Flow-pressure control valve system

Claim 2

A valve system, comprising a source of fluid under pressure, a load, a main valve for controlling flow of fluid between said source and said load, first and second pilot stages for controlling said main valve alternatively, and transfer means for shifting the control of said main valve from one to the other of said pilot stages.

Claim 3

A valve system in accordance with claim 1 including first and second sources of input signals for controlling said first and second pilot stages respectively.

Claim 4

A valve system in accordance with claim 1 in which said first and second pilot stages are for controlling first and second different conditions of the fluid flowing to said load.

Claim 5

A valve system in accordance with claim 3 in which said transfer means is responsive to one of said conditions.

Claim 6

A valve system in accordance with claim 3 in which said conditions are rate of flow and pressure respectively.

Claim 7

A valve system in accordance with claim 1 in which said first and second pilot stages are each jointly responsive to input and feedback signals indicative of desired and actual values of first and second conditions respectively of the fluid between said main valve and said load.

Claim 8

A valve system in accordance with claim 6 in which said transfer means includes means for initially establishing control by said first said pilot stage and for shifting control to said second pilot stage in response to the attainment of a predetermined magnitude of said second condition.

Claim 9

A valve system, comprising, a source of fluid under pressure, a load, a main valve for controlling the flow of fluid between said source and said load, first and second sources of input signals representing desired values of first and second conditions of fluid flowing to said load, means for generating first and second auxiliary signals representing actual values of said first and second conditions respectively, first and second pilot stages jointly responsive to said first input and auxiliary signals and to said second input and auxiliary signals respectively for controlling said main valve, and transfer means for shifting the control of said main valve from one to the other of said pilot stages.

Claim 10

A valve system, comprising, a source of fluid under pressure, a load, a main valve for controlling the flow of fluid between said source and said load, first and second sources of input signals representing desired values of first and second conditions of fluid flowing to said load, means for generating first and second auxiliary signals representing actual values of said first and second conditions respectively, first and second pilot stages jointly responsive to said first input and auxiliary signals and to said second input and auxiliary signals respectively for controlling said main valve, and transfer means for shifting the control of said main valve from one to the other of said pilot stages.

Claim 11

A valve system in accordance with claim 8 in which said first and second conditions are rate of flow and pressure respectively.

Claim 12

A valve system in accordance with claim 9 in which said means for generating said first auxiliary signal includes a restrictor having an orifice the effective area of which varies as the square root of the pressure drop thereacross.

Claim 13

A valve system in accordance with claim 8 in which said transfer means is responsive to one of said conditions.

Claim 14

A valve system in accordance with claim 8 in which each of said pilot stages includes a flapper urged toward one or the other of a pair of oppositely directed nozzles in accordance with one of said input signals and each of which includes means responsive to one of said auxiliary signals for urging said flapper in a direction opposite to that toward which it is urged by said input signal.

Claim 15

A valve system in accordance with claim 8 in which said transfer means includes means for initially establishing control by said first pilot stage and for shifting control to said second pilot stage in response to a predetermined magnitude of said second condition.

Claim 16

A valve system in accordance with claim 13 in which each pilot stage includes means for generating a differential pressure in a pair of conduits for application to said main control valve and in which said transfer means includes an auxiliary valve for selectively connecting one or the other of said pairs of conduits to said main control valve.

Claim 17

A valve system in accordance with claim 14 in which said transfer means includes a switching valve operable In response to the magnitude of said second condition for actuating said auxiliary valve.

Claim 18

A valve system particularly suitable for controlling the insertion of the charge into a forging press, comprising, a main control valve for supplying fluid through a conduit to said press under controlled conditions of velocity and pressure, a first source for a first signal representing the desired variation in velocity of fluid flow under initial conditions, a second source for a second signal representing a predetermined threshold pressure, first means disposed in said conduit for generating a third signal indicative of the actual velocity of the fluid flowing therethrough, second means for generating a fourth signal indicative of the actual pressure in said conduit, a first pilot stage jointly responsive to said first and third signals for controlling said main valve, a second pilot stage jointly responsive to said second and fourth signals for controlling said main valve, transfer means for shifting the control of said main valve from said first to said second pilot stage, an electric circuit for switching said second signal to a larger value when actuated, means responsive to the attainment by said fourth signal of a value approaching said threshold pressure for actuating said transfer means and said electric circuit, and means including a capacitor for smoothing the application of said larger value signal to said second pilot stage, whereby the fluid flowing to said press flows with a velocity dictated by said first signal until the pressure reaches said threshold value after which the pressure rises gradually to a maximum value corresponding to said larger value of said second signal.

Claim 19

A valve system particularly suitable for controlling the insertion of the charge into a forging press, comprising, a main control valve for supplying fluid through a conduit to said press under controlled conditions of velocity and pressure, a first source for a first signal representing the desired variation in velocity of fluid flow under initial conditions, a second source for a second signal representing a predetermined threshold pressure, first means disposed in said conduit for generating a third signal indicative of the actual velocity of the fluid flowing therethrough, second means for generating a fourth signal indicative of the actual pressure in said conduit, a first pilot stage jointly responsive to said first and third signals for controlling said main valve, a second pilot stage jointly responsive to said second and fourth signals for controlling said main valve, transfer means for shifting the control of said main valve from said first to said second pilot stage, an electric circuit for switching said second signal to a larger value when actuated, means responsive to the attainment by said fourth signal of a value approaching said threshold pressure for actuating said transfer means and said electric circuit, and means including a capacitor for smoothing the application of said larger value signal to said second pilot stage, whereby the fluid flowing to said press flows with a velocity dictated by said first signal until the pressure reaches said threshold value after which the pressure rises gradually to a maximum value corresponding to said larger value of said second signal.