US2735410A - armbrust etal - Google Patents

Description

Feb 21, 1956 R. J. ARMBRUST ErAL 2,735,410

WATER BY-PASS REGULATOR FOR STEAM GENERATOR CONTROL MECHANISM Filed Mach l, 1952 5 Sheets-Sheet l @mx @@aj n L k. 3 1| OOWMO /I Lw 2 H||i OO Oooo L i Si Em m .nhl onmwooooooooHooowoooooo umm. Owwwwoooo OOHHUOOOwUwwW OO n mAH @NH .l n\\ um o m1 om m mw Feb- 21, 1956` R. J. ARMBRUST x-:TAL 2,735,410

WATER BY-PASS REGULATOR FOR STEAM GENERATOR CONTROL MECHANISM 3 Sheets-Sheet 2 Filed March l, 1952 D m m m Feb- 21, 1956 R. J. ARMBRUsT ET AL 2,735,410

WATER BY-PASS REGULATOR FOR STEAM GENERATOR CONTROL MECHANISM C20-'fwww INV NTO S.

United States Patent O Roy' J. Armbrust and Joseph E. La Rocque, assignors to Vapor Heating Corporation, a corporation of Delaware Application March 1, 1952, Serial No. 274,362

Chicago, lll., Chicago, iii.,

S Claims.

The present invention relates to steam generator control systems and more particularly to a water by-pass regulator for such systems.

The improved by-pass regulator of the present invention has, for-illustrative purposes, been shown and described in connection with a steam generator control system in which the delivery of uid fuel to the fire chamber is proportionately controlled in relation to the volume of feed water delivered to the boiler steam generator. Such steam generator control system includes a constant delivery pump and a by-pass regulator so disposed in the system that the volume of feed water delivered to the steam generator or boiler is a function of the extent to which water is by-passed from the delivery side of the pump back to the feed water supply. The by-pass regulator involves in its general organization a by-pass valve having a spring loaded mechanism associated therewith which is actuated by steam pressure developed by the boiler so that the extent of opening of the valve is substantially directly proportional to the generated steam pressure. As steam pressure rises above the pressure required to open the valve, the extent of opening thereof is progressively increased to by-pass increasing amounts of feed water and thus reduce the effective delivery of water by the pump. At such time as the by-pass valve becomes fully open, substantially all of the feed water delivered by the pump is returned to the supply and practically no water is delivered to the boiler.

The system further includes a flow-responsive control mechanism which is responsive to the momentary rate at which feed water is being supplied to the boil and the function of which is to automatically regulate the supply of fuel to the burner, as well as to regulate the forced draft to the latter to maintain a correct balance between fuel and air and thus re the boiler in a manner commensurate with the rate atv which water is being supplied thereto.

In a system of the character briey outline above, the delivery of feed water and fuel are increased and decreased in relation to the demand for steam and when there is no demand for steam at low iire, the delivery of fuel and water may be temporarily discontinued. However, it has been found that in such systems, employing a water coil type of boiler, that when the ow responsive control mechanism shutsoi-the supply if fuel temporarily and also shuts olf the circulation of-water, the residual heat in the tire chamber of the boiler evaporates the static water remaining in the coils of the boiler and thus4 greatly increases the deposition of scale therein and shorten their period of usefulness. It has also been found that upon retiring of the steam generator and the application of feed water to the hot dried out coils thereof, under the control of the ilow responsive mechanism, there is an immediate tendency toward the creation of superheated steam. This phenomenon reduces the life of the boiler by contributing to the formation of 4cracks, in the tubing.

Efforts have been made heretofore to overcome the above limitations by continuously circulating water through the coils during the temporary olf-tire condition, but it was found highly undesirable, since the coils unduly cooled and thereby induced excessive deposits of soot during retiring. The continuous circulation of water, built up pressures which produced hydraulic locking effects and thereby caused the ow responsive mechanism to return the generator to its olf-lire condition before reestablishing an adequate steam supply.

The present invention is designed to overcome the above noted limitations that are attendant upon prior control systems of the type briefly outlined above and, toward this end, contemplates the provision of a water bypass regulator, which when associated with control systems of this character, will retard or delay the creation of an off-tire condition of the steam generator when the delivered steam pressure rises above a predetermined maximum until such time as a further predetermined rise in steam pressure indicates that an off-fire condition is in fact desirable and at which time such an olf-fire condition is allowed to obtain. A

A principal object of the present invention, therefore, is to provide a pressure responsive Water by-pass regulator which will function in the manner brietly outlined above and which will allow a relatively small amount of water circulation through the steam generator coils to take place immediately after the lire is shut olf from the generator so as to absorb a portion of the residual heat and prevent drying out the coils during such time as the steam pressure remains in the vicinity of the pressure Iwhich it attains when the off-tire condition is first initiated, but which will cause a complete by-passing of water and a consequent termination of feed water supply to the boiler if a still further and predetermined steam pressure rise takes place during the period that the tire is shut oit.

