US3243891A - Control devices for driers - Google Patents

Description

April 5, 1966 T. R. SMITH 3,243,891

CONTROL DEVICES FOR DRIERS Filed April 2'7, 1962 (FAse/c' United States Patent 3,243,891 CONTROL DEVICES FOR DRIERS Thomas R. Smith, Newton, Iowa, assignor to The Maytag Company, Newton, Iowa, a corporation of Delaware Filed Apr. 27, 1962, Ser. No. 190,675 4 Claims. (Cl. 34-45) This is a continuation-in-part of applications of Thomas R. Smith, Ser. No. 40,663, filed July 5, 1960, now forfeited, and Ser. No. 22,323, filed Apr. 14, 1960, now abandoned.

This invention relates to devices for directly determining the condition of fabrics employed in a control system of a machine for drying fabrics, and more particularly, to electrodes for contacting and completing an electrical circuit through fabrics.

Many attempts have been made to control the termination point of drying operations as related, directly, or indirectly, to the condition of the fabrics. Elberty Patent No. 2,045,381, for example, relies upon the change in conductivity of the fabrics as the moisture is removed in order to discontinue operation of a drying machine at the moment electrical conductivity of the fabrics, as sensed directly between conductors in the drum, attains a predetermined value.

In other control systems, the humidity of the air within the drier is measured to determine when the drying operation should be terminated, instead of direct measurements of the electrical conductivity of the fabrics, illustrated in Horecky Patent No. 2,820,304, for example. Humidity determinations are an unreliable index of the condition of the fabrics, and control. systems dependent thereon contain an inherent deficiency.

. In still other systems attempts have been made to control the termination of the drying period by thermostats in the drier. In these systems the thermostats operate to shut-off the heaters when the temperature within the drying cabinet rises above a set value which occurs when most of the clothes have been dried. Again, the control does not insure that all of the fabrics have been dried.

It is an object of the present invention to provide a control system for a clothes drier responsive to the dry condition of the fabrics being treated. It is a further object of the invention to provide a system for controlling termination of a drying operation that is responsive to the direct determination of the electrical conductivity of the fabrics, so as to obtain reliable shut-off of the drying operation. It is a still further object of the invention to provide a system whereby direct response of the control to the dryness or conductivity of fabrics is made practical or feasible for home laundry clothes driers. Further objects and advantages of this invention will become evident as the description proceeds and from an examination of the accompanying drawings which illustrate several embodiments of the invention and in which similar numerals refer to similar parts throughout the several views.

In the drawings:

FIGURE 1 is a view in vertical section, partly broken away showing a drier which incorporates the control system of the invention;

FIGURE 2 is an enlarged view in longitudinal section of one of the bafiies in the drum, illustrating the arrangement of electrodes thereon;

FIGURE 3 is a sectional view of one form of electrode of the invention; and

FIGURE 4 is a sectional view of a modified form of electrode.

Briefly described, the invention relates to a control systemin which conductors, electrodes, or probes, directly "ice contact fabrics being dried to directly determine their electrical conductivity. The conductors, electrodes, or probes, which are mounted in a revoluble drum, are made or coated with a material that is a good electrical conductor when wet or moist, but a poor electrical conductor when dry.

Referring now to the drawings, FIGURE 1 shows a clothes drier having a base frame 10 which serves as a support for upstanding channel b-ase members 11 and 12 which together with cross piece 14 support the hollow blower housing casting 17. Housing 17 includes a tubular portion 21, a divider wall 20 having a rearwardly flared inner portion defining an intake into an impeller chamber, and radially directed longitudinal webs 22 which converge toward each other to provide a retainer member 23. A passageway 26 is located between the tubular portion 21 and the bearing retainer member 23 which transverses the supporting webs Within member 23 is journalled a revoluble drum drive shaft 31 which projects from both ends of the housing 17. Affixed to drum drive shaft 31 at the rear of the cabinet is a large pulley 33 which is driven by motor 34 through motor pulley 36, main drive belt 37, a speed reduction system (not shown) and belt 40.

