FIELD OF THE INVENTION
- BACKGROUND OF THE INVENTION
The present invention relates to methods and apparatus for drying articles using a combination of heating and cooling elements incorporated into the spin cycle of a washing machine.
Current household clothes washers use water as the cleaning fluid. Normal horizontal and vertical axis washers use anywhere between about 60 liters (16 gallons) and about 189 liters (50 gallons) to wash a typical load of clothes. A large amount of energy is expended in the conventional wash process due to the use of hot water to improve wash effectiveness and the hot air drying process during which the retained water is evaporated. The high energy requirements of conventional home laundry systems increase the operational cost for the consumer and puts a strain on the environment, depleting natural resources and contaminating water.
Recently, use of a cyclic siloxane composition for washing purposes was disclosed in U.S. Pat. No. 4,685,930 and No. 6,063,135, which is intended to replace conventional perchloroethylene (PERC) professional dry cleaning solvent, which has been shown to be hazardous to human health as well as a danger to the environment. Additionally, the use of a siloxane solvent in laundering has shown to result in reduced wrinkling, superior garment care and better finish than water washing. Current technology provides dry cleaning machines that use the cyclic siloxane dry cleaning process in both home and commercial settings. Further improvements on washing using a cyclic siloxane and siloxane/water mixture have also been suggested. The present invention augments this implementation with a specific methodology that optimizes the spin and dry cycle.
Centrifuging or spin extraction of the solvent at the end of the wash process is not a new idea. This is a common and effective method of extracting the solvent prior to commencement of the drying cycle. By removing wash solution through centrifugation, less heated drying time is required which is energy expensive. Thus, removing wash solution through centrifugation has a much lower energy cost than heated drying, however there is a limit to the amount of wash solution that can practically be removed during spin extraction.
Most dry-cleaning and water-wash processes involve a spin extraction cycle. Literature on the commercial implementation of a siloxane-based system includes a spin cycle, generally at about 350-750 rpm. Often this spin cycle is accompanied by heated air or a vacuum stage to enhance the evaporation of the wash solution. These aspects of spin/dry cycles are discussed in U.S. Pat. Nos. 6,063,153 and 6,086,635.
While these spin and dry cycles do produce a dried article, they do not have the combined advantages of energy savings and minimized dry time that overcome the disadvantages of high energy and operational cost associated with prior art spin and dry cycles. These cycles are merely a carryover from traditional spin and dry cycles used in common water based washing machines. There have been no significant improvements to these cycles in recent years.
- SUMMARY OF THE INVENTION
Thus, there is a need for an integrated wash and dry system design in a siloxane-based home laundry machine that minimizes the overall cycle time and energy usage. It would be desirable to implement a spin and dry cycle while simultaneously conditioning the system using a cooling unit, heating unit and optionally a supplemental heater to lower the solvent retention in the washed articles. Furthermore, specifically optimizing the system to minimize total cycle time and energy usage through the use of the components in a particular sequence has not been addressed in the prior art. It is to these perceived needs that the present invention is directed.
The present invention provides a drying methods utilizing a combination of features during the spin cycle of this laundry machine to minimize cycle time and energy usage. Specifically, this involves including a heating system, which heats the drum during the spin cycle resulting in lower retention at the end of the spin cycle, and conditioning of the air through a condenser. Design implementation involves several features that are specifically designed for consumer use in an in-home or coin-op laundry setting. These features ensure the entire unit fits within the space envelope of a conventional home laundry system, low cycle time and energy usage and ability to operate the machine on normal house power outlets, i.e. from 100 to 250V.
In an embodiment of the present invention, a method for drying articles is provided comprising, providing a wash basket within a wash drum inside a washing machine and an air stream which follows an air flow path through the wash basket and through the machine. Then engaging a heating unit located along the air flow path, engaging a cooling unit located along the air flow path, and spinning the wash basket with the heating unit and cooling units engaged.
In another aspect of the present invention, an apparatus for drying articles is provided comprising, an air stream which follows an air flow path through a washing machine comprising a wash basket, a heating unit located along the air stream, a cooling unit located along the air stream, and a supplemental heater located along the air stream.
