US2180580A - Control system - Google Patents

Description

K. CLARK CONTROL SYSTEM Nov. 21, 1939.

Original Filed March s, 193'? 2 Sheets-Sheet l Ksuonu. CLnRn 771C614 s M ATTORNEYS Nov. 21, 1939. K. CLARK CONTROL SYSTEM Original F iled March 5, 1957 Z Sheets-Sheet 2 I a 4 a a 6 z 4 8 m M H INVENTOR; KENDFILL CL HR %:Cane M ATTORNEY 5 Patented Nov. 21, 1939 UNITED STATES PATENT OFFICE 2,180,580 CONTROL SYSTEM Kendall Clark, South Bend, Ind., asslgno International Engineering Corporation, cago, 111., a corporation of Illinois Refiled for abandoned application Serial No.

128,739, March 3, 1937. This application January 3, 1938, Serial No. 183,148

the starting of the motor immediately, or at least within a very short time, starts the flow of combustible mixture.

My novel stack swit the numeral I2, is mounted on the means such as a flanged fitting bolted thereto and having a circular opening coincident with an stack through which passes a tubuured in the flange 14 us, such as a set screw de the stack and the other 6 Claims.

This invention relates to control systems, for oil burners and the like, and especially to systems including thermostaticallycontrolled circuits for turning on and 01f the motor and ignition means of the burner.

' An object of the invention is to provide simple and effective means for first actuating both the motor and the ignition means and then turning off the ignition means after the burner ignites, without interfering with continued operation of the motor, and finally turning the motor off automatically on failure of ignition (regardless of room temperature) after an interval determined by the time normally required to act te a stack switch or the like affected by the h t of the burner. Preferably the ignition circuit includes a safety device which renders the entire system inoperative after prolonged operation of the ignition means without igniting the fuel at the burner. Important features of novelty relate to the structure of the stack switch, as well as its arrangement in the control circuit. These features, and various other structural features and desirable arrangements, will be apparent from the following description of the illustrative embodiments shown in the accompanying drawings, in which:

Figure 1 is a longitudinal section of my novel stack switch;

Figure 2 is a transverse section on the line 22 of Figure 1;

Figure 3 is a partial exploded view showing in detail several elements of my novel switch;

Figure 4 is a wiring diagram of a novel oil burner control circuit using resistance ignition and my novel switch and adapted to control a splitphase induction motor;

Figures 5 and 6 are elevational and sectional views respectively of two modifications of a novel resistance ignition unit to be used in the circuit of Figure 4; and

Figures 7, 8, and 9 are wiring diagrams of modifled control circuits employing my novel switch and spark ignition, and adapted to control a split phase induction motor, a repulsion induction motor and a shaded pole induction motor respectively.

Referring to Figure 1 of the drawings there is shown a chimney or stack I!) through which the gases of combustion from an oil burner are adapted to pass. The oil burner may be of any type such as, for example, that-"shown in my copending application Serial No. 117,459, filed December 24, 1936, in which a motor is adapted to actuate a fan and fuel pump to supply a combustible mixture of oil and air to a furnace and in which ch, indicated generally by opening in the lar member 16 removably see by any desired mea that one end is insi n 20 on the inside end ofthe at to which is brazed or lical bi-metallic element It so that the bodily from the stack by 8 and withdrawing the A flattened portio tube l6 provides a se welded one end of a he 22 of less diameter tha switch may be removed loosening the set-screw I switch from the flange l Threaded into the out a combination bolt and bus between which and first, the bottom of a cup ing 26; and second, a serie 28 preferably of copper, bushing and spaced by was non-heat-conducting material.

In the bushing 24 is journalled having formed on its inside end (i.

t 34 (Fig. 3) adapted t d therein the bent-in, free end (1 having at its other itch housing 26, first second, a cylindrical er end of the tube I6 is hing 24 having a head [5 are compressed: -shaped switch housof heat radiating fins fitting tightly to the hers 30 of any suitable a long shaft 32 the stack) a $10 and have secure of the bimetal helix 22, an end, projecting into the sw a squared portion 36; and

36 engages a clutch to be ms a bearing 40 the other end of which 42 of decreased diam- 44 for the open end eferably made of The central part The squared portion described below, for one end of a shaft is provided with a portion eter journalled in a closure I of the cup. This closure is pr electrical insulating material. of the shaft 40 is supported by an insulating partition 43 separating the switching elements from the clutch elements previously mentioned.

