Abstract:
A lancing mechanism for puncturing skin is provided. The lancing mechanism comprises a lance having a penetration end which is adapted to puncture skin. The penetration end of the lance is movable from a first position to a second position during a forward stroke and between the second position and the first position during a return stroke. A forcing plunger applies a force to the lance to move the lance from the first position to the second during the forward stroke. The forcing plunger is adapted to engage the lance during the forward stroke to move the penetration end of the lance from the first position to the second position and to disengage the lance when the penetration end of the lance approaches the second position. A first resilient member coupled to the lance moves the first end of the lance from the second position to the first position during the return stroke.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to blood monitoring devices, and, more particularly, to a lancing mechanism for lancing a user&#39;s skin to obtain a sample of blood for analysis.  
         BACKGROUND OF THE INVENTION  
         [0002]    It is often necessary to quickly obtain a sample of blood and perform an analysis of the blood sample. Preferably, the obtaining of blood is as painless as possible. One example of a need for painlessly obtaining a sample of blood is in connection with a blood glucose monitoring system where a user must frequently use the system to monitor the user&#39;s blood glucose level.  
           [0003]    Those who have irregular blood glucose concentration levels are medically required to regularly self-monitor their blood glucose concentration level. An irregular blood glucose level can be brought on by a variety of reasons including illness such as diabetes. The purpose of monitoring the blood glucose concentration level is to determine the blood glucose concentration level and then to take corrective action, based upon whether the level is too high or too low, to bring the level back within a normal range. The failure to take corrective action can have serious implications. When blood glucose levels drop too low—a condition known as hypoglycemia—a person can become nervous, shaky, and confused. That person&#39;s judgment may become impaired and that person may eventually pass out. A person can also become very ill if their blood glucose level becomes too high—a condition known as hyperglycemia. Both conditions, hypoglycemia and hyperglycemia, are both potentially life-threatening emergencies.  
           [0004]    One method of monitoring a person&#39;s blood glucose level is with a portable, hand-held blood glucose testing device. The portable nature of these devices enables the users to conveniently test their blood glucose levels wherever the user may be. In order to check the blood glucose level, a drop of blood is obtained from the fingertip using a separate lancing device. The lancing device contains a needle lance to puncture the skin. Once the requisite amount of blood is produced on the fingertip, the blood is harvested using the blood glucose testing device. The blood is drawn inside of the testing device which then determines the concentration of glucose in the blood. The results of the test are communicated to the user via a display on the testing device.  
           [0005]    Many prior art lancing devices implement a spring coupled to the actual lance to move the lance to its penetration depth. The lance is drawn back to compress the spring. When released, the spring extends thus forwardly propelling the lance to its penetration depth. One problem associated with some prior art lancing devices is that the penetration depth of those lances is dependant on a spring constant which is a measure of the spring&#39;s stiffness. The mechanical qualities of a spring, including the stiffness, tend to degrade over time with use. Accordingly, over time, the penetration depth of many prior art lances may vary. When the penetration depth of the lance lessens over time, the lance may not produce a laceration deep enough to draw the requisite volume of blood necessary for blood glucose analysis. An insufficient lancing can result in an erroneous analysis if the user does not recognize that the lancing has not produced the requisite volume of blood for analysis. Or, if the user does recognize an insufficient lancing has occurred, the user must re-lance resulting in another laceration in the user&#39;s skin and more pain. The user may eventually have to replace the lance which has degraded over time.  
           [0006]    Another related problem associated with many of the aforementioned prior art lancing devices is that when the spring forwardly advances the lance to its penetration depth, the spring extends past its static length. The spring then retracts the lance; however, due to the oscillatory nature of the spring, the lance is retracted past its static length. The lance continues to oscillate in this manner thus entering the laceration created in the user&#39;s skin several times. Put another way, with each actuation of a prior art lancing device, a user&#39;s skin is lanced several times which results in a larger laceration. A larger laceration in the user&#39;s skin translates into more pain for the user and a longer time for the laceration to heal.  
           [0007]    Accordingly, there exists a need for a lancing mechanism which moves a lance a known stroke not dependent on a spring constant and the extension of the spring past its static length.  
