US2740863A

US2740863A - Controls for heating burners

Info

Publication number: US2740863A
Application number: US388146A
Authority: US
Inventors: Basci Joseph
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-02-20
Filing date: 1953-10-26
Publication date: 1956-04-03
Anticipated expiration: 1973-04-03

Description

April 3, 1956 J. BASCI CONTROLS FOR HEATING BURNERS Original Filed Feb. 20, 1951 2 Sheets-Sheet 1 "V 8 .1 5 i ll m .w 7

INVENTOR. JOS E PH BASCI ATTOEN April 1955 J. BASCI 2,740,863

CONTROLS FOR HEATING BURNERS Original Filed Feb. 20. 1951 2 Sheets-Sheet 2 Q g. g

THEEMOSTAT JNVENTOR. JOSEPH BASCI AT TOP/VEY.

FLAME United States Patent CONTROLS FUR HEATING BURNERS Joseph Basel, iOOiilJlll, N. Y.

Original application February 2%], 1951, Serial No. 211,924, now Patent No. 2,669,298, dated February 16, 1954. Divided and this application October 26, 1953, Serial No. 388,146

3 Claims. ((31.200-124) This invention relates to new and useful improvements in burner control systems and more particularly to an improved electronic safety control system for fluid or gas burners.

This application is a division of my application Serial Number 211,924, filed February 20, 1951, now U. S. Patent No. 2,669,298, granted February 16, 1954-.

In the operation of oil burners it is desirous to prevent an abnormal discharge of fuel into the burner in the event of ignition failure or the premature extinguishment of the flame; and in the operation of gas fired furnaces, ovens, etc., it is desirous to prevent the flow of gas through the main burner when the igniting medium is not functioning, or when the main burner flame is pre maturely extinguished. Further, it is desirous to shut down the burner in the event of an open or short circuit in the control means therefor, a power failure, or the excessive overheating of the burner walls, and, in some instances, to reactuate the igniting means in the event of flame failure.

One object of the invention is the provision of a highly efiicient control system which is applicable to'both gas and oil burners and which is effective to provide all of the desirous results listed above.

According to the invention there is provided a flame sensitive device which in the case of an oil burner may be a photo-tube and which in the case of a gas burner may be a flame rod, an electronic amplifier controlled by the flame sensitive device, control circuits operated by the amplifier,.and a thermal switch actuated by a continued non-operation of said control circuits.

Another object of the invention is the provision of control circuitry for concomitantly reactuating the ignition means in the event of flame or ignition failure and for initiating an operation of the thermal switch, which, however, does not operate if theflame is reignited.

Another object of the invention is the provsion of a highly etficient thermal switch capable of positive operation at the expiration of a definite, predetermined time period and capable also of being reset manually within a short time after operation thereof.

A controlling factor in the manufacture and marketing of control systems of the type involved is cost, both original and maintenance.

A further object of the invention, therefore, is to construct the device of the invention in such manner that the same is capable of being manufactured economically, is capable of long life with a minimum of maintenance, and is adapted to rapid disassembly for adjustment and repairs.

Other objects and features of the invention will become apparent from the following description when read in the light of the accompanying drawings of which:

Fig. 1 is a perspective view of the control unit of the invention in condition for mounting;

Fig. 2 is an exploded perspective view of the several component parts of the unit;

Fig. 3 is a perspective view of the unit that'illustrates the means for securing two of the casing components thereof together;

Fig. 4 is a sectional view on line 44 of Fig. l, with many non-essential details left out;

Fig. 5 is a detached side elevational view of the thermal switch of the invention, said switch being shown in mounted condition in Fig. 2;

Fig. 6 is a detached edge view of said switch;

Fig. 7 is a detached elevational view of the opposite side of the switch;

Fig. 8 is a fragmentary, enlarged sectional view of the switch, and,

Fig. 9 is the wiring diagram of the invention.

Referring first to the wiring diagram of Fig. 9, the circuit illustrated therein is primarily adapted to an oil burner but is readily adapted for use with a gas burner. As shown, the circuit includes an ordinary three wire thermostat 15, a high limit control unit 16, the burner motor 17, the burner ignition unit 18, a transformer 20 having its primary coil 21 connected to A. C. supply and having a pair of

secondary coils

22 and 23, a pair of relays KY1 and KY2, a thermal switch 24, and electronic amplifier 25, preferably a dual triode such as a l2SN7, and a photo-tube 26 situated adjacent the burner flame and controlling said amplifier. For rotary pottype oil burners, the photo-tube 26 is replaced by a flame rod 27. For gas burners with pilot flame control, the flame rod 27 is used on the pilot flame, the main gas valve replaces the motor 17, and the ignition circuits are eliminated.

