Two stage filter system for vacuum cleaners

Abstract

In a vacuum cleaner, a two stage filter system includes a primary inner filter such as a conventional vacuum cleaner filter, and a secondary outer filter with an enhanced surface area that is a self-cleaning, flexible interlocking knitted fabric having a rest position at atmospheric pressure, and a stretched position when under vacuum of a vacuum cleaner, the fabric having at least enough stretchability to increase its surface area, including fabric and interstices, by at least 2% in its stretched position from its rest position. When the vacuum cleaner is operating, the secondary filter is in its stretched position and collects dust and debris, and when the vacuum cleaner is off, the secondary filter relaxes, returns to its rest position and its surface area contracts to be self-cleaning, and a portion of the dust and debris to fall from the filter.

Description

REFERENCE TO RELATED APPLICATION(S)

This application is a continuation in part of co-pending U.S. Utility patent application Ser. No. 13/986,281, docket number MMS-106A, filed on Apr. 18, 2013 by the present inventor, said application titled “VACUUM CLEANER FILTER KIT WITH ENHANCED SURFACE AREA FILTER” and also claims priority based on U.S. Provisional Patent Application Ser. No. 61/967,166, filed on Mar. 12, 2014 by the present inventor, titled “FILTERPAL PRE FILTER SYSTEM FOR MOBILE AND STATIONARY VACUUM CLEANERS ”.

BACKGROUND OF INVENTION

a. Field of Invention

The invention relates generally to vacuum cleaners, including stationary and portable vacuum cleaning devices of all sizes and shapes. More specifically, the present invention relates to both new and retrofitted vacuum cleaners to provide a two stage filter system. In this present invention filter system, there is a primary filter, being an inner filter, and being any conventional or unconventional vacuum cleaner filter, but in some preferred embodiments, this primary filter is a folded filter (sometimes called an accordion filter). The present invention system also has a secondary filter, being an outer filter, that is positioned atop the inner filter and this outer filter has an enhanced surface area filters. The present invention outer filters have increased relative surface areas and have stretchability that creates a self-cleaning feature. These characteristics in turn provide more efficient vacuuming and more use between filter cleanings. In addition, it has been found that these present invention outer filters protect the inner filters (that are much more difficult and complicated to clean) and last for much longer periods of time as compared to conventional filters. Thus, the outer filters preserve the inner filters, extend their useful life and retard or prevent punctures and other potential physical damage. In some embodiments, the invention also involves an advanced outer filter attachment mechanism for quick insertion and quick removal to and from the vacuum cleaner for easy cleaning. The present invention is a means of improving the performance of original equipment manufacturers' filters by reducing clogging and increasing their life span. For example, the outer (secondary) filter of the present invention converts the standard vacuum, such as a shop vacuum, from a single stage filter system to a two stage filter system.

b. Description of Related Art

The following patents and applications are representative of various types of vacuum cleaners and filter systems:

United States Patent Application No. 2012/0279185 A1 to Appelo describes a vacuum cleaner primary filter cage wall element that is adapted to form, together with at least one complementary filter cage wall element, a tubular baghouse filter cage segment. The filter cage wall elements are provided with snap-locks, for snapping a first long side of the primary filter cage wall element to a secondary long side of the complementary filter cage wall element, and for snapping a secondary long side of the primary filter cage wall element to a first long side of the complementary filter cage wall element.

U.S. Pat. No. 8,533,906 B2 to Liu describes vacuum cleaner comprising a receptacle having a working air inlet and an associated filter, the filter in communication with and downstream from the working air inlet, is disclosed. The vacuum cleaner further includes a housing containing a motor and having a cooling air outlet from the motor and a working air outlet, the working air outlet in communication with the working air inlet of the receptacle through a working air impeller, wherein the cooling air is directed to the receptacle, and the cooling air passes through the filter before exiting the working air outlet of the housing.

