US2653578A - Positioner for fluid operated motors - Google Patents

Description

1 Sept. 29, 1953 Q B, MOORE 2,653,578

POSITIONER FOR FLUID OPERATED MOTORS Filed Sept. 8, 1949 2 Sheets-Sheet 1 ATTORNEY p 29, 1953 c. B. MOORE 2,653,578

POSITIONER FOR FLUID OPERATED MOTORS Filed Sept. 8, 1949 2 Sheets-Sheet 2 26 III/III;

1 I ,62 ag POSITIONER ATTORNEY Patented Sept. 29, 1953 UNITED STATES PATENT OFFICE POSITIONER FOR FLUID OPERATED MOTORS and Robert Buhner Application September 8, 1949, Serial No. 114,541

Claims.

This invention relates to positioners and more particularly to apparatus for providing accurate positioning of a fluid motor of the type employed with motor operated valves and in other applications.

It is the principal object of the present invention to provide a positioner which will be accurate in its operation with adequate sensitivity and speed.

It is a further object of the present invention to provide a positioner which may be directly built into the diaphragm chamber of a motor operated valve.

It is a further object of the present invention to provide a positioner having an improved arrangement of range spring, pressure responsive element, and pilot valve.

It is a further object of the present invention to provide a positioner having a range spring supported directly by the diaphragm of the pressure responsive motor.

It is a further object of the present invention to provide a positioner in which the control elements are mounted directly on the casing of the motor diaphragm of the fluid operated motor.

It is a further object of the present invention to provide a positioner having a controlling diaphragm and in which the pressure effective on the fluid operated motor is cancelled out.

It is a further object of the present invention to provide a positioner in which the throttling range may be controlled by variation in diaphragm sizes in the control mechanism.

It is a further object of the present invention to provide a positioner with provisions for a stabilizing action.

It is a further object of the present invention to provide a positioner having an improved bypass valve arrangement.

It is a further object of the present invention to provide a positioner having a bypass which will permit of removing the indicating gages from the circuit without interference with the operation of the motor.

Other objects and advantageous features of the invention will be apparent from the specification and claims.

The nature and characteristic features of the invention will be more readily understood from the following description, taken in connection with the accompanying drawings forming part hereof, in which:

Figure 1 is a top plan view of a positioner in accordance with the present invention;

Fig. 2 is a vertical sectional view taken approximately on line 2-2 of Fi 1;

Fig. 3 is a horiozntal sectional view, partly diagrammatic, taken approximately on the line 33 of Fig. 2 and showing the bypass valve in one position;

Fig. 3A is a fragmentary view similar to Fig. 3 showing the bypass valve in another position;

Fig. 4 is a vertical sectional View, partly diagrammatic, taken approximately on the line 44 of Fig. 3; and

Fig. 5 is a fragmentary vertical sectional view taken approximately on the line 55 of Fig. 2.

It should, of course, be understood that the description and drawings herein are illustrative merely, and that various modifications and changes may be made in the structure disclosed without departing from the spirit of the invention.

Like numerals refer to like parts throughout the several views.

Referring now more particularly to the drawings, in which a preferred embodiment of the invention is illustrated, upper and lower sections I 0 and I I of a diaphragm motor casing are shown with a motor diaphragm I2 interposed therebetween in the usual manner. The diaphragm I 2 has a stem I3 connected thereto for movement therewith and the stem I3 is connected to a valve plug (not shown) or other controlling element to be positioned.

The lower casing section I I has a downwardly extending portion I 4 with a shoulder I5 at the lower end thereof for engagement by one end of a diaphragm return compression spring IS. The other end of the spring I6 is in engagement with the under side of the motor diaphragm I 2.

The upper casing section It] has an upper end wall I? on which a bypass valve housing I8 is secured. Above the housing I8, diaphragm housing sections I9 and 20 and an upper housing 2| are secured.

Within the interior of the upper casing section I0 and the housing I8, diaphragm connectors are provided which include a range determining compression spring 22 in engagement with the motor diaphragm I2 and with a spring abutment 23 carried on a connector 24. The connector 24 is in turn in abutting relation to a diaphragm assembly hereinafter described. The connector 24 extends on opposite sides of a sealing diaphragm 89 which centers it and the seat or abutment 23 for the spring 22 and permits removal of the parts above the housing l8 without loss of fluid while the motor diaphragm i2 is in opera tion.

