WO1997011632A1

WO1997011632A1 - Improved method for employing wet/dry vacuum cleaners for wet material collection

Info

Publication number: WO1997011632A1
Application number: PCT/US1996/013946
Authority: WO
Inventors: Richard W. Giannetta; Raymond M. Wnenchak; John J. Scanlon
Original assignee: W.L. Gore & Associates, Inc.
Priority date: 1995-09-29
Filing date: 1996-08-26
Publication date: 1997-04-03
Also published as: AU6907296A

Abstract

The present invention is an improved method of employing a wet/dry vacuum cleaner to collect liquid and wet materials. The method of the present invention employs a liquid impenetrable filter (10), preferably comprising an expanded polytetrafluoroethylene filtration medium and a liquid-tight gasket seal (24). By employing a hydrophobic filter that is liquid impenetrable, the present invention provides wet pick-up without the need to remove the wet/dry vac filter and without the risk of filter degradation. Numerous benefits are provided with the present invention, including better filtration for both wet and dry material collection, effective aerosolized liquid containment, and easy filter cleaning and rejuvenation.

Description

TITLE OF THE INVENTION

IMPROVED METHOD FOR EMPLOYING WET/DRY

VACUUM CLEANERS FOR WET MATERIAL COLLECTION

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to improved methods for employing vacuum cleaner devices designed to handle both dry and wet cleaning situations.

2. Description of Related Art A variety of vacuum cleaners are presently available that can effectively pick-up both dry and wet materials. These devices are found in a variety of forms, but all generally comprise a large holding tank with a suction unit mounted on top of the tank. Dry or wet materials are drawn through a hose into the holding tank during suction. These devices are sold by a number of companies under trademarks, such as SHOP VAC, SEARS CRAFTSMAN,

GENIE, HOOVER, BLACK & DECKER, etc. This class of vacuum cleaner is commonly referred to as "wet/dry vacs."

In the case of dry material pick-up, it is important that dust blown into the tank of a wet/dry vac is not blown into the air outside the tank through the vacuum exhaust. In order to avoid this situation, all of these vacuums are sold with some form of filter mounted between the tank and the exhaust to contain dry dust contamination within the vacuum's tank. Typical filters sold with these vacuum cleaners comprise a flat or pleated paper that is attached to the base of the suction unit within the tank. One common complaint of wet/dry vacs is that their filters are not suitable for use with wet materials. When the typical wet/dry vac filters are exposed to water or even wet materials (e.g., wet leaves), the water tends to wet-out the paper filters and quickly destroys them under the harsh conditions of vacuuming. Accordingly, manufacturers recommend that the conventional filters be removed whenever wet pick-up occurs. However, stores continue to do a brisk business in replacement filters for those individuals who have forgotten or refused to remove the filters when encountering wet conditions.

Wet vacuum cleaning is further complicated by a number of other factors. First, while wet dirt and the like are inclined to stay in the tank and not become entrained into the exhaust from the vacuum, the cleaning of mixed dry and wet materials without a filter in place usually leads to dust spewing from the exhaust. Second, even in instances where only liquid is being collected, the liquid tends to become aerosolized and exhausted from the vacuum. Third, most wet/dry vacs include cut-off valves to prevent liquid from being drawn through the suction unit when the tank becomes filled with liquid However, these valves tend to engage only at the last minute, usually resulting in at least some spillage or dispersion of liquid from the vacuum cleaner Another problem with typical wet/dry vac filters is that they tend to provide only marginal filtration of fine dust particles For use in heavy duty shop applications, fine dust filtration may not be a major concern However, there are instances where it is desirable to have the strong suction and large capacity of a wet/dry vac, but fine dust particle filtration is desired Several years ago W L Gore & Associates, Inc , introduced a fine- particle filter for a specialized application of filtering dry toner particles found in photocopy machines and the like These filter units comprise a pleated membrane of expanded polytetrafluoroethylene (PTFE) mounted around a perforated metal core While these filters have proven very effective at filtering extremely fine, dry toner particles in these applications, these filters were not designed for wet pick-up applications and have not been employed with wet materials

