Abstract:
A lancet device includes a main body in which is located a lancet drive shaft  20  having a lancet holder  22  at its front end. A front housing flap  12  is hinged to the front of the main body portion and opens to allow insertion/withdrawal of a lancet. A multi-function cocking/ejection element  16  is operable both to cock the drive shaft prior to firing and to eject a lancet from the lancet holder after firing. The cock/eject element also unlatches the front flap  12.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to lancing devices and in particular, but not exclusively, to lancing devices for use with a removable lancet. 
     2. Description of the Related Art 
     There are many instances where a user needs to prick the skin to draw a bead of blood for test purposes. To reduce the possibility of cross-infection or contamination, it is known to provide a lancing device with removable or disposable lancets which are removed and disposed after each use. Although a lancing device is reusable for an extended period, it is nevertheless desirable to reduce the component count in order to reduce manufacturing and assembly costs. It is also desirable to reduce the amount of handling of the lancet by the user. 
     U.S. Pat. No. 5,423,847 discloses a lancet injector which uses two elastomeric bands to drive the lancet forwardly and to rapidly withdraw the lancet from the skin. The injector includes a separate chassis disposed within a housing, a shaft, an ejector and a separate slide member. Movement of the ejector is controlled by engagement with the chassis during various phases of operation of the device. The device is complicated to manufacture and assemble given the number of components. In particular, the injector requires a separate slide member and a chassis in addition to the other components. 
     SUMMARY OF THE INVENTION 
     In one aspect, this invention provides a lancing device comprising an outer housing, a drive shaft disposed in the housing for movement between a rearward and a forward position, said drive shaft having a lancet holder means at its forward end for receiving in use a lancet, a drive spring urging said drive shaft in a forward direction, a latch for latching said drive shaft in a rearward cocked position with the drive spring energised, a trigger for unlatching said drive shaft from its rearward position, and a cocking/ejecting element having an externally accessible manually operable portion and being arranged to be moveable in the rearward direction to cock the drive shaft, the cocking/ejecting element further being operable to eject a lancet from the lancet holder. 
     Although other movements are possible, e.g. rotary, said cocking/ejecting element is preferably moveable forwardly to eject a lancet from said lancet holder. 
     Said latch preferably includes an abutment provided on the interior of the housing, which cooperates with a corresponding abutment on the drive shaft, one of said abutments being resiliently deflectable out of engagement with the other. For example said shaft or a portion thereof may be resiliently deflectable, and said trigger means may comprise an externally accessible trigger button operable to engage and displace the abutment on said shaft. 
     The housing may be generally opaque in at least a rearward portion thereof, and said trigger button may comprise a transparent or translucent member having an internal space, with said shaft having an indicator portion on its rearward end which projects into said space when said shaft is in its rearward position, thus indicating the device is cocked. 
     Said cocking/ejecting element may comprise a spring support portion disposed interiorly of the housing and acted upon by opposing spring means. 
     Said cocking/ejecting element may have a cocking abutment for engaging said shaft and urging it rearwardly when said cocking/ejecting element is moved rearwardly, and an ejection finger extending forwardly and operable to enter the lancet holder to eject a lancet when said cocking/ejecting element is moved forwardly. 
     In one arrangement, the outer housing may have a forward portion hingeable with respect to the remainder thereof between an open position in which there is access to said lancet holding means, and a closed position ready for lancing, and said hingeable forward portion may be latchable in said closed position. In this case, said cocking/ejecting element may have an unlatching element disposed to unlatch said hinge portion when said cocking/ejecting element is moved forwardly. 
     Although the invention has been described above, it extends to any inventive combination or sub-combination of features set out above, or in the following description or claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       The invention may be performed in various ways, and an embodiment thereof will now be described by way of example only, reference being made to the accompanying drawings, in which: 
         FIG. 1  is a general perspective view of a lancing device in accordance with this invention; 
         FIG. 2  is a perspective view of the lancing device of  FIG. 1 , when in the cocked position, but with part of the casing removed and other parts cut away for clarity; 
         FIG. 3  is a longitudinal section view through the lancing device of  FIGS. 1 and 2 ; 
         FIG. 4  is a top plan view of the lancing device of  FIGS. 1 to 3 ; 
         FIGS. 5 to 8  are views similar to  FIG. 2  but showing the device during various phases of its operation, and 
         FIG. 9  is an exploded view of the lancing device of  FIGS. 1 to 8 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring initially to  FIG. 1 , the illustrated embodiment of lancing device comprises an outer main housing made up of housing halves  10 ,  11  to the forward end of which is hingedly attached a housing flap  12  on the front of which is mounted a rotary adjustable nose piece  14  for controlling the penetration depth of the lancet. The lancing device is designed to receive a lancet which, on firing, projects its tip through an aperture in the nose piece  14 . Cocking of the lancet, unlatching the housing flap  12  and ejection of the lancet from the housing is achieved using a multi-function cocking/ejection element  16 . Once cocked, the lancet is fired by pressing a trigger button  18  which projects from the rear of the housing  10 . 