A switch arm 46 formed of a strip of brass or r the like having contact points 48 secured on ope faces adjacent one end and having its other cylindrically passes through a A spring 52 urges the the parti-cylindrical end tinuous contact with a main conto the closure 44. This contact is enter at the center 56 and 58 adjacent 55 and the pin 38 for end formed partislot 50 in the shaft arm radially so that maintains con tact 54 secured formed .on an are having its 0 of the shaft, and it has humps each end of the are adapted to act as latches for the arm 46 in its respective contact engaging positions.

The contact 54 is secured to the closure 44 by means of a rivet 68 having a long prong on the outer end adapted to receive a plug-in socket or the like 62, and similar rivets 64 and 66, also adapted to coact with the socket, carry contacts 68 and 18 respectively which engage with the contacts 48 in opposite position of the switch arm. The contacts 68 and I8 are resiliently mounted by means of spiral springs I2 secured in the inside projections of the rivets 64 and 66 respectively.

Another contact I4 is mounted on a spring support I6 secured in the rivet 66 which passes over the switch arm 46 so that the contact is positioned directly behind the contact 78 permitting the switch to close and open two circuits simultaneously.

An important minor feature of the invention ,is a novel slipping clutch connection between the shafts 32 and 48 comprising a C-shaped stamping I8 pierced at the back of the C with a square hole 88 fitting on the squared portion 38 of the shaft 32 and having the arms of the C closely formed around the shaft 48 and held in tight frictional -84 of a single-phase A. C. line.

engagement therewith by a garter spring 82. This clutch permits continued expansion or contraction of the bimetallic element 22 after the switch has been operated.

In operation, when no gases are passing through the stack I8 the bimetal element 22 is cold and urges the arm 46 in the counter-clockwise direction so that contacts 48, 68 and I4 are closed and the partly-cylindrical end of the arm 46 is to the right of the hump 58. The switch is now said to be on the cold side.

In this position the burner is brought into operation, and the gases of combustion passing the bimetal element 22 cause it to wind up moreclosely urging the arm 46 in the clockwise direction, but it is held in place by the hump 58 until the force exerted is sufiicient to compress the spring 52, whereupon the arm snaps to the other side closing the contacts 48 and 78, the particylindrical end of the arm 46 passing over the hump 56. This is called the.hot side of the switch.

Whenever gases cease to flow in the stack the bimetal element cools and unwinds and the arm snaps in the opposite direction. An important minor feature of the invention resides in making the hump 58 higher than the hump 56 whereby in returning to the cold side in'sufficient energy is stored in the bimetal element to move the arm over the hump 58, thus creating a delay period in which the bimetal element must cool further and store up suiiicient energy to lift the arm over the hump 58 While the foregoing refers to a specific embodiment it is clear that a great number of variations in arrangement of contacts and delay action might be worked out for particular circuit requirements.

Referring now to the control circuit diagram of Figure 4 there are 'shown the two wires 82 and Connected in series in the line 82 is the usual room thermostat 86 of any desired type adapted to close the circuit when heat is called for, together with a limit switch 88 (adapted to open the circuit upon over pressure in a steam heating system or upon excessive temperature in hot air and hot water systems), and a time delay switch 98-. The wire 82 terminates at the main contact 54 of the stack switch I2. 7

In this case the time delay switch is illustrated as a bi-metal element 92 anchored at one end and closing the circuit by a contact at its other end, a heating coil 84 on a separate circuit and a latch 86, adapted to'hold the bimetal element away from the contact when deformed by the heat in the coil 94, thereby requiring manual operation to reestablish the circuit.

