Abstract:
The present invention generally relates to a blood withdrawal system for withdrawing blood for diagnostic purposes. The blood withdrawal system comprises housing with a lancet, which can be moved within the housing. The housing also includes a lancet drive with a drive spring and a cocking mechanism that includes an actuation element. The blood withdrawal system of the present invention also includes a lancet ejection mechanism that can be moved from an active position to remove the lancet to a passive position where such removal of the lancet is not possible.

Description:
REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application is a continuation of U.S. application Ser. No. 10/913,638, filed Aug. 6, 2004 which claims priority to German Patent Application No. 10336933.3, filed Aug. 7, 2003, which are hereby incorporated by reference in their entirety. 
     
    
     TECHNICAL FIELD  
       [0002]     The invention generally refers to a blood withdrawal system for withdrawing blood for diagnostic purposes.  
       BACKGROUND  
       [0003]     Lancets are used in analytical-diagnostic applications to withdraw a small amount of blood from a part of the body (usually the finger or the earlobe) by pricking the lancet into the body part to generate a wound. If done manually, specially, trained personnel are required for this purpose. However, puncturing is associated with considerable pain.  
         [0004]     Blood withdrawal systems consisting of a puncturing device and corresponding lancets which are specifically adapted to the corresponding puncturing device have been in use for a long time. Typically, a housing of the puncturing device contains a lancet drive by which a lancet is punctured mechanically through the skin. The driving element for the puncturing motion is a spring. Early in the development very simple designs were common in which the lancet was attached directly to one end of a compression spring which was arranged in an elongated housing. An example of such a lancing devise is shown in U.S. Pat. No. 4,469,110.  
         [0005]     However, blood withdrawal systems of this type fail to satisfy the difficult requirements that must be met when the regular monitoring of certain analytic blood values are required. This particularly applies to diabetics who have to monitor their blood sugar level frequently in order to keep this level within certain limiting values by suitably adapting the insulin injections. Scientific investigations have shown that an intensive therapy involving at least four blood analyses per day can dramatically reduce the extremely severe late consequences of diabetes mellitus such as retinopathy which eventually leads to blinding of the patient.  
         [0006]     However, with such intensive therapy it is desirable that the withdrawal of blood is associated with as little pain as possible. Numerous blood withdrawal systems aiming for an improvement in this area have been developed.  
         [0007]     A typical withdrawal of blood by means of a blood withdrawal system requires two basic functions. Firstly, the puncturing device must be brought to a state in which it is ready for puncturing by tensioning the drive spring. This is called the “cocking phase”. Subsequently, the lancet drive is triggered and the relaxing motion of the drive spring drives the lancet. This is called the “drive phase”.  
         [0008]     In previous blood withdrawal systems, the puncturing phase was the kinematic reverse of the cocking phase. In other words, the drive was cocked simply by pushing the lancet, after puncturing, back into its original position in which the spring was tensioned.  
         [0009]     However, better results, in particular with regard to the lowest possible pain level while keeping the handling simple, are achieved when the lancet drive is designed such that the two functions are uncoupled from each other. Accordingly, it is preferable that in a cocking phase, the motion of an actuation element of a cocking mechanism is transmitted by an input-side coupling mechanism to the drive spring such that the spring is tensioned. And in a drive phase, the relaxing motion of the drive spring is transmitted by an output-side coupling mechanism to the lancet such that the lancet performs the puncturing motion at high speed.  
         [0010]     The two coupling mechanisms usually consist of different structural elements. In any case, the motions performed during the two phases differ from each other (rather than being the kinematic reverse of the other phase). Blood withdrawal systems of this type are known, for example, from the following publications: U.S. Pat. No. 4,442,836; U.S. Pat. No. 5,318,584; U.S. Pat. No. 6,409,740; U.S. Pat. No. 6,419,661; and EP 1 254 632 A1.  
