|WO/2010/138462||WATER FILTERING AND PURIFICATION METHOD AND ADAPTER KIT|
|JP57015811||AUTOMATIC WASHING CONTROL DEVICE FOR RAPID FILTER BASIN|
1. A system for filtration, re-circulation, and monitoring fryer oil, said system comprising: a fryer having a top end and a bottom end, said bottom end having a drain and a pre-filter screen located at said bottom end of said fryer and over said drain, said fryer having a return inlet;
means for discharging heated oil from said fryer to an inlet pipe, said inlet pipe being heat resistant and pressurized;
means for pumping, having an inlet, an outlet and a controlling means, said inlet connected to said inlet pipe of the discharging means, said controlling means having an active status and a non-active status;
a filter housing, being heat resistant and pressurized, said filter housing positioned after said outlet of the pumping means, said filter housing having a heat resistant seal and a lid, creating a low pressure seal so as to transfer pressure from the pumping means to said means for discharging heated oil from said fryer, said filter housing having a pressure regulator and relief system, said filter housing having a filtration media contained therein;
a drainage line connecting to an outlet of said filter housing, said drainage line having a valve means engaged to a return pipe means and a waste pipe means, said return pipe means transferring filtered oil back to said fryer, said waste pipe means transferring filtered oil to a waste container;
a flow control valve, being located in said drainage line;
a re-circulation means connected to said flow control valve through a filter discharge pipe to re-circulate filtered oil back into said inlet of the pumping means and said filter housing, creating a re-circulation loop through said filter housing, when said means for discharging is closed and the pumping means continues to operate, said re-circulation means having a controller means for activation of said flow control valve; and
a back- flush line connecting said return pipe to cleaning outlet, said cleaning outlet positioned by said drain and said pre-filter screen, said back-flush line having a valve means to regulate filtered oil flow from said return pipe to said cleaning outlet, filtered oil dislodging particulate matter from said drain and said pre-filter screen.
2. The system of Claim 1 , wherein said filter housing is comprised of a pressure relief valve means, limiting pressure produced in said filter housing by the pumping means.
3. The system of Claim 1, wherein said filter housing is comprised of a pressure relieving valve means to discharge pressurized air in said filter housing.
4. The system of Claim 1, wherein said filtration media is removable.
5. The system of Claim 1, wherein said lid of said filter housing is comprised of a hinge assembly, latched in place with said heat resistant seal, being pressurized and weather resistant when closed and having an open position for access to said filtration media.
6. The system of Claim 1, further comprising:
a base plate supporting the pumping means and said filter housing at a distance from said fryer.
7. The system of Claim 1, wherein said filter housing and said lid connect at edges thereof with a detachable compression latch.
8. The system of Claim 2, wherein said pressure relief valve means maintains a pressure within said filter housing greater than pressure of the pumping means, the re-circulation means operating with filtered oil when said return inlet of said fryer is closed.
9. The system of Claim 1, wherein said valve means in said drainage line is a manually operated three-way valve or series of manually operated valves.
10. The system of Claim 1 , wherein said valve means in said drainage line is a control valve, activated electronically or pneumatically by a switch of a programmable controller.
11. The system of Claim 1, wherein said back-flush line and said valve means of said back- flush line are controlled manually or electronically.
12. The system of Claim 1, further comprising:
a control means regulating operation of the pumping means and the re-circulation means..
13. The system of Claim 1, wherein said return pipe has a glass panel portion.
14. The system of Claim 1, wherein said filter housing has a glass panel portion.
FIELD OF THE INVENTION
 The present invention relates to deep oil fryers used for food preparation. More particularly, the present invention relates to an automated control system for filtration, re-circulation, and monitoring fryer oil.
