referring now to fig1 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 . 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 . 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 . 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 . the lance 12 which is positioned in the housing in a pre - firing position ( fig1 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 ( fig3 a ) disposed within the housing 14 . the tab 40 and the corresponding linear slot 41 maintain the linear alignment of the base 34 . 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 ( fig1 a ) to a post - firing position ( fig3 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 . 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 . the operation of the lancing mechanism 12 will now be described starting with fig1 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 fig1 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 . 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 . turning now to fig2 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 . turning now to fig3 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 . 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 fig3 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 . 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 . turing now to fig4 a and 4 b , the lancing mechanism 10 is shown with the slider 28 drawing the forcing plunger 20 from the post - firing position ( fig3 a ) to the pre - firing position ( fig1 a ). the slider 28 , which is biased in the far right position by a third compression spring 70 as shown in fig3 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 fig4 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 fig4 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 . 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 . 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 .
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 .