Single valve diaphragm pump with decreased sensitivity to ambient conditions

• US 4,594,058 A
• Filed: 11/26/1985
• Issued: 06/10/1986
• Est. Priority Date: 06/01/1984
• Status: Expired due to Term

• Current Assignee: Johns Hopkins University
• Original Assignee: Johns Hopkins University
• Inventors: Fischell, Robert E.
• Primary Examiner(s): Croyle, Carlton R.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/801,513
• Time in Patent Office: 196 Days
• Field of Search: 417/413, 417/417, 417/557, 417/559, 417/395, 128/DIG. 12, 128/DIG. 13, 604/123, 604/126, 604/153, 92/60, 92/99, 92/104
• US Class Current: 417/413.1
• CPC Class Codes: A61M 2005/14264 with means for compensating influence from the environment
• CPC Class Codes: A61M 5/14224 Diaphragm type
• CPC Class Codes: A61M 5/16809 by repeated filling and emptying of an intermediate volume pressure infusion using positive displacement pumps A61M5/142
• CPC Class Codes: F04B 43/0027 without valves
• CPC Class Codes: F04B 43/04 Pumps having electric drive
• CPC Class Codes: F04B 53/10 Valves; Arrangement of valves
• CPC Class Codes: Y10S 128/12 Pressure infusion

Abstract

A single valve diaphragm pump is disclosed which generally includes: a pump housing, a flexible diaphragm reciprocally movable in the pump housing; an inlet filter means; and, an outlet valve. The flexible diaphragm conforms in shape to a portion of the pump housing when the diaphragm is in its actuation or rest position. The pump eliminates an inlet check valve and replaces it with an inlet filter means. The invented pump has a stroke volume which is extremely constant even though ambient pressure and reservoir pressure may vary over a considerable range. Furthermore, the invented pump provides a practical means for preventing gas bubbles from entering into the pump chamber. The invented pump can have application as a medication pump for use external to or implanted within a living body.

Claims

1. A positive displacement pump, comprising:

a pump chamber;

a passageway providing bidirectional fluid communication between said pump chamber and a source of liquid to be pumped;

an outlet valve and conduit in fluid communication with said pump chamber;

a variable volume means for increasing the volume of said pump chamber during an intake stroke and for decreasing the volume of said pump chamber during an output stroke, wherein liquid is drawn through said passageway into said pump chamber during said intake stroke, said output stroke being rapid compared to said intake stroke; and

,

an inlet filter means having a flow resistance characteristic which is identical for both inflow and outflow and is positioned in said passageway for permitting filling of said pump chamber at a first, comparatively slow rate during said intake stroke and cooperates with said variable volume means for generating sufficient fluid pressure in said pump chamber during a second, comparatively rapid output stroke to open said outlet valve and eject a substantial volume of liquid from said pump chamber.

2. The apparatus of claim 1, wherein said variable volume means comprises:

a diaphragm defining a boundary of said pump chamber;

a means for moving said diaphragm during said output stroke from a rest position wherein said pump chamber has a maximum volume to an actuation position wherein said pump chamber has a minimum volume; and

,

a means for returning said diaphragm during said intake stroke to said rest position.

3. The apparatus of claim 2, further comprising a housing having a first wall and a second wall, said diaphragm contacting along the surface of said first wall when in said rest positioning thereby conforming to the contour of said first wall, said diaphragm contacting along the surface of said second wall when in said actuation position thereby conforming to the contour of said second wall.

4. The apparatus of claim 1, further comprising a housing having an upper wall and a lower wall, and said variable volume means further comprising:

a diaphragm operably attached to said housing and positioned between said upper wall and said lower wall, said diaphragm and said lower wall defining a boundary of said pump chamber, said diaphragm reciprocally movable from a first rest position where said diaphragm contacts along the inner surface of said upper wall thereby conforming to the shape of said inner surface of said upper wall to an actuation position where said diaphragm contacts along the inner surface of said lower wall thereby conforming to the shape of said inner surface of said lower wall;

a means for moving said diaphragm during said output stroke from said rest position where said pump chamber has a certain maximum volume value to said actuation position where said pump chamber has a certain mininum volume value; and

,

a means for returning said diaphragm to said rest position during said intake stroke.

5. The apparatus of claim 3 or 4, wherein said means for moving further comprises:

a solenoid coil for providing a magnetic field in response to a current pulse; and

,

an armature means mechanically coupled to said diaphragm, for moving said diaphragm from said rest position to said actuation position in response to said magnetic field.

6. The apparatus of claim 5, wherein said means for returning said diaphragm to said rest position comprises the natural spring force of said diaphragm.

7. The apparatus of claim 1, wherein said inlet filter means is a filter having sufficiently small pore size to prevent bubbles of gas from entering said pump chamber.

8. The apparatus of claim 7, wherein said input fiter means is a ceramic filter.

9. The apparatus of claim 8, wherein said ceramic filter has a pore size of 1 to 20 microns.

10. The apparatus of claim 6, wherein said outlet valve and conduit further comprises:

an exit port chamber in fluid communication with said pump chamber;

a spring loaded check valve in fluid communication with said exit port chamber; and

,

an exit tube in fluid communication with said spring loaded check valve, wherein said spring loaded check valve is biased to allow fluid flow from said pump chamber into said exit tube in response to fluid pressure build-up in said pump chamber during said output stroke.

11. A positive displacement pump, comprising:

a pump housing having an upper wall and a lower wall;

a diaphragm operably attached to said housing and positioned between said upper wall and said lower wall, said diaphragm and said lower wall defining the boundary of said pump chamber, said diaphragm reciprocally movable from a rest position where said diaphragm contacts along the inner surface of said upper wall thereby conforming to the shape of said inner surface of said upper wall to an actuation position where said diaphragm contacts along the inner surface of said lower wall thereby conforming to the shape of said inner surface of said lower wall;

an electromagnetic means for moving said diaphragm during an output stroke from said rest position wherein said pump chamber has a certain maximum volume to said actuation position wherein said pump chamber has a certain minimum volume;

a spring means for returning said diaphragm during an intake stroke to said rest position, said output stroke being rapid compared to said intake stroke;

a passageway providing bidirectional fluid communication between said pump chamber and a source of liquid to be pumped;

an outlet valve and conduit in fluid communication with said pump chamber; and

,

an inlet filter means having a flow resistance characteristic which is identical for both inflow and outflow and is positioned in said passageway for permitting filling of said pump chamber at a first, comparatively slow rate during said intake stroke and cooperates with said variable volume means for generating sufficient fluid pressure in said pump chamber during a second, comparatively rapid output stroke to open said outlet valve and eject a substantial volume of liquid from said pump chamber.