Abstrict Blood lancet device for withdrawing blood for diagnostic purposes,
in which with the aid of a lancet drive (3) in a housing (1) a lancet
holder (6) with a lancet (34) positioned in it and moveable along
a predetermined, straight puncture path is moved until the tip (35)
of the lancet emerges from the outlet (84), in order to produce
a wound in a body part adjoining the outlet (84). The lancet holder
(6) also serves to retract the lancet (34) into a position in which
the tip (35) is again positioned within the housing (1). In order
to make possible a puncture involving especially little pain, the
lancet drive (3) has a rotary/sliding transmission system (4) whose
input side (16) is formed by a transmission member which is rotatable
about an axis of rotation parallel to the predetermined puncture
path. This input-side transmission member (5) of the rotary/sliding
transmission system is coupled with the elastic drive element (9)
of the lancet drive (3) and converts a torque transmitted to the
transmission member (5) into a longitudinal displacement in the
direction of the predetermined puncture path, which is transmitted
to the lancet holder (6).
Claims What is claimed is:
1. Blood lancet device for withdrawing blood for diagnostic purposes,
comprising
a lancet (34) comprising a metal needle (166176) with a tip (35),
a housing (1) with an outlet (84) for the tip (35) of the lancet
(34).
a lancet holder (6) located within the housing and connectable
to the lancet (34) for holding the lancet (34),
a lancet guide means (15b) located within the housing for guiding
the lancet holder (6) for movement on a predetermined puncture path,
and
a lancet drive means (3) located within the housing for moving
the lancet (34) in a puncturing and retraction direction comprising
an elastic drive element (9), a locking device (83) for locking
said lancet drive in a first position in which the elastic drive
element (9) is in a tensioned state and for releasing the tension
of the elastic drive element (9) to accomplish a puncturing movement
during which the lancet holder (6) is moved at high speed along
the predetermined puncture path in a puncturing direction until
the tip (35) emerges from the outlet (84) to produce a wound in
a body part adjoining the outlet (84) and following which the lancet
holder (6) is retracted to a position in which the tip of the lancet
(34) is positioned within the housing,
the lancet drive (3) further comprising a rotary/sliding transmission
system (4) with an input-side transmission member (5) rotatable
about an axis of rotation (A) parallel to the predetermined puncture
path and coupled to the elastic drive element (9) to be rotated
thereby, and with an output-side transmission member connected to
the rotatable input-side transmission member (5) for longitudinal
displacing the lancet holder (6) in response to rotation of said
input-side transmission member (5).
2. Blood lancet device according to claim 1 in which the rotary/sliding
transmission system (4) comprising a cam drive mechanism with a
recess (39) forming a driver cam (40), a driver pin (52) enagaging
said recess such that at least a part of the puncturing and retraction
movement is determined by a relative movement between the driver
pin (52) and the recess (39), the drive pin (52) travelling along
the recess (39).
3. Blood lancet device according to claim 1 in which the input-side
transmission member (5) is in the form of a cylindrical sleeve (15)
within which is located a piston-shaped part (20) which, during
the longitudinal displacement in the direction of the puncture path,
slides with a cylindrical outer wall (20b) within the sleeve (15).
4. Blood lancet device according to claim 3 in which the piston-shaped
part (20) is connected to the lancet holder (6).
5. Blood lancet device according to claim 1 comprising a tensioning
device (137) with an operating element (155) accessible from outside
of the housing, said operating element being coupled to the input-side
transmission member (5) of the rotary/sliding transmission system
in such a way that the elastic drive element (9) can be brought
into the tensioned state by rotation of the operating element (155)
with respect to the housing (1).
6. Blood lancet device according to claim 5 in which the coupling
of the operating element (155) of the tensioning device (137) with
the rotary/sliding transmission system (4) has a free-wheeling mode
and an elastic return element (140) in order to return the operating
element (155) to the starting position after the tensioning of the
drive element (9).
7. Blood lancet device according to claim 1 in which the locking
device (83) comprising a locking pin (153) firmly connected with
the input-side transmission member (5) and in the tensioned state
of the lancet drive (3) engages with a stationary locking recess.
8. Blood lancet device according to claim 1 in which the elastic
drive element (9) is a spatially wound coiled spring (10) located
coaxially to the axis of rotation (A) of the rotary/sliding transmission
system (4).
9. Blood lancet device for withdrawing blood for diagnostic purposes,
comprising
a lancet (34) comprising a metal needle (166 176) with a tip (35),
a plastic body (165) connected to said metal needle (166 176),
and a lancet positioning means (169 178),
a housing (1) with an outlet (84) for the tip (35) of the lancet
(34),
a lancet holder (6) located within the housing and contacting the
lancet (34) for holding the lancet (34) and movable within the housing
(1) along a predetermined puncture path, and
a lancet drive means (3) located within the housing for moving
the lancet in a puncturing direction comprising an elastic drive
element (9), a transmission system driven by said elastic drive
element to contact and move the lancet positioning means (169 178)
through a precisely defined maximum longitudinal displacement, and
wherein the lancet holder accurately positions the lancet positioning
means (169 178) relative to the lancet drive (3) means such that
the puncture depth at which during the puncturing movement tip (35)
of the lancet (34 175) emerges from the outlet (84) varies by no
more than at most .+-.0.15 mm with unchanged setting of the blood
lancet device and successive puncturing movements.
