WO2006038044A2

WO2006038044A2 - Skin lancing apparatus

Info

Publication number: WO2006038044A2
Application number: PCT/GB2005/050176
Authority: WO
Inventors: Tony Cummings
Original assignee: Owen Mumford Ltd
Priority date: 2004-10-08
Filing date: 2005-10-06
Publication date: 2006-04-13
Also published as: WO2006038044A3

Abstract

A lancet wheel (1) comprising a plurality of radially extending lancets (13) and a lancing device (16) for firing these lancets is provided. The lancet wheel comprises means (2b, 2e) for attaching the wheel to the lancing device so that the wheel is rotatable about its axis, and the device is arranged in use to provide a driving force to the lancet wheel in a direction parallel to the plane of the wheel .

Description

Skin Lancing Apparatus

The present invention relates to skin lancing apparatus and in particular to such apparatus comprising multiple lancets.

In the medical field, it is often required to take small samples of blood from a subject for the purpose of testing or analysing the blood. A common way of achieving this is by using a small needle to pierce the skin at a location where blood vessels are close to the surface. The combination of a needle and its holder is commonly known as a lancet.

Known lancing systems comprise a spring-activated pen-like device to which disposable lancets are attached. The lancets consist of a needle embedded at one end within a plastics holder. A user clips a new lancet onto the end of the pen device and removes a protective plastic cover. The firing mechanism within the pen is then cocked, and the end of the pen placed in contact with the subject's skin and fired, causing the needle to pierce the subject's skin. After use, the lancet is removed from the pen device and disposed of. Lancets are typically provided in packs of 50 or so, packed loosely or stacked in some suitable container.

A known alternative lancing system comprises a separate driving pen and a cartridge of lancets. The cartridge contains lancets stacked side by side or arranged on a carousel mechanism and which may be extracted one at a time using the driving pen. The user must manually introduce the pen to extract a lancet from the cartridge.

Such known systems present users with a number of problems. These include:

• Lancet reuse is relatively easy, whether by design or by accident, creating a risk of contamination and infection. A user may sometimes forget that the pen contains an old lancet instead of a fresh one.

• Each use generates a used lancet which must be disposed of. Disposal may be difficult for a user who is for example travelling.

• It is inconvenient for the user to have to attach and detach a lancet from the firing device for each pricking operation. US6,616,616 describes a lancet system comprising a plurality of lancets and a transport unit for moving the lancets in turn to a withdrawal or lancing location. A drive unit is provided for driving a lancet in the withdrawal position so as to prick the skin of a subject.

US Patent No. 4,794,926 discloses a lancing system for drawing blood samples from a subject which includes upper and lower housings for containing a "wheel" of lancets, each spoke of the wheel having a downward-pointing needle tip for breaking the skin of the patient. Each spoke is fixed only at the centre of the wheel and can flex up and down at its free end. The wheel is rotated such that the lancets are brought in turn to a lancing position where each lancet is raised up a ramp and, when a trigger is activated, the lancet comes off the ramp under its own spring motion, the needle tip protruding from the bottom surface of the lower housing to penetrate the subject's skin. A disadvantage of this system is that the spring force applied to each lancet may not be sufficient to penetrate the subject's skin, resulting in the need to use another lancet in the wheel.

It is an objective of the present invention to overcome the disadvantages of the skin lancing systems described above. In particular, it is an object of the present invention to provide a system having a large number of lancets which are moved automatically into and out of a firing position. It is also an object of the present invention to provide a skin lancing system which can generate enough force to ensure skin penetration.

In accordance with a first aspect of the present invention, there is provided a lancet wheel comprising a plurality of radially extending needles suitable for piercing tissue when the wheel is moved in the plane of the wheel, and means for attaching the wheel to a lancing device so that the wheel is rotatable about its axis.

The needles may project from a single moulded plastics part. The single moulded plastics part may comprise a plurality of fingers with the needles embedded in the respective ends thereof. Each of the fingers may be flexible. A compressible feature for encasing the radially extending needle may be disposed at the end of each finger. There may be a finger which does not have a needle embedded therein. The fingers may be spaced at equiangular separations. The ends of the fingers may be tapered.

A central portion of the lancet wheel may comprise a clutch surface for aligning lancets in conjunction with a lancing device and for preventing unnecessary rotation of the lancet wheel with respect to the lancing device. The clutch surface may comprise a substantially continuous ring of radially extending grooves coaxial with the axis of the wheel, the angular separation of the grooves corresponding to the angular separation of the fingers in the lancet wheel.

The lancet wheel may comprise drive engagement means comprising a substantially continuous ring of axially extending grooves coaxial with the axis of the wheel, the angular separation of the grooves corresponding to the angular separation of the fingers in the lancet wheel. The ring of grooves on the drive engagement means may comprise a portion where no groove is provided.

The lancet wheel may have upper and lower surfaces, wherein the clutch surface and drive engagement means are disposed upon the lower surface of the lancet wheel.

The lancet wheel may further comprise a releasable attachment mechanism for attaching the lancet wheel to a lancet firing device. The lancet wheel may have upper and lower surfaces and a passage through its centre for receiving a spindle of a lancet firing device, wherein the releasable attachment mechanism comprises a support adjacent the passage projecting upwards from the upper surface of the wheel, the upper end of the support being capable of flexing toward and away from the wheel axis, and the releasable attachment mechanism further comprising an arm extending from the upper end of the flexible support so as to intersect with the axis of the wheel, the arm having a slot formed therein for receiving a wheel-mounting spindle of a lancet firing device.

The lancet wheel may further comprise a wheel cover arrangement arranged in a non- use position to cover the ends of the lancets in the lancet wheel, and in a use position to be partially raised to expose the ends of the lancets in the lancet wheel. The wheel cover arrangement may comprise an outer ring and an inner ring connected to the outer ring by a plurality of radially extending flexible members, the cover arrangement being attached to the wheel at the inner ring, and the outer ring extending downwards to cover the ends of the lancets in the non-use position. The outer ring may further comprise a plurality of lateral tabs arranged such that, in use, an application of upward force to the lateral tabs causes the flexible members to bend upwards at their outer extent, thereby raising the outer ring away from the lancets of the lancet wheel.

In accordance with a second aspect of the present invention, there is provided a device for firing lancets suitable for piercing tissue, comprising a housing and a mounting means disposed within the housing for mounting a lancet wheel, the device further comprising driving means for driving the lancet wheel in a direction parallel to the plane of the wheel.

The mounting means may comprise a carriage which is slidably fixed within the housing. The housing may comprise a track within which the carriage is slidably fixed. The carriage may comprise a wheel-mounting spindle projecting from the carriage for receiving a lancet wheel, the spindle having an annular wheel-locking groove formed therein.

The device may further comprise a rib arranged in use to cooperate with a drive engagement means of a lancet wheel to rotate the lancet wheel into a subsequent lancet position during motion of the carriage within the device. The rib may be disposed upon the housing and extend in a direction parallel to the direction of motion of the carriage.

The carriage may comprise a clutch surface complimentary to a clutch surface provided on a lower surface of a lancet wheel for aligning lancets and for preventing unnecessary rotation of the lancet wheel with respect to the lancing device. The clutch surface may comprise a substantially continuous ring of radially extending grooves coaxial with the axis of a lancet wheel, the angular separation of the grooves corresponding to the angular separation of the lancets in the lancet wheel.

The driving means may comprise a firing spring for imparting a firing force to the carriage, disposed between the carriage and a reaction plate. The device may comprise at least one firing button, wherein the firing spring, when compressed, is releasable by the firing button.

The driving means may further comprise a cocking mechanism for loading the firing spring. The device may comprise a cocking button, wherein the cocking mechanism comprises a cocking spring disposed between the reaction plate and the cocking button. The device may further comprise means for releaseably connecting the cocking button to the carriage upon depression of the cocking button, the carriage further comprising a rearward-projecting flexible leg member with a laterally-projecting snap member formed thereupon arranged such that when the carriage is in a retracted position, the snap member is disposed adjacent the firing button, the flexible leg member is ramped against an inclined surface at a rear end of the device, and the cocking button is released from the carriage.

The device may further comprise stop means formed integrally with the housing and disposed such that the stop means opposes relative motion of the carriage and the housing when the carriage is in the retracted position through contact with the snap member. The firing button may further comprise an inwardly-facing catch arranged such that depression of the firing button causes separation of the snap member and the stop means, allowing the firing spring to drive the lancet wheel into a firing position.

The device may further comprise ramp members disposed at a forward end of the device, arranged such that, in use, the two lancets of a lancet wheel adjacent the forwardmost lancet are biased away from the front of the device when the lancet wheel is in a firing position.

