Filtering method and filter chamber sealing arrangement

A liquid filter method includes use of a filter media belt enclosed by sealably mated cover pan and floor pan defining a vacuum chamber connected to a sealed clean liquid tank, with clean liquid pumped out continuously to draw liquid to be filtered into an upper region of the filter chamber via an inlet hose connected to a source of liquid to be filtered. The cover pan is lifted after the vacuum is relieved to allow indexing of the filter media belt. A main control valve to the clean liquid tank is closed and pumping liquid continues during indexing. A vacuum control device limits the maximum vacuum developed in the clean liquid tank and a vacuum pump removes air from the tank for priming and to eliminate excess accumulated air. A hose seal for the cover is mounted to the filter belt to be moved in and out by the belt movement, allowing cleaning of the seal. A double loop hose seal creates an intervening space into which liquid is directed to minimize air leaks.

BACKGROUND OF THE INVENTION

This invention concerns filtration apparatus of a type used in industrial operations to remove contaminants from a liquid used during manufacturing. After machining such parts as engine blocks, manifolds, it is usual to wash the parts to remove chips, grinding swarf, cutting fluid residue, etc. The parts are conveyed through an enclosed washer chamber where spray jets wash off these contaminants, with the spray liquid and washed off material collected in a tank beneath the washer chamber.

It is necessary to remove the chips and other debris from the liquid to allow continued reuse of the liquid in the washing sprays, and in the past, an inclined filter media belt filter was mounted within the tank, periodically indexed to remove accumulated filtrate, the liquid drawn through the filter media belt to be filtered. A drag conveyor is also periodically indexed to convey accumulated solids out of the tank for disposal. See U.S. Pat. No. 6,042,726 for an example of such a filter.

In this arrangement, the filter apparatus is difficult to service, as the belts and conveyor are enclosed within the washer collector tank.

In some versions, the feeding of disposable media over the belt to remove fine particles would require access to the rear of the tank, which is often difficult in many installations.

To pump the contaminated liquid to an external filter would require a separate tank to receive the liquid in order to allow belt indexing, increasing the floor space and cost of the equipment required.

This situation is also presented with other stand alone equipment such as individual grinders and other machine tools having a dedicated chip cutting fluid collection tanks below the machining zone.

It is the object of the present invention to provide a filter apparatus for removing contaminants received in a tank such as a washer collection tank or other equipment, which apparatus is not necessary to be disposed within the tank and does not itself require a separate collection tank and which can quickly carry out the periodic indexing of a filter media belt to clean solids therefrom.

SUMMARY OF THE INVENTION

The above recited object, and others which will be understood upon a reading of the following specification and claims are achieved by a filter apparatus mounted above a clean tank. A downwardly facing upper pan is movable relative a floor pan to bring a perimeter flange into engagement with a hose seal disposed on the lower pan to create a sealed filter chamber. A vacuum box is mounted below the lower floor pan and connected to the clean tank by a piping connection to transfer fluid to a clean tank, the piping extending out from one side of the vacuum box, down to the level of the clean tank and back into one side of the clean tank. The piping connection has a main control valve located along the length of the fluid connection.

A pump is connected to the clean tank for pumping filtered liquid back to the utilizing equipment, which pumping generates a negative pressure in the clean tank (and also the vacuum box).

A filter belt loop has an upper segment extending into the filter chamber over one segment of the hose seal which extends entirely around the filter chamber and onto a perforated plate supported on a set of elongated bars fixed on the lower pan, and out of the filter chamber over another segment of the hose seal.

A vacuum pump is provided to evacuate air from the tank to prime liquid flow drawn into an inlet pipe connected to the upper pan and extending into the collecting tank containing the liquid to be filtered. Upon opening of the control valve, liquid is drawn into the vacuum chamber, passing through the filter belt and into the vacuum box and thence into the clean tank.

