US2829857A

US2829857A - Pneumatic trip valves

Info

Publication number: US2829857A
Application number: US529184A
Authority: US
Inventors: Ray S Williams
Original assignee: Hagan Chemicals and Controls Inc
Current assignee: Hagan Chemicals and Controls Inc
Priority date: 1955-08-18
Filing date: 1955-08-18
Publication date: 1958-04-08
Anticipated expiration: 1975-04-08

Description

April s, 1958 a SIGNAL INPUT R, s. WILLIAMS PNEUMATIC TRIP VALVES Filed Aug. 18. 1955 INVENTOR. RAY 5. WILLIAMS BY W W I AzfyS.

United States Patent 9 PNEUMATIC TRIP VALVES Ray S. Williams, Orrville, Ohio, assignor to Hagan Chemicals & Controls, Inc, a corporation of Pennsylvania This invention relates to pneumatic trip valves of the type in which a valve having on and oil positions is held in one of those positions so long as a signal pressure on the diaphragm of the valve is above a predetermined value, held in the other of said positions when the signal pressure'is below said predetermined value, and remains in said other position until reset.

Anobject of this invention is to provide a trip valve that embodies a main diaphragm and a main valve operated thereby having an on position and an off position, the valve being urged towards one of those positions by a spring or the like, and to the other of its positions by a diaphragm which is responsive to an input signal pressure; and to provide an auxiliary diaphragm and an exhaust trip valve associated therewith for exhausting the input signal pressure when that pressure falls below a predetermined minimum value whereby the main valve will be actuated immediately to its other position and remain in that position until the auxiliary trip valve has been manually closed thereby resetting the main valve.

.Another object of the invention is to provide a valve of. the type set forth in the preceding object which is provided with a main valve having an on*position and an off or exhaust position, the valve being held in its on position so long as the input signal pressure is above a predetermined minimum value and which im- =mediately is actuated to its exhaust position when the in put signal pressure falls below said predetermined minimum value.

A still further object of the invention is to provide a valve as set forth in the preceding objects in which the auxiliary valve is provided with means whereby the minimum input signalpressure at which the main valve is actuated to its exhaust position, may be adjusted.

The foregoing and other objects and advantages of the invention will be apparent to those of ordinary skill in the art to which the-invention pertains from the following description taken in conjunction with the accompanying drawings.

In the drawings: t

Figure 1 is a view in vertical section of a valve arranged and constructed in accordance with an embodiment of the invention; and I Fig. 2 is a view in section showing a modified form of main valve thatmay be embodied in the valve of Fig. i.

In Fig. l of the drawings a valve embodying a fornr of the invention is illustrated that comprises a main diaphragm and a main valve assembly A and an auxiliary minimum signal pressure, er ihausts the signal pressure Patented Apr. 8, 1958 ice to atmosphere, thereby causing the main valve to be immediately actuated to its off or pressure supply dump position.

The main valve may be used to control the supply of operating oil at the required pressure to a steam turbine governor or other mechanism so long as the signal pres sureis above the minimum value and to automatically shut off the supply by diverting the oil back to the oil supply tank for the oil pressure supply pumps, when the signal pressure falls below the set value. The valve of Fig. 1 is provided with means whereby the main valve can not be operated until the auxiliary valve has been manually closed and the signal pressure has been re stored to a value above the minimum.

The main diaphragm valve assembly A comprises a main diaphragm 2, specifically a bellows, and a main valve 2'. Diaphragm 2 is disposed within a cylindrical housing 3 having an annular flange 4 at its upper end. The flange 4 is secured to housing 3 by welding, for example, to provide a pressure tight joint. A cap 5 is mounted on and secured to the flange 4 as shown, a gasket 6 being employed to provide a pressure tight joint.

The auxiliary diaphragm and valve assembly B includes an auxiliary diaphragm 7, specifically illustrated as a bellows, and a valve 7. The lower end of the bellows 7 may be secured by Welding, brazing, or in any other suitable manner, to the upper face of the cap 5 as shown. A port 8 in cap 5 places the interior of the auxiliary diaphragm 7 in communication with a char her 9 formed by the diaphragm 2, the cylinder 3, the cap 5 and a valve body It? at the lower end of cylinder 3.

