Abstract:
An improved spindle and bearing combination for a drug delivery device is provided that has a first connection between the spindle and bearing comprising a web and a second connection that replaces the first connection when the web is severed that allows the spindle to rotate relative to the bearing.

Description:
THE TECHNICAL FIELD OF THE INVENTION 
       [0001]    The present invention relates to a drug delivery device containing an improved spindle used to expel a medicament from a container where the spindle is initially manufactured and assembled into the device having a pressure bearing rigidly attached to its distal end. Before a first dose of medicament is delivered, the pressure bearing is sheared off the spindle causing it to become rotationally connected to the spindle and thus allowing the piston rod to rotate about the bearing surface. 
       DESCRIPTION OF RELATED ART 
       [0002]    Most drug delivery devices use a spindle to advance an elastic (rubber) piston positioned within one end of a container of medicament to cause the medicament to exit the opposite end of the container. In some delivery devices it is necessary to rotate the spindle during dose delivery relative to the rubber piston. To accomplish this movement a bearing plate or disk is positioned at the distal end of the spindle abutting the proximal face of the non-rotatable rubber piston. This bearing plate is typically connected with a universal joint type connection, i.e. one where the spindle can freely rotate and articulate about the center point of the top surface of the plate. As the spindle is rotated and moved in an axial direction the bearing is prevented from rotating because of its engagement with the non-rotatable piston causing both the bearing plate and piston to also move in the axial direction imparting a pressure to the medicament causing it to be expelled from the distal end of the container. Prior to my invention the spindle and bearing were necessarily manufactured as two separate parts, which were then snapped together before being assembled into the drug delivery device. A common example of a drug delivery device is an injection device that contains a multi-dose cartridge. A more specific example would be a pen-type injection device containing a cartridge of insulin that is designed for repeated injections by persons without formal medical training occurs, i.e., patients. This is increasingly common amongst those having diabetes where self-treatment enables such persons to conduct effective management of their diabetes. 
         [0003]    Maintaining or reducing the cost of drug delivery devices at reasonable prices is a priority for manufacturers of such devices. One way this can be accomplished is to minimize the number of parts in a device or to improve the assembling steps needed to fabricate the device. My invention achieves both of these cost saving features by providing a spindle and bearing surface that has a first connection between the spindle and disk-shaped bearing that changes to a second connection before a first dose of medicament is delivered to the user. My invention is of greater value when the device is designed as a disposable device rather than reusable device because a disposable device must be as inexpensive as possible to manufacture and easy to dispose of (preferably being suitable for recycling). To meet these requirements the number of parts required for assembly of the device and the number of material types the device is made from need to be kept to a minimum. These and other advantages will become evident from the following more detailed description of the invention. 
       SUMMARY OF THE INVENTION 
       [0004]    The improved spindle and bearing combination of my invention for use in a drug delivery device comprises a rotatable spindle having a distal end and a disk-shaped bearing attached to the distal end through a first connection comprising a web that fixedly attaches the bearing to the spindle to prevent independent movement of the bearing relative to the spindle. In a preferred embodiment the spindle has at least one helical groove positioned longitudinally along the spindle. This first connection is changed to a second connection when the web is severed and disconnected. This second connection is a rotating joint connection, i.e. one where the spindle can freely rotate. Shearing of the web can occur by applying an axial force to the spindle and bearing combination after the combination has been assembled into the drug delivery device. Alternatively, a rotational force can be applied to the bearing plate to shear the web. Either force can be applied by the manufacturer of the device or by the user immediately before or during the delivery of a first dose of medicament. 
         [0005]    The term “drug delivery device” according to instant invention shall mean a single-dose or multi-dose, disposable or re-useable device designed to dispense a selected dose of a medicinal product, preferably multiple selected doses, e.g. insulin, growth hormones, low molecular weight heparins, and their analogues and/or derivatives etc. 
         [0006]    Said device may be of any shape, e.g. compact or pen-type. Dose delivery may be provided through a mechanical (optionally manual) or electrical drive mechanism or stored energy drive mechanism, such as a spring, etc. Dose selection may be provided through a manual mechanism or electronic mechanism. Additionally, said device may contain components designed to monitor physiological properties such as blood glucose levels, etc. Furthermore, the said device may comprise a needle or may be needle-free. In particular, the term “drug delivery device” shall mean a disposable multi-dose pen-type device having mechanical and manual dose delivery and dose selection mechanisms, which is designed for regular use by persons without formal medical training such as patients. Preferably, the drug delivery device is of the injector-type. 
         [0007]    The term “engaged” according to instant invention shall particularly mean the interlocking of two or more components of the drive mechanism/drug delivery device, e.g. a spline, thread, or meshed teeth connection, preferably the interlocking of helical grooves or threads of components (“rotationally engaged” or “threadedly engaged”). 
