US2016769A - Compensating attachment for pressure controllers - Google Patents

Description

Oct. 8, 1935. v COLBY 2,016,769

' COMPENSATING ATTACHMENT FOR PRESSURE CONTROLLERS Filed May 28, 1932 INvENruR:

M 4? Mg MMWL Patented Oct. 8, 1935 PATENT OFFICE COMPENSATING ATTACHMENT FOB PRESSURE CONTROILERB Harold L. Colby, Milton, Masa, assignor to Eldon MacLeod,

Wostwcod, Masa, Frank A. Morrison, Newton, Masa, Cameron MacLeod Bcrwyn, Pa.,

Leslie Soule, Dedham, Mass., and Sullivan A.

Sargent, Jr

Needham, Masa, trustees, doing business as l'irason Neila'n-Regniatol' Company,

Boston, Mass.

Application May 28', 1932, Serial No. 614,233

' 4 Claims.

This invention relates to control mechanism and particularly to control mechanism having a compensating action and utilizing an independent fluid pressure pilot control. a

5 The invention herein constitutes an improvement on the type of control mechanism disclosed in Annin Patent No. 1,991,309, granted February 12, 1935, and lies in providing a compensating attachment therefor. It has been found by experience that the Pressure controller embodied in Annin Patent No. 1,991,309 is not suitable for all types of installation without mechanical adjustment. In some industrial plants in which the device is installed, for instance, the motor valve may be placed too far away from the pilot control mechanism, or the motor valve may be too large for the fluid capacity, or the piping arrangement of the compressed air to the motor valve may be such as to 'interp'ose a resistance to the to air flow, thereby causing a time lag which the instrument cannot automatically handle. As a consequence in these installations, fluctuations and a hunting action in the control will occur unless extensive adjustment is made.

I have been able to successfully overcome these difllculties by providing'a second Bourdon tube attached to the cleaver arm closing and opening the exhaust port of the pilot control which is actuated by the pressure from the central diaso phragm chamber as the exhaust port isclosed.

The action of this second Bourdon tube is opposite in direction to that of the first Bourdon tube which is actuated by the pressure of the medium being controlled. Thus, as Annins exhaust port 85 is closed and pressure in the central diaphragm chamber I5 is built up, this accumulating pressure operates through my second Bourdon tube to open the port partially. Time lag before the motor valve is operated and the usual over-travel 1 or hunting" action is prevented, because the orig-v inal impulse of the pilot control mechanism is offset or compensated before such over-travel can occur. This compensating action produces a stabilizing condition and renders-this type of control suitable for all types of installation without mechanical adjustment,

Other objects of this invention will appear in the following description and appended claims reference being had to the accompanying drawing formed a part ofthis specification.

. Tne drawing is a front elevation of my control mechanism with the compensating attachment, part of the control mechanism being broken away to show the interior thereof.

i Before explaining in detail the present inven- 'a corresponding link 1| tion, it'is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawing, since the invention .is capable of other embodiments and of being 5 practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. and it is not intended to limit the invention beyond the terms m of. the several claims hereto appended as considered in view of the prior art and the requirements thereof.

The numeral i designates a feed line controlled by a diaphragm motor valve 2, and this motor 15 valve is operable by fluid pressure through a pipe phragms 9, III, II, l2. In this manner, the casing 20 is divided into five chambers l3, l4, l5, l6, and I1. Fluid pressure from an independent pressure system is admitted to the casing through a pipe it, into the chamber l3 controlled by a reducing or supply valve l9 of the diaphragm 9. The 5 chamber i3 communicates with the chamber il in any suitable manner, as by a pipe or duct 20. The diaphragm l2 supports a waste valve 2|, controlling an exhaust 22. The aforesaid pipe I communicates with the chambers l3 and i1 Noro mally, when the diaphragms are at rest, the waste valve I9 is closed and the supply valve 2| .open, cutting off the supply of fluid pressure to the diaphragm motor valve 2 and wasting the pressure in the pipe 3 through the discharge duct ,5 22.

From the pipe l8 extends a pipe 23, which com-' municates through a duct 4 I to the center chamber ii. The lower portion of the duct 4i terminates in an orifice 25, covered by a dial 215, which 0 in turn is provided with a seriesof ports 21, for registration with the orifice of this pipe. On a pivot 28 is mounted a lever 29, terminating at one end in a plate 30, and this plate rests against the surface of the dial 26. The opposite end of 4,5 the lever 29 is connected by a link 3|, to which is attached at its bottom end, a horizontal lever 19 pivotally suspended at its middle from the link 3|. From one end of lever 19 is suspended the link 31a connected to the helical or Bourdon tube 5 32. From the other end of the lever is suspended connecting with the helical or Bourdon tube I2. The Bourdon tube 12 is arranged so as to move oppositely to Bourdon tube 32, and as the flrstBourdon tube 32 acts to move the cleaver arm 29 through'links 3 I a, lever 10 and link 3| in one direction, the second Bourdon tube 12 acts through the same links and lever to move the cleaver arm 29 in the opposite direction.

