US2363595A

US2363595A - Condition responsive device

Info

Publication number: US2363595A
Application number: US377112A
Authority: US
Inventors: Frederick D Joesting
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1941-02-03
Filing date: 1941-02-03
Publication date: 1944-11-28
Anticipated expiration: 1961-11-28

Description

O 1944? F. D. JOESTING' CONDITION RESPONSIVE DEVICE Filed Feb, s, 1941 2 sheets-sheet 1 w -n l3 an I 3 Fig.3

- IN\ IENTOR .Irzizrick D. Hauling M, 1/

ATTORNEY Nov. 28, 1944.

F. D. JOESTING CONDITION RESPONSIVE DEVICE Filed Feb. 5, 1941 2 Sheets-Sheet 2- 1* mum. m

I III ATTORNEY Patented Nov.t28 ,.1944- I a CONDITION RESPONSIVE nnvrcr.

Frederick D. Joesting', Chicago, Ill; assignor' to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn, a corporation of Delaware Application February a, 1941, Serlal No. 377,112

(Cl. ass-a6) 8 Claims.

. The present invention relates to the structure of a control instrument for use with air conditioning equipment and is particularly directed to an instrument; adapted to vary the pressure of 'a control fluid in accordance with variations in a condition such as temperature, pressure or humidity. l

The invention has as one of its objects the provision of a control instrument in which both the control point and the operating differential may be adjusted to the desired values.

Another object of the invention is to provide an instrument the control point of which may be determined by aseparate condition responsive instrument.

Another object is to provide an instrument utilizing a rod and tube thermostatic element or any other condition responsive element of a relatively non-resilient type for operating a control valve which must be capable of assuming a predetermined position at all values of the condition within the operating. range of the instrument.

Another object is to provide an operating differential adjustment for such an instrument, the

setting of which may be changed with substantially no effect on the control point.

Another object is to provide a condition responsive device in which the pressure of the fluid being controlled acts to assist the condition responsive element in positioning the control valve.

A further object is to provide a condition responsive device which may be changed readily from "direct acting to reverse acting.

Further objects of the invention will be apparent from the specification and from the drawings, in which Figure 1 is a sectionalized-view of a rod and tube actuated pneumatic control incorporating certain features of the invention,

Figure 2 is a front elevation of the instrument shown in Figure 1 and having the cover removed, Figure 3 is a sectional view similar to Figure 2, taken on line 3-3 of Figure 1,

Figure 4 is a sectional view of another embodi-* ment of theinvention. the type known in the art trol,

Figure 5 is a sectional elevation taken substantially on line 55 of Figure 4, and

Figure 6 is a sectional view taken substantially on line i6 of Figure 4.

Figure 7 showsthe valve unit arrangement of the device of Figures 4, 5 and 6-when the control is set up to separate "reverse acting.

This instrumentis of as, a "submaster" con- The instrument shown in Figures 1 to 3 of the drawings is or the type known in the art as a master control and is adapted to vary the air pressure in a branch air line for the purpose of varying thecontrol point of a submaster control. The device employs a rod and tube thermostatic element which operates a three way valve through a system of levers and a spring is incorporated in the linkage in order that the valve mayassume its intermediate position at various positions of the thermostatic element.

Referring to Figures 1 the instrument is provided with a base 10 to which is secured a tube II and a. rod l2 of a Brod and tube thermostatic element. The base It) is provided with a screw-threaded portion M by means of which the instrument may be mounted on a. duct, such as used in air conditioning systems or in a water pipe, tank or the like. The rod and tube element is positioned on the inside of the duct, pipe or tank while the remainder of the device extends outside. Suitably secured to the front part of the base In is a frame IE on which the various lever hereinafter to be described, are pivoted. An adjusting knob l1 extends beyond the frame I B and is provided with a pointer l8 which cooperates with suitable indicia on the front surface 01 the frame l6 for indicating the control point of the instrument. The adjusting knob I! at its inner end is screwthreaded internally and cooperates with screwthreads on the outer end of the rod I12 so that rotation of the knob I1 changes the length of the rod and tube element.