U.S. Pat. No. 8,206,482 B2 to Williams et al. describes vacuum cleaner filters, in particular replaceable vacuum cleaner filters suitable for both dry and wet/dry type vacuum cleaners, as well as systems incorporating the use of such filters and methods for their use. The filters include a plurality of adjacently positioned pleats arranged in a closed circumferential, cylindrically-shaped path, a top end cap having a central orifice capable of constricting a post on a vacuum filter cage, and optionally a molded end ring oppositely-spaced from the top end cap for engagement with the motor housing of a vacuum cleaner.

U.S. Pat. No. 6,428,610 B1 to Tsai et al. describes a filter media for a high efficiency particulate air (“HEPA”) filter including a multiplicity of adjacent electrostatically charged piles of nonwoven fabric. The invention further includes a method of making a HEPA filter.

U. S. Pat. No. 6,113,663 to Liu describes a vacuum cleaner having a dual filter assembly includes a filter cage, a primary filter disposed on the filter cage, and a secondary filter disposed downstream of the primary filter. A float valve between the primary filter and the secondary filter inhibits liquid from coming into contact with the secondary filter.

U.S. Pat. No. 6,110,248 to Liu at al. describes a dual filter assembly for a vacuum cleaner that includes an annular inner filter mountable on a filter cage of the vacuum cleaner. The inner filter has a lower end and a retaining ring is attached to the lower end. An annular outer filter is removably mounted surrounding the inner filter, with a lower end of the outer filter supported by the retaining ring.

U.S. Pat. No. 5,855,634 to Berfield describes a filter retainer for a vacuum cleaner that includes a filter cage having several ribs. At the bottom of the filter cage is a lip which includes a plurality of notches. A cylindrical filter having open ends is slid over the filter cage. A cap is placed at the bottom of the filter in order to hold the filter to the filter cage. The cap has a pair of ramps which engage notches on the rim of the filter cage. As the cap is rotated, the cap is pushed towards the filter so that a lip on the cap engages a bottom of the filter.

U.S. Pat. No. 5,783,086 to Scanlon et al. describes an improved method of employing a wet/dry vacuum cleaner 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 a place of a conventional wet/dry vacuum filter, it has been determined that the filter can be retained in place at all times during operation, regardless of the material being collected.

U.S. Pat. No. 5,308,485 to Griffin et al. describes a filter assembly for use in a baghouse having a cell plate provided with openings. The filter assembly includes a collar, filter bag, tubular supporting cage and locking ring. The filter bag filters particulate material and extends from below the cell plate. The collar supports the filter bag and has a longitudinally extended portion and a flange portion. The longitudinally extended portion is affixed to the filter bag below the cell plate, while the flange portion extends along the cell plate as a rim above a respective opening. The collar acts as a gasket to seal a respective opening in the cell plate. The tubular supporting cage has a longitudinally extended portion that structurally supports the filter bag. The locking ring is integrally fixed to the supporting cage and locks an arrangement of the filter bag, collar and cage in place. The locking ring also can include a venturi affixed thereto to assist in filtering and cleaning operations.

U.S. Pat. No. 5,308,369 to Morton et al. describes a cylindrical filter bag including a wire mesh cage with an access opening in the cage proximate to the open end of the filter bag. A resilient snap band is provided around the outer circumference of the cylindrical filter bag. The snap band includes a pair of felt rings formed around the band and an annular groove between the rings. The snap band thus provided can be depressed into the access opening in the wire mesh cage to allow the filter bag to be readily positioned in an airtight manner within a circular hole provided in the tube sheet of a dust collector. The hole in the tube sheet is provided with a collar having a radially extended flange portion that is attached to the top surface of the tube sheet to center the collar above the hole. The wire tube mesh cage of the filter bag is further provided with a reinforcing sleeve that mates with the tube sheet collar, and a venturi that is positioned concentrically within the sleeve.

U.S. Pat. No. 5,069,696 to Bruno describes a shop type vacuum cleaner including an externally mounted filter including a filter housing including a filter element and an elongated inlet tube slidably received within an exhaust outlet opening from the vacuum cleaner debris compartment.