The auxiliary valve '7 comprises an exhaust valve member 11 having an exhaust port 12 that terminates in a valve seat 13 at its upper end. The valve member 11 is provided with an annular flange M to which the upper end of the diaphragm 7 is secured as by welding or in any other suitable manner. The interior of the valve member 11 is provided with a depending annular flange 17 for engaging the top of cap 5 and thereby limiting the amount the diaphragm 7 can be compressed. The exhaust port 12 is controlled by a movable valve mem ber 18 adapted to seat on seat 13 and close the exhaust port 12. The valve member 18 is provided with a reduced portion 19 at its'upper end that passes through a bushing 20 in a plate 2i. The plate 21 is supported by posts 22 (only one of which is shown) that are secured to the cap 5 at their lower ends. As shown, screws 23 pass through the plate 21 and into the upper ends of the posts to hold the plate 21 in place. The space between the cap plate ll and the cap 5 may be enclosed by a cylindrical housing 24.

As shown in Fig. l, upward movement of the valve member 18 is limited by a shoulder 25 that abuts the inner end of the bushing 20. The lower portion of the valve 18 is provided with a shoulder 26 that serves as a stop for a collar 27 to retain 'a spring 28.

The bellows 7 and its valve member 11 are urged in a direction to unseat the exhaust port seat 13 from the valve 18. The means illustrated comprises a lever 30 having an aperture 31 therein through which the portion 11 of the valve extends as shown. One end of lever 30 is secured to a fulcrum or hinge spring 32 that is anchored to a lug 33 secured to the cap 5 by a screw 34. The free end of the lever 39 is urged upwardly by a lightspring 35 the strength of which is just sutficient to urge the lever 30 upwardly.

The lever 30 is provided with an adjustable spring 37- the upper and lower ends of which are retained by

retainers

38 and 39. The retainer 38 may be urged downwardly to adjust the compression ,force in spring 37 by means of an adjustable screw 40 threaded through the plate 21. The inner end of the screw engages a ball 41 housed in a socket 42 in the upper end of the retainer 38.

The upper end of the bellows 2 is secured as by welding to a thrust plate 44 and thelower end is joined at 45 to a plate 46 by a weld or other suitable means. Plate 46 is secured by screws 47 as shown to body 10. The upper face of the thrust plate 44 is provided with upwardly projecting lug members 50 that limit the upward travel thereof.

The underside of the thrust plate 44 is provided with a cylindrical member 51, the lower end of which limits the downward travel of the plate 44 under the compression of the signal pressure input to the chamber 9. The bellows 2 is urged upwardly against the input pressure by a compression spring 52, the upper end of which is retained in a flanged cup member 52'.

The main valve 2' comprises the body 10 having a valve bushing 54 located in a bore 55 in the body. The bushing has a flange 56 for receiving the lower end of spring 52. The downward travel of diaphragm 2 is limited when the lower end of cylinder 51 strikes flange 56. A valve plug 60 operates in bushing 54, the upper end of which is provided with a socket 61 that receives the lower end of a stem or link 61' which, as shown, is provided with a spherical member or ball 62. The upper end of the socket 61 is threaded to accommodate a retainer bushing 63. Between the inner end of the retainer bushing 63 and the ball 62 is a spring 64 that provides a flexible coupling between the link 61 and the plug 60.

The plug 60 controls an exhaust or drain, port 67 that has communication with a supply port 68 through a valve port 69 in the bushing 54. The port 68 is provided with an inlet fitting 70 that supplies oil, for example, at the required pressure to the governor mechanism of a turbine. The supply to the governor mechanism of the turbine may be taken off the port 68 through a fitting 72 or it may be taken off directly from the supply pipe 73.

When the valve plug 60 is in the position shown, the oil supply is dumped, so to speak, through the exhaust port 67 which leads to a reservoir from which supply pumps (not shown) deliver the oil at the proper pressure to the supply pipe 73. The valve plug dumps the supply pressure to the controlled mechanism when the signal pressure is below the minimum set value.

When the plug is in its lowermost position, that is, in the position where the port 69 is closed, full pressure is supplied to the mechanism requiring the pressure.

The tension of spring 52 is such that a minimum input signal pressure is required to move the valve plug 61} to its on position, that is, the position in which the port 69 is closed. Therefore, it follows that if the pressure supplied to chamber 9 is below that value, the plug will move upwardly and open the supply to drain or exhaust. However in order to obtain a quick trip action in the event the signal input pressure to chamber 9 falls below a predetermined value, it will be observed that the auxiliary diaphragm 7 will contract under the influence of the spring 37 until its exhaust seat is disengaged from the valve member 18. At that time, the input signal pressure is exhausted to atmosphere through the exhaust port 12, thereby quickly dropping the input signal pressure on the bellows 2 and eflecting a quick movement of the plug 60 to its dump or trip position. a

As the signal input pressure decreases, it will be observed that the valve member 11 moves downwardly through the aperture in the lever 30 but because of the elongating action of the spring 28, valve 18 cannot move downwardly, therefore, valve member 18 is kept off exhaust seat 13. Since the valve member 18 is kept away from the exhaust seat 13 once that valve has been opened, it follows that the plug valve 60 cannot be returned to its on position until the input signal pressure has been has been closed. To provide for that closing, the portion 19 of the valve 18 that passes through the bushing 20, is pushed downwardly to the position where valve 18 engages and closes the exhaust port seat 13. As soon as that exhaust port is closed, the pressure in chamber 9 will rise to the minimum value or above, and again move the valve 60 to its on position.

