US2154761A - Safety control switching mechanism for fluid fuel burners - Google Patents

Description

|. E. MCCABE A r l 18, 1939.

SAFETY CONTROL SWITCHING MECHANISM FOR FLUID FUEL BURNERS Original Filed Oct. 1, 1935 2 Sheets-Sheet 1 IL-IQ l I I l I INVENTOR.

A TTORNE Y.

April 18, 1939. MCCABE 2,154,761

SAFETY CONTROL SWITCHING MECHANISM FOR FLUID FUEL BURNERS Ofiginal Filed Oct. 1, 1935 2 Sheets-Sheet 2 A TTORNEY.

Patented Apr. 18, 1939 UNITED STATES PATENT OFFICE SAFETY CONTROL SWITCHING MECHANISM 1 FOR- FLUID FUEL BURNERS Ira E. McCabe, Chicago, Ill.

7 Claims.

This invention relates to a safety control switching mechanism for fiuid fuel burners and more particularly to a burner of the type in which the fuel is ignitedby a pilot light. This application is a. division of this applicant's prior co-pending application, Serial No. 43,075, filed October 1, 1935.

There is on the market at the present time, a gas burner for warm air heaters provided with a continuously burning gas pilot mounting a 'reciprocable actuator rod responsive to the presence or absence of heat of said pilot in conjunction with an electric switch in a circuit for controlling an electrically operated valve in the gas supply to the burner. It is an object of this in vention to provide a safety control for such a device, including an electric circuit requiring the manual closing of two switches therein beforethe pilot can be ignited, and thereafter allowing one of said switches to be opened upon the closingof the switch responsive to the heat of the pilot flame to establish a circuit in parallel with the first circuit maintaining the supply of fuel to the pilot open but shutting off said supply 25, upon the extinguishing of the pilot light and upon the reversing of the other manual switch to establish a circuit in series with the pilot light controlled circuit to open the gas supply to the burner. Said latter circuit may be controlled by switch responsive to the temperature within the heater whereby the burner may be supplied with fuel intermittently as long as the pilot light is burning but shut off immediately the pilot becomes extinguished and requires. a manual operation of the two switches before the burner can "again operate. The reversal of said manual switch to control the gassupply may, if so desired, establish at the same time a parallel circuit to operate a motor driven fan blower. While the embodiment of this invention disclosed herein is designed as a safety control for a fired warm air heater, such as may be located in the space or room wherein the heat is desired and people are present, (and should unburned gas escape or be present when attempts are made to re-llght an extinguished pilot, it, would be extremely hazardous) its application. to any fluid fuel burner ignited by a pilot is obviously within the scope thereof.

With these and other objects in view, reference is made to the accompanying sheets of drawings, illustrating an embodiment of this invention, with the understanding that minor detail. changes may be made without departing 55 from the scope thereof.

In the drawings- Figure l is a wiring diagram of the control circuits indicating in full lines the path of the current when both manual switches are first closed. g

Figure 2 is a similar diagram indicating in full lines the path of the current after the switch responsive to the heat of the pilot has closed and one of the manual switches opened.

Figure 3 is a similar diagram illustrating the path of the current after the second manual switch has been reversed with the thermostatic switch responsive to the temperature of the heater closed, as in normal operation.

Figure 4 is a view in elevation of the bracket supporting one end of the actuator rod responsive to the presence or absence of heat from the burning pilot and the covered switching mechanism operated thereby.

Figure 5 is an enlarged detail top plan view of the switching mechanism, with the cover and mercury tube switch removed.

Figure 6 is a view in front elevation of Figure 5 with the tube clip removed and the magnet arm carrying sleeve shown partly in section.

Figure 7 is a view in side elevation of Figure 5 looking thereon from the right.

Figure 8 is a similar view looking thereon from the left.

Figure 9 is a detail view in elevation of the pilot responsive thermal member.