         SUMMARY OF THE INVENTION  
         [0008]    A lancing mechanism for puncturing skin is provided. The lancing mechanism comprises a lance having a penetration end which is adapted to puncture skin. The penetration end of the lance is movable from a first position to a second position during a forward stroke and between the second position and the first position during a return stroke. A forcing plunger applies a force to the lance to move the lance from the first position to the second during the forward stroke. The forcing plunger is adapted to engage the lance during the forward stroke to move the penetration end of the lance from the first position to the second position and to disengage the lance when the penetration end of the lance approaches the second position. A first resilient member coupled to the lance moves the first end of the lance from the second position to the first position during the return stroke. 
       
    
    
       [0009]    The above summary of the present invention is not intended to represent each embodiment, or every aspect, of the present invention. Additional features and benefits of the present invention will become apparent from the detailed description, figures, and claims set forth below.  
       BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    Other objects and advantages of the invention will become apparent upon reading the following detailed description in conjunction with the drawings in which:  
         [0011]    [0011]FIG. 1 a  is a side view of a lancing mechanism shown in a pre-firing position according to one embodiment of the present invention;  
         [0012]    [0012]FIG. 1 b  is a perspective view of a lancing mechanism shown in a pre-firing position according to one embodiment of the present invention;  
         [0013]    [0013]FIG. 2 a  is a side view of a lancing mechanism shown at the approximate conclusion of a forward stoke of a lance according to one embodiment of the present invention;  
         [0014]    [0014]FIG. 2 b  is a perspective view of a lancing mechanism shown at the approximate conclusion of a forward stoke of a lance according to one embodiment of the present invention;  
         [0015]    [0015]FIG. 3 a  is side view of a lancing mechanism shown in a post-firing position according to one embodiment of the present invention;  
         [0016]    [0016]FIG. 3 b  is perspective view of a lancing mechanism shown in a post-firing position according to one embodiment of the present invention;  
         [0017]    [0017]FIG. 4 a  is a side view of a lancing mechanism shown in a mid-return position according to one embodiment of the present invention; and  
         [0018]    [0018]FIG. 4 b  is a perspective view of a lancing mechanism shown in a mid-return position according to one embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]    Referring now to FIGS. 1 a  and  1   b , a lancing mechanism  10  of the present invention will be described in greater detail. The lancing mechanism  10  includes a lance  12  disposed within a housing  14 . The lance  12  has a sharp penetration end  16  which is capable of puncturing skin to obtain of drop of blood for analysis. To obtain a sample of blood, the penetration end  16  of the lance  12  extends beyond the housing  14  through an aperture  18  disposed in the housing  14  to puncture a user&#39;s skin. After making the initial laceration in the user&#39;s skin, the lance  12  is drawn back within the housing  14 .  
         [0020]    The lancing mechanism  10  is designed to fire the lance  12  without experiencing the aforementioned oscillations associated with prior art lancing devices. During a forward stroke, the penetration end  16  of the lance  12  is moved to its penetration depth while engaged by a forcing plunger  20  via a linkage  22 . Once the penetration end  16  of the lance has reached its penetration depth, the lance  12  beings its return stroke wherein a first compression spring  24  causes the lance  12  to ascend back into the bounds of the housing  14 .  
         [0021]    The forcing plunger  20  provides the force necessary to move the penetration end  16  of the lance  12  through a user&#39;s skin to the penetration depth. The forcing plunger  20  transmits the force provided to it by a second compression spring  26  through the linkage  22  to the lance  12 . In order to produce the requisite force, the forcing plunger  20  is drawn back to the pre-firing position with a slider  28  thus compressing the second compression spring  26 . In the pre-firing position, the forcing plunger  20  is held in place by a trigger  30 . When depressed, the trigger  30  releases the forcing plunger  20  thus firing the lancing mechanism  10 .  
         [0022]    The lancing device  10  of the present invention remedies the aforementioned problems associated with prior art lancing devices by moving the lance  12  a known length during a forward stoke with a linkage  22 . The penetration depth of the lance is not based on a spring constant and the extension of that spring past the static length of the spring.  
         [0023]    The lance  12  which is positioned in the housing in a pre-firing position (FIG. 1 a ) is movable in the direction indicated by arrow A during the forward stroke and in the direction indicated by arrow B during the return stroke. The housing  14  contains a first channel  32  which constrains the lateral movement of the lance  12 . The first channel  32  is substantially parallel to a longitudinal axis of the lance  12 . The lance  12  has a base  34  which travels along with the lance  12  in a second channel  36 . The first compression spring  24  is disposed in the second channel  36  between the base  34  and a shelf  38  formed at the intersection of the second channel  36  and the first channel  32 . The base  34  contains an outwardly extending tab  40  which mates with a corresponding linear slot  41  (FIG. 3 a ) disposed within the housing  14 . The tab  40  and the corresponding linear slot  41  maintain the linear alignment of the base  34 .  