Another object of the invention is to provide a regulator which, after an off-tire condition of the generator has been attained and a demand for steam is resumed, will establish a limited tlow of feed water to the generator coils immediately prior to retiring of the generator so as to insure that the coils will be filled with water when actual retiring of the boiler occurs, after which the system will operate in the usual manner with the rate of flow of feed water to the boiler serving to control the supply of fuel to the fire chamber as Well as the supply of combustion air under pressure.

A, preferred embodiment of the invention is. illustrated in the accompanying drawing, wherein:

Fig. l is a. schematic diagramY of asteam generating system with-whicl1 the improved feed water by-passv regulator has been incorporated and showing the major components of the system;

Fig. 2 isv a. front elevationall view of the improvedl bypass regulator comprising the present invention;

Fig. 3 is a sectional view taken substantially along the line 3-3 of Fig. 2;

Fig. 4 is a perspective view, somewhat schematic in its representation, of a How-responsive control unit utilizedin connection withy the system of Fig. l. Certain parts of the control unity are-broken away, and other parts have been omitted as to` avoid masking other parts thereof which will facilitate-an understanding thev principles of operation of the by-pass regulator ofV Figs. 2 and 3.

Fig. 4a is asectional viewtaken substantially alongthe line 4a-4a of Fig. 4.

Fig. 5' is a front elevationalview if the complete control unit of'Fig. 4;

Fig. 6 is aside elevational view of aVVK portion of the controlunit shown in Fig. 5;4 and Fig. 7 is a rear view of the structure. showninFig.' 6.

3 Steam generating system The schematic diagram of Fig. l discloses an operable steam generating system. V It includes a number of more or less conventional instrumentalities embodied in the system and affected by the operation of the improved feed water by-pass regulator hereinafter described. The steam generator is designated as a whole by the reference character 10.

The generator 10 is of a known water tube type and is capable of functioning either as a hot water boiler or as a steam generator. It is comprised of several concentric groups of coiled tubing7 operatively connected together in series and identied at 12, 13, 14 and 15. The space 16 embraced by the coils 12 constitutes a heating chamber above which is disposed the iire chamber 17. A fuel burner 18 is surmounted by a spray head or nozzle 19 which, when liquid fuel is employed, functions as an atomizer.

Feed water is supplied to the boiler 10 from a reservoir 20, the water being withdrawn from the reservoir and forced through the various coils 12 to 15 inclusive of the boiler by means of a pump 21. The ow of the feed water from the reservoir extends through conduit 22, pump 21, conduit 23, a flow responsive control mechanism 24 (further illustrated in Figs. 4 to 7 inclusive) and conduit 25 to the intake end of the outer group 15 of the boiler tubing. A check valve 26 disposed in the conduit 25 prevents reverse ow of water in the event of failure of the pump 21. Steam and hot water emerge from the generator through a conduit 27 and pass to a steam separator 28 wherein the residue of hot water is separated from the steam for return to the reservoir Z through a conduit 29. Steam may be drawn from the separator 28 through a conduit 30 having a shut olf valve 31 associated therewith.

The upper end of the steam separator 28 is connected by a conduit 32 to the upper end of a pressure chamber 33 associated with the improved feed water by-pass regulator device 34 of the present invention. The regulator is in the form of a valve assembly in which the inlet port of the valve per se thereof is connected through a conduit 35 to the feed water conduit 23. The outlet port of the valve is connected through a return conduit 36 with the reservoir 20. When the pressure of a steam issuing from the separator 28 rises above a predetermined maximum, the valve element 37 of the bypass regulator 34 opens to divert feed water from the conduit 23 through the conduits 35 and 36 to return the same to the reservoir 20. The pump 21 has a constant output and thus the return of water delivered to the generator through the conduit 25 is a function of the proportion of water diverted through the conduits 35 and 36, that is to say, is a function of the extent to which the valve 37 is opened. The valve 37 itself and the actuating mechanism therefor will be described in detail subsequently and for the present it is deemed sufcient to state that the valve is spring loaded so that its opening is proportional to the generated steam pressure. By such an arrangement the volume of Water delivered to the control unit 24 is reduced to the extent of the volume diverted back to the reservoir 20. The control unit 24 is so designed as to control the delivery of fuel to the atomizing nozzle 19 in proportion to the flow of feed Water through the unit 24. Consequently the fuel delivered is proportionally reduced in relation to the volume of water diverted through valve 37 hack to the reservoir 20. It will be evident-that as steam pressure rises above the pressure required to actuate the by-pass regulator 34, the delivery of feed water to the control device 24 is reduced and vice versa.

