Bellowed fluid delivery apparatus

A fluid-delivery apparatus for delivering a constant volume of medicament to a patient, the apparatus comprising:

• a housing defining a passageway,
• a bellowed ampoule positioned to lie in the passageway of the housing, the ampoule including first and second and being formed to define a cavity configured to contain the medicament,
• a piston formed for movement in the housing to press the second end of the ampoule toward the first end, and
• a piston-drive system cooperating with the piston, the piston-drive system adjusting the movement of the piston in the housing so that the medicament is delivered in uniform increments from the first end of the ampoule.

A fluid-delivery apparatus for delivering a constant volume of medicament to a patient, the apparatus comprising:

• a housing defining a passageway,
• a bellowed ampoule positioned to lie in the passageway of the housing, the ampoule including first and second and being formed to define a cavity configured to contain the medicament,
• a piston formed for movement in the housing to press the second end of the ampoule toward the first end, and
• a piston-drive system cooperating with the piston, the piston-drive system adjusting the movement of the piston in the housing so that the medicament is delivered in uniform increments from the first end of the ampoule, wherein
• the piston-drive system includes a cam formed for rotation about a shaft and in mechanical communication with the piston, and the cam includes a cam surface that changes in radius to dispense successive equal volumes of medicament from the ampoule.

A method for determining the amount of fluid delivered from a bellowed ampoule positioned in a cylindrical housing having a radius of r0 that is substantially equal to an outermost radius of the ampoule, the method comprising the steps of:

• calculating the relative encroachment function Err of the bellowed ampoule from the equation
• Err=Ψ·(1−Ψ/3), where Ψ≡(c/r0){square root over (1−(z/c)2)},
• z is the height of one half-fold of one bellow of the ampoule, and c is length of an upper panel of one bellow,
• depressing the ampoule a pre-determined distance in the housing changing the height z of one half-fold of one bellow, and
• determining the cumulative volume dispensed Vd from the bellowed ampoule from the equation
• Vd=V0−(πr02nz)·[1−Err],
• where V0 is the initial volume of the filled reservoir and n is the number of half folds in the bellowed ampoule.

A method for delivering a constant linear volume of fluid from a bellowed ampoule positioned in a cylindrical housing having a radius of rthat is substantially equal to an outermost radius of the ampoule, the method comprising the steps of:

• calculating the relative encroachment function Err of the bellowed ampoule from the equation
• Err=Ψ·(1−Ψ/3), where Ψ≡(c/r0){square root over (1−(z/c)2)},
• z is the height of one half-fold of one bellow of the ampoule, and c is length of an upper panel of one bellow,
• determining the cumulative volume dispensed Vd from the bellowed ampoule from the equation
• Vd=V0−(πr02nz)·[1−Err],
• where V0 is the initial volume of the filled reservoir and n is the number of half folds in the bellowed ampoule, and
• compressing the ampoule in the housing at a rate sufficient to achieve a constant linear flow of fluid from the ampoule in accordance with the equation ⅆ z / ⅆ V d = ( - π ⁢ ⁢ n · [ r 0 2 · [ 1 - Err ] + ( 1 + 2 ⁢ ⁢ ψ / 3 ψ ) · z 2 ] ) - 1 .