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Medication infusion pump with improved pressure reservoir

  • US 5,514,103 A
  • Filed: 06/14/1994
  • Issued: 05/07/1996
  • Est. Priority Date: 06/14/1994
  • Status: Expired due to Term
First Claim
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1. A medication infusion pump, comprising:

  • a pump housing having a medication chamber formed therein for receiving a supply of a selected medication;

    pump means within said housing for delivering the medication from said medication chamber to a patient;

    a pressure reservoir having a selected liquid-vapor pressure fluid therein, said pressure reservoir being mounted within said pump housing and defining a movable wall exposed to said medication chamber, said pressure fluid being adapted to undergo sufficient liquid-vapor phase change for expanding and contracting the volumetric size of said pressure reservoir in response to the quantity of the medication within said medication chamber to maintain the medication under a predetermined and substantially constant pressure; and

    spacer means within said reservoir for preventing contraction of the pressure reservoir beyond a minimum open internal volume at least slightly greater than the liquid phase volume of the pressure fluid, whereby at least a portion of the pressure fluid remaining in a vapor phase at all times.

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