Blood lancet system for blood withdrawal for diagnostic purposes
with a housing, a lancet holder movable in the housing for holding
an exchangeable lancet, and a lancet drive for driving the pricking
movement of the lancet holder with the lancet contained herein.
The housing has a cap at the front end in pricking direction which
can be removed in order to remove a used lancet from the lancet
holder. The lancet and the housing cap are coupled, during the attachment
of the housing cap, by a coupling mechanism comprising coupling
elements matched to each other and enabling the extraction of the
lancet from the lancet holder simultaneously with removing the housing
1. Blood lancet system for blood withdrawal for diagnostic purposes,
comprising lancets and a pricking apparatus with a housing, a lancet
holder movable in the housing for holding an exchangeable lancet,
and a lancet drive for driving a pricking movement of the lancet
on a predetermined pricking path, wherein the housing comprises
a cap to be attached at a forward end thereof in pricking direction,
the cap being removable for removing a used lancet out of the housing,
and the lancet and the cap are adapted to be coupled, during attaching
the cap to the housing, by a coupling mechanism comprising matching
coupling elements, thereby enabling the extraction of the lancet
from the lancet holder simultaneously with removing the cap.
2. Blood lancet system according to claim 1 comprising an ejector
which is movable in the housing in the pricking direction for ejecting
the lancet from the lancet holder, is a component of the coupling
mechanism, and has at a first end thereof a first of the matching
coupling elements and at a second end thereof a lancet contact element
contacting the lancet during the ejection thereof.
3. Blood lancet system according to claim 2 wherein a second of
the matching coupling elements is arranged at the cap.
4. Blood lancet system according to claim 2 or 3 wherein the ejector
has an intermediate part guided by a guide element such that it
is movable parallel to the pricking path, the front end of the intermediate
part being connected to the coupling element and the rear end of
the intermediate part being connected to the lancet contact element.
5. Blood lancet system according to claim 4 wherein the movable
intermediate part comprises a sleeve surrounding a lancet which
is inserted in the holder.
6. Blood lancet system according to claim 1 wherein at least one
of the coupling elements has a protrusion, which is elastically
biased in a direction transversal to the pricking direction and
which latches during the coupling of the lancet and the cap into
a corresponding recess of the other coupling element.
7. Blood lancet system according to claim 1 wherein the lancet
comprises a lancet body made of plastic, a lancet needle fixed in
the lancet body, and a tip cover element covering the lancet tip,
the tip cover element being connected to the lancet body via a breaking
point such that it can be removed after the insertion of the lancet
into the lancet holder in order to expose the lancet tip protruding
from the lancet body.
8. Blood lancet system according to claim 1 wherein the cap has
a contact surface for contacting the blood lancet apparatus to the
skin, the cap can be fixed to the housing at a defined position
in the pricking direction, and the longitudinal position of the
cap in the pricking direction can be adjusted by an adjustement
device in order to adjust the pricking depth.
 This invention is concerned with a blood lancet system for
blood withdrawal for diagnostic purposes.
 In case of various illnesses it is necessary to investigate
the human blood with respect to a component (analyte) contained
therein. To this end it is oftentimes sufficient to withdraw a small
amount of blood from the body by generating a small prick wound.
A particularly important such case is diabetes mellitus, which requires
the blood to be investigated in regular intervals for its glucose
 For generating the necessary prick wound, commonly blood
lancet systems are used which comprise a pricking apparatus and
replaceable lancets, adapted to this apparatus. The housing of the
pricking apparatus contains a lancet adapted for holding the lancet
in a replacable manner. During the pricking process, the lancet
is driven by a lancet drive, also integrated in the lancet apparatus,
in a way that the lancet is moved quickly in the pricking direction,
until the lancet tip protrudes from an opening at the front end
of the pricking apparatus, thus generating a small prick wound in
the body part pressed against the front end. Thereafter the lancet
is moved back (against the pricking direction).