The diaphragm assembly preferably includes a 3 compound diaphragm of the type shown in the prior application of Charles H. Thompson, for Pneumatic Control Apparatus, Serial No. 21,835, filed April 19, 1948, interposed between thebypass housing l8 and the housing section 19, and having a supply connection 25a extending between the separated diaphragms. An diaphragm 26 is interposed between the housing section l9 and housing section 20. The diaphragm 26 is of different and preferably larger eifective area than the diaphragm 25. An upper diaphragm 21 is interposed between the housing section 20 and the upper housing section 2|, and preferably has the same effective area as the diaphragm 25. The diaphragms 25, 26 and 21 are preferably connected together for simultaneousmovement by a connector 28 and provide chambers 29, 30, 3| and 32 to which reference will be made. The chamber 3| is vented to the atmosphere through a port 33.

The upper face of the diaphragm 21 has one end of a zero adjusting compression spring 35- in engagement therewith, the other end of the spring 35 being in engagement with a spring abutment 36, the position of which is adjustable by means of an adjusting screw 31 sealed against fluid leakage by a packing ring 34, carried in the upper housing 2|.

Within the upper housing 2| a pilot valve is provided which includes a valve rod 38 hav-- ing a valve ball 39 carried thereon and an upper stem section 40. A compression spring 5| mounted on the upper stem section 40 is in engagement with the ball 39 and with an interior abutment in a closure plug 4|.

The closure plug 4| may also have mounted thereon a cover 42 held' in removable engagement by screw 43 for enclosing the upper end of the adjusting screw 31.

The valve ball 39 is adapted to seat under certain conditions on a valve seat 45' formed in a sleeve 46 secured in the upper housing 2| and along which the abutment member 36 is guided in its adjustment. The lower end of the valve rod 38 is preferably provided with a seating portion 41 for seating engagement in a valve seating member 48 connected to and movable with the diaphragm connector 28. The valve rod 38 preferably has a flattened face 49 on one side thereof (see Fig. 4) for providing a continuous flow of a limited quantity of fluid, for purposes to be explained. The valve seatin member 48 is provided with passageways 50 in communication with the chamber 3| between.

the diaphragm 26 and the diaphragm 21.

The bypass housing section with a fluid connection. which isadapted. to be. connected by a connector 56- to a suitable source of fluid under pressure, such. as pressure regulated and filtered air. The housing section H! is also provided with a fluid. connection 51 which is adapted to be connected by a fluid connection 58 to the control or instrument pressure which is intended to determine the positioning of the motor diaphragm 2 and rod I3.

Within a tapered bore in the housing section N a bypass valve plug 60 is provided, held in position by a spring 6| and with an externally disposed operating head 62 and indicating stop finger 63 (see Fig. 5). The valve plug 69 is movable between stops 52a and 621) from a position in which the diaphragm assembly is effective, indicated on Fig. 5 as Positioner, to a position for bypassing the diaphragm assembly, indicated on Fig. 5 as Bypass.

intermediate I6 is provided.

The valve plug 60 is provided with a passageway 64 for communication, at the Positioner setting, with the supply connection 55 and with passageways 65 extending through the housing sections |8, I9, 20 and 2| to a valve chamber 66 in which the valve ball 39 is located. The passageway 25a extends to and communicates with the passageway 65 for supplying fluid between the diaphragms of the compound diaphragm 25.

A branch connection 61 in the upper housing 2|' and in communication with the passageways 65 provides for the mounting in the housing 2| of an indicating pressure gage 68 for indicating the magnitude of the supply pressure.

The valve plug 60 is also provided with a passageway 10 for communication, at the Positioner setting, with the control or instrument pressure connection 51 and with passageways 1| which extend through the housing sections [8 and I9 to the chamber 30 wherein this control pressure is efiective.

A branch connection 12 provides for the mounting in the housing 2| of an indicating pressure gage 13 for indicating the magnitude of the control pressure.

The valve plug 60 is also provided with a passageway 14 for establishing communication, at the Positioner setting, between the chamber 32 and the space above the motor diaphragm l2 through passageways 15 which extend through the housing sections I9, 20 and 2| and passageways 16 which extend through the housing section l8. The passageway 15 is preferably restricted and for this purpose a restricted section 150. may be employed. A branch 15b connects to the chamber 29. A branch connection 11 in the housing 2| in communication with the passageways 16 provides for the mounting of an indicating pressure gage 18 for indicating the magnitude of the fluid pressure applied against the motor diaphragm l2.

The valve plug 60 is also provided with a passageway 19 connected to the passageway 10 for establishing communication at the Bypass setting between the fluid connection 5'! and the passageways 16, the passageway 14 in this position connecting the passageways 65 and 1|.

