Patent Publication Number: US-2022233118-A1

Title: Lancing device

Description:
TECHNICAL FIELD 
     The present invention relates to a lancing device. The present invention particularly relates to a lancing device that creates a skin stimulus during use and/or a lancing device that includes features which allow alignment of components of the lancing device during assembly and/or a lancing device that is activated by movement of a sleeve and/or the lancet is urged forward by an elastomeric component. 
     BACKGROUND ART 
     Blood sampling is an important part of daily routine for some people and in many cases may even be employed at home wherein the user may self-administer and/or may not be a trained medical professional. Accordingly lancing devices are commonly used to provide a simple, reliable and repeatable method of collecting blood samples. Lancing devices are used to make a small incision at a sample site on the skin (typically for example a finger tip) to draw a sample of blood. Such devices may also be referred to as capillary blood sampling devices. Single use lancing devices are used for convenience and in order to reduce risk of infection and/or cross contamination between uses. 
     Known blood sampling devices employ a spring or other biasing member which forces a sharp skin piercing lancet tip into the sample site following triggering of the device. For convenience and clarity, the skin piercing part of the lancet may generally be referred to herein in as a lancet “needle”; it will however be appreciated that this is non-limiting and the lancet could be formed with any suitable incision member for example a generally cylindrical needle, a sharp edge or a blade element. Typically, the lancet “needle” will be metal and the lancet will also include an injection moulded plastic lancet body. 
     SUMMARY OF THE INVENTION 
     The invention provides a lancing device comprising:
         a housing having a forward end and a rearward end, the housing defining a passage having an aperture in the forward;   a lancet comprising:
           a lancet body,   a lancet tip supported at a forward end of the lancet body so as to project from the lancet body, and   an impact surface defined in the forward end of the lancet body at a first predetermined distance from the lancet tip;   wherein the lancet is mounted in the passage so as to be axially moveable with respect to the housing between a first position in which the lancet tip is positioned within the housing, and a second position in which the lancet tip extends through the aperture and beyond the forward end of the housing;   
           an urging member which engages the lancet at least when the lancet is in the first position, and which can be energised to urge the lancet from the first position to the second position; and   a sleeve located within the housing and around the forward end of the lancet body, wherein the sleeve has a front portion that that projects through the aperture in the housing and defines an opening through which the lancet tip can project, wherein the front portion has
           a front surface, and   an internal stop surface located at a second predetermined distance from the front surface, wherein the internal stop surface is arranged to be engaged by the impact surface of the lancet body when in the second position, wherein the second predetermined distance is smaller than the first predetermined distance;   
           wherein in use, the energised urging member can move the lancet body from the first position towards the second position to cause the lancet tip to project through the opening in the sleeve by a predetermined amount before the impact surface on the lancet body engages the internal stop surface of the sleeve.       

     By arranging for the lancet body to impact the sleeve after the tip has pierced the skin, the front surface of the sleeve can provide an enhanced nerve stimulation so that pain perception can be reduced. The needles of hypodermic injection devices can also cause pain when inserted into the skin of a patient, and the present invention extends to such contact activated injection devices where the insertion of the needle into the skin is triggered by contact of the device with the patient body. 
     The sleeve can be movable between a first sleeve position in which the front portion projects a first distance from the aperture, and a second sleeve position in which the front portion projects a second distance from the aperture, wherein the second distance is less than the first distance; and the sleeve can comprise a holding structure that can be moved into and out of engagement with the lancet body, such that when the holding structure is engaged with the lancet body, movement of the sleeve from the first sleeve position to the second sleeve position moves the lancet body to the first position and energises the urging member. In this way, the device can be primed and fired by applying pressure to the skin. 
     Moving the holding structures out of engagement with the lancet body can release the lancet body to move to the second position under the influence of the urging member. 
     The diameter of the housing can be smaller at the forward end than at the rearward end. The holding structures can comprise outwardly-biased resilient legs that are held in engagement with the lancet body by the inner wall of the forward end of the housing when in the first sleeve position, and are released from engagement with the lancet body when the sleeve is moved to the second sleeve position. The engaged parts of the legs and lancet body can comprise complementary sloped surfaces. The resilient legs can comprise locking members that engage in the housing to hold the sleeve in the second sleeve position. 
     The resilient legs can also comprise retaining structures, wherein the retaining structures are positioned such that they will engage formations on the lancet body after recoil from the impact surface and hold it in the housing so that the lancet tip is within the housing. Alternatively, the sleeve further comprises the retaining structures. 
     The retaining structures can comprise inwardly biased legs. Each leg can comprise an abutment surface and the lancet body comprises a cooperating abutment surface, wherein the lancet body abutment surface abuts the leg abutment surface to prevent forward movement of the lancet in the passage. The lancet body cooperating abutment surface can be located rearwardly of the leg abutment surface when the lancet body is in the first position and wherein forward movement of the lancet body from the first position to the second position splays the leg outwardly such that the lancet body abutment surface can move past the leg abutment surface. 
     The front surface of the sleeve can comprise a skin contacting surface including a flat base surface and a plurality of projections extending from the flat base surface. 
     The urging member can comprise an elastomer or a spring. 
     The invention also provides a method of operating a lancing device, comprising:
         with the sleeve in the first sleeve position and the holding structure engaged with the lancet body, placing the front surface of the sleeve in contact with a skin surface;   urging the housing towards the skin surface to move the sleeve towards the second sleeve position and move the lancet body to the first position and energise the urging member; and   moving the holding structures out of engagement with the lancet body to releases the lancet body to move to the second position under the influence of the urging member.       

     In accordance with a first aspect of the present invention, there is provided a blood sampling device comprising:
         (i) a housing having a forward end and a rearward end, said housing defining an aperture in said forward end and comprising an interior surface defining a passage;   (ii) an urging member mounted in said passage and comprising an elastomer;   (iii) a lancet comprising a lancet body supporting a lancet tip at a forward end thereof, said lancet being moveably mounted in said passage and arranged to move from:
           (a) a primed position in which said lancet body tensions said elastomeric portion and said lancet tip is located in said housing,   to   (b) a lancing position in which said lancet tip projects through said aperture in said housing;   
           (iv) an actuating means comprising a holding feature, the actuating means being moveable from:
           (A) a holding configuration in which said holding feature holds said lancet to prevent forward movement of said lancet to said lancing position,   
           to:
           (B) a release configuration in which said holding feature does not hold said lancet;   
           wherein said urging member is arranged to urge said lancet forwardly in said housing from said primed position to said lancing position when said actuating means is in said release configuration.       

     The use of an urging member comprising an elastomer which is arranged to urge the lancet body forwardly in the housing means that metal springs, such as metal coil springs, do not have to be used. Springs are easily damaged and increase the time and costs associated with assembly due to their tendency to tangle or corkscrew together. Thus, the use of an urging member comprising an elastomeric portion reduces the complexity and costs associated with manufacture. In addition, no metal components are required in the device (other than the needle), reducing the environmental impact of the device. This is important for single use devices. To further reduce the environmental impact of the device, some or all components (other than the needle) may be formed from bio-based polymers. 
     The elastomer may be formed of at least one of silicone, polyurethane, neoprene, polyisoprene and/or thermoplastic elastomers. The urging member may be formed of at least one of silicone, polyurethane, neoprene, polyisoprene and/or thermoplastic elastomers. The urging member may be an elastomer. 
     The lancet may be moveable rearwardly in said passage from a pre-primed position in which said urging member is relaxed and said lancet tip is located in said housing to said primed position to tension said urging member, i.e. to tension said elastomer. The actuating means is in a holding configuration in the pre-primed position. The actuating means can be in a holding configuration during rearward movement of the actuating member in said passage such that it moves said lancet rearwardly in said passage from said pre-primed position to said primed position. The holding feature may be arranged to move said lancet into said primed position. The holding feature may be arranged to contact said lancet to move it into said primed position. Having a pre-primed position in which said elastomeric portion is relaxed is beneficial because it means that the device does not have to have stored energy. This also means that the blood sampling device may be formed of bio-based materials which are not good at carrying stored kinetic energy, thus improving the environmental impact of the device. In addition, storing an elastomer under tension for a long period of time may impact its performance when used. Providing a pre-primed position in which said elastomeric portion is relaxed obviates this problem as there is no stored energy. 
     The primed position may include a plurality of positions in which said lancet body tensions said elastomeric portion and said lancet tip is located in said housing, i.e. any position between the pre-primed position in which the elastomeric portion is relaxed and a momentary position prior to firing of the lancet when the actuating means is moving to the release configuration. 
     The actuating means can comprise a sleeve movably mounted in said passage and projecting through said aperture in said housing. Thus, the blood sampling device can be a contact activated blood sampling device. The blood sampling device can be a contact activated single use lancing device. The sleeve may define an aperture in a forward end thereof and when the lancet is in the lancing position, said lancet tip may project through said aperture in said sleeve. 
     Rearward movement of said sleeve in said passage may move said lancet rearwardly from said pre-primed position to said primed position. 
     The holding feature can be at least two holding arms on said sleeve, preferably three holding arms on said sleeve. The lancet body may comprise a sloped surface and each of said at least two holding arms may comprise a cooperating sloped surface arranged to contact said lancet body sloped surface when said sleeve is in said holding configuration to prevent forward movement of said lancet body in said passage. Thus, when said sleeve is in said holding configuration, for example when said lancet is in the pre-primed position and optionally during movement of said lancet from said pre-primed position to said primed position, the sloped surfaces on the holding arms may contact the sloped surface on the lancet body to prevent forward movement of the lancet body in the passage. When said sleeve is in said holding configuration the sloped surfaces on the holding arms may contact the sloped surface on the lancet body to prevent forward movement of the lancet body relative to said sleeve. 
     The sleeve can be moveable rearwardly in said housing from said holding configuration to said release configuration. This may move said lancet rearwardly in said passage from said pre-primed position to said primed position. The sleeve may comprise a skin contacting front surface and application of pressure to the skin contacting front surface may move the sleeve rearwardly in the housing from the holding configuration to the release configuration. 
     The passage can comprise a rearward portion and a forward portion immediately adjacent said passage rearward portion, said passage forward portion having a smaller diameter than said passage rearward portion, wherein at least one holding feature is at least partially located in said passage forward portion when said sleeve is in the holding position such that it is urged radially inwards, and rearward movement of said sleeve in said passage moves at least one holding feature radially outwards such that said sleeve is in said release configuration. The at least one holding feature may be biased radially outwards. Movement of the at least one holding feature radially outwards such that said sleeve is in said release position may be caused by the at least one holding feature being biased radially outwards and/or the lancet body urging against the at least one holding arm under the force of the urging member. 
     The housing may be formed of a front housing portion connected to a rear housing portion. The front housing portion may comprise an inner portion located inside said rear housing portion to form said forward portion of said passage. 
     The interior surface of said housing and said sleeve can comprise cooperating latching surfaces configured to prevent said sleeve moving forwardly in said passage when said sleeve is in said release configuration. The rear end of the inner portion of the front housing portion may be the latching surface on the interior surface of the housing. Thus, the front housing portion may project radially further into the passage than the rear housing portion and the latching surface of said housing may be formed by the rear end of said front housing portion. This is beneficial because it means that the device cannot be used. The sleeve is in the release configuration and cannot be moved into the holding configuration so it cannot be used to re-prime the lancet. 
     One of said front housing portion and said rear housing portion may comprise a detent and the other of said front housing portion and said rear housing portion may comprise at least one cooperating protrusion configured to snap fit with said detent to attach said front housing portion to said rear housing portion. Providing a front housing portion and a rear housing portion which may be snap fitted together means that all of the internal components of the blood sampling device can be inserted into one of the front housing portion and a rear housing portion along the longitudinal axis of the device, simplifying assembly. 
     The sleeve can be arranged to move said lancet rearwardly in said passage from said pre-primed position to said primed position. The cooperating sloped surfaces on the at least two holding arms and said lancet body may cooperate with one-another to prevent forward movement of said lancet body in said housing when said sleeve is in said holding configuration. Thus, when said sleeve is moved rearwardly in said housing, the lancet is moved rearwardly in said passage. 
     The urging member may have no stored energy in an initial assembled configuration. An initial assembled configuration can be the configuration in which the device is stored, i.e. the configuration the device is in before the user starts an injection. This means that bio-based materials can be used which are not good at carrying stored kinetic energy, thus improving the environmental impact of the device. In addition, storing an elastomer under tension for a long period of time would impact its performance when used so providing a device having no stored energy in an initial configuration, i.e. in which it is stored, obviates this problem. 
     The blood sampling device may further comprise a hollow support member and said urging member may comprise a transverse elastomeric portion supported by and covering one end of said hollow support member. The hollow support member may be a tubular support member. The transverse elastomeric portion transverses the passage. The transverse elastomeric portion is a planar radial portion in that it is planar when the elastomeric portion is relaxed. The elastomeric portion may be cup shaped, the base of the cup forming the transverse elastomeric portion. The elastomeric portion can be overmoulded onto said hollow support member. The elastomeric portion may be chemically bonded to said hollow support member. 
     The lancet body can comprise a domed rearward end arranged to contact said elastomeric portion when said lancet is in said primed position. This ensures that the rearward end of the lancet body does not damage the elastomeric portion. Damage to the elastomeric portion could prevent firing of the device or reduce the force with which the elastomer can urge the lancet forwardly in said housing. 
     The lancet body can comprise an alignment portion on an external surface thereof and said hollow support member can comprise a complementary alignment portion on an internal surface thereof, wherein one of said alignment portions comprises a plurality of alignment splines and the other of said alignment portions comprises at least one cooperating alignment member arranged to engage between at least two of said plurality of alignment splines in an initial assembled configuration to prevent relative rotation between said lancet body and said support member. If the support member is non-rotatably mounted, for example, affixed, in the passage, relative rotation between said lancet body and said passage is also prevented. 
     The alignment portion on an external surface of said lancet body may be a splined portion comprising a plurality of splines, and said complementary alignment portion on an internal surface of said hollow support member may be an inner splined portion comprising a plurality of splines. 
