US2590022A - Control device - Google Patents

Description

March 18, 1952 LARKIN 2,590,022

CONTROL DEVICE Filed Aug. 2, 1948 Fig).

T0 PUMP L 0A D Inventor: Thqmas E. Lab-kin,

b d. m

y His ttorney.

nated as droop, and the -;droop to the control, as ;of the decay of this opposite control to zero is called dc-drooping.

is a view at section 2-2 of Fig. 1,

.. speed control resistance 21.

Patented Mar. 18, 1952 CONTROL DEVICE Thomas E. Larkin, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application August 2, 1948,v Serial No. 42,031

6 Claims.

,My invention relates to control systems for mechanical, or hydraulic electric functions and, .more particularly, stabilization and-regulation.

to such systems requiring object of my invention is to provide an improved, inexpensive, reliable stabilization control device for mechanical, loontrolsystems.

hydraulic or electric My invention decreases the possibility of hunttroduction of a stabilization signal, which then ;is,gradually reduced to zero. This temporary reduction or recalibration for stabilization is desigprocess of applying drooping. The process Previously, this effect has been obtained by variousmechanical, hydraulic and electronic d vices, but all have been more complicated and costly than the present system.

For a better understanding of my invention,

;-reference is made to the accompanyin drawing ofa particular embodiment thereof in which Fig.

1 *a partly sectional schematic view and Fig. 2 looking in the direction of the arrows.

Referring to the drawing, piston l acts against 'thespring l' in the cylinder 2. The piston is actedupon bythe delivery pressure of a hydraulic :pump 3' through the tube 2". Piston rod 4 operates a brush 5 over the resistance 6 of a potentiometer 1 in series connection with the field of the-pump driving motor 3, directly controlling the speed of operation of the pump according to out- ;put pressure as a load function of the pump. At the same time, the motion of the piston rod is communicated to the bar 8 parallel to the piston ,rod and rigidly connected to it by the link 9. Bar-:8 rigidly connects the free ends of two identical bellows l and II of an input bellows set, anchored at l2 and I3. An output set of two identical bellows l4 and I is similarly anchored at I6 and I! and similarly connected at their free ends by a bar l8. Tubes l9 and 2!] connect corresponding pairs of bellows of the two sets and are interconnected by a tube 2| in which is a variable valve 22. Movement of the bar I 8 is communicated by a pin 23 in the bar l8 through a lever 24 pivoted at 25 to a brush 26 mounted on the lever 24. This brush is operated over a reverse Adjustable springs 2 29 and 30 biasthe lever 24 to a central position with the brush 26 centrally positioned on 'the resistor 21 as indicated in Figure 1.

The springs 29 and 30 come to rest against stop 3i constructed and positioned so as to provide positive centering of the lever 24. Individual adjusting screws 32 and 33 allow droop in the two directions to be either equal or unequal. The springs 29 and 30 are preferably made of a bimetal so that their tension will increase when the temperature falls to compensate for the increased viscosity of the oil in the system. The above described apparatus, including components numbered 23 through 33 may be referred to below as a stabilization signal device.

Since operation of the control is reversible for the two directions of piston movement, the cycle of operation for but one direction of piston movement will be described. The piston I moving to the right carries with it the piston rod 4 and the brush 5 decreasing the series resistance in the shunt motor field, causing motor 3 to run slower. The same motion of the piston rod is communicated through the link 9 to the bar 8, compressing the bellows H and forcing oil through the tube 20 to expand the bellows I5. At the same time, oil from bellows .I4 is forced through tube 19 to expand the bellows ID. The resulting movement of the bar 18 is transmitted through the pin 23 and the lever 24 pivoted at 25 to move the brush 26 to the right over the resistor 21 and by so doing increases the series resistance in the field of the driving motor 3. The amount of droop thus introduced can be made any desired percentage, such as ten per cent, of the resistance change of the'potentiometer l madeabove.

De-drooping is accomplished as follows: As the bar [8 moves-to the left, the lever 24 acts against the spring 30, which applies arestoring force to the lever and hence to the bellows I5 forcing oil through the restricted duct provided by the valve 22 until the lever again occupies its center position and the resistance of the resistor 27 is again-returned to normal. The length of time to return the lever to zero is varied by the adjustments of the valve andthe biasing springs.

It will be seen that the magnitude of the deflectionof the lever 24 will bedependent not only upon the magnitude of the deflection of the bar 8, but also upon the speed of deflection of the bar 8. This is true because, if the bar 8 is deflected very slowly, the compression of the fluid in tube 2.0 due to the compression of the bellows M will be completely accommodated by the passage of hydraulic fluid through .valve 22 without requiring any deflection of lever 24 due to expansion of bellows 15. If an intermediate speed of deflection of the bar 8 is obtained, the fluid compression due to compression of the bellows II will be only partially accommodated by the passage of hydraulic fluid through valve 22 and a small deflection of lever 24 will result, etc.

Bellows 34 communicating into the connecting tube I9 is a reservoir for variations in oil volume due to temperature change. It is controlled by the spring 35, which applies a pressure greater than that required to move the brush 26.