         [0011]     Despite the extensive development efforts which resulted in the constructions described in these documents and numerous others, there is a strong interest to have a blood withdrawal system which optimally satisfies the difficult and to some extent contrary requirements i.e minimal pain sensation, simple handling, compact design as slim as possible, cost-efficient fabrication. Therefore, there is a need in the industry to improve the design of such blood withdrawal systems that will satisfy such requirements.  
       SUMMARY  
       [0012]     The present invention relates to a blood withdrawal system which comprises a housing with an exit opening for the tip of a lancet, which is mobile within the housing along a predetermined puncturing path. The system also comprises a lancet; drive with a drive spring and a cocking mechanism.  
         [0013]     The cocking mechanism including an actuation element which is coupled to the drive spring via: an input-side coupling mechanism such that the drive spring is tensioned in a cocking phase of the motion of the lancet drive upon motion of the actuation element. The drive spring is coupled to the lancet via an output-side coupling mechanism such that the lancet, during a drive phase of the motion of the lancet drive, is moved at high speed along the pre-determined puncturing path in the puncturing direction driven by the relaxing motion of the drive spring until the tip of the lancet exits out of the exit opening to generate a wound.  
         [0014]     The actuation element of the cocking mechanism is coupled to a track control mechanism comprising a control track part and a control traveler. The control traveler performs a relative motion with respect to the control track part during at least a part of the cocking phase in which motion it travels along the control track of the control track part whereby at least a part of the motion of the lancet drive is controlled.  
         [0015]     According to the invention an additional control track mechanism is provided in addition to the coupling mechanisms, effecting the transmission of force from the actuation element to the drive spring (cocking phase) and from the drive spring to the lancet (drive phase). This additional control track mechanism is coupled to the actuation element of the cocking mechanism and controls at least a part of the motion of the lancet drive. It consists of two parts, which are designated components of the track control mechanism, namely a control track part and a control traveler. Its controlling or steering effect, is based on an interaction of the control track part and the control traveler with the lancet drive during the motion of the lancet drive. This interaction includes a motion of the control traveler relative to the control track, in which the control traveler follows, i.e. travels along, the control track and thereby affects a lancet drive controlling or steering function during at least a part of the cocking phase and/or in the puncturing phase.  
         [0016]     The required guidance of the control traveler along the control track can be achieved by different constructive measures. The control track can be formed by a groove, in the control track part whose width is adapted to the dimensions of the control traveler such that the latter is guided precisely within the control track. The guiding effect can also be achieved by implementing the control track in the form of a slide surface against which the control traveler is pressed by spring action. In any case, one of the components is coupled to the actuation element of the cocking mechanism such that it is moved synchronously with the actuation element. The coupling can be rigid or movable. In the case of a movable coupling, common coupling elements, such as levers, can, for example, be used to connect the actuation element of the cocking mechanism to the “input-side” component of the track control mechanism to which the actuation element is coupled. Preferably, this input-side component is the control track part, whereas the output-side component of the track control mechanism (which is coupled to the lancet drive such that it transmits the steering effect of the track control mechanism to the lancet drive) is preferably formed by the control traveler.  
         [0017]     The relative motion of the control traveler with respect to the control track part can be realized by different combinations of motions of the two components of the track control mechanism. For example, in a section of the relative movement the control track part can be moved, while the control traveler is stationary with respect to the housing of the puncturing device. In other sections, the movement along the control track can be based on a motion of the control traveler while the control track part is stationary. Finally, both components of the track control mechanism can be moved simultaneously. Details depend on the individual case at hand. Preferably, the control track part is moved during at least a part of the desired control period in a translational motion, whereas the control traveler preferably moves at least partly on a circle.  
         [0018]     The actuation element of the cocking mechanism is usually realized in the form of a cocking button which projects from the rear end (opposite from the puncturing opening) of an elongated housing and generally is actuated by pressing with the thumb. However, the invention is also suitable for use with other actuation elements of the cocking mechanism, e.g. a pusher which is movable along the wall of the housing or an actuation element which can be moved by pulling and is formed, for example, by the rear part of the housing. Hereinafter, reference shall be made to a cocking button for exemplary purposes without limiting the generality.  