A collar 2|] is carriedby a shoulder on-the inner end of the adjusting knob I! in order to transmit movements of the thermostatic element to a primary lever 22 which is pivoted in the irame Hi on a pin 23. The collar 2|! is provided with a pair of knife-edges which engage V- shaped notches in the lever 22. Since the tube ll of the thermostatic element has a higher coeflicient of expansion than the rod l2, as the temperature increases the rod I2 will be moved to the right as seen in Figure 1 which will cause the effective primary lever 22 to rotate counterclockwise about t to3 of the drawings,

function of the spring 28 will be more fully pointed out hereinafter.

A three-way vave unit 30 is secured to the lower port'on ofthe base ID. This valve unit 30 is similar to the valve unit described in detail n my co-pending application, Serial No. 350,003, filed August 2, 1940, now Patent No. 2,326,226 dated August 10, 1943. Briefly, the unit includes a pressure inlet valve which is opened as the actuating rod 3| is depressed, and an exhaust valve which is opened as the actuating rod 3| is movedvoutwardly or to the left as seen in Figure 1 and a diaphragm 32 which is subject on its under side to branch line pressure. Under the diaphragm 32 is a ball 33 which serves to position'a valve operating lever 34. The three-way valve is not shown but may be of any of the usual types. It is preterably of the type described in my above mentioned co-pending application. Between the position in which the inlet valve is opened and thermostat located inside a space being cooled during the summer months in such. away that the indoor temperature will be maintained at a temperature less than outdoor temperature by an amount which increases as the outdoor temperature increases. Hence, a relatively wide differential must be providedin this instrument. As shown in Figure 2, the angle member 42 cooperates with suitable indicia indicating. the

the position inwhich the exhaust valve is opened is .a neutral position in which branch line pressure is maintained at a constant value. In operation the, unit will be in neutral position with both inlet and exhaust valves closed except when the temperature .is changing and a change in branch line pressure is called for.

A secondary lever 35 is pivoted in the frame IS on a pin 36 and at its lower end engages the valve actuating rod 3|. An auxiliary lever 38 is pivoted in the frame IS on a pair of pivots 39. It'will be noted that the levers 35 and 3B are disposed in generally parallel relationship. An abutment is provided between

levers

35 and 38 in the form of a screw 4| which extends between the two levers but which is secured to an angle member 42 which is adjustable lengthwise on the auxiliary. lever 38 by loosening a clamping screw 44 which secures the angle member 42 to the lever 38. The auxiliary lever 38 is provided with a longitudinal slot 43 in which the angle 'member 42 and the screws 4| and 44 may be moved. The outer end of the angle member 42 extends through an opening in the frame l6 and cooperates with suitable indicia thereon for. indicating. the operating difierentialor throttling range of the instrument. It will be noted that longitudinal adjustment of the abutment between the two levers may be made without altering the length of the screw 4|. As illustrated in Figure 1, the screw 4| has been adjusted so that the

levers

35 and 38 are not exactly parallel but so that the two levers are slightly closer together at their upper extremi ties. Therefore, as the ab'utment between the two levers is moved upwardly, the lever 33 will rotate slightly in a counter-clockwise direction if it be assumed that the lever 35 remains stationary. The purpose of this arrangement will be described hereinafter.

The upper ends of the primary lever 22 and the auxiliary levers 38 are connected by means of a tension spring 46 which engages a knifeedge portion of the lever 22 and is held in the lever 38 by means of an adjusting screw 41..

Therefore, it will be. seen that as the primary lever 22 is moved in a clockwise direction the spring 46 will be be transmitted through the auxiliary lever 38 and the secondarylever 35 to depress the valve actuating rod 3| and open the inlet valve.

A suitable cover 48 is provided to enclose the lever and valve mechanisms.

tensioned, and this force will As previously mentioned, the instrument of throttling range in degrees of temperature.

