US2552973A - Oil burner primary safety control - Google Patents

Description

y 1951 A L. JUDSON 2,552,973

OIL BURNER PRIMARY SAFETY CONTROL Filed June 20, 1949' .SMOKE PI PE COMBUSTION CHAMBER (RE LAY 5AFETY TIMER RELAY BURNER (GNVUOH BURNER MOTOR THERMOSKTAT mufie/v TUF OR mow ALbE-RT L. JUDSOE Patented May 15, 1951 OIL BURNER PRIMARY SAFETY CONTROL Albert L. Judson, Portland, reg., assignor to Iron Fireman lllanufaoturingv fiompany, Portland, Oreg.

Application June 20, 1949, Serial N 0. 100,131

3 Cla ms.

ing motor and the ignition mechanism of such a burner.

Considered broadly, the present invention has for its purpose the provision of an oil burner primary control having a simple and easily understood circuit scheme and yet which will be reliable in operation and include the several desirable safety features which such a control should have.

It is a further purpose of this invention to provide a control scheme and mechanism which is complete with all required safety features and includes the feature of intermittent ignition well known in the art.

A further purpose is to provide such a scheme and mechanism which can be simplified by leaving out the ignition circuit and connecting the ignition transformer in parallel with the burner motor without eliminating any of the safety features of the control.

Still a further purpose is to provide such a scheme and mechanism which can be further simplified by the elimination of the transformer and its low voltage control circuit, and by placing the operating coil of the relay in the place normally held in the scheme by the primary winding of the transformer. be seen that this will result in a line voltage control much more compact and more economical to build than anything shown in the prior art and yet which will continue to include all the essential operational and safety features possessed by the more complete control. In the simplified control the line voltage limit control positioned as shown in the figure becomes the operating control or pilot instrument.

How my improved oil burner primary control is arranged and the advantages thereof will be apparent from the following description referring to the attached drawing in which the single Figure 1 is a conventionalized diagram showing the mechanisms of the control. positioned in the circuits thereof.

Referring to the figure, there is shown a combustion chamber connected by a smoke pipe to a chimney. For purposes of description it is assumed that the combustion chamber is surrounded by a chamber through which is circulated a heating medium such as air or water which is transported in the usual way to a space to be heated. The thermostat is assumed to be in the space or medium Whose temperature is to be 0011? From the figure it will 2 trolled and the limit control is assumed to be so actuated as to be responsive to the temperature of the heating medium surrounding the com-bustion chamber.

As shown in the figure, tension spring 62 through lever 46, adjustable fulcrum it i, and lever 59 biases temperature insensitive stern il toward the smokepipe where it engages on the inner end of temperature sensitive tube 40. As the temperature in the smokepipe increases, stem 41 recedes into the smokepipe and the left end of lever 46 is moved downward by spring E52. As the temperature in the srnckepipe decreases, tube 4%! con-tracts forcing stem 4| downward and the left end of lever 46 upward against the bias of spring 62. l he relative movements of stem tl and lever 46 is adjustable by right or left movement of. fulcrum EI and is indicated by pointer 54 on scale 55. Held in lever 4e are friction blocks 52 which frictionally engage stem 43 and cause stem 58 to travel with lever 45 within the range of movement determined by the adjustable stop in the cooling direction and by the limit of throw of resilient switch arm M8 in the heating direction. Resilient switch arm I48 is biased toward the open position of contact pairs Il'2I31 and 2l2-213. Switch arm IE8 and associated moving contacts I l2, W2, and stationary contacts I31, 213 form, therefore, a two circuit single throw switch which is responsive to the increase or decrease of combustion temperature through the above recited system of levers.

The safety timing switch has two bi-metal blades I49 and H2 substantially parallel and similarly affected by ambient temperature. Additionally blade I I2 is affected by its associated electric resistance heater H5, when the circuit in Which the heater is connected is energized. Resilient blade I48 carries insulating rigid bar I16, to which it is riveted with silvered rivets. Bar I16 is secured with a hollow rivet to conducting resilient leaf spring I80. Leaf spring we is secured with silvered rivets to stiff conducting bridge I18. A depending tongue on bi-metal blade I49 inserts through slots in bar Ilt, leaf I and bridge I18 and bears laterally on bridge I18 to compensate for the effect of ambient temperature on blade H2 and therefore to maintain the proper relation of the right end of bridge I18 with the lower end of blade II2 with which it is normally engaged. When electric current passes through resistance heater I I5 for a predetermined time, bi-metal blade II2 warps to the right and slides off the end of bridge I18 which is biased upward by both support I48 and leaf I80.

When i this occurs the circuit from blade I 48 to blade I I2 is interrupted both at the junction of bridge I18 and blade H2 and by the separation of the rivet heads at the left end of bridge I18 from the rivet heads at the lower end of blade I48. To reset the switch it is necessary to allow blade I I2 to cool and then manually to press the right end of bridge I18 downward until blade I I2 can spring back into place over the right end of bridge I18.

