US2415913A - Apparatus for maintaining a condiction of substantially constant value - Google Patents

Description

Feb. 18, 1947. E, SCH DT 2,415,913

APPARATUS FOR MAINTAINING A CONDITION OF SUBSTANTIALLY CONSTANT VALUE Filed Feb. 9, 1944 4Sheets-Sheet l Feb. 18, 1947. E, x. SCHMIDT 2,415,913

APPARATUS FOR MAINTAINING A CONDITION OF SUBSTANTIALLY CONSTANT VALUE Fild Feb. 9, 1944' 4. Sheets-Sheet 2 Feb. 18, 1947. scH T 2,415,913 A APPARATUS FOR MAINTAININGA CONDITION OF SUBSTANTIALLY CONSTANT VALUE Filed Feb. 9, 1944 4 Sheets-Sheet 3 TIM? 1 2, 2 RoTAT|o-s oFcAM 77. l a. Movemnt of 79 when making contact due to conditions shown below. Lift 01 Contact 78 pr'evenfs drop of 79,

thus closing contacts 78 MOVEMENT F79 and 79.

MOVEMENTOF 78 m7 '28 n ao X Ll/ MOVEMENT OF 78 I57 I27 Izo m4 5 hL- I [39 I 130' 1a: :30" I36 5 130 I ,I50 Lever 6! moved //I3I counterclockwise -I to and held ina. I a

I89 [3 given position.

M "Duration 01 contact??? '79 dr'o s to make J 78 drags to break Lever 6| in normal positlon shown in Fig. 1.

Feb. 18, 1947.

E. x. SICHMI'DT APPARATUS FOR MAINTAINING A CONDITION OF SUBSTANTIALLY CONSTANT VALUE Filed Feb. 9, 1944 4 Sheets-Sheet 4 3 RoTAT|oNs 0F CAM 77. I MOVEMENT OF 78 Lever I20 moved by cam H4.

LevewIZO Held in lowered position by a. step on I24.

79 drops to ma Ke 78 drops to br'eaK Duration of con c ac:

Patented Feb. 18, 1947 APPARATUS FOR DIAINTAINING A CONDI- TION OF SUBSTANTIALLY CONSTANT VALUE Edwin K. Schmidt, Nashota, Wis., assignor to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Application February 9, 1944, Serial No. 521,700

12 Claims. 1

This invention relates to apparatus for maintaining a condition of substantially constant value.

An object of the invention is to provide a simplified control apparatus of the aforementioned character.

Another object is to provide novel means for efi'ecting adjustment of the rate of supply of a medium which provides the condition the value of which is controlled.

Another object is to provide novel means for controlling the direction of change in the rate of supply of the medium which supports said condition.

Another object is to provide for use of a ringtype liquid drag in apparatus of the aforementioned character.

Another object is to provide apparatus of the aforementioned character including a plurality of power-driven cams for electric circuit control;

the operating means for one of said cams including a set of planetary gearing, and the operation of said gearing being subject to modification by th action of said liquid drag.

Another and more specific object of the invention is to provide novel apparatus for proportioning and mixing flowing combustible gases whereby the total heating value per unit volume of the mixture thereof is maintained substantially constant.

Other objects and advantages of the invention will h reinafter appear.

The accompanying drawings illustrate certain embodiments of the invention which will now be described, it being understood that the embodiments illustrated are susceptible of modification in respect of certain structural details thereof within the scope of the appended claims.

In the drawings, Figure 1 illustrates schematically and diagrammatically a gas mixing control system having my improved control elements embodied therein; said control system being adapted to maintain substantially constant the total heating value per unit volume of the combustible gaseous mixture provided thereby.

Fig. 2 is a View, partly in vertical section and partly in elevation, of certain of the control elements shown in Fig. 1.

Fig. 3 is a vertical sectional View of the ringtype liquid drag device shown in Figs. 1 and 2.

Fig. 4 is a fragmentary perspective view of a modified form of certain of the elements shown in Fig. 1.

Fig. 5 is a side elevational view of one of the cam members shown in Fig. 1.

Fig. 6 is a similar view of the other cam member shown in Fig. 1, and

Figs. 7 to 11, inclusive, are graphs illustrating the cyclic movements of the contacts controlled by the respective cam members and showing the size of the arc gap provided therebetween under difierent conditions, and the manner in which the duration of engagement of the contacts is modified in each of the devices of Figs. 1 and 4,

a, respectively.

Referring to Figs. 1 to 3, the numeral If] designates a conduit through which a combustible gaseous fluid of relatively high quality or total heating value per unit volume is adapted to flow. It may be assumed that the gaseous fluid flowing in conduit Ill is subject to relatively wide variations both in its volumetric rate of flow and in the quality or total heating value per unit volume thereof. The numeral H designates a conduit through which air or other combustible gaseous fluid of relatively low quality or total heating value per unit volume is adapted to flow. The fluids flowing in conduits I0 and H are adapted to be combined within the relatively larger conduit l2 to provide a flowing combustible gaseous mixture; the total heating value per unit volume of which mixture it is desired to maintain substantially constant.

It is therefore necessary to provide some means for automatically controlling the rate of flow of fluid through one. or the other of the conduits ID and H in order that the quality or total heating value per unit volume of the gaseous mixture flowing in conduit I2 shall be maintained sub stantially constant. For this purpose I have shown a valve l3 of suitable form within conduit H; said valve being movable toward its fully open or its closed position to control the volumetric rate of flow of fluid through conduit ll. It will be apparent to those skilled in the art, that, if desired, the valve [3 might be located within the conduit I!) (to control the volumetric rate of flow of the gaseous fluid of relatively high quality or total heating value per unit volume) instead of the arrangement illustrated.

Operation of valve l3 in one direction or the other selectively is subject to selective energization of the respective windings of a split-field reversible motor I4. Such energization of motor I4 is subject to control by the means hereinafter described.

In accordance with well known practice, a continuous and volumetrically constant sample'of the combustible gaseous mixture in conduit I2 is conducted through pipe 15 to a suitable calorimetric device l 6 which is adapted to continuously ascertain the total heating value per unit volume of such mixture. Calorimeter l5 may be of the character disclosed in Patent No. 1,625,277, granted April 19, 1927, to Horace N. Packard. A calorimeter of the general character shown in said Patent No. 1,625,277 is likewise illustrated at the left-hand side of Fig. 2 of my prior Patent No. 2,002,279, granted May 21, 1935; said calorimeter in Patent No. 2,002,279 being designated by the numeral 520. It is to be understood that the calorimeter l5 shown diagrammatically in Fig. 1 hereof is provided with means, including a galvanometer needle such as shown at l3l in Fig. 3 of said Patent No. 2,002,279, which is operabl in a direction and to a degree corresponding to the direction and degree of departure of the total heating value per unit volume of the gaseous mixture from the value preselected therefor.

Calorimeter it also has means associated with 2 said galvanometer needle (not shown) to provide for power operation of an indicating element, which is designated in Fig. 1 hereof by the numeral ll. Said power-operated means is of the character shown in Fig. 3 of Patent No. 2,002,279; the same being of the general character shown in Leeds Patent No. 965,824, granted July 26, 1910, and in Leeds Patent No. 1,125,699, granted January 19, 1915. Thus said power-operated means is adapted to effect operation of a rod or shaft iii, in Fig. 1 hereof, in a direction and to a degree corresponding to the direction and degree of deflection of the galvanometer needle.

The indicating element or arm H is rigidly attached to shaft l8 adjacent the forward end of the latter, and at a predetermined rotary angle with respect thereto, as by means of a set screw l9 or the like. A suitably calibrated scale is adapted to be mounted in a fixed position with respect to the indicating arm H, whereby the latter is adapted to indicate the instantaneous direction and degree of departure of the total heating value per unit volume of the gaseous mixture from the value preselected therefor.

