Patent Description:
The German patent application <CIT> discloses a filter arrangement including a receptacle for a fuel filter and a fuel filter which comprises a first filter material and a further filter material surrounding the first filter material. The filter arrangement is configured such that fuel to be filtered flows through the first filter material and then the further filter material.

In the British patent <CIT>, a filtering device is disclosed comprising two concentric, perforated tubes, a main filter element disposed between the perforated tubes, a preliminary filter element disposed around the outer one of the perforated tubes and two annular cover plates, one disposed at each end of the perforated tubes. The outer rim of each cover plate is formed as a flange so as to overlap the ends of the preliminary filter element. Each cover element being formed of a moldable plastics material and being thickened at its inner rim to form a sealing ring, the ends of the perforated tubes being embedded in the cover plates.

The <CIT> relates to a filter element comprising an upstream filter and a downstream filter made of the same or a different material and installed into one housing or container. Said downstream filter is fixed to said housing, said upstream filter is fixed to the downstream filter, both filters are concentrically arranged to each other, and when the downstream filter is not contaminated, only the upstream filter can be replaced with a fresh one.

The German utility model registration <CIT> discloses a one-way filtering showerhead including a filter assembly arranged at a water inlet of a showerhead body and equipped with a one-way water flow unit, a filter carrier and an initial filter net. The filter carrier is provided with a water flow hole and the first filter net is arranged in the filter carrier corresponding to the water flow hole.

The German patent application <CIT> discloses a filter consisting essentially of a hollow porous filter medium with a cylindrical end wall wherein end caps made of a thermoplastic material which differs from the material the hollow porous filter medium is made of are connected to the cylindrical end wall by welding without the use of additional welding material.

The <CIT> discloses a filter cartridge including a wound depth filter or a cylindrical seamless depth filter and a pleated filter having a lower micron retention rating than the depth filter. The depth filter and the pleated filter surround a central opening. The cartridge is sealed and an appropriate inlet or outlet is provided in order to assure a sequential fluid flow first through the depth filter and then through the pleated filter.

The British patent application <CIT> relates to a tubular filter for removing oil mist from a stream of air or other gas. It comprises a coalescing layer and a drainage layer. The lower end of the coalescing layer is sealed into and closed by an end cap while the lower end of the drainage layer is generally uncompressed and unobstructed, extends axially below the end of the coalescing layer and locates within an outer annular zone of the end cap which provides channels through which coalesced oil drops can drain. The lower saturated part of the drainage layer is enclosed by a sleeve and shielded from the air flow to minimize re-entrainment.

The US patent application <CIT> discloses a filter system for spas and swimming pools having a primary filter containing a porous membrane made of multiple plies. A micro filter for filtering particles surrounds the primary filter.

The present invention provides for ameliorating at least some of the disadvantages of the prior art. These and other advantages of the present invention will be apparent from the description as set forth below.

A filter device according to the invention is set out in claim <NUM> and comprises an embodiment of the filter arrangement located in a housing having an inlet and an outlet and defining a fluid flow path between the inlet and the outlet, wherein the filter arrangement is arranged in the housing across the fluid flow path, such that undesirable material is removed from fluid as the fluid passes through the filter device. Preferably, the filter device comprises a point of use shower head device or a point of use faucet head device, and the host filter comprises a sterilizing grade water filter.

The filter arrangement comprising a host filter comprising (a) a hollow cylindrical porous host filter element having a first end and a second end; (b) a first end cap arranged at the first end or the second end of the hollow cylindrical porous host filter element, the first end cap having an outer diameter; and, (c) an outer surface; the filter arrangement further comprising (d) a porous fibrous hollow cylindrical prefiltration element compression fit on the outer diameter of the first end cap, and covering the exposed outer surface of the host filter.

