US2808879A

US2808879A - Air gas mixer

Info

Publication number: US2808879A
Application number: US453636A
Authority: US
Inventors: George E Markley
Original assignee: Individual
Current assignee: Individual
Priority date: 1954-09-01
Filing date: 1954-09-01
Publication date: 1957-10-08
Anticipated expiration: 1974-10-08

Description

Oct. 8, 1957 G. E. MARKLEY AIR GAS MIXER Filed Sept. 1, 1954 INVENTOR. 650265 E. MAE/(l 5) BY% W HIS A T'TOENE Y AIR GAS MIXER George E. Markley, Cleveland Heights, Ohio Application September 1, 1954, Serial No. 453,636

3 Claims. (Cl. 158-118) This invention relates to mixing devices of the aspirator type and more particularly to a venturi type mixer for mixing air and fuel for use in a gas burner. Heretofore it has been common practice to provide a mixer which embodies the venturi principle where air is passed through the venturi at high velocity causing a low pressure at the orifice of the venturi where gas at constant zero or positive pressure is admitted. The amount of gas flowing into the mixer is determined by the velocity of the air at the orifice which is in turn determined by the area of the orifice and its ratio to the area of the outlet port or ports as well as by the valve in the gas line.

In the past it has been proposed to provide such mixers where the area of the venturi orifice and throat may be adjusted for various size port openings of the burners, so that the required high velocity of air at the orifice and throat be maintained thereby providing sufiicient suction of the gas into the mixing chamber.

.One method of such adjustment contemplates the substitution of different sized rods which extend through the orifice and throat into the mixer chamber-the larger the rod, the smaller the area. Although this means of adjustment is satisfactory, it makes it necessary to shut down the burner when the rods are being exchanged, and requires the stocking of many sized rods to provide for the various adjustments, which rods are removed and larger or smaller ones inserted.

By my present invention, I provide a mixer where the need for different sized rods for the same size mixer is eliminated making it unnecessary to carry alarge number of rods in stock. This in itself is an advantage because there is no need to shut off the gas while making the adjustment for the proper proportions of fuel and air, and, the adjustment is of a substantiallycontinuous and gradual nature, which is simple to make and saves considerable time in effecting it. .Furthermore, should the character of the gas change, it can be quickly readjusted from its original setting without replacing any parts.

It is therefore an object of my invention to provide an improved gas and fuel mixer which requires a minimum or no substitution of parts to adjust the mixer for different character fuels.

It is another object of my invention to provide an adjustable mixer where the adjustment is readily accessible and wherein no special tools are needed toreifect the adjustment.

Another object of the invention is to provide a structure that increases its capacity range to handle fuel and fiuid mixtures.

Another object of my invention is to provide a mixer structure where the mixing of the fuel and combustion supporting fluid is enhanced.

Another object of my invention is to provide a mixer which is economical to manufacture.

These and still other objects of the invention will become more apparent from the following description of an embodiment thereof and which description is illustrated by the accompanying drawings.

Uraiwd. S at s re o ice In the drawings:

Fig. 1 is an end elevation of a device embodying my invention;

Fig. 2 is a side elevation view thereof; and

Fig. 3 is a vertical medial sectional view, with a portion shown in elevation.

In the drawings, like parts have been designated by like reference characters.

Generally speaking, my improved mixer is in the form of a venturi where the gas is sucked into the venturi at the junction of the orifice and throat, and mixes with the air flowing through the orifice, in the mixer chamber. The effective area of the orifice and throat for minimum air flow is controlled by a hollow tube which extends through the orifice and throat of the venturi. Air may be admitted to this tube, which extends into the mixer chamber, and escapes into the mixer chamber beyond the throat of the venturi. The amount of air admitted to the tube may be controlled by a valve, from the outside, to enable an accurate adjustment of the mixture.