10. Blood lancet device according to claim 9 comprising means for
adjusting the puncture depth of the lancet (34) within an adjustment
range which includes adjustment values of less than 2 mm.
11. Blood lancet device according to claim 10 characterized in
that the adjustment range includes adjustment values of less than
1.3 mm.
12. Blood lancet device according to claim 9 comprising means
for adjusting the puncture depth of the lancet (34) in steps, the
interval between steps being at least 0.2 mm and at most 0.4 mm.
13. Blood lancet device according to claim 9 in which said positioning
means (169 178) is accurately located with respect to the needle
(166 176) of the lancet (34) and a stop (170) on the lancet drive
means (3), and
wherein the lancet (34 175) is held in the lancet holder (6) in
such a way that the positioning means (169) is elastically pressed
against the stop (170).
14. Blood lancet device according to claim 9 in which the puncture
depth varies at most by .+-.0.1 mm.
15. Blood lancet device according to claim 14 in which said driver
output member (40) is configured to have a cam segment 42 with an
apex 43 which precisely defines the maximum longitudinal displacement
of the needle (166 176).
16. Blood lancet device according to claim 9 in which the puncture
depth varies at most by .+-.0.05 mm.
17. Blood lancet device for withdrawing blood for diagnostic purposes
comprising
a lancet (34) comprising a metal needle (166 176) with a tip (35)
and a plastic body (165),
a lancet holder (6) for holding the lancet (34),
a lancet drive means (3) for driving the lancet needle (166 176)
along a predetermined straight path, the driving means comprising
a driver input member rotatable about an axis parallel to the straight
path, a driver output member connected to the lancet and the driver
input member for converting the rotation of the driver input into
longitudinal movement of the lancet along said straight path, and
means for accurately positioning the metal needle (166 176) of
the lancet (34) relative to the driving means, thereby accurately
to control the puncture depth of the tip (35), the positioning means
comprising a positioning means surface (169) on the needle (166
176), a stop (170) on the lancet holder (6) for abutting the positioning
means surface (169), and elastic means for pressing the positioning
means surface (169) against the stop (170).
Description The invention relates to a blood lancet device for withdrawing
blood for diagnostic purposes, said blood lancet device having a
housing with an outlet for the tip of a lancet, a lancet holder
for holding the lancet and movable within the housing along a predetermined,
straight puncture path, and a lancet guide for guiding the lancet
holder on the predetermined, straight puncture path. During the
puncturing and retraction movement the lancet holder is moved by
a lancet drive, which has an elastic drive element, commonly a metal
spring. It is lockable in an initial position, in which the elastic
drive element is in a tensioned state, by the use of a locking device.
After the locking device is unlocked, the elastic drive element
is released, and its movement is converted via the lancet drive
into the puncturing movement, the lancet held in the lancet holder
being moved at high speed along the predetermined puncture path
in the puncturing direction until its tip emerges from the outlet,
in order to produce a wound in a body part pressed against the outlet
(finger or ear lobe). Immediately thereafter the lancet is retracted
by the lancet drive.
In order to obtain a small volume of blood from the finger or ear
lobe for diagnostic purposes, in medical practice lancets are used,
these being pricked into the appropriate body part by the doctor
or laboratory personnel manually or with the use of a simple piece
of apparatus. The lancet must, of course, be sharp and sterile.
However, no other particularly stringent requirements are stipulated
in medical practice because withdrawals of blood in individual patients
are performed at long time intervals, and the puncture is performed
by trained, specially educated personnel.
By contrast, the requirements relating to blood lancet devices
intended for use by the patient himself are considerably more stringent.
They are necessary above all to enable particularly high-risk patients
groups to monitor specific analytical values in their blood on a
regular basis within the scope of home-monitoring.
This applies in particular to diabetics, who must monitor their
blood glucose level frequently and regularly in order to keep within
specified reference limits as constantly as possible by adjusting
their insulin injections to requirements, which depend on food intake,
physical activity, and other factors. This is extremely important
for the health of these patients and to avoid serious delayed damage,
for example blindness and amputation of body parts.
For this reason small, simple to use and relatively low-cost analysis
systems have been developed, usually comprising blood test strips
and an accessory evaluation instrument. Although these have meant
that the opportunity of analysis can now be offered to all patients
without problems and at relatively low cost, self-monitoring of
blood glucose values has not yet become as widespread among diabetics
as one would like. A principal reason for this is the pain associated
with the production of the puncture wounds necessary for the withdrawal
of blood.
Numerous different blood lancet devices intended as suitable for
producing the puncture wounds necessary for the withdrawal of blood
easily and with relatively little pain have been developed. Examples
are described in U.S. Pat. Nos. 4442836 4469110 4535769
and 4924897. Blood withdrawal instrument and lancet are mutually
adapted, and are also described as a blood sampling system. Despite
some progress, even with these known blood lancet devices intended
in particular for use by the patient himself, the pain produced
by the puncture is still excessive.
