US3760790A

US3760790A - Gas fireplace unit

Info

Publication number: US3760790A
Application number: US00181086A
Authority: US
Inventors: W Voges; E Hodges
Original assignee: ROLSCH ENAMEL AND Mfg CO
Current assignee: ROLSCH ENAMEL AND Mfg CO
Priority date: 1971-09-16
Filing date: 1971-09-16
Publication date: 1973-09-25
Anticipated expiration: 1990-09-25

Abstract

This invention relates to a gas fireplace unit and particularly to one that produces an authentic fire free from pollutants such as carbon monoxide and soot. The unit includes a grill, a burner pipe mounted on the grill, a plurality of gas jets having sized orifices mounted vertically in the burner pipe, and means for supplying a regulated amount of gas to the burner pipe to control the pressure in the pipe within prescribed limits. An imitation fuel such as gas logs is positioned on the grill relative to the jets such that the flames do not impinge on the logs. Clean yellow authentic flames are produced from the tips of the jets by proper control of the gas pressure in the burner and sizing of the jet orifices.

Description

United States Patent 11 1 Vogeset al.

1451 Sept. 25, 1973 [22] Filed:

[ GAS FIREPLACE UNIT [75] Inventors: William R. Voges, Earl J. Hodges,

both of Belleville, Ill.

[73] Assignee: Rolsch Enamel & Mfg. Co.,

Belleville, lll.

Sept. 16, 1971 211 Appl. No.: 181,086

Primary ExaminerEdward G. Favors. Attorney-Rogers, Ezell, Eilers & Robbins [57] ABSTRACT This invention relates to a gas fireplace unit and particularly to one that produces an authentic fire free from pollutants such as carbon monoxide and soot. The unit includes a grill, a burner pipe mounted on the grill, a plurality of gas jets having sized orifices mounted vertically in the burner pipe, and means for supplying a regulated amount of gas to the burner pipe to control the pressure in the pipe within prescribed limits. An imitation fuel such as gas logs is positioned on the grill relative to the jets such that the flames do not impinge on the logs. Clean yellow authentic flames are produced from the tips of the jets by proper control of the gas pressure in the burner and sizing of the jet orifices.

19 Claims, 21 Drawing Figures GAS FIREPLACE UNIT BACKGROUND OF THE INVENTION Gas fireplace units have long been used as a substitute for real log or coal fires because of their convenience. The flames are produced by gas, either natural gas or LP gas, and the logs, while having the appearance and texture of real wood logs, are of a permanent noncombustible material.

The problem, however, with these units has been to produce a clean yellow flame. A clean blue flame is produced by mixing primary air with the gas before it is burned, thereby providing complete combustion and producing a clean flame. However, to make the flame yellow requires the elimination or reduction of the amount of primary air with only secondary air, air that mixes with the gas just at the base of the flame, to produce combustion. With the prior art units, the amount of secondary air that can be mixed is by itself insufficient for complete combustion. The result is a yellow but very dirty flame producing carbon monoxide, soot, and other forms of pollution, the soot collecting on the logs or other-fuel substance on which the flames impinge.

In practice, many prior art units of this type are designed with a means for adjusting the amount of primary air mixture. The manufacturer adjusts the primary air at the factory to produce a clean blue flame. But since real log fires. have primarily yellow flames, the customer, after the unit is installed in his fireplace, usuallyadjusts the unit to eliminate the primary air and produce a yellow flame that is authentic looking but dirty.

SUMMARY OF THE INVENTION The gas fireplace unit of this invention produces an authentic, clean yellow flame. It can be used in a builtin or free-standing type fireplace and includes two embodiments: one for use with natural gas in which no primary air is used; and one for use with liquid petroleum (LP) gas in which only a small amount of primary air is used to insure complete combustion due to its high B.T.U. content.

Both units include a grill on which an imitation fuel substance such as a plurality of imitation gas logs or coals are mounted. The logs, for example, are of the permanent noncombustible type commonly used in gas log units to give the appearance of an authentic log fire.