The control mechanism 24 is responsive to the rate at which feed water is supplied to the boiler at any moment and it is capable of instantly and accurately regulating the supply of fuel and air for combustion purposes to the burner 17. Y

Fuel, usually oil or gas, is supplied to the spray head or nozzle 19 through a conduit 38 having disposed therein a valve 39 associated with the control unit 24 and which controls the rate of fuel supplied to the burner. The valve 39, in turn, is automatically controlled in accordance with the rate at which feed water is supplied at any particular instant to the boiler 10. In order to progressively vary the amount of fuel delivered by the valve 39 to the burner, the valve is provided with a spring pressed valve element 40 (Fig. 5) having a V-slot il formed therein and communicating with the outlet port 42 for delivering fuel to the conduit 38 leading to the spray head or nozzle 19. When the valve element 40 is depressed, the effective valve opening is decreased to thereby decrease the amount of fuel passing through the valve and consequently through the conduit 38 leading to the burner. When pressure on the valve stern 43 is relieved, the valve 40 is moved upwardly by the valve spring 44 to increase the effective opening of the V-slot 41.

When oil is used as a fuel, compressed air is delivered to the spray head for atomizing purposes through a conduit 45 (Fig. l). The volume of air supplied to the burner 17, in the form of a forced draft from a blower 46, is controlled by a damper 47 which is automatically controlled by the flow control device 24 under the influence of the rate of feed water supplyA and, as a consequence, in accordance with the fuel supply rate.

Flow control unit The control mechanism 24 is illustrated in some detail in Figs. 4 to 7 inclusive and comprises several appropriately formed body castings 48, 49, 5h, 51 and 52 which, conjointly, constitute a self-contained unit. The body castings 4S, 49 and 50 are bolted together to form a housing having an interior cavity which is divided into two chambers 53 and 54 by a flexible diaphragm 55, the peripheral margin of which is clamped between the opposing annular faces 56 and 57 of the body castings 48, 49 and 50. The casting 5i! has a feed water inlet port 58, while the castings 48 and 49 have a feed water outflet port 59 leading to the boiler through the conduit 25. The diaphragm 55 has a central opening through which there extends a shouldered bushing 60 having a central opening 61 providing an orifice through which feed water may ilow from the chamber 53 to the chamber 54. A tapered pin 62 extends axially through the orifice 61 and thus constricts the latter to an extent dependent upon the axial position of the pin 62 relative to the diaphragm 55. The lower end of the pin 62 is secured to the casting 50.

From the above description it will be evident that the effective area of the orifice 61 may be varied by adjusting the axial position of the pin 62. This adjustment is performed at the factory and ordinarily is a permanent one. Manifestly, when feed water passes through the unit 24, the diaphragm 59 will yield in proportion to the resultant hydraulic pressure differential between the two chambers 53 and 54.

An arm or pitman 63 is connected at one end to the diaphragm 55 and is connected as at 64 to the distal or free end of a level arm 65 keyed or otherwise secured to a shaft 66 journalled in bushing 67. A hub 68 is secured to the shaft 66 at the end remote from the lever arm 65 and has secured thereto the inner end of a spiral spring 68a, the outer end of which is anchored to a cup member 69 disposed within the body casting 51. The cup 69 is adapted to be held against rotation within the casting 51 in any desired position of adjustment to vary the tension of the spring 68a which serves as a restoring means for the diaphragm 59 and affords a definite load against which the diaphragm 55 operates.

A second shaft 70 coaxial with the shaft 66 is connected to the latter and is piloted in a third and hollow tubular shaft 71,'. The shaft 71 is formed with an arm 72 tothe free end of which is secured a crank pin 73.