     The hollow support member can comprise an alignment portion on an external surface thereof and said housing can define a complementary alignment portion on said interior surface of said housing, wherein one of said alignment portions can comprise a plurality of alignment splines and the other of said alignment portions can comprise at least one cooperating alignment member arranged to engage between at least two of said plurality of alignment splines in an initial assembled configuration to prevent relative rotation between said hollow support member and said passage. If relative rotation between said lancet body and said support member is prevented and relative rotation between said hollow support member and said passage is prevented, relative rotation between said lancet body and said passage is prevented. 
     The alignment portion on an external surface of said hollow support member may be a splined portion comprising a plurality of splines, and said complementary alignment portion on said interior surface of said housing may be a splined portion comprising a plurality of splines. 
     The complimentary alignment portion on said interior surface of said housing may comprise a plurality of splines and each spline may comprise a flange arranged to provide a seat for said transverse elastomeric portion. The elastomeric portion may form a friction fit between the complimentary alignment portion and the hollow support member. This means that no adhesive is required to affix the elastomeric portion in the passage. The elastomeric portion may block the passage between the splines in the complimentary alignment portion on said interior surface of said housing. 
     Alternatively, the lancet body can comprise an alignment portion on an external surface thereof and said housing can define a complementary alignment portion on said interior surface of said housing, wherein one of said alignment portions can comprise a plurality of alignment splines and the other of said alignment portions can comprise at least one cooperating alignment member arranged to engage between at least two of said plurality of alignment splines in an initial assembled configuration to prevent relative rotation between said lancet body and said passage. 
     The alignment portion on an external surface of said lancet body may be a splined portion comprising a plurality of splines, and said complementary alignment portion on said interior surface of said housing may be a splined portion comprising a plurality of splines. 
     At least one alignment spline can comprise a guiding surface at one end thereof configured to guide an alignment member to a position between it and a neighbouring one of said alignment splines during assembly. Each alignment spline can comprise a guiding surface at one end thereof configured to guide an alignment member to a position between it and a neighbouring one of said alignment splines during assembly. The, or each, guiding surface can be a helical guiding surface, i.e. a curved, twisted, spiral or corkscrew surface. The helical surface forms a portion of a helical turn such that it acts to guide an alignment member both longitudinally and rotationally to a position between it and a neighbouring alignment spline during assembly. By providing such a guiding surface at one end of each alignment spline, the exact orientation of respective components during assembly does not matter. Even if the alignment member does not initially align with a gap between two neighbouring alignment splines, the guiding surface will guide it to a position between it and a neighbouring one of said alignment splines during assembly. The alignment splines may be equidistantly spaced. 
     The at least one cooperating alignment member can be at least one alignment pin. This is a simple structure that is easily guided into the correct position during assembly. 
     The at least one cooperating alignment member can be at least one alignment spline. An alignment spline provides a greater contact surface and therefore greater stability and structural strength than an alignment pin. The at least one cooperating alignment member may be a plurality of alignment splines. There may be the same number of alignment splines on each alignment portion. 
     The elastomeric portion can be arranged to span the width of said passage, i.e. the elastomeric portion can extend across the passage. The elastomeric portion may be at least one of a single piece of elastomeric material forming a continuous barrier across the passage, a mesh, a web, an elongate strip extending across the passage. Preferably, the elastomeric portion is a single continuous piece of elastomeric material traversing the passage. The elastomeric portion may block the passage. 
     The sleeve can comprise a skin contacting front surface and application of pressure against said skin contacting front surface can move said sleeve rearwardly in said housing from said holding configuration to said release configuration. Thus, the blood sampling device may be a contact activated blood sampling device. 
     The skin contacting front surface may be a textured surface. The skin contacting front surface includes a flat base surface and a plurality of projections extending/projecting from said flat base surface. The textured surface and the projections alike stimulate the skin so as to ‘confuse’ the nerve endings and alleviate the perceived pain experienced when the lancet tip penetrates the skin to make an incision. 
     In accordance with a first aspect of the present invention, there is provided a blood sampling device comprising:
         (i) a housing having a forward end and a rearward end, said housing defining an aperture in said forward end and comprising an interior surface defining a passage;   (ii) a sleeve movably mounted in said passage and projecting through said aperture in said housing, said sleeve comprising at least one holding feature and at least one blocking feature;   (iii) a lancet comprising a lancet body supporting a lancet tip at a forward end thereof, said lancet being moveably mounted in said passage and moveable from:
           (a) a primed position in which said lancet tip is located in said housing,   
           to:
           (b) a lancing position in which said lancet tip projects through said aperture in said housing,   
           to:
           (c) a safe position in which said lancet tip is located in said housing and said blocking feature blocks forward movement of said lancet in said passage,   wherein said sleeve is moveable from:   (A) a holding configuration in which said at least one holding feature holds said lancet to prevent forward movement of said lancet to said lancing position,   
           to:
           (B) a release configuration in which said at least one holding feature does not hold said lancet; and   
           (iv) an urging member configured to urge said lancet forwardly in said passage from said primed position to said lancing position when said sleeve is in said release configuration;   wherein said lancet is arranged to rebound in said passage from said lancing position to said safe position.       

     The lancet may be urged forwardly from said primed position to said lancing position with sufficient force to rebound off the front surface of said passage. Alternatively, said sleeve may comprise an internal abutment surface and the lancet may be urged forwardly from said primed position to said lancing position with sufficient force to rebound off the internal abutment surface of said sleeve. 
     The sleeve may define an aperture in a forward end thereof and when the lancet is in the lancing position, said lancet tip may project through said aperture in said sleeve. 
     The sleeve may be an actuator. Providing a single component which comprises both a holding member to prevent firing of the device prior to use and a blocking member which actively prevents the sharp tip from projecting out of the front of the device once injection has been completed simplifies the device. It also obviates the need for a return spring which can be difficult to handle and can therefore increase the cost of manufacture. The sleeve may be formed of a plastic material. The sleeve may be formed of a bio-based polymer. This reduces the environmental impact of the device. 
     The at least one holding feature can be at least two holding arms, preferably three holding arms. 
     The lancet body may comprise a sloped surface and each of said at least two holding arms may comprise a cooperating sloped surface arranged to contact said lancet body sloped surface when said sleeve is in said holding configuration to prevent forward movement of said lancet body in said passage. This prevents the lancet from moving to said lancing position before the device is actuated by the user. Thus, when said sleeve is in said holding configuration, for example when said lancet is in the pre-primed position and optionally during movement of said lancet from said pre-primed position to said primed position, the sloped surfaces on the holding arms may contact the sloped surface on the lancet body to prevent forward movement of the lancet body in the passage. When said sleeve is in said holding configuration the sloped surfaces on the holding arms may contact the sloped surface on the lancet body to prevent forward movement of the lancet body relative to said sleeve. 
     The lancet body sloped surface may be a chamfered surface. The cooperating sloped surfaces on each of the holding arms may be chamfered surfaces. 
     The at least one blocking feature may be at least one blocking leg i.e. an elongate member, preferably three blocking legs. The, or each, blocking leg may be located within a holding arm. The, or each, blocking leg may be located circumferentially within a holding arm. Each holding arm may comprise two fingers defining a gap therebetween and the, or each, blocking leg may be located within a gap defined between the two fingers in a holding arm. There may be only one blocking leg located within each blocking arm. The sleeve may comprise three blocking legs and three holding arms, each blocking leg being located within a separate holding arm. 
     The, or each, blocking leg can be resiliently deformable. Movement of said lancet from said primed position to said lancing position can deflect the or each blocking leg radially outwardly i.e. splay the or each blocking leg so that the lancet can move forwardly past it or them. The force provided by the urging member may be sufficient to splay the or each blocking leg outwardly. 
     The or each blocking leg may comprise an abutment surface and said lancet body may comprise a cooperating abutment surface, wherein said lancet body abutment surface abuts said at least one blocking leg abutment surface when said lancet is in said safe position to prevent forward movement of said lancet in said passage. This keeps the lancet in the safe position and reduces the chance of accidental needle stick injuries. Rearward movement of said lancet from said lancing position to said safe position can move said lancet body abutment surface rearwardly past said at least one blocking leg abutment surface. 
     The lancet body abutment surface and said at least one blocking leg abutment surface can be complementary sloped surfaces. The lancet body abutment surface and said at least one blocking leg abutment surface may be chamfered surfaces. 
     The lancet body sloped surface may also be the lancet body cooperating abutment surface. The lancet body may comprise an annular projection having a forwardly sloping front surface which forms said lancet body sloped surface and said lancet body abutment surface. 
     The lancet body cooperating abutment surface can be located rearwardly of said at least one blocking leg abutment surface when said lancet is in said primed position, and forward movement of said lancet body from said primed position to said lancing position can splay said at least one blocking leg outwardly such that said lancet body abutment surface moves past said at least one blocking leg abutment surface. This is because the force provided by the urging member for forward movement of said lancet from said primed position to said lancing position is sufficient to splay the at least one blocking leg. When the lancet moves to the safe position the blocking leg abutment surface moves into blocking alignment with the lancet body abutment surface. The lancet does not have sufficient energy to splay the at least one blocking leg when it is in the safe position. 
     The sleeve can comprise a skin contacting front surface and application of pressure against said skin contacting front surface may move said sleeve rearwardly in said housing from said holding configuration to said release configuration. Thus, the blood sampling device may be a contact activated lancing device. Said skin contacting front surface can be a textured surface. The skin contacting front surface can include a flat base surface and a plurality of projections projecting/extending forward from said flat base surface. The textured surface such as the projections are designed to stimulate the skin so as to ‘confuse’ the nerve endings and alleviate the perceived pain experienced when the lancet tip penetrates the skin to make an incision. This effect is exaggerated for a contact activated lancing device. 
     The sleeve can be moveable rearwardly in said housing from said holding configuration to said release configuration. Rearward movement of said sleeve in said passage can move said lancet rearwardly from a pre-primed position in which said urging member is relaxed and said lancet tip is located in said housing to said primed position in which said urging member is primed and said lancet tip is located in said housing. The actuating means is in a holding configuration when the lancet is in the pre-primed position. The actuating means may be in a holding configuration during rearward movement of said sleeve in said passage to move said lancet rearwardly from said pre-primed position to said primed position. This therefore prevents the lancet from moving forwardly to said lancing position. The at least one holding feature may be arranged to move said lancet into said primed position. The at least one holding feature may be arranged to contact said lancet to move it into said primed position. Having a pre-primed position in which said urging member is relaxed is beneficial because it means that the device does not have to have stored energy. This also means that the blood sampling device may be formed of bio-based materials which are not good at carrying stored kinetic energy, thus improving the environmental impact of the device. 
     The primed position may include a plurality of positions in which said lancet body tensions said elastomeric portion and said lancet tip is located in said housing, i.e. any position between the pre-primed position in which the elastomeric portion is relaxed and a momentary position prior to firing of the lancet when the actuating means is moving to the release configuration. 
     The passage may comprise a rearward portion and a forward portion immediately adjacent said passage rearward portion, said passage forward portion having a smaller diameter than said passage rearward portion, wherein at least one holding feature is at least partially located in said passage forward portion when said sleeve is in the holding position such that it is urged radially inwards, and rearward movement of said sleeve in said passage moves at least one holding feature radially outwards such that said sleeve is in said release configuration. The at least one holding feature may be biased radially outwards. Movement of the at least one holding feature radially outwards such that said sleeve is in said release configuration may be caused by the at least one holding feature being biased radially outwards and/or the lancet body urging against the at least one holding arm under the force of the urging member. 
     The housing may be formed of a front housing portion connected to a rear housing portion. The front housing portion may comprise an inner portion located inside said rear housing portion to form said forward portion of said passage. 
     One of said front housing portion and said rear housing portion may comprise a detent and the other of said front housing portion and said rear housing portion may comprise at least one cooperating protrusion configured to snap fit with said detent to attach said front housing portion to said rear housing portion. Providing a front housing portion and a rear housing portion which may be snap fitted together means that all of the internal components of the blood sampling device can be inserted into one of the front housing portion and a rear housing portion along the longitudinal axis of the device, thereby simplifying assembly. 
     The housing and said sleeve can comprise cooperating stop surfaces configured to prevent said sleeve moving forwardly in said passage when said sleeve is in said release configuration. The rear end of the front housing portion may form the engagement surface when the front housing portion comprises an inner portion located inside said rear housing portion to form said forward portion of said passage. Preventing the sleeve moving forwardly in the passage when the sleeve is in the release configuration is beneficial because it means that the device cannot be reused. As the sleeve is in the release configuration it cannot re-prime the lancet. 
     The urging member can comprise an elastomer. The urging member may comprise an elastomeric urging member supported by and covering one end of a hollow support member. The hollow support member may be a tubular support member. The elastomeric portion may be planar in a relaxed position and arranged to transverse the passage in use, for example, span the width of the passage. The elastomeric portion may be overmoulded onto said hollow support member. The elastomeric portion may be chemically bonded to said hollow support member. 
     The lancet body may comprise a domed rearward end arranged to urge at least a portion of said elastomeric portion rearwardly when said lancet is in said primed position to tension said elastomeric portion. Providing a domed rearward end ensures that the rearward end of the lancet body does not damage, for example pierce, the elastomeric portion. Damage to the elastomeric portion could prevent firing of the device or reduce the force with which the elastomer can urge the lancet forwardly in said housing. 
     The lancet body may define a splined portion on an external surface thereof and said hollow support member may define a complementary splined portion on an internal surface thereof, said lancet body splined portion and said support member complementary splined portion being configured to engage to prevent relative rotation between said lancet body and said support member in an initial assembled configuration. The support member may be non-rotationally mounted in said passage. The support member may be affixed in said passage. In such cases, relative rotation between the lancet body and the passage is prevented. The lancet body splined portion and/or the hollow support member complementary splined portion may comprise a plurality of splines. 
     The support member may define a splined portion on an external surface thereof and said housing may define a complementary splined portion on said housing interior surface, said support member splined portion and said housing complementary splined portion being configured to engage to prevent relative rotation between said support member and said passage in an initial assembled configuration. An initial assembled configuration can be the configuration in which the device is stored, i.e. the configuration the device is in before the user starts an injection. The hollow support member splined portion and/or said housing complimentary splined portion may comprise a plurality of splines. 
