US3291186A - Control device - Google Patents

Description

ec. 13, 1966 B. A. LINDBERG CONTROL DEVICE 2 Sheets-Sheet 2 Filed Dec 31, 1964 2 4 PRESSURE lncheswoter INVENTOR. 5126222 A ZINDBEKG A'TJTOF/VEY United States Patent Delaware Filed Dec. 31, 1964, Ser. No. 422,736

2 Claims. (Cl. 158-113) This invention relates to safety pilots and, more particularly, to pilot generator asernblies of the type wherein a pilot burner for a main burner heats a thermoelectric generator which, in turn, controls a safety valve or other control valve for supplying gas to the main burner and also to the pilot burner, if desired. More particularly, this invention relates to these assemblies wherein a burner of the non-aerated target type is used in combination with a thermoelectric unit.

Safety pilot assemblies of the above-mentioned type are well known in the heating controls art. Many varieties have been placed on the market in an effort to provide a device of simple structure and long life which will give a steady electrical output independent of varying operation conditions, such as varying gas supply pressure.

One of the chief sources of trouble in the earlier devices has been the mortality rate of the thermoelectric units which have been prematurely burned out due to the excessively high temperatures to which they can be exposed. These high temperatures are caused by operating conditions which vary from the expected norm.

Thus, it is an object of this invention to provide a safety pilot wherein the flame sensing unit is uniformly heated at various fuel pressures.

It is another object of this invention to provide a pilot generator assembly in which a uniform output is obtained over a wide range of fuel pressures, but which has the additional advantage of being very simple structurally.

A further object of this invention is to provide a pilot burner-generator assembly in which the generator is protected from overheating, thus increasing its useful life.

It is a further object of this invention to provide a pilot generator assembly which takes advantage of the short drop out time provided by use of very thin thermoelectric units.

It is yet another object of this invention to provide an assembly of the aforementioned type in which the thermoelectric unit is heated to an ideal temperature at normal fuel pressures.

It is still another object of this invention to provide a pilot burner-generator assembly which will operate satisfactorily not only in the normally vertical position thereof but in a tilted position, operation thereof being satisfactory in either a tilted forward position of 45 or in a tilted position of 90 to the side.

It is yet another object to provide a thermoelectric unit having a novel configuration for use in pilot generator assemblies.

FIGURE 1 is a vertical sectional view of a pilot burner with the thermoelectric unit shown in combination there- With;

FIGURE 2 is a plan view of the pilot generator assemblv;

FIGURE 3, on sheet 2 of the drawings, is an elevational view of the construction of a preferred thermoelectric unit partly in cross section with a center portion thereof broken away;

FIGURE 4a is a cross sectional view taken along line 4a4a of FIGURE 3;

FIGURE 4b is a fragmentary view of a modification of the thermoelectric unit of FIGURE 4a having two banks of thermocouples.

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Patented Dec. 13, 1866 FIGURE .5 is a side view of another thermoelectric generator for use in combination with the pilot burner.

FIGURES 6a and 6b, on sheet 1 of the drawings, are schematic representations of a pilot generator assembly in the ignited condition, operating at normal fuel pressures and showing the flame pattern;

FIGURES 7a and 7b are similar schematic representa tions of a pilot generator assembly in the ignited condition, operating at higher than normal pressure; and

FIGURE 8, on sheet 2 of the drawings, is a curve showing the electrical output versus fuel pressure of a preferred embodiment of the invention.

Referring to FIGURES l and 2, the pilot generator assembly consists of a bracket member 12 holding a thin rectangular thermoelectric unit 14 with its relatively wide flat surface exposed to a pilot burner 16. Bracket 12 is formed of a heavy gauge metal to which is welded a mounting plate 18. A guide 26*, for receiving and positioning thermoelectric unit 14 parallel to the vertical axis of pilot burner 16, is also formed on bracket 12. Guide 20 is particularly designed to position thermoelectric unit 14 with its flat surface exposed to pilot burner 16. Spring clip 22 attached to guide 20 serves to hold the thermoelectric unit in position.

