US2037582A - Thermostat control for gas burners - Google Patents

Description

April 14, 1936. R MaCGREGQR ETAL 2,037,582

THERMOSTAT CONTROL FOR GAS BURNERS Invent ors John A. MacGregor Leon 7.' Folsom Samuel h. Edwards April 1936- J. R. M GREGOR ET AL 2,037,582

THERMOSTAT CONTROL FOR GAS BURNERS Filed Nov. 4, 1955 s Sheets-Shet WHERE.

flu) eniors John A. McGregor Leon 7.' Fo/som Samuel H. Edwards Patented Apr. 14, 1936 UNITED STATES,

THERMOSTAT CQNTROL FOR GAS BURNERS John R. 'MacGregor,

Albany, Leon T. Folsom,

Berkeley, and Samuel H. Edwards, Richmond, Calil'., assignors to Standard Oil Company of California, San Francisco, Calif., a corporation of Delaware Application November 4, 1933, Serial No. 696,648

-2 Claims. (01.236-1) This invention relates to a temperature responsive control for a gas burner, and particular- 1y to one which forms a part of a portable heater such as is used to keep the temperature in a compartment, such as a refrigerator car carrying perishable food products, from becoming too low. In severe winter weather, when temperatures of 10-40 degrees below zero, Fahrenheit, are sometimes encountered, it becomes necessary to pro- 10 tect perishable foodstuffs, such as apples, from exposure to temperatures below 32 degrees F. while they are being transported. Thismay conveniently be done by a portable heater consisting of a small tank of liquefied petroleum gas 15 such as propane, which is burnedin a suitably controlled gas burner. This invention relates particularly to a temperature responsive control device for such a burner.

The service requirements for such a control mechanism are unusually severe, as it must be accurate enough to hold the air temperature in a car within a range of a few degrees at about 32 F., and yet not be damagedor lose its adjustment from the jarring, shocks and general rough treatment that it receives while travelling, prac ticallytunattended, in a refrigeratorcar for a period of five to fifteen days. There must also be provision for safety under all conditions, such as an accidental extinguishing of the gas burner 30 flame, so that the car will not become filled with an inflammable or explosive gas-air mixture, with possible disastrous results. Another feature that has sometimes been overlooked'is the requirement that the calibration shall remainconstant for changes in atmospheric pressure,

so that changes in elevation 016000 to 8000 feet, while passing from sea lever over high mountain passes, will not aifect the operation. Temperature responsive devices which balance the vapor mtension of a volatile liquid in a suitable flexible walled bulb against atmospheric pressure would have this objectionable lack of calibration stability. This is avoided in this example by the use of bimetallic thermostat elements.

. 5 A suitable portable heater structure in which this invention may be used is disclosed and claimed in a copendlng application of Carl C. Claesson, Serial No. 666,558, illed April 17, 1933,

. which matured into Patent No. 1,987,603 on Jan-1 50 uary 15, 1935.

This consists generally of a .casing or stack, in which a suitable burner is mounted, and to which a standard cylindrical tank of liquefied petroleum gas such as propane, may be secured while the deviceis to be used. A de- 55 irable form of burner is that shown and claimed in a copending application of John R. MacGregor, Serial No. 691,904 filed October 3, 1933, which matured into Patent No. 2,001,739 on May 21,

1935." This burner is adapted to burn equally well with a high or a low .flame, thus requiring 5 no separate pilot burner orother ignition means, and is particularly adapted to be controlled by a device such as that to be described below.

It is an object of this invention to provide a compact and simple temperature responsive control device for a single gas burner, which will increase or decrease the gas flow as required by -changing temperature conditions.

Another object is to provide a gas burner control device which will automatically and positive- I 1y shut ofi all the .gasto the burner when the flame becomes extinguished from any cause.

Another object is to provide a gas burner control means which will be sensitive to a tempera- 4 ture change of two or there degrees Fahrenheit,

which will be adjustable in setting, and which may be operated by unskilled attendants.

' Another object is to provide a gas burner control device which forms a compact and simple unit with the burner to be controlled, and which may be easily and simply operated and adjusted. These and other objects and advantages of this invention will be more fully apparent from the following detailed description of a preferred embodiment, and from the accompanying drawings, which supplement the description and form a part of this specification.

In the drawings:'-

Figure 1 is a vertical part sectional elevation of a burner assembly involving a preferred em- 5 bodiment of this invention and showing the relation between-the temperature controller, bumer and safety shut-off means.