An object of the present invention is therefore to provide a blood
lancet device which in a simple construction will perform the puncture
in such a way as to lead to a reduced perception of pain.
In a blood lancet device of the type initially described this object
is achieved according to a first principal aspect of the invention
in that the lancet drive has a rotary/sliding transmission system
which has a transmission member rotatable about an axis of rotation
parallel to the predetermined puncture path and via which a torque
introduced on the input side of the rotary/sliding transmission
system is converted into a longitudinal displacement in the direction
of the predetermined puncture path, the rotatable transmission member
of the rotary/sliding transmission system is coupled with an elastic
drive element, and the output-side longitudinal displacement of
the rotary/sliding transmission system is transmitted to the lancet
holder.
The term "transmission system" is employed here in the
general sense, that is, as a kinematic device used for the coupling
and conversion of movements, in the present case the movement during
the release of the elastic drive element (which hereinafter without
limiting the general applicability is also described as a drive
spring) being converted into the movement of the lancet holder and
of a lancet which is held in it preferably exchangeably.
The rotary movement of the input-side transmission member is preferably
converted into a translational movement parallel with the axis of
rotation of said transmission member with the aid of a cam drive
mechanism, at least part of the puncturing movement and preferably
also of the retraction movement being determined by a relative movement
of a driver pin in a recess forming the driver cam, in which the
pin travels along a driver cam formed by the recess. The recess
which forms the driver cam may be provided either in the component
forming the rotatable transmission member, or in an adjacent displaceable
component. Correspondingly, the pin is rigidly connected either
to an adjacent displaceable component or to the component forming
the rotatable transmission member.
In the preferred design, the rotatable transmission member of the
rotary/sliding transmission system has a cylindrical sleeve within
which is located a piston-shaped part which, during longitudinal
displacement in the direction of the puncture path, slides with
a cylindrical outer wall within the sleeve, in which case the sleeve
should be rotatable, but not displaceable in the axial direction,
and the axially displaceable piston-shaped part located within it
should be non-rotatable. In this case the piston-shaped part is
preferably a component part of the lancet holder or firmly connected
to it.
The blood lancet device according to the invention is characterised
above all in that the vibrations during the puncturing and retraction
movement are very slight because, apart from the lancet holder itself,
no other components are accelerated and braked in the puncturing
direction. Within the scope of the invention it has been found that
this low level of vibration greatly contributes to a painless puncture.
Furthermore, the invention permits a simple construction of the
drive with little play with few components and good guiding of the
lancet holder. Vibrations during the puncturing and retraction movement
are thereby largely avoided with low costs of manufacture. As was
observed within the scope of the invention, this too is a major
contribution towards reducing the perception of pain.
In addition, the invention allows a handy and compact construction,
in which the housing preferably has an elongated shape ("pencil
shape"), and its longitudinal axis runs parallel to the puncturing
direction. This permits convenience of storage and simplifies operation.
According to a second principal aspect of the investigation, which
should not only be regarded as a preferred embodiment but also has
independent importance, the lancet drive and the holding of the
lancet in the lancet holder are designed in such a way that the
puncture depth at which during the puncturing movement the lancet
tip emerges from the outlet varies by no more than at most 0.15
mm, preferably by at most 0.1 mm, and especially preferably by at
most 0.05 mm with unchanged setting of the blood lancet device and
successive puncturing movements.
The puncture depth should be easily and precisely adjustable by
the user. In addition, the adjustment range preferably includes
unusually low puncturing depths of between 0.5 mm and 2.0 mm, the
range between 0.7 mm and 1.3 mm being of particular importance.
Within the scope of the present invention it has been observed that,
surprisingly, the blood volume required in medical practice for
analysis, commonly between 1 and 50 .mu.l and in the majority of
cases between 10 and 30 .mu.l, can be obtained with distinctly reduced
pain in the overwhelming majority of people even at these low puncture
depths, if an extremely high reproducibility of the depth of the
puncture at a specific, unchanged setting of the apparatus is simultaneously
ensured.
Admittedly a reproducible puncture depth is also aimed for with
previously known blood lancet devices, such as that described in
U.S. Pat. No. 4442836. Investigations in the context of the present
invention have, however, shown that in all conventional blood lancet
devices the variations in the puncture depth during successive puncture
movements considerably exceed the previously mentioned limit values
(at least about .+-.0.3 mm). The setting mechanism for setting the
puncture depth is preferably designed so as to be adjustable stepwise,
the interval between steps being at least about 0.2 mm and at most
about 0.4 mm, preferably about 0.3 mm, at least within the above-mentioned
preferred adjustment range (0.5 to 2.0 mm preferably 0.7 to 1.3
mm). The complete adjustment range can of course extend beyond the
partial ranges mentioned and also include greater puncture depths
in order to take account of the requirements of the relatively few
individuals in whom an insufficient blood volume can be obtained
with the deep puncture depths mentioned (for example owing to a
particularly thick stratum corneum).
The reproducible puncture depth can be achieved by known mechanical
means as long as relatively high-grade materials are used during
manufacture and close tolerances are observed in production. However,
the lancet drive described in connection with the first principal
aspect of the invention is especially preferred.