The device as described isof the reverseacting type which means that as the temperature increases the pressure in the branch line will be decreased. As mentioned previously the spring 28 exerts enough force in a clockwise direction to hold the lever 22 in engagement with the knife-edges on the collar 20 at all times. This spring acts in opposition to and in stronger than the spring 46, enabling the spring 46 to produce 15 pounds per square inch pressure in the branch line when the knife-edges on the collar 20 are exerting no force on the lever 22.

The throttling range of the instrument is selected by movement of the angle member 42. the outwardly extending portion of this member indicating the number of degrees through which the temperature must vary in order to vary the branch line pressure from one extreme to the other. If the range of branch line pressure is from three to thirteen poundsand the instru,

ment set up as shown in Figure 2, the branch line pressure will be thirteen pounds when the temperature is 50 and three pounds when the temperature is since the, differential adjustment is set at 45.

It will be noted that as the abutment between the

levers

35 and 38 is moved upwardly the changes in force transmitted by the spring 46 to the valve actuating rod 3| will result in smaller changes of force at the valve than when the abutment between these levers is moved to lower positions. Therefore, greater changes intemperature will be required to change the force transmitted to the valve when the abutment is moved to the upper positions than when it is moved to lower positions. Hence, the operating differential or throttling range is greater when the abutment between the

levers

35 and 38 is moved upwardly. Changes in temperature at the rod and tube element serve to position theupper end of the primary lever 22 and therefore change the force transmitted by the spring 46 'to the auxiliary lever 38, and this force will depend on the temperature alone for any given setting of the control point and throttling range adjustments since'the secondary lever 35 always balances out at the same position. 'As previously pointed out, when the lever 35 is move the right, the inlet valve of the "valve unit3'05is opened admitting pressure beneath the diaphragm 32 and when this pressure has beenbuilt up to exactly counter bala'nce the force,

exhaust valve to open position and the pressure under the diaphragm will be exhausted until the force due to the branch line pressure under the diaphragm exactly equals the force applied by the secondary lever 35. It will be seen therefore that the spring 46 comprises a resilient member between the valve actuating rod, which always balances out at the same position, and the thermostatic element whose position depends on temperature. Changes in temperature result in changes in branch line pressure without any change in position of the auxiliary lever 35.

As previously pointed out, the distance between .the lower ends of

levers

35 and 38 is greater than the distance between the upper ends of these levers. By distance between the lovers .is meant the distance between the surfaces of these levers engaged by the abutment screw 4| and the angle member 42. It will be seen therefore that as the screw 4| is moved upwardly, the tension of spring 46 will increase, assuming, of course, that the primary lever 22 and the secondary lever 35 remain stationary. This arrangement is provided so-that as the operating differential of the instrument is changed there will be substantially no change in the control point of the device as indicated by the pointer |8.' If the

levers

35 and 38 were exactly parallel and the diiferential adjustment moved to a position giving a high differential, a given force applied to the auxiliary lever- 38 would result in a smaller force at the valve unit and the branch line pressure would be varied. As illustratedin Figure 1, moving the differential adjustment upwardly will'result in an increased tension of spring 46 which will substantially counteract the effect in the decrease in leverage. 7 Although this arrangement employ- ,ing two straight levers enables the. differential to .be adjusted with very little change in the con-.

.trol point, it would be necessary to provide one of these levers with a curved surface in order to exactly. compensate for changes in leverage;

' It should be pointed out that a given angle between the

levers

35 and 38 will enable the control 'point to remain constant as the differential adjustment is varied only at ione place in the control range and that branch line pressure will be varied by movements of the differential adjustment if the temperature is at any value other than the control point selected.