Thus in Fig. 1 the shaft l8 and arm H are shown in their intermediate or neutral positions (as indicated by the radial alinement of arm ll with the point designated 2! on scale 20; which point may have the proper or desired legend, such as a given predetermined total heating value, associated therewith) to indicate attainment or maintenance of the desired total heating value per unit volume of said mixture.

Also rigidly attached to shaft 55, as by means of a set screw '22, is an arm 23. Arm 23 is preferably arranged for positioning thereof in a vertical plane with respect to the axial center of shaft N3 in the neutral position of the latter, as illustrated. Mounted upon and rotatable with respect to shaft 10 is a toroid or ring-type liquid drag member designated in general by the numeral 24. As shown in Figs. 1 to 3, member 25 comprises an endless hollow or tubular ring.

or annulus 25, which is provided at a given point thereof with a fixed plate 26 (Figs. 2 and 3) having an opening or orifice 21 of predetermined size formed therein. Member 25 has a pair of projections or studs 28 and 29 rigidly attached to the exterior thereof and symmetrically positioned with respect to plate 25, whereby in the absence of liquid within member 25 the latter will be balanced with respect to shaft 18. A pair of like coiled tension springs 30 and 3! each d have one end attached to arm 23, and said springs have their opposite ends attached to the rods 28 and 29, respectively; whereby member 25 is biased to the intermediate or neutral position thereof with respect to arm 25 as illustrated in the neutral position of shaft is.

As shown in Fig. 3 member 25 is preferably half filled with a suitable liquid, such as mercury, designated by the numeral 32; the orifice plate 26 being gradually movable (along with member 25) through the body of liquid 32 in one direction or the other to a given degree from the neutral position thereof best illustrated in Fig. 3 upon prior rotary movement of shaft l3 in a corresponding direction and to such given degree, as hereinafter set forth.

As shown in Fig. 2 the hub portion 33 of member 25 has a bore of greater diameter than shaft 58, and said hub is provided at its opposite ends with peripheral grooves forming races for sets of ball- bearings 35 and 35. The ball-bearings 34 are retained within their race by a member 55 which is rigidly secured to shaft l8, as by means of a set-screw 37!; and the ball-bearings 35 are retained within their race by one end of the hub portion 38 of an arm member 39; said hub portion 33 being rigidly secured to shaft I8, as by means of a set-screw 50.

Arm member 39 preferably extends upwardly in a vertical plane with respect to the axis of shaft H8 in the neutral position of the latter; and said member is provided with an integral hollow bearing portion ll which extends in a direction parallel to the axis of shaft l8. A shaft 42 is rotatably mounted within bearing portion 4|; the forward end of shaft 02 having a relatively small spur gear 53 rigidly and non-rotatably attached thereto in any suitable manner (Figs. 1 and 2), and the rearward end of shaft 52 having a relatively larger spur gear 04 rigidly and non-rotatably attached thereto in a similar manner.

Rigidly secured to the rear face of member 25 in any suitable manner (as by spot-welding or riveting) is a gear segment 25, which is arranged concentrically with respect to the axis of shaft l8, and the teeth of which gear segment preferably extend radially a slight distance beyond the periphery of member 25. Gear 43 is arranged to mesh at all times with segment 45. Gear #34 is arranged below and adapted to mesh at all times with a concave gear segment 45, which is riveted or otherwise rigidly attached to the angularly offset upper ends (see ll, Fig. 2) of the pair of opposed arms 58 and d9 of a Y-shaped integral upward extension 50 of a member the hub portion of which is designated by the numeral 5i. Said hub portion ii is provided with an opening f larger diameter than shaft l8, and the former is provided at its opposite ends with groovesor races to accommodate sets of ballbearings 52 and 53; ball bearings 52 being retained within their race by the adjacent end of hub portion 38; and ball bearings 53 being retained within their race by a member 54 which is rigidly secured to shaft 50, as by means of a set-screw 55.

Preferably formed integrally with and extending downwardly from hub portion M is an inverted substantially T-shaped element 56, the oppositely extending arms 51 and 58 of which have their lower edges arranged in the form of a relatively large arc concentric to the axis ofshaft E8. Th adjacent portions of the lower edges of arms 51 and 56 arecurved upwardly toward each other to provide the downwardly facing concave cam surface 58 (Fig. 1) which is adapted for cooperation with a roller or wheel 58 rotatably supported at the free end of the relatively long arm 6! of a substantially L-shaped lever which is supported by but freely rotatable with respect to the outer end of a shaft 52. Shaft '62 is driven, through suitable speed-reducing gearing .63, by an electric motor 64.

The relatively short arm 65 (Fig. 1) of said L- shaped lever is formed as shown at 66 to provide a bearing for a relatively small spur gear 61. Gear 5! is normally driven by a spur gear 58, of the same size as gear 67, the integral hub 63 of gear 63 being rigidly secured to shaft 62 for rotation thereby, as by means of a set-screw 1e; and gear 6'! meshes with a relatively large internally-toothed gear H to provide for driving of the latter at a predetermined speed which is substantially slower than the speed of rotation of shaft 62. In the particular form of the invention herein illustrated it may be assumed that gear H is provided with three times as many teeth as each of gears 6i and 68, wherefore gear H and cam '56 complete one rotation during each three complete rotations of shaft 52 and cam Tl. Gear 7| has formed integrally therewith a disk portion '52 and a relatively long hub portion 13, the bore of which is of a size to permit rotation of shaft 62 with respect thereto while providing a proper bearing for gear H. A bushing '14 may be attached to the forward end portion of shaft 62, as by means of a set-screw 75, to restrain lever 5! against displacement forwardly of said shaft; and a bushing (not shown) similar to that shown at '54 may be attached to shaft 62 at the rear end of hub portion it to retain gear H in properly assembled position.

l-Iub portion l3 has attached thereto a cam member which is preferably shaped as illustrated. Although I have herein shown cam 16 formed integrally with hub 73, it will be understood by those skilled in the art that such cam may comprise an element formed separately from hub 13 and provided with means for removably and adjustably securing the same to said hub. Cam I6 is adapted to control the position of a downwardly spring-biased contact member '18.

Thus as shown there is associated with cam i6 a rod or plunger 83, having at its lower end the block or foot portion 81 which is adapted to hear at all times against the surface of said. cam. Rod 86 is supported and guided for reciprocating movement thereof by a pair of perforated fixed bracket arms, fragments of which are shown at 82 and 83. Contact 73 is rigidly secured to the upper end of rod 80, as shown; a coiled compression spring being interposed between the lower surface of bracket arm 83 and the upper surface of a nut or other shouldered member 85 adjustably positioned upon said rod through the medium of the threaded portion 55 on the latter. Suitable means (not shown) may be provided for locking nut 85 in its adjusted position. As best illustrated in Fig. 5, the surface of cam 76 is in the form of the segment of a circle throughout two-thirds of its periphery, and in the form of a true spiral throughout the remaining one-third of its periphery or angle of travel; the high and low portions of said cam being separated by a radially extending shoulder 16 relatively to which the block 8! is adapted to move with asnap action in a given rotary position of cam 18.

A cam i1 (reversely arranged with respect to cam 15) is rigidly secured to shaft 52 for rotation therewith and the same has associated therewith a rod 81 having a block 88 at the lower end thereof which is adapted to continuously bear against the surface of said cam 77!. As will be noted the surface of cam H is in the form of a true spiral throughout its periphery; the high and low portions of which are separated by a radially extending shoulder H relativelyto which the block 88 is adapted to move with a snap action in a given rotary position of cam Ti. Rod 8? is supported and guided by bracket arms 89 and Gil; a spring 9! being interposed between bracket 9i! and an adjustable nut 92, in the manner aforedescribed, to provide for snap movement of contact 19 downwardly when block 88 moves relatively to radial shoulder li of said cam in a given rotary position of the latter. Contact 19 is adapted to overlie contact 18 as shown; and the arrangement is preferably such that both engagement and disengagement of contacts l8 and i9 is effected with a snap action.

