Patent Publication Number: US-2005143771-A1

Title: Lancing device with combination depth and activation control

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application claims the priority benefit of U.S. Provisional Patent Application Ser. No. 60/526,213, filed Dec. 2, 2003, the entirety of which is hereby incorporated herein by reference for all purposes. 
    
    
     TECHNICAL FIELD  
      The present invention relates generally to medical devices and, more particularly, to a lancing device for penetrating the skin of a human or animal subject for sampling of blood and/or other body fluids.  
     BACKGROUND OF THE INVENTION  
      Lancing devices are used to penetrate the skin of a subject and obtain a sample of blood or other body fluid, as in the testing of blood sugar levels by diabetics. Typically, a lancet having a sharp point is translationally mounted within a housing portion of a lancing device. The lancet is driven by a spring or other biasing means to cause the sharp point to extend a small distance through an opening in the housing and into the subject&#39;s skin, creating a wound from which the sample of body fluid is collected. The housing optionally includes a pressure surface for “pumping” the wound to enhance sample size, and may also incorporate a capillary tube or other sample collection media. The endcap of the housing or a portion of the housing adjacent the lancet opening may include an open window or a transparent section for viewing the sample collection site, and may also include one or more sample size indicators for comparing the size of a sample to a desired sample size. Example lancing devices are shown in U.S. Pat. No. 5,356,420; U.S. Pat. No. 5,397,334; and U.S. Pat. No. 5,439,473, all of which are hereby incorporated herein by reference.  
      Lancing devices typically are intended either for a single use or for multiple uses. Single-use lancing devices generally are disposed of after one use. For example, in a hospital or clinic, it is desirable to provide a single-use lancing device that can be used on a patient and then disposed of to eliminate any risk of infection to subsequent patients or caregivers from exposure to residual body fluids remaining on the lancing device. Accordingly, single-use lancing devices oftentimes include a disabling mechanism to prevent accidental or intentional re-use of the device. Various forms of disabling mechanisms are available, and are well known in the art. For example, the disabling mechanism may comprise a return spring for retracting the sharp point of the lancet back into the housing after a single use, break-away elements or a frangible link in the cocking or triggering mechanism to prevent re-arming or re-firing the device after a single use, a locking element, and/or a shield for blocking travel of the lancet.  
      Because single-use lancing devices normally are disposed of after one use, they generally are relatively simple in construction so that they can be economically manufactured in large quantities. To keep the design simple and economical, known single-use lancing devices do not include adjustability features. For example, known single-use lancing devices typically do not provide for adjustment of the depth of penetration of the lancet needle beneath the surface of the subject&#39;s skin. Accordingly, users of single-use lancing devices have little or no ability to adjust the depth and/or size of the wound in order to control the fluid sample size. While one user may be able to obtain a sufficient sample from a relatively small wound, another user who bleeds less freely may require a larger wound size to generate a sample of the same size. As a result, a user may be forced to suffer the pain of a lancet stick that is deeper than necessary to collect a sample of adequate size, or may need more than one lancet stick to generate a sufficient sample size. The lack of depth adjustment also renders previously known single-use lancing devices generally unsuitable for use in sampling from different body sites. For a given user, obtaining a sample of a specified size from a forearm sampling site typically requires a greater depth of penetration than obtaining the same size sample from a fingertip sampling site. Thus, previously known single-use sampling devices render it difficult or impossible for a user to obtain just the proper sample size from a single lancet stick, or to sample from different sites on the body.  
      Accordingly, a need exists for lancing devices providing depth adjustment of the lancet needle. In addition, it would be desirable for such lancing devices to be simple and economical in design, manufacture, and use so that they could be incorporated into single-use lancing devices. Furthermore, such lancing devices are needed that permit individual users to obtain the proper size and depth of wound for drawing fluid, without unnecessarily and repeatedly sticking oneself, without enduring the pain of deeper than needed sticks, and without the risk of contamination from any previous users. It is to the provision of lancing devices meeting these and other needs that the present invention is primarily directed.  
     SUMMARY OF THE INVENTION  
      Briefly described, the present invention provides an improved lancing device that includes a housing, a lancet, and a combination depth and activation control assembly. The lancet includes a lancet needle, a lancet body that holds the needle, and a spring that propels the lancet body. The lancet is operable to travel from a charged position ready for activation, to an extended position with the lancet needle extending out of the housing, then to a retracted position with the lancet needle returned to within the housing.  
