Injection Device Having Variable Dosing

Abstract

An injection device for injecting medicament in a patient comprises a housing configured to house a fluid reservoir that has one of a plurality of volumes of medicament. An injection conduit fluidly coupled to the fluid reservoir defines a fluid pathway from the fluid reservoir to the patient. A firing mechanism is coupled to the fluid reservoir and is configured to expel the medicament from the fluid reservoir through the injection conduit. A volume setting mechanism is coupled to the firing mechanism and is configured to select the one of the plurality of volumes of medicament for the firing mechanism to expel. A dose setting mechanism is configured to select all or a fraction of the one of the plurality of volumes of medicament that is injected from the injection conduit when the firing mechanism is actuated.

I/We claim: 
     
         1 . An injection device for injecting medicament in a patient comprising:
 a housing configured to house a fluid reservoir having one of a plurality of volumes of medicament;   an injection conduit fluidly coupled to the fluid reservoir configured to define a fluid pathway from the fluid reservoir to the patient;   a firing mechanism coupled to the fluid reservoir and configured to expel the medicament from the fluid reservoir through the injection conduit;   a volume setting mechanism coupled to the firing mechanism and configured to be adjusted to select the one of the plurality of volumes of medicament for the firing mechanism to expel; and   a dose setting mechanism configured to be adjusted to select a fraction of the one of the plurality of volumes of medicament that is injected from the injection conduit when the firing mechanism is actuated.   
     
     
         2 . The injection device of  claim 1 , wherein the volume setting mechanism includes a nut and the firing mechanism includes a ram and a biasing member, the nut being threadably coupled to the ram, the nut being releaseably retained against a force of the biasing member in an initial position by a latch. 
     
     
         3 . The injection device of  claim 2 , wherein the nut includes a plurality of indentations each configured to engage with a projection of the latch. 
     
     
         4 . The injection device of  claim 3 , wherein each of the plurality of indentations includes a ring shaped groove extending circumferentially around the nut. 
     
     
         5 . The injection device of  claim 2  further comprising a guard that is slideably coupled to the housing, wherein the guard is configured to release the latch from the nut. 
     
     
         6 . The injection device of  claim 5  further comprising a biasing member coupled to the guard and configured to bias the guard toward a distal end of the injection device, the guard configured to extend axially past the injection conduit. 
     
     
         7 . The injection device of  claim 6 , wherein the guard extends further distally in a locked position than in an initial position. 
     
     
         8 . The injection device of  claim 2 , wherein the nut is rotatable relative to the latch. 
     
     
         9 . The injection device of  claim 2 , wherein the nut is configured to couple to the latch in one of a plurality of positions along an axial length of the nut, each of the plurality of positions along the axial length of the nut corresponding to one of the plurality of volumes of medicament for the firing mechanism to expel. 
     
     
         10 . The injection device of  claim 2 , wherein the volume setting mechanism includes a ram extension threadably coupled to the ram, the ram extension configured to extend the length of the ram to one of a plurality of positions corresponding to one of the plurality of volumes of medicament for the firing mechanism to expel. 
     
     
         11 . The injection device of  claim 2 , wherein the ram is rotatably fixed and axially moveable relative to the dose setting mechanism. 
     
     
         12 . The injection device of  claim 2 , wherein the latch includes a latch arm releaseably retaining the nut in the initial position and a stop engaging the nut in a fired position, a distance between the latch arm and the stop being fixed. 
     
     
         13 . The injection device of  claim 1 , wherein the volume setting mechanism includes a retainer and a latch and the firing mechanism includes a ram and a biasing member, the latch being coupled between the biasing member and the ram, the latch being retained against a force of the biasing member in an initial position by the retainer. 
     
     
         14 . The injection device of  claim 13  further comprising:
 a stop having a plurality of axially extending and radially projecting slots each extending a different axial depth, wherein the ram includes a wing extending radially from the ram and configured to engage one of the plurality of slots in a fired position. 
 
     
     
         15 . The injection device of  claim 14 , wherein the stop and the retainer are integrally connected. 
     
     
         16 . The injection device of  claim 14 , wherein the dose setting mechanism is rotatably coupled to the ram to radially align the wing with one of the plurality of slots in the initial position. 
     
     
         17 . The injection device of  claim 13 , wherein the ram includes a prime screw threadably coupled to the end of the ram, the prime screw configured to couple the ram to a piston. 
     
     
         18 . The injection device of  claim 17 , wherein the ram remains in contact with the piston independent of the position of the dose setting mechanism. 
     
     
         19 . The injection device of  claim 13 , wherein the latch includes a plurality of axially spaced indentations each configured to engage with a projection of the retainer. 
     
     
         20 . The injection device of  claim 13  further comprising:
 a guard that is slideably coupled to the housing, wherein the guard includes a sidewall configured to prevent radial motion of the retainer in the initial position and an aperture in the sidewall configured to allow radial motion of the retainer in a retracted position. 
 
     
     
         21 . The injection device of  claim 13 , wherein the ram is rotatably fixed and axially moveable relative to the dose setting mechanism. 
     
     
         22 . The injection device of  claim 21 , wherein the dose setting mechanism includes a shaft extending partially into and radially keyed with an inner shaft of the ram in the initial position and a fired position. 
     
     
         23 . The injection device of  claim 13 , wherein the latch is axially fixed and rotatably moveable relative to the ram. 
     
     
         24 . The injection device of  claim 1 , wherein the firing mechanism includes a spring and the position of the spring being independent from the position of the dose setting mechanism. 
     
