US3322415A - Method of drying and initial input control for modulated gas dryer - Google Patents

Description

May 30, 1967 .1. P. LUX 3,322,415

METHOD OF DRYING AND INITIAL INPUT CONTROL FOR MODULATED GAS DRYER Filed Jan. 5, 1965 2 Sheets-Sheet 1 TEMPEQA TUEE INVENTOR. dose 0 r? 460:

ATTQRNEYS ISY May 30, 1967 P LUX 3,322,415

- J. METHOD OF DRYING AND INITIAL INPUT CONTROL FOR MODULATED GAS DRYER Filed Jan. 5, 1965 2 Sheets-Sheet 2 (Jose ob P 4 ax ATTORNEYS United States Patent Corporation, Benton Harbor, Mrch., a corporation of Delaware Filed Jan. 5, 1965, Ser. No. 423,447 6 Claims. (Cl. 263) The present invention relates to heating systems, particulanly to gas fired heating systems for clothes dryers.

Typically, the length of a drying cycle in a clothes dryer is preselected by means of a timing mechanism, the operator having the option to select different drying cycles for different types of fabrics. This type of system is not entirely satisfactory since the correct drying time can vary substantially as between two loads of fabrics of the same general character.

Some improvements in operation are effected by providing a dryer assembly in which the supply of fuel gas to the burner is varied or modulated in response to the dryer drum air or exhaust air temperature. A system of this type has been described in the Fleer et al. US. Patent No. 3,084,865 issued Apr. 9, 1963. While the control device shown in this patent works reasonably well with ordinary fabrics, experience has shown that it may not be satisfactory for the drying of delicate fabrics, particularly those containing synthetic resins. This is due to the fact that there is a substantial time lag between the initial ignition of the burner at the start of the cycle, and the time at which the temperature responsive device in the exhaust of the dryer takes over and controls the inlet of gas to the burner. During this interval, the inlet temperature to the dryer drum may become quite high While the exhaust air is still at a moderate temperature. Such execessive inlet temperatures may lead to softening and even fusion of fabrics containing synthetic fibers.

One of the objects of the present invention is to provide an improved heating system for clothes dryers with a dual control, one of which is responsive to the exhaust temperature, while the other is responsive to temperatures in proximity to. the burner to control the temperature shortly after the burner is ignited.

Another object of the present invention is to provide an improved temperature control system for gas-fired clothes dryers and the like employing a pair of cooperating heat sensing elements which modulate the gas input to the burners to control the warm up time in the dryer so as to prevent scorching or fusing of delicate fabrics.

Still another object of the present invention is to provide an improved control system for gas fired burners which is relatively inexpensive and foolproof in operation.

A further description of the present invention will be made in conjunction with the attached sheets of drawings in which:

FIGURE 1 is a somewhat schematic view of a clothes dryer embodying the improvements of the present invention;

FIGURE 2 is a cross-sectional view of the gas burner control of the present invention;

FIGURE 3 is a graph illustrating temperature versus time at different locations in the dryer; and

FIGURE 4 illustrates a modified temperature sensing means which can be employed in another form of the present invention.

As shown in the drawings:

In FIGURE 1, reference numeral 10 indicates generally a gas fired clothes dryer including a rotatable drum 11 therein, with an access door 112 being provided for introducing fabrics into the interior of the drum 11. The drum 11 rotates about a shaft 13 on which is mounted a pulley 14. A suitable drive belt connects the pulley 14 to a drive motor (not shown). The periphery of the drum 11 is supported for rotation on spaced rollers 16 secured to a base 17 of the machine. Another pulley 18 is also driven by a suitable motor (not shown) and operates a blower 19 to direct heated air from the interior of the drum 11 through an exhaust generally indicated at reference numeral 21.

The burner 22 fed from a gas line 23 provides the heat necessary for drying the fabrics in the drum 11. The control of the gas feed from the gas line 23 to the burner 22 is accomplished by means of a control unit which is illustrated generally at reference numeral 24 in FIGURE 1, and which is more fully shown in FIGURE 2.

