US2660806A - Clothes drying system - Google Patents

Description

, 1953 H. A. WHITESEL CLOTHES DRYING SYSTEM Dec. 1

2 Sheets-Sheet 1 Filed July 18, 1950 INVENTOR #Amy 4. awn-1a. BY

M a; 46''A 7/ Dec. 1, 1953 H. A. WHITESEL CLOTHES DRYING SYSTEM 2 Sheets-Sheet 2 Filed July 18, 1950 INVENTOR.

WAX/4') 14, W/V/Ti/[Z naonno'baoooda n a o a o c O a o O 0 ooooouooocooo Patented Dec, 1, 1953 UNITED STATES PATENT OFFICE CLOTHES DRYING SYSTEM Harry A. Whitesel, Abington, Pa., assignor to Philco Corporation, Philadelphia, Pa., a corporation of Pennsylvania Application July 18, 1950, Serial No. 174,485

3 Claims. 1

The invention hereinafter disclosed and claimed relates to a method of and apparatus for drying fabric articles such, for example, as clothing and the like, and is especially concerned with driers of the type commonly used for household laundry purposes.

While of broader applicability, the concepts of the present invention are of particular utility when embodied in apparatus which includes a heat pump operable, in a continuous refrigeration cycle, to heat the air brought in contact with clothes to be dried and, subsequently, to condense-out moisture from the circulating stream of drying air.

In considering the apparatus of the present invention it is to be borne in mind that household drying machines of several types have for some time been available, notable among these earlier machines being tumbler type driers employing electrical resistance elements to heat the drying While the tumbler type of machine is advantageous in that it imparts considerable flufliness to the clothes during the drying operation, such machines, in common with other types hereto fore available, have given less than complete satisfaction for a variety of reasons. Importantly, in the apparatus of the prior art the heat and moisture transfer characteristics have not been good and, additionally, the power requirements of the machines have been unduly high. Further, while both the earlier machines and the machine of my invention require power for circulation of air, the apparatus of this invention differs from machines commonly used heretofore in that there is no rotating drum, with its attendant mechanical complexities and power requirement. Highly satisfactory results have been obtained with apparatus constructed in accordince with this invention, in which apparatus the total power input is no greater than 1 /4, l:.w., whereas the power input to previous machines frequently amounted to more than i kw. A difference of this order is, of course,

reflected in a substantial reduction in operating 1 costs.

Most prior machines have also been disadvantageous for the reason that the clothes are subjected to excessive wear and tear in the drying process, this wear and tear resulting in the formation of a large amount of lint which tends to clog the air flow passages and creates a service problem. Finally, driers of the type commonly in use at this time require 220 volt circuits in the household wiring and, in most in- 2 stallations, the machines discharge many pounds of water into the air of the room in which they are installed, thus creating a serious condensation problem.

Thus, and. with the foregoing in mind, it is a primary object of my invention to provide a novel and eifective clothes drying system in which clothes may be dried under conditions such that the heat and moisture transfer rates are considerably more rapid than those obtained by conventional driers and the power require ments are very substantially reduced. In the achievement of these general objectives, the apparatus of the invention utilizes means for maintaining a pressure differential across the clothing so that the drying air is forced or drawn through the clothes, rather than merely being blown over the exposed surfaces of the fabric.

The air films between fabric strands are narrower than those formed on the outer surface of cloth, and, since both heat transfer and moisture diffusion rates improve with decreased film thickness, my novel system of drying is highly effective. This phase of the invention will be considered more fully in a subsequent portion of this specification.

The invention also has as an object the provision of household drying apparatus in which no special wiring is required and the moisture removed from the dried clothing may be disposed of conveniently through an ordinary drain.

It is an additional feature of my novel drying system that highly effective drying and satisfactory fiuiiiness are achieved without the necessity of resorting to tumbling devices, and a novel foraminous rack or barrier is, in the preferred embodiment, utilized to achieve this advantage.