The one side of motor 17 and ignition unit is are connected by a lead 28 to one supply line 36. The other side of the motor, however, is connected by

leads

31 and 32 through a normally opened contact 33 of relay RYl to the other supply line 34, and ignition unit 18 is connected with lead 31 by

leads

35 and 36 through normally closed contacts 37 of relay RY2. Thus a normally open contact is provided in the motor circuit, and, said open contact along with a normally closed contact control operation of the ignition unit. Motor control relay RYI is connected by a lead 38 with one side of secondary coil 23 and by a lead 46 with a normally open contact 41 of the thermostat 15. Closure of contact 41 completes a circuit through a second contact 42 of the thermostat, lead 43, normally closed contacts 44 of relay RYZ, lead 45, thermal switch 24 and lead 46 to the other side of transformer coil 23.

The construction thus far described is such that operation of thermostat l5 energizes relay RYI which closes contacts 33 and initiates operation of ignition unit 18- and motor 17.

Relay RYI is also provided with normally open contacts 47 which are connected by an extension 48 of lead 4-6 with one side of coil 23 and by a lead at) to the heater filament 51 of amplifier 25. By means of a surge limiting resistor 52 and the lead 38, the other side of the heater filament is connected back to coil 23. Thus, onenergization of relay RY a circuit is completed to heater 51 through contacts 47 and surge limiting resistor 52.

Completing a circuit to a heater filament, normally occasions a current surge equal to six or seven times the normal current drawn by the heater, which greatly reduces the life of the tube. By inserting the resistor 52 in the circuit this current surge is limited to approximately twice the normal value which not only lengthens the life of the tube, but also lessens the standby power requirenients and eliminates the need for a special heater winding on transformer 28. This arrangement, of-course, is highly advantageous in that it lowers both the initial and maintenance costs of the device.

Amplifier 25 may be connected in any desired manner but preferably is connected as shown in Fig. 9. Forconvenience, the two halves of amplifier 25 will be referred to as tubes A and B, the left hand one in Fig. 9 being tube A. As shown the cathode 55 of tube A is connected to a tap of coil 22. The grid 58 of tube A is connected by a lead 60 through a large resistor 61 to the anode 62 of photo-tube 26. A large resistor 63 and a capacitor 64 are connected across

leads

56 and 60.

Resistances

63 and 61 and condenser 64 must be properly proportioned to provide proper bias for tube A and to provide a time constant of the proper value to maintain the bias during the negative swings of the coil 22.

Suggested values for these resistors and for the other circuit components will be listed at the end of the description. The anode 65 of tube A is directly coupled to the grid 58 of tube B and through a large resistor 66 and lead 67 to the other end of transformer coil A smaller resistor 68 also connects said anode to the cathode of tube B. The anode of tube B is connected through the coil of relay RYZ and a lead 69 to lead 67 and transformer coil 22. By means of a lead 70 and a capacitor 71, the cathode of tube B which is connected to the tap of coil 22, is coupled back to the anode 62 of photo-tube 26.

The operation is as follows: Assuming that a flame is causing photo-tube 26 to conduct, the latter rectifies the A. C. voltages applied through lead 70 from the tap of coil 22. Thus, a pulsating D. C. bias is applied to tube A causing the latter to become non-conductive. The charge on condenser 64 maintains the bias at a level sufi'icient for cutoff during the negative swings of coil 22. When tube A is cut off, the potential of its plate rises causing an increased current flow in tube B. This energizes relay RYZ. In order to maintain relay KY2 energized during the negative swings of coil 22, a large capacitor 72 is connected across the coil thereof.

The construction of the amplifier is such that when photo-tube 26 is conducting, or rectifying, the relay RY 2 is energized, but when the photo-tube becomes non-rectifying the cathode to grid connection of tube A is opened and the relay is deenergized.