The housing may comprise an aperture through which the lancet wheel may be inserted into the device, the aperture having a lid for closing the aperture.

The device may further comprise depth adjustment means for varying the location of the firing position of the carriage. In accordance with a third aspect of the present invention, there is provided a lancet firing device in accordance with the second aspect of the invention in conjunction with a lancet wheel in accordance with the first aspect of the invention.

In accordance with a fourth aspect of the invention, there is provided a method of piercing skin, comprising mounting a lancet wheel into a lancet firing device, the lancet wheel comprising a plurality of radially extending lancets, the tips of the lancets extending radially outwards in the plane of the wheel; driving the lancet wheel in a direction perpendicular to its axis; and rotating the lancet wheel to the next lancet position.

According to a fifth aspect of the present invention there is provided a skin pricking apparatus comprising a lancet carousel holding a multiplicity of lancets arranged circumferentially around the centre of the carousel, the lancets being disposed with their needle tips pointing in an axial direction, and a firing device within which the lancet carousel is mounted for rotation about its axis, the firing device comprising: a lancet firing mechanism including a finger actuable trigger for causing a driving force to be applied to a lancet located in a lancet firing position; and indexing means coupled to said trigger for applying a substantially tangential force to the carousel upon activation of said trigger, so as to rotate the carousel to a subsequent firing position.

Preferably, the trigger and the indexing means are arranged to move in the same or substantially parallel planes.

Preferably, the carousel comprises a cog disposed coaxially with the axis of rotation of the carousel within the device. The teeth of the cog have the same angular pitch as the lancets. Said indexing means is arranged to engage an aligned tooth of the cog upon each activation of the firing mechanism.

Preferably, the indexing means is pivotable about a pivot point, the device comprising means for deflecting the indexing means out of engagement with the carousel and return means for returning the indexing means back into engagement with the carousel. Where the carousel comprises a cog for facilitating indexing, the arrangement is such that the indexing means engages a tooth of the cog in one direction of travel and is deflected substantially out of engagement in the reverse direction of travel.

According to a sixth aspect of the present invention there is provided a skin pricking apparatus comprising a lancet carousel holding a multiplicity of lancets arranged circumferentially around the centre of the carousel, the lancets being disposed with their needle tips pointing in an axial direction, and a firing device within which the lancet carousel is mounted for rotation about its axis, the firing device comprising: a casing; a hammer pivotally attached to the casing and biasing means for biasing the hammer into engagement with a lancet located in a firing position so as to drive the lancet to a lancing position; a lever pivotally attached to the casing and moveable about its pivot point to rotate the hammer against the biasing means to a cocked position, the lever and the hammer being rotatable in substantially the same plane or in substantially parallel planes; and release means for facilitating disengagement of the lever from the hammer in the cocked position.

Opposing surfaces of the hammer and the lever are preferably shaped such that the lever is in blocking engagement with the hammer over a part of its rotational travel, from a resting position to a position in which the hammer is cocked, and such that the members disengage upon further rotational travel of the lever in the same direction, thereby providing said release means.

Preferably, the pivot point of the hammer is located radially inside the pivot point of the lever, with respect to the centre of the carousel.

The apparatus may further comprise indexing means pivotally attached to said lever for applying a substantially tangential force to the carousel upon rotation of the lever, so as to rotate the carousel to the next firing position. The indexing means is moveable in substantially the same plane as the hammer and the lever or in a plane substantially parallel thereto.

According to a seventh aspect of the present invention there is provided a skin pricking apparatus comprising a lancet carousel holding a multiplicity of lancets arranged circumferentially around the centre of the carousel, the lancets being disposed with their needle tips pointing in an axial direction, and a firing device within which the lancet carousel is mounted for rotation about its axis so as to move lancets into and out of a firing position, the firing device comprising: a casing; a hammer pivotally attached to the casing and biasing means for biasing the hammer; cocking means for moving the hammer to a cocked position against the action of said biasing means; release means for releasing the hammer from the cocked position so as to allow the biasing means to drive the hammer into engagement with a lancet located in a firing position; and the hammer comprising latch means for latching the hammer to the engaged lancet, whereby the lancet once driven out of the carousel to a lancing position is withdrawn by return of the hammer towards the cocked position.

According to an eighth aspect of the present invention there is provided a skin pricking apparatus comprising: a lancet carousel holding a multiplicity of lancets arranged circumferentially around the centre of the carousel, the lancets being disposed with their needle tips pointing in an axial direction, each lancet comprising spring biasing means for biasing the needle tips towards a position in which they project from the carousel, and locking means associated with each lancet for releaseably locking a biasing means in its compressed state; a firing device within which the lancet carousel is mounted for rotation about its axis, the firing device comprising a finger actuable trigger for engaging the locking means of a lancet located in a firing position to release the biasing means of that lancet causing the needle tip to be driven to a lancet firing position; and indexing means for rotating the carousel to the next firing position following firing.

For a better understanding of the present invention and in order to show how the same may be carried into effect reference will now be made by way of example to the accompanying drawings in which:

Figure 1 illustrates a lancet wheel and cover (detached) in accordance with an embodiment of the present invention;

Figures 2a and 2b are plan views of the lancet wheel of Figure 1;

Figures 3a and 3b are cross-sections through the lancets of the lancet wheel of Figure 1; Figure 4 illustrates the lancet wheel of Figure 1 with its cover attached and flexed upwards;

Figure 5 illustrates the underside of the lancet wheel of Figure 1;

Figure 6 is a perspective view of a lancet firing device for use with the lancet wheel of

Figure 1; Figure 7 is a perspective view of the internal components of the device of Figure 6;

Figure 8 is a cross-section through the lancet device illustrated in Figure 7;

Figure 9 is a cross-section of the lancet wheel of Figure 1 mounted upon the device of

Figure 6;

Figure 10 is a close-up cross-section of a firing mechanism of the device of Figure 6; Figure 11 is a plan view cross-section of the lancet firing device of Figure 6 with its upper casing removed and the lancet wheel of Figure 1 attached;

Figure 12 is a side-view cross-section of the lancet wheel of Figure 1 and the firing device of Figure 6;

Figures 13 to 19 illustrate the firing mechanism of the device of Figure 6; and Figures 20 to 22 illustrate a depth adjustment mechanism of the device of Figure 6 in accordance with a further embodiment of the present invention.

Figure 23 shows a perspective view of a lancing device according to an embodiment of the present invention;

Figure 24 shows a perspective view of an internal firing mechanism of the device of Figure 23;

Figure 25 shows a perspective view of a multi-lancet carousel for insertion into the device of Figure 23; Figure 26 shows the device of Figure 23 with the outer housing removed and the carousel of Figure 25 inserted;

Figure 27 is an axial cross-sectional perspective view of the arrangement of Figure 26 in a first operational configuration; Figure 28 is an axial cross-sectional perspective view of the arrangement of Figure 26 in a second operational configuration;

Figure 29 is an axial cross-sectional perspective view of the arrangement of Figure 26 in a third operational configuration;

Figure 30 is an axial cross-sectional perspective view of the arrangement of Figure 26 in a fourth operational configuration;

Figure 31 shows a perspective view of an alternative internal firing mechanism of the device of Figure 23;

Figure 32 shows a perspective view, in partial cut-away and exploded views, of a multi- lancet carousel for use with a device comprising the firing mechanism of Figure 31; Figure 33 shows a detail of the carousel of Figure 32;

Figure 34a shows a reverse side view of the firing mechanism of Figure 31, with the carousel in place;

Figure 34b is an axial cross-sectional perspective view of the firing mechanism of

Figure 31 with the carousel of Figure 33 inserted, in a first operational configuration; Figure 35 shows the arrangement of Figure 34 in a second operational configuration;

Figure 36 shows the arrangement of Figure 34 in a third operational configuration;

Figure 37 shows the arrangement of Figure 34 in a fourth operational configuration;

Figure 38 shows a detail of the arrangement in the fourth configuration;

Figures 39 to 41 show sequential details of the arrangement during a release phase; Figure 42 shows a perspective view of a multi-use lancing device according to a further embodiment of the invention;

Figure 43 shows a perspective view of an internal firing mechanism of the device of

Figure 32;

Figure 44 shows a perspective view of a multi-lancet carousel for use with the device of Figure 42, in both partial cut-away and exploded views;

Figures 45 to 47 illustrate the construction of a lancet mounting tube of the carousel of

Figure 42;

Figure 48 illustrates in detail a lancet of the carousel of Figure 42; Figure 49 illustrates axial cross-section and exploded views of the multi-use lancing device with carousel;

Figure 50 shows the device of Figure 42 with the carousel inserted, in a first operational configuration; Figure 51 shows the arrangement of Figure 50 in a second operational configuration;

Figure 52 shows a detail of the carousel in the second configuration with a needle protecting foam cover in a compressed state;

Figure 53 shows the arrangement of Figure 50 in a third operational configuration;

Figure 54 shows the arrangement of Figure 50 in a fourth operational configuration; Figure 55 illustrates a detail of an alternative lancet construction with a needle protecting cover in a compressed state;

Figures 56 and 57 illustrate a user removable seal for sealing the lancet carousel of

Figure 44;

Figure 58 shows a further user removable seal for the carousel of Figure 44; and Figure 59 illustrates a modification to the firing and indexing mechanism of Figure 43.