U.S. Pat. Application No. 4,906,265 to Berfield describes installing a dry material paper filter on the filter cage of an electric vacuum cleaner, a disk of porous paper filtering material or of cloth type fabric, laid over the panel enclosing the bottom of the filter cage and a ring is pressed up over the paper or cloth filter and over the panel. As the ring is drawn up over the filter cage, it folds and presses the paper or cloth filter around the filter cage. At the top of the filter cage, the ring secures the filter to the cage. An additional filtering sleeve may be disposed around the filter cage before the filter is installed over the cage and over the sleeve with the attachment ring. The sleeve may be of foam or other wet material filtering material. The filter installed with the ring is of dry filtering material, like paper or cloth. A marking or disk at the center of the filter helps a user place the filter over the filter cage before the ring is used to fold the filter into place.

U.S. Pat. Application No. 3,830,042 to MacDonnell describes a disposable filter bag for the intake air housing of a locomotive that has a generally rectangular box-shaped extended configuration and is of pliable sheet stock of full flow depth filter material to be collapsible for folding into compact form. The bag is mounted between external and internal cage-like frames that stabilize the extended configuration of the bag.

U.S. Pat. Application No. 3,478,498 to Sauermann describes a filter that comprises a frame and a filter element carried by the frame to define therewith an internal chamber. The filter element consists of two apertured supporting layers and a filter layer of fibrous filter material sandwiched therebetween. A plurality of supporting bars is located in the internal chamber and engage the inner surfaces of the filter element. A plurality of deflecting bars engage the outer surfaces of the filter element intermediate the reinforcing bars and deflect the filter element intermediate such reinforcing bars inwardly into the chamber.

Notwithstanding the prior art, the present invention is neither taught nor rendered obvious thereby.

SUMMARY OF INVENTION

The present invention is directed to vacuum cleaner filters. Specifically, in a vacuum cleaner having a motorized vacuum system and a dust collecting canister with an air flow inlet and a canister outlet connected thereto, the present invention is a two stage filter system, being positioned within the canister at the canister outlet, wherein, when the vacuum cleaner is operating, there is a vacuum at the canister inlet and in the canister. The two stage filter system includes: (a) a primary filter, being an inner filter, connected to the canister outlet; and (b) a secondary filter positioned over the primary filter and attached to at least one of the canister outlet and the primary filter, the secondary filter being an outer filter, the secondary filter being a self-cleaning, flexible fabric filter selected from the group consisting of synthetic fabric, natural fabric and combinations thereof, the fabric having a rest position at atmospheric pressure, and a stretched position when under the vacuum of the operating vacuum cleaner, the knitted fabric having at least enough stretchability to increase its surface area, including fabric and interstices, by at least 2% in its stretched position from its rest position. When the primary filter and the secondary filter are in the vacuum cleaner and the vacuum is operating, the secondary filter is in its stretched position and collects dust and debris, and when the vacuum cleaner is subsequently not operating, the secondary filter relaxes, returns to its rest position and its surface area contracts to be self-cleaning, the contracting causing a portion of the dust and debris to fall from the secondary filter.

In some embodiments of the present invention vacuum cleaner two stage filter system, the secondary filter has fabric that includes continuous filaments and cut filaments to create a brushed fabric.

In some embodiments of the present invention vacuum cleaner two stage filter system, the secondary filter is woven or knitted.

In some embodiments of the present invention vacuum cleaner two stage filter system, the secondary fabric having at least enough stretchability to increase its surface area, including fabric and interstices, by at least 5% in its stretched position from its rest position.

In some embodiments of the present invention vacuum cleaner two stage filter system, the secondary fabric having at least enough stretchability to increase its surface area, including fabric and interstices, by at least 10% in its stretched position from its rest position.

In some embodiments of the present invention vacuum cleaner two stage filter system, the fabric filter has a fabric structure heft of about 2 to about 16 ounces per square yard.

In some embodiments of the present invention vacuum cleaner two stage filter system, the fabric filter has a fabric structure heft of about 2 to about 16 ounces per square yard.

In some embodiments of the present invention vacuum cleaner two stage filter system, the cage includes a clasping mechanism for holding the secondary filter in position, selected from the group consisting of a clamp, a wire, an elastic band and a two component fastener.