     The splined portion on said housing interior surface may comprises a plurality of splines and each spline may comprise a flange arranged to provide a seat for said elastomeric portion in an initial assembled configuration. The initial assembled configuration can be the configuration in which the device is stored, i.e. the configuration the device is in before the user starts an injection. This provides support for the elastomeric portion. The elastomeric portion may form a friction fit between the complimentary alignment portion and the hollow support member. This means that no adhesive is required to affix the elastomeric portion in the passage. The elastomeric portion may block the passage between the splines in the complimentary alignment portion on said interior surface of said housing. 
     Said lancet body may define a splined portion on an external surface thereof and said housing may define a complementary splined portion on said housing interior surface, said lancet body splined portion and said housing complementary splined portion being configured to engage to prevent relative rotation between said lancet body and said passage in an initial assembled configuration. The lancet body splined portion and/or said housing complimentary splined portion may comprise a plurality of splines. 
     At least one of said splined portions may comprise a helical guiding surface at one end of the or each spline, i.e. a curved, twisted, spiral or corkscrew surface. The helical surface forms a portion of a helical turn such that it acts to guide a spline both longitudinally and rotationally to a position between it and a neighbouring spline during assembly. 
     Each of said splined portions may be rotationally symmetrical, i.e. they look the same after some rotation by a partial turn. At least one of said splined portions may have rotational symmetry Order 6. All of said splined portions may have rotational symmetry Order 6. At least one of said splined portions may have rotational symmetry Order 8. All of said splined portions may have rotational symmetry Order 8. The rotational symmetry is about the longitudinal axis when the device is assembled. This eliminates the need for rotary alignment during assembly. If each of said splined portions is rotationally symmetrical and at least one of said splined portions comprises a helical guiding surface at one end of the or each spline, there is no need for any rotary alignment during assembly. 
     One or more of said passage, said lancet body and said support member may be rotationally symmetrical, i.e. they look the same after some rotation by a partial turn. Each of said passage, said lancet body and said support member may be rotationally symmetrical, i.e. they look the same after some rotation by a partial turn. 
     The device may further comprise a removable safety cap for at least partially covering said lancet tip, said removable safety cap comprising a graspable portion external to said housing and a stem substantially located within said housing i.e. within said passage. The graspable portion can comprise diametrically opposed gripping surfaces. This helps the user to grip and twist and/or pull the safe safety cap for removal. The stem can be frangibly connected to a forward surface of said lancet body and rotation of said graspable portion relative to said lancet body can break said frangible connection such that said cap can be removed from said housing. When relative rotation between the lancet body and the passage is prevented, for example, by splined engagement between components, rotation of the graspable portion of the safety cap by the user will ensure that the graspable portion rotates relative to the lancet body. This rotation will sever the frangible connection between the lancet body and the safety cap such that the safety cap can be removed from the housing. This exposes the sharp tip of the lancet so that the blood sampling device may be used. 
     The at least one blocking feature and said at least one holding feature can be integrally formed with said sleeve. 
     The blood sampling device can be a contact activated single use lancing device. 
     In accordance with a first aspect of the present invention, there is provided a blood sampling device comprising:
         (i) a housing having a forward end and a rearward end, said housing defining an aperture in said forward end and comprising an interior surface defining a passage;   (ii) a lancet comprising a lancet body supporting a lancet tip at a forward end thereof, said lancet being moveably mounted in said passage; and   (iii) an urging member mounted in said passage and configured to urge said lancet forwardly in said passage from:
           (a) a primed position in which the lancet tip is located in said housing,   
           to:
           (b) a lancing position in which said lancet tip projects through said aperture in said housing;   
               wherein said housing defines an alignment portion in said passage and said lancet body defines a cooperating alignment portion on an external surface thereof;   wherein one of said alignment portion and said cooperating alignment portion comprises a plurality of alignment splines and the other comprises at least one cooperating alignment member arranged to engage between at least two of said alignment splines in an initial assembled configuration to limit relative rotation between said housing and said lancet body,   wherein at least one of said alignment splines comprises a guiding surface at one end thereof configured to guide a cooperating alignment member to a position between it and a neighbouring one of said alignment splines during assembly.   

     According to a second aspect of the present invention, there is provided a blood sampling device comprising:
         (i) a housing having a forward end and a rearward end, said housing defining an aperture in said forward end and comprising an interior surface defining a passage;   (ii) a lancet comprising a lancet body supporting a lancet tip at a forward end thereof, said lancet being moveably mounted in said passage;   (iii) a hollow support member mounted in said passage; and   (iv) an urging member supported by said hollow support member in said passage and configured to urge said lancet forwardly in said passage from:
           (a) a primed position in which said lancet tip is located in said housing,   
           to:
           (b) a lancing position in which said lancet tip projects through said aperture in said housing;   
               wherein said hollow support member defines an alignment portion on an internal surface thereof and said lancet body defines a cooperating alignment portion on an external surface thereof;   wherein one of said alignment portion and said cooperating alignment portion comprises a plurality of alignment splines and the other comprises at least one cooperating alignment member arranged to engage between at least two of said alignment splines in an initial assembled configuration to limit relative rotation between said hollow support member and said lancet body,   wherein at least one of said alignment splines comprises a guiding surface at one end thereof configured to guide a cooperating alignment member to a position between it and a neighbouring one of said alignment splines during assembly.   

     Thus, in both the first and second aspect, the alignment portion and the cooperating alignment portion are adapted to cooperate with one another. The alignment and cooperating alignment portions can also be referred to as first and second alignment portions. Alternatively, they can be referred to as a female alignment portion (in the passage) and a male alignment portion (on an external surface of the lancet body) respectively. 
     Providing such an arrangement significantly improves the ease of manufacture. By providing such a guiding surface at one end of at least one alignment spline, the exact orientation of respective components during assembly does not matter. Even if the alignment member does not initially align with a gap between two neighbouring alignment splines, the guiding surface will guide it to a position between it and a neighbouring one of the alignment splines during assembly. The alignment splines can be equidistantly spaced. 
     Each alignment spline can comprise a guiding surface at one end thereof configured to guide an alignment member to a position between it and a neighbouring one of the alignment splines during assembly. As such, it does not matter which orientation the lancet is inserted into the housing. When the lancet body is inserted into the housing the, or each, alignment member will contact a guiding surface on an alignment spline to guide it between the alignment spline and a neighbouring one of the alignment splines. Thus, manual rotation of the respective components in not required. This is a significant benefit in an automated assembly process as no rotary alignment is required. The alignment portion comprising a plurality of alignment splines can be rotationally symmetrical. This further eliminates the need for rotary alignment. 
     The urging member can comprise an elastomer. The elastomer can be overmoulded onto the hollow support member. The elastomer can be chemically bonded to the tubular support member. The urging member can comprise a transverse elastomeric portion supported by and covering one end of the hollow support member. The transverse elastomeric portion can be planar in a relaxed position and arranged to transverse the passage in use, for example, span the width of the passage. The urging member can be overmoulded onto the tubular support member. The urging member can be chemically bonded to the tubular support member. 
     The lancet body can comprise a domed rearward end arranged to contact the transverse elastomeric portion of the urging member. The lancet body can comprise a domed rearward end arranged to urge at least a portion of the transverse elastomeric portion rearwardly when the lancet is in the primed position to tension the transverse elastomeric portion. Providing a domed rearward end ensures that the rearward end of the lancet body does not damage, for example pierce, the urging member. Damage to the urging member could prevent firing of the device or reduce the force with which the urging member can urge the lancet forwardly in the housing. 
     The hollow support member can be non-rotatably mounted in the passage. For example, the hollow support member can be affixed to the interior surface of the housing using an adhesive. 
     The housing can define an alignment portion (a female alignment portion) in the passage and the hollow support member can define a cooperating alignment portion (a male alignment portion) on an external surface thereof, wherein the alignment portion in the passage and the cooperating alignment portion on an external surface of the hollow support member are arranged to engage to prevent relative rotation between the hollow support member and the passage in the initial assembled configuration. An initial assembled configuration can be the configuration in which the device is stored, i.e. the configuration the device is in before use, i.e. before a lancing operation is commenced. 
     At least one of the alignment portion in the passage and the cooperating alignment portion on an external surface of the hollow support member can comprise a plurality of alignment splines and the other can comprise at least one cooperating alignment member arranged to engage between at least two of the alignment splines. 
     The alignment portion in the passage can comprise a plurality of alignment splines and two or more of the splines, for example three or more, for example all of the splines, can comprise a flange arranged to provide a seat for the urging member in the initial assembled configuration. The flange can be arranged to provide a seat for the urging member in the initial assembled configuration. The initial assembled configuration can be the configuration in which the device is stored, i.e. the configuration the device is in before the user starts an injection. This provides support for the urging member. The urging member can be sandwiched between the hollow support member and the seat. The urging member can comprise a circumferential portion surrounding at least a portion of the hollow support member. The circumferential portion can form a friction fit between the hollow support member and the alignment splines in the passage. This means that no adhesive is required to affix the urging member in the passage or to affix the urging member to the hollow support member. The transverse elastomeric portion can block the passage between the splines in the alignment portion in the passage. 
     At least one of the alignment portion in the passage and the cooperating alignment portion on an external surface of the hollow support member can be rotationally symmetrical i.e. they look the same after some rotation by a partial turn. At least one of the alignment portion in the passage and the cooperating alignment portion on an external surface of the hollow support member can have rotational symmetry Order 6, for example if it comprises 6 alignment splines. At least one of the alignment portion in the passage and the cooperating alignment portion on an external surface of the hollow support member can have rotational symmetry Order 8, for example if it comprises 8 alignment splines. The rotational symmetry is about the longitudinal axis when the device is assembled. 
     Both of the alignment portion in the passage and the cooperating alignment portion on an external surface of the hollow support member can be rotationally symmetrical i.e. they look the same after some rotation by a partial turn. Both of the alignment portion in the passage and the cooperating alignment portion on an external surface of the hollow support member can have rotational symmetry Order 6, for example if they both comprise 6 alignment splines. Both of the alignment portion in the passage and the cooperating alignment portion on an external surface of the hollow support member can have rotational symmetry Order 8, for example if they both comprise 8 alignment splines. The rotational symmetry is about the longitudinal axis when the device is assembled. 
     The, or each, guiding surface can be a helical guiding surface i.e. a curved, twisted, spiral or corkscrew surface. The helical surface forms a portion of a helical turn such that it acts to guide an alignment member both longitudinally and rotationally to a position between it and a neighbouring alignment spline during assembly. 
     The at least one cooperating alignment member can be at least one alignment pin. This is a simple structure that is easily guided into the correct position during assembly. 
     The at least one cooperating alignment member can be at least one alignment spline. An alignment spline provides a greater contact surface and therefore greater stability and structural strength than an alignment pin. The at least one cooperating alignment member can be a plurality of alignment splines. An alignment portion and its corresponding cooperating alignment portion can comprise the same number of alignment splines as each other. In some embodiments, each alignment portion and its corresponding cooperating alignment portion comprises the same number of alignment splines as each other. The alignment portion and its corresponding cooperating alignment portion therefore can have complimentary profiles. 
     Each alignment spline on an alignment portion can engage between two alignment splines as its corresponding cooperating alignment portion and vice versa. An alignment portion and its corresponding cooperating alignment portion can for example each comprise six alignment splines. An alignment portion and its corresponding cooperating alignment portion can each comprise eight alignment splines. 
     The female alignment portion and the male alignment portion can engage to prevent relative rotational movement between the lancet body and the housing. Thus, no rotational movement between the two components is possible. 
     Each alignment spline on at least one alignment portion or at least one cooperating alignment portion can comprise a guiding surface at one end thereof configured to guide an alignment spline or a cooperating alignment member to a position between it and a neighbouring one of the alignment splines during assembly. 
     An alignment portion and its corresponding cooperating alignment portion engage to prevent relative rotational movement between the lancet body and the housing or to prevent relative rotational movement between the lancet body and the hollow support member. Thus, no rotational movement between the two components is possible. For example, the alignment portion on the housing and the cooperating alignment portion on the lancet body can engage to prevent relative rotational movement between the lancet body and the housing. The alignment portion on the hollow support member and the cooperating alignment portion on the lancet body can engage to prevent relative rotational movement between the lancet body and the hollow support member. The alignment portion on the housing and the cooperating alignment portion on the support member can engage to prevent relative rotational movement between the housing and the urging member. 
     Both of the female alignment portion and the male alignment portion can be rotationally symmetrical, i.e. they look the same after some rotation by a partial turn. Both of the female alignment portion and the male alignment portion can have rotational symmetry Order 6. Both of the female alignment portion and the male alignment portion can have rotational symmetry Order 8. The rotational symmetry is about the longitudinal axis when the device is assembled. 
     At least one of the alignment portion in the passage and the cooperating alignment portion on an external surface of the lancet body can be rotationally symmetrical i.e. they look the same after some rotation by a partial turn. At least one of the alignment portion in the passage and the cooperating alignment portion on an external surface of the lancet body can have rotational symmetry Order 6, for example if it comprises 6 alignment splines. At least one of the alignment portion in the passage and the cooperating alignment portion on an external surface of the lancet body can have rotational symmetry Order 8, for example if it comprises 8 alignment splines. The rotational symmetry is about the longitudinal axis when the device is assembled. 
     Both of the alignment portion in the passage and the cooperating alignment portion on an external surface of the lancet body can be rotationally symmetrical i.e. they look the same after some rotation by a partial. Both of the alignment portion in the passage and the cooperating alignment portion on an external surface of the lancet body can have rotational symmetry Order 6, for example if they both comprise 6 alignment splines. Both of the alignment portion in the passage and the cooperating alignment portion on an external surface of the lancet body can have rotational symmetry Order 8, for example if they both comprise 8 alignment splines. The rotational symmetry is about the longitudinal axis when the device is assembled. 
     At least one of the alignment portion on an internal surface of the hollow support member and the cooperating alignment portion on an external surface of the lancet body can be rotationally symmetrical i.e. they look the same after some rotation by a partial turn. At least one of the alignment portion on an internal surface of the hollow support member and the cooperating alignment portion on an external surface of the lancet body can have rotational symmetry Order 6, for example if it comprises 6 alignment splines. At least one of the alignment portion on an internal surface of the hollow support member and the cooperating alignment portion on an external surface of the lancet body can have rotational symmetry Order 8, for example if it comprises 8 alignment splines. The rotational symmetry is about the longitudinal axis when the device is assembled. 
