Servo-systems

Claim 2

A fluid operated servo-system for the control of the setting of a progressively acting servo-valve assembly, including a pilot valve, a main valve movable to produce a fluid output pressure, and an actuator having a range of settings, comprising: fluid signal input means; a Bourdon tube, coupled to one end of the pilot valve, and coupled and responsive to said fluid signal input means, for rotatably displacing the pilot valve to or from a predetermined position with a force dependent upon the pressure within said fluid signal input means; a movable cam, having at least one eccentric cam surface, responsive to the output of the actuator; means for coupling said cam to the actuator, so that changes in the output of the actuator cause movement of said cam; a cam follower, for engaging said eccentric cam surface, responsive to movement of said cam; a lever, pivotably mounted at one end, and coupled at the other end to the pilot valve, for engaging said cam follower and responsive to movement thereof; a bell crank, coupled to the other end of the pilot valve; spring means, coupled at one end to said lever and at the other end to said bell crank, for rotatably biasing the pilot valve in a predetermined direction, said lever varying the biAsing force of said spring means over a predetermined range of values in response to movement of said cam and said cam follower caused by change in the actuator output; and adjustment means, for varying the velocity ratio of said lever and thereby changing said predetermined range of said biasing force values, the relationship between the fluid signal input pressure and the main valve fluid output pressure being determined by the contour of said eccentric cam surface, and the relationship between the change in the fluid signal input pressure and the corresponding change in the main valve fluid output pressure being determined by the velocity ratio of said lever.

Claim 3

The servo-system as recited in claim 1, wherein said cam is provided with a plurality of eccentric cam surfaces, each contoured so as to correspond to a unique servo-valve assembly input-output relationship, and wherein said cam follower is adjustable so that each of said plurality of cam surfaces is engaged by said cam follower.

Claim 4

The servo-system as recited in claim 2, wherein said cam follower comprises a lever arm, pivotably mounted at one end, and having a bearing rotatably mounted therein for engaging said eccentric cam surfaces.

Claim 5

The servo-system as recited in claim 3, wherein said lever further comprises a slide member, slidably mounted on said lever, and a bearing, rotatably mounted on said slide member for engaging said cam follower and pivoting said lever in response to movement of said cam follower.

Claim 6

The servo-system as recited in claim 4, wherein said adjustment means comprises a threaded bolt, rotatably mounted on said lever at one end and threadably engaged through said slide member at the other end, for adjusting the position of said slide member on said lever.

Claim 7

The servo-system as recited in claim 3, wherein said actuator comprises a cylinder, a pair of pistons slidably disposed in opposite directions within said cylinder, said cylinder being coupled to the pilot and main valves of the servo-system assembly so that said pistons are responsive in two directions to fluid pressure output from the main valve, said cam rotating in response to movement of said pistons within said cylinder, thereby adjusting the biasing force of said spring means and the force required to be exerted by said bellows to displace the pilot valve.

Claim 8

The servo-system as recited in claim 6, wherein said means for coupling said cam to the actuator comprises a rack and pinion gear system for translating linear movement of said pistons into rotational movement of said cam.

Claim 9

The servo-system as recited in claim 3, wherein said spring means is a coil spring.

Claim 10

The servo-system as recited in claim 3, wherein said fluid signal input means comprises an air inlet passage.

Claim 11

A fluid-operated servo-system for the control of the setting of a progressively acting servo-valve assembly, including a pilot valve, a main valve movable to produce a fluid output pressure, and an actuator having a range of settings, comprising: fluid signal input means; resilient bellows, coupled at one end to one end of the pilot valve, and having an air chamber thereof coupled to said fluid signal input means so that said bellows are responsive to pressure within said fluid signal input means and progressively displace the pilot valve to or from a predetermined position with a force dependent upon the pressure within said fluid signal input means; a movable cam, having at least one eccentric cam surface, responsive to the output of the actuator; means for coupling said cam to the actuator, so that changes in the output of the actuator cause movement of said cam; a cam follower, for engaging said eccentric cam surface, responsive to movement of said cam; a lever, pivotably mounted at one end, and coupled at its other end to the other end of said bellows, for engaging said cam follower and responsive to movement thereof, said lever varying the biasing force of said bellows over a predetermiNed range of values in response to movement of said cam and said cam follower caused by change in the actuator output; first spring means, coupled at one end to said lever and fixed at the other end with respect thereto, for biasing the lever in a predetermined direction; and adjustment means, for varying the velocity ratio of said lever and thereby changing said predetermined range of biasing force values created by said bellows, the relationship between the fluid signal input pressure and the main valve fluid output pressure being determined by the contour of said eccentric cam surface, and the relationship between the change of said fluid signal input pressure and the corresponding change in the main valve fluid output pressure being determined by the velocity ratio of said lever.