The control system of the present invention includes a pair of temperature responsive sensors 26 and 27, the former being positioned in the exhaust 21, and the latter being positioned in proximity to the burner 22. For best results, the sensor 27 is not located directly in the flame of the burner, but in sufficiently close proximity so that it responds quickly to increases in temperature at the burner. The sensor 26 includes a bulb 28 filled with a readily expansible liquid such as xylene, and is connected to the control unit by means of a line29. The sensor 27 also includes a bulb 31 connected to the control unit 24 by means of a line 32.

Turning now to FIGURE 2, it will be seen that the control unit 24 includes a valve body portion '36 having a threaded inlet 37 for receiving the gas supply line 23 in threaded engagement. Gas flow to the burner is controlled by the operation of a solenoid valve having a tapered valve seating face 38 arranged to seat against a resilient valve seat 39. The valve face 38 is attached to an armature 41 arranged for reciprocation along the axis of a solenoid coil 42. A spring 43 urges the valve face 38 into seating engagement with the seat 39, and energization of the solenoid unseats the valve face 38 from the valve seat 39 to permit gas flow from an inlet passageway 43 to a passageway 44.

Threadedly secured to the valve body 36 is a tube 46 which extends into the inlet 47 of the burner 22. At one end of the tube 46 there is provided a shouldered orifice plug 48 which has a cylindrical outlet bore 49 and an enlarged frusto-conical bore 51 communicating therewith. A valve element generally indicated at reference numeral 52 is arranged to be received in varying positions within the combined bores 51 and 49 and thereby meter the amount of gas flow entering the burner 22. The type of valve element shown in FIGURE 2 is more completely described in Fleer et a1. Patent No. 3,084,865 issued Apr. 9, 1963. The valve element 52 has a conically pointed end portion 53 whose base diameter is larger than the diameter of the cylindrical bore 49, and the included angle of the conically pointed end portion 53 is the same as the included angle of the frusto-conical bore 51 so that the tapered surface of the conical point and the wall of the bore 51 engage in seating relation as the valve element is moved toward the orifice. The tapered end ofv the valve element 53 is provided with a longitudinally extending flat surface 54 which permits a certain amount of gas to bleed through the bore 49 when the valve element 52 is seated and provides for varying the flow of gas proportional to the axial movement of the valve 52.

The valve element 52 has a reduced diameter stem 56 which is received through an apertured guide plate 57 so that the tapered end of the valve element 52 is slidably guided by the frusto-conical bore 51. Near the end of the stem portion 56 there is provided a collar 58. A spring 59 extends between the collar 58 and one face of the plate 57 to urge the valve element 52 out of seating relation with the bore 49. The end of stem 56 is threaded and receives a threaded adjustment nut 62 the position of which governs the closing of the valve as will be apparent from the subsequent disclosure. A flat leaf spring 61 is secured to the valve element 52 to bias the valve element transversely to make sure that the conical end portion 53 will be engaged with the wall of the conical bore 51 and prevent vibration of the valve element in the assembly.

The position of the valve element 52 with respect to the bores in the plug 48, is controlled in one instance by a pivoted lever generally indicated at reference numeral 64. The lever 64 includes one arm 63 having an aperture 65 through which the threaded end of stem 56 extends. Arm 63 is normally spaced from adjustment nut 62, but upon an increase in exhaust temperature above a pre determined point, the arm 63 engages nut 62 by means of operation of mechanism hereinafter described. The lever 64 is pivoted at a pin 66 and has a shorter arm portion 67 engaging a pushrod 68 of the temperature responsive device. The latter includes a rigid outer housing 69 secured to the valve body 36 by means of fastening means 71. Inside the rigid wall 69 there is a flexible wall 72 bearing against a headed end 73 of the pushrod 68. A spring 74 normally urges the headed end 73 against the flexible wall 72. When the temperature rises in the exhaust 21, however, the expansion of the liquid within the bulb 28 and the conduit 29 and contained in an expansion chamber 76 behind the flexible wall 72 exerts suflicient pressure on the flexible wall 72 to move the pushrod 68 to the left as seen in FIGURE 2, thereby pivoting the lever 64 in the counterclockwise direction about the pivot pin 66. The resulting pivotal movement of the lever moves arm 63 into engagement with nut 62 and thereby moves the valve element 52 to the right as shown in FIGURE 2 and decreases the effective area through which the gas can flow to the burner 22.

