Abstract:
A medication delivery pen is provided including a leadscrew having a plurality of threads; a driver coaxially disposed about at least a portion of the leadscrew; a dosing ring non-rotatably disposed on the driver, the dosing ring also being slidable along the driver; and, a dose knob coaxially disposed about the dosing ring. At least one tooth is formed on one of the dose knob and the dosing ring, and at least one groove is formed on the other of the dose knob and the dosing ring, with the groove being formed to receive the tooth. The dosing ring is selectively movable relative to the dose knob from a first position where the tooth and the groove are spaced apart to a second position where the tooth is received within the groove, the dosing ring being rotatable with the dose knob with the dosing ring being in the second position. Incorrect dosage settings of the inventive pen may be easily corrected by a user via a novel dial-back feature that enables the user to reset the dose amount without expelling medication and without having to dial the dose knob to an extended, reset position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a Continuation of U.S. patent application Ser. No. 10/406,302, filed on Apr. 3, 2003 now U.S. Pat. No. 6,932,794. 

   BACKGROUND OF THE INVENTION 
   This invention relates to medication delivery instruments and, more particularly, to medication delivery pens, such as those used in administering insulin. 
   Various medication delivery pen designs are known in the prior art, including that shown in U.S. Pat. No. 6,248,095, which issued on Jun. 19, 2001, to one of the inventors herein and the assignee hereto. To administer a dose of medication, such as insulin, using the pen of U.S. Pat. No. 6,248,095, and as is commonly done with other medication delivery pen designs, a dose knob is manually rotated until a desired dose amount is set. Thereafter, a needle cannula is inserted into a patient and a button located at the end of the dose knob is depressed resulting in the administration of the desired dose. U.S. Pat. No. 6,248,095 is incorporated herein by reference in its entirety. 
   Prior art medication delivery pens, however, suffer from the drawback that if the dose knob is adjusted beyond a desired dose (i.e., an error in dosing is made), a waste of time or medication results in correcting to the desired amount. In one manner of correcting for the mistake, the dose knob can be “dialed back” to the lower dose amount and there set. However, such “dialing back” will result in the wasteful expulsion of medicine commensurate to the amount corrected. For example, if the pen is “dialed back” from a 300 μl dosage to a 250 μl dosage, 50 μl will be wastefully expelled. Alternatively, some pens, such as that disclosed in U.S. Pat. No. 6,248,095, provide for a reset mechanism which allows for the dose knob to be disengaged and returned to a zero position without “dialing back”. Such reset typically involves “dialing out” the dose knob to its fullest extent where it is disengaged and then returning the dose knob back to a start position. Although it is possible to reset the pen, additional time and effort is required to do so. 
   SUMMARY OF THE INVENTION 
   The present invention provides a medication delivery pen which overcomes the deficiencies of the prior art. The medication delivery pen includes a leadscrew having a plurality of threads; a driver coaxially disposed about at least a portion of the leadscrew; a dosing ring non-rotatably disposed on the driver, the dosing ring also being slidable along the driver; and, a dose knob coaxially disposed about the dosing ring. At least one tooth is formed on one of the dose knob and the dosing ring, and at least one groove is formed on the other of the dose knob and the dosing ring, with the groove being formed to receive the tooth. The dosing ring is selectively movable relative to the dose knob from a first position where the tooth and the groove are spaced apart to a second position where the tooth is received within the groove, the dosing ring and the dose knob being rotatable with the dosing ring in the second position. 
   With the subject invention, the dose knob can be dialed freely in both directions, without causing medicine to be administered, particularly upon “dialing back”. In addition, resetting of the dose knob is altogether avoided in allowing for a downward-correction in dosage amount. 
