System for withdrawing blood

Blood collection system

The present invention relates to a system for extracting body fluids from a part of the body, in particular the fingertip, by means of a small puncture.

In the field of clinical diagnosis it is necessary to take samples of body fluids, especially blood, in order to detect substances contained in it. When a larger amount of blood is needed, it is usually drawn with a syringe or similar suitably coupled to a blood vessel. However, the present invention corresponds to a sector in which sample quantities of a few ml or even less are sufficient to determine the analytical parameters. Such a procedure is widespread, especially for the measurement of blood sugar level, but also, for example, to determine coagulation parameters, triglycerides, HBA 1c or lactate. In the field of diabetes, the blood sugar level control system has been imposed by the diabetics themselves (the so-called domestic control). This is necessary to adjust the blood sugar level to a value in the normal range by adequate doses of insulin. If, on the other hand, a diabetic has a drop in sugar (hypoglycemia), he may lose consciousness and even die. If a diabetic has too high a blood sugar level, he can suffer serious consequences such as loss of vision and gangrene in the long term. For the extraction of blood that requires a measurement of the level of sugar, small hand-held devices, known as lancet devices, have been generalized, which users and clinical and auxiliary staff can easily and reliably handle. Recently, systems for extracting interstitial fluids have also been known, with which the relevant analyzes can be carried out in principle.

A growing problem in this sector is pollution and injuries caused by used lancets. In many of the commercially available devices, the lancet is removed or ejected after the puncture process. In such a case, the discovered needle or lancet can cause wounds that cause infections in certain circumstances. Therefore, in some countries there are already attempts to ban those blood collection systems in which the needle tip is freely accessible after use.

In the documentation of the technical state there are descriptions of various variants of blood collection systems in which the needle is protected after the puncture process. In US Patent 5,314,442 a hood is described in which a lancet is placed. To carry out a puncture process, the lancet is moved inside the hood by means of a pusher or the like and goes out through an opening. After the puncture the lancet goes back inside the hood and flexible elements in the lancet prevent the needle from being able to exit again without the action of the pusher. Similar in principle are described in US patents 4,990,154 and 5,074,872 and in international patent application WO 00/02482. In DE 198 55 465 another system is described in which a lancet is retracted in the hood by means of a built-in spring. Although the aforementioned documents already solve the problem of contamination or of a user's injury, the coupling of the drive mechanism to the lancet is simply carried out by means of a pressure adjustment. In this case the puncture depth of the needle is limited by a stop. However, it has been proven that when the lancet reaches the top, the needle vibrates, which increases the pain of the puncture. In EP 0 565 970 this problem is described in more detail.

Therefore, the objective of the present invention was to propose a system for extracting body fluids that would prevent contamination or infection by used lancets and also allow the user to puncture with very little pain. Another objective was to simplify the systems of the technical state, make them cheaper and, above all, devise a system whose size could be reduced. This last point is of special importance to offer a system that works with lancet loaders and allows the user to replace it with an unused lancet, without the need to carry out complicated manipulations.

Said objectives are solved by means of extraction systems for body fluids whose execution forms have a drive unit equipped with a pusher that moves from a rest position to an advanced position during a puncture process. The systems also carry a puncture unit where a lancet with a needle is located, which remains inside the puncture unit when the pusher is in the rest position and by action thereof advances towards the puncture position in such a way, that the needle leaves, at least partially, from the puncture unit through an opening. An essential feature of the system is that the pusher and lancet are positively coupled to each other to effect the puncture process.

It is characteristic of a positive union that with a small force the lancet can be coupled with the pusher. In principle there are two variants to achieve a positive union. In the first variant the coupling between the lancet and the pusher includes a retainer. In the context of the present invention this form is designated as a retention device. If the retention device is in the lancet, the pusher has a retainer; if, on the other hand, the retention device is in the pusher, the retainer is located in the lancet. Figures 1 and 2 show practical configurations. This variant of the positive joint is preferably obtained so that a longitudinal movement in the direction of the puncture causes a transverse movement of the retainers of a retention device (first open), which are closed around a fastening zone. When the retention device is closed, the retainer is preferably caught from behind (at least partially), so that when the pusher moves back the lancet is dragged - at least until the probable opening of the retention device. It is also preferable that the retention device and the clamping area are geometrically adjusted to each other, so that, once the coupling in the direction of the puncture movement is established, there is only a small, or none, tolerance and both the advance and the recoil of the pusher in that direction translates into a movement without play of the lancet. This can be achieved by making the longitudinal extension of the chamber in the closed retention device coincide with the longitudinal extension of the clamping area or is slightly higher (see Figure 1). In another embodiment of this variant there is a cavity in the holding area and retainers along the retention device, mutually adapted so that the transport in the direction of the puncture takes place almost without play (see figure 2).