In some embodiments of the present invention vacuum cleaner two stage filter system, the secondary filter is a washable, reusable filter.

In some embodiments of the present invention vacuum cleaner two stage filter system, the secondary filter is a washable, reusable filter.

The present invention is also directed to a vacuum cleaner filter kit to create a two stage filter system, for retrofitting a secondary filter with an enhanced surface area over a primary existing filter of an electric power (or otherwise powered) vacuum cleaner having a motorized vacuum system and a dust collecting canister with an air flow inlet and canister outlet connected thereto. The present invention filter kit includes: (a) a fabric filter for positioning over the primary filter and attaching to at least one of the canister outlet and the primary filter, the fabric filter being a self-cleaning, flexible fabric filter selected from the group consisting of synthetic fabric, natural fabric and combinations thereof, the fabric having a rest position at atmospheric pressure, and a stretched position when under the vacuum of the operating vacuum cleaner, the knitted fabric having at least enough stretchability to increase its surface area, including fabric and interstices, by at least 2% in its stretched position from its rest position; and, (b) an attachment mechanism for attachment of the fabric filter to at least one of the canister outlet and the primary filter. When the primary filter and the fabric filter are in the vacuum cleaner, the fabric filter is an outer filter that is a secondary filter, and when the vacuum is operating, is in its stretched position and collects dust and debris, and when the vacuum cleaner is subsequently not operating, the secondary filter relaxes, returns to its rest position and its surface area contracts to be self-cleaning, the contracting causing a portion of the dust and debris to fall from the secondary filter.

In some embodiments of the present invention vacuum cleaner filter kit to create a two stage filter system, the secondary filter has fabric that includes continuous filaments and cut filaments to create a brushed fabric.

In some embodiments of the present invention vacuum cleaner filter kit to create a two stage filter system, the secondary filter is knitted or woven.

In some embodiments of the present invention vacuum cleaner filter kit to create a two stage filter system, the secondary fabric having at least enough stretchability to increase its surface area, including fabric and interstices, by at least 5% in its stretched position from its rest position.

In some embodiments of the present invention vacuum cleaner filter kit to create a two stage filter system, the secondary fabric having at least enough stretchability to increase its surface area, including fabric and interstices, by at least 10% in its stretched position from its rest position.

In some embodiments of the present invention vacuum cleaner filter kit to create a two stage filter system, the fabric filter has a fabric structure heft of about 2 to about 16 ounces per square yard.

In some embodiments of the present invention vacuum cleaner filter kit to create a two stage filter system, the attachment mechanism is a clasping mechanism for holding the secondary filter in position, selected from the group consisting of a clamp, a wire, an elastic band and a two component fastener.

In some embodiments of the present invention vacuum cleaner filter kit to create a two stage filter system, the secondary filter is a washable, reusable filter.

Additional features, advantages, and embodiments of the invention may be set forth or apparent from consideration of the following detailed description, drawings, and claims. Moreover, it is to be understood that both the foregoing summary of the invention and the following detailed description are exemplary and intended to provide further explanation without limiting the scope of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate preferred embodiments of the invention and together with the detail description serve to explain the principles of the invention. In the drawings:

FIG. 1 is a block diagram of some embodiments of the present invention, setting forth the parameters of some present invention two stage filter systems for vacuum cleaners;

FIG. 2 is a block diagram of some embodiments of the present invention, setting forth the parameters of some present invention retrofit kits to create two stage filter systems with existing filtered vacuum cleaners;

FIG. 3 is a front, partially cut view of one embodiment of a present invention two stage filter system in a rest position;

FIG. 4 is a front, partially cut view of the embodiment of a present invention two stage filter system shown in FIG. 3, but in a functioning vacuum position; and,

FIG. 5 shows a side cut view of a present invention filter kit for creation of a retrofit-based two stage filter system for existing vacuum cleaners with filters.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention involves vacuum cleaner filter kits with enhanced functionality, increased suction and self-cleaning and numerous other unique features that will become more apparent in the following discussion. The invention is a a vacuum cleaner having a motorized vacuum system and a dust collecting canister with an air flow inlet and a canister outlet connected thereto, with a unique two stage filter system, more fully developed below. The present invention is also a vacuum cleaner filter kit to create a two stage filter system, for retrofitting a secondary filter with an enhanced surface area over a primary existing filter of an electric power vacuum cleaner having a motorized vacuum system and a dust collecting canister with an air flow inlet and canister outlet connected thereto.