Accordingly, it is a primary purpose of the present invention to provide a method of using a wet/dry vac that allows for the pick-up of either wet or dry materials while assuring adequate filtration of both dry and wet materials at all times

It is another purpose of the present invention to provide a method of using a wet/dry vac that significantly increases the operative life of the vacuum filter These and other purposes of the present invention will become evident from review of the following specification

SUMMARY OF THE INVENTION The present invention is an improved method of employing a wet/dry vacuum cleaner ("wet/dry vac") for wet material pick-up By employing a hydrophobic and air permeable filter material, such as an expanded polytetrafluoroethylene (PTFE), with a tight gasket around its edge in place of a conventional wet/dry vac filter, it has been determined that the filter can be retained in place at all times during operation, regardless of the material being collected Preferably, the present invention comprises a method of collecting wet materials that provide filtration of both wet and dry materials during the collection process The preferred method comprises mounting a filter of expanded PTFE and a tight gasket element on a suction unit of a wet/dry vac and then employing the vacuum to collect wet materials The expanded PTFE filter creates a barrier to stop virtually all liquid, including aerosolized liquid, from exiting the tank of the wet/dry vac The expanded PTFE material is an extremely effective filter, filtering both dry and wet materials to a very fine level while maintaining full suction on the vacuum cleaner Further, the filter employed with the present invention provides such an effective seal that liquid leakage will not occur through the filter even when the vacuum cleaner has become completely filled This reduces risk of liquid from being discharged out vac exhaust Finally, the method of the present invention provides for the regular removal and wet cleaning of the filter employed with the present invention This increases the operative life of the filter and assures maximum filtration efficiency at all times

DESCRIPTION OF THE DRAWINGS

The operation of the present invention should become apparent from the following description when considered in conjunction with the accompanying drawings, in which

Figure 1 is a three-quarter perspective view of the bottom of one embodiment of a filter for use in the present invention shown in exploded orientation above a suction unit of a conventional wet/dry vac,

Figure 2 is a three-quarter perspective view of the top of the filter unit shown in Figure 1 , and

Figure 3 is a three-quarter perspective view of the bottom of another embodiment of a filter for use in the present invention shown in exploded orientation above a suction unit of another brand of conventional wet/dry vac

DETAILED DESCRIPTION OF THE INVENTION

The present invention employs an expanded polytetrafluoroethylene

(PTFE) membrane laminate filter cartridge in a wet/dry vac to provide effective filtration for collection of both dry and wet material By using the process of the present invention, the filter cartridge may be used during wet or dry pick-up with no risk of filter degradation or diminished filtering capabilities during wet

Figures 1 illustrate one embodiment of a filter cartridge 10 for use with the present invention Figure 1 shows the filter cartridge 10 mounted on the suction unit 12 of one form of commercially available wet/dry vacuum cleaner The wet/dry vac shown is a Model 917744 SEARS CRAFTSMAN wet/dry vac available from Sears, Roebuck & Co , Chicago, IL

Typical of most wet/dry vacs, the vacuum cleaner illustrated in Figure 1 comprises the suction unit 12 that mounts on top of a tank (not shown) for collecting contamination in the form of dirt, dust, and water and other liquids, etc The suction unit 12 includes an opening (not shown) that a vacuum cleaner hose is attached to, an exhaust 14, a safety valve 16 for shutting off the suction unit 12 when liquid fills the tank, and catches 18a, 18b for securing the suction unit 12 to the tank A conventional wet/dry vac of this type employs a pleated paper filter on a hub 13 of the suction unit to filter dirt and dust before it reaches the vacuum motor or the vacuum exhaust 14 As has been noted, the paper and fabric filters work adequately well for dry particle pick-up, but will rapidly degrade when exposed to water and other liquids Accordingly, the paper filter must be removed prior to liquid or wet material collection A further problem with paper filters is that they are not easily cleaned (with cleaning primarily limited to shaking or lightly brushing the filter) Accordingly, the filters are generally not cleaned, but are merely thrown away when they become filled with dust