According to a second variant of the positive joint, both the retention device and the holding area are essentially non-deformable and the inclusion of the holding area in the retention device takes place when the fixed forms of the other move inwards. both units Since the units are non-deformable, it is impossible for total inclusion to occur. The forms must be sufficiently open so that they can move inside each other. This internal movement takes place (at least with a linear component) in the transverse direction of the puncture and there is a coupling that also has virtually no play in the puncture direction (see Figure 4). Finally, a coupling produced by a movement with components both perpendicular and parallel to the puncture direction is possible (see figure 7).

The blood collection system according to the present invention has a drive unit provided with a pusher that moves a lancet from a rest position to a puncture position. A series of drive mechanisms are known in the technical state that can be used in the field of blood sampling devices. Specifically, drive mechanisms that take their energy from prestressed springs are used in large quantities. Preferably, drive units are used which allow guided movement of the pusher and lancet due to the coupling by positive connection. Guided movement means that the lancet punctures the body along a predetermined path and is removed from the body by receding along a path equally preset at a certain time. In the current systems of the technical state based on a combination of a spring and a stop, the travel time depends on a series of parameters, such as manufacturing tolerances (friction conditions, spring force) and even the surface of the skin. It has been shown that a guided movement of the lancet, for example by means of a slide, as described in EP 565 970, is better for puncture pain. As regards the drive unit, the preferred mechanisms of EP 565970 and US 4,924,879 are taken as reference.

An important aspect is a puncture unit that can be removed from the drive unit, in which at least one lancet is located. The puncture unit comprises a housing where the lancet is placed in the rest position. Thus, contamination or injury with the lancet can be avoided before or after use. The housing can be configured to carry a single lancet or it can be in the form of a charger with several lancets. Generally the lancets are placed in separate chambers inside a loader, in order to prevent the new ones from becoming contaminated with those already used. The puncture unit housing is advantageously configured so that it can be installed in the drive unit. For this, the puncture unit may have, for example, the shape of a cap that is inserted into the drive unit. These embodiments are described for example in US Patents 5,314,442, US 4,990,154 and US 5,074,872. Other embodiments are also possible in which the puncture unit is fixedly connected to the drive unit

or is an integral part of it. This can be especially advantageous in systems with a charger, so that the entire unit is discarded once the charger is consumed. In the case of a puncture unit in the form of a magazine, it may, for example, have adjacent chambers containing the lancets and are placed one after the other with respect to the drive unit, so that the lancets can be coupled to the pusher of the drive unit. Also advantageous is a drum-shaped magazine with chambers parallel to the longitudinal axis of the drum, in which the lancets are located. Similar to the drum of a revolver, a magazine of this type can be placed repeatedly in the drive unit.

Another requirement of the puncture unit is the sterility of the lancets, which must be guaranteed for a long period of time. The puncture unit can be sterilized by gamma radiation, as usual in the technical state. To keep it in sterile conditions, the puncture unit can be packaged in a welded polyethylene bag. In another embodiment, the puncture unit openings (for the entry of the pusher and the exit of the needle tip) are sealed with a foil. It can be a separable sheet that the user can remove before use. However, thin sheets that are perforated when using the pusher or lancet can be used, thus saving additional manipulations to the user. Said sheets can already be generated as an integral part of the puncture unit, during its manufacture, which is generally an injection molding process.

In another advantageous embodiment, the needle tip is protected from contamination by an elastomer that is removed before puncture or punctured during puncture, to expose the needle tip. This type of needle protection against contamination is described in patent application WO 01/66010, which is taken here for reference.

Inside the puncture unit there is one or several lancets provided with a needle. Apart from other possible devices in the lancet that facilitate its positive attachment to a pusher, lancets according to the present invention are employed. This type of lancet generally has a basic plastic body that has a metal needle. However, there may also be lancets without a separate basic body (for example metal needles with a thickening at the rear end, as a support area).