         [0019]     The track control mechanism which is separate from the mechanical elements required in the lancet drive for cocking (by transmission of force from the actuation element to the lancet drive), but coupled to the cocking button of the lancet drive achieves several advantageous functions.  
         [0020]     Due to the fact that the track control mechanism is coupled to the cocking button of the lancet drive, but is independent of the transmission of force, it becomes possible to assign additional functions (aside from the cocking of the lancet drive) to the cocking button, such as, for example, the triggering of the drive phase (puncturing motion) or the removal of a used lancet from the puncturing device. This allows “one-hand operation”.  
         [0021]     The track control mechanism can be used to establish defined intermediate positions of the cocking button which characterize intermediate stages in the handling of the blood lancet system, and thus clearly indicate to the user the status of the system (for example, “relaxed”, “cocked”).  
         [0022]     By providing a “reversing section” in the control track it is possible to realize an operation of the cocking button of the “push-button switch type”, as will be illustrated in more detail below.  
         [0023]     By means of one-way sections of the control track, which are also described in more detail below, it is possible to ensure that the journey of the traveller along the control track is possible in only one direction and consequently to achieve a certain sequence of steps without undesired repetition. An important example is a “re-cocking lock” preventing repeated cocking of the drive.  
         [0024]     The blood withdrawal system of the present invention also includes a lancet ejection mechanism with a release element which is borne in the housing such that it can be switched between a passive position and an active position. The lancet ejection mechanism is activated when the release element is in its active position such that actuating an actuation button of the lancet ejection mechanism removes a used lancet from the housing. The lancet ejection mechanism is inactivated when the release element is in its passive position such that actuating the actuation button does not lead to the ejection of a lancet.  
         [0025]     The front end of the housing with the puncturing opening is formed by a cap, which can be removed in order to remove used lancets. The cap, when attached, interacts with the release element such that it is in its passive position, and the release element is switched to its active position upon removal of the cap.  
         [0026]     The term “ejection mechanism” is generally used to designate a combination of mechanical elements which together allow removal of the lancet from the puncturing device by moving an actuation button without having to touch the lancet. In this context, “ejection” does not mean that the lancet is accelerated during its removal from the device. Rather, it is usually considered to be advantageous if the ejection mechanism only opens a lancet holder of the puncturing device such that the lancet falls out by the effect of gravity.  
         [0027]     The ejection mechanism is nonfunctional as long as the cap is attached to the front end of the housing of the puncturing unit. The mechanism is activated only upon removal of the cap whereby possible mishandling is prevented. Furthermore it is possible to use the cocking button simultaneously as actuation button of the ejection mechanism without adversely affecting its other functions, for example by restricting its possible path of motion. This is also explained in more detail below.  
         [0028]     It is preferable to use both features of the invention in lancet systems whose lancet drive includes a drive rotor which is driven by the drive spring and rotates about an axis, wherein the drive rotor, driven by the drive spring in the drive phase of the lancet drive, performs a rotational motion which is transformed into the puncturing motion by the output-side coupling mechanism. A rotor drive of this type is used, for example, in U.S. Pat. No. 5,318,584; U.S. Pat. No. 6,409,740 and U.S. Pat. No. 6,419,661.  
         [0029]     It is particularly preferable to use the present invention in combination with a special rotor drive as described in EP 1384438 A1 (and its equivalents: U.S. Ser. No. 10/445,606 and JP 149780/2003). The entire content of the previous application is incorporated herein by reference.  
         [0030]     In the rotor drive described therein, the end of the drive spring which is remote from the drive rotor is supported by a rotatable tensioning element, which can be rotated in the same direction, in which the drive rotor rotates during the drive phase, in order to tension the drive spring while the rotation of the drive rotor is inhibited. The tensioning element is locked against a reverse motion during the drive phase such that the drive rotor performs a rotational motion after the inhibition is released, which rotational motion is transformed into the puncturing motion by the drive-side coupling mechanism. In such a drive the mentioned elements are rotated in the same direction in an alternating manner during the cocking phase and during the drive phase. This principle is designated “One Way Alternating Drive and Cocking”, or OWADAC for short.  