An intermediate area of the Shaft 70, is milled on two sides, as shown at 74, 75 in Figs. 4 and 4a, to form a rotary valve element 76 of generally rectangular cross section. The valve element 76 closely lits the bore of the shaft '71 and normally functions as a closure for two ports 77 and 7S formed in the shaft 71. The port 77 is in continuous communication with the port 79 formed in a bushing 9fL xed in an opening in a casting 52, the said port 79 communicating with a supply port 80 formed in the casting 52 and leading from a conduit 81 (see also Figs. 4, 4a and 5) for supply of oil under pressure to the valve 76. The port 78 communicates with an outlet slot 71@ `formed in the shaft 71` The outlet end of said slot "71n opens into the crank chamber 82 at a location adjacent the crank arm 72. Another set of ports 83 and 84 are arranged in quadrature to the ports 77 and 78. The conduit branch 35a (see Fig. 1) is connected by conduit 35 to a pump 86 so as to supply uid fuel under pressure to ports 79, 80 leading to the valve 76. Another conduit 87 serves to return pressure fluid from the crank chamber S2 to a supply reservoir or oil tank 37a.

The ports S3 and 84 are connected through conduits 8S and S9 (Figs. 4 and 4a) to a hydraulic motor in the form of two cylinders 90 and 91 having respective pistons 92 and 93 reciprocable therein. The pistons 92 and 93 are connected by rods 9d and 9S respectively to the crank pin 73. When the diaphragm 55 is subjected to a pressure differential it yields proportionately and produces a corresponding rotation of the shafts 66 and 79. Thus the valve clement 76, which is integrally formed with the shaft 79, is rotated to an extent proportional to the deection of the diaphragm S5.

When feed water flow is initiated to the control device 2d, the movement of diaphragm 55 is transmitted to valve 7o so as to bring the entrance port 77 into communication with port S3, whereupon duid pressure is delivered through conduit SS into cylinder 90 and thereby move the pistons 92 and 93 toward the right in Fig. 4. Simultaneously the ports 84 and 78 are brought into communication so that fluid expelled by piston 93 will discharge through conduit S9 through said ports 84 and '78 into channel '71a and thence through the crank chamber S2 and conduit 87 to the reservoir 87a. The resultant movements of the pistons 92 and 93 are communicated through the rods 94 and 95, crank pin 73 and arm 72 to the shaft 71, thus causing the latter to rotate in the same direction as the shaft 70 by a follow-up action. When the shaft 71 has rotated to such an extent that the ports 77 and 78 are closed by the valve portion 76 of the shaft 70 as shown in Fig. 4a, ow of oil to the cylinder 90 is terminated thus stopping the movement of the pistons. By tracing the flow of motive iiuid under the inuence of the position of the valve 76, it will be seen that the hollow shaft 71 promptly follows any movement of the shaft 70 by a fast follow-up action and the force expended in rotating the shaft 71 is not derived from the shaft 7o but rather from the oil pump 86. As a consequence, any variation in the load imposed upon the shaft 71 is not reflected in the load upon the diaphragm S. Thus, when movement of the shaft 71 is employed for controlling the operation of the fuel supply valve 39 and damper 47, variations in the force required to move these elements will not influence the response of the diaphragm 55 or the extent of movement of either controlled element.

When ever feed water is flowing, the valve element 76 will be in an oft-normal position and will remain so until a change occurs in the rate of flow. An increase in the rate of flow will cause the diaphragm 55 to move upwardly thus enlarging the feed water orifice 61 while a decrease in the rate of iiow will cause the diaphragm to move inthe opposite direction to diminish the effective size of the orifice 51. Should the ow o f feed water be attenti terminated. the diaphragm will return to its normal. Pesition while at the same time a cam 9,6 (Fig. 1) mounted on the shaft 71 rocks a lever 97 to actuate a microswitch 98 and thereby opens a normally closed electrical circuit through a solenoid valve 99 to shutl olf all delivery of fuel to the spray head or nozzle 19.

in order to regulate the fuel valve 39 and air damper 47- to properly proportion the amount of fuel and air delivered to the lire chamber 17 in proportion to the rate of passage of feed watenthrough the diaphragm orifice o1, a pair of adjustable cam plates 1 00 and 101 (Figs. 5, 6 and 7) are provided. The cam plate 100 operates the fuel supply valve 3 9 while the cam plate 1101 operates the damper 47. The c am plates are supported on oppositely extending radial arms 10Z and-103 and are adjustable by means of sorews 104 s o that the cam surfaces Sint-a (Fig. 7) and lilla (Fig. 6) are of such angularity as to bring about the correct degree of actuation of the valve and damper for each increment c'l angular displacement of shaft 71.