The relay switch comprises three stationary contacts I34, I45, and I40 and three moving contacts 84, 96 and 90 carried respectively on resilient switch blades 83, 95 and89. The relay operator comprises frame I84, coil I85, armature I86 hinged to frame I84 and toggle compression spring I94 biasing armature I86 to open position as shown. Operating lever I26 linked to armature I86 by adjustable stop screw I3I and arcuate spring I98 allows the switch contacts to close when coil I85 is energized and opens the switch contacts due to the action of Spring I94 overcoming the bias of blades 83, 95, and 89 when the coil is ole-energized.

The timing relay comprises resilient bi-metal blade I60 carrying moving contacts I66 and I61 and normally biased to close moving contacts I66 and I61 on stationary contacts I56a and I61a respectively. Associated with blade I60 is electric resistance heater 260 which, when energized, heats blade I60, causing it to warp upwardly and open switch contact pairs I66I68a and I61- In tracing the circuits of this control it is well to remember that the electric service line is connected to terminals IOI and I02. Terminal IOI is usually considered the hot terminal and I02 the ground terminal. The limit control or other high voltage pilot instrument if used is usually connected into the hot wire leading up to terminal IOI. Inside the instrument of the present invention it is simplest to trace the circuits starting from terminal IOI and proceeding to terminal I02. The circuits included in the complete control are:

A first circuit including wire I42, wire I39,

contacts I40, 90, relay switch blade 89, wire 85,

terminal I03, and the burner motor having its other terminal connected to terminal I02.

A second circuit including wire I42, bi-metal blade I69, contacts I66, I66a, wire 265, blade I48, bridge I18, blade II2, heater II5, wire H1, 200 and the primary winding of transformer 14 Whose other terminal is connected to terminal I02 by wire I99.

A third circuit which includes wire I42, bimetal blade I48, contacts I12, I31, wire I32, relay switch contacts I34, 84 and blade 83 connected to wires II1 and 200. ,7

A fourth circuit including wire I42, bi-metal blade I48 contacts 212, 213, wire 26I, and heater 260 whose other terminal is connected to terminal I02 by wire 262. 7

A fifth circuit which is a low voltage control circuit complete in itself and which includes the secondary winding of transformer 14, wire 202, relay coil I85, wire 203, terminalI to which is connected a thermostat or other pilot instrument, terminal I06, and wire 20I backto the other side of the transformer secondary.

A sixth circuit which includes wire I42, bimetal blade I60, contacts I61, I61a, wire I44, contacts I45, 96, blade 95, wire 9|, and terminal I04 between which and terminal I02 isconnected the ignition transformer of the oil burner control system.

From the drawing it is evident that the control can be simplified by eliminating the sixth circuit and connecting the burner ignition apparatus in parallel with the burner motor between terminal I03 and I02.

Also from the drawing it is evident that the control can be further simplified by eliminating the transformer and the fifth circuit and connecting the relay coil I in the place in the second circuit shown for the primary of the transformer. In this case the limit control would become the pilot instrument or, if desired, a line voltage thermostat or additional pilot instrument can be connected in the service line leading up to terminal IOI.

As shown schematically in the drawing the oil burner is not in operation since the thermostat is satisfied and open. Assume then that the thermostat cools off and closes, thus indicating a need for the generation of additional heat. The primary transformer 14 is energized from lines IOI and I02 through the timing relay contacts I66, I66a and through the safety timer. When the thermostat closes relay coil I85 is energized from the secondary coil of transformer 14 and the secondary load reflected in the primary circuit starts resistor II5 of the safety timer to heat up. Also armature I 86 is attracted by coil I85 and rocks lever I26 and allows relay blades 83, 95, 89 to close their respective pairs of relay contacts. The burner motor is energized from lines IOI and I02 through relay contacts 90, I40. The burner ignition system is energized from lines IOI, I02 through timing relay contacts I61, I510, and relay contacts 95, 96. Supposedly then the burner is in operation and hot products of combustion are being formed in the combustion chamber and beginning to find their way through the smoke pipe to the chimney and heating heat sensitive sleeve 40 on the way. As sleeve 40 heats it expands inwardly of the smoke pipe taking with it heat insensitive rod II which through the system of levers shown allows spring 62 to pull the left end of lever 40 down taking with it stem 48 engaged by friction blocks 52. Stem 48 pressing on lever I48 closes stack element contacts I12, I31 and 212, 213. As seen from the drawing the closing of contacts I12, I31 completes a second circuit from lines IOI, I02 through the primary of transformer 14 via relay contacts 84, I34 and therefore makes the safety timer ineffective to open the primary circuit. The closing of contacts 212, 213 energizes timing relay resistor 260 from lines IOI, I 02 which after a short delay heats bimetal I60 sufliciently to open contacts I66, I66a and I61, I61a thereby deenergizing the ignition system, taking the safety timer out of circuit and leaving the burner in normal operation.