It will be remembered that as described above, an operation of thermostat effects energization of motor starting relay RY1 which through the contacts associated therewith closed the motor and ignition circuits through a thermal switch and also closes a circuit for the heater of amplifier 25. Normally, closure of the motor and ignition circuits effects lighting of the flame in the burner, which through photo-tube 26 and amplifier results in energization of relay RYZ. This opens the normally closed

contacts

37 and 44 of said relay which open the ignition unit circuit and the circuit for relay RY1 through thermal switch 24 respectively. However, normally open contacts 75 of relay RY2 are closed and complete circuit for relay RYl which does not include thermal switch 24.

This circuit includes the lead which is also connected to contact 44, a lead 76, closed contacts 77 of energized relay KY1, a lead 78, a common contact 80 of thermostat 15, contact 41 of the latter, lead 40, relay RY1, lead 38, transformer coil 23, leads 46 and 48, closed contacts 47 of relay RYl, lead and a lead 81 connected back to contacts 75.

The construction is such that immediately following a successful operation of ignition unit 18 under control of thermostat 15, photo-tube 26 and amplifier 25 effect both the inactuation of said ignition unit and also the shunting of the thermal switch 24 so that the latter does not heat up sufiiciently to open the circuit and turn off motor 17.

Thermal switch 24 preferably is of the unique construction to be described hereinafter but may be of any type capable of opening positively in approximately 50 seconds due to the heat provided by approximately one watt of power, and capable also of being reset manually within a short period of time. 7

Thus, if the ignition unit 18 fails to ignite a flame within the predetermined period of approximately 50 seconds the thermal switch 24 opens and prevents the further pumping of fuel into the burner by deenergizing relay RY1. Further, if the flame should be extinguished prematurely, the photo-tube 26 becomes non-rectifying and relay KY2 is deenergized, bringing ignition unit 18 and thermal switch 24 back into the circuit. This, of course, results either in a successful operation of the ignition unit 18 or in the opening of thermal switch 2 4. Tube failures and short or open circuits in either relay RY2 or RY1 also result in opening of thermal switch 24, since the shunt circuit for thermal switch 28 includes

contacts

75 and 47 in series with each other. Thus, accidental closure of either

contacts

75 or 47 is not sufiicient to short-circuit thermal switch 24, but rather both

contacts

75 and 47 must be simultaneously closed to establish a bypass or short-circuit for thermal switch 24.

It is believed evident that the opening of thermostat 15 conditions the device for the next operation.

It is desired, that thermal switch 24 open in the event relay RYZ remains energized after thermostat 15 is opened, for example, when high infra-red emission occurs due to overheated burner walls. This is accomplished by a circuit which includes said switch, lead 46, transformer coil 23, resistor 52, heater 51, leads 50 and 81, closed contacts 75 of energized relay RY2 and lead 45.

The thermal switch of the invention is illustrated in detail in Figs. 5-8 and includes a plate 85 having a shelf 86 bent off therefrom at one end and a shelf 87 at the other end. A large opening 88 in plate 85 extends into shelf 87 so that the latter resembles a pair of ears interconnected by a crosspiece.

Shelves

86 and 87 are interconnected by bolts 90 which extend through sleeves 91 positioned between the shelves and which are provided with nuts 92 for securing the unit in place. Riveted to plate 85 between

shelves

86 and 87 and spanning the portion of opening 88 adjacent shelf 87 is a plate 93 of an insulative material such as Bakelite. A tail 94 of plate 93 projects beyond shelf 87 and has secured thereto a pair of terminals 95 for the

leads

46 and 45, 76 of the wiring diagram of Fig. 9. Secured in a hole in plate 93 and extending between the

shelves

86 and 87 is a hollow stem 96 of brass or other conductive material, said stem having wound thereon a heating coil 97 which is insulated therefrom by a coating 98 of high temperature insulation. One end of the coil, however, is soldered to an annular flange or collar 100 of the stem near the free end of the latter. The other end of the coil is connected by a lead 101 with one of the terminals 95. Mounted within stem 96 but fixed against rotation by a layer of solder 102 fixing it to the stem is a tubular pivot shaft 103 for a pinion 104. At the free end of stem 96 the end of shaft 103 is flared out at 105 and abuts a bearing washer 106 positioned between said flare and an annular collar 107 of said stem. A bearing washer 108 is also provided between pinion 104 and the fixed end of stem 96.

