US2015952A - Electric circuit control - Google Patents

Description

Oct. 1, 1935. MQ 2,015,952

ELECTRIC CIRCUIT CONTROL Fild March 50, 1925 C 2 Sheets-Sheet 1 11v VENTOR By ZZ/VCUABE" TTORNE Y Fiq. 1

Oct. 1, 1935.

I. E. M CABE ELECTRIC CIRCUIT CONTROL Filed March 30, 192

5 2 Sheets-Sheet 2 1N VENTOR [5. MC: C1255 6 A TTORNE Y I Patented Oct. 1, 1935 UNITED STATES PATENT OFFICE 2,015,952 v ELECTRIC cmom'r CONTROL Ira E. McCabe, Chicago, .111. Application March 30, 1925, Serial No. 19,3l 7 Claims. (Cl. 158-28) This invention relates to improvements in electric circuit controls and more particularly to a double unit pressure or temperature actuated control of this character. It is an object of this invention to provide a control of the character described particularly adapted to be employed as a safety device in an electrically operated domestic oil burner circuit but this device is not limited to such a use as it may be employed in any circuit desired and actuated by changes of either pressure or temperature without departing from the scope of this invention.

The control constructed in accordance with this invention is illustrated on the accompanying cult of an electrically operated domestic oil burner, although as aforesaid it is not limited to this use.

In the drawings:

Figure 1 is a diagrammatical illustration of the wiring of this control in an electrically operated oil burner system. v

Figure 2 is a rear view of the control box, with the cover removed.

Figure 3 is an enlarged detail view of the time element unit of this control.

Figure 4 is a front view of the control box.

Figure 5 is an enlarged detail view of the 30 thermal or pressure actuated unit of this control.

' As illustrated in Figure 1, it is preferable to house the control in a box or casing I located upon or near the burner mechanism and is here shown upon the blower fan casing 2 at the end of the 35 casing 3 of the motor which operates the fan and also supplies oil to the burner nozzle at the fire box end of the air conduit 4 leading from the fan blower tothe fire box 5 of a furnace of boiler 6. The knife switch S connects one termi- 40 nal of the motor through lead 1 to one pole of.

the outside commercial source of electricity, the other pole being connected by the switch to a lead 8 passing through a room thermostat, boiler or furnace control and then through the improved safety control to the other terminal of the motor. While the room thermostat T and boiler or furnace control C are not necessary to this invention, they are illustrated as they are customary in such circuits. 50 The safety device comprises two coacting units contained in casings 9 and i0 preferably carried on opposite sides of the rear wall of the box I.

The unit on the inner side of the box I contained within the casing 9 comprises. a rocking 55 mercury tube switch II, which may be termed a sheets of drawings as a safety device in the cirsecondary switch, pivotally mounted on the casing and having two terminals l2 and I3 extending within the tube adjacent one end adapted to be connected by the mercury in the tube when that end is depressed and, having a spring 14 5v normally rocking the tube to elevate the terminals and disconnect them with a counterweight i6 acting in case the spring fails or deteriorates to rock the tube in the same direction. The terminal i2 of the switch is flexibly connected to the lead 8 of the motor circuit and the terminal l3 is fiexibly connected to the binding post H on the back of the casing therebelow, so that in one position of the tube the circuit is closed between the lead 8 and the binding post i1 and when the 15 tube is rocked by the spring or counterweight to the other position the circuit is broken. The rocking frame carrying the tube is provided with 2. depending pawl iii of spring metal adapted to normally engage a ratchet wheel carried on 20 top of a shaft 2| rotatably mounted in a metal cup 22 having a depending projection 23 rigidly secured to the back of the casing. The cup between the shaft 2! and its side walls and bottom is filled with solder which when, cold holds the shaft immovable but when melted allows the rotation thereof within the cup. An electric heating element 24 is led from the binding'post l1, wound about the cup projection 23 and thence to a binding post 25 upon the back of the casing! so that when current passes therethrough the cup will be heated and the solder melted allowing the tube switch to be rocked with the dependins pawl engaged in the ratchet turning the shaft in the cup. When the tube is in open circuit position and the heating element out of circuit,

it is necessary to manually depress the pawl and rock the switch to closed position where the pawl will engage the ratchet and hold it in that position until the solder in the cup is melted. The amount of time required for the solder to melt is in proportion to the amount of heat generated by the electrical heating element and this can be regulated, as desired, by the number of wraps of the heat generator about the cup pro- 4 jection or the distance of the heat generating coils from the cup, as the projection must first be heated and its heat transmitted to the walls of the cup before the solder is melted.

