Offset cam for piston pump

Patent metadata

Field	Value
Publication number	US-9611840-B2
Application number	US-201113698935-A
Country	US
Kind code	B2
Filing date	May 19, 2011
Priority date	May 19, 2010
Publication date	Apr 4, 2017
Grant date	Apr 4, 2017

Abstract

A pump assembly comprises a cam and a piston. The cam rotates in a plane about an eccentric axis, and has a circumferential side wall. The piston engages the circumferential side wall of the cam, and runs along a piston axis which lies in the plane of the cam. The piston axis is parallel to but not coincident with a reference line perpendicular to and intersecting the eccentric axis.

First claim

The invention claimed is:

1. A pump assembly comprising:
a cam with a geometric center, wherein the cam rotates in a plane about an eccentric axis offset from the geometric center by a first distance, and has a circumferential side wall; and
a piston engaging the circumferential side wall of the cam, and which runs along a piston axis;
wherein the piston axis lies in the plane of the cam, and is parallel to a reference line perpendicular to the eccentric axis and intersecting the eccentric axis, but separated from the reference line by a second distance equal to the first distance.

2. The pump assembly of claim 1 , wherein the cam is a circular cam.

3. The pump assembly of claim 1 , further comprising a cylinder having a fluid inlet port and a fluid outlet, and through which the piston translates.

4. A pump assembly comprising:
a circular cam rotating in plane, the circular cam comprising:
an eccentric axis of rotation;
a circumferential side wall parallel to the eccentric axis of rotation; and
a geometric center separated from the eccentric axis of rotation by a first distance; and

a piston lying in the plane, the piston comprising:
a cam follower engaging the circumferential side wall such that rotation of the circular cam applies force on the piston; and
a shaft which travels along a piston axis separated from the eccentric axis of rotation by a second distance equal to the first distance;

wherein:
the circular cam exerts a maximum force on the piston when the piston axis is perpendicular to the circumferential side wall where the cam follower engages the circumferential side wall; and
the maximal force applied by the circular cam on the piston is substantially in line with the piston axis.

5. The pump assembly of claim 4 , further comprising a hollow cylinder with an inlet port and an outlet, and wherein the piston travels inside the cylinder such that:
the cylinder fills with fluid through the inlet port while the piston is retracting out of the cylinder; and
the piston pumps fluid out the cylinder through the outlet while the piston is extending into the cylinder.

6. The pump assembly of claim 5 , wherein the piston spends a greater fraction of each revolution of the cam traveling into the cylinder than retracting from the cylinder.

7. A pump assembly comprising:
a base;
a cam mounted on the base to rotate in a plane, the cam having:
an axis of rotation;
a circumferential side wall parallel to the axis of rotation; and
a geometric center displaced from the axis of rotation by a first distance;

a fluid-carrying cylinder which attaches to the base, and which has an inlet port and an outlet;
a piston situated in the fluid-carrying cylinder and driven by rotation of the cam, the piston comprising:
a shaft extending along a piston axis lying in the plane, the piston axis parallel to a reference line perpendicular to and intersecting the axis of rotation of the cam, but separated from the reference line by a second distance equal to the first distance;
a cam follower engaging the circumferential side wall;

wherein fluid enters the cylinder via the inlet port, and is expelled from the cylinder by travel of the piston through the cylinder.

8. The pump assembly of claim 7 , further comprising a spring which retains the piston against the cam.

9. The pump assembly of claim 8 , wherein the spring extends between the fluid-carrying cylinder and a platform on the piston.

10. The pump assembly of claim 7 , wherein the force exerted by the cam on the piston is substantially in line with a single axis of translation of the piston.

Assignees

• Celotta Daniel W
• Holman John C
• Graco Minnesota Inc

Inventors

• Celotta Daniel W
• Holman John C

Classifications

• F04B53/162

  Adaptations of cylinders · CPC title

• F04B1/0413

  Cams · CPC title

• F04B9/042 Primary

  the means being cams · CPC title

• F04B53/16

  Casings; Cylinders; Cylinder liners or heads; Fluid connections · CPC title

• F04B9/045

  the means being eccentrics · CPC title