Processing fluid according to the invention is defined in claim <NUM> and comprising passing fluid through a filter arrangement comprising a porous fibrous hollow cylindrical prefiltration element and a host filter, wherein the porous fibrous hollow cylindrical prefiltration element is compression fitted on the host filter, and removing undesirable material from fluid as the fluid passes through the fluid arrangement. Preferred embodiments of the method comprise passing water through a point of use shower head device or a point of use faucet head device, wherein the host filter comprises a sterilizing grade water filter, and dispensing sterile water from the device.

A filter device according to an embodiment of the invention comprises an embodiment of the filter arrangement located in a housing having an inlet and an outlet and defining a fluid flow path between the inlet and the outlet, wherein the filter arrangement is arranged in the housing across the fluid flow path, such that undesirable material is removed from fluid as the fluid passes through the filter device. The filter device comprises a point of use shower head device or a point of use faucet head device, and the host filter comprises a sterilizing grade water filter.

In accordance with an embodiment of the invention, a filter arrangement is provided comprising a host filter comprising (a) a hollow cylindrical porous host filter element having a first end and a second end; (b) a first end cap arranged at the first end or the second end of the hollow cylindrical porous host filter element, the first end cap having an outer diameter; and, (c) an outer surface; the filter arrangement further comprising (d) a porous fibrous hollow cylindrical prefiltration element compression fit on the outer diameter of the first end cap, and covering the exposed outer surface of the host filter.

In some embodiments, the prefiltration filter element covers the outer surface of an outer cage of the host filter. In other embodiments, the prefiltration filter element covers the upstream surface of the hollow cylindrical porous host filter element.

In an embodiment of the filter arrangement, the host filter includes an outer cage surrounding the hollow cylindrical porous host filter element, the outer cage having an external surface providing the outer surface of the host filter. In another embodiment of the filter device, the hollow cylindrical porous host filter element has an upstream surface providing the outer surface of the host filter.

A method of producing a filter arrangement is disclosed but not covered by the present invention, the method comprising compression fitting a porous fibrous hollow cylindrical prefiltration element over a host filter comprising (a) a hollow cylindrical porous host filter element having a first end and a second end; (b) a first end cap arranged at the first end or the second end of the hollow cylindrical porous host filter element, the first end cap having an outer diameter; and, (c) an outer surface; such that the prefiltration element is compression fit on the outer diameter of the first end cap, and covers the exposed outer surface of the host filter.

An embodiment of processing fluid according to an embodiment of the invention comprising passing fluid through a filter arrangement comprising a porous fibrous hollow cylindrical prefiltration element and a host filter, wherein the porous fibrous hollow cylindrical prefiltration element is compression fitted on the host filter, and removing undesirable material from fluid as the fluid passes through the fluid arrangement. The present method comprises passing water through a point of use shower head device or a point of use faucet head device, wherein the host filter comprises a sterilizing grade water filter, and dispensing sterile water from the device.

Advantageously, the use of a prefiltration filter element can increase the life and/or dirt holding capacity of the host filter. Moreover, the prefiltration filter element can be produced and used at a fraction of the cost of the host filter, and may increase the filter life to blockage by several fold with little effect on the pressure drop across the prefiltration filter element and host filter.

Prefiltration filter elements, which comprise porous fibrous hollow cylindrical elements, can be produced by a variety of processes, including meltblowing. They can comprise woven or nonwoven material.

If desired, the prefiltration filter element can include multiple layers of different fiber diameters and/or densities and/or pore structures that provide different filtration efficiencies.

Prefiltration filter elements can be used with filters with and without outer cages, fully covering the exposed upstream area or surface area of the host filter or host filter outer cage such that there is no bypassing of the host filter.

In accordance with aspects of the disclosure, the prefiltration filter element can be used with a variety of porous hollow cylindrical host filters and porous hollow cylindrical host filter elements (especially porous fibrous hollow cylindrical host filters and host filter elements) and filter devices including such filters and filter elements. One example of a suitable filter and filter device is disclosed in <CIT>.

Each of the components of the invention will now be described in more detail below, wherein like components have like reference numbers.

<FIG> shows an embodiment of a prefiltration filter element <NUM> comprising a porous fibrous hollow cylindrical element for use with a host filter, the prefiltration filter element <NUM> having a first end <NUM>, a second end <NUM>, and a thickness T.

