Abstrict A blood lancet is disclosed that has a base; a needle mounted to
the base; a cap that slides relative to the base, and a locking
member located inside between the base and cap. In use, the base
and cap are initially at an expanded position and the needle is
retracted below a hole in the cap. When the user is ready to draw
a blood sample, the user positions a finger on the cap and squeezes
the base and cap together. The locking member initially resists
the movement of the cap until sufficient force is applied to snap
the locking member into the cap, which permits the cap to quickly
retract to expose the needle and prick the user's finger. This movement
also spreads apart two cantilever springs that bias the cap back
toward the initial expanded position. When the user stops squeezing
the base and cap together, the springs push the cap and the locking
member, which is now engaging the cap, to the expanded position.
Two prongs in the base, which are released from a deflected position
when the locking member moves, move to a position to block the locking
member and cap from moving back. After use, the needle is protected
by the cap at the expanded position and the lancet is locked and
cannot be re-used.
Claims What is claimed is:
1. A lancet, comprising: a base; a needle affixed to the base;
a cap slidably coupled to the base for movement relative to the
base between an expanded position and a contracted position, wherein
the cap includes a hole through which a tip of the needle extends
when the cap is at the contracted position, and wherein the tip
of the needle is not exposed when the cap is at the expanded position;
a spring that biases the cap toward the expanded position; a locking
member disposed between the base and the cap that engages the cap
when the cap is moved to the contracted position; and a latch that
locks the cap in the expanded position after the locking member
engages the cap and the cap returns to the expanded position.
2. A lancet as recited in claim 1 wherein the cap and base nest
within each other, wherein the cap and the base include a barbed
structure and a mating socket structure providing a sliding coupling
between the cap and the base, and wherein the barbed structure engages
an end of the socket structure at the expanded position.
3. A lancet as recited in claim 1 wherein the base and the cap
include a cantilever member and a tapered mating surface that provide
the spring, wherein the tapered mating surface contacts a free end
of the cantilever member and deflects the cantilever member when
the cap is moved toward the contracted position.
4. A lancet as recited in claim 1 wherein the locking member and
the cap include a barbed structure and a mating structure, wherein
the barbed structure and mating structure engage when the cap is
moved to the contracted position to lock the locking member to the
cap.
5. A lancet as recited in claim 1 wherein the latch includes a
prong structure on the base that blocks movement of the locking
member and cap from the expanded position toward the contracted
position after the locking member engages the cap.
6. A lancet as recited in claim 5 wherein the prong structure includes
two prongs that are spread apart by the locking member when the
locking member is not engaging the cap and that move to a position
to block movement of the locking member and cap toward the contracted
position when the locking member engages the cap and the cap is
in the expanded position.
7. A lancet as recited in claim 1 further comprising a removable
cover coupled to the base that covers the tip of the needle until
the removable cover is removed.
8. A lancet as recited in claim 1 wherein the cap includes a grasping
structure and the base includes a protruding end, and wherein the
cap can be moved from the expanded position to the contracted position
to expose the tip of the needle by holding the grasping structure
of the cap and pushing on the protruding end of the base.
9. A lancet, comprising: a base; a needle affixed to the base,
wherein the needle defines a needle axis; a cap slidably coupled
to the base for movement relative to the base in the direction of
the needle axis between an expanded position and a contracted position,
wherein the cap includes a hole through which a tip of the needle
extends when the cap is at the contracted position, and wherein
the tip of the needle is not exposed when the cap is at the expanded
position; a sliding coupling between the base and cap that includes
a barbed structure and a mating socket structure, wherein the barbed
structure engages an end of the socket structure to limit movement
at the expanded position; a spring that biases the cap toward the
expanded position, wherein the base and the cap include a cantilever
member and a tapered mating surface that provide the spring, wherein
the tapered mating surface contacts a free end of the cantilever
member and deflects the cantilever member when the cap is moved
toward the contracted position; a locking member disposed between
the base and the cap that engages the cap when the cap is moved
to the contracted position, wherein the locking member and the cap
include a barbed structure and a mating structure, wherein the barbed
structure and mating structure engage when the cap is moved to the
contracted position to lock the locking member to the cap; and two
prongs coupled to the base that are spread apart by the locking
member when the locking member is in an initial position and that
move to a position to block movement of the locking member and cap
toward the contracted position after the locking member engages
the cap and the cap is moved to the expanded position.