BACKGROUND OF THE INVENTION
 A fast food restaurant will filter the oil in each vat of the fryer once or twice per day. The typical deep fryer system in a restaurant will include a plurality of fryer vats. Most prior art fryer oil filters require the fryer to be shut down, a drain valve opened and gravity flow of oil into an open filter box. The oil normally moves through the filter by gravity flow, then into the pump inlet line located below the filter. The open drain valve and gravity flow of oil requires the complete emptying of the fryer oil into the filter box, which removes the fryer from service during the process. Often, accumulations of solids and particles blocks or restricts flow of oil from the fryer, requiring prodding or scraping to free the particles from the drain line to facilitate flow. Traditional methods of filtering oil in restaurants have several problems. For example, the fryer must be deactivated for extended periods of time. Fryer filtration time is normally dependent upon gravity flow through a filter, which requires a time period for the oil to reside in an open filter box. The filter box subjects the oil to airborne contaminants. Also, the oil is cooled, which requires later re-heating and releasing unpleasant oil and particulate odors from the open filter box after use. The gravity-based flow through the filter is affected by the size and type of filtration material and mesh matrix under ambient pressure.
 Another problem with prior art oil filtration is the variable consistency and quality of oil caused by irregular filtration schedules. Restaurants, particularly large restaurant chains, have difficulty with regards to maintaining consistent procedures between establishments. In the case of fryer oil filtration, frequency of filtering the oil is typically controlled by the need for the fryers to be operable during busier times. In some cases, this variable frequency of filtration translates into an uneven filtration of oil during certain times of the day or during particular days of the week. In addition, filtration often depends on employee availability to empty and clean the fryer and prepare the filter for service.  Still another problem with prior art oil filtration is the inefficiency of the filtration process. The most efficient and quickest prior art filtration systems require a very low viscosity oil. Higher temperature oils, in the typical fryer temperature range of 350- 400°F, have low viscosity and are more easily filtered than oils at cooler temperatures. Filtering hot oil allows the hot oil to be directly returned to the fryer, reducing energy used to re-heat cool oil. Therefore, filtering the hot oil is more energy efficient and easier to filter compared to cool oil. Additionally, filtering hot oil requires less time than waiting for the oil to cool, and the quality of filtered hot oil is greater than the quality of filtered cool oil.
 However, filtering hot oil requires several safety concerns to be addressed, primarily prevention of burns and avoidance of slipping hazards. Typically used portable filters carry the risk of tipping and spilling hot oil on the floor. The United States Occupational Safety and Health Administration even publishes restaurant recommendations for employee safety regarding hot oil filtration and storage. There are also contamination concerns. Almost all systems are designed for indoor use in the kitchen area of the restaurant and are non-sealed systems, most being either the open vat style or having a simple lid. When oil is discharged into these open atmospheric filters inside the restaurant, it allows the odors of old oil to discharge into the restaurant. None of these filter systems are designed to be used away from the kitchen in an outdoor environment to help remove these odors from the kitchen. Restaurants need a safer, better filtration system that eliminates the burn hazards of handling hot oil, in addition to resolving the odor and grease problems traditionally associated with oil filtration indoors.
 Various patents have issued and applications published relating to the filtration, recirculation, and monitoring fryer oil. For example, U.S. Patent No. 5,228,985, issued to Wells et al., describes a portable cooking oil filtering unit that has an outer housing completely enclosing all the filter stages and providing access to the stages for maintenance purposes via doors and removable closures. The housing has an inlet conduit for connection to a cooking vat drain outlet, and an outlet conduit for returning filtered oil to the cooking vat. A first stage filter in the housing is connected to the inlet conduit for filtering relatively large size particles from the oil, and the filtered oil is connected to at least one additional filter stage for filtering smaller particles from the oil. A pump is connected downstream of the final filter stage, between that filter stage and the outlet conduit, for drawing oil through the filter stages under vacuum rather than pumping it through the filters under positive pressure. One of the filter stages is accessible to allow oil-life enhancing chemicals to be added to the oil.
 U.S. Patent No. 4,913,922, issued to Hawkes et al., describes a method and apparatus arrangement for continuous cooking of food in hot oil with clarification, purification and recycle of oil. Particulates-laden oil from the cooker is passed through a comminutor then through a precoat filter to remove particulates. The filter bed may also contain a quantity of an adsorbent to remove free fatty acid from the oil before reuse. Elevated temperatures are maintained and the operation is conducted in an oxygen-poor environment. An apparatus arrangement includes a cooker, a comminutor and an enclosed precoat filter through which all oil passes. Appropriate piping and controls are provided.
