US2119894A - Primary control - Google Patents

Description

June 7, 1938 A, STRAND: 2,119,894

PRIMARY CONTROL I I Original Filed Nov. 6, 1934 ATTORNEYS Patented June 7, 1938 UNITED STATES PATENT OFFICE Application November 6, 1934, Serial No. 751,713 Renewed November 5, 1937 1 Claim.

The invention relates to heat controlling devices, and more particularly to special safety devices of the type used with oil burning heating furnaces and generally known as primary controls.

The objects of the invention include the provision of a relatively inexpensive, dependable, highly eflicient and sensitive device of the type above indicated.

Various further and more specific objects, features and advantages will clearly appear from the detailed description given below, taken in connection with the accompanying drawing which forms a part of this specification and illustrates, merely by way of example, embodiments of the invention.

In the drawing:

Fig. 1 is a section taken through the control;

Fig. 2 is a section taken on the line 22 of Fig. 1;

Fig. 3 is a section on the line 33 of Fig. 1; and

Fig. 4 is a wiring diagram illustrating diagrammatically the relation of the pyrostat, the thermostat and the oil burning equipment.

In the following description and in the claim, various details will be identified by specific names for convenience, but they are intended to be as generic in their application as the art will permit.

Like reference characters denote like parts in the several figures of the drawing.

In the drawing accompanying and forming part of this specification, certain specific disclosure of the invention is made for the purposes of explanation, but it will be understood that the details may be modified in various respects without departure from the broad aspect of the invention.

Referring now to the drawing, and more particularly to Figs. 1 and 2, the regulating equipment, or control device, is installed for the most part in a box denoted in general by III. The box comprises a metal body II and a pair of removable metal covers I2 and I3. Installed within the box is an insulating panel I4 on which is mounted the safety timing device I5, which determines the permissible time in which the oil burner must start, the clutch and switch indicated by I! controlled by stack coil I6, auxiliary ignition switch I00 controlled by stack coil I6, and starting relay I8. In general, the switches and relays are mounted on one side of the panel I4 with the connections and binding posts on the other side of the panel.

For mounting the box III, a hole is cut in the flue adjacent the oil burning furnace and the box I0 is mounted in a manner illustrated particularly in Fig. 1. The box may be mounted either on a vertical or horizontal portion of the flue. In the form indicated, the box is mounted on a horizontal portion of the flue, indicated by 20. If the flue were vertical, it would merely be necessary to turn the box I0, 90, as will be understood by those skilled in the art.

The hole in the stack flue 20 is indicated by 2I and a plate 22 provided with hooks 23 is fitted to the curvature of the stack 20. A two-part strap 24 having hooks which engage the hooks 23 and having a pair of ears through which a tightening bolt (not shown) passes, firmly clamps the box to the flue. It Will be understood that the plate 22 is curved to fit the particular curvature of the flue and the strap 24 is cut to fit the circumference of the flue.

A hollow sleeve 21 passes through the plate 22 and has a large nut 29 and a small nut 28 firmly clamped against the plate 22. Lock nut 30 is provided to insure locking of the assembly. The sleeve 21 projects from the plate 22 and passes through a hole in the wall of the box body I I and has a pair of nuts 3I for clamping the box body to the sleeve.

Passing through the sleeve 21 and free to rotate therein is a rod 32 having a toothed wheel 33 and a cam I III of insulating material secured thereto, as indicated in Fig. 1. Rod 32 also has a pin 34' engaging the end of sleeve 21 for holding the rod 32 in axial position.

The stack coil I6 is made of suitable bi-metallic material, as is Well known in the art, and one end is secured to nut 29 by screw I29 and the other end is secured to the rod 32 by another screw, as will be understood by those skilled in the art. Thus, the raising and lowering of the temperature in the stack winds and unwinds the stack coil, causing rotation of the control rod 32.

Referring now to the stack switch and clutch II, the toothed wheel 33 cooperates with a yieldable strap 35 mounted on an insulating bar 36. The strap 35 has a finger I35 which engages in the notches of the notched wheel 33 so that rotation of the wheel operates the switch contacts 39.