<FIG>, <FIG>, <FIG>, <FIG> and <FIG> show an illustrative host filter <NUM>. Using <FIG> and <FIG> for reference, an illustrative host filter <NUM> comprises a first end cap <NUM> (having an outer diameter OD), an outer cage <NUM> having an outer surface, an inner core <NUM>, and a porous fibrous hollow cylindrical host filter <NUM> comprising a porous fibrous hollow cylindrical host filter element <NUM>. While the host filter illustrated in <FIG>, <FIG>, <FIG>, <FIG> and <FIG> includes an outer cage and an inner core, the cage and core are optional, and the host filter can include either an outer cage or an inner core, or can lack both an outer cage and an inner core.

<FIG> shows an isometric view, and <FIG> shows a side view, of the host filter <NUM> without the prefiltration element <NUM>, and <FIG> shows an isometric view, and <FIG> shows a side view, of an embodiment of the filter arrangement <NUM>, wherein the prefiltration filter element <NUM> is compression fit over the filter (i.e., compression fit over the OD of first end cap <NUM>), and covering the exposed outer surface of the outer cage <NUM>, such that there is no bypassing of the host filter during use.

Thus, with respect to the filter device housing, <FIG> show an illustrative showerhead filter device <NUM> comprising a filter device housing <NUM> receiving the filter arrangement <NUM>, the housing having a hollow handle <NUM> including a device housing inlet wherein fluid enters the device, a first portion <NUM>, and a second portion <NUM> including the device outlet, wherein the housing defines a fluid flow path between the inlet and the outlet with the filter arrangement across the fluid flow path.

<FIG> show an illustrative faucet head filter device <NUM>' comprising a filter device housing <NUM>' receiving the filter arrangement <NUM>, the housing having a first portion <NUM>' including the device housing fluid inlet and a second portion <NUM>' including the device housing outlet, wherein the housing defines a fluid flow path between the inlet and the outlet with the filter arrangement across the fluid flow path.

As noted above, the host filter can include either an outer cage or an inner core, or can lack both an outer cage and an inner core. For example, <FIG>, <FIG>, <FIG>, and <FIG> show another host filter <NUM>' similar to the host filter <NUM>, but without an outer cage. Thus, illustrated host filter <NUM>' comprises a first end cap <NUM> (having an outer diameter OD), and an inner core <NUM>, and a porous fibrous hollow cylindrical host filter <NUM> comprising a porous fibrous hollow cylindrical host filter element <NUM>, and the filter arrangement <NUM>' comprises the host filter <NUM>' and the prefiltration element <NUM>.

<FIG> show another illustrative showerhead filter device <NUM> comprising a filter device housing <NUM> receiving the filter arrangement <NUM>', the housing having a hollow handle <NUM> including a device housing inlet wherein fluid enters the device, a first portion <NUM>, and a second portion <NUM> including the device outlet, wherein the housing defines a fluid flow path between the inlet and the outlet with the filter arrangement across the fluid flow path.

<FIG> show another illustrative faucet head filter device <NUM>' comprising a filter device housing <NUM>' receiving the filter arrangement <NUM>', the housing having a first portion <NUM>' including a fluid inlet wherein fluid enters the device, and a second portion <NUM>' including the device outlet, wherein the housing defines a fluid flow path between the inlet and the outlet with the filter arrangement across the fluid flow path.

A prefiltration filter element can have any suitable pore structure as long as it does not significantly affect the liquid flow (e.g., water flow) characteristics of the host filter (which can also have any suitable pore structure). Typically, the pore structure of the prefiltration element, e.g., a pore size (for example, as evidenced by bubble point, or by KL as described in, for example, <CIT>, or evidenced by capillary condensation flow porometry), a pore rating, a pore diameter (e.g., when characterized using the modified OSU F2 test as described in, for example, <CIT>), or removal rating that reduces or allows the passage therethrough of one or more materials of interest as the fluid is passed through the element, is larger than that of the host filter.

