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 . the blood withdrawal system 1 shown in fig1 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 . 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 . 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 . the cylinder guide 16 illustrated in fig1 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 . 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 . 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 fig1 , 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 . 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 . 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 . fig1 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 . fig1 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 . 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 . there are no transverse forces , so the total force exerted by the control element 22 is directed in or against the puncturing direction . 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 . as an alternative to the translation element 10 shown in fig1 , 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 . 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 . fig2 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 . 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 . in the exemplary embodiment illustrated in fig2 , 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 . 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 . 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 . fig3 shows a longitudinal section along the central axis a of the housing from fig2 . 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 . it can be seen clearly in fig3 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 . 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 . 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 .
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 .