The present invention includes an apparatus and method used in conjunction for the spin extraction and drying cycles during cleaning of fabrics, textiles and the like at home or in a coin-op laundry setting. The methods and apparatus of the present invention are particularly well suited for solvent based cleaning.
Features of a method for drying articles of the present invention may be accomplished singularly, or in combination, in one or more of the embodiments of the present invention. As will be appreciated by those of ordinary skill in the art, the present invention has wide utility in a number of applications as illustrated by the variety of features and advantages discussed below.
BRIEF DESCRIPTION OF THE DRAWINGS
As will be realized by those of skill in the art, many different embodiments of a method for drying articles according to the present invention are possible. Additional uses, objects, advantages, and novel features of the invention are set forth in the detailed description that follows and will become more apparent to those skilled in the art upon examination of the following or by practice of the invention.
FIG. 1 is a diagram of a washing machine including an embodiment of the present invention.
FIG. 2 is a diagram of an embodiment of the system of the present invention.
FIG. 3 is a diagram of the vapor compression system of an embodiment of the present invention.
FIG. 4 is a diagram of an embodiment of the present invention wherein the supplemental heater receives heat from the compressor.
FIG. 5 is a chart showing wash fluid retention as a function of spin acceleration.
FIG. 6 is a chart showing wash fluid retention as a function of spin time.
In a first aspect of the present invention, an apparatus for drying articles is provided in which the articles are dried after a cleaning process wherein the drying is achieved in less time and at a lower energy cost than has been previously achieved. The components of the drying apparatus may be employed in a home based or coin op laundry machine, or scaled up in a commercial laundry. This application describes an embodiment comprising the home based washing machine, specifically a washing machine designed for home use that uses a cyclic siloxane wash fluid, a water based wash, or a combination of the two. However, it is well within the scope of this invention that the methods and apparatus disclosed herein may be employed in washing machines of any size.
Referring to FIG. 1, the apparatus of the present invention comprises a washing machine 10 designed to use a siloxane based dry cleaning fluid, water, or a combination of siloxane based cleaning fluid and water. It is recognized that the present invention may be employed with other solvent-based cleaning systems to decrease dry cycle time and energy costs.
The term “articles” as used herein describes generally fabrics, textiles, garments, linens, and any other material commonly cleaned in a home water based washing machine, or commercial dry cleaning apparatus.
In one embodiment of the present invention, the apparatus for drying is incorporated into a washing machine 10 generally comprising a wash basket 20 enclosed in a wash drum 22. The wash basket 20 is perforated or otherwise has apertures therein to allow liquid and vapor to pass through while retaining the articles. The wash drum has a wash fluid entrance port or ports 54 through which wash fluid is pumped from a reservoir 50 by a pump 40. In other embodiments of the present invention, the wash fluid is allowed to drain via gravity into the wash drum 22. The wash basket 20 is rotated by means of a motor 30 and drive system. The motor and drive system are capable of spinning the basket 20 at various speeds, for example at high speed for a spin cycle and a lower speed for a tumble/dry cycle.
The washing machine 10 also comprises a wash fluid exit port or ports 60 in the wash drum 22 which allow the wash fluid to drain away from the articles upon completion of a wash cycle. Additionally, there is a wash fluid drainage line 12 from the chiller to collect and transport condensed wash fluid vapor. The wash fluid is drained into a working tank 54 for storage or disposal. In one embodiment of the present invention, the wash fluid is fed into a cleaning or regeneration system 13 to clean the wash fluid, separate any water from the siloxane based fluids and return the cleaned wash solution to the fluid reservoir 50.
The apparatus of the present invention is incorporated into the aforementioned washing machine, or a similar machine through the addition of a blower 80, heating unit 90, and chiller/vapor compressor 11 as seen in FIG. 1. FIG. 2 shows the article drying apparatus 100 of an embodiment of the present invention. Air entering the wash drum 10 is heated by a heating unit 120 to increase the temperature of the air entering the wash drum 10 and thereby increase the rate of evaporation of wash fluid from the articles into the air stream.