 U.S. Patent No. 4,646,793, issued to Sherratt, describes a cooking oil and grease recycling apparatus for collecting hot cooking oil from fryer vats in restaurants and industrial food preparation companies and replacing it with fresh oil or grease. Holding tanks are connected to the frying vats by piping, which includes valves and pumps to permit the used oil or grease from the frying vats to flow into a holding tank. The holding tanks are in a location accessible for trucks to connect a hose for pumping the used liquid oil or grease into the truck tank. A second hose is connected from the truck tank to pump new, fresh oil or grease into a distribution tank which are mounted above the frying vats at any convenient place in the restaurant. The invention also includes a portable system preferably including a pump to distribute oil to the frying vat and a holding tank.
 U.S. Patent No. 6,783,685, issued to Hwang, describes an invention that is directed to an oil treatment apparatus and method for treatment of oil which transports oil to be treated from a source through a first conduit to a treatment station. The treatment station includes a filter system capable of extracting particulate material from the oil and removing the particulate material from the filter system as it is removed from the oil. The treated oil may then be transported for reuse, preferably in a continuous cycle with the source of the oil. A prefiltering system may be used to further enhance maintaining the quality of the oil and/or in efficiently treating the oil while accommodating throughput requirements. The prefiltering system may include a comminuter to reduce the size of larger particles in the oil, a coarse filtering system to remove larger particles, and a system to introduce a treatment material to the oil or other systems to facilitate processing. The filtering system is designed to remove particles from the oil having a size of fifteen microns or smaller in the preferred embodiment.
 U.S. Patent Publication No. 2002/0174778, issued to Petrusha, describes a system for removing cooking oil from a fryer vat that includes a storage tank for storing cooking oil. The storage tank is disposed remotely from the fryer vat and in fluid communication with the fryer vat through a fixed piping system. A pump is arranged to transfer cooking oil from the fryer vat to the storage tank through the fixed piping system. A shut-off valve for directing cooking oil transferred by the pump to the storage tank is also provided. The shut-off valve is movable between an open position wherein the shut-off valve permits cooking oil to flow through the fixed piping system to the storage tank and a closed position wherein the shut-off valve blocks flow of cooking oil through the fixed piping system to the storage tank. A level sensor is arranged to detect whether the cooking oil in the storage tank is at a predetermined level. When the level sensor detects that the cooking oil in the storage tank is at the predetermined level, the shut-off valve moves from the open position to the closed position or the pump stops transferring cooking oil to the storage tank. An alarm device can provide an audio or visual alarm signal when the level sensor detects that the cooking oil is at the predetermined level.
 U.S. Patent No. 6,202,543, issued to Moya et al., describes a system for use with a hot oil fryer of the type which cooks food products in hot oil. Particulates from the food are shed into the hot oil in the fry during the cooking operation. The fryer has an inlet to receive hot oil, and an outlet for recirculation of hot oil.
 U.S. Patent No. 5,964,258, issued to Schoenbauer et al., describes a bulk cooking oil supply and disposal transport system and method for the supply of cooking oil to and the removal of waste oil from a receiving facility. The system includes a transport vehicle with a supply and a waste oil container. An oil conduit system is connected with the supply and waste container to selectively deliver and remove oil through oil fittings. Pumps and valves are disposed within the oil conduit system for restricting the flow of the cooking oil therethrough. A first fluid meter measures the amount of cooking oil delivered to the receiving facility and a second fluid meter measures the amount of waste oil removed from the receiving facility. A control device receives signals indicating the level or amount of oil delivered or removed through the oil conduit system. Signals are generated by sensors at the receiving facility or from the fluid meters monitoring flow through the system. A data reporting device is provided on the vehicle to document the amount of cooking oil delivered to and the amount of waste oil received from the receiving facility.
 It is an object of the present invention is to provide an oil filtration system that can be operated while the fryer remains in service.
