US3038978A - Flame detector - Google Patents

Description

June 12,v 1962 L B, WAGNER 3,038,978

FLAME DETECTOR Filed Jan. 16, 1959 I3 4 4/ INVENTOR. I-r-VI n n/vp B, Wie/vae.

arent Patented June l2, 19152 3,038,978 FLAME DETECTOR Leland B. Wagner, Goshen, Ind., assignor to Penn Controls, Inc., Goshen, Ind., a corporation Filed Jan. 16, 1959, Ser. No. 787,270 7 Claims. (Cl. 24m-133) This invention relates generally to combustion responsive devices and in particular to a flame detector adapted for mounting within the blast tube of a conventional oil burner.

In conventional oil burner installations the combustion responsive switch, forming a part of the control for the burner, is mounted at a location in the burner stack where it can properly indicate the presence or absence of combustion. Since this location is relatively remote from the burner liame itself, and because of the thermal inertia of the oil tired furnaces heat exchange surfaces and stack, the reaction time of such remotely mounted combustion responsive switches is prolonged. Further, since the combustion responsive switch is mounted separately from the burner at a location dictated by the particular inst-allation, this control cannot be pre-wired Kby the burner manufacturer.

It is an object of the present invention to provide a flame detector switching device adapted for mounting within the blast tube of an oil burner to directly view the burner iiame.

A further object of the present invention is to provide a flame detector switching device of the type referred to which utilizes a novel slip-friction coupling between the switch element land the temperature responsive element for causing the switch to operate in response to a predetermined temperature change rather than in response to the existence of a predetermined temperature level.

A further object of the present invention is to provide a flame detector for use with oil burners which responds rapidly to the presence or absence of a burner flame.

These and other objects will become apparent as the description proceeds with reference to the `accompanying drawings in which:

FIG. l isa side sectional view of an apparatus embodying the present invention.

FIG. 2 is an end View of the apparatus shown in FIG. l.

FIG. 3 is a fragmentary sectional View taken generally along the line 3 3 of FIG. 2.

FIG. 4 is an end view of `a portion of the apparatus shown in FIG. l.

FIG. 5 is an end View of the apparatus taken from the end opposite that shown in FIG. 2.

FIG. 6 is a side View of the apparatus, partially in section, with certain of the parts eliminated to more clearly show the contact arrangement.

Referring to the drawings, the ame detecting apparatus includes a cylindrical housing 10, having welded thereto a clamp structure 11 which may be tightened around the nozzle of an oil burner by means of a bolt 12 (FIG. 5). One end of the housing is closed by means of a disc or plate 13, which may be formed of Bakelite or similar material. rI`he plate 13 is retained by means of back-up rings 14, the assembly thus formed being retained against an internal shoulder 16 formed in the housing by staking at spaced points on the margin of the housing as indi- :ated at 17.

The inner surface of the plate 13 is undercut to receive a portion of an off-set contact bracket 18, the bracket being attached yby means of a rivet 18a to an external contact member 19. Threaded into the bracket 18 is a screw 21, carrying a stationary contact 22. As may be seen in FIG. 5, the head of the screw 21 is accessible through an aperture in the plate 13 and thus may be adjusted with relation to the bracket 18 from the exterior of the housing.

A second bracket 23 is similarly attached to la contact member 24 and at its free end carries a stationary contact 26. A third bracket 27 extends from the plate 13 and is attached to a contact memlber 28.

The open end of the housing is closed by an end cover plate 29, which rests against an internal shoulder formed in the housing. As may best be seen in FIG. 3 an annular mounting member 32 abuts the plate 29 and has formed therein diametrically opposed notches 33 having inclined sidewalls 33a. A matching annular member 34 abuts the member 32 and is provided with diametrically opposed notches having inclined side walls 36. The `adjacent notches in the members 32 and 34 thus provide substantially V-shaped depressions having inclined side walls 33a and 36.

Seated in the depressions are the ends of a bimetal element 37 which extends diametrically across the housing. Extending from the inner face or" the member 37 and freely through an aperture 38 in the plate 29 is a thrust member 39 having a generally rectangular crosssectional configuration. Two annular holddown rings 41 and 42 are stacked over the member 34 and these parts are held in assembled relation by staking of the housing margin as indicated `a1: 43.