The invention further extends to certain novel structural details and arrangement, hereinafter described and shown in the accompanying drawings, which illustrate a preferred embodiment of my invention.

In the drawings;

Figure l is a View, in perspective, of a cabinet type drier incorporating apparatus constructed in accordance with the invention;

Figure 2 is a sectional illustration, on an enlarged scale, taken generally through the ver tical, longitudinal midplane of the apparatus illustrated in Figure 1;

Figure 3 is a sectional view taken as indicated by the line 3-3, applied to Figure 2;

Figure 4 is a fragmentary view of a section of metallic foraminous material which may to ad- 3 vantage be utilized in the rack or barrier above referred to; and,

Figures and 6 are diagrammatic views showing the manner in which fabrics are disposed upon the racir, or barrier, and illustrative of the manner in which a pressure differential is caused to exist across the clothing to be dried.

Now making more detailed reference to the drawings, and initially to Figures 1 and 2 thereof, it will be seen that the drying apparatus of my invention may conveniently be housed in a metallic shell forming a conventional rectang w lar cabinet indicated, generally, by the reference numeral Iii. The cabinet is provided with a topaccess opening H adapted to be closed by a lid shown at I2.

Within the cabinet, and in especial accordance with the invention, is disposed a drying rack l3 which is preferably corrugated, or serpentine in cross-sectional configuration, as appears to good advantage in Figure When viewed in plan, the Width of the raclr structure is such as to span the distance between the vertically extending front and back walls of the cabinet. The right hand end of the rack structure, as viewed in Figure 2, is secured to an adjacent end wall of the cabinet, as is shown at M, whereas the left hand end of the structure bears against an upstanding baiile l5, as shown at Ill. The bafiie also spans the distance between the front and rear walls of the cabinet and comprises a portion or the duct work which directs the drying air across the upper surface of the rack. It is desirable that the edge portions of the rack lie closely adjacent the cabinet walls, to avoid leakage of air.

As indicated hereinabove the rack constitutes a foraminous barrier interposed in the path of the circulating air and, to this end; it is preferably fabricated of sheet metal provided with a multiplicity of small apertures or piercings ll, these being shown to good advantage in Figure 4'. While a perforated metal raclc is to preferred, it will be understood that, insofar as the broader aspects of this invention are concerned, the rack may be fabricated of other materials uch, for example, as relatively heavy fabric. Further, certain of the advantages of the invention may be realized without corrugating the barrier or rack, although the corrugated arrangement is to be preferred.

The spacing and diameter of the apertures ll isbest determined in the light of the type of use to which the machine is to be put, since the ratio of apertured area to total area dependent upon the amount of drying surface incorporated in the rack and upon the differential air pressure to either side of the raclc. The cabinet should be sealed. Also, to at least some extent, the average thickness of the fabrics to be dried may to advan tage be kept in mind in designing the rack. Clothes to be dried are draped or arranged across the rack structure, preferably in such a way as substantially to cover the rack, and the raclr. is such as to meet the requirements of this invention, if, when supporting. a normal amount of clothes to be dried, there exists an appreciable pressure difference across the clothes when the machine is in use. The difference in pressure be,- tween the space above the rack and the space just below the same may advantageously be approximately equal to A; inch of water, when the rack is not loaded with clothes, and in the reg on of to inch of waterwhen the rack is loaded and in normal use.

As is shown in Figure 2, the space within the cabinet is divided, through the agency or" a hori- Zontally extending partition or baiiie l8, into an upper compartment 19 which houses the rack, and a lower section 2! within which is disposed a blower and the elements of the drying apparatus. The blower, indicated at 2 i, is of the centrifugal type and is provided with a scroll which terminates in an upwardly presented mouth or opening through which air discharged by the blower is forced upwardly behind the baffle and is discharged across the upper surfaces Ci the rack structure l3 through an aperture 23 formed by disposing the uppermost edge of the baffie iii at somedistance beneath the lid l2. The blower is, in the embodiment illustrated, driven by a motor shown at 2d, through the agency of the illustrated pulley and belt assembly.