 It is an object of the present invention to provide an oil filtration system that is closed and maintains the temperature of the oil.
 It is another object of the present invention to provide an oil filtration system with a positive pressure filter housing.
 It is another object of the present invention to provide an oil filtration system with recirculation or "polishing" means for flow of the hot oil.
 It is still another object of the present invention to provide an oil filtration system having an automated means to control pumping of the hot oil through the oil filtration system.
 It is still another object of the invention to provide an oil filtration system with a means to inspect the oil for coloration.
 It is an object of the present invention is to provide an oil filtration system which keeps the oil in the best possible environment.
 These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.
BRIEF SUMMARY OF THE INVENTION
 The present invention provides a filtration system that allows for controlled drainage from the fryer, such that the fryer is in operable condition while the oil is being filtered. The invention also provides for a controller that can be programmed with a timer to regulate pump operation. The oil re-circulation or "polishing" and return flow back into the fryer is automated. The present invention maintains fresh and cleaned oil for constant use in a deep fryer. Besides prolonging fryer oil life, there are benefits of reduced costs, less down-time for the fryer, reduced employee labor, fewer safety hazards, and improved quality of fried food.
 A unique feature of this system is the filter housing rated for positive pressures, such that the system is weather resistant for outdoor storage and filtration. The present invention is ideal for use in restaurants due to elimination of stale oil odors from an open filtration box. Another unique feature is that the filter housing is not dependent upon gravity flow of liquid, because oil is pressurized by a pump to flow through filter media. This feature further allows for a variety of filter media and filter sizes that would not have been compatible using ambient pressure.
 Another unique feature of this system is that the pump is located between the fryer and the filter. The pump is for hot oil service with small particulate matter entrained in the oil. A pre-filter is installed in the base of the fryer, above the drain, for removal of larger particulate matter. The return back-flush of filtered oil through the fryer drain allows this pre-filter and fryer drains to remain relatively clean from clogging by particulate matter and debris.
 The above objectives are accomplished by providing a filtration system which is sealed while in operation, eliminating exposure to hot oil during the filtration process and enhancing filtration quality and energy efficiency.
 The invention will be more readily understood from a reading of the following specification and by reference to the accompanying drawings forming a part thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
 FIGURE 1 is a schematic view of a fryer oil system of the present invention.
 FIGURE 2 is another schematic view of the fryer oil system of the present invention, showing a fresh oil storage system, new oil supply system, nitrogen blanketing system, and relief nitrogen supply.
 FIGURE 3 is a partial sectional view and partial schematic view of the filtration housing of the present invention.
 FIGURE 4 is a partial elevation view and partial schematic view of the fryer oil system of the present invention, showing an embodiment with a pre-filter large solids filter being located inside the bottom of the fryer prior to the drain.
DETAILED DESCRIPTION OF THE INVENTION
 Referring now in more detail to the drawings, the present invention is a system for filtration, re-circulation, and monitoring fryer oil.
 FIGURE 1 shows a deep fryer unit (1) with a pre-filter (60) for removal of larger solids, a vat drain (2) and valve (3) attached to common fryer discharge piping (4), through which the hot oil to be filtered flows to the oil pump (12) inlet. The oil pump (12) is powered by a motor (13). The oil is discharged from the pump (12) and flows through the discharge piping (6) through a flow regulator (5) into the filter housing (7) inlet. The filter housing is under positive pressure supplied by the pump (12) and is weather sealed by the weather resistant pressure seal (8). The oil flows through the filter media (9), through the filter housing drain and filter oil transfer line (11). A drain (10) is provided for cleaning and oil removal if required. A pressure relief valve (14) is installed on the filter housing (7) to prevent too much pressure, with discharge through piping (17) to the waste oil storage tank. The pressure relief valve (14) will open if the pressure from the pump discharge exceeds the relief valve (14) set pressure. The pressure relief valve is attached to the filter housing to prevent positive pressure from exceeding the capacity of the filter housing (7). An air relief line (18) is installed on the filter housing (7) to allow any positive air pressure within the filter housing (7) to be discharged prior to opening the lid of the filter for access.