Now assume that during this ignition period no ignition occurred or for any reason element 48 was not heated by the products of combustion. Then spring 62 could not have closed I12, I31 and 212, 213. The timing relay would not have operated, the ignition system would continue to operate and the resistor II5 of the safety timer would heat bimetal I I2 until it moved away from bridge I18 and thus allowed the safety timer to break the transformer primary circuit and completely deenergize the control, shutting down the burner. In this case bridge I18 of the safety timer would have to be reset in position on the end of blade II2 after blade II2- had cooled sufiiciently to return it to a resettable position. Similarly if at any time when the burner is in normal operation, should the element 40 drop in temperature, thus indicating a combustion difficulty or fiame failure the contraction of element 4!! would force lever 46 to overcome the bias of spring 62 and raise stem 48 allowing contacts I12, I31 to open and deenergize the primary of transformer M. In this case however the control could start a new starting cycle of its own accord as soon as timing relay blade 160 had cooled sufliciently to close contacts I56, "36a and again energize the primary of transformer 14 through the safety timer. Normal shutdown would, of course, be by the opening of the thermostat which would return the control circuits to the condition shown in the drawing.

It should be noted that by a pre-determination of the resistance of the timing relay heater 260 and its thermal location with respect to the bi-metal blade I60 of the timing relay a desirable adjustment of the delay in the operation of the timing relay with respect to the operation of the combustion responsive switch is made Possible.

Having thus described the mechanism, circuits, and use of the present invention with respect to the prior art, I claim:

1. In a control system for an oil burner, a first circuit including a first pair of relay switch contacts and a burner motor, a second circuit including a first pair of timing relay contacts, a normally closed safety timing switch having an electrically energizeable actuator, and the primary coil of a transformer, a third circuit in cluding a first pair of combustion responsive switch contacts and a second pair of relay switch contacts, a fourth circuit including a second pair of combustion responsive switch contacts and an actuator for said timing relay, a fifth circuit including the secondary coil of said transformer, an actuator for said relay, and condition responsive means for closing said fifth circuit to energize said relay actuator, a sixth circuit including a second pair of timing relay contacts, a third pair of relay switch contacts, and ignition means for said burner, said first, second, fourth, and sixth circuits being connected in parallel across a source of electric power, said third circuit being connected in parallel with that part of said second circuit which includes said first pair of timing relay contacts and said safety timing switch, means for closing said relay contacts when said relay actuator is energized and for opening said relay contacts when said relay actuator is de-energized, means for opening said timing relay contacts when said timing relay actuator is energized and for closing said timing relay contacts when said timing relay actuator is de-energized, and means responsive to an increase in combustion temperature to close said combustion responsive switch contacts and responsive to a decrease in combustion temperature to open said combustion responsive switch contacts.

2. In a control system for an oil burner, a first circuit includin a first pair of relay switch contacts and a burner motor, a second circuit including a pair of timing relay contacts, a normal- 1y closed safety timing switch, having an electrically energizable actuator and the primary coil of a transformer, a third circuit including a first pair of combustion responsive switch contacts and a second pair of relay switch contacts, a fourth circuit including a second pair of combustion responsive switch contacts and an actuator for said timing relay, a fifth circuit including the secondary coil of said transformer, an actuator for said relay, and condition responsive means for closing said fifth circuit to energize said relay actuator, said first, second and fourth circuits being connected in parallel across a source of electric power, said third circuit being connected in parallel with that part of said second circuit which includes said first pair of timing relay contacts and said safety timing switch, means for closing said relay contacts when said relay actuator is energized and for opening said relay contacts when said relay actuator is deenergized, means for opening said timing relay contacts when said timing relay actuator is energized and for closing said timing relay contacts when said timing relay actuator is de-energized, and means responsive to an increase in combustion temperature to close said combustion responsive switch contacts and responsive to a decrease in combustion temperature to open said combustion responsive switch contacts.

3. In a control system for an oil burner, a first circuit including a pair of timing relay contacts, a normally closed safety timing switch having an electrically energizeable actuator and means comprising a burner control device, a second circuit including a first pair of combustion responsive switch contacts, a third circuit including a second pair of combustion responsive switch contacts and an actuator for said timing relay, said first and third circuits being connected in parallel across a source of electric power, said second circuit being connected in parallel with that part of said first circuit which includes said pair of timing relay contacts and said safety timing switch, means for opening said timing relay contacts when said timing relay actuator is energized and for closing said timing relay contacts when said timing relay actuator is de-energized, and means responsive to an increase in combustion temperature to close said combustion responsive switch contacts and responsive to a decrease in combustion temperature to open said combustion responsive switch contacts.

/ ALBERT L. JUDSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,910,721 Taylor May 23, 1933 1,991,185 Williams Feb. 12, 1935 2,021,407 Erickson Nov. 19, 1935 2,022,188 Denison Nov. 26, 1935 2,117,021 Cotea May 10, 1938 2,195,649 Hallenbeck Apr. 2, 1940 2,230,732 Tapp et a1. Feb. 4, 1941 2,486,612 Pratt Nov. 1, 1949

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