The embodiment described below comprises two main parts: a disposable lancet wheel which comprises a number of radially-projecting lancets, and a multi-use device into which the lancet wheel is placed. The device has a mechanism for cocking and firing the lancet wheel, and for rotating the lancet wheel around to the next position after each use. After all of the lancets have been used, or at any time when only some of the lancets have been used, the lancet wheel may be safely removed from the device and the wheel disposed of. The device provides a convenient and safe delivery mechanism for the lancets.

Figure 1 illustrates the lancet wheel 1 and a wheel cover 2. The lancet wheel 1 comprises a single moulded plastics part providing a central disc-shaped portion 3 through which a central mounting hole 3 a is provided. A cylindrical collar 4 is disposed around the central hole 3a on the upper side of the lancet wheel. The cylindrical collar 4 has two vertical slots 4a, 4b formed therein to isolate a support 5. The support 5 can flex slightly towards and away from the central axis of the wheel. At the upper end of the support 5 there is an inward-projecting arm 6 which projects into the area above the central hole 3a within the collar 4. The arm 6 has a slot 7 formed within it. The slot 7 is irregularly shaped such that the diameter of the aperture presented by the slot to the area above the central hole 3 a increases when the support 5 is pushed towards the axis of the wheel. The shape of the slot is illustrated in Figure 2a, with diameter X above the axis of the wheel. Figure 2b show the support 5 moved in slightly, with diameter Y (Y>X) above the axis of the wheel. The arm 6 cooperates with a lancet firing device to form a clutch spring 15 which acts to bias the wheel downwards when in use.

A plurality of equally-spaced lancet fingers 8 project radially from the periphery of the central disc portion 3. There are a large number of lancet fingers, approximately forty. A needle 13 is embedded in the end of each lancet finger 8 and projects therefrom. The needle 13 is the portion of the wheel used to penetrate the subject's skin. One of the lancet fingers 9 acts as a blank and has no needle embedded therein. The blank lancet finger can be used as an indicator to show how many lancets have been used. Each needle 13 is covered by a compressible feature 14. This feature may be made from, for example, foam, rubber or a thermoplastic elastomer (TPE) material. The foam may be a closed cell foam in order to keep the needles sterile before use and encased after use to prevent contamination.

Figures 3a and 3b illustrate possible arrangements of the compressible feature 14. In Figure 3a, the compressible feature takes the form of a "bellows" which comprises a solid tube of compressible material surrounding the needle. When this material is compressed to expose the needle, it expands radially outward from the needle axis.

Alternatively, Figure 3b shows a "thin sheaf type compressible feature which comprises a narrow tube section of compressible material which closely surrounds the length of the needle and a larger end portion at the needle tip. Upon compression of the thin sheaf feature, the narrow tube section crumples along its length and does not result in any significant lateral expansion of compressible material.

The lancet wheel cover 2 is formed from a single moulded plastics part and is circular in cross-section, being shaped so as to cover the upper surface and circumference of the lancet wheel 1, including the needles 13. Figure 4 shows the wheel cover 2 in situ upon the lancet wheel 1 with the periphery of the cover flexed upwards (see below). The cover comprises an outer ring 2a which covers the needles to prevent the user accidentally touching the needles, and an inner ring 2b which provides a central aperture 2e that corresponds to the cylindrical collar 4 of the lancet wheel. The inner ring and outer ring are connected by flexible members 2c which can flex in an upward direction to expose the needle ends of the lancet fingers. The cover is also provided with two tabs 2d upon the outer ring. Application of an upward force (by elements formed on a mounting carriage of a firing device - see below) to the tabs 2d causes upward flexure of the outer ring. In the Figures referred to below when describing the lancet firing device and which show the lancet wheel, the wheel cover is omitted for clarity. The elements which cause the cover to flex upwards are also omitted.

Considering the underside of the lancet wheel 1, illustrated in Figure 5, a first clutch member 10 is provided beneath the cylindrical collar 4 and comprises a ring of v-shaped grooves, the grooves extending radially outwards from the centre of the lancet wheel 1. Arranged concentrically about the first clutch member 10 is an indexer 11 which comprises a further ring of v-shaped grooves, differing from the first clutch member 10 in that the direction of the grooves is axial. The indexer 11 is provided with an indexer stop 12 which comprises a portion of the indexer 11 having no groove. The position of the indexer stop 12 is located at a fixed angular displacement from the lancet blank 9 which has no needle embedded therein. The angular separation of the grooves on the first clutch member 10 and on the indexer 11 corresponds to the angular separation of the lancet fingers 8 on the lancet wheel 1.

The lancet firing device 16 is illustrated in Figure 6 and comprises a teardrop-shaped body formed from upper and lower housings 17a and 17b. The front end of the firing device has a small indent 16a for receiving a fingertip for lancing. A substantially circular aperture 16b is formed towards the front end of the upper housing and is closable using a transparent lid 16c pivoted at its rear end to a point on the upper housing 17a. The circular aperture is shaped so as to receive a lancet wheel.

The internal components of the lancet firing device 16 will now be described with reference to Figure 7, which illustrates the device with an upper housing section, including the lid, removed. The device 16 comprises the lower teardrop-shaped housing 17b and a peripheral side wall 18 formed from a single moulded piece of plastics. Disposed towards the larger, forward, end of the teardrop-shaped lower housing 17b is a carriage 19 for supporting and moving the lancet wheel, the carriage being aligned with the longitudinal axis of the housing. The carriage is mounted on a pair of rails 40 moulded integrally with the lower housing 17b. The rails and the mounting of the carriage thereon is best illustrated in Figure 8 which shows a cross-sectional view of the device which is transverse with respect to the direction of the rails. Lower features of the carriage snap into the rails to prevent removal of the carriage.

The carriage comprises a cylindrical, wheel-mounting spindle 20, fixed to and projecting from the upper surface of the carriage 19. The wheel-mounting spindle 20 is shaped so as to be received by the central hole of a lancet wheel 1 as will be described below. An annular groove 20a is formed in the upper end of the wheel-mounting spindle 20 for receiving the slot 7 of the arm 6 of the lancet wheel 1, as illustrated in Figure 9.

Disposed around the base of the wheel-mounting spindle 20, on the upper surface of the carriage, is a second clutch member 21 which comprises a ring of v-shaped grooves, the grooves projecting radially outwards from the wheel-mounting spindle 20. The number and shape of the grooves in the second clutch member are such that they are complimentary to those on the first clutch member 10 of the lancet wheel 1, the two clutch members together forming a clutch mechanism.

A needle exit point 22 is provided at the forward end of the housing within the side wall, in line with a firing end of the carriage 19, and within the finger indent 16a. The inner surface of the exit point 22 is provided with two opposing ramps 23 which provide sloping surfaces forming a v-shape pointing towards the inner portion of the housing. There is a gap between the two ramps 23 at the apex of the v-shape to allow the end of a single lancet finger through the gap to the exit point 22.

A cutaway 17c is formed at a rear end of the housing to provide access for a cocking button 24 which is mounted within the rear end of the housing. The cocking button 24 is arranged to move slidably in line with the longitudinal axis of the housing. The cocking button is hollow and open at its inward-facing end. The leading edge of the cocking button 24 comprises two small catches 24a, 24b which extend sideways, slightly wider than the cocking button itself. A cocking button spring 25 is mounted within the cocking button 24 at one end, projecting into the device. The cocking button spring 25 is a relatively strong spring. The other end of the cocking button spring 25 is attached to one side of a fixed plate 26 which is formed upon the device housing.

