Abstract:
A skin pricking apparatus includes a casing  1 , a lancet  19  located within the casing, and a firing mechanism  5,13,31  for causing a needle tip  22  of the lancet  19  to be driven through an opening  14  in the casing to prick the skin of a user. The firing mechanism including a mechanical interlock  6,27  which is released by substantially simultaneous external pressure applied separately to two spaced apart components  5,13  of the firing mechanism by a user.

Description:
FIELD OF THE INVENTION 
     The present invention relates to skin pricking apparatus and in particular, though not necessarily to a skin pricking apparatus for use in providing a sample of blood. 
     BACKGROUND 
     In the medical and related diagnostic and testing fields, it is often required to take small samples of blood from a subject for the purpose of testing or analysing the blood. A common way of achieving this is by using a small needle to pierce the skin at a location where blood vessels are close to the surface. The combination of a needle and its holder is commonly known as a lancet. In order to avoid infection and contamination, lancets are preferably intended for single use and are disposable. They must therefore be compact to allow users to carry multiple lancets on their person, and cheap to manufacture. 
     A number of disposable lancet devices are currently on the market. These include the Unistic™ manufactured and marketed by Owen Mumford Ltd (Woodstock, UK). The current designs comprise a moulded plastics casing within which is mounted a short, spring-loaded needle. A trigger is formed in the casing which, when depressed, releases the lancet causing the tip to be fired out through an opening in the casing. Some of the current designs require a user to preload or cock the spring prior to firing. In other designs, the lancet devices are supplied already cocked. It is also generally necessary for users to remove a cap from the front of the device or the needle tip prior to firing. Users must therefore perform at least two steps, and sometimes three, in order to perform the blood sampling procedure. 
     There exists a desire for a lancet device or apparatus which is simpler to operate than current designs. Of course, any improved design must meet high standards with regard to manufacturing costs. It must also be reliable, ensuring that lancet devices are provided to users in an operable condition. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the present invention there is provided a skin pricking apparatus comprising a casing, a lancet located within the casing, and a firing mechanism for causing a needle tip of the lancet to be driven through an opening in the casing to prick the skin of a user, the firing mechanism comprising a mechanical interlock which is released by substantially simultaneous external pressure applied separately to two spaced apart components of the firing mechanism by a user. 
     Embodiments of the invention have the advantage that accidental firing of the apparatus is at the very least extremely unlikely, given that pressure must be applied to the apparatus simultaneously at two different locations. Nonetheless, firing is essentially a one-step process. 
     Preferably, the firing mechanism comprises:
         force applying means for applying a force to the lancet to drive the needle tip through said opening;   a finger actuable trigger for coupling to said force applying means to activate that means; and   trigger locking means moveable between a first position in which coupling of the trigger to the force applying means is precluded and a second position in which coupling is allowed.       

     Preferably, said finger actuable trigger and said trigger locking means are molded integrally with said casing. 
     Preferably, said trigger and said trigger locking means are arranged to be movable in substantially mutually perpendicular directions. More preferably, said trigger locking means is moveable in a direction substantially parallel to the direction of travel of the lancet through the casing. 
     Preferably, the trigger locking means comprises a contact plate through which said opening is formed, the contact plate having an outer contact surface for engaging an area of a user&#39;s skin to be pricked. More preferably, the contact plate is coupled to the casing by one or more spring means arranged to bias the contact plate outwardly with respect to the casing. At least one such spring means may be attached to the casing by a flexible hinge, whereby during assembly the trigger locking means can be folded inside the casing. An advantage of this particular arrangement is that the user must apply the lancet device to the skin with a particular force in order to ensure sufficient movement of the contact plate. This is desirable as it makes it unlikely that the user will flinch sufficiently during firing to prevent a successful skin prick. 
     Preferably, the finger actuable trigger comprises a stop member arranged to engage a surface of the trigger locking means when the locking means is in said first position, and is arranged to be co-located with a passage through the trigger locking means when the trigger locking means is in said second position. 
     Preferably, said force applying means comprises a compressed spring, coupled between the lancet and the casing. The firing mechanism comprises a latch formed on the lancet or on the inside of the casing which engages a catch formed on the other of the lancet or casing. A lancet release member depends from the firing button to engage the catch or lancet when the trigger locking means is in said second position. 
     According to a second aspect of the present invention there is provided a skin pricking apparatus comprising a casing, a needle located within the casing, and a lancet firing mechanism, the firing mechanism comprising:
         force applying means for applying a force to the needle to drive the needle through an opening in the casing to prick the skin of a user;   a finger actuable trigger for releasing the force applying means;   a trigger lock comprising a contact area for contacting a region of a users skin which is to be pricked, the lock being moveable by pressure applied to the contact area between a trigger locking position and a trigger release position       

     According to a third aspect of the present invention there is provided a lancet for pricking a user&#39;s skin, the lancet comprising:
         a body of a substantially rigid plastics material;   a needle having one end embedded in said body, leaving the other end including a sharpened needle tip to protrude from the body; and   a flexible plastics cover covering the entire exposed length of the needle, the cover being formed of such material and with such dimensions that an axial force applied to the cover relative to the body causes at least an axial portion of the cover to concertina along the needle, thereby exposing the needle tip.       