 When common pricking apparatuses are in their use state,
the lancet holder is covered by a housing cap which forms the front
end of the pricking apparatus housing and has a small opening through
which the lancet tip can protrude during the pricking process. The
pricking opening is surrounded by a contact surface which serves
for contacting the blood lancet apparatus to the body part from
which the blood shall be withdrawn during use of the blood lancet
apparatus (usually the finger tip or the ear lobe).
 For avoiding infections, the lancets are disposable elements
designed for a single use. In order to insert a new lancet, the
housing cap covering the lancet holder is removed, and the lancet
is inserted into the lancet holder. The housing cap is also removed
for removing used lancets.
 Blood lancet systems are not only used by medical staff,
but also, and to a large extent, by non-experts. This is particularly
true for the therapy control of diabetics. It was determined that
serious damages occurring in conjunction with diabetes (e.g. blindness)
can be dramatically reduced if the glucose concentration of the
diabetic's blood is measured very often (four to five times a day),
adjusting the insulin injections very exactly, using these measurements.
The willingness and the ability of diabetics to check their blood
that often in the scope of home-monitoring highly depends on the
optimal function of the blood lancet system used.
 An important part of this function are the handling steps
necessary for the insertion of new and the removal of used lancets.
On one hand, they should be as simple as possible, and on the other
hand there should be maximum safety against injury and infection
risks. At the same time, the cost, in particular with respect to
the disposable material, should be as low as possible.
 During the insertion of the lancet, the sharp tip of the
lancet needle is usually covered by a tip cover element made of
plastic and allowing a secure handling of the lancet. Once the lancet
is inserted, the tip cover element must be removed and the housing
cap must be attached. After the pricking process, the housing cap
must be removed, so that the lancet becomes accessible again. Then,
the lancet can be manually removed. The risk of injury at the lancet
tip, however, is very high, in particular taking into account that
a large share of the users is handicapped by high age, bad vision
or trembling hands.
 In order to simplify the removal of the used lancet, many
apparatuses are equipped with a manually operated ejection mechanism.
For example, U.S. Pat. No. 5318584 describes a blood lancet system
in which the blood lancet can be ejected from the lancet holder
by means of an ejection rod; the ejection rod is actuated by pressing
an actuation button provided at the rear end of the pricking apparatus.
U.S. Pat. No. 4442836 describes an apparatus having an ejection
mechanism designed in a way that the used lancet is automatically
thrown out when re-tensioning the apparatus after each pricking
process. However, such ejection mechanisms require a relatively
complicated and expensive construction. The handling is not as easy
as desirable, taking into account the health state of many users.
 EP 0 958 783 A1 describes a blood lancet apparatus which
is equipped with so-called engagement means at the cap, which can
be moved by the user from a first position, not in engagement with
the lancets, into a second position, where they contact the lancet
pressing it against the opposite interior wall of the cap. For actuation
of the engagement means, a button may be provided which protrudes
laterally from the cap. After the pricking process the user must
first press this button, thus clamping the lancet in the cap, then
take off the lancet together with the cap, and finally dispose the
lancet. This requires an additional, difficult handling step, causing
a severe problem for many users.
 With the aim to achieve optimal simplicity and operational
safety some known blood lancet systems have the lancet integrated
into the cap, so that the lancet and the housing cap together form
a replaceable, disposable unit. Such designs are described in EP-0595148
A1 and in U.S. Pat. Nos. 4990154 and 5628765. A disadvantage
of this design is the high material consumption, because the entire
disposable design unit, including the housing cap, has to be disposed
after each use. Due to the high cost these systems are only appropriate
for application areas with high safety and hygienic requirements,
in particular for the use in hospitals. In the home-monitoring area,
on one hand safety risks are lower since the blood lancet systems
are always used by the same patient, on the other hand the cost
for the integrated lancet-cap-disposables is not acceptable.