A gas burner is mounted to the grill between the logs and includes a pressure regulator to regulate the'gas pressure from the gas supply, a valve operable by a suitable knob or handle at the output of the pressure regulator, and a burner pipe at the output of the valve in which are mounted a series of gas jets spaced along its length. The unit also includes a pilot and thermocouple safety device as commonly found on gas burners. Means are provided for controlling the pressure of the gas in the pipe and the flow of gas through each of the jets, thereby creating the conditions for the proper mixing of secondary air with the gas to provide complete combustion and a clean yellow flame without the use of primary air.

The unit also includes support means for positioning the logs or other imitation fuel substance in relation to the jets such that none of the flames from the jets impinge thereon. Hence, soot that otherwise would be produced on the fuel substance by the lowering of the flame temperature as the flame strikes the substance is eliminated.

Where imitation logs are used, at least one log may be positioned above the burner pipe. The jets are spaced such that some of the jets are directly beneath the log and others are positioned outside. Those beneath the log are designed with sized orifices and produce either a horizontal flame or a relatively short flame so as not to impinge on the upper log. The primary function of these jets is to transfer the flame to the outer jets when the unit is turned on. The outer jets also have sized orifices and tips with vertical slots aligned parallel to the burner pipe to produce clean yellow flames of various heights simulating a real log fire. Because these outer jets are located outside the edges of the upper log their flames do not impinge thereon.

While no primary air is necessary in the natural gas unit, a small amount is supplied in the LP unit because of the high B.T.U. content of LP gas. Thissmall amount of primary. air is supplied through small ports near the lower end of the jets.

Hence, this invention provides a unique combination of gas pressure and flow control, jet design, and fuel placement to produce an authentic clean yellow flame.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of one embodiment of the gas fireplace unit of this invention;

FIG. 2 is a front elevational view of the gas unit of FIG. 1;

FIG. 3 is a plan view on an enlarged scale of the gas unit of FIG. 1 with the logs shown in dashed lines;

FIG. 4 is a front elevational view of the gas unit of FIG. 3 without the logs;

FIG. 5 is a view in section taken along the line 5-5 of FIG. 3;

FIG. 6 is a plan view of one type of gas jet used in the gas unit of FIG. 1;

FIG. 7 is a front elevational view of the gas jet of FIG.

FIG. 8 is a view in section taken along the line 88 of FIG. 7;

FIG. 9 is a view in section taken along the line 99 of FIG. 6;

FIG. 10 is a plan view of another type of gas jet used in the gas unit of FIG. 1;

FIG. 1 l is a side elevational view of the gas jet of FIG. 10;

FIG. 12 is a view in section taken along the line 12-12 of FIG. 10;

FIG. 13 is a plan view of another embodiment of the gas fireplace unit of this invention with the logs shown in dashed lines;

FIG. 14 is a front elevational view of one type of gas jet used in the gas unit of FIG. 13;

FIG. 15 is a view in section taken along the line 1s 1s of FIG. 14;

FIG. 16 is a plan view of another type of gas jet used in the gas unit of FIG. 13;

FIG. 17 is a front elevational view of the gas jet of FIG. 16;

FIG. 18 is a view in section taken along the line 18-18 of FIG. 16;

FIG. 19 is a plan view of another type of jet used in the gas unit of FIG. 13;

FIG. 20 is a front elevational view of the gas jet of FIG. 19; and

FIG. 21 is a view in section taken along the line 21-21 of FIG. 19.

A DETAILED DESCRIPTION OFPREFERRED EMBODIMENTS In FIGS. 1 through 12 of the drawings there is shown one embodiment of the gas fireplace unit of this invention for use with natural gas. Referring primarily to FIGS. 1 through 5, a gas log unit includes a steel grill 22 on which is supported

artificial logs

24, 26, and 28. The grill 22 has base members and 32 having

leg portions

33, 34, and 35 and 36, respectively, formed at their ends. The

base members

30 and 32 support a plurality of parallel cross members each having upwardly turned ends 41 and 42 to define a cradle for supporting the

logs

24, 26, and 28.

