US2138244A

US2138244A - Control apparatus

Info

Publication number: US2138244A
Application number: US187037A
Authority: US
Inventors: Estel C Raney
Original assignee: Ranco Inc
Current assignee: Robertshaw US Holding Corp
Priority date: 1938-01-26
Filing date: 1938-01-26
Publication date: 1938-11-29
Anticipated expiration: 1955-11-29

Description

Nov. 29, 1938. I E. c. RANEY 2,138,244

CONTROL APPARATUS Filed Jan. 26, 1938 2 Sfieets-Sheet 1 ATTORNEY Patented Nov. 29", 1 938 Estel C. Raney, 'Ranco Incorporated; poration of Ohio Columbus, Ohio, asalgnor to Columbus, Ohio, a cor- Application renames, 1938, Serial No. 187,037

s Claims. (c1. 158-28) This invention relates to improvements in control apparatus and particularly to control apparatus for fuel burning systems.

An object of the invention is to provide a control system, for electrically operated fuel burning apparatus, comprising a device for controlling energization of the apparatus and a control circuit for the device, the control circuit having a switch therein which is adapted to be opened by the device when the device causes deenergization of the apparatus and which is closed automatically. by a time mechanism but only after a predetermined time after the opening thereof by the device to thereby insure a time lapse before reenergization of the apparatus in the event there is a demand for operation of the fuel burning apparatus substantially immediately after a cessation of demand.

0 Another object of the invention is to provide a control system for an electrically operated fuel burning apparatus, including an ignition circuit having mechanism for controlling the same, which system comprises a device for controlling en-- ergization of the apparatus and a control circuit for controlling the device, the control circuit having a switch therein adapted to be opened when the apparatus is deenergized, and comprises timing mechanism for reclosing the control circuit switch after the ignition circuit is conditioned for operation by the control mechanism therefor. 'A still further object of the invention is to provide a control system for a fuel burning apparatus, including an electric ignition circuit having a time mechanism for opening thesame,

35 which system comprises a device for causing energization and deenergization of the apparatus, the device being controlled by a control circuit having a switch therein, and the device being operative, when the device operates to deenergize the apparatus, to open the control circuit switch and to close the ignition circuit, and comprises ,timing means for reclosing the switch in the control circuit after a predetermined time period.

Other and further objects and advantages will 40 be apparent from the following description, reference being had to the'accompanying drawings wherein a preferred form of embodiment of the present invention is clearly shown.

In the drawings:

50 Fig. 1 is a diagrammatical showing of the control apparatus in an oil burner system, the system being inoperative, and

Fig. 2 is similar to Fig. 1, and shows the parts of the control apparatus in the positions assumed 55 during normal operation of the fuel burner.

A transformer relay device III is provided for controlling the circuit of the fuel feeding apparatus, and to also provide-current for a low voltage control circuit for controlling operation of the' device. The transformer relay device l0 com- 5 prises an A shaped iron core I2, having a primary coil l4 wound on the cross member l3, and asecondary coil l6, wound on the cross member 15. The primary coil I 4 is connected in-a' high voltage circuit, as for example the usual 110 volt household circuit, one side being connected to the line wire 20 and the other side to the wire 22, safety switch 24 and line wire 25. The primary coil' is adapted to be energized at all times, except when the safety switch 24 may be opened.

A control circuit, adapted to be energized by the secondary coil It, may be traced, starting at one side of the secondary coil l6,. through wire 28, contact arm 66 of a room thermostat 80,

contacts

68 and 12, contact arm 10 and wire 18, heater coil 30, wire 3|, heater coil 32, contacts 56 and 54'of switch 34 and wire 36. The secondary coil l6 has fewer turns than the pri-' mary coil 4 so that a low voltage current is induced in the secondary coil, when the control 5 circuit is closed, as is well understood in the electric art. An armature 38, pivotally supported on a leg '45 of the transformer core I2, is adapted to be magnetically attracted to a similar opposite leg 46 when the circuit of the secondary I6 is closed. The magnetic attraction is provided by the fiow of flux in a path from the leg 45, through the armature and across to the leg 48,'established due to a counterfiux created in the' cross member I 5 whenthe secondary coil I6 is energized, which causes the flux to take the path described above. When the secondary circuit is opened, the armature is adapted to drop away from the leg 48 by the force of gravity. The armature 38 is provided with an extension 40, preferably of a dielectric 40 material, upon which is mounted a pair of