The present invention provides an entirely new process for wet/dry vac operation An extremely durable filter cartridge is provided that includes filtration media that is capable of being exposed to repeated exposures to water without degradation Particularly preferred is a hydrophobic material that provides a barrier to liquid penetration Suitable filtration materials that can be used with the present invention include expanded polytetrafluoroethylene (PTFE) membrane, expanded ultra high molecular weight polyethylene (UHMW

PE) membrane, microporous open cell polymers (such as, polyurethane foam), dense paper filters treated to be hydrophobic (such as treatment with Milease F-95 available from Zeneca Inc , Wilmington, DE, or Scotch Guard available from 3M, St Paul, MN), etc It is particularly preferred to employ an expanded PTFE filter with the present invention Expanded PTFE made in accordance with United States Patents 3,953,566, 3,962,153, 4,096,227, and 4,187,390, all incorporated by reference, is formed by heating and rapidly expanding PTFE in at least one direction When processed in this manner, the expanded PTFE forms a microscopic structure of polymeric nodes interconnected by fibrils Space between the nodes and fibrils are micropores that allow the passage of air and water vapor, but are too small to permit passage of liquid water or even fine water droplets The expanded PTFE filter material for use with the present invention comprises a single layer of expanded PTFE membrane, approximately 0 2 to 0 127 mm thick The final sheet ideally has the following properties porosity of 70% to 95%, and a permeability range of 2 to 60 or more cfm/ft² at 12 7 mm

(0 5 inch) H₂O Preferably, the sheet comprises a thickness of 0 02 to 0 05 mmmm,, aa ppoorroossiittyy of 90 to 95%, and permeability of 5 to 10 cfm/ft² at 12 7 mm

Pore size measurements may be made by the Coulter Porometer™, manufactured by Coulter Electronics, Inc , Hialeah, FL The Coulter

Porometer™ is an instrument that provides automated measurement of pore size distributions in porous media using the liquid displacement method

(described in ASTM Std F316-86) Air permeability may be measured by clamping a test sample in a gasketed flanged fixture which provided a circular area of approximately 3827mm² (69 85 mm diameter) (6 square inches (2 75 inches diameter)) for air flow measurement The upstream side of the sample fixture is connected to a flow meter in line with a source of dry compressed air

The downstream side of the sample fixture is open to the atmosphere Testing is accomplished by applying a pressure of 12 7 mm (0 5 inch) of water to the upstream side of the sample and recording the flow rate of the air passing through the in-line flowmeter (a ball-float rotameter) The sample is conditioned at 70°F and 65% relative humidity for at least 4 hours prior to testing Results are reported in terms of Frazier Number which is air flow in cubic feet/minute/square foot of sample at 12 7 mm (0 5 inch) water pressure

The filter material is then laminated to a porous backing material, such as a porous polyester nonwoven, paper, felt, sintered polypropelyne, polyethylene, polyimide, polyamide, etc In order to increase expose surface area, the filter material can then be folded into multiple pleats and then installed in a "rippled" or " pleated" orientation into the filtration apparatus The pleated material can be formed into a cylinder or "tube" and then bonded together such as through the use of an adhesive (e g , hot-melt glue, etc ), ultrasonic welding, etc

As is shown in Figures 1 and 2, the final composite filter sheet material

20 is preferably pleated into a tube having approximately 0 5 to 3 pleats per cm To form the filter cartridge 10 from the tube, the tube is mounted with an end plate 22 at one end and a tight gasket element 24 at its opposite end The end plate 22 and gasket element 24 are ideally provided with grooves 26, 28, respectively, into which the filter sheet 20 is mounted The filter sheet 20 can be held in the grooves through any suitable means, including through the use of an adhesive, a potting compound 30, etc It is important that the seal between the filter sheet 20 and the end plate 22 and the gasket element 24 are liquid tight so as to avoid leakage therethrough

The gasket element 24 can be formed from any suitable material that will retain its elastic and conformable properties over time and can provide a snug and air, liquid-tight seal Preferred material for the gasket is urethane, such as GORE BOND I3P3 brand urethane available from W L Gore &