         [0031]     The invention is illustrated in more detail hereafter on the basis of exemplary embodiments shown in the figures. The illustrated and described features can be used individually or in combination to create further preferred embodiments of the invention. In the figures: 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0032]      FIG. 1  shows, a partially cut-open perspective view of a blood withdrawal system according to the invention;  
         [0033]      FIG. 2  shows a perspective view of a drive module of the lancet drive used in the blood withdrawal system according to  FIG. 1 ;  
         [0034]      FIG. 3  shows an exploded perspective view of components of the module of  FIG. 2 ;  
         [0035]      FIG. 4  shows a perspective view of a module according to  FIG. 2  in a partially assembled state;  
         [0036]      FIG. 5  shows a perspective view of a lancet holder of the blood withdrawal system according to  FIG. 1 ;  
         [0037]      FIG. 6  shows a perspective view of a subunit of the blood withdrawal system according to  FIG. 1  consisting of a drive module according to  FIG. 2  and a lancet holder according to  FIG. 5 ;  
         [0038]      FIG. 7  shows a perspective view of a part of the blood withdrawal system shown in  FIG. 1  as seen from the other side (“control side”);  
         [0039]      FIG. 8  shows an exploded view of a control track part and a drive rotor with control traveller;  
         [0040]      FIG. 9  shows a side view onto parts of an ejection mechanism with a release element in its passive position; and  
         [0041]      FIG. 10  shows a side view onto parts of an ejection mechanism with a release element in its active position; 
     
    
     DETAILED DESCRIPTION  
       [0042]     The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention or its application or uses.  
         [0043]     The blood withdrawal system  1  shown in the figures consists of a puncturing device  2  and lancets  3  (shown in  FIG. 7 ). The mounting and the guide means for a lancet  3  in puncturing device  2  are shown in  FIG. 7 . Holding latches  4   a  of a lancet holder  4  encompass the rear part of lancet body  6 . A lancet tip  6  projects forward from the lancet body  5 .  
         [0044]     During the puncturing process, the lancet holder  4  is guided by means of a housing part (not shown) serving as guide means. Thereby indirectly the required guidance of the lancet on a predetermined puncturing path (here along the main axis A of puncturing device  2 ) is provided. Thus, the lancet is indirectly guided via the lancet holder  4 .  
         [0045]     However, the invention can also be used with puncturing devices, in which the lancet is “directly guided”, i.e. resides directly in a part of the housing providing the required guidance during the puncturing motion (a cartridge containing a plurality of lancets, for example). More details can be taken from EP 1384438 A1.  
         [0046]     The housing  8  of puncturing device  2  contains a lancet drive  9 . The lancet drive  9  moves the lancet in a high speed along the puncturing direction (shown by arrow  10 ) until the lancet&#39;s tip exits from an exit opening  11 , while a contact surface  12  of puncturing device  2 , which surrounds exit opening  11 , is pressed against a body part (not shown herein). This generates a wound in the body part for the withdrawal of blood. The housing  8  of the puncturing device preferably has an elongated shape. The end with exit opening  11  is designated herein as front end, and the opposite end is designated rear end. The front end of housing  8  is formed by a removable cap  7 .  
         [0047]     FIGS.  1  to  6  illustrate the design features of the lancet drive  9 , which are required for the transmission of force during the cocking phase and during the drive phase. As shown, during the cocking phase, in order to tension the spring, the force exerted onto a cocking button  14  is transmitted by a cocking mechanism (designated in its entirety as  13 ) to a drive spring  16  (shown in  FIG. 4 ). Preferably as shown in  FIG. 2 , the drive spring  16  is Integrated into a drive module  15 . During the drive phase, the drive spring  16  relaxes and drives a drive rotor  17  whose rotational motion, in turn, transforms into the translational puncturing motion of lancet holder  4 . This transmission of force in the present invention is identical to that described in EP 1384438 A1.  
