Abstract:
A blood withdrawal system for producing blood from a body part for diagnostic purposes, comprising a housing with a lancet guide capable of guiding a lancet on a predetermined puncturing path and a lancet drive for driving a puncturing movement of a lancet on the predetermined path. The lancet drive comprises a drive rotor driven by a drive spring and rotates about an axis during the puncturing movement, and a coupling mechanism which converts the rotational movement of the drive rotor into a puncturing movement, wherein the lancet is moved during a forward phase of the puncturing movement in the puncturing direction until its tip penetrates into the body part to create a wound and is retracted from the skin during a retraction phase of the puncturing movement. The coupling mechanism includes a translation element coupled to the lancet and guided by a guide on a movement path.

Description:
BACKGROUND OF THE INVENTION  
     RELATED APPLICATION  
       [0001]     This application is related to and claims priority to European Application Serial No. 06016069.4, filed Aug. 2, 2006, the disclosure of which is expressly incorporated by reference herein.  
         [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a blood withdrawal system for producing blood from a body part for diagnostic purposes.  
         [0004]     2. Description of the Related Art  
         [0005]     To take blood in small amounts for diagnostic purposes from a body part, e.g., from a finger or earlobe, lancets are used; these lancets have a tip which punctures a wound in the corresponding body part. This is done manually by specially trained personnel or by using special blood withdrawal systems including a puncture device and respective lancets.  
         [0006]     A lancet drive for driving a puncturing movement of the lancet is provided in the housing of the puncture devices and is formed in many devices as a rotor drive in which the rotation of a drive rotor is converted into a translational movement of the lancet and/or a lancet holder.  
         [0007]     Such rotor drives have long been known. For example, a connecting rod for converting rotational movement to translational movement is disclosed in U.S. Pat. No. 4,924,879. In the disclosed embodiment, transverse forces are transferred via the connecting rod to the lancet. The transverse forces have a negative influence on the guidance of the lancet. In addition, the size of the wound formed in a body part is increased, which is perceived as painful by the patient.  
         [0008]     With other rotor drives, a recess is provided in the drive rotor. The recess acts as a control cam being traced by a pin during the rotation. This control cam design allows very different relationships between the rotational movement and the translational movement, depending on the shape of the control cam. For example, a different control cam can be traced during the puncturing movement in the puncturing direction than during the retraction phase of the puncturing movement. Such a cam control is known from EP 1034740 A1, for example, in which a rotor which rotates about the longitudinal axis of the blood withdrawal device is provided.  
         [0009]     EP 1504718 A2 also describes a blood withdrawal system having a drive rotor which rotates about an axis running perpendicular to the longitudinal direction of the system. Here again, a control cam is formed by a recess in which a control pin engages.  
         [0010]     In known blood withdrawal devices, the control pins must be formed to be small in some cases due to the geometry, so there is the risk that the pin might break. These known devices also have in common the fact that the drives are force-guided, i.e., the coupling between the rotor and the lancet is such that each position of the rotor unambiguously corresponds to a position of the lancet.  
         [0011]     Despite extensive development work in this field and the significant improvements thereby achieved, there is a great interest in a blood withdrawal system in which the creation of the wound is associated with the least possible pain, while the system is as simple as possible to operate, has a compact design and nevertheless has a certain sturdiness and is also inexpensive to manufacture.  
       SUMMARY OF THE INVENTION  
       [0012]     A blood withdrawal system according to one embodiment of the present invention comprises a housing and a lancet drive for driving a puncturing movement of a lancet along a predetermined puncturing path. The lancet drive has a drive spring and a drive rotor. The drive rotor is driven by the drive spring and rotates about an axis during the puncturing movement. The lancet drive also includes a coupling mechanism for converting the rotational movement of the drive rotor into the puncturing movement of the lancet. In a forward phase of the puncturing movement, the lancet is moved in the puncturing direction until its tip penetrates into the body part to create a wound. The coupling mechanism also moves the lancet in a retraction phase of the puncturing movement, which follows the forward phase, with the lancet being withdrawn from the skin during the retraction phase.  