The space at the inner end of the valve plug 60 is vented to the atmosphere through a vent passageway 8 I.

The mode of operation will now be pointed out.

The conditions with the bypass valve plug 69 in the Positioner setting will be taken up first.

Fluid under pressure, such as air from a regulated source and at a predetermined pressure is supplied to the fluid supply connection 58 and is effective through the passageway 64 in the plug 60,. the passageways 65 and in the chamber 66. The pressure of the fluid supplied is indicated on the gage 68.

Fluid is admitted to the chamber 32 in accordance with the positioning of the valve ball 39 with respect to the seat 45. The fluid in the chamber 32 is effective on the upper side of the diaphragm 21 and is further exhausted to the atmosphere through the action of the seating portion 41 on the stem 38 with respect to the seating member 48. The discharge to the atmosphere takes place through the passageways 50, the chamber 3| and the vent port 33.

The pressure effective in the chamber 32 is also effective on the under side of compound diaphragm 25 in the chamber 29 through re- (a stricted passageway a, passageways 15 and branch passageway 15b, and is also effective in the space above the motor diaphragm I2, from the passageways 15 through the passageway '14 in the valve plug 60 and passageways it.

The pressure applied in the space above the motor diaphragm i2 is also available at the indicating gage l3.

The instrument or control pressure is efl'ective through the connections 58 and 51, and passageway 1| to the chamber 38 and is available at the indicating gage 13. Since the diaphragm 26 has a larger eilective area than the diaphragm the net effective of pressure applied in the chamber is in an upward direction. Upon an increase in the control pressure the diaphragm assembly because of the upward force exerted thereon will be moved upwardly, thereby moving the seating member 48 closer to the seating portion ll and reducing the discharge and moving the valve ball 39 further from its seat 45 thus increasing the pressure efiective in the chamber 32 and therefrom in the space above the motor diaphragm I2.

The increase in pressure on the motor diaphragm l2 moves the same downwardly and decreases the force exerted in the spring 22 so that the upward force exerted by the spring 22 on the diaphragm assembly is also reduced. The action will be terminated when the decrease in force from the spring 22 equals the increase in force caused by the change in the control or instrument pressure.

The action upon a decrease in the instrument or control pressure will be the reverse of that just described with the fluid being exhausted past the valve member A1.

The condition with the bypass valve plug 60 in the Bypass setting will now be described,

The instrument or control pressure is effective through the connections 58 and 51 and through the passageways l9 and 14 and down through passageways 16 to the space above the motor diaphragm I2. The air supply will be cut off by the positioning of the passageway 64, and by the positioning of the passageways 10 and 14 access of fluid to the passageways H and 65 will also be cut off. The passageways 65 and H are then connected together by the passageway 14 so that any air trapped in the chamber 30 will be bled off through the passageway 33. The three indicating gages 68, I3 and 78 will be disconnected from their sources of pressure and may be removed for checking and cleaning and in this position there will be no pressure supplied above the casing I8, so that the entire superstructure may be removed for cleaning and servicing.

The flat portion 59 of the tapered end 4'! prevents complete closing of the exhaust port at this location at any time. When the positioner is in equilibrium the valve seating portion 49 will be in engagement with the seat above the passageways 59 but a bleed will occur at the flat portion s9 and the valve ball 39 will be a short distance from its seat to make up the fluid discharged past the flat portion 49. The positioner wil1 move to equilibrium rapidly without any detent or dead spot which might occur if the supply port and exhaust port were sealed.

It is preferred to provide a restricted passageway, such as the section 75a, between the chamber 32 and the chamber 29 below the diaphragm 25. The diaphragms 25 and 21 have the same effective areas so that when there is fluid flow in a direction to increase the valve pressure there will be a difierential in the pressure applied on the diaphragms 25 and 21 in a direction to force the diaphragm assembly downward. This force opposes that effective in the chamber 30 but diminishes to zero at equilibrium and provides a stabilizing action which keeps the motor diaphragm l2 from overshooting. Upon a decrease of fluid flow the converse will occur.

If the upper diaphragm 21 were larger than the diaphragm 25 then at equilibrium, after flow through the restricted passageway 15a has ceased and the pressures on these diaphragms had become equal, the forces on the diaphragm assembly would be unequal because of the dilference in eifective areas. The direction of the resultant force would oppose the direction of the force exerted by the instrument or control air in the chamber 3!! and therefore a larger pressure change in the chamber 30 would be required to produce the same net change in position as compared with that required when the areas are equal.