A firing spring 27 is attached at one end to the other side of the fixed plate 26 and is a weaker spring than the cocking button spring 25. The axes of both springs are aligned with the longitudinal axis of the lancet firing device. The other end of the firing spring 27 is attached to a plate 28 which is an integral part of the carriage 19 and is moveable therewith. Two firing buttons 29 are provided towards the same end of the device as the cocking button, disposed one to each side of the device. The firing buttons 29 are overmoulded with TPE material 30 which protrudes onto the inner surface of the buttons. The inner portion of the TPE material 30 is used to apply a light force to the firing buttons to keep them in place. As the firing buttons are pressed, the TPE is compressed against and acts as a return spring after release to force the firing buttons back out to their normal position. The arrangement of the firing button overmould is illustrated in Figure 10. The firing buttons are provided with small firing button catches 29a on their internal surfaces.

An indexer rib 37, which may be formed as part of the lower housing 17b is disposed on the upper surface of the lower housing 17b adjacent the moveable plate 28. The indexer rib 37 is fixed in place and comprises a tapered piece of plastic running parallel to the longitudinal axis of the device.

The remainder of the structure of the lancet firing device will now be described with reference to Figure 11. Disposed either side of the cocking button 24 on the internal surface of the device are two opposed v-shaped ramps 31 which each have one surface running parallel to an internal edge of the cocking button 24 and a sloping surface running back to the side wall of the device.

Disposed towards the rear end of the carriage 19 are two pairs of rearwardly-projecting legs which run parallel to the longitudinal axis of the device. Both pairs of legs are formed from moulded plastics and form part of the carriage 19. The first, inner, pair of legs 32 run either side of and parallel to the cocking button 24. At the far end of the inner legs 32 are latches 33. The latches 33 provide sloped surfaces that run parallel to the corresponding respective sloping surfaces of the ramps 31. The second, outer, pair of legs 34 also run parallel to the cocking button but are disposed at a wider separation. Each of the outer legs 34 is flexible about its point of attachment to the carriage 19. Each of the outer legs 34 has a snap member 35 which has a sloping outwardly facing surface with a lip formed therein. A pair of stops 36 are formed integrally with the housing and are shaped to allow the sloping surfaces of the snap members 35 to ride over them as the carriage is pulled to a cocking position (see below) until the lips are snapped inwardly to lock the carriage in a cocked position.

For ease of reference, a summary of the reference numerals used to describe aspects of the certain of the embodiments is provided in Table 1 below.

The details of the loading and operation of the lancet firing device will now be described. The lancet firing device 16 is initially empty, i.e. a lancet wheel 1 has not been loaded within the device. The lancet wheel 1 is loaded into the lancet firing device when the carriage is in a "resting position". The wheel must be correctly aligned with respect to the device, and this may be achieved by aligning a mark on the wheel (e.g. one of the lancet fingers is coloured or distinctively shaped) to a feature on the device. Alternatively features on the protective case and the casing may provide for alignment for the wheel. This ensures that all of the lancets are used before the device prevents further firing.

The cylindrical collar 4 of the lancet wheel is aligned with the wheel-mounting spindle 20 and the lancet wheel lowered thereupon. The diameter X of the slot 5d corresponds to the external diameter of the annular groove 20a and is less than the diameter of the upper end of the spindle. The user therefore has to squeeze the support 5 towards the axis of the wheel, thereby presenting diameter Y of the slot to the upper end of the spindle. Since diameter Y is larger than that of the upper end of the spindle, the wheel can then be lowered. The user then releases the support 5 which flexes back out, and the slot 5d then rests securely around the annular groove 20a in the spindle with the wheel and carriage locked securely together. Upon any subsequent upward motion of the wheel with respect to the carriage, the arm 6 is held in place with respect to the spindle by the annular groove whilst the support 5 of the wheel is flexed, providing a resultant downward force which biases the wheel back down onto the carriage. This is shown in the cross-sectional view of Figure 12, in which the arm 6 is held in place against the spindle and the support is flexed.

During loading of the lancet wheel, the first clutch member 10 mates with the second clutch member 21. The two clutch members lock together to form a clutch mechanism which prevents the wheel from rotating freely within the device. The clutch mechanism also aligns the lancet fingers with the needle exit point. The two tabs 2d on the wheel cover are pushed upwards by engagement with complimentary features provided on the carriage (see Figure 4), thereby flexing the outer ring 2a of the wheel cover 2 upwards and exposing the lancet needles 13 as described above. The lid of the device is then closed and it is ready for use.

The lancing process consists of two separate actions. Firstly the device is "cocked", which involves rotating the carriage round so that the next needle to be used is aligned with the needle exit point, and loading the firing spring. Secondly, the device is fired such that the carriage is driven forwards and the needle is exposed at the needle exit point, the carriage then retracting and pulling the exposed needle back into the device housing.

The cocking process involves the user pressing in the cocking button 24, which compresses the cocking button spring 25 against the fixed plate 26. At the forwardmost point of the cocking button's motion, i.e. when the cocking button spring 25 is compressed, the cocking button catches 24a, 24b ride up along the latches 33 on the inner legs, forcing them out slightly. When the leading edge of the cocking button has passed the latches 33, the inner legs move back into their original position. This configuration is shown in Figure 15. When released by the user, the cocking button spring expands under its own restoring force against the fixed plate 26, returning the cocking button to its outer position as shown in Figure 16. Since the cocking button catches are biased against the catches 33 on the inner legs, the carriage is drawn backwards with the cocking button. As the carriage is drawn backwards, the sloped surfaces of the snap members 35 slide against and past the sloped surfaces of the stop means 36. The outer legs are flexible about their point of attachment to the carriage, and bend in, away from their usual position as they are biased against the stop means, moving back out to their original position once they have passed the stop means.

As the cocking button 24 returns to its original outer position, the latches 33 at the ends of the inner legs are biased against and slide along the cocking button ramps 31 as they are forced outwards. This position is illustrated in Figure 17. In doing so, the carriage is released from the cocking button catches. The process of drawing the carriage 19 back compresses the firing spring 27 against the fixed plate 26.

During this withdrawal of the carriage, the grooved indexer 11 on the lancet wheel comes into contact with the tapered edge of the indexer rib 37 formed in the housing. This contact begins to push the lancet wheel 1 around to the next lancet position. The first clutch member 10 of the wheel is rotated by this action towards the next groove position. The rotation of the first clutch member against the second clutch member 21 of the carriage 19 causes the lancet wheel 1 to ride upwards relative to the carriage against the action of the clutch spring 15 which is effectively locked to the carriage, freeing the lancet wheel to rotate. The force exerted by the arm pushes the lancet wheel downward after the apex of the groove has been overcome, closing the two clutch members together in the next position. The next lancet finger is then aligned with the exit point.

When the carriage 19 is fully detached from the cocking button 24, the carriage begins to move forward under the restoring force of the firing spring 27. However, as the carriage moves forward, the lips of the snap members 35 meet the right-angled leading edges of the stop means 36, locking the carriage in place. The position of the carriage 19 at this point is described as the "cocked" position and is illustrated in Figure 18. The device is now ready to be fired. Simultaneous depression of the firing buttons 29 (resulting in compression of the TPE overmoulding) causes the firing button catches 29a, 29b to come into contact with the outer protrusion snap members 35 that are biased against the two stop means 36. The firing button catches 29a, 29b force the outer protrusion snap members 35 away from the stop means 26. The firing spring is then able to expand, its expansion forcing the plate 28 and therefore the carriage 19 forwards. The forwardmost lancet finger 6 is in line with the needle exit point and as the finger approaches the needle cover, feature 14 comes into contact with the inner side of the casing at the needle exit point. Since the needle cover feature is compressible, the forward motion of the lancet finger causes the material to be compressed, thereby exposing the needle 13 as illustrated in Figures 3a and 3b. The two lancet fingers adjacent the forwardmost lancet are flexed away from the forwardmost lancet by the two ramps 23, ensuring adequate clearance room for the lancet being fired. The carriage 19 continues its forward motion under expansion of the firing spring 27 until further motion is prevented by the carriage coming into contact with a carriage stop 19a formed upon the base of the housing, at which point the needle protrudes from the device, lancing the subject as it does so. This position is shown in Figure 19.

At this point, the spring is overextended and will begin to contract, pulling the carriage and wheel with it. The needle is consequently withdrawn back into the device. The device is then ready to be cocked and fired again, as described above.