A considerable improvement in the reproducibility of the puncture
depth is achieved via a preferred embodiment in which the metal
needle of the lancet has a positioning element and the lancet holder
a stop for the positioning element, and the lancet is held in the
lancet holder in such a way that the positioning element is pressed
elastically against the stop.
Lancets always have a metal needle with one end ground to a point.
The posterior part of the lancet needle at the opposite end from
the tip is commonly enclosed in a lancet body made of a plastic
material (U.S. Pat. No. 3358689). During manufacture the lancet
needle is usually positioned in a plastic injection mould and the
lancet body injected onto it. Lancets of this type are fixed in
the lancet holder with the aid of the lancet body. The depth of
the puncturing movement is usually limited in that, during the puncture,
the anterior edge of the lancet body impinges on a stop rigidly
connected with the lancet device housing in the zone of the blood
lancet outlet. The puncture depth is also influenced by several
tolerances. Above all, within the scope of the present invention
it has been observed that the production tolerance of the position
of the needle tip relative to the position of the plastic body is
an important reproducibility-impairing factor.
In this proposed design the variation in the puncture depth from
one lancet to another is influenced only by the tolerance of the
distance between the positioning element and the tip of the metal
needle. As illustrated below using examples, the positioning element
can be formed by the posterior end of the needle, or by a projection
positioned at a distance to one side of the needle. In this way,
it is perfectly possible to maintain very close tolerances for the
distance between the positioning element and the lancet tip by the
usual metal working techniques.
The invention is explained in greater detail below using an example
of an embodiment schematically represented in the following figures:
FIG. 1 A longitudinal sectional view of a blood lancet device;
FIG. 2 A sectional view of a blood lancet device according to FIG.
1 along the line 1--1;
FIG. 3 A sectional view of a blood lancet device according to FIG.
1 along the line 2--2;
FIG. 4 A sectional view of a blood lancet device according to FIG.
1 along the line 3--3;
FIG. 5: A side view of the lancet holder of the blood lancet device
according to FIG. 1;
FIG. 6: A projection of the contours of the driver cam recess of
the lancet holder according to FIG. 5 in one plane;
FIG. 7: A partially cutaway diagram of the ram and lancet holder
of a blood lancet device according to FIG. 1;
FIG. 8: A perspective sectional view of the housing cylinder of
a blood lancet device according to FIG. 1;
FIG. 9: A partially cutaway diagram of a sealing sleeve and sealing
cap of a blood lancet device according to FIG. 1;
FIG. 10: A side view of the cylindrical sleeve of a blood lancet
device according to FIG. 1;
FIG. 11: A preferred embodiment of the lancet holding device and
lancet, partly in side view and partly in sectional view;
FIGS. 12 and 13: two orthogonal sectional views of an alternative
preferred embodiment of the lancet holding device and lancet;
FIG. 14: A graphical representation illustrating the function of
the invention.
Within the housing 1 of the blood lancet device 2 shown in FIG.
1 a lancet drive 3 is located, said drive having a rotary/sliding
transmission system 4 with a rotatable input-side transmission member
5 and a lancet holder 6 displaceable in the direction of the axis
of rotation A of the transmission member 5. The torque introduced
on the input side 16 of the rotary/sliding transmission system 4
is produced by an elastic drive element 9 of the lancet drive 3.
In the preferred embodiment described, the elastic drive element
9 is a spirally wound coiled spring 10. This is supported against
a spring stop 11 on the housing 1 with one end 12 and with the
other end 13 into an axial slit 14 on the input side (right-hand
side in the figure) of the transmission member 5 which takes the
form of a cylindrical sleeve 15. The spirally wound coiled spring
10 is located co-axially to the axis of rotation A of the rotary/sliding
transmission system 4.
Positioned within sleeve 15 is lancet holder 6. A piston-shaped
part 20 whose outer diameter is somewhat smaller than the internal
diameter of sleeve 15 is a component part of lancet holder 6 and
with its cylindrical outer wall 20b can slide along the internal
wall of sleeve 15. The internal wall of sleeve 15 thus forms a lancet
guide 15b during the puncturing and retraction movement. The sleeve
15 is fixed in housing 1 regarding axial displacement, and can rotate
only about axis of rotation A.
Lancet holder 6 is overall designed roughly as a hollow cylinder
with an approximately constant internal diameter (FIG. 5 and FIG.
7). In the lancet take-up part 22 lancet holder 6 is provided with
two notches in its casing wall 26 into which two symmetrical and
roughly axially parallel tongues 27 extend. These are each connected
on one side to the piston-shaped part 20. The free end of both tongues
27 is formed into a lug 29 the distance between said lugs in the
non-tensioned state of tongues 27 being smaller than the internal
diameter of lancet holder 6. If a lancet 34 (shown in FIG. 1) is
positioned in lancet holder 6 tongues 27 with the elastically inwardly
pressed lugs 29 formed on them grip lancet 34 like a pair of tongs.
The posterior end of lancet 34 adjoins the face 37 of a stay 36
which is diametrically located in lancet holder 6.
