No. 5318584 and
the publications cited therein.
The end piece 46 is coupled to a swiveling arm 49 which collides
with a bracket 55 when the lower end piece 46 is opened. Bracket
55 and lancet holder 3 interact in a way that an inserted lancet
will be automatically thrown out of lancet holder 3 due to the
collision with swiveling arm 49 when the end piece 46 is opened.
An adjusting device 50 for adjusting the pricking depth is located
at the short side of the end piece 46 opposite from the hinge 47.
It allows the adjustment of the distance (in pricking direction)
between end piece 46 and the housing 1. The longer that distance
is, the smaller becomes with unchanged movement path of the lancet
holder 3 the pricking depth. A knurled screw 51 is provided for
adjusting the adjusting device 50. It is accessible from the outside
through a recess in the housing wall (not represented).
The design represented in FIGS. 4 and 5 has a housing more sleek
and compact than the lancet device represented in FIGS. 1 to 3.
It corresponds, however, to the latter with respect to most technical
characteristics. Components with the same function are identified
by the same numerals.
A special characteristic of this design is the double-symmetric
form of the drive rotor 16. Its pressure surface 23 thus, has two
vertexes 27 with correspondingly adjacent propelling and tensioning
sections 30 and 31. This allows a smaller design. The rotor 16 can
be kept particularly small, if the position of the pressure element
24 is shifted laterally from the longitudinal axis of lancet holder
3. By this, the operating cam can be oriented in a way that its
lower reverse points, with respect to the rotation axis 15 are
oriented approximately in the same direction as the vertexes 27
of the pressure surface 23. At the same time, the condition that
the pivot 43 moves along the lower reverse point 44 within the propelling
angle section of the drive rotor movement, is complied with.
A further special characteristic of the design represented in FIGS.
4 and 5 becomes apparent from the separate representation of the
components in FIGS. 6 and 7. In FIGS. 1 to 3 the pressure surface
23 has a continuous convex bow in the vicinity of the vertexes 27
so that the tensioning movement passes, without stop, to the propelling
movement of the drive rotor 16 once the tensioning lever 33 is
operated. The drive rotor represented in FIG. 6 however, has a
small recess 52 at the vertexes 27 the shape of which makes the
pressure element 24 latch into it. In order to trigger the transition
towards the propelling angle section of rotor movement 16 and thus
the pricking movement, an additional triggering mechanism is provided.
In the represented case, it is realized by two additional thrust
pieces 53 of the drive rotor 16 and a special shape of the swiveling
arm 36 of the tensioning lever 33. These elements are matched in
a way that the meshing of the swiveling arm 36 and the thrust piece
34 is interrupted in the moment when the pressure element 24 latches
into recess 52. By a short release and new actuation of key 35
the swiveling arm 36 meshes again with one of the additional thrust
pieces 53. This triggers the pricking movement.
Numerous further designs of this invention are possible. The drive
rotor is preferably N-symmetric (N=234). Generally, a non-symmetrical
design is possible, too. In particular, a drive rotor with only
one vertex and a cam-shaped form of the pressure surface 23 can
be applied. The pressure surface is preferably a continuous surface
completely surrounding the axis. However, it may be interrupted
if other constructive measures assure that the drive rotor reaches
a state where the pressure element 24 approaches a vertex 27 followed
by a propelling section with the described characteristics. Generally,
the pressure surface 23 is a surface generated by the movement of
a straight line in space (ruled surface), with the generating line
proceeding parallel to the axis of the drive rotor. However, a certain
inclination or bending of the pressure surface 23 is possible, too,
if the functions described herein are not impaired thereby.
This invention combines the advantages of a simple and robust mechanical
system with a highly precise lancet guide. It can be realized with
few components and allows simple assembly. Most parts are made of
plastic and can be cheaply produced in large quantities, in particular
in die-cast technology. The drive spring consists of spring steel
and has a simple geometry, allowing a cheap production, too.
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