Additionally the entering air is conditioned to provide maximum wash fluid evaporation and absorption before leaving the drum 110. The air is conditioned through a cooling unit comprising a chiller 130 that condenses vapor in the air and provides a drier air stream capable of absorbing more wash fluid. This vapor compression cycle comprises cooling coils 130 that have a refrigerant, for example fluorocarbon R-22, as a working fluid. The refrigerant is condensed using a compressor as is known in the art and allowed to expand in the cooling coils while absorbing energy. As the air stream passes the cooling coils 130, any vapor, be it siloxane vapor or other cleaning fluid, will condense leaving the air stream drier and able to pick up more cleaning fluid as it passes through the wash basket.
The amount of condensate will depend on a number of factors including the relative saturation of the air, the rate at which heat is extracted through the cooling coils and the surface area of the cooling coils, as well as other factors known to those skilled in the art. The properties of the cleaning fluid, such as vapor pressure, will also affect the rate of condensation. Thus, the size of the cooling coils and compressor will vary depending on the needs of the particular application, and will be apparent to one skilled in the art.
In another embodiment of the present invention, the heating unit and cooling unit together comprise a vapor compression system. Such a system is commonly known as a heat pump or vapor compression system and is shown in FIG. 3. The vapor compression system comprises the heating unit 120, the chiller 130 a compressor 135, a pressure reducing device 125, and a working fluid, such as a refrigerant like fluorocarbon R-22. The compressor 135 compresses the working fluid causing it to become a hot high pressure gas. This hot compressed gas runs through the heating coils in the heating unit 120 where some of the heat is transferred to the air stream cooling the working fluid and turning it into a liquid. The liquid working fluid runs through an expansion valve 125 where it is allowed to expand and become a cold low pressure gas. This cold low pressure gas then passes through the cooling coils where the gas absorbs heat from the air stream. This cools the air stream and causes moisture in the air stream to condense on the exterior of the cooling coils. At the same time the working fluid absorbs this heat and returns to the compressor 135.
In a further embodiment of the present invention a supplemental heater 140 is provided to assist the heating unit 120 in heating the air stream prior to entering the wash drum 110. In one embodiment of the present invention, the supplemental heater 140 comprises a resistive element 142, which is used to heat water that carries heat to a heat exchanger in the supplemental heater to transfer the heat to the air stream. Instead of water, other acceptable heat transfer mediums include, but are not limited to, glycol, water-glycol mixtures, synthetic oil, mineral oil, air, or silicones.
In another embodiment of the present invention, the supplemental heater 140 operates to employ the heat given off by the compressor associated with the chiller 130 to further heat the air stream. As the compressor compresses the working fluid in the chiller 130, heat is produced. This heat is then captured by a heat transfer medium and carried to the supplemental heater. In one embodiment of the present invention, water is circulated through the compressor to extract heat and carry it to the supplemental heater where the heat is transferred to the air stream. This provides additional heat to the sir stream with minimal additional energy cost to the system.
The supplemental heater allows more precise control of the air stream than is possible using only the heating unit described above. It also provides the option of providing significant additional heat, which would be required for drying in a water based wash cycle which would require higher temperatures for drying. In another embodiment of the present invention, the supplemental heater is capable of controlling the temperature of the air stream between 100° F. and 170° F. and provides between 0 and 6000 Watts of power.
In one embodiment of the present invention, the components of the apparatus are combined in no particular order. However, in another embodiment, the chiller 130 is located along the air stream immediately after the drum 110 so that any vapor in the air stream can be removed and recycled or disposed. The air stream then passes the heating unit 120 and, optionally, the supplemental heater 140 before entering the drum 110. A blower 150 is positioned at one or more points along the air route to move the air stream along. Preferably the blower 150 is located after the chiller 130 such that the air entering the blower is substantially free from vapor which can harm the blower components. The blower may be any air movement means known in the art such as a fan.