         [0048]     The components of drive module  15  include a drive rotor  17  and a tensioning element  19 . As shown specifically in  FIG. 1 , the drive module  15  and the dive rotor  17  are rotatable about a common axis C which extends perpendicular to the puncturing direction  10  and to the longitudinal axis A of the puncturing device  2 .  
         [0049]     In order to cock the lancet drive  9 , the cocking button  14 , which is movable in a translational motion, is pushed together with a force transmission part  20  in puncturing direction  10 . One component of the force transmission part  20  is a toothed rack  21 , driving a pinion gear  22  which is coaxial to the tensioning element  19 . The pinion gear  22  is connected to the tensioning element  19  by means of a free-wheel device  23  such that the two parts are coupled to each other during the cocking motion, but uncoupled from each other during the return of the force transmission part  20 , and cocking button  14 , under the effect of a restoring spring  14   a.    
         [0050]     As shown in  FIG. 2  the free-wheel device  23  is realized by means of two elastic latches  24 , which are connected to the pinion gear  22 . The latches  24  are located in a recess  25  of the tensioning element  19 , the recess  25  face away from the drive rotor  17  and have two limit stops  27 , at which the ends of the latches  24  abut in the coupling rotation direction (clockwise in  FIG. 2 ), whereas the pinion, gear  22  can rotate freely relative to the tensioning element  19  in the reverse direction.  
         [0051]     The rotation of the tensioning element  19  tensions the drive spring  16 , which is a helical spring borne in a recess  28  of the tensioning element  19  which recess faces towards the drive rotor  17 . The force transmission part  20  with toothed rack  21 , the pinion gear  22 , the free-wheel device  23  and the actuation element  10  jointly form an input-side coupling mechanism  29 , which transmits the force exerted onto the cocking button  14  to the drive spring  16  during the cocking phase.  
         [0052]     The output-side coupling mechanism  30 , which transmits the force of the spring  16  to the lancet  3  during the drive phase, includes a control curve  31  which is formed by a circumferential groove  32 . In the example shown, the control curve  31  takes the shape of a circle which is eccentric with respect to axis C. A control pin  33 , which is a component of the lancet holder  4 , travels along the control curve  31  during the rotation of drive rotor  17 . To fix a lancet, the lancet holder  4  is provided with elastic arms  35  and a limit stop element  36 , whose shapes are adapted to the corresponding shape of the lancet body  5  such that lancet  3  is held in an exactly reproducible longitudinal position within lancet holder  4 .  
         [0053]     The rear end of lancet holder  4  with control pin  33  extends through a circumferential slit of the drive module  15  in such a manner that there is no interference with the rotational motion of the components of module  15 . In the embodiment shown this is achieved by means of a separating disc  37  made from metal, which is placed on a plateau  38  of drive rotor  17  in such a manner that a circumferential gap with a sufficient width to accommodate lancet holder  4  remains between the disc and the parts of the rotor  17  which are radially outwards from control curve  31 . In the embodiment of the lancet drive  9  shown, the motion phases of the drive follow the OWADAC principle as follows:  
         [0054]     During the cocking phase, the rotatable tensioning element  19 , driven by cocking button  14  via force transmission part  20  by means of toothed rack  21  and pinion; gear  22 , rotates in a predetermined direction (clockwise in  FIGS. 1 and 2 ), whereby the drive spring  16  is tensioned, while the rotation of drive rotor  17  is inhibited (by means of the trigger mechanism described in more detail below).  
         [0055]     In the drive phase, the drive spring  16  drives the drive rotor  17  (after release of the inhibition), while simultaneously the tensioning element  19  is locked against a reverse rotation (for example by an elastic catch, not shown herein, engaging a recess of tensioning element  19 ).  