As illustrated in the drawings, there is provided a base housing or body It which is formed to provide an air chamber 11. Air under pressure is admitted to this chamber through a pipe which may connect to the threaded boss 13. The interior of the chamber may be of circular cross section, although the invention is not limited to any particular form of cross section, and is provided with a converging end wall or diaphragm 14 which terminates in an incoming orifice 15 for the air.

The body of the housing, beyond the air chamber, is provided with an annular gas chamber 17 which surrounds the orifice forming wall 1 2- and also the incoming mixture orifice, later to be described. Gas is admitted to this chamber through a conduit, not shown, which connects to a threaded boss 18. This boss 1d may be threaded at opposite ends to enable it to be conveniently attached to the gas line, the opening not used being closed by a conventional pipe plug.

The end of the body remote from the air inlet has a threaded boss 2th adapted to receive the mixer chamber and throat member 21.

The mixer and throat member includes a threaded intermediate part 32 for threaded engagement in the boss 20, being provided with a flange 23 which abuts the boss 2% of its outer face to accurately position the throat. From the intermediate part there is provided an inwardly extending throat 25 which is coaxial with the incoming orifice 15 and spaced therefrom by. a gap. 26. The throat 25 is formed with a mixture orifice .27. It will be noted that the mixture orifice 27 is larger than the orifice 15. it can also be seen from the drawings that the gas chamber surrounds both the throat and the orifice and that a gas passageway into the throat is pro-- vided by virtue of the gap 26 between thethroat 'and the orifice wall. U

The interior of the throat is substantially of uniform diameter, except for a slight flare at the edge, from the opening toward the mixing chamber, as shown at.28, and then merges with the outwardly inclined wall 33 of "the mixer chamber. The end of the chamber is provided with a cylindrical portion 31 which may be internally threaded at 22 and by which it may be connected to the manifold of a burner not shown and which force forms the exit orifice. i

It will be apparent that the structure describedpr o vides a venturi where the air velocity is increased at the throat and hence gas at zero or some positive pressure is educed through the gap 26 and mixes with the air in the mixer chamber. 7

Heretofore, it has been proposed to reduce the cross i atented Oct. 8, 1957 port or ports by the use of a rod coaxial with the orifice and throat. It changes in balance of the mixture were desired difierent sized rods were substituted as well as the exit or burner orifice. These rods had to extend well into the mixtu e chamber beyond the throat in order to eliminate the undesired turbulence due to end effects of the rods.

In the present invention, 1- provide a tube whieh is coaxial with the orifice and throat a d through whieh air is admitted, the amount of air being controlled by a valve. To this end, the end of the body it) is machined flat at 35 and provided with a threaded opening in axial alignment with the orifice and throat. A plug having a threaded stem 36 and a flat head 37 is screwed in the opening. The plug is provided with an axially extending stem 38 which supports a tube 39,, the tube extending out.- board of the stem and coaxial with the orifice and throat and into the mixing chamber.

The plug is provided with a bore 41 that exten s inwardly from the outer end and connects with a threaded opening which opens to the interior of the tube. The threaded opening provides a support for a threaded stem 42 of a piston or valve 43. The stem being slotted for receiving a screw driver, may be rotated to move the valve longitudinally in the tube.

The end of the bore may be closed with a removable pipe plug 44 which protects the bore from dirt and protects the same from accidental movement or against tarnpering by unauthorized persons and prevents leakage of airoutwardly of the bore.

The tube is provided with a plurality of ports 46 of which there may be four, spaced 90 apart. The main desideratum being that the ports be large enough to admit the desired quantity of air and that the valve be large enough and the stem .long enough so that the ports may be completely closed if desired.

The .endoi theplug 37 may be provided with seats for the reception of a spanner wrench for assembly of the plugiinthe valve'housing.