     Both of the alignment portion on an internal surface of the hollow support member and the cooperating alignment portion on an external surface of the lancet body can be rotationally symmetrical i.e. they look the same after some rotation by a partial turn. Both of the alignment portion on an internal surface of the hollow support member and the cooperating alignment portion on an external surface of the lancet body can have rotational symmetry Order 6, for example if they both comprise 6 alignment splines. Both of the alignment portion on an internal surface of the hollow support member and the cooperating alignment portion on an external surface of the lancet body can have rotational symmetry Order 8, for example if they both comprise 8 alignment splines. The rotational symmetry is about the longitudinal axis when the device is assembled. 
     One or more of the passage, the lancet body, the internal surface of the support member and the external surface of the support member can be rotationally symmetrical, i.e. they look the same after some rotation by a partial turn. Each of the passage, the lancet body and the support member can be rotationally symmetrical, i.e. they look the same after some rotation by a partial turn. 
     The device can further comprise a removable safety cap for at least partially covering the lancet tip, the removable safety cap comprising a graspable portion external to the housing and a stem substantially within the housing. The graspable portion can comprise diametrically opposed gripping surfaces. This helps the user to grip and twist and/or pull the safe safety cap for removal. The stem can be frangibly connected to a forward end, e.g. a front surface, of the lancet body and rotation of the graspable portion relative to the lancet body can break the frangible connection such that the cap can be removed from the housing. When relative rotation between the lancet body and the passage is prevented, for example, by splined engagement between components, rotation of the graspable portion of the safety cap by the user will ensure that the graspable portion rotates relative to the lancet body. This rotation will sever the frangible connection between the lancet body and the safety cap such that the safety cap can be removed from the housing. This exposes the sharp tip of the lancet so that the blood sampling device can be used. Until the safety cap is removed, the sharp tip can be hermetically sealed in the safety cap. 
     The blood sampling device can further comprise a sleeve movably mounted in the passage and projecting through the aperture in the housing wherein the sleeve can comprise at least one holding feature and is moveable from a holding configuration in which the at least one holding feature holds the lancet to prevent forward movement of the lancet to the lancing position to a release configuration in which the at least one holding feature does not hold the lancet. The sleeve can be rotationally symmetrical, i.e. it looks the same after some rotation by a partial turn. The sleeve can have rotational symmetry Order 3. 
     The at least one holding feature can be at least two holding arms, preferably three holding arms. The lancet body can comprise a sloped surface and each of the at least two holding arms can comprise a cooperating sloped surface arranged to contact the lancet body sloped surface when the sleeve is in the holding configuration to prevent forward movement of the lancet body in the passage. This prevents the lancet from moving to the lancing position before the device is actuated by the user. Thus, when the sleeve is in the holding configuration, for example when the lancet is in the pre-primed position and optionally during movement of the lancet from the pre-primed position to the primed position, the sloped surfaces on the holding arms can contact the sloped surface on the lancet body to prevent forward movement of the lancet body in the passage. When the sleeve is in the holding configuration the sloped surfaces on the holding arms can contact the sloped surface on the lancet body to prevent forward movement of the lancet body relative to the sleeve. 
     The lancet body sloped surface can be a chamfered surface. The cooperating sloped surfaces on each of the holding arms can be chamfered surfaces. 
     The sleeve can comprise a skin contacting front surface and application of pressure against the skin contacting front surface can move the sleeve rearwardly in the housing from the holding configuration to the release configuration. Thus, the sleeve can be an actuator. The blood sampling device can be a contact activated device. The blood sampling device can be a contact activated single use lancing device. 
     The skin contacting front surface can be a textured surface. The skin contacting front surface can include a flat base surface and a plurality of projections extending/projecting from the flat base surface. The textured surface such as the projections are designed to stimulate the skin so as to ‘confuse’ the nerve endings and alleviate the perceived pain experienced when the lancet tip penetrates the skin to make an incision. 
     Rearward movement of the sleeve in the passage can move the lancet rearwardly from a pre-primed position in which the urging member is relaxed and the lancet tip is located in the housing to the primed position in which the urging member is primed and the lancet tip is located in the housing. The actuating means is in a holding configuration in the pre-primed position. The holding feature can be arranged to move the lancet into the primed position. Having a pre-primed position in which the urging member is relaxed is beneficial because it means that the device does not have to have stored energy. This also means that the blood sampling device can be formed of biobased materials which are not good at carrying stored kinetic energy, thus improving the environmental impact of the device. Thus, one or more of the lancet body, the sleeve, the housing and the support member can be formed of a bio-based polymer. All of the lancet body, the sleeve, the housing and the support member can be formed of a bio-based polymer. 
     According to a third aspect of the present invention, there is provided a method of assembling a blood sampling device according to any preceding embodiments of the blood sampling device comprising the steps of:
         (i) providing a front housing portion defining an aperture in a forward end ( 16 ) thereof and a rear housing portion;   (ii) inserting an urging member into one of said front housing portion or said rear housing portion;   (iii) inserting a lancet comprising a lancet body supporting a lancet tip at a forward end thereof into one of said front housing portion or said rear housing portion;   (iv) affixing said front housing portion to said rear housing portion to form a housing comprising an interior surface defining a passage with said urging member and said lancet located in said passage;       wherein said housing defines an alignment portion in said passage and said lancet body defines a cooperating alignment portion on an external surface thereof;   wherein one of said alignment portion and said cooperating alignment portion comprises a plurality of alignment splines and the other comprises at least one cooperating alignment member,   wherein at least one alignment spline comprises a guiding surface at one end thereof which guides a cooperating alignment member to a position between it and a neighbouring one of said alignment splines to limit relative rotation between said housing and said lancet body.   

     According to a fourth aspect of the present invention, there is provided a method of assembling a blood sampling device according to any preceding embodiments of the blood sampling device comprising the steps of:
         (i) providing a front housing portion defining an aperture in a forward end ( 116 ) thereof and a rear housing portion;   (ii) inserting an urging member and a hollow support member into one of said front housing portion or said rear housing portion wherein said hollow support member supports said urging member;   (iii) inserting a lancet comprising a lancet body supporting a lancet tip at a forward end thereof into one of said front housing portion or said rear housing portion;   (iv) affixing said front housing portion to said rear housing portion to form a housing comprising an interior surface defining a passage with said hollow support member, said urging member and said lancet located in said passage;       wherein said hollow support member defines an alignment portion on an internal surface ( 212 ) thereof and said lancet body defines a cooperating alignment portion on an external surface thereof;   wherein one of said alignment portion and said cooperating alignment portion comprises a plurality of alignment splines and the other comprises at least one cooperating alignment member,   wherein at least one alignment spline comprises a guiding surface at one end thereof which guides a cooperating alignment member to a position between it and a neighbouring one of said plurality of alignment splines to limit relative rotation between said hollow support member and said lancet body.   

     The method can be an automated assembly process. As no rotational alignment is needed for any of the components of the blood sampling device, this provides a much more efficient automated assembly process. With regards to equipment, having free orientation on assembly (i.e. it does not matter what rotational orientation the components are assembled in) saves a significant amount of time, thus reducing cost. Furthermore, having free orientation on assembly removes one of the considerable causes of assembly failure, namely the incorrect orientation of assembly components. The below assembly process will be described as a manual process for simplicity but the same principles of orientation free assembly apply equally to an automated assembly process. 
     A significant portion of the cost associated with single use lancing devices is associated with the assembly of the parts. It would therefore be desirable to provide a device structure enabling simplified assembly. 
     Whilst the invention has been described above, it extends to any inventive combination of the features set out above, or in the following description. These and other aspects of the present invention will be apparent from the following specific description, in which embodiments of the present invention are described, by way of examples only, and with reference to the accompanying drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded side view of a blood sampling device; 
         FIG. 2  is a side perspective view of the front housing portion of the blood sampling device of  FIG. 1 ; 
         FIG. 3  is a side sectional view of the rear housing portion of the blood sampling device of  FIG. 1 ; 
         FIG. 4  is a perspective side view of the sleeve of the blood sampling device of  FIG. 1  in a holding configuration; 
         FIG. 5  is a perspective side view of the sleeve of the blood sampling device of  FIG. 1  in a release configuration; 
         FIG. 6  is a perspective side view of the support member of the blood sampling device of  FIG. 1 ; 
         FIG. 7  is a perspective side view of the support member supporting the elastomeric urging means of the blood sampling device of  FIG. 1 ; 
         FIG. 8  is a sectional view of the rear end of the blood sampling device of  FIG. 1  in an initial assembled configuration; 
         FIG. 9  is a perspective side view of the lancet and safety cap of the blood sampling device of  FIG. 1  in an initial assembled configuration; 
         FIG. 10  is a perspective side view of the lancet and sleeve of the blood sampling device of  FIG. 1  with the sleeve in a holding configuration; 
         FIG. 11( a )  is a side sectional view of the blood sampling device of  FIG. 1  in an initial assembled configuration; 
         FIG. 11( b )  is a side sectional view of the blood sampling device of  FIG. 1  in a pre-release configuration; 
         FIG. 11( c )  is a side sectional view of the blood sampling device of  FIG. 1  in a firing configuration; 
         FIG. 11( d )  is a side sectional view of the blood sampling device of  FIG. 1  in a lancing configuration; 
         FIG. 11( e )  is a side sectional view of the blood sampling device of  FIG. 1  in a safe position after firing; 
         FIG. 12( a )  is a part-transparent side view of the sleeve and front housing portion of the blood sampling device of  FIG. 1  in an initial assembled configuration; 
         FIG. 12( b )  is a part-transparent side view of the sleeve and front housing portion of the blood sampling device of  FIG. 1  in a holding configuration; 
         FIG. 12( c )  is a part-transparent side view of the sleeve and front housing portion of the blood sampling device of  FIG. 1  in a holding configuration; and 
         FIG. 12( d )  is a part-transparent side view of the sleeve and front housing portion of the blood sampling device of  FIG. 1  in a release configuration. 
         FIG. 13  is an exploded side view of a second blood sampling device; 
         FIG. 14  is a side perspective view of the front housing portion of the blood sampling device of  FIG. 13 ; 
         FIG. 15  is a plan view of the rear housing of the blood sampling device of  FIG. 13 ; 
         FIG. 16  is a perspective side view of the rear housing portion of the blood sampling device of  FIG. 13 ; 
         FIG. 17  is a side sectional view of the rear housing portion of the blood sampling device of  FIG. 13 ; 
         FIG. 18  is a perspective side view of the sleeve of the blood sampling device of  FIG. 13  in a holding configuration; 
         FIG. 19  is a perspective side view of the sleeve of the blood sampling device of  FIG. 13  in a release configuration; 
         FIG. 20  is a side view of the lancet and safety cap of the blood sampling device of  FIG. 13 ; 
         FIG. 21( a )  is a side sectional view of the blood sampling device of  FIG. 13  in an initial assembled configuration; 
         FIG. 21( b )  is a side sectional view of the blood sampling device of  FIG. 13  in a pre-release configuration; 
         FIG. 21( c )  is a side sectional view of the blood sampling device of  FIG. 13  in a firing configuration; 
         FIG. 21( d )  is a side sectional view of the blood sampling device of  FIG. 13  in a lancing configuration; 
         FIG. 21( e )  is a side sectional view of the blood sampling device of  FIG. 13  in a safe position after firing; 
         FIG. 22( a )  is a part-transparent side view of the sleeve and front housing portion of the blood sampling device of  FIG. 13  in an initial assembled configuration; 
         FIG. 22( b )  is a part-transparent side view of the sleeve and front housing portion of the blood sampling device of  FIG. 13  in a holding configuration; 
         FIG. 22( c )  is a part-transparent side view of the sleeve and front housing portion of the blood sampling device of  FIG. 13  in a holding configuration; 
         FIG. 22( d )  is a part-transparent side view of the sleeve and front housing portion of the blood sampling device of  FIG. 13  in a release configuration. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A list of reference signs used herein is given in the “Reference signs” section immediately prior to the claims. 
     Directional descriptors as used in the following description of the preferred embodiments of the present invention, such as “upper”, “lower”, “top”, “bottom”, “front”, “rear”, etc. relate to the invention when in the preferred orientation. However, it will be clear to the skilled person that the device may be in any orientation and therefore the directional descriptors would be changed accordingly. 
     “Front” as used herein will be understood to refer to the end of the lancing device (or components thereof) which, in use, is closest to the sample site end of the device (i.e. the end which is pointed at the skin). “Rear” as used herein will be understood to refer to the end of the lancing device (or components thereof) which, in use, is furthest from the sample end of the device (i.e. the end which is pointed away from the skin). “Forward” and “rearward” will, likewise, be understood to refer to the directions orientated towards the front and rear of the device. 
     The terms axial, radial and circumferential are used herein to conveniently refer to the general directions relative to the longitudinal direction of the device (or components thereof). The skilled person will, however, appreciate that these terms are not intended to be narrowly interpreted (and for example, the device may have a non-circular and/or irregular form). Typically, regardless of the specific and aesthetic design of the lancing device, the device will be generally elongate and have a longitudinal axis that is generally aligned with the lancing needle and the forward/rearward direction of travel of the lancet in use, as such, the longitudinal axis of the device will substantially coincide with (or be parallel to) the axial direction of the lancet. 
     Embodiment 1 
     Referring to  FIGS. 1 to 12 ( d ), a blood sampling device  100  includes a front housing portion  115  and a rear housing portion  130 , a sleeve  140 , a lancet  160  having a needle  161 , a hollow support member  200  (also described as a tubular support member and a support member) and an urging member  180 . The urging member  180  is an elastomer. When the blood sampling device  100  is assembled, the front housing portion  115  and the rear housing portion  130  fit together to form a housing  110  and their respective inner/interior surfaces  122 ,  132  together define a housing interior surface  110 A defining a passage  111  in which the support member  200 , urging member  180 , sleeve  140  and lancet  160  are housed. Each of the components are generally concentrically arranged around the axis of the needle  161 . 
     Referring to  FIGS. 1 and 2 , the front housing portion  115  is a plastic hollow cylinder having a forward end  116  and an open rearward end  117 . The forward end  116  comprises a forwardly sloping bulbous head  119  defining a circular aperture  118  in the front face thereof. The bulbous head  119  projects radially outwardly from a tubular portion  124  such that a seat  123  is formed by its rear end. Spaced slightly rearwardly of the bulbous head  119  on the outer surface  121  of tubular portion  124 , there is a circumferential detent  120 . 