     Preferably, the cover is formed of such material and with such dimensions that it does not recover to cover the needle tip following removal of said axial force. 
     Preferably, the flexible plastics cover comprises a head portion surrounding the needle tip and a sleeve portion which is narrower than the head portion, surrounding the remainder of the needle, whereby in use said axial force is applied to the head of the cover and the sleeve portion concertinas along the needle in response. 
     Preferably, said flexible plastics cover is of a thermoplastic elastomer material. 
     Preferably, an overmolding process is used to provide said flexible plastics cover. 
     The lancet of the third aspect of the invention may be used in a single use skin pricking apparatus. Multiple such lancets may be used in a multi-use device, e.g. where the lancets are mounted on a revolving carousel. 
     According to a fourth aspect of the present invention there is provided a method of manufacturing the lancet of the above third aspect of the present invention, the method comprising forming said flexible plastics cover by overmolding a flexible plastics material on top of the needle. 
     According to a fifth aspect of the present invention there is provided a method of manufacturing a skin pricking apparatus, the method comprising:
         molding a single plastics component comprising upper and lower casing sections coupled together by at least one hinge, and a trigger locking section coupled to one of the upper and lower casing sections by at least one hinge;   locating a lancet comprising a lancet needle, within one of the upper and lower casing sections, and locating spring means between the lancet and the casing; and   folding the trigger locking section about its hinge(s) into one of the upper and lower casing sections, and folding the casing sections together about their hinge(s) to close the casing around the lancet and the spring means.       

    
    
