Fuel pumps for use in conduction with gas turbine engines

Claim 2

A fuel pump comprising a housing having an inlet and a pumping chamber into which the inlet opens, a rotor in said housing, said rotor including a centrifugal impeller in the pumping chamber in the housing, a first outlet communicating with said chamber, a first non-return valve controlling said first outlet, a plurality of pistons slidable in bores in the housing opening at one end into the chamber, cam means on said impeller engageable with said pistons for reciprocating said pistons in said bores as the rotor is rotated, resilient means urging said pistons in a direction towards the chamber, a second outlet in the housing, passage means in the housing and rotor connecting said bores to said inlet and to the second outlet, and a second non-return valve controlling said second outlet, said first and second outlets being interconnected, the arrangement being such that at low speeds, the pistons are reciprocated by the cam means and fuel is pumped from the inlet to the second outlet as the pressure at the periphery of the pumping chamber is lower than the passage means in the housing so that the second non-return valve opens and the first non-return valve closes, and as speed increases, the pressure at the periphery of the pumping chamber increases and when the same exceeds the pressure in the passage means in the housing sufficiently to overcome the action of the resilient means, the pistons are urged by the pressure out of engagement with the cam means thereby avoiding loads on the pump caused by the pumping action of the pistons.

Claim 3

The fuel pump as claimed in claim 1 in which said bores extend in a direction parallel to the axis of the rotor, which includes a shaft portion extending along an axial bore in the housing, said bores being connected to said axial bore by cross bores in the housing and said shaft portion having recesses therein whereby said cross-bores are successively connected to the inlet and said second outlet as the rotor is rotated.

Claim 4

A fuel pump for use with gas turbine engines comprising a housing having an inlet and a pumping chamber into which the outlet opens, a rotor in the housing, the rotor having a shaft portion extending along an axial bore in the housing, a centrifugal impeller carried by the shaft portion and being located in the pumping chamber, a plurality of pistons slidable in bores in the housing, said bores extending in a direction parallel to the axis of the shaft portion of the rotor and opening at one end into the pumping chamber, cam means on the impeller engageable with said pistons for reciprocating said pistons in said bores as the rotor is rotated, resilient means urging said pistons in a direction towards the pumping chamber, a first outlet in the housing communicating with the periphery of the pumping chamber, a first non-return valve controlling the first outlet, a second outlet in the housing, a second non-return valve controlling said second outlet, means connecting said first and second outlets, the bores for the pistons communicating with cross bores in the housing, said shaft portion having a pair of recesses at an axial position corresponding to the position of the cross bores, each recess extending circumferentially around the shaft portion through an angle somewhat less than 180*, axial passage means in the shaft portion connecting one of the recesses to the inlet, said shaft portion having an axial groove, said housing having a groove connected to the second outlet and to said axial groove in the shaft portion, and means connecting the axial groove in the shaft portion to the other recess, the arrangement being such that at low speeds, the pistons are reciprocated by the action of the cam means on the impeller and fuel is pumped from the inlet to the second outlet as the pressure at the periphery of the pumping chamber is lower than that in the groove in the housing so that the second non-return valve opens and the first non-return valve closes, and as speed increases, the pressure at the periphery of the pumping chamber increases and when the same exceeds the pressure in the groove in the housing sufficiently to overcome the action of the resilient means, the pistons are urged by the pressure out of engagement with the cam means thereby avoiding loads on the pump caused by the pumping action of the pistons.

Claim 5

A fuel pump for use with gas turbine engines comprising a housing having an inlet and a pumping chamber into which the outlet opens, a rotor in the housing, the rotor having a shaft portion extending along an axial bore in the housing, a centrifugal impeller carried by the shaft portion and being located in the pumping chamber, a plurality of pistons slidable in bores in the housing, said bores extending in a direction parallel to the axis of the shaft portion of the rotor and opening at one end into the pumping chamber, cam means on the impeller engageable with said pistons for reciprocating said pistons in said bores as the rotor is rotated, resilient means urging said pistons in a direction towards the pumping chamber, a first outlet in the housing communicating with the periphery of the pumping chamber, a first non-return valve controlling the first outlet, a second outlet in the housing, a second non-return valve controlling said second outlet, means connecting said first and second outlets, the bores for the pistons communicating with cross bores in the housing, said shaft portion having a pair of recesses at an axial position corresponding to the position of the cross bores, each recess extending circumferentially around the shaft portion through an angle somewhat less than 180*, axial passage means in the shaft portion connecting one of the recesses to the inlet, said shaft portion having an axial groove, said housing having a groove connected to the second outlet and to said axial groove in the shaft portion, and means connecting the axial groove in the shaft portion to the other recess, the arrangement being such that at low speeds, the pistons are reciprocated by the action of the cam means on the impeller and fuel is pumped from the inlet to the second outlet as the pressure at the periphery of the pumping chamber is lower than that in the groove in the housing so that the second non-return valve opens and the first non-return valve closes, and as speed increases, the pressure at the periphery of the pumping chamber increases and when the same exceeds the pressure in the groove in the housing sufficiently to overcome the action of the resilient means, the pistons are urged by the pressure out of engagement with the cam means thereby avoiding loads on the pump caused by the pumping action of the pistons.