         [0056]     FIGS.  7  to  9  show the essential design elements of the track control mechanism  40  and the ejection mechanism  41 , which are located, relative to drive rotor  17 , on the side of puncturing device  2 , which is opposite from the drive side  42  shown in  FIG. 1  and is called control side  43 .  
         [0057]     The components of the track control mechanism  40  include a control track part  45  and a control traveler  46 , which, in the embodiment shown, is a pin fixed to drive rotor  17 . Because the control traveler  46  is fixed to the drive, rotor  17 , it can move only on a circular path about axis C thereof. Drive spring  16  exerts a torque (which varies in magnitude depending on its tensioning state, but always acts in the same direction) onto drive rotor  17  and thereby on control traveler  46  (in clockwise direction in the Figures).  
         [0058]     In the assembled state, drive rotor  17  is located adjacent to the control track part  45  in such a manner that the control traveler  46  is positioned within a control track  47  of control track part  45  (this position of the control traveler  46  is indicated by broken lines in  FIG. 8 ). A relative movement of control traveler  46  with respect to the control track part  45  results, on the one hand, when the control track part  45  is moved parallel to the longitudinal axis A of the puncturing device  2  and, on the other hand, by means of the motion of the control traveler  46  on a circular path about axis C. The translational motion of control track part  45  results from the coupling thereof with cocking button  14 . In the preferred embodiment shown, the control track part  45  and the force transmission part  20  with toothed rack  21  are manufactured as one part and are formed approximately U-shaped such that in the assembled position the two legs of the U extend on the two sides of drive module  15 , i.e. force transmission part  20  on drive side  42  and control track part  45  on guide side  43 . The rear end of components  20 ,  45 , which are connected to each other, is attached to cocking button  14  such that both parts are moved equally in a translational motion by actuation of cocking button  14 .  
         [0059]     Due to the actuation of cocking button  14  and the biasing action of the drive spring (resulting in a rotational motion of the drive rotor  17 ), the control traveler  46  travels along a control path  47 , shown as dash-dot lines in  FIG. 8 , as defined by control profiles  49 ,  50 ,  51  embossed into control track part  45 . The most important functional positions of the control track are identified in  FIG. 8  by means of letters to which reference is made in the following explanation:  
         [0060]     a) This, is the initial position of the traveller  46  when the lancet drive is not loaded and the cocking button projects the farthest from housing  8 . In this state the axis C of the drive rotor  17  is in positional.  
         [0061]     b) Here the control traveller  46  is positioned in a pocket  52  of the guide profile  50 , which is shaped such that the control traveller  46  can be driven out only in one direction (continuing the previous motion). The section of control track  47  defined by pocket  52  is called one-way section  53 , since the control traveller, once driven into the one-way section  53 , can be driven out only in one direction. Thus, the control traveller  46  is capable of a relative motion with respect to the control track part  45  only in one direction of control track  47  beyond one-way section  53 . This arrangement provides a safety function since multiple cocking of the lancet drive, which may lead to damage, is prevented.  
         [0062]     c) When the cocking button  14  is depressed further (resulting in a forward motion of control track part  45 ), the control traveller  46  is driven by the action of the drive spring to this position in front of a locking wall formed by the guide profile  51 , which prevents further depression of the cocking button.  
         [0063]     d) When cocking button  14  is released, resulting in a rearward motion of control track part,  45 , the control traveller reaches this position, which corresponds to a stable intermediate position and in which the lancet drive is ready to be triggered, i.e. for starting the drive phase. Here, the cocking button is in a position which clearly differs from its initial position (corresponding to control track position a) and can additionally be labeled (e.g. by a color mark on the shaft of the cocking button  14 ). Thereby it is unambiguously indicated to the user that the device is in its cocked state and ready for use.  
         [0064]     The section of the control track between the positions c and e forms a reversing section  54 . Because of the U-shape of this section, the control traveller  46  can be driven out of reversing section  54  only after performing a relative motion with respect to control track part  45  in the reverse direction of the previous motion. This provides for actuation of the cocking button with a stable intermediate position as with a push-button switch.  