     Referring to  FIG. 3 , the rear housing portion  130  is a plastic hollow cylinder having an open forward end  131  and a closed rearward end  135  defining a convex base  136 . Spaced slightly rearwardly from the open forward end  131  on the interior surface  132  of the rear housing portion  130  are three equidistantly spaced radial protrusions  133  which form a snap fit with the circumferential detent  120  on the outer surface  121  of the front housing portion  115  when the blood sampling device  100  is assembled. The interior surface  132  of the rear housing portion  130  has eight equidistantly spaced elongate ribs (i.e. splines)  137  extending from the rearward end  135  to around half way up the length of the rear housing portion  130 , defining a splined portion  137 A. Each elongate rib  137  has a sloped helical guiding surface  138  on the front end thereof. Each elongate rib  137  also has a curved face  230  around half way along the length of the elongate rib  137  and a flange  231  arranged to provide a seat for the urging member  180  when the blood sampling device  100  is assembled. The curved face  230  and the flange  231  divide each elongate rib  137  into three sections—a shallow forward portion  232  which is in front of the curved face  230  and has the helical guiding surface  138  at its front end; an intermediate portion  233  having an intermediate depth located between the curved face  230  and the flange  231 ; and a deep rearward portion  234  which is behind the flange  231  and has the largest depth, i.e. it projects radially further in to the passage  111 . The eight equidistantly spaced elongate ribs (i.e. splines)  137  provide a rotationally symmetrical alignment portion on the interior surface  132  of the rear housing portion  130 . The interior surface  132  of the rear housing portion  130  is rotationally symmetrical. 
     Referring to  FIGS. 4 and 5 , the sleeve  140  comprises a forward end  141  and a rearward end  146 . The forward end  141  has a front face in the form of flat base surface  142  defining a central opening aperture  143  through which the sharp tip  162  of the lancet  160  can project in use. The flat base surface  142  also comprises a plurality of projections  144  arranged in an annular array around the central aperture  143 . The projections  144  are designed to stimulate the skin so as to ‘confuse’ the nerve endings and alleviate the perceived pain experienced when the lancet tip penetrates the skin to make an incision. 
     The forward end  141  of the sleeve  140  also comprises a cylindrical tubular portion  145  extending rearwardly from the flat base surface  142  to around one third of the total length of the sleeve  140 . At the rear end of the tubular portion  145  there is an annular seat  147  having the same internal diameter as the tubular portion  145  but a larger external diameter than the tubular portion  145  such that it projects radially outwardly from the rear end of the tubular portion  145 . There are three equidistantly spaced gaps  149  in the annular seat  147 . 
     Holding structures or features in the form of three holding arms  148  are equidistantly spaced around the annular seat  147  and extend rearwardly from the annular seat  147  for around two thirds of the total length of the sleeve  140 , i.e. to the rearward end  146  of the sleeve  140  (i.e. about twice the length of tubular portion  145 ). Each holding arm  148  comprises two fingers  150  separated by a gap  151 . Each gap  151  is aligned with a gap  149  in the annular seat  147 . The two fingers  150  of each holding arm  148  are joined at their rearward ends such that there is no gap between them, i.e. forming a joined rearward end  158 . The joined rearward end  158  of each holding arm  148  comprises a flange  152  which projects radially outwardly and a sloped surface  153  on its internal rear end surface. Each holding arm  148  is biased outwardly such that it splays outwardly in its natural resting (i.e. relaxed) position as shown in  FIG. 5 . This is the release configuration of the sleeve  140 . The three holding arms  148  are resiliently deformable. This means that they can be pressed inwardly towards each other into a holding configuration as shown in  FIG. 4  and will return to their splayed release configuration as shown in  FIG. 5  on removal of this inward pressure. 
     Blocking features in the form of three resiliently deformable blocking or retaining legs  154  extend rearwardly from the tubular cylindrical portion  145  of the sleeve  140 . Each blocking leg  154  is located in a gap  149  in the annular seat  147  and the corresponding gap  151  in a holding arm  148 , i.e. each blocking leg  154  is located between the two fingers  150  of a holding arm  148 . In this embodiment, all of the blocking legs  154  are longitudinally aligned with the tubular portion  145  of the sleeve  140 , i.e., none of the blocking legs  154  are splayed outwardly. This means that when the sleeve  140  is in its release configuration shown in  FIG. 5 , the rearward end of each blocking leg  154  is positioned radially inwardly relative to the rearward end of each holding arm  148 . The rear end of each blocking leg  154  has a chamfered surface in the form of abutment surface  155  on the inner rearward edge thereof. 
     Referring to  FIGS. 11( b ) to 11( e )  the inner surface  157  of the tubular portion  145  of the sleeve  140  comprises a portion of reduced diameter  159   a  which extends rearwardly from the flat base surface  142  and an immediately adjacent portion of increased diameter  159   b  which extends rearwardly to the annular seat  147 . The join between this portion of reduced diameter  159   a  and the immediately adjacent portion of increased diameter  159   b  forms an abutment surface  156  on the inner surface  157  of the sleeve  140 . 
     Referring to  FIG. 9 , the lancet  160  comprises a lancet body  165  moulded around a needle  161 . The lancet body  165  has a forward end  166  and a rearward end  170 . The rearward end  170  comprises a substantially cylindrical tail  171 . The cylindrical tail  171  has a domed rear end  270 . Immediately forward of the cylindrical tail  171  and merging with the cylindrical tail  171  is a substantially cylindrical main body portion  172  which has the same diameter as the cylindrical tail  171 . 
     The main body portion  172  has six elongate ribs (i.e. splines)  174  equidistantly spaced around its circumference, defining a splined portion  172 A. Each elongate rib/spline  174  extends axially from the rear end of the main body portion  172  to around two thirds of the length of the main body portion  172 . The rearward end of each elongate rib/spline  174  has a sloped helical guiding surface  175 . The forward end of each elongate rib/spline  174  merges with a circumferential protrusion  176  which projects radially outwardly on the main body portion  172 . The circumferential protrusion  176  has a chamfered front face in the form of sloped surface  177 . The outer surface of the main body portion  172  is rotationally symmetrical. This does not include non-functioning features such as indentations on the outer surface of the main body portion  172  which are formed by the manufacturing process. 
     The forward end  166  of the lancet body  165  has a frustoconical portion  178  having a planar front surface  167 . The sharp tip  162  of the needle  161  projects from the front surface  167  of the lancet body  165 . The front end of the frustoconical portion  178  has a smaller diameter than the rear end. The rear end of the frustoconical portion  178  has a smaller diameter than the front end of the main body portion  172  such that a front seat  179  is formed by the front end of the main body portion  172  between the circumferential edge of the main body portion  172  and the circumferential edge of the rear end of the frustoconical portion  178 . 
     An elongate safety cap  190  is integrally moulded with the front surface  167  of the lancet body  165  such that the sharp tip  162  of the lancet needle  161  is initially concealed within the safety cap  190 . The safety cap  190  comprises a graspable portion  191  which is external to the housing  110  when the blood sampling device  100  is assembled and a stem  193  which is substantially located within the housing  110  when the blood sampling device  100  is assembled. The stem  193  has a frustoconical rearward end  194  which forms a frangible connection  195  with the front surface  167  of the lancet body  160 . The graspable portion  191  comprises diametrically opposed axially extending detents  192  which act as gripping surfaces for the user. 
     Referring to  FIGS. 6 and 7 , the support member  200  is hollow, i.e. tubular with a generally circular cross-section. The support member  200  has a forward end  201  and a rearward end  202 . It has an external stepped profile that creates three adjoining sections that decrease in diameter along its longitudinal axis from its forward end  201  to its rearward end  202 . 
     The section at the forward end  201  is a collar  203 . Extending rearwardly from the collar  203  on the external surface  204  (i.e. outer surface) of the support member  200  are a plurality of elongate ribs (i.e. splines)  205  equidistantly spaced around the circumference of the collar  203 , defining a splined portion  205 A. Each elongate rib  205  extends axially from the forward end of the collar  203  to around two thirds of the length of the main body section  206 . The rearward end of each elongate rib  205  has a sloped helical guiding surface  215 . The forward end of each elongate rib  174  merges with the collar  203 . 
     The middle section is the main body section  206  over which the collar  203  and the elongate ribs  205  are moulded. The elongate ribs  205  therefore protrude radially outwardly from the outer surface of the main body section  206 . 
     The section at the rearward end is a tubular support section  207 . The front end of the tubular support section  207  is attached to the rear face  208  of the main body section  206 . It has a smaller diameter than the main body section  206  such that the rear face  208  of the main body section  206  forms a support seat  209 . The rear end  210  of the tubular support section  207  is open, i.e. it has a circular aperture  211 . The outer surface of the support member  200  is rotationally symmetrical. 
     An elastomeric urging member  180  is provided over the tubular support section  207 , i.e. it covers the tubular support section  207 . The elastomeric urging member  180  is cup shaped in that it has a circumferential portion  280  which extends around the circumference of the tubular support section  207  and is supported by the support seat  209 , and a transverse portion  281  which extends over the rear end  210  of the tubular support section  207 . The transverse portion  281  therefore spans the width of passage  111  i.e. the diameter of the passage  111 . The transverse portion is generally planar when it is not under tension from the lancet. The elastomeric urging member  180  is overmoulded onto the support member  200  in this embodiment. As such, the chemical fusion between the two components bonds them together. However, the two components could alternatively be formed separately and then attached together during assembly of the blood sampling device  100 . Fusion is not required because the transverse portion  281  is sandwiched between the rear end  210  of the tubular support section  207  and the flanges  231  of the elongate ribs  137  of the housing  110  when the blood sampling device  100  is assembled. Suitable elastomeric materials have high elongation elasticity and efficient energy return. For example, silicone, polyurethane, neoprene, polyisoprene, thermoplastic elastomers could all be used as the elastomeric urging member  180 . 
     The support member  200  also has an internal stepped profile that creates two adjoining sections corresponding to the main body section  206  and the tubular support section  207  that decrease in diameter along its longitudinal axis from its forward end  201  to its rearward end  202 . A plurality of elongate ribs (i.e. splines)  213  are equidistantly spaced around the internal surface  212  (i.e. an inner surface) of the main body section  206 , and define inner splined portion  213 A. The elongate ribs  213  run the length of the main body section  206 . The forward end of each elongate rib  213  has a sloped helical guiding surface  214 . 
     Assembly of the blood sampling device  100  will now be described. None of the components of the blood sampling device  100  require manual rotational alignment during assembly, simplifying manufacture. In addition, none of the components require manual connection, each can simply be inserted into the housing. It is noted that the assembly of the blood sampling devices  100  may be fully automated (i.e. no manual assembly) and in large numbers. With regard to equipment, having free orientation on assembly (i.e. it does not matter what rotational orientation the components are assembled in) saves a significant amount of time, thus reducing cost. Furthermore, having free orientation on assembly removes one of the considerable causes of assembly failure, namely the incorrect orientation of assembly components. The below assembly process will be described as a manual process for simplicity but the same principles of orientation free assembly apply equally to an automated assembly process. 
       FIG. 11( a )  shows the blood sampling device  100  in an initial assembled configuration. To assemble the blood sampling device  100 , the front housing portion  115  is held with its forward end  116  facing downwards and its open rearward end  117  facing upwards. The sleeve  140  is inserted into the front housing portion  115  via the open rear end  117  such that the forward end  141  of the sleeve  140  projects through the circular aperture  118  in the forward end  116  of the front housing portion  115 . The annular seat  147  of the sleeve  140  abuts the inner surface  122  of the forward end  116  of the front housing portion  115  which prevents further forward movement of the sleeve  140 . The inner surface  122  of the front housing portion  115  has a larger diameter than the tubular cylindrical portion  145  of the sleeve  140  but a smaller diameter than the holding arms  148  when they are splayed and the sleeve  140  is in the resting configuration ( FIG. 5 ). As such, insertion of the sleeve  140  into the front housing portion  115  forces the holding arms  148  radially inwardly so that the sleeve  140  is in the holding configuration ( FIG. 4 ). The rotational orientation of the sleeve  140  relative to the front housing portion  115  does not matter as the inner surface  122  of the front housing portion  115  is rotationally symmetrical. 
     The lancet  160  and frangibly connected safety cap  190  are then inserted into the front housing portion  115  via the open rear end  117 , safety cap  90  first. The diameter of the safety cap  190  is smaller than the diameter of the central aperture  143  in the flat base surface  142  of the sleeve  140  so that it passes through the central aperture  143  on insertion. The diameter of the forward end  166  of the lancet body  165  is smaller than the internal diameter of the rear end  146  of the sleeve  140 , i.e. the distance between the rear ends of the holding arms  148 . Therefore, the forward end  166  of the lancet body  165  passes through the rear ends of the holding arms  148  on insertion. However, the diameter of the circumferential protrusion  176  having a sloped surface  177  is larger than the diameter of the rear end  146  of the sleeve  140  when the sleeve  140  is in the holding configuration. As such, when the sloped surface  177  contacts the sloped surface  153  on the internal surfaces of the rear end of the holding arms  148 , further forward movement of the lancet  160  is prevented, i.e. movement of the sloped surface  177  past the sloped surfaces  153  on the holding arms  148  is prevented. The rotational orientation of the lancet  160  and frangibly connected safety cap  190  relative to the front housing portion  115  and the sleeve  140  does not matter. 
     Referring to  FIG. 8 , the rear housing portion  130  is held with its closed rearward end  135  facing downwards and its open forward end  131  facing upwards. The support member  200  and the overmoulded elastomeric urging member  180  affixed to the support member  200  are then inserted into the rear housing portion  130  via the open forward end  131 . The urging member  180  and rearward end of the support member  200  are inserted first. The diameter of the circumferential portion  280  of the urging member  180  is smaller than the diametric distance between opposing elongate ribs  137  in the shallow forward portion  232 , substantially the same as the diametric distance between opposing elongate ribs  137  in the intermediate portion  233  and larger than the diametric distance between opposing elongate ribs  137  in the rearward portion  234 . As such, when the support member  200  and the overmoulded elastomeric urging member  180  are inserted into the rear housing portion  130 , the curved faces  230  of the elongate ribs  137  guide urging member  180  such that the transverse portion  281  of the urging member  180  rests against the flanges  231  of the elongate ribs  137  and the circumferential portion  280  of the urging member  180  is located between and interacts with the intermediate portion  233  of each of the elongate ribs  137 . Thus, the periphery of the transverse portion  281  of the urging member  180  is sandwiched between the flanges  231  of the elongate ribs  137  and the rear end  210  of the tubular support section  207  of the support member  200 . The circumferential portion  280  is sandwiched between the tubular support section  207  of the support member  200  and the intermediate portion  233  of each of the elongate ribs  137 . There is also an interference fit between the urging member  180 , the tubular support section  207  of the support member  200  and the intermediate portion  233  of the rib  137 . 