In the diagrammatical views shown in Figures 1, 2, and 3, a normally closed thermostatic switch T of commercial construction is located within the warm air heater, not shown, and is responsive to the temperature therein. A three-way switch K is normally located within the vicinity of the heater. A normally open momentary contact push button switch P is preferably located in the vicinity of the opening in the warm air heater for lighting the gas pilot GP. When the switch K is manually thrown to the uppermost closed position, as shown inFigure 1, and the switch P closed, a circuit is completed through the wire L from the commercial line, or other source of electricity, through the push button switch P, the wire I, binding post 2 of switch K, through switch K to binding post 3 thereof, thence through wire 4 to lower binding post 5 of switch K and from thence by wire 6 through the windings of a solenoid operated valve V in the gas supply pipe PS to the pilot light burner GP, and from thence to the return line L' to the source of electricity. The push button switch P is normally open and no gas can be supplied to the pilot light burner, so that when it is desired to ignite the pilot it is necessary to first manually close the switch K, as shown in Figure 1, and then depress the push button switch P while the pilot light is being ignited by a match or other flame.

The heat from the burning pilot GP, through a means hereinafter described, closes the switch S. The actuating means is responsive to the presence or absence of the flame of the pilot and is adapted to open or close the switch S, as the case may be, in an adjustable period ranging from 1 to 10 seconds. The operation of the switch may thus be said to be immediate with the establishment or failure of the flame. Upon the closing of the switch S, a circuit is established by wire I from the lead L through the closed switch S, wire 8, binding post 5 of the lower position of the switch K and wire 6 through the solenoid windings of valve V in the return lead L. It is, therefore, seen that as long as the pilot light is burning, the push button switch P may return to its normally open position and the solenoid will remain energized to hold open the valve V to supply gas to the pilot, but should the pilot become extinguished before the burner B is ignited, the switch S will open said circuit and the valve V will close preventing gas from escaping through the pilot burner. This circuit is illustrated in Figure 2.

After the pilot light has been ignited, it is necessary to throw the knife switch K manually into its lowermost position, as shown in Figure 3, in order to ignite the burner flame. When the switch K is in its lowermost position, a circuit is established from binding post 5 through switch K to binding post 9 and by wire In through the normally closed thermal switch T and wire ll.

through the windings of the solenoid or motor operated valve G in the gas supply pipe PS to the burner and thence to the return line L. It is to be noted here that the main valve G controls only the fuel supply FS for firing the heater and that the pilot valve V is connected in the supply line ahead of the valve G. The closing of switch K in its lowermost position, therefore, establishes a circuit through the pilot light switch S to binding post 5 and through both valves V and G to maintain the valve V open to supply gas to the pilot GP and to open and hold open the valve G to supply gas to the burner B. When the temperature within the heater reaches the degree set to open the thermostatic switch T, the valve G will be closed while the valve V will remain open so that when the temperature within the heater descends below the setting of the thermostat T, the valve G will be opened and the burner flame ignited by the continuously burning pilot, whereby the valve G may be intermittently operated as long as the pilot is burning. Should the pilot become extinguished at any time during the operation of the heater burner, the circuit therethrough will be broken which will also break the circuit to the valve G and the burner cannot be again ignited until the switch K is manually thrown to its uppermost position, the push button P be depressed and the pilot ignited. In warm air heaters, it is desirable to have a circulating fan operated by a motor, such as the motor M shown in the said diagram. In order that the motor may be operated while the burner is in operation, one pole of the motor is connected to binding post 9 by wire [2 and the other pole by wire l3 to the return lead L.

From the above description, it is seen that this system provides a safe system at all times, the features of which are:

1. The entire system is shut down immediately upon failure of the pilot flame. This insures against the circulation for any extended length of time of unburned gas and prevents the accumulation of gas within the heater which would explode when attempts were made to re-light the pilot flame.

2. The requirement of the manual operation of two switches to re-light the pilot flame, one switch being a double throw type and the other of the type which automatically opens when not manually held closed. The double throw switch, when operated to prepare the circuit by which the other switch opens the pilot valve, breaks the circuit to the main gas valve. It is thus assured that the main valve cannot be opened during the lighting of the pilot flame to fire the burner and possibly burn the person engaged in the lighting thereof.