It is to be understood that motor 64 is provided with electrical connections (not shown) to 7 effect operation thereof at a predetermined constant speed. For instance, motor 66 may be connected with lines L L which are shown as the source of current supply for motor Hi. Thus cazn Ti will be driven at a predetermined reduced speed, through the medium of gearing t3, in the same direction as shaft 52; as indicated at $3 in 1; whereas cam its will be normally driven in the opposite direction (indicated by arrow fi l) at a still further reduced speed (such speed of cam l5 corresponding to one-third of the speed of cam ill in the particular arrangement herein illustrated), through the medium of planetary gearing 3, 5? and ll.

The arrangement is such that so long as e1ement 58 remains in its neutral or intermediate position, illustrated, the contacts '28 and i9 will remain in disengaged relationship to each other. As an incident to movement of element in one direction or the other from said neutral position the contactor arm W of a switch 9? is moved in a corresponding direction to effect engagement of one of the oppositely facing contact tips carried thereby with one of the Contact tips di or 91" respectively carried by flexible or resilient stationary contact members 8'5 and til Such engagement of a contact tip of arm t l with one of the relatively stationary contact tips 9"! or 97 presets a circuit for energization of the wind ing 95* or of one or the ther of the electromagnetically operable relays and 55; such energization being subject to simultaneous engagement of the aforementioned contacts 18 and "ll-9. As aforeindicated, movement of contactor arm Ell is in response to the direction of divergence of the value of the condition to be controlled (total heating value per unit volume of the combustible mixture, in the particular adaptation of the invention illustrated herein) with respect to a value preselected therefor. Inasmuch as arm 39 is rigidly attached to shaft i8, movement of the latter in one direction or the other will ef fect corresponding movement of arm The gear 34 carried by arm 39 will tend to roll freely in mesh with the teeth of segment Z5; and in view of the greater size of gear with respect. to gear 53 also carried by arm gear 2 3 will (by reason of its toothed connection with segment 35) bias the toroid or ring-type liquid drex menu ber 25 to move in a direction and to a degree corresponding with the direction and degree of movement of shaft 55. The bias of member 25 under such conditions will be accentuated by the action of one or the other of the springs 30, 3|. Such movement of member 25 will, however, be resisted by the restraint afforded by the orifice 21 in plate 25 to movement of the body of liquid 32 As a consequence member 25 will temporarily remain substantially stationary; the slow rate of rotary movement thereof permitted being controlled by the rate of flow of the liquid 32 in one direction or the other through the orifice 2"! in plate 25.

By reason of such resistance to movement of member 25, gear &3 will be compelled to roll over the gear segment it: in mesh with the teeth of the latter. The consequent rotation of shaft 42 (Fig. 2) will cause rotation of gear l i, and because gear 44 is substantially larger than gear 43 the teeth of gear to will cooperate with gear segment 46 to effect a given degree of angular movement of hub member 55 in one direction or the other with respect to shaft [8. Such movement of hub 5! will effect movement of arm W whereby one of the contact tips carried thereby is engaged with one or the other of the contact tips di or 9?. At the same time element 55 is moved from the neutral position shown in Fig. 1 so that the cam surface 59will act to effect depression of roller (it and counterclockwise movement of lever arms 6! and 65 as a function of the degree of deflection of the indicating arm i? with respect to the neutral point 2! on scale as. Thus the arm 9? cooperates with one or the other of the contact arms ar or di in response to the direction of variation in the total heating value per unit volume of the combustible fluid flowing in conduit 12 (as determined by oalorimetric device It); whereas element 5% acts upon lever B! to an extent determined both by the degree or amount of variation in the total heating value per unit volume of such fluid with respect to the value preselected therefor and by the rate at which such variation takes place.

Upon such counterclockwise movement of lever arms 6i and 85 (Fig. 1) gear 5? will be caused to move bodily toward the left over gear 68, thus eifecting a corresponding degree of rotation of gear ii in a counterclockwise direction, as indicated by the arrow t l The corresponding counterclockwise movement of cam '56 (which is superimposed upon or differentially related to the normal movement thereof in a clockwise direction, as aforedescribe-d) has the net result of delaying the time at which the block 8% will drop from the high point of said cam. Due to such delay the block 88 will drop from the high point of cam ll prior to dropping of block 8i from the high point of cam 15, This will result in engagement of contact 58 with contact 78 to complete a circuit for one or the other or the coils 85 or sli depending upon which of the contact tips di or 9' has been engaged by arm $7 The duration of engagement of contact is with contact 18 will, of course, depend upon the degree of reverse movement or retardation. of cam it, which as aforeindicated is in accordance with the degree of angular movement of element 56.

More particularly, arm 97* is adapted upon movement thereof toward the right (from the neutral or intermediate position thereof illustrated in Fig. l) to effect engagement of contact tip 91 with a tip Si'i carried by the flexible or resilient stationary contact member er Contact member 91 is electrically connected by conductor Hit? With one terminal of the operating winding 95* of switch 95, the other terminal of which winding is electrically connected by con ductor I!!! with line L Thus upon engagement of top 91 with top 91 an energizing circuit for winding is preset for completion upon engagement of the aforementioned contacts 78 and 19.

Similarly, upon movement of arm 91 toward the left (Fig. 1) the contact tip (not shown) upon the opposite face thereof is adapted to engage the contact tip 9'! carried by the other flexible stationary contact member Si Contact member 91 is electrically connected by conductor R32 to one terminal of thewinding 95 of switch 963, the other terminal of which winding is electrically connected by conductor N33 with line L Thus upon engagement of said last mentioned tip of arm 97 with tip 91 an energizing circuit for winding 98* is preset for completion upon engagement of said contacts 18 and '19.

It may be assumed that upon an increase in the total heating value per unit volume of the combustible mixture flowing in conduit l2, with respect to the value preselected therefor, the calorimetric device 56 will effect movement of shaft it in a direction to cause movement of indicating element ll and contact arm Q'l toward the right. The consequent engagement of tip 91 with tip 9'? will preset the energizing circuit of winding 95 for completion upon engagement of contacts 13 and 19, as aforedescribed; and upon energization of winding 95 the contacts 95* thereof will be closed to complete a circuit for the split-field reversible motor is to effect operation of the latter in a direction to cause movement of valve [3 toward its fully opened position. Such circuit of motor It extends from line L by conductor EM through contacts 95* of switch 95, thence by conductor Hi5 through one of the split-field windings of said motor it, and by the common conductor I06 to line L As will be understood, such movement of valve l3 toward its fully opened position will be effected in a step-by-step manner; due to the operation of cams i6 and H (the former having been reversed or retarded to a given degree in the manner aforedescribed) to effect engagement of contacts 18 and it after each three complete rotations of cam ll, whereby contact '19 is dropped into engagement with contact 78 at a given instant of time prior to disengagement thereof due to dropping of contact i8 by the action of cam 16. In practice the motor is may be provided with a built-in series of speed-reducing gears, as represented by the numeral Hi or any other suitable means may be employed to insure a relatively slow rate of adjustment of valve l3 during engagement of contacts 13 and 79.

It will be apparent that upon movement of shaft H3 in the direction indicated by arrow till, as just described, the arm 23 will be moved to a corresponding degree; said arm acting through coiled tension spring 3i to tend to effect movement of the ring-type liquid drag member 25 to a like degree. However, due to the presence of orifice plate 26 (Figs. 2 and 3) at the mid-point of the body of liquid 32, such as mercury, within the closed ring 25, said ring will lag behind arm 23 to a degree controlled by the rate of passage of the liquid through the orifice 21 in said plate. As will be apparent, such movement of arm 23 relatively to ring 25 will effect a corresponding increase in the tension of spring M, with a resultant decrease in the tension of spring 3!). Inasmuch as arm member 39 is constrained to move jointly with arm 23 (both being rigidly attached to shaft I8); whereas the movement of ring 25 is restrained, or limited to a relatively slow rate, by the coaction of orifice 21 with the body of liquid 32; it is obvious that gear 43 will be caused to ride over the teeth of segment 45, thus causing counterclockwise rotation of shaft 42 (Fig. 1).