contact bars

42 and 44 of switches 4'! and 49 and are adapted to bridge two sets of

stationary contacts

48 and 50, respectively, when the armature is raised against the leg 46. Bridging the contacts 45 48 and closes the-switch 41 which controls the fuel burner motor 8 and the ignition transformer 90, and a holding circuit switch 49 connected in the control circuit. These circuits will be traced hereinafter. The armature 38 also carries a con- 50 tact arm 52, which is preferably formed of spring metal, having the contact 54 of switch 34 on the end thereof. The contact 54 is adapted to engage the contact 56 carriedona thermostatic element 00, to be described later. Thus the device ll 55 serves a dual purpose of, providing a transformer for the low voltage control circuit anda relay device for'controlling the fuel feeding motor and the control circuit.

The operation of the transformer relay I is controlled by the room thermostat 60, which is connected in the low voltage circuit. The thermostat 60 comprises a bimetal strip 62 anchored at one end, as at 93, and having a contact 94 carried on the opposite end. A contact carrying arm 66, preferably of spring metal, is anchored at one end and has a double contact member 68 carried thereon adjacent the free end. The contact arm 66 is normally biased against an adjusting screw 89, which forms a stop therefor. A second contact arm I0, also of spring metal, and normally biased against a fixed stop I3, is anchored at one end, and has a contact 12 on the free end thereof. The bimetal strip 62 is connected by the wire I5, to one of the contacts 50 of switch 49. The contact arm 66 is connected to the wire 28, and the contact arm I0 is connected in the low voltage circuit by the wire 18. The temperature at' which the thermostat 60 operates to energize the transformer relay device I0,may be adjusted by a hand screw 59 which is adapted to vary the position of the bimetal with respect to the contact 68,-and consequently vary the temperature at which the bimetal will engage the contact 68. The operation of the thermostat 60 will be described hereinafter.

A timing mechanism, provided for delaying the closing of the switch 34, comprises a bimetallic strip 80 suitably anchored at one end, as at 8|, having the contact 56 secured to the free end thereof. The side of the strip 90 having the lowest coeflicient of expansion is uppermost, so that the heat generated by the heater element 32, connected in the low voltage circuit and disposed in heat transfer relation with the bimetallic strip 90, will cause the bimetallic strip 80 to flex upwardly against a stop 32. The bimetal strip 80 is preferably relatively massive so that it will cool relatively slowly and remain against the stop 82 for several minutes after deenergization of the heater coil 32.

An ignition device, indicated at 89, is adapted to be energized by an ignition transformer 90. The circuit of the primary 9I of the transformer may be traced from high voltage line 25, safety switch 24, wire 22, wireI, primary 9|, ignition switch 92, wires 9 and II, motor switch 41 and line. wire 20. The ignition switch 92 is a toggle operated switch and comprises two oppositely disposed

switch members

93 and 94 which are pivoted each at one end in suitable pivot means, such as the V shaped notches 99 formed in a suitable bracket member 91. A tension spring I00 is'connected adjacent the free ends of the

