US3264750A - Dryer control apparatus - Google Patents

Description

Aug. 9, 1966 Filed 001;. 1, 1 963 A. BERENBAUMY DRYER CONTROL APPARATUS 2 Sheets-Sheet 1 A. BERENBAUM DRYER CONTROL APPARATUS Aug. 9, 1966 2 Sheets-Sheet 2 Filed Oct. 1, 1963 HTTO/F/VE) blower.

United States Patent 3,264,750 DRYER CONTROL APPARATUS Arthur Berenbaum, Philadelphia, Pa., assignor to Philco Corporation, Philadelphia, Pa., a corporation of Delaware Filed Oct. 1, 1963, Ser. No. 313,063 4 Claims. (Cl. 34-45) This invention relates to the drying of fabrics. It provides certain improvements in a domestic dryer of the type which exposes laundry to hot air and concurrently to tumbling agitation.

In household dryers as built and operated up to now it was impossible to obtain uniform dryness in large pieces of fabric, for instance in the surface of a tablecloth or bed sheet. Due to certain conditions, including the ordinary tumbling motion itself, balling-up of the fabrics occurred and damp spots were retained in the dried fabrics. The householder was forced either to tolerate this non-uniform drying or to use a rather expensive commercial type of dryer, provided with separate drive systems-one system for an alternately reversing tumbling basket and another for the usual unidirectional air blower. In domestic dryers, which used a single drive system, the tumbling rotation along with the blower operation was kept unidirectional, during the drying process, and the unidirectional tumbling caused ballingup and non-uniform drying.

Some special types of dryers are known, one of which reverse both tumbling and blower rotation at the start of a cooling operation. However, unidirectional tumbling has been used in all domestic machines throughout the drying operation itself, and non-uniform results have therefore persisted as a problem.

My invention provides a domestic dryer with a reversible tumbling basket, an air blower the rotation of which can be reversed with relatively low loss of air blowing power or efficiency, and means for concurrently reversibly driving said basket and blower during a drying operation. I have found that such a unit is not only inexpensive but also capable of unexpectedly effective service. When the new unit is operated with suitable cyclic reversals, during the drying process, it provides a gain in effectiveness of drying, compared with the work of the usual unidirectional dryers.

This gain is achieved despite the fact that the blower operation as such involves a slight loss of mechanical efficiency in term of volume of air delivered, against a uniform load, per unit of power applied to operate the Of course there are limits to the loss of mechanical efficiency which can be tolerated; however, so long as the arrangements are such that the mechanical loss on reversal remains within about fifty percent, as is preferred, a gain in drying effectiveness is readily obtained. This, is appears, has not been noted before.

Thus it is a primary object and advantage of my invention to provide effective control over the danger of balling-up of fabrics in a dryer, while also maintaining real economy of dryer construction. The invention has made this possible by providing the combination of a hot air blower reversible with low loss, as aforesaid; a reversible tumbling device; and simple means reversibly driving said blower jointly with said tumbling device. This arrangement is new; none of the earlier drying machines, including those with reversible drives, was equipped with a reversible blower of the indicated type. Nor did any of them operate with concurrent cyclic reversals of fan and basket, during the drying of fabrics, to utilize the peculiar relationship between mechanical efficiency of the fan and general effectiveness of the dryer.

3,264,75tl Patented August 9, 1966 Upon a study of this new technique I discovered further advantages and features thereof. I found that certain slight variations of the hot air streams, produced by the new machine, facilitate the disposal of lint removed from the fabrics in the drying operation. I also found that certain measuring impulses can very readily be derived even from the slightly varying air streams, for purposes of process control. Briefly, the new combination yields improved uniformity of drying results, as well as economy of dryer contruction; provides uniquely effective disposal of lint; and allows great simplicity of process control. For fuller explanation, I will now refer to the drawing appended hereto, wherein:

FIGURE 1 shows one form of the new dryer in exploded front perspective view; FIGURE 1A is a fragmentary rear elevational view of a detail from FIGURE 1; and FIGURE 2 is a fragmentary side view of the machine, drawn on a smaller scale.

FIGURE 3 is a diagram of dryer operation in accordance with the new method, and FIGURE 4 is a diagram of electric circuits used with the apparatus of FIGURE 1 to achieve full automatic operation under this method.