My invention may be adapted for operation with hydraulic or mechanical controls as well as with the electrical control disclosed above. It will be understood that other modifications may be made without departing from the invention. The appended claims are therefore intended to cover any such modifications within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A control ssytem for a drive means connected to a variable load for varying the speed of said drive means in response to variations in said load, said system comprising a. control device movable in response to said load variations, hydraulic means responsive to movements of said control device to apply drooping and delayed de-drooping characteristics to said system, said hydraulic means comprising a pair of input bellows and a pair of output bellows, said bellows each having one fixed end and one free end, an input connector means interconnecting said free ends of said input bellows and connected to said control device to be actuated thereby, an output connector means interconnecting said free ends of said output bellows, means providing intercommunication between associated ones of said pairs of bellows to transmit motion from said input connector means to said output connector means, a member connecting said output connector and said control device for applying a drooping characteristic to said control system, means for biasing said member to a predetermined position, a connection between the interiors of said output bellows to provide for the return of said member to said predetermined position in accordance with its bias and to apply a time delayed de-drooping characteristic to said control system.

2. A control system for a drive means connected to a variable load for varying the speed of said drive means in response to variations in said load, said system comprisin a control device movable in response to said load variations, hydraulic means responsive to movements of said control device to apply drooping and de-drooping characteristics to said system, said hydraulic means comprising a pair of input bellows and a pair of output bellows, said bellows each having one fixed end and one free end, an input connector means interconnecting said free ends of said input bellows and connected to said control device to be actuated thereby, an output connector means interconnecting said free ends of said output bellows, means providing intercommunication between associated ones of said pairs of bellows to transmit motion from said input connector means to said output connector means, a speed droop control device, a pivoted output lever connected to said output connector means and engaging said speed droop control device to provide a drooping characteristic in 75 in accordance with said control system, a restricted duct connectin the interiors of said output bellows, a biasing means arranged to engage said output lever to provide opposing forces to movement thereof in either direction, a stop means arranged to cooperate with said biasing means to positively center said lever, said biasing means tending to restore said lever to its center position with a time delay determined by said restricted duct to de-droop said control system.

3. A control system for a drive means connected to a variable load for varying the speed of said drive means in response to variations in said load, said system comprising a control device movable in response to said load variations, hydraulic means responsive to movements of said control device to apply drooping and de-drooping characteristics to said system, said hydraulic means comprising a pair of input bellows and a pair of output bellows, said bellows each having one fixed end and one free end, an input connector means interconnecting said free ends of said input bellows and connected to said control device to be actuated thereby, an output connector means interconnecting said free ends of said output bellows, means providing intercommunication between associated ones of said pairs of bellows to transmit motion from said input connector means to said output connector means, a speed droop control device, a'pivoted output lever connected to said output connector means and engaging said speed droop control device to provide a drooping characteristic in said control system,a duct connecting the interiors of said output bellows, an adjustable valve in said duct, individually adjustable biasing springs arranged to engage said lever to provide a restoring force to return said lever to a center position upon rotation of said lever from said center position by said output connector, and stop means positioned to cooperate with said springs and said lever to positively center said lever after a delay depending upon the adjustment of said springs and said valve.

4. In a control system of the type having a control device positioned in accordance with an operating condition of an apparatus to be controlled, a stabilization device comprising an input member connected to said control device for positioning thereby, a stabilization signal device adjustably spring biased to a predetermined central position for providing a stabilization signal for said system in accordance with a deflection from said central position, a hydraulic.

coupling interconnectin said=input member and said signal device for deflecting said signal device in accordance with the magnitude and speed of a change in position of said input member, said hydraulic coupling including a bypass valve for causing slippage of said hydraulic coupling under the restoring force of the spring bias of said signal device to cause said signal device to return to said predetermined central position after a predetermined time interval dependent upon the magnitude of said deflection.

5. In a control system of the type having a control device positioned in accordance with an operatin condition of an apparatus to be controlled, a stabilization device comprising an input member connected to said control device for positioning thereby, a' stabilization signal device normally adjustably spring biased. to a predetermined central position but connected to provide a stabilization signal for said system a deflection from said cantra-l position, a hydraulic coupling interconnecting said input member and said signal. device for deflecting said signal device in accordance with the magnitude and speed of a change in position of said input member, said hydraulic coupling including a bypass valve for causing slippage of said hydraulic coupling under the restorin force of the spring bias of said signal device to cause said signal device to return to said predetermined central position independent of the position of said input member after a predetermined time interval dependent upon the magnitude of said deflection.

6. A hydraulic stabilization device for an automatic positioning control system comprising a v of mechanically interconnected bellows, hydraulic first pair of hydraulic bellows mechanically interconnected for movement in response to movements of a control member within the system to be stabilized, movement in a particular direction compressing one of said bellows and expanding the other of said bellows, a second pair pair with one bellows of said second pair, said second pair of bellows being biased by spring devices to a predetermined centered position, a passage including an adjustablethrottling valve interconnecting said hydraulic ducts, and a stabilization signal device connected for positioning in accordance with the position of said second pair of bellows. I

THOMAS E. LARKIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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