Filter and retainer assembly for piston pump

1. A cartridge for use in a pump comprising:

a sleeve having a bore;

a piston having a first portion that is disposed within the bore of the sleeve and a second portion that extends from the first portion outwardly from the sleeve, the second portion of the piston adapted to engage an eccentric for reciprocating the first portion of the piston relative to the sleeve in response to rotation of the eccentric;

a retainer having a first end that engages the sleeve and maintains the first portion of the piston within the bore of the sleeve and a second end that defines a retainer end face including a piston aperture;

a filter assembly having an end distal to the retainer that includes an aperture through which the second portion of the piston extends and an end proximal to the retainer that defines a filter end face, the filter assembly being a separately formed element from the retainer where the retainer end face is axially opposed to and moveable relative to the filter end face; and

a seal that retains the filter assembly on the second portion of the piston.

2. The cartridge of claim 1 wherein the retainer is formed from a first material and the filter assembly is formed from a second material that is different from the first material.

3. The cartridge of claim 2 wherein the filter assembly includes a filter frame and a filter screen, the filter frame being formed from the second material and the filter screen is formed from a third material that is different from the second material.

4. The cartridge of claim 1 wherein the retainer includes an attachment projection that cooperates with a groove formed on the sleeve to form a snap-fit connection therebetween.

5. The cartridge of claim 1 wherein the retainer includes a generally smooth inner surface that is retained onto the sleeve by an interference fit.

6. A pump comprising:

a housing having a cylinder bore;

an eccentric supported by the housing; and

a cartridge configured to be assembled into the cylinder bore, the cartridge comprising:

a sleeve having a bore;

a piston having a first portion disposed within the bore of the sleeve and a second portion extending from the first portion, the second portion of the piston extending outwardly from the sleeve and engaging the eccentric such that the first portion of the piston is reciprocated relative to the sleeve in response to rotation of the eccentric;

a retainer having a first end that engages the sleeve and maintains the first portion of the piston within the bore of the sleeve and a second end that defines a retainer end face including a piston aperture;

a filter assembly having an end distal to the retainer that includes an aperture through which the second portion of the piston extends and an end proximal to the retainer that defines a filter end face, the filter assembly being a separately formed element from the retainer where the retainer end face is axially opposed to and moveable relative to the filter end face; and

a seal that retains the filter assembly on the second portion of the piston.

7. The pump of claim 6 wherein the retainer is formed from a first material and the filter assembly is formed from a second material that is different from the first material.

8. The pump of claim 7 wherein the filter assembly includes a filter screen, and wherein the filter frame is formed from the second material and the filter screen is formed from a third material that is different from the second material.

9. The pump of claim 6 wherein the retainer includes an attachment projection that cooperates with a groove formed on the sleeve to form a snap-fit connection therebetween.

10. The pump of claim 6 wherein the retainer includes a generally smooth inner surface that is retained onto the sleeve by an interference fit.

11. A method of assembling a cartridge of a pump configured for use in a vehicular hydraulic braking system comprising the steps of:

a. inserting a piston having a first portion and a second portion into a sleeve having a bore such that the first portion is positioned within the sleeve bore and the second portion of the piston extends outwardly from the sleeve;

b. engaging a retainer onto the sleeve such that the first portion of the piston is retained within the sleeve bore by the retainer;

c. inserting a separately formed filter assembly having an aperture over the piston second portion after engaging the retainer to the sleeve outer surface such that the second portion of the piston extends through the filter assembly aperture and where opposed faces of the retainer and filter assembly are moveable relative to each other; and

d. inserting a seal over the second portion of the piston such that the seal retains the filter assembly on the second portion of the piston.

12. The method of claim 11 further including a step e. of inserting the cartridge into a cylinder bore of a pump housing.

13. The method of claim 12 wherein step e. includes inserting a glide ring into the cylinder bore prior to inserting the cartridge.

14. The method of claim 13 wherein step e. includes inserting a backing ring after inserting after inserting the glide ring and before inserting the cartridge.

15. The method of claim 11 wherein step b. includes engaging a snap fit protrusion extending from the retainer into a groove provided on the sleeve outer surface and step c. includes assembling the filter assembly to the piston second portion in a clearance fit relationship.