In yet another embodiment of the present invention, shown in FIG. 4, the components of the article drying apparatus 200 are arranged in a manner to minimize the energy used by the machine. After leaving the drum 210 air, laden with wash fluid vapor 212, passes through the cooling coils 230. The cooling coils 230 are fluidly connected to a compressor 232 which compresses the working fluid and transfers it 234 to the cooling coils 230. The compressed working fluid is allowed to expand in the cooling coils 230 during which it absorbs heat and cools the coils. As the air leaving the drum 212 passes the cool coils 230, wash fluid vapor will condense and is returned to a wash fluid storage tank though a return line 216. The result is an airflow 238 that contains less wash fluid vapor than the airflow leaving the drum 212. Once the working fluid has absorbed heat through the cooling coils 230 it makes the return trip 236 to the compressor 232 to be recompressed.
The air leaving the cooling coils 238 is moved through the system via a blower 250 or other air mover to a heating unit 220 where the temperature of the airflow is increased. Air leaving the heating unit continues to the supplemental heater 240 where it is further heated to the desired temperature before reentering the drum 210. The supplemental heater 240 is in fluid connection with the compressor 232 such that water circulating between the supplemental heater 240 and the compressor 232 carries heat discharged by compression 244 to the supplemental heater 240 and then returns 246 to the compressor to retrieve more heat. The air stream leaving the supplemental heater 248 is hot and relatively free of moisture so as to effectively remove more wash fluid from the articles in the wash drum 210.
The above described apparatus is employed according to the following methods in order to minimize drying time and energy usage during a cleaning cycle. The following methods are illustrative of some embodiments of the present invention and modifications and variations will be apparent to those skilled in the art.
A second aspect of the present invention comprises a spin and dry cycle for a washing machine which minimizes total drying time and energy usage. In one embodiment of the present invention, the method of drying begins with the completion of a wash cycle. Referring to FIG. 1 as an exemplary apparatus for performing the methods of the present invention, the wash cycle generally comprises placing the articles in a horizontally rotating wash basket 20 of the solvent cleaning system 10. The cleaning basket 20 is rotated by means of an electrical motor 30. The wash cycle is then initiated after a cleaning fluid 50 is pumped into the wash basket 20 by pump 40. The cleaning fluid constituents are presented for illustration and without limitation as cyclic siloxane, water, detergents, sanitizing agents and other related materials desired for effective washing.
The basket 20 containing the articles and cleaning fluid is agitated for a predetermined period of time to ensure proper contact and mixing between the cleaning fluid and the articles. Once the articles and cleaning fluid are sufficiently agitated, a check valve 60 is opened, and the cleaning fluid is drained into a working tank 54. The wash basket 20 is then centrifuged by the electric motor 30 to extract the residual cleaning fluid left in the articles. As the basket 20 is spun, any remaining cleaning fluid is thrown to the outsides of the wash basket 20 and allowed to drain in to the working tank 54. It is at this point in the wash cycle that the method of the present invention is employed.
In one embodiment of the present invention, a method of drying articles is provided comprising engaging at least one of a heating, cooling or supplemental heating element during the spin cycle. This includes the heating coils, the condenser and cooling coils, the supplemental heater and the blower. In another embodiment of the present invention, the heating coils, condenser coils and supplemental heater are turned on during the spin cycle while the blower remains off. After the spin cycle is completed, a dry cycle begins and the blower is engaged to assist air flow through the other components and to the wash basket.
The spin and dry cycles in an embodiment of the present invention are similar to those generally known to one skilled in the art of laundering. A spin cycle removes excess wash fluid primarily through centrifugal extraction by spinning the basket at a high rate of speed. A typical spin cycle comprises a basket spin rate of about 500 to about 1200 rpm and will produce a force of 150-300 g on the articles in the basket, depending on the size of the basket. This force pulls the water through and away from the articles and outside the wash basket. In contrast, a dry cycle rotates the basket much more slowly to tumble the articles while forcing air past the articles to absorb wash fluid from the articles to the air. In a dry cycle, the wash basket typically rotates no faster than 100 rpm to ensure efficient contact between the passing air and the articles to produce uniform drying.
Depending on the size of the drum, the rpm needed to achieve a certain g force would be different. The equation relating the drum diameter, rpm and g force is given by:
where G is the centrifugal force applied, expressed as a factor over acceleration due to gravity, D is the drum diameter in meters, N is the drum rotation speed in revolutions per minute (RPM) and 9.81 is the acceleration due to gravity in m/s2. For example, a drum diameter of 0.54 m and speed of 1000 RPM results in 300 g force. A larger drum diameter would need a higher speed to achieve this G force.
