MXPA97008496A - Fil device - Google Patents

Abstract

The present invention relates to a filter device (10) that filters air pollutants, for magnetic disk unit systems. The filter has layers of permeable fabric material that allow flow through the filter. An adsorptive liquid paste (18) is deposited with a discrete pattern or configuration on a layer (16) with a cover layer mounted on the adsorptive deposit. The liquid paste preserves a surface area of adsorptive material, for the improved adsorption of contaminants. The liquid paste is placed on the base material using a sieve or other similar application method

Description

FILTER DEVICE FIELD OF THE INVENTION The present invention relates to a filter device, and in particular to a filter device that is used with computer disk unit systems.

BACKGROUND OF THE INVENTION The magnetic disk drives that are used in large quantities in the computer industry require a clean environment to function. Contaminants can lead to corrosion and other component problems. It has been found that even the environmental levels of urban pollution can lead to corrosion which will also lead to the failure of the disk drives. To overcome these problems, systems can be equipped with filter devices that remove particulates and contaminants in the form of condensable, corrosive vapors from the system air. The filter systems used REF .: 25916 include vents, recirculation filters and static bags. Hard drives with files usually need to be vented to the atmosphere of the surrounding environment to prevent the formation of excessive pressure on the main disk cover. During operation, the discs with the file will be heated and the air will flow out of the main disc cover. The thermal circulation of the assembly will result in a flow of air outward and inward of the cover. The organic vapors condense on the surface of the disc, causing the head to stick to the surface of the disc (static adhesion). The new technology of thin films, used in the discs of greater density and the metals of high resistance to the weight, used in the assembly of the disk with archives, are very susceptible to the corrosion as such. They have developed, chemical or adsorptive vents, for the elimination of gaseous pollutants or in the form of vapor, in addition to the elimination of pollutants in the form of particles. As the magnetic disk units become more and more compact, smaller and smaller components are required. Therefore, the size of the filters and especially the thickness of the filters needs to become more and more compact, while providing greater protection. The reduced size and airflow generated by the high-speed mechanisms can cause a pressure difference to occur through a vent or a recirculation filter. Therefore, it is necessary for the filter device to provide adequate flow through the filter, to prevent a large difference in pressures within the disk unit. If a large pressure difference is developed through a filter, leakage of unfiltered matter will occur in seals, bearings or other moving parts. In the recirculation filters, a large differential pressure increases the cleaning time of the disk drive, during the ignition and rotary operation. An example of a filter device, of the prior art, is represented by US Patent No. 4,657,570 which has an Air Filter Device, assigned to Donaldson Company, Inc., the assignee of the present invention. Although the filter device provides for air filtration in magnetic disk drive systems, the activated carbon portion for the adsorption of corrosive gases and potential condensates must be cut off, and the construction is relatively complicated. Therefore, the device has higher manufacturing costs and requires more time for assembly. In addition, the filtering portion needs to be cut, which therefore leads to possible contamination of the filtering device, during assembly. In the conditions, extremely clean, that are needed for the filtering devices, the cutting of the portions of the filter media can cause problems of contamination and quality control. It can be seen then that filter devices are needed, new and improved, for disk drive systems. These devices should filter the air and remove gaseous contaminants that may contaminate the drive system. In addition, the disk devices should have a construction that provides a very narrow profile with adequate free space in the disk drive system. That device should not be expensive and should be easy to manufacture without contamination during the assembly process, the present invention focuses on these problems as well as other problems associated with the filter devices for disk unit systems.