 In a preferred embodiment, the waste air discharge piping (18) has a backflow prevention device (61) and is connected to the waste oil storage container (21) at a fitting (20), but it could also be discharged to atmosphere. Filtered oil from the pump (12) can also be directed through a valve, or means of selection for filtered oil flow (24) and through a piping and backflow prevention device (23), through the waste oil inlet to waste oil storage container (22) and into the waste oil storage container (21). Filtered oil from the filter (7) can also be directed through a valve, or means of selection for filtered oil flow (24) through the oil return line (25) and to a designated fryer (1) through that return oil valve (26) or by means of the valve (27) also called means of selection for hot oil return sprayer, through that flexible sprayer line (28) and the oil return spray device (29) back into the designated fryer vat (1). Typically fryer baskets (not shown in some depictions) are used in the fryer vats (1) for frying food. Each vat will be filled with cooking oil during frying operations.
 FIGURE 2 is a view showing a new oil storage tank (33) with sight level glass (34) and a pressure relief valve (35) which discharges through a relief discharge line (36). The new oil storage tank (33), if required by local government codes, is contained within a new oil spill containment basin (43), which is not required under current governmental regulations for certain smaller quantities of oil contained within the storage tank (33). It is only sometimes necessary per local environmental codes and restrictions.
 A supply truck (not shown) can attach a fill hose (not shown) to the new oil inlet fill nozzle (44) to supply fresh oil to the oil storage tank (33). In a preferred embodiment, the oil inlet fill nozzle (44) provides a sealed coupling with the fill hose (not shown) fitting. A nitrogen or inert gas supply source (47) discharges through a nitrogen regulator (48), through a backflow prevention device (49), through a valve (50) and pressure indicator (51), providing regulated nitrogen blanketing to the new oil storage tank (33). An oil supply line to the fryers (45), equipped with a valve (46), provides oil through the supply line (45) to the fryer fill valve (54) at each fryer location. The new oil storage tank (33) is further provided with a man-sized access or cleaning port (52), so that there is an electronic level indicator (53), in addition to the sight level glass (34). The waste oil storage tank (21), in a preferred embodiment, is provided with a sight level glass (30), a nitrogen inlet and air inlet fitting (31), which has a valve for air inlet (32) which allows filtered air to enter the waste oil storage tank (21) after passing through the air filter (37) which removes airborne contaminants.
 The waste oil storage tank (21 ) is further equipped with a man-sized access or cleaning port (38), an electronic waste tank level indicator (39), a pressure relief valve (40), an air inlet nozzle (20) for receiving air flow from the filter housing (7) through the air piping (18) and a back-flow prevention device (61). Filtered oil, which is selected to go to the waste oil storage tank (21), will be pumped from the oil pump (12) through the selection valve (24), passing through the back-flow prevention device (23) and through the waste oil storage tank inlet piping (22) into the waste oil storage tank (21). A waste oil storage tank discharge nozzle (41) provides an attachment means for a suction truck (not shown) and suction hose (not shown) to attach to the waste oil storage tank (21) for waste oil removal. The waste oil spill containment basin (42) is provided as shown, but is not required in most embodiments because the waste oil volume in most cases is less than the level required by governmental entities for waste oil containment. However, the waste oil spill containment basin (42) is shown because it may be required in some jurisdictions depending upon local ordinances.
 FIGURE 3 details a preferred embodiment of the filtration housing (7), showing oil inlet piping (6), pressure regulator fitting (5), pressure indicator (61), a pressure relief valve (14) being attached to the filter housing (7) to prevent positive pressure from exceeding the capacity of the filter housing (7), a discharge line from the pressure regulator (17), filtered oil discharge piping (11), hinged lid closure with clasps (2) for maintaining positive pressure in filter housing (7), removable filtration media (9), an oil drain point from the filter discharge piping (10), flow control valve (57) for re-circulation piping inlet of pump (12), and a fryer drain line piping (4) to the pump inlet. Figure 3 further details a control panel (54) with a display (53) for control of oil delivery to fryers, recirculation of filtered oil, return of oil back to fryers, pump operations and tank level monitoring. The display also has a possible output to an external alarm system (55) if the tank level indicators reveal dropping oil levels which vary from standard use, which may indicate theft of oil. The control panel (54) may also be equipped with a timer (56) to control timed operations of the pump and recirculation system.