By adjusting the compression spring 37 as for example, by increasing it, it will be apparent that the diaphragm 7 will uncover exhaust port 12 at a higher minimum value of signal input pressure. Similarly, if the tension in the spring 37 is decreased, the exhaust port 12 will be uncovered at a lower value of minimum input signalpressure. Thus, it is possible to so adjust the auxiliary valve 11 that the trip point of the main valve 60 can be controlled over a relatively wide range.

In Fig. 2 a modified form of main valve is illustrated which can be substituted for the valve plug 60 of Fig. l and its body. The main valve 75 illustrated in Fig. 2 is designed to control the supply of operating air pressure to a sending port 76 that leads to apparatus to be controlled. As shown, the valve 75 is provided with a body '77 having an inlet port 78 provided with a supply pipe fitting 79 which is connected to a source of supply of compressed air at substantially constant pressure. The supply port is provided with a seat 80 that is controlled by a valve 81. Valve 81 is provided with a stem 82 having at its upper end a socket 83 for receiving the ball 62 of the stem 61. The stem 82 is urged by a spring 84 in a direction to seat the valve 81 on the seat 80.

So long as the signal input pressure to chamber 9 is above the predetermined minimum value, valve 81 will be held in its open position, but as soon as the input signal pressure trip point is reached, that is, the point where the exhaust port 12 is connected to exhaust, the valve 81 will be seated on the seat 80 and pressure to the supply port 76 is cut ofi.

Having thus described the invention, it will be apparent to those of ordinary skill in the art to which the invention pertains, that various modifications and changes may be made in the illustrated embodiments without departing from either the spirit or the scope of the invention.

Therefore, what is claimed as new and desired to be secured by Letters Patent is:

l. A pneumatic trip valve comprising a signal input pressure responsive main diaphragm, an on and elf valve actuated thereby, the on and off valve being held fin one of said positions by the main diaphragm when the signal pressure is above a predetermined minimum value, means urging said main diaphragm in a direction to position the on and oif valve in another of said positions an auxiliary diaphragm responsive to the pressure input signal and an exhaust valve member having a port communicating with the interior of said auxiliary diaphragm and with the signal input pressure, the exhaust valve member being actuated by said auxiliary diaphragm, means urging said auxiliary diaphragm and its exhaust valve member with a predetermined force towards open position, a valve member for closing the port in said diaphram exhaust'valve member the valve being maintained closed by the auxiliary diaphragm so long as the signal input pressure is above said predetermined minimum value, means urging said auxiliary diaphragm exhaust valve member to a position to exhaust the input signal pressure from the main and auxiliary diaphragms when the signal pressure falls below said predetermined minimum value and thereby causing the on and off valve to be actuated to the position in which it is normally urged, means for holding said auxiliary valve member open after the input signal pressure has dropped below said predetermined minimum value, and means for manually actuating said valve member to a position to close the exhaust port in the auxiliary diaphragm valve member to reset the on and off valve to the position in which it 0 is held by said main diaphragm when the input signal pressure is above the predetermined minimum value.

2. A trip valve as in claim 1 in which the on and off valve has an inlet port, an outlet always in communication with the inlet port and an exhaust port, and a plug valve for controlling the exhaust port, the plug being connected to the input signal pressure responsive diaphragm, the plug being urged to a position in which the exhaust port is uncovered, the input signal pressure when above said minimum value holding the valve plug in position to close the exhaust port.

3. A trip valve as in claim 1 in which means are provided for adjusting the force which holds the auxiliary diaphragm valve closed whereby the minimum pressure at which the plug valve is actuated from one to the other 6 phragm and the other end of which is provided with an exhaust port having a seat, means are provided for holding the same away from said seat when said auxiliary valve is open, and that a lever having a biasing spring is provided for urging the auxiliary bellows and its exhaust port and seat away from said movable valve member against the force of the input signal pressure on said auxiliary bellows, the lever and biasing spring actuating said auxiliary valve to open position and holding it open While the input signal pressure is below said minimum value.

5. A trip valve as in claim 4 in which the spring for said lever is provided with means for so adjusting its tension that the value of the minimum input signal pressure required to open said auxiliary valve can be preset.

References Cited in the file of this patent UNITED STATES PATENTS 1,716,244 Sager June 4, 1929