         [0013]     The coupling mechanism includes a translation element coupled to the lancet which has two guide walls each with a guide surface. The translation element is guided by a guide on a translational movement path. The coupling between the translation element and the lancet is formed so that a movement of the translation element on the translational movement path in a first direction produces a movement of the lancet in the forward phase of the puncturing direction. Likewise, the movement of the translation element in a second direction produces a movement of the lancet in the retraction phase in the direction opposite the puncturing direction. The two guide walls of the translation element each have a contact surface, with one contact surface being oriented in the first direction of the translation element and the other contact surface being oriented in the second direction of the movement of the translation element.  
         [0014]     The orientation of the contact surface in the direction of the movement of the translation element is such that the surface normal of the contact surface has a component in the direction of movement of the translation element. The contact surface thus runs across the direction of movement of the translation element. The contact surface extends perpendicular to the direction of movement, so that the surface normal has only one component in the direction of movement of the translation element.  
         [0015]     The operative connection between the movement of the translation element and the movement of the lancet can be accomplished through any suitable coupling. The translation element can be coupled directly to the lancet. The coupling can comprise, for example, an angle lever or a deflection to transmit the direction of movement of the translation element in a predetermined direction of the lancet movement.  
         [0016]     The drive rotor of the blood withdrawal system has a control element with a control surface which runs around a center of the control element and is oriented radially outward from the center. During the puncturing movement, the control element rotates together with the drive rotor. The axis of rotation runs at a distance from the center of the control element. The control element is driven together with the drive rotor by the drive spring. The control surface of the control element is in contact with the guide surfaces on the guide walls of the translation element during the rotation of the drive rotor such that the movement of the translation element is controlled by the control element at least during a portion of the forward phase of movement and at least during a portion of the retraction phase of the puncturing movement.  
         [0017]     A very direct conversion of the rotational movement of the drive rotor into a translational movement of the translation element can be implemented in this manner. This permits good guidance, so that suitable wounds are created in the patient&#39;s skin. In addition, very rapid puncturing of the body part can be implemented, resulting in a reduced pain perception by the patient. This type of coupling mechanism generally requires very few components, and accordingly, the blood withdrawal system may be manufactured inexpensively. Furthermore, complex mechanisms can be omitted, such as those required when using control cams.  
         [0018]     The control surface of the control element is preferably a lateral surface in the sense that it is formed by a generating line which runs parallel to the axis of rotation of the drive rotor. However, the generating line need not necessarily be a straight line. If the generating line is curved, then it may be curved in such a manner that the resulting control surface has an outward convex curvature. It may run parallel to the axis of rotation along a line of its maximum distance from the center of the control element.  
         [0019]     In embodiments, since the control element rotates about an axis of rotation spaced apart from the center of the control element, the control element thus executes an eccentric rotation in which its own center is different from the axis of rotation.  
         [0020]     The guide walls of the translation element are oriented in such a manner that the first contact surface is oriented in the puncturing direction while the other contact surface of the second guide wall is oriented in a direction opposite the puncturing direction. This arrangement yields a direct interaction between the translation element and the lancet. The direction of movement of the translation element then corresponds to the direction of movement of the lancet. The contact surface is oriented in or against the puncturing direction. The surface normal of the contact surface thus has a component which is oriented in the direction of puncturing or in the direction opposite the puncturing direction. The surface may be oriented perpendicular to the puncturing direction.  
         [0021]     The control surface of the control element is in contact with the guide surfaces of the translation element and therefore controls the movement of the translation element at least partially during the forward phase and the retraction phase, so at least a partial coupling is implemented. The lancet is thus guided directly by the control element via the coupling mechanism in parts of the forward phase and of the retraction phase of movement. This partial coupling can also be extended to the entire puncturing movement. In this case, the lancet is force-guided by the drive rotor. The result is direct coupling. Each position of the control element corresponds to a position of the translation element and thus ultimately to a position of the lancet. This coupling may be generally referred to as a synchronous coupling because the position of the control element can be allocated to a defined position of the lancet.  
         [0022]     In embodiments of the invention, the control element can be formed in such a manner that its axis of rotation is either inside the control element or as an alternative, outside of the control element. If the axis of rotation is arranged inside the control element, then the control element can preferably be formed by a circumferential wall of the drive rotor. In embodiments of the invention, the control element may be part of the drive rotor.  
         [0023]     If the axis of rotation is outside of the control element, and in rotation of the drive rotor the control element is turning on a circular path about the axis of rotation, the control element can still be a part of the drive rotor. In particular, the control element can be formed by a pin mounted on the drive rotor. It should be noted that the drive rotor need not necessarily be in the form of a disk or wheel. The geometry of the drive motor is not limited to a cam-type design. For example, the pin-shaped control element of the drive motor may be mounted on the end of a rotating arm.  
