Arrangement for pumping a filtered fluid

Claim 2

Arrangement for pumping a filtered fluid, comprising a feed pump; main pump means including a main pump, and a consumer conduit through which said main pump discharges; feed conduit means connecting said feed pump with said main pump so that only fluid pumped by said feed pump into said feed conduit means flows into said main pump; filter means in said feed conduit means having a working condition causing a normal pressure differential in said feed conduit means, said filter means being disposed across the flow cross section of said feed conduit means so that all the fluid flowing in said feed conduit means to said main pump means flows through said filter means, and no fluid in unfiltered condition bypasses said filter means and flows into said main pump; pressure responsive means connected with said feed conduit means upstream and downstream of said filter means and being in a normal inoperative position when said normal pressure differential indicates said working condition of said filter means, said pressure responsive means moving to an actuated position in response to a predetermined pressure differential different from said normal pressure differential and indicating a faulty filtering action of said filter means; and control means for said main pump means operated by said pressure responsive means in said actuated position to terminate discharge from said main pump into said consumer conduit.

Claim 3

Arrangement as claimed in cLaim 1 wherein said main pump discharges a constant amount of fluid; wherein said control means include a control valve means having an operative position connecting said main pump with said consumer conduit, and a control position in which said main pump idles; and wherein said pressure responsive means include a pressure responsive valve responding to said predetermined pressure differential to move to said actuated position, and connecting in said actuated position said feed conduit between said feed pump and said filter means with said control valve means for moving the same from said normal position to said control position.

Claim 4

Arrangement as claimed in claim 1 wherein said control means include hydraulic regulating means for said main pump; and wherein said pressure responsive means include a pressure responsive valve responding to said predetermined pressure differential to move to said actuated position, and connecting in said actuated position said feed conduit between said feed pump and said filter means with said hydraulic regulating means so that fluid flowing from said feed pump to said hydraulic regulating means operates the latter to set said main pump to pump a minimum amount of fluid.

Claim 5

Arrangement as claimed in claim 1 wherein said pressure responsive means include a pressure responsive valve including a movable valve member, and a spring biassing said valve member into said normal inoperative position; wherein said control means include a control conduit; wherein said valve in said actuated position connects said feed conduit and said control conduit, respectively; wherein said predetermined pressure differential overcomes the force of said spring and moves said valve member to said actuated position; and wherein said control means are hydraulic control means operated in said actuated position of said valve by fluid flowing from said feed pump through said valve and said control conduit.

Claim 6

Arrangement as claimed in claim 1 comprising a discharge conduit connected with said feed conduit downstream of said filter means; and a pressure limiting valve in said discharge conduit spring biassed to a first position closing said discharge conduit when the pressure in said feed conduit is low, and at least a second position for supplying fluid to said control means for holding the same in a normal position in which said main pump discharges through said consumer conduit fluid fed by said feed pump at a normal pressure.

Claim 7

Arrangement as claimed in claim 1 wherein said control means include a control valve means including a control valve member, a valve casing, and a spring biassing said control valve member to a first position closing said consumer conduit; comprising a return conduit connecting said valve casing with said feed conduit downstream of said filter means and being connected with said consumer conduit in said first position so that said main pump idles, said control valve member having a second working position closing said return conduit and opening said consumer conduit; first and second control conduits connected with said valve casing so that pressure in said first control conduit acts on said control valve member to move the same to said first position, and pressure in said second conduit acts on said control valve member to move to said second working position; wherein said pressure responsive means include a pressure responsive valve connecting in said actuated position said feed conduit between said feed pump and said filter means with said first control conduit so that at said predetermined pressure differential said control valve member closes said consumer conduit; and comprising a pressure limiting valve connected with said feed conduit downstream of said filter means and including a limit spring urging said pressure limiting valve to a closed position, said pressure limiting valve moving to an operative position connecting said feed conduit with said second control conduit when the pressure in said feed conduit overcomes the force of Said limit spring so that said control valve member is moved to said second working position.

Claim 8

Arrangement as claimed in claim 6 wherein said pressure limiting valve in said closed and operative positions disconnects said feed conduit from a discharge outlet, and has a third position assumed at high pressure in said feed conduit for connecting said feed conduit with said discharge outlet and with said second control conduit.