      In one aspect of the invention, the control assembly includes a control member, a release member, and an engagement surface on the lancet body. The control member includes a control interface and a control shaft. The control shaft has stop surfaces for depth control and an engagement surface for disengaging the release member from the engagement surface for activation control. In this configuration, the control member serves the dual purposes of setting the depth of the puncture and activating the lancet travel. Thus, the user manipulates a single component, the control member, to select the desired lancing depth and to initiate the lancing stroke.  
      In example embodiments, the control interface is a knob that rotates between a locked position and multiple depth setting positions. The control shaft extends from and rotates with the control knob, and is supported by a support arm that extends laterally from the housing. In addition, the control shaft has multiple stop surfaces, each offset a different thickness from the rotational axis of the shaft and positionable in alignment with the lancet body engagement surface. So by rotating the control knob, the user can selectively position the desired stop surface in alignment with the engagement surface to limit to travel of the lancet and thereby select the puncture depth of the lancet.  
      In addition, the release member is movable between a set position holding the lancet in the charged position and an activation position released from holding the lancet in the charged position. In the set position, the release member engages the lancet body engagement surface to hold the lancet in the charged position. Depressing the control knob moves the control shaft laterally so that it contacts and pushes the release member to the activation position. In this position, the release member is moved out of the way of the lancet body engagement surface, thereby releasing the lancet to be launched under the charge stored in the spring.  
      In another aspect of the invention, the lancet body includes an operating section with an inner wall forming an opening. The spring is positioned within the opening and mounted between the lancet body and the housing. For example, the spring may be mounted to the lancet body inner wall at a forward portion of the lancet body and to the support arm that extends laterally from the housing and into the opening. And the control shaft is supported by the arm so that the stop surfaces are alignable with the engagement surface at a rearward portion of the lancet body. In this way, the travel of the lancet is stopped by the impact of the lancet body engagement surface against one of the stop surfaces, and this impact is rearward and thus remote from the forward portion where the needle is, resulting in a less needle vibration and associated pain.  
      In yet another aspect of the invention, the lancing device includes a safety interlock feature. The safety interlock includes one or more lock tabs that align with and fit into one or more lock openings when the control knob is in the unlocked depth setting positions. But when the control knob is in the locked position, the lock tabs do not align with and do not fit into the lock openings, so the control knob cannot be depressed. In one example, one lock tab extends radially from the control shaft and the mating lock opening is formed in the housing and in communication with the control opening through which the control shaft extends. And in another example, two lock tabs extend from and are parallel to the control shaft axis, and two mating lock openings are formed in the housing in positions spaced apart from and on opposite sides of the control opening. In this way, the safety interlock prevents the control knob from being depressed when in the locked position, and permits the control knob to be depressed to activate the device when in one of the depth setting positions.  
      In still another aspect of the invention, the housing has a plurality of ridges or other protrusions with gaps between them. For example, four ridges may positioned in a generally circular arrangement so that when the control knob is in the locked position or one of the depth setting positions, the lock tabs are positioned in the gaps or the lock openings between the ridges. In addition, the housing may be provided with a deflection member that permits the control member to move laterally slightly out of the housing so it does not bind when engaging the ridges. In this way, the ridges, gaps, and deflection member provide a smoothly operable control member with discrete and readily perceivable depth setting and locked positions.  
      And in a further aspect of the invention, the sterility cap is keyed to the housing. For example, the sterility cap may have one or more tabs extending from it, and the housing may have one or more recessed portions that allow the tabs to fit through only when the tabs are aligned with the recessed portions, or vice versa. In this way, the sterility cap can only be removed after it has been manipulated by the user to align the key tabs and recessed portions. And the key tabs help reduce the spring load on the release member, support arm, and lancet body when the device is in the charged position during shipping and storage.  
      These and other aspects, features and advantages of the invention will be understood with reference to the drawing figures and detailed description herein, and will be realized by means of the various elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following brief description of the drawings and detailed description of the invention are exemplary and explanatory of preferred embodiments of the invention, and are not restrictive of the invention, as claimed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an upper front perspective view of a lancing device according to a first example embodiment of the present invention, showing a housing, a lancet sterility cap, and the external components of a combination depth and activation control assembly.  