Vacuum cleaners are very efficient devices, except that they fill up quickly and the sooner or later (usually sooner), the original equipment manufacturers' (OEM) filters require cleaning. This is a dirty, tedious and thankless task that sometimes requires washing and repeated removal of the debris from the inner curves of the OEM filters each time they are cleaned. Typically, the OEM filters in home vacuums and shop vacuum machines have small surface areas. They are not designed to be reused or cleaned, and they do indeed clog quickly. When the filter fails, the user removes it from the shop or other vacuum. Debris collected by the OEM filter disperse into the air, where they may be inhaled in by the user. The user then disposes of the filter, or worse scrubs and scrubs it to get the dirt out. If thrown away, this assures that the user will purchase more filters, while used filters crowd landfills.

The present invention dual filter (two stage) filtering protects the OEM filter (the primary filter). The outer (secondary) filter of the present invention is a flexible fabric type media that fits over a conventional OEM filter. This layer traps debris and prevents clogging, increasing the life of the OEM filter. As a result, fewer purchases or cleanings of conventional OEM filters are necessary. The user saves money and reduces the number of disposable filters in landfills and eliminates the extensive efforts typically needed to clean a primary filter. Further, the present invention secondary filters, sometimes referred to as “FilterPal”, may be washed and re-used. Covering the OEM filter with FilterPal converts the filter system from single stage to double stage. The result is a small drop in pressure with less force pushing the particles through the OEM filter. FilterPal can be attached in a number of ways including clamps, bands and other fasteners. The flexibility of FilterPal allows it be influenced by external forces such as pressure drop and vibration. Variations in pressure drop that occur during start up and shut down change the shape of FilterPal and tend to dislodge debris held to the surface during normal operation.

Additionally, even when the vacuum is off, merely the vibration caused by rolling it across a floor (general motion) causes the debris to fall off the FilterPal surface. This action cleans the FilterPal's surface and partially restores its performance, rendering it self-cleaning, the very opposite end of the cleaning spectrum required for cleaning primary filters, and hence a quantum leap forward for vacuum cleaner filtration, as well as for eco-friendly solutions to these previously significant problems.

FIG. 1 is a block diagram of some embodiments of the present invention, setting forth the parameters of some present invention two stage filter systems for vacuum cleaners. In FIG. 1, block 1 represents any vacuum cleaner. Vacuum cleaner 1 includes power source and controls 3. These could be house current, batteries or other power source and the controls could be merely an on/off switch. There is an air suction motor or vacuum motor 5 with an air exhaust 7. The vacuum motor 5 is connected to the primary filter 11 via the canister outlet 9. In a normal vacuum cleaner, the primary filter keeps dirt and debris from exiting while allowing the suction air to pass through, and the primary filter quickly becomes clogged and eventually blocks the air exhaust enough that the vacuum cleaner will not properly function. In the present invention, the flexible interlocking fabric secondary filter 13 protects the primary filter and functions to stretch when in use and relax when not in use to cause dirt and debris to fall off This drastically extends useful life and decreases filter replacement costs significantly. This dirt and debris enters canister 15 via canister inlet 17, which is typically connected to a vacuum cleaner hose or nozzle. Other advantages of this two stage filtering are discussed in detail in Table I below.

FIG. 2 is a block diagram of some embodiments of the present invention, setting forth the parameters of some present invention retrofit kits to create two stage filter systems with existing filtered vacuum cleaners. Retrofit vacuum cleaner kit 21 includes a secondary filter 23 of flexible interlocking fiber, especially knitted fiber, and attachment means 27 for attachment of the secondary filter to a primary filter. Block 29 lists possible attachment means for this purpose.