 On this basis, the invention addresses the problem to provide
a blood lancet system, in particular for home-monitoring, which
allows a riskless and simple removal of used lancets from the lancet
holder without a need to touch the lancet and with as little expense
 This problem is solved by a blood lancet system for blood
withdrawal for diagnostic purposes, comprising lancets and a pricking
apparatus with a housing, a lancet holder movable in the housing
for holding an exchangeable lancet, and a lancet drive for driving
a pricking movement of the lancet on a predetermined pricking path,
wherein the housing comprises a cap to be attached at a forward
end thereof in pricking direction, the cap being removable for removing
a used lancet out of the housing, and the lancet and the cap are
coupled to each other, while the cap is attached to the housing,
by a coupling mechanism comprising coupling elements matched to
each other, thereby enabling the extraction of the lancet from the
lancet holder simultaneously with removing the cap.
 In contrast to the mentioned lancet-cap-disposables, the
lancet used with the instant invention is a separate element, produced
and distributed independently from the housing cap. It is the only
disposable part. The cap can be used permanently, thus it can be
produced with higher quality. The use is very simple as the pulling-off
of the housing cap and the removal of the used lancet is performed
in a single handling step.
 In contrast to the design described in EP 0958783 the invention
does not require any additional handling steps, as the coupling
of the cap with the lancet is performed automatically during the
procedure of the handling steps which are anyway necessary and common.
 In the most simple case, the coupling mechanism acts directly
between the housing cap and the lancet. Generally, lancets have
a lancet body made of plastic, surrounding the metal lancet needle.
The first of the matched coupling elements can be provided at this
lancet body. The second coupling element is provided, preferably,
directly at the cap (at its inner wall). For example, the lancet
body may have a groove-type recess running in the direction of its
longitudinal axis, in which a catch may latch in, which latch protrudes
from an elastic tongue fixed at the inside wall of the cap. When
the cap is attached, the protruding catch latches into the groove.
The dimensions of the groove are designed in such a way that the
lancet movement in pricking direction, required for the pricking
process, is possible.
 An embodiment in which the coupling mechanism includes an
additional part designated as ejector, is preferred. The ejector
is arranged in the housing in a way that it is movable in the pricking
direction. It is provided with a lancet contact element which contacts
the lancet during the ejection process, thus pressing or pulling
it out of the holder. For this design type, a first of the matched
coupling elements is arranged at the ejector, and, preferably, a
second of the matched coupling elements is arranged at the cap.
 The invention is explained in more detail with reference
to an embodiment represented in the figures. The features described
there can be applied single or in combination in order to create
preferred embodiments of the invention.
 FIG. 1 shows a perspective exploded view of the front part
of a blood lancet apparatus according to the invention,
 FIG. 2 shows a longitudinal section through the blood lancet
apparatus in the state of utilization (lancet inserted, ejector
 FIG. 3 shows a longitudinal section according to FIG. 2
during the removal of the cap (lancet free, ejector pulled out)
 FIG. 4 shows a perspective view of the lancet holder, the
lancet and the ejector in the position according to FIG. 2
 FIG. 5 shows a perspective representation according to FIG.
4 without the lancet holder,
 FIG. 6 shows a longitudinal section according to FIG. 2
in reduced scale in a handling stage just after inserting a new
 FIG. 7 shows a longitudinal section according to FIG. 6
in a handling stage in which the housing cap is attached,
 FIG. 8 shows a longitudinal section according to FIG. 6
in a handling stage in which the housing cap is removed,
 FIG. 9 shows a longitudinal section according to FIG. 8
in a slightly later handling stage during removing of the housing
 The blood lancet system 1 represented in FIGS. 1 to 5 consists
of a pricking apparatus 2 and exchangeable lancets 3 adapted to
be used together with the pricking apparatus 2. The lancets 3 have
a lancet body 4 made of plastic and a needle 5 fixed in the lancet
body 4; the sharp tip 6 of the lancet needle 5 protrudes from the
lancet body in the pricking direction symbolized by the arrow 7.
For the unused lancet 3 represented in FIG. 1 the tip 6 is covered
by a tip cover element 8 which is connected to the lancet body
4 via a breaking point 9 in a way that it can easily be removed
by turning and pulling, thus exposing the tip 6.