BRIEF DESCRIPTION OF THE INVENTION The present invention is directed to a family of filter devices such as those commonly used in magnetic disk drive systems. In accordance with the present invention, the filter device uses a base layer having an adsorptive liquid paste deposited on the base in a discrete pattern or configuration. The adsorptive liquid paste is a dispersion of adsorptive material such as activated carbon or catalytic material for the removal of air contaminants from the system of the disk unit. A cover layer is applied on the deposit of the adsorptive liquid paste, to provide an area around the tank, for the purpose of sealing it. The adsorptive liquid paste can contain other additives to eliminate various types of contaminants. However, in a preferred embodiment, the liquid paste does not contain a binder or latex to hold the adsorptive material together. The removal of the commonly used binder material provides a maximum surface area of the adsorptive material for the adsorption of the contaminants. In a preferred method for manufacturing the filter device, a device of the type of a rotating fabric or sieve is used to apply the adsorptive liquid paste. In a preferred method, the liquid paste is deposited on a rotating screen which is coupled to the base layer. The cohesive strength of the liquid paste allows the liquid paste to be transferred from the screen to the base layer, in a discrete pattern. It can be appreciated that some drying may be required before applying the cover layer, to help maintain the shape of the adsorptive component deposited. Then individual filters of the resulting composite material and sealed edges are cut. An adhesive portion can be applied to one side of the filter device so that it can be mounted to the disk drive system. Various types of support and filter materials can be combined to support and retain the adsorptive deposit, having the properties for the intended use and application. These and other various advantages and features of novelty, which characterize the invention, are pointed out with particularity in the claims appended hereto, which form a part thereof. However, for a better understanding of the invention, its advantages, and objectives obtained through its use, reference should be made to the drawings forming an additional part thereof, and to the accompanying description in which it is illustrated and presented preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, where the reference numbers and letters, the same, designate corresponding elements through several views: Figure 1 shows a top view, of the upper part, of a filter device in accordance with the principles of the present invention; Figure 2 shows a side elevational view of the filter device shown in Figure 1; Figure 3 shows a top view, of the bottom part, of the filter device shown in Figure 1; Figure 4 shows an elevation view, lateral, with separation of parts, of the vacuum filter device, shown in Figure 1; Figure 5 shows a flow diagram of the manufacturing method of the filter device shown in Figure 1; Figure 6 shows a top view, of the upper part, of a sheet of material with the adsorptive layer adhered during manufacture of the filter device shown in Figure 1; Figure 7 shows a diagrammatic view of the cloth or screen device shown in Figure 1; Figure 8 shows an elevation view, lateral, with separation of parts, of a second embodiment of a filter device in accordance with the principles of the present invention; and Figure 9 shows an elevation, side view, with separation of parts, of a third embodiment of a filter device in accordance with the principles of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED MODALITY (S) (S) Referring now to the drawings, in which similar reference numbers designate a corresponding structure, through the views, and referring in particular to Figure 1, a filter device, generally designated as 10, is shown. first mode, the filter device 10 is a suction filter. The filter device 10 includes an active area 12 of the filter means, surrounded by a sealed outer portion 14.