Gear 44, which is rigidly connected with shaft 42, is likewise constrained to move in a counterclockwise direction, thus effecting movement of the upward extension 5!) toward the left to a degree which is substantially greater than the degree of movement of arm member 39. As a result the inverted T-shaped extension 53 is moved toward the right (Fig. 1) to a degree greater than the degree of angular rotation of shaft [8. At the same time the arm fil of switch 9'! is moved to effect engagement of its tip 91 with the tip 9'! of contact arm 57; thereby presetting the aforementioned energizing circuit for winding 95 for completion upon engagement of contacts l8 and T9. The degree of movement of extension 56 toward the right serves, as aforedescribed, to insure engagement of contacts 13 and 19 during each complete rotation of cam 15, to effect movement of valve I3 toward its fully opened position. The degree of opening adjustment of valve I3 upon each complete rotation of cam 18 under the conditions just mentioned is proportional to the degree to which arm ii] is rotated in a counterclockwise direction. The amount which arm BI is rotated in a counterclockwise direction depends upon the shape of depression 59 and the angular position of arm 55 which is related to the position of indicating arm H in a useful, but complicated, manner due to the action of restraining ring and the associated gearing.

As will be understood, the ring 25 is biased by springs 39 and 3| in a manner to establish a fixed relationship between the angular position of arm I! and ring 25. When this condition is established, a fixed angular relationship between arm 5'! and arm will be established. Due to the retarding action of the liquid in ring member 25 to movement in either direction, the corresponding movement of ring 25 is delayed, thus causing a greater degree of angular movement of arm 55 than the degree of angular movement of arm l'l.

Such angular displacement of arm 56 is (in effect) added to the angular displacement of arm H, and the absence of further change in the angular position of arm H, the angular displacement of arm with respectto arm il gradually decreases to zero as th flow of liquid through the orifice 2? in plate (Fig. 3) permits ring 25 to assume its normal angular position with respect to arm l l.

fter valve has been intermittently adjusted toward its fully open position to such a degree as to bring the combustible mixture flowing in conduit l2 back to the total heating value preselected therefor, it is obvious that the calorimetric device it will cause rotation of shaft 53 in a clockwise direction (as indicated numeral H33 in 1), whereby the contact tip :Tl will be disengaged from tip di to insure against further adjustment of valve is toward its fully opened position. Such movement of shaft EB will result in an increa" the tension of spring 353 with a corre decrease in the tension of spring at, thei causing the gearing 35, 3d, and to over :e in a manner similar to but in the opposite direction from that aforedescriloed, to gradually reset the various parts 5", iii, 65, etc, to the normal positions thereof shown in Fig. 1. When the contact arm 91* is thus moved to its intermediate or neutral position, both of the possible circuits for motor M will be interrupted, and hence, the automatic resetting operation of the other parts of the device will take place without any effect upon the adjustment of valve 53.

As a result of adjustment of valve 53 in the manner aforedescribed, the arm Il may tend to return to its normal position (shown in Fig. 1) before ring 25 has attained its normal angular relationship to said arm, in which relationship the bias effects of both spring 38 and 3| upon ring 25 will be equal to each other. Under such conditions the degree of deflection of arm 39 with respect to arm 53 will be gradually decreased until ring 25 has attained such normal angular relationship to arm I 1. Further movement of arm l'i toward its normal position (Fig. 1) would then cause angular displacement of arm 39 toward arm 48 or @9 (as the case may be), and as a result of the displacement lever 56 will-reach the normal position (wherein that contact on arm 91 which was last active is disengaged from its associated stationary contact and roller 6% is positioned at the inner end of the double cam surface 55) before arm it reaches the normal position thereof shown in Fig. 1. It is thus ap-- parent that the position of arm 56 is related not only to the total heating value per unit volume of the mixture as indicated by arm it, but the position of arm 56 is also affected by the rate and direction of change in the position of said arm IT. This feature is of great practical importance in that it substantially prevents hunting operation of valve I3.

In the event of a decrease in the total heating value per unit volume of the combustible gaseous mixture flowing in conduit 2, with respect to the value preselected therefor, the device will operate in a manner similar to that aforedescribed (but in the opposite sense) to effect the required degree of closing adjustment of valve I3. Thus if it be assumed that the various parts of the device are in the neutral or stabilized positions thereof illustrated in Fig. 1; it is obvious that upon a decrease in the total heating value per unit volume of the combustible mixture from the preselected value, the calorimetric device it will cause a corresponding degree of clockwise rotation of shaft 18, with resultant substantially immediate engagement of the tip (not shown) on arm ti with contact tip el on the flexible arm 91 This will preset an energizing circuit for the operating winding at of switch 86, for completion upon engagement of contacts i3 and 19; said circuit when completed extending from line L by conductor 89 through contacts 19 and ?8, by conductor through the tip (not shown) on the left-hand face of arm 97 to tip 5? and flexible contact arm $1 by conductor m2 through said winding 9%, and by conductor its to line L The movement of shaft H3 in a clockwise direction from its neutral position will have caused corresponding movement of arm member 38 toward the right; and due to the restraint or resistance to movement offered by ring 25, the

gear 43 will ride toward the right over segment 25; the consequent rotation of shaft 32 in a clockwise direction likewise eifecting clockwise rotation of gear i t whereby the upward extension 59 is moved toward the right and the downward extension 56 is moved toward the left. The righ the mixture in conduit I2 is brought back to normal by the adjustment of valve I3.

Upon energization of winding 96 the contacts 96 of switch 96 are closed, thus completing an alternative energizing circuit for motor Id, which circuit may be traced from line L by conductor I69 through said contacts 96 by conductor IIll through the other section of the split-field winding of motor I l, and by the common conductor I86 to line L Such circuit provides for operation of motor I in a direction to effect movement of valve I3 toward its fully closed position; the cams I6 and I! cooperating to insure intermittent completion of such reverse circuit for the motor; whereas the aforedescribed degree of automatic adjustment of cam I6 provides the desired control of the period of engagement of contacts I8 and I9 during each complete rotation of cam which period is directly proportional to the degree of departure (decrease) of the total heating value per unit volume of the combustible mixture from the value preselected therefor and the rate and direction of change.

Upon re-attainment of the desired total heating value per unit volume of the mixture the shaft I8 will be rotated toward its intermediate or neutral position illustrated; and in consequence both circuits for motor I4 will eventually be interrupted. As aforeindicated, upon neutral or intermediate positioning of contact arm 91 the other parts of the device, if displaced, will be automatically returned to their preset or neutral positions illustrated without affecting the adjustment of valve I3.

It will be understood by those skilled in the art that if desired the relative size of the orifice 2'! in plate or barrier 26 within ring may be increased or decreased, to thereby vary the time required for the follow-up action of said ring 25 and the parts associated therewith.

Attention is called to the fact that the driving means for shaft IB (within calorimetric device I 6) includes a well known form of friction clutch. Hence if shaft I8 should tend to rotate in either direction at the instant when, or shortly after, block BI has dropped from the high point of cam I6, the radial shoulder "Iii on cam I6 may abut against said block 8I to temporarily prevent the desired reverse or retarding movement of cam I6. Such reverse movement of cam IE will, of course, be effected gradually as the shoulder 16 tends to move away from block 8|, as an incident to the normal direction of rotary movement of said cam; such temporary resistance to adjustment of the parts being accommodated by slipping of the clutch which drives shaft I8. Excessive strain upon any of the parts of the device is therefore avoided.

insufficient to provide for operation of the lever arm SI of Fig. 1. Under these conditions I prefer to provide a modified device of the character illustrated in Fig. 4. In Fig. 4 the stub shaft i I l is rigidly attached to gear 6i and rotates in the bearing formed adjacent the free end of arm I I2 of a lever which is pivotally supported by shaft 52; the other arm I 53 of said lever being arranged at a predetermined angle (preferably a right angle) to arm IE2. Shaft III has rigidly at tached thereto a cam or eccentric lid. Cam H4 is adapted to continuously engage a roller IIE rotatably supported upon a bearing shaft H 5 fixed to a part I I! of a stationary bracket another part of which is designated by numeral lit. Bracket part IIB has a portion He bent at substantially a right angle thereto, and a coiled com-- pression spring is interposed between portion I I3 and lever arm H3 to insure the aforementioned continuous engagement of cam li iwith roller H5.