Claim 9

Arrangement as claimed in claim 1 wherein said control means include hydraulic regulating means for said main pump; wherein said pressure responsive means include a pressure responsive valve responding to said predetermined pressure differential to move to said actuated position, and connecting in said actuated position said feed conduit between said feed pump and said filter means with said hydraulic regulating means so that fluid flowing from said feed pump to said hydraulic regulating means operates the latter to set said main pump to pump a minimum amount of fluid; and wherein said regulating means further include manually operated means, and hydraulic arresting means for arresting said manually operated means.

Claim 10

Arrangement as claimed in claim 8 comprising a pressure limiting valve connected with said feed conduit; wherein said hydraulic arresting means include a cylinder, and a piston forming in said cylinder first and second chambers; said first chamber being connected by said pressure responsive valve with said feed conduit upstream of said filter means, and said second chamber being connected by said pressure limiting valve with said feed conduit downstream of said filter means; and wherein said hydraulic arresting means further include an arresting member operated by said piston so that said manually operated means are arrested when high pressure fluid from said feed conduit is supplied to said first chamber, and are released by high pressure fluid supplied to said second chamber.

Claim 11

Arrangement as claimed in claim 1 wherein said pressure responsive means include a valve casing, two conduits connecting said valve casuing with said feed conduit upstream and downstream of said filter means, a valve member in said casing between said conduits so that the pressure differential caused by said filter means acts on said valve member, and a spring acting on said valve member and urging the same into said normal inoperative position, said predetermined pressure differential overcoming the force of said spring and urging said valve member to said actuated position; and wherein said control means include a bypass conduit means connecting the inlet and outlet of said main pump and having ports on said valve casing, and a duct means formed in said valve member and connecting said ports in said actuated position of said valve member so that fluid is pumped by said main pump through said bypass conduit and said duct means and discharge through said consumer conduit is terminated.

Claim 12

Arrangement as claimed in claim 10 wherein said control means include a check valve in said feed conduit downstream of said filter means and upstream of said bypass conduit for protecting said filter means.

Claim 13

Arrangement as claimed in claim 1 wherein said control means include hydraulic regulating means for said main pump; wherein said pressure responsive means include a pressure responsive valve responsive to said predetermined pressure differential to move out of said normal inoperative position to said actuated position, and connecting in said actuated position said feed conduit with said hydraulic regulating means to operate the latter to set said main pump to pump a reduced amount of fluid; wherein said pressure responsive valve in said normal inoperative position connects said feed conduit with a discharge outlet; and wherein said pressure responsive valve includes a spring urging the same to said normal inoperative position.

Claim 14

Arrangement as claimed in claim 12 wherein said regulating means include a cylinder, and a differential pistoN and piston rod in said cylinder forming in the same a piston chamber and a piston rod chamber; wherein said piston chamber is connected with said feed conduit in said actuated position of said pressure responsive valve, and with said discharge outlet in said normal inoperative position; and wherein said piston rod chamber is connected with said consumer conduit.

Claim 15

Arrangement as claimed in claim 13 wherein said regulating means include manually operated means for moving said piston and piston rod in said cylinder to a position in which said regulating means set said main pump to maximum output which is reduced by said regulating means when said predetermined pressure differential prevails at said filter means and fluid from said consumer conduit flows into said piston rod chamber while said piston chamber is connected with said discharge outlet.

Claim 16

Arrangement as claimed in claim 12 comprising a pressure limiting valve connected with said feed conduit between said feed pump and said filter means and having a discharge outlet for discharging fluid from said feed conduit when the pressure in the same exceeds a normal pressure.

Claim 17

Arrangement as claimed in claim 1 wherein said main pump has a constant output volume; and wherein said control means include a conduit connecting the inlet and outlet of said main pump, and a control valve in said conduit having a position connecting said inlet with said outlet for idle circulation.

Claim 18

Arrangement as claimed in claim 1 wherein said control means include regulating means for said main pump; and wherein said pressure responsive means in said actuated position operate said regulating means to reduce the output volume of said main pump.

Claim 19

Arrangement as claimed in claim 1 wherein said pressure responsive means include a valve having a discharge outlet closed in said normal inoperative position, and connecting said feed conduit upstream of said filter means with said discharge outlet in said actuated position so that the flow through said filter is reduced when said predetermined pressure differential indicates a faulty condition of said filter means.