     The rotational orientation of the support member  200  relative to the rear housing portion  130  during insertion of the support member  200  and the overmoulded elastomeric urging member  180  does not matter, i.e. the support member  200  can be inserted in any orientation. If the elongate ribs  137  on the interior surface  132  of the rear housing portion  130  are not rotationally aligned with the elongate ribs  205  on the external surface  204  of the support member  200 , the helical guiding surfaces  138  of the elongate ribs  137  contact the helical guiding surfaces  215  of the elongate ribs  205  so that the support member  200  self-aligns with the rear housing portion  130 , i.e. no manual rotation is required from the user. Each of the elongate ribs  205  on the external surface  204  of the support member  200  is guided in between two elongate ribs  137  on the interior surface  132  of the rear housing portion  130  and vice versa by interaction of the respective helical guiding surfaces  138 ,  215 . Therefore, the rear housing portion  130  and the support member  200  cannot rotate relative to each other when assembled. 
     The open forward end  131  of the rear housing portion  130 , which now contains the non-rotatably engaged support member  200  and the overmoulded elastomeric urging member  180 , is connected to the open rearward end  117  of the front housing portion  115  which contains the sleeve  140  and the lancet  160 . The rotational orientation of the rear housing portion  130  relative to the front housing portion  115  does not matter, i.e. the rear housing portion  130  can be placed on the rear end of the front housing portion  115  in any orientation. If the elongate ribs  213  on the internal surface  212  of the support member  200  are not rotationally aligned with the elongate ribs  174  on the outer surface of the lancet body  165 , then the helical guiding surfaces  214  of the elongate ribs  213  contact the helical guiding surfaces  175  of the elongate ribs  174  so that the support member  200  and thus the non-rotatably engaged rear housing portion  130  self-aligns with the lancet body  165 , i.e., no manual rotation is required from the user. Each of the elongate ribs  213  on the internal surface  212  of the support member  200  is guided in between two elongate ribs  174  on the outer surface of the lancet body  165  and vice versa by the interaction between the respective helical guiding surfaces  214 , 175 . Therefore, the support member  200  and the lancet  160  cannot rotate relative to each other when assembled. As the support member  200  and the rear housing portion  130  also cannot rotate relative to each other, none of the lancet  160 , the support member  200  and the rear housing portion  130  can rotate relative to one another. 
     It is noted that instead of providing elongate ribs on each of the rear housing portion  130 , the external surface  204  of the support member  200 , the internal surface  212  of the support member  200  and the lancet body  165 , any combination of splines having guiding surfaces (such as the helical guiding surfaces of this embodiment) and protrusions which can fit in between the splines could be used. Other alternative arrangements would be apparent to the skilled person. 
     The rear housing portion  130  is pushed forwardly over the front housing portion  115  until the three equidistantly spaced radial protrusions  133  on the interior surface  132  of the rear housing portion  130  are positioned in the circumferential detent  120  on the outer surface  121  of the front housing portion  115 . The three radial protrusions  133  form a snap fit in the circumferential detent  120 , securing the front housing portion  115  and the rear housing portion  130  together. The rearward end  117  of the front housing portion  115  is located within the forward end  131  of the rear housing portion  130  to form a portion of the passage  111  having a reduced diameter in the portion of overlap. The rear housing portion  130  is prevented from moving further forward by abutment of the forward end  131  of the rear housing portion  130  with the seat  123  formed by the rear end of the bulbous head  119  of the sleeve  140  and the front housing portion  115 . 
     As such, in the initial assembled configuration, the front housing portion  115  and the rear housing portion  130  form a housing  110  having a forward end  112  and a rearward end  113 . The housing  110  has an aperture  118  in said forward end  112  and the inner surface  122  of the front housing portion  115  and the interior surface  132  of the rear housing portion together form an interior surface of the housing  110  defining a passage  111 . The passage  111  is narrower in the forward end  112  of the housing  110  because the front housing portion  115  is located inside the rear housing portion  130 . The urging member  180 , the support member  200 , the lancet  160 , the stem  193  of the safety cap  190  and the rearward end  146  of the sleeve  140  are located in the passage  111  in the initial assembled configuration. The forward end  141  of the sleeve  140  and the graspable portion  191  of the safety cap  190  project through the aperture  118  in the forward end  116  of the housing  110 , i.e. they are not located in the passage  111  in the initial assembled configuration. The urging member  180  is relaxed, i.e. it is not under tension, in the initial assembled configuration and the domed rear end  270  of the cylindrical tail  171  of the lancet  160  is not urging the urging member  180  rearwardly. This is beneficial because it means that the elastomer does not have any stored energy in the initial assembled configuration, increasing the life of the blood sampling device  100 . 
     The components of the blood sampling device  100  could be assembled in a different order so long as the arrangement of components in the blood sampling device  100  is the same after assembly. For example, the urging member  180  and lancet  160  with frangibly connected safety cap  190  could be inserted into the rear housing portion  130  before inserting the sleeve  140  and the front housing portion  115 . 
     Referring to  FIGS. 11( a )-( e ) and 12( a )-( d ) , operation of the blood sampling device  100  will now be described. Referring to  FIG. 11( a ) , when the blood sampling device  100  is in the initial assembled configuration, the first step to be taken by the user is removal of the safety cap  190 . The safety cap  190  may be removed by holding the graspable portion  191  and twisting it relative to the housing  110  about the direction of pricking P. As each of the elongate ribs  213  on the internal surface  212  of the support member  200  is located between two elongate ribs  174  on the outer surface of the lancet body  165  and vice versa, the lancet body  165  cannot rotate relative to the support member  200 . As each of the elongate ribs  205  on the external surface  204  of the support member  200  is located between two elongate ribs  137  on the interior surface  132  (i.e. inner surface) of the rear housing portion  230  and vice versa, the support member  200  cannot rotate relative to the rear housing portion  230 . Thus, the lancet body  160  cannot rotate relative to the rear housing portion  130 . 
     As such, the twisting action of the graspable portion  191  rotates the safety cap  190  relative to the housing  110  and the lancet body  165 . This breaks the frangible connection  195  between the safety cap  190  and the lancet  160  such that the safety cap  190  can be removed from the housing  110 . Withdrawal of the safety cap  190  in the pricking direction P exposes the sharp tip  162  of the needle  161  inside the housing  110 . Thus, until this time the needle  161  is hermetically sealed prior to use. The blood sampling device is in a pre-primed position (not shown) in which the sharp tip  162  is located in the housing  110  (i.e. within the passage  111 ) but the urging member  180  is not yet primed. Abutment of the sloped surface  177  on the lancet body  165  with the sloped surfaces  153  on the internal surfaces of the holding arms  148  prevents the lancet  160  from moving forwardly in the passage  111  because the sleeve  140  is in the holding configuration (first sleeve position), i.e. movement of the sloped surface  177  past the sloped surfaces  153  is prevented. Abutment of the annular seat  147  of the sleeve  140  against the inner surface  122  of the forward end  116  of the front housing portion  115  prevents forward movement of the sleeve  140  in the passage  111 . Thus, the blood sampling device  100  is held in the pre-primed position until actuated by the user. 
     To operate the blood sampling device  100 , the user holds the housing  110  and places the flat base surface  142  of the sleeve  140  (which is the forwardmost part of the blood sampling device  100  in the pre-primed position) against the surface of the skin from which blood is to be sampled. The annular array of projections  144  therefore contact the skin of the user, stimulating the skin so as to ‘confuse’ the nerve endings and alleviate the perceived pain experienced when the lancet tip penetrates the skin to make an incision. To actuate the blood sampling device  100 , the user presses the housing  110  towards the skin. This causes the housing  110  to move forwardly relative to the sleeve  140  as the sleeve  140  is held against the surface of the skin, i.e. the sleeve  140  moves rearwardly in the passage  111 . 
     Passage  111  comprises a rearward portion  111 R and a forward portion  111 F immediately adjacent rearward portion  111 R, forward portion  111 F having a smaller diameter than rearward portion  111 R. Holding arms  148  are located in passage forward portion  111 F when sleeve  140  is in the holding configuration such that they are urged radially inwards, and rearward movement of sleeve  140  in passage  111  to passage rearward portion  111 R results in holding arms  148  moving radially outwards such that sleeve  140  is in the release position. In certain embodiments this movement of holding arms  148  is as a result of them moving to their relaxed position. In other embodiments, this movement is as a result of sloped surface  177  of lancet body  165  (which abuts sloped surface  153  of holding arms  148 ) deflecting holding arms  148  radially outwards. Front housing portion  115  comprises an inner portion  115 A which is located inside rear housing portion  130  to form forward portion  111 F of passage  111 . 
     Referring to  FIG. 12( b ) , the holding arms  148  are held inwardly by the front housing portion  115  during this initial rearward movement of the sleeve  140  in the passage  111  so the sleeve  140  is maintained in the holding configuration. As such, the sloped surface  177  on the lancet body  165  continues to abut the sloped surfaces  153  on the internal surfaces of the holding arms  148 , preventing movement of the sloped surface  177  past the sloped surfaces  153  and thus forward movement of the lancet  160  relative to the sleeve  140 . As such, the lancet  160  also moves rearwardly in the passage  111  with the sleeve  140  from the pre-primed position to a primed position. The domed rear end  270  of the cylindrical tail  171  of the lancet  160  is urging the transverse portion  281  of the urging member  180  rearwardly. As the periphery of the transverse portion  281  of the urging member  180  is sandwiched between the flanges  231  of the elongate ribs  137  in the rear housing portion  130  and the rear end  210  of the tubular support section  207  of the support member  200 , the urging member  180  cannot move longitudinally in the passage  111 . Thus, the transverse portion  281  of the urging member  180  is resiliently deformed rearwardly in the passage. This places the urging member  180  under tension. As the cylindrical tail  171  of the lancet  160  is domed, it does not pierce the transverse portion  281  of the urging member  180 . The blood sampling device  100  is now in the pre-release configuration shown in  FIG. 11( b )  and the lancet  160  is in a primed position. The sharp tip  162  is located in the housing  110  (i.e. within the passage  111 ) in the primed position and the urging member  180  is primed, i.e., it is stretched from its resting position so that it is under tension. 
     If the user continues to push the blood sampling device  100  towards the skin, the sleeve  140  will continue to move rearwardly in the passage  111 . Referring to  FIG. 12( c ) , the holding arms  148  start to splay outwardly as the flange  152  of each holding arm  148  moves rearwardly past the rearward end  117  of the front housing portion  115  because the diameter of the passage  111  is larger behind the front housing portion  115 . The urging member  180  which is now under tension is also urging against the domed rear end of the cylindrical tail  171  of the lancet body  165  which urges the lancet body  165  forwardly. As such, the sloped surface  177  on the lancet body  165  urges against the sloped surfaces  153  on the internal surfaces of the holding arms  148 , forcing the holding arms  148  apart. However, as the front surface  152 F of each flange  152  is not yet rearward of the rearward end  117  of the front housing portion  115 , the holding arms  148  are still held inwardly by the front housing portion  115  and the sleeve  140  is still in the holding configuration. The lancet  160  is still in a (first) primed position because it cannot yet travel forwardly past the holding arms  148 . The sharp tip  162  is located in the housing  110  (i.e. within the passage  111 ) in the primed position and the urging member  180  is primed, i.e., it is stretched from its resting position so that it is under tension. 
     Referring to  FIG. 12( d ) , when the sleeve  140  moves sufficiently rearwardly in the passage  111  (second sleeve position), the flange  152  of each holding arm  148  is rearward of the rearward end  117  of the front housing portion  115 . The three holding arms  148  splay outwardly under their own resilient bias and under the urging force of sloped surface  177  on the lancet body  165  against the sloped surfaces  153  on the internal surfaces of the holding arms  148 . The blood sampling device  100  is in the firing configuration shown in  FIG. 11( c )  and the sleeve  140  is in the release configuration. This movement of the sleeve  140  from the holding configuration to the release configuration is very quick due to the sharp 90° angle between the front surface  152 F of each flange  152  and the rearward end  117  of the front housing portion  115 . As such, the three holding arms  148  spring outward into the release configuration as soon as the front surface  152 F of each flange  152  is rearward of the rearward end  117  of the front housing portion  115 , i.e. the front surface  152 F of each flange  152  acts as a release point. The diameter of the circumferential protrusion  176  of the lancet body  165  is smaller than the internal diameter of the rear end  146  of the sleeve  140  when it is in the release configuration, i.e. the diameter of the circumferential protrusion  176  of the lancet body  165  is smaller than the distance between the rear ends of the holding arms  148 . As such, the circumferential protrusion  176  and thus the sloped surface  177  of the lancet body  165  can move forwardly in the passage  111  past the sloped surfaces  153  and the lancet  160  fires forwardly under the force of the urging member  180 . 
     As the lancet  160  moves forwardly in the passage  111 , the sloped surface  177  of the lancet body  165  contacts the abutment surfaces  155  on the inner rearward edge of each of the three blocking legs  154 . The lancet  160  cannot push the sleeve  140  forwardly in the passage  111  because the forward surface (stop surface)  152 F of each flange  152  on each of the holding arms  148  abuts stop surface  117 S of the rearward end  117  of the front housing portion  115 , preventing forward movement of the sleeve  140 , i.e. the stop surface  117 S of rearward end  117  and the forward surface (stop surface)  152 F act as cooperating latching surfaces. The sleeve  140  is also held in position by the user holding the blood sampling device  100  against the skin. As lancing is near instantaneous, upon reaching the release point, it would not be possible for the user to release pressure before firing of the blood sampling device  100  is finished. However, the force of the urging member  180  is sufficient for the lancet body  165  to splay the three blocking legs  154  outwardly by urging the sloped surface  177  on the lancet body  165  firstly past the abutment surfaces  155  on the inner rearward edge of each of the three blocking legs  154  and then past the inside face of each of the blocking legs  154 . 
