US3191660A - Safety flame detector - Google Patents

Description

June 29, 1965 H. A. MUDD SAFETY FLAME DETECTOR 3 Sheets-Sheet 1 Filed March 7, 1963 mw-szvron HARRY A. MUDD.

ATTORNEYS June 29, 1965 H. A. MUDD 3,191,660

SAFETY FLAME DETECTOR 3 Sheets-Sheet 2 Filed March '7, 1963 INVHVTOR. HARRY A. MUDD ATTORNEYS June 29, 1965 M D 3,191,660

SAFETY FLAME DETECTOR Filed March 7, 1963 1 3 Sheets-Sheet 3 INVENTOR.

a HARRY A. MUDD BY yuinfiw/wf ayu ATTORNEYS United States Patent M of Delaware Filed Mar. 7, 1963, Ser. No. 263,597 4 Claims. (CL 158-122) This invention relates to an improved safety flame detector for use with a fuel burner, as described in my prior application, Serial No. 149,943, filed November .3, 1961, for Safety Flame Detect-or, of which this application is a continuation-in-part. The detector is of simplified design inherently providing a sturdy element with'built-in resistanceto the effects of high combustion temperatures and thermal and mechanical shock. Mor specifically, the invention resides in a safety flame detector element preferably constructed from a strip of sheet metal stock. The construction is such that but one end of the element need be exposed to high temperatures and is such that the degree of response to these high temperatures increases with increased length from one end to the other of the strip. This permits the operation of responsive controls at its opposite end from that exposed to high temperatures Within a relatively cool zone, away from the flame, to enhance the reliability of the device by dispensing with the necessity of expensive, sensitive, responsive controls which are also designed to resist the effects of high temperature. The safety flame detector element of this invention may also be referred to as a flame switch and is intended for use in a system such as shown in my co-pending application, Serial No. 56,284, filed September 15, 1960, for Direct Ignition for Fuel Burners. This flame switch is useful for the same applications described in the aforesaid patent application, and, in fact, may be applied to burner ignitors and burners useful for the various purposes mentioned therein.

It is one of the objects of this invention to provide a fuel burner having a flame sensitive control for an ignitor.

It is another of the objects of this invention to provide a safety flame detector for use in combination with a burner and an ignitor for the burner. i

It is still another object of this invention-to provide a safety flame detector element which is formed of a strip of sheet metal stock.

It is still another object of this invention to provide a safety flame detector element of a Single strip of sheet metal stock in which changes in the length of the element are permissible.

It is still another object of this invention to provide a safety flame detector element of a single strip of sheet metal stock in which changes in length affect the degree of mechanical response.

Other objects of this invention will appear from the following detailed description which is in such clear, concise and exact terms as will enable any one skilled in the art to make and use the same when taken in conjunction with the accompanying drawings, forming a part thereof and, in which:

FIG. 1 is a perspective view of an assembly including a fuel burner, an ignitor and a safety flame detector organization according to this invention;

FIG. 2 is a similar view of FIG. 1 showing the same organization with a different type of ignitor;

FIG. 3 is a similar view of FIG. 1 showing the same assembly using a still different type of ignitor; and

FIG. 4 is a perspective view of an assembly including a fuel burner, an ignitor, and a safety flame switch of different form showing the preferred location of these 3,191,660 Patented June 29, 1965 parts of the assembly for this different form of switch.

In the drawings, the same parts are indicated by the same reference characters. In each of the views of the drawings, the assemblies illustrated include fuel burners, all of which are indicated by the reference character B, all include an ignition, illustrated generally by the reference character C, and all include a safety flame detector or flame switch, indicated by the reference character A. Since in each instance, the burners indicated as B are identical in construction and the safety flame detector, 01' flame switch, A is identical in construction, it would serve no useful purpose to describe these elements in detail in each of the views of the drawings. Accordingly, the detailed description of these elements, A and B, will appear immediately hereafter in the detailed description of FIG. 1. It will be understood that the descriptions relative to FIGS. 2 and 3 need not repeat the detailed description since the description with respect to FIG. 1 will serve for all.

Turning now to FIG. 1, the fuel burner B has a burner section 1 with a plurality of gas jets in its upper surface, indicated as 2. Extending from the burner B is a mixing tube 4 which in turn connects with a mixing chamber 5 provided with a mixing valve 6. A fuel supply tube 8 connects with the mixing chamber 5 at one end and at its opposite end is provided with some form of coupling means to connect with a gas manifold from which the gas is supplied through the tube 8, mixing chamber 5, mixing tube 4 to the jets 2 in the burner B. Since this is a familiar construction, a further detailed description is deemed unnecessary.

