US2022826A - Electric control apparatus for fuel burners - Google Patents

Description

Dec. 3, 1935. A. l.. RUBEL l 021825 ELECTRIC CONTROL APPARATUS FOR FUEL BURNERS l Filed oct. 16, m53

RELAY SWITCH latenleol Dec. 3, 1935 ELECTRICI CONTROL APPARATUS FOR FUEL BURNERS Abraham L. Rubel, Des Moines, Iowa, assignor to Penn Electric Switch Co., Des Moines, Iowa, a

corporation of Iowa Application october y1e, 193s, serial No. 693,800

2 Claims.

An object of my present invention is to provide control apparatus for the electric circuit of a fuel burner, such apparatus being of simple construction and operable to automatically take 5 care of various emergencies arising during the operation of the burner.

A further object is to provide an automatic controller-including a combustion switchV which is opened when combustion occurs in order to break the circuit through a lock-out switch so that upon combustion occurring the lock-out switch will not thereafter lock out.

Still a further object is to provide control apparatus including a room thermostat operated relay which normally initiates and terminates operation of a fuel burner and which initiates operation of ignition mechanism for the fuel burner, termination of the operation of the ignition mechanism being eected by an ignition trip mechanism which in turn is operated by a combustion switch, the combustion switch including a lost motion connection to delay the operation of the ignition trip mechanism.

A further object is to provide control apg; paratus including a combustion switch having a friction connection for one of the movable contacts and a lost motion connection which provide for de-energizing the relay and re-cycling by re-establishing the starting circuit, respectively, so that between relay de-energization and re-cycling a purging period is provided, thus allowing the combustion chamber of a furnace or the like to be cleared of dangerous gases by the natural draft therein before the ignition mecha.-

'35 nism is re-energized by establishment of the starting circuit and thus eliminating an explosion upon such re-energization.

Another object is to provide a control structure in which ignition contacts are normally closed, but the ignition current does not flow through them until a room thermostat is also closed, these contacts being so mounted on aJ tacts of a combustion switch which have the peculiarity of closing only after the combustion switch moves from cold to hot position and then starts to return toward cold position, such peculiarity being elected by a frictional mounting 5 for one of the contacts of the switch.

With these and other objects in view my invention consists in the construction, arrangement and combination of the various parts of my device, whereby the objects contemplated are 10 attained, as hereinafter more fullyi set forth, pointed out in my claims, and illustrated in the accompanying drawing, in which:

Figure 1 is an electrical diagrammatic view of an electric control apparatus for fuel burners'15 embodying my invention.

Figure 2 is a simplified wiring diagram of the same.

Figure 3 illustrates different successive positions of a combustion switch shown in Figure 1. 20 Figures 4 and 5 are different successive views of the relay switch shown in Figure 1 during its operation.

Figure 6 is a sectional View on the line 6 6 of Figure 1 showing details of a combustion switch 25 which I employ; and

Figure 7 is a front view of the ratchet and lost motion mechanism of the combustion switch.

On the accompanying drawing, a plurality of contacts are illustrated. Lock-out switch con- 30 tacts are shown at Ill. A relay switch has motor contacts I2 and I4, ignition contacts I6 and holding contacts I8. The relay switch includes an ignition trip mechanism having contacts 20.

A combustion switch is provided with ignition trip contacts 22, relay de-energizing contacts 24 and starting contacts 26.

The lock-out switch alsoincludes a cam 28 spring actuated to separate the normally closed contacts Ill but normally held from doing so by4 a bimetal latch 30. The latch 3l! is adapted to be warped to unlatched position by a lock-out switch heater 32 when it is hot.

The relay switch includes a relay coil 34 divided into two separate coils 34a.` and 34h by a central connection. An armature 35 normally held spacedfrom the coil 34 is adapted to be attracted thereby whenthe coil is energized. A bridge piece 38 carried by the armature 36 connects one of the contacts l2 with one of the 50 contacts I4, when the relay is energized as in Figure 4, thereby eliminating a pig-tail connection.

ture 36 to the position of Figure 1. spring 42 carries one of the contacts I6.

An ignition trip mechanism is provided in the relay switch and includes contacts 26 and 26a. The contact 26a serves as an armature for an electromagnet 44.