The system described thus far is one which is commonly used for making the gas feed to the burner responsive to exhaust temperatures. However, such a system is subject to the previously mentioned disadvantage that delicate fabrics might be scorched or even fused while the exhaust temperature is being built up to the point where the temperature responsive device can reduce the gas flow to the burner. To overcome this difficulty, the present invention provides a second temperature sensing means responsive to temperatures in close proximity to the burner 22. The bulb 31 is positioned fairly close to the burner 22, but not directly in the flame. The conduit 32 connected to the bulb 31 feeds into an expansion chamber 78 located on one side of a flexible wall 79 confined within a rigid wall 81. A pushrod 82 having a headed end portion 83 bearing against the flexible wall 79 is responsive to movements of the flexible wall 79 due to the thermal expansion of the liquid contained within the bulb 31, the conduit 32 and the expansion chamber 78. A spring 84 normally urges the headed end 83 against the flexible wall 79. Spring 84 is of suflicient strength to overcome the biasing force of spring 59. The opposite end of the pushrod 82 is connected by means of a pivot pin 85 to a lever 86 pivotal about a pivot pin 87.

The free or lower end 88 of lever 86, as seen in FIG- URE 2, is in registry with the end of stem 56 and abuts a rounded end 85 formed on the stem 56 so that pivotal movement of lever 88 may effect movement of the valve element 52 either to the right under the force of spring 84 or to the left by expansion of the liquid in bulb 31 which overcomes spring 84 and allows spring 59 to move valve element 52 to the left.

In modulated gas systems of the type described in the Fleer et a1. United States Patent No. 3,084,865 issued Apr. 9, 1963, the gas control valve is in its fully open position at the start of operation and gradually closes in response to an increase in a sensed control temperature at one point in the system to be controlled. In accordance with the principles of this invention the gas control valve is in at least a partially closed position at the start of operation and first moves to a more open position under the influence of a first control temperature followed by a gradual closing under the influence of a second control temperature.

Referring to FIGURES l and 2 wherein the control unit 24 is shown in its off or cold position the operation of the control mechanism of the system is as follows. The dryer motor is energized to drive the blower and the tumbling drum and at the same time burner 22 is ignited. Since the control valve is in a partially closed position the burner will supply heat at a reduced input. However, even at reduced heat input the sensing bulb 31 is heated to the point where the liquid therein expands. As the liquid in bulb 31 expands pushrod 82 is forced to the right as viewed in FIGURE 2. This movement of pushrod 82 to the right, moves the free end 88 of the lever 86 to the left as viewed in FIGURE 2 and allows stem 56 to move to the left under the influence of spring 59. Thus the control valve begins to open allowing more gas to reach burner 22 and increasing the heat input to the dryer. Obviously, as more and more heat input is supplied, the bulb 31 will be heated more and more causing more and more expansion of the liquid within the bulb which in turn allows increased opening of the control valve. Opening of the control valve will continue until stem 56 moves to a position where nut 62 engages lever 64. At this time, if sensing bulb 28 has been heated to the point where it is effective to move pushrod 68 to the left as viewed in FIGURE 2, the lever 64 will be effective to begin closing the control valve as previously described. The remainder of the drying cycle proceeds as in the prior art systems.

A graphical representation of the temperature conditions involved in the dryer will be found in FIGURE 3 of the drawings. In that figure, graph A is a representative plot of the temperature at the exhaust in the prior art systems. In the absence of the inlet control tem perature sensed by the bulb 31, the temperature in the drum adjacent to the burner 22 would rise rapidly as indicated in curve B, and would then taper off when the valve element 52 came under the control of the temperature sensing element located in the exhaust 21. As a result of the addition of the inlet temperature sensor, the temperature adjacent the burner is represented by the graph C, and includes a moderately rising initial portion which exists until such time as the bulb 31 is heated sufficiently by the burner 22 to actuate the valve element 52. Then, the rise in temperature is much more rapid and ultimately, the temperature is decreased along a gradually decreasing slope by the action of the exhaust sensing element. Graph D represents the exhaust temperature in relation to time in a dual sensor system. The rise in exhaust temperature is much more gradual than in a single sensor system, but eventually catches up after the danger of high inlet temperatures has passed. With this type of temperature-time relationship, there is no tendency to scorch or fuse the fabrics, and drying proceeds under more carefully controlled conditions than exist in the absence of the second sensing means.