The instrument as shown in Figure 1 and as reviously described is a reverse acting instrumerit. The instrument may be changed to operate direct acting "by removing the pin 23 by means of which the primary lever 22 is pivoted in the frame l6 from the'position shown above .gthe knife edges and reinserting it in the frame "and the lever 22 in the hole 49 on the opposite side of the rod element. Further, the screw 26,; nut 21, and compression spring 28 are re- "j' moved asgthey are not necessary in the direct acting" instrument since the spring 46 now tends. to rotatethe lever 22 about the pivot 49 to engage the knife edges. In this case it will be seen that increases in temperature will result in the primary lever 22 being rotated in a clockwise direction which will tension the spring 46 and move theauxili'ary lever 38 and secondary lever 35 to'the right, which will open the pressure supply valve within the valve unit 30 to increase the branch line pressure. Otherwise the device operates the same when set up to operate "direct acting as previously described in connection with the (reverse acting instrument.

the lower end of the primary lever 65.

which a master control responds.

The instrument includes a base 55 which is provided with a screw-threaded portion 56 which may serve to mount the instrument on the wall of a duct or in a water pipe, tank or the like. As

in the case of the master control, heretofore described, the temperature sensitive element comprises a rod and tube member having a high expansion tub 58 secured to the base 55 and a low expansion rod 59 which is enclosed within the tube 56 for the greater part of its length. An adjusting knob 6| has a portion 62 which is threaded internally to cooperate with threads on the outer end of the rod 59. A collar 64 abuts the portion 62 and is provided with a pair of knife edges which engage suitable V-shaped notches in a primary lever 65. A pair of knife edges 6'|- are mounted on the base 55 and engage The knob 6| is provided with a pointer 61 which cooperates with suitable indicia (not shown) for indicating the control point of the instrument. A frame 10 is suitably mounted on the base 55 and extends beneath the knob 6| and the pointer 61 and may be provided with the indicia above referred to. An auxiliary lever 12 is mounted at its lower end in the frame III at the pivots 13 which comprise openings in through which portions of the lever 12 extend. A tension spring15 extends between the primary lever 65 and the auxiliary lever 12 and is secured in a knife edge to the lever 65 and secured to the auxiliary lever 12 by means of the screw 16.

A valve unit 18 is mounted on the base 55 and is similar to the valve unit described in connection with Figures 1 to 3. This valve unit includes an actuating rod 19, a diaphragm 8|, and a ball 82 which serves to transmit movements of the diaphragm 8| to a valve positioning lever 80. In-

ternal portions of the valve which are not shown include a pressure inlet valve and an exhaust valve which may be opened selectively by positioning the actuating rod 19 and the diaphragm 8|.

The valve actuating rod 19 includes an extension 83 which engages a secondary lever 85 which ispivoted in the-frame 10 by means of the pivot 88 and is further pivoted by means of a pivot 88 in a supporting partition 89 which extends between the base 55 and the frame 10. An abutment screw 9| extends between the auxiliary lever 12 and the secondary lever 85 and serves the purpose both of transmitting the force exerted by the lever 12 to the lever 85 and of providing an adjustable diiferential for the instrument. For this purpose the screw 9| may be moved in the slot 93 which is shown in Figure 5 as being a diagonal slot cut in,

moved upwardly it approaches the axis on which the secondary lever 85 is pivoted.

The operation of thedevice as thus far described is as follows: Of an increase in temperature the rod 59 will move the primary lever 65 i in a clockwise direction to increase the tension on the spring 15. This will move the auxiliary lever 12 slightly in a clockwise direction as seen in Figure'4. Referring now to Figure 6, the abutment the frame 18.

screw 9| will be moved downwardly which will result in a counter-clockwise rotation 03 the secondary lever 85 to move the valve actuating rod 19 downwardly. This will result in opening the pressure inlet valve to increase the branch line pressure and increase the upward force on the diaphragm 8| until there is suihcient pressure beneath the diaphragm to return the valve to tral position and reclose the inlet valve. Likewise, on a decrease in the spring I5 will be reduced so that the auxiliary lever 12 will be moved slightly in a counterclockwise direction as seen in Figure 4, and the secondary lever will be moved in a clockwise direction as seen in Figure 6. This will result in the valve actuating rod 19 being raised and the exhaust valve being opened to reduce the pressure in the branch line beneath the diaphragm 8| until the exhaust valve is again closed.