Slidably received upon the member 39 is a slide arm 44, which has a reversely bent end portion 44a. The reversely bent portion 44a and the adjoining sections of the arm 44 are apertured, as indicated at 46 in FIG. 4, to freely accommodate the thrust member 39. The arm 44 has rigidly secured thereto a block 47 which mounts a resilient means taking the form of a leaf-type spring 48. The free end of the spring bears against the extending end portion of the thrust member 39 and applies a frictional force tending to resist relative movement between the thrust member and the arm.

A screw 49 threaded into the arm 44 serves to electrically attach one end of a pig-tail lead wire 51 to the arm 44, the other end of the lead 51 being attached by means of screw 52 to the bracket 27. The free end of the arm 44 has rigidly secured thereto a `depending movable contact member 53, the free end of which is adapted to selectively engage one or the other of the contacts 22 and 26.

As will be evident from FIG. 6, the contact members 24, 19 and 28 are counter-bored to receive the ends of wires 54 which may be joined in an armoured cable. it will be understood that the contact member 19 is electrically connected to the stationary contact 22, the contact member 24 is electrically connected to the Contact 26, and the contact member 28 is electrically connected to the movable contact 53. Y

In operation, with the housing clamped upon the nozzle of an oil burner the bimetal member 37 will be facing the burner flame and will receive radiant heat therefrom. As shown in FIG. 2, the bimetal member is in a transitory, intermediate stage, and the movable contact 53 is thus positioned intermediate of the contacts 22 and 26. When the bimetal member 37 is in its cold position, that is, prior to ignition of the burner, the relative position of the thrust member 39 and the arm 44 will be such as to engage the contacts 53 and 26. When the burner is ignited, radiant heat from its flame and surrounding refractory surfaces will cause the bimetal member to bow inwardly, moving the thrust member 39 inwardly. The arm 44 will be displaced by this motion of the thrust member so that the contact S3 will be disengaged from the contact 26. After a predetermined temperature rise of the bimetal member 37, the contact 53 will be moved into engagement with the contact 22. Further inward movement of the bimetal member will cause a slippage 3 of the thrust member 39 relative to the arm 44, and the contact 53 will be maintained in engagement with contact 22.

Upon extinction of the burner flame, the initial drop in temperature through a predetermined range of the bimetal member 37 will move the thrust member 39, and consequently the arm 44, so that the contact 53 disengages the contact 22 and subsequently engages the contact Z6. As the temperature of the bimetal falls below the predetermined range the additional outward movement of the thrust member 39 will cause slippage between the arm 4d and the thrust member with the contact 53 being retained in engagement with the contact 26. The arrangement is thus such that the initial change in temperature through a predetermined range in either a heating or cooling direction causes operation of the switch structure.

The arrangement above described provides a sensitive device which reacts rapidly to temperature change. From a cold start the contacts 53 and 26 are separated within a time period of approximately one second. The contacts 53 and 22 are closed in a time period of approximately five seconds from a cold start. On shutdown after a normal running period of the burner, the contacts 53 and 26 are reclosed within approximately twenty seconds from shutdown, this time period being comparable with a time period of approximately ninety seconds required for closing of the closed cold contacts of conventional combustion responsive switches. Upon the occurrence of flame failure shutdown during a running period, the contacts 53 and 22 are opened in approximately two seconds.

This sensitivity of the apparatus may be credited to the direct exposure of the bimetal member 37 to heat radiation frorn the burner or refractory surfaces, and also to the means for mounting the bimetal member 37. The inclined faces 33a and 36 of the depressions seating the ends of the bimetal member have a preferred inclination of approximately twenty degrees from the horizontal as viewed in FIG. 3. This leaves the ends of the bimetal member free to move as the bimetal element flexes in response to temperature change and provides, in effect, a free hinge support for the bimetal member as it moves in response to temperature changes.

Material such as epoxy resin may be applied to the area of juncture of the plate 29 and the housing to reduce the possibility for the entry of soot or dust into the housing. It will be understood, however, that the interior of the housing is not hermetically sealed and the thrust member 39 extends freeley through the aperture 33 in the plate 29.

While the invention has been disclosed and described in some detail in the drawings and foregoing description, they are to be considered as illustrative and not restrictive in character, as modications may readily suggest themselves to persons skilled in this art and within the broad scope of the invention, reference being had to the appended claims.

