US3840044A

US3840044A - Fluid pressure system

Info

Publication number: US3840044A
Application number: US00297567A
Authority: US
Inventors: L Harris; B Burrus
Original assignee: Combustion Engineering Inc
Current assignee: INVALCO Inc; Combustion Engineering Inc
Priority date: 1972-10-13
Filing date: 1972-10-13
Publication date: 1974-10-08
Anticipated expiration: 1991-10-08
Also published as: CA984699A

Abstract

A float is arranged responsive to a liquid level and actuates a fluid pressure relay to develop an output fluid pressure which controls the liquid level. Additionally, a second relay is mounted on the first to be actuated by the float to annunciate a predetermined extreme end of the range of level.

Description

United States Patent [19] Harris et al.

[ 1 FLUID PRESSURE SYSTEM [75] Inventors: Lewis K. Harris; Bill S. Burrus,

both of Tulsa, Okla.

[73] Assignee: Combustion Engineering, Inc., New

York, NY.

22 Filed: 0ct.13, 1972 21 App1.No.: 297,567

[52] US. Cl 137/413, 137/85, 137/270, 137/557 [51] Int. Cl. Fl6k 31/34 [58] Field of Search 137/84, 85, 86, 270, 270.5, 137/271, 413, 414, 557

[56] References Cited UNITED STATES PATENTS 3,120,241 2/1964 Parks 137/413 Oct. 8, 1974 3,413,997 12/1968 Taylor ..l37/270X Primary Examiner-William R. Cline Assistant ExaminerDavid R. Matthews Attorney, Agent, or Firm-Arthur L. Wade [5 7] ABSTRACT A float is arranged responsive to a liquid level and actuates a fluid pressure relay to develop an output fluid pressure which controls the liquid level. Additionally, a second relay is mounted on the first to be actuated by the float to annunciate a predetermined extreme end of the range of level.

7 Claims, 4 Drawing Figures PATENTEU 8 74 SHEET. 1 BF 3 xave 0333 inc/1.00 7081 N03 PATENIEU 81974 3.840.044

I SHEU 29F 3 MOVE 0.73;]

A 7ddfl$ 1 FLUID PRESSURE SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to fluid pressure relays responsive to positioned primary elements. More specifically, the invention relates to that type of relay with a control pressure developed internally on a flexible wall and arranged to meet the demand for both snapacting and throttling output modes.

2. Description of the Prior Art The fluid pressure relay has been extensively developed in the prior art. The primary element may be a simple float responding to a liquid level. However, on the other hand, the primary element could take other forms to establish a range of positions which, in turn, are transduced into a range of fluid pressures in the relay. These control pressures actuate valving structure within the relay to develop the output of the relay as a range of fluid pressures.

It is fundamental that these simple fluid pressure relays have a control pressure chamber with a flexible wall with which to transduce the fluid pressures into motion to actuate the valving mechanism of the relay. The more popular means to develop this control fluid pressure is a simple nozzle restricted by a flapper to regulate the chamber pressure.

The flexible wall is usually referred to as a diaphram. The valving mechanism is mechanically connected to this movable element. From this point, the form of the valving mechanism, the number of chambers and the interconnection of the chambers is the subject of continual development in the art. There is a continuous need to simplify these arrangements While retaining flexibility in converting the relay. to provide both a throttling mode and a snap-acting mode.

Finally, the inherent characteristic of the flappernozzle cooperation to develop the control pressure in the relay as an input makes possible the addition of a second fluid pressure relay to coordinate an annuncia- I tion of predetermined positionsof the primary element with the fluid pressure output of the control relay.

SUMMARY OF THE INVENTION Another object of the invention is to provide a second fluid pressure relay arranged to be actuated by the common primary element to annunciate in coordination with the output of the first fluid pressure relay.

The invention contemplates the single diaphram of a fluid pressure relay actuating a valve element comprising two portions. The relay chambers are first connected together, and to a supply fluid pressure and exhaust, in the snap-acting mode so the valve element portions move as a single unit to perform the valving functions to establish the relay output. The chambers are then readily connected to route the exhaust through a passage in the valve element portion connected between the exhaust and the relay output chamber in the throttling mode. This arrangement routing the exhaust through the valve element portion not connected to the diaphram, and valving this exhaust with the valve element portion connected to the diaphram, results in the requirement of but the one diaphram for the relay.

The invention further contemplates an arrangement and form for a fluid pressure relay actuated by a primary element-positioned flapper restricting the control chamber nozzle which can be readily placed adjacent a second nozzle chamber which utilizes the same supply of fluid pressure used by the relay. The primary element is then arranged to actuate the flapper for the second nozzle at predetermined positions of the primary element so that an annunciating fluid pressure signal is generated to indicate a specific condition has been reached which is sensed by the primary element.