Once all of the lancets have been fired, the indexer stop 12 in the indexer stops the wheel rotating any further because there is no indexer groove for the indexer rib 37 to push round. The blank indicator lancet will be in the forwardmost position so that any re-cocking and firing will not result in a lancet protruding from the device. The user will then appreciate that the wheel must be changed. The blank indicator lancet finger 9 can be made shorter (or, for example, distinctively coloured) than the other lancet fingers in order to emphasise that it does not contain a needle. To remove a used lancet, the lid is opened. The device may include a mechanism for locking the device when the lid is opened, to prevent accidental firing. The user can then remove the wheel from the firing device by squeezing in the support 5 such that the wider portion of the slot 7 is aligned with the upper end of the wheel-mounting spindle 20 and lifting the wheel up off the spindle. As the wheel is removed, the outer ring 2a of the wheel cover falls back into place since the upward force on the tabs 2d has been removed, thereby covering the needles and permitting safe disposal of the used lancet wheel.

A modification of the above embodiments is illustrated in Figures 20 to 22, which show a mechanism for adjusting the depth to which the lancet tips penetrate the skin. This is achieved by varying the position of the mechanical stop 19a on the device housing. Figure 20 shows a depth adjustment button 38 on the underside of the device 16. The depth adjustment button 38 causes an indexed stepped block 39 to be moved into one of a plurality of available positions, each position adjusting the furthest forward position that the carriage can reach. Figures 21 and 22 show the two extrema of the depth adjustments provided by the depth adjustment button 38. In Figure 21, the forward position of the carriage is further away from the exit point 22 than in Figure 22. Once the device incorporating this feature is cocked and fired, the carriage hits the block 39 and, since the tip of the lancet is of a fixed length, more of the lancet tip will be exposed in the embodiment of Figure 21 than in the embodiment of Figure 22, thereby providing different levels of skin penetration by the needle tip.

In summary, the sequence of steps used to operate the lancet firing device described above is as follows:

(a) The lid of the lancet firing device is opened;

(b) The lancet wheel is inserted into the firing device;

(c) The lid of the firing device is closed; (d) The device is cocked by pressing the cocking button;

(e) The finger to be lanced is held over the needle exit point and the firing buttons pressed;

(f) The device is re-cocked and fired as necessary until all of the lancets have been used; (g) The lid of the device is opened; and

(h) The lancet wheel is removed and disposed of. It will be appreciated by the person skilled in the art that various modifications may be made to the above embodiment without departing from the scope of the present invention as set out in the accompanying claims. For example, the embodiment described above comprises a resilient latch formed on the lancet wheel and which co- operates with the carriage spindle to allow axial movement of the wheel relative to the carriage (for the purpose of engaging and disengaging the clutch mechanism during rotation of the wheel). In an alternative embodiment, a resilient or sprung member may be formed on the carriage, e.g. as a part of the spindle, to provide for axial movement of the wheel. In such an arrangement, the spindle may be inserted through a hole in the centre of the wheel, with the spindle having a rotatable head which can be moved, following insertion of the spindle into the hole, to lock and unlock the wheel to and from the device.

There is illustrated in Figure 23 a reuseable lancing device 1 ' which is formed generally of moulded plastics parts. These include an outer housing 2' of generally cylindrical shape having a base, and a lid 3' attached to the housing at one edge by a hinge to facilitate access to the inside of the housing by opening the lid. Formed in the lid 3' is a depressed region 4' having a centrally located hole 5' passing therethrough. A button or trigger 6' projects through a slot 7' formed in the side of the housing 2', and forms part of a firing mechanism which is described further below. In Figure 23, a resting position of the button 6 is shown in solid lines and is indicated by reference "A". An intermediate position is shown in dashed lines and is indicated by reference "B". This represents a cocked position of the device. A fired position of the device is also shown in dashed lines and is indicated by reference "C".

In the following description of the device, reference will be made to Figures 24 to 30. For ease of understanding, the elements shown in these Figures are upside down with respect to Figure 23. Reference to pressing or depressing the button therefore represents upward movement of the button in these Figures.

Figure 24 illustrates an internal firing mechanism 8' of the device of Figure 23. This mechanism fits snugly within the outer housing 2', and indeed certain components of the firing mechanism may be formed integrally with the housing. The mechanism comprises a rectangular reaction plate 9', which is fixed to the housing 2', the plate having a cylindrical spindle 10' projecting outwardly therefrom. A generally L-shaped hammer 11' having a head 12' is mounted on the spindle 10' so that it can rotate thereabout. The spindle 10' also supports a torsion spring 13', the projecting leaves of which are biased against a first stop 14' which projects from the plate 9' and a second stop 15' which projects from the hammer 11'. This arrangement is such that the spring 13' biases the head 12' of the hammer in a downward direction with respect to Figure 24.

The button 6' is generally L-shaped in vertical cross-section, with a fixing plate 16' extending upwardly from the end of the button. The fixing plate 16' is mounted with respect to the reaction plate 9' on a spindle 17' so as to allow the button to rotate about the spindle. The opening 18' in the fixing plate through which the spindle 17' extends is generally oval in cross-section. A coil spring 19' extends between the fixing plate 16 and a projection from the reaction plate 9', tending to rotate the button 6' clockwise about the spindle 17' as viewed in Figure 24. In the resting position, the spindle 17' tends to rest against the lower end surface of the opening 18', again as viewed in Figure 24.

The upper end of the fixing plate 16' is shaped to provide a first flat cam surfaces 20' for engagement with an end of the hammer opposed to the head end. An arcuate return surface 22' is contiguous with the cam surfaces 20'.

Figure 25 illustrates a lancet carousel 23' (with partial cut-away) suitable for use with the device of Figures 23 and 24. The carousel 23' comprises a generally cylindrical casing 24' with a series of axially aligned lancet mounting tubes 25' disposed around its periphery, within the casing. The tubes are equally spaced from one another. At their lower ends, the tubes 25' have a small circular opening to the exterior of the casing (these openings are not visible in Figure 25). At their upper ends, the tubes 25' have a larger cut-away opening 26' to the exterior of the casing 24'. A lancet 27' is mounted within each of the tubes, and comprises an enlarged plastics head 28', cylindrical in shape. A needle 29' is embedded in the head such that its sharpened tip points away from the head. Each lancet 27' is oriented such that the base 30' of the enlarged head 28'is exposed through the upper cut-away openings 26' of the tubes, and the needle points toward, and is aligned axially with, the corresponding lower circular opening in its mounting tube. Each lancet needle 29' is surrounded by a coil spring 31' which acts against the enlarged head 28' to bias the lancet upwards and prevent movement of the lancet within the tube prior to firing.

An alignment spindle 32' projects from the top of the carousel 23' (as viewed in Figure 25) and is designed to mate with a circular recess formed in the housing 2'. An alignment "cog" 33' extends around the base of the spindle 32'. A number of "pips" (not shown) is provided in a circular arrangement around the base of the casing 24'. These mate with respective dimples formed on the underside of the lid 3' of the housing. These serve to align the carousel relative to the housing, whilst still allowing the carousel to rotate within the housing.

A first stage in the operation of the device of Figure 23 is the cocking of the firing mechanism. This involves loading the torsion spring to bias the hammer to a raised position. With reference to Figure 23, a user places the pad of his or her finger into the depression 4' formed in the lid 3', and depresses the button 6'. Figure 26 illustrates the configuration of the firing mechanism, with the carousel 23' loaded, after the button 6' has been depressed to some extent causing compression of the spring 19'. The pressure exerted on the button 6' tends to maintain the spindle 17' in contact with the lower surface of the opening 18'. In the Figure, the button 6' has been rotated sufficiently to bring the cam surface 20' of the fixing plate 16' into contact with the end surface of the hammer 11'. Further depression of the button 6' to the intermediate position (position "B" in Figure 23) causes the hammer 11' to be rotated in a clockwise direction, against the action of the torsion spring 13', raising the head 12' of the hammer above the carousel 23'. During this motion, the cam surface 20' of the button slides over the end surface of the hammer 11'. This configuration is illustrated in Figure 27.

As the user continues to depress the button 6' (position "C" in Figure 23), the button 6' reaches a point where the edge of the cam surface 20' slips over the end surface of the hammer 11', releasing the hammer and allowing it to be driven in a counter-clockwise direction by the torsion spring 13'. The torsion spring drives the head of the hammer to and beyond its resting potion, causing the hammer to impact on a lancet located in the firing position. This action drives the lancet down through its tubing, compressing the surrounding coil spring and pushing the lancet needle out through the lower opening of the carousel and through the aligned opening in the lid. This configuration is illustrated in Figure 28

In this configuration, the hammer 11' exerts no significant force on the lancet 27'. The compressed spring 31' now forces the lancet back into its tube, retracting the lancet needle 29'. This process happens very rapidly, whilst the user is continuing to depress the button 6', compressing the spring 19' still further. The user then releases the button 6' which is returned towards its resting position by re-extension of the return spring 19'. The arcuate return surface 22' of the button 6' slips over the edge of the hammer during this action. As the hammer is prevented from rotating further by the lancet, as the surface 22' slips over the hammer, the opening 18' slides across the spindle 17'. The device is returned to the resting configuration which is illustrated in Figure 30, with the opening 18' having been pulled back so that its "lower" surface is again in contact with the spindle 17'. In this position, the head 12' of the hammer is located within the carousel.