         [0024]    The housing  14  contains a third channel  42  which constrains the lateral movement of the forcing plunger  20 . The third channel  42  is substantially parallel to a longitudinal axis of the forcing plunger  20 . The forcing plunger  20  is disposed within the housing  14  substantially perpendicular to the lance  12 . The second compression spring  26  is disposed between a base  44  of the forcing plunger  20  and the a base  46  of the third channel  42 . The forcing plunger  20  moves in the direction indicated by the arrow C from a pre-firing position (FIG. 1 a ) to a post-firing position (FIG. 3 a ). The movement of the forcing plunger  20  from the pre-firing position to the post-firing position coincides with the forward and return stroke of the lance  12 . The forcing plunger  20  has a rounded end  48  which contains outwardly extending tabs  50  which mate with corresponding slots  52  disposed in the housing  14 . The combination of the outwardly extending tabs  50  and the corresponding slots  52  aide in maintaining the linear movement of the forcing plunger  20  when advancing from the pre-firing position to the post-firing position.  
         [0025]    The housing  14  contains an hollow portion  54  to accommodate the rotation of the linkage  22  during the operation of the lancing mechanism. The linkage  22  is pivotally coupled to the base  34  via a pin  56 . The linkage  22  has a curved receiving end  58  which is designed to engage the rounded end  48  of the forcing plunger  20 . When the forcing member moves in the direction indicated by the arrow C, the forcing member  20  contacts the linkage  22  thus forcing the lance  12  downward in the direction indicated by arrow A.  
         [0026]    The operation of the lancing mechanism  12  will now be described starting with FIGS. 1 a  and  1   b.  In order to lance a user&#39;s skin, a user holds the lancing mechanism  10  by a handle portion  60  of the housing  14  in a manner such that the portion of the housing  14  containing the aperture  18  is pressed against the user&#39;s skin. In FIGS. 1 a  and  1   b,  the forcing plunger  20  is shown in the pre-firing position. The user depresses the trigger  30  of the lancing mechanism  10  to release the forcing plunger  20 . Upon being released, the forcing plunger  20  rapidly accelerates in the direction indicated of the arrow C. In the pre-firing position, the rounded end  48  of the forcing plunger  20  is substantially in contact with the curved receiving end  58  of the linkage  22 . The curved receiving end  58  contains a lip  62  which maintains the contact between the curved receiving end  58  of the linkage  22  and the rounded end  48  of the forcing plunger  20 . The linear movement of the plunger  20  in the direction of the arrow C forces the linkage  22  to move linearly in the direction of arrow A and to rotate in the clockwise direction. In turn, the aforementioned movement of the linkage  22  forces the lance  12  linearly downward in the direction of the arrow A.  
         [0027]    To summarize, depression of the trigger  30  fires the forcing plunger  20 . The forcing plunger  20  rapidly advances from the pre-firing position in the direction of arrow C. The forcing plunger  20  engages the linkage  22  which intern propels the lance  12  downward in the direction of arrow A.  
         [0028]    Turning now to FIGS. 2 a  and  2   b,  the linkage  22  has rotated in the clockwise position such that it is shown in approximately the twelve o&#39;clock position. When in the twelve o&#39;clock position, the linkage  22  has also been moved downward by the forcing plunger  20  a distance sufficient for the lance  12  to extend beyond the housing a distance X about equivalent to the penetration depth. The forward stroke of the lance  12  concludes when the distance X is at a maximum. The forcing plunger  20  continues to move in the direction of the arrow C which in turn further rotates the linkage  22  in the clockwise direction.  