In order to carry out the puncture process, it is important that the pusher of the drive unit and the lancet are coupled together by means of a positive joint. In this the present invention differs essentially from the technical state, where the coupling between lancet and actuator is of a mechanical type by means of a pressure adjustment (US patents 5,314,442, US 4,990,154, US 5,074,872), of an interlocking (WO 00 / 02482), of a clamp (US patent 3,030,959) or of a simple tightening (patent DE 19855465). A positive joint is characterized by a reliable mechanical coupling between the drive and the lancet, which does not require an important clamping force to move the lancet in the direction of the puncture. In the devices of the technical state that work with a pressure adjustment, a spring (eg patent DE 198 55 465) or a retaining element (eg, must be included in the cap carrying the lancet) WO 00/02482) designed so that the lancet does not leave the hood when the puncture unit is coupled to the drive unit. However, springs in the puncture unit increase manufacturing costs, which is particularly burdensome because the puncture unit is consumable material. On the other hand, to overcome a retention element an additional force is required by the drive unit and this impulse also produces vibrations of the needle that have a negative impact on the pain of the puncture. In addition to systems that operate with a snap fit, a guided movement that includes a recoil of the lancet is problematic because it can release the coupling. The interlocking described in WO 00/02482 solves this problem, but it is difficult to perform technically. In particular, it is difficult to establish an interlocking of this type in a continuous manufacturing process, because slight variations of the material or process conditions reduce the functionality of the device. Another drawback of the device described in WO 00/02482 is that the interlocking takes place in a segment of the path that serves to puncture the body. The dynamic oscillations and the vibrations produced during the interlocking have a negative impact on the pain of the puncture. Another disadvantage of the device is that the needle remains still after puncturing the body and does not actively retract. The needle only recoils when the cap is removed from the drive mechanism. On the other hand, with a positive pusher and lancet connection according to the present invention, a coupling between the two can be achieved, without having to exert a special force in the direction of the puncture and in addition the positive connection can be advantageously used to actively retract the needle after the prick. This possibility of actively controlling the time-travel curve of the needle by means of the drive unit makes it possible to establish a very painless puncture process.

Figure 8 schematically depicts the force (F) -recurrence (s) curves of the coupling processes of the drive to the lancet in case of pressure adjustment (a), interlocking (b) and positive connection (c). As can be seen, when using a pressure adjustment the force increases intensely until the lancet is released from the position in which it was held by a retaining element or a spring. In the case of an interlocking, the force increases during blocking and decreases at the end of the coupling. In the case of a positive union the forces necessary to retract the retention elements are very small.

Another property of the positive bond is shown in the comparison with US Patent 3,030,959. In an apparatus according to this US patent the needles placed in a tube are successively mounted by means of a device similar to a mechanical holder. In addition to the problems of contamination by used needles, which this device leaves unresolved, it is well known that the positioning of the needles in the axial direction (that is, in the puncture direction) is not defined. Just as in a mechanical pencil the user can freely decide the length of the protruding pencil tip, the axial positioning of the needles also depends in this case on the user's adjustment. On the other hand, according to the principle of the positive connection, the lancets and the drive unit have clamping areas and retainers that adapt to each other. Thanks to the geometric configuration of the clamping area and the retention device, it is possible to achieve that the axial positioning of the lancets is well defined and therefore the depth of the puncture can be controlled exactly. The use of a positive joint makes it possible to avoid a force tip in the axial direction during the coupling of the lancet with the pusher and obtain an exact axial positioning. In a positive connection one form (retention device) surrounds the other (clamping area). Circling means in this sense a movement of parts of the device perpendicular to the puncture direction or a positively engaged coupling of two molding pieces invariably. In a preferred embodiment, the retention device is open and closes around the holding area when it is inserted therein. This inclusion can take place especially by means of a longitudinal movement that becomes a movement of retainers of the retention device with transverse components with respect to the direction of the longitudinal movement. In practice, an advantageous possibility of transforming a longitudinal movement into a transverse movement consists in introducing the retention device by means of a longitudinal movement in a narrowing channel (eg. in a pod) or move it inside it (see figure 1). The narrowing in this case refers not only to channels that progressively narrow, but also in general to channels whose interior width decreases in the longitudinal direction. In this sense a channel does not have to be a body closed by a surrounding surface. If the retention device has two opposite hooks, such as in Figure 1, two walls with a smaller separation from each other are sufficient. On the other hand it is also possible to close the retention device by canceling a tense position (see figure 2), for example by moving the device

retention towards a widening channel.