The log 24 is located toward the back of the grill 22 and is held in this position by means of a short vertical member 44; the log 26 is located toward the front of the grill 22 and is held in position by a short vertical member 46; and the log 28 is located at an angle on top of

logs

24 and 26, as best shown in FIG. 1, and held in position by means of

vertical members

48 and 49 which extend upward above the tops of the

logs

24 and 26. The

vertical members

44, 46, 48, and 49 are mounted at their lower ends to the grill 22 by any suitable means such as welding or bolting, with their upper ends extending into suitable notches or holes (not shown) in the

logs

24, 26, and 28. In this way the positions of the logs are fixed relative to the grill and the burner jets, as will be explained, to prevent impingement of the flames on the logs.

A burner assembly is mounted to the grill 22 on top of a metal plate 56 and between the

logs

24 and 26. The assembly includes a pressure regulator 57 mounted to the underside of the grill 22 and having an inlet 58 for connection to a source of natural gas and an outlet connected by a conduit 59 to the input of a combination control valve and pilot safety device 60. The control valve 60 has a suitable control knob 62 for operation of the valve. The valve 60 has an orifice at its output the size of which regulates the gas flow therethrough. The gas flowing through the orifice is fed through a conduit elbow 64 into a burner pipe 66. In the top of the burner pipe 66 are a series of threaded holes spaced along the length of the pipe into which

burner jets

70 and 71 are mounted.

The safety pilot portion of the valve 60 has a small gas outlet through which gas is fed through a small conduit 75 to a pilot 76. A portion of the flame from the pilot 76 is directed on a thermocouple 78 which is electrically connected through a conduit 79 to a control circuit ofa type commonly known in the art, in the control valve and pilot safety device 60, which automatically shuts off the gas to the pilot 76 and burner pipe 66 whenever the thermocouple 78 drops below a prescribed temperature. The pilot 76 and thermocouple 78 are mounted to the grill 22 near the side and approximately midway between the ends of the burner pipe 66.

The jets of the type 70 are located at the outer ends of the burner pipe 66 and outside the log 28 so that the flames therefrom do not impinge upon the log 28. Referring to FIGS. 10 through 12, the jets 70 each have an outer brass cylindrical jacket 80 with a tapered externally threaded lower end 82. A compressible sleeve 84 is mounted within the jacket 80 with its lower end just above the threaded portion 82. The sleeve 84 has a large opening 86 at its lower end. A tapered ceramic ring 88 is mounted within the sleeve 84 near its lower end and has an orifice 90 of a size depending on the location of the jet on the burner pipe 66 and the gas pressure within the pipe. The orifice 90 must be free of burrs and sized to control the flow of gas from the jet such that a proper quantity of secondary air will be mixed with the gas to provide a yellow flame and complete combustion. The sizes of the orifices 90 in the jets 70 vary slightly to produce flames of different heights for an authentic appearance.

A flashback prohibitor 96, such as a U-shaped wire screen, is positioned above the sleeve 84 to prevent the igniting of the gas at the orifice 90. A dome-shaped ceramic tip having a vertical slot 102 is mounted in the top of the jacket 80 with a bottom edge 101 resting on an inwardly extending annular shoulder 103 of the jacket 80. The purpose of the slot 102 is to produce a fan-shaped flame.

The jets 70 are screwed into the threaded holes toward the outer ends of the pipe 66 and oriented with their slots 102 parallel to the pipe 66 so that the broad sides of the flames from the jets 70 are seen when the gas log unit is viewed from the front. Other suitable means for mounting the jets in the pipe 66 could also be used.

The gas in the pipe 66 is fed through the bottom of the jacket 80, the opening 86, the orifice 90, the screen 96, and the slot 102 where it is ignited to produce a flame.

The jets 71 are located toward the middle of the pipe 66 in the space between the

logs

24 and 26 and under the log 28. Referring to FIGS. 6 through 9, the jets 71 have a brass cylindrical jacket 105 with a tapered externally threaded lower end 106 and an inwardly extending shoulder 107. A hollow ceramic tip 108 is mounted in the upper end of the jacket 105 with its lower end 109 resting on the shoulder 107. The tip 108 has a head portion 111 extending above the jacket 105 and with an annular groove 112 around its side. At the bottom of the annular groove 1 12 are diametrically aligned

apertures

114 and 115 with a series of spaced apertures l 16 therebetween around one side of the tip. The apertures 116 are smaller than the

apertures

114 and 115. The groove 112 creates turbulence at the apertures 1 14 through 1 16 for more thorough mixing of secondary air with the gas.