   These and other features of the subject invention will be better understood through a study of the following detailed description and accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side-elevational view of a medication delivery pen constructed in accordance with the subject invention; 
       FIG. 2  is an exploded view of a medication delivery pen constructed in accordance with the subject invention; 
       FIG. 3  is a cross-sectional view of a body useable with the subject invention; 
       FIG. 4  is a cross-sectional view taken along line  4 — 4  of  FIG. 3 ; 
       FIG. 5  is a cross-sectional view of a driver useable with the subject invention; 
       FIG. 6  is an enlarged perspective view of a proximal end of the driver shown in  FIG. 5 ; 
       FIG. 7  is a cross-section of a medication delivery pen constructed in accordance with the subject invention; 
       FIG. 8  is a cross-sectional view taken along line  8 — 8  of  FIG. 7 ; 
       FIG. 9  is a cross-sectional view taken along line  9 — 9  of  FIG. 7 ; 
       FIG. 10  is a cross-sectional view taken along line  10 — 10  of  FIG. 7 ; and, 
       FIGS. 11 and 12  are partial cross-sectional views showing, respectively, the medication delivery pen in a rest state and in an initial dosing state. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   With reference to the Figures, particularly  FIG. 1 , a medication delivery pen is shown and generally designated with the reference numeral  10 . The medication delivery pen  10  may be used for the administration of various medications, including insulin; the medication not comprising a part of the present invention. In addition, the term “medication” is used in an illustrative and non-limiting manner to refer to any substance that may be injected into a patient for any purpose. The medication delivery pen  10  of the present invention may also be reusable or disposable. 
   With reference to  FIG. 2 , the medication delivery pen  10  generally includes a cap  12 , a cartridge holder  14 , a spinner  16 , a body  18 , a dose knob  20 , a dosing ring  22 , a driver  24 , a leadscrew  26 , a dosing ring adaptor  28 , and a thumb button  30 . The cartridge holder  14  is formed to accommodate a drug cartridge  32 , which may be of any conventional design. By way of non-limiting example, the drug cartridge  32  may include an elastomeric septum  34  at a proximal end thereof and an open distal end  36  which exposes a slidable plunger  38  ( FIG. 7 ). Drug medication is contained within the drug cartridge  32  between the septum  34  and the plunger  38 . As will be described in more detail below, the spinner  16  is configured to engage the plunger  38  and force forward movement thereof in expelling drug from the drug cartridge  32 . A needle (not shown) is required to administer drug from the medication delivery pen  10 . The needle may be a double-ended cannula which is threadedly mounted onto threads  40  of the cartridge holder  14 . One end of the cannula is exposed for insertion into a patient, while the second end of the cannula is disposed to pierce the septum  34  of the drug cartridge  32 . After administration of the dose, the needle is removed, with the septum  34  self-sealing. The cap  12  is formed to releasably mount onto the cartridge holder  14 , such as with a snap fit, to limit contamination of the septum  34  and the surrounding portions of the cartridge holder  14 . A resilient holding arm  13  may extend from the cap  12  to provide holding force for the pen  10  in a patient&#39;s pocket. One or more windows  35  may also be provided in the cartridge holder  14  to give a visual indication of the drug level in the drug cartridge  32 . 
   With reference to  FIG. 3 , the body  18  is generally cylindrical, having threads or detents  42  onto which the cartridge holder  14  is formed to be mounted. A bulkhead  44  extends across the interior of the body  18  through which an aperture  46  is formed. The aperture  46  is defined to allow the passage therethrough of the leadscrew  26 , yet the aperture  46  is shaped (e.g., being rectangular) to prevent rotation of the leadscrew  26  therewithin. The body  18  also includes an interiorly-supported cylindrical wall  48  which defines a channel  50  therethrough. A transverse recess  53  is defined between the aperture  46  and the channel  50  which is bounded by wall  55 , that may be continuous or discontinuous. In addition, a dose setting thread  54 , as known in the prior art, is formed on the interior of the body  18 , along with a window  56  for dosage selection. A pointer  58  defined on the body  18  may extend into the window  56  to clearly point out a selected dosage level. 
   With reference to  FIG. 5 , the driver  24  includes proximal and distal ends  60  and  62 , respectively, with a snap ring  64  being formed at the proximal end  60 . The snap ring  64  is formed to pass through the channel  50  of the body  18  and lock onto the wall  48  in the recess  53  ( FIG. 7 ). With the snap ring connection, the driver  24  is fixed axially relative to the body  18 , yet is able to rotate relative thereto. Internal threads  68  are also provided to threadedly engage threads  70  of the leadscrew  26 . Additionally, as shown in  FIG. 2 , ledge  72  and one or more longitudinal keyways  74  are defined on the exterior surface of the driver  24 . 
