Bleaching and dyeing; fluid treatment and chemical modification – Fluid treatment – Manipulation of liquid
Reexamination Certificate
1999-09-24
2001-11-13
Stinson, Frankie L. (Department: 1746)
Bleaching and dyeing; fluid treatment and chemical modification
Fluid treatment
Manipulation of liquid
C068S0180FA, C068S0180FA, C008S159000
Reexamination Certificate
active
06314601
ABSTRACT:
FIELD OF THE INVENTION
The present invention concerns washing and dry cleaning apparatus, and particularly concerns dry cleaning apparatus for use with carbon dioxide based dry cleaning systems.
BACKGROUND OF THE INVENTION
Numerous different apparatus for washing garments and fabrics are known. Examples of patents on washing machines include U.S. Pat, No. 1,358,168 to McCutchen, U.S. Pat. No. 1,455,378 to Allen, U.S. Pat. No. 2,357,909 to Ridge, U.S. Pat. No. 2,816,429 to Kurlancheek, and U.S. Pat. No. 3,444,710 to Gaugler. Such apparatus is, in general, adapted to home use with water-based cleaning systems.
Non-aqueous cleaning apparatus, known as “dry cleaning” apparatus, is also known. Dry cleaning employs an organic solvent such as perchloroethylene in place of an aqueous system. Dry cleaning apparatus is not, in general, employed in the home, and is instead situated at a store or central plant. Problems with convention dry-cleaning systems include the toxic nature of the solvents employed.
Carbon dioxide has been suggested as a dry cleaning medium. See, e.g., U.S. Pat. No. 4,012,194 to Maffei. One apparatus is described in U.S. Pat. No. 5,467,492 to Chao et al. This apparatus has apparently been supplanted by the apparatus described in U.S. Pat. No. 5,669,251 to Townsend et al. Townsend describes a dry cleaning system having a hydraulically rotated basket that rests on roller bearings. U.S. Pat. No. 5,267,455 to Dewees et al. describes a dry cleaning system in which carbon dioxide as a cleaning medium is transferred between vessels by means of a second purge gas such as nitrogen. U.S. Pat. No. 5,850,747 to Roberts et al. describes a carbon dioxide cleaning system incorporating a temperature compensating compressor. PCT Application WO 97/33031 to Taricco describes a super-cooled fluid temperature controlled cleaning system. None of these references provides a substantial discussion of how to control a carbon dioxide cleaning apparatus.
PCT Application WO 99/13148 to S. Shore describes a dry cleaning system that cycles through eight modes, including a loading (or “idle”) mode, a prefill mode, a pressurization mode, a wash mode, a reclaim mode, a vent mode, a make-up mode (or storage fill mode) and a distillation mode. It will be noted from FIG.
3
A and
FIG. 8
therein that, during the idle mode, numerous valves (including valves
9
,
11
,
18
,
20
,
22
,
27
,
29
,
35
and
49
) are maintained in a closed position. This creates enclosed areas within the pipes and ancillary vessels of the apparatus. While acceptable for short term periods, it will be readily seen that it is undesireable to create enclosed spaces that are potentially charged with a pressurized gas in such a large industrial apparatus during prolonged periods of idleness (e.g., during night time, holidays, power failures, etc.). The risks of creating such enclosed pressurized chambers are exacerbated if apparatus is then held in an elevated temperature environment, as may well be found in a cleaning plant.
Accordingly, there is a need for improved carbon dioxide cleaning systems that are equipped for periods of sustained idleness or inactivity, whether expected or unexpected, and methods of operating such equipment.
SUMMARY OF THE INVENTION
The present invention provides a method of controlling a carbon dioxide cleaning apparatus. The apparatus comprises a wash vessel, a working vessel containing a carbon dioxide cleaning medium and operatively associated with the wash vessel, a pump operatively associated with the wash vessel, a condenser connected to the working vessel, a still operatively associated with the working vessel (which still may be a separate still or incorporated into other system components as explained below), a compressor operatively associated with the wash vessel, and a pressure release valve operatively associated with said working vessel. At least one filter is included in the system, but the filter and still may be consolidated together in a single vessel. The apparatus includes a suitable controller which, operating in association with appropriate valves in the apparatus, is used to place the apparatus in a cleaning cycle for washing articles therein, a waking cycle separate from the cleaning cycle during which distillation, recharging and other maintenance and preparatory function can be performed, or a resting cycle or resting state for long term periods of idleness. The method of operating the system comprises the steps of:
(a) initiating a cleaning cycle, the cleaning cycle comprising the steps of (i) filling said wash vessel with carbon dioxide cleaning medium from said working vessel, (ii) washing articles to be cleaned in said wash vessel, and (iii) draining said carbon dioxide cleaning medium from said work vessel;
(b) initiating a resting cycle, said resting cycle comprising the steps of placing said condenser, said pump, said still and said filter (when the filter is a separate vessel from the still) in fluid communication with said working vessel and not said wash vessel so that all carbon dioxide cleaning medium in said system is held at a low energy state and ventable through said pressure release valve; and, typically,
(c) initiating a waking cycle, said waking cycle typically comprising the steps of removing at least one of said condenser, said pump, said still and said filter from fluid communication with said working vessel. The waking cycle may include a recirculating step for the liquid cleaning medium, and/or a step of emptying carbon dioxide gas from the wash vessel back to the working vessel. The waking cycle can then be followed by the cleaning cycle described above.
Preferably, the rest cycle includes the step of circulating the cleaning medium through at least a portion of the system so that the cleaning medium is kept at a substantially uniform temperature throughout the system, and the constituent ingredients in the cleaning medium are maintained at a substantially uniform concentration throughout the system. Where a recirculating step is not included with the rest cycle, the recirculating step can be carried out at the beginning of the waking cycle as noted above.
An advantage of the resting cycle is that all carbon dioxide in the system is in fluid communication with the working vessel. The door to the wash vessel may be open or closed, but is preferably closed and sealed to provide an additional cooling mechanism as described below. Since the working vessel is in fluid communication with the pressure release valve, liquid carbon dioxide within the system can boil off if the temperature increases and vent (or “burp”) through the pressure release valve. Such boiling allows the system to self-cool during periods of sustained idleness, in addition to the other cooling mechanisms described below. Preferably the door to the wash vessel is closed for safety reasons as well. Locking the door during periods of inactivity is a good practice for all enclosures, and also allows one to detect any leaks in the isolation valves that separate the system from the wash tank. This functions as a nightly check on the continuity of the valving.
Thus, a particular aspect of the present invention is a method of cooling a carbon dioxide dry cleaning apparatus between wash cycles or during other periods of inactivity, the apparatus including a wash vessel and a working vessel operatively associated with the wash vessel. The method comprising the steps of:
(a) transferring carbon dioxide cleaning medium from the wash vessel to the working vessel after a wash cycle so that the working vessel contains liquid a cleaning medium comprising carbon dioxide;
(b) opening the wash vessel to remove articles that have been cleaned therefrom; then
(c) closing and sealing the wash vessel; and then
(d) transferring a portion of the liquid carbon dioxide from the working vessel to the wash vessel as a gas, so that the pressure in the working vessel decreases and the cleaning medium in the working vessel is cooled (which transferring step may be carried out periodically or continuously).
The
Brainard David E.
Cole Michael E.
McClain James B.
Worm Steve L.
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