|Publication number||US2078479 A|
|Publication date||Apr 27, 1937|
|Filing date||Feb 6, 1935|
|Priority date||Feb 6, 1935|
|Publication number||US 2078479 A, US 2078479A, US-A-2078479, US2078479 A, US2078479A|
|Inventors||John E Briggs|
|Original Assignee||John E Briggs|
|Export Citation||BiBTeX, EndNote, RefMan|
|Referenced by (19), Classifications (10)|
|External Links: USPTO, USPTO Assignment, Espacenet|
April 27, 1937. J. E. BRIGGS WATER CONTROL FOR BOILERS Filed Feb. 6, 1935 2 Sheets-Sheet 1 INVENTOR. c/O/fl? f Brig ATTORNEYS.
April 27, 1937. J. E. BRIGGS WATER CONTROL FOR BOILERS Filed Feb. 6, 1955 2 Sheets-Sheet 2 1N VENTOR.
Patented Apr. 27, 1937 UNITED STATES PATENT OFFlCE 16 Claims.
This invention relates to liquid level control devices and more particularly to automatic elec tric control mechanism for regulating the operation of boilers, tanks, and other fluid receptacles.
An important feature ofthis invention is that the two important incidences of boiler operation, the replenishing with water and the production of heat, are both controlled automatically by an improved electric controller, an important advantage of which is the increased efliciency and safety with which the boiler operates.
An object of this invention is to provide an improved electric controller which is adapted to permit the water level in the tank or boiler to fluctuate in a normal operating range without calling the electrical controller into operation, but when the water level fluctuates to extremes the electric controller is called into operation to restore the boiler to its normal operating range.
Another object of this invention is to provide a compact, inexpensively designed, electric controller for boilers, tanks, et cetera, which is adaptable for all types of such devices, whether they are small conventional house boilers or very large steam boilers. A novel relay switch mechanism is employed to accomplish this object and includes a single movable member adaptable in its movement to close various circuits controlling the operation of the boiler. Because of its relatively few parts, this switch is adapted to be designed as a small, unitary structure which can be inconspicuously installed adjacent the boiler.
Various other objects and advantages of my invention will more fully appear from the following specification, appended claims, and accompanying drawings, wherein:
Figure 1 is a diagrammatic illustration of my electric controller and the associated parts of a boiler which it controls, and
Figure 2 is a modification of the device illustrated in Figure 1.
In the embodiments of the invention illustrated in both Figs. 1 and 2 numeral ill indicates a boiler furnace such as may be employed to heat a house or small building. The boiler portion of the furnace is indicated at 12 and a feed pipe it is adapted to supply water to the boiler. The heat producing apparatus is indicated generally at I6 and may comprise a conventional fuel burner to which fuel is delivered by the pipe it. A blower may be employed if necessary to create a draft of air for the burner. The type of fuel burner is not limited to that disclosed in the drawings, but may be any type such as a fluid or powdered fuel burner, or it may be a heating apparatus provided with an automatic stoker.
Referring more particularly to Fig. l, a chamber 22 f water level gauge type is secured to the that and provided with two communications 24 and 24' with the boiler so that the water level in the chamber is the same as that in the boiler. Positioned within this chamber are two electric contact members or electrodes, the shorter of the two being indicated at 26 while the longer is des ignated as 28. These electrodes are insulatively mounted within the chamber at their terminal plugs 30 so that the only electrical relationship that the electrodes have with the furnace is through the water and then only when the water is in contact with the electrodes.
Both the water feed pipe 14 and the fuel delivery pipe l8 are provided with electrically oper ated valve devices 32 and 34 respectively. These devices may be of similar construction. Valve device 32 is provided with an electromagnetic coil 36 adaptable to influence the valve member 38 to open position. Likewise valve device 34 is provided with an electromagnetic coil 40 adapted to affect the valve member 42 to open position. A main line circuit, which may possess the conventional house voltage, is indicated at H and the circuits to the coils 36 and 40 are placed across this line to receive current therefrom. The circuit for coil 36 isindicated at 46. The circuit for coil fill is indicated at 48.