As illustrated in the diagram of the wiring in Figure 1, the binding post 25 is connected by the lead 8 to the motor terminal and alsd'thecircuit from binding post I1 is completed through the unit in casing ill and binding post 25 to the motor. The heating element 24 is in a shunt circuit from lead 8, the main circuit normally passing through the unit in casing in, and as long as the main circuit remains closed through the other unit will not generate sufiicient heat to melt the solder but when the circuit through the unit in casing I0 is broken the full current in the motor circuit passes from binding post i'I to binding post 25 generating suiiicient heat in element 24 to release the shaft 20 and 9.1- low the pawl 19 to rotate the ratchet on the shaft and the spring or weight rock the switch tube to break the circuit therethrough.

It is preferable to place this unit which includes the safety switch for the motor circuit upon the rear wall of a box or casing and also locate the knife or other type of switch S connecting the motor circuit to the source of commercial cur rent in the same box, which is provided with a cover normally closed, for convenience as the switch S must be manually operated to place the burner mechanism in operative connection with the commercial current and manually rock the safety tube switch to closed position. Also for the purpose of convenience it is preferable to locate the other unit cooperating with the safety tube switch mechanism on the outer side of the back oi! the box opposite the safety switch casing 9.

The unit in the casing ill in circuit with one side of the safety tube switch and the motor also includes'a rocking mercury tube switch 26, which may be called an automatic primary switch, preferably operated by a snap movement such as more fully described in my prior pending applications Serial Nos. 538,916, 585,698, and 596,408, filed February 24, 1922; September 1, 1922; and

October 23, 1922, which on October 29, 1929 became Patents Nos, 1,734,015. 1,734,016 and 1,734,017 respectively. This switch is also provided with two terminals 21 and 28 entering the tube adjacent one end, so that when rocked to the limit of its movement in one direction the mercury closes the contact between the terminals and when rocked to the limit of its movement in the opposite direction the contact is broken sharply by the snap movement. Both of these terminals are connected byyfiexible leads 29 to binding posts upon the back of the easing III which in turn are connected by leads ill to the binding posts I! and 25 of the'other unit, as shown in the diagram.

The snap movement of this switch is supplemented by a counterweight ii on the rocking frame of the tube which upon failure of the spring will rock the switch to the open position. This snap movement is normally operated by a Bourdonor pressure tube 32 the free end of which is connected by a. pivoted link It to an operating arm 34 pivoted at one end to the back of the casing and having at its free end a pivoted operating link 35 having a slidable and pivotable engagement at its other end with the operating movement of the snap device, said link having a longitudinal slot 38 at this end in which the slidable pivot 31 to. said movement member is carried andover .which said link may travel. A coil spring I! attached to said pivot and to the opposite end of said link normally retains the innermost end of the slot in contact with said pivot and normally is of sufiicient tening or straightening of the Bourdon tube operates to close said circuit and upon further movement in an outward direction overcomes the link spring 38 and allows the slotted end of the link to travel over the pivot 3'! mounted in said 5 slot 35 for a purpose hereinafter described. The opposite end of the Bourdon or pressure tube is in communication with a pipe 39 leading to a point within the furnace or boiler to transmit the heat or pressuretherein to act upon the 10 Bourdon tube. In'the construction illustrated the furnace end of the tube is sealed and is located to be susceptible to the variations of temperature of the fire box thereof by sealing within the pipe and Bourdon tube a liquid which as 15 the temperature increases will expand and cause the tube to straighten and upon cooling will contract and cause the tube to coil. This pipe if communicating to the interior of a boiler would cause the Bourdon tube to act similarly in ac-go cordance with variations of pressure with the boiler.