The invention claimed is:

l. A llame detector switching device adapted to be mounted within the blast tube of an oil burner to receive radiant heat from the burner flame, said device comprising a tubular housing having a closed end and an open end facing the burner flame, switching means mounted within said housing, two annular members coaxially mounted within said housing adjacent the open end thereof, a centrally apertured end cover extending across the open end. of said housing and disposed inwardly of said annular members, the adjacent inner marginal edges f said annular members having diametrically opposed notches therein dening depressions having inclined side faces, a temperature responsive bimetal element extending diametrically across said housing and having its ends seated in said depressions, a thrust member extending from the inner face of said bimetal element and through the central aperture in said cover plate for operating said switching means, the inclined side faces of said depressions forming in effect a free hinge support for said bimetal element as it moves in response to changes in radiant heat from the burner.

2. A flame detector switching device as claimed in claim l in which the included angle between the inclined side faces of said depressions is approximately 40.

3. A flame detector switching device adapted to be mounted within the blast tube of an oil burner to receive radiant heat from the burner llame, said `device comprising a tubular housing having a closed end and an open end facing the burner flame, spaced opposed stationary switch contacts supported within said housing, a temperature responsive bimetal element extending diametrically across the open end of said housing, a thrust member extending into said housing from the inner face of said bimetal element and adapted to be moved linearly as said element responds to temperature change, a clutch arm slidably mounted on said thrust member, a leaf spring acting between said thrust member and said arm to resist movement of said arm along said member, and a contact element carried by said arm extending between said stationary contacts and engaging one or the other thereof depending upon the direction of motion of said thrust member.

4. A ilame detector switching device adapted to be mounted within the blast tube of an oil burner to receive radiant heat from theburner llame, said device comprising a tubular housing having a closed end and an open end facing the burner flame, spaced stationary switch contacts supported within said housing, a temperature responsive bimetal element extending diametrically across the open end of said housing, a thrust member extending into said housing from the inner face of said bimetal element and adapted to be moved linearly as said element responds to temperature change, a clutch arm slidably mounted on said thrust member, resilient means acting between said thrust member and said arm to resist movement of said arm along said member, and a contact element carried by said arm and adapted to engage one or the other of said stationary contacts depending upon the direction of motion of said thrust member.

5. A radiant heat detecting switching device adapted to receive radiant heat from a source thereof, said device comprising a tubular housing having a closed end and an open end facing the radiant heat source, spaced stationary switch contacts supported within said housing, a temperature responsive bimetal element extending diametrically across the open end of said housing, a thrust member extending into said housing from the inner face of said bimetal element and adapted to be moved linearly as said element responds to temperature change, a clutch arm slidably mounted on said thrust member, resilient means acting between said thrust member and said arm to resist movement of said arm along said member, and a contact element carried by said arm and adapted to engage one or the other of said stationary contacts depending upon the direction of motion of said thrust member.

6. In a flame detector switching device for receiving radiant heat from a llame, the combination of a tubular housing having a closed end and an open end facing the burner flame, spaced opposed stationary abutments supported within said housing, one of said abutments being a switch contact, a temperature responsive bimetallic element extending diametrically across the open end of said housing, a thrust member extending into said housing from the inner face of said bimetallic element and adapted to be moved linearly as said element responds to temperature change, a clutch arm slidably mounted on said thrust member, a leaf spring acting between said thrust member and said arm to resist movement of said arm along said member, and a contact element carried by said arm extending between said stationary abutments ber, and a leaf spring acting between said thrust member 1() and said arm to resist movement of said arm along said member, said clutch device connecting said bimetallic strip to said contact element to bring said contact element into engagement with one or the other of said abutments `depending upon the direction of motion of said bimetallic strip.

References Cited in the le of this patent UNITED STATES PATENTS 2,207,601 Shakespeare et al July 9, 1940 2,220,978 Shakespeare et al. Nov. 12, 1940 2,503,259 Hall Apr. 11, 1950 2,679,566 Clark May 25, 1954 2,714,644 Harrison Aug. 2, 1955 2,732,461 Huber Jan. 24, 1956 2,825,786 Deubel Mar. 4, '1958 2,882,371 Bishofberger Apr. 14, 1959

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