       FIG. 2  is a lower front perspective view of the lancing device of  FIG. 1 .  
       FIG. 3  is a rear perspective view of the lancing device of  FIG. 1 .  
       FIG. 4  is a rear exploded view of the lancing device of  FIG. 1 , showing a lancet and the internal components of the control assembly.  
       FIG. 5  is a front exploded view of the lancing device of  FIG. 1 .  
       FIG. 6  is a front view of the lancing device of  FIG. 1 , with a front housing piece and spring removed, showing the lancet in a charged position ready for activation.  
       FIG. 7  is a front view of the lancing device of  FIG. 6 , showing the lancet launched to an extended position for lancing the user&#39;s skin.  
       FIG. 8  is a front view of the lancing device of  FIG. 6 , showing the lancet returned by the spring to a retracted position within the housing.  
       FIG. 9  is a cross sectional view of the lancing device taken at line  9 - 9  of  FIG. 1 , showing the lancet in the charged position of  FIG. 6 , and the control assembly in a “deep” depth position and a “set” activation position.  
       FIG. 10  is a perspective cutaway view of the lancing device of  FIG. 9 , showing the control assembly in a “released” activation position and the lancet launched towards the extended position of  FIG. 7 .  
       FIG. 11  is a perspective view of the interior surface of the front housing piece of the lancing device of  FIG. 1 .  
       FIG. 11A  is a side view of a detail of the front housing piece of the lancing device of  FIG. 11 .  
       FIG. 12  is a perspective view of the exterior surface of the front housing piece of  FIG. 11 .  
       FIG. 13  is a perspective view of a portion of the lancing device of  FIG. 1 , showing the control assembly in a “locked” activation position.  
       FIG. 14  is a front perspective view of a lancing device according to a second example embodiment of the present invention, showing a housing, a lancet sterility cap, and the external components of a combination depth and activation control assembly.  
       FIG. 15  is a rear perspective view of the lancing device of  FIG. 14 .  
       FIG. 16  is a front exploded view of the lancing device of  FIG. 14 , showing a lancet and the internal components of the control assembly.  
       FIG. 17  is a perspective view of a portion of the lancing device of  FIG. 14 , showing the control assembly in a “locked” activation position.  
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS  
      The present invention may be understood more readily by reference to the following detailed description of the invention taken in connection with the accompanying drawing figures, which form a part of this disclosure. It is to be understood that this invention is not limited to the specific devices, methods, conditions or parameters described and/or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting of the claimed invention. Also, as used in the specification including the appended claims, the singular forms “a,” “an,” and “the” include the plural, the term “or” means “and/or,” and reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” or “approximately” one particular value and/or to “about” or “approximately” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment.  
      With reference now to the drawing figures,  FIGS. 1-13  show a lancing device  10  according to a first example embodiment of the present invention. The lancing device  10  is a single use, disposable device. In alternative embodiments, the lancing device is adapted to accept replaceable lancets for use as a reusable lancing device.  
      As shown in  FIGS. 1-5 , the lancing device  10  includes a housing  12   a  and  12   b  (collectively referred to as “the housing  12 ”), a lancet  16 , and a combination depth and activation control assembly  18  (the “control assembly”  18 ). The housing  12  may be made of two pieces  12   a  and  12   b  that couple together, as shown, or it may be made of more or fewer pieces, as desired. The lancet  16  includes a puncturing element such as a needle  20  for puncturing skin and a lancet body  14  that holds the needle  20 . The lancet body  14  includes a needle-holding  13  section and an operating section  15 . The needle  20  is covered by a removable sterility cap  22  that is easily removed to use the lancing device  10 . The lancing device  10  is operable to extend the needle  20  through an opening  24  in the housing  12  to puncture a user&#39;s skin.  
      The housing  12 , the lancet  16 , and the combination depth and activation control assembly  18  may all be molded of a plastic material. If desired, the lancet body needle-holding section  13 , the lancet body operating section  15 , and the lancet needle  20  may be integrally molded into a single piece of plastic, or they may be separately made and assembled together, in which case the lancet needle may be made of metal or another material. It will be understood that other materials and fabrication techniques can be suitably employed, as would be recognized by a person of ordinary skill in the art.  