To index the belt to clean accumulated solids, a vacuum breaker valve is opened to allow air into the filter chamber to relieve the vacuum, and drain the dirty liquid from the filter chamber. The main control valve is thereafter closed. A power cylinder lifts the upper pan from the hose seal to allow the filter media belt to be advanced to carry the belt segment on which the solids have accumulated out of the chamber to be discharged.

The recirculation pump continues to be operated during indexing to insure an uninterrupted supply of clean liquid and to maintain a vacuum in the clean tank. The vacuum level increases during pumping to a predetermined maximum level, with an air bleed vacuum control device introducing air into the clean tank when the maximum vacuum is reached to prevent an excessive vacuum level from developing which could interfere with the pumping of clean liquid out of the tank.

Upon reopening the main control valve, liquid to be filtered is again quickly drawn into the vacuum chamber, through the filter belt and into the clean tank via the vacuum box.

The vacuum pump is operated as necessary to eliminate excess air until a predetermined liquid level is restored in the tank sensed by a liquid level switch.

The hose seal may be mounted to filter belt sewn into pockets formed by a fabric cover piece to be carried out and washed when the filter belt is indexed out to clear accumulated solids and to be washed.

In this case, the hose seal may be comprised of two concentric hose loops spaced apart. The space between the hose seals is flooded with low pressure clean liquid which acts to prevent air leaks.

DETAILED DESCRIPTION

In the following detailed description, certain specific terminology will be employed for the sake of clarity and a particular embodiment described in accordance with the requirements of 35 USC 112, but it is to be understood that the same is not intended to be limiting and should not be so construed inasmuch as the invention is capable of taking many forms and variations within the scope of the appended claims.

Referring to the drawings,FIG. 1shows the filter apparatus according to the present invention, which includes a clean liquid tank12, and a recirculating filter media belt14disposed within an enclosure16affixed atop the clean tank liquid tank12.

An inlet hose18is connected to an inlet pipe20extending down into a collection tank22for receiving liquid to be filtered, as from a parts washer.

The clean tank12could itself also be received inside the collection tank22which would typically be of much larger volume.

The inlet hose18is connected to a rotatable inlet fitting24affixed to the top of a cover pan26so as to be in communication with a vacuum filter chamber28defined between the inside the cover pan26and a floor pan30.

The rectangular cover pan26has an outwardly projecting perimeter flange32which overlies a hose seal34resting on the upper surface of the floor pan30and coextensive with the flange30.

The hose seal34comprises a length of distensible elastomeric sealed tube36filled with a liquid38(FIG. 2B) and having its ends connected with a coupling40(FIG. 2B) so as to define a sealed closed vessel. The hose seal34can accommodate misalignments of the flange32such as caused by tilting of the cover pan26since pressure on one portion will force liquid to another portion to expand the tube36to fill any gaps.

The cover pan26is mounted for guided up and down movement by actuation of a power cylinder40having a rod42pinned to a clevis44affixed to the top of the cover pan26. Two slotted front tabs46and rear tabs48having shorter slots are welded to the front and rear corners respectively of the cover pan26.

Guide pins50are fixed to extend into the slotted tabs46,48to limit upward travel and to guide movement of the cover pan26, with side rollers52. Rollers52on the tab sides locate the cover pan26side to side (FIG.1A).

The cover pan26is tilted by the affect of the unequal slots when the cover pan26is raised, causing it to be higher at the discharge end to allow the filter cake to pass out when the filter media belt58is indexed.

The floor pan30has a series of spaced apart parallel bars54overlain with a perforated plate56to define a support for a permanent media belt58extending through the vacuum chamber28atop the perforated plate56. The bars54and the perforations in the plates provide openings allowing flow through the filter belt58and through the perforated plate56. The permanent media belt58has ends connected to form a loop driven by a shaft mounted reducer60around an idler roller62when an index cycle is initiated, the return segment thereof passing beneath the floor pan30.

A vacuum box64is mounted below an opening in the floor pan30, connected to a pipe connection66extending to one side of the enclosure16and into the upper end of the clean tank12, a main control valve68installed therein to open or close fluid communication between the vacuum box64and the clean tank12.