   Preferably, as more clearly shown in  FIG. 4 , a plurality of ratchet teeth  52  extend from the cylindrical wall  48 . In addition, one or more ratchet fingers  66  are formed on the proximal end  60  of the driver  24  and are located in proximity to the snap ring  64 . The ratchet fingers  66  are positioned within the channel  50  when the driver  24  is locked in the recess  53  ( FIG. 7 ). Preferably, the ratchet teeth  52  and the ratchet fingers  66  cooperate to allow the driver  24  to rotate in only one direction relative to the body  18 . The ratchet teeth  52  and the ratchet fingers  66  provide a measure of protection against unwanted rearward movement of the leadscrew  26 , as described more fully below. 
   Dosing ring  22  is formed with one or more grooves  76  at a proximal end  78  thereof; a plurality of longitudinal ribs  80 ; a snap ring  82  in proximity to a distal end  84  thereof; and, inwardly extending splines  86  formed and located to be disposed in the keyways  74  of the driver  24 . As best shown in  FIG. 9 , in assembling the pen  10 , the dosing ring  22  is mounted onto the driver  24  with the splines  86  extending into the keyways  74 . As a result, the dosing ring  22  cannot be rotated relative to the driver  24 . However, the splines  86  are formed such to allow the dosing ring  22  to axially move along the length of the keyways  74 . Also, as shown in  FIG. 9 , the grooves  76  are preferably formed on the proximal end  78  to face axially and are formed about the entire periphery thereof, more preferably, at equal intervals. The grooves  76  are separated by partitions  88 , which may be rounded to facilitate engagement of the grooves  76  with the teeth of the dose knob  20  described below. 
   The dose knob  20  is generally tubular having open proximal and distal ends  90  and  92 , respectively. A textured handle  94  is formed in proximity to the distal end  92  which is engageable by a user to rotate the dose knob  20  in setting the pen  10  to a desired dosage amount. The dose knob  20  includes one or more thread portions  95  ( FIG. 11 ) formed to threadedly engage the dose setting thread  54  of the body  18 . Accordingly, the dose knob  20  may be rotated within the body  18  resulting in translation of that rotation to axial displacement of the dose knob  20  relative to the body  18  in setting a desired dosage. Dosage indicia (not shown) may also be disposed externally of the dose knob  20 . 
   The dose knob  20  preferably includes one or more ratchet arms  96  formed to be biased inwardly. With reference to  FIG. 8 , with the dose knob  20  being coaxially disposed about the dosing ring  22 , the ratchet arms  96  are aligned with the longitudinal ribs  80  so that rotation of the dose knob  20  relative to the dosing ring  22  results in the ratchet arms  96  acting against the ribs  80  in a ratcheting manner giving a user an audible signal of such rotation. In contrast to the prior art, the dose knob  20  can freely rotate in both directions relative to the dosing ring  22  with the rachet arms  96  acting against the ribs  80  during both rotational directions of the dose knob  20 . 
   The dose knob  20  is also formed with one or more lips  98  ( FIG. 2 ) which are forced in proximity to the proximal end  90  and from which extend one or more teeth  100 . The teeth  100  are formed and positioned to be received in the grooves  76  formed on the dose knob  20  and preferably face axially with regard to the longitudinal axis of the dose knob  20 . With reference to  FIG. 10 , the teeth  100  are much less in number than the grooves  76  to facilitate alignment. 
   The dosing ring  22  is mounted onto the dosing ring adaptor  28  with the snap ring  82  of the dosing ring  22  snapping into locking channel  102  defined in the dosing ring adaptor  28 . As such, the dosing ring  22  and the dosing ring adaptor  28  are movable in concert with each other. In an alternative embodiment, the dosing ring adaptor  28  and the dosing ring  22  may be formed unitarily. 
   The leadscrew  26  may be of any conventional type and is formed with a threaded end  103 . The spinner  16  includes a threaded aperture  105  formed to threadedly engage the threaded end  103  in mounting the spinner  16  onto the leadscrew  26 . Alternatively, the thumb button  30  is of any conventional design and formed to snap onto the dose ring adaptor  28 . The thumb button  30  may be unitarily formed with the dose ring adaptor  28 . 