         [0024]     In embodiments of the blood withdrawal system, at least the contact surfaces of the translation element are made from friction-optimized materials that are in contact with the control element. The entire translation element may be made of friction-optimized materials. It is also possible to provide the contact surfaces or the entire translation element with a coating having friction-optimized properties, such as all materials that are mixed with Polytetrafluoroethylene (PTFE) including Polyoxymethylene (POM) PTFE, for example. This reduces friction between the control element and the translation element. Wear is also reduced. On the whole, this yields simple handling of the device because the rotational movement of the control element is converted into the translational movement of the translation element without any significant friction losses.  
         [0025]     The guidance of the translation element during its translational movement is formed by guide rails which may be arranged in the housing of the blood withdrawal system. Alternatively or additionally, a cylinder guide can also be used. In embodiments, the blood withdrawal system may be in the form of an elongated cylinder. The housing of the blood withdrawal system can serve as a guide for the translation element. Other types of guidance are also conceivable as long as they fulfill the purpose of ensuring the straightest possible puncturing path of the lancet and of avoiding any vibration that might occur.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]     The above-mentioned and other features of this invention and the manner of obtaining them will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the present invention taken in conjunction with the accompanying drawings, wherein:  
         [0027]      FIG. 1  shows a cross-sectional view of a first embodiment of a blood withdrawal system;  
         [0028]      FIG. 2  shows a cross-sectional view of a basic diagram of a second embodiment of a blood withdrawal system, and  
         [0029]      FIG. 3  shows a detailed view of a coupling mechanism of the blood withdrawal system according to  FIG. 2 .  
         [0030]     Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of the present invention, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate and explain the present invention. The exemplifications set out herein illustrate embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
     
    
     DETAILED DESCRIPTION  
       [0031]     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings, which are described below. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. The invention includes any alterations and further modifications in the illustrated devices and described methods and further applications of the principles of the invention, which would normally occur to one skilled in the art to which the invention relates.  
         [0032]     The blood withdrawal system  1  shown in  FIG. 1  in the form of a basic schematic diagram has an elongated housing  2  with an opening  4  provided on its distal end  3 . A lancet guide  5  is provided in the interior of the housing  2 , guiding a lancet  6  on its puncturing path. The lancet  6  may also be guided by the housing  2  on its puncturing path, with the inside wall of the housing  2  functioning as the lancet guide  5 .  
         [0033]     The lancet  6  is coupled to a coupling mechanism  7  and is held by it in such a manner that the tip  8  of the lancet  6  is in the same position even if a new lancet  6  is coupled to the coupling mechanism  7 . The coupling mechanism  7  includes a lancet holder  9 , being adapted to the lancet  6 . In the depicted embodiment, a translation element  10  in the form of a cage  11  is connected to the lancet holder  9  of the coupling mechanism  7 . The cage  11  has a distal guide wall  12  and a proximal guide wall  13  as well as two side walls  14 .  
         [0034]     The translation element  10  of the coupling mechanism  7  is guided by a guide  15  connected to the housing  2  on a linear movement path. The guide  15  is formed as a cylinder guide  16  in the depicted embodiment and cylinder guide  16  guides the translation element  10  during the puncturing movement of the lancet  6 . The guide  15  can be formed by the housing  2 . In particular in the case of cylindrically formed housings  2 , the cylinder guide  16  may already be formed by the inside wall of the housing  2 . The guide  15  can also be implemented by the same component as the lancet guide  5 , e.g., the lancet guide  5  can simultaneously function as the guide  15 . In particular, when the housing  2  forms the lancet guide  5 , housing  2  can simultaneously serve as a guide for the translation element  10 .  
         [0035]     The cylinder guide  16  illustrated in  FIG. 1  forms a guide space  17  in the interior, which is bordered by a proximal wall  18 . In the direction of the distal end  3 , the guide space  17  is closed by a distal wall  19  having a bore  20 . The lancet holder  9  of the coupling mechanism  7 , being connected in one piece to the translation element  10 , passes through the bore  20 . The proximal wall  18  and the distal wall  19  of the guide space  17  are spaced apart from one another in such a manner that they do not restrict the path of movement of the translation element  10 .  
