US2278249A - Hydraulic control mechanism - Google Patents

Description

March 31, 1942. c, ls 2,278,249

HYDRAULIC CONTROL MECHANISM Filed July 20, 1940 Inventor- Charles H. Davis, by 47 His Attorney.

Patented Mar. 31, 1942 HYDRAULIC CONTROL MECHANISM Charles H. Davis, Saugus, Mass., assignor to General Electric Company, a corporation of New York Application July 20, 1940, Serial No. 346,585

2 Claims.

The present invention relates to hydraulic control mechanism for moving a valve or like element to be controlled between two fixed positions. The invention is of particular significance in connection with extraction and mixed pressure type elasticfiuid turbines including a valved conduit connected to an intermediate stage and a mechanism for moving the valve in such conduit from fully open towards closed position upon the occurrence of certain operating conditions. In an extraction turbine, for example, it is desirable to close or disconnect the extraction conduit upon shut-down of the turbine in order to prevent backflow of elastic fluid through the extraction conduit.

One object of my invention is to provide an improved construction and arrangement of hydraulic control mechanisms in which the number of levers and springs is reduced to a minimum.

Another object of my invention is to provide an improved, hydraulically actuated 3-way valve.

For a consideration of what I believe to be novel and my invention, attention is directed to the following description and the claims appended thereto in connection with the accompanying drawing.

In the drawing Fig. 1 illustrates a hydraulic control mechanism supplied to an extraction turbine and embodying my invention; and Fig. 2 shows the mechanism of Fig. 1 in a difierent operating position.

The arrangement comprises an elastic fluid extraction type turbine 9 having a shaft and a valved inlet conduit II and an extraction conduit l2 connected to an intermediate stage of the turbine to conduct elastic fluid from such stage to a consumer such as a heating plant. Upon shut-down of the turbine 9, especially in the case of emergency when the inlet of the turbine is suddenly disconnected from the source of elastic fluid supply, it is desirable also to disconnect the extraction conduit l2 in order to prevent backfiow of elastic fluid therein, that is, flow of fluid from the consumer to the turbine. This is accomplished by the provision of a known type swing valve l3 supported on the inner wall of the conduit [2 by a fulcrum 14.

According to my invention I provide an improved construction and arrangement of hydraulic control mechanism for automatically closing the valve l3 upon the occurrence of a certain turbine operating condition. In the present instance I have shown a mechanism for automatically closing the valve I3 as the turbine speed reaches a predetermined high value. The control Lil) mechanism comprises a hydraulic motor having an operating cylinder IS with a. piston l6 movably disposed therein and biased on one side by an operating fluid such as oil under pressure against a compression spring I! on the opposite side of the piston. The piston has a stem l8 pivoted to one end of a lever l9 which has an intermediate point supported on the fulcrum 20 .and another end pivoted to a lever or actuat ing rod 2| for moving the valve I3. In Fig. 1 the piston i6 is shown in the right-hand end position holding the fulcrumed lever IS in one end position and permitting the valve l3 to swing towards open position by the action of the flow of fluid through the conduit l2. In Fig. 2 the piston I6 is shown in its left-hand end position in which it holds the lever l 9 in the opposite end position than above and causes closing of the valve I3. The means for moving the piston [6 from one end position to the other end position to effect closing of the valve l3 comprises a hydraulic system with a primary valve 22 and a secondary valve 23.

The primary valve 22 is a 3-way valve of known construction including a cylinder 24 having an inlet port 25, a fluid pressure supply port 26 and a drain port 21. A movable valve member in the form of two valve heads 28 and 29 secured to a stem 30 is disposed in the cylinder 24 to control the flow of fluid therethrough. The movable valve member is biased by a spring 3| towards a trigger 32 having two notches 33 and 34. The trigger is supported on a fulcrum 35 and normally held in engagement with the upper end portion of the stem 30 by a compression spring 36 engaging a finger 31 of the trigger. The finger 31 is cooperatively associated with a bolt type emergency governor of known construction including a fiyweight 38 disposed within a recess of the turbine shaft Hi. If during operation the turbine speed rises beyond a certain value the fiyweight 38 is forced outward by centrifugal action towards the finger 31 of the trigger and thereby causes at a certain speed disengagement between the trigger and the valve stem 30, thus permitting the latter to move upward from its engagement with the notch 33 of the trigger into engagement with the notch 34 as shown in Fig. 2.

