US2380640A - Safety control apparatus for gaseous fuel burners - Google Patents

Description

July 31,1945. 6, E SK IN 2,380,640

SAFETY CONTROL APPARATUS FOR GASEOUS FUEL BURNERS Filed Nov. 8, 1941 SAMUEL G. EsKw.

ATTORNEX Patented July 31, 1945 UNITED STATES assam PATENT mm I SAFETY CONTROL APPARATUS FOR GABEOUS FUEL BUBNEBS 4 Claims. ('01. 15811'l.1)

This invention relates to safety control apparatus for gaseous fuel burners embodying control relays of the bimetallic type.

Gaseous fuel burners are often arranged to beignited by electric or other ignition means which is energized or otherwise rendered operable sometime prior-to the passage of fuel to the main burner. In the event that ignition does not occur within reasonable time, it is important that the ,fuel supply be automaticallyshut oil so that hazardous conditions do not arise. 'One of the objects of this invenscrews carried by the clamp 20. A portion 30 of the bimetal strip 28 projects beyond the clamp and is thereby adapted to be exposed to a flame. Extending from adjacent the end of the bimetallic strip 28 within the housing ill is a flexible conductor 32 having its opposite end anchored in position on the portion H of the housing. The flexible conductor 32 is insulated from the housing It by a strip 34 of insulating material interposed between the conductor 82 and the housing iii. A terminal 36 projects through both the conductor 32 and the insulation It to the exterior of the housing l0 and serves to secure the parts together by engagement with a nut 38. Preferably, a bushing ll of insulating material islnterposed between the nut 38 and the exterior face of portion ll of the housing ill to provide the necessary insulation.

Other objects and advantages will become apparent from the following description taken in connection with the accompanying drawing, wherein: V

Fig. l is a plan view of the control relay of this invention;

Fig. 2 is a longitudinal sectional view of the relay;

Fig. 3 is an enlarged cross-section taken on the line 3-3 of Fig. i; and

Fig. 4 is a diagrammatic view of the safety control apparatus embodying the control relay.

Referring more particularly .to the drawing. the control relay may comprise a housing ill of sheet metal or other suitablematerial shaped in III by being secured to an insulating block 44 thereon. -'A terminal 48 extends through the bimetallic element 42 and insulating block 44 to the exterior of the housing ill, and is secured by means of the nut 4t engaging with an inthe form of arectangular box having a side portion l2 and top and bottom portions I4 and It respectively. The three portions named may be connected by an end n rtion II and provided with a bifurcated projectim 20- at the opposite end which projects from too housing proper to form a clamp. If desired, the section 2| of the housing It adjacent the clamp 20 may be reduced in width by bending the bottom it inwardly intermediate its ends forming a shoulder portion 22. The terms top," bottom" and side" are purely relative and do not necessarily indisulating bushingv 50 carried by the terminal 0. The bushing 50 serves to insulate the terminal 46 and'nut 48 from the housing It.

A flexible conductor 52 is positioned between the bimetallic element 42 and the portion ll of the housing I! and is anchored at one end to the housing by a terminal 54. Preferably, the insulating block it is provided with a reduced extension I! which the conductor 52 partly overlies. The terminal 54 extends through the con ductor l2 and insulating extension 56 to the exterior of the housing 10, and is secured by means of the nut Bl engaging with an insulating bushing 00 carried by the terminal ill. As in the previous instances. the bushing serves to insulate the terminal 84 and nut 58 from the housing ill.

The bimetallic element 42 and the flexible conductor I2 terminate at their free ends adjacent the shoulder 22 of the housing I0. Interposed between these free ends is the free end of a flexible conductor 02 which extends beyond the shoulder 22 into the reduced section II of the housing and is anchored to the portion I. thereof by a terminal M. An insulating strip 6! is interposedbetween the conductor 02 and the interior face of portion .ll of the housing. The terminal 04 projects exteriorly of the housing II and is secured in position by means oi a nut l8 engaging with the usual insulating bushin: II carried on the terminal ll.

Suitable contact making and breaking means conductor I! which is insulated from the bimetallic element It by an insulating washer it interposed therebetween. The parts described may be secured together by means oi the nut I. engaging with the threaded end oi the contact element or button I1.

A contact button It has a threaded end prolectins through the free end oi the bimetallic element 48, and through the free ends or the flexible conductors "and The bim'etallicelement Cl and the iienibl conductor ll are engaged in good electrical contact at their iree ends and are button I. by an insuiati'ngbushing'l! carried on the contact button It. The flexible'conductof'li ll insulated from both the bimetallie element 4 and the flexible conductor .2 by' an insulating washer II but is in electrical contact with the contact button 8|. The parts described may be secured in position by means oi the nut ll engaging with the threaded end oi the contact button II.