It will be seen that the operating differential of the device will be at a maximum when the screw 9| is moved to its uppermost position as seen in Figure 5 since in this position the greatest change in the tension of spring 15 will be required to pro,- duce a given change in force on the valve actuating rod I9. Similarly, the operating differential willbe decreased as the screw 9| is moved downwardly so that the spring I5 has a greater leverage onthe secondary lever 85. It may be pointed out here that the levers I2 and 85 may be so formed and the separation of the levers 'I2 and 85 as determined by the effective length of the screw 9| which serves as an abutment between thes two levers may be so selected that as screw 9| is moved in the slot 93 to adjust the differential of the device, the tension of the spring 15 will be varied to eliminate any change in the control point. This construction was heretofore described in connection with the device of Fi s. 1, 2 and 3.

As previously noted, this instrument is of the sub-master type and for that purpose it is provided with a bellows 96 which is secured at one of its ends to the base 55 and at its opposite end operates against a compression spring 91 which is supported by a bracket 98 which in turn is suitably secured to the frame 10. A lever I is pivoted at IIlI in the bracket 98. A rod I03 extends between the bellows 9B and the lever I09 for the purpose of transmitting the force exerted by the bellows to the lever. A screw I is mounted in a slot I06 in the auxiliary lever 12. This temperature, the tension of edges I I4 are moved farther toward the right, as seen in Figure 6, the boosting efiect is lessened.

screw serves as an adjustable abutment between the auxiliary lever 12 and the lever I00. As the screw I05 is moved downwardly, the force due to a given pressure inthe bellows 96 tending to rotate the auxiliary lever 12 in a counter-clockwise direction is reduced.

The bellows 96 is supplied with pressure from the branch line of a fmaster control, and as the pressure is increased in this bellows the branch line pressure as determined by the valve unit 18 will be reduced and the control point of the instrument will be raised when the various parts of the instrument are arranged as shown in the drawing and as heretofore described.

thirteen pounds (as is commonly the range of The amount of change in control point for a variation in pressure within the bellows 96 from three to this device.

'I I0 subject on its lower side to branch line pressure, which is the same pressure as that existing under the diaphragm ill in the valve unit 18. The diaphragm III] is adapted to exert a force upwardly through a rod II2 on a booster lever H3. The booster lever is pivoted by means of knife edges H4 in the frame 10 and the supporting partition 89. The knife'edges II4 abut the frame 10 and the partition89 on the upper edges of slots H6. The knife edges ||4 are carried by a plate II! which is adjustable lengthwise oi the booster lever 3- when the screw H9 is loosened. Since the same pressure is exerted beneath the diaphragm H0 in the booster unit I09 the lever II3 werepivoted midway of its length,

the boosting efiect would be 100% and substantially no force would be required to move the valve actuating rod I9 downwardly. As the knife The force required to be exerted downwardly on the valve actuating rod 19 to balance a pressure of 10 pounds per square inch beneath the diaphragm 8| may in this way be reduced from 18 ounces to approximately 5' ounces. Thus, the force which must be transmitted by the rod and I tube element through the various levers is meterially reduced. In this way the control may be rendered much more accurate in its operation, and at the same time smaller and less expensive parts may be used. Likewise, the standard valve unit utilized in various other instruments such as the master control of Figures 1 to 3 may be employed as the valve unit I8 01 As pointed outbefore, the present device is direct acting as described because increases in temperature at the rod and tube will/operate through the various levers to increase the branch line pressure. In order to change the device to a reverse acting instrument, the screw 9| extending between the auxiliary lever 12 and the secondary lever must be removed from the diagonal slot 93 and inserted in the diagonal slot I2I. With the screw 9| in this slot, downward movements of the auxiliary lever 12 as seen in Figure 6, will cause a clockwise rotation of the secondary lever 85. Furthermore, the valve actuating rod I9 must be provided with an extension I23, as shown in Figure 'l, by means of which the secondary lever 85 may exert an upward force on the actuating rod I9. A compression spring I24 operatesagainst an abutment nut I25 located on the rod I I2 of the booster unit I09. This spring is adjusted, so that it exerts a force on the valve actuating rod 19 and the booster lever I|3 which will cause a branch line pressure of 15 pounds per square inch to be maintained when no force is exerted on the actuating rod 19 through the secondary lever 85.