Figure 2 is an end elevation of the burner and controlmechanism shown in Figure 1. 40 Figure 3 isa plan of the burner and control mechanism shown in Figure 1, and illustrates the burner safety shut-off thermostat and lever in its cold or actuated position.

Figure 4 is a horizontal sectional view through the valve body on the line IV-IV of Figure 2, and illustrates the temperature control and safety shut-off valves.

Figure 51s a horizontal sectional view on the broken line V-V of Figure 2 and illustrates the. temperature control thermostat.

Figure 6 is asectional view of the'spiral bimetallic thermostat element used for tempera-. ture control, on line VI-VI of Figure 5.

Referring to the drawings and particularly 55 in calibration.

to Figures 1 and 4, the numeral H represents a valve body, which may preferably be a casting provided with two side plates l2 and i3 which cooperate with recesses" in body ii to form a gas inlet chamber i4 and a valve chamber i5. Plate i2 is made with a threaded opening i6 into which a suitable gas supply pipe (not shown) may be screwed. Both plates are secured to body H by bolts il and nuts I8 and are made gas tight by gaskets i9.

The burner structure generally designated 29 is mounted on the top ofvalve body 4 i by screws 2i. The exact construction of the burner is not important, but one which will give a stable flame at a gas rate of as low as 0.1 cu. ft. per hour from liquefied petroleum gas such as propane, and yet properly burn as high as 15 cu. ft. of such gas per hour, is desirable. This type of burner acts as its own pilot, and avoids the complication and expense of a double unit of main and pilot burners.

The safety shut-oif thermostat element 22 may conveniently be mounted within the tube of the burner, adjacent its outer end, as shown in Figures 1 and 3. The thermostat element 22 is of. the usual bimetal and is so exposed to heat from the flame that the low pilot flame which burns when the ambient temperature is above the desired minimum will cause it to remain in its expanded or latched position, while the higher heat from the burner when fullgas flow is admitted will not cause permanent deformation and change Thermostat element 22 in this example is bent to approximately a circle or hoop, with one end fixed to the burner tube 29,

by a screw 23, and the other end free tomove outwardly when its temperature is increased. Figures 1 and 3 show the thermostat element 22 in its cold or released position.

Safety shut-01f thermostat element 22 is provided with a hole 24 near its outer or free end, into which the outer end 25 of the shut-ofi valve stem 26 is adapted to pass when the temperature of 22 is low due to an'absence of flame in the burner 29. Valve stem 26 is preferably bent as shown at 21 to form a convenient handle for holding the safety shut-01f valve, to be described below, in its open position during the lighting of the burner 20. A spring 28 is secured to the body of burner 29 and also to valve stem 26 to urge the latter in a counter-clockwise direction, so that it will tend to rotate its upper end 25 to enter hole 24 in the thermostat element 22 if the element moves to its cold or contacted position shown in Figure 3.

The lower end of safety shut-off valve stem 26 extends through a hole 29 in the base of burner 20 into a corresponding hole 39 in valve body H which opens into the gas inlet chamber M (Figures 1 and 4) A resilient grommet 3|, the flange of which is clamped between the burner base plate and a recess 32 in valve body H, and which fits tightly about the valve'stem 26, prevents gas leakage to the atmosphere from gas inlet chamber l4. The slight rotation of the stem 26 in moving the valve on its lower end from open to closed position is readily taken up by torsion in the body of grommet 3|.

The partition or wall in valve body II which separates the gas inlet chamber [4 from the valve chamber I5 is drilled with a small passage 33 as shown in Figures 1 and 4, and the inlet end of the passage is provided with a nozzle or valve jet 34. A valve arm 35 is secured to the lower end of the stem 26 as by a set screw 36, and carries a tip projecting into the passage 52.

small resilient valve disc 3'! which may be of rubber. This disc 3'! is adapted to seat upon and close the valve jet 34 when the safety shut-off thermostat element 22 is cold and allows the end 25 of the valve stem 23 to enter the hole 24, as shown inFigure 3. Thus, when the burner-is cold'or is without a flame, the gas passage 33 between the gas inlet chamber i4 and the valve chamber i5 is positively closed.