Referring to FIGURE 1: a basket 10 is provided for the drying of fabrics. Two pieces of fabric to be dried are very schematically shown at 11 and 12. The basket can be rotated about a generally horizontal axis 13 by a roller of known type, schematically shown at 14. The roller, in the embodiment illustrated, is directly actuated by shaft 15 of a reversible electric motor 16. The fabrics are thereby rotated in and with basket 10 and subjected to centrifugal force by such rotation. This centrifugal force, combined with gravity, holds the fabrics to the inside walls of the basket in the lower and side portions of the basket, but gravity overcomes the centrifugal force in the upper portions and causes the fabrics to fall away from the basket walls. Thus the fabrics are tumbled, in alternately reversing paths, as the basket alternately rotates in directions R-l, R-2. This alternately varied tumbling counteracts the ballingup of fabrics, which would otherwise occur at certain times and would interfere with uniform drying. Some details of the balling-up process, and of the method of counteracting it, will be noted hereinafter.

Shaft 15 has an extension 17, driving rotor 18 of a centrifugal air blower or fan 19. The fan, as mentioned, is reversible with a certain variation of airblowing power. As shown in the drawing, it is advantageously equipped with curved blades having concave sides, which face forwardly, that is, toward the blower outlet when approaching this outlet during normal rotation. Thus the opposite blade surfaces are convex in forward direction with respect to fan rotation in the opposite sense.

According to the new mode of operation this fan re verses with the tumbling basket during the drying process. When the blower wheel rotates in one direction r2, with concave sides forward as is usual for efficient operation of such fans, it furnishes a strong current 22 of air for the drying of fabrics 11, 12. When rotating in the opposite direction r-l, with convex sides forward, the wheel propels an air current 21 of the same order of magnitude which may, however, be about 30 or 40 or percent less voluminous than current 22, as measured against a uniform load. In this latter connection it is to be noted, incidentially, that the mass of fabrics, undergoing drying, constitutes a rather variable load. The effective area or sail-like effect of the fabrics, present in the basket during a drying run, does not remain uniform. It increases greatly when the fabrics are no longer Wet or damp but when they reach a certain degree of dryness. The amounts of air passing through the fabrics, per

second of fan rotation (either r-1 or r-2), are therefore modified at least as strongly by these varying degrees of dryness of the fabrics as by the reversal of sense of'rotation r-1, r-2. This fact, among others, had not been noted in former attempts to construct a truly effective dryer.

The drawing illustrates a conventional electric system for heating the circulating air. An air current 22-a obtained from the ambient atmosphere enters a stationary back'section of the machine, where electric heater 23 is provided in a suitable holder structure 24, and provision is made to pass the air over this heater. The hot air then enters tumbling drum through a perforated back wall 25. thereof. Used air 22-b is withdrawn through a perforated front wall 26 of the rotary drum, whereafter the air current enters a stationary collector housing 27 having an open annular front and guiding the air to suction pipe 20 of blower 19, for discharge at 28.

The drawing indicates how the. larger air currents 22-i passthrough the tumbling drum. In accordance with'the invention these larger drying currents alternate with the smaller drying currents 21, 21'. exert drying effects of the same kind and of more or-less similar magnitude. only to allow the use of a reversible blower, which in turn simplifies the combined reversible tumbling, dry- Both types of current I Their exact magnitudes are varied ing and driving system and thereby makes truly uniform drying of large fabrics available in:an inexpensive dryer,

system.

In connector housing 27, as best shown in FIGURE 1A, air is received in -.an annular chamber and is withdrawn at the bottom 27A thereof, Local velocities of air currents21 as Well as 22are much lower at the top 27B than at the bottom 27A, thereby leading to-a tendency for lint 37 to accumulate, starting in upper portions of housing 27. Such tendencies are'also encountered where obstacles, such as hinge structure 36, are interposed no the air flow in the annular chamber.

Attempts were made in the past to prevent or counter? act such collection of lint, for instance by special forms,

result of the fact that'alternate air currents R1', R-2' are caused by the alternate drum rotations, and are superposed on primary air currents 21, 22.

The dryer is shown in FIGURE 2 as having a stationary cabinet 29, provided with a door 30 suitably engaging an aperture 31 in the stationary, annular air collector housing 27, so that fabrics can be introduced into and removed from rotary basket 10 through this aperture when the door is opened. Air is prevented from passing through this aperture when the door is closed, so that air is then forced to enter collector 27 exclusively from the interior of basket 10 and thus to follow the course which has been described. Door 30 isheld in the hinge structure 36 of housing 27, shown in FIGURES l and 1A.