As shown in Figure 2, the filter device 10 has an extremely narrow profile. Referring to Figure 3, the aspirator filter device 10 includes an annular adhesive layer 28 attached thereto. The adhesive layer 28 is fixed to the filter device and includes a second adhesive side with a release paper layer, which can be removed to fix the filter in the proper position on the housing, for a magnetic disk drive or other apparatus. Although the filter device 10 is shown in a circular manner, it can be appreciated that other shapes such as rectangles, ovals or other common shapes can also be used. Referring now to Figure 4, there is shown a part separation view of the filter device 10. The filter device 10 includes a number of layers fused or otherwise joined to contain an adsorptive deposit 18 in the active area 12 of the filter media. The adsorptive deposit 18 is normally placed in a discrete pattern on a base material 16 which in a first embodiment includes three layers combined to form the base. In the preferred embodiment, the adsorptive deposit 18 is an adsorptive liquid paste which is deposited with a process of the printing type with cloth or sieve, as explained below. In the embodiment shown, the composite base 16 includes a support layer 20 which receives a membrane 22 of HEPA or ULPA efficiency. Mounted on the membrane layer 22 is a support layer 24 based on adsorptive material, which receives the adsorptive deposit 18. In the preferred embodiment, the three layers 20, 22 and 24 are joined together in a base sheet 16 prior to the deposition of the adsorptive layer 18. It can be seen that discrete deposits of the adsorptive layer 18 can be placed on the base sheet 16 in multiple rows for higher production volumes, as shown in Figure 6. Covering the adsorptive deposit 18 there is a cover layer 26 which extends beyond the edges of the adsorptive layer to seal the adsorptive material 18 within the filter device 10. In the preferred embodiment, the backing layer 20 is an open, polymeric screen, or a woven material, while the layer 24 supporting the adsorptive material, and the cover layer 26 are permeable fabrics, either woven or nonwoven materials. The two-sided adhesive layer 28 is applied to the cover layer. The adhesive layer 28 is annular and preferably has an opening of smaller diameter than the diameter of the adsorptive layer 18. Referring to Figure 5, steps for the manufacture of the filter device are detailed. As explained above, the three layers 20, 22 and 24 combine to form a base 16. The adsorptive materials 18 are prepared as a liquid paste for application to the base 16 with a discrete pattern or configuration. The liquid paste is then deposited on the base 16 through the sieve or through another transfer process. After drying and application of the adhesive to the base and of the adsorptive layers of the filter, to join the cover layer 26 to the composite base 16, individual filter devices 10 are cut from the resulting composite material, as shown in Figure 6. The edges are then welded, whereby the adsorptive material 18 is sealed in the filter 10. The adhesive rings are then applied and the suction filter device 10 is ready for use. Referring to Figure 7, in this the application steps of the adsorptive layer. In a first method, the adsorptive layer 18 is applied on a sieving apparatus 36 of the rotating type. The screening apparatus 36 includes a cylinder 38 and an opposite roller 40, complementary. Cylinder 38 includes a screen portion 42 located along its periphery. A pump 44 supplies the adsorptive liquid paste on the screen 42. Then the excess is removed and the screen 42 rotates with the cylinder 38 to mate with the base material 16. The adsorptive material can be printed either on a stationary sheet or on a moving fabric, with the rotary screen printing device 36. In the screen 42 a pattern of the desired deposit is created by any of the processes well known in the industry such as by the use of a woven screen, with deposited dough, or with a metal screen etched with acid. The adsorptive liquid paste is applied to the back of the screen 42 and pressed into the openings of the screen 42 by a rubber paddle, roller or similar device. When the rotating screen is coupled to the base layer 16, the cohesive strength of the adsorptive layer is such that when the screen 42 is pressed onto the base 16 of the filter, the adsorptive material of the screen 42 is transferred to the base 16. The mesh and the thickness of the screen should be sized according to the type of adsorptive material 18 and according to the amount of material to be deposited. In the case of an adsorptive liquid paste 18, of activated carbon, the weight of the adsorptive layer is 20 to 100 grams per square meter. For example, in a 2.54 cm (1 inch) filter, the reservoir will have a mass of 4 to 20 milligrams per device 10. It can be appreciated that the weight of the adsorptive layer 18 will depend on the density of the adsorptive material, which is deposited. Following the deposition of the adsorptive layer 18, the liquid paste will be moist and may require drying. Therefore, the base 16 which has deposited thereon, the liquid paste, can be passed through a drying apparatus 46. Furthermore, after drying, an adhesive spray 48 can apply adhesive to apply the cover layer 26. In the preferred embodiment, the edges are sealed with an ultrasonic sealing device 50. The adsorptive liquid paste 18 can use various types of active materials including activated carbon, activated alumina, molecular sieves, ion exchange resins or other resins and functional polymers, diatomaceous earths, silica or clays. In addition, adsorptive materials can be impregnated with other chemical compounds for selective adsorption. These impregnated materials include inorganic materials that can be impregnated using either an aqueous solution or an organic solution. A specific choice of the impregnating solution depends on the use and application that you intend to give. For example, if they are being removed, acid ash such as sulfur oxide, or nitrogen oxide, hydrogen sulfide, hydrochloric acid and sulfur-based acids, the carbon may be impregnated with water-soluble carbonate, bisulfite, sulfate or salts. of hydroxide. In addition, polymeric amines or low molecular weight amines can be used to remove acid gases and acidic organic vapors such as carboxylic acids, alcohols, and phenols. Organic and inorganic halides, such as potassium iodide, can be impregnated in the carbon to remove basic vapors such as N-met ilpyrrolidone and other organic amines. The liquid paste can also be impregnated with sulfate salts to remove ammonia and other low molecular weight amines. If the area is contaminated with aldehydes and ketones, such as formaldehyde and methyl ethyl ketone, the carbon can be impregnated with 2,4-dinitrophenylhydrazine. Catalytic materials such as copper or nickel, or oxides of manganese, copper or nickel can also be added. The liquid paste can also have a viscosity modifier added, resin or latex. A viscosity modifier is preferably used to prevent the formation of sheets or films of adsorptive materials. In a preferred embodiment, the liquid paste does not contain a latex or binder to keep adjacent to the adsorptive material, whereby a maximum surface area of the adsorptive material is provided for the adsorption of the material. In a preferred embodiment, the liquid paste loses very little of its adsorptive surface area. A preferred embodiment of the liquid paste will retain more than 80% of the surface area capacity of the activated carbon. Referring now to Figure 6, there is shown a large sheet of base material 16 having deposits 18 of adsorptive material placed thereon. It can be appreciated that the method of the present invention provides a rapid method for producing filter devices 10 in large quantities without contamination, because the cutting of the carbon materials is carried out as it is done in the previous adsorptive devices. It can be appreciated that the layers of the filter device 10 may be of any type of woven or nonwoven materials that are tight enough to contain the adsorptive reservoir 18. The layers may be single or multiple plies, depending on the desired properties of the composite material. . It has been found that fabrics having suitable surface densities for the deposition of the adsorptive or catalytic layer are particularly useful. It should be noted that one side of the composite material should have sufficient void volume within which the adsorptive layer can be deposited to maintain the shape of the adsorptive or catalytic layer when it is taken by the rollers, to ensure contact of the adhesive and the layers of cloth. An example of a preferred embodiment of the filter device includes an adsorptive liquid paste having a composition of 7 grams of xanthan gum which is soaked with isopropyl alcohol. This is mixed with 20 grams of potassium carbonate and 653 grams of water. To the thickened solution are added 320 grams of activated carbon PCB-G which can be obtained from Calgon Corporation. After mixing the solution, the liquid paste is ready for application. The adsorptive liquid paste has the following adsorption capacity and the following surface area characteristics.