The other line 84 terminates at the junction of two parallel circuits one of which 85 has connected therein, in series, the running or inductive winding 88 of a split phase induction motor I88 which operates the fuel pump and fan (not shown) of the oil burner. The wire 85 terminates at the prong 66 of the stack switch and is thus connected to both contacts 68 and 74 so that contact is made with it on both the hot and cold sides of the switch.

The other parallel circuit I82, connected to the line wire 84, has connected in series in it a resistance ignition element I84 which may be of the type described below, the starting or resistive winding I86 of the motor I88 and the heating coil 94 of the time delay switch 98. The line I82 terminates at the contact I8 of the stack switch. v I It will be noted that instead of employing the usual resistance element in connection with the splitphase coil, whereby energy is wasted, the ignitionand delay switch resistances are substituted thereby causing the heretofore wasted energy to serve a useful purpose.

In operation, assuming the room thermostat to be open the stack switch will be on the cold side with the contact 48 in engagement with contacts 68 and I4. As the space to be heated grows colder, the room thermostat 86 closes the circuit 82 and current fiow's through both circuits 85 and I82 energizing the starting and running windings I86 and 88 of the motor I88 and thereby starting the motor to supply the combustible mixture to the furnace.

At the same time the ignition'element I84 is heated by the current in the circuit I82 and ignites the mixture. With combustion established, the hot gases in the stack I8 gradually heat up the bimetallic element 22 until the switch snaps to the hot side. This opens both circuits 85 and I82 but instantaneously reestablishes circuit 85 through the contact I8 and the motor I88 coptinues to run, energized solely by the running winding 98 in the manner of a simple single phase induction motor.

When the space being heated is warm enough the room thermostat 86 breaks circuit 82 stopping the motor. The gases in the stack gradually cool off permitting the switch I2 to return to the cold side.

system out of operation until the trouble is discovered and the switch 88 reset.

If combustion should fail while the burner is in previously described delay in returning permits the furnace to cool to the point where it is safe to restart without danger of explosion in event that the continued running of the motor, while the stack switch was cooling off enough to open the circuit 85, has resulted in discharging a lot of oil into the furnace. Upon restarting, if the condition which caused failure of combustion has not been remedied the time delay switch will lock out the system;

It will be noted that this system provides intermittent ignition providing long life for the ignition element.

Figure 5 shows .a novel and desirable type of ignition element I04 adapted for. use in this system, the particular feature of which is that it automatically limits its temperature. It comprises a rod I08 of silica or similar material which becomes a conductor at elevated temperatures and the resistance of which decreases with increase of temperature. The rod is supported in brackets IIO which in the circuit of Figure 4 would be connected in the circuit I02. A resistance winding II2 of chrome nickel wire or similar material is connected to the brackets and wound around the rod. When a certain temperature is reached the rod I08 becomes conducting shunting the current from the wire II2.

In Figure 6 the resistance wire I I2 is enclosed in a silica tube I08 thereby eliminating oxidation and causing the element to last indefinitely.

The circuit of Figure 7, in which identical elements have the same reference numerals, is similar to that of Figure 4 with the exception that intermittent spark ignition is used instead of resistance ignition. It is desirable to apply full line voltage to the primary of the ignition trans former, consequently, instead of being connected in series with the circuit I02, a circuit II4 paralleling I02 is employed in which the primary of the ignition transformer H8 is connected. An

ignition spark-gap H8 is connected-across the high voltage secondary of the transformer. The operation is the same as in Figure 4. The circuit of Figure 8 is for controlling a burner employing a repulsion induction motor 800 and in this figure elements corresponding exactly to elements in the previous circuits are designated by the same reference numerals and corresponding elements are indicated by the same reference numerals plus 200.

As is well known in the art this type of motor comprises a standard single phase induction stator winding 208, and a squirrel cage or wound induction rotor (here shown as a squirrel cage rotor) on which is superimposed a commutator winding-having brushes I20 set generally electrical degrees from the axis of the reversing field created by the induction winding.

To obtain starting torque the commutator brushes I20 are short circuited. When the motor approaches synchronous speed the short circuit may be opened and the motor operates as a single phase induction motor.