The fuel supply valve 39 is provided with an actuating arm 105 which carries a carri roller 106 which bears against the cam surface 1005:. The movements of the cam roller 106 are transmitted to the valve stem 43.

The damper 47 (Figi) is actuated by link connections including a link (Figs. 1 and 6) connected to a link 107 which is pivotally secured to the upper end or" a supporting arm 10S (Fig. 6). The said link 107 carries a cam roller 109 bearing against the cam surface foin. Movements of the cam plate 101 imparts movements, through the roller 109, to the links 107 and 110 and these movements are transmitted to the damp-er 47.

The two arms 102, and 103 (Fig. 5) are integrally formed on a hub 111 which is keyed to the shaft 71.

The pistons 92 and 93 of the control unit 24 (Fig. 4), the fuel valve 39 (Fig. 5) and air damper 47 (Fig. 1) are shown in their intermediate positions. Movement of the piston 92 to the right as seen in Fig. 4 represents a movement which will increase the supply of fuel and air to the burner 17. Thus, a counter-clockwise movement of the cams 10i) and 101 (Fig. 5) increases the delivery of fuel while a clockwise movement (shown by the arrows in Figs. l and 6) of these cams decreases such delivery. ,in order to maintain a relatively steady movement of the control unit 24 in a direction to increase the delivery of fuel and to insure a quick movement of the unit when it is desired to shut off theV tire, valve 112Uis interposed in the conduit 8 8 for delivering pressure fluid to the cylinder 9i). This valve is of asymmetrical construction whereby it restricts the flow of fluid through conduit 88 into the cylinder 9i) and consequently retards the power movement of the piston 92 in a direction toward the right in Fig. 4 but permits unobstructed tlow of the fluid in the opposite direction and therefore permits quick movement of the piston 92 to the left in Fig. 4 so as to reduce or shut-off the delivery of fuel and establish an off fire condition of the steam generator.

Water luy-pass regulator it has been previously pointed out that it is not desirable to allow an off fire condition of the steam generator to obtain each time the steam pressure developed at the outlet 30 of the boiler rises above a predetermined maximum until such time as it has been ascertained that such an off re condition is justified.V Accordingly, in order to prevent immediate and rapid movement of the cam carrying members 102 and 103 in a clockwise direction as viewed in Fig. 5 to thus shut off the supply of fuel through the conduit 38 leading to the burner, the improved feed water by-pass regulator 34 of the present invention is employed. As will be explained presently, the by-pass regulator 34 is designed to maintain the cam members 100 and 101 in suchpositionsV that a low re condition is maintained in the steam generator when the pressure of steam in the conduit 32 risesr to 20 except for a very small amount.

a predetermined maximum and to continue such low re condition in effect until a still higher predetermined maximum pressure has been attained at which time the valve 37 associated with the regulator 34 becomes fully opened so as to by-pass substantially all of the feed water issuing from the pump 21 back to the reservoir When a still higher predetermined maximum pressure of steam in the conduits 30, 32 has been attained, the by-pass valve is fully opened and even this small amount of fluid is returned to the reservoir so that no feed water whatsoever is conducted to the steam generator coils.

The operative relation which the feed water by-pass regulator 34 bears to the herein described control system is clearly illustrated in Fig. 1. This regulator is adapted to vary the amount of water by-passed from the pump outlet conduit 23 and returned to the reservoir 26 in response to the steam pressure developed in the conduit section 30. The amount of water not thus bypassed continues on to the ow control unit 24 and causes operation of this device in the manner previously described to bring about certain conditions at the steam generator or boiler 111 to satisfy the requirements for which the regulator 34 is especially designed and which will be explained subsequently.

The by-pass regulator is shown in detail in Figs. 2 and 3. The regulator involves in its general organization a lower valve assembly A, an intermediate yoke assembly B and an upper pressure chamber or diaphragm chamber assembly C.

The valve assembly A includes a generally tubular valve casing 117 having an inlet port 114 communicating with the by-pass conduit section and an outlet port 115 which communicates with the return conduit section 36 through an attachment nipple 116. The casing 117 is provided with a central bore 118 therein, the lower end of which is threaded to receive therein a removable and adjustable valve seat element 119 providing a seat for the valve element 37. The valve 37 is carried on the lower end of a valve stem 120 which extends centrally through the bore 11S and which is slidably disposed in a valve bushing 121. A suitable seal 122 prevents passage of water upwardly along the valve stern 120. The valve 37 is maintained normally seated on the valve seat by means of a coil spring 123 which bears at its lower end against a bushing 121 and at its upper end against the under surface of a pilot collar 124 suitably mounted on the valve stem 120.