members

93 and 94, for biasing the members to one side or the other of thedead center position of the members established with respect to the spring I00. The free end of the member 93 has a contact bar I02 suitably secured thereto through an insulated part which is adapted to bridge contacts I04 to close the switch 92. The free end of the member 94 is limited in movement between the upper and lower surfaces of a recess I06 provided in a sliding member I08. The contact carrying member 93 is limited in movement by the contacts I04 and the end of a relatively light weight push rod IIO, which is adapted to slide vertically in suitable guides I09 and is so disposed as to be engaged by the under side of the armature 39. The switch 92 is adapted to be opened by the upward movement of the member I08, which raises the end of the member 94 until the center of the spring I00 is moved above the pivot of the member 94, whereupon the tension of the spring I00 causes the member 94 to be snapped'to the upper surface of the recess I06. This throws the center of the spring I00 above the pivot of the member 93-, thereby causing the spring I00 to snap the member 93 against the push rod IIO, raising the latter against the armature as shown in Fig. 2 and opening the switch. The switch is adapted to be closed by the push rod IIO when the armature 39 drops, due to the opening of the control circuit. Thus the ignition switch is always positively closed when the motor circuit is opened. Slight'movement of member I08 downwardly moves the free end of the member 94 downwardly so that the center of the spring I00 moves below the pivot 'of the member 94 and thereby causes the member 94 to be snapped against the lower surface of the stop I06 by the tension of the spring I00.

The safety switch designated generally at 24, is connected in the high voltage circuit, and in series with the primary I4 of the transformer relay I0, the ignition circuit and the motor circuit and is constructed similarly to the ignition switch 92, having two oppositely disposed switch members III and H2 pivoted at II3, with a spring I I5 connecting the members adjacent their free ends. A contact bar I20, is carried on the free end of the member III, and is adapted to bridge contacts I24. The free end of the member H2 is limited in movement between the stop I I6 and a shoulder II9 located on the slide member I08, and the end of the member III is limited in movement between the contacts I24 and a stop H1. The safety switch 24 is adapted to be opened by the upward movement of the member I08 which moves the member II2 upwardly until the spring H5 is moved above the pivot of the member I I2, whereupon the tension of the spring H5 snaps the member II2 upwardly against the stop H6. This movement throws the center of the spring II5 above the pivot of the member III and the tension in the spring II5 snaps the member III upwardly against the stop I I1, thus opening the switch at the contacts I24. To reclose the'safety switch, the member H2 must be moved manually to the shoulder II9 when the member I09 is in its lower position, so that the spring I I9 will be moved below the pivot of the member III and snap the member III downwardly and close the contacts I24. When the

switches

24 and 92 are closed and the burner system is inoperative, the member II2 forms a greater angle with the horizontal plane than the corresponding member 94 of the switch 92 so that an equal upward rate of movement of the ends of the members 94 and H2 will cause the switch 92 to be opened prior to the opening of the switch 24.

The slide member I09 is adapted to be moved in a vertical plane, by a timing device, to operate the

switches

92 and 24. Member I03 is guided by guides H8. The timing device comprises a bimetal member I40, anchored at one end, as at I42, having the heating-element 30 disposed in heat transfer relation therewith; The free end of the bimetal I40, extends into a recess I44, formed inthe slide member I00. The side the bimetal having the lowest coefficient of expansion. is uppermost, so that when the heater 30 is energized, the bimetal will flex upwardly,

bimetal I40 is adapted to cool readily and assume its normal position as shown in Fig. 1, shortly following 80, moving member I08 against a stop I01.

The upward movement of the member I08 is adapted to be arrested, at a predetermined point, by a combustion responsive device I50, such as a device that is responsive to temperatures produced in the stack of the fuel furnace. The de- 10 vice I50, comprises a spiraled bimetal element I52, preferably placed in the stack of the furnace. which is adapted whenheated, to rotate a rod I54 clockwise. A crank member I 58, having a slide bar neeted to the end of the rod I54 by the usual friction clutch, well known in the stack control is a slight change in temperature in the stack.

When the bar I58 is moved to the right it is engaged by the surface I 82 thereby arresting further upward movement of the member I08. The bimetal I52 is adapted to rotate the rod I54 clockwise when it is heated, and consequently move the bar I58 to the right, and on cooling,

to move the bar I58 to the left. The detent I2I is positioned so that the upward movement of the member I08 may be arrested after the ignition switch 92 has been opened, but before the safety switch 24 is opened.