A disposable media roll70may be mounted below the enclosure16and fed onto the permanent media belt58(started by use of pull bars in the well known manner). Such disposable media can be used depending on the nature of the solids to be filtered out to prevent rapid clogging of the permanent media belt58by very fine particles.

When indexed, the permanent media belt58is advanced to dump accumulated filter cake out to a receptacle72.

A rotary beater brush74may also be provided to aid in dislodging the solids, and an array of spray nozzles76receiving clean liquid under pressure forms jets directed at the inside of the belt58at the other end cleans the entrapped particles. A sloping floor78of the enclosure16collects the spray liquid and dislodged solids directs the same to a drain80.

A main pump82is connected to the lower level of the clean tank12to return clean liquid to the washer or other utilizing equipment (not shown).

A vacuum is developed in the clean tank12as the liquid is pumped out to cause liquid to be filtered to be drawn up the draw pipe20into chamber28, through the belt58(and disposable media if used), into the vacuum box64and connection66, and into the clean liquid tank12. The pump82is continuously operated to supply clean liquid to the utilizing equipment.

Due to the vacuum condition in the chamber28, a large downward pressure force is exerted on the cover pan26, compressing the hose seal34beneath the flange32to insure a complete seal.

A vacuum pump84is also connected to the upper region of the clean tank12to be able to evacuate air until a predetermined liquid level is reached sensed by a liquid level switch90. This is done to prime the system at start up to speed filling of the tank12with liquid at that time.

The vacuum pump84also can eliminate entrained air in the liquid accumulating in the upper region of the tank12.

In order to carry out an indexing of the media belt58, a vacuum breaker valve86is connected to the fitting24to allow air to enter the system and eliminate the vacuum condition.

The liquid in the inlet hose18will then flow back down into the tank22.

When the vacuum is relieved as sensed by a vacuum switch88, the control valve68is immediately operated by the apparatus controls (not shown) to be closed.

The cover pan26can then be raised and the belt58advanced to carry the segment thereof which was in the chamber28out of the chamber to position a fresh segment atop the perforated plate56.

In the meantime, the pump82has continued to draw clean liquid from the tank12, increasing the vacuum level therein.

A vacuum control device88limits the vacuum level to a predetermined maximum (12″ hg) which allows the pump82to continue pumping smoothly.

The indexing cycle can be completed in a short time, i.e., 30 seconds at a belt speed of 40 ft/minute, and the tank12should be sized to allow clean liquid to be continuously pumped during that interval.

After the cover pan26is again lowered, vacuum breaker valve86closed and control valve68reopened, liquid is again drawn into inlet hose18and is collected in the clean tank12after passing through the filter chamber28.

The vacuum pump84is operated to eliminate excess air until liquid rises to a maximum level, sensed by a liquid level switch90.

Thus, a filter apparatus has been provided which is located above the tanks and is thus readily accessible for service.

A rapid priming and indexing is enabled to minimize the filter downtime to reduce the capacity required for a given installation.

FIGS. 5-10show another embodiment of the invention incorporating certain variations over the apparatus described above. All of the details mentioned above are not shown in these drawings.

As seen inFIG. 5, the cover paw92is hinged on the left side at94to be swung up to open when a cylinder96is operated, a toggle linkage98connecting the cylinder rod100to the cover pan92. The cylinder is mounted on a trunnion102mounted to a fixed tank cover104.

An optional disposable media roll106is mounted above the cover pan92in order to not be wet by seepage from the chamber defined within the upper cover pan92and lower pan108having the vacuum box110.

The woven filter belt112is driven by a pair of chain loops114, each secured to a respective side edge by a series of plastic clips116(FIG. 10) secured to each side edge of the belt112with rivets118. Polypropylene tape strips120are bonded to each side edge for reinforcement.

Each chain loop114has a series of connection pins122fit into a respective clip116to connect each chain loop114to a respective side edge. This connection and drive of a filter belt is well known in the art and is described in U.S. Pat. No. 3,807,559.