As can be seen in FIG. 1 FIG. 5 FIG. 7 and FIG. 11 the casing
38 of piston-shaped part 20 is provided with a groove-shaped recess
39 with a rectangular cross-section, said recess forming a driver
cam 40 for rotary/sliding transmission system 4. The line of the
contours of recess 39 in one plane is shown in FIG. 6. It will be
recognised that recess 39 has two cam segments 41 42 with constant
groove width. The first cam segment 41 is formed along a circumferential
line of casing 38 of cylindrical part 20 in the preferred case
described the angular distance between the start 41a and the end
41b of the first cam segment 41 being about 140.degree.. In the
zone of the end 41b of the first cam segment, recess 39 changes
into the second cam segment 42 which, with identical groove width,
connects the start 41a and the end 41b of the first cam segment
41. In so doing the second cam segment 42 follows an arcuate course.
Like the first cam segment 41 it is located symmetrically in relation
to axis 44. At the start 42a the second cam segment 42 has a straight
piece 45 which steadily changes into a curved piece 46 which after
an apex 43 travels symmetrically to axis 44 to the end 42b. Here
too the end 42b of the second cam segment 42 corresponds to the
start 41a of the first cam segment. The two cam segments 41 42
form the annularly closed driver cam 40.
Positioned on the cylindrical sleeve 15 (FIG. 1) is a roughly axially
parallel elastic tongue 51 attached on one side, at the free end
of which there is a driver pin 52 which points into the interior
of the sleeve 15 said driver pin engaging with the recess 39 of
the piston-shaped part 20 and being able to travel along the driver
cam 40 formed by recess 39 via a relative movement with the piston-shaped
part. The groove width of recess 39 is co-ordinated with the diameter
of the cylinder of driver pin 52 in such a way that, at least over
the greater part of driver cam 40 driver pin 52 is positively interlocked
with recess 39. In order to set the relative movement between driver
pin 52 and recess 39 a ramp-like step 54 55 is provided ahead
of the end 41b, 42b of each of the two cam segments 41 42 in recess
39 (FIG. 6), said ramp-like step 54 55 rising evenly from the groove
base 56 then finishing with a flank 57 68 dropping perpendicularly
to groove base 56. Thus, at the end of each cam segment 41 42 driver
pin 52 comes to lodge in such a way that it can move only in the
direction of the end 41b, 42b of the other cam segment 41 42.
Positioned in the cylindrical recess 58 of the piston-shaped part
20 is a cylindrical part 60 of a ram 59 (FIG. 7). The longitudinal
axis of ram 59 corresponds to the longitudinal axis of lancet holder
6 and axis of rotation A of sleeve 15. Almost along its whole longitudinal
axis, the cylindrical part 60 of ram 59 has a diametrical slit 62
via which the cylindrical part 60 of the ram forms a fork 61. The
distance between the two plane-parallel surfaces 63 64 of fork
61 is co-ordinated to the thickness of stay 36 in such a way that
the cylindrical part 60 of ram 59 in the piston-shaped part 20 of
lancet holder 6 is axially movable, the plane-parallel surfaces
63 64 sliding over the two surfaces 65 66 of stay 36. On the closed
side 67 of the fork 61 ram 59 changes into a bar 71 with cruciform
cross-section, said bar being located in such a way that it too
can slide within the cylindrical recess 58 of piston-shaped part
20. Positioned at the end of ram 59 is an operating knob 76 with
a roughly square cross-section.
On the bar 71 of ram 59 there is a tongue 77 which on impinging
on a stay 70 of the cylindrical sleeve 15 limits the axial displacement
of the ram 59 within the lancet holder 6.
Ram 59 is positioned in the blood lancet device 2 in such a way
that the operating knob 76 projects through a corresponding opening
78 in housing 1 through which ram 59 is mounted non-rotatably with
respect to housing 1 (FIG. 1). A ledge 79 formed at the transition
of the bar 71 to the operating knob serves as the stop on housing
1 on axial displacement of ram 59. Bar 71 is inserted through the
spirally wound coiled spring 10.
If driver pin 52 of cylindrical sleeve 15 is positioned at the
start 41a of the first cam segment 41 of driver cam 40 coiled spring
10 is in a non-tensionned state (FIG. 1 and FIG. 6). By rotation
of cylindrical sleeve 15 to the right, driver pin 52 within driver
cam 40 of the piston-shaped part 20 is moved to the end 41b of the
first cam segment 41 and coiled spring 10 coupled to sleeve 15
is induced into a tensioned state. The fact that ram 59 is non-rotatably
mounted in housing 1 and stay 36 is positioned within fork 61 prevents
lancet holder 6 from also rotating when the sleeve 15 rotates. During
this rotation of sleeve 15 to the right no longitudinal displacement
is executed by lancet holder 6 since the first cam segment 41 travels
along a circumferential line of piston-shaped part 20. At the end
of the slope of step 54 there is a non-sloping surface segment 54a
which still is a little below the top edge of the side walls of
cam 40. The bending stress of tongue 51 causes driver pin 52 to
be pressed against groove base 56 at the end of the first cam segment
41b. Via vertical flank 57 of step 54 sleeve 15 with driver pin
52 is prevented from being able to move back along the first cam
segment 41 due to the now tensioned state of coiled spring 10.