The pilot burner 16, for heating thermoelectric unit 14 is of the non-aerated type and, generally consists of a burner body 26 which is formed out of bracket 12, a target member 28 and a spud assembly 30. Spud assembly 30 has a series of Stepped diameter portions terminating in a small diameter cylinder 32 and an orifice 34. The orifice cup and cylinder 32 serves to control and direct the flow of fuel to target member 28 against which the fuel impinges and mixes with air for combustion purposes. On the under side of plate 34 there are three radial indentations which improve the mixing of fuel flowing through the orifice plate.

Target 28 has an upwardly inclined plate 36 arranged so that a jet of fuel issuing through orifice cup 34 will impinge on the under surface thereof and be deflected at an angle toward thermoelectric unit 14. The preferred angle has been found to be approximately 30 with respect to the top surface of the bracket 12. Target 28 also has a pair of downwardly extending and outwardly inclined side walls 37 and 38 which serve to provide a flame, when the fuel is ignited, having a spreading sheetlike form. The single flame that issues from target 28 and which is directed upwardly thereby is for the purpose of heating thermoelectric unit 14 and igniting a main burner (not shown).

Thermoelectric unit 14 generally consists of a plurality of series connected thermocouples 40, as shown in FIGURE 3. The thermocouples are placed inside a housing which consists of a rectangular steel sheath 42 enclosing the upper hot junctions of the thermocouples. The lower portion of sheath 42 is contained in a two piece receptacle 44 which is formed by plate 46 and plate 48. Plate 48 has bent edges forming flanges 50 and has ears 52 bent over and engaging plate 46. Plate 48 also has a second :pair of ears 54 which are bent over to engage metal wrapped leads 56 which are connected to the end elements of the thermoelectric unit. One of the ears may also serve as an abutment with which spring clip 22 may cooperate to hold the thermoelectric unit in guide 20 as shown in FIGURE 1. It is preferred that spring clip 22 be formed of a single rectangular sheet of metal having one end lanced and bent to form the hook portion thereof since the sharp edge provided thereby serves better in holding the thermoelectric unit in the guide. The upper or hot junctions of thermoelectric unit '14 are electrically insulated from the upper edge of steel sheath 42 by an insulating rod 63 which may be of ceramic or the like. The space between the remainder of the thermocouples and the sheath along the sides and at the bottom is filled with a cement. The exterior configuration of the thermoelectric unit 14 is critical to the invention as it is necessary that it be thin and have a relatively wide (flat surface to be presented to the pilot burner flame. This configuration is provided by steel sheath 42.

FIGURE 4b shows a modification of the thermoelectric unit described in connection with FIGURES 3 and 4a. In this modification, one side of steel sheath 42 is deep enough to accommodate two banks of thermocouples 40 While the edges of sheath 42 are in the same rela tive position as before in order to be engaged and held by guide means 20.

FIGURE 5 is a side view of a thermoelectric unit having the preferred thin, flat configuration. It should be noted that in this embodiment clip 22 is in a slightly different form and is mounted on the thermoelectric unit. In this arrangement clip 22 engages :giuide 20 when the thermoelectric unit is inserted into it.

Operation Mounting the pilot burner with respect to the thermoelectric unit as shown schematically in FIGURES 6a and 611 so that the flat generator surface is parallel to the vertical axis of the pilot burner and the target member is inclined at an angle of approximately 60 with respect to the flat generator surface provides a desirable flame 62, which at normal iuel pressures has its hottest portion 64 (shaded area) in close proximity to the thermoelectric unit 14 thus activating the unit to provide electrical energy for control purposes.

When the flame strikes the flat surface of thermocouple unit 14, a back pressure is produced which softens the flame. At higher than normal fuel pressures the flame has previously had a tendency to rise from the front surface or the thermoelectric unit causing undesirable noise. However, with the configuration as shown here, the flame rolls over the edges of the target because of back pressures which are produced at the flat surface of the thermoelectric unit. A flame formed at higher fuel pressures is shown in FIGURES 7a and 7b Where it can be seen that the hottest portion 64 (shaded area) of flame 62 envelopes the thermoelectric unit 14 but is further away and hence, does not fneat it to higher temperatures.

