Background of the Invention Pumps are frequently used to create a pressure differential across two sides of a filter in a filtration system. Examples of filters which utilize pressure differentials created using a pump include perforated drum and disc filters. In operation, these filters are typically immersed in a liquid compartment filled with a contaminated liquid. A pump connected to the interior of the filter evacuates liquid creating a pressure differential in which the interior is at a lower pressure than the pressure outside of the filter.

Contaminated liquid then passes through the perforations from the liquid compartment into the interior. A contaminant filter cake eventually forms on the exterior of the filter. Periodically, the exterior of the filter is scraped to remove the filter cake.

The pump may pump the filtered liquid to an end use. For instance, filtered machine tool coolant pumped to machine tools for cooling and lubricating purposes.

A primary disadvantage to using drum and disc filters is that the magnitude of the pressure differential is limited in order to prevent structural damage to the filter. Consequently, the rate and quality of filtration is limited.

Using a higher differential to force liquid through a thick filter cake provides for removal of smaller particulate than using a thin filter cake.

Another type of filter which utilizes pressure differentials is a cylindrical filter. A cylindrical filter is capable of handling higher pressure differentials than the differentials capable of being handled by drum and disc

filters. In operation, a pump pumps contaminated liquid into the interior of the cylindrical filter causing the pressure on the liquid to be higher than the pressure outside of the filter. Because of the pressure differential, filtered liquid passes through perforations in the cylindrical filter with contaminants of the liquid being captured on the inside of the filter. The cylindrical filter structural member is mechanically loaded in tension in the circumferential or hoop direction.

The contaminants eventually build up on the inside of the cylindrical filter to a point which limits the ability of the liquid to pass through the perforations. Thus, filtration must eventually be interrupted to remove the filter cake from within the cylindrical filter. After the filter cake is removed from within the cylindrical filter it is placed in a briquette. The briquette squeezes liquid from the filter cake to produce a compact briquette of waste material.

The process of filtering liquid, removing the wet filter cake from the cylindrical filter, and then squeezing liquid from the wet filter cake to create a generally liquid free briquette is time consuming. Further, the filtration process must be stopped while the filter cake is removed from the cylindrical filter. Consequently, the supply of filtered liquid is interrupted when using a conventional cylindrical filter.

Summary Of The Invention It is an object of the present invention to provide a cylindrical filter which not only filters contaminants from liquids but also squeezes liquids from contaminants captured within the filter to form briquettes.

It is a further object of the present invention to provide a filtration system using a plurality of interconnected cylindrical filters to continuously provide a supply of filtered liquid.

It is another object of the present invention to provide a filtration system using a plurality of interconnected cylindrical filters in which

at least one of the filters may be shut down and cleaned while at least one of the other filters supplies filtered liquid.

In carrying out the above objects and other objects, the present invention provides a cylindrical filter for filtering contaminants from a contaminated liquid. The cylindrical filter includes a filter chamber having an outer housing and a perforated filter basket disposed within the housing.

An open annular region is defined between the housing and the filter basket.

The filter chamber further includes an elongated cylindrical bore within the filter basket having first and second ends.

An inlet fluidly communicates with the cylindrical bore of the filter basket and an outlet fluidly communicates with the open annular region.

Contaminated liquid passes through the inlet into the filter basket with liquid passing through the perforations of the filter basket into the open annular re- gion and then out of the outlet while contaminants are captured and form a filter cake on the inner surface of the basket. A first cylinder including a first piston and a first piston head seals with the first end of the cylindrical bore of the filter basket. A second piston head seals with the second end of the cylindrical bore of the filter basket. The first piston head is movable relative to the second piston head to remove the filter cake from the filter basket and compress the contaminants into a briquette.

In accordance with the above described cylindrical filter, a filtration system is also provided.

These and other features, aspects, and embodiments of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings.

Brief Description Of The Drawings FIGURE 1 is a schematic view of a filter system utilizing a plurality of interconnected cylindrical filters in accordance with the present invention ;

FIGURE 2 is a top view of a cylindrical filter in a closed position ready to filter a contaminated liquid ; FIGURE 3 is a side view of the cylindrical filter shown in Figure 2 ; FIGURE 4 is a side view of the cylindrical filter, partially in section, in the closed position ; FIGURE 5 is a side view of the cylindrical filter, partially in section, in an open or index position with a briquette being ejected from the filter ; FIGURE 6 is an elevational view of a first end plate ; and FIGURE 7 is an elevational view of a second end plate.