Figure 1: representation of a cut through a puncture unit that carries a lancet provided with a

retention device

Figure 2: representation of a cut through a part of a system that carries a retention device in

drive unit

Figure 3: representation of a cut through a complete system and steps for its use

Figure 4: part of the system with non-deformable retention device in the puncture unit

Figure 5: Puncture unit loader

Figure 6: system formed by the drive unit and the puncture unit

Figure 7: system with an indeformable retention device

Figure 8: force-travel diagram for different types of coupling

Figure 9: Puncture unit with sterile protection

Figure 10: Drum-shaped loader Figure 1 shows a blood collection system, according to a first embodiment, in the drive phases I, II and III. Only partial aspects of the system are represented in Figure 1. The representation is missing the pusher drive unit (10) and the drive unit housing, to which the puncture unit (20) is fixed. The device described in EP 0 565 970 is especially suitable as the drive unit for the pusher (10).

The phases shown in Figure 1 show the formation of the coupling by positive connection between the pusher

<dl><dt>(10)</dt><dd> and the lancet (30), as well as the puncture process itself. For each of the three phases 2 cuts are shown through the longitudinal axis.</dd></dl>

The phases shown in Figure 1 show the formation of the coupling by positive connection between the pusher

<dl><dt>(10)</dt><dd> and the lancet (30), as well as the puncture process itself. For each of the three phases, 2 cuts are shown through the longitudinal axis of the system in planes perpendicular to each other. In the representation on the left of phase I it can be seen that the lancet (30) is located inside a sheath (40). The lancet shown (30) has a basic plastic body and a steel needle (31) injected into it. On the opposite side of the needle tip the lancet has a retention device with two hook-shaped retainers (32a, 32b). When directing the pusher</dd></dl>

<dl><dt>(10) </dt><dd>towards the lancet, a thicker part of the pusher, at its front end, which serves as a holding area </dd></dl>

<dl><dt>(11)</dt><dd> it penetrates between the hooks (32a, 32b) and finally runs into the rear end of the needle (phase II). It is also possible for the pusher to abut the basic body of the lancet instead of the rear end of the needle. However, direct contact with the needle is advantageous, because its industrial production can be controlled very accurately and therefore also the puncture depth. As it advances, the pusher moves the lancet inside the sheath (40) towards the outlet opening (41), until finally the needle tip comes out through said opening and punctures a tissue located below. In the passage from phase II to phase III it can be seen that the lancet retention devices (32a, 32b) close around the clamping area (11) of the pusher as soon as the lancet is slid into the sheath (40). The lancet retaining device grips the pusher retainer forming a positive joint, which not only allows an advance movement of the lancet to take place to perform the puncture, but also an active recoil of the lancet, virtually without play, controlled by the drive unit. This is ensured by the support of the end of the holding area at the end of the needle and by the hooks (32a, 32b) that hold the rear end of the holding area. The length of the clamping zone and the longitudinal extension of the chamber in the closed retention device are mutually adapted so that the operation of the lancet in the puncture direction has no play. Thanks to the insertion of the lancet and the retention device in a narrowing sheath, the longitudinal movement of the lancet in the puncture direction becomes a transverse movement of the retainers that allows the formation of a positive union with the area of clamping the drive. As can be seen in the figures, the sheath (40) has an intermediate zone (40b) that is narrower compared to the upper zone (40a). With this narrowing the lancets remain inside the sheath if the pusher does not act. In this way it can be ensured that the needle remains inside the sheath (40) without activating, thus avoiding the injuries or contamination that a protruding needle tip can cause. The slide of the lancet through the sheath, towards the outlet opening (41) is effectively prevented, because the hooks (32a, 32b) have a heel that rests on a ridge of the intermediate zone (40b). The inclination of these edges and the flexibility of the hooks can be mutually adjusted so that, on the one hand, the insertion into the narrowing takes place with little effort and, on the other, an involuntary sliding is efficiently prevented. In order to avoid a slide of the lancet out of the sheath in the direction opposite to the puncture, in the embodiment shown, a larger piece (40c) is provided at the lower end of the sheath, as well as another correspondingly widened part (30a) at the lower end of the basic body of the lancet. </dd></dl>

As can be seen in figure III, when entering the holding area (11) the tip of the needle end is still inside the sheath (40). This is advantageous because the shaking caused by this movement does not affect the puncture process in the tissue and thus prevents the puncture from hurting due to this cause.