Associates, Inc , Newark, DE

It should be understood that the filter used in the present invention may be constructed in a variety of manners For instance, the end cap 22 may be constructed from plastic, metal (preferably non-corrosive metal), etc Further it may be possible to employ a filter with no end cap, using instead a gasket element on both sides of the filter

As is shown in Figure 2, the filter cartridge 10 for use in the present invention is formed with non-corrosive parts so as to avoid rust and other problems that can be encountered with wet material collection Preferably, as is shown, the filter is formed from a sufficiently stiff and resilient filter sheet that does not require a cage, perforated core, or other internal stiffener to maintain the shape of the filter during use

Especially preferred for use with the present invention is to employ a pleated filter sheet where the tips 32 of the pleats have been treated to protect against wear and damage of the filter media along the tips 32 of the pleats during use The preferred pleats are treated by heat and pressure densification and/or polymer coating Filter may be supported by hub 1 , 52 as shown in Figures 1 and 3, respectively

When constructed in the manner disclosed, the filter cartridge 20 has one open end 34 surrounded by the gasket element 24 that is adapted to snugly fit over the exhaust section of the suction unit 12 of the wet/dry vac The precise shape and proportions of the gasket element 24 will vary between different wet/dry vacs Additionally, various wet/dry vacs have different mounting mechanisms to secure the filter in place For example, the filter unit shown in Figure 1 includes a washer 36, bolt 38, and adjustable nut 40 The bolt 38 passes through an opening 42 in the end plate 22 to hold the filter cartridge 10 in place on the suction unit 12 The gasket element 24 forms a tight fit against a sealing surface 44 on the suction unit 12 in this embodiment when retained in place using the bolt 38 and nut 40

Another embodiment of wet/dry vac that can be employed with the present invention is shown in Figure 3 This drawing represents a suction unit for a SHOP VAC brand wet/dry vacuum, Model 500A Conventional filters on this type of wet/dry vac are held in place using an elastic band or mounting ring around the paper filter In order to adapt an expanded PTFE filter to this application, a modified gasket element 46 has been provided that holds the filter cartridge in place on the suction unit 12 without the need of separate mounting means As is shown, the end plate 48 in this embodiment contains no mounting hardware and merely provides a tight seal to the interior of the filter cartridge The gasket element 46 forms a tight fit a sealing surface 50 around hub 52 to prevent liquid from passing through to the exhaust of the vacuum cleaner Again, adhesive, potting material 54 or similar material is used to form a tight seal on the ends of the filter material

The present invention employs the above described filter cartridges in the following manner First, the filter cartridge is mounted on the wet/dry vacuum cleaner in the manner previously described so as to form a liquid tight seal between the tank and the vacuum cleaner exhaust Next, the vacuum cleaner is employed in a conventional manner to pick-up debris When liquid or wet material is encountered, no modification to the vacuum need occur The durable vacuum filter combined with a liquid tight seal around the filter assures that liquid will not destroy the filter and provides an effective barrier to liquid escaping from the tank Among the important advantages of the process of the present invention is that aerosolized liquid that is generated when liquid is drawn into the tank is also effectively filtered With liquid pick-up using conventional wet/dry vac operation, liquids tend to form a fine mist or "aerosol" that will attack and destroy conventional paper and cloth filters causing liquid leakage through the exhaust once the filter becomes saturated If the vacuum cleaner is run without a filter, the aerosol will spew out the vacuum cleaner's exhaust The filter employed with the present invention provides a barrier to the escape of aerosolized liquid from the tank, with liquid mist condensing on the filter and dripping down into the tank This provides significant benefits by effectively containing the aerosolized liquid while also protecting the suction unit 12 from contamination or attack by the liquid These benefits are particularly desirable where the wet/dry vac is being used to collect corrosive, hazardous, noxious, or similar materials where complete containment is important In fact, it is believed that this aspect of the present invention may allow conventional wet/dry vacs to be used for many new applications that were previously impossible due to the risk of aerosolizing and dispersing hazardous liquid substances Another important feature of the process of the present invention is that it provide far more secure liquid pick-up Until the present invention, the collection of liquid has always been a constraint for wet/dry vac operation Since the vacs can collect a large amount of liquid in a relatively short period of time, there is always a distinct risk that the tank will completely fill with liquid and the liquid will then be expelled from the exhaust or sucked into the motor or fan on the unit In order to avoid this problem, wet/dry vacs include some form of shut-off valve 16 to prevent liquid from overfilling the tank The problem with these valves is that they tend to engage only at the last minute and some liquid spillage can occur With the present invention, the filter unit itself serves as an extremely effective valve to prevent any liquid from exiting the tank, even when the tank is completely filled If the unit completely fills with liquid with a filter of the present invention in place, suction will diminish and cease as the filter becomes covered with liquid In this instance, the only risk of spillage is the release of liquid in the vacuum cleaner hose back to the area being cleaned when the drum is completely filled Accordingly, when employed with a conventional wet/dry vac, the filter provides an additional layer of protection that liquid will not overfill the tank Further, the filter unit employed with the present invention is so effective at isolating liquid from the exhaust that it is believed possible to completely dispense with a shut-off valve entirely from the wet/dry vac This provides a cost savings for the manufacturer and allows for the construction of simpler, lighter, and easier to assemble wet/dry vac units