Adjacent the mixing chamber 5 and integrally formed thereon is a boss, or the like, 10 which has an upper flat surface formed to receive a bracket 11. Screws 13 secure the bracket 11 to the boss 10. The upstanding leg of the bracket 11 is apertured to receive a screw 14 which is in turn threaded into the base of induction coil 16. Within the induction coil 16 is a core piece 18 and this core piece projects from the opposite end of the coil 16 from thebracket supported end. An insulating block of flexible material 20 is firmly aflixed to the projecting end of the core piece 18, and this'insulating block of flexible material in turn carries a pair of fingers 22 and 24 which project from opposite sides of the block 20. The inner projecting ends of the fingers 22 and 24 form armatures 26 and 28 located on opposite sides of the core piece 18. The outer projecting portions of the fingers 22 and 24 carry contacts 30 and 32 normally held in engagement by the flexible material of the insulating block 20. Thus, the block 20 performs the function of a pivotal support, or fulcrum, for the fingers 22 and 24, so that the ends 26 and 28 thereof acting as the armatures may be attracted inwardly by the core 18 to separate the contact points 30 and 32 whenever the coil 16 is energized. When the coil is de-energized by the separation of the points 30 and 32, the points will return into contact. The

make and break action of the points 30 and 32 creates the sparks for ignition of the fuel issuing from the jets 2 of the burner B so as to ignite the fuel as it issues from the jets 2 and light the burner B.

In order to determine whether. the ignitor operation is necessary, there is a flamedetector A which in turn controls a micro switch 35 connected into an electrical circuit in series with the ignitor contact points 30 and 32. When a flame is detected from the burner B, micro switch 35 is open to disable the ignitor C. On the other hand, if no flame is detected by the flame detector A, switch 35 is closed and the electrically controlled ignitor will then operate whenever its circuit is energized.

Projecting from the mixing tube 4 is an integral boss 36 tapped to receive a pair, of screws 37 and 38 to secure the fixed jaw 40 of the safety flame detector in position with respect to the burner B. The boss 36 forms a stationary means for mounting the safety flame detector A. Located beside the fixed jaw 40 is a movable jaw 42, and the two are interconnected at 43 which leaves the movable jaw 42 free at its inner end to move with respect to the fixed jaw 40. This movement actuates the switch 35 through a structure including a tab 45 integral with movable jaw 42 and mounting an adjusting screw 47 held by a lock nut 48. Aligned with the adjusting screw 47 is the button 49 of the micro switch 35 which is in turn secured in fixed relation to the fixed jaw on an extension piece 50 therefrom.

At the inboard end of the safety flame detector A is a bridge 52 upon which the flame from burning fuel can impinge. Integral extension 54 connects one end of the bridge 52 with the fixed jaw 40. Integral extension 55 connects the other end ofthe bridge 52 with the movable jaw 42 intermediate its length.

Safety flame detector A is preferably constructed from a single strip of sheet metal punched out to form the slot separating the movable jaw 42 from the fixed jaw 40 and to form the bridge 52 connected by legs 54 and 55 with the fixed jaw 40 and movable jaw 42. The same punch- :ing operation can separate the end of the movable jaw 42 from the extension 50 and a subsequent bending operation forms the tab 45. The slot between the two jaws more or less follows the outer, lower contour of the fixed jaw 40 where it angles upwardly at, or from, the point 58. This point is approximately in vertical alignment with the outside edge of the leg 55. The end of the slot between the two jaws terminates approximately in vertical alignment with the inside edge of the leg 54. In the presently prefered embodiment, the strip of metalfrom which the element is formed-is .047 inch stainless steel type 304 non-magnetic. The fixed jaw is approximately inch wide, the slot inch wide and the upper jaw about inch wide.

inches.

Turning now to the electrical circuit, lead 60 extends from a power source to one terminal of micro switch The over-all length is approximately 35, the other terminal of which is connected by a B is opened, leads 63 and 60 are both energized.