The contact 26a retains the contacts I6 engaged as in Figures 1 and 4 whether the relay is'or is not energized providing the electromagnet 44 is not energized and permits them to separate providing the relay is energized and the magnet is then energized.

The combustion switch includes a rotatable rod 46 and a bimetal coil 48 responsible to temperature in the combustion chamber of a furnace. One end of the coil 48 is secured to the rod 46 as at 41 and the other end is stationarily anchored as at 49 to a housing 5I for the combustion switch. 'Ihe combustion switch also includes a toothed disk 52 and a lost motion connection between the rod 46 and the toothed disk comprising an arm 56 on the rod and spaced stops 54 on the disk. The disk 52 is rotatably mounted on the rod 46. A leaf spring 56 carrying one of the contacts 26 is adapted to coact with the periphery of the toothed disk 52 to be operated thereby during rotation thereof such cooperation being shown in Figure 7; lthe free end of the spring 56 tends to remain in the position of Figure 3 (A) and the full line position of Figure 7 so that, due to its path of movement describing an arc 53, it can be swung immediately upon the toothed disk beginning to rotate and after a predetermined degree of rotation permits the teeth thereof to slip past it as in Figure 1 and Figure 3 (C).

The combustion switch further includes a frictional mounting comprising a plate 58 for one of the contacts 24, the arm carrying this contact and also the arm carrying the upper contact 22 being actuated from the leaf spring 56. All of the arms carrying the contacts 22, 24 and 26 are leaf springs except the one carrying the upper contact 24 and having the plate 58 which can be of rigid material and pivoted at 6I. The plate 58 is caused to frictionally engage the insulating block 55 which indirectly supports the contacts 22, 24 and 26 by means of a spring washer 59 on the pivot 6 I.

A transformer 66 is provided for furnishing current for the relay coil 34, the lock-out switch heater 32 and the ignition trip magnet 44.

Terminals L and L for line wires, I for ignition mechanism, M for motor and R and R for a room thermostat or main control switch, are illustrated in Figure 1. These are also illustrated The leaf in Figure 2 and a motor, ignition mechanism and a room thermostat are indicated as Motor, Ign. and Room therm., respectively. The primary and secondary of the transformer 66 are indicated at Pri. and Sec..

Practical operation The circuit connections with the various coils, heaters, contacts, etc., are all fully shown in Figures 1 and 2. 'I'he parts in Figure 1 and the contacts in Figure 2 are in normal or non-operating position.

Starting circuit ing contacts 26 of the combustion switch to the upper end of the transformer secondary.

This causes the armature 36 to be attracted whereupon its contacts I2, I4 and I8 are closed and I6 are held closed or in their normal position 5 by the ignition trip armature 26a as shown in Figure 5. N

The closing of the contacts I2 and I4 establishes both the motor circuit and the ignition circuit from the terminal L through the lock-out l0 switch contacts I6, the contacts I2 and I4 and the contacts I6 which are already closed. Closing of the holding contacts I8 provides a holding circuit for the relay which is energized under certain circuit conditions. 15

Running circuit If combustion occurs, the starting contacts 26 will rst be opened by reason of the bimetal coil 48 slightly rotating the toothed disk 52, as shown 20 in Figure 3 at A. This breaks the starting circuit, but permits the current from the upper end of the relay coil 34a to ow through the coil 34h and the holding contacts I8, thus holding the relay in its energized position. Passage of the 25 current through the coil 34h, instead of the shunt circuit including theA contacts 26, reduces the current so that the lock-out switch heater 32 will not become hot enough to trip the lock-out switch to open circuit position. 3o

If combustion does not occur, then the secondary current from the transformer 66 will be oi higher value because it is choked only by the coil 34a and not by the coils 34a and 34h so that the heater 32 will heat up suiliciently to trip the 35 lock-out switch.

If combustion does occur,the running circuit just described will normally be maintained until the room thermostat opens it because of a rise of the temperature in the room to a predetermined degree.