The stack switch comprises a switch frame 31 suitably bolted to the insulating panel I4 and having opposed ears 90 and 9 I, each of which has small recesses. Seated in these recesses are switch elements 38 and 40 connected by coil spring 4| which furnishes the toggle action and also holds the switch elements in their depressed seats. The switch element 49 is H-shaped, as indicated in Fig. 1, and carries the insulating block 35. The switch element 38 is U-shaped and carries the spring contacts 39 engageable with stationary contacts 92 and 93.

Thus, when the stack begins to cool, a small rotation of the toothed wheel 33 in the direction of the arrow operates to throw the toggle switch, causing the contacts 39 to close with a snap action. For example, assuming the full operating temperature of the stack to be about 700 F., contacts 39 will close at, say, 550 F. Further rotation of the toothed wheel 33, caused by further cooling of the stack, merely causes the spring finger M5 to yield and engage succeeding teeth of the toothed wheel. When the stack begins to heat up, a small rotation of the toothed wheel 33 in the opposite direction will then cause the contacts 39 to open with a snap action. Further rotation of the toothed wheel 33, caused by further heating of the stack, merely causes the spring finger 35 to yield and slide over the toothed wheel as during cooling of the stack.

Referring to the auxiliary ignition switch iil l, this switch is for the purpose of keeping the ignition in operation until the fire is hot enough to maintain itself without going out.

The auxiliary ignition switch comprises a collar liiii secured to the rod 32 by an appropriate set screw. Located adjacent the collar iilfi is an insulating member Iii! loosely mounted on rod 32. Insulating member lfli is provided with a flange iii! having a notch H35 in which is disposed loosely pin H24 attached to collar N95 for a purpose hereinafter described more in detail.

The insulating member lili is provided with a raised cam portion I08 having gradually sloping ends on which rides a spring contact member ia'iii which cooperates with a fixed contact I63 also secured to the insulating base Hi. The insulating member iili is maintained in axial position by the collar E95 on the one hand, and the spring contact member E82 bearing against the annular flange ID! on the other hand.

The construction of the auxiliary ignition switch is such as to give a quick break between contacts H22, H33. These contacts are closed whenever the temperature of the stack is substantially below full operating temperature. For example, assuming the full operating temperature of the stack to be about 700 F., contacts H32, )3 close at, say, about 550 F. and remain closed at all temperatures below this point.

Heating of the stack causes rod 32 to rotate in a direction indicated by the arrow in Fig. 3. As full stack temperature is approached, say, at 550 F. in the example given above, the rod 32 has driven the insulating member 10! so that the rounded projection on leaf spring N32 is just about to ride off of cam surface N18. The cam surface ma having a sloping end, the contact Hi2 will ride oif of cam surface Hi8 quickly causing a quick break between contacts I02, I03.

This quick break action is caused by the loose fit of pin H14 in notch 15 which permits the insulating member lill to ride freely on shaft 32 in the direction of the arrow in Fig. 3 under the action of the spring contact I02 operating on the end of cam surface E06.

When the stack is cooling and the insulating member I!!! is rotating in a direction opposite to the arrow in Fig. 3, the gradually sloping end of cam surface I 08 permits spring contact N32 to ride up this surface closing contacts I02, I93.

Referring now to the safety timing device I5,

this device is for the purpose of giving the oil burner a given time in which to start the fire. If the fire does not start, say, Within 90 seconds, the safety device turns off the oil burner and its starting apparatus.

The safety timing device 15 comprises, in general, an asbestos insulating mandrel 45 mounted in a pair of square asbestos blocks 46 and having a coil of resistance wire 47 wound thereon. A bi-rnetallic strip 48 is anchored to a fixture 148 fixedly secured to the insulating base 14 and carries a piece of insulation 49. The heating coil 4'! and bi-metallic strip 48 is enclosed in a boxlike housing H5 screwed to the insulating base and through which projects the insulating piece 49.