The opposite or forward end of the drum drive shaft 31 is rigidly connected to the drum spider member 46 which has radiating spokes 51 that support rim 52. A heat resistant sealing member 54 encircles the front periphery of blower housing 17 and the circular shoulder 55 located on the rear portion of drum spider 46.

A horizontally mounted tumbling drum has a rear wall 61 which is secured to rim 52 for support and rotation by shaft 31. Rear drum wall 61 is imperforate except for a central exhaust opening 62.

The periphery of rear wall 61 is flanged to form a supporting shoulder for the imperforate cylindrical side wall 65 which carries the clothes elevating vanes 66 for tumbling clothing within drum 60 during rotation of the latter member. Cylindrical side wall 65 is connected to the front drum wall 67.

Front wall 67 has a centrally located access opening 68 and a circular perforate portion 69 located concentrically to access opening 68. This perforate portion 69', formed by several concentric rows of holes, serves as the air intake into drum 60.

The cabinet 70 which is fastened to base frame 10 and which encloses the entire drying mechanism has an access opening 71 aligned to drum access opening 68 thereby allowing both of openings 68 and 71 to receive the door gasket 72. The door 73 is hinged to form with gasket 72 an airtight seal for cabinet 70.

Fastened to cabinet 70 is the shroud or cowling member 74. Located between shroud 74 and the front drum wall 67 is an open coil electric heating element 75 which extends completely around the inside of cowling member 74 to raise the temperature of air passing through perforate portion 69 in the front drum wall 67. It will be understood that a gas heater may be used in place of the electrical element.

Air flow into drum 60 through the perforate area 69 and into the blower housing 17 is produced by rotation of the revoluble impeller member 76 located in blower housing 17. Fan pulley 77 is connected to the driving motor 34 by main drive belt 37. The blower housing casting 17 supports a cycling thermostat 7 8 which is connected in series with the heating element 75 in order to maintain the interior of drum 60 at the proper selected drying temperature.

In order to measure the electrical conductivity or resistance for determining the condition of dryness of the 3 fabrics, electrodes or probes 80, 81 are mounted within the drum 60. In the form shown, a pair of electrodes of opposite polarity are spirally wound about each of the drum bafiles 66 to provide a maximum amount of contacting or probing surfaces exposed to the fabrics placed within the drum. As best illustrated in FIGURE 2, the electrodes are preferably set in recesses or grooves in the bafll'es containing therebetween outwardly projecting shoulders, or ridges, 95'to' prevent shorting therebetween by metallic objects sometimes attached tothe fabrics, for example, metal buttons, clips, buckles, and the like.

In order to reduce further the response of the electrodes to metallic objects, the electrodes 80, 81 are formed with materials that are good electrical conductors when wet, or moist, and relatively poor electrical conductors when dry. This may be accomplished by ordinary fabric coating as shown in FIGURE 3. As shown, the electrode 80' has an outer layer of fabric 101. The fabric is more electrically conductive when wet than dry. Other suitable coatings may include layers of chemicals having the same characteristics.

Alternatively the electrodes 80, 8 ay be formed of metals possingsimilar properties, for mple, aluminum wire with an anodic coating, as sh'own'in FIGURE 4. As shown, the electrode 80" is formed of aluminum, the outer surface of'whi'ch is anodized at 102. Special preference is given to anodized aluminum wire since it additionally resists wear and if it is chipped or worn tend'sto be self repairing in the environment of a drier.

Electrical energy is supplied to electrode 80 by lead 84 that is connected to brush 85 which engages the stationary slip ring 86 while the drum 60 is rotating. The slip ring" 86 may be supported on an electrically insulative band 87 mounted on housing 17; Slip ring 86 is in turn connected to a lead 90 which runs to the control unit 92. Electrode 81 may also be supplied with electrical energy of the opposite polarity to electrode 80 by similar arrangement of brushes and slip rings. It is preferred, however, to ground electrode 81 to the rotatable drum 60', so that it is supplied by current from lead 91 which is also grounded to the framework of the drier.