      As shown in  FIGS. 6-8 , when the lancing device  10  is activated, the lancet  16  travels from a charged position (see  FIG. 6 ) to an extended position (see  FIG. 7 ) then to a retracted position (see  FIG. 8 ). The lancet  16  is moved through these positions by the charge of an operating spring  26 . Preferably, the spring  26  is positioned within an opening  28  defined by an inner wall  29  of the operating section  15  of the lancet body  14 . And the spring  26  is preferably mounted between the lancet body inner wall  29  and an arm  30  extending laterally from the housing  12  and into the opening  28 . For example, the spring  26  may be a coil spring that charges under compression and has flared ends or other portions, with a first flared portion  26   a  held by first flanges  31   a  on the arm  30  and a second flared portion  26   b  held by second flanges  31   b  on the lancet body inner wall  29 . And the operating section  15  of the lancet body  14  may include a forward portion where the second flanges  31   b  and the needle-holding section  13  are positioned, and a rearward portion with an engagement surface  38  for limiting the lancet travel. (As used herein, “forward” means towards the lancing site and “rearward” means away from it.) In the depicted embodiment, the operating section  15  of the lancet body  14  is provided by a generally rectangular peripheral wall whose interior surface is the inner wall  29 , which defines the opening  28  and the engagement surface  38 .  
      In alternative embodiments, the lancet body may be provided by a solid body, two spaced apart panels with one central, four corner, or another arrangement of connecting posts, or other structures. The opening may be provided by a slot or other-shaped opening in the body. The spring may be provided by a torsion spring, leaf spring, other spring, other biasing element that functions like a spring, or combination thereof adapted for use to move the lancet. And the spring may be mounted between the lancet body and the housing by being integrally formed as a part of the body or housing, by flanges or couplings in other arrangements, or by other spring-mounting configurations known in the art.  
      In the charged position of  FIG. 6 , the lancing device  10  is ready to be activated to launch the lancet  16 . With the lancet body operating section  15  in the charged position as shown, the spring  26  (not shown) is compressed and thereby stores a charge. The control assembly  18  secures the lancet  16  in the charged position and is operable to release the lancet for launching by the spring  26 , as described in detail with reference to  FIGS. 9-13 .  
      In the extended position of  FIG. 7 , the control assembly  18  has been activated to launch the lancet  16  to travel until a piercing end  21  of the needle  20  extends out of the housing  12  to pierce the skin. The travel of the lancet  16  is limited and stopped in the extended position when the engagement surface  38  on the inner wall  29  at the rearward portion of the lancet body operating section  15  contacts a stop surface  42 . In the depicted embodiment, the stop surface  42  is defined on an adjustable control shaft to provide depth adjustment, though other stop surface arrangements may be used. In this configuration, the impact between mechanical members that stops the lancet travel occurs at the rearward portion of the lancet body  14 , remote from the forward portion where the needle is. This provides greater stability and less vibration, and thus a cleaner and more painless puncturing, relative to conventional lancing devices in which the lancet travel is limited by the front exterior surface of the lancet body contacting the front interior surface of the housing.  
      As the lancet  16  travels from the charged position toward the extended position, the spring  26  is discharged to propel the lancet. Before the lancet  16  reaches the extended position, the spring  26  completely discharges its stored charge. Because the spring  26  is coupled to the lancet body  14 , as the lancet body continues traveling to the extended position, the spring recharges under tension.  
      After the lancet  16  is momentarily stopped in the extended position, where the needle  20  is at its puncture depth, the lancet is now returned to the retracted position of  FIG. 8  by the recharged spring  26 . In the retracted position, the lancet needle  20  is safely within the housing  12  so that it will not stick a person handling the lancing device  10 . In the retracted position, the spring  26  is in a neutral, uncharged state.  
      The lancing device  10  may be shipped and stored ready for use with the lancet  16  in the charged position of  FIG. 6 . Or the lancing device  10  may be shipped and stored with the lancet  16  in the retracted position of  FIG. 8 , in which case the user pushes in the sterility cap  22  to move the lancet to the charged position for use.  