The operation. of the safety timing device [5 opens the contacts 53, 59 and closes the contacts 54, 60. The former removes power from the oil burning equipment and ignition and the latter operates a buzzer 1'! located at a convenient place to call attention to the fact that the oil burner did not start.

The spring contact 53 is anchored at one end by bracket ISO to the insulating base M and nor mally tends to take a position with the contacts 53, 59 open.

Upward movement of the spring contact 53 engages an insulating plate 5! which causes leaf spring 5 to engage contact 60 to ring the buzzer. Spring member 53 is held down, however, by a latch 52 pivoted at I52 and locked by trigger 5i pivoted at it. A rod 5'! passes through trigger 5! and through insulating piece 49 and a coil spring 58 surrounds rod 51.

For manually starting the oil burner after the oil burner has failed to start and the timing device has been operated, a push-button 55 is provided. The push-button passes through the wall of the box body H and engages a leaf spring I55 carrying an insulating finger 5B which engages the catch 52 to reset the pyrostat.

Thus, when electric energy is applied to the heating coil 41, the bi-metallic strip 48 is heated and moves slowly upwardly. At the end of the permissible period, say, 90 seconds, it has moved upwardly sufficiently to lift the trigger 5!, releasing catch 52 and causing the spring contact 53 to break with contact 59 and causing engagement of contacts 54 and 6B.

The attendant hearing the buzzer knows that the oil burner failed to start. He then pushes the push-button 55 which causes insulating plate 50 to engage the cam surface 55!? of the catch 52,

causing the latter to seat within the angle seat E53 of the trigger 5i. Setting of catch 52 causes contacts 53, 59 to make and contacts 54, 6!! to break.

Referring now to the starting relay I8, this relay comprises a coil 65 wound on an insulating sleeve 55 which is secured to a brass supporting angle 80 secured to the insulating base l4. Within the insulating sleeve 66 is an iron bushing Hit. The armature of the relay comprises a rod 61 having a magnetic armature piece 68 which has a brass guide strap H secured thereto which is adapted to slide along the surface of insulating base !4 to keep the relay armature in proper position.

At the top of the armature rod 6'! is an insulating piece 59 which supports a spring strap 10 engaging contacts '52. When current passes throughwinding 65, the iron armature 68 moves upwardly, closing contacts Hi and 12.

Referring now to Fig. 4, which discloses the wiring diagram, similar reference characters are used as far as possible to indicate corresponding parts. The thermostat, which may be of the low voltage type, 'is mounted in a part of the building it is desired to keep at constant temperature and is connected in circuit with a step-down transformer I8, a relay I6 and a safetystat I5.

The safetystat may be mounted on the furnace and may be an aquastat in the case of a hot water heating system, a pressurestat in the case of a steam heating system or another thermostat in the case of a hot air heating system. The safetystat is normally closed and plays no part in the ordinary operation of the temperature control but only operates under abnormal conditions, as will be understood by those skilled in the art.

The buzzer IT, or other alarm, is located in a convenient part of the building and may operate on the full 110 volt alternating current. If a low voltage buzzer is desired, obviously, a step down transformer similar to transformer 19 may be interposed between the buzzer TI and the A. C. line.

In the form shown, the oil burning equipment may include a motor, an oil valve and an ignition device, as indicated. The particular construction of this equipment forms no part of the present invention and will vary with the different types of oil burning systems. For example, the motor may operate an air fan for supplying air for combustion. In some cases, no oil valve is required, but when one is provided, it is automatically opened at the same time the motor is started. The ignition device Will supply a hot spark for igniting the combustible mixture of oil and air.

It will be understood that any type of thermostat may be used with this control equipment. The thermostat shown is a low voltage thermostat operable on, say, 14 volts. The present pyrostat may also operate with a 110 volt thermostat of the type disclosed in copending application Serial No. 569,916, filed October 20, 1931. The manner of substituting the 110 volt thermostat at the points A, B and C is explained in copending application Serial No. 716,058, filed March 1'7, 1934, Heat controlling device.