It is preferred to design the system so that after phases I, II and III the pusher (10) goes back in the opposite direction decoupling from the lancet and it is completely inside the sheath again. For coupling the pusher to the lancet there are two main variants. In the first variant the housing, the drive unit and the puncture unit are adapted to each other so that at the beginning the pusher is completely outside the puncture unit (20) (as represented for phase I). A disadvantage of this embodiment is that the pusher must travel a relatively long way to puncture, but it has the advantage that the pusher is completely out of the sheath and therefore a transverse movement can take place. Therefore, the first variant can be used advantageously for systems provided with a lancet loader in which several pods are moved, one after the other, under the pusher. In a second variant, a position according to phase II or even towards phase III is already reached by coupling the puncture unit to the drive unit. In this form of execution, the pusher must be kept very low, which technically favors the construction.

Figure 2 shows a second embodiment in which the lancet (130) has a holding area (131) and the drive unit has a retention device (132a, 132b). Figure 2 shows again the part of the system used to retain the lancet, but not the drive unit. Regarding this embodiment, it is also advantageous to use a drive unit that moves the pusher (110) in a guided manner. At its front end the pusher carries a retention device in the form of two hooks (132a, 132b) joined together by a flexible bridge (133) (or by a joint). This set forms a spring. In phase I these hooks are open, as their rear ends are held together by a sheath (140). Upon inserting the lancet (130) the sheath is displaced against a spring (141), so that the rear ends of the hooks are released and their anterior ends close around the holding area (131) of the lancet forming a joint positive. The lancet holding area has a recess (cavities) in which the hooks of the retention device fit. The length (in the direction of puncture) of the fitted ends of the retention device and the length of the recesses are practically the same and therefore this arrangement allows a guided and basically no play puncture movement. In this embodiment there is also a transformation of a longitudinal movement of the retention device into a transverse movement of the retainers.

Figure 3 shows a system based on the principle of positive coupling coupling according to Figure 2. The drive unit 100 is based on the Softclix® apparatus described in EP B 0 565 970. This document shows, above all, , how the rotational movement of the sheath 171 produced by the drive spring 170 is transformed into a translational movement of the pusher 110. The tensioning of the actuating spring when the button 172 is pressed and a corresponding suitable mechanical transmission are described in the European patent application with the reference number EP 0 010 2503.0. The drive unit has at its front end a retention device with two retainers, in particular the hooks (132a, 132b). As illustrated in Figure 2, these hooks are described in the European patent application with reference number EP 0 010 2503.0. The drive unit has at its front end a retention device with two retainers, in particular the hooks (132a, 132b). As illustrated in Figure 2, these hooks are connected to each other in an intermediate zone by a flexible bridge (133) or a joint. To the other side of the bridge

(133) opposite the hooks the retention device is held by a sheath (140), so that the hooks are open. The sheath (140) is held in position by a spring (141) that is in the retention device. In Figure 3I a puncture unit can also be seen, where there is a lancet (130) placed in a cap (121). The lancet has at its rear end a clamping zone (131) that is engaged by the retention device (132a, 132b). The outer body of the lancet has a narrow anterior area and a flange (122) between this narrow area and the clamping area (131). The tip of the lancet is protected against contamination and mechanical impacts by a plastic piece (123) that can be unscrewed. The cap (121) has a passage inside the narrow area of ​​the lancet, as well as an enlarged section area that is suitable to accommodate the flange (122). Within this widened channel of the hood there is a flange (124) that prevents independent sliding of the flange into the extended channel. In addition, the cap has a sheath (125) that serves to reverse the sheath (140) of the drive unit when the puncture unit is supported on the drive unit. This process is recognizable when contemplating figures 3I and 3II. When the sheath (125) pushes the sheath (140) the retention device is released and hooks the lancet holding area, as shown in Figure 3II. Then the system is ready for use by pressing the button