     Referring to  FIG. 11( d ) , the sharp tip  162  of the needle  161  projects through the central aperture  143  in the flat base surface  142  of the sleeve  140  and thus also through the aperture  118  in the forward end  116  of the housing  110 , to puncture the skin of the user, drawing a sample of blood from the user. This is the lancing configuration of the blood sampling device  100  in which the lancet  160  is in a (second) lancing position. The lancet  160  continues to move forwardly in the passage  111  until the front seat impact surface  179  formed by the main body portion  172  of the lancet  160  strikes the abutment surface  156  on the inner surface  157  of the sleeve  140 . The contact between the front seat and the abutment surface creates an impulse that is felt by the user as enhanced stimulation from the surface  142  and projections  144  of the sleeve  140 . The relative distances between the tip  162  and the seat  179 , and the abutment surface  156  and the front surface  142  of the sleeve  140  mean that the impulse arrives shortly after the tip  162  pieces the skin, the creating nerve confusion and reducing the sensation of pain. 
     Referring to  FIG. 11( e ) , the front seat  179  formed by the main body portion  172  of the lancet  160  strikes the abutment surface  156  on the inner surface  157  of the sleeve  140  with sufficient force to rebound. The lancet  160  therefore travels rearwardly in the passage  111  to retract the sharp tip  162  of the needle  161  into the housing  110 . This rearward movement is assisted by the blocking legs  154  returning from their outwardly splayed position to their normal position parallel to the needle axis. This ensures that the sloped surface  177  on the lancet body  160  moves rearwardly past the abutment surface  155  on the rear end of the blocking legs  154 . When the front seat  179  formed by the main body portion  172  of the lancet  160  strikes the abutment surface  156  on the inner surface  157  of the sleeve  140  a significant amount of energy is lost. Therefore, there is not enough energy in the lancet  160  to re-tension the urging member  180 . The urging member  180  therefore does not re-fire the lancet  160  forwardly in the passage  111  and the lancet  160  does not move forwardly with sufficient force to re-splay the blocking legs  154  and travel forwardly in the passage again. Thus, re-firing of the blood sampling device  100  is prevented and the lancet  160  is held sufficiently rearwardly from the aperture  118  in the forward end  118  in the housing  110  that the sharp tip  162  is safe. Thus, the risk of the user accidentally pricking themselves with the used lancet is significantly reduced. As discussed above, the sleeve  140  cannot move forwardly in the passage  111  because the forward surface (stop surface)  152 F of the flanges  152  on each of the holding arms  148  abuts the rearward end  117  of the front housing portion  115 , preventing forward movement of the sleeve  140 . Therefore, the device cannot be re-used. 
     Embodiment 2 
     Referring to  FIGS. 13 to 22 ( d ), a blood sampling device  1  includes a front housing portion  15  and a rear housing portion  30 , a sleeve  40 , a lancet  60  having a needle  61  and an urging member  80 . The urging member  80  is a compression spring. When the blood sampling device  1  is assembled, the front housing portion  15  and a rear housing portion  30  fit together to form a housing  10  and their respective inner/interior surfaces  22 ,  32  together define a housing interior surface  10 A defining a passage  11  in which the urging member  80 , sleeve  40  and lancet  60  are housed. Each of the components are generally concentrically arranged around the axis of the needle  61 . 
     Referring to  FIG. 14 , the front housing portion  15  is a plastic hollow cylinder having a forward end  16  and an open rearward end  17 . The forward end  16  comprises a forwardly sloping bulbous head  19  defining a circular aperture  18  in the front face thereof. The bulbous head  19  projects radially outwardly from a tubular portion  24  such that a seat  23  is formed by its rear end. Spaced slightly rearwardly of the bulbous head  19  on the outer surface  21  of the tubular portion  24 , there is a circumferential detent  20 . 
     Referring to  FIGS. 15 to 17 , the rear housing portion  30  is a plastic hollow cylinder having an open forward end  31  and a closed rearward end  35  defining a convex base  36 . Spaced slightly rearwardly from the open forward end  31  on the interior surface  32  of the rear housing portion  30  are three equidistantly spaced radial protrusions  33  which form a snap fit with the circumferential detent  20  on the outer surface  21  of the front housing portion  15  when the blood sampling device  1  is assembled. The interior surface  32  of the rear housing portion  30  has eight equidistantly spaced elongate ribs (i.e. splines)  37  extending from the closed rearward end  35  to around half way up the length of the rear housing portion  30 , defining a splined portion  37 A. Each elongate rib  37  has a sloped helical guiding surface  38  on the front end thereof. The eight equidistantly spaced elongate ribs (i.e. splines)  37  provide a rotationally symmetrical alignment portion on the interior surface  32  of the rear housing portion  30 . The interior surface  32  of the rear housing portion  30  is rotationally symmetrical. 
     Referring to  FIGS. 18 and 19 , the sleeve  40  comprises a forward end  41  and a rearward end  46 . The forward end  41  has a front face in the form of a flat base surface  42  defining a central aperture  43  through which the sharp tip  62  of the lancet  60  can project in use. The flat base surface also comprises a plurality of projections  44  arranged in an annular array around the central aperture  43 . The projections  44  are designed to stimulate the skin so as to ‘confuse’ the nerve endings and alleviate the perceived pain experienced when the lancet tip penetrates the skin to make an incision. 
     The forward end  41  of the sleeve  40  also comprises a cylindrical tubular portion  45  extending rearwardly from the flat base surface to around one third of the length of the sleeve  40 . At the rear end of the tubular portion  45  there is an annular seat  47  having the same internal diameter as the tubular portion  45  but a larger external diameter than the tubular portion  45  such that it projects radially outwardly from the rear end of the tubular portion  45 . There are three equidistantly spaced gaps  49  in the annular seat  47 . 
     Three holding arms  48  are equidistantly spaced around the annular seat  47  and extend rearwardly from the annular seat  47  for around two thirds of the length of the sleeve  40 , i.e. to the rearward end  46  of the sleeve  40 . Each holding arm  48  comprises two fingers  50  separated by a gap  51 . Each gap  51  is aligned with a gap  49  in the annular seat  47 . The two fingers  50  of each holding arm  48  are joined at a rearward end  58  of the respective holding arm  48  such that there is no gap between them, i.e. forming a joined rearward end  58 . The joined rearward end  58  of each holding arm  48  comprises a flange  52  on its external surface which projects radially outwardly from the forwardly adjacent portion of the joined rearward end  58 . The front surface  52 F of the flange  52  is arranged at a 90° angle to the immediately forwardly adjacent portion of the joined rearward end  58 . 
     The internal rear end surface of the joined rearward end  58  of each holding arm  48  is a sloped surface  53 . Each holding arm  48  is biased outwardly such that it splays outwardly in its natural resting position as shown in  FIG. 19 . This is the release configuration of the sleeve  40 . The three holding arms  48  are resiliently deformable. This means that they can be pressed inwardly towards each other into a holding configuration as shown in  FIG. 18  and will return to their splayed release configuration as shown in  FIG. 19  on removal of this inward pressure. 
     Three resiliently deformable blocking legs  54  extend rearwardly from the tubular cylindrical portion  45  of the sleeve  40 . Each blocking leg  54  is located in a gap  49  in the annular seat  47  and the corresponding gap  51  in a holding arm  48 , i.e. each blocking leg  54  is located between the two fingers  50  of a holding arm  48 . In this embodiment, all of the blocking legs  54  are longitudinally aligned with the tubular portion  45  of the sleeve  40 , i.e., none of the blocking legs  54  are splayed outwardly. This means that when the sleeve  40  is in its natural resting position shown in  FIG. 19 , the rearward end of each blocking leg  54  is positioned radially inwardly relative to the rearward end of each holding arm  48 . The rearward end of each blocking leg  54  has a chamfered surface in the form of abutment surface  55  on the inner rear edge thereof. 
     Referring to  FIGS. 21( b ) to 21( e ) , the inner surface  57  of the tubular portion  45  of the sleeve  40  comprises a portion of reduced diameter  59   a  which extends rearwardly from the flat base surface and an immediately adjacent portion of increased diameter  59   b  which extends rearwardly to the annular seat  47 . The join between this portion of reduced diameter  59   a  and the immediately adjacent portion of increased diameter  59   b  forms an abutment surface  56  on the inner surface  57  of the sleeve  40 . 
     Referring to  FIG. 20 , the lancet  60  comprises a lancet body  65  moulded around a needle  61 . The lancet body  65  has a forward end  66  and a rearward end  70 . The rearward end  70  comprises a substantially cylindrical tail  71  shaped and dimensioned such that the urging member  80  can fit over it. Immediately forward of the cylindrical tail  71  is a substantially cylindrical main body portion  72  which has a larger diameter than the cylindrical tail  71 . As such, the rear end of the main body portion  72  provides a rear seat  73  at the front of the cylindrical tail  71 . The rear seat  73  has a larger diameter than the urging member  80  such that when the blood sampling device  1  is in an initial assembled configuration, the urging member  80  abuts the rear seat  73 . 
     The main body portion  72  has eight elongate ribs (i.e. splines)  74  equidistantly spaced around its circumference, defining a splined portion  72 A. Each elongate rib  74  extends axially from the rear end of the main body portion  72  to around two thirds of the length of the main body portion  72 . The rearward end of each elongate rib  74  has a sloped helical guiding surface  75 . The forward end of each elongate rib  74  merges with a circumferential protrusion  76  which projects radially outwardly on the main body portion  72 . The circumferential protrusion  76  has a chamfered front face in the form of sloped surface  77 . The outer surface of the main body portion  72  is rotationally symmetrical. This does not include non-functioning features such as indentations on the outer surface of the main body portion  72  which are requirements of the manufacturing process. 
     The forward end  66  of the lancet body  65  has a frustoconical portion  78  having a planar front surface  67 . The sharp tip  62  of the needle  61  projects from the front surface  67  of the lancet body  65 . The front end of the frustoconical portion  78  has a smaller diameter than the rear end. The rear end of the frustoconical portion  78  has a smaller diameter than the front end of the main body portion  72  such that a front seat  79  is formed by the front end of the main body portion  72  between the circumferential edge of the main body portion  72  and the circumferential edge of the rear end of the frustoconical portion  78 . 
     An elongate safety cap  90  is integrally moulded with the front surface  67  of the lancet body  65  such that the sharp tip  62  of the lancet needle  61  is initially concealed within the safety cap  90 . The safety cap  90  comprises a graspable portion  91  which is external to the housing  10  when the blood sampling device  1  is assembled and a stem  93  which is substantially located within the housing  10  when the blood sampling device  1  is assembled. The stem  93  has a frustoconical rearward end  94  which forms a frangible connection  95  with the front surface  67  of the lancet body  65 . The graspable portion  91  comprises diametrically opposed axially extending detents  92  which act as gripping surfaces for the user. 
     Assembly of the blood sampling device  1  will now be described. Importantly, none of the components of the blood sampling device  1  require manual rotational alignment during assembly, improving the ease of manufacture. In addition, none of the components require manual connection, each can simply be inserted into the housing. It is noted that the assembly of the blood sampling devices  1  may be fully automated (i.e. no manual assembly) and in large numbers. With regards to equipment, having free orientation on assembly (i.e. it does not matter what rotational orientation the components are assembled in) saves a significant amount of time, thus reducing cost. Furthermore, having free orientation on assembly removes one of the considerable causes of assembly failure, namely the incorrect orientation of assembly components. The below assembly process will be described as a manual process for simplicity but the same principles of orientation free assembly apply equally to an automated assembly process. 
       FIG. 21( a )  shows the blood sampling device  1  in an initial assembled configuration. To assemble the blood sampling device  1 , the front housing portion  15  is held with its forward end  16  facing downwards and its open rearward end  17  facing upwards. The sleeve  40  is inserted into the front housing portion  15  via the open rear end  17  such that the forward end  41  of the sleeve  40  projects through the circular aperture  18  in the forward end  16  of the front housing portion  15 . The annular seat  47  of the sleeve  40  abuts the inner surface  22  of the forward end  16  of the front housing portion  15  which prevents further forward movement of the sleeve  40 . The inner surface  22  of the front housing portion  15  has a larger diameter than the tubular cylindrical portion  45  of the sleeve  40  but a smaller diameter than the holding arms  48  when they are in their splayed resting position ( FIG. 19 ). As such, insertion of the sleeve  40  into the front housing portion  15  forces the holding arms  48  radially inwardly so that the sleeve  40  is in the holding configuration ( FIGS. 18 and 22 ( a )). The rotational orientation of the sleeve  40  relative to the front housing portion  15  does not matter as the inner surface  22  of the front housing portion  15  is rotationally symmetrical. 
     The lancet  60  and frangibly connected safety cap  90  are then inserted into the front housing portion  15  via the open rear end  17 , safety cap  90  first. The diameter of the safety cap  90  is smaller than the diameter of the central aperture  43  in the flat base surface of the sleeve  40  so that it passes through the central aperture  43  on insertion. The diameter of the forward end  66  of the lancet body  65  is smaller than the internal diameter of the rear end  46  of the sleeve  40 , i.e. the distance between the rear ends of the holding arms  48 . Therefore, the forward end  66  of the lancet body  65  passes through the rear ends of the holding arms  48  on insertion. However, the diameter of the circumferential protrusion  76  having a sloped surface  77  is larger than the diameter of the rear end  46  of the sleeve  40  when the sleeve  40  is in the holding configuration. As such, when the sloped surface  77  contacts the sloped surface  53  on the internal surfaces of the rear end of the holding arms  48 , further forward movement of the lancet  60  is prevented, i.e. movement of the sloped surface  77  past the sloped surfaces  53  on the holding arms  48  is prevented. The rotational orientation of the lancet  60  and frangibly connected safety cap  90  relative to the front housing portion  15  and the sleeve  40  does not matter. 
     The compression spring  80  is then placed on the cylindrical tail  71  of the lancet body  65 . As above, the inner diameter of the compression spring  80  is larger than the diameter of the cylindrical tail  71  of the lancet body  65  so the forward end  81  of the compression spring  80  passes over the cylindrical tail  71  until it comes to rest against the rear seat  73 . The rear seat  73  has a larger diameter than the compression spring  80  so the compression spring  80  is prevented from moving forward past it. The rotational orientation of the compression spring  80  does not matter. 