3. The requirement of manipulation of the double throw switch after igniting the pilot flame to place the main gas valve in control of the thermostat as long as the pilot flame continues to burn. The operation of the burner, therefore, depends upon the continuous burning of the pilot flame and ends substantially with the extinguishment thereof.

4. While it is necessary to actuate the manual switches in the prescribed sequence when placing the burner in operation, failure to do so, while not accomplishing the desired results, will neither result in establishing hazardous conditions nor inflict injury to the person attempting to operate the burner. Thus, protection is afforded at all times while the burner is in or out of operation, or during the process of placing it in operation.

It is obvious that this system may be applied to any electrically operated and controlled fluid fuel burner employing gas ignition by simply controlling the burner mechanism through the thermostat T.

As heretofore stated, the switching mechanism for opening and closing the switch S is responsive to the presence or absence of a flame at the pilot. and the mechanism illustrated in Figures 5 to 8, inclusive, is an improvement of a device now on the market including a horse shoe thermal element such as disclosed in the patent to O. W. Hahn, No. 2,064,909 of December 22, 1936, which is provided with means for reciprocating an actuating rod through a casing to the switch operat ing mechanism extending said rod when the pilot is burning, and withdrawing said rod when the pilot is extinguished which means includes attaching to the end of the rod adjacent the pilot a strip of metal readily expandible in the pres ence of heat and readily contractible as soon as the heat is removed. This preferred means for reciprocating an actuating rod is shown in Figure 9.

In Figure 4, a bracket l 4 is shown supporting a base plate 15 and a sleeve l6 extending in the opposite direction which surrounds a reciprocating actuating rod l1 operated in the manner hereinbefore described. In this figure, a cover I8 is shown surrounding the improved switching mechanism and attached to the base l5. A switch supporting bracket having a horizontal portion l9 and a depending right angular portion 20 extending from one end is secured to the base l5 by screws 2| with the horizontal portion arranged centrally above the portion of the actuating rod 11 passing through the base [5 with the portion provided with an outstanding right angular member 22. The member 22' supports a switch carrying clip 23 for engaging a tube switch 24 between resilient arms 25 formed integral with said clip 23. The'mercury tube switch 24 is of the type normally held in a vertical position with a globule of mercury 26 contained in the lower end thereof in contactwith one terminal 21 of the switch, the other terminal 28 of which is resiliently mounted and normally assumes a position out of contact with the mercury, said latter terminal being provided with an armature 29 of magnetic metal adapted to be drawn to-the adjacent side of the tube by the influence of a magnetic field of a magnet to cause the terminal 26 to contact the mercury 26 and close the circuit through the switch, such'a switch construction being disclosed in this applicants Patent No. 2,085,316, granted June 29, 1937.

A fixed magnet 30 is mounted upon a right angular extension 3| at the lower end of an arm 32 secured to a sleeve 33 rotatably mounted upon a bearing 33a which in turn is mounted upon a reduced portion at one end of the shaft 34 carried upon a right angular extension 35 of a bracket 36. A spring 31 normally tending to cause rotation of the arm 32 to move the magnet 30 to contact the adjacent wall of the mercury tube switch 24 is mounted at its upper end 38 by rivets 39 to the horizontal arm'l9 of the switch supporting bracket. The bracket 36 is mounted upon the upper portion 36 of the spring 31 by rivets 40 with the top of the bracket 36 approximately in line with the under side of the bracketportion IS.

The portion 22 of the switch carrying bracket is provided at its lower end adjacent the base l5 with a right angular portion 50 extending from the side opposite the mercury tube switch 24 which portion mounts screw threaded adjustable stops 5| and 52 one above the other with the lower stop 52 provided with a member 52a carried parallel to the base I5 and extending in the direction of the stop 5|. A stop arm54 secured to a sleeve 53 mounted on the end of the shaft 34 opposite the magnet arm is provided with an extension 54a which extends between the stop 5| and the extension 52a of the stop 52-whereby the oscillating movement of said arm may be adjustably limited.