In the operation of the new dryer, as in any. domestic laundry drying machine, the tumbling rotation often tends to cause balling-up when the machine. is loaded with a typical load of fabrics, including a variety of items such as sheets, tablecloths and bath towels.

fabrics load still contains an average of about 30 to 20% moisture, as measured in accordance with the well-known American Gas Association (A.G.A.) test. Such a condition usually exists for a substantial time, typically 5 to 15 minutes, during a later portion of the drying cycle. During this extended portion of the cycle the. heavier fabrics, such as bath towels, may still contain 50%, or more, of water.

In FIGURE 1 the symbol 11 schematically indicates such a tablecloth or bed sheet or the like. repeatedly carries the .sheet, along with other fabrics,

This balling-up; tendency is particularly pronounced when the drying process has reached the point where a typical, completev Rotation ;R-1

4 counterclockwise up on the side of the :dryer basket. Thereupon; as forward portions of the sheet are carried to higher levels, they tend to drop back in the basket, as indicated by the folding. over of fabric-11.; Heavier fabrics (not shown). are likely meanwhile to tumble onto lower. or middle portions of sheet '11. This leads to gradual envelopment of such fabrics in outer portions of the folding sheet, and thusbeginsforrnation of a roll or ball of fabrics, Such roll or ball then continues to tumble, along with other fabrics both large and small, whereby balling-up of fabrics progresses, In some cases a ball is formed with comprises. most if not all of the. fabrics in the basket. in a mere fraction of one minute.

This can lead to very substantial vibration of the machine, continuing for several minutes, and of course the continued existence of such a ball has a very deleterious effecton the drying.- The outer layerof such a ball deprives the :inner layers of direct .contact with'the air' current, so that the outer portions become muchdrier thanthe inside; Not only are the enveloped towels and heavy fabrics left with more-retained water than the,

anddoes-so -WlthOllti10SS of economy and without impair-V ment of effectiveness in :other respects. Concurrently with the alternately reversing tumbling motions R+1, R- 2 whereby ditferentfabric portions are successively exposed, the air blower. direct-coupled .to the tumbling system'and' cyclically reversing therewith (r-l, r-2) maintains a current of drying air, wherein drying currents 21f alternate with only slightly faster CUIIBIIISE 22. of the same kind, these several air currents'being advantageously kept at approximately similar, elevated temperatures.

Thus a cycle of drying operations is used which is best shown in F'IGUR EIS and wherein successive reversals of rotation R411, R.-1-2 are applied, for instance automatically, to keep the fabrics substantially unfolded. The reversals can follow one another,- for instance at intervals of five minutes. vThey leadto a drying cycle v of formerly unparalleled effectiveness. Although incipient folding, or

formation of fabric balls may still occur, itnow occurs in successive, opposite: directions, so that it-never leads to major envelopment of fabrics.

While the fabrics: are thustreversiblyj tumbled, elevated E and slightly spaced-temperature levels are maintained in I air stream'22, ias is further shown by parallel horizontal lines TL-ll and TL-12. This can'be done automatically,

for instance by a well-known thermostat control unit 32 generally shown in FIGURE 1. The airistream is initially heated from room temperature (not shown) to level T L- 12 (FIGURELB) by operation of heater. 23. and blower =19 FIGUREil). Theheater is then alternately de-energized when temperature 11-11 is reached,; nudge-energized when the temperature-hasfallen to TL.'12 (FIGURE 3);

The energized condition of the heater produces rising. portions of the temperature .curve, drawn in full lines, while thede-energized condition produces; falling portions of said curve. This latter conditionucan also be designated outthe drying cycle, to fabrics which are kept unfoldedv and prevented from iballing-up by the successive reversing rotations R-1 1,i R- 12.

A ball of substantial size can be formed Upon a very detailed review of the new drying process it may be noted that the periodic relative cooling and heating of the air stream, provided in order to maintain the proper average temperatures, is slightly affected by the differences in velocity of said air stream, which differences are caused by the reversals of blower 19 (FIG- URE -1).