Lever arm H3 has riveted or otherwise rigidly attached thereto a resilient extension I29 the free end IZI of which is bent upwardly at substantially a right angle thereto. As will be understood, the continuous rotation of shaft E32 causes continuous rotation of gear 51, with the result that cam I M cooperates with roller H5 to effect cyclic up and down movement of the free end I2I of extension I211. The arrangement is such that when the cam 'I'I attached to shaft 62 is in a position where cam follower 88 (see Fig. 1) is about to drop and for a given period thereafter the end IEI of extension I2!) can assume the position thereof shown in Fig. 4. During the remainder of the period represented by (or corresponding to) one revolution of shaft 82 the lever extension is gradually moved downwardly from the position thereof illustrated, thus moving the end I2I downwardly from the middle or intermediate one of the opposed sets of steps I22 and I23 formed upon the lower edge of a specially formed approximately T-shaped member I2 4.

The shape of cam I it is such that end portion I2I will be moved entirely out of engagement with member I24 during each complete rotation of cam II4. It is therefore apparent that the end portion I2I of extension IZEI does not interfere to any substantial degree with the normal functioning of shaft I8 and the parts associated therewith for efiecting movement of said member I2 t. As cam TI approaches the rotary position thereof at which the follower 88 drops to its lower extreme position the end I2I of lever I28 (through the action of cam lI l) tends to move to the position thereof illustrated (l ig. 4), so that when the aforementioned follower 88 drops, said end IZI will be in the position shown and there will be no rotary displacement of cam it with respect to earn Ii; unless member 3261 has been moved toward the right or left from its normal or neutral position, to correspondingly limit the degree of upward movement of lever end I2. With said end IZI restrained against movement to its upper extreme position illustrated by engagement thereof with one of the steps of the groups I22, I23 on either side of said end I2 I cam l6 will be retarded to an extent depending upon the angular or rotary position of lever I28.

Referring now to Figs. 7, 8 and 9 which graphically illustrate the various positions assumed by cam operated switch contacts I8 and I9 under different conditions, in respect of the device of Fig. 1. Thus in Fig. '7 the zigzag line illustrates the relatively slow upward movement I25 and quick downward movement I25 of contact 19 resulting from each complete rotation of cam H with respect to the block or follower 88; the effect of three complete rotations of cam 11 being illustrated.

In Fig. 8 the horizontal portion 526 of the upper line illustrates the substantially stationary positioning of contact I8 afforded by engagement of block 55 (Fig. l) with the concentric portion of cam '15 (see Fig. during two thirds of a complete rotation of the latter. li'he upwardly inclined portion I 2'! of said line illustrates the upward movement of contact 78 effected by cooperation of the true spiral formation of one third of the p riphery of cam IS with the block 5!; cam 78, as aforestated, being normally driven at one-third of the speed of cam TI.

The two lines in the lower portion of Fig. 8 graphically illustrate the variations in spacing of, or are gap between, the contacts 78 and '59 under normal conditions; that is to say, so long as element remains in the intermediate or neutral position thereof shown in Fig. Assuming that the variable distance between base line 529 and lines see, i3! represents the positions attained by contact 2'8 with respect to contact 59, it will be noted that the arc gap is initially increased, as represented by the upwardly inclined line I38, then rapidly reduced, as indicated by the vertical line I3I (which represents the drop-oi? of block 83 from the high portion of cam '57) to provide the normal minimum arc gap represented by the space I32. The rise I32! and fall I3I of contact H3 is repeated during the second complete rotation of cam 11. During the third complete rotation of cam Tl the spiral onethird portion of cam l6 cooperates with block at to effect upward movement of contact '18 at the same speed as the rise of contact 7%, where-- fore the aforementioned normal minimum arc gap {32 is maintained, as shown by the parallel relationship of line I33 to line I29. Under normal conditions both contacts I8 and '59 will drop to the lower extreme positions at the same time to maintain such normal minimum arc. gap, whereupon earn it will act to lift contact 18 upwardly away from contact 78 in the manner illustrated by the fragment of the upwardly inclined line I38 to repeat the aforedescribed cycle of operations.

In the upper portion of Fig. 9 the horizontal portion of the line represents the substantially stationary positioning of contact ill during two-thirds of a complete rotation of cam I6, as in Fig. 8. However, in Fig. 9 it is assumed that during engagement of the aforementioned concentric portion of cam I6 with block 8I the element 55 has been moved to a given degree in one direction or the other from the neutral position thereof illustrated in Fig. 1. As a result the cam 76 will have been reversed, or retarded from its normal clockwise direction of movement for a period represented by the horizontal portion i 54 (between dotted vertical lines), so that the beginning of the upward movement of 78 (represented by the upwardly inclined line I21, as in Fig. 8) is delayed.

With reference to the lower portion of Fig. 9 it will be noted that the variations in value of the arc gap between contacts 13 and ii! are the same as those illustrated in the lower portion of Fig. 8, during two complete rotations of cam '17. Due to the retarding or setting back of cam 75 as just described the arc gap will be gradually increased for the period represented by the relatively short upwardly inclined line I38 (which represents the rise of contact '59 while contact I8 remains substantially stationary). Then upon upward movement of contact I8 (as represented by line I21 in the upper portion of Fig. 9) said are gap will be maintained constant at the value represented by the distance between horizontal lines I35 and I29, until the point in time represented by I38 is reached, whereupon block 83 will drop 01f the high point of cam 11 to provide for engagement of contact I?! with c intact 13; the latter then being at that point in its rise designated by numeral I37 (Fig. 9). The period of engagement of contacts 78 and 79 is represented by the thick horizontal line I38; such period, of course, being directly proportional to the degree of lateral movement of element 56 in either direction from its normal position.

More particularly, the rise of contact It will continue beyond point I3! throughout the remainder of the length of the spiral one-third portion of the periphery of cam 15, and contact l3 will drop at the point in time represented by numeral I39 (Fig. 9), to disengage the same from contact 19. In the meantime the engagement of contact 79 with contact I5 will withhold block 88 from engagement with cam 'l'I, so that the normal increase in the arc gap represented by dotted line Iiiil is not possible. However, such rotation of cam TI insures that upon dropping of contact 18 as aforedescribed the cam l! positively limits the degree of downward movement of contact F9 to thereby provide a relatively large arc gap, as represented by the vertical line I43, between the separated contacts '58 and 19.

Referring again to Fig. '7 and to Figs. 10 and 11, which jointly illustrate graphically the various positions assumed by cam operated switch contacts is and 19 under different conditions, in respect of the modified form of device shown in Fig. 4. Thus as aforestated the cam TI of Fig. 4 is identical with the cam I? of Fig. 1 and is adapted to effect the aforedescribed cyclic up and down movements of contact 19, as indicated by the series of upwardly inclined lines I25 and the vertically downwardly extending lines I25 in Fig. 7.

