Fuel pump apparatus

1. A hydraulic head assembly comprising:

a hydraulic head having a first bore and a pumping chamber;

an adapter having a second bore, the adapter being connected to said hydraulic head such that said first and second bores form a substantially continuous pumping element bore; and

a pumping element disposed within said pumping element bore for pressurising fuel in the pumping chamber;

wherein a first seal is formed between the pumping element and the hydraulic head; and

a second seal is formed between the pumping element and the adapter,

wherein the hydraulic head comprises a turret through which the first bore extends, the adapter being connected to said turret,

wherein the adapter comprises a mounting section for mounting the adapter to the hydraulic head,

wherein the mounting section comprises a collar for cooperating with the turret,

wherein the collar is an interference fit with an external sidewall of the turret.

2. A hydraulic head assembly as claimed in claim 1 , wherein the first seal is a high pressure seal; and the second seal is a low pressure seal.

3. A hydraulic head assembly as claimed in claim 1 , wherein the adapter comprises a polymeric seal for cooperating with the pumping element.

4. A hydraulic head assembly as claimed in any claim 1 , wherein a leakage path is formed between the turret and the adapter.

5. A hydraulic head assembly as claimed in claim 4 comprising a collection chamber in communication with the leakage path.

6. A hydraulic head assembly as claimed in claim 1 , wherein the adapter comprises a backleak bore.

7. A hydraulic head assembly as claimed in claim 6 , wherein the backleak bore extends transversely through the adapter.

8. A hydraulic head assembly as claimed in claim 1 comprising a plurality of said hydraulic heads and of said adapters.

9. A hydraulic head assembly as claimed in claim 8 , wherein said hydraulic heads are said adapters are arranged in an in-line configuration.

10. A pump comprising:

a hydraulic head assembly having:

a hydraulic head having a first bore and a pumping chamber;

an adapter having a second bore, the adapter being connected to said hydraulic head such that said first and second bores form a substantially continuous pumping element bore; and

a pumping element disposed within said pumping element bore for pressurising fuel in the pumping chamber;

wherein a first seal is formed between the pumping element and the hydraulic head; and

a second seal is formed between the pumping element and the adapter,

wherein the hydraulic head comprises a turret through which the first bore extends, the adapter being connected to said turret,

wherein the adapter comprises a mounting section for mounting the adapter to the hydraulic head,

wherein the mounting section comprises a collar for cooperating with the turret,

wherein the collar is an interference fit with an external sidewall of the turret.

11. A hydraulic head assembly as claimed in claim 1 , wherein the hydraulic head includes a body with which the turret is integrally formed and within which the pumping chamber is located.

12. A hydraulic head assembly as claimed in claim 11 , wherein the interference fit retains the adaptor to the hydraulic head.

13. A hydraulic head assembly as claimed in claim 11 , wherein the interference fit mounts the adaptor to the hydraulic head.

14. A hydraulic head assembly as claimed in claim 11 , wherein an upper portion of the external sidewall comprises a first annular band having an enlarged diameter which engages an internal sidewall of the collar, thereby forming a first interference joint and wherein a lower portion of the internal sidewall comprises a second annular band having a reduced diameter which engages the external sidewall, thereby forming a second interference joint.

15. A hydraulic head assembly as claimed in claim 11 , wherein the adaptor includes a locating channel on an outer periphery thereof which is configured to receive an O-ring therein such that the O-ring is captured axially between opposing surfaces of the locating channel, wherein the locating channel is not located within the hydraulic head.

16. A pump as claimed in claim 10 , wherein the hydraulic head includes a body with which the turret is integrally formed and within which the pumping chamber is located.

17. A pump as claimed in claim 16 , wherein the interference fit retains the adaptor to the hydraulic head.

18. A pump as claimed in claim 16 , wherein the interference fit mounts the adaptor to the hydraulic head.

19. A pump as claimed in claim 16 , wherein an upper portion of the external sidewall comprises a first annular band having an enlarged diameter which engages an internal sidewall of the collar, thereby forming a first interference joint and wherein a lower portion of the internal sidewall comprises a second annular band having a reduced diameter which engages the external sidewall, thereby forming a second interference joint.

20. A pump as claimed in claim 16 , wherein the adaptor includes a locating channel on an outer periphery thereof which is configured to receive an O-ring therein such that the O-ring is captured axially between opposing surfaces of the locating channel, wherein the locating channel is not located within the hydraulic head.