Best Mode For Carrying Out The Invention Figure 1 illustrates a filtration system 20 having a plurality of interconnected cylindrical filters 22a-e arranged in a parallel configuration.

Each of filters 22a-e are generally identical to one another. An exemplary filter 22 and its operation will first be described. Then, the overall operation of filtration system 20 employing filters 22a-e will be described.

Referring now to Figures 2-5, filter 22 includes a filter chamber 24 disposed inboard between a ram cylinder 26 and a plug cylinder 30. Ram cylinder 26 and plug cylinder 30 are generally conventional hydraulically operated cylinders. Ram and plug cylinders 26 and 30 are supported by respective ram and plug frames 32 and 34. Ram frame 32 includes a pair of top bars 36 and a pair of bottom bars 40. A cross-bar 42 extends laterally across ram frame 32 and serves to anchor ram cylinder 26. A first end plate 44 of filter chamber 24 supports the inboard ends of top and bottom bars 36 and 40. The outboard ends of top and bottom bars 36 and 40 are threaded and may be readily affixed to supports (not shown).

In a similar fashion, plug frame 34 has a pair of top bars 50 and a pair of bottom bars 52. A cross-bar 54 extends laterally across the

outboard end of plug frame 34. The end of plug cylinder 30 is anchored to cross-bar 54. A second end plate 56 of filter chamber 24 is disposed at the inboard end of plug frame 34 and supports the inboard ends of top and bottom bars 50 and 52. The outboard or distal ends of top and bottom bars 50 and 52 are threaded so as to be affixed to supports (also not shown). Hydraulic lines (not shown) are attached to fluid couplings 72 and 74 to operate ram cylinder 26 in a manner conventional for hydraulic cylinders.

Ram cylinder 26 includes a fluid cylinder 60, a piston 62, and a piston head 64. The end of fluid cylinder 60 has a pair of ears 66 through which cross-bar 42 passes thereby attaching fluid cylinder 60 to the outboard end of ram frame 32. Fluid couplings 72 and 74 pass fluid into and out of fluid cylinder 60 to axially control the movement of piston 62 and piston head 64.

Referring now more specifically to Figures 4 and 5, piston head 64 includes an annular backing plate 80 to which an elastomeric annular plate 82 is mounted by a plurality of fasteners. A mounting collar 84 mounts backing plate 80 to piston 62.

Plug cylinder 30 includes a fluid cylinder 90, a piston 92, and a piston head 94. Piston head 94 includes a backing plate 96, a plurality of circumaxially spaced column members 98, and an inboard baffle plate 100 spaced from backing plate 96. Backing plate 96 has openings 102 therein.

Ears 91 located at the outboard end of fluid cylinder 90 receive crossbar 54 therethrough to anchor the end of plug cylinder 30 relative to plug frame 34.

Referring now generally to Figures 2-5, filter chamber 24 includes outer housing 104, a cylindrical perforated filter basket 106 disposed radially within the outer housing, the aforementioned first and second end plates 44 and 56, a pair of top bars 110, and a pair of bottom bars 112. Bars 110 and 112 are used to clamp end plates 44 and 56 against outer housing 104 and filter basket 106. An annular open region 108 is defined between outer housing 104 and filter basket 106. An inlet coupling 114 is fluidly connected with outer housing 104 to permit contaminated liquid to enter the outer

housing 104 and filter basket 106. Similarly, an outlet 116, in fluid communication with open region 108, permits filtered liquid to leave filter 22.

A T-coupling 118 is attached to coupling 116. A vent 120 affixes to outer housing 104 and is in communication with open region 108. End plates 44 and 56 have respective inner bores 122 and 124, as best seen in Figures 6 and 7, for sealing receiving piston heads 64 and 94.

During a normal filtering operation, piston head 64 of ram cylinder 26 seals with inner bore 122 of end plate 44 while piston head 94 of plug cylinder 30 seals with inner bore 124 of end plate 56, as illustrated in Figure 4. Contaminated liquid enters inlet 114 and passes to the open region defined between backing plate 96 and baffle plate 100 of piston head 94 of plug cylinder 30. Contaminated fluid then passes axially through openings 102 of baffle plate 100 to fill the interior of filter basket 106. Air within filter chamber 24 is exhausted through vent 120. Filtered fluid passes through perforations in filter basket 106 and into annular open region 108. The filtered liquid then leaves filter 22 by way of outlet coupling 116 and T- coupling 118.