FIG. 3 is a front, partially cut view of one embodiment of a present invention two stage filter system in a rest position and FIG. 4 is a front, partially cut view of the embodiment of a present invention two stage filter system shown in FIG. 3, but in a functioning vacuum position wherein the secondary fabric is stretched. Both Figures are discussed collectively, as follows.

In FIG. 3, basic vacuum cleaner 30a has a housing 31 with a canister 33 inside. The canister 33 is typically removable and may be a plastic or other structure. There is a primary filter 43 inside canister 33 and connected to canister outlet 37. There is also a flexible fabric secondary filter 45a and an attachment means (not shown, but a snap ring, an elastic band or any other attachment means may be used). Secondary filter 45a is in its rest or relaxed position in FIG. 3. FIG. 4 illustrates the same vacuum cleaner as in FIG. 3, but now running and hence shown as vacuum cleaner 30b. The motor 39 pulls air out of the canister 33, thereby pulling dirt and debris into canister 33 via canister inlet 43. The secondary filter is pulled in to the primary filter 43 and stretches. The dirt and debris enter the canister 33 and remain there as secondary filter 45b collects and holds some of the dirt and debris against its surface when the vacuum cleaner motor 39 is on (control 41 is the on/off switch). When the vacuum cleaner is off, the secondary filter 45a relaxes and the debris and dirt falls off.

FIG. 5 shows a side cut view of a present invention filter kit for creation of a retrofit-based two stage filter system for existing vacuum cleaners with (primary) filters. Secondary filter 51 includes a closed base 53, an open top 55 and closed sidewalls 57 that are flexible and allow passage of air but not dust, dirt or debris. There is a connection means 59, being a sewn in rubber band, but could as well be a snap ring, a separate rubber band, clips, hook and loop connectors, or any other viable connection means.

The following Table I illustrates the improvements achieved when both a primary and a secondary filter of the present invention are employed as compared to a single (primary or OEM filter alone). In summary, some of the important features of the present invention filter kits are shown in Table I:

	TABLE I
	Primary or oem filter alone	Primary and Secondary filter.
Washability	The construction of the oem filter	The secondary filter is construction of
	is ridged, folded media made of	knitted or woven fabric that is
	materials that are not expected	washable by hand or in a washing
	to be wetted. Attempts to	machine. The interaction of the
	remove particles by washing can	washing process with the fp media is
	cause the filter to fall apart. It	regenerates the fp to original state.
	can also convert the fine debris	The action of soap and water is
	from a powder to a self-	effective of dissolve and/or and
	hardening mud like compound	removing the particles by dissolving
	such as is the case with plaster or	and or floating the debris particles
	concrete. When this happens the	away.
	filter can be come totally ecluded
	and totally clogged and must be
	discarded and replaced.
Filter types	Disposable, designed to be	Reusable, cleanable, designed for many
	discarded and replaced.	uses.
	Generally difficult or impossible
	to clean.
Filter cleaning and or recovery of the filter achieved by removing the debris, so as to restore the original air
flow volume. There are several methods used to clean or regenerate a filter as described below.
Back flushing. The practice of	This practice is very undesirable	Filterpal is subject to the same
reversing the flow of air to	because if not executed in special	limitations and in general back flushing
“blow or discharge the	equipment the debris becomes	is not a safe way to clean and restore it.
particles from the surface of	air born and can be breathed in	A SAFE WAY TO BACK FLUSH flush a
the filter.	by the operator. It is particularly	filterpal is to dangle in a pipe attached
	dangerous indoors with the air	to the vacuum side of a vacuum cleaner
	born debris is concentrated by	and allow the reverse flow of the air to
	the entrapment within the walls	dislodge and remove the particles. The
	of the room.	debris is trapped the filter in the
		receiving vacuum cleaner.
Reaction to accelerations.	The primary does not react to this	The retention of particles by a soft and
Filters are frequently jarred by	well because the mass of the	very flexible media such as a knitted
slamming them against a hard	debris particles is so small that	fabric, is facilitated by the debris being
surface, the slamming action	slamming the filter against a hard	stopped by the soft fabric surface and
dislodges the debris from the	surface does not produce an	or becoming lodged in the spaces
surface. It is analogous to	acceleration necessary to	between the fibers. As the openings of
what happens to a person	produce a force of sufficient	the fabric become clogged by the
when their vehicle strikes a	magnitude to dislodge the	debris the increase pressure drop can
brick wall.	particle. One might use the	cause the opening in the fabric to be
	analogy of a jamming a ground	stretched and change shape. These
	ball into an unyielding square	changes in size and shape can increase
	passage. The wedging action	the particle trapping capacity of the
	produce a very high clamping and	media by adjusting to the increased
	holding forces	pressure drop. The debris becomes
		part of the filtering mechanism and the
		ability of the fabric to yield adjusts the
		pressure drop as to maintain the flow.
Reaction to turning the	The ridged system holds trapped	The flexible nature of the FP systems
vacuum source on and off.	particle is a ridged, un yielding	allows the filter surface to react to the
The normal operation of a	matrix. This means that it does	change in vacuum pressure.
vacuum cleaner involves	not react to the fact that the	When the vacuum is turned on the
turning it on to pick up and	vacuum is on or off. The particles	flexible filter bag will tend to take the
remove debris and turning it	that are stacked on top of the	shape of any supporting structure, in
off when the task is done. The	trapped or wedged particles are	this case the oem filter. When the
reaction of the two types of	held in place by the vacuum force	vacuum is turned of the filter bag will
filters is described	when the motor is on. When the	tend to return to a relaxed state which
	motor is turned off these	changes is shape and size. This change
	particles are not held in place by	has the effect of loosening and dis
	vacuum and depending on static	larging the particles that have been
	charge, stickiness and wedging	deposited and held in place by the
	characteristics they are free to	presence of vacuum force. There for,
	fall off the face of the filter.	the turning off of the vacuum pressure
		causes a change in shape and size of
		the filter surface which tends to release
		a much larger amount of the trapped
		particles. The result is that the flexible
		media is self-cleaning to a much greater
		degree than the ridged media.
		Stretching and/or shaking the media
		when the vacuum is turned off will
		result in most of the debris falling off,
		which can restore or regenerate the
		filter to it's “clean state” capacity.

Although particular embodiments of the invention have been described in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those particular embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims.

Claims

1. In a vacuum cleaner having a motorized vacuum system and a dust collecting canister with an air flow inlet and a canister outlet connected thereto, a two stage filter system, being positioned within said canister at said canister outlet, wherein, when said vacuum cleaner is operating, there is a vacuum at said canister inlet and in said canister, said two stage filter system comprising:

(a) a primary filter, being an inner filter, connected to said canister outlet; and

(b) a secondary filter positioned over said primary filter and attached to at least one of said canister outlet and said primary filter, said secondary filter being an outer filter, said secondary filter being a self-cleaning, flexible fabric filter selected from the group consisting of synthetic fabric, natural fabric and combinations thereof, said fabric having a rest position at atmospheric pressure, and a stretched position when under said vacuum of said operating vacuum cleaner, said knitted fabric having at least enough stretchability to increase its surface area, including fabric and interstices, by at least 2% in its stretched position from its rest position; and,

such that when said primary filter and said secondary filter are in said vacuum cleaner and said vacuum is operating, said secondary filter is in its stretched position and collects dust and debris, and when said vacuum cleaner is subsequently not operating, said secondary filter relaxes, returns to its rest position and its surface area contracts to be self-cleaning, said contracting causing a portion of said dust and debris to fall from said secondary filter.

2. In a vacuum cleaner, the two stage filter system of claim 1, wherein said secondary filter has fabric that includes continuous filaments and cut filaments to create a brushed fabric.

3. In a vacuum cleaner, the two stage filter system of claim 1, wherein said secondary filter is a fabric selected from the group consisting of knitted fabric, woven fabric and combinations thereof.