         [0036]     There is a drive rotor  21  inside the cage  11  of the translation element  10 . The drive rotor  21  belongs to a lancet drive, which also includes parts not shown here, in particular a drive spring and a tension device for applying tension to the drive springs. During the puncturing movement of the lancet  6  the drive rotor  21  is driven by the drive spring and rotates about an axis  26 .  
         [0037]     A circumferential wall  23  of the drive rotor  21  oriented radially outward forms a control surface  27  in the embodiment shown here. In the embodiment according to  FIG. 1 , the drive rotor  21  thus also forms the control element  22 . Its center  24 , corresponding to the center of the control surface  27 , is spaced apart from the axis of rotation  26 . During rotation, the center  24  of the control element  22  runs on a circular path around the axis of rotation  26 .  
         [0038]     The control element  22  has a control surface  27  oriented radially outward from its center  24 . The control surface  27  is formed such that the surface normals are directed radially outward from the center  24  along a line revolving about the center  24 .  
         [0039]     The control surface  27  of the control element  22  is in contact with a contact surface  28  of the distal guide wall  12  of the translation element  10  and with a contact surface  29  of the proximal guide wall  13  of the translation element  10 . The contact surface  28  is oriented against the puncturing direction of the lancet  6 , while the contact surface  29  is oriented in the puncturing direction.  
         [0040]      FIG. 1  shows a permanent coupling of the control element  22  to the translation element  10  in which the control element  22  is substantially in contact with both contact surfaces  28  and  29  at the same time. In embodiments, the control element  22  is arranged to reduce the amount of friction between the element  22  and the surfaces  28  and  29 . Such a coupling may be referred to as a forced coupling. The lancet  6  is force-guided, i.e., each position of the rotating control element  22  correlates with an unambiguous position of the translation element  10  and/or the lancet  6 .  
         [0041]      FIG. 1  shows the position of the control element  22  at the point of reversal of the puncturing movement. During the subsequent retraction phase of the puncturing movement, the control element  22  exerts a force on the contact surface  29  and forces the translation element  10  against the puncturing direction of the lancet  6 . During the forward phase, the control element  22  acts with a force on the contact surface  28  and moves the translation element  10  in the puncturing direction. The rotational movement of the control element  22  is thus easily converted into a translational movement of the translation element  10 , wherein a force of the control surface  27  acts on at least one of the contact surfaces  28 ,  29  during the rotation of the control element  22  about the axis of rotation  26 .  
         [0042]     The contact surfaces  28  and  29  of the translation element  10  preferably run in a plane perpendicular to the axis of rotation  26 . Therefore, forces acting across the puncturing direction are prevented.  
         [0043]     There are no transverse forces, so the total force exerted by the control element  22  is directed in or against the puncturing direction.  
         [0044]     In one embodiment, at least the contact surface  28  of the translation element  10  is directed substantially perpendicular to the puncturing direction of the lancet  6 . Both contact surfaces  28  and  29  may be directed perpendicular to the lancet  6 . Therefore, the friction between the control element  22  and the translation element  10  is reduced and tilting of the translation element  10  on its translational path in the puncturing direction and against the puncturing direction is inhibited. A good transfer of force is supported by the guide  15 , so that a vibration-free puncturing of the lancet  6  into the body part is achieved on the whole.  
         [0045]     As an alternative to the translation element  10  shown in  FIG. 1 , the distance between the distal guide wall  12  and the proximal guide wall  13  can be greater than the diameter of the control element  22 . The distance between the two guide walls  12  and  13  is selected by taking into account the diameter and eccentricity of the rotor, so that the control element  22  is in contact with one of the two contact surfaces  28 ,  29  of the translation element  10  during at least half of the puncturing movement, such that each position of the control element  22  correlates with a position of the translation element  10  and thus of the lancet  6 . During the forward phase, the force of the control element  22  is transferred at least temporarily to the contact surface  28 , and during the retraction phase, the force exerted by the control element  22  is transferred at least temporarily to the contact surface  29 . In this embodiment, there is not a continuous force-guided coupling between the control element  22  and the translation element  10 .  