Even though the blower is off during the spin cycle, some airflow results due to the high centrifugal force imposed during spin extraction. This force will pull some air through the system and past the heating unit, cooling coils and supplemental heater. Generally, the airflow during centrifugal extraction is between 0 and about 5 percent of the airflow when the blower is turned on. However, the rate of spin and the configuration of the airflow system will ultimately determine the flow rate. The effect of starting the system during the spin cycle is a more efficient cycle, which results in lower retention of the cleaning fluid in the articles at the end of spin cycle. This results in a lower spin cycle time and lower dry cycle time which results in an overall energy savings.
In another embodiment of the present invention, the blower is turned on during the spin cycle to assist the natural air flow past the components of the system. The blower is operated 20% or less of the maximum airflow produced during the drying cycle. This will enhance the evaporation of wash fluid during the spin cycle with only an incremental energy expense.
Once the spin cycle has completed, the drying cycle is begun. The dry cycle comprises engaging the heating unit, condenser and cooling coils, and the blower. In a further embodiment of the present invention, the supplemental heater is engaged as well. These components are engaged until a satisfactory amount of wash fluid has been removed from the articles. Generally, this will be substantially all of the wash fluid such that the articles feel dry to the touch.
In another embodiment, the system and method of the present invention are used to dry water saturated clothes. This may be accomplished, for example, in a traditional water based wash cycle as is presently used in home based laundering. By dehumidifying the air stream before it enters the wash drum, the air will be able to pick up more moisture from the articles resulting in a decrease in total dry time. The air then passes back through the cooling coils and the water condenses to allow the air to be passed back through the system and into the drum. In another embodiment of the present invention, the air is optionally discharged from the machine through a vent similar to a standard clothes dryer. Fresh air is then pulled into the machine and passed through the system as described above.
The method of drying articles described in the various embodiments of the present invention is adaptable to a wide range of article drying situations. While the preferred methods involve a home based siloxane cleaning machine, the methods can be used equally well in a commercial or coin-op machine. Furthermore, while the cycles and dry times are disclosed for the preferred embodiment, one skilled in the art will appreciate that these times will vary for machines of larger or smaller size. A minimal amount of experimentation will determine the appropriate cycle times for any given machine size.
The drying cycle time typically ranges between about 15 minutes and about 60 minutes for a standard laundry load capacity range between about 0.9 kg (2 lbs.) and about 6.8 kg (15 lbs.). The sensible heat required to dry the clothes, which requires the maximum power the machine needs, is between 430 watts and 6300 watts.
In another embodiment, the drying time is between 20 and 60 minutes for a capacity of between 6 and 12 lbs of articles. In this case, the power required is between 1300 watts and 5200 watts. In each of these cases, the power can easily be handled on a household circuit with a maximum voltage of 240V and a maximum amp rating of 30 amps. In some embodiments, it can also be run on 220V, 20 amp or 220V, 30 amp or 110V 15-20 amp circuits. All of these outlet types are typically available in homes for current cooking and drying appliances, and require no additional installation difficulties.
FIG. 5 shows the effect of Spin Speed during the spin cycle on the residual moisture content (RMC) of wash fluid in the articles at the end of the spin cycle. RMC can be used to measure residual fluid content for any wash fluid and is not limited to water. This data was generated using an 18 in diameter wash drum spinning at 1000 rpm for 10 minutes. This produced a force of approximately 225 g on the articles within the wash drum. The figure shows that an acceleration of approximately 300 g is required to attain asymptotic behavior, i.e. no change in retention is observed for larger acceleration. Therefore, no energy or time savings are realized by increasing the spin past this point. Also shown is the effect of heating the system by starting compressor at the start of spin cycle. An asymptotic gain of about 5% is obtained for cotton. The earlier the asymptotic behavior begins, the better time and energy savings that can be realized as a result of the spin cycle. Therefore, by engaging the condenser coils during the spin cycle, the energy needed by the motor to reach asymptotic behavior is reduced.