In the upper portion of Fig. 10 the horizontal portion I 5! of the solid line indicates the substantially stationary positioning of contact I8 during the initial two-thirds of the complete rotat n of cam (Fig. 4); said portion I4: corresponding exactly with. the horizontal portion 25 of the line shown in Fig. 8. The upwardly inclined dotted line 127 in 10 corresponds with the full line ii! in Fig. 8, and indicates the rate and degree of upward movement of contact 38 which would be effected during the final onethird of a complete rotation of cam 15 if there were no movement of lever 528 and the parts associated therewith. As aforesaid, however, it is necessary in the device of Fig. 4 to intermittently efiect counterclockwise movement of lever 52E to its lower extreme position to permit substantially free movement of element i24 (Fig. 4) to any position to which. it may be biased by rotary movement of 58 (see Fig. l) in one direction or the other. As aforedescribed such movement of lever i2 3 effected by cooperation of cam or eccentric i M (Fig. 4;) wi h roller I I5; the necessary counterclockwise movement of lever arm [i2 being transmitted to shaft III and to gear 5'! to tend to eifect counterclockwise movement of gear H as shown by the arrow M2 .tion thereoi illustrated.

in Fig. 4. The result of such tendency to re verse the direction of driving of gear "H is to temporarily substantially neutralize or nullify the normal driving thereof in a clockwise direction, wherefore little or no upward movement of contact is provided, as indicated by the horizontal continuation MS of the line l il in Fig. 10. Inasmuch as cam i it makes three complete revolutions during each rotation of gear ll it will be understood that said cam permits return of gear 6? to its illustrated normal position prior to the time when a complete rotation of gear l'i has beenefiected; and accordingly the rate of upward movement of contact '88 is accelerated, as indicated by the upwardly extending curved portion Hit of the line.

As shown in the lower portion of Fig. 10 the upwardly inclined lines 53% and the vertical lines lfii illustrate the variations in distance (or are gap) between contacts '68 and 753 during the initial two-thirds of a complete rotation of cam it (Fig. i), in the same manner as shown in the lower portion of 8. However, as shown at M in the lower portion of Fig. the eiTect of the bodily movement of gear til (due to the action of cam lid) is to temporarily gradually increase above the normal minimum and then gradually decrease to said normal minimum the arc gap between contacts l8 and "it during the final onethird of a complete rotation of gear 'ii and cam '56. The net result is that under normal conditicns engagement of contacts is and i9 is posi tively prevented.

In the upper portion of Fig. ll the lines corresponding with those shown in the upper portion of Fig. 3.6 have been given like numerals of reference. In Fig. 11, however, it is assumed that lever E28 is restrained against movement to its upper extreme position, shown in Fig. 4, by engagement of lever end iiii with one of the steps H22 or l23, due to movement of element 2 3 in one direction or the other from its neutral or intermediate position. As a result the normal movement of contact '58 represented by the upper portion M ll of curved line i l l will not take place, but line i ii will merge into the upwardly inclined line l l l which is parallel with the aforementioned dotted line E2? The contact iii will drop to engage contact '58 at the point marked M8 on line Mfr, thus completing the circuit as indicated at 38 in Fig. 11. Engagement of contacts 53 and "it is maintained until contact 58 drops, at point i ll, thus providing the are gap represented by line l d in Fig. 11; the contact l9 having been lifted in the meantime, as indicated by the dotted line section wil of upwardly angled line 538. As will be understood, the duration of engagement of contacts it and it, as represented by heavy line 538 in Fig. 11 will vary in accordance with the degree of divergence of element from the neutral posi- Ehe substantial similarity of the manner of operation of the device of Fig. 4 with respect to that of Fig. 1 will be apparent from the foregoing descriptions of these devices.

Although I have herein disclosed my invention as applied to control of the total heating value per unit volume of a mixture of combustible gaseous fluids, it is to be understood that the invention is adaptable for use in the control of various other conditions, such as water-level control, pressure control, temperature control, etc.; that is to say, in those devices wherein the particular condition is to be controlled by adjustment of the rate of suppl of a medium which supports the condition.

I claim:

1. In apparatus for maintaining substantially constant the value of a condition, in combination, adjustable means for effecting a flow of a me dium supporting the condition, means continuously responsive to the instantaneous value of said condition, means subject to control by said second mentioned means and including a rotatable liquid drag device responsive to both the instantaneous value and the rate of change in value of said condition with respect to a value preselected therefor for intermittently effecting adjustment of said first mentioned means, said third mentioned means also including a pair of continuously operable power driven cams and a pair of switch contacts respectively operable thereby, the drive of one of said cams including a set of planetary gearing, and means for subjecting said planetary gearing to control in accordance with the rotary position of said liquid drag device to thereby vary the degree of adjustment per unit of time of said first mentioned means throughout a relatively wide range, to thus increase or decrease the rate oi flow of said medium in accordance with both the instantaneous value and. the rate of change in Value of said condition with respect to said preselected value.

2. In apparatus for control of a condition, in combination, means for continuously delivering a medium to support said condition, means for controlling the rate of delivery of said medium whereby said condition is maintained at a predetermined substantially constant value, said last mentioned means including means responsive to the direction, degree and rate of variation in such value with respect to said predetermined value, means controlled by said variation responsive means to control the direction of variation in the rate of delivery of said medium supporting said condition, cam operated switching means included in circuit with said direction control means for eifecting adjustment of the rate of delivery of said medium to maintain said condition at said predetermined substantially constant value, said switching means including a pair of cams having a common drive, one of said cams being driven at a constant speed and the other cam being normally driven at a different speed through the medium of planetary gearing, said planetary gearing including an oscillatable retarding arm whose variable operative position is subject to control by said variation responsive means, said arm in any operative position thereof being adapted to correspondingly control the degree of adjustment per unit of time of the rate of delivery of said medium, said arm being so related to said cams as to provide for inoperation of said switching means when said condition is of said predetermined substantially constant value, a double-inclined cam member operable by said variation responsive means, a ring type liquid drag member also operable by said variation responsive means and spring-biased to move in either direction to a degree corresponding to the movement of the latter, gear segments connected with said drag member and said double-inclined cam member respectively, an element rigidly connected with a part of said variation responsive means for movement with the latter, a gear continuously engaged with the gear segment on said drag member, a second gear continuously engaged with the other gear segment, a shaft to which said gears are non-rotatably connected,

and said last; mentioned element having means for supporting. saidv shaft for rotation. with respect thereto.

3. In apparatus for control of a condition, in combination, means for continuously delivering a medium to support said condition, means for controlling the rate of delivery of said medium whereby said condition is maintained at a predetermined substantially constant value, said last mentioned means including means responsive to the direction, degree and rate of variation in such value with respect to said predetermined value, means controlled by saidivariation responsive means to control the direction of variation in the rate of delivery of said medium supporting said condition, cam operated switching mean includ ed in circuit with said direction control means for eiiecting adjustment of'the rate of delivery of said medium to maintain said condition at said predetermined substantially constant value, said switching means including a pair of cams having a common drive, one of said cams being driven at a constant speed and the other cam being normally driven at a difierent speed through the medium. of planetary gearing, said planetary gearing including an oscillatable retarding arm whose variable operative position is subject to control by said variation responsive means, said arm in any operative position thereof being adapted to correspondingly control the degree of adjustment. per unit of time of the rate of delivery of said medium, said arm being so related to said cams as to provide for inoperation of said switching means when said condition is of said predetermined substantially constant value, a double-inclined. cam member operable by said variation responsive means, a ring type liquid drag member also operable by said variation responsive means and spring-biased to move in eitherdirection to a degree corresponding to the movement of the latter, gear segments connected with said drag member and said doubleinclined cam member respectively, an element rigidly connected with a part of said variation responsive means for movement with the latter, a gear continuously engaged with the gear segment on said drag member, a second year continuously engaged with the other gear segment, a shaft to which said gears are nonrotatably connected, said last mentioned element having means for supporting said shaft for rotation with respect thereto, a switch contactor movable with said second mentioned gear segment in one direction orthe other according to the direction of. movement of said variation responsive means, and a pair of resilient stationary contacts with which said contactor is adapted to engage selectively to preset one or the other of a pair of alternative circuits for completion upon closure of said cam operated switching means.