An automatic relay controller for controlling these circuits is indicated generally at 50. The relay control consists of a coil 52 and an armature 54 provided with switch contacts operable to close and open circuits in a manner to be hereinafter described. The coil 52 derives its power from the secondary of a transformer 56 placed in the main line. The relay coil circuit 58 con= nects directly with the shorter electrode 26 in the water level chamber.
Both the valve circuits 46 and 48 are open at 6B and 62 respectively. They are adapted to be closed by insulated bridging elements 64 carried by the armature 54. In the position of the controller assumed in Fig. 1 the valve circuit is closed at til by its respective bridging element "5Q while the valve circuit 58, positioned on the opposite side of the movable armature, is open at 62,
The longer electrode 28 is provided with a circult 66 extending to the relay controller and is adapted to be connected into the relay circuit 58 when the armature has been raised to its upper pflsition. in this position a bridging element 64 will connect the circuit of the longer electrode into the relay circuit so that the relay coil 52 will now have branch circuit 68 and branch circuit 66 in communication with the water in the boiler. This second branch circuit, the electrode 28 and its lead 66, forms a retention circuit for the relay coil retaining the latter in energized condition even after the means which has caused the energization of the coil has been rendered inoperative. This operation will be described in more detail hereinafter.
To describe the operation of the automatic controller illustrated in Fig. 1 it is assumed that the water level in the boiler is below the end of longer electrode 28. The main line switch A is closed and due to the closure of the coil circuit at 68, valve member 38 is withdrawn to open position permitting feeding of water through conduit II to the boiler. The water level rises within the boiler and its contact with the longer electrode 28 produces no effect for the latter is in open circuit position at the relay controller. The water continues to rise until it approaches the shorter electrode 26, and during this interim the valve device 34 is cutting off the flow of fuel to the heat producing apparatus. When the water contacts the upper or shorter electrode 26, the relay coil 52 is grounded through the water and the furnace completing the circuit 68 and energizing the coil 52.
Upon energization of coil 62, the armature 64 is raised, breaking the valve circuit 46 at 68 and closing both the valve circuit 48 at 82 and the branch relay circuit 66. The valve device 82 is thereby de-energized cutting off the feed of water to the boiler, while valve device 84 is energized opening the delivery of fuel to the burner. The production of heat by the burner converts the boiler water into steam and the water level falls below electrode 26. However, the relay coil 62 is still retained in energized condition due to the fact that its circuit is completed through the branch circuit 66 to the longer electrode 28. Not until the water level drops below the end of the longer electrode will the relay controller be returned to its de-energized condition. At this point the fuel delivery will be cut of! while the water feed will be opened and the controller will be ready to commence its cycle of operations all over again. It is to be noted that the automatic control is entirely electrical in character and that it regulates the water level between two extremes providing a normal operating range for the boiler.
Conventional house voltage is not satisfactory for establishing a circuit through water, and for that reason a transformer or converter 66 has been employed in the controller for stepping up the voltage through the relay control circuit. This insures the establishment of a circuit through the water when the water is in contact with the electrodes.
In Fig. 2 I have shown a modification of the controller illustrated in Fig. 1. A third electrode is employed in this arrangement and instead of one relay controller, two separate controllers are included. This arrangement is particularly desirable for large steam boilers where it is undesirable to periodically cut off the heating apparatus. Such an arrangement may be adapted, for instance, for locomotive steam boilers. In that case the heating apparatus generally indicated at i6 and including the fuel delivery l8 may be a coal consuming furnace provided with an automatic stoker for delivery of coal thereto.