Table 1 Typical Adsorption Capacity in Balance Toluene 4.4 mg H2S 3.4 mg Cl2 8.7 mg HCl 1.6 mg N0X 4.0 mg Table 2 Surface area of Brunauer Emmett Teller (BET) Charcoal PCB-G 968 m2 / g Liquid paste 841 m2 / g In the described embodiment, the liquid paste is pumped into the rotating screen with a repeating circular path of 1.78 cm (0.7 inches). The deposition of 13 milligrams ± 4 milligrams, in dry weight, of liquid paste, is printed, either on a polyethylene base or similar hydrophobic or non-hydrophobic wicking cloth, having an air permeability, Frazier, of at least 1.22 cubic meters per minute per square meter (4 cubic feet per minute per square foot) at a pressure drop of 1.27 cm (one-half inch) of water, as measured by the Frazier permeability analyzer. In addition, other permeable, non-woven materials, such as nonwoven polyester, folded by centrifugation, which is laminated to a membrane, can be used. For the proper distribution of PCB-G activated carbon, a fine sieve is typically used. The resulting filter device 10 will typically have a diameter of 2.54 cm (1 inch) with the adsorptive capacity as set forth above. Many filters of the prior art have low Frazier permeabilities, which are in the vicinity of 0.0003 cubic meters per minute per square meter (0.1 cubic feet per minute per square foot) which causes a large pressure drop across the filter. The permeability of the filters 10 of the present invention are much greater, and typically have Frazier permeabilities that are in the range of 0.092 to 0.17 cubic meters per minute per square meter (0.3 to 0.57 cubic feet per minute per square foot). Therefore, the present invention experiences a much lower pressure drop and avoids the problems of the prior art, while maintaining high adsorptive capacity. Referring now to Figure 8, a second embodiment of the filter device is shown which has an adsorbent bag configuration, generally designated 10A. The adsorbent bag 1 OA is mounted on an inner surface of the magnetic drive system or another system for generally filtering contaminants and removing corrosive elements. In the adsorbent bag filter 10A, the adsorptive deposit layer 18 is placed on a base layer 32 which is preferably a hydrophobic permeable membrane. An adhesive layer 28 is applied over the adsorptive layer 18. The adhesive layer 28 and the membrane layer 22 seals around and retains the adsorptive layer 18. The adhesive layer 28 is fixed to an interior of the magnetic disc drive or other system, removing a layer of release paper. As air circulates through the inside of the magnetic disk drive or other system, the magnetic bag filter 1 OA removes contaminants. Referring now to Figure 9, a third embodiment of a filter device is shown in accordance with the principles of the present invention, generally designated by 10B. The filter device 10B is a filter of the recirculation type, to filter the air as it is recirculated through the magnetic disk drive or other system. The recirculation filter 10B includes an adsorptive layer 18. The adsorptive liquid slurry 18 is deposited on a base layer 34 which is similar to the base layer 16 for the suction filter device shown in Figure 4. However, for a recirculating filter 10B, a pair of base layers 34 sandwich the adsorptive layer 18 therebetween. In addition, the cover layers 32 are bonded onto the base layers 34. The cover layers 32 can be woven polyester or other material that Provide a satisfactory permeability. It can be appreciated that with this arrangement, the air flow can pass through the recirculation filter 10B, in any direction, without the formation of pressure on any of the sides. It can be appreciated that the different filter modes, which include the suction filter 10, the adsorbent bag filter 1 OA and the recirculation filter 10B can be combined by various combinations for the removal of contaminants or can be used individually. For example, the suction filter can be used with an adsorbent bag and / or with a recirculation filter. Likewise, the others can be combined for multiple filtration configurations depending on the filtration needs of the system. It should be understood, however, that although in the preceding description numerous features and advantages of the present invention have been set forth, together with details of the structure and operation of the invention, the description is only illustrative, and changes can be made in detail, especially with respect to the shape, size and arrangement of parts, within the principles of the invention to the extent indicated by the broad and general meaning of the terms in which the appended claims are expressed. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following:

Claims (28)

1. A filter for use in a disk drive system, characterized in that it comprises: a base layer having a receiving surface of adsorptive material and an outer surface; an adsorptive layer comprising an adsorptive material deposited on the receiving surface, of adsorptive material, of the base layer, in a discrete pattern or configuration, to form an area of adsorbent and active filtration media and an area of adsorbent media; and a cover layer comprising a permeable fabric mounted to the base layer and enclosing the adsorptive material, wherein the filter has a Frazier permeability of at least 0.092 cubic meters per minute per square meter (0.3 cubic feet per minute per square foot ) at a pressure drop of 1.27 cm of water (half an inch of water), where the filter is provided for particulate filtration and for gas adsorption.