Bourdon tube 12 is actuated by the air pressure leading to it through pipe 73 from duct 4|. By an alternative arrangement (not shown) air may be fed to the Bourdon tube 12 from the same system but directly from the central. diaphragm chamber I5.

The operation of the device will be obvious from the specification and drawings of Annin Patent No. 1,991,309, to which reference is hereby made. Assuming that the mechanism illustrated' herein is set for maintaining an exact back pressure in the main feed line I, the diaphragms 9, i9, II and I2 are at rest, and diaphragm motor valve 2 is held closed by its spring 34. If back pressure builds up in the main feed line I it passes through pipe 33 to the helical tube 32, tending to unwind the latter and thereby to turn lever 29 as to gradually reduce the size of the exprovided with a compensati haust orifice 25. On the closing of exhaust orifice 25 pressure in diaphragm chamber l5 builds up, forcing waste valve 2| supply valve l9 open, allowing pressure from pipe l8 to enter directly into chamber I3, fiow through pipes 20 and 3 to diaphragm motor valve 2 which opens against the tension of its spring 34 to relieve the back pressure. Then compensation occurs. As pressure in feed line I actuates Bourdon tube 32 to close'the exhaust port 21 by means of the cleaver arm 29, pressure in duct 4| .is built up and fiows to the second Bourdon tube 12 which, acting in an opposite direction, tends to move cleaver arm 29 port 21. By means of this compensating attachment, the. adjustable Rotaport feature, comprising dial 26 and ports 21 varying in size can be eliminated, and one exhaust port substituted, if desired. It will also be Bourdon tube is mentioned herein in the specification, a helical tube or other pressure responsive element can be substituted. t Thus it will be seen that the control mechanism disclosed in Annin Patent No.- 1,991,309 is g action supplied by pressure from the pilot control mechanism. In this way any time lag before the motor valve is operated and the usual over-travel or hunting action, is prevented, because the original impulse of the pilot control system operating the motor valve is ofiset or compensated before such.overtravel can occur.

I claim:

1. Control mechanism of the class described, a

diaphragm motor valve governing the supply of a. medium under control, an air pressure system for operating said motor valve ordinarily exhausting to the atmosphere, an exhaust port through which said pressure system ordinarily exhausts to the atmosphere, a closurearm for closing said exhaust port, a tube responsive to.

the pressure of the medium under control for actuating said closure arm, pilot valve means including independent supply and waste valves governing the supply and waste of pressure in said system, and diaphragm mechanism acted on by said pressure and actuating said supply and waste valves to divert said pressure to operate said motor valve on the closing of said exhaust port by the closure arm, a second tube responsive to the pressure in said pressure system and acting in a acting the movement and port 22 closed and to open slightly the exhaust ply and waste of pressure understood that where direction opposite to the first tube for counterof said closure arm as actuated by the first tube.

2. Control mechanism of the class described, a diaphragm motor valve governing the supply of a medium undercontrol, an air pressure system for operating said motor valve ordinarily exhausting to the atmosphere, an exhaust port through which said pressure system ordinarily exhausts to the atmosphere, a closure arm for closing said exhaust port, a tube responsive to the pressure of the medium under control for actuating said closure arm, pilot valve mechanism including a pair of diaphragms dividing said mechanism into two outer chambers and an inner chamber, a supply valve and a waste valve in said outer chambers governing the supply and waste of pressure in said system, said pressure expanding said inner chamber and actuating said supply and waste valves to divert said pressure to the motor valve for operating the same on the closing of said exhaust port by the closure arm, a second tube responsive to the pressure in said pressure system and acting in a direction opposite to the first tube for counteracting the movement of said closure arm as actuated by the first tube.

3. Control mechanism of the class described, a control valve governing the supply of a medium under control, an independent pressure system for operating said control valve ordinarily exhausted to the atmosphere, 'an exhaust valve governing the exhaust from said system, means responsive to a variable of the medium under control for actuating said exhaust valve, pilot valve mechanism including a pair of diaphragms dividing said mechanism into two outer chambers and an inner chamber, a supply valve and a waste valve in said outer chambers governing the supin said system, said pressure expanding said inner chamber and actuating said supply and waste valves to divert said pressure to the control valve for operating the same onthe closing of said exhaust valve, and means in said pressure system for counteracting the movement of said exhaust valve as actuated by the variable of the medium under control.

4. Control mechanism of the class described, a diaphragm motor valve governing the supply of a medium under control, an air pressure system for operating said motor valve ordinarily exhausting to the atmosphere, an exhaust port through .which said pressure system ordinarily exhausts to the atmosphere, means for adjusting pressure to the motor valve to operate the same on the closing of said exhaust port by said closure arm, a second Bourdon tube responsive to the pressure in said pressure system and acting in a direction opposite to the first tube for counteracting the movement of said closure arm as actuatw by the first tube, including a second lever connected at its ends to said Bourdon tubes and a link connected at one end to said closure arm and 70 at its other end pivotally supporting said second lever intermediate its ends.

HAROID L. COLBY.

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