     
       DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the present invention and in order to show how the same may be carried into effect reference will now be made by way of example to the accompanying drawings in which: 
         FIG. 1  is a perspective view of a single use lancet device; 
         FIG. 2  is a perspective view of a moulded component used to form a casing of the lancet device of  FIG. 1 ; 
         FIG. 3  is a perspective view of a lancet and spring driver of the lancet device of  FIG. 1 ; 
         FIG. 4  shows a cross-section through the lancet device of  FIG. 1  in a vertical plane; and 
         FIG. 5  shows a cross-section through the lancet device of  FIG. 1  in a horizontal plane. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     There is illustrated in  FIG. 1  an assembled single use lancet device designed for pricking a users skin to provide a small blood sample. Typically a user pricks the pad of his or her finger, leaving a small spot of blood on the finger. This spot can then be collected, e.g. using a test strip, for use in performing some measurement or test. The lancet device of  FIG. 1  is assembled from three separate components. These are illustrated in  FIGS. 2 and 3 . 
       FIG. 2  illustrates a casing  1  which is formed as a single moulded component. The casing is shown opened out, and has a lower casing section  2 , an upper casing section  3 , and a trigger locking section  4 . Considering first the upper casing section  3 , this comprises a trigger button  5  which is free on three sides but which is integral with the body of the casing on a fourth side, i.e. the rearmost side. The trigger is able to flex at the point of attachment to the casing body so that it can be pressed downward (as viewed in  FIG. 1 ) by finger pressure. Depending from the lower surface of the trigger (again as viewed in  FIG. 1 ) are a lancet release member  6  and a trigger stop member  7 . The lancet release member  6  is significantly longer than the trigger stop member  7 . 
     Two ribs  8   a ,  8   b  formed on the inside surface of the upper casing section  3  together form a lancet guide track. 
     Considering now the lower casing section  3 , this provides on its inner surface a pair of trigger release guides  9  (only one of which is shown in  FIG. 2 , with the other being symmetrically located on the other side of the lower casing), a lancet catch  10 , and a spring retainer member  11 . The lower casing section  2  is attached to the upper casing section  3  by a pair of flexible hinges  12   a ,  12   b.    
     The trigger locking section  4  of the upper casing section  3  comprises a front skin contact area or plate  13 . This has an opening  14  provided therein to allow for passage of the needle tip. A number of pips  15  are disposed around the central opening  14  and are designed to create a tactile sensation upon contact with the skin which distracts the user from the actual skin pricking act. Projecting inwardly from the contact plate  13  are a pair of moulded platform “springs”  16   a ,  16   b . A first of these springs  16   a  is attached at its innermost end to a flexible hinge  17  which connects the locking section  4  to the lower casing section  2 . The innermost end of the other platform spring  16   b  is provided with a pillar  18  which engages a corresponding hole  28  formed in the lower casing section when the casing sections are folded together. A central blocking structure  26  extends inwardly from the contact plate, with a trigger release hole  27  extending through an end thereof. 
       FIG. 3  illustrates a lancet  19  which comprises a plastics body  20  of generally cuboid shape. The end of a needle  21  (see  FIGS. 4 and 5 ) is embedded in the body  20 , leaving the sharpened tip  22  of the needle to project outwardly from the body. Moulded integrally with the body  20  are a flexible latch  23  and a spring retaining knob  24 . The exposed portion of the needle  21  including the tip  22  is overmolded with a flexible and elastic plastics cover  25 , e.g. of thermoplastic elastomer (TPE) such as SANTOPRENE or EVOPRENE (alternatively, the material may be polyurethane or polyurethane foam, silicon rubber, or liquid silicon rubber). This cover  25  has an enlarged, generally frustoconical shaped, head  29 , which covers the tip of the needle. The overmolding narrows in a stepwise manner to provide a narrow sleeve  30  which covers the remainder of the needle. The overmolding also covers the end surface of the body  20 . The overmolding ensures sterility of the needle prior to use. Also illustrated in  FIG. 3  is a steel coil spring  31  which, in the assembled device, engages the knob  24 . 
     The casing  1  comprises a number of components which mate together once the casing is folded, and which allow the various components of the lancet to be secured in place. These are apparent from the Figures, but will not be explained in any further detail as their construction and function will be readily apparent to the person of skill in the art. 
     The lancet is assembled by locating the lancet  19  within the lower casing section  2 , and locating the spring  31  between the knob  24  and the spring retainer member  11 . The spring  31  is compressed, such that the end of the latch  23  on the body  20  flexes inwardly to allow the latch to pass over the lancet catch  10 . The latch  23  then springs back to engage the catch  10 , locking the lancet  19  in place. The three components of the casing are then folded together and locked in place. It is noted that once assembled, the trigger locking section  4  is supported by the trigger release guides  9 , preventing downward deflection of the locking section. 
     Operation of the lancet device will now be described with reference to  FIGS. 4 and 5 , which show the lancet device in the ready-to-use configuration. In this configuration, the firing button  5  is in its resting position, with the lowermost end of the lancet release member  6  sitting above, but not in contact with, the latch  23  of the lancet. The front plate of the trigger locking section  4  is not experiencing any externally applied pressure, and as such the platform springs  16   a , 16   b  are fully extended, i.e. the trigger locking section is in an extended position. In this position, the wall of the blocking structure  26  of the trigger locking section is directly beneath the trigger stop member  7 . This wall is engaged by the trigger stop member in the event that a user exerts any downward force on the trigger button, preventing engagement of the latch  23  by the lancet release member. 
     In order to operate the lancet, a user holds the lancet device in one hand, with his or her thumb placed over the firing button  5 . The contact plate  13  of the trigger locking section  4  is then brought into contact with the area of skin to be pricked, e.g. the pad of a finger on the user&#39;s other hand. Pressure is applied to push the contact plate  13  inwardly relative to the body of the lancet device, compressing the platform springs  16   a ,  16   b  in the process. A force of at least 1N, more preferably around 6N, must be applied to overcome the resistance of the platform springs  16   a , 16   b . Simultaneously, the user depresses the firing button  5 . At some point in the travel of the trigger locking section  4 , the trigger release hole  27  will be aligned beneath the trigger stop member  7 , allowing the trigger stop member  7  to pass through the hole  27 . This will happen quickly, and as the button  5  advances the lancet release member  6  will come into contact with the latch  23 . The sloping side surface of the member  6  will push the latch back against the body  20  of the lancet, causing the latch  23  to be released from the lancet catch  10 . The spring  31  will then drive the lancet  19  through the casing  1  until the head  29  of the overmolded section on the needle contacts the inner surface of the contact plate, surrounding the opening  14  therein, preventing further progress of the head  29 . (In an alternative arrangement, the opening  14  may be large enough to allow passage of the head  29 , in which case the user&#39;s skin provides the stop surface for the head.) 
     The spring  31  continues to apply a force to the lancet  19 , driving the tip of the needle through the head  29 . This results in the a concertina-ing of the sleeve  30  around the needle. The needle tip  21  is driven out through the opening  14  in the contact plate  13 , and pierces the skin of the user. At this point, the spring  31  is slightly over extended and begins to contract, pulling the lancet and with it the needle tip back through the opening in the contact plate into the casing. 
     An important feature of this embodiment is that the overmolded cover  25  covering the lancet needle is of such material and such dimensions that it does not return fully to its original position following firing. Thus, after firing, the tip of the needle remains uncovered. This has two significant advantages. Firstly, and assuming that the needle tip is visible through the casing (the casing may be formed of a transparent plastics material), this provides the user with a visual indication that the device has been fired. Secondly, it prevents the cover  25  from performing a wiping action across the needle tip which might otherwise result in a droplet of blood falling from the tip and giving rise to a contamination/infection risk. 
     It will be appreciated that, one used, the lancet device cannot be reused, as the spring  31  has been released and it is not possible for a user to recock it. This is prevented by the presence of the trigger locking section  4 , and in particular the contact plate which, if depressed by external pressure will move inwardly only to a very limited extent, defined by the position of a contact plate stop ribs formed on the inside surfaces of the upper and lower casing sections. 
     It will be appreciated by the person of skill in the art that various modifications may be made to the above described embodiments without departing from the scope of the present invention.