4. In a condition controlling system, in combination, a member adapted to assume a given position upon attainment of a predetermined value of the condition, said member being movable in one direction or the other with respect to said position in accordance with variations in the value of said condition, an element rigidly attached to said member for movement with the latter, a pair of gears rigidly connected with each other and supported bysaid element for rotation jointly with'respect thereto, a ring type liquid drag member rotatably supported by said member first mentioned, spring means interposed between said first mentioned member and said drag memberrwhereby the latter is biased to move in a direction and to a degree corresponding to the movement of the former, an orifice plate fixed within said drag member cooperating with the liquid to limit such movement of the drag memher to a predetermined relatively slow rate, a gear segment rigidly attached to said drag memher with which one gear of said pair is adapted to continuously engage, a second gear segment rotatably supported by said first mentioned member with which the other gear of said pair is adapted to continuously engage, a cam member rigidly attached to said last mentioned gear segment, a substantially L-shaped lever with one arm of which said cam member is adapted to engaga'a planet gear rotatably supported by the other arm of said lever, planetary gearing of which said last mentioned gear forms a part, a switch contactor operating cam associated with said planetary gearing, a shaft for normally driving said planetary gearing at a predetermined speed, a second switch contactor operating cam rigidly attached to said shaft, said cams being jointly operable under normal conditions to maintain said switch contactors disengaged from each other, means including said cam member and said lever acting upon movement of said. first mentioned member from its given position to effect intermittent engagement of said contactors for periods of time corresponding to the instantaneous relative positions of said first mentioned member and said cam member, said last mentioned means also including a switch contactor movable in one direction or the other according to the direction of movement of said first mentioned member, a pair of resilient stationary contacts with which said, contactor is adapted to selectively engage to preset one or the other of a pair of alernative circuits for completion upon engagement of said cam-operated contactors; an adjustable valve the position of which is adapted to control the rate of delivery of a medium whereby the-value of said condition is maintained substantially constant, a reversible electric motor for controlling the position of said valve, and means for subjecting said motor to control by said alternative circuits respectively.

5. In a gas mixing control system, in combina-' tion, a pair of branch conduits through which gaseous fluids of substantially different total heating value per unit volumes are respectively adapt-'- ed to fiow, a main conduit into Which said branch conduits are adapted to d scharge for mixtureof said fluids, a calorimetric device which withdraws a continuous sample of the mixture from said main conduit and continuously ascertains the total heating value per unit volume thereof, power operated means including an oscillatable shaft associated with said calorimetric device for continuously indicating the instantaneous total heatingvalue per unit volume of said mixture, an adiustablexvalvein one of said branch conduits, means responsive to movements of said power operated means for effecting adjustments, of said valve whereby said total heating value per unit volume is maintained substantially constant, said last mentioned means including a ring type liquid dragmember and a double-inclined concave cam member supported upon said shaft for rotation with respect thereto, spring means interposed between said shaft and said drag member to bias the latter to move in a directionand to a degree corresponding to the movement of said shaft, gear segments respectively attached to said drag member and said cam member; an arm rigidly attached to saicl'shaft, a second shaft having-bearing engagement with said arm, a gear continu- 37 gaged with the segment on said drag member, a relatively larger gear continuously engaged with the segment on said cam member, said gears being rigidly connected to opposite ends of said second shaft, a substantially L- shaped lever one arm of which is adapted for cooperative engagement with said cam member, a planet gear rotatably carried bythe other arm of said lever, planetary gearing of which said planet gear forms a part, means including a motor operated shaft for normally driving said 'planet gear at a substantially constant speed, a cam associated with said planetary gearing, a switch contactor operable by said cam, a second cam rigidly attached to said motor operated shaft and normally rotatable at a substantially higher speed than said cam first mentioned, a second switch contactor operable by said second cam, said cams under normal conditions being adapted to insure against engagement of said switch contactors, said lever When operated to a given degree by said concave cam member being adapted to effect adjustment of the cam associated with said planetary gearing to thereby effect a corresponding period of engagement of said contacts per unit of time, a reversible electric motor for effecting adjustment of said valve, and means subject to control by said switch contactors for completing a circuit for said motor for operation of the latter in one direction or the other.

6. In a gas mixing control system, in combination, a pair of branch conduits through which gaseous fluids of substantially difierent total heating values per unit volume are respectively adapted to flow, a main conduit into which said branch conduits are adapted to discharge for mixture of said fluids, a calorimetric device which withdraws a continuous sample of the mixture from said main conduit and continuously ascertains the total heating value per unit volume thereof, power operated means including an oscillatable shaft associated with said calorimetric device for continuously indicating the instantaneous total heating value per unit volume of said mixture, an adjustable valve in one of said branch conduits, means responsive to movements of said power operated means for effecting adjustments of said valve whereby said total heating value per unit volume is maintained substantially constant, said last mentioned means including a ring type liquid drag member and a doubleinclined concave cam member supported upon said shaft for rotation with respect thereto, spring means interposed between said shaft and said drag member to bias the latter to move in a direction and to a degree corresponding to the movement of said shaft, gear segments respectively attached to said drag member and said cam member, an arm rigidly attached to said shaft, a second shaft having bearing engagement with said arm, a gear continuously engaged with the segment on said drag member, a relatively larger gear continuously engaged with the segment on said cam member, said gears being rigidly connected to opposite ends of said second shaft, a substantially L-shaped lever one arm of which is adapted for cooperative engagement with said cam member, a planet gear rotatably carried by the other arm of said lever, planetary gearing of which said planet gear forms a part, means including a motor operated shaft for normally driving said planet ear at a substantially constant speed, a cam associated with said planetary gear,- ing, a, switch contactor operabl by. said cam, a

second cam rigidly attached to said motor operated shaft and normally rotatable at a substantially higher speed than said cam first mentioned, a second switch contactor operable by said second cam, said cams under normal conditions being adapted to insure against engagement of said switch contactors, said lever when operated to a given degree by said concave cam member being adapted to effect adjustment of the cam associated with said planetary gearing to thereby effect a corresponding period of engagement of said contacts per unit of time, a reversibleeleotric motor for efiecting adjustment of said valve, means subject to control by said switch contactors for completing a circuit for said motor for operation of the latter in one direction or the other, said last mentioned means including a switch contactor rigidly attached to said first mentioned shaft, and a pair of resilient stationary contacts with which said contactor is engageable selectively to effect completion of a circuit for said motor for operation of the latter in one direction or the other.

7. In apparatus for maintaining substantially constant the value of a condition, in combina tion, means including an adjustable valve for effecting a flow of a medium supporting the condition, means for continuously ascertaining the instantaneous value of said condition, means including a rotatable liquid drag device, movable by said last mentioned means in response to the direction, amount and rate of variation in value of said condition with respect to a value preselected therefor, movable means responsive to the direction of movement of said second mentioned means for presetting one or another of a pair of alternative electric circuits adapted when closed respectively to control the direction of adjustment of said valve to thereby change the rate of flow of said medium supporting the condition, a set of electrical contactors common to said alternative circuits, a corresponding number of rotary cams individual to the respective contactors to effect operation of the latter relatively to each other, common driving means for said cams, the

rate of speed of one of said cams being main- 'tained substantially constant, another of said cams being driven at a different speed through the medium of a planetary transmission, said planetary transmission including a pivoted L shaped lever whose movement is subject to 'control by said first 'mentioned movable means whereby such movement of said lever is made proportional to the degree and rate of movement of saidmovable means in either direction from a given position of the latter, and said lever'wh'e'n so moved acting through said planetary' transmission to retard or accelerate the movement of said last mentioned cam, for the purpose set forth.

8. In apparatus for control of a condition, in combination, means including a plurality of branch conduits and a main conduit leading therefrom for continuously delivering a medium to support said condition, means including an ad-' justable valve in one of said branch conduits for controllng' the rate of delivery of said medium through said main conduit whereby said condition is maintained ata predetermined substantially constant value, said last mentioned means including means responsive to the direction and degree of variation in such value with respect to said predetermined value, electrical switching means controlled by said variation responsive means to control the direction of adjustment'of said'valve to thereby vary the rate or delivery of said medium supporting. said condition, cam operated electrical switching means included in circuit with said direction control switching means for efiecting variation in the rate of adjustment of said valve to thereby assist in maintaining said condition at said predetermined substantially constant value, saidcam operated switching means including a pair of cams having a common power drive, one of said cams being driven at a constant speed and the other cam being normally driven at a slower speed through the medium of planetary gearing, and said planetary gearing including a movable arm whose position is subject to control. by said variation responsive means, to thereby vary the degree of adjustment of said valve per unit of time, whereby the rate ofdelivery-of saidmedium is subject to control in accordance with the instantaneous position of said'arm.