Still another important benefit of the process of the present invention is that the filter can be easily removed, fully cleaned, and then re-mounted in the vacuum cleaner Since the filter employed with the present invention is completely waterproof, the filter can be completely washed inside and out of dirt and contamination with no compromise of the filtration efficiency of the filter As a result, the operative life of the filter when used in conjunction with the present invention is dramatically increased over conventional filters Finally, the filter used in the present invention provides dramatic improvements over previous wet/dry vac operations As has been explained, currently manufacturers recommend that filters be removed from the wet/dry vac when liquid or wet material pick-up occurs In these instances, the vacuum cleaners effectively operate with little or no filtration occurring. This unfortunately results in dust dispersion from the vacuum when wet and dry material is simultaneously collected. Another problem is that conventional wet/dry filters provide only marginal filtration efficiencies even when the paper filters are in place.

By contrast, the filter employed with the present invention provides excellent particle filtration at all times. The preferred expanded PTFE filter for use in the present invention provides a filtration efficiency of 60 to 99% or more efficient at 0.3 microns. Ideally, the filter has an efficiency of 99.7 to 99.9 at 0.3 microns. This is manifold better performance than conventional wet/dry vac filters, which typically have a filtration efficiency of about 10 to 20% at 0.3 microns when operated dry and virtually no long-term filtration efficiency when operated wet.

Without intending to limit the scope of the present invention, the following examples illustrate how the present invention may be made and used:

Example 1

A cartridge for use in the present invention was constructed by first taking an expanded PTFE membrane, made in accordance with U. S. Patent

3,953,566 to Gore, with the following properties:

A permeability of 21 ft³/min and 0.5 inch H₂O. A Mullen burst of about 2 psi and a thickness of approximately 2 mils (0.05 mm).

This material is commercially available from W. L Gore and Associates

Inc., Newark, DE, under the trademark GORE-TEX.

The expanded PTFE membrane material was laminated to a 6 oz Reemay Style 2024 polyester thermoplastic nonwoven acquired from Reemay, Inc., Old Hickory, TN. Lamination was accomplished by applying 260°C heat and 206 KPa (30 psi) pressure for a period of about 0.1 seconds. The resulting laminate had the following properties:

A permeability of 9 ft³/min at approximately 0.5 inch H₂O and a Mullen burst tester measurement of about 150 psi.