Operation Referring to Fig. 4, assume the oil burner is out and the temperature of the room in which the thermostat is located is above the temperature at which the thermostat contacts will close. The following will then be the condition of the control device. The stack contacts 39 are closed, the safety contacts 59 are closed, starting relay contacts 12 are open, the main thermostat contacts are open, the contacts of relay 15 are open. and the contacts of safetystat 15 are closed. The auxiliary ignition contacts I92, I93 will be closed since at this time the stack temperature will be considerably below the ignition cut-off temperature (of 550 F., for example).

When the temperature of the room drops to the set temperature, main thermostat contacts close, applying energy to the relay 16, closing its contacts, and applying energy to the safety heating coil 41, the ignition, the starting relay I8 and the motor and oil valve. The starting relay I9 operates, closing contacts 12 which applies voltage to the motor, oil valve and ignition independently of contacts 39. The solenoid of the starting relay I8 also is maintained energized independently of the contacts 39. If the fire starts up before the safety device I5 operates, the heat in the stack causes the stack coil I6 to turn the rod 32 in the opposite direction to the arrow in Fig. 2, opening the stack contacts 39, thereby removing voltage from the safety timing device I5. If the stack was cold at the time the fire starts, the contacts 39 will open at, say, 200 F.

As the temperature of the stack rises still further, continued rotation of the rod 32 in direction of the arrow in Fig. 3 causes the cam surface I96 to ride off spring contact I92, causing a quick break between contacts I92, I93.

The oil burner continues to burn until the temperature of the room goes above set temperature when the thermostat contacts open, causing conacts of relay I6 to open, removing energy from the motor and oil valve and unlocking the starting relay I8, opening contacts 12. The oil burner goes out and, as soon as the stack cools only a small amount, the rotation of the rod 32 in the direction of the arrow in Fig. 2 closes the stack contacts 39. Auxiliary ignition contacts I92, I93 will also close as soon as the stack temperature falls below the predetermined value at which cam IN is set to operate them. This may be at about the same time as contacts 39 close or it may be somewhat before or after they close.

The closing of the stack contacts 39, as well as the auxiliary ignition contacts, by a small temperature drop in the flue places the apparatus almost immediately in readiness to start the oil burner should the temperature of the room drop below the set temperature, and it is not necessary to wait until the stack cools down to place the apparatus in readiness to start.

If for any reason the oil burner does not start up within the time limit of the safety timing device I5, say, within 90 seconds, the upward movement of the bi-metallic strip 49 raises trigger 5I, releasing catch 52 and permitting the spring contact 53 to break with contact 59, removing voltage from the motor, oil valve, ignition and safety timing device I5. The upward movement of spring contact 53 closes contacts 54 and 69, causing the buzzer 11 to ring, calling attention to the fact that the oil burner did not start.

The attendant upon hearing the buzzer presses the push-button 55 which closes contacts 53 and 59, opening the buzzer contacts 69 and 54.

Closing of the main contacts 59 and 53 applies voltage to the motor, oil valve and ignition as well as to the safety timing device I4. If the fire does not start within, say, 90 seconds, the safety timing device I4 will again operate, opening contacts 53, 59 and closing contacts 54, 69 to again call attention to the fact that the oil burner failed to start.

If the electric power should fail when the temperature of the room is above the set temperature. nothing will happen since there is no power on the control system. If the electric power should fail when the temperature of the room is below the set temperature and the thermostat is calling for heat, the contacts of relay 16 open, contacts of the starting relay I8 open, and the power is removed from the motor and oil valve causing the fire to go out.

As soon as the electric power goes on, contacts of relay I6 close and the system again starts up in the regular way, providing the stack contacts 39 and ignition contacts I92, I93 are closed. If the electric power had not been oif for sufficient time to cause the stack to cool off and thereby close the stack contacts 39 and ignition contacts I92, I93, the oil burner will not start up until the stack does cool off the slight amount necessary to close contacts 39 and also the amount necessary to close contacts I02, I03.