     
         25 . The injection device of  claim 1 , wherein the dose setting mechanism includes a knob rotatably coupled to the housing. 
     
     
         26 . The injection device of  claim 1  further comprising a guard slideably coupled to the housing and configured to extend axially past the injection conduit and lock relative to the housing after removing the injection conduit from the patient. 
     
     
         27 . The injection device of  claim 1 , wherein the injection conduit comprises a needle. 
     
     
         28 . The injection device of  claim 27  further comprising a syringe containing the fluid reservoir, wherein the needle is fixed to the syringe. 
     
     
         29 . The injection device of  claim 1 , wherein the injection device is configured to prevent resetting after the firing mechanism is actuated so as to prevent a subsequent injection of the medicament by the injection device, thereby configuring the injection device as a single-use injector. 
     
     
         30 . The injection device of  claim 1  further comprising a safety cap coupled to a distal end of the housing, the safety cap being coupled to the firing mechanism such that decoupling the safety cap from the housing allows the firing mechanism to advance a predetermined distance relative to the fluid reservoir to prime the fluid reservoir. 
     
     
         31 . The injection device of  claim 1 , wherein actuating the dose setting mechanism advances the firing mechanism a predetermined distance relative to the fluid reservoir to prime the fluid reservoir. 
     
     
         32 . The injection device of  claim 1 , wherein the firing mechanism is configured to deliver each of the selected fraction of the one of the plurality of volumes of medicament over a generally equal amount of time as compared to one another. 
     
     
         33 . The injection device of  claim 1 , wherein the fraction is only greater than or equal to 0.5. 
     
     
         34 . The injection device of  claim 1 , wherein the selected fraction results in a residual volume remaining in the fluid reservoir after delivery of 0.18 ml or less. 
     
     
         35 . An injection device for injecting medicament in a patient comprising:
 a firing mechanism having an actuator and configured to be selectively preset during assembly to one of a plurality of positions based on a maximum volume of medicament to be delivered to the patient; and   a dose setting mechanism configured to be selectably adjusted upon use, independent of the preset of the firing mechanism, to select a fraction of the maximum volume of medicament to be delivered to the patient.   
     
     
         36 . An injection device for injecting medicament in a patient comprising:
 a housing configured to house a fluid container having a piston and a fluid reservoir having one of a plurality of volumes of medicament, the fluid container including an injection conduit fluidly coupled to the fluid reservoir configured to define a fluid pathway from the fluid reservoir to the patient;   a ram coupled to the piston and configured to expel the medicament from the fluid reservoir through the injection conduit;   a spring biasing the ram toward the fluid container in an initial position;   a nut threadably coupled to the ram, the nut having a plurality of ring shaped grooves or projections;   a latch fixed relative to the housing and engaging a predetermined one of the plurality of ring shaped grooves or projections to retain the ram in one of a plurality of axial positions against a force of the spring in the initial position, the nut being rotatable relative to the latch in the initial position; and   a dose setting knob rotatably coupled to the housing and rotatably fixed and axially moveable relative to the ram in the initial position.   
     
     
         37 . An injection device for injecting medicament in a patient comprising:
 a housing configured to house a fluid container having a piston and a fluid reservoir having one of a plurality of volumes of medicament, the fluid container including an injection conduit fluidly coupled to the fluid reservoir configured to define a fluid pathway from the fluid reservoir to the patient;   a ram coupled to the piston and configured to expel the medicament from the fluid reservoir through the injection conduit, the ram having a radially extending wing;   a latch axially fixed and rotatably moveable relative to the ram, the ram having a plurality of radial features;   a spring biasing the latch toward the fluid container in an initial position;   a retainer fixed relative to the housing and engaging a predetermined one of the plurality of radial features to retain the ram in one of a plurality of axial positions against a force of the spring in the initial position;   a stop having a plurality of axially extending and radially projecting slots each extending a different axial depth, the ram being rotatable to align the wing with one of the plurality of slots in the initial position and the wing configured to engage the one of the plurality of slots in a fired position; and   a dose setting knob rotatably coupled to the housing, the ram being rotatably fixed and axially moveable relative to the dose setting knob.   
     
     
         38 . A method for assembling an injection device comprising:
 inserting a fluid container having a fluid reservoir including one of a plurality of volumes of medicament into a housing, the fluid container including an injection conduit fluidly coupled to the fluid reservoir configured to define a fluid pathway from the fluid reservoir to the patient;   setting a volume setting mechanism based on a size of the one of the plurality of volumes of medicament;   coupling the volume setting mechanism to a firing mechanism; and   coupling the firing mechanism to the fluid reservoir, the firing mechanism configured to expel the medicament from the fluid reservoir through the injection conduit, the firing mechanism being coupled to a dose setting mechanism configured to select all or a fraction of the one of the plurality of volumes of medicament that is injected from the injection conduit when the firing mechanism is actuated.   
     
     
         39 . An injection device for injecting medicament in a patient comprising:
 a housing configured to house a fluid reservoir;   an injection conduit fluidly coupled to the fluid reservoir configured to define a fluid pathway from the fluid reservoir to the patient;   a firing mechanism coupled to the fluid reservoir and configured to expel the medicament from the fluid reservoir through the injection conduit; and   a safety cap coupled to a distal end of the housing, the safety cap being coupled to the firing mechanism such that decoupling the safety cap from the housing allows the firing mechanism to advance a predetermined distance relative to the fluid reservoir to prime the fluid reservoir.