From .a ,designconsideration, it is desirable that a tube of sufficient diameter be used to reduce .the area of the orifice and .throat, so that a ,minimum flow .of air, of sufiiient velocity, is realized fora given burner port area for optimum combustion. The required minimum flow of airmay providemore suction of the gas into-the mixer thanis needed when the gas demand is small, but this does ,not afiect its .efficiency. In practice, if there is more gas beingdrawn into the mixer chamber than is actually needed, the gas system may be regulated, externally of the mixer, to supply only that amount required foroptimum combustion. .It hasqbeen determined by the artisans in thisfield that. optimum combustion is obtained, for any givensize burner, when the ratio of the orifice and throat area to theburner port area is approximately 112 /2, and the ratio ofair to .gas in the mixing chamber is 1021.

The presentdeviceis designed so that when the valve is-cIosed, preventing any air from flowing through the tube, the required minimum flow of air at the required velocity, is realized for a given size burnersystem having a known port area, and the gas drawn into the mixer is actuallymore than required for optimum combustion. Thereaftenthe gassupply is regulated, as hereinbefore stated, to supply only the quantity required for theoriginal burner system.

Then, should it be desirable to use the mixer on a burner-system having a greater port area, for instance, one having a total port area of two times the original burner system, it is .at once realized that additional air has to be admitted .into the; mixing chamber in order to provide a mixture of air .and gas ofthe correct proportiontor optimum. combustion.

Generally, if the burner port area is doubled,. the fuel required to. maintainyoptimum conditionsistwo times {the original .quantity. 7

i .The ainadmittedthroughthe:orifice.-15,is. then insutfiascents .7

cient to result in an optimum combustion mixture for the larger burner system, since the tube establishes a minimum or standard quantity of air required for optimum conditions for the original burner system.

Additional air is admitted into the mixer chamber 21 through ports 46 which are placed in the tube on the air input side of the mixer. The air flows through the tube, and is allowed to escape into'the mixing chamber. The air flowing through the orifice and throat is of sufficient velocity to draw the required amount of gas needed for the larger burner system into the mixing chamber. The air adm ted thread; he tu e is the; r ul ted b the valve 43 until the desired optimum combustible mixture is attained in the nlixingchamber for the larger burner system. Thus, the mixture of air and gas may be adjusted so that the mixer can be used on any combination of burner system, within the limits of the mixer which ar es b she by the minimum flow of ai t ead; t rifice and thr at. th m ximum quan 'Q sas d awn into the mixer, and the amount of air flowing through he tube- B c us t au il a ai 11 0111 he an f h tube 39 in o the m xi g ch mbe h s flow n o P ai s h p opa a o o he unw te eddi nd u bu nce at t a pqint u al ass ts i th a r w st tm- This enables a much shorter tube to be used and perr nits a shorter overall length irom the entire structure.

, It will be appreciated that the tube inlet ports could be closed by a sleeve over the outside which could be moved longitudinally or rotated circurnf erentially or that other types of valves could be used to admit air to the ime.

It is believed, however, that the broader concept of the inven on ompr es the admi si o ai n t e fuel mixer stream beyond the throat to enable the higher velocity at the throat to be maintained and still permit adiu t o the ar pe n op r ons o a an gas wi out changing the size of the air inlet orifice. That further the introduction of air through the end of the tube eliminates undesired turbulent effects and provides abetter fuel-.air rnixture.

H i thu s esc ibes m ven ion am aw e h numerous and extensive departures may be made from theernbodirnent shown without departing from the ispirit and scope of the invention as defined in the appended claims I claim:

1. A gas and air mixer comprising a housing tormedto provide a walled air chamber forconnection' to a supply of .=a i-r under pressure; a circular .air orifice in a wallet the air chamber; the housing formed to provide a Walled han berhaving :aiirixture outlet for connection to a burnerapparatus having a burner port of predetera ed re iapq tion of th m x n ch m opp thenai tureoutlet being circular in cross-section and having a;c1rc ular inlet orifice opening thereinto coaxial therewith and coaxial with. the circular air orifice,- with a space between the orifices; an elongated tube of circular crosssection supported on the housing and having an intermediate portion in the air chamber, andextending .coaxiallythrough the orifices withclea-rance therearound and continuing into the mixing chamber and open at one end in the mixing chamber and closed at its opposite end; the said clearance around the tube providing an annular passageway of restricted predetermined area; the housing formedto provide a gas chamber for connection to a gas supply and surrounding the inlet orifice andsaid space; whereby ainunderpressurein the air chamber fiows ,throughthe annular passageway and draws gas fromthe gas chamber, and the air and gas flow longitudinally over the; outside; of the tube into the mixing chamber and mix therein; the area of the v annular pas.Sageway having a presel cte ra t th b n Po t ar tocau p eselsv P s r ted vs q in th nir ns s a be a d .ca sefi burne pe u suprli siv h' h utat at sai Pressure';n'1eans to adjust the rp g ghambenpressureto adapt it to best operation of the burner, comprising a tube and mixing chamber and orifices causing mixing of the gas and air and supplemental air to occur with the minimum of turbulence.

2. A gas and air mixer comprising a housing formed to provide a walled air chamber for connection to a supply of air under pressure, an air orifice in a wall of the air chamber; the housing formed to provide a Walled mixing chamber having a mixture outlet for connection to a burner apparatus having a burner port of predetermined area; a portion of the mixing chamber opposite the mixture outlet having an inlet orifice opening thereinto coaxial with the air orifice, with a space between the orifices; an elongated tube supported on the housing and having an intermediate portion in the air chamber, and extending coaxially through the orifices with clearance therearound and continuing into the mixing chamber and open at one end in the mixing chamber and closed at its opposite end; the said clearance around the tube providing a passageway of annular restricted predetermined area; the housing formed to provide a gas chamber for connection to a gas supply and surrounding the inlet orifice and said space; whereby air under pressure in the air chamber flows through the passageway and draws gas from the gas chamber, and the air and gas flow longitudinally over the outside of the tube into the mixing chamber and mix therein; the area of the passageway having a preselected ratio to the burner port area, to cause preselected pressure to develop in the mixing chamber and cause the burner port to be supplied with the mixture at said pressure; means to adjust the mixing chamber pressure to adapt it to best operation of the burner, comprising a valve port through the wall of the tube at its intermediate portion in the air chamber through which supplemental air flows from the air chamber through the tube and discharges from its open end directly into the mixing chamber, and a valve constructed to be operated by an operator from outside the housing to adjust-ably vary the effective size of the valve port, to adjustably vary the supplemental air flow.

3. A gas and air mixer comprising a walled housing formed to provide a walled air chamber for connection to an air supply under pressure, and a Walled mixing chamber for connection to a burner apparatus having an efiective port opening of predetermined area, and aligned orifices in walls of the air chamber and mixing chamber spaced apart, and a walled gas chamber around the orifices communicating with said space; a tube extending through the aligned orifices with clearance therearound and open at an end in the mixing chamber; the clearance around the tube providing a restricted passageway of fixed area through which air from the air chamber flows to the mixing chamber and draws in gas from the gas chamber to flow with the air to the mixing chamber and mix therewith; the area of the restricted passageway having a ratio to the area of the burner port that causes pressure to develop in the mixing chamber; means to adjust the pressure in the mixing chamber for best operation of the burner apparatus comprising a portion of the tube disposed in the air chamber and having a valve port in its tube wall communicating between the air in the air chamber and the tube interior whereby air may flow from the air chamber through the tube directly into the mixing chamber, and a valve operable from outside the housing to variably change the effective size of the valve port.

References Cited in the file of this patent UNITED STATES PATENTS 1,064,106 Stewart June 10, 1913 1,293,041 Coleman Feb. 4, 1919 2,128,711 Maslen Aug. 30, 1938 2,228,171 Lutherer Jan. 7, 1941 2,351,697 Nielsen June 20, 1944 FOREIGN PATENTS 399,396 Great Britain Oct. 5, 1933