 FIG.4 details a preferred embodiment of the invention as disclosed in the preceding discussion and details. A primary large solids filter (60) is located within the fryer near the oil drain prior to the discharge piping (4). Hot oil from the fryer vat (1) flows through the pre-filter (60), through vat drain (2) through the vat drain valve (3), and through the main drain piping (4) into the pump inlet. A flow control valve (15) regulates re-circulation flow from filtered oil return piping (58) back through the oil pump to be re-circulated through the filter. A back-flow connection for fryer drain back flush (59) is connected to filtered oil return piping (58) to regulate and control a flow of oil back through the drain valve (3), fryer drain (2) and pre-filter (60) in order to control sediment deposits in the bottom of fryer (1) and assist with improved, unrestricted flow of oil through drain (2) and valve (3) by back-flushing pressurized oil and eliminating sediment and large particle deposition. Figure 4 further details a preferred embodiment of the filtrated oil return system to the fryers in accordance with earlier disclosures and invention discussion. An oil return piping (25) is shown to return the oil to the fryer vats (1) through means of piping (25) and selection valve for fryers (26), a flow control valve (27) or manual valve for selection of a flexible hose pressure wand (29).
 The present invention is this system for filtration, re-circulation, and monitoring fryer oil. There is a fryer having a top end and a bottom end, the bottom end having a drain and a pre-filter screen located at the bottom end of the fryer over the drain. The fryer also has a return inlet. A means for discharging heated oil from the fryer to an inlet pipe is a valve. The inlet pipe is heat resistant and pressurized.
 The oil flows to a means for pumping, having an inlet, an outlet and a controlling means, the inlet connected to the inlet pipe, the controlling means having an active status and a non-active status. The oil pump system has the capacity for high temperature fryer oils with small particulate matter. The controlling means is an on/off switch, starter switch or programmable controller means to activate / deactivate the pump motor, which is connected to either a standard 110-120 volt AC electrical source or a 220V-440V electrical source dependent upon the motor rating.
 The pressurizing pump moves the oil through a filter housing, being heat resistant and pressurized by the pump. The filter housing is positioned after the outlet of the pumping means and has a heat resistant seal and a lid, creating a low pressure seal so as to transfer pressure from the pumping means to the means for discharging heated oil from the fryer. The pressure also prevents airborne contamination from entering the oil filtration system housing through the drain of the fryer. The filter housing also has a pressure regulator and relief system and a filtration media contained therein. The filtration media is comprised of paper, cloth, steel mesh or other heat resistant filter media to remove solid particles from the fryer oil. Filter media may also include a plurality of different, layered filter media to provide adequate oil filtration, such as steel screen mesh and filter paper, or cloth filter / paper filter layered media. The filter media is also removable, such that the materials can be cleaned and replaced or just replaced.
 The pumping means and the filter housing can be automated. Pressure sensors and computer monitors regulate the activity of the flow of oil and activation of valves. The system can be adjusted for individualized use according to the application in a particular setting, such as a restaurant.
 A drainage line connects to an outlet of the filter housing, the drainage line having a valve means engaged to a return pipe means and a waste pipe means. The return pipe means transfers filtered oil back to the fryer, and the waste pipe means transfers filtered oil to a waste container. A flow control valve, located in the drainage line, controls the flow of filtered oil from the filter housing to the valve means of the drainage line. The pumping means and filter housing are mounted on a base plate away from the fryer or fryers, such that the drainage line can extend back to the fryers. The valve means in the drainage line is a manually operated three-way valve or series of manually operated valves, being controlled and activated electronically or pneumatically by a switch of a programmable controller.