       FIGS. 9-13  show details of the control assembly  18 . First, details of the activation control will be described with reference to  FIGS. 9 and 10 . A control member  31  includes a control interface  32  (such the knob shown) and a shaft  34  extending from it and into the housing  12 . The control shaft  34  is supported by the arm  30  and engages a release member  36 . Preferably, the same arm  30  both supports the control shaft  34  and holds the spring  26 , but separate structures may be provided. And the arm  30  may have a recess  31  (see  FIG. 4 ) for cradling the shaft  34  and preventing or minimizing lateral movement. The release member  36  may be an integral part of the housing  12  or a separate piece that is assembled to the housing. In addition, the release member  36  has a catch surface  37  that engages the engagement surface  38  on the lancet body operating section  15 , thereby holding the lancet  16  in the charged position. And the release member  36  is preferably biased toward the locked position and has a ramped section  41  adjacent the catch surface  37 . When the lancet  16  is pushed inward to the charged position, the lancet body  14  engages the ramped section  41  and temporarily moves the release member out of the way.  
      The release member  36  is movable between a set position holding the lancet  16  in the charged position and an activation position released from holding the lancet  16  in the charged position. The release member  36  is preferably a leaf spring, pivotal lever, plunger, or other structure that is movable between the set position and the activation position in response to movement of the control shaft  34  between a set position and an activation position. In addition, the release member  36  may have a generally vertical guide surface  35   a , and the housing  12  may have a generally vertical surface section  35   b  that is positioned on the opposite side of the lancet body  14  to help guide the lancet body, and thus the lancet needle  20 , thereby reducing vibration and associated pain.  
      In the depicted embodiment of  FIG. 9 , for example, the release member  36  and the control shaft  34  are in the set position. Depressing the control knob  32  moves the control shaft  34  laterally into the housing  12 . The control shaft  34  has a release surface  33  on the opposite side of the lancet body  14  from the control knob  32 . Moving the control shaft  34  causes the release surface  33  to push the release member  36  (in the direction indicated by the directional arrow) to the activation position (not shown). In this position, the catch surface  37  of the release member  36  is moved out of the way of the engagement surface  38  on the lancet body operating section  15 , thereby releasing the lancet  16  to be launched under the charge stored in the spring  26 . When the control knob  32  is released by the user, the control shaft  34  and release member  36  return to their original positions, as shown in  FIG. 10 .  
      In addition, the release member  36  may have a weak segment  40  such as a notch, recess, or other thinner wall portion. The weak segment  40  is designed to fail upon activation so that the lancing device  10  can not be charged and used again. It will be understood by persons skilled in the art that other disabling mechanisms can be used.  
      Referring additionally to  FIGS. 11-13 , there are shown additional details of the activation control and details of the depth control of the control assembly  18 . The depth control is provided by two stop surfaces  42   a  and  42   b  (collectively, the “stop surfaces  42 ”). Preferably, the stop surfaces  42  are defined on or in the control shaft  34  and have different thicknesses as measured from the rotational axis  39  of the control shaft. The stop surfaces  42  may be provided by recesses in or protrusions on the control shaft  34 . In alternative embodiments, the control shaft is provided with three or another number of stop surfaces on or in the control shaft, thereby providing more lancet puncture depth adjustment positions. And other alternative embodiments include a single depth lancing device with the single stop surface defined by the control knob, the arm, or another structural component.  
      In the depicted embodiment, the control shaft  34  has a first stop surface  42   a  defined by a recessed surface and a second stop surface  42   b  defined by the outer surface of the shaft, thereby providing two depth settings. The second stop surface  42   b  is thicker (farther from the rotational axis  39  of the control shaft  34 ) than the first stop surface  42   a . Thus, when the control knob  32  is turned so that its control indicator  44  aligns with a deep depth indicator  46  on the housing  12 , the control shaft  34  is positioned with the first stop surface  42   a  facing and aligned with the engagement surface  38  of the lancet body  14  (see  FIG. 6 ). In this position, the lancet  16  is free to travel farther (see  FIG. 7 ) than it would in the shallow depth setting.  