The sleeve 53 of the stop arm 54 is provided with a shoulder having a sliding engagement with the surface of the portion 35 of the bracket 36 and is held in frictional contact therewith by a coiled spring 46 surrounding the sleeve 53 and bearing at one end against said shoulder and at the other end against the magnet arm bearing which bears against a washer disc 41 held in position by a nut 48 threaded upon the screw threaded end 49 of the reduced portion of the shaft 34.

In order that the magnet arm will move with the stop arm 54, as movement is imparted to the bracket 36 by the spring 31, the stop arm is provided with a second extension 54b in the form of a fiat spring extending in the direction of the magnet arm and adapted to contact the edge of said arm under tension. The extension 54b not only keeps the magnet arm in alignment with the stop arm 54 and causes arm 32 to move with arm 54b, but also restores the magnet to its proper position when it is moved as a result of the device being struck or jarred, which shocks, without the spring extension 5417, would cause the magnet arm with the weight of the magnet carried beneath it, to creep toward the mercury switch 24 and close the circuit therethrough.

The actuating rod |1 passes through apertures provided therefor in the base I5, portion 38 of the spring 31 and bracket 36 and is reciprocably mounted therein. The end of the actuating rod I! is provided with a cubical member 4| axially drilled upon a diameter to engage the rod and the exterior end of the actuating rod is provided with a lock nut 42 having a plurality of similar oppositely disposed parallel faces, each of which are provided with a central groove 43 adapted to engage one of the transverse, edges of the cubical member 4| to lock the nut. To maintain the opposite transverse edge horizontal in a position to form a knife edge engagement with a V groove 36a in the bracket 36 a distance below the top thereof, the cubical member 4| is provided with a stud 44 extending axially from one side thereof and the portion 35 of the bracket 36 is provided with a notch 45 to receive the stud 44 to prevent rotation of the member 4| and at the same time to allow a back and forth movement thereof.

The cubical member 4| is so adjusted upon the actuator rod l1 that when the pilot is extinguished, the rod I is at the end of its travel away from the switching mechanism and the transverse edge of said member bears against the bracket 36 with sufficient force to bend the spring 31 about the lower edge of the bracket l9 and cause the bracket 36 secured thereto, the shaft 34 mounted thereon, and the stop arm 54 and magnet arm 32 carried thereby to move the magnet 30 away from the switch 24 to break the circuit therethrough, and when the actuator rod is moved in the opposite direction by the heat of the burning pilot, the spring 31 is freed to move the magnet 30 into contact with the switch 24 to close the circuit therethrough.

During this movement of the magnet 30, the extension 54a of the stop arm 54 reciprocates between the stops 5| and 52a upon the extension of the switch carrying bracket portion 22 and as the magnet arm is caused to move with the stop arm 54 through the spring connection 54b, as previously described, the travel of the magnet may be adjustably limited thereby as the stop I arm 54 is mounted for frictional engagement with the bracket 36 by the spring pressed sleeve 53 carrying said arm allowing continued movement of the bracket 36 after the arm has engaged a stop and at the same time causing immediate movement in the opposite direction simultaneously with the slightest movement of the actuator rod I! in the opposite direction; r

In the embodiment of this invention as herein'before described, it is desirable that in igniting the pilot, the said switching mechanism respond immediately so that it is only necessary for a momentary closing of the push button switch P. By the construction illustrated in Figures 5 to 8, inclusive, the mechanism may be so adjusted that a movement of but .005 of an inch in either direction will operate the switch 24 within a minimum of 1 seconds to a maximum of 10 seconds following the ignition of the pilot to establish the circuit to close the circuit therethrough to maintain the gas supply to the pilot.