As the filtration process continues, more and more contaminants are captured forming a filter cake within filter basket 106 with the filter cake increasing in thickness. The filtration rate of filter 22 drops while the pressure inside filter chamber 24 increases due to the increasing thickness of the filter cake. When the rate of filtration is unacceptably low, filter chamber 24 must be cleaned.

To effect cleaning of filter chamber 24, the supply of contaminated liquid is discontinued to filter 22. Air is then introduced through inlet 114 to blow liquid out of the accumulated filter cake. Ram cylinder 26 is then actuated with piston head 64 moving toward piston head 94 of plug cylinder 30. Inward movement of piston head 64, and in particular annular plate 82, causes filter cake to be scraped from the inside of filter basket 106. Piston head 64 continues to move toward piston head 94 with the filter cake being squeezed therebetween. A briquette (B) of filtered material

is created which has essentially most of the liquid squeezed therefrom. Liquid squeezed from the filter cake drains out outlet 116. Next, plug cylinder 30 is activated to retract piston 92 and piston head 94 to the position shown in Figure 5. Ram cylinder 26 is further actuated to move its piston head 64 toward plug cylinder 30 thereby ejecting briquette (B) from filter 22.

After briquette (B) is removed, ram cylinder 26 and plug cylinder 30 are actuated such that piston heads 64 and 94 again seal within inner bores 122 and 124 of end plates 44 and 56. If desired, a liquid containing a pre-coat of filter material may then be cycled through filter 22 to create an initial layer of filter cake. Contaminated liquid is then again introduced into inlet 114 so that the filtration process can be repeated.

Referring now to Figure 1, filtration system 20 includes a return line 150 which dumps contaminated liquid into a dirty liquid reservoir or sump 152. A pump 154 pumps the contaminated liquid from sump 152 to the plurality of interconnected filters 22a-e. Located downstream of pump 154 is a branched inlet passageway 156. Inlet passageway 156 includes respective inlet conduits 160a-e, each having a respective inlet valve 162a-e.

Each of inlet valves 162a-e is controlled by electrically operated actuators 164a-e. Inlet conduits 160a-e, although not explicitly shown, are attached to respective inlets 114 of the respective filters 22a-e. On the exit or down- stream side of filters 22a-e, filter system 20 has outlet conduits 166a-e, each of which has an outlet valve 170a-e controlled by actuators 172a-e. The combined outlet conduits 166a-e are part of an overall branched outlet passageway 174. Outlet conduits 166a-e are connected to a respective branch of T-coupling 118 of filters 22a-e. Filtered liquid from branched outlet passageway 174 passes downstream to a desired end use, such as to machine tools where the filtered liquid cools and lubricates machine tools and again picks up contaminants with the contaminated liquid returning to sump 152 by way of return conduit 150.

Filtration system 20 also includes an air supply 176, an air compressor 180 which provides pressurized air to the air supply, and a

branched air passageway 182. Branched air passageway 182 includes five air conduits 184a-e which connect to inlet conduits 160a-e downstream from inlet valves 162a-e. Air conduits 184a-e have respective electrically controlled air valves 186a-e for controlling the flow of air to filters 22a-e. Air is supplied to filters 22a-e after a filtration cycle has been completed to blow liquid out of the filter cake prior to the compacting of the filter cake into a briquette (B).

Filtration system 20 also includes a pre-coat system 190. Pre- coat system 190 includes a hopper 192, a sump 194, a pump 196, and a branched pre-coat passageway 200. Hopper 192 stores a fibrous pre-coat material such as HF-40 which is sold by Henry Filters, Inc. of Bowling Green, Ohio. Pre-coat passageway 200 includes conduits 202a-e which connect to respective inlet conduits 160a-e as shown. The flow of pre-coat material to inlet conduits 160a-e is controlled by electrically actuated pre-coat valves 204a-e. On the downstream side of filters 22a-e is a branched pre-coat return passageway 206 which returns liquid from the filters to sump 194. Pre- coat return passageway 206 includes return conduits 210a-e which are fluidly connected to a respective branch of T-couplings 118 of filters 22a-e opposite that of outlet conduits 166a-e. The flow of liquid through return conduits 210a-e to sump 194 is controlled by actuated valves 212a-e. Sump 194 may also receive liquid through a refill line 214 connected to branched outlet passageway 174.

