Vacuum release mechanism

A method of preparing a replaceable fluid reservoir for insertion into a dispenser housing, wherein said reservoir has coupled thereto a pump assembly which when activated dispenses fluid from said reservoir,

• said pump assembly including,
• a chamber-forming element having a chamber, said chamber having chamber wall, an outer open end and an inner end in fluid communication with said reservoir, and
• one-way valve means disposed across said chamber permitting fluid flow therepast through the chamber only from the reservoir outwardly towards the outer open end, said one-way valve means permitting air to be drawn therepast towards the outer open end under a first negative pressure while permitting fluid to be drawn therepast under a second negative pressure which is further below atmospheric pressure than said first negative pressure,
• said method comprising the steps of:
• substantially filling said reservoir with fluid, and
• evacuating air from said reservoir by applying a vacuum to a portion of said chamber which is spaced outwardly from said one-way valve means,
• said vacuum providing vacuum pressure at least as far below atmospheric pressure as said first negative pressure to draw out air from said chamber and said reservoir.
• wherein said pump assembly includes a piston forming element configured to be slidably received in the chamber, and wherein axially inward and outward sliding of said piston forming element in said chamber dispenses said fluid,
• said piston element comprising:
• an axially extending stem,
• a disc extending radially outwardly therefrom to a resilient outer edge portion,
• a flexible bladder carried on the stem having an interior cavity enclosed but for being open to an access port,
• the bladder coupled to the outer edge portion of the disc,
• the bladder having an inherent resiliency biasing the bladder to assume a first shape, the resiliency of the bladder permitting the bladder be deformed to assume a second shape different than the first shape and with the inherent bias urging the bladder to reassume the first shape,
• in moving from the first shape to second shape the bladder moving a segment of the resilient outer edge portion,
• the piston element coaxially slidably received in the chamber with the outer edge portion of the disc engaging the chamber side wall to restrict fluid flow through the chamber past the disc having regard to the pressure differential across the disc,
• the method further including during the step of evacuating air, deforrming the bladder to its second shape.