The modification in Fig. l is provided with a chamber 18 in which are mounted electrodes adapted to be aflected by different levels of water in the boiler. An electrically controlled valve device 12, similar to that at 32 in Fig. l, is employed for controlling the water feed to the boiler. Likewise, a valve device 14, similar to that at 84 in Fig. l, is utilized for controlling the fuel delivery. Both these valve devices are placed across the main line circuit 18 to receive power therefrom as in Fig. 1.
In place of one automatic relay controller as in Fig. 1 two are employed in this modification. The relay switch for controlling the water feed valve 12 is indicated generally at 18. The relay switch for controlling the fuel delivery valve II is indicated generally at 80. Both the circuits of these relay switches derive their power from separate secondary windings of the transformer 82.
The relay circuit which includes the switch l8 includes two electrodes 84 and 88 which perform functions similar to the electrodes described in Fig. 1. Instead, however, of establishing circuits through the water to be grounded on the furnace, these two electrodes establish a circuit through the water between themselves and thus, in this manner, close the relay circuit for the switch 78. The circuit of the electrode 86 is provided with a branch 81 leading to a ground connection. This ground circuit 81 is open except when relay switch 18 is in raised position.
A third electrode 88 is included in the relay circuit of the relay 88 and it is adapted to establish a circuit through the water to the furnace to be grounded thereon in order to close the relay circuit for the switch 88. This relay circuit is broken at the spaced contacts 80, but is adapted to be closed upon energization of the relay coil and withdrawal of the core into the coil. A push button switch 82 is capable of momentarily closing the relay circuit across the open terminals at 88 in order to start the sequence of operations. The arrangement of the switch 82 and the open contacts at 88 is used for heating apparatuses which are not capable of automatically firing themselves but must be fired by the operator. For those furnaces or heating devices which are capable of restarting without human assistance, as for instance by a pilot light, the arrangement of the switch devices 88 and 82 may be done away with and the relay circuit extend unbrokenly to the electrode 88.
In the operation of the modification shown in Fig. 2 it is first assumed that the water in the boiler is at a level between the two longer electrodes 86 and 88. Main switch A is then closed. The push button switch 82 is then momentarily closed. Due to the fact that electrode 88 in the circuit of the relay 88 is grounded through the water in the boiler, the coil of the switch 88 will be energized. Energization will close the circuit to the fuel valve device 16 and cause the opening of the valve. Thereafter the heating apparatus will function at all water levels above the end of the longest electrode 88.
The level of the water being between the ends of the two electrodes 86 and 88, the relay switch I8 will remain unenergized due to the fact that relay circuit is open between the electrodes 84 and 86. Accordingly, the switch I8 is in its lower position closing the circuit to the water feed valve 12 causing the opening of the latter and the delivery of water to the boiler. The water level thence rises in the boiler contacting the electrode 86. The contact of the water with this electrode has no eifect upon the circuit of relay '38 due to the break in the relay circuit still existing be tween the two electrodes 84 and 88. Upon the water level rising to the shortest electrode 86 the circuit of the relay 78 is closed through the water between the electrodes 84 and 88 and the coil of relay 18 is energized raising the switch armature to upper position and closing the branch circuit 81 to ground.
The raising of the armature switch in relay breaks the valve circuit to valve 1? permitting the latter to close and cutting off the delivery of water to the boiler. The conversion of water into steam lowers the water level out of contact with the electrode 84, but due to the fact that the circuit of relay 18 is grounded both through the electrode 88 and the water in the boiler and through the branch circuit 81 of the relay at the switch I8, the switch is retained in upper position, much in the same manner as in the operation of the device in Fig. 1 until the water falls below the middle electrode 88. Therefore, a normal operating range is permitted the water level in the boiler in which the water level may fluctuate without calling the automatic control lers into operation.