         [0046]     As an alternative to the translation element  10 , which is formed as a cage  11 , a translation element  10  comprising a distal guide wall  12  and a proximal guide wall  13  without connecting walls is also possible. These guide walls  12 ,  13  can be formed as webs, for example, which protrude away from a base body of the translation element. The control element  22  need not be surrounded. The contact between the control element  22  and the distal guide wall  12  and/or the proximal guide wall  13  must be ensured for only a portion of the forward phase and a portion of the retraction phase, so that at least temporary coupling between the control element  22  and the translation element  10  is implemented.  
         [0047]      FIG. 2  shows an alternative embodiment of a blood withdrawal system  1 , which has a housing  30  with a lancet guide and a lancet drive (not shown). A lancet  31  is connected to a coupling mechanism  32 , comprising a translation element  33  which has a cage  34  with guide walls  34 A and  34 B and two opposing guide rods  35 ,  36 . The guide rods  35 ,  36  extend along a central housing axis A, wherein the guide rod  35  is arranged between the cage  34  and the lancet  31 . The guide rod  36  extends from the cage  34  away from the lancet  31 . The rods  35 ,  36  are guided in the puncturing direction by a guide consisting of guide elements  37 .  
         [0048]     A drive rotor  38  is also arranged on the housing central axis A and may be rotated by a drive spring (not shown) of the lancet drive during the puncturing movement of the lancet  31 . The drive rotor  38  rotates about an axis of rotation  39 . A rotor arm  40 , which is attached to the drive rotor  38 , can also be in one piece with the drive rotor  38 , as shown here. A control element  41  which is surrounded by the cage  34  is fixedly coupled to the distal end of the rotor arm  40 .  
         [0049]     In the exemplary embodiment illustrated in  FIG. 2 , the axis of rotation  39  is outside of the control element  41  and the control element  41  rotates on a circular path  42  (shown with a dotted line) which describes a circle about the axis of rotation  39  in the rotation of the drive rotor  38 .  
         [0050]     The control element  41  is always connected to the cage  34  in its rotational movement about the axis of rotation  39 . The control element  41  is thus in contact with the contact surfaces  43 ,  44  of the cage  34 , so that there is a direct coupling between the drive rotor  38  and the translation element  33  and thus ultimately with the lancet  31 .  
         [0051]     The cage  34  itself is also guided in the housing  30 , where the inside walls of the housing  30  are formed as guide rails  45 . Transverse forces are minimized in particular due to the embodiment of the translation element  33  as a cage  34  with the contact surfaces  43 ,  44  perpendicular to the puncturing direction. The transfer of force in the puncturing direction and in the direction opposite the puncturing direction is optimized.  
         [0052]      FIG. 3  shows a longitudinal section along the central axis A of the housing from  FIG. 2 . The drive rotor  38 , which consists of only a bearing shaft, is fixed to the rotor arm  40 . A drive mechanism (not shown) is arranged on the end (not shown) of the drive rotor  38  in the form of a shaft (not shown). At its other end, the rotor arm  40  is connected to the control element  41 , which is preferably formed as a pin  46 . Due to the rigid coupling via the rotor arm  40 , there is a fixed connection between the pin  46  and the drive rotor  38 . The pin  46  transmits the forces exerted by the drive rotor  38  to the contact surfaces  43  and  44  of the cage  34  of the translation element  33 .  
         [0053]     It can be seen clearly in  FIG. 3  that the pin  46  cannot slip out of the cage  34  because it protrudes beyond the cage  34  and there is too little play between the pin  46  and the straight contact surfaces  43 ,  44  of the cage  34 . In particular, the pin  46  is prevented from slipping out if the guide is formed so that the translation element  33  can execute only a translational movement into and against the puncturing direction of the lancet  31 , and if a movement in the two other directions in space, in particular a tilting, is excluded.  
         [0054]     The coupling of the translation element  32  and the lancet  31  is such that a movement of the translation element  32  in a first direction causes a movement of the lancet  31  in the forward phase in the puncturing direction. A movement of the translation element  32  in a second direction causes a movement of the lancet  31  in the retraction phase opposite the puncturing direction. The guide surfaces  43 ,  44  are oriented so that the one guide surface is oriented in the first direction of movement of the translation element  32  and the other guide surface is oriented in the second direction of movement of the translation element  32 .  
         [0055]     While the invention has been taught with specific reference to these embodiments, one skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the invention. The described embodiments are to be considered, therefore, in all respects only as illustrative and not restrictive. As such, the scope of the invention is indicated by the following claims rather than by the description.