Bleaching and dyeing; fluid treatment and chemical modification – Fluid treatment – Special forms and forming
Reexamination Certificate
1999-12-27
2001-07-31
Coe, Philip R. (Department: 1746)
Bleaching and dyeing; fluid treatment and chemical modification
Fluid treatment
Special forms and forming
C008S158000, C068S012030, C134S001000, C134S06400P, C134S12200P
Reexamination Certificate
active
06266836
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention deals with a method and ultrasonic system for continuous cleaning of solid materials that have a large surface, in the form of sheets or plates, especially flexible materials such as fabrics, plastics, etc.
Ultrasonic energy has been used commercially in industrial cleaning of pieces of rigid materials, especially those that have complex geometries. The cleaning action of high intensity ultrasounds may be mainly attributed to effects related to the phenomenon of acoustic cavitation (formation and implosion of bubbles), such as erosion, agitation and dispersion of the dirt, causing of chemical reactions on the surfaces to be cleaned, penetration of the cleaning solution in pores and cracks, etc.
2. Description of the Related Art
The application of ultrasounds for washing flexible materials and particularly textiles has been tried over the last few years. The strategies have been directed towards the production of cavitation in the entire volume of liquid in which the materials to be cleaned are placed. These systems have not achieved commercial development possibly because they have significant inconveniences. Thus, the use of a large volume of liquid tends to imply a high consumption thereof. On the other hand, it is practically impossible to achieve a homogeneous distribution of the acoustic field in the entire washing volume. This causes a waste of energy (in the areas of low acoustic energy the cavitation threshold is not reached and cleaning does not take place) and causes the washing to be irregular. In order to overcome this situation the washing time must be increased, treatment must be done with a low proportion of material to be washed per volume of liquid and this material must be moved so that it passes through the areas of maximum energy of the washing cavity. Besides, there are other difficulties that come from the gas content in the liquid and from the presence of bubbles between the materials to be washed. In fact, in Spanish patent no. 9401960 good results are only achieved by degassing the liquid so that the concentration of gas is less than 50% of the saturation concentration. Likewise, degassing methods of the washing liquid are proposed in patents EP9320-1142.2 and FR-9304627.
The previous problems have implied practical limitations which, up until now, have hindered the industrial-commercial development of ultrasonic systems for washing of textiles and flexible materials. Nowadays, conventional washing processes in batches that require a significant consumption of water, detergent and energy are used in industrial laundries. Besides the handling system is very elaborate. The continuous washing processes which at times have been tried to be introduced have not been successful due to the low level of cleaning achieved when traditional washing methods have been used.
The process and ultrasonic system that the present invention refers to has some characteristics that manage to solve to a large degree the problems posed by the previous ultrasonic systems, such as the requirement of large volumes of water, the need to agitate the pieces or degassing. At the same time, this process proves to be suitable for continuous treatment thanks to its action being rapid.
SUMMARY OF THE INVENTION
The process that the present invention refers to is based on the use of ultrasonic energy which, as it is known, may be a useful tool to improve and speed up the washing process. The difference that characterizes this invention is that ultrasonic vibrations are applied to the materials to be washed by means of vibrating plates that are put in direct contact with these materials that have to be submerged in a shallow layer of liquid. This cleaning process may be complemented by immediate rinsing and, once out of the liquid, ultrasonic energy may be applied once again by contact to eliminate an important part of the liquid content in the washed material, producing a predrying effect. Likewise, the invention refers to a device capable of carrying out the described process. This device is especially suitable to treat materials with a large surface, that is to say, in the form of a band, strip or sheet. It is characterized in having the necessary means to apply acoustic energy directly on the materials to be washed, by means of plate-shaped radiators activated by piezoelectric or magnetostrictive exciters. These radiators may be in contact with the materials or very close to them, the contact surface being submerged in the washing liquid. This liquid, which may be any cleaning solution, generally an aqueous based one, does not need to be degassed.
The process object of this patent comprises the following steps: a) wetting the material in a cleaning solution, b) eliminating the dirt or contaminating substances from the material by means of applying high intensity ultrasonic vibrations by vibrating plates in contact with or very close (at least 10 mm) to the material; c) rinsing in a layer of water or clean liquid that may also be aided by ultrasonic vibrations; and d) predrying the material by applying ultrasonic vibrations by contact with the material outside of the liquid.
Elimination of the dirt or of the contaminating substances is produced as a result of exposure of the material to the vibrations (or very close acoustic field) of the large surface plate-shaped ultrasonic radiators. The cleaning effect is so rapid that it permits the material to be cleaned to pass continuously by the vibrating surface (or through its very close acoustic field), at a certain rate, in the range of some cm(s) in such a way that the material occupies the area of the intense acoustic field during a short time.
The large surface vibrating plates oscillate at the excitation frequency that is made to correspond with one of the flexural resonant modes thereof. The very close acoustic field proves to be almost as efficient as the direct vibration itself of the plate because its displacement is proportional to the vibration amplitude of the same.
Although the flexural vibration of the plates implies amplitude maximums and minimums, the homogeneity in the washing effect is achieved by displacing the material in such a way that each part of the material has been exposed during the same total time to areas of intense acoustic field. For example, we can take as an example rectangular plates vibrating flexurally with nodal lines parallel to the longest side and that produce a uniform washing effect on material that slides parallel to or in contact with the surface in the direction marked by the shortest side.
The cleaning solutions to be used may be an aqueous based one with surface active agents which may or may not contain other additives such as enzymes, whiteners, etc.; they may also be non-aqueous based. Besides, the liquid means may have any concentration of dissolved gas.
After the step of eliminating dirt, the material is then rinsed. This rinsing step is, likewise, done in a liquid layer and may also be enhanced by applying ultrasounds in a similar way to the process of eliminating contaminants.
There may be one or several cleaning and rinsing steps. Afterwards and before the conventional drying process, a predrying or dewatering step by means of applying the ultrasonic vibration plates in contact with the material working in air, may be applied. Thus, a process of atomization and pumping of a great deal of the liquid contained in the material towards the outside is produced and this process facilitates the subsequent drying.
Besides the described washing process, a device to carry out the process is also an object of this patent. The device is comprised of:
A washing system or system for eliminating the formed contaminants by at least one plate that vibrates flexurally, excited at ultrasonic frequency in one of its resonant modes and with at least one of its surfaces submerged in the cleaning solution. The shape of the plate may be square, rectangular, circular or any other one. The thickness of the plate may be constant, but it m
Corral German Rodriguez
Gallego Juarez Antonio
Najera Vazquez de Parga Gonzalo
van der Vlist Piet
Vazquez Martinez Fernando
Coe Philip R.
Consejo Superior de Investigaciones Cientificas
Klauber & Jackson
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