LATCH MECHANISM FOR PREVENTING LANCET OSCILLATION IN A LANCING DEVICE
A lancing device including a latch that pivots between a non-blocking position allowing a lancet carrier and a lancet to advance and retract through a first forward and reverse lancing stroke and a blocking position preventing further/excess/secondary oscillation of the lancet carrier and lancet. The pivotal latch can pivot about an axis perpendicular (e.g., for an L-shaped latch) or parallel/coaxial (e.g., for a sleeve latch) to the advancement and retraction motion of the lancet carrier and lancet.
1 . A device for lancing skin, comprising:
a housing;
a lancet having a sharp tip for puncturing the skin during a lancing stroke;
a lancet carrier holding the lancet and movable through the lancing stroke from a retracted position, through a forward portion of the lancing stroke, to an advanced position puncturing the skin, and through a return portion of the lancing stroke;
a drive mechanism operable to drive the lancet carrier through the lancing stroke;
a charging mechanism operable to charge the drive mechanism;
a latch mechanism operable to permit the lancet carrier to travel through the lancing stroke but prevent excess oscillation of the lancet carrier, wherein the latch mechanism includes a latch member comprising a spring-biased latch retainer; and
a ramp which extends outwardly from an extension extending from the housing, and wherein the ramp contacts an inner surface of the latch retainer and deflects the latch retainer away from the latch member from a neutral state to a charged state.
2 . The lancing device of claim 1 , wherein the latch mechanism includes a latch member comprising a spring-biased latch retainer, a latch-pivoting element of the charging mechanism, and a pressed surface and a latch-engaging element of the lancet carrier, wherein the latch member includes a charge-pivot face, a pressing surface, a drive-pivot face, and a drive-stop face, and wherein the latch member pivots between a blocking position, an intermediate non-blocking position, and a press non-blocking position, and is spring-biased to the blocking position.
3 . The lancing device of claim 2 , wherein operating the charging mechanism to charge the drive mechanism moves the latch-pivoting element of the charging mechanism into engagement with the charge-pivot face of the latch member to pivot the latch member from the blocking position to the intermediate non-blocking position, wherein the latch retainer retains the latch member in the intermediate non-blocking position to prevent reverse pivoting of the latch member.
4 . The lancing device of claim 3 , wherein as the lancet carrier travels along the forward portion of the lancing stroke the latch retainer is withdrawn from engagement with the ramp and the latch member reverse pivots to the press non-blocking position with the pressed surface of the lancet carrier interfering with the pressing surface of the latch member to prevent reverse pivoting of the latch member to the blocking position.
5 . The lancing device of claim 4 , wherein as the lancet carrier travels along the return portion of the lancing stroke the pressed surface of the lancet carrier clears interference with the pressing surface of the latch member and the latch member reverse pivots to the blocking position.
6 . The lancing device of claim 5 , wherein with the latch member in the blocking position if the lancet carrier is driven along the forward portion of the lancing stroke a second time the drive-stop surface of the latch member engages and blocks the latch-engaging element of the lancet carrier to prevent excess lancet-carrier oscillation.
7 . The lancing device of claim 1 , wherein the latch member is pivotally coupled to the housing by a pivot pin, the pivot pin comprising an axis transverse to the angular motion of the latch member.
8 . The lancing device of claim 1 , wherein the latch retainer is in the form of a resilient finger.
9 . The lancing device of claim 1 , wherein the latch member includes a leg having a first end and a second end, a foot extending perpendicularly and laterally offset from the second end of the leg, wherein a drive-stop surface is formed on a rear face of the foot, a charge-pivot face is formed on a front face of the foot opposite the drive-stop surface, and a pressing surface is formed between the drive-stop surface and the charge-pivot face.
10 . The lancing device of claim 9 , wherein the pressing surface is defined by a corner chamfer extending between the drive-stop surface and the charge-pivot face.
11 . The lancing device of claim 1 , wherein the lancet carrier includes a spring retainer, a latch-engaging element of the lancet carrier is formed by a forward face of the spring retainer, and a pressed surface of the lancet carrier is formed by a lateral face of the spring retainer.
12 . The lancing device of claim 1 , wherein the ramp comprises a front ramped portion and a rear ramped portion, wherein an interaction of the latch retainer with the front ramped portion induces the latch member to pivot to a blocking position and an interaction of the latch retainer with the rear ramped portion induces the latch member to pivot to and be retained in an intermediate non-blocking position.
13 . The lancing device of claim 12 , wherein the ramp is arcuate and elongated, and includes a tipping point between the front and rear ramped portions.
14 . The lancing device of claim 12 , wherein a drive-pivot face is engaged by a latch-engaging element as the lancet carrier travels along the forward portion of the lancing stroke to withdraw the latch retainer from engagement with the rear ramped portion the ramp to permit reverse pivoting of the latch member from the intermediate non-blocking position to a press non-blocking position.