A second passage 38 leads from valve chamber I 5 into the center partition of valve body i i (Figure 4) and is also provided with a nozzle or valve jet 39. A continuation 34 of passage 38 leads upwardly through the center of the valve body It and is threaded at its upper end to receive a burner nozzle (Figure 1). Passage 84 is preferably fairly large to provide a gas volume to prevent collapse of the flame when valve 39 is shut suddenly. Burnerbody 20 is suitably drilled as at 4! to allow the nozzle 40 to project upwardly as shown. Air for combustion in the burner '29 may be inspirated through a plurality of holes 42.

A temperature control valve stem 43 is fitted at its upper end with a valve arm 44, set screw 45 and a resilient valve disc 43, which latter is adapted to seat upon nozzle or valve jet 39 and thus shut ofi the gas passage 38 to burner nozzle 49. Valve stem 43 passes downwardly through a hole 41, sealed by a resilient grommet 48 and then engages'a temperature control thermostat mechanism generally designated 49 through the medium of the offset or crank section 50. The lower end of valve stem 43 is preferably received and supported by a bearing such as the ball bearing cup 5|, which may be suitably supported on the bottom plate of the thermostat mechanism.

Thus, when the ambient temperature in the compartment in which the heater is placed falls below the predetermined minimum to which thermostat 49 is adjusted, the crank section 50 will be moved by, thermostat 49 to cause a clockwise rotation of valve stem 43 (Figure 4) to open the valve jet 39 and allow gas to pass from valve chamber I 5 into burner nozzle 49, provided, however, that the safety shut-ofi" valve nozzle 34 has previously been opened as explained 'above.

In order to provide a small flow-of gas from valve chamber 15 to burner nozzle 40 when the ambient temperature is above the predetermined minimum and valve nozzle 39 is closed, so that a low or pilot flame will burn at the top of burner 20, a small by-pass passage 52 is provided, as

shown in Figure 1, between valve chamber 15 and gas passage 84. In order to control the gas flow through passage 52, a tapered needle valve 53 is mounted in the bore 54 in valve body I l with the Needle valve 53 is preferably fitted with a spring 55 and a soft packing ring 56 between the two metal washers 51 to prevent excessive gas leakage during adjustment. Bore 5 4 is preferably sealed ofi by a threaded plug 58 and a gasket 59.

Referring now to Figures 1, 5 and 6, the temperature' control thermostat 49 of the embodiment illustrated utilizes two bimetallic spirals 60 secured to' two slotted. spindles 6|, which are rotatably mounted between two plates 62 and 63.

The thermostat 49 is symmetrical about its longitudinal center line, and, in Figure 5, the left illustrates in detail its construction and the e v 2,087,582 method of adjustment, to center the pivot points' described below.

The center tongue or end 64 of each bimetallic spiral 60 is retained inthe slot 65 of its corresponding spindle 6| as shown'in Figure 6. The outermost end of each spiral 60 is provided with one or two recessed cups 66 into which the hardened steel pivot points 61 of the connecting link 68 are received. In the example shown in Figure 5 the right hand spiral has one recess, and the left hand spiral two recesses for a corresponding number of pivots on link 68.

Connecting link 68 is formed as shown in Figures 1 and 5 with-two forks 68 and 10, fork 69 being the smaller and nearer the pivots 61 and 10 being the lower and longer. Fork 69 is adapted to closely'contact the crank section 50 of the temperature control valve stem 43. I Movement of the bimetallic spirals 60 due to ambient temperature change will be communicated to link 68, causing it to rotate about a center between the pivots 61. This"causes an increasedmovement of the upper fork 69, which in turn moves crank A 58 of valve stem 43 to open or close valve 44 and gas passage 38 leading to the burner 20. The lower fork 10 is adapted to straddle the lower bearing 5|, with a limited clearance as shown, and acts as a limit stop to prevent too much motion of the link 68-and crank 58. Link 68 is therefore a floating connection between the bimetallic elements 68, whose efforts are cumulaopposite effect, and

tive, and valve stem 43. Normal side thrusts are substantially balanced, and have no appreciable effect upon the valve stem- 43, which is only actuated by motions of the cups 66 on the spirals 68 substantially parallel to link 68.

Bimetallic spirals 88 are arranged with the metal having the higher expansion coefficient on the inside so that an increase in ambient temperature will cause the spirals to unwind. This will cause the outer ends and cups 66 to move counter-clockwise with respect to spindles 8|. This movement of cups 66 will cause the link 68 to turn in a clockwise direction about-the center between the opposed pivots 81, and the fork 69 will move crank 58 of valve stem 43 to decrease or shut off the gas .to burner 28. A decrease in ambient temperature will obviously have the increase the gas flow.