 In the embodiment shown, the housing 10 of the pricking
apparatus 2 is designed with an elongated shape, similar to a pencil
(so-called pencil-design). The longitudinal axis 11 of the pricking
apparatus 2 runs in the pricking direction 7.
 A lancet holder 12 is located in the housing 10. The lancet
3 is fixed in the lancet holder 12 by means of an appropriate clamping
device in an exactly reproducible longitudinal position. In the
represented case, the lancet holder 12 has two holder tongues 12a,
pretensioned radially towards the interior of the holder and engaging
with corresponding recesses 4a of the lancet body 4. Further characteristics
of this fixing design can be taken from U.S. Pat. No. 5318584.
The lancet holder is guided and arranged in a way that it can be
moved forward, with as few vibrations as possible, in pricking direction
7 inside the housing 10 until the lancet tip 6 protrudes from an
opening 13 thereby generating a prick wound in a body part 25 (FIG.
2) touching a contact surface 14 which is ring-shaped and surrounds
the opening 13.
 The pricking movement of the lancet holder 12 and a lancet
3 held thereby is driven by a lancet drive, designated as a whole
as 15. The lancet drive is preferably designed according to the
principles described in U.S. Pat. No. 5318584. This includes use
of a cam control. A control pivot 16 (FIG. 4) is arranged at the
lancet holder; it meshes, acting as operating cam, into a recess
of a drive rotor 17 (only partially visible in FIGS. 2 and 3). The
drive rotor 12 performs a turn around the longitudinal axis 11 of
the housing 10. The rotation of the drive rotor 17 with the operating
cam located therein, leads to a corresponding longitudinal movement
of the control pivot 16 and thus of the lancet holder 12 in pricking
direction 7. Further characteristics of this preferred lancet drive
15 can be taken from the US patent mentioned before.
 The front end, in pricking direction, of the housing 10
is formed by a cap 20 covering the insertion end designed for inserting
the lancet 3 into the lancet holder 12. The cap 20 is removeably
fixed at the housing 10. To this end different fastening principles
can be used, as long as a precise and reproducible definition of
the longitudinal position of the housing cap 20 with respect to
the lancet holder 12 is provided. For the design shown, a latch
fastening is used, in which a bulge 22 provided at the cap 20 latches
into a corresponding recess 23 of a housing part 24. Instead of
such a latch fastening, a thread fastening can also be used.
 In the embodiment shown, the housing part 24 to which the
cap 20 is fastened, is adjustable in its longitudinal position in
relation to the rest of the housing 10 and thus in relation to the
lancet holder 12 by means of a thread 26. This allows an adjustment
of the pricking depth. The more the housing part 24 and thus the
cap 20 where the contact surface 14 is located, are shifted forwardly,
in pricking direction 7 the smaller becomes the pricking depth,
for a given lowest position of the lancet holder 12 in pricking
 A coupling mechanism 28 by which the lancet 3 and the housing
cap 20 are coupled automatically to each other while the housing
cap is attached the housing 10 includes an ejector 30 moveably
arranged in pricking direction 7. It can best be seen in its entirety
in FIG. 5. Generally, the ejector 30 may be formed by any constructive
part comprising in its forwardly located section, with respect to
the pricking direction, a coupling element 34 for coupling to the
housing cap 20 and in its rearwardly located section a lancet contact
element 31 which may contact the lancet 3 in such a way that movement
of the lancet contact element 31 in pricking direction 7 causes
ejection of the lancet 3 from the lancet holder 12. The part of
the ejector 30 between the lancet contact element 31 and the coupling
element 34 is designated intermediate part 33.
 In the embodiment shown, the lancet contact element 31 is
formed by two ejector rods 32 pushing against the rear end of the
lancet 3. A coupling element 34 of the ejector 30 and a corresponding
coupling element 35 of the housing cap 2 are adapted to each other
such that the cap 20 is coupled to the ejector 30 and thus indirectly
to the lancet 3 during attachment of the housing cap 20 to the
housing 10. In the represented case, the ejector-side coupling element
34 is embodied by three segments of a radial collar 37 protruding
radially outwardly from a sleeve 38 surrounding the lancet holder.