The tip 108 is formed in an outwardly extending shoulder 117 just below the groove 112. The top edge of the jacket 105 is turned inwardly over the shoulder 117 to hold the tip in place. The jets 71 are mounted in the pipe 66 with the axes of the

ports

114 and 115 parallel to the pipe 66.

The gas from the pipe 66 is fed through the bottom end of the jacket 105 and into the hollow tip 108. From there the gas escapes through the

apertures

114, 115, and 116.

OPERATION To operate the gas log unit 20, the valve 60 is opened by turning the control knob 62 allowing gas to flow from the gas supply through the pressure regulator 57, the primary orifice in the valve 60, and into the burner pipe 66. From there the gas is fed into each of the

jets

70 and 71.

With the pilot 76 on, the flame from the pilot ignites the gas from the

ports

114, 115, or 116 of the jet 71 adjacent the pilot 76. The flame from the port 1140f this jet 71 ignites the gas from the port 115 of the jet 71 to its left as viewed in FIG. 3 of the drawings, which in turn progressively lights the gas in the port 1 16 and the port 114 of the left jet 71. The gas from the port 114 of the left jet 71 in turn ignites the gas from the jet 70 to its left which ignites the gas from the jet 70 at the ex treme left.

The gas from the port 115 of the middle jet 71 ignites the gas from the port 114 of the jet 71 to its right which in turn progressively ignites the gas from its

ports

116 and 115. The flame from the port 115 ignites the gas from the jet 70 to its right which in turn ignites the gas from the jet 70 at the extreme right. In this manner the entire burner is ignited.

The flames from the outer jets 70 are vertical and are of varying heights depending on the sizes of the orifices 90 to give an authentic appearance. The flames from the jets 71 are horizontal and generally serve the primary purpose of igniting the outer jets 70. Because the flames from the jets 71 are within the space between the

logs

24 and 26 and under the log 28, and the flames from the jets 70 are outside the log 28, none of the flames impinge, and hence no soot is deposited, on any of the logs. This is one of the important features of the invention.

Another important feature is the production of a clean yellow flame of sufficient height and shape to look authentic. This is accomplished through a combination of controlling the gas pressure in the burner pipe 66 with the pressure regulator 57 and a properly sized primary orifice in the valve 60, and controlling the gas flow through each individual burner jet for proper flame height and mixing of secondary air with the gas for complete combustion by properly sized orifices in each jet.

To produce a clean yellow flame with natural gas it is necessary to maintain the temperature of the flame between approximately l,200 and 1,400 Fahrenheit. If the temperature drops much below 1,200, the flame becomes dirty due to incomplete combustion. If the temperature increases much above l,400 the flame becomes blue. In order to maintain this temperature range, it is necessary to maintain the pressure in the burner pipe 66 in a range between approximately 0.05 to 0.75 inches water gauge (IWG). This is accomplished with the pressure regulator 57 and the size of the primary orifice inthe control valve 60. By then properly selecting the orifice sizes in each of the jets, clean yellow flames can be produced. The lower the pressure in the pipe 66 the larger the orifices must be and vice versa. If the pressure in the pipe 66 is much below 0.05 IWG, the resultant flame will be too small (probably less than an inch) and too blue due to the large amount of secondary air that mixes with the relatively small amount of gas no matter how large the jet orifice is. If the pressure in the pipe increases much above 0.75 IWG the resultant flame will be dirty due to incomplete combustion caused by blowing the flame away from the jet.

For a 24-inch natural gas log unit (one with a grill 24 inches long) it has been found that the optimum burner pipe pressure for producing clean yellow flames of approximately two to seven inches high is in the approximate range of 0.35 to 0.50 IWG. To produce flames of from approximately 2 to 7 inches high within the optimum pressure range in the pipe 66, the sizes of the orifices 90 in the jets are approximately between No. 40 DMS and No. 52 DMS. These optimum pressure ranges and orifice sizes are meant by way of example only, it being understood that for different applications, such as for example larger or smaller gas log units, the optimum pressure range in the pipe 66 and the sizes of the orifices would be larger or smaller as required. However, the temperature of the resultant flame must be approximately l,200 to 1,400 Fahrenheit, and the flame height and log placement must be such that the flames do not impinge on the logs..