It is not necessary that the second sensing means, represented by the bulb 31, be located physically in close proximity to the burner 22. As illustrated in the form of the invention shown in FIGURE 4, the bulb 31 is surrounded by an electric heating coil 97, and can be positioned remotely from the burner 22. The function of the heating coil 97 is to provide suflicient heat to the bulb 31 to open the control valve before the regulation afforded by the bulb 28 comes into effect, to thereby control operation of the valve element 52 in the interval between initial ignition of the burner, and the time when the exhaust sensor takes over.

While the principle of system operation remains the same with independent heating means it will be evident that by providing a heating means for bulb 31 which is not responsive to the temperature of the burner 22, opening of the control valve may be regulated to give a more nearly stragiht line temperature to time relationship as illustrated by graph E in FIGURE 3.

From the foregoing description it will be apparent that the principle of the invention is to provide a control system for a dryer or the like wherein the initial heat input is at a reduced rate in comparison to the heat input capacity, followed by a modulated increase in heat input either up to or below capacity, followed by a modulated decrease in heat input to a predetermined terminal amount. The method of drying provided by the principle of the invention is an improvement principally directed to a solution of the problem of synthetic fabric fusion and therefore it will be further apparent that means such as a solenoid or electromagnet 91 may be employed to deactivate lever 86 in the event it is desirable to provide a so-called normal drying cycle for the dryer wherein the initial heat input is at maximum capacity. Such a cycle would proceed in the manner of prior art modulated systems but would provide the advantage of a selection of cycles having the shortest drying time consistent with safety to the fabrics being dried.

From the foregoing, it will be seen that the control system of the present invention provides an improved means for more careful control of the temperatures involved in various portions of a clothes dryer. The system of the present invention is particularly applicable to the drying of synthetic resin fabrics which have heretofore posed substantial difiiculties in conventional dryers. While the invention has been described in connection with a clothes dryer, it is equally applicable to other dryers and in particular to laundry appliances of the combination washer-dryer type.

It should be evident that various modifications can be made to the described embodiments without departing from the scope of the present invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. The method of drying in a laundry appliance which includes the steps of (1) driving a stream of air through a drying circuit including a treatment zone to assist in drying materials placed in the treatment zone and directing gas fuel through a burner circuit for combustion at a burner located at one point in said drying circuit to temperature-condition the stream of air supplied to the treatment zone,

(2) applying a continuous biasing force to a metering device at one point in the burner circuit tending to allow full rate of flow of gas fuel through said burner circuit,

(3) counteracting said continuous biasing force with a first biasing force regulated by a control device starting the initial flow of gas fuel at an intermediate rate of flow of gas fuel through said burner circuit,

(4) removing said first biasing force to progressively increase the rate of supplying heat energy to the treatment zone and thereafter (5) counteracting said continuous biasing force with a second biasing force regulated by a control device providing a terminal reduced rate of flow of gas fuel through said burner circuit to progressively decrease the rate of supplying heat energy to the appliance,

(6) and regulating steps (4) and (5) as a function of the relative inlet and outlet conditions of the air stream flowing through the treatment zone.

2. The method of claim 1 and further characterized by controlling the removal of said first biasing force in step (4) as a function of heat input temperature into the treatment zone.

3. The method of claim 1 and further characterized by controlling the application of said second biasing force in step (5) as a function of variations in exhaust temperature from the treatment zone.

4. A heating system for a laundry appliance comprising means forming an air flow drying circuit including a treatment zone, air translating means including air inlet and outlet means for driving a stream of air flowing through said treatment zone and a burner associated with said air inlet means for adding heat energy to the air stream,

conduit means forming a fuel circuit through which a supply of gas fuel is driven to the burner for combustion,

valve means in said fuel circuit including a valve seat forming an opening through which the gas fuel flows and a valve head cooperable with said seat for controlling the flow of gas fuel to the burner,

continuous biasing means loading said valve head towards an open position,

a control device connected to said valve head and operable as a function of the treatment zone exhaust temperature to counteract said continuous biasing means and to progressively decrease the rate of supplying heat energy to the treatment zone, and

a second control device connected to said valve head and having means producing a force to counteract said continuous biasing means temporarily at the start of a drying cycle to prevent opening of said valve head,

thereby to prevent excessive temperature build up in the treatment zone before said first control device is effective,

said second control device comprising,

a temperature sensor in the air inlet means, and translation means between said sensor and said valve head to transmit from said sensor to said valve head as a function of variations of said air inlet temperature forces which are opposite to said counteracting means force. 5. A heating system as defined in claim 4 and further characterized by auxiliary heating means on said temperature sensor for selectively heating said sensor as a part of a programmed drying cycle.