In the interest of simplicity and economy, the heater generally remains uniformly energized except when cycling off under the control of thermostat 33; the blower reversals, however, cause slightly different loads on the heater, thereby in turn producing slightly different temperatures in the air stream, for instance during relative heating. The points of change-over are indicated by breaks in the temperature curve, emphasized by the use of black dots. For comparison with the so established, exact temperature conditions, a curve of average air temperatures is shown in broken lines.

It will be clear from FIGURE 3 that successive tumbling operations R41, R-12 occur concurrently with successive heating and relative cooling operations H-II, C, H42 etc., as the tumbling system rotates in alternate directions while the blower produces drying air streams 21, 22 etc. These several operations are concurrent but not necessarily exactly in phase, thereby resulting in the slight discontinuities of direction of the temperature curve, occurring upon each reversal from R- l l to R-12 and vice versa and shown by the black dots in FIGURE 3. These discontinuities are of minor significance in comparison with the basic cycling of the heater itself, as is clearly indicated by the curve. Thus it will be seen that the application of hot dry air as effected in the new dryer operation is no less effective than in ordinary dryers, while the concurrent tumbling R-1=1, R l-2 leads to drying results of considerably enhanced effectiveness and economy.

This advantageous operation can be achieved automatically by the simple control circuit shown in FIGURE 4. The circuit includes an operating thermostat 33 which alternately provides for energization of air heater 23 and a timer motor TM. As usual a safety or high level thermostat 34 can also be provided. Initially, manual control knob 35 of switching apparatus 32 is operated to turn a shaft and cam mechanism of timer motor TM and thereby to effect contact between the several terminals T-1, T-2, T-3 of a multiple pole switch. This operation energizes a starting winding SW-l of motor 16, through a switch R-l, R-2, R-3 normally occupying the illustrated position, and thereby initiates rotation of roller 14 and tumbling basket 10 in a first direction R- l. When such rotation has been brought to some predetermined speed the starting winding is automatically de-energized, as usual, by centrifugal switch CS in motor 16 and the motor continues to operate by means of running winding RW which is now energized by a circuit L4, T-l, T-2, RW, L-Z.

The initial manual closure of switch T-l, T-2, T-3 has also energized heater 23 through operating thermostat 33, which at this time is in heater energizing position as the operating temperature levels have not been reached as yet. Heater circuit is closed from L-I via T1, T-2, T-3, 33, 34 and H to L-3. When the upward temperature limit is reached the thermostat automatically turns to heater de-energizing position and assumes a position (broken lines) wherein it energizes timer motor TM. This motor now turns the cam mechanism by a certain increment, which in most cases is insufficient to modify the positions of the cam switches. The timer motor is deenergized when the heater is re-energized upon establishment of the lower temperature limit. Cycles of alternate heater and timer operations can then repeat themselves for some time, as already noted.

Concurrently, cycles of rotor operation are effected with the help of circuits which may for instance comprise a vibration sensing control unit CU, known by itself and the function of which can therefore be described very briefly.

This unit closes a normally open switch A pursuant to rotation R 1 and consequent balling-up and incipient vibration. (It opens a normally closed switch B pursuant to rotation R-2 and consequent balling-up and incipient vibration.) Closure of switch A establishes a circuit L- l, T l, T-2, A, RR, B, L2 through a motor reversing relay coil RR which then, as indicated, reverses the position of pole R-Z in the starting system of the motor, and closes a normally open switch R4 in the circuit of a heater in a time delay unit TD. The resulting heating of this unit then causes a bimetal switch element SW slowly to open and thereafter gradually to re-close circuit for running winding RW, thus stopping motor 16 shortly after reversal of R2 and then re-starting the motor in reversed direction.

A corresponding reversal occurs if and when the reversed tumbling causes control CU to open switch B, which de-energizes relay RR and returns the starting switch pole R2 to its normal, illustrated position. Cycles of alternately reversing tumbling operations R-11, R 12 (FIGURE 3) are thus performed concurrently with heater cycles H- l-l, C, etc., until the latter cycles have moved timer TM to the point where it opens switch T 1, T-2, T3 and thus completes the operation.