         [0029]    Turning now to FIGS. 3 a  and  3   b , as the forcing plunger  20  continues to travel in the direction indicated by the arrow C, the curved receiving end  58  of linkage  22  continues to engage the forcing plunger  20  during which the linkage  22  continues its clockwise rotation. However, once the forward stroke is complete, the linkage  22  is no longer being forced downward by the receiving member  20 . The continued movement by the forcing member  20  in the direction of arrow C creates room for the first compression spring  24  to advance the lance  12  and in turn the linkage  22  upward in the direction of the arrow B. The linkage  22  continues to rotate in the clockwise direction, until the linkage  22  contacts a wall  64  which prohibits any further clockwise rotation of the linkage  22 . When the linkage  22  contacts the wall  64 , the lip  62  of the curved receiving end  58  is substantially in the horizontal position allowing the forcing plunger  20  to push the past the lip  62  and continue to travel in the direction of the arrow C until contacting a slider  28 .  
         [0030]    After the linkage  22  has disengaged the forcing member  20 , the first compression spring  24  forces the lance  12  and the linkage  22  upward to the position shown in FIGS. 3 a  and  3   b . No.oscillation of the lance  12  occurs because the first compression spring  24  is prohibited from extending to its static length. The outwardly extending tab  40  on the base  34  of the lance  12  engages an upper end  68  of the slot  41  to prevent any further movement of the lance in the direction of the arrow B.  
         [0031]    To summarize, a firing of the lancing mechanism  10  results in only one forward and one return stroke of the lance  12 . The lancing mechanism  10  eliminates the multiple oscillations of the lance into and out of the laceration created in the user&#39;s skin which is a problem associated with some prior art lancing devices. This problem is remedied because the length of the forward stroke of the lance  12  of the lancing mechanism  10  is not dependant on the spring constant of a spring which moves a prior art lance and the extension of that spring past its static length. In the present invention, the forward stroke of the lance  12  is dependant on the length of the linkage  22 . Accordingly, in various embodiments of the present invention, the length of the linkage  22  is varied in order to change the penetration depth of the lancing device  12 . The penetration depth of the lancing mechanism  10  remains consistent over the life of the lancing mechanism  10  because the penetration depth is dependant on the length of the linkage  22 . Conversely, the penetration depth of a prior art lance tends to degrade over time because the mechanical properties of the spring which moves the lance tend to degrade over time. Any oscillations of the lance  12  due to the first compression spring  24  are suppressed and do not cause repeated lancings because the combination of the tab  40  and the slot  41  prohibit the spring  24  form extending past its static length.  
         [0032]    Turing now to FIGS. 4 a  and  4   b , the lancing mechanism  10  is shown with the slider  28  drawing the forcing plunger  20  from the post-firing position (FIG. 3 a ) to the pre-firing position (FIG. 1 a ). The slider  28 , which is biased in the far right position by a third compression spring  70  as shown in FIG. 3 a , is used to move the lancing mechanism  10  back into the pre-firing position. After the lance has been fired, the user simply slides the slider  28  to the left as viewed in FIG. 4 a  to ready the lancing mechanism  10  for firing. The sliding of the forcing plunger  20  pushes the linkage  22  into place for firing. As the plunger  20  slides to the left as viewed in FIG. 4 a , a backside  72  of the forcing plunger  20  contacts the linkage  22  causing the linkage  22  to rotate in the counterclockwise direction to the firing position. Once the forcing plunger  20  pushes past the linkage  22 , a wire spring (not shown) biases the linkage  22  back in the clockwise direction so that the curved receiving end  58  of the linkage  22  engages the rounded end  48  of the plunger. The third spring  70  biases the slider  28  back to the right so that the slider  28  does not interfere with the forcing plunger  20  during the firing of the lancing mechanism  10 .  
         [0033]    The lancing mechanism  10  is designed to be light-weight and compact allowing the user to carry the lancing mechanism  10  on the user&#39;s person. In order to reduce the weight of the lancing mechanism  10 , the various structural components such as the housing  14 , the forcing plunger  20 , the linkage  22 , the slider  28 , the trigger  30 , etc. are made out of a light-weight, rigid material such as, for example, plastic. The lancing mechanism  10  is also designed so that the user can operate the mechanism  10  with a single hand thus freeing the fingers of the user&#39;s other hand for lancing. In operation, the user grasps the handle  62  portion of the housing  14  with the user&#39;s left-hand, for example. The user contacts the portion of the housing  14  containing the aperture  18  against the user&#39;s skin, such as the skin on one of the user&#39;s right-hand fingers. The user then depresses the trigger  30  with a left-hand finger or thumb to fire the lancing mechanism.  
         [0034]    While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that it is not intended to limit the invention to the particular forms disclosed, but, to the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims.