US2288715A - Pilot burner control - Google Patents

Description

l July 7, 1942- s. .KARRER Erm. PIVLoT-4 BURNER coNTRoL Filed uaylo, 195g y, up

mi `l latented July 7, 1942 OFFICE m01 BURNER CONTROL Sebastian Karrer, Washington, D. C., and Channing W. Wilson, Baltimore, Md., assignors to Consolidated Gas Electric Light and Power Company of Baltimore, Baltimore, Md., a corporation of Maryland Application May 10, 1939, Serial N0. 272,898

7 Claims. (Cl. 158-99) This invention relates to means for predetermining the flow of gas through passageways to pilot burners and the like, and more particularly to means for minimizing obstruction of such a passageway by the particles of gum, dust, scale, rust, etc., which are usually present in the gas.

In the construction o'f devices for controlling the flow of gas to pilot burners it has heretofore been the usual practice to employ a needle valve or a stop cock to provide an opening which is adjustable in size or a fixed orifice tubular in nature. Experience has demonstrated that such constructions are susceptible to stoppage, and consequently require frequent cleaning, because the finely divided material, such as gum,'dust, scale, rust, etc., that is suspended in the gas, and carried along with it, deposits and accumulates in the opening provided by the needle valve, stop cock, or tubularorice, with a resultant decrease and even cessation of gas flow to the pilot burner.

. vices which have been stopped up in service has revealed that the deposition of material takes place where vthere is a sudden change in direction of the gas iiow, and that in the usual needle valve, for example. wherein the passage at the valve is in the form of an annulus whose width is relatively -small when compared with its circumferential extent, the shape of passage used tends to accelerate the rapidity with which the material is deposited and accumulated, while in a stop cock which is partially closed, for example, there is a decided narrowing of the passageway because of the ellipsoidal shape of the opening when the stop cock is adjusted for slow gas flow.

, result that needle valves and stop cocks are being used generally notwithstanding the tendency of the passageways thereby provided to become restricted, or even closed, by accumulation of the fine particles usually present in the gas.

We have discovered that the obstruction of the passage for gas flow to the pilot burner by particles of suspended matter carried by the gas can n be minimized and largely avoided by controlling orifice and the thickness of the plate, or to express it otherwise, between the diameter of the orifice and its length.

It is therefore an object of the present invention to provide means for predetermining gas flow to a pilot burner which will largely prevent the deposit of solid particles therein and thereby avoid the need for frequently cleaning the same.

Another object of this invention is to provide a meansfof the type characterized which avoids the annular or ellipsoidal character of passageway heretofore existing when needle valves and stop cocks have been used.v to the end that the area of passage provided for obtaining the desired gas flow may be had without such constriction of any dimension of said area as to tend to facilitate obstruction thereof by an accumulation of particles therein. is made less than a certain maximum value which has been found to be critical.

Another object of this invention is to provide means of the type characterized in association with screening or filtering means which removes particles of a size exceeding a predetermined value.

Other objects will appear as the description of the invention proceeds.

The invention is capable of receiving a variety of mechanical expressions, some of which are illustrated on the drawing, but it is to be expressly understood that the drawing is for purposes of illustration only and is not to be construed as definitions `of the limits of the invention, reference being had to the appended claims for that purpose. i

Referring in detail to the accompanying drawing, wherein the same reference characters indicate corresponding parts in the several figures,

Fig. 1 illustrates an embodiment wherein the present invention is incorporated in a screw;

Figs. 2, 3 and 4 illustrate other constructions in which the present vinvention may be embodied.

In order to minimize orovercome the obstruction of such a gas flow passage as heretofore referred to, wehave discovered that in place of the usual needle valve, stop cock, tubular orifice or the like,

the gas flow should be controlled by a small, substantially circular orifice made in a sheet of thin metal vand having `the length of the orifice (i. e.,

the gas flow by means of an orifice in a plate,y

provided the ratio between the diameter lof the the dimension in the direction of the thickness of the plate)` such that the ratio of length to diameter does not exceed 0.2. In measuring the length of the orifice any roughness or burr surrounding the orifice must be taken into consideration, and therefore it isimportant that the orifice be cleanv ly made with right angle corners at the faces of the plate, and without any raggedness or irregularities which have the effect substantially of changing the predetermined size of the orifice, or which will tend to catch and retain fine particles suspended in the gas. Moreover, as corrosion of the plate tends to produce a roughness around the orifice, and may therefore increase its effective length or decrease its diameter as just pointed out, the plate is preferably made of a metal such as aluminum or stainless steel which is noncorrodible by the gas. By employing a circular orifice a uniform transverse dimension is obtained, as well as the largest linear dimension for a given area of opening. The diameter and consequent area of said opening will of course vary in different installations in accordance with the rate of gas fiow desired for the particular installation, but the ratio of the length to the diameter of the orifice has been found to be critical and should not exceed the aforesaid figure of 0.2. When such ratio is maintained the tendency of solid particles suspended in the gas to impinge on and attach themselves tothe wall of the orifice is minimized and largely eliminated, whereby experience has demonstrated that such a gas control orifice may be used for a relatively long period of time, if not indefinitely, without becoming materially restricted by deposition of particles therein. The explanation of this phenomenon appears to be that the direction of the streamlines of gas flow changes when entering the orifice, so that there is imparted to the suspended particles traveling with the gas along said streamlines a tendency to be displaced therefrom by centrifugal force in a tangential direction toward the orifice wall, and if the aforesaid ratio is maintained the curvature of the path does not give rise to a centrifugal force sufficient to displace the particles from the streamlines while they are passing through by a distance great enough to cause impingement on the orifice wall, but while that is now believed to be the explanation of the results obtained we do not wish to be bound thereby if any other phenomenon not now ap' preciated may hereafter be found to explain the results obtained in full or in part.

Referring now to the drawing, the embodiment shown in Fig. 1 illustrates a construction that is of particular utility in controlling the fiow of gas to certain pilot burners which are in use on many gas ranges, and comprises a screw I threaded at II for entry into a suitable opening,

and having an unthreaded portion I2 of smaller volume of gas to pass therethrough in a unit of time, dependent upon the requirements of the installation. Plate I1 is of such thickness that the ratio of the length of the orifice I8 to its diameter as above explained does not exceed l0.2. The structure illustrated in Fig. 1 also provides a valve for closing off the gas flow, and to this end the enlarged outer end of the screw I0 is interiorly.

threaded at I8 to receive a screw 20 whose inner end 2| is formed to seat on a shoulder surrounding the passage I5 and act as a. valve to prevent communication between the aperture or apertures I4 and said passage I5.

In Fig. 2 the invention is embodied in a tapered bushing 21 which may be readily driven into the end of a standard pilot tube, said bushing having an inwardly directed shoulder at 22 against which the thin apertured disk I1 is retained in any suitable way, as by a sleeve 23 forced into or otherwise suitably secured in the bore of the bushing 21 to hold the disk I1 flxedly in position. Sleeve 23 may obviously 4extend the full length of the bushing 21, but the present embodiment as shown employs intermediate its length a finemesh gauze or screen 24 to prevent particles of a size that would stop up the orifice I8 from reaching the chamber on the inlet side of said orifice. To this end the meshes of the screen are preferably so fine that their diagonal dimension is smaller than the diameter of the orifice I8. Screen 24 is retained in position by forming the sleeve 23 in two sections and clamping the screen therebetween, the outer section 25 being held in the bore of bushing 21 in any suitable way. As shown the end of the bushing is rolled or forced over the end of sleeve section 25, as shown at 28, to lock the sleeve sections, screen and apertured disk in the bore of the bushing.

In Fig. 3 the embodiment illustrated includes a sleeve 21 provided with a mounting flange 28 and an inwardly directed shoulder 22 against which is seated an apertured disk I1 retained in position in any suitable way as by an internal sleeve or sleeves 30 forced or otherwise suitably secured in the bore of the sleeve 21. As here shown sleeve 30 is made in two sections, which may conveniently take the form of split spring rings that are sprung into clamping engagement with the bore of the sleeve 21, and clamp between the same a filter, fine-mesh gauze or screen, or other suitable iiltering element 3I to remove vfrom the gas any particles that might otherwise obstruct the orifice I8.

In Fig. 4 still another embodiment of the invention is shown consisting of a housing made in two parts 33 and 34, which may be separated at the threaded portion 35. These housing parts 33 and 34 have recesses or chambers 40 and 4I, which together form a gas passageway, across which is disposed a filtering means 32 held fixedly in position by screwing the housing parts 33 and 34 tightly together. Gas enters the housing through tubular passageway 42, passes through the valve means consisting of a screw 36 having a beveled. end 31, which is preferably opened wide when gas flow is desired to provide a relatively unrestricted gas passage, but which may be forced tightly against v alve seat 38 when it is desired to shut off the gas iiow completely. A screw 39 closes the aperture by which access may be gained to valve 36, 31. After passing through the valve means the gas enters the recess 4 I, and thence passes through the filter 32 into recess 40. From said recess it passes through the orifice I8 in the thin disk I1 held by a sleeve 23 in a tapered bushing 21, which may be similar in construction to that shown in Fig. 2, and vthence to the pilot burner. 'I'he rate of gas flow through the device to the pilot burner is controlled by the area of the orifice I8 selected in accordance with the requirements of the particular installation, and the valve means 36, 31 is preferably used only to shut off the gas flow completely.

It will therefore be perceived that the present invention provides means for controlling the iiow of gas to a pilot burner or the like which, by

reason of its form and dimensions, minimizes or largely eliminates the obstruction to gas ow arising from accumulation of particles such as have heretofore collected on the passage walls where needle valves, stop cocks, tubular orifices or the like have been used. Experience has demonstrated that controlling means constructed in accordance with the present invention are substantially free of accumulation of solid particles at the orifice after relatively long periods of service and the present indication is that they may be used almost indeilnitely without need for cleaning or otherwise servicing.

While the embodiments of the invention illustrated on the drawing have been described with considerable particularity, itis to be expressly understood that the invention is not restricted thereto, as the present invention may be embodied in a wide'variety of constructions dependent upon the requirements of the individual installation, as will now be readily apparent to those skilled in the art. It is also to be expressly understood that the area of the orifice may be varied as required to provide the desired rate of gas ilow to suit the requirements of the particular installation provided that the critical ratio of length to diameter herein disclosed is not exceeded. Reference is thereforek to be `had to the claims appended hereto for a deiinition oi the limits of the invention.

What is claimed is:

l. In a device for constricting the ilow of gas to a pilot burner, and in combination with means providing a passage for gas ilow, a relatively thin disk disposed across -said passage and containing a substantially cylindrical orifice the ratio of the entire length of said orifice through said disk to its diameter being not""`in excess of 0.2.

2. In a device for constricting the ilow or gas to a pilot burner, and in combination with means providing a passage forgas now, a relatively thin disk of non-corrodible material disposed across said passage and containing a substantiallycylindrical orifice the ratio of the entire length of said oriiice through said disk to its entire length of said orifice through said disk to its diameter being not in excess of 0.2, said oriiice having its peripheral wall throughout its periphery at substantially right angles to the faces of said disk.

4. In a device for constricting the flow of gas to a pilot burner, and in combination with means providing a passage for gas ilow. a relatively thin disk disposed across said passage and containing a substantially cylindrical orifice the ratio of the entire length of said oriiice through said disk to its diameter being not in excess of 0.2, and

filtering means disposed in said passage on the inlet side of said disk and provided with apertures whose maximum dimensions are less than the diameter of said oriilce. i

5. In a device for constricting the ilow of gas to a pilot burner, and in combination with means providing a passage for gas ilow, a relatively thin disk disposed across said passage and containing a substantially cylindrical oriilce the ratio oi' the entire length of said orice through said disk to its diameter being not in excess of 0.2, and a iine-mesh screen disposed in said passage on the inlet side of said disk and having apertures whose diagonals are less than the diameter o! said orice.

6. As an article of manufacture to be installed for constricting the now of gas to a pilot burne a screw containing a passage having one or more inlet openings and an outlet opening communicating therewith, a relatively thin disk carried in unitary relationship by said screw and disposed across said passage, said disk containing a substantially cylindrical orifice the ratio of the entire length of said oriilce through said disk to its diameter being not in excess of 0.2, and valve means mounted in the passage of said screw for closing said passage.

'7. As an article of manufacture to be installed for constricting the ilow of gas to a pilot burner. a bushing containing a passage and having en interior shoulder, a relatively thin disk carried in unitary relationship by said bushing and disposed across said passage, said disk containing a substantially cylindrical oriiice the ratio of the entire length of said oriiice through said disk to its diameter being not in excess of 0.2. and means in saidl bushing for retaining said disk against said shoulder.

A SEBASTIAN KARRER.

C HANNING W. WILSON.

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