A locking device 83 locks the cylindrical sleeve 15 in this position
of the driver pin 52 (FIG. 1 and FIG. 2). If the locking device
83 is released, the spring tension of coiled spring 10 causes a
torque to be transmitted to the input side 16 of the rotary/sliding
transmission system 4 sleeve 15 being rotated back in the opposite
direction to the former direction of rotation and driver pin 52
travelling along the second cam segment 42 (FIG. 1 and FIG. 2).
In the process, on the output side 17 of the rotary/sliding transmission
system 4 piston-shaped part 20 which is fixed to prevent rotary
movements, is displaced longitudinally within housing 1 in the direction
of outlet 84 of said housing 1 until driver pin 52 has reached apex
43 of the second cam segment 42 and the tip 35 of the lancet 34
emerges through the outlet 84. When driver pin 52 is positioned
at the apex 43 of the second cam segment 42 the tip 35 of the lancet
34 has reached its maximum longitudinal displacement in the direction
of the puncture path.
Because the blood lancet device is pressed against the skin with
a pressure surface 82 surrounding outlet 84 the puncture depth
corresponds to the distance between tip 35 and pressure surface
82 (in the direction of the puncture path).
The retraction movement of the lancet 34 is complete when the driver
pin has reached the end 42b of the second cam segment 42 which
is identical with the start 41a of the first cam segment 41. Before
it reaches this point it slides over the slope of a second ramp-like
step 55 which again has a non-sloping surface segment 55a and a
vertical flank 68 at its end. The slope here is longer and less
steep in order to slow down the movement as little as possible.
Because of this the driver pin 52 can only continue to move only
along the first cam segment 41.
The puncturing and retraction movement of lancet 34 is achieved
by converting the rotary movement about the axis of rotation A of
the spirally wound coiled spring 10 and of transmission member 5
into a longitudinal displacement of lancet holder 6 in the direction
of the predetermined puncture path and thereafter in the opposite
direction.
In an alternative embodiment of the invention it can also be provided
that the interlocking of recess 39 and driver pin 52 is present
only in partial sections, in particular the section between the
start 41a and the apex 43 of the second cam segment 42.
In the embodiment shown in FIG. 1 housing 1 of blood lancet device
2 comprises a number of elements. The cylindrical sleeve 15 is positioned
in a housing cylinder 85 open on one side. Here, cylindrical sleeve
15 projects with its face 87 out of the open end 90 of the housing
cylinder 85. On casing surface 91 of housing cylinder 85 in the
area of the open end 90 there are three encircling stays 92 93
94 (FIG. 8), the first 92 and second 93 stay with their outer edges
92a, 93a being a greater distance away from casing surface 91 than
the outer edge 94a of the third stay 94. On the outer edges 92a,
93a of these two stays 92 93 a cover ring 100 is supported, which
has an opening 102 for taking a key 103 for the release of locking
device 83 (FIG. 2). On the first face, which points towards lancet
tip 35 cover ring 100 is open whereas the second face is provided
with a circular recess, the diameter of which roughly corresponds
to the diameter of casing surface 91 of housing cylinder 85. For
fixing housing cylinder 85 cover ring 100 has a torsion protection
device and a bead 107 which follows a course along the casing internal
surface in the direction of the circumference, said bead 107 being
positioned between the first stay 92 and the second stay 93 of the
housing cylinder 85 (FIG. 1).
Attached flush to the open end of cover ring 100 is an intermediate
ring 110 which is supported on the second stay 93 of housing cylinder
85 and, with a bead 113 following a course on the inside in the
direction of the circumference, on the third stay 94 of housing
cylinder 85 (FIG. 1). The intermediate ring 110 surrounds an extended
collar 114 of a tension sleeve 115. The tension sleeve 115 has been
axially pushed roughly in the position of the lancet take-up part
22 onto the cylindrical sleeve 15 and is fixed with this regarding
displacement in the direction of the longitudinal axis. In addition,
a notch 116 is provided in the casing of the cylindrical sleeve
15 along a roughly hemi-circumferential line, with which notch 116
a gripping device 117 of the tension sleeve 115 engages (FIG. 4).
For screwing on a sealing ring 120 on the end of the tension sleeve
115 facing outlet 84 there is an outer thread 121 while sealing
ring 120 is provided with a corresponding internal thread 122 (FIG.
1 and FIG. 9). By means of a second internal thread 123 a sealing
cap 124 with an external thread 125 is screwed into the end of sealing
ring 120 facing outlet 84. Sealing cap 124 is closed at the first
face 126 with the exception of puncture opening 84 the outer surface
126a of face 126 being placed on an area of skin during the use
of the blood lancet device 2. The puncture depth is set using thread
123 125 with which sealing cap 124 and sealing ring 120 are connected.
Lancet drive 3 and adjustability via thread 123 125 are so co-ordinated
with the dimensions of the lancet 34 to be used that the puncture
depth is adjustable within a desired adjustment range, which in
a preferred practical embodiment ranges from 0.7 mm to 2.2 mm, successive
puncture movements with unchanged setting of the blood lancet device
2 varying in respect of the puncture depth by at most 0.15 mm, preferably
by at most 0.1 mm, and especially preferably by at most 0.05 mm.