It should be noted that the stack contacts 39 open directly as soon as the fire starts and then close directly as soon as the fire stops and the stack temperature drops a small amount. Ignition contacts 902, I83, however, remain closed for a considerable time after the fire has started in order to insure starting. When the fire stops, they close at about the same time as contacts 32. if for any reason the fire should go out for a short interval, either because the electric power fails or because the house is over-heated for a short period from some other source, such as from a kitchen oven, the system does not have to wait until the stack gets cold for the fire to start.

In case of flame failure, due to water in the oil (with motor going and the oil valve open) a small drop in temperature in the stack closes the stack contacts 39 and ignition contacts I02, I03, turning on the ignition and putting power on the safety timing device it). If the fire does not start within the time limit of the safety device I5, the safety contacts 53, 59 open and the ignition is turned off, the motor stops, the oil valve closes, starting relay !8 releases and the buzzer TI rings.

Whenever the fire does not start (or restart in case of temporary failure of flame due to any cause) after the time set when the ignition is turned on, the safety device I5 operates to shut down the oil burning system and to ring the buzzer. The attendant must press the push-button which resets the safety timing device I 5 and the system restarts in the regular way, as above described. If the oil burner refuses to start after a number of repeated attempts by pushing push-button 55 something is wrong and repairs must be made to the system.

Thus, a control system has been described which is relatively simple, is made of inexpensive parts and is very easy to assemble. The system takes care of failure of the fire to start within a predetermined period. It takes care of failure of the electric power. As soon as the fire goes out, the stack only has to cool a relatively small degree to place the system in condition for restarting when the thermostat calls for heat.

The system also provides for prolonged operation of the ignition to insure complete starting of the oil burner and eliminating the necessity for recycling. The auxiliary ignition contacts are especially useful in certain cases, as for example, on some types of rotary burners because in some cases, without the auxiliary ignition contacts, the fire will start up sufficiently to operate the stack switch I! cutting off ignition and then go out because sufficient heat has not been developed within the walls of the fire box to maintain the proper combustion.

Both the main control of the ignition and the auxiliary ignition control are necessary because the auxiliary switch holds on the ignition until the fire is really established, while the main control switch I? opens the circuit to the safety mechanism I5 to prevent its operating if the fire actually starts, although full temperature is not obtained until some time subsequent. It will be noted that the main or stack contacts 39 operate with any predetermined change in stack temperature, while the auxiliary contacts I02, I03 operate at a fixed temperature.

It will be understood that the alarm illustrated by the buzzer 'Il may be any kind of an audible or visible alarm. Furthermore, it will be understood that the control device may be mounted in any part of the furnace where it will be subject to the heat of the flame, as for example, in the fire door as well as in the fiue, as illustrated. Furthermore, it will be understood that the safetystat i5 may be located in the volt side, for example between the point C and the relay I6 on the low voltage thermostat control, if desired.

This application is a continuation in part of application Serial No. 716,058, filed March 17, 1934, Heat controlling device.

While certain novel features of the invention have been disclosed and are pointed out in the annexed claim, it will be understood that various omissions, substitutions and changes may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

In a system for controlling oil burners or the like having a control switch; a starting relay comprising a solenoid and a pair of starting contacts; a stack switch having a first pair of contacts and a bridging member, and auxiliary contacts; a safety heating device including a heating coil and a switch controlled thereby; a fuel feeding device; and an ignition device; a main circuit comprising said control switch, said safety switch and a network therebetween all serially connected across the power line, said network comprising a first circuit including said starting contacts and said fuel-feeding device serially connected between said control switch and said safety switch, a second circuit including the first contacts of the stack switch and the safety heating coil serially connected between said control switch and said safety switch, athird circuit including the bridging member of the stack switch, the auxiliary contacts of the stack switch and the ignition device serially connected, the ignition device being disposed next to said safety switch, said solenoid being connected to the bridging member of said stack switch and to said safety switch, and an interconnection between said bridging member and a point in said first circuit between the starting contacts and said fuel-feeding device.

AUGUST A. STRAND.

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