To cause this unit to also act as a thermometer or pressure gauge a plate is secured to the snap movement mechanism with a portion 40 extend- 25 ing over the path of movement of the free end of the pivot operating arm which end is bent back to form a pointer and that part of the plate over which the pointer passes is provided with a pressure or temperature scale. The cov 30 er of the casing i0 is provided with a glass covered aperture. through which this plate scale and pointer are visible. In the type of burner illustrated the Bourdon tube is actuated by variations of temperature and in this case the 35,

link spring and indicator scale are calibrated and constructed to indicate temperatures from that which first throws the switch to close the circuit and therebeyond to the end of travel of the pointer limited by the slot in the link arm. 49

By observing the operation of the burner mechanism and temperatures indicated by the unit in casing ID the most efficient operating tempera- 'ture is ascertainable and the oil and air supply cuit, the main current passing through the safe- 50 ty switch passes through the other unit to the j motor, so that when the temperature of the fire box falls upon extinguishing or failure of the burner flame the Bourdon tube of the second unit acts to break the circuit through the auto- 55 matic primary switch of the second unit, and

when this occurs, the full strengthof the. current to the motor passes through the shunt circuit which produces sufilcient heat about the heating element to release the safety or sec- 6 ondary switch and thereby break the motor circuit between the knife switch 8 and the motor, independently of any thermostats or pressure controls that may be in the motor circuit.

In the application of this invention illustrated upon the drawings it is necessary that the heating element of the safety switch holding device be adjusted not to melt the solder thereof when the safety switch is manually closed after the burner flame is ignited until after the fire box 7 temperature has reached the point to throw the Bourdon tube operated switch to closed positi'on which immediately places the safety switch .in direct circuit with the motor and. the heating element in shunt therewith.

The release of the safety switch holding means forms an adjustable time element which during initial starting of the burner mechanism will release to break the motor circuit if the burner flame fails to ignite, will not be released .by the normal operation of the mechanism controlled by a room thermostat or boiler control,

but will release the safety switch if the burner flame fails or becomes extinguished from abnormal causes while the mechanism is operating.

What I claim is:

l. The combination with a heating element, of a burner, a motor for operating said burner, a power circuit for said motor, a resistance unit connected in the power circuit in series with said motor, a switch for controlling said power circuit, a switch under the influence of combustion conditions of the burner, said switch being normally open and operating upon the estab ishment of combustion to close and thereby s ortcircuit the resistance unit prevention further heating thereof, and means for opening the power circuit operable upon a predetermined temperature developed in the resistance unit.

2. The combination with an electric machine, of a power circuit therefor, an automatic primary switch for said circuit, a secondary switch movable manually to closed and automatically to open position, a shunt circuit connected across the automatic primary switch, said shunt circuit including a resistance element, and a thermostatic element in association with the resistance element for opening said secondary switch.

3. In combination with an electric machine, a power circuit therefor, an automatic switch in said power circuit, a shunt circuit connected across the automatic switch, a resistance element in said shunt circuit, a secondary switch in said power circuit, and means operable by the resistance element of said shunt circuit to open the secondary switch. 7

4. In combination with an electric machine,

a power circuit therefor, an automatic switch in said power circuit, a shunt circuit connected across the automatic switch, a resistance element in said shunt circuit, a secondary switch in said power circuit, means operable by the resistance element of said shunt circuit to open the secondary switch, and a manual switch for cutting out the power circuit.

5. In combination with an electric machine, a power circuit therefor, an automatic switch in said power circuit, a shunt circuit connected across the automatic switch, a secondary switch movable manually to closed position and automatically to open position, and means operated by the shunt circuit for operating said secondary switch from closed to open position. a

6. In combination with a fluid fuel burner having an electrically operated means controlling fuel feed, a control system comprising a circuit including said means, cut-out means having an actuator rendered operative upon energization of said circuit, to thereafter deenergize the circuit, and a shunt about said cut-out actuator having a combustion responsive switch which is closed when combustion is established to render said cut-out means inoperative to 3pm the circuit.

7. In combination with a fluid fuel burner having an electrically operated means controlling fuel feed, a control system comprising a circuit including said means, cut-out means having an actuator rendered operative upon energization of said circuit including an electric resistance unit adapted upon energization of said circuit to actuate the cut-out means to thereafter deenergize said circuit within a predetermined time, and a shunt about said electric resistance unit having a combustion responsive switch which is closed when combustion is established within said predetermined time to render said cut-out means inoperative to open the circuit.

IRA E. MCCABE.

Images