In order that the user of the blood lancet device 2 can set what
is, for him, the optimal puncture depth stepwise and not have to
make a re-adjustment with each use, an engaging device 130 is envisaged,
as FIG. 9 shows. To this end, on its casing internal surface 120a
sealing ring 120 is provided with radially encircling, evenly distributed
nubs 131. Between each pair of these nubs 131 there lodges an engaging
tongue 132 which is fastened to sealing cap 124 on one side and
parallel to the longitudinal axis on casing 127 of sealing cap 124
so that it lodges almost free of play in the free zone between two
nubs 131. By twisting of sealing cap 124 and sealing ring 120 in
opposite directions, the elastically formed engaging tongue 132
slides past a nub 131 and comes to lodge in the next free zone between
two nubs 131. To monitor the puncture depth, sealing ring 120 bears
a mark 133 with the aid of which the puncture depth set can be
read off against a scale 134 on sealing cap 124.
By rotation of the sealing ring 120 of the tensioning device 137
to the right with respect to the housing cylinder 85 the tensioning
sleeve 115 with the cylindrical sleeve 15 which are engaged with
the catch 117 and the first face 138 of the notch 116 is also turned
(FIG. 1 and FIG. 4). The blood lancet device 2 is thereby tensioned.
At the start of the rotation to the right, driver pin 52 is at the
start of the first cam segment 41 and travels along this to the
end 41b, step 55 positively determining the direction of movement.
During this rotation to the right, lancet holder 6 remains in its
position in housing 1 without executing a movement. This has the
advantage that during the rotation to the right the lancet tip 35
does not emerge through opening 84 and an undesirable risk of injury
due to the tensioning procedure is thereby excluded.
Simultaneously with the rotation to the right the spirally wound
coiled spring 10 and an elastic retraction element, which in the
described preferred embodiment is similarly in the form of a spirally
wound coiled spring 140 are induced into a tensioned state. In
the process, return spring 140 is supported on the one hand on the
housing cylinder 85 and on the other on the tensioning sleeve 115
(FIG. 1). The rotation to the right is ended by the meeting of a
stop stay 149 on the housing cylinder 85 and a stop lug 151 of the
cylindrical sleeve 15 (FIG. 8 and FIG. 10). In the process driver
pin 52 at end 41b of the first cam segment 41 comes to lodge behind
the vertical flank 57 of step 54 and an elastic locking tongue
153 (FIG. 2) of the locking device 83 snaps into a corresponding
locking recess 154 positioned on the casing 85a of the housing cylinder
85 and locks the blood lancet device 2 in the tensioned state.
The tensioning device 137 therefore has an operating element 155
(in the described preferred case the sealing ring 120) accessible
from outside the housing 1 said operating element being coupled
with the input side 16 of the rotary/sliding transmission system
4 in such a way that, by rotation of operating element 155 with
respect to the housing 1 the elastic drive element 9 of the lancet
drive 3 is induced into the tensioned state (FIG. 1).
On the release of the sealing ring 120 the spring tension of the
return spring 140 comes into play and turns the mutually coupled
elements consisting of the tensioning sleeve 115 sealing ring 120
and sealing cap 124 back into their starting position, the rotary/sliding
transmission system 4 not being moved. Because the drive sleeve
15 is engaged only on rotation to the right of sealing ring 120
a free-wheeling function is achieved. Because operating element
155 after the tensioning of the drive element 9 is returned to
the starting position, it remains at rest during the puncture movement.
After the release of the locking device 83 by pressing the button
103 the puncturing procedure is initiated. In the process the elastic
locking pin 153 fastened to the drive sleeve 15 is moved from the
locking recess 154 of the housing cylinder 85 into the interior
space of the housing cylinder 85 as a result of which the drive
sleeve 15 is released for rotary movements with respect to housing
1 (FIG. 2). The mounting of button 103 is designed in such a way
that when the blood lancet device 2 is non-tensioned the button
is held in a depressed position. Only in the tensioned state of
the coiled spring 10 is the button 103 pressed outwards. The operating
status of the blood lancet device 2 can thus be ascertained from
the position of the button 103. The button 103 is enclosed by the
covering ring 100 by which it is also held in place with respect
to the housing 1.
The spring tension of the coiled spring 10 now introduces a rotation
of the drive sleeve 15 to the left. During this rotation to the
left, driver pin 52 travels along the second cam segment 42 of the
driver cam 40 as described.
Because the blood lancet device 2 according to the invention has
a small accelerated mass in the direction of the longitudinal movement
of lancet 34 the puncture is very largely vibration-free. This
is an important requirement for a puncture with little pain, as
was demonstrated in investigations in the context of the invention.
The described guiding of the lancet holder 6 within the rotary/sliding
transmission system further contributes to the vibration-free and
therefore also pain-free puncture.