'It is quite obvious that other forms of temperature responsive devices could be substituted for thermostat 49 and particularly bimetallic elements 88, but the example shown has proved quite practical in actual tests of the device.

The initial pivot adjusting device and also the temperature setting adjustment mechanism is shown in detail in Figures 1, 5 and 6. In order to center the cups 66 on spirals 60 so that the pivots 81 will be in proper alignment, each slotted spindle 8i, and therefore the spiral 68 is connected to its temperature adjusting lever 1i through the medium of a superimposed auxiliary lever 12. The bore or lever 12 through which spindle 6| passes is fitted with a tongue 13 which engages the slot 65 in spindle 6|. "The outer end of auxiliary lever 12 is adapted to be clamped to temperature adjusting lever 1i by a screw- 14 which passes through a transverse slot 15 in lever 15. A nut 16 retains the auxiliary and temperature adjusting levers 12 and 1|, the spacing washer 11, and the bimetallic spiral 68 on the spindle 6|, the spiral being prevented from slipping off the lower end by the tongue 64 seating in the bottom of slot 65.

The position of bimetallic spirals 68 with rein a clockwise direction,

'lever 18 is adjusted, that obviously governs the temthey will cause the temperaspect to pivots 61 perature at which ture control valve stems43 to open and shut the burner valve 44. This is controlled by the temperature adjusting levers 1| through the medium of the control lever 18. Lever 18 is pivoted on rivet 19 and has a downwardly depending arm which engages as shown in Figures 1 and ,5. The outer ends of both levers H are urged together and held in contact witharm 80 by a tension spring 8|.

Inasmuch as both spirals 60 are wound'in the same direction, the two adjusting levers 1| must also be moved in the same direction, which is accomplished by the arrangement shown. A suitably calibrated scale 82 on the top of plate 62 end of the scale.

to light burner 20, and assuming gas by-pass 52 to be open to a point which will allow a required minimum gas flow, the handle 21 of the safety shut-off valve stem 26 is moved which withdraws the end 25 of the valve stem from hole 24 in safetyshut-oil thermostat element 22, and also opens the safety shut-off valve 35. This permits gas from the supply tank (not shown) to how from inlet chamber l4 through passage 33 into valve chamber l5, thence through by-pass 52 into pas sage 38 and to burner nozzle 40. This gasthen may be ignited by any suitable means, such as a lighted match, at the top of burner 20. In a few seconds the safety shut-off thermostat 22 will have expanded to its latched position (not shown) against the tube of burner 20. The han- In operation,

both the levers ll may be provided, as well as limit stops 83 at the dle 21 of shut-off valve stem 26 may then be released, and tip 25 will not be ablejto reenter hole 24 in element 22 because of the displacement due to the latters expansion.

Should the ambient temperature to which the temperature control thermostat 49 is exposed'be below that at which the temperature control thermostat will have which will admit a ,large' flow of gas throughpassage 38 into burner nozzle-40 and it will burn at the top of burner 28. When the ambient temperature has risen a few degrees above the minimum desired, thermostat 49 will tend to close valve #4 and thereby reduce the rate of gas consumed. In actual practice, this temperature differential has been found to be approximately 3 degrees Fahrenheit, which is well within the tolerance specified for refrigeropened valve 44,

ator cars carrying perishable fruit and the like.

this invention has been described and illustrated 65 limited to that. arrangement, and all such modifi-. cations and changes as come within the scope ofit is to be understood that the invention is not the following claims are embraced thereby. I We claim:

1. In combination with a. gas appliance hav- "ing a burner therein, a casing, a gas passage in said casing communicating with said burner, a valve for said passage, a stem for said valve, a crank in said stem, opposed bimetallic elements adjacent said casing and responsive to ambient temperature, a floating link cumulatively actuated by said elements, said link cooperating with said valve stem crank to open said valve upon a decrease in ambient temperature and close said valve upon an increase in ambient temperature.

2. In combination with a, gas appliance hairing a burner therein, a casing, a gas passage in said casing communicating with said burner, a

10 valve for said passage, a stem for said valve, op

aeemee posed bimetailic elements adjacent said casing and responsive to ambient temperature, a floating link cumulatively actuated by said elements,

said link moving said valve stem to open said valve upon a decrease in ambient temperature and close said valve upon an increase in ambient temperature.

JOHN R. MACGREGOR. LEON T. FOLSOM. SL H. EDWARDS.

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