 Another inventive feature is the re-circulation means connected to the flow control valve through a filter discharge pipe to re-circulate filtered oil back into the inlet of the pumping means and the filter housing. The re-circulation loop of the filtered oil through the filter housing is known in the industry as "polishing" the oil, in the event that the pump is operating while the return inlet on the fryer is closed. The means of controlling the "polishing" recirculation flow control valve is manually, on/off switch or by programmable controller.
 Still another feature is the back-flush line connecting the return pipe to cleaning outlet. The cleaning outlet is positioned by the drain and the pre-filter screen. The back- flush line has a valve means to regulate filtered oil flow from the return pipe to the cleaning outlet, such that the filtered oil dislodges particulate matter from the drain and the pre-filter screen on the bottom end of the fryer. The back-flush line and the valve means of the back-flush line are controlled manually or electronically.
 The filter housing can also include a pressure relief valve means, limiting pressure produced in the filter housing by the pumping means or a pressure relieving valve means to discharge pressurized air in the filter housing. The pressure relief valve means also maintains a pressure within the filter housing greater than pressure of the pumping means, the re-circulation means operating with filtered oil when the return inlet of the fryer is closed. The pressure relieving valve means allows the operator to discharge any internal pressure prior to opening the filter casing for servicing, reducing the risk of injury.
 The other features of the filter housing include a hinge assembly, latched in place with the heat resistant seal, being pressurized and weather resistant when closed and having an open position for access to the filtration media. The filter housing and the lid connect at edges thereof with a detachable compression latch. A glass panel portion can also be placed in the filter housing or in the return pipe. The clear sight glass may either be installed in the return pipe or contained in housing with a white or reflective material backing in order to judge oil coloration. Color coding strips may be located next to the sight glass for evaluating the oil.
 The system of the present invention is unique because the oil flows directly from the fryer into the pump inlet, with pressurized discharge from the pump to a pressure rated filtration unit. The system allows the filtration unit to be located at a distance from the fryer without regard to gravity flow of the oil. This inventive system allows the fryer oil to be continuously filtered, while the fryer remains in service.
 The present invention also includes a control panel for automation. While the fryer remains in active service, controlled flow of re-circulation oil can be maintained. Also, the discharge drain from the fryer will remain relatively clean. The automated means can either be set for periodic operation or continuous operation, while the flow rate can be varied to either empty the fryer of oil or regulate the discharge and return in order to maintain a constant fryer oil level while also providing the needed filtration.
 Additionally, the hot oil temperature is maintained in a closed and pressurized system and returned to the fryer with only minimal thermal loss, being adequate for continuous frying of foods without the need for re-heating. The positive pressure filter housing filters the cooking oil and enhances the flow of oil from the fryers into the filter. The oil is pressured through the filter media, allowing for much finer filtration in less time than can be achieved through gravity filtration. It also allows the filter system to be located independently of the pump, without relying on gravity flow of the fryer oil.
 The present invention further returns a portion of the filtered oil to the drain on the fryer, back- flushing the drain and pre-filter and reducing the build up of food particles that can block the flow of oil.
 The present invention also includes a means to inspect the oil for coloration by means of a sight glass in order to compare oil color to accepted restaurant standards. Typically, oil is sampled in a glass tube or beaker in order to judge oil color and freshness. This invention allows for an in-line sight glass to visually inspect the oil coloration prior while filtration is ongoing.
 Generally, the system of the present invention keeps the oil in the best possible environment, reducing exposure to oxygen, humidity and airborne contaminants while also reducing cooling of the oil. This sealed, positively pressurized system reduces contamination of the oil by preventing contact with surrounding air during filtration and pumping operations. The sealed filtration system also helps maintain the temperature of the oil, which eliminates the need to re-heat the oil prior to use. This system can eliminate the need for taking the fryer out of service for filtration, allows for more periodic filtration of the oil at multiple times during the day including continuous filtration while the fryer remains in operation. This improves the overall quality of the oil, leading to less variability in fried food quality and consistency for the restaurant.
 The foregoing disclosure and description of the invention is illustrative and explanatory thereof. Various changes in the details of the illustrated construction can be made within the scope of the appended claims without departing from the true spirit of the invention. The present invention should only be limited by the following claims and their legal equivalents.