To replace the lancet 34 sealing ring 120 with the sealing cap
124 is screwed off by rotation to the left. By pressing on the operating
knob 76 ram 59 is moved in the direction of the outlet of the housing
along the axis of rotation A (FIG. 1 and FIG. 7). In the process
the face 61a of the fork 61 presses on lancet 34 which is thereby
ejected. The axial movement of the ram 59 is limited by the tongue
77 of the ram, said tongue impinging upon the stay 70 of the cylindrical
sleeve 15. The new lancet 34 is inserted into the lancet take-up
part 22 of the lancet holder 6 and pushed in as far as the first
face 37 of the stay 36. In the process the ram 59 is pushed back
and the lancet 34 is gripped firmly by the two lugs.
In order to obtain good reproducibility of the puncture depth with
unchanged setting of the blood lancet device 2 an exactly reproducible
positioning of the lancet 34 in lancet holder 6 is necessary. The
preferred embodiments for holding the lancet shown in FIGS. 11 to
13 serve this purpose.
The lancet 34 shown in FIG. 11 comprises as usual a plastic body
165 and a metal needle 166. It is however of a novel design in that
the posterior end 167 of the metal needle 166 projects beyond the
posterior end 168 of the plastic body 165. The rearward face of
the posterior end 167 serves as the positioning element 169. Said
positioning element adjoins a stop 170 of the lancet holder 7 which
in the case shown is formed by stay 36.
The holding of the lancet 34 in the lancet holder 6 is designed
in such a way that the lancet 34 is pressed back with positioning
element 169 against stop 170 (in opposition to the puncturing direction).
In the embodiment shown, this is achieved in that the V-shaped recesses
171 with which the lugs 29 of the elastic tongues 27 engage, are
designed and disposed in such a way that the posterior sloping surface
29a adjoins a corresponding sloping surface 171a of the recesses
171 and a force component in opposition to the puncturing direction
results from the pressure of the tongues 27 in the direction of
axis A.
The body 165 of the lancet 134 is preferably not round but, for
example, square. Via a corresponding shape of the interior space
of the lancet take-up part 22 protection against torsion is ensured.
The embodiment shown in FIGS. 12 and 13 is distinctive above all
in that the needle 176 is not round in cross-section, but consists
of a thin flat material. The shape of the needle can be appreciated
in FIG. 12 in side view of the narrow edge, and in FIG. 13 in side
view of the surface.
FIG. 12 represents a tip protection device 177a removable by rotation,
said tip protection device being injected--as is also common practice
with other lancets--together with the plastic body 177 on to needle
176 and removed before the lancet is used.
The needle 176 is held in a plastic body 177 which in this case
also has V-shaped recesses 171 which interlock with the lugs 29
of the elastic tongues 27 of the holder 6 in the same way as in
FIG. 11 to produce a resultant force component which acts on the
lancet in opposition to the puncturing direction.
In this case a peg-shaped projection 178 positioned at a distance
to one side of the needle 176 serves as the positioning element
169 said projection 178 adjoining a lower face 179 of the take-up
part 22 of the lancet holder 6 forming the stop 170.
A lancet of this type is easily manufactured in a punching process.
Said lancet is characterised by particularly close tolerances of
the distance between the lancet tip 35 and the positioning element
169 and thus by a particularly good reproducibility of the puncture
depth. Furthermore, the flat shape permits a relatively broad construction
of the lancet tip in the plane of needle 176. In this way a relatively
large blood sample volume is achieved with little pain using a small
puncture depth.
As mentioned above, in the context of the present invention it
was observed that, surprisingly, an adequate volume of blood by
comparison with the greatly reduced puncture depths commonly used
in the past can be obtained if care is simultaneously taken to ensure
that the puncture depth is very accurately reproducible.
In FIG. 14 results obtained in 30 test subjects with the blood
lancet device according to the invention are presented in graph
form. The number N of test subjects is plotted along the x-axis,
and the blood volume obtained in .mu.l along the y-axis. The five
curves show the results using puncture depths of 0.3 mm, 0.5 mm,
0.7 mm, 0.9 mm, and 1.1 mm. It is seen that using a puncture depth
of 0.3 mm, inadequate blood volumes were obtained in the great majority
of cases. In the case of twenty-one patients the blood volumes were
below 10 .mu.l.
On increasing the puncture depth to 0.5 mm, and even more on further
increasing it to 0.7 mm or 0.9 mm, the number of patients in whom
an adequate blood volume was produced increased very markedly. For
example, FIG. 14 shows that using puncture depths of 0.7 mm and
0.9 mm, blood volumes of 20 .mu.l and above were already obtained
in 2/3 of the test subjects. With modern analytical equipment this
volume is frequently sufficient for an exact analysis.
Using a puncture depth of 1.1 mm the blood volume obtained once
again distinctly increases. In this case it is below the 20 .mu.l
limit value only in 4 patients, i.e. fewer than 15% of the total
number of participants.
Bearing in mind that previously known blood lancet devices commonly
operate with puncture depths in excess of 2 mm in order to obtain
an adequate quantity of blood, the present results clearly show
that within the scope of the invention a marked reduction in pain
is achievable in the large majority of patients via a reduction
in the puncture depth, and that nevertheless an adequate blood volume
can be obtained. |