WO2006025886B1

WO2006025886B1 - Low-friction reciprocating pump

Info

Publication number: WO2006025886B1
Application number: PCT/US2005/017599
Authority: WO
Inventors: Harald Kretzinger; Thomas M Arens
Original assignee: Lincoln Ind Corp; Harald Kretzinger; Thomas M Arens
Priority date: 2004-08-27
Filing date: 2005-05-19
Publication date: 2008-05-29
Also published as: US20060045782A1; DE112005002063T5; WO2006025886A3; WO2006025886A2; JP2008511794A

Abstract

A reciprocating pump for pumping a fluid, especially for pumping a fluid such as UV ink which is subject to solidification when exposed to frictional forces. The pump has an internal displacement chamber with an inlet, and outlet, and a plunger which is reciprocally movable in the chamber. The plunger reciprocates through an axial passage in the housing at one end of the chamber, the passage being sized to receive the plunger with a clearance fit. First and second seals are positioned in the axial passage. Each seal is annular in shape and extends between the plunger and housing in sealing contact therewith. The pump housing is free from a bearing which contacts the plunger or guides its motion, such that the sealing contacts between the plunger and seals are the only contacts of the plunger in the housing.

Claims

AMENDED CLAIMS received by the International Bureau on 07 Mars 2008 (07.03.2008)

1. A reciprocating pump for pumping a fluid, comprising: a pump housing having an internal displacement chamber with an inlet, and outlet, a longitudinal axis, and opposite ends,- a plunger which is reciprocally movable in the chamber along said axis; an axial passage in the housing at one end of the chamber through which the plunger axially reciprocates; and first and second annular seals in the axial passage generally co-axial with the passage and spaced from one another longitudinally of the passage, each of said first and second annular seals being constituted solely by a single one-piece seal sized for sealing contact with the plunger; wherein the pump housing is free from a bearing which contacts the plunger or guides its motion, wherein the plunger is free from direct engagement with the housing, and wherein said sealing contacts of the plunger with the first and second seals are the only contacts of the plunger in the housing,

2 , A reciprocating pump as set forth in claim l wherein the axial passage comprises an intermediate section between said seals which is sized to receive the plunger therethrough with a clearance fit .

3. A reciprocating pump as set forth in claim 2 wherein said intermediate section of the axial passage defines a minumum clearance region for the plunger in the housing.

4. A reciprocating pump as set forth in claim 2 wherein the plunger has an outer diameter Dl, the intermediate section of the axial passage has an internal diameter D2, and a ratio of D2 to Dl is greater than 1.01.

5. A reciprocating pump as set forth in claim 2 wherein the plunger has an outer diameter Dl, the intermediate section of the axial passage has an axial length Ll, and a ratio of Ll to Dl is within a range between 0.5 and 1.0.

6. A reciprocating pump as set forth in claim 2 wherein the axial passage has internal shoulders at opposite longitudinal ends of said intermediate section, and wherein each of said seals is positioned adjacent a respective shoulder in the axial passage.

7. A reciprocating pump as set forth in claim 1 further comprising a threaded nut received in the housing, and wherein the axial passage has an internal shoulder therein, one of said seals being retained at a position adjacent said internal shoulder by the threaded nut.

8. A reciprocating pump as set forth in claim 1 wherein each seal has a generally U-shaped cross-section with two opposing legs in respective sealing contact with the plunger and housing.

9. A reciprocating pump as set forth in claim 8 wherein said two legs of each seal are asymmetrical .

10. A reciprocating pump as set forth in claim I wherein the housing comprises a pump head, a cylinder attached to the head, and a gland attached to the head generally opposite the cylinder, and wherein said axial passage is disposed in the gland.

11. A reciprocating pump as set forth in claim 1 wherein the pump is a single-acting pump which, during an upstroke, receives fluid through the inlet into the chamber without simultaneous discharge through the outlet, and which, during a downstroke, discharges fluid from the chamber through the outlet.

12. A reciprocating pump as set forth in claim 1 further comprising a drain comprising an annular groove in the axial passage for draining fluid which is located between the first and second seals.

13. A_. reciprocating pump as set forth in claim 1 in combination with a container for supplying fluid to the inlet of the chamber, and a tube for delivering fluid from the outlet of the σhaπiber to a device requiring fluid, and wherein the tube is free from valves between the outlet and the device .

14. A reciprocating pump as set forth in claim 1 wherein said axial passage has a longitudinal portion, between said first and second seals which defines a minumum clearance region for the plunger in the housing, said minimum clearance region being free of any seals or bearings that contact the plunger and having a relatively- short axial length Ll of less than 1.0 inch, and wherein the plunger has an outer diameter Dl, said minimum clearance region haa an internal diameter D2 , and wherein D2 is larger than D1 by at least about 0.015 inch such that the plunger has a relatively loose clearance fit in said minimum clearance region of the axial passage, said relatively loose clearance fit of the plunger in said minimum clearance region and saie relatively short axial length of said minimum clearance region combining to reduce friction and solidification of the UV ink due to shear forces ,