10. A lancet, comprising: a base; a needle affixed to the base,
the needle defining a needle axis; a cap engaging the base with
a means for limiting movement of the cap relative to the base in
a direction parallel to the needle axis between an expanded position
and a contracted position, the cap having a hole through which the
needle protrudes at the contracted position; means for biasing the
cap toward the expanded position; a locking member positioned between
the base and cap and having means to engage the hole of the cap
when the cap is moved to the contracted position; and means for
locking the cap in the expanded position after the locking member
engages the hole of the cap and the cap moves to the expanded position.
11. A lancet as recited in claim 10 wherein the means for limiting
movement includes a sliding latch that limits movement of the cap
relative to the base at the expanded position at one extreme and
at the contracted position at another extreme.
12. A lancet as recited in claim 11 wherein the cap and base nest
within each other, wherein the latch includes a barbed structure
on one of the cap and the base and a mating socket structure on
the other of the cap and the base, and wherein the barbed structure
engages an end of the socket structure at the expanded position
to limit further outward movement of the cap.
13. A lancet as recited in claim 12 wherein the means for biasing
the cap toward the expanded position includes a cantilever spring
on one of the cap and the base and a mating surface on the other
of the cap and the base, and wherein the spring provides a force
on the mating surface to bias the cap toward the expanded position.
14. A lancet as recited in claim 13 wherein the base includes two
cantilever springs, and wherein the cap includes a tapered mating
surface that contacts a free end of the cantilever springs and deflects
the cantilever springs when the cap is moved toward the contracted
position.
15. A lancet as recited in claim 10 wherein the locking member
is centered on the needle axis and includes a clearance hole through
which the needle protrudes.
16. A lancet as recited in claim 10 wherein the means to engage
the hole of the cap includes a barbed structure on one of the locking
member and the cap and a mating structure on the other of the locking
member and the cap, wherein the barbed structure and mating structure
engage when the cap is moved to the contracted position to lock
the locking member to the cap.
17. A lancet as recited in claim 10 wherein the means for locking
the cap in the expanded position includes a prong structure on the
base that blocks movement of the locking member from the expanded
position toward the contracted position when the locking member
engages the cap and the cap is moved to the expanded position.
18. A lancet as recited in claim 17 wherein the prong structure
includes two prongs that are spread apart by the locking member
when the locking member is not engaging the cap and that move to
a position to block movement of the locking member and cap toward
the contracted position when the locking member engages the cap
and the cap is in the expanded position.
Description BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates generally to blood sampling devices,
and relates more particularly to a single-use, disposable, blood
lancet that exposes a needle to prick a user's finger and then retracts
the needle and locks to prevent re-use.
[0003] 2. Description of the Relevant Art
[0004] Blood lancets are devices that are used to prick the skin
of a patient to obtain a small quantity of blood for testing. Blood
lancets are commonly used to obtain a drop or two of blood from
the capillaries in a person's finger. Diabetics, for example, regularly
use blood lancets to obtain blood samples to test for blood sugar
level.
[0005] A typical blood lancet has a needle or other sharpened point
that is forced forward to cut through skin and into subcutaneous
capillaries. Penetration force may be provided by a spring or other
mechanical device. Among the design considerations for a blood lancet
is its depth and speed of penetration of the needle, which is important
to minimize discomfort to the user. After the needle penetrates
the skin, it is retracted into the lancet, sometimes with the aid
of another spring or mechanism.
[0006] Some lancets are designed for single use because the needle
or sharpened tip can become dull and make re-use painful. Single
use also eliminates the possibility of transmitting disease to a
subsequent user. A typical single-use lancet locks after use and
requires either the needle or the entire lancet to be disposed.
SUMMARY OF THE INVENTION
[0007] In summary, the present invention is a blood lancet that
has a base; a needle affixed to and protruding outwardly from the
base; a cap slidably coupled to the base for movement in a direction
parallel to the needle between an expanded position and a contracted
position; a spring that biases the cap toward the expanded position;
a locking member that engages the cap when the cap is moved to the
contracted position; and a latch that locks the cap in the expanded
position after the locking member engages the cap and the cap returns
to the expanded position. The needle protrudes through an access
hole in the cap and is exposed at the contracted position, but is
withdrawn inside the cap at the expanded position. Preferably, the
base, cap, and locking member are composed of plastic and may be
injection molded.