In this case as the temperature increases the primary lever 65 will be moved in a clockwise direction and the tension of spring I5 will be increased which will move the auxiliary lever I2 slightly in a clockwise direction. As seen in Figure 6 (assuming the screw 9| to be in the slot I2I) the secondary lever 85 would then be rotated in a clockwise direction and the resulting upward force on thevalve actuating rod will open the exhaust valve to reduce the pressur beneath the diaphragm 8| and in the branch line. In this case when thetemperature increases, the secondary lever 85 is moved to oppose the spring I 24 which acts on the booster lever.

The spring I24 is incorporated in the instrument, both when it is direct acting and when it is "reverse acting. As described above, when the instrument is "reverse acting, the spring I24 supplies the force necessary to maintain maximum branch line pressure. When the instrument is set up to be direct acting the abutment nut I25 is adjusted so thatthe spring I24 exerts only a slight upward force which will slightly preload the various parts.

As seen in Figure 6, the base 55 is provided with three openings I21, I28 and I29 to which pipe lines may be connected. The three lines would include a pressure supply line, a branch line leading to the equipment being controlled and the control line leading to the "master control. The supply line will lead only to the main valve unit I8, the branch line will lead to both the valve 18 and the booster unit I09, while the "master" control line will lead to the bellows 96.

In certain claims the condition responsive element is described as having a relatively high spring rate. By this phrase I mean that the element is relatively stiff and unyielding. The rod and tube'element of the illustrative embodiments is such a condition responsive element. In this type of element changes in the value of the condition result in actual movement of some portion of the element 'rather thanmerely in a building up or lessening of force within the element.

While only two embodiments of the present invention have been shown and described, it is to be understood that the various features of novelty may be readily applied to other devices and I am therefore to be limited only by the scope of the appended claims.

I claim as my invention: 1. In a temperature responsive device for controlling the pressure in a. control line, a rod and tube thermostatic element, a valve unit including a flexible wall subject on one side. to control'line pressure and also including means for positioning a three way valve positioned by said flexible wall for controlling the pressure in the control line, a pivoted primary lever positioned by said thermostatic element, a pivoted secondary lever movable with said flexible wall, an auxiliary lever pivoted at a point spaced from the pivot of said and which are mounted to rotate about different axes, said connecting means also including a device operatively connecting the overlapping portions of said levers, follow up means for returning said control device to its neutral position by balancing the force exerted by said resilient means, said connecting device being adjustable along said levers to adjust the leverage through which force is transmitted from said condition responsive device to said control device for adjusting the differential of operation, said overlapping portions of the levers being slightly out, of parallel relation when said control device is in neutral position so that adjustment of said connecting device will vary the tension of said resilient means to compensate for the change in the said leverage and the control point of said apparatus will not be changed upon adjustment of the differential thereof. V

3. Control apparatus of the character described comprising in combination, a condition responsive device having a relatively high spring rate and including a. portion whose position is deter posed generally parallel with respect to said secondary lever a spring between said primary and auxiliary levers, and a connection between said secondary and auxiliary levers adjustable lengthwise thereof for adjusting the temperature differential necessary to vary the control line pressure through its operating range.