In FIGS. 13 through 21 there is shown a second embodiment of this invention for use with LP rather than natural gas. This unit differs in certain details from the first described unit due to the higher B.T.U. content of LP gas requiring the addition of a relatively small amount of primary air for complete combustion.

In many respects the LP unit is similar to the natural gas unit. It also has the grill 22, artificial gas logs 24, 26, and 28,

vertical members

44, 46, 48, and 49 for positioning the logs in the grill such that the flames from the jets do not impinge thereon, the pressure regulator 57,

the valve and pilot safety device 60 and the control knob 62, and the burner pipe 66. Also included is the pilot 76 and thermocouple 78 connected to the valve and pilot safety device 60 by gas conduit 75 and electrical conduit 79. The operation of these components is the same as in the first described embodiment.

Like the natural gas unit 20 the unit has a plurality of

jets

122, 123, 124, and all of one type, 126 and 127 of another type, and 128 and 129 slightly different from the

jets

126 and 127. The jets 122 through 125, like the jets 70 of the first described embodiment, are located toward the ends of the pipe 66 to produce vertical flames simulating a real log fire. These jets are located outside the log 28 so that the flames do not impinge thereon. The jets 126 through 129 are located between the

jets

123 and 124 and like the jets 71 of the first described embodiment are between the

logs

24 and 26 and under the log 28 for the primary purpose of transferring the flame to the outer jets when the unit is ignited.

The jets 122 through 125 are identical so that only the jet 122. need be described. Referring to FIGS. 14 and 15 the jet 122 includes a brass jacket 131 having a hexagon-shaped portion 132 and a lower externally threaded tapered end 133. The inside of the jacket 131 is formed in a hollow cylindrical chamber 135. A ceramic tip 137 is mounted in the top of the jacket 131 and includes a smooth orifice 139 that communicates with the chamber 135.

A brass flame spreader 141 has a lower cylindrical portion 143 and an upper fan-shaped poriton 145. The lower cylindrical portion 143 has a series of air ports 147 around its circumference that communicate with the space above the tip 137 for supplying a small amount of primary air to the gas. The flame spreader 141 is mounted over the upper portion of the jacket 131 with its lower edge resting on the hexagon portion 132.

The top of the fan portion is formed in a slot 150 extending the entire width of the fan. A dome-shaped screen 152 is located approximately at the junction between the lower and upper portions of the flame spreader 141 to prevent flashback.

To mount the jet 122, its lower threaded end 133 is screwed into a threaded hole in the burner pipe 66 such that the chamber 135 communicates with the interior of the pipe and the slot 150 is aligned parallel to the pipe.

In operation the gas in the pipe 66 is fed through the chamber 135, orifice 139, and into the lower portion of the flame spreader 141. Here primary air is drawn in through the air ports 147 to mix with the gas, which mixture is fed through the screen 152 to the slot 150. Here the gas is ignited to produce a clean yellow flame simulating a real log fire.

The slot 150 in the jet 122 is larger than the slot 102 in the jet 70 to prevent a building of back pressure in the jets that would inhibit the mixing of the proper amount of primary air. The amount of primary air used is small (about an equal amount of primary air and gas) as compared to prior art units, and while sufficient when combined with secondary air at the tip of the jet to produce a clean flame, is not so much to cause a blue flame. Except for the use of a small amount of primary air and a larger slot, the jet 122 operates basically in the same manner as the jet 70, with its orifice 139 sized to control the fluid flow through the jet to produce a clean yellow flame. The sizes of the orifices 139 vary slightly to produce flames of different heights and thereby give an authentic appearance.

The

jets

126 and 127 are identical so that only the jet 126 need be described. Referring to FIGS. 16 through 18, the jet 126 includes a brass outer jacket 155 having a lower tapered externally threaded end 157, a hexagon portion 159, and a cylindrical neck portion 161 above the hexagon portion 159. The inside wall of the jacket 155 at the base of the sleeve portion 161 is formed in an annular inwardly extending shoulder 163. The bottom of the jacket 155 has an opening 165 that communicates with a hollow chamber 167.