In one aspect of the invention, it is of significance that a heat pump is employed-in combi nation with the novel rack or barrier-the heat pump serving to heat the air brought in contact with the clothing, andto condense moisturefroin the stream of dryin air; This heat pump com,- prises a complete refrigeration system including a compressor 25, condenser 29; and evaporator 2%, the aforesaid elements being connected inseries flow circuit through the agency of suitable. suction and feed conduits 2a and 29; r sp tiv As will be understood, this refrigeration: system, per se, is conventional in nature and includes a suitable flow restrictor (not shown) such for example as a capillary tube, and thesystem is operable in response to closingof: the switch. appears ing at it, and through the agency ofwhichswitch the compressor is connected across the supply line The refrigerant passes through a. con.- tinuous cycle, when the machine is in operation, during which cycle air is heatedby the condenser 25, forced upwardly and across the-top of'the racl: by the blower 2|" and, after passing through the meshes of the clothes arranged upon the rack, the circulating air is confined by the earlie it in such manner as to pass through evaporator 21;. In passing in heat exchange relation with the evaporator, which may, for example, bemains tained at about F., the air is cooled and a substantial portion of the moisture absorbed in passing through the damp clothes is condensed out and delivered to a sump 33, from whence it may be disposed of in any convenient *nanner.

For proper drying of the clothes efiicient operation of the heat pump, the circulating air should be at a temperature considerably in excess of normal ambient temperatures, A temperature of about 166 F. is desirable, and both the heat pump and the cabinetry are designed with this in mind. The cabinet is, of course, so ned as to minimize heat loss therefrom. In order to raise the circulating air to this temperature without objectionable delay, there proviced a resistance heating element 34 connected across the supply line 32 through, a therrnosensitive switch blade 35. When the drier is placed in operation, by closing of the switch {lathe heater energized and remains in operation until the circulating attains the predetermined temperature desired, at which time switch blade 35 moves awayfrom its associated contacts and breaks the circuit to the heater 34.

As indicated hereinabove, the heat transfer and moisturediffusion rates are unusually good in the apparatus of my invention, and the power requirements are very low. ihe basis for achievement of these advantageous results: will now be explained.

aeedsbe When cloth is dried by air blown over its surface, there is a laminar film of air next to the cloth through which the heat from the air must be conducted and through which the evaporated l isture must be diffused. The thickness of this 1' 1n varies with the air velocity, but it is generally much greater than the distance between strands of cloth. This means that when air is forced "'hrough the cloth the thickness of air film hrough which heat or moisture must be transferred is less than for the surface type of drying. Consequently, the rates of heat and moisture transfer are greater. Also, the amount of fiber surface exposed to the air is greater in the case where air is drawn through the cloth, which further increases the total quantity of heat transferred for a given amount of cloth face surface and for given air temperature and water vapor pressure conditions.

Further, and with particular reference to the unusuaily low power requirement of machines embodying the present invention, it is to be borne mind that water evaporates from fabrics at the wet bulb temperature of the surrounding air. Sensible heat from the air flows into the clothes as a result of the differential between the dry and wet bulb temperatures, whereas water vapor containing latent heat flows away from the clothes as a result of the differential in vapor pressure between the water in the cloth-which corresponds to the wet bulb temperature-and that in the air, which corresponds to the dewpoint temperature.

Because of the more efficient heat transfer when the clothes are dried by forcing air through them, the temperature and vapor pressure differences are less than when clothes are dried by blowing air across their exterior surfaces. The lesser total temperature differential between dewpoint and dry-bulb causes a correspondingly lower difierential between the evaporator and condenser temperatures of the heat pump system. The reason for this is that the evaporator removes the moisture from the air and the evaporator temperature has a fixed relation to the dew-point temperature of the air, while the condenser adds sensible heat to the air and its temperature has a fixed relation to the dry-bulb temperature of the air. The power required to drive a heat pump at a given evaporator temperature decreases with a decrease in the temperature differential between evaporator and condenser.