9. In apparatus for control of a condition, in combination, means including a plurality of branch conduits and a main conduit leading therefrom for continuously delivering a medium to support said condition, means including an adjustable valve in one of said branch conduits for controlling the rate of delivery of said medium through said main conduit whereby said condition is maintained at a predetermined substantially constant value, said last mentioned means including-movable means responsive to the direction, degree and rate of variation in such value with respect to said predetermined value, electrical switching means controlled by said variation responsive means to control the direction .of adjustment of said valve to thereby vary the rate of delivery of said medium supporting saidcondition, cam operated electrical switching means included in circuit with said direction control switching means for effecting variation in the rate of adjustment of said valve per unit of time to thereby assist in maintaining said condition at said predetermined value, said cam operated switching means including a pair of cams having a common power drive, one of said cams being driven at a substantially constant speed and the other cam being normally driven at apredetermined slower speed through the medium of planetary gearing, said planetary gearing including a movable lever whose. position is subject to control bysaid variation responsive means,said lever when moved to any one of a number of its operative positions being adapted to correspondingly adjust said planetary gearing to thereby control the degree'oi adjustment per unit of time of the rate of delivery of said medium, and said lever being so related to said cams as to provide for inoperative positioning of the former when said condition is of said predetermined value.

10. In apparatus for control of a condition, in combination, means including a plurality of branch conduits and a main conduit leading therefrom for continuously delivering a medium to support said condition, means including an adjustable valve in one of said branch conduits for controlling the rate of delivery of said medium through said main conduit whereby said condition is maintained at a predetermined substantially constant value, said last mentioned means including movable means responsive to the direction, degree and rate of variation in such value with respect to said predetermined value, electrical switching means controlled by said variation responsive means to control the direction of adjustment of said valve to thereby vary the rate of. delivery of said medium supporting said condition, cam operated electrical switching meanszincluded in circuit withsaid direction control switching means for efiecting variation in therate of adjustment of said valve per unit of time to -thereby assist' in maintaining said condition at: said predetermined value, said cam operated switching means including a, pair of camshaving-a common drive, one of said cams being normally driven at a predetermined slower speed through the medium of planetary gearing, said planetary gearing including a movable lever whose position is subject to control by said variation'responsive means, said lever when moved to anyone of anumber of its operative positions being adapted to adjustsaid planetary gearingto thereby control the degree of adjustment per unit of-time' of the rate of delivery of said medium, said lever being-so related to said cams as top-rovide for inoperative positioning of the former when said condition is of said predetermined value, said second mentioned means also including a double-acting cam member adapted for cooperation with said lever, said cam member being operable by said variation responsive means, a ring type liquid drag member also operable by said last mentioned means and spring-biased to move in either-direction to a degree corresponding to movement of the latter, gear segments con nected with said drag member and said cam member respectively; an element rigidly connected with said variation responsive means for movement with the latter, a gear continuously engaged with the gear segment on said drag member; a second gear continuously engaged with the other gear. segment, a shaft to which said gears are non-rotatably connected in spaced relationship toeach other, and said last mentioned element having means for supporting said shaft for rotation with respect thereto.

11; In a.condition controlling system, in com bination, means including a plurality of branch conduits and a main conduit leading therefrom for continuously deliverin a medium to support the condition, means including an adjustable valve .in one of said branch conduits for controlling the rate of delivery of said medium through said main conduit whereby said condition is maintained at a predetermined substantially constant value, said last mentioned means also including a member adapted to assume a given position upon attainment of said predetermined value of said condition, said member being movable in one direction or the other with respect to said position in accordance with variations in the value of said condition, an element rigidly attached to said member for movement with the latter, a pair of gears rigidly connected with each other and supported by said element for rotation jointly with respect thereto, a ring type liquid drag member rotatably supported by said member first mentioned, spring means interposed between said first mentioned member and said drag member whereby the latter is biased to move in a direction and to a degree corresponding to the movement of the former, an orifice plate fixed within said drag member cooperating with the liquid therein to limit such movement of the drag member to a relatively sloW rate, a gear segment rigidly attached to said drag member with which one gear of said pair is adapted to continuously engage, a second gear segment rotatably supported by said first mentioned member with which the other gear of said pair is adapted to continuously engage, a cam member rigidly attached to said last mentioned gear segment, a substantially L-shaped lever with one arm of which said cam member is adapted to engage, a planet gear rotatably supported by the other arm of said lever, planetary gearing of which said last mentioned gear forms a part, an electric switch contactor, an operating cam therefor associated with said planetary gearing, a shaft for normally driving said planetary gearing and said cam at a predetermined speed, a second electric switch contactor, an operating cam for the latter rigidly attached to said shaft, said cams being jointly operable under normal conditions to maintain said switch contactors disengaged from each other, means including said cam member and said lever acting upon movement of said first mentioned member from its aforementioned given position to effect intermittent engagement of said switch contactors for periods of time corresponding to the instantaneous relative positions of said first mentioned member and said cam member, and associated power operated adjusting means for said valve subject to control by said contactors when engaged with each other.

12. In a condition controlling system, in combination, means including a plurality of branch conduits and a main conduit leading therefrom for continuously delivering a medium to support the condition, means including an adjustable valve in one of said branch conduits for controlling the rate of delivery of said medium through said main conduit whereby said condition is maintained at a predetermined substantially constant value, said last mentioned means also including a member adapted to assume a given position upon attainment of said predetermined value of said condition, said member being movable in one direction or the other with respect to said position in accordance with variations in the value of said condition, an element rigidly attached to said member for movement with the latter, a pair of gears rigidly connected with each other and supported by said element for rotation jointly with respect thereto, a ring type liquid drag member rotatably supported by said member first mentioned, spring means interposed between said first mentioned member and said drag member whereby the latter is biased to move in a direction and to a degree corresponding to the movement of the former, an orifice plate fixed within said drag member cooperating with the liquid therein to limit such movement of the drag member to a relatively slow rate, a gear segment rigidly attached to said drag member with which one gear of said pair is adapted to continuously engage, a second gear segment rotatably supported by said first mentioned member with which the other gear of said pair is adapted to continu-" ously engage, a cam member rigidly attached to said last mentioned gear segment, a substantially L-shaped lever with one arm of which said cam member is adapted to engage, a planet gear rotatably supported by the other arm of said lever, planetary gearing of which said last mentioned gear forms a part, an electric switch contactor, an operating cam therefor associated with said planetary gearing, a shaft for normally driving said planetary gearing and said cam at a predetermined speed, a second electric switch contactor, an operating cam for the latter rigidly attached to said shaft, said cams being jointly operable under normal conditions to maintain said switch contactors disengaged from each other, means including said cam member and said lever acting upon movement of said first mentioned member from its aforementioned given position to effect intermittent engagement of said switch contactors for periods of time corresponding to the instantaneous relative positions of said first mentioned member and said cam member, said last mentioned means also including a switch contactor movable in one direction or the other according to the direction of movement of said first mentioned member, a pair of resilient stationary contacts with which said last mentioned contactor is adapted to selectively engage to preset one or another of a pair of alternative circuits for completion upon engagement of said cam-operated switch contactors, and associated power operated adjusting means for said valve subject to control by all of said switch contactors jointly. EDWIN X. SCHMIDT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,349,521 Schmidt May 23, 1944 2,169,863 Anderson Aug. 15, 1939 2,020,847 Mitereff Nov. 12, 1935

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