It is further contemplated that the relay be provided with a proportional band feature and adjustable dampening for the response of the relay to the primary element.

Other objects, advantages and features of this invention will become apparent to one skilled in the art upon consideration of the written specification, appended claims, and attached drawings, wherein;

FIG. 1 is a sectioned elevation of a level control, including a fluid pressure relay, the assembly embodying the invention and arranged in the throttling mode of re sponse to the float;

FIG. 2 is similar to FIG. 1 but with relay arranged in DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 discloses a fluid pressure relay 1, embodying the invention, responsive to a float 2 as a primary element sensing a liquid level 3 as a variable condition. The float is connected to the relay by a mechanical connection to a flapper 4 which restricts nozzle 5 to determine the value of the control fluid pressure in chamber 6.

Diaphram 7 is a flexible element arranged as a wall of the chamber 6. The variations of control fluid pressure within chamber 6 moves diaphram 7. Connected to the outside of diaphram 7 is the first portion 8 of a valve element.

The output chamber 9 of the relay is valved by portion 8 to the outside of diaphram 7. Supply chamber 10 is valved by second portion 1-] into the output chamber 9. A constant supply of fluid pressure is connected directly to chamber 10. This same supply of fluid pressure is connected to chamber 6 by passageway 10A. A passageway 12 is extended through second valve portion 11 to connect the output chamber 9 to exhaust when the relay functions in a throttling mode. During the throttling mode, passageway 12 is valved by the first valve portion 8.

Manually controlled switch 13 has two positions. In the first position, the outside of diaphram 7 is deadended while the passageway 12 is connected to exhaust. In its second position, the outside of diaphram 7 is connected to exhaust while passageway 12 is deadended. In its first position, the switch 13 places the relay in its throttling mode of operation. In its second position, the switch 13 places the relay in its snapaction mode of operation.

THROTTLING MODE FIG. 1 discloses the relay 1 in its throttling mode, switch 13 positioned to connect passageway 12 to exhaust. Valve portion 8 cooperates with the seat about its end of passageway 12 as dictated by the nozzle pressure on diaphram 7. The very simple arrangement disclosed makes the function of the parts almost obvious. If the throttling by flapper 4 of nozzle 5 causes the chamber 6 pressure to fall, or reduce, the pressure in output chamber moves the diaphram 7 and valve portion 8 away from valve part 11. The pressure in chamber 9 reduces, following the control pressure. An increase in nozzle pressure causes the valve portions 8, 11 to introduce pressure from the supply chamber into output chamber 9. The output pressure follows the control, or nozzle, pressure of chamber 6. The output pressure of chamber 9 is always arranged to regulate valve 14 which influences the liquid level 3.

SNAP-ACTION MODE FIG. 2 discloses the relay 1 in its snap-acting mode, switch 13 positioned to connect the outside of diaphram 7 and chamber 9 to exhaust and dead-end passageway 12. The valve portions 8 and II will move as a unit after this connection is made with switch 13.

Again, cooperation of the disclosed structure is almost obvious. As pressure in control chamber 6 builds, or increases, the force on the unit formed by valve portions 8, 11 will unseat the valve element between supply chamber 10 and output chamber 9. The chamber 9 pressure suddenly rises to the value of the supply pressure through the large seat capacity. When the control pressure falls to the snap valve, the valve portions 8, ll suddenly move as a unit to exhaust chamber 9 and isolate chamber 10.

FEEDBACK Referring to both FIGS. 1 and 2, attention is directed to passgeway l5 connecting chamber 9 with chamber 6. This passageway is controlled by valve 16. In both modes of operation, passageway 15 can be opened to bleed off fluid pressure of chamber 9 to nozzle chamber 6 and modify the output fluid pressure of valve 14.

In the FIG. I throttling mode, the increase in output fluid pressure is conducted back to the nozzle chamber 6. Because the valve 16 restricts the flow in passageway 15, the feedback action always lags behind the output pressure changes developed in chamber 9. However, the differential pressure across diaphram 7 does reduce at the rate set by valve 16, dampening the response of the output fluid pressure to the nozzle chamber pressure. The resulting action is similar to proportional band response.

If the feedback circuit l5, 16 is employed as shown in the FIG. 2 snap-acting mode of the relay, the nozzle pressure would have to increase above the normal snapping pressure to throw the valve portions 8, 11 and increase the output pressure to that of the supply. Correspondingly, to snap the valve portions 8, 11 to exhaust chamber 9, the nozzle chamber pressure must decrease below the normal snapping pressure.

This simple feedback circuit is readily adapted to all forms of an actual reduction to practice of the invention. It is readily available for manual adjustment of the modification it gives to the function of the control in either the throttling or snap-acting mode of operation.