2. Control apparatus of the character described comprising in combination, a condition responsive device having a relatively high spring rate and including a portion whose position is determined by the value of the condition, a control device having a neutral position in which it exerts no control function and which is movable in one direction from its neutral position to exert a control function and in the other direction from neutral to exert an opposite control function, connecting means by which said condition responsive levers which at least partially overlap each other lap each other and which tion responsive member mined by the value of the condition, control valve means for controlling the pressure in a control line, said valve means having a neutral position in which the control line pressure remains the same and which is movable in one direction to increase the control line pressure and in the opposite direction to decrease the control line pressure, connecting means by which said condition responsive device moves said control valve means, said connecting means including resilient means, and a pair of levers which at least partially overare mounted to rotate aboutdifierent axes, said connecting means including a connecting device operatively connecting the overlapping portions of said levers, follow up means responsive to the control linepressure for returning said valve means to neutral position by balancing the force exerted by said resilient means, said adjusting device being adjustable along said levers to adjust the leverage through which force is transmitted from said condition responsive device to said valve means for adjusting the differential of operationthereof, said overlapping portions of the levers being slightly out of parallel relation when said control device is in neutral position so that adjustment of said connecting device said resilient means in the said leverage and the control point of said apparatus will not be changed upon adjustment of the differential thereof.

4. In a condition responsive device for controlling the pressure in a control line, a condition responsive member having a relatively high spring rate, an element, the position of which is determined by the value of the condition through response of said member thereto; valve means for determining the pressure in the control line, a lever pivoted on an axis at one angle for positioning said valve means, an auxiliary lever pivoted on an axis at a. different angle than said first angle, resilient means connecting said element and said auxiliary lever, and an abutment between said levers positionable along'a line at an angle intermediate said one angle and said different angle for adjusting the operation differential of the device.

5. In a condition responsive device for controlling the pressure in a control line, a condihaving a relatively high spring rate, .an element, the position of which is determined by said member as it responds to the will vary the tension of to compensate for the change from a source independent of value of the condition, valve means for determining the pressure in the control line, .a valve actuating lever for positioning said valve means, an intermediate lever pivoted on an axis at right angles to the pivot for said valve actuating lever, resilient means connecting said element and said intermediate lever, an abutment between said intermediate lever and said valve actuating lever positionable along a path that approaches one of said pivots as it recedes from the other for adjusting the operating differential of the device, and an expansible chamber subject to control line pressure tending to rotate said valve actuating lever.

6. In a condition responsive device for controlling the pressure in a control line, a condition responsive member, an element, the position of which is determined by said condition responsive member, valve means for determining the pressure in the control line, a pivoted valve actuating lever for positioning said valve means, an intermediate lever disposed generally parallel with respect to said valve actuating lever having a pivot spaced lengthwise of said intermediate lever from .thepivot for said valve actuating lever, resilient means connecting said element and said intermediate lever, a connection between said levers, a first expansible chamber subject tocontrol line pressure for positioning said valve actuating lever and a second expansible chamber adapted to be subjected to varying pressures said control line and acting against one of said levers for varying the control point of the device by changes in pressure of said second expansible chamber against said one of said levers.

7. In a condition responsive device trolling the pressure in a control line,

for cona condition responsive member, an element connected therewith, the position of which is determined by the value of the condition affecting said member, a first expansible chamber subject to control line pressure, valve means for controlling the pressure in the control line, means connecting said element with said expansible chamber and said valve means, a lever, and a second expansible chamber subject to said control line pressure and acting through said lever in opposition to said first expansible chamber, the leverage of said lever being less for said second expansible chamber than for said first expansible chamber for thereby reducing the force required by said condition; responsive member to actuate said valve means.

8. In a condition responsive device for controlling the pressure in a control line, a condition responsive member, an element connected therewith, the position of which is determined by the value of the condition affecting said member, a first expansible chamber subject to control line pressure, valve means for controlling the pressure in the control line, means connecting said element with said expansible chamber and said valve means, a lever, and a second expansible chamber subject to said control line pressure and actingthrough said lever in opposition to said first expansible chamber,-'the leverage of said lever being less for said second expansible chamber than for said first expansible chamber thereby reducing the force required by said condition responsive member to actuate said valve means, and means for varying the relative effects of said first and second expansible chambers by changing the leverage relationship thereof with respect to said first and second expansible chambers.

FREDERICK D. JOESTING.