Consequently the brushes I20 have been connected in a circuit 882 between terminals 84 and 08 of the stack switch so as to be short-circuited' on the cold"- side and open circuited on the hot" side of the switch.

With some loss of starting torque the time delay switch heating coil 04 and the ignition transformer H6 may be connected in series in the line 302 and supplied with current by the induced voltage in the commutator winding.

If the loss of starting torque is too great, ignition current may be supplied by means of a lowloss relay as shown in the circuit of Figure 9.

. Figure 9 shows my novel circuit for a shaded pole motor. In'this, figure elements identical to those in preceding figures are designated by the same reference numerals as used where the element first appears plus 300.

This type of motor may have a squirrel cage rotor and a stator with salient poles each of which is divided intounequal parts by a slot paralleling the rotor axis. The main field winding 398 is wound around the whole pole and the shading winding 408 comprises a few turns around the smaller portion of the pole. This winding is usually short circuited and has a voltage induced in it by the current in the main field which unbalances the -field and creates a starting torque.

In this novel circuit, leads are taken from the shading winding and connected in the circuit 402 extending between the terminals 60 and 04 as in the preceding figure so as to be short-circuited when the switch is on the cold side and open circuited when on the hot side.

In series in the circuit 402 are the relay switch heating coil 04 and a low loss relay I22, the armature I24 of which is adapted to close a circuit I20 connected across the power lines 8284 and in which is connected the ignititon transformer I I8.

It is absolutely necessary to provide the relay I22 they are in all respects analogous to that of Figure 4.

While several illustrative embodiments have been described in detail, it is not my intention to limit the scope of the invention to those particular embodiments, or otherwise than by the terms of the appended claims. The present application is a refiling of my application No. 128,739, filed March 3, 1937. I

.I claim:

1. A control system for an oil burner, or the like, comprising, in combination with the burner and its motor and igniter, said motor having starting and running windings, a source of electric current and a room-thermostat control therefor, two circuits one of which includes the motor starting winding and igniter and the other of which includes the motor running winding and not the igniter, a safety device in said one circuit actuated by operation of. the igniter for more than a predetermined time and which when so actuated renders the entire system inoperative, and a control device including thermostatic means affected by heat from the operation of the burner and a switch actuated thereby when the burner is cold to connect said circuits in parallel to said source of current ready for oper- I like, comprising, in combination with the burner and its motor and igniter, said motor having starting and ig windings, a source oi elec tric current and a rccm-theostat control therefor, two'circuits one of which includes the motor starting winding and igniter and the other of which includes the motor running winding but not the igniter, and a control device including thermostatic means afiected by heat from the operation of the burner and aswitch actuated thereby when the burner is cold to connect both of said circuits to said source of current ready for operation of the motor and igniter when the room-thermostat calls for heat and actuated after the burner has been in. operation a relatively short time to disconnect said one circuit from said source and to leave said other circnit connected thereto.

3. A controlsystem for an oil burner or the like comprising, in combination with the motor and ignition circuits of a burner,'said motor having a starting winding and a running Winding in difierent ones of said circuits, a thermostaticallycontrolled device afiectedand actuated by heat from the burner when it is on and which device automatically closes the circuits through both of the motor windings and through the ignition when it is cold and which, as it heats up when the burner starts, opens the circuit through the grantee starting winding and the ignition while leaving the circuit through the running winding closed. 4. An oil burner or the like comprising in combination with a repulsion induction motor having a commutated wound rotor, an electrically energized ignition element, and means to energize the ignition element in an electrical series circuit with only the commutated wound rotor.

" 5. An oil burner or the like comprising in combination with a split phase induction motor having starting and running windings, electric ignition means for igniting the burner, and means to energize the electric ignition means in an electrical series circuit with only the starting winding of the motor.

6. An oil burner or the like comprising in combination with a split phase induction motor having starting and running windings, electric ignition means for igniting the burner, electrical switching means to start the burner and the motor with the starting winding of the motor and the electric ignition means electrically energized in series, and thermostatic switching means responsive to an increase in the heat from the burner to deenergizethe starting, winding of the motor and the ignition means. I

KENDALL CLARK.

Images