Figures 26 to 30 illustrate an indexing mechanism 34' (omitted from Figure 24) for causing the carousel to rotate a new lancet into the firing position prior to the release of the hammer. This is best illustrated in Figure 26. The mechanism 34' comprises an indexing arm 35' which is pivotably mounted on a spindle (not shown in the Figures) provided on the fixing plate 16' of the firing button 6'. Movement of the arm 35' is restricted by upper and lower stops 36' provided on the reaction plate 9', although a small amount of axial movement (relative to the axis of rotation of the carousel) is allowed. As the button 6' is depressed (i.e. moves upwards in the orientation shown in Figure 26), the arm 35' is pushed radially inwards. The leading surface 37' of the arm (or "pawl") engages one of the teeth of the cog 33' provided on the carousel, causing the carousel to be rotated to the next firing position. After firing and release of the button, the arm 35' is withdrawn. An inclined surface 38' formed behind the leading surface 37' causes the arm to slide up over the cog, allowing the arm to return to its resting position without causing rotation of the carousel.

Figure 31 illustrates a firing mechanism 100' for use with the device of Figure 23, according to a further embodiment of the present invention. The mechanism 100' is similar in principle to that of Figure 24, with the button 101' and indexing arm (omitted from Figure 31 but illustrated in later figures) being substantially identical. The hammer 102' operates on a similar principle to that of the mechanism of Figure 24, being raised and released by depression of a firing button 101', and being biased by a torsion spring 103'. Pivotally attached to an end of the hammer 102' is a plate 104' from which depends a lancet grasping tool 105'. This tool 105' comprises a cylindrical shaft 106' which is slidable mounted in a support collar 124' fixed to the reaction plate 125'. To the end of the shaft 106' is fixed a cup-shaped plunger 107'. The plunger is hidden in the illustration of Figure 31 but can be seen in Figures 34 to 41 to be described below. A pair of slots 108' extend through an upper surface of the plunger 107' adjacent to where the plunger is fixed to the shaft 106'. A number of small pips 109' (e.g. three, only one of which is illustrated in the Figure) are formed in a ring around an inner surface of the plunger 107'.

A cup-shaped cover 110' has an integral collar 111' which surrounds the shaft 106', above the plunger 107', such that the shaft can slide freely through the collar. A pair of shafts 112' depend from the inner surface of the cover 110', adjacent to the collar, and engage respective ones of the slots 108' formed in the plunger. As the plunger moves up and down with respect to the cover, the shafts slide up and down within the slots.

Figure 32 illustrates a lancet carousel 113' for use with a device comprising the firing mechanism 100' of Figure 31. Figure 32 illustrates a partial cut-away view of the carousel, as well as an axially exploded view. Figure 33 illustrates in partial cross- section a detail of the carousel 113'. The carousel comprises a series of mounting tubes 114' equally spaced around its periphery. The tubes 114' are open at the upper ends. Each tube has formed integrally therein a pair of standoff clips 115a', 115b', which extend vertically upwards from a lower surface of the tube. Whilst fixed at their lowermost ends, the clips 115' are able to deflect outwardly at their upper ends with respect to the tube. Each clip has a stop member 116' formed on an inner surface thereof, the stop member having an inclined upper deflecting surface 117'. Located within each tube 114' is a lancet 118' having an enlarged, cylindrical head 119' and a needle 120' projecting therefrom. The sharpened tip of the needle 120' projects downwardly and is aligned with a slot 121' in the lower surface of mounting tube, extending between the bases of the standoff clips 115'. The lower surface 122' of the enlarged head 119', at the entry side of the needle, is slightly sloping around its periphery, and a groove 123' extends circumferentially around the centre of the head. In the stored and unused state which is illustrated in Figure 33, a lancet sits with its head entirely above the stops formed in the standoff clips, but in contact therewith so as to prevent significant movement of the lancet prior to firing.

The device and the carousel are provided with registration means for aligning the slot formed in the base of the mounting tube which is currently in the firing position, with the hole passing through the depression in the lid. This may be for example the arrangement of pips and dimples described above with reference to the embodiment of Figures 23 to 30.

Referring now to Figure 34b, this shows a reverse side view of the firing mechanism. A reverse side cam plate 127' is fixed to the firing button 101', with a cam surface 128' of the cam plate engaging an end of the hammer 102'. The cam plate 127' acts to raise the hammer to its resting position, and maintain it in this position prior to firing.

Considering now the operation of the firing mechanism 100' and carousel 113', Figure 34a illustrates the resting position of the device. In this configuration, the plunger 107' sits within the cover 110', with the lower rim 126' of the cover sitting on the surface of the carousel, aligned with one of the mounting tubes. Figure 35 illustrates the configuration of the firing mechanism 100' as the user starts to depress the button 101' (bearing in mind that the mechanism in the Figures is shown upside down). This action brings the first cam surface 129' into engagement with the hammer, raising the hammer 102' and at the same time indexes the carousel to place a new and unused lancet in the firing position (in the same way as described with reference to the embodiment of Figures 23 to 30). When the hammer 102' has reached its uppermost position, in which it is strongly biased by the torsion spring 103', and the button is further depressed, the hammer is released as described above with reference to the first embodiment. This drives the plunger 107' down through the cover 110' (which is prevented from moving downwards by the carousel) and into contact with the head of the lancet 118' as illustrated in Figure 36. The presence of the pips 109' on the inner surface of the plunger 107' cause the plunger to expand slightly as it is pushed down over the head 119' of the lancet.

When the pips 109' on the inner surface of the plunger 107' encounter the groove 123' extending around the lancet head 119', they engage the groove, effectively locking the plunger to the lancet. Continued downward travel of the hammer 102', see Figure 37 and the detail of Figure 38, results in downward motion of the engaged lancet 118', causing the standoff clips 115' to splay apart and allowing further travel of the lancet.

The lancet needle 120' exits from the aligned slot 121' in the mounting tube 114', puncturing the skin of the user. Continued downward pressure on the button 101' brings the second cam surface 130' on the firing plate of the button into engagement with the hammer as described above, causing the button to slide outward and allowing the first cam surface 129' to subsequently pass over the end of the hammer. The cam surface

128' on the reverse side cam plate 127' then comes into engagement with the hammer, raising the hammer back towards its resting position and with it the plunger and attached lancet.

The sequence of events which enables release of the lancet 118' from the hammer 102' is illustrated in Figures 39 to 41. As the hammer 102' and plunger 107' move upwards, the shafts 112' of the cover penetrate and pass through the respective slots 108' in the plunger 107', engaging the upper surface of the lancet head 119'. The resulting force exerted on the lancet overcomes the gripping force of the pips 109' within the groove 123', and pushes the lancet out of the plunger. Once released, the lancet 118' is free to drop back into its mounting tube 114', coming to rest on the standoff clips 115'.

Figure 42 illustrates a device 200' according to yet another embodiment of the present invention. The device comprises an outer casing 201' with a lid 202' hingeably attached thereto. The lid can be opened to allow insertion of a lancet carousel into the device. A firing button 203' extends through the casing and is depressed by a user to both fire a lancet and advance the carousel to the next location.

Figure 43 illustrates a firing mechanism 204' of the device. A firing and indexing arm 205' is fixed to the button. The arm comprises an indexing finger 206' which has an upper triangular section (or pawl) 207' for engagement with the indexing cog 208' of a lancet carousel. The indexing finger is able to move to a small extent in an axial direction with respect to the axis of rotation of the carousel in order to engage and disengage the triangular section with and from the indexing cog of the carousel. The operation of the indexing mechanism is similar to that described with reference to the first and second embodiments, with the carousel being rotated by the pressing of the button 203', just prior to firing. A firing finger 209' projects from an end of the arm 205' distal from the button.

Figure 44 illustrates in partial cut-away and in axial exploded view a lancet carousel 210' for use with the device 200' of Figure 42. The carousel 210' is generally cylindrical, having axially extending lancet mounting tubes 211' equally spaced around its periphery. Figures 45 to 47 illustrates in detail the construction of each mounting tube 211'. A basic hollow tube is moulded as a single piece and comprises a link arm 212' which is attached to the tube body by flexible joints. The link arm 212' has an upper lancet locking catch 213', and a lower trigger surface 214'. In the resting state, the locking catch 213' projects into the interior of the tube. Depression of the trigger surface 214' causes the link arm 212' to pivot slightly, moving the catch 213' radially outward with respect to the tube. In order to maintain sterility of the interior of the tube, the lower half of the lancet is over moulded with some flexible plastics material 215'. This still allows for movement of the link arm upon depression of the trigger surface. It is noted that the construction and operation of the mounting tube is similar in principle to the lancets marketed by Owen Mumford (Woodstock, England) under the brand name Unistik®, although that product is not provided with the overmoulding 215'.