Figure 9 represents the commercial device heretofore referred to which is responsive to the presence or absence of the pilot light for imparting movement to the actuating rod l which includes the horse shoe shaped thermal element 55 in which the outer heel 56 is fixed to the end of the sleeve l6. The nozzle 51 of the pilot passes through an opening 53 provided therefor in the sleeve I6 to enter within the horse shoe, as shown.

The other heel 59 of the horse shoe extends through an opening provided therefor in the upper side of the sleeve l6 and is attached to the end of the actuating rod H. The toe of the horse shoe element is provided with a plurality of circular openings 60 which reduces the metal directly above the nozzle 51 of the pilot, so that as soon as the pilot is ignited, the heat therefrom immediately acts upon this reduced portion of the thermal member and from its shape will impart an immediate movement to the actuating rod l1. Likewise, immediately upon extinguishing the pilot, a movement in the opposite direction will be imparted to the actuating rod. It has also been found advantageous to provide a guide SI for the resilient terminal 28 of the mercury tube switch 24, as shown in Figure '7. The guide BI is welded or otherwise secured at its upper end to the rigid portion of 20 the terminal 28 and is of approximately the same rigidity as said main portion with the lower end terminating in a coil 62 through which the lower end of the terminal 28 slides in the making and breaking of the circuit through the switch and prevents the spring carrying the armature 29 from being sprung and shifting the position of the terminal 28.

What I claim is:

1. A switching mechanism for controlling the operation of a fluid fuel burner ignited by a flaming pilot operated by a reciprocable actuating rod responsive to heat from the flame of the pilot to move in one direction and upon failure of said flame to move in the opposite direction, including a normally open magnetically operated switch, a magnet normally supported at an inoperative distance from said switch, and means operated by a movement of the actuating rod to bring said magnet into and out of operative rela tion to said switch including a spring mounting said magnet adapted to be engaged by the actuator rod upon movement away from said switch to move the magnet away from said switch against the tension of the spring, the movement of the actuating rod in the direction of the switch freeing the spring to move the magnet in operative relation to said switch.

2. The structure of claim 1 wherein adjustable stops are provided to limit the travel of the magnet and wherein said magnet operating means includes a clutch to move the magnet to engage the stops upon movement of the actuating rod and thereafter allow further movement of the rod in the same direction.

3. A switching mechanism for controlling the operation of a fluid fuel burner ignited by a flaming pilot including a base, an actuating rod responsive to heat from the pilot flame having its free end mounted to reciprocate through said base, a normally open magnetically operated electric switch mounted upon said base, a magnet for operating said switch, a swinging arm mounting the magnet at one end, a resilient support for the other end mounted on the base, and means upon the free end of the actuating rod coacting with said resilient support when the heat from the pilot flame expands the actuating rod to allow the support to swing the magnet toward the switch to close the circuit therethrough and upon extinguishment of the pilot flame to act upon the support to swing the magnet away from the switch to open the circuit therethrough.

4. The structure of claim 3 wherein the free end of the reciprocating rod mounts an adjustable block for making a knife edge contact with said resilient support.

5. The structure of claim 3 wherein said resilient support includes adepending integral member normally engaging the base below its mounting.

6. The structure of claim 3 wherein one end of the swinging arm is mounted upon a shaft carried in a bracket secured to the resilient support with a flat spring carried on said bracket adapted to engage a fiat surface of the arm surrounding the shaft to allow movement of the arm in response to shocks or jars and return the arm to the normal position when the magnet is withdrawn from operative relation to the switch.

'7. The structure of claim 3 wherein one end of the swinging arm is mounted upon a shaft carried in a bracket secured to the resilient support, a stop arm secured to a sleeve mounted on said shaft and having frictional engagement with said bracket, said stop arm including a flat resilient member extending parallel to the shaft adapted to engage a flat surface of the swinging arm surrounding the shaft and having a depending portion provided with a stop extending at an angle therefrom, and adjustable abutments supported on opposite sides of said stop to limit the movement of the magnet in opposite directions and thereafter allow further movement of the actuating rod and causing reverse movement of the actuating rod to immediately move the swinging arm in said reverse direction.

IRA E. MCCABE

Images