The yoke assembly B includes a yoke proper 125 which is carried at the upper end of an irregular shaped body 126 having attachment lugs 127 formed thereon whereby the entire by-pass assembly may be mounted on a stationary support. The lower end of the body 126 is provided with a socket portion 127 into which the upper end of the valve casing extends and in which it is secured by means of a tangential lock bolt assembly 128. A plurality of cap screws 129 serve to secure the yoke proper 125 to the upper end of the body 126.

The yoke 125 is in the form of a casting having a vertical bore 130 formed therein in which there is slidably disposed a tubular rack 131 having rack teeth 132 formed on one side thereof. The nature and function of the rack together with its associated operating mechanism which is supported in the yoke 125 will be described presently.

The diaphragm or pressure chamber assembly C includes a lower body or base member 133 and an upper cover member 134, the two members forming therebetween the pressure chamber 33 across which there extends a flexible impervious diaphragm 135. The marginal portion of the diaphragm is clamped between the body portion 133 and the cover portion 134 by means of a series of bolts 136. The cover member 134 is provided with an inlet passage 137, communicating with the conduit section 32 (see also Fig. 1) and with the interior of the pressure chamber 33 above the diaphragm 135. A diaphragm plunger 138 is slidably disposed in a bore 139 provided in the body 133 and is provided with an enlarged head 141i underlying the diaphragm 135 and in tace-to-ace contact therewith. The lower end of the plunger 141) is guided in a bore 141 formed in the upper portion ot the yoke.

The lower end of the diaphragm plunger 149 carries a valve-operating rod 142 which extends downwardly through the yoke proper and tubular rack 131 and has its lower end designed for engagement with the upper end of the vatve stem 120 thus allowing the valve 37 to normally remain closed under the inuence ot the coil spring 123.

From the above description it will be seen that downward movement of the plunger 138 will not occur until such time as sufficient pressure has been built up in the pressure chamber 33 above the diaphragm to overcome the resistance of the springs 143, 144.

Means are provided for adjustably varying the pressure exerted by the springs 143, 144 on the plunger 138 so that the by-pass adapter unit may be set to operate within a predetermined range. Accordingly, the upper end of the previously mentioned tubular rack 131 is adapted to bear against the under side of a spring seat 145 so that upward movement of the rack within the bore 130 will elevate the spring seat from its positions of support on the yoke 125 and thus compress the springs 143, 144 to increase the pressure thereof against an upper spring seat 146 and the diaphragm plunger 138. Toward this end the yoke 125 is provided with a transverse bore 147 therein, in which there is rotatably journalled a shaft 148 carrying a pinion 149 which meshes with the teeth 132 provided on the rack 131. An operating lever 158 has itsmedial regions secured to a hub 151 adjustably secured, by a locking screw assembly 152, to the shaft 148 so that turning movement of the lever 15) about the axis of rotation of the shaft 148 will cause rotation of the pinion 149 and consequently impart vertical movement to rack 131. As shown in Fig. 2 angular swinging movement of the lever in a clockwise direction will cause elevation of the rack 131 while counterclockwise motion thereof will cause lowering of the rack.

The upper portion of yoke 125 has secured thereto by means of studs 153 a plate 154 provided with indicia marks indicating steam pressure in pounds, and with a series of apertures 155 adapted to receive a locking pin 156, carried on the lever 150, to lock the lever in a selected position. In Fig. 4 the lever 150 is shown as being set at pounds of steam pressure and at this particular setting it is intended that when the pressure of steam in the conduit 30 and in pressure chamber 33 exceeds a predetermined pressure the plunger 138 will move downwardly against the opposing spring tension and move the valve element 37 from its seat thus commencing the by-passing of feed water as previously described.

Still referring to Figs. 2 and 3 the body member 133 of the pressure chamber assembly C is provided with a laterally extending beam 157 having an enlarged head portion 158 formed at the outer end thereof. Mounted beneath the beam 157 is an operating lever D comprising a pair of spaced parallel side members 159, 160 which are maintained in spaced relationship by means of spacing stud 161. The arms 159, 160 straddle the medial regions of the diaphragm plunger 13S and a pivot pin 162 extends through the plunger 138 and provides a pivotal connection for both side members of the arm assembly D on the plunger 138. The rear end of the arm assembly D is pivoted on a pin 163 carried by the body portion 133. The unbalanced weight of the forward or free portion of the arm assembly and the plunger 138 or in other words the normal force exerted by the springs 143, 144 upwardly on the plunger 138 is sucient to maintain the arm assembly D in an elevated position, but with capacity for vertical movements; there being sucient looseness in the pin connection 162 to permit the arm assembly D to assume' different positions in response to vertical' movements of the plunger 138.