6. A heating system for a clothes dryer comprising a burner,

metering means including a metering orifice positioned to introduce a fuel gas into said burner,

a valve means positioned for partial seating in said orifice to thereby regulate the fiow of gas through said orifice,

a spring urging said valve element away from seated relation with said orifice,

a first temperature responsive means located in the exhaust from said dryer,

means actuated by said first temperature responsive means to urge said valve element toward seated relation with said orifice,

a second temperature responsive element disposed in proximity to said burner,

and means actuated by said second temperature responsive means to urge said valve element toward orifice opening position.

References Cited UNITED STATES PATENTS 2,142,042 12/1938 Bowdein et a1. 3431 2,597,032 5/1952 Ray 15828 3,045,993 7/1962 Sidaris 26333 X 3,132,853 5/1964 Fleer et al. 26333 3,191,917 6/1965 Pittendreigh 26333 X FOREIGN PATENTS 926,061 5/1963 Great Britain.

FREDERICK L. MATTESON, IR., Primary Examiner. D. A. TAMBURRO, Assistant Examiner.

Claims (1)

1. 4. A HEATING SYSTEM FOR A LAUNDRY APPLIANCE COMPRISING MEANS FORMING AN AIR FLOW DRYING CIRCUIT INCLUDING A TREATMENT ZONE, AIR TRANSLATING MEANS INCLUDING AIR INLET AND OUTLET MEANS FOR DRIVING A STREAM OF AIR FLOWING THROUGH SAID TREATMENT ZONE AND A BURNER ASSOCIATED WITH SAID AIR INLET MEANS FOR ADDING HEAT ENERGY TO THE AIR STREAM, CONDUIT MEANS FORMING A FUEL CIRCUIT THROUGH WHICH A SUPPLY OF GAS FUEL IS DRIVEN TO THE BURNER FOR COMBUSTION, VALVE MEANS IN SAID FUEL CIRCUIT INCLUDING A VALVE SEAT FORMING AN OPENING THROUGH WHICH THE GAS FUEL FLOWS AND A VALVE HEAD COOPERABLE WITH SAID SEAT FOR CONTROLLING THE FLOW OF GAS FUEL TO THE BURNER, CONTINUOUS BIASING MEANS LOADING SAID VALVE HEAD TOWARDS AN OPEN POSITION, A CONTROL DEVICE CONNECTED TO SAID VALVE HEAD AND OPERABLE AS A FUNCTION OF THE TREATMENT ZONE EXHAUST TEMPERATURE TO COUNTERACT SAID CONTINUOUS BIASING MEANS AND TO PROGRESSIVELY DECREASE THE RATE OF SUPPLYING HEAT ENERGY TO THE TREATMENT ZONE, AND A SECOND CONTROL DEVICE CONNECTED TO SAID VALVE HEAD AND HAVING MEANS PRODUCING A FORCE TO COUNTERACT SAID CONTINUOUS BIASING MEANS TEMPORARILY AT THE START OF A DRYING CYCLE TO PREVENT OPENING OF SAID VALVE HEAD, THEREBY TO PREVENT EXCESSIVE TEMPERATURE BUILD UP IN THE TREATMENT ZONE BEFORE SAID FIRST CONTROL DEVICE IS EFFECTIVE, SAID SECOND CONTROL DEVICE COMPRISING, A TEMPERATURE SENSOR IN THE AIR INLET MEANS, AND TRANSLATION MEANS BETWEEN SAID SENSOR AND SAID VALVE HEAD TO TRANSMIT FROM SAID SENSOR TO SAID VALVE HEAD AS A FUNCTION OF VARIATIONS OF SAID AIR INLET TEMPERATURE FORCES WHICH ARE OPPOSITE TO SAID COUNTERACTING MEANS FORCE.

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