A lancet 216' is provided within each mounting tube 211'. As best shown in Figure 48, each lancet comprises an enlarged plastics head 217' with a needle 218' embedded therein and projecting from one end of the head. Projecting from the other end of the head is a locating member 219'. A coil spring 220' surrounds the locating member 219' and is used to provide a driving force for the lancet. A groove 221' extends circumferentially around the head of the lancet. This provides a means for engaging the locking catch 213' of the link arm 212' when the coil spring 220' is compressed, securing the lancet in a cocked position.

Each lancet needle 218' is encased in a cylinder of closed cell foam 222' which is compressible to some extent, as best illustrated in Figure 48. Prior to firing of a lancet, this foam cylinder maintains sterility of the needle. Following use and as will be described below, the cylinder also acts to encase the needle, preventing contamination or infection by a used needle. It is noted that the inside diameter of the tube 211' is slightly greater than the diameter of the foam cylinder 222' to allow for radial expansion of the cylinder during firing.

In order to further aid the understanding of the third embodiment, Figure 49 shows an axial cross-section through the device 200' with the lancet carousel 210' inserted. This Figure illustrates a spring closure 223' mechanism comprising a coil spring which is compressed when the hinged lid is closed on the housing. As well as providing a registration seat for the carousel, the mechanism 223' allows for a small axial movement of the carousel relative to the lid, sufficient to allow rotation of the carousel between consecutive pips which define the firing positions. Figure 49 also illustrates an exploded view of the main device components.

Referring now to the partial cross-sectional views of Figures 50 to 54, operation of the device of Figure 42 will now be described. As the button is depressed (Figure 50), the indexing finger 206' on the indexing and firing arm 205' contacts one of the teeth on the cog 208' of the carousel 210'. The cog and the carousel are pushed around until a new and unused lancet is located in the firing position. Towards the end of its travel, the firing finger 209' of the arm engages the trigger surface 214' of the link arm 212'. As the trigger surface is pushed by the firing finger, the link arm is pivoted, releasing the locking coil spring 220' surrounding the locating member 219' to extend, driving the lancet 216' through the mounting tube 211' until the foam cylinder 222' surrounding the lancet needle 218' encounters the end of the tube (Figure 41). The foam cylinder is compressed in the axial direction, with the needle being driven through and out of the end of the cylinder. The needle 218' then passes out of the opening in the end of the tube, and that in the lid of the device, lancing the subjects finger as is illustrated in the detail of Figure 52. At this point, the spring 220' is slightly over extended, and begins to draw back, bringing the needle back within the tuning. At the same time, the foam cylinder 222' re-expands to cover the needle. This configuration is illustrated in Figure 53.

Release of the firing button 203' allows the firing button to return to its resting position under the action of a return spring (not shown). During its return motion, the button draws the indexing and firing arm with it. This configuration is illustrated in Figure 54, with the inclined surface of the triangular section 27' of the firing finger 206' causing the finger to be deflected downwardly so as to allow the finger to be drawn back across the cog 208'. Rotation of the carousel by this action is prevented by the engagement of the registration pips and dimples.

Figure 55 illustrates an alternative construction for the lancet needle cover. Rather than using a compressible foam for this purpose, an elastomeric sheath 224' may be used. When the end of the sheath is pressed against the upper surface of the lancet mounting tube, the needle is able to penetrate the sheath and pass out through the small opening in the end of the tube. Upon withdrawal of the lancet, the sheath expands to once again cover the needle.

In order to maintain the sterility of the lancet carousel 210', the end through which the lancets will project during lancing may be covered with a foil or cellophane seal. This is illustrated in Figures 56and 57, where the cover 225' is peeled off following loading of the carousel 210' into the device 200', and prior to first use. Alternatively, the seal may remain in place during use, with the lancet needles penetrating the cover during lancing. This is illustrated in Figure 58.

It will be appreciated by the person of skill in the art that various modifications may be made to the above described embodiments without departing from the scope of the present invention. For example, considering the embodiment illustrated in Figures 42 to 54, a further anti-rotation pawl may be provided on the reverse side of the cog 208'. This second pawl has a similar shape to the pawl 207', but with the opposite inclination, such that the vertical face of the pawl engages the cog to prevent reverse rotation. The second pawl is spring mounted such that it can be deflected downwards by forward rotation of the carousel. This construction is illustrated in Figure 59, with the second pawl being identified by reference numeral 400'.

Table 1

Claims

CLAIMS:

1. A lancet wheel comprising a plurality of radially extending needles suitable for piercing tissue when the wheel is moved in the plane of the wheel, and means for attaching the wheel to a lancing device so that the wheel is rotatable about its axis.

2. A lancet wheel as claimed in claim 1 and comprising a central moulded plastics part, said needles projecting radially outward therefrom.

3. A lancet wheel as claimed in claim 2, wherein the central moulded plastics part comprises a plurality of radially extending fingers with the needles embedded in the respective ends thereof.

4. A lancet wheel as claimed in claim 3, wherein each of the fingers is flexible.

5. A lancet wheel as claimed in any one of claims 3 to 4, further comprising a radially extending finger which does not have a needle embedded therein.

6. A lancet wheel as claimed in any one of claims 3 to 5, wherein the fingers are spaced at equiangular separations.

7. A lancet wheel as claimed in any one of claims 3 to 6, wherein the ends of the fingers are tapered.

8. A lancet wheel as claimed in any one of the preceding claims and comprising a compressible or deformable feature disposed on the end of each needle so as to encase at least the tip of each needle.

9. A lancet wheel as claimed in any preceding claim, wherein a central portion of the lancet wheel comprises a clutch surface for aligning needles in conjunction with a lancing device and for preventing unnecessary rotation of the lancet wheel with respect to the lancing device.

10. A lancet wheel as claimed in claim 9, wherein the clutch surface comprises a substantially continuous ring of radially extending grooves coaxial with the axis of the wheel, the angular separation of the grooves corresponding to the angular separation of the needles in the lancet wheel.

11. A lancet wheel as claimed in any preceding claim, comprising drive engagement means including a substantially continuous ring of axially extending grooves, the ring being coaxial with the axis of the wheel and the angular separation of the grooves corresponding to the angular separation of the needles in the lancet wheel.

12. A lancet wheel as claimed in claim 11, wherein the ring of grooves on the drive engagement means comprises a portion where no groove is provided.

13. A lancet wheel as claimed in any one of claims 9 to 12 having upper and lower surfaces, wherein the clutch surface and drive engagement means are disposed upon the lower surface of the lancet wheel.

14. A lancet wheel as claimed in any preceding claim, wherein the lancet wheel further comprises a releasable attachment mechanism for attaching the lancet wheel to a lancet firing device.

15. A lancet wheel as claimed in claim 14 having upper and lower surfaces and a passage through its centre for receiving a spindle of a lancet firing device, wherein the releasable attachment mechanism comprises a support adjacent the passage projecting upwards from the upper surface of the wheel, the upper end of the support being capable of flexing toward and away from the wheel axis, and the releasable attachment mechanism further comprising an arm extending from the upper end of the flexible support so as to intersect with the axis of the wheel, the arm having a slot formed therein for receiving a wheel-mounting spindle of a lancet firing device.

16. A lancet wheel as claimed in any preceding claim, further comprising a wheel cover arrangement arranged in a non-use position to cover the ends of the lancets in the lancet wheel, and in a use position to be partially raised to expose the ends of the lancets in the lancet wheel.

17. A lancet wheel as claimed in claim 16, wherein the wheel cover arrangement comprises an outer ring and an inner ring connected to the outer ring by a plurality of radially extending flexible members, the cover arrangement being attached to the wheel at the inner ring, and the outer ring extending downwards to cover the ends of the lancets in the non-use position.

18. A lancet wheel as claimed in claim 17, wherein the outer ring further comprises a plurality of lateral tabs arranged such that, in use, an application of upward force to the lateral tabs causes the flexible members to bend upwards at their outer extent, thereby raising the outer ring away from the lancets of the lancet wheel.