      In the shallow depth setting (not shown), the control knob  32  is turned so that the control indicator  44  aligns with a shallow depth indicator  48  on the housing  12 . In this setting, the control shaft  34  is positioned with the thicker second stop surface  42   b  facing and aligned with the engagement surface  38  of the lancet body  14 . In this position, the lancet  16  travel is stopped sooner by the thicker stop surface  42   b , resulting in a shallower puncture depth.  
      In this configuration, the control assembly  18  includes common structures for controlling both the puncture depth of the lancet needle  20  and the activation of the lancing stroke. In particular, the control assembly  18  includes the control member  31  which has multiple stop surfaces  42  for stopping the lancet travel at different points (to control the puncture depth) and a release surface  43  for engaging the release member  36  to disengage it from the lancet body  14  (to control the lancet activation). By providing common structures that function for dual purposes, the number of parts is reduced and the ease of manufacture is increased. This results in a simpler, less costly device.  
      The activation control further includes a unique safety interlock feature wherein the control knob  32  has a locked position and one or more depth setting positions (e.g., the shallow and deep settings described herein). With the control knob  32  in the locked position, it cannot be depressed to activate the lancet  16 . And with the control knob  32  moved to one of the depth setting positions, it can be depressed to activate the lancet  16 . In this way, the lancing device  10  remains locked and cannot be accidentally activated until the user selects a depth setting. Conventional single use lancing devices do not have a safety interlock feature and are shipped ready for firing, so occasionally a lancet is inadvertently activated before intended.  
      In the lancing device  10  shown, for example, the housing  12  has a control opening  50  through which the control shaft  34  extends, with the control opening and control shaft preferably generally circular in cross-section. The housing  12  has at least one lock opening  51  in communication with the control opening (see  FIG. 11A ). The lock opening  51  is adjacent a deflection member  52 , which has a radiused edge that is coaxial with the control opening  50 . And the control shaft has at least one lock tab  54  (see  FIG. 4 ) extending radially from it. When the control knob  32  is in the locked position (see  FIG. 13 ), the lock tab  54  does not align with the lock opening  51 , so the control knob cannot be depressed to activate the lancet  16 . But when the control knob  32  is turned (e.g., 90 degrees) to one of the depth setting positions, the lock tab  54  aligns with and can fit through the lock opening  51 , so the control knob can be depressed to activate the lancet  16 . It will be understood that another number of lock tabs and openings can be provided.  
      As another example, in the lancing device  10  shown, the housing  12  additionally has two lock openings  56  spaced apart from and on opposite sides of the control opening  50 . And the control knob  32  has two lock tabs  58  extending from it generally parallel to the control shaft axis  39 . When the control knob  32  is in the locked position (see  FIG. 13 ), the lock tabs  58  do not align with the lock openings  56 , so the control knob cannot be depressed to activate the lancet  16 . But when the control knob  32  is turned to one of the depth setting positions, the lock tabs  58  align with and can fit through the lock openings  56 , so the control knob can be depressed to activate the lancet  16 .  
      In addition, the housing  12  may have a plurality of protrusions  60  extending from its outer surface with gaps  61  between them. For example, the protrusions  60  may be provided by four ridges positioned in a generally circular arrangement with the two gaps  61  and the two lock openings  56  interposed between the ridges. In this way, when the control knob  32  is in the locked position or one of the depth setting positions, the lock tabs  58  are positioned in the gaps  61  or in the lock openings  56  between the ridges  60 . This creates discrete positions that are readily sensible (e.g., snap sound and/or tactile perception) by the user.  
      In order to maintain a nice tight fit, but not a binding fit, between the ridges  60  and the lock tabs  58  when turning the control knob  32 , at least one deflection member  52  may be provided. The deflection member  52  is defined by two slits or other spaced-apart openings in communication with the control opening  50 . The deflection member  52  functions as a leaf spring that deflects slightly outward when the lock tabs  58  engage the ridges  60 , thereby permitting the control shaft  34  to back slightly out of the housing  12 . The control shaft  34  has a collar  43  that holds it in place so that it can rotate but not move laterally out of the housing  12 , except by movement of the deflection member  52  (see also  FIGS. 4 and 10 ). In alternative embodiments, a spring or other biasing structure may be provided for this function.  
