Pressure relief valve with orifice

1. A pressure relief valve, comprising:

a housing including an inlet chamber adapted to be in communication with an outlet of a pump and an outlet chamber adapted to be in communication with a pump inlet, the housing including a bore having a first end in communication with the inlet chamber, a plurality of orifices in communication with the outlet chamber, and a main spill aperture axially spaced apart from the plurality of orifices and in communication with the outlet chamber;

a piston axially moveable within the bore between a first position whereat the piston seals the inlet chamber from the outlet chamber, a second position whereat the inlet and outlet chambers are in fluid communication with one another via only the plurality of orifices, and a third position whereat the inlet and outlet chambers are in fluid communication with one another via the plurality of orifices and the main spill aperture; and

a spring biasing the piston toward the first position;

where in each orifice of the plurality of orifices is axially spaced apart from adjacent orifices of the plurality of orifices, and wherein at least one of the plurality of orifices having a diameter being different from a diameter of the other orifices of the plurality of orifices.

2. The pressure relief valve of claim 1 , wherein the housing includes an aperture aligned with the bore, the aperture being closed by a plug attached to the housing, the spring having one end engaging the plug and an opposite end engaging the piston.

3. The pressure relief valve of claim 2 , wherein the housing includes a wall separating the bore from the outlet chamber, the plurality orifices and the main spill aperture extending through the wall.

4. The pressure relief valve of claim 3 , wherein the wall includes an uninterrupted land separating the plurality of orifices and the main spill aperture.

5. The pressure relief valve of claim 1 , wherein the piston includes first and second coaxially aligned recesses, the first recess being in receipt of the spring, the second recess being in communication with the inlet chamber, the piston including a transversely extending aperture through which fluid flows when the piston is at the third position.

6. The pressure relief valve of claim 1 , wherein the piston allowing fluid to flow through the plurality of orifices but not the main spill aperture when located at an axial position between the second and third positions.

7. The pressure relief valve of claim 1 , wherein an axial distance between adjacent orifices of the plurality of orifices is adjustable to vary a discharge pressure versus discharge flow relationship of the pump.

8. The pressure relief valve of claim 1 , wherein each of the plurality of orifices having a diameter being different from a diameter of each of the other orifices of the plurality of orifices.

9. The pressure relief valve of claim 8 , wherein the different diameters of the plurality of the orifices reduce in size from the first end towards the main spill aperture.

10. The pressure relief valve of claim 1 , wherein the main spill aperture having a pocket portion with an offset leading edge.

11. The pressure relief valve of claim 1 , wherein the main spill aperture having a sloped leading edge.

12. The pressure relief valve of claim 1 , wherein the main spill aperture including a first main spill aperture and second main spill aperture laterally spaced apart from one another by a land.

13. The pressure relief valve of claim 12 , wherein each of the first and second main spill apertures includes an offset leading edge.

14. A pressure relief valve, comprising:

a housing including an inlet chamber adapted to be in communication with an outlet of a pump and an outlet chamber adapted to be in communication with a pump inlet, the housing including a bore having a first end in communication with the inlet chamber, a plurality of orifices in communication with the outlet chamber, and a main spill aperture axially spaced apart from the plurality of orifices and in communication with the outlet chamber;

a piston axially moveable within the bore between a first position whereat the piston seals the inlet chamber from the outlet chamber, a second position whereat the inlet and outlet chambers are in fluid communication with one another via only the plurality of orifices, and a third position whereat the inlet and outlet chambers are in fluid communication with one another via the plurality of orifices and the main spill aperture; and

a spring biasing the piston toward the first position;

wherein each orifice of the plurality of orifices is axially and radially spaced apart from adjacent orifices of the plurality of orifices, and wherein at least one of the plurality of orifices having a diameter being different from a diameter of the other orifices of the plurality of orifices.

15. The pressure relief valve of claim 14 , wherein an axial distance between adjacent orifices of the plurality of orifices is adjustable to vary a discharge pressure versus discharge flow relationship of the pump.

16. The pressure relief valve of claim 14 , wherein the piston allowing fluid to flow through the plurality of orifices but not the main spill aperture when located at an axial position between the second and third positions.

17. A pressure relief valve, comprising:

a housing including an inlet chamber adapted to be in communication with an outlet of a pump and an outlet chamber adapted to be in communication with an inlet of the pump, the housing including a bore having a first end in communication with the inlet chamber, a plurality of orifices in communication with the outlet chamber, and a main spill aperture axially spaced apart from the plurality of orifices and in communication with the outlet chamber;

a piston axially moveable within the bore between a first position whereat the piston seals the inlet chamber from the outlet chamber, a second position whereat the inlet and outlet chambers are in fluid communication with one another via only the plurality of orifices, and a third position whereat the inlet and outlet chambers are in fluid communication with one another via the plurality of orifices and the main spill aperture; and

a spring biasing the piston toward the first position;

wherein each orifice of the plurality of orifices is axially spaced apart from adjacent orifices of the plurality of orifices, and wherein the axial distance between adjacent orifices of the plurality of orifices is adjustable to vary a discharge pressure versus discharge flow relationship of the pump.

18. A pressure relief valve, comprising:

a housing including an inlet chamber adapted to be in communication with an outlet of a pump and an outlet chamber adapted to be in communication with an inlet of the pump, the housing including a bore having a first end in communication with the inlet chamber, a plurality of orifices in communication with the outlet chamber, and a main spill aperture axially spaced apart from the plurality of orifices and in communication with the outlet chamber;

a piston axially moveable within the bore between a first position whereat the piston seals the inlet chamber from the outlet chamber, a second position whereat the inlet and outlet chambers are in fluid communication with one another via only the plurality of orifices, and a third position whereat the inlet and outlet chambers are in fluid communication with one another via the plurality of orifices and the main spill aperture; and

a spring biasing the piston toward the first position;

wherein each orifice of the plurality of orifices is axially and radially spaced apart from adjacent orifices of the plurality of orifices, and wherein the piston allows fluid to flow through the plurality of orifices but not the main spill aperture when located at an axial position between the second and third positions.