It will be noted that a frictionless coupling is provided between the diaphragm assembly and the motor diaphragm I2, the range spring 22 engaging respectively with the diaphragm l2 and the connector 24 which is in engagament with the diaphragm 25. The pressure in the space above the motor diaphragm l2, with which the chamber 29 is in communication, is effective upwardly on the diaphragm assembly but at equilibrium is cancelled out by the pressure effective on the same area and in the opposite direction in the chamber 32 against the diaphragm 21.

The coaxia1 arrangement of pilot valve, diaphragm assembly and range spring permits of a compact arrangement for mounting axially with the motor diaphragm although other and noncoaxia1 mountings could be employed.

I claim:

1. In a positioner for a movable member in an expansible chamber, a plurality of spaced pressure responsive members separated to provide a plurality of chambers and connected together for simultaneous movement, a resilient connector between said spaced members and said movable member, a connection to a source of pressure fluid, a pilot valve coaxially mounted with respect to said spaced members, said pilot valve having an upper seat in communication with said connection and a lower exhaust seat, a plunger member movable with respect to said seats and positioned by said pressure responsive members, means for continuously delivering fluid from one side of one of said seats to the other side thereof when said plunger member is in closing relation to said seat, a fluid connection for applying the pres. are fluid from said pilot valve against said movable member, and a connection from a source of variable control pressure to one of the chambers for applying a pressure therein for positioning said plunger.

2. In a positioner for a movable member in an expansible chamber, a connection to a variable control pressure fluid, a connection to a regulated supply of pressure fluid, means including a pilot valve for delivering actuating pressure fluid to said movable member, indicating means for indicating the pressure of at least one of said fluids, and a bypass valve having members including passageways for establishing communication between said expansible chamber and said pilot valve in one position, said members cutting oh the pressure fluids to said 7 indicating means in another position and said bypass valve having passageways for delivery of the control pressure fluid to said movable membar in said other position.

3. In a positioner for movable member in an expansible chamber, a connection to a variable control pressure fluid, a connection to a regulated supply of pressure fluid, means including a pilot valve for delivering actuating pressure fluid to said movable member, indicating means for indicating the pressure of said control pressure fluid, said supply pressure fluid and said actuating pressure fluid, and a bypass valve having members including passageways for establishing communication between said expansible chamber and said pilot valve in one position, said members cutting off the pressure fluids to a plurality of said indicating means in another position and said bypass valve having passageways for deliv-- cry of the control pressure fluid to said movable member in said other position.

4. In a positioner for a movable member in an expansible chamber, a plurality of spaced pressure responsive members separated toprovide a plurality of pressure fluid chambers and connected together for simultaneous movement, said chambers including. balancing and compensating chambers efiective in opposed directions to each other, and a control pressure chamber, a. resilient connector between said spaced members and said movable member, a connection to a source of pressure fluid, a pilot valve coaxially mounted with respect to said spaced members and controlled by the positioning of said spaced members, a fluid connection for applying the pressure fluid from said pilot valve in said balancing chamber, a connection from a source of variable control pressure to the control pressure chamber for applying a pressure therein for actuating said valve, and fluid connections from the expanslble chamber to the balancing chamber and to the compensating chamber, the connection to the compensating chamber including a predetermined restricted passageway.

5. In a positioner for a movable member in an expansible chamber, a plurality of spaced pressure responsive members separated to provide a plurality of pressure fluid chambers and connected together for simultaneous movement, a resilient connector between said spaced members and said movable member, a connection to a source of pressure fluid, a pilot valve coaxially mounted with respect to said spaced members, said pilot valve having an upper seat in communication with said connection and a lower exhaust seat, a plunger member movable with respect to said seats and positioned by said pressure responsive members, means for continuously delivering fluid from one side of one of said seats to the other side thereof when said plunger is in closing relation to said seat, fluid connections for applying the pressure fluid from said pilot valve against opposing face portions of said movable member and in said expansible chamber, one of said last mentioned connections including a restricted passageway, and a connection from a source of variable control pressure to one of the chambers for applying a pressure therein for positioning said plunger.

COLEMAN B. MOORE.

References Cited in. the flle of this patent UNITED STATES PATENTS Number Name Date 2,264,262 Erbguth Nov. 25, 1941 2,285,540 Stein et al June 9, 1942 2,382,941 Moore Aug. 14, 1945 2,411,748 Kelley Nov. 26, 1946 2,432,705 Williams Dec. 16, 1947 2,543,120 McLeod, Jr. et al. Feb. 27, 1951

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