In the structure, just described, the heated element is the bridge 52. This bridge is exposed directly to the heat from the burning fuel issuing from the jets 2 of the burner B. At high temperature, bridge 52 will expand and, of course, at low temperature it will contract. When contracted, movable jaw 42 raises upwardly with respect to the fixed jaw-40 and closes the micro switch 35, so that when the leads 60 and 63 are energizeed, coil 16 is excited causing the core 18 to attract the armatures 26 and 27 opening the points 30 and 32 to cause sparking. When the burner B lights, bridge portion 52 will expand thereby tending to separate leg 55 from leg 54 which are connected with the movable and fixed jaws respectfully. This action causes movable jaw 42 to approach fixed jaw 40 and therby open the micro switch 35 de-energizing the circuit through the lead 61, contacts 30, 32, lead 62, coil 16 and lead 63. Thus, the ignitor operates only when the flame detector A indicates that the burner B is not in operation. The detector A may be formed from a strip of metal of any length desired, but preferably it is long enough so that the micro switch 35 is located in a relatively cool zone of operation. This dispenses with the use of an expensive construction for the micro switch which will resist high temperatures. The movable jaw 42 acts as a mechanical multiplication system to magnify the minute changes in length of the bridge 52. Consequently, the longer the jaws of the element, the greater the movement of the inner end of the movable jaw 42 in response to changes in length in the bridge 52. This multiplication dispenses with a highly accurate micro switch 35 and one which is operated by three to five hundredths ofran inchmovement will be entirely satisfactory. Such switches are available commercially and are relatively inexpensive. It should be noted that the flame detector A does not depend for operation upon changes in temperature in the jaws, and further that changes in temperature in the jaws have no effect whatsoever on the operation. The longer the jaws, of course, the greater the multiplication, but at the same time changes in temperature or changes in temperature gradient along the jaws will have no effect upon its operation. Only the bridge portion 52 needs to be located near the flame in order for the device to operate satisfactorily, and this itself need not be located in the flame in order to produce the very minute amount of expansion necessary to operate the micro switch. This is because of the multiplying effect due to the length of the element in the flame detector A. Even the small flame from a pilot light is sufficient to provide the heating necessary to operate such a device, and even in such a case impingement of the flame is not absolutely necessary.

The flame detector A may be used with other types of ignitors, for example, the igniter C shown in FIG. 2. In this view, the burner B and the flame detector A are exactly the same as shown in FIG. 1, and the same parts thereof are indicated by the same reference characters. Parts in the ignitor C, shown in FIG. 2, which correspond generaly with those shown in the ignitor shown in FIG. 1, are indicated by the same reference characters with added. This description will be limited to the differences between this modification and that above described. In FIG. 2, the bracket 111 is attached to the transformer 116 by a screw 114 extending through the bracket 111 into the base of the transformer 116. Connected with the primary in the transformer 116 are a pair of leads 163 and 161. Lead 163 may extend from a source of current by way of a solenoid operated gas inlet valve so that when the valve is energized to open the gas line to the burner B, lead 163 is connected with a source of electric current. Likewise, lead 161 is connected to a source of current by way of a micro switch 35 so that when the micro switch 35 is closed, transformer 116 is energized. The secondary from the transformer 116 connects with fingers 122 and 124 which in turn connect at and 132 with the opposite ends off a glow coil 131 positioned over the gas jets 2 of the burner B.

The operation of the construction, shown in FIG. 2, is identical with the operation of the structure shown in FIG. 1 except that when the micro switch 35 closes, transformer 116 is energized thereby transmitting a low potential to a glow coil 131 heating up the glow coil to the ignition point for the fuel issuing from the jets 2. When the jets ignite as in FIG. 1,.the flame detector responds due to heating of the bridge 52 opening the switch 35.

In the modification shown in FIG. 3, the ignitor C takes the form of a pilot light, or flame, arranged to be directed at the bridge 52 of the flame detector A. These In this modification, similar elements of the ignitor C which perform a similar function to those heretofore described will be indicated by the same reference character with 200 added.

In this modification, lead 260 extends from a source,

of electrical power to the micro switch 35. Leads 261 and 262 connect the coil 216 of the solenoid pilot valve 220 in series with the micro switch 35. The valve 220 in turn has an armature 226 carrying a valve which seats on the inlet to the valve 228. Extending from the outlet of the solenoid valve 220 is a pipe 222 to which is attached a jet 230 for the pilot light.

The operation of this modification is similar to those heretofore described except that the switch 35 remains closed so long as either the burner or the pilot light is in operation. When both are extinguished, switch 35 is opened de-energizing the circuit so that neither valve 270 nor 220 can open. In order to restart the system when this happens, it is necessary to press downwardly on the tap 45 allowing switch 35 to close. This completes the circuit from 260 to 262 to open the valve 220 permitting pilot 230 to be relighted. The heat from the pilot will hold the switch open thereafter.