An inner brass sleeve 170 has a lower externally threaded end portion 171 that screws into the lower end of the jacket 155 below the shoulder 163, and an upper hollow cylindrical portion 173 having an inwardly extending annular shoulder 175. A ceramic tip 180 having a smooth orifice 181 at its upper end is mounted inside the upper portion 173 of the inner sleeve 170 with its lower end resting on the shoulder 175. The tip 180 is hollow below the orifice 181 to define a chamber 183 that communicates with the chamber 167.

Another brass sleeve 190 has a lower externally threaded end 191 that screws inside the upper sleeve 161 with its lower end resting on the shoulder 163. Just above the jacket 155 the sleeve 190 has a plurality of primary air ports 193 that communicate with a chamber 195 above the orifice 181. The sleeve 190 has a conical-shaped top 197 having a vertical port 199 communicating with the chamber 195 and a horizontal port 201 also communicating with the chamber 195. A narrow slot 203 extends from the port 199 to the port 201 and also communicates with the chamber 195.

In operation the

jets

126 and 127 are screwed into threaded holes in the pipe 66 with the slots 203 parallel to the pipe 66 and facing toward its center. With the chamber 167 in communication with the chamber inside the pipe 66, the gas in the pipe is fed through the opening 165, the chamber 167, and the orifice 181 to the chamber 195 above the orifice. A small amount of primary air is drawn through the air ports 193 and mixed with the gas. The air-gas mixture then flows out the

ports

199 and 201 and the slot 203 where it is mixed with secondary air and ignited to produce a clean yellow flame.

The

jets

128 and 129 as shown in FIGS. 19 through 21 are identical to the

jets

126 and 127 except that they have no vertical port 199 at the top, but have a second side port 210 in the wall of the sleeve 190 diametrically opposite the port 201. A narrow slot 212 extends between the

ports

210 and 201 across the top of the jet. The

jets

128 and 129 are mounted in the pipe 66 with the slot 212 oriented parallel to the pipe.

OPERATION The unit operates as follows:

When the valve 60 is opened, gas is fed through each of the jets 122 through 129. The gas from these jets is a combination of LP gas and a small amount of primary air to insure complete combustion due to the high B.T.U. content of LP gas. The gas from the ports 201 of the

jets

128 and 129 is ignited by the pilot 76. This in turn ignites the gas from the slots 212 and the ports 210. With the gas from the ports 210 ignited, the gas from the ports 201 of the

jets

126 and 127 is ignited which in turn ignites the gas from the ports 199 by way of the slots 203. The gas from the jets 122 through is generally fan shaped due to the fan-shaped portion of the flame spreader 141. Hence the short vertical flames from the ports 199 of the

jets

126 and 127 ignite the gas from the

jets

123 and 124 which in turn ignite the gas from the

jets

122 and 125. In this manner the entire burner assembly 55 is ignited.

Just as with the first described embodiment (see FIG. 5) the log 28 is positioned well above the tops of the jets 126 through 129. Of course, the flames from the ports 201 of the

jets

126 and 127 and the

ports

201 and 210 of the

jets

128 and 129 are horizontal and therefore do not impinge on the logs. The

slots

203 and 212 are very narrow to produce only enough flame to cause transfer from one jet to the next so as not to impinge on the log 28. The vertical ports 199 of the

jets

126 and 127 are sized such that the flames therefrom are high enough to ignite the gas from the

jets

123 and 124, but not so high as to impinge on the log 28. Hence in this embodiment, like the first described embodiment, none of the flames from any of the jets impinge on the logs, and therefore no soot is deposited.

Also like the first described embodiment, in order to produce a clean yellow flame it is necessary to maintain the temperature of the flame produced with LP gas within the approximate range of 1,200 to 1,400 Fahrenheit. It has been found that in order to maintain this temperature range with LP gas, it is necessary to control the pressure in the burner pipe 66 to within the approximate range of 0.1 to 13 IWG. Otherwise, with pressures below 0.1 IWG, the resultant flame is too small and too blue, and with pressures much above 13 IWG, the flame becomes dirty.