The host filter can include additional elements, layers, or components, that can have different structures and/or functions, e.g., at least one of any one or more of the following: support, drainage, spacing and cushioning. Illustratively, the host filter can also include at least one additional element such as a mesh and/or a screen.

Typically, prefiltration elements are slightly flexible and slightly stretchable to provide a desired interference fit, with compression, such that the ends of the prefiltration elements do not need to be sealed or bonded to the host filter. If desired, temporary tooling (such as, but not limited to, a guide dolly) can be used as a lead-in to assist the slide over the widest part of the host filter.

The host filter and prefiltration filter element are typically disposed in a housing comprising at least one inlet and at least one outlet and defining at least one fluid flow path between the inlet and the outlet, wherein the filter and prefiltration filter element is across the fluid flow path, to provide a filter device. Preferably, the filter device and filter arrangement are sterilizable. Any housing of suitable shape and providing at least one inlet and at least one outlet may be employed.

The housing can be fabricated from any suitable rigid impervious material, including any impervious thermoplastic material, which is compatible with the fluid being processed. For example, the housing can be fabricated from a metal, such as stainless steel, or from a polymer. In a preferred embodiment, the housing is a polymer, such as an acrylic, polypropylene, polystyrene, or a polycarbonated resin.

The following example(s) further illustrate the invention but, of course, should not be construed as in any way limiting its scope.

This example demonstrates the improved result using a prefiltration filter element with a host filter compared to the host filter without the prefiltration filter element.

Host filters comprising porous fibrous hollow cylindrical filter elements with end caps, outer cases and inner cores; and filter housings, are produced as generally described in <CIT>. The host filters are arranged on filter device housing portions including the filter device outlets.

Prefiltration filter elements are produced by melt-blowing, cut to length, and compress fit over the widest diameter (the upper endcap) of the host filter by sliding the prefiltration element over a guide dolly on top of the host filter, and subsequently removing the guide dolly. The prefiltration filter elements fully cover the exposed upstream area or surface area of the host filter (i.e., covering the exposed upstream area of the outer cages) such that there is no bypassing of the host filter.

The thickness of the prefiltration filter element (about <NUM>) does not exceed any constraints of the housing into which the host filter fits or is encapsulated into. No additional sealing, bonding, or retaining (e.g., adhesive, melting, or clips) is utilized. The housing does not contact the outer surface of the prefiltration element.

The porosity of the prefiltration filter element is greater than that of the host filter.

After dust loading, about a <NUM>-<NUM>% flow loss is observed in filter devices including prefiltration filter elements, in contrast with about a <NUM>% loss in the controls.

Additionally, filter devices including prefiltration filter elements exhibit over twice the throughput over controls to the same degree of blockage (clean vs. end of life flowrate at a fixed inlet pressure).

Claim 1:
A filter device (<NUM>; <NUM>'; <NUM>) comprising a housing (<NUM>) having an inlet and an outlet and defining a fluid flow path between the inlet and the outlet, and a filter arrangement (<NUM>; <NUM>') arranged across the fluid flow path and comprising a host filter (<NUM>; <NUM>'), said host filter (<NUM>; <NUM>') comprising
(a) a hollow cylindrical porous host filter element (<NUM>) having a first end and a second end;
(b) a first end cap (<NUM>) arranged at the first end or the second end of the hollow cylindrical porous host filter element (<NUM>), the first end cap (<NUM>) having an outer diameter (OD); and,
(c) an outer surface;
wherein the filter arrangement further comprises a porous fibrous hollow cylindrical prefiltration element (<NUM>), filter device being characterized in that the porous fibrous hollow cylindrical prefiltration element (<NUM>) is compression fit on the outer diameter (OD) of the first end cap (<NUM>), and covering the exposed outer surface of the host filter (<NUM>; <NUM>'), and in that the filter device (<NUM>; <NUM>'; <NUM>) comprises a point of use shower head device or a point of use faucet head device, and the host filter (<NUM>; <NUM>') comprises a sterilizing grade water filter.