When the water level falls below the middle electrode 86, the ground connection of relay circult 18 is broken and the switch of the relay l8 falls to close the circuit to the water feed valve control. This operates to cause the feeding of the water to the boiler. But unlike the operation in Fig. 1, the heating apparatus continues to function at this stage. If the conversion of water into steam should exceed the introduction of water into the boiler, the water level will continue to fall until it drops below the longest electrode 88 at which point the ground connection of the relay 80 through the water in the boiler will be broken causing the latter, through the opening of the switch at 80, to tie-energize valve device 14 and cut oil the supply of fuel. It is seen, therefore, that the heating apparatus continues to function when the water level fluctuates in its normal operating range as well as when the water level falls below this range. It is only when the water level falls extremely low that the functioning of the heating apparatus is prevented.
The relay control 88 and its associated electrode 88 operate as an automatic safety appli ance preventing the operation of the heat producing apparatus when there is no or very little water in the boiler. At all other times however the heating apparatus functions, even when water is being introduced into the boiler. Cince the relay is tie-energized after the water level drops below electrode 88, it is necessary for the operator to momentarily push the button switch 92 to restart the sequence. This provision en= ables the operator to prepare the heating appa ratus for ignition when the fuel is delivered. those heating devices which are automatically ignited, the switch arrangement 98 and 92 may be dispensed with as previously explained. arrangement in Fig. 2 is particularly those boiler operations where it is undesh have the heating apparatus cut oil unless absolutely essential.
It is obvious that instead of the electric valve devices 32 and 12 for controlling the introduction of water, some other electrical apparatus may be used as, for example, an electric pump. The
electric pump would talre the place of the va ve device without disturbing the circuits previon established for valve devices. Or it ate it pump may be used, and the valve devices 32 and i2 may be employed to control the delivery oi steam to the pump. The control over the water feed would be the same as that described in connection with Figs. l and 2.
In the figures, a boiler 62 is shown. It is clearly within the concept of the invention to apply the control devices to any form of a liquid container. The controller could be associated with a tani; in place of the boiler. As an era ample, a tank: could be connected in the return line of a heating system between the radiators or the condensers and the boiler. The tank would receive the condensed products from the radiators and deliver the water to the boiler. The electric controllers would be divided between the tanl: and the boiler. That is, two of the electrodes 84 and 86 may be positioned in the tank while electrode 88 would be retained in the boiler. The electric control system would function substantially the same as described in connection with the drawings.
Various modifications will be apparent to those skilled in the art, and for that reason I intend to limit myself only within the scope of the append ed claims.
1. In an automatic electric controller for controlling the operation of a boiler having a water inlet and an apparatus for producing heat, elec tric means for controlling the delivery of water through said inlet into the boiler, electric means for controlling said heating apparatus, electric means for controlling said heat and water con trol means associated with said boiler and pro vided with contacts adapted to be electrically affected by different water levels in the boiler, all of said electric control means having the circuits opened and closed by a single movable element in accordance with the water levels in the boiler as the same affect the contacts of the electric means associated with the boiler.
2. In an automatic electric controller for con= trolling the operation of a boiler having a water feed inlet and a fuel. consuming apparatus for producing heat, electrically operated means for controlling the feeding of water through said inlet into the boiler, electrically operated means for controlling the delivery of fuel to said heat pro duclng apparatus, a relay controlcircuit for corn trolling the operation 01' said means and including a contact adapted to be electrically affected by the water level in boiler, a switch under control of said relay for opening and closing the circuits to said control means and adapted when the water level affects said contact in the boiler to render the control means for the water iced operative to cut off the feeding of water, and retention circuit for said relay also having a contact adapted to be affected by the water in the boiler but at a lower level than said first men tioned contact, said retention circuit adapted to cause the switch to be retained under control or the rel y in water teed cut off position until the water ie cl in boiler ails below the last men the fo er. auto-.- ttic electric controller for a steam us a water feed p l Comprising, in n, electric operateolvalve dvice eeci pipe adapted upon energizatiorl to op -s and permit the delivery oi water to holler, a relay ii'icluding two branch circuits ill till
having an electric contact adapted to be affected by a different level of the water in the boiler to close and open the relay circuit, said relay controlling a.switch in said valve circuit adapted upon the water level rising to the higher contact to open said switch and permit the valve to cut off the water feed and further adapted to maintain said valve in cut off position until the water level has fallen below the lower contact at which time the relay will permit the switch to close whereby the water feed pipe will be opened to fill the boiler.