For a 24-inch LP gas log unit, the optimum pressure in the pipe 66 is between about 3 to 4 IWG. At this optimum pressure, clean yellow flames from two to nine inches high are produced from the jets 122 through 125 by sizing the orifices 139 to the equivalent of a No. 55 to a No. 68 hole; approximately one-inch flames are produced from the

jets

126 and 127 with the orifices 181 sized to the equivalent of a No. 80 hole; and horizontal flames are produced from the jets 128 and 129 I of sufficient lengths to ignite the

jets

126 and 127 with their orifices 181 sized to the equivalent of a No. 79 hole.

In each of the jets 122 through 129 the primary air ports are sized to draw an amount of primary air approximately equal to the quantity of gas flowing through the jet. This one-to-one ratio is maintained fairly constant for changes in pressure and orifice sizes within the acceptable pressure range since the amount of primary air drawn through the ports is proportional to the rate of gas flow through the jet.

Just as with the first described embodiment, these optimum figures are meant by way of example only, it being understood that other gas pipe pressures could be used within the acceptable pressure range depending on requirements.

Although these embodiments have been described with gas logs as the imitation fuel, other types of imitation fuel could be used such as imitation coals. Also the units can be used in free-standing as well as built-in fireplaces.

Therefore, there have been described novel gas log units for use with both LP and natural gas which produce authentic yellow flames simulating real log fires without producing carbon monoxide, soot, and other pollutants.

Various changes and modifications may be made within this invention as will be readily apparent to those skilled in the art. Such changes and modifications are within the scope and teaching of this invention as defined by the claims appended hereto.

What is claimed is:

l. A gas unit comprising a grill, a burner pipe mounted to the grill, a plurality of jets mounted in the burner pipe, each having an orifice through which gas from the pipe flows, means for supplying a regulated amount of gas to the burner pipe to control the pressure in the pipe within prescribed limits, the jet orifices and the pressure in the burner pipe being such as to produce a clean yellow flame from the jets, andan imitation combustible substance positioned over the burner pipe and in relationship to the jets such that the flames do not impinge on the substance.

2. The unit of claim 1 wherein the imitation substance is at least one imitation log.

3. The unit of claim 1 wherein the regulated gas supply means controls the pressure in the pipe within a range, and the sizes of the jet orifices are such, so as to produce flames from the jets of temperatures between 1200 and 1400 degrees Fahrenheit.

4. The unit of claim 1 wherein the gas is natural gas and the regulated gas supply means controls the pressure in the burner pipe to between approximately 0.05 to 0.75 lWG.

5. The unit of claim 4 wherein the regulated gas supply means controls the pressure in the burner pipe to between approximately 0.35 to 0.50 IWG.

6. The unit of claim 1 wherein the gas is liquid petroleum gas and the regulated gas supply means controls the pressure in the burner pipe to between approximately 0.1 to 13 IWG.

7. The unit of claim 6 wherein the regulated gas supply means controls the pressure in the burner pipe to between approximately 3 to 4 lWG.

8. The unit of claim 2 wherein there are a plurality of logs, at least one of the logs being positioned in front of and generally parallel to the burner pipe, and at least one other log being positioned over the burner pipe.

9. The unit of claim 8 wherein some of the jets are located outside the edges of the upper log and produce sub-stantially vertical flames, and other jets are positioned under the upper log with their tips spaced from the bottom side of the upper log and produce generally horizontal flames directed substantially parallel to the burner pipe, whereby none of the flames impinge on any of the logs.

10. The unit of claim 9 wherein still other jets are located under the upper log with their tips spaced from the bottom side of the upper log, the last-named jets producing substantially vertical flames of heights so as not to impinge on the upper log.

11. The unit of claim 1 wherein the jets are spaced such that the igniting of one jet transfers the flame to ignite the remaining jets.