As further generally indicated in FIGURE 4 the automatic cam system and timer dial are designed so that manual initial rotation of the timer dial from point h to a closes switches T- 1, T2, T-3 and T4, T S thereby energizing timer motor TM-1 irrespective of operating thermostat "OT and providing a timed drying period, wherein the dial moves from position a .to b. At this point switch T4, T-S opens, as a result of which the further operation is dependent on the position of operating thermostat OT. During each ensuing cooling cycle C (FIG- URE 3) this thermostat energizes timer TM through switch T1, T-2, T-3, thereby shifting the dial by some part of the distance from b to c. Such motions of the timer system are intermittent, as operating thermostat OT from time to time returns to heater energizing posi tion and stops the timer motor, but ultimately the timer system arrives in position 0, where switch T-4, T-5 is again closed while at this time the other switches are closed only between T-1 and T-2 and the heater accordingly is de-energized, thus providing timed cooling, from c to d.

FIGURE 4 also shows further timer positions 2, g to indicate that the illustrated system can provide for other types of operation, for instance for an air-fluff operation between positions e and f with switches T'-l1, T2, T4, T-S closed for some period of time, or a purely timed operation without intervention of thermostat control, between positions g and h. It is believed that these latter operations, which are known to the art, need not be described in further detail at this point.

Modifications of the control system are of course available in various forms, as will be obvious to persons skilled in this art. It is also possible to construct the dryer itself, as well as its driving and heating system and other attachments, in ways different from those shown in FIG- URE 1. For instance, while the motor, shalfting, tumb ling roller, and blower rotor are shown as a coaxial system, such elements can be interconnected, instead, by belting or chains or other equivalent means.

Therefore, while only a single embodiment has been illustrated and described, the details thereof are not to be construed as limitative of the invention. The invention contemplates such variations of the method and apparatus as come within the scope of the appended claims.

I claim 1. A domestic dryer, comprising a basket to reversibly tumble a load of fabrics; a heater for heating a current of air; a reversibly rotatable blower for discharge of air in uniform direction but at a slightly different rate depending on the blowers sense of rotation, to pass said current of air through said load; reversible drive means common to said basket and blower; control means automatically operable for causing energizations and deener-, gizat-ions of the heater in a program of successive periods, and for causing a cycle of reversals of the drive means to be performed during said program; and timer means for first causing operation of said control means, whereby to perform said program and cycle and thus to dry the fabrics by reversible tumbling in a current of ,hot air,

and for later causing timed operation ofsaid drive means apart from said heater, whereby to cool the fabrics by tumbling in a current of cool air.

2.'A dryer as described in claim 1, wherein said control means also includes means for automatically revers-- ing said drive means in responseto vibration of said basket.

3.'A dryer as described in claim 1 including, as part 7 of said control means, a thermostat exposed to said cur- Si spectively, saiddeenergizations and energizations of the heater.

4. A dryer as described in claim 1 including as part of said timermeans: :first' switch means operable by said timer means to cause said operations of said control and drive means; and-additional switch means in series with part :of the first switch means, for said .reversals of the drive means.

References; Cited by the Examiner UNITED STATES PATENTS FREDERICK L., 1\/I A"['IESON, JR., Primary Examiner.

WILLIAM F. ODEA, Examiner.

20 D. A. .TAMBURRO, Assistant Examiner.

Claims (1)

1. A DOMESTIC DRYER, COMPRISING A BASKET TO REVERSIBLY TUMBLE A LOAD OF FABRICS; A HEATER FOR HEATING A CURRENT OF AIR; A REVERSIBLY ROTATBLE BLOWER FOR DISCHARGE OF AIR IN UNIFORM DIRECTION BUT AT A SLIGHTLY DIFFERENT RETE DEPENDING ON THE BLOWER''S SENSE OF ROTATION, TO PASS SAID CURRENT OF AIR THROUGH SAID LOAD; REVERSIBLE DRIVE MEANS COMMON TO SAID BASKET AND BLOWER; CONTROL MEANS AUTOMATICALLY OPERABLE FOR CAUSING ENERGIZATIONS AND DEENERGIZATIONS OF THE HEATER IN A PROGRAM OF SUCCESSIVE PERIODS, AND FOR CAUSING A CYCLE OF REVERSALS OF THE DRIVE MEANS TO BE PERFORMED DURING SAID PROGRAM; AND TIMER MEANS FOR FIRST CAUSING OPERATION OF SAID CONTROL MEANS, WHEREBY TO PERFORM SAID PROGRAM AND CYCLE AND THUS TO DRY THE FABRICS BY REVERSIBLE TUMBLING IN A CURRENT OF HOT AIR,

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