         [0008]    The term “spindle” according to instant invention shall mean a component adapted to operate through/within the housing, designed to translate axial movement through/within the drug delivery device, preferably from a driver to the piston, for the purpose of discharging/dispensing an injectable product. The spindle may be flexible or not. It may be a simple rod, a lead-screw, a rack and pinion system, a worm gear system, or the like. The spindle shall further mean a component having a circular or non-circular cross-section. It may be made of any suitable material known by a person skilled in the art. 
         [0009]    In a preferred embodiment, the spindle comprises at least one, more preferably two, external and/or internal helical grooves or threads. In another preferred embodiment of the spindle, a first helical groove is located at a first end and a second helical groove is located at a second end of the spindle, whereby the said groves may have the same or, preferably, opposite dispositions and may overlap each other. In another preferred embodiment the spindle invention comprises grooves having the same leads at the first and the second end. 
         [0010]    In yet another preferred embodiment of instant invention the lead of the first helical groove of the spindle shall be greater than the lead of the second helical groove. More preferred, the ratio of the leads of the helical grooves of the said first and the second helical grooves 1:1.01 to 1:20, even more preferred 1:1.1 to 1:10. Preferably, one of the said grooves is designed to engage a driver to impart either rotation, axial or a combination of rotational and axial movement to the spindle. 
         [0011]    The term “first end” according to instant invention shall mean the proximal end. The proximal end of the device or a component of the device shall mean the end, which is closest to the dispensing end of the device. 
         [0012]    The term “second end” according to instant invention shall mean the distal end. The distal end of the device or a component of the device shall mean the end, which is furthest away from the dispensing end of the device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    Without any limitation, the instant invention will be explained in greater detail below in connection with a preferred embodiment and with reference to the drawings in which: 
           [0014]      FIG. 1  shows a side view of my invention where the spindle is connected to disk-shaped bearing by a web such that the bearing cannot move independently of the spindle. 
           [0015]      FIG. 2  shows a close up cross-sectional view of the web of  FIG. 1 . 
           [0016]      FIG. 3  shows a side cross-sectional view of an example of a drug delivery device where my invention can be used. 
           [0017]      FIG. 4  shows a close up cross-sectional view of the second connection after the web of  FIG. 1  is sheared. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0018]    Referring first to  FIG. 1  there is shown a spindle  1  have two overlapping helical grooves  2  running longitudinally along the spindle having attached to its distal end  3  a disk-shaped bearing  4 . Although two helical grooves are depicted a single groove or no groove could also be used. Preferably the combination of the spindle and bearing is fabricated as a single molded part of a polymer material, such as plastic, however, a metal or combination of different materials could be used provided that the material of construction of web  5  can be broken or sheared upon application of a rotational or axial force. The strength or robustness of the web need only be sufficient to allow for the assembly of the combination of the spindle and bearing in a drug delivery device  6  like the representative device shown in  FIG. 3  where bearing  4  is abutting piston  7 . 
         [0019]    Once the combination spindle and bearing of my invention is assembled into the delivery device, the manufacturer or the user will impart a rotational or axial force to the spindle. This will cause the web of the first connection to break allowing the spindle to rotate relative to the stationary bearing thus forming a second rotating joint connection. The web can be of any shape or design as long as it is strong enough to hold the bearing to the distal end of the spindle during assembly of the drug delivery device and is weak enough to shear when a rotational or axial force is applied to the spindle. One preferred web design is where the thickness of the plastic is reduced in a circumferential line at the point where the bearing face and the spindle meet. A rotational or axial force applied to the spindle will be transferred to this circumferential line of thin plastic and will shear the spindle from the proximal face of the bearing. The shape of the distal end of the spindle and the proximal face of the bearing is configured to allow the formation of a rotational connection between the separate parts after the web shear is broken. In a preferred configuration the web is designed such that upon shearing the respective pieces of the web form a type of snap fit or snap lock that holds the bearing to the spindle, yet allows the spindle to rotate with respect to the bearing. A most preferred design is where no pieces are broken off of from the spindle or the bearing that could fall into the device and cause a malfunction. This is illustrated in  FIG. 4  where the resulting web shears  8  remain attached to the spindle and bearing. Because the web deforms and stretches during the breaking process, the result is two cooperating pieces  8  that work together retain the bearing on the spindle. 
         [0020]    Although the web that is shown in  FIGS. 1 ,  2  and  4  is an annular ring, it could also take other forms provided that the bearing is free to rotate in the second connection and adequately secured in the first connection. 
         [0021]    The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying current knowledge, readily modify and/or adapt for various application such specific embodiments without departing from the generic concept, and therefore such adaptations and modifications are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation. 
         [0022]    The means, materials, and steps for carrying out various disclosed functions may take a variety of alternative forms without departing from the invention. Thus, the expressions “means to . . . ” and “means for . . . ”, or any method step language as may be found in the specification above or the claims below, followed by a functional statement, are intended to define and cover whatever structural, physical, chemical or electrical element or structure, or whatever method step, which may now or in the future exist which carries out the recited function, whether or not precisely equivalent to the embodiment or embodiments disclosed in the specification above, i.e., other means or steps for carrying out the same function can be used; and it is intended that such expressions be given their broadest interpretation within the terms of the following claims.