In the modification shown in FIG. 4, the burner B and ignitor C are identical with those heretofore described in FIG. 1 and are arranged relative to one another and mounted in exactly the same way. The flame detector A, however, takes on a modified form and a different mounting from that shown in FIG. 1 and will be described in detail. With this exception, the modification shown in FIG. 4 is the same as that heretofore described in detail referring to FIG. 1, and a repetition of this description is not necessary to an understanding of the modification in FIG. 4, since the only difference between the two, FIGS. 1 and 4, is the specific construction of the flame detector A. For this reason, similar elements in the burner B and ignitor C will be given the same reference characters as used in FIG. 1 with 300 added. Corresponding parts of the flame detector A and the flame detector A will be given the same reference characters also with 300 added. Since the structures in FIGS. 1 and 4 are similar, this description will be confined to the differences.

Referring now to FIG. 4, the mixture tube 304 is formed with a boss 310 having a pair of'tapped screw holes in its upper surface. One leg of a U-shaped bracket 311 is secured on the boss 310 by the screws 313 threaded into the tapped holes in the boss 310. The vertical leg of the U-shaped bracket 311 is apertured to receive the screw 314 which in turn secures the ignitor C in position, all in the same manner as described in FIG. 1. The opposite leg of the U-shaped bracket 11 is also provided with a pair of tapped holes to receive the screws 337 and 338 which secure the fixed jaw 340 of the flame detector A in position on the burner B. The safety flame detector A is preferably constructed from a single strip of sheet metal punched out to form a slot separating the movable jaw 342 from the fixed jaw 349. The strip of sheet metal is also punched out to form the bridge 352 connected by the legs 354 and 355 with the movable jaw 342 and the fixed jaw 340, respectfully, the same punching operation is such as to separate the end of the movable jaw 342 from the end of the fixed jaw 340 and at the same time form the extension 350 on the fixed jaw 340. This slotting operation can be combined with a metal forming step in which the tap 345 is bent at right angles to the movable jaw 342. The slot between the tWo jaws more or less follows the outer contour of the movable jaw 342 Where it angleslaterally at the point 358. This point 358 is approximately in alignment lengthwise of the flame detector A with the inside edge of the leg 354. The end of the slot between the two jaws terminates approximately in alignment longitudinally of the flame detector A with the inside edge of the leg 355.

At the inboard end of the safety flame detector A is a bridge 352 upon which the flame from the burning fuel of the burner B can impinge. From the bridge 352 are two integral extensions 354 and 355 referred to here as legs. Integral leg 355 connects one end of the bridge 352 with the movable jaw at its inboard end. Extension, or leg, 355 connects the end of the bridge 352 opposite the 6 leg 354 with the fixed jaw 340 intermediate its length. The mounting of the flame detector A is such that the bridge 352 extends over the burner B and is disposed in approximately a horizontal plane.

At the outboard end of the flame detector A, movable jaw 342 is formed with the right angularly extending tab 345. The tab 345 in turn has a threaded aperture for receiving and adjusting screw 347 which may be secured in place by a lock nut, or the like, 348. The free end of the adjusting screw 347 is thus disposed to actuate the button 349 of the micro switch 335 mounted on the extension 350 of the fixed jaw 340. The micro switch 335 is the type which is opened by contact with the end of the adjusting screw 347 moving the button 349 inwardly of the switch housing and is closed when the movable jaw 342 moves the adjusting screw 347 out of contact with the button 349. The micro switch 335 is connected in a circuit including the lead 360 from a power source to the micro switch, a lead 361 from the micro switch to a contact arm 322, a lead 362 from the other contact arm 324 to the coil 316 and a lead from the coil 316, indicated as 363, to a suitable power source.

The operation of the modification shown in FIG. 4 is exactly the same as that heretofore described with respect to FIG. 1. The sole difference between these two modifications is in the mounting of the flame detector A and in the specific construction thereof. In the prior modification in FIG. 1, the leg or extension 55 connects intermediate the length of the movable jaw 42 and the extension, :or leg, 54 connects with the end of the fixed jaw 40. The modification in FIG. 4 shows the reverse arrangement of this connection. As has been before pointed out, the particular flame detector, shown herein, has many advantages, one of which being that its length over-all can be varied widely. It can be as long as eight or ten inches, or, on the other hand, as short as half that length and still operate satisfactorily. Tests have shown that the temperature at the bridge portion 352 at the extreme end ofthe flame detector can be as high as 1225 to 1275, and yet the temperature at the inboard end adjacent the micro switch will be no more than even under adverse conditions. In other words, there is an extreme temperature drop in the flame detector A, or A, at points removed outwardly of the bridge 52, or 352. For example, at the ends of the legs 54 and 55, or 354 and 355, the temperature is only 500, or much less than half the temperature of the bridge.