Claim 12

A fluid-operated servo-system for the control of the setting of a progressively acting servo-valve assembly, including a pilot valve, a main valve movable to produce a fluid output pressure, and an actuator having a range of settings, comprising: fluid signal input means; resilient bellows, coupled at one end to one end of the pilot valve, and having an air chamber thereof coupled to said fluid signal input means so that said bellows are responsive to pressure within said fluid signal input means and progressively displace the pilot valve to or from a predetermined position with a force dependent upon the pressure within said fluid signal input means; a movable cam, having at least one eccentric cam surface, responsive to the output of the actuator; means for coupling said cam to the actuator, so that changes in the output of the actuator cause movement of said cam; a cam follower, for engaging said eccentric cam surface, responsive to movement of said cam; a lever, pivotably mounted at one end, and coupled at its other end to the other end of said bellows, for engaging said cam follower and responsive to movement thereof, said lever varying the biasing force of said bellows over a predetermiNed range of values in response to movement of said cam and said cam follower caused by change in the actuator output; first spring means, coupled at one end to said lever and fixed at the other end with respect thereto, for biasing the lever in a predetermined direction; and adjustment means, for varying the velocity ratio of said lever and thereby changing said predetermined range of biasing force values created by said bellows, the relationship between the fluid signal input pressure and the main valve fluid output pressure being determined by the contour of said eccentric cam surface, and the relationship between the change of said fluid signal input pressure and the corresponding change in the main valve fluid output pressure being determined by the velocity ratio of said lever.

Claim 13

The servo-system as recited in claim 10, further comprising second spring means, coupled at one end to the other end of the pilot valve, and fixed at the other end with respect thereto, for biasing, in conjunction with said bellows, the pilot valve in a predetermined direction, said lever varying the biasing force of said second spring means and said bellows over a predetermined range of values in response to movement of said cam and said cam follower caused by change in the actuator output.

Claim 14

The servo-system as recited in claim 11, wherein said cam is provided with a plurality of eccentric cam surfaces, each contoured so as to correspond to a unique servo-valve assembly input-ouput relationship, and wherein said cam follower is adjustable so that each of said plurality of cam surfaces is engaged by said cam follower.

Claim 15

The servo-system as recited in claim 12, wherein said cam follower comprises a lever arm, pivotably mounted at one end, having a bearing rotatably mounted therein for engaging said eccentric cam surfaces.

Claim 16

The servo-system as recited in claim 13, wherein said lever further comprises a slide member, slidably mounted on said lever, and a bearing rotatably mounted on said slide member, for engaging said cam follower and pivoting said lever in response to movement of said cam follower.

Claim 17

The servo-system as recited in claim 14, wherein said adjustment means comprises a threaded bolt, rotatably mounted on said lever at one end and threadably engaged through said slide member at the other end, for adjusting the position of said slide member on said lever.

Claim 18

The servo-system as recited in claim 13, wherein said actuator comprises a cylinder, a pair of pistons slidably disposed in opposite directions within said cylinder, said cylinder being coupled to the pilot and main valves of the servo-system assembly so that said pistons are responsive in two directions to fluid pressure output from the main valve, said cam rotating in response to movement of said pistons within said cylinders, thereby adjusting the biasing force of said second spring means and said bellows, and the force required to be exerted by said bellows to displace the pilot valve.

Claim 19

The servo-system as recited in claim 16, wherein said means for coupling said cam to the actuator comprises a rack and pinion gear system for translating linear movement of said pistons into rotational movement of said cam.

Claim 20

The servo-system as recited in claim 13, wherein said first and second spring means are coil springs.

Claim 21

The servo-system as recited in claim 13, wherein said fluid signal input means comprises an air inlet passage.