ANN UNCIATION CIRCUIT Both FIG. 1 and FIG. 2 disclose a nozzle chamber 20 mounted on the relay body 1. This chamber is readily connected to the supply chamber 10 by a passage 21, which is a continuation of passageway 10A, and restriction of nozzle 22 by flapper 23 produces an output fluid pressure in conduit 24. Flapper 23 is mounted upon float arm 25 of float 2. Both flappers, connected to float 2 in this manner, restrict flow from their respective nozzles.

In FIG. 1, flapper 23 is maintained in its lower position of extension from float arm 25 by spring 26. Spring 26 is not strong enough to interfere with the normal travel of float arm 25 in throttling nozzle 5 over the normal range of float movement. However, at a predetermined lower level of float 2, flapper 23 is lifted from nozzle 22 to significantly lower the pressure in chamber 20. This signal can be utilized in various ways. In the disclosure, the more obvious usage is indicated as actuating an annunciating structure 27.

In FIG. 2, flapper 4 is arranged to reciprocate in a hole in float arm 25 under the urging of spring 28. Flapper 23 is in a fixed position on arm 25. Normally, spring-loaded flapper 4 throttles nozzle 5 over the regulating range. However, when level 3 rises beyond the normal range of control, flapper 4 comes to rest on nozzle 5 and nozzle 23 approaches nozzle 22 to increase the output of chamber 20 to a predetermined value annunciated by device 27. Spring 28 permits flapper 23 to continue its approach to nozzle 22 for the annunciation by letting flapper 4 slide upward in its hole against the force of spring 28.

The disclosure of FIG. 3 may be regarded as overlapping with that of FIGS. 1 and 2. However, FIG. 3 does disclose specifically how both high and low alarms and the throttling control can all be actuated from a common float arm 30. Throttling flapper 31 and its nozzle 32 has spring 33 urging flapper 31 toward nozzle 32. Low level flapper 34 is mounted on float arm 30 and is urged toward its nozzle 35 by spring 36. Both springs must be sized so their combined force is not great enough to prevent high level flapper 37 being carried close enough to nozzle 38 to effect the annunciation of a predetermined high liquid level.

FIG. 4 discloses a mechanical arrangement with which to achieve an adjustment of the proportional band relationship between the movement of float arm 40 and the change in the control fluid pressure output of chamber 41. The adjustment is achieved by the mechanical arrangement between the float arm 40 and the flapper 42 and nozzle 43.

Flapper 42 is pivoted at 44 to restrict flow from nozzle 43. The point at which float arm 40 contacts flapper 42 determines the relative vertical movement of float arm 40 to that of the flapper 42 restricting the fluid flow from nozzle 43. More specifically, the distance 45 establishes this flapper movement-float arm movement relationship.

The point of contact between arm 40 and flapper 42 is adjustable. First, the point is horizontally adjustable. Thumbscrew 46 is mounted on sliding block 47 and block 47 is slidable within slots 48. Set screws 49 are loosened and block 47-thumbscrew 46 are moved to establish a desired distance 45 from pivot 44. Set screws 49 are then tightened and the ratio between the vertical movements of float arm 40 and flapper 42 is fixed.

If distance 45 is relatively small, a small rise in float arm 40 will cause a rather large change in the output fluid pressure. For example, say the particular small value of distance 45 establishes a proportional band setting of percent. A level rise of 0.5 inch sensed by float arm 40 would cause the fluid pressure output to go from 3 psi to psi. The expected result of such large control action would keep the level to very near a fixed value.

Then, if distance 45 was made relatively large by moving contacting block 47 to the right as viewed in FIG. 4, a proportional band of 90 percent would be readily obtained. This would result in perhaps a 6 inch change in level, giving the 3 psi to 15 psi range of the output fluid pressure. With a proportional band of 90 percent, it would be expected that there would be nearly constant feed rates to the locus of the float.

It is also to be noted that reversal of the relation between fluid pressure output and float arm movement is possible. Block 47 is simply moved to the left, to the left of pivot point 44 as viewed in FIG. 4. The proportional band can then be adjusted as before, except the reaction of the fluid pressure output of 41 will be in the opposite direction to what it was in the first arrangement.

From the foregoing, it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and inherent to the apparatus.

it will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the invention.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted in an illustrative and not in a limiting sense.

The invention, having been described, what is claimed is:

1. A control system, including,

a primary clement positioned by a variable condition,

a first flapper structure connected to the primary element and positioned by the primary element which is positioned by the variable condition,

a first relay controlled by pressure in its nozzle cooperating with the first flapper structure to develop a first fluid pressure relay output,

a means arranged to regulate the variable condition and to be controlled by the fluid pressure output of the first relay,

a second relay mounted adjacent the first relay controlled by pressure in its nozzle cooperating with a flapper structure to develop a second fluid pressure output,

a second flapper structure connected to the primary element and positioned by the primary element to cooperate with the nozzle of the second relay to develop the second fluid pressure output,

a source of fluid pressure for both relays,

and a means connected to the second fluid pressure output to communicate a predetermined value of the variable condition.