A pin 164 extends across the two arm members 159, 160 and carries a roller 165 thereon. The roller 165 is designed for cooperation with a friction block 166 in a manner thatV will be described presently to retard or restrict downwardly swinging movement of the arm assembly D.

The friction block 166 is adjustably secured by means of an anchoring screw 167 to a tiltable pressure plate 168 pivoted as at 169 to the enlarged head 158 of the beam 157. The plate 168 engages a plunger 169 which extends into a bore 174i provided in the head-158 and the inner end of the plunger 169a bears against a spring 170 disposed within the bore 171'. The compression of spring 170 may be adjusted by a adjusting screwA 171 threadedly received Withinthe bore 170'.

The friction block 166 is provided with a protuberance or lip 1.72 which is positioned in the pathY of movement of the` roller 165 and it functions to restrain downward movement of the arm D and consequently the plunger 138 and the further opening of by-passA valve 37 until the steam pressure rises slightly above the pressure setting of theby-pass control'.

When steam pressure in the pressure chamber 33 is below the setting ofthe operating lever 150 as indicated in pounds of pressure on the indicia plate 155, the roller 165 occupies a position above the lip 172. As steam pressure rises in the conduit section 39, and consequently in the pressure chamber 33, the plunger 138 forces the swinging arm assembly D downwardly and the roller moves downwardly and approaches the lip 172. When the steam pressure attains the value for which the by-pass instrument is set, the roller engages the lip 172 and is retarded in its downward movement until such time as a predetermined higher pressure of steam has been developed.

In the control system illustrated, for the desired results, the adjusting screw 171 is manipulated so that the pressure of the spring 171i upon the plunger 169EL and the plate 16S will force the plate against the block 166 and the roller 165 and prevent the latter from riding over the lip 172 until such time as approximately 35 pounds of pressure over and above the pressure for which the instrument is set, as indicated by the position of the lever 150, has been built up in the pressure chamber 33. At such time, the pressure of the roller 165 against the lip 172 is sufficiently great as to cause the roller to snap or ride over the lip and allow a consequent lowering of the plunger 138 with its attendant valve-opening action. Thereafter the roller 165 may continue to move downwardly on the surface 173 in response to said accumulated excess pressure thereby permitting the valve 37 to move to its fully open position and permitting concurrent movement of the shaft 71 and its cam 96 (Figs. l and 5) to bring about the closing of the fuel nozzle valve 99. During this condition of operation the feed water pump 21, blower 46 and fuel pump 86, all being operated from the same motor 174, may continue, the oil pressure from pump 86 being by-passed through pressure relief valve 175 to the return conduit 87.

The contour of the lip 172 is designed according to engineering exigencies so that as the roller 165 will move upwardly over the lip 172 in the event of pressure differential drop of approximately l pounds. Toward this end, the under surface of lip 172 is formed with a gradual slope 176.

When the by-pass regulator 34 is properly installed and adjusted in the control system illustrated in Fig. l, the various parts of the system are coordinated so that under conditions of normal fire and normal demand for steam the arm assembly D is elevated and the roller 165 rides on the upper regions of the friction block 166. Under such conditions the by-pass valve 37 remains closed and there will be full delivery of feed water to the generator 10.

As the demand for steam decreases as evidenced by a rise in steam pressure in the conduit section 13, and pressureycli-amber segu-1e plunger 140 is' forceedownward-ty and the roller 11654 moves dow"w'ardly*. Whenappr'oiiitmately the pressure for which the instrlnnent'- lis s'et has been attainedV in the pressure chamber, the roller moves into engagement withA the lip 172 and by this time the valve 37 has opened to an extent suiiic'ient to by-pass water through' the valve and decrease'y the: flow of water tothe control unit 24; The responseV of the control unit- 24 at this particular time' will be such' that a condition of low or one-third tire is maintained at the boiler. j

When the roller moves over the lip- 1:72l and: assumes a position' at or near th'elower surface of the lip, the response of the control u'nit' 24'y is such asA to shut oi the supply of fuel` and' air tothe burner 18z but stillmaintain a small amount' of water circulation through the generator coils because of the con'ljnued'loper'ation of pumpv 21. The reduced delivery of feed' water, 0f course', is due to a materially decreased flow of water' toY the unit 24' occasioned by a Wider opening of theA valv'e 37".