Each chain loop passes through upper chain guides124secured to a box tube frame member126welded to a tank bottom pan108. Lower chain guides128are also included with a chain take up mechanism130(FIG.8).

A chain drive is more positive and simpler and can be used here since a complete four sided seal may be used to seal the side edges since the belt side edges project out of the housing filter chamber.

Each chain loop114is driven by a drive sprocket132on each end of a rotatably mounted drive shaft134around which the belt passes powered by a right angle drive unit136.

A rotatably mounted tool shaft138has idler sprockets140on each end to recirculate the chain loops114(FIG.6). The filter belt112passes around the shafts134and138.

The drive shaft134also drives a sprocket142powering a beater shaft144which has arms which engage the belt112after being indexed out of the filter chamber to remove the filtered out debris accumulated during cleaning. Spray headers146are also provided to clean the filter belt112.

A perforated plate148supports the filter belt112allowing filtered liquid to be collected in vacuum box110after passing through the belt112.

The vacuum box110is normally placed in fluid communication with the interior of the clean tank150via fluid conduits152and main control valve152.

A Vee shaped collection trough156is formed on the top of the clean tank150, with an outlet158provided for recirculating drained liquid wash to the dirty liquid tank (not shown).

An ejector162is utilized as the vacuum pump to remove air from the clean liquid tank150as described above, connected to the outlet from main pump166. The clean liquid flowing from the ejector162may be used to flush the trough156as indicated in FIG.5. Suitable sensors as described above in connection with a vacuum pump would be used to control the ejector162.

A special sealing arrangement180A is incorporated in this embodiment. The fixed seal described above can sometimes lead to accumulation of solids in the spaces around the hose seal over extended periods. Also, chips sometime lodge against the seal and create an air leak into the vacuum chamber lowering the vacuum and reducing the efficiency of the filter. This necessitates manual removal and cleaning of the seal.

In this embodiment, a hose seal arrangement180A is incorporated into the belt112so that the seal is moved out with the segment of the filter belt112receiving liquid flow during a cleaning cycle to remove accumulated solids.

The hose seal arrangement180A includes two looped hose seals164A,164B which are nested one within the other with an intervening space therebetween. The hose seals164A,164B are each filled with a liquid as in the seal described above. The hose seals164A, B are held in a generally rectangular pattern by respective stitched pockets170,172matched to the perimeter of the flanges166of the cover pan92and facing flange168of the bottom pan108when the filter belt112is indexed in its operation position. The stitched pockets are formed by a fabric border layer174sewn to the underside of the belt112, with stitching rows176forming the pockets170,172.

The ends of the belt112are connected by conventional clipper lacing178(FIG. 11) and snaps (not shown) to form an endless loop passing around the shafts138,134(FIG.6).

A tube182is connected to tap a source184of low pressure clean filtered liquid to direct the same into an intervening space186between the hose seals164A,164B to fill the same with liquid under low pressure.

The filter belt112and border piece174are porous to allow the liquid to fill the intervening space both above and below the belt112. The belt112and border piece174can be coated with polyurethane in the areas over and under the pockets170to improve wear resistance in the well known manner.

A second identical sealing arrangement180B can also be provided at a second location on the belt112in order to provide a spare in the event the belt112or seal arrangement180A becomes worn out or clogged. Normally, the same belt segment surrounded by the first seal arrangement180A would be indexed back into service after each cleaning cycle to prevent dry out and shortened belt life, and the second sealing arrangement180B indexed into position only as a replacement after the first belt segment is no longer functional.

The presence of the liquid in space186tends to prevent leakage of air in the event a chip gets caught beneath the belt112in the region of the hose seals164A, B. In that event, only a minor seepage would result, and plugging the liquid leak normally occurs by itself as solid particles flow to the leak and tend to clog the leak point. Air leaks can interfere with efficient operation of the filter a result of the consequence loss of vacuum while a minor liquid leak is normally significant of no consequence. Thus, this seal arrangement provides the reliability of the filter and reduces maintenance requirements.