The operation of a pilot burner-generator assembly in accordance with this invention may be even more clear ly shown by referring to FIGURE 8, on sheet 2 of the drawin which is a plot of electrical output of the thermoelectric unit 14 against the pressure of the fuel supplied to pilot burner 16. This graph shows that at normal fuel pressures of from 2 to 5 inches water column, the output of the thermoelectric unit is highest, approximately 475500 milliv-ol-ts. When the fuel pressure is increased above the normal range, the output assumes a slightly lower but very stable value of approxi mately 475 millivolts.

From the above description of the structure and operation of the pilot burneragenerator assembly, it is apparent that due to the shape of the thermoelectric unit 4 and the shape of and angle at which the flame provided by the target member strikes the thermoelectric unit, a safe, highly uniform temperature is provided :for activating the thermoelectric unit despite variations in fuel pressure. Further, this arrangement has been found to operate satisfactorily in various positions. For example, the device will function when tilted to the side as far as and when tilted to the front as far as 45.

While the preferred modification of the invention has been described in detail above, it is deemed to be obvious that various changes may be made in the preferred modification without departing from the spirit of the invention. Therefore, the scope of the invention should be determined solely from the appended claims.

What is claimed is:

1. In a safety pilot assembly of a non-aerated type, the combination comprising:

target means including an inclined plate upon which fuel is adapted to impinge to form a single spreading sheet of flame;

a thermoelectric unit including:

a plurality of thermocouples with the hot junctions thereof disposed at one end and the cold junctions thereof disposed at the other end;

a sheath having a substantially flat, thin, closed end portion enclosing said hot junctions, and

an insulator rod positioned lengthwise between said end portion of said sheath and said hot junctions, and

bracket means spacing said thermoelectric unit with said end portion of said sheath laterally and slightly above said target means so that said flame will strike said sheath at an oblique angle to divert the flame in such a manner that said end portion of said sheath is enveloped by the flame and heated substantially uniformly independent of fuel pressure variations.

.2. A substantially flat (generally rectangular thermoelectric generator for use in conjunction with safety pilot burners comprising:

a plurality of electrically connected thermocouples in a side-by-side relationship with the hot junctions thereof disposed at one end and the cold junctions disposed at the other end;

a rectangular metal sheath with a closed end portion enclosing said hot junctions, and

an insulator rod positioned lengthwise between said closed end portion of said sheath and said hot junctions.

References Cited by the Examiner UNITED STATES PATENTS 2,311,785 2/1943 Sparrow 1364.13 2,605,296 7/1952 Bodey 126--4.13 3,078,916 2/ 1963 Loveland 15 81 13 3,120,261 2/1964 Gonzalez 1581 13 3,155,143 11/1964 Jackson et al. 1581 13 FREDERICK L. MATTESON, JR., Primary Examiner.

E. G. FAVORS, Assistant Examiner.

Claims (1)

1. IN A SAFETY PILOT ASSEMBLY OF A NON-AERATED TYPE, THE COMBINATION COMPRISING: TARGET MEANS INCLUDING AN INCLINED PLATE UPON WHICH FUEL IS ADAPTED TO IMPINGE TO FORM A SINGLE SPREADING SHEET OF FLAME; A THERMOELECTRIC UNIT INCLUDING: A PLURALITY OF THERMOCOUPLES WITH THE HOT JUNCTIONS THEREOF DISPOSED AT ONE END AND THE COLD JUNCTIONS THEREOF DISPOSED AT HTE OTHER END; A SHEATH HAVING A SUBSTANTIALLY FLAT, THIN, CLOSED END PORTION ENCLOSING SAID HOT JUNCTIONS, AND AN INSULATOR ROD POSITONED LENGTHWISE BETWEEN SAID END PORTION OF SAID SHEATH AND SAID HOT JUNCTIONS, AND BRACKET MEANS SPACING SAID THERMOELECTRIC UNIT WITH SAID END PORTION OF SAID SHEATH LATERALLY AND SLIGHT-

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