It is to be mentioned that solder 102 may be of any commercially available type which will melt and free shaft 103 from stem 96 in approximately 50 seconds due to the heat generated by coil 97 with about one watt of power.

Cooperating with pinion 104 is a pawl 110 of beryllium copper or the like which is connected by a lead 111 with the terminal 95 to which the heater coil is not connected. Pawl 110 is secured to the flattened end of a rod 112 of Bakelite or the like which is slidably mounted in holes in shelf 86 and in a shelf 113 at the edge of opening 88. A pin 114 projects through rod 112 and into a slot 115 in plate 85, that extendslongitudinally of the rod and limits the amount of longitudinal movement thereof. Slot 115 also prevents rotative or chattering movements of rod 112. A spring 116 is wound on rod 112 and acts between shelf 113 and pin 114 to move the rod in a direction to rotate pinion 104 counterclockwise in Fig. 7.

The construction is such that normally solder 102 is effective to prevent rotation of pinion 104 and a circuit is completed from one terminal 95 to the other through lead 101, coil 97, stem 96, solder 102, shaft 103, pinion 104, pawl 110 and lead 111. However, if solder 102 should be melted by coil 97, the pinion 104 is rotated by pawl 110 which moves out of contact therewith to the dot-dash position of Fig. 7 and the switch is opened.

To reset the switch all that is required is to allow a few moments for the solder 102 to reharden, and to push rod 112 back to its initial position, the pawl 110 readily springing to clear the upper portion of the pinion.

For convenience of installing and servicing the control device of the invention, the same is assembled in unitary form as shown in Figs. 14. The relays RYl and RY2, transformer 20, thermal switch 24 and amplifier 25 are mounted on one face of a rectangular box like chassis 117 which includes two

main plates

118 and 120 each having a side wall 121 and an

end wall

122 or 123 bent off therefrom. The side walls 121 and the

end walls

122 and 123 are, of course, oppositively located. Secured to plate 120 and to end wall 123 of plate 118 are the pivot supports 124 of a hinge which also includes a removable pivot pine 125. Thus

plates

118 and 120 with their oppositively disposed

walls

121 and 122 or 123 form a box which is openable about

hinge

124, 125 but which may be locked in closed condition by the engagement of a wide head screw 126 in an open end slot 127 in end wall 122. Screw 126 is threaded into a bracket 128 secured to plate 118, and when drawn up, effectively prevents swinging movement of plate 120 about pivot pin 125.

The circuitory associated with relays RYI and RY2, transformer 20, thermal switch 24 and amplifier 25 is secured to the rear face of plate 118 and is covered and protected by an insulative plate 129 bolted to the bracket 128 and to another bracket 130. Secured to the forward face of plate 120 are a pair of insulative blocks 131 each having thereon a plurality of screw terminals to which the appropriate leads of a cable 132 extending from the circuit elements on plate 118, are connected. The end wall 122 and side wall 121 of plate 120 are provided with suitable capped openings 133 through which cables 134 are extended to connect the unit with a source of supply, a thermostat, a burner motor, etc.

Plate 120 is provided with suitable holes 135 by which the same may be mounted on a convenient wall or the like. The elements mounted on plate 118 are covered and protected by a deep sheet metal cover 136 which embraces the plate 118 and slight portions of the side walls 121 and end

walls

122 and 123. Cover 136 is secured in place by a pair of screws 137 which are threaded into the

end Walls

122 and 123 and engage in open end slots 128 in the edge of the cover. in order to accommodate the reset rod 112 of thermal switch 24 a hole 140 is provided in cover 136.

It will be seen, therefore, that in the event thermal switch 24 operates as described above, the reset rod 112 projects to the dot-dash line position of Fig. 1 through the cover hole 140, and can be reset merely by pushing it to the full line position illustrated. And, if it is desired to service the elements mounted exteriorly of chassis 117, all that is required is to loosen screws 137 and remove cover 136. Further, to service the interior of chassis 117, the latter may be swung open on

hinge

124, 125 by loosening screw 126 or may be completely disassembled by removing pivot pin 125.

There has been provided, therefore, a highly efiicient control unit for the purpose set forth that is not only economical in initial cost but also in installation and main tenance.

Suggested values for the several circuit constants are as follows:

Resistor 61 -r l8-20 megohms. Resistor 63 18-2O megohms. Resistor 66 100,000 ohms. Resistor 68 15,00022,000 ohms. Resistor 52 40-50 ohms. Condenser 64 .Ol mfd.