(172) and unscrewing the protective piece (123) of the lancet. Now, with the device shown in Figure 3II, a puncture process is carried out by placing the front end of the cap (120) on a part of the fabric and activating the drive unit when a firing mechanism is pressed. Once the puncture process is finished, the cap is removed from the drive unit in the direction of the longitudinal axis, whereby the flange (122) goes back until it is behind the flange (124) and the contaminated needle tip can no longer Get out of the hood. The puncture unit that is in the state represented in Figure 3III can be discarded or reused for other extraction processes after coupling it to the drive unit. Figure 4A shows a puncture unit that has a sheath (240) in which a metal needle (231) is located. The sheath (240) has a thin transverse wall (250) that holds the metal needle in the sheath. This transverse wall is preferably molded of plastic at the same time as the needles are coated. As the thickness of this wall is relatively low, the mechanical connection between the sheath and the needle can be undone during the puncture process, so that the needle slides protruding from the wall (250). The outlet opening of the sheath is sealed with a thin sheet (260) that is perforated during the puncture process. At its upper end the needle (231) has an injected holding area (232). To stabilize it, the needle has a narrowing around which the clamping area (232) is injected, thus avoiding axial sliding through the unit. The needles can be held in the sheath by scraping its outer surface or by curving the needle in the area of ​​the sheath. The pusher

(210) of this embodiment presents at its lower end a retention device (211) comprising the clamping area (232) in the form of a positive joint, as shown. The retention device (211) is open laterally, so that the pusher is guided by parallel displacement relative to the needle, with the retention device (211) at the height of the holding area (232), and can be engaged with the needle holding area by transverse displacement relative to the axis of the needle or the puncture direction. Once the positive connection is thus achieved, the needle can be actuated by the pusher (210) in the direction of puncture and also actively in the opposite direction. In the example shown, the lancet holding area has a recess (cavity) in which a projection of the retention device fits during engagement, so that both bodies are joined together, practically without play, in the direction of puncture.

Figure 4B shows a magazine formed by puncture units (220) according to Figure 4A. Referring to the coordinate system shown, the pusher (210) can be engaged with the lancet holding area moving in the Y direction (perpendicular to the drawing plane) and the positive joint can also be canceled in the same direction. Once the positive junction is undone, the pusher can move in the X direction (right / left) at the height of another lancet and hook it again with the movement in the Y direction. In this way the lancets of the lancets can be spent successively charger. Once the positive bond is established, the needles can be actively moved in the Z direction, both positively and negatively (up / down).

As an alternative to the coupling according to Figure 4B, which requires the movement of the pusher both in the x direction and in the y direction, the coupling can also be performed by a movement only in the x direction. In this case, the pusher has, for example, two opposite hooks, between which it is intended to pass in the x-direction of the lancet holding area. Then, when moving in the x direction, the pusher can go from lancet to lancet to perform a puncture process in the z direction. When the pusher is at the height of a lancet in the x direction, the pusher retention device takes the lancet holding area forming a positive joint and it can move guided in the z direction by the pusher, which then performs a puncture movement and also actively removes the lancet.

An automatic operation system is shown in figure 5, with puncture units according to figure 1.

As can be seen in the top view (figure 5B), the puncture units (20, 20 ', etc.) are attached to a tape

conveyor The conveyor belt (301) rotates around two rollers spaced apart (302, 303). One of the rollers is driven by a motor, so that the puncture units pass successively through a coupling position (305). In this position, as shown in Figure 4A, a positive coupling of a pusher (10) to a puncture unit (20) located in the puncture position (305) can take place.

Figure 6 shows a drive unit coupled to a puncture unit, analogously to the embodiment of Figure 1. The drive system represented corresponds to the European patent application whose reference number is 00102503.0. In this drive system, by pressing a button (420) against the tension of a spring (418) a sheath (414) is rotated axially, whereby a second spring (415) is tensioned. The sheath (414) is locked in an end position and the second spring (415) is tensioned. When the user removes the lock, the spring (415) is tensioned and the sheath (414) rotates in the opposite direction to the tensioning process. In the sheath

(414) there is a groove that serves as a slide for the propellant cylinder (408), which carries on its outer surface a rod or the like that fits into the groove. In this way, the rotation of the sheath (414) becomes a translation of the propellant cylinder, which transmits its impulse to the pusher (480), which has a clamping area at its front end.