The operation of the control system is as follows: Assuming theapparatus to be temporarily inoperative, the parts will be as shown in Fig. 1, and when the room containing the thermostat 80 cools, the bimetal 82 will flex to the right due to' the decrease intemperature, and the contact move against the left surface of contact 40 54 will 88. This, however, does not complete the control circuit but on continued cooling of the room the bimetal 62 will continue to'fiexuntil it moves the contact 88 against the contact I2. A circuit is then established through the secondary I5,

wire 28, contact arm 88, and contacts 88 and I2,

contact arm .10, wire I8, heater element 80, wire 3|, heater element 82, contacts 58 and 54, arm 52,

and wire 86. The closing of the control'circuit causes the transformer relay I0 to attract the armature '38 to the leg 48, therebyelosing the switches 41 and 49. The switch 41 establishes a circuit for the fuel feeding ,motor 8 which may be traced as follows: line wire 25, safety switch 24,

wires

22 and 28, motor 8, wire II, switch 41 and line, wire 20. The motor- 8 thereby energized, operates to pump fuel into the furnaceand to supply the necessary air to support combustion. The ignition device 89, is energized at the 60 same time since the switch 92 is in its closed position and connected in parallel with the motor 8 and through the motor switch 41.

The switch 49 establishes a holding circuit around the contacts 59 and I2, and connects 5 contacts 54 that the low voltage circuit will not be opened until after the contacts 84 and 58 have separated. The holding circuit may, be traced through the secondary coil I 6, wire 28, contacts 68 and 84, of room thermostat 80, wirei5, contests 50 and 44, wires 9 and 18,. heater 88, wire 3i, heater 32, contacts 58 and 54, and wire 85. Thus the secondary circuit is maintained closed although contact 68 separates from contact I2.

7 The closing of the secondary circuit energizes deenergization of the heater I58 slidably connected thereto, is conand 88 in the low voltage circuit, so

' the heater coil 82, which causes the bimetal 80 to to follow the contact 58 as the bimetal 80 flexes upward, to maintain the switch 34 closed. The heater 30 is also energized and within several seconds causes the bimetal element I40 to move slowly upward, moving the bar I08 therewith. A predetermined upward movement of the member I08 opens the switch 92 which deenergizes the ignition device. The time required for the bimetal I40 to be heated sufliciently tocause opening of the switch 92, is such that under normal conditions the fuel of the burner should be ignited. The establishment of combustion causes the bimetal I52 to become heated by the products of. combustion and thereby cause the bar I58 to be moved into the path of travel of the shoulder I82 arresting upward movement of the member I08, to prevent opening of the safety switch 24. After combustion is established, the room ther.- mostat is warmed to a predetermined degree, the bimetal 62 is flexed to the left, and upon initial movement thereof, contacts I8 and I2 will be separated. This separation, however, will not affect the circuit due to the holding circuit established around these contacts by the switch 49, as described above. As the bimetal 82 flexes further to the left due to continued warming thereof, the contact arm 66 finally rests against the screw stop 88 and the contact 64 will then separate from contact 88 and break the control circuit. The opening of the control circuit causes the armature 88 to' drop, opening switches 41, 49, and 84 and closing the ignition switch 92, as described above. The contact 54 carried by the armature 38, will drop from the contact 58, but the switch bimetal 80 remains flexed against the stop 82, by the heat-already transmitted thereto from the heater 82. The bimetal 80 will require several minutes to cool and will then assume its position as shown in Fig. 1. mits purging of the fuel burning system of any 84 .will remain open since the' This time lapse perunburned fuel that might have collected in the furnace.

When armature 88 drops, it will move the ignition-switch arm 88 downwardly and either close the switch 92 or move the arm to a position in which it will be snapped closed upon a slight lowering of the toggle arm 94. The thermostat I40 is arranged to move the slide bar I08 downwardly'far enough to cause the arm 94 to be moved beyond its dead center position, i. e. to a position in which it retains the switch 92 closed, before thermostat 80 cools to the temperature at which it closes contact 58 on contact 54.