Ignition trip circuit This circuit may be traced from the terminal R through the ignition trip de-energizing con 45 tacts 26 and 26a, the magnet 44 and the ignition trip contacts 22 of the combustion switch when they close. It is desirable to.A have them close after a delayed period of time however. Ac-

cordingly, the spring arm 56, due to its tendency to assume a substantially central position will move the toothed disk 52 to the position of Figure 3 at A after the arm 56 of the combustion switch moves from cold toward hot position, the left stop pin 54 following it by reason of the arm 55 56 rotating the toothed disk 52 until the position at A is assumed, whereupon the arm 56 will move from the left stop pin to the right one. After it engages the right one, as at B, both contacts 24 will be moved downwardly but will not become 30 engaged.

Finally, the contacts 22 will become engaged, thereupon energizing the ignition trip magnet 44 and attracting the armature 26a. This will permit the spring arm 42 of the relay switch to o5 spring upwardly from the position of Figure 4 to the'- position of Figure 5, the contacts 26 and 26a during this operation becoming separated so that after ignition trip occurs, current will no longer flow through the ignition trip circuit.

Failure of combustion after establishment After combustion has once been established, if it should fail for any reason, the combustion switch will move from the hot position of Fig- 75 mc s ci o back through the pcciucns D. n F and G to the cold position of Figure l. Y

In the D position, the arm 50 has moved counter-clockwise and the spring -56 has caused the right stop pin 54 to follow it, first separating the ignition trip contacts 22 so that they are in initial position. Further movement, as at E,

will permit the spring 56 to allow the lower contact 24 to contact with the upper one, thus establishing a relay de-energizing circuit by reason of the contacts 2l shunting. the-relay coil 34. This opens the motor contacts I2 and Il, thus de-energizing thefmotor and the ignition mechanism and opens the holding contacts I8, thus placing them all -in position as for initial opera-i tion.

v When ,the armature 36- of the relay switch moves to its initial position, the bridge piece 3Q engages the arm lll of the leaf spring I2, pulling it from the position of Figure 5 tothe position of Figure 1, thereby permitting the armature 20a to assume its position'of Figure 1 to hold the contacts le engaged when the relay is again energized` as in- Figure 4.

The combustion switch then moves to the position of F in Figure 3, the arm 5l swinging from the right hand stop pin 5l toward the left one y to provide a time period in which purging can occur. Finally the contacts 2l will be opened, as at G, and then the contacts 26 will be closed as in Figure 1. Upon such closing of the contacts 26, the controller re-lnitiates the starting circuit, thus re-cycling the burner. 'I'he burner will recycle two or three times if it cannot operate properly after one purging period, whereupon the successive heatings of the lock-out switch heater 32 will be sumcient to trip the lock-out switch. The trouble must then be remedied and Aout departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims, any modified forms of structure or use of mechanical equivalents which may be reasonably included within their scope. 5

I claim as-my invention;

1. A control system for a fuel burner having a motor controlled fuel feeding means andignition mechanism comprising in circuit, a main control switch, a first relay having contacts conlo trolling the motor circuit and a holding circuit for said relay which are .closed only when the relay is energized and ignition contacts which are closed when the relay is de-energized, a second relay controlling trip mechanism which when energized permits said ignition. contacts to open and a combustion responsive switching mechanism having flrst contacts controlling energization of said first relay which arepclosed in the absence of combustion and open immediately after combustion is obtained, second contacts controlling energization of said second relay which are closed in the; presence of combustion and which open immediately upon cessation of` combustion and third contacts which close and remain closed for a time period subsequent to the opening of the second contacts and Vthen open prior to the reclosing of the first contacts, said third contacts, when closed, eifectuating dieenergization of said first relay. 2. A control system for a fuel burner 'ving a motor controlled fuel feeding means and tion mechanism comprising in circuit, a main control switch, a rst relay having contactscontrolling the mctcr circuit which cre c1osca only when the 3-5 relay is energized and ignition contacts which are closed when the relay is de-energlzed, a sec ond relay controlling trip mechanism; which when energized permits said ignition contacts to open and a combustion responsive switching 40 mechanism having iirst contacts controlling energization of said first relay which are closed in the Y absence of combustion and open immediately after combustion is obtained and second contacts' controlling energization of said second relay which are closed in the presence of combustion and which open immediately upon cessation of combustion.

ABRAHAM L. RUBEL.

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