4. An all electric automatic controller for steam boilers having a water inlet and a fuel consuming apparatus for producing heat which comprises, in combination, electric operating mechanism for controlling the delivery of water through said water inlet into the boiler, electric operating mechanism for controlling the supply of fuel to said fuel consuming device, a plurality of electric contacts adapted to be affected by dif ferent levels of water in the boiler to close circuits, and electric means associated with said contacts providing an automatic governor for regulating the operation of said electric operating mechanisms to limit the fuel delivery when the water level is low in the boiler and to limit the delivery of water through said inlet into the boiler when the water level is high in the boiler.
5. Automatic electric control apparatus for a boiler having a water feed inlet and a fuel consuming apparatus for producing heat comprising, in combination, electrically operated valve means for controlling the feeding of water through said inlet, electrically operated valve means for controlling the delivery of fuel to said heat producing apparatus, electric control means for controlling the operation of said valve means and including a pair of electrodes adapted to be contacted by difierent water levels in the boiler, and a switch mechanism having a single movable member operable for controlling the circuits to said water and fuel valve means and adapted in one position to open the water valve means circuit and close the fuel valve means circuit and in another position to open the fuel valve means circuit and close the water valve means circuit.
6. Automatic control mechanism for controlling the heating of a boiler and feeding water thereto comprising, in combination, a boiler, an auxiliary water tank connected to the boiler to maintain a war r level variable in accordance with the water the boiler, a pair of electric contacts extending 'nto said tank and each arranged to be affected at different levels of the water in the tank, a relay circuit associated with said contacts, electrical means for controlling the delivery of fuel for heating the boiler, electrical means for controlling the delivery of water to said boiler, said relay provided with a single movable element operable in one position to close the circuit to the fuel control means and operable in another position to close the circuit to said water control means.
7. Automatic control mechanism for a conventional house furnace having a fuel system for delivering fuel for combustion and a boiler provided with a water inlet through which water may be delivered comprislng,'in combination, electrically operated means for controlling the delivery of fuel, electrically operated means for controlling the delivery of water to said boiler, a unitary relay mechanism adapted to control the circuits of both of said electrically operated means, a single movable element in said relay mechanism operable in one position to close the circuit to said water control means and in another position to close the circuit to said fuel control means, and a pair of electrodes associated in the relay circuit and extending into contact relationship with the water in the boiler at different levels so as to energize and de-energize the relay as the water level varies within the boiler.
8. Automatic control mechanism for controlling the heating of a boiler and the feeding of water thereto, comprising, in combination. a boiler, an auxiliary tank connected to said boiler to maintain a water level variable in accordance with the water in the boiler, a water feed pipe for delivering water to said boiler, a fuel feed pipe for delivering fuel to a heat producing apparatus, valves in each of said pipes each under control of a separate electromagnetic means, a relay control mechanism for controlling the circuits of said electromagnetic means and including a single movable member operable in one position to open one of said electromagnetic circuits and to close the other and in another position to open the latter circuit and close the former circuit, said relay control mechanism including two electrodes extending downward unequal distances in the auxiliary tank so that the relay control is affected by different water levels in the boiler.
9. Automatic electric control mechanism for controlling the heating of a boiler and the feeding of water thereto which comprises, in combination, a boiler, a heat producing apparatus, a water feed pipe for delivering water to said boiler, a fuel delivery means for delivering fuel to said apparatus, an auxiliary tank connected to said boiler to maintain a water level variable in ac cordance with the water in the tank, electric means for controlling the feeding of water through said water feed pipe, electric means for controlling the fuel delivery means, an electric control mechanism for controlling said water feed control means and including two electrodes extending downward unequal distances in said auxiliary tank, an electric control mechanism for controlling said fuel delivery means and including an electrode extending downward in said auxiliary tank to a greater depth than said other two electrodes, said first two electrodes adapted to be affected by water levels so as to cause the water feed control to tend to maintain the water level within a range between the ends of said electrodes, and said longest extending electrode adapted to be affected upon the lowering of the water level below its end to cause the cut off of the delivery of fuel to said heat producing apparatus.