An exemplary operation of filtration system 20 will now be described. Contaminated liquid, such as machine tool coolant containing machine chips and other debris, is returned by return conduit 150 to dirty liquid sump 152. Pump 154 then pumps the contaminated liquid from dirty liquid sump 152 through branched inlet passageway 156 to three of the five respective filters 22c-e. Filters 22a-b are undergoing other operations to be described later. In order for contaminated fluid to pass from pump 154 to a particular filter 22, its respective inlet valve 162 in an inlet conduit 160 must be open.

As shown in Figure 1, filters 22c, 22d, and 22e are receiving and filtering contaminated liquid from sump 152 and pump 154. Contaminat- ed liquids pass into inlets 114 and through the openings 102 in baffle plates 100 to reach the interior of filter baskets 106. Because the contaminated liquid enters into the center of filter baskets 106, the opportunity to knock a filter media pre-coat from the inner walls of filter baskets 106 is reduced.

Contaminants are captured within filter baskets 106 as liquid passes through perforations in the filter baskets reaching annular regions 108 defined between the baskets and outer housings 104. The filtered liquid then proceeds to exit through outlets 116 to respective outlet conduits 166c-e of branched outlet passageway 174. Valves 170c-e are open. The filtered liquid is then returned to a source, such as machine tools, for further use. After the filtered liquid has been again contaminated, the contaminated liquid is returned to sump 152 by way of return conduit 150.

While this filtering process is continuously occurring in filters 22c-e, at least one of the filters, i. e. filter 22a in this exemplary embodiment, may be cleaned. In this case, inlet valve 162 is closed to prevent fluid from being pumped from pump 154 to filter 22a. Likewise, pre-coat valve 204a is closed. Also, outlet valve 170 is closed preventing a back flow of pressurized liquid from branched outlet passageway 174 into filter chamber 24a. Further, valve 212a is also closed. Air from air supply 176 is passed to filter chamber 24a by opening air valve 186a to partially dry the filter cake therein. Then, air valve 186a is closed.

Ram cylinder 26 is activated to scrape and compress filter cake inside filter chamber 24a. After sufficient liquid has been squeezed from the filter cake to form briquette (B), plug cylinder 30 is actuated to open filter chamber 24a so that briquette (B) can be disposed of as depicted in Figure 5.

Ram and plug cylinders 26 and 30 are then returned to their normal operating positions as shown in Figure 4.

In the event that very fine particulate are to be filtered from the contaminated liquid of dirty liquid sump 152, it may be desirable to pre-coat

filters 22 prior to returning a particular filter to its filtering operation. For example, while a filtering operation is going on in filters 22c-e, and while a briquette (B) is being formed and ejected from filter 22a, a filter pre-coat can be applied to a filter basket 106 such as in filter 22b. In this case, inlet and outlet valves 162b and 170b are closed to remove filter 22b from the normal filtration operation. Similarly, air valve 186b is closed. A pre-coat media, from hopper 192 is mixed with liquid in sump 194. The liquid and filter pre- coat mixture in sump 194 is pumped by pump 194 through branched pre-coat passageway 200. Only pre-coat valve 204b of pre-coat valves 204a-e is opened. The liquid and pre-coat mixture is introduced into filter 22b with the inner walls of filter basket 106 being coated with the filter pre-coat media.

Liquid filtered from the pre-coat liquid mixture passes out of filter 22b and is returned by way of return conduit 210b to sump 194 by opening valve 212b.

The above described loop of liquid flow is continued until a desired amount of pre-coat is disposed within filter basket 106 of filter 22b.

Generally, the amount of time necessary to achieve a desired pre-coat thickness inside the filter basket 106 for a particular type of size and contaminant to be filtered is determined experimentally prior to the system 20 being put into full production operation. Pre-coat inlet valve 204b and outlet valve 212b are closed when sufficient pre-coat has been accumulated. Inlet valves 164b and outlet valve 170b are then opened to return filter 22b to the filtration operation.

As described above, the individual filters 22a-e are periodically cleaned, pre-coated with filter media, and placed into filtration operations to keep filtration system 20 continuously producing a filtered liquid.

Thus it is apparent that there has been provided, in accordance with the present invention, a cylindrical filter that fully satisfies the objects, aims, and advantages set forth above. While the present invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those with ordinary skill in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.