     The rear housing portion  30  is then placed over the rearward end  70  of the lancet body  65 , the compression spring  80  and the rearward end  17  of the front housing portion  15 . The rotational orientation of the rear housing portion  30  relative to the other components does not matter i.e. the rear housing portion  30  can be placed on the rear end of the device  1  in any orientation. If the elongate ribs  37  on the interior surface  32  of the rear housing portion  30  are not rotationally aligned with the elongate ribs  74  on the outer surface of the lancet body  65 , the helical guiding surfaces  38  of the elongate ribs  37  on the interior surface  32  of the rear housing portion  30  will contact the helical guiding surfaces  75  of the elongate ribs  74  on the outer surface of the lancet body  65  so that the rear housing portion  30  self-aligns with the lancet body  65 , i.e. no manual rotation is required. Each of the elongate ribs  37  on the interior surface  32  of the rear housing portion  30  is guided in between two elongate ribs  74  on the outer surface of the lancet body  65  and vice versa. Therefore, the rear housing portion  30  and the lancet  60  cannot rotate relative to each other when assembled. It is noted that instead of providing elongate ribs on each of the rear housing portion  30  and the lancet body  65 , one of the components could be provided with splines having guiding surfaces (such as the helical guiding surfaces of this embodiment) and the other could be provided with a single protrusion. Other alternative arrangements would be apparent to the skilled person. 
     The rear housing portion  30  is pushed forwardly until the three equidistantly spaced radial protrusions  33  on the interior surface  32  of the rear housing portion  30  are positioned in the circumferential detent  20  on the outer surface  21  of the front housing portion  15 . The three radial protrusions  33  form a snap fit in the circumferential detent  20 , securing the front housing portion  15  and the rear housing portion  30  together. The rearward end  17  of the front housing portion  15  is located within the open forward end  31  of the rear housing portion  30  to form a portion of the passage  11  having a reduced diameter in the portion of overlap. The rear housing portion  30  is prevented from moving further forward when pushed by abutment of the open forward end  31  of the rear housing portion  30  with the seat  23  formed by the rear end of the bulbous head  19  of the front housing portion  15 . 
     As such, in the initial assembled configuration, the front housing portion  15  and the rear housing portion  30  form a housing  10  having a forward end  12  and a rearward end  13 . The housing  10  has an aperture  18  in said forward end  12  and the inner surface  22  of the front housing portion  15  and the interior surface  32  of the rear housing portion together form an interior surface of the housing  10  defining a passage  11 . The passage  11  is narrower in the forward end  12  of the housing  10  because the front housing portion  15  is located inside the rear housing portion  30 . The compression spring  80 , the lancet  60 , the stem  93  of the safety cap  90  and the rearward end  46  of the sleeve  40  are located in the passage  11  in the initial assembled configuration. The forward end  41  of the sleeve  40  and the graspable portion  91  of the safety cap  90  project through the aperture  18  in the forward end  16  of the housing  10 , i.e. they are not located in the passage  11  in the initial assembled configuration. 
     The components of the blood sampling device  1  could be assembled in a different order so long as the arrangement of components in the blood sampling device  1  is the same after assembly. For example, the compression spring  80  and lancet  60  with frangibly connected safety cap  90  could be inserted into the rear housing portion  30  before inserting the sub-assembled sleeve  40  and the front housing portion  15 . 
     Referring to  FIGS. 21( a )-( e ) and 22( a )-( d ) , operation of the blood sampling device  1  will now be described. Referring to  FIG. 21( a ) , when the blood sampling device  1  is in the initial assembled configuration, the first step to be taken by the user is removal of the safety cap  90 . The safety cap  90  may be removed by holding the graspable portion  91  and twisting it relative to the housing  10  about the direction of pricking P. As each of the elongate ribs  37  on the interior surface  32  of the rear housing portion  30  is located between two elongate ribs  74  on the outer surface of the lancet body  65  and vice versa, the lancet body  65  cannot rotate relative to the housing  10 . As such, the twisting action of the graspable portion  91  rotates the safety cap  90  relative to the housing  10  and the lancet body  65 . This breaks the frangible connection  95  between the safety cap  90  and the lancet  60  such that the safety cap  90  can be removed from the housing  10 . Withdrawal of the safety cap  90  in the pricking direction P exposes the sharp tip  62  of the needle  61  inside the housing  10 . Thus, until this time the needle  61  is hermetically sealed prior to use. The blood sampling device is in a pre-primed position (not shown) in which the sharp tip  62  is located in the housing (within the passage  11 ) and the compression spring  80  is not yet primed. Abutment of the sloped surface  77  on the lancet body  65  with the sloped surfaces  53  on the internal surfaces of the holding arms  48  prevents the lancet  60  from moving forwardly in the passage  11  because the sleeve  40  is in the holding configuration, i.e. movement of the sloped surface  77  past the sloped surfaces  53  is prevented. Abutment of the annular seat  47  of the sleeve  40  against the inner surface  22  of the forward end  16  of the front housing portion  15  prevents forward movement of the sleeve  40  in the passage  11 . Thus, the blood sampling device  1  is held in the pre-primed position until actuated by the user. 
     To operate the blood sampling device  1 , the user holds the housing  10  and places the flat base surface of the sleeve  40  (which is the forwardmost part of the blood sampling device  1  in the pre-primed position) against the surface of the skin from which blood is to be sampled. The annular array of projections  44  therefore contact the skin of the user, stimulating the skin so as to ‘confuse’ the nerve endings and alleviate the perceived pain experienced when the lancet tip penetrates the skin to make an incision. To actuate the blood sampling device  1 , the user presses the housing  10  towards the skin. This causes the housing  10  to move forwardly relative to the sleeve  40  as the sleeve  40  is held against the surface of the skin, i.e. the sleeve  40  moves rearwardly in the passage  11 . 
     Passage  11  comprises a rearward portion  11 R and a forward portion  11 F immediately adjacent rearward portion  11 R, forward portion  11 F having a smaller diameter than rearward portion  11 R. Holding arms  48  are located in passage forward portion  11 F when sleeve  40  is in the holding configuration such that they are urged radially inwards, and rearward movement of sleeve  40  in passage  11  to passage rearward portion  11 R results in holding arms  48  moving radially outwards such that sleeve  40  is in the release position. In certain embodiments this movement of holding arms  48  is as a result of them moving to their relaxed position. In other embodiments, this movement is as a result of sloped surface  77  of lancet body  65  (which abuts sloped surface  53  of holding arms  48 ) deflecting holding arms  48  radially outwards. Front housing portion  15  comprises an inner portion  15 A which is located inside rear housing portion  30  to form forward portion  11 F of passage  11 . 
     Referring to  FIG. 22( b ) , the holding arms  48  are held inwardly by the front housing portion  15  during this initial rearward movement of the sleeve  40  in the passage  11  so the sleeve  40  is maintained in the holding configuration. As such, the sloped surface  77  on the lancet body  65  continues to abut the sloped surfaces  53  on the internal surfaces of the holding arms  48 , preventing movement of the sloped surface  77  past the sloped surfaces  53  and thus forward movement of the lancet  60  relative to the sleeve  40 . As such, the lancet  60  also moves rearwardly in the passage  11  with the sleeve  40  from the pre-primed position to a primed position. This compresses the compression spring  80  between the rear seat  73  formed by the main body portion  72  of the lancet body  65  and the rearward end of the passage  11  formed by the rear housing portion  30 . The blood sampling device  1  is now in the pre-release configuration shown in  FIG. 21( b )  and the lancet  60  is in a primed position. The sharp tip  62  is located in the housing  10  (within the passage  11 ) in the primed position and the compression spring  80  is now primed i.e. it is compressed from its resting position. 
     If the user continues to push the blood sampling device  1  towards the skin, the sleeve  40  will continue to move rearwardly in the passage  11 . Referring to  FIG. 22( c ) , the holding arms  48  try to splay outwardly as the flange  52  of each holding arm  48  moves rearwardly past the rearward end  17  of the front housing portion  15 . This is because the diameter of the passage  11  is larger behind the front housing portion  15 . The compression spring  80  is also urging against the rear seat  73  formed by the main body portion  72  of the lancet body  65  which urges the lancet body  65  forwardly. As such, the sloped surface  77  on the lancet body  65  urges against the sloped surfaces  53  on the internal surfaces of the holding arms  48 , forcing the holding arms  48  apart. However, as the front surface  52 F of each flange  52  is not yet rearward of the rearward end  17  of the front housing portion  15 , the holding arms  48  are still held inwardly by the front housing portion  15  and the sleeve  40  is still in the holding configuration. The lancet  60  is still in a primed position because it cannot yet travel forwardly past the holding arms  48 . The sharp tip  62  is located in the housing  10  (within the passage  11 ) in the primed position and the compression spring  80  is primed i.e. it is compressed from its resting position. 
     Referring to  FIG. 22( d ) , when the sleeve  40  moves sufficiently rearwardly in the passage  11 , the flange  52  of each holding arm  48  is rearward of the rearward end  17  of the front housing portion  15 . The three holding arms  48  splay outwardly under their own resilient bias and under the urging force of sloped surface  77  on the lancet body  65  against the sloped surfaces  53  on the internal surfaces of the holding arms  48 . The blood sampling device  1  is in the firing configuration shown in  FIG. 21( c )  and the sleeve  40  is in the release configuration. This movement of the sleeve  40  from the holding configuration to the release configuration is very quick due to the sharp 90° angle between the front surface  52 F of each flange  52  and the rearward end  17  of the front housing portion  15 . As such, the three holding arms  48  spring outward into the release configuration as soon as the front surface  52 F of each flange  52  is rearward of the rearward end  17  of the front housing portion  15 , i.e. the front surface  52 F of each flange  52  acts as a release point. The diameter of the circumferential protrusion  76  of the lancet body  65  is smaller than the internal diameter of the rear end  46  of the sleeve  40  when it is in the release configuration, i.e. the diameter of the circumferential protrusion  76  of the lancet body  65  is smaller than the distance between the rear ends of the holding arms  48 . As such, the circumferential protrusion  76  and thus the sloped surface  77  of the lancet body  65  can move forwardly in the passage  11  past the sloped surfaces  53  and the lancet  60  fires forwardly under the force of the compression spring  80 . 
     As the lancet  60  moves forwardly in the passage  11 , the sloped surface  77  of the lancet body  65  contacts the abutment surfaces  55  on the inner rearward edge of each of the three blocking legs  54 . The lancet  60  cannot push the sleeve  40  forwardly in the passage  11  because the forward surface (stop surface)  52 F of the flange  52  on each of the holding arms  48  abuts stop surface  17 S of the rearward end  17  of the front housing portion  15 , preventing forward movement of the sleeve  40 , i.e. the stop surface  17 S of the rearward end  17  and the forward surface (stop surfaces)  52 F act as cooperating latching surfaces. The sleeve  40  is also held in position by the user holding the blood sampling device  1  against the skin. As lancing is near instantaneous, upon reaching the release point, it would not be possible for the user to release pressure before firing of the blood sampling device  1  is finished. However, the force of the compression spring  80  is sufficient for the lancet body  65  splay the three blocking legs  54  outwardly by urging the sloped surface  77  on the lancet body  65  firstly past the abutment surfaces  55  on the inner rearward edge of each of the three blocking legs  54  and then the inside face of the blocking leg  54 . However, the force of the compression spring  80  is sufficient for the lancet body  65  to splay the three blocking legs  54  outwardly by urging the sloped surface  77  on the lancet body  65  firstly past the abutment surfaces  55  on the inner rearward edge of each of the three blocking legs  54  and then past the inside face of each of the blocking leg  54 . 
     The lancet  60  continues to move forwardly in the passage  11  until the front seat  79  formed by the main body portion  72  of the lancet  60  abuts the abutment surface  56  on the inner surface  57  of the sleeve  40 . This is the lancing configuration of the blood sampling device  1  in which the lancet  60  is in a lancing position. Referring to  FIG. 21( d ) , the sharp tip  62  of the needle  61  projects through the central aperture  43  in the flat base surface of the sleeve  40  and thus also through the aperture  18  in the forward end  16  of the housing  10 , to puncture the skin of the user, drawing a sample of blood from the user. The impact of the seat  79  on the abutment surface provides the same effect as described above in relation to Embodiment 1. 
     Referring to  FIG. 21( e ) , the front seat  79  formed by the main body portion  72  of the lancet  60  strikes the abutment surface  56  on the inner surface  57  of the sleeve  40  with sufficient force to rebound. The lancet  60  therefore travels rearwardly in the passage  11  to retract the sharp tip  62  of the needle  61  into the housing  10 . This rearward movement is assisted by the blocking legs  54  returning from their outwardly splayed position to their normal position parallel to the needle axis. 
     This ensures that the sloped surface  77  on the lancet body  65  moves rearwardly past the abutment surfaces  55  on the rear end of the blocking legs  54 . When the front seat  79  formed by the main body portion  72  of the lancet  60  strikes the abutment surface  56  on the inner surface  57  of the sleeve  40  a significant amount of energy is lost. Therefore, there is not enough energy in the lancet  60  to re-compress the compression spring  80 . The compression spring  80  therefore does not re-fire the lancet  60  forwardly in the passage  11  and the lancet  60  does not move forwardly with sufficient force to re-splay the blocking legs  54  and travel forwardly in the passage again. Thus, re-firing of the blood sampling device  1  is prevented and the lancet  60  is held sufficiently rearwardly from the aperture  18  in the forward end  16  of the housing  15 , such that the sharp tip  62  is safe. Thus, the risk of the user accidentally pricking themselves with the used lancet is significantly reduced. As discussed above, the sleeve  40  cannot move forwardly in the passage  11  because the forward surface (stop surface)  52 F of the flanges  52  on each of the holding arms  48  abuts the rearward end  17  of the front housing portion  15 , preventing forward movement of the sleeve  40 . Therefore, the device cannot be re-used. 
     It will be apparent to a person skilled in the art that modifications and variations can be made to the described embodiment without departing from the scope of the invention as defined by the appended claims. Any incorporation of reference signs in the claims is solely to ease their understanding, and does not limit the scope of the claims.