The saiety control apparatus for a gaseous iuel burner embodying the control relay described may be arranged as shown in Fig. 4. In this arrangement aftran siormer II has its primary coll I! connected to a source of current supply and its N connected at one end to the terminal oi a switch II. In this instance, the switch it may b carried. by the operating handle oi a thermostat ll having a main valve controlling the flow oi gaseous fuel through the conduit Ill 'Ihe other terminal oi the switch ll oi thermostat I carries a wire III connected to one terminal oi an electromagnetic iuel valve I controlling the now of fuel through the conduit ill after the main iuel valve II is opened. The elec- 1 tromagnetic iuel valve Ill may b or any well known iorm comprising a solenoid serving to maintain the valve closed when deenergised.

The other terminal oi the electromagnetic valve I" is connected to a wire III which is connected at one end to a suitable electric ignition device indicated diagrammatically at Ill. stance the ignition device may be in the iorm of an electric resistance igniting coil positioned within the oven or other chamber oi a domest c range, a portion or which is shown diagrammatieally at Ill. The opposite end oi the ignition coil III is connected by a wire ill to one end oi a resistance cull ill. the other end oi which is connected .by "a wire iii to the terminal N of the control relay.

The terminal as oi the control relay, which is electrically connected to terminal 84 thereoi carries a wir III which is connected to the opposite end oi the secondary l4 oi the transformer ll. 'lhe conduit III conveys gaseous fuel irom a source oi supply to a b r In connected thereto and which may be positioned within the oven or otherchamber Ill in position to be ignited by-the ilnition coil Ill.

In order to permit the ignition coil III to reach igniting temperature 'beiore any iuel flows irom the burner I", means are provided to mainta n theeiectromagnetic valve I in closed position ior a-psedetennined period oi time aiter the isnition coil III has become energised. Aooos'dir ly. a time delay relay is provided temporarily toshimt the coil oi the electromagnetic valve I and prevent the valve irom opening until after a predetermined period oi time.

The time delay relay. in this instance, is in the form oi a mercury switch III having one terminal connected by a wire I to the wire ill and the other terminal thereoi connected by a wire I" to the wire Ill. The mercury switch III is preierably oi the type having a spediied time delay period upon opening and an taneous closing and is arranged to be u ally closed. Switches oi this pe are disclosed in ts Nos. 1,778,439 and 2,224,873 among others. to which reierence may be had ior a iuller description. The operating coll ill ior the mercury switch iii may be connected at one end by a wire ll. to-thewire Ill andatthsotberendtothswin Ill by a wire Iii.

The proiecting end ll oi the bimetallic strip 2| 'oi the control relay projects into the oven 1 ll djacent in the burner ill and is thereby eaposed to the burner flame. The contacts I! and II at the control relay are normally open and. in the absence oi a name at the burner III, the current flowing through the bimetallic strip it heats it and causes it to warp sumciently to close the contacts 12 and II. when, however, the end ll of the bimetallic strip ll is heated by the burner name, this strip also warps and causes the contact I! to retain open circuit relation with the contact II.

This ability of the contact making and breakinh device toassume diiierent positions depending on the presence or absence or a llama at the burner I10 is made use oi in this invention to providesaiety control ior the burner. To this end, the terminal '0 or the relay is connected by a wire I to th wire ill and the terminal I is connected by a wire Ill to the wire I. Closing oi the contacts II and 12 will thus complete a shunt around the electromagnetic iuel In this inthe ilnition coil Ill.

valve ill.

The operation Movement oi the tion will causejthe main fuel valve in conduit Ill to be opened. Current in the secondary circuit then flows through the wire III to the electromsinetlc iuel valve to the shunt of normally closed.

oi the device is as iollow s:

the mercury switch III which is The current through the wires and III at the shunt continues through the wire Ill to the isnition coil Ill and through the wire "I, resistance coil Ill and wire III to terminal l4 oi the control relay. The current passes by way oi conductor I! through the bimetallic strip I! of the relay to the terminal II and thence through wire Ill connected thereto,'bac'.r tothe secondary l4 oi the transiormer ll. thus completing the secondary circuit. The current in this circuit heats the ignition coil III to ignition tem-' perature and, at the expiration oi the predetermined delay period, the mercury switch ill opens and removes th shunt irom the electromasnetic iuel valve Ill. Upon energization oi this valve and movement thereoi to open position, iuei then passes to theburner III where it is ignltedby During this cycle oi operation the current is heating the bimetallic strip 4! oi the relay and causing it towarp, moving'the contact ll toward the contact ll. However, assuming that ignition oi theburner in has occurred in normal operation. the flame thereirosn is concurrently heating the projecting end a oi the bimetallic main switch as to closed poolm which remains closed due

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