FIG. 6 shows the effect of spin time on retention of wash fluid in the articles at the end of the spin cycle. This data was generated using a 22 in diameter drum spinning at 1000 rpm thereby producing about 312 g of force. The initial conditions were 100% cotton articles with 100% retention after the wash cycle, i.e. the articles are completely saturated with water. Based on an average of seven test runs, retention after an 8 minute heated spin cycle is 28.2% with a standard deviation of 1.4% for a 100% cotton load. This test demonstrates that an optimal spin time of 8 minutes is required. Spin cycles of longer duration results in minimal reduction of wash fluid.
| || || || || ||Supp || || || || |
| || ||Duration ||Motor ||Pumps ||Heater ||Compressor ||Fans ||Total Power ||Energy |
|# ||Cycle ||(min) ||(W) ||(W) ||(W) ||(W) ||(W) ||(W) ||(kWh) |
|1 ||Initial RMC = 36% (5 min spin cycle) |
| ||Spin ||5 ||190 ||294 ||810 ||857 ||0 ||2151 ||0.18 |
| ||Dry ||41 ||100 ||294 ||810 ||857 ||140 ||2201 ||1.5 |
| ||Spin + Dry Time= ||46 || || || || || ||Spin + Dry KWh= ||1.7 |
|2 ||Initial RMC = 30% (7 min spin cycle) |
| ||Spin ||7 ||190 ||294 ||810 ||857 ||0 ||2151 ||0.25 |
| ||Dry ||36 ||100 ||294 ||810 ||857 ||140 ||2201 ||1.3 |
| ||Spin + Dry Time= ||43 || || || || || ||Spin + Dry kWh= ||1.6 |
|3 ||Initial RMC = 28% (8 min spin cycle) |
| ||Spin ||8 ||190 ||294 ||810 ||857 ||0 ||2151 ||0.29 |
| ||Dry ||35 ||100 ||294 ||810 ||857 ||140 ||2201 ||1.3 |
| ||Spin + Dry Time= ||43 || || || || || ||Spin + Dry kWh= ||1.6 |
|4 ||Initial RMC = 28% (10 min spin cycle) |
| ||Spin ||10 ||190 ||294 ||810 ||857 ||0 ||2151 ||0.36 |
| ||Dry ||35 ||100 ||294 ||810 ||857 ||140 ||2201 ||1.3 |
| ||Spin + Dry Time= ||45 || || || || || ||Spin + Dry kWh= ||1.6 |
|5 ||Initial RMC = 35% (8 min spin cycle, non heated) |
| ||Spin ||8 ||190 ||294 ||0 ||0 ||0 || 484 ||0.065 |
| ||Dry ||49 ||100 ||294 ||810 ||857 ||140 ||2201 ||1.8 |
| ||Spin + Dry Time= ||57 || || || || || ||Spin + Dry kWh= ||1.9 |
Table 1 demonstrates the impact of engaging the supplemental heater, compressor and blower during the spin cycle and dry cycle on spin and dry cycle time and energy requirements. This demonstrates how critical the spin conditions are to total cycle time and energy usage. As spin time increases, retention decreases and consequently drying time and energy usage decrease. As shown in FIG. 6, asymptotic behavior is reached at 8 minute spin time, after which no reduction in retention is observed. This is observed in Case 4 of Table 1. While the drying time remains the same, the total cycle time and energy usage increases compared to Case 3. For a non-heated spin, retention is about 35% higher, as shown in Case 5. Since the compressor and supplemental heater are switched on at the start of drying and not at the start of spin, longer time is required to reach the desired drum inlet air temperature. Consequently, the drying time and total energy usage increases. Data is based on the worst fabric case (maximum retention) of 100% cotton load.
Although the present invention has been described with reference to particular embodiments, it should be recognized that these embodiments are merely illustrative of the principles of the present invention. Those of ordinary skill in the art will appreciate that the method of the present invention may be implemented in other ways and embodiments. Accordingly, the description herein should not be read as limiting the present invention, as other embodiments also fall within the scope of the present invention.