[0008] In operation, the lancet is initially configured so that
the locking member is disengaged from the cap and the cap and base
are in the expanded position, so that the needle is retracted below
the outer surface of the cap. A protective cover may be present
to ensure sterility, but is removed when the user is ready to draw
a blood sample. To use the lancet, the user positions a finger (or
other body part) on the cap and squeezes the base and cap together.
The locking member initially resists the movement of the cap toward
the contracted position until sufficient force is applied to force
a barb of the locking member into the access hole of the cap, thus
permitting the cap to quickly travel to the contracted position.
This movement rapidly exposes the needle, which passes through the
access hole in the cap and pricks the user's finger. The movement
toward the contracted position also spreads apart two cantilever
springs to generate a force that biases the cap back toward the
expanded position. When the user stops squeezing the base and cap
together, the cantilever springs push the cap to the expanded position.
The cap and the locking member, which is now engaged in the access
hole of the cap, move toward the expanded position. Two prongs of
the base, which were initially spread apart by the locking member,
come together once the locking member has moved outwardly to the
expanded position to prevent the locking member and cap from moving
back to the contracted position. Thus, the needle is protected by
the cap at the expanded position and the lancet is locked and cannot
be re-used.
[0009] The features and advantages described in the specification
are not all inclusive, and particularly, many additional features
and advantages will be apparent to one of ordinary skill in the
art in view of the drawings, specification and claims hereof. Moreover,
it should be noted that the language used in the specification has
been principally selected for readability and instructional purposes,
and may not have been selected to delineate or circumscribe the
inventive subject matter, resort to the claims being necessary to
determine such inventive subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is an end view of a base, which is a component part
of a blood lancet according to the present invention.
[0011] FIG. 2 is a sectional view of the base of FIG. 1.
[0012] FIG. 3 is an end view of a cap, which is a component part
of the blood lancet according to the present invention.
[0013] FIG. 4 is a sectional view of the cap of FIG. 3.
[0014] FIG. 5 is an end view of a locking member, which is a component
part of the blood lancet according to the present invention.
[0015] FIG. 6 is a sectional view of the locking member of FIG.
5.
[0016] FIG. 7 is a sectional view of the blood lancet according
to the present invention, shown in a first position where a needle
is retracted but ready for use.
[0017] FIG. 8 is a sectional view of the blood lancet, shown in
a second position where the needle is exposed to prick the user's
finger to obtain a blood sample.
[0018] FIG. 9 is a sectional view of the blood lancet, shown in
a third position where the needle is retracted and locked after
a single use.
[0019] FIG. 10 is a sectional view of an alternative embodiment
of the blood lancet of the present invention, shown in a first position
where the needle is retracted but ready for use.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] The drawings depict various preferred embodiments of the
present invention for purposes of illustration only. One skilled
in the art will readily recognize from the following discussion
that alternative embodiments of the structures and methods illustrated
herein may be employed without departing from the principles of
the invention described herein.
[0021] The present invention is a single-use, disposable, blood
lancet 10 that exposes a needle 14 to prick a user's finger and
then retracts the needle and locks to prevent re-use. As shown in
the drawings, the lancet 10 consists of four parts, a base 12 a
needle 14 inserted into the base, a cap 16 and a locking member
18. The base 12 cap 16 and locking member 18 are preferably injection-molded
plastic pieces composed of a suitable plastic material. The individual
components will first be described, in reference to FIGS. 1-6 and
then the operation of the lancet will be described, in reference
to FIGS. 7-9.
[0022] The base 12 is shown in more detail in FIGS. 1 and 2. The
base 12 includes a central boss 20 projecting upward from the center
of the base. The central boss 20 has a central hole 22 into which
the needle 14 (FIGS. 7-9) is inserted. The needle 14 is oriented
along a central axis of the lancet. The base 12 also has two cylindrical
prongs 24 that project upwards next to the central boss 20. Two
cantilever springs 26 project upwards above the cylindrical-shaped
lower portion of the base 12. The inside edges 28 of the outer ends
of the cantilever springs 26 are rounded. The inside of the sidewalls
30 of the base 12 have undercuts 32 located below the cantilever
springs 26. The cantilever springs 26 and undercuts 32 interact
with complementary features on the cap 16 as explained below.