4. In a vacuum cleaner, the two stage filter system of claim 1, wherein said secondary fabric having at least enough stretchability to increase its surface area, including fabric and interstices, by at least 5% in its stretched position from its rest position.

5. In a vacuum cleaner, the two stage filter system of claim 1, wherein said secondary fabric having at least enough stretchability to increase its surface area, including fabric and interstices, by at least 10% in its stretched position from its rest position.

6. In a vacuum cleaner, the two stage filter system of claim 1, wherein said fabric filter has a fabric structure heft of about 2 to about 16 ounces per square yard.

7. In a vacuum cleaner, the two stage filter system of claim 3 wherein said fabric filter has a fabric structure heft of about 2 to about 16 ounces per square yard.

8. In a vacuum cleaner, the two stage filter system of claim 1 wherein said cage includes a clasping mechanism for holding said secondary filter in position, selected from the group consisting of a clamp, a wire, an elastic band and a two component fastener.

9. In a vacuum cleaner, the two stage filter system of claim 1 wherein said secondary filter is a washable, reusable filter.

10. In a vacuum cleaner, the two stage filter system of claim 4 wherein said secondary filter is a washable, reusable filter.

11. A vacuum cleaner filter kit to create a two stage filter system, for retrofitting a secondary filter with an enhanced surface area over a primary existing filter of an electric power vacuum cleaner having a motorized vacuum system and a dust collecting canister with an air flow inlet and canister outlet connected thereto, said filter kit comprising:

(a) a fabric filter for positioning over said primary filter and attaching to at least one of said canister outlet and said primary filter, said fabric filter being a self-cleaning, flexible fabric filter selected from the group consisting of synthetic fabric, natural fabric and combinations thereof, said fabric having a rest position at atmospheric pressure, and a stretched position when under said vacuum of said operating vacuum cleaner, said knitted fabric having at least enough stretchability to increase its surface area, including fabric and interstices, by at least 2% in its stretched position from its rest position; and,

(b) an attachment mechanism for attachment of said fabric filter to at least one of said canister outlet and said primary filter;

such that when said primary filter and said fabric filter are in said vacuum cleaner said fabric filter is an outer filter that is a secondary filter, and when said vacuum is operating, is in its stretched position and collects dust and debris, and when said vacuum cleaner is subsequently not operating, said secondary filter relaxes, returns to its rest position and its surface area contracts to be self-cleaning, said contracting causing a portion of said dust and debris to fall from said secondary filter.

12. The vacuum cleaner filter kit to create a two stage filter system of claim 11, wherein said secondary filter has fabric that includes continuous filaments and cut filaments to create a brushed fabric.

13. The vacuum cleaner filter kit to create a two stage filter system of claim 11, wherein said secondary filter is a fabric selected from the group consisting of knitted fabric, woven fabric and combinations thereof.

14. The vacuum cleaner filter kit to create a two stage filter system of claim 11, wherein said secondary fabric having at least enough stretchability to increase its surface area, including fabric and interstices, by at least 5% in its stretched position from its rest position.

15. The vacuum cleaner filter kit to create a two stage filter system of claim 11, wherein said secondary fabric having at least enough stretchability to increase its surface area, including fabric and interstices, by at least 10% in its stretched position from its rest position.

16. The vacuum cleaner filter kit to create a two stage filter system of claim 11, wherein said fabric filter has a fabric structure heft of about 2 to about 16 ounces per square yard.

17. The vacuum cleaner filter kit to create a two stage filter system of claim 13 wherein said fabric filter has a fabric structure heft of about 2 to about 16 ounces per square yard.

18. The vacuum cleaner filter kit to create a two stage filter system of claim 11 wherein said attachment mechanism is a clasping mechanism for holding said secondary filter in position, selected from the group consisting of a clamp, a wire, an elastic band and a two component fastener.

19. The vacuum cleaner filter kit to create a two stage filter system of claim 11 wherein said secondary filter is a washable, reusable filter.

20. The vacuum cleaner filter kit to create a two stage filter system of claim 14 wherein said secondary filter is a washable, reusable filter.