Changes in and modifications of the construction described may be made without departing from the spirit of my invention or sacrificing its advantages.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. A safety flame detector responsive to flame temperature to operate a switch in an electric control for a fuel burner, the improvement in said safety flame detector comprising, a single plate-like element formed from a strip of sheet material and adapted to be mounted along side a fuel burner, said element having a heat sensitive end and elongated fixed and movable jaws separated by a slot extending from one end of said plate-like element to said heat sensitive end and interconnected at said heat sensitive end and open at said one end, said jaws extending to a location away from a zone heated by burning fuel, a bridge on said element at said heat sensitive end formed in said plate-like strip and having legs at spaced points on the adjacent ends of said fixed and movable jaws, one leg being connected at said interconnected end and a second leg spaced therefrom and connected to said movable jaw, stationary means for mounting said fixed jaw to position said bridge to be exposed to a flame whereby changes in size of said bridge due to increase in temperature of said bridge moves said movable jaw toward said fixed jaw to actuate a switch.

2. A flame detector for use with a fuel burner comprising a single plate-like element formed from a single strip of sheet metal having a heat sensitive end and adapted to be mounted beside the fuel burner with said heat sensitive end projecting toward the flame, elongated jaws'separated by a slot extending from one end of said strip of sheet metal to said heat sensitive end, said slot being open at said one end, and said jaws being interconnected at said heat sensitive end, a bridge formed in said strip of sheet metal at said heat sensitive end and having opposite ends connected by legs in said strip of sheet metal, one of said legs being connected adjacent the interconnection between said jaws, and a second leg spaced from the first-mentioned leg and connected to one of said jaws substantially a bridge length distant from said interconnection, so that changes in temperature of said bridge changing its dimensions act on said jaws to produce a degree of strain on said jaws at their interconnected ends and said jaws act to multiply this degree of strain into significant mechanical movement between the jaws at their opposite ends to close said jaws with increase in temperature of said bridge.

3. The device of claim 2 wherein one of said elongated jaws is fixed and theother movable, and said second leg is connected to said movable jaw.

4. The device of claim 2 wherein one of said elongated jaws is fixed and the other movable, and said second leg is connected to said fixed jaw.

References Cited by the Examiner UNITED STATES PATENTS 651,067 6/00 Cram 158-28 2,000,294 5/35 Newell 15s 140 2,192,632 3/40 Beam 158-28 2,308,272 1/43 English 73363.3 2,333,102 11/43 Higley 158-14O 2,635,003 4/53 Perl 158125 FOREIGN PATENTS 878,359 9/61 Great Britain.

JAMES W. WESTHAVER, Primary Examiner.

20 MEYER PERLIN, Examiner.

Claims (1)

1. A SAFETY FLAME DETECTOR RESPONSIVE TO FLAME TEMPERATURE TO OPERATE A SWITCH IN AN ELECTRIC CONTROL FOR A FUEL BURNER, THE IMPROVEMENT IN SAID SAFETY FLAME DETECTOR COMPRISING, A SINGLE PLATE-LIKE ELEMENT FORMED FROM A STRIP OF SHEET MATERIAL AND ADAPTED TO BE MOUNTED ALONG SIDE A FUEL BURNER, SAID ELEMENT HAVING A HEAT SENSITIVE END AND ELONGATED FIXED AND MOVABLE JAWS SEPARATED BY A SLOT EXTENDING FROM ONE END OF SAID PLATE-LIKE ELEMENT TO SAID HEAT SENSITIVE END AND INTERCONNECTED AT SAID HEAT SENSITIVE END AND OPEN AT SAID ONE END, SAID JAWS EXTENDING TO A LOCATION AWAY FROM A ZONE HEATED BY BURNING FUEL, A BRIDGE ON SAID ELEMENT AT SAID HEAT SENSITIVE END FORMED IN SAID PLATE-LIKE STRIP AND HAVING LEGS AT SPACED POINTS ON THE ADJACENT ENDS OF SAID FIXED AND MOVABLE JAWS, ONE LEG BEING CONNECTED AT SAID INTERCONNECTED END AND A SECOND LEG SPACED THEREFROM AND CONNECTED TO SAID MOVABLE JAW, STATIONARY MEANS FOR MOUNTING SAID FIXED JAW TO POSITION SAID BRIDGE TO BE EXPOSED TO A FLAME WHEREBY CHANGES IN SIDE OF SAID BRIDGE DUE TO INCREASE IN TEMPERATURE OF SAID BRIDGE MOVES SAID MOVABLE JAW TOWARD SAID FIXED JAW TO ACTUATE A SWITCH.

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