10. Automatic electric control mechanism for controlling the heating and feeding of water in a tank which comprises, in combination, a tank, means for feeding water to said tank, means for heating the water, electric mechanism for controlling the feeding of water to said tank, electric mechanism for controlling the operation of said heating means, an electric relay system for controlling said electric mechanisms and including a plurality of electrodes extending into contact relationship with the water in tank, said electrodes adapted to electrically affect the relay system upon contact with the water so as to cause the water delivery and heating means to alter their operation in accordance with the water level in the tank.
11. Automatic electric control mechanism for controlling the heating and feeding of water in a boiler which comprises, in combination, a boiler, a conduit to said boiler through which water is conducted, a heating apparatus for heating the water in said boiler, an electric device for controlling said water conduit, an eiwtric device for controlling said heating apparatus, a main circuit including both said electric devices, a relay circuit including a plurality of electrodes adapted to be afiected by different levels of water in said boiler and relay switches controlling the circuits to said electric devices, said relay circuit adapted to be rendered operative when the water level in the boiler contacts said electrodes and establishes a circuit through the water in the boiler, and a transformer between said main circuit and said relay circuit operable to step up the voltage for the relay circuit whereby adequate voltage is provided for effective electric transmission through the water in the boiler.
12. Electric control mechanism for boilers comprising, in combination, a boiler having a water feed thereinto, a heating apparatus for converting the water in the boiler to steam, an electric control device for controlling the feed of water to 25 said boiler, an electric control device for controlling said heating apparatus, a plurality of electric terminals associated with said boiler each adapted to be affected by a difierent level of the water in the boiler, electric means including said 30 terminals in circuit adapted to control said devices to shut off the feed of water when the level of the water in the boiler rises dangerously high and to shut down the operation of the heating apparatus when the water level in the boiler falls 35 dangerously low, said means including a retention circuit adapted when once the feed of water has been shut ofi to prolong this condition until the water level falls to a predetermined level in the boiler at which time it will function to open 40 the feed of water to the boiler.
13. Electric control mechanism for boilers comprising, in combination, a boiler having a water feed thereinto, a heating apparatus associated with said boiler for converting the water in '45 the boiler to steam, an electric control device for controlling the feed of water to said boiler, an electric control device for controlling said heating apparatus, a plurality of electric terminals associated with said boiler each adapted to be affected 50 by difierent levels of water in the boiler, electric means including certain of said terminals in circuit adapted to control said water control device to shut oil the feed of the water when the water level rises dangerously high in the boiler and to 55 feed water when the water level falls relatively low in the boiler, and second electric means including one of said terminals in circuit adapted to control said heat control device to shut down the operation of said heating apparatus when the 50 water level in the boiler falls to an even lower level than said relatively low level which functions to open the feed of water to the boiler.
14. An electrically controlled heating apparatus comprising, in combination, a chamber containing water, a heating device, said chamber furnishing water for the production of steam by said heating device, a conduit opening into said chamber through which water is adapted to flow and vary the water level in said chamber, electric mechanism controlling the delivery of water through said conduit, electric mechanism controlling the operation of said heating device, electric relay means controlling said heat and water control mechanisms, said relay means electrically connected to a plurality of electrodes extending into said chamber and each arranged to be contacted by a different water level in said chamber and upon such contact to establish a circuit through the water, said electrodes affecting the control exercised by said relay means over said water and heat control mechanisms in accordance with the water level in said chamber.
