Positive displacement pumps

(19)

(11)

EP 0 972 936 A3

(12)	EUROPEAN PATENT APPLICATION

(88)	Date of publication A3:
	19.07.2000 Bulletin 2000/29

(43)	Date of publication A2:
	19.01.2000 Bulletin 2000/03

(21)	Application number: 99305492.3

(22)	Date of filing: 12.07.1999

(51)	International Patent Classification (IPC)⁷: F04B 1/04, F02M 59/10, F04B 9/04

(84)	Designated Contracting States:
	AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE
	Designated Extension States:
	AL LT LV MK RO SI

(30)

Priority:

14.07.1998 GB 9815272

(71)	Applicant: Lucas Industries Limited
	London W1Y 4DJ (GB)

(72)	Inventors:
	Parker, Stephen Michael Redhill, Surrey RH1 5TW (GB) Cooke, Michael Peter Gillingham, Kent ME7 1DR (GB) Thornthwaite, Ian Roy Gillingham, Kent ME7 3PJ (GB) Collingborn, Peter Alban Gillingham, Kent ME8 8RX (GB)

(74)	Representative: Goodenough, Nigel et al
	A.A. Thornton & Co. 235 High Holborn London WC1V 7LE London WC1V 7LE (GB)

(54)	Positive displacement pumps

(57) A high pressure positive displacement pump, for example suitable for delivering fuel to a fuel injection system comprises one or more pumping assemblies (2,3,4). Each pumping assembly comprises a cylinder block (11) which defines a pumping cylinder (12) in which a pumping plunger (13) is slidably mounted. Each pumping plunger is connected to a tappet assembly (20) which comprises a tappet shell (21) slidably mounted in a bore (22). In use, the tappet assemblies engage a cam (6) to drive the pumping plungers in the pumping direction. A working fluid chamber (30) is defined on the side of each tappet assembly (20) opposite to the cam (6). In use, pressurised working fluid is delivered to the working fluid chamber (30) to drive the tappet and pumping plunger in the return direction. The arrangement obviates the need to provide a return spring for the pumping plungers.

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