         [0065]     e) By depressing the cocking button  14  again, the control traveller  46  reaches this position, in which the contact between control traveller  46  and control track part  45  is interrupted. The control traveller is free allowing the drive rotor  17  to perform a rapid rotational motion about rotor axis C, which at this point of time is in position e 1 . The cocking button  14  therefore performs two functions, namely cocking and triggering.  
         [0066]     f) The rotational motion is terminated when the control traveller  46 ; again contacts control track part  45  (i.e., in the case shown, its guide profile  49 ) in this position.  
         [0067]     g) Under the action of the restoring spring  14   a , the cocking button  14  and, jointly with the button, the control track part  45  are moved backwards again, whereby the control traveller reaches its initial position via this position. Position g again marks a one-way section  55 , in which the control traveller is positioned in a pocket  56 , which prevents a motion against the predetermined direction of control track  47 .  
         [0068]     FIGS.  8  to  10  show the essential parts of the ejection mechanism, which in its entirety is designated  41  and consists, in the embodiment shown, of cocking button  14 , control track part  45  and a release element  61 . These elements are each borne in such a manner that they can be displaced in a translational motion in the puncturing direction  10  (and therefore in the direction of axis A of the device). They form a force transmission chain, which is symbolically indicated by arrow  70  and by which the motion of an actuation button of the lancet ejection mechanism is transmitted to the lancet holder  4 , in such a manner that the lancet  3  is released and can fall out of the holder  4  by the action of gravity. In the embodiment shown, the actuation button of the lancet ejection mechanism simultaneously is the actuation element of the cocking mechanism, i.e. the cocking button  14 . Though this is not absolutely required, it is particularly preferred. In this embodiment a single actuation button performs three functions (cocking, triggering, ejecting).  
         [0069]     The release of the lancet in the embodiment shown is achieved by pushing sliding latches  62 , which are provided on the release element  61 , between the elastic latches  4   a  of the lancet holder  4  and a counter-bearing  63  of the lancet holder  4  which extends oblique-outwards. This causes the holding latches  4   a  to be pressed apart and release the lancet  3 .  
         [0070]     As long as the removable cap  7 , which forms, the front end, of housing  8 , is attached, the lancet ejection mechanism  41  is inactivated, i.e. actuation of the cocking button  14  does not result in ejection of the lancet. Removal of the cap switches the lancet ejection mechanism  41  to its active state.  
         [0071]     The switching between the active and the passive state is achieved by means of a change in the position of the release element as shown in  FIGS. 9 and 10 . In  FIG. 9 , the release element is in its passive position, in which the force transmission chain  70  between the cocking button and the lancet is interrupted: cap  7  includes a counter-bearing  64 , shown by dashed lines in  FIG. 9 , which, as long as the cap is attached, pushes against the front end of an actuation part  65  on the release element  61 . This causes a pressure part  68  of the release element to be pressed against an oblique surface  69  which is fixed relative to the device and shown only schematically in  FIG. 9 . The release element is held in the horizontal position shown in  FIG. 9 . If the front end of control track part  45  is displaced, as indicated by arrow  66 , this motion is not transmitted to the release element  61 , since the two parts are not mutually engaged.  
         [0072]     In contrast, when the cap  7  is removed, the pressure exerted by the counter-bearing  64  on the actuation part  65  ceases and the release element  61  is moved under the action of a leaf spring  67  to the position shown in  FIG. 10 . In this position, the rear end of release element  61  is within the movement path of control track part  45 , such that a forward motion of the control track part  45  (upon actuation of the cocking button  14 ) is transmitted to the release element  61  and thereby also to the lancet.  
         [0073]     As any person skilled in the art will recognize from the previous description and from the figures and claims, modifications and changes can be made to the preferred embodiment of the invention without departing from the scope of the invention as defined in the following claims.