2. A filter according to claim 1, characterized in that the adsorptive material comprises activated carbon.

3. A filter according to claim 2, characterized in that the activated carbon is impregnated with a solution selected from the group of water soluble carbonate, bisulfite, sulfate and hydroxide salts.

4. A filter according to claim 1, characterized in that the adsorptive material comprises an adsorptive material selected from the group of activated carbon, activated alumina, molecular sieves, ion exchange resins, functional resins and polymers, diatomaceous earths, silica or clays.

5. A filter according to claim 4, characterized in that the adsorptive material comprises a catalytic material selected from the group consisting of copper, nickel, manganese oxides, copper oxides, and nickel oxides.

6. A filter according to claim 1, characterized in that the adsorptive material comprises an agent for the removal of acid, selected from the group of low molecular weight amines and polymeric amines.

7. A filter according to claim 1, characterized in that the adsorptive material further comprises organic or inorganic halides.

8. A filter according to claim 1, characterized in that the adsorptive material further comprises sulfate salts.

9. A filter according to claim 1, characterized in that the adsorptive material is impregnated with 2,4-dinitrophenolhydrazin.

10. A filter according to claim 1, characterized in that the adsorptive liquid paste comprises a viscosity modifier.

11. A filter device according to claim 1, characterized in that it also comprises a layer of adhesive, annular, applied to one side of the filter device.

12. A filter according to claim 1, characterized in that one between the base layer and the cover layer, comprises a non-woven protective layer and a HEPA membrane.

13. A filter according to claim 2, characterized in that the adsorptive material retains an adsorptive surface area capacity of at least 80% of the activated carbon material.

14. A filter according to claim 1, characterized in that the base layer comprises a multilayer structure including a support layer, a high efficiency membrane and a layer that supports adsorptive material.

15. A filter according to claim 1, characterized in that the adsorptive material is in the form of a moistened liquid paste.

16. A filter according to claim 1, characterized in that the filter is a suction filter.

17. A filter according to claim 1, characterized in that the filter is a recirculation filter.

18. A filter according to claim 1, characterized in that the filter is manufactured by a process comprising the steps of: (a) placing the base layer near a screen member; (b) depositing the adsorptive material, through the screen member, on the adsorptive material receiving surface of the base layer; (c) applying an adhesive on the base coat; and (d) applying a cover sheet on the base layer and the adsorptive material.

19. A filter according to claim 18, characterized in that it also comprises a layer of adhesive, annular, applied to one side of the filter.

20. A filter according to claim 18, characterized in that the base layer comprises a non-woven protective layer and a HEPA membrane.

21. A filter according to claim 18, characterized in that the adsorptive material comprises activated carbon.

22. A filter according to claim 20, characterized in that the adsorptive material comprises a viscosity modifier.

23. A filter according to claim 18, characterized in that the filter is a vacuum filter or a recirculation filter.

24. A method for manufacturing a filter, characterized in that it comprises the steps of: supplying a base layer to a rotary screen printer, wherein the base layer includes a receiving surface of adsorptive material; applying a liquid paste of adsorptive material, with a discrete pattern or configuration, to the adsorptive material receiving surface of the base layer; and applying a cover layer to the base layer to enclose or cover the discrete pattern of the liquid paste of adsorptive material; wherein the filter is provided for the filtration of particles and for the adsorption of gases.

25. A method according to claim 24, characterized in that the rotary screen printer comprises a screen, and the adsorptive material is applied to a back portion of the screen and pressed onto the adsorptive material receiving surface of the base layer.

26. A method according to claim 24, characterized in that the adsorptive material is pressed in the openings or holes of the screen, by means of a pallet or roller.

27. A method according to claim 26, characterized in that the roller comprises a screen portion, and wherein the liquid paste is supplied through the screen portion, to the adsorptive material receiving surface, of the base layer.

28. A method according to claim 24, characterized in that the adsorptive material is applied as a soaked paste, and subsequently dried.