The drive unit also has a clamping area (450) in which a puncture unit can be fitted or screwed. The puncture unit contains a cap (470) that has a surface to tighten on the skin area. In the hood there is a sheath (471) in which a lancet (472) is housed that has retention devices at its opposite end to the needle tip. The lancet retention device corresponds to the retention devices (32a, 32b) of Figure 1. In Figure 6 it can also be seen that a positive connection between lancet and pusher is already achieved by fixing the cap (470) on the drive device.

Figure 7 shows a system for extracting body fluids, which has a series of analogies with the system represented in Figure 3. It refers especially to the description of the drive and the tension mechanism

corresponding to figures 3 and 6. The system according to figure 7 has a puncture unit (120 ') with a cap (121') and a lancet (130 '). In the hood (121 ') there is an axial passage that can pass through the body of the

lancet during the puncture process. Preferably, both the passage and the body of the lancet are mutually adjusted so that, during the puncture process, the lancet can be guided in axial direction with very little play in the transverse direction. At its rear end the hood has a thread (126) on which it can

screw a corresponding thread (127) of the drive unit (100 '). At the opposite end of the needle tip the lancet has one or more (in the case represented 2) stems (131 ') that establish a positive connection with the retention device (132') when placing or screwing the cap on the drive unit. For it

the retention device has a recess or groove with an axial part (134a) and a perpendicular part

(134b) to the first. By placing the hood on the drive unit, the stems (131 ') reach the part

axial groove (134) and run through it to the height of the perpendicular part of the groove. When the cap (120 ') is screwed onto the drive unit (100'), the rod (131 ') moves from the end of the axial part, through the perpendicular part of the groove, to the opposite end. As can be seen in Figure 7II, the lancet is axially held by the retention device (132 ') by the rods, whereby the lancet can perform a guided puncture movement. The housing of the stems in a perpendicular part of the grooves allows the lancet to perform a movement to remove the tip of the needle and also to back off. As can be seen in Figure 7, the positive connection between the lancet and the retention device can be achieved without the need for a clamp or an interlocking. Obviously, the coupling principle between the lancet and the retention device shown in Figure 7 is also reciprocal, that is, it can take place with a retention device in the lancet and a holding area in the pusher or in the drive.

Figure 9 shows a development of the system of Figure 1. The pusher (10 ') has a clamping area (11') that has a surrounding oblique surface in its upper part, which, as seen in Figure 9B , fits the oblique surfaces of the hooks (32a ', 32b') during the puncture process. The end of the pusher rests on the end of the needle, while compression of the hooks (32a ', 32b') causes the tightening of the

chamfers of the inner side of the hooks on the chamfers of the upper part of the clamping zone, so that the clamping zone presses the end of the needle and a non-matching joint is formed between the clamping zone and the lancet in the puncture direction With this adjustment, a very precise clamping can be achieved by a positive connection between the lancet and the pusher that compensates for the manufacturing tolerances, thus preventing both the puncture movement and the recoil movement.

Furthermore, the retention device constituted by the hooks (32a ', 32b') is configured so that the free ends of the hooks fit into recesses of the sheath (40 '). This prevents the lancet (30 ') from sliding involuntarily out of the sheath (40'). As can be seen in the passage from figure 9A to figure 9B, at the beginning of the puncture process the free ends of the hooks are first released from the recesses and during the introduction into the narrowed sheath the hooks are tightened by gripping the fastening area of the pusher.

In figure 9 it can also be seen that the tip of the needle (31 ') is inserted in a material (35). East

material (35) is preferably an elastomer that tightly envelops the tip of the needle, effectively protecting it from contamination. Suitable elastomers can be used: styreneoligoblock copolymers, thermoplastic polyolefins, thermoplastic polyurethanes, thermoplastic copolyesters and thermoplastic copolyamides. The elastomer is pierced by the needle when puncturing, as shown in Figure B.

For this, the sheath (40 ') has a plate (36) with a central hole in its lower part. The plate prevents the

The elastomer exits through the hole and the needle pierces it when it exits through the central hole. When the lancet recedes, the elastomer remains next to the needle, but now the tip is free (see figure C).

Figure 10 shows a section (figure A) and a perspective (figure B) of a cylindrical lancet loader according to figure 1 or figure 9. New lancets can easily be attached to the drive with such a loader. For this, for example, the pusher may be in a fixed position with respect to the lancet loader and the drum-shaped magazine shown in figure 10 is rotated like a revolver, so that the unused lancets are placed in the coupling position with the pusher