The sleeve 38 has recesses in the area of the collar 37 separating
the segments of the radial collar 37 from each other and allowing
an elastic deformation, radially to the inside, of the sleeve 38
in the area of the radial collar 37.
 In the embodiments shown, the coupling element 35 provided
at the housing cap 20 is formed by a ring-shaped protrusion 41 located
at the inside wall 40 of the housing, arranged and adapted in such
a manner that during the attachment of the cap 20 the sleeve 38
is slightly compressed in the area of the radial collar 37 and
the radial collar 37 latches, after passing the narrow formed by
the ring-shaped protrusion 41 into a recess 43 which is located
before the ring-shaped protrusion 41 in pricking direction 7.
 Numerous variations of the coupling mechanism 28 are possible,
provided that, on one hand, the coupling between the housing cap
20 and the lancet 3 (preferably indirectly via an ejector 30) is
effected during attaching of the housing cap 20 onto the housing
10 (after previously having inserted the lancet 3 as a separate
part into the lancet holder 12), and, on the other hand, the lancet
3 is during the removal of the cap 20 simultaneously pulled out
of the lancet holder 12. The represented coupling principle, in
which at least one of the coupling elements 3435 is biased elastically
in such a manner that it latches into a corresponding recess (here,
the recess 43) of the other coupling element 35 is preferred, because
it allows a particularly simple handling. However, an appropriate
coupling can also be obtained, e.g., by a bayonet joint.
 Furthermore, the contact between a lancet contact element
31 provided at the ejector 30 and the lancet, which is necessary
for the removal of the lancet 3 from the lancet holder 12 must
not necessarily be embodied by a push-out device, which pushes against
the lancet from its rear end, as the ejector rod 32 does. A design
which pulls the lancet 3 out of the lancet holder 12 is also possible
in which case a lancet contact element provided at a correspondingly
shaped ejector may latch into a corresponding recess of the lancet
body, conveniently from the side.
 The embodiment shown, in which the intermediate part 33
of the ejector 30 which joins the ejector-side coupling element
34 with the lancet contact element 31 is at least partially sleeve-shaped,
is particularly preferred, as the sleeve 38 allows a precise guiding
of the lancet holder 12 contained therein. Other designs are also
possible. For example, the ejector can be formed by two or more
rods arranged preferably rotation-symmetrically in pricking direction.
At the front section of these rods, coupling elements for coupling
to the cap 20 may be provided, and at their rear section, a lancet
contact element 31 may be present.
 FIGS. 6 to 9 show, complementary to the FIGS. 2 and 3 some
more handling stages of the blood lancet system 1 according to the
 The lancet is gripped at the tip cover element 9 and inserted
into the holder 12 (FIG. 6) with the housing cap 20 removed. Thereafter,
the tip cover element 9 is turned off and the housing cap 20 is
attached, its protrusion 41 pressing against the radial collar 37
of the sleeve 38 thus pushing the ejector 30 backwards, until its
axial backward movement is stopped by a thrust block (FIG. 7).
 If the housing cap (20) is further pushed backwards (into
the position represented in FIG. 2), the ring-shaped protrusion
41 comes into an axial position behind the radial collar 37 so
that the coupling elements 3435 latch into each other.
 After the pricking process, which is not different from
previously known blood lancet systems, the housing cap 20 is removed
again. During removal it reaches the position represented in FIG.
8 where the ring-shaped protrusion 41 is in contact with the radial
collar 37. Thus, if the housing cap 20 is moved further in forward
direction (in pricking direction 7), the ejector 30 is moved forward,
pushing by means of its lancet contact element 31 (ejector rod 32)
the lancet 3 out of the holder in forward direction. The lancet
then falls into the housing cap 20 or remains unattached in the
lower section of the housing 10. After taking off the housing cap
20 the used lancet 3 can be disposed into a waste bin without having
to touch it.