The Mullen's burst test (Federal Std. 191 A, Method 5512) is performed in the following manner. The test consists of clamping a test specimen in a fixture, applying water under pressure against the inner surface, and visually observing the outward facing surface of the specimen until the specimen ruptures (Burst) The pressure at which these events occur is recorded

The laminate was then pleated using a pleating machine The pleated pack was then sealed together into a cylinder using a DEXTER HYSOL® 232

EVA hot melt glue This cylinder was then attached to a gasket on one end and an end plate on the opposite end The attachment between the filter material and the gasket and end plate was sealed using a urethane potting compound, GORE BOND I3P3 available from W L Gore & Associates, Inc , of Newark, DE

This filter was employed in a 16 Gallon SEARS CRAFTSMAN Wet/Dry Vac The vacuum cleaner was used to pick-up water from a tub and it did so without any water or mist spraying out of the exhaust of the vacuum Once the tank of the vac was filled with water, with the filter totally surrounded by water, the flow stopped and no water exited the exhaust

While particular embodiments of the present invention have been illustrated and described herein, the present invention should not be limited to such illustrations and descriptions It should be apparent that changes and modifications may be incorporated and embodied as part of the present invention within the scope of the following claims

Claims

The invention claimed is 1 A method for employing a wet/dry vac for collecting wet material that comprises providing a filter cartridge comprising a hydrophobic and air permeable filtration membrane and a liquid-tight gasket, the filtration membrane being sufficiently hydrophobic so as to withstand repeated exposure to water without degradation, providing a wet/dry vac, the vac having a suction unit and an air exhaust mounting the filter cartridge on the suction unit of the wet/dry vac so as to cause the filter cartridge to serve as a barrier to liquid passing through the air exhaust, employing the wet/dry vac to collect wet material, whereby wet liquid becomes aerosolized within the vac, whereby the filter cartridge blocks the aerosolized liquid from exiting the vac through the exhaust 2 The method of claim 1 that further comprises providing as the filter material at least one membrane of expanded polytetrafluoroethylene 3 The method of claim 1 that further comprises allowing the vac to fill completely with wet material, whereby the filter cartridge provides a barrier to liquid exiting through the exhaust once the vac is filled with wet material 4 The method of claim 1 that further comprises after a period of use, removing the filter cartridge from the wet/dry vac, washing the filter cartridge with water to remove dirt therefrom, and re-mounting the filter cartridge on the suction unit of the wet/dry vac so as to cause the filter cartridge to serve as a barrier to dust and water passing through the air exhaust 5 The method of claim 1 that further comprises employing the filter as a safety valve to prevent liquid from passing out the air exhaust 6 The method of claim 5 that further comprises employing the filter to cease suction when the wet/dry vac becomes filled with water 7 The method of claim 1 that further comprises employing the filter cartridge for both dry and wet material pick- up, whereby the filter provides dust filtration 8 A method for employing a wet/dry vac for collecting wet material that comprises providing a filter cartridge comprising at least one membrane of expanded polytetrafluoroethylene (PTFE) and a liquid-tight gasket, the expanded PTFE membrane being hydrophobic and air permeable, providing a wet/dry vac, the vac having a suction unit and an air exhaust, mounting the filter cartridge on the suction unit of the wet/dry vac so as to cause the filter cartridge to serve as a barrier to liquid passing through the air exhaust, employing the wet/dry vac to collect wet material, whereby wet liquid becomes aerosolized within the vac, whereby the filter cartridge blocks the aerosolized liquid from exiting the vac through the exhaust 9 The method of claim 8 that further comprises allowing the vac to fill completely with wet material, whereby the filter cartridge provides a barrier to liquid exiting through the exhaust once the vac is filled with wet material 10 The method of claim 8 that further comprises after a period of use, removing the filter cartridge from the wet/dry vac, washing the filter cartridge with water to remove dirt therefrom and re-mounting the filter cartridge on the suction unit of the wet/dry vac so as to cause the filter cartridge to serve as a barrier to dust and water passing through the air exhaust 11 The method of claim 8 that further comprises employing the filter as a safety valve to prevent liquid from passing out the air exhaust 12 The method of claim 11 that further comprises employing the filter to cease suction when the wet/dry vac becomes filled with water 13 The method of claim 8 that further comprises employing the filter cartridge for both dry and wet material pick- up, whereby the filter provides dust filtration