InFig. 1 the movable valve member is positioned to connect the supply port 25 with the fluid pressure port 26, at the same time closing the drain port 21, whereas in Fig. 2 the pressure port 26 is connected to the drain port 21 and the supply port 25 is disconnected, covered by 48 and horizontal bores 49 and 50.

the lower valve head 28. The supply port is connected to a source of fluid under pressure by means including a conduit 39.

The secondary valve 23which broadly con stitutes a pilot three-way valve for controlling the hydraulic motor l5, I8 is connected to the primary valve, more specifically to the pressure port 26 thereof by a pipe and to the source of fluid under pressure, in the present instance to the conduit 39, by a pipe 41. The secondary valve 23 comprises a casing 42 forming a lower cylinder 43 of large diameter and an upper cylinder 44 of small diameter. A differential piston 45 is disposed in the cylinders and has a shoulder 46 which in the position oi! Fig. 1 engages a shoulder formed by-the casing, thus limiting the upward movement of the piston. The upper or small diameter portion of the piston 45 has three bores forming channels, a central or axial bore 41, the upper end of which is closed by a plug In the position of the piston shown in Fig. 1 the bores form a channel connecting a first or inlet port 5| with a second or fluid pressure supply port 52, thus permitting the supply of fluid under pressure to a the operating cylinder I5 from the conduit 39 through the pipe 4|, the inlet port ii, the channel 49, 41, 50 and a flanged conduit 53 connecting the secondary valve 23 to the cylinder l5. The lower end of the casing 42 is connected to the pipe 40 whereby the differential piston is held in its upper position, as shown in Fig. 1 by the fluid pressure exerted on the lower end of the piston, the active area of the piston being proportional to the difference of the squares of the diameters of the large and small diameter pistons.

During emergency condition the primary valve '22 is moved from the position shown in Fig. 1

to that of Fig. 2 in which, as pointed out above. the port 26 is connected to the drain port 21. This permits the draining of fluid from the lower portion of the casing 42, thereby causing downward movement of the differential piston from the position shown in Fig. 1 into that of Fig. 2 by the action of fluid pressure on the upper portion of the large diameter piston and also by gravity of the piston itself. In its lower position the differential piston disconnects the ports iii and 52 and opens a third or drain port 54 formed by the upper end of the casing 42, thereby permitting draining of fluid from the operating cylinder [5 through the ports 52 and 54.

From the inoperative position of Fig. 2, the control mechanism may be manually readjusted into operating position by moving the stem 30 of the primary valve downward until its upper end portion engages the lower notch 33 of the trigger. In this position the supply port 26 of the primary valve is again connected to the inlet port 25, thus permitting the flow of operating fluid to the lower end of the casing 42 of the secondary valve 23 and thereby causing upward movement of the differential piston into the position shown in Fig. 1 and thus establishing connection of the operating cylinder with the source oi iluid under pressure. Thus the resetting of the secondary valve is accomplished hydraulically. This valve has only one movable part, namely, the differential piston and is otherwise free from stems. levers, springs and like elements. Broadly, the secondary valve constitutes a three-way valve which in one position connects a first port with a second port and in another position disconnects the first and second ports and connects the second port with a third port.

The secondary valve 23 also constitutes a safety valve in that its position is automatically reversed upon failure of the oil pressure from the supply conduit 38. Loss of oil pressure in the conduit 39 reduces the oil pressure on both sides of the piston 45 permitting the piston 45 s to drop to its lower end position (Fig. 2) by the action of gravity. This causes closing of the port 50 and opening of the port 54, permitting the piston IE or the hydraulic motor to move into its leIt-hand position by the action of the spring 11 and resulting in closing or the valve l3 in the extraction conduit I2.

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

1. A valve comprising a casing having a lower large diameter bore, an upper small diameter bore, a first port near the upper end of the large bore and another port near the lower end of the large bore, a second port and a third port communicating with the small bore, a differential piston in the bores and having passages to connect in one position the second port to the first port and in another position to connect the second port to the third port, and means to limit upward movement of the large diameter part of the diiferential piston to a point below the connection of the first port with the large bore.

2. A valve comprising a casing having a lower large diameter bore and an upper small diameter bore, a differential piston having a large diameter part slidably disposed in the large diameter bore and a small diameter part slidably disposed in the small diameter bore, an intermediate portion of the small diameter piston part forming a. shoulder in cooperative relation with the lower end of the small diameter bore to limit upward movement of the piston, the casing having ports respectively communicating with the lower and upper end of the large diameter bore and two other ports communicating with the small diameter bore, the differential piston having a channel for connecting one of the first mentioned ports with one or the Other ports in the upper end position of the piston and the small diameter bore permitting communication between the other ports in the lower end position only of the piston.

CHARLES H. DAVIS.

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