   With reference to  FIGS. 7 ,  11  and  12 , the dosing ring adaptor  28  includes an inwardly extending shoulder  104 . With the pen  10  being fully assembled, a biasing means  106 , such as a coil spring, is preferably disposed between the ledge  72  of the driver  24  and the shoulder  104  of the dosing ring adaptor  28 . Consequently, the dosing ring adaptor  28  is urged distally within the pen  10 , along with the dosing ring  22 . Stop member  108  may be provided on the dosing ring adaptor  28  formed to abut against inwardly-extending ring  110  defined on the dose knob  20  under force of the biasing means  106  to limit distal movement of the dosing ring adaptor  28 . 
   Referring to  FIG. 11 , in a rest state, the dosing ring  22  is urged into a rest position with the grooves  76  being spaced from the teeth  100  of the dose knob  20 . Accordingly, the dose knob  20  can be freely rotated without rotating the dosing ring  22 . In this manner, the dose knob  20  can be rotated within the body  18  (with rotational movement being translated into axial displacement) and set to a desired dosage in a manner similar to prior art devices. With the dose knob  20  thus translating, the dosing ring adaptor  28 , the biasing means  106  and the dosing ring  22  move therewith, while the dosing ring  22  remains in its rest position. The dosing ring  22  slides axially along the driver  24  as a proper dose is selected. The subject invention, unlike the prior art, allows the dose knob  20  to be “dialed back” freely if a desired dosage amount is inadvertently by-passed, without the undesirable and costly effect of expelling medication. 
   In a preferred embodiment, with a desired dosage amount being set, the ratchet arms  96  advantageously provide holding force to maintain the desired radial position of the dose knob  20  relative to the dosing ring  22 , and, thus, to the driver  24 . In other words, the dose knob  20  cannot rotate without overcoming this holding force. 
   The needle cannula may be attached to the pen  10  prior to or after setting the desired dosage, as a matter of user preference. Once the needle cannula has been prepared, attached to the cartridge holder  14 , and inserted into the patient, the thumb button  30  is depressed. Initially, the applied force will act against the biasing means  106  causing initial straight-line motion of the dosing ring adaptor  28  and eventual interengagement of the grooves  76  and the teeth  100 , as shown in  FIG. 12 . Additional force will cause the dose knob  20  to rotate in descending along the dose setting thread  54  in a proximal direction. With the interengagement of the grooves  76  and the teeth  100 , the dosing ring  22  rotates with the dose knob  20 . In turn, the driver  24  rotates with the dosing ring  22  (due to the interengagement of the keyways  74  and the splines  86 ), and the threads  68  of the driver  24  rotate about the threads  70  of the leadscrew  26 . Since the leadscrew  26  cannot rotate because of its fixed positioning in the aperture  46 , the leadscrew  26  axially translates in a proximal direction to urge the spinner  16  against the plunger  38  in expelling medication from the drug cartridge  32 . The volume of the drug to be expelled is calibrated to the settings of the dose knob  20 . 
   Once a dose has been administered, the thumb button  30  is released, causing the dosing ring  22  to return to its rest position. The dose knob  20  can then be adjusted to a zero position ready for the next drug administration. The spinner  16  does not move in setting a dosage amount and, thus, is at a zero position after each dose administration. In the preferred embodiment, to maintain the spinner  16  position accurately, the interengagement of the ratchet teeth  52  and the ratchet fingers  66  prevents undesired rearward rotation of the driver  24  that would result in the leadscrew  26  possibly translating distally. The administration process is repeated until the drug cartridge  32  is spent. If the pen  10  is reusable, the cartridge can be replaced, whereas, if the pen is disposable, the entire pen  10  may be disposed of. 
   As will be appreciated by those skilled in the art, various modifications can be made with the spirit of the invention being maintained. For example, grooves may be formed on the dose knob and teeth on the dosing ring, or a combination thereof. 
   While the invention has been described in relation to the preferred embodiments with several examples, it will be understood by those skilled in the art that various changes may be made without deviating from the spirit and scope of the invention as defined in the appended claims.