[0023] The cap 16 has a structure that allows it to nest with the
base 12. An open center 34 provides clearance for the central boss
20 and prongs 24 of the base 12. The cap has a partially-cylindrical
portion 36 with barbs 38 that extend into and engage the undercuts
32 of the base 12. (FIG. 7). The cap 16 has a curved outer surface
40 with an access hole 42 through which the needle 14 protrudes
and into which the locking member 18 engages when the lancet is
used. (FIG. 8). The access hole 42 is counterbored at the outer
surface 40 to a larger diameter at the surface than the diameter
44 of the remainder of the hole. An outer surface 46 of the cap
16 below the cylindrical portion 36 is tapered.
[0024] The locking member 18 has a barbed portion 48 at one end
that engages the access hole 42 in the cap 16. There is a slight
interference fit between the outside diameter of the barbed structure
48 and the inside diameter of the collar 44 to that the locking
member will snap into the access hole when sufficient force is applied.
The locking member also has two relieved areas 50 sized to receive
the prongs 24 of the base 12.
[0025] The assembly and operation of the lancet 10 will now be
described with respect to FIGS. 7-9. The lancet 10 is shown in FIG.
7 ready for use with the cap 16 and base 12 in an expanded position
relative to each other. The cap 16 is coupled to the base 12 with
its barbs 38 engaging an upper edge of the undercuts 32 of the base
12 which limits any further outward movement of the cap relative
to the base. The rounded edges 28 of the cantilever springs 26 of
the base 12 touch the tapered outer surface 46 of the cap 16 to
provide an outward bias force on the cap to hold it in the expanded
position. The needle 14 projects upward from the base 12 but the
tip of the needle is positioned safely below the outer surface 40
of the cap 16. The locking member 18 is positioned between the base
12 and cap 16 resting on the top of the central boss 20 with the
barbed portion 48 oriented toward the access hole 42 of the cap.
The two prongs 24 of the base 12 are spread apart by the relieved
areas 50 of the locking member 18. This is the condition in which
the lancet 10 is assembled and supplied to the user.
[0026] FIG. 8 shows the lancet 10 in use with the cap 16 and 12
in a contracted position that exposes the tip of the needle 14.
Initially, the lancet 10 is in the expanded position, shown in FIG.
7. To use the lancet 10 the user places a finger (or other body
part) over the outer surface 40 of the cap 16 over the access hole
42 and squeezes the cap and body 12 together. In response, the
cap 16 slides further into the base 12 until the barbed portion
48 of the locking member 18 starts to engage a flared lower edge
52 (FIG. 7) of the access hole 42. The outer diameter of the barbed
portion 48 is slightly larger than the inner diameter 44 of the
access hole. The cap 16 stops at this position (not shown) until
the squeezing force is sufficient to deform the barbed portion 48
so that it enters the access hole 42. Once the barbed portion 48
of the locking member 18 enters the access hole 42 of the cap 16
the cap travels quickly to the fully contracted position shown in
FIG. 8. Basically, the locking member 18 snaps into the access hole
42 of the cap 16 allowing the cap to travel downward (further into
the base) until it bottoms out. The rapid movement of the cap 16
when the locking member 18 snaps into place quickly exposes the
tip of the needle 14 through the access hole 42 to prick the user's
finger.
[0027] Moving the cap 16 and base 12 to the contracted position
shown in FIG. 8 sets up the lancet 10 to move to the expanded position
shown in FIG. 9. Note in FIG. 8 that the cantilever springs 26 have
been forced outward by the tapered surface 46 of the cap 16. The
cantilever springs 26 apply a bias or spring force that tends to
move the cap 16 upward relative to the base 12 but that movement
does not start until the user stops squeezing the cap and base together.
Also note that the locking member 18 is now attached to the cap
16 because the barbed structure 48 has expanded outward into the
counterbored area of the access hole 42.