The aforesaid differential between air dry-bulb and dew-point temperatures does not affect the power input to a conventional clothes drier, which uses electrical heat directly, and reduction in said differential does not, therefore, result in a saving of power in clothes driers utilizing resistance heaters.

Returning, for summary purposes, to a con sideration of the apparatus in use (reference should be made to the diagrammatic representations of Figures 5 and 6), the clothes to be dried are hung or draped across the peaks and through the valleys which define the serpentine racla it, it being desirable that the rack be substantially covered with articles to be dried. The position occupied by the fabrics, prior to initiation of operation of the machine, is illustrated in Figure 5 from which it will be apparent that the fabrics F are draped loosely across the convollltions of the rack.

Due to the pressure drop occasioned by the fact that the loaded rack constitutes a foraminous barrier, the clothes bear tightly against the structure of the rack when the machine is placed in operation, this condition being illustrated in Figure 6. At the conclusion of an operating period, of duration sufficient to cause complete drying of the clothes, operation of the heat pump and of the blower is discontinued and the dried fabrics may be readily lifted from the machine.

While a preferred embodiment of my invention has been illustrated in the accompanying drawings and described in this specification, it will be evident that the invention is susceptible of various changes and modifications, without departing from the essential spirit thereof. it will be understood, however, that such changes and modifications are contemplated as may come within the terms of the appended claims.

I claim:

1. In apparatus for air drying fabric articles, a cabinet, partition means dividing the interior of said cabinet into a pair of separate compartments, a foraminous support member upon the upper surface of which fabric articles are draped during drying, said support member extending through one of said compartments and spanning the distance between the walls thereof to subdivide the latter into an upper chamber and a lower chamber, the foraminous nature of said support member providin restricted communication between said chambers, means including ductwork providing communication between the other of said compartments and said upper chamber, means providing a passage in said partition through which the said other compartment is in communication with said lower chamber, air heating means within said other compartment, and means for causing a forced circulatory how of air from said other compartment through said ductwork and into said upper chamber, the air thence passing through the fabric articles and the support member and thereafter flowing from said lower chamber through said passage and into said other compartment.

2. Apparatus in accordance with claim 1, and further including a refrigerating system having an evaporator disposed in the path of air flowing from said lower chamber through said passage and to said other compartment, said sys tern further having a condenser disposed in the path of air flowing through said other compartment and toward said upper chamber.

3. In apparatus for air drying fabric articles, a cabinet, partition means dividing the interior of said cabinet into an upper compartment and a lower compartment, a corrugated support member upon the upper surface of which fabric articles are draped during drying, said support member extending through said upper compartment and spanning the distance between the Walls thereof to divide the latter into an upper chamber and a lower chamber, said member further being perforated to provide restricted communication between said chambers, duct means extending through said partition means and providing communication between said lower compartment and said upper chamber, means providing a passage through said partition and placing said lower chamber in communication with said lower compartment, air propelling means having an intake disposed in communication with said lower compartment and an exhaust disposed in communication with said duct means, so as to induce a forced flow of air from the exhaust through said duct means into said upper ohambeiy thence through the fabric. articles and the said support member into said lower chamber, and thereafter through saidpas-. sage, and lower compartment to the intake, of said propelling means, and a. refrigerating sy tem having an evaporator disposed in the path of air passing out of said lower chamber and into said lower compartmentand having a con, denser disposed. in the path. of, air passing through said, lower compartment. toward said upper chamber.

HARRY A. WHITIESEL.

Referenees Cited in the file of" this patent UNITED STATES. PATENTS Number Name Date 761,041 Gathmann May; 24,1904

Number Number 15 ,117 9. 3 214.62

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