19. A device for firing lancets suitable for piercing tissue, comprising a housing and a mounting means disposed within the housing for mounting a lancet wheel, the device further comprising driving means for driving the lancet wheel in a direction substantially parallel to the plane of the wheel.

20. A device as claimed in claim 19, wherein the mounting means comprises a carriage which is slidably fixed within the housing.

21. A device as claimed in claim 20, wherein the housing comprises a track within which the carriage is slidably fixed.

22. A device according to claim 20 or 21, the carriage comprising fixing means for mating with the lancet wheel so as to permit limited movement of the wheel relative to the carriage in the direction of the wheel axis, whilst biasing the wheel towards the carriage.

23. A device according to claim 22, said fixing means comprising a resilient member.

24. A device according to claim 22, said fixing means being arranged to mate with a resilient member attached to the wheel.

25. A device as claimed in any one of claims 20 to 24, wherein the carriage comprises a wheel-mounting spindle projecting from the carriage for receiving a lancet wheel, the spindle having an annular wheel-locking groove formed therein.

26. A device as claimed in any one of claims 20 to 25, further comprising a rib arranged in use to cooperate with a drive engagement means of a lancet wheel to rotate the lancet wheel into a subsequent lancet position during motion of the carriage within the device.

27. A device as claimed in claim 26, wherein the rib is disposed upon the housing and extends in a direction parallel to the direction of motion of the carriage.

28. A device as claimed in any one of claims 20 to 27, wherein the carriage comprises a clutch surface complimentary to a clutch surface provided on a lower surface of a lancet wheel for aligning lancets and for preventing unnecessary rotation of the lancet wheel with respect to the lancing device.

29. A device as claimed in claim 28, wherein the clutch surface comprises a substantially continuous ring of radially extending grooves coaxial with the axis of a lancet wheel, the angular separation of the grooves corresponding to the angular separation of the lancets in the lancet wheel.

30. A device as claimed in any one of claims 20 to 29, wherein the driving means comprises a firing spring for imparting a firing force to the carriage, disposed between the carriage and a reaction plate.

31. A device as claimed in claim 30, comprising at least one firing button, wherein the firing spring, when compressed, is releasable by the firing button.

32A device as claimed in claim 30 or 31, wherein the driving means further comprises a cocking mechanism for loading the firing spring.

33. A device as claimed in claim 32, comprising a cocking button, wherein the cocking mechanism comprises a cocking spring disposed between the reaction plate and the cocking button.

34. A device as claimed in claim 33, further comprising means for releaseably connecting the cocking button to the carriage upon depression of the cocking button, the carriage further comprising a rearward-projecting flexible leg member with a laterally- projecting snap member formed thereupon arranged such that when the carriage is in a retracted position, the snap member is disposed adjacent the firing button, the flexible leg member is ramped against an inclined surface at a rear end of the device, and the cocking button is released from the carriage.

35. A device as claimed in claim 34, further comprising stop means formed integrally with the housing and disposed such that the stop means opposes relative motion of the carriage and the housing when the carriage is in the retracted position through contact with the snap member.

36. A device as claimed in claim 35, wherein the firing button further comprises an inwardly-facing catch arranged such that depression of the firing button causes separation of the snap member and the stop means, allowing the firing spring to drive the lancet wheel into a firing position.

37. A device as claimed in any one of claims 19 to 36, further comprising ramp members disposed at a forward end of the device, arranged such that, in use, the two lancets of a lancet wheel adjacent the forwardmost lancet are biased away from the front of the device when the lancet wheel is in a firing position.

38. A device as claimed in one of claims 20 to 37, wherein the housing comprises an aperture through which the lancet wheel may be inserted into the device, the aperture having a lid for closing the aperture.

39. A device as claimed in any one of claims 20 to 38, further comprising depth adjustment means for varying the location of the firing position of the carriage.

40. A lancet firing device as claimed in any one of claims 20 to 39 in combination with a lancet wheel as claimed in any one of claims 1 to 18.

41. A method of piercing skin, comprising mounting a lancet wheel into a lancet firing device, the lancet wheel comprising a plurality of radially extending lancets, the tips of the lancets extending radially outwards in the plane of the wheel; driving the lancet wheel in a direction perpendicular to its axis; and rotating the lancet wheel to the next lancet position.

42. Skin pricking apparatus comprising a lancet carousel holding a multiplicity of lancets arranged circumferentially around the centre of the carousel, the lancets being disposed with their needle tips pointing in an axial direction, and a firing device to which the lancet carousel is mounted for rotation about its axis, the firing device comprising: a lancet firing mechanism including a finger actuable trigger for causing a driving force to be applied to a lancet located in a lancet firing position; and indexing means coupled to said trigger for applying a substantially tangential force to the carousel upon activation of said trigger, so as to rotate the carousel to a subsequent firing position.

43. Apparatus according to claim 42, the trigger and the indexing means being moveable in substantially parallel planes.

44. Apparatus according to claim 42 or 43, the carousel comprises a cog disposed coaxially with the axis of rotation of the carousel, and having teeth arranged to engage said indexing means, the angular spacing of the teeth corresponding to that of the lancets within the carousel.

45. Apparatus according to claim 42, the indexing means comprising a pawl for engaging a tooth of the cog which is aligned with the pawl.

46. Apparatus according to any one of claims 42 to 45, the indexing means being pivotally attached to said trigger.

47. Apparatus according to any one of claims 42 to 45, wherein the indexing means is coupled to said trigger for linear movement therewith.

48. Apparatus according to any one of claims 42 to 47, the lancet carousel being a detachable unit, and the apparatus comprising means for releasable coupling the carousel to the firing device.

49. Apparatus according to claim 48 and comprising registration means for registering the carousel in one of a plurality of firing positions, relative to the firing device.

50. Apparatus according to claim 48 or 49, the apparatus comprising a casing inside which is fixed the firing device, the casing comprising a chamber for receiving the lancet carousel.

51. Skin pricking apparatus comprising a lancet carousel holding a multiplicity of lancets arranged circumferentially around the centre of the carousel, the lancets being disposed with their needle tips pointing in an axial direction, and a firing device within to the lancet carousel is mounted for rotation about its axis, the firing device comprising: a casing; a hammer pivotally attached to the casing and biasing means for biasing the hammer into engagement with a lancet located in a firing position so as to drive the lancet to a lancing position; a lever pivotally attached to the casing and moveable about its pivot point to rotate the hammer against the biasing means to a cocked position, the lever and the hammer being rotatable in substantially parallel planes; and release means for facilitating disengagement of the lever from the hammer in the cocked position.

52. Apparatus according to claim 51, opposing surfaces of the hammer and the lever being shaped such that the lever is in blocking engagement with the hammer over a part of its rotational travel, from a resting position to a position in which the hammer is cocked, and such that the members disengage upon further rotational travel of the lever in the same direction, thereby providing said release means.

53. Apparatus according to claim 51 or 52, the pivot point of the hammer being located radially inside the pivot point of the lever, with respect to the centre of the carousel.

54. Apparatus according to any one of claims 51 to 53 and comprising indexing means pivotally attached to said lever for applying a substantially tangential force to the carousel upon rotation of the lever, so as to rotate the carousel to the next firing position.

55. Apparatus according to claim 54, the indexing means being moveable in a plane substantially parallel to the plane in which the hammer moves.

56. Skin pricking apparatus comprising a lancet carousel holding a multiplicity of lancets arranged circumferentially around the centre of the carousel, the lancets being disposed with their needle tips pointing in an axial direction, and a firing device within which the lancet carousel is mounted for rotation about its axis so as to move lancets into and out of a firing position, the firing device comprising: a casing; a hammer pivotally attached to the casing and biasing means for biasing the hammer; cocking means for moving the hammer to a cocked position against the action of said biasing means; release means for releasing the hammer from the cocked position so as to allow the biasing means to drive the hammer into engagement with a lancet located in a firing position; and the hammer comprising latch means for latching the hammer to the engaged lancet, whereby the lancet once driven out of the carousel to a lancing position is withdrawn by return of the hammer towards the cocked position.

57. Skin pricking apparatus comprising: a lancet carousel holding a multiplicity of lancets arranged circumferentially around the centre of the carousel, the lancets being disposed with their needle tips pointing in an axial direction, each lancet comprising spring biasing means for biasing the needle tips towards a position in which they project from the carousel, and locking means associated with each lancet for releaseably locking a biasing means in its compressed state; a firing device within which the lancet carousel is mounted for rotation about its axis, the firing device comprising a finger actuable trigger for engaging the locking means of a lancet located in a firing position to release the biasing means of that lancet causing the needle tip to be driven to a lancet firing position; and indexing means for rotating the carousel to the next firing position following firing.