12. The unit of claim 1 wherein the orifices in some of the jets are sized to produce flames of different heights.

13. A gas log unit comprising a grill, a burner pipe mounted to the grill, a plurality of jets mounted in the burner pipe, each jet having a smooth orifice through which the gas from the pipe flows, means for supplying a regulated amount of gas to the burner pipe to control the pressure in the pipe within prescribed limits, the jet orifices and pressure in the burner pipe being such as to produce flames from the jets at a temperature between approximately 1200 and 1400 degrees Fahrenheit, a plurality of imitation gas logs, atleast one of the logs being positioned on the grill in front of and generally parallel to the burner pipe, and at least another of the logs being positioned over the burner pipe, the jets being spaced on the burner pipe such that some are located outside the edges of the upper log and some are located under the upper log with their tips spaced from the bottom side of the upper log, the outer jets producing substantially vertical flames some of which rise past the sides of the upper log but which do not impinge thereon, some of the inner jets producing generally horizontal flames substantially parallel to the burner pipe so as not to impinge on the logs, the jets being spaced such that igniting one jet'transfers the flame to ignite the remaining jets.

14. The gas log unit of claim 13 wherein the outer jets have slotted tips for producing fan-shaped flames.

15. The gas log unit of claim 13 wherein the orifices in the outer jets are sized to produce flames of different heights.

16. The gas log unit of claim 13 wherein others of the inner jets produce substantially vertical flames of heights so as not to impinge on the upper log.

17. A gas unit comprising a grill, a burner pipe mounted to the grill, a plurality of jets mounted in the burner pipe each having an orifice through which gas from the pipe flows, means for supplying a regulated amount of gas to the burner pipe to control the pressure in the pipe within prescribed limits, and at least one log positioned over the burner pipe and in relation to the jets such that the flames do not impinge on the log.

18. The unit of claim 17 wherein some of the jets are located outside the edges of the log and produce substantially vertical flames, and other jets are positioned under the log with their tips spaced from the bottom side of the log and produce generally horizontal flames directed substantially parallel to theburner pipe, bottom side of thelog, the last-named jets producing whereby none of the flames impinge on' the log. substantially vertical flames of heights so as not to im- 19. The unit of claim 18 wherein still other jets are pinge on the log. located under the log with their tips spaced from the

Claims

1. A gas unit comprising a grill, a burner pipe mounted to the grill, a plurality of jets mounted in the burner pipe, each having an orifice through which gas from the pipe flows, means for supplying a regulated amount of gas to the burner pipe to control the pressure in the pipe within prescribed limits, the jet orifices and the pressure in the burner pipe being such as to produce a clean yellow flame from the jets, and an imitation combustible substance positioned over the burner pipe and in relationship to the jets such that the flames do not impinge on the substance.

4. The unit of claim 1 wherein the gas is natural gas and the regulated gas supply means controls the pressure in the burner pipe to between approximately 0.05 to 0.75 IWG.

7. The unit of claim 6 wherein the regulated gas supply means controls the pressure in the burner pipe to between approximately 3 to 4 IWG.

13. A gas log unit comprising a grill, a burner pipe mounted to the grill, a plurality of jets mounted in the burner pipe, each jet having a smooth orifice through which the gas from the pipe flows, means for supplying a regulated amount of gas to the burner pipe to control the pressure in the pipe within prescribed limits, the jet orifices and pressure in the burner pipe being such as to produce flames from the jets at a temperature between approximately 1200 and 1400 degrees Fahren-heit, a plurality of imitation gas logs, at least one of the logs being positioned on the grill in front of and generally parallel to the burner pipe, and at least another of the logs being positioned over the burner pipe, the jets being spaced on the burner pipe such that some are located outside the edges of the upper log and some are located under the upper log with their tips spaced from the bottom side of the upper log, the outer jets producing substantially vertical flames some of which rise past the sides of the upper log but which do not impinge thereon, some of the inner jets producing generally horizontal flames substantially parallel to the burner pipe so as not to impinge on the logs, the jets being spaced such that igniting one jet transfers the flame to ignite the remaining jets.

18. The unit of claim 17 wherein some of the jets are located outside the edges of the log and produce substantially vertical flames, and other jets are positioned under the log with their tips spaced from the bottom side of the log and produce generally horizontal flames directed substantially parallel to the burner pipe, whereby none of the flames impinge on the log.

19. The unit of claim 18 wherein still other jets are located under the log with their tips spaced from the bottom side of thelog, the last-named jets producing substantially vertical flames of heights so as not to impinge on the log.