[0028] When the user releases the squeezing force, the lancet 10
moves to the expanded and locked position shown in FIG. 9. The cantilever
springs 26 act on the tapered surface 46 to force the cap 16 outward
relative to the base 12. The outward travel is stopped when the
barbs 38 of the cap 16 contact the upper edges of the undercuts
32 of the base 12. The tip of the needle 14 is once again recessed
and protected below the outer surface 40 of the cap 16. When the
locking member 18 moves upward with the cap 16 the prongs 24 of
the base disengage the relieved areas 50 of the locking member.
disengaged, the prongs 24 straighten out and move below the lower
surface 54 of the locking member 18. This action serves as a latch
to prevent re-use of the lancet 10. The prongs 24 prevent the locking
member 18 and cap 16 from moving back to the contracted position,
thus locking the needle below the upper surface 40 after a single
use.
[0029] The amount of actuation or squeezing force needed to actuate
the lancet is determined by the structure of the barbed portion
48 of the locking member 18 and the interference fit between the
barbed portion and the inner diameter 44 of the access hole 42.
[0030] An alternative blood lancet 70 is shown in FIG. 10. The
lancet 70 is similar in construction and function as the lancet
10 described above, with a few differences. Lancet 70 has a base
72 a cap 74 a needle 76 and a locking member 78.
[0031] The base 72 of lancet 70 includes an outer member 80 and
an inner member 82 that has prongs 84 that lock the locking member
78 and cap 74 in the expanded position after use. The inner member
82 includes a removable cover 86 that can be removed to expose the
needle by breaking it off at an undercut area 88. The needle 76
is thus protected prior to use. The inner member 82 has a circumferential
groove 90 that mates with a matching ridge 92 in the interior of
the outer member 80 to lock the two members together to form the
base 72.
[0032] The lancet 70 has cantilever springs 94 that are internal
to the structure, instead of external as in lancet 10. An inner
surface of the cap 74 provides a tapered surface 96 that deflects
the free ends of the springs 94 inward when the cap and base are
moved together to the contracted position (not shown). The springs
94 of lancet 70 work the same way as the springs 26 of lancet 10
to bias the cap 74 toward the expanded position.
[0033] The lancet 70 has a sliding coupling between the base 72
and cap 74 like lancet 10 but has the barbed portion 98 on the
base 72 and the mating undercuts 100 on the inside surface of the
cap 74. The sliding coupling operates the same way in lancet 70
to limit the outward movement of the cap 74 relative to the base
72.
[0034] Lancet 70 is actuated somewhat differently than lancet 10.
Lancet 70 has grasping wings 102 on the exterior surface of the
cap 74 that allow the user to hold the cap between two fingers and
push on the exposed end 104 of the base 72 with the thumb to expose
the tip of the needle 76. This is somewhat different from the lancet
10 which can be actuated by placing one finger over the hole 42
in the cap 16 the thumb over the rounded end of the base 12 and
squeezing to expose the tip of the needle and prick the finger in
one action. The wings 102 of lancet 70 permit a user to first expose
the tip of the needle and then prick the finger to obtain a blood
sample, thus giving the user a higher degree of control.
[0035] From the above description, it will be apparent that the
invention disclosed herein provides a novel and advantageous single-use,
disposable, blood lancet. The foregoing discussion discloses and
describes merely exemplary methods and embodiments of the present
invention. As will be understood by those familiar with the art,
the invention may be embodied in other specific forms without departing
from the spirit or essential characteristics thereof.
[0036] For example, some features described above operate through
the interaction of complementary structures on two different pieces,
such as the barbs 38 on the cap 18 and the undercuts 32 on the base
12 or the barbed portion 48 of the locking member 18 and the counterbored
region of the access hole 42 of the cap 16 or the cantilever springs
26 of the base and tapered surface 46 of the cap. The same functions
could be performed with different but equivalent embodiments of
the invention by switching the complementary structures between
the two parts. In other words, the base could have barbs that nest
inside and engage undercuts in the cap, instead of the other way
around as shown herein.
[0037] Accordingly, the disclosure of the present invention is
intended to be illustrative, but not limiting, of the scope of the
invention, which is set forth in the following claims. |