      In addition, the sterility cap  22  is preferably keyed to the housing  12  so that the cap can only be removed after it has been manipulated by the user. For example, the sterility cap  22  may have sheath portion with that extends into the housing  12  and one or more tabs  62  or other male key surfaces extending from it (see, e.g.,  FIGS. 6 and 9 ). And the housing opening  24  may be sized and shaped to receive the cap  22  through it and have one or more recessed portions  25  or other female key surfaces that allow the tabs  62  to fit through only when the tabs are aligned with the recessed portions (see, e.g.,  FIG. 2 ). Or vice versa—the housing  12  may have the tabs and the sterility cap  22  may have recessed portions that are alignable with the tabs. The lancing devices are provided with the tabs  62  not in alignment with the recessed portions  25  so that, in order to remove the sterility cap  22  to use the lancing device  10 , the user must rotate the cap until the tabs  62  and the recessed portions  25  are aligned. This prevents accidentally removing the sterility cap  22  before intended. And with the key tabs  62  not aligned with the key recessed portions  25 , the key tabs contact the interior forward wall of the housing  12 . This prevents the lancet  16  from being launched prematurely and also helps reduce the spring load on the release member  36 , support arm  30 , and lancet body  14  when the lancing device  10  is in the charged position during shipping and storage.  
      It will be understood that several of the unique features of the lancing device  10  may be provided independently of each other. For example, the present invention includes lancing devices that have the control assembly but not the safety interlock or the keyed sterility cap, as well as lancing devices that have the safety interlock and/or the keyed sterility cap but not the control assembly.  
      To use the lancing device  10 , a user rotates the control knob  32  from the locked position to the desired puncture depth setting position. Then the user turns the sterility cap  22  until the keying permits its removal, removes the cap from the lancet needle  20 , and discards the cap. Next the user positions the lancing device  10  against the skin at the desired lancing site and depresses the control knob  32  to activate the device. Thus, the user manipulates a single component, the control member  31 , to select the desired lancing depth (by rotation) and to initiate the lancing stroke (by lateral movement/pushing inward). After use, the user disposes of the used lancing device  10 .  
      Turning now to  FIGS. 14-17 , there is shown a lancing device  110  according to a second example embodiment of the present invention. Similarly to the lancing device  10  of the first example embodiment, the lancing device  110  includes a housing  112   a  and  112   b  (the “housing  112 ”), a lancet  116 , and a combination depth and activation control assembly  118  (the “control assembly”  118 ). The lancet  116  includes a needle  120  with a sterility cap  122  and a lancet body  114  with a needle-holding  113  section and with an operating section  115  holding the spring  126 . And the control assembly  118  includes the control member  131 , the release member  136 , and the engagement surface  138  of the lancet body  114 . The control member  131  includes the control knob  132  and the control shaft  134  with the stop surfaces  142  and release surface  143 .  
      In this embodiment, however, the control shaft  134  is coupled to the release member  136  so that they move together. For example, the control shaft  134  may extend through an aperture  170  in the release member  136  and have a retainer head  172  to secure it in place with the engagement surface  138  contacting the release member. In alternative embodiments, the control shaft  134  is coupled to the release member  136  by a bendable or expandable member at the end of the control member, by a threaded nut that screws onto mating threads on the control shaft, or by other couplings known in the art.  
      In addition, the housing  112  has recesses  174  in the gaps  161  between the ridges  160 , with the recesses sized and shaped to receive the lock tabs  158 . This feature further enhances the user&#39;s tactile perception of the discrete locked and depth positions.  
      Furthermore, the housing  112  has a slightly bowed-in shape for enhanced ergonomics. And the lancet body  114  has a slightly different design, including angled flanges  131   b  for retaining the spring  126  and the addition of guide wings  176  for enhanced guidance of the lancet  116  within the housing  112 .  
      Accordingly, the present invention provides a number of advantages not found in known prior art devices. The combination depth and activation control assembly is operable to control both the puncture depth and the activation of the device, thereby enabling a low-cost disposable lancing device with depth adjustment capability. The safety interlock feature prevents accidental activation of the lancing device before intended. And the keyed sterility cap requires manipulation of the cap to remove it, thereby preventing accidental removal of the cap before intended.  
      While the invention has been described with reference to preferred and example embodiments, it will be understood by those skilled in the art that a variety of modifications, additions and deletions are within the scope of the invention, as defined by the following claims.