The automatic control unit 92 may be secured to the upper portion of the cabinet. Leads 90, 91 enter the control unit and are connected to the control circuit to be described hereinafter.

Bafiles 66 are formed of electrically non-conductive material in order to insulate the electrodes. However, the electrodes are electrically shorted by contacting the wet fabrics during tumbling. Ordinarily, a plurality of baffles 66 are mounted within the drum 60, each of which is provided with electrodes 80, 81, and the respective electrodes of'all the battles connected in parallel although a single baflie provided with electrodes may be used. Referring now to FIGURE 2, which illustrates the baffles in detail, the wire electrodes 80, 81 are spirally wound on the surface of the baflles; the ends 96, 9'7 being secured to the bottom interior of the baffles by suitable insulators. The leads 83, 84 from the electrodes are elect'r'ically connected to the control system and are preferably insulated. To further insure minimum current leakage from electrodes 80, 81,. insulation may be advantageously provided on the entire electrode except in the area of fabric contact, namely, the crown area 93 of the baflles. In the crown area 93, the electrodes are bare to permit electrical shorting by Wet fabrics during tumbling.

The bafiles may be formed of synthetic resinous materials so as to be electrically insulative, and may be hollow. The shoulders, or ridges 95 are molded into the surface. Screw sockets 99 are formed in the base of the bafiles for mounting to the interior surface of the drum.

Since the electrodes contact the fabrics for determining fab c e e t i al conducti ity, sh ing f t e e e trodes by metallic objects is, of course, undesirable. By positioning shoulders, or ridges 95, however, between ad acent electrodes of a height greater than the outer diameter of the electrodes, simultaneous contact by flat'metallic objects of adjacent electrodes is avoided. Thus, fabrics because of their limp, flexible nature, drape over the shoulders, or ridges to complete an electrical circuit through the electrodes. On the other hand, metallic objects because of their inherent rigidity, are prevented from contacting adjacent electrode pairs by the shoulders, or ridges 95. The result is selective determination of fabric electrical resistance.

In addition, because the electrodes are formed of ma terials that are good electrical conductors when wet and poorer electricalconductors when dry, as explained 'hereinabove, response of the automatic control unit to the electrical properties of metallic objects in the load are reduced.-

In the drawings and specification there have been set forth several embodiments of the invention, and although specific terms are employed, these are used in a generic and descriptive sense only, and not for purposes of limitation. Changes in form and the proportion. of parts, as well as the substitution of equivalents are contemplated, as circumstances may suggest or render expedient, without departing from the spirit or scope of this invention as further defined in the following claims.

I claim:

1. In a drier having an electrical control system for termination of the drying operation, a revoluble drum for tumbling the fabrics, means for rotating said druirr to tumble the fabrics, heating means for drying fabrics in said drum, and at least one pair of spaced electrodespositioned within said revoluble drum for contacting the" fabrics as they are tumbled, said electrodes including meis tu're absorptive material on the surface of at least one of said electrode pair with the absorptive material on said' one electrode being spaced and insulatedfrom the second of said electrode pair, said absorptive material being a good electrical conductor having conductance characteristics above a first value when moist for selectively ef-' fecting completion of a circuit through the fabrics con" tacting said pair of electrodes when said fabrics are wet? and preventing completion of a circuit through said ah sorptive material in the absence of contact by said wet" fabrics, and further being a relatively poor electrical conductor having conductance characteristics below said first value when dry for preventing completion of a circuit through metallic objects when said fabrics are dry.