15. An automatic electric controller for tanks comprising, in combination, a tank adapted to contain liquids, a conduit opening into said tank through which liquid is adapted to flow and vary the level of the liquid in the tank, an electrically operated device controlling the passage oi liquid through said conduit, an electric relay mechanism controlling the circuit of said liquid control device, said relay mechanism having a circuit including an electrode arranged in said tank for contact with relatively high levels of the liquid in the tank, said electrode adapted upon contact with the liquid to affect the control exercised by said relay mechanism over the circuit of said liquid control device, a second circuit for said relay mechanism including an electrode arranged in said tank for contact with relatively low levels of liquid in the tank, said second circuit and electrode therefor forming a retention circuit for said relay mechanism adapted to retain the relay mechanism in the condition it assumed when the liquid level rose high enough in the tank to contact said first mentioned electrode until the liquid level falls below the second mentioned electrode.
16. An electrically controlled heating apparatus comprising, in combination, a chamber adapted to contain water, a heating device, a conduit connected to said chamber and through which water is adapted to flow and vary the height of the water level in the chamber, electric mechanism controlling the passage of water through said conduit, electric mechanism controlling the operation of said heating device, an electric relay means adapted to control the circuits of both of said electric control mechanisms, a movable element in said relay means operable in one position to close the circuit of said water control mechanism and in another position to close the circuit of said heating device, and means responsive to the water level in said chamber and electrically connected to said relay means to vary the operation or the latter in accordance with the water level in the chamber.
JOHN E. BRIGGS.
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US2449538 *||Jul 27, 1943||Sep 21, 1948||Hubbard & Co||Control apparatus|
|US2462076 *||Jan 27, 1945||Feb 22, 1949||Burton Dryden James||Tank filling control|
|US2482732 *||Dec 29, 1945||Sep 20, 1949||Goodrich Co B F||Electrohydraulic brake|
|US2487933 *||Jul 30, 1945||Nov 15, 1949||William O Martin Inc||Boiler high and low water control and alarm system|
|US2511637 *||Feb 11, 1947||Jun 13, 1950||Campbell Soup Co||Pump for heterogeneous mixtures|
|US2514630 *||Dec 7, 1946||Jul 11, 1950||Cook Electric Co||Liquid level control|
|US2519134 *||Dec 6, 1946||Aug 15, 1950||V Ray Van Wey||Pressure control switch|
|US2566260 *||Apr 10, 1946||Aug 28, 1951||Photoswitch Inc||Electrical control|
|US2573035 *||Jul 29, 1944||Oct 30, 1951||Photoswitch Inc||Electronic level control|
|US2608609 *||May 2, 1947||Aug 26, 1952||Fitch Henry M||Liquid level control equipment|
|US2614543 *||Apr 1, 1947||Oct 21, 1952||Hood James W||Forced circulation boiler|
|US2766406 *||Mar 5, 1953||Oct 9, 1956||Bendix Aviat Corp||Liquid level control system|
|US2805652 *||May 1, 1953||Sep 10, 1957||Stout Minor W||Water level responsive controls for combustion apparatus|
|US2806455 *||Feb 12, 1953||Sep 17, 1957||Bell & Gossett Co||Apparatus for preventing overheating of a hot water boiler|
|US2972041 *||May 14, 1958||Feb 14, 1961||Martin Mosny||Device for controlling the level of molten slag|
|US3190268 *||Feb 26, 1963||Jun 22, 1965||Macdonald Hugh D||Combination low-water cut-out and gauge glass|
|US3193141 *||Aug 23, 1963||Jul 6, 1965||Swift & Co||Device for measuring and dispensing variable amounts of liquid|
|US7992527 *||Dec 9, 2005||Aug 9, 2011||Potter Electric Signal Company, Llc||Water feed controller for a boiler|
|US20060124078 *||Dec 9, 2005||Jun 15, 2006||Merwin Jeffrey C||Water feed controller for a boiler|
|U.S. Classification||122/448.1, 303/1, 122/14.2, 122/14.3, 361/194, 122/504, 361/178|