2. The control system of claim 1, wherein,

the primary element is a float and the variable condition is liquid level.

3. The level control system of claim 1, in which,

the two relays are mounted upon each other as a single unit connected to the common source of fluid pressure.

4. The level control system of claim 1, in which,

the second flapper structure is connected to the primary element so as to develop values for thesecond control fluid pressure having relationships different from the relationships between the values for first control fluid pressure output and the positions of the primary element.

5. The level control system of claim 1, including,

a switch means in the connection of the first relay and the source of fluid pressure which is adaptable for manual manipulation to convert the relay output from throttling to snap-acting.

6. A fluid pressure relay for use in the control system of claim 1 as the first relay, and including,

a control fluid pressure chamber connected to the nozzle,

a source of fluid pressure connected to the control chamber,

a flexible element arranged as a wall of the control fluid pressure chamber,

a first portion of a valve element connected to the flexible element,

a fluid pressure output chamber valved by the first portion of the valve element to the side of the flexible element outside of the control fluid pressure chamber,

a fluid pressure supply chamber connected to the source of fluid pressure of the control chamber and valved to the output chamber,

a second portion of a valve element arranged to valve fluid pressure of the supply chamber to the output chamber,

a passageway in the second portion of the valve element and controlled by the first portion of the valve element in exhausting fluid pressure from the output chamber,

and a switch means for alternatively connecting exhaust to the passageway and the outside of the flexible element,

whereby the output chamber fluid pressure is given a throttling mode relation to the fluid pressure of the control chamber when the switch means is in its first position and a snap-acting mode relation to the fluid pressure of the control chamber when the switch means is in its second position.

7. A fluid pressure relay for use in the control system of claim 1 as the second relay, and including,

a control fluid pressure chamber connected to its nozzle,

a connection from the source of fluid pressure for the control chamber of the first relay to the control fluid pressure chamber of this second relay,

and a means connected to receive the output fluid pressure of the control chamber of this second relay to manifest a predetermined value of the output fluid pressure.

a: 1: a :k

Claims

1. A controL system, including, a primary element positioned by a variable condition, a first flapper structure connected to the primary element and positioned by the primary element which is positioned by the variable condition, a first relay controlled by pressure in its nozzle cooperating with the first flapper structure to develop a first fluid pressure relay output, a means arranged to regulate the variable condition and to be controlled by the fluid pressure output of the first relay, a second relay mounted adjacent the first relay controlled by pressure in its nozzle cooperating with a flapper structure to develop a second fluid pressure output, a second flapper structure connected to the primary element and positioned by the primary element to cooperate with the nozzle of the second relay to develop the second fluid pressure output, a source of fluid pressure for both relays, and a means connected to the second fluid pressure output to communicate a predetermined value of the variable condition.

2. The control system of claim 1, wherein, the primary element is a float and the variable condition is liquid level.

3. The level control system of claim 1, in which, the two relays are mounted upon each other as a single unit connected to the common source of fluid pressure.

4. The level control system of claim 1, in which, the second flapper structure is connected to the primary element so as to develop values for the second control fluid pressure having relationships different from the relationships between the values for first control fluid pressure output and the positions of the primary element.

5. The level control system of claim 1, including, a switch means in the connection of the first relay and the source of fluid pressure which is adaptable for manual manipulation to convert the relay output from throttling to snap-acting.

6. A fluid pressure relay for use in the control system of claim 1 as the first relay, and including, a control fluid pressure chamber connected to the nozzle, a source of fluid pressure connected to the control chamber, a flexible element arranged as a wall of the control fluid pressure chamber, a first portion of a valve element connected to the flexible element, a fluid pressure output chamber valved by the first portion of the valve element to the side of the flexible element outside of the control fluid pressure chamber, a fluid pressure supply chamber connected to the source of fluid pressure of the control chamber and valved to the output chamber, a second portion of a valve element arranged to valve fluid pressure of the supply chamber to the output chamber, a passageway in the second portion of the valve element and controlled by the first portion of the valve element in exhausting fluid pressure from the output chamber, and a switch means for alternatively connecting exhaust to the passageway and the outside of the flexible element, whereby the output chamber fluid pressure is given a throttling mode relation to the fluid pressure of the control chamber when the switch means is in its first position and a snap-acting mode relation to the fluid pressure of the control chamber when the switch means is in its second position.

7. A fluid pressure relay for use in the control system of claim 1 as the second relay, and including, a control fluid pressure chamber connected to its nozzle, a connection from the source of fluid pressure for the control chamber of the first relay to the control fluid pressure chamber of this second relay, and a means connected to receive the output fluid pressure of the control chamber of this second relay to manifest a predetermined value of the output fluid pressure.