When the roller moves into the extreme' lower regions the valve 37 is fully open and'allV of the feed water issuing from the pump 21 is by-p'a'ssed soA that no` water isV fed to the control unit or tothe boiler through the conduit 25.

From the above descriptionlit will be appreciated that the maintenance of a small supply: of Water tothe boiler coils duringv the' initial loff re condition of the latter, while the roller is immediately below the lip 172, serves to prevent drying out of the boiler coils due to residual heat in the tire chamber 17. By the same token, circulation of a limited amount of feed water through the coils serves to prevent developing"flash steam in the boiler coils and the consequent creation of superheated steam when the steam generator again resumes operation with a consequent tendency for the creation of thermal cracks.

After an on tire condition of the generator 10, a decrease in steam pressure in the chamber 33 will allow the roller 165 to move upwardly on the surface of the friction block 166 as previously described until it again encounters the lip inclined surface of the lip 172. At this point the lip will prevent further upward movement of the roller until a pressure differential drop of approximately l5 pounds is established in the chamber 33. rfhe roller will then move upwardly over the lip, thus partially closing the valve 37 and decreasing the amount of Water by-passed to the reservoir 2) so that sufficient feed water is passed to the control unit 24 to establish the previously described low or onethird lire condition; of the generator.

it will be evident to those skilled in the art that the new' principle of operation underlying the described feed water by-pass regulator is susceptible to a considerable variety of embodiments. It is to be understood therefore that the invention contemplates all modifications in principle and structure as comes under the scope of the appended claims.

We claim:

l. In combination with a steam generator having a re chamber, a fuel line for delivering liuid fuel to said fire chamber, a fuel valve in the lluid line, a feed water conduit leading to said generator, and a pump of uniform capacity for delivering feed Water through said conduit to the generator; of means for varying the delivery of Water to the generator in relation to the steam pressuretherein and for varying the delivery of fuel to the tire chamber in relation to the flow of water to the generator comprising a normally closed bleeder valve communicating with the feed water conduit at a location intermediate the pump and the generator, a pressure actuated structure responsive to the steam pressure in the generator and operatively associated with said bleeder valve to open the same to an extent commensurate with the steam pressure developed in the generator and thereby vary the delivery of feed water to the generator, a control unit interposed in the feed water conduit and ine 11 cluding an element responsive to the ow of water to the generator and operatively associated with said fuel valve for proportionately varying its open position in relation to the rate of flow of feed water to the generator, and means associated with said pressure actuated structure for delaying further movement thereof when a predetermined maximum steam pressure is attained, said delaying means being rendered ineffective upon the develop- -ment of a predetermined higher steam pressure in the generator.

2. The combination structure defined in claim l characterized in that said delaying means comprising a lever connected near one end to said pressure actuated structure and the other end of the lever being swingably in a predetermined path, and a yieldable abutment positioned in the path of movement of the last mentioned end of said lever and adapted to be engaged by said lever at the extremity of a predetermined movement thereof inY response to the movement of said pressure actuated structure, said abutment being adapted to yield to release said lever and said pressure actuated structure for further movement when said predetermined higher steam pressure is developed in the generator.

3. A combination structure as deiined in claim 2 characterized in that means are provided for varying the yieldable extent of said abutment so as to vary the amount of steam pressure required above said maximum to release said lever and said pressure actuated structure for further movement. -4. The combination structure as defined in claim El characterized in that the under-surface of said abutment constitutes a cam surface whereby the said lever will readily return to a position above said abutment.

5. The combination structure as defined in claim 4 characterized in that an anti-friction roiler is mounted on the end of said lever adjacent said abutment for engagement with said abutment.

References Cited in the iile of this patent UNITED STATES PATENTS 726,442 MacDonald Apr. 28, 1903 1,480,942 McKee Jan. 15, 1924 1,670,615 Eggleston May 22, 1928 1,821,112 Muren Sept. l, 1931 1,971,177 French Aug. 21, 1934 2,062,925 Ofeldt Dec. 1, 1936 2,405,573 Frisch Aug. 13, 1946 2,422,178 Blizard June 17, 1947 2,493,678 Marini Ian. 3, 1950 2,536,184 Johnson Jan. 2, 1951 2,572,195 Proctor Oct. 23, 1951 2,573,680 Arnold Nov. 6, 1951 2,599,872 Slonneger June 10, 1952

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