Therefore, after a cessation of operation of the thermostat is readjusted for a warmer room temperature immediately after it has opened the control circuit, the closing of the circuit is nevertheless, delayed for an interval of predetermined time from the time that the room thermostat last opened the control circuit. This time delay is sufficient, not only for insuring that the ignionce being established, the stack thermostat I50 will immediately cool and cause the bar I58 to be withdrawn from the stop I62 substantially immediately after a slight change in temperature of the stack, whereupon the bimetal H0, being biased upwardly by the heat of the heater 30, will immediately move the member I08 upward to cause opening of the safety switch and deenergization of the entire system, which remains so until thesafety switch is manually reset, as described above.

While the form of embodiment of the present invention as herein disclosed'constitutes a preferred form, it is to be understood that other forms might be adapted, all coming within the scope of the claims which'follow.

. I claim:

l. A control system for a fuel burning device, comprising in combination, electrically operated means for controlling the fuel burning device; a circuit for said means includinga switch; an electromagnet for closing the switch; an ignition circuit; electrical timing means including mechanism for opening the ignition circuit after a determined time of operation thereof; a control circuit for the electromagnet'including a switch, said electromagnet being movable when deenergized to open said switch; said electromagnet and timing mechanism cooperating to condition the ignition circuit for operation a predetermined time after deenergization of the control circuit, said timing mechanism being movable from one position to another for closing and being timed to prevent the reclosing of the second switch prior to conditioning of the ignition circuit and returnable to the said one position when the control circuit is reenergized; and means for controlling the control circuit.

2. In a fuel burning system, in combination, a fuel feeding device; a control circuit for said device; a switch in said circuit; electrically operated means for operating the switch; a control circuit for said electrically operated means; a switch in said control circuit; an ignition circuit including a switch therein; timing means rendered operable by the control circuit to open said ignition switch within apredetermined period after energization of the fuel feeding device; means for opening the second switch upon deenergization of the fuel feeding device; and timing means for reclosing the said second switch; said first mention timing means including means for reclosing the ignition switch, and said last mentioned timing means being adapted to reclose the second switch subsequent to the reclosing of the ignition switch.

3. A control system for a fuel burning apparatus, comprising in combination, electrically operated means for actuating the fuel burning apparatus; a control circuit for said means; an

the second switch ignition circuit,

ignition device and a circuit therefor; means for controlling the ignition circuit including a switch, movable means associated with the ignition switch and having a position for retaining the ignition time, said timing mechanism being rendered operative and inoperative by the control circuit; said control circuit including a switch therein arranged to be opened when the fuel burning apparatus is rendered inoperative by the control circuit; and a second timing mechanism for reclosing the switch in-the control circuit, the first and second mentioned timing mechanism being so computed that the movable member is in the first mentioned position when the second mentioned timing mechanism recloses the switch in the control circuit.

4. In a fuel burning system; electrically operated fuel feeding means; an electrically operated device for controlling said fuel feeding means; a control circuit for said device having a switch therein; means including a time operated device for opening the switch when the fuel feeding device is deenergized and for closing the switch a predetermined time after deenergization of the fuel feeding means; an ignition circuit including a switch; means including a time operated device for opening the said last'switch a predetermined .time after energization of the fuel feeding means and for closing the said switch prior to the closing of the first mentioned switch.

5. In a fuel burning system; electrically operated fuel feeding means; an electrically operated devicefor controlling said fuel. feeding means; a control circuit for said device "having a switch therein; means including a time operated device for opening the switch when the fuel feeding device is deenergized and for closing the switch a predetermined time after deenergization of the fuel feeding means; an ignition circuit including a switch; means including a time operated device for opening the said last switch a predetermined time after energization of the fuel feeding means and for closing the said switch prior to the closing of the first mentioned switch, said time operated devices comprising an electroresponsive thermostat connected in the control circuit.

6. In a fuel burning system, in combination, a fuel feeding device; a control circuit for said device; a switch in said circuit; electrically operated means for operating the switch; a control circuit for said electrically operated means; a switch in said control circuit having a timing mechanism associated therewith, said switch being opened by the electrically operated means, and closed by said timing device a determined time after the opening thereof; an ignition circuit including a switch; means including timing mechanism for causing the opening of the switch a predetermined time after energization of the the said last means being adapted to reclose the ignition switch prior to the closure of the second mentioned switch.

ESTEL C. RANEY.