     Referring now more particularly to  FIGS. 2 to 9 , arranged internally of the housing  10 ,  11  for longitudinal sliding movement is a lancet drive shaft  20  of generally cruciform cross-section along part of its length. At its forward end there is provided a generally cylindrical lancet holder  22  having an internal space of generally cylindrical form for receiving a lancet  24 . The forward half of the drive shaft has the vertical rib of the cruciform cut away to receive the cocking/ejection member  16  as to be described in more detail below. To the rear of the cut away portion the tips of the cruciform members define rearward facing thrust surfaces  26  for the lancet drive spring  28 , the opposite end of which engages an internal wall  30  in the housing halves  10 ,  11 . To the rear of the thrust surfaces  26 , the upper and lower ribs of the cruciform drive shaft are formed as flexible barbed fingers  32  having heads  34  which, when the drive shaft is urged rearwardly to its cocked position, latch behind the internal wall  30 . The shaft continues rearwardly beyond the heads  34  to be formed as an indicator cylinder  36  which, when the lancet drive shaft  20  is cocked, slides into the portion of the trigger button  18  that projects rearwardly from the device to provide an indication that the device is cocked and live. The trigger button  18  is made transparent for this purpose. At the front end of the lancet drive shaft, a coil spring  38  surrounds the lancet holder and is designed to cooperate with a front end wall  40  of the housing half  11  as the shaft shoots forward after driving, to damp the forwardmost movement of the shaft. 
     The housing flap  12  is held by hinge lugs  42  to the housing halves  10 ,  11 . Whilst not shown, there may be a spring urging the housing flap  12  to the open position and there may be a damper associated with the hinge to damp the opening movement. The housing flap  12  has a rearwardly extending finger  44  with a barbed head  46  that latches in a recess  48  formed in a channel  50  in the housing halves  10 ,  11 . The nose piece  14  is captively mounted on the front end of the housing flap  12  and urged rearwardly by a compression spring  52  acting between an inwardly directed flange on the nose piece  14  and an outwardly directed flange  54  on a cylindrical extension of the nose flap  12 . Projecting at diametrically opposed locations on the flange  54  are two forwardly projecting V-head projections  56 . These projections cooperate with a series of aligned recesses  58  on an inner wall portion of the nose piece  14 . The recesses  58  are of progressively increasing axial extent and the arrangement is such that the nose piece  14  can be pulled forwardly against the bias of the compression spring  52  and then twisted to align the head  56  with the required recess and then released. A pointer  59  on the housing flap  12  cooperates with indicia  60  on the outside of the nose flap to indicate the penetration depth. 
     The cocking/ejection member  16  has an externally projecting slider  62  which projects through a slot  64 . The slider  62  is integrally formed on a longitudinal strip  66  at the forward end of which is an unlatching surface  68  which runs in the slot  50  to cooperate with the barbed head  46  of the housing flap  12 . At its rear end, the strip  66  is integral with a spring support ring  69  which is acted upon in the forward direction by a rearward compression spring  70  and in the rearward direction by a forward compression spring  72 . At its other end, the rearward compression spring engages the interior wall  30  on the housing  10 ,  11 . At the forward end, the forward compression spring  72  engages an interior wall  74  on the housing half  11 . 
     Extending radially inwardly from the spring support ring  68  there is a cocking rib  76  (see  FIG. 3 ) designed to cooperate with a corresponding cocking rib  80  formed on the shaft  20 . Extending from the front surface of the cocking rib  76  is an elongate ejector finger  82  which extends forwardly along the central axis of the shaft  20 . The ejector finger  82  is designed to be movable forwardly into the lancet holder  22  from the rear so as to eject a lancet  24  held therein. 
     In operation, assuming that the device is in the configuration of  FIGS. 2 and 3 , that is with a lancet  24  loaded in the holder  22  and the shaft  20  in the cocked position with the lancet drive spring compressed and the heads  34  on the shaft latched behind the interior wall  30 , the indicator cylinder  36  is projecting into the trigger button  18  to show that the device is armed. The user, having selected the appropriate penetration depth by pulling and twisting the nose piece  14 , offers the device up to the skin and then presses the trigger  18 . Forward movement of the trigger  18  squeezes the heads  34  towards each other thus releasing the lancet drive shaft  20  so that it shoots forward under the influence of the lancet drive spring  28  to cause the tip of the lancet  24  to project momentarily through the aperture in the nose piece  14 , as shown in  FIG. 4 , as the damping spring  38  on the outside of the lancet holder  22  is compressed against the end wall  40  with the lancet thereafter being urged back into the housing by the action of the spring  38 . 
     The user then slides the cocking/ejection member  16  forwardly so that the release surface  68  on the forward end of the strip  66  disengages the barbed head  46  of the housing flap so that the flap can hinge open, with continued forward movement of the slider  62  causing the ejection finger  82  to eject the lancet  24  from the lancet holder  22 , as shown in  FIGS. 7 and 8 . 
     For the next operation, the nose flap may be opened if necessary by pushing the slider  62  forward, a lancet  24  may be loaded into the holder  22  and the housing flap  12  snapped shut. The drive shaft is then cocked by sliding the slider  62  rearwardly until the heads  34  on the shaft snap passed and locate against the interior wall  30 , and the operation continues as before. 
     The indicator cylinder may include or be replaced by an LED or other suitable electrical or electronic indicator switched by a suitable detector detecting when the device is cocked and containing a lancet. The indicator could be associated with the shaft or located elsewhere within or on the housing.