2. In an apparatus for drying fabrics having a control system for terminating the drying operation a revoluble drum for drying fabrics, means for rotating said drum to tumble the fabrics, heating means for drying fabrics in said drum, at least one bafile member mounted on the interior surface of said drum for engaging the fabrics, at least one pair of spaced electrodes positioned onsaicl baifie member, said electrodes including moisture absor tive material on the surface of at least one of said electrode pair, said absorptive material being a good electrical conductor having conductance characteristics above a first value when moist and relatively poor electrical conductor having conductance characteristics below said first value when dry, and insulation means covering a first portion of at least said one electrode, and absorptive material said one electrode having a second portion exposed for contact by the fabrics to selectively limit completion of a circuit between said pair of electrodes to an electricaf path through the wet fabrics.

3. In a drier having a control system for terminating; the drying operation, a revoluble drum for drying fabrics; means for rotating said drum to tumble the fabrics, heat-. ing means for drying fabrics in said drum, baffle members; mounted on the interior surface ofsaid drum for engag-. i s he fab i t l ast one of said bafile membersformed of electrically insulative materials, and at least one pair of spaced electrodes positioned on said baffle member, said electrodes including moisture absorptive material that has relatively higher electrical conductivity when moist than when dry on the surface of at least one of said electrode pair, the absorptive material on said one electrode being spaced and insulated from the second of said electrode pair of selectively effecting completion of a circuit through the wet fabrics contacting said pair of electrodes and preventing completion of a circuit through said absorptive material in the absence of contact by said wet fabrics.

4. In an apparatus for drying fabrics, having a control system for terminating the drying operation, a revoluble drum for drying said fabrics, means for rotating said drum to tumble the fabrics, heating means for drying said fabrics in said drum, and at least one pair of spaced electrodes positioned within said drum and electrically exposed for contacting the fabrics as tumbled, said exposed electrodes including moisture absorptive material that has relatively higher electrical conductivity when moist than when dry on the surface of at least one of said electrode pair, the absorptive material on said one electrode being spaced and insulated from the second of said electrode pair.

References Cited by the Examiner UNITED STATES PATENTS 1,526,127 2/1925 Flick 204-58 2,045,381 6/1936 Elberty 34-55 2,234,858 3/1941 Brown 338-35 2,237,006 4/1941 Koller 338-35 2,364,996 12/ 1944 Osterheld 338-245 2,381,299 8/1945 McCulloch 338 2,617,972 11/1952 Nutter 33835 2,714,149 7/1955 Craig 33835 2,793,526 5/1957 Dalglish 33835 2,820,304 1/1958 Horecky 34-45 2,991,641 7/1961 Woodling 34-45 X FOREIGN PATENTS 877,553 9/1961 Great Britain.

OTHER REFERENCES Publication: Electronics (Maytag Electronic Dryers), 10 pages, 1960.

ALDEN D. STEWART, Primary Examiner.

NORMAN YUDKOFF, PERCY L. PATRICK,

Examiners. JOHN J. CAMBY, Assistant Examiner.

Claims (1)

1. IN A DRIER HAVING AN ELECTRICAL CONTROL SYSTEM FOR TERMINATION OF THE DRYING OPERATION, A REVOLUBLE DRUM FOR TUMBLING THE FABRICS, MEANS FOR ROTATING SAID DRUM TO TUMBLE THE FABRICS, HEATING MEANS FOR DRYING FABRICS IN SAID DRUM, AND AT LEAST ONE PAIR OF SPACED ELECTRODES POSITIONED WITHIN SAID REVOLUBLE DRUM FOR CONTACTING THE FABRICS AS THEY ARE TUMBLED, SAID ELECTRODES INCLUDING MOISTURE ABSORPTIVE MATERIAL ON THE SURFCE OF AT LEAST ONE OF SAID ELECTRODE PAIR WITH THE ABSORPTIVE MATERIAL ON SAID ONE ELECTRODE BEING SPACED AND INSULATED FROM THE SECOND OF SAID ELECTRODE PAIR, SAID ABSORPTIVE MATERIAL BEING A GOOD ELECTRICAL CONDUCTOR HAVING CONDUCTANCE CHARACTER-

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