Condenser 71 .002 mfd.

Condenser 72 4 mfd.

Amplifier 25 12SN7;

Phototube 26 922 (vacuum). Transformer coil 22 225 volts, center tap 200 volts. Transformer coil 23 24 volts.

While there has been described a preferred embodiment of the invention it is to be understood that many changes in details of the construction can be made without departing from the spirit of theinven'tion.

I claim:

1. A thermal switch comprising a rigid frame, an insulative manual reset rod endwise slidably mounted in the frame, spring means tensioning said rod in one endwise direction, an insulative panel secured to said frame, terminal lugs mounted on said insulative panel for placing the switch in an electric circuit a conductive stem projecting through and secured in said panel, a second conductive stem located within the first, a layer of low temperature melting solder fixing said stems together and conecting them electrically, a conductive pinion fixed on one end of the second stem, a conductive spring pawl electrically connected to one of said terminal lugs secured to said rod and engaging said pinion to make electrical. contact therewith and to prevent endwise movement of the rod by said spring, a heating coil wound on the outer stern and electrically insulated therefrom except for one end, said one end making electrical contact with said outer stem, the other end of said heating coil being electrically connected to the other of said terminal lugs said coil being adapted to melt said solder in a predetermined amount of time to allow said pawl to rotate said pinion and move out of contact therewith.

2. A thermal switch comprising a rigid frame plate having ears bent oif therefrom and an opening therein, an insulative manual reset rod endwise slidably mounted in said ears, a pin projecting through the rod, a slot in said plate through which said pin projects to guide the rod and limit the amount of endwise movement thereof, a spring acting against said pin to move the rod in an endwise direction, an insulative panel mounted in said opening, a conductive stem projecting through and secured in said panel, a second conductive stern located within the first, a layer of low temperature melting solder fixing said stems together and connecting them electrically, a conductive pinion fixed on one end of the second stem, a conductive spring pawl forming part of the electrical conductive path through the switch in operation secured to said rod and engaging said pinion to make electrical contact with said pinion and to prevent endwise movement of the rod by said spring, a heating coil forming part of the electrical conductive path through the switch in operation wound on the outer stern and electrically insulated therefrom except for one end, said coil being adapted when the current passing through the switch exceeds a predetermined amperage to melt said solder in a predetermined amount of time to allow said pawl to rotate said pinion and move out of contact therewith, and terminal lugs to which said pawl and the other end of the heating coil are connected electrically.

3. A thermal switch comprising a rigid frame plate having ears bent otr' therefrom and an opening therein, an insulative manual reset rod endwise slidably mounted in said ears, a pin projecting through the rod, a slot in said plate through which said pin projects to guide the rod and limit the amount of endwise movement thereof, a

amaees 7 spring acting against said pin to move the rod in an endwise direction, an insulative panel mounted in said opening, a conductive stem projecting through and securedin said panel, a pair of annularcollars on said stern, one near and the other at the free end thereof, a second conductive stem located within the first, a flared end on the second stem adjacent the said end collar, a bearing Washer between said flared end and said end collar, 2. layer of low temperature melting solder fixing the two stems together and connecting them electrically, a conductive pinion fixed on the other end of the second stem, a bearing washer between said pinion and the end of the outer stern, a con ductive spring pawl secured to said rod and engaging said pinion to prevent endwise movement of the rod by said spring and to make electrical contact with said pinion, a heating coil wound on the outer stem and electrically insulated therefrom, one end of said coil being connected to the collar near to the face end of said stem, said coil 8 being adapted when electric current passes therethru to melt said solder in-a predetermined amount of time to allow said pawl to rotate said pinion and move out of contact therewith, and terminal lugs to which said pawl and the other end of the heating coil are electrically connected.

References Cited in the file of this patent UNITED STATES PATENTS 1,569,815 Kirkland Jan. 12, 1926 1,678,800 Baker July 31, 1928 1,752,514 Van Valkenburg Apr. 1, 1930 1,966,926 Darnell et al July 17, 1934 1,978,713 Knight Oct. 30, 1934 2,276,085 Pearson Mar. 10, 1942 2,532,265 Zickrick Nov. 28, 1950 2,597,068 Cobb May 20, 1952