Abstract:
The present invention provides a combination continuous and batch filtration system for a recirculating fryer where the continuous filter and batch filter assemblies are integrated into a single unit, utilizing a common pump. This unit is substantially compact and is therefore able to fit within the frame of most recirculating fryers. The outlets of the continuous filter and the batch filter are connected to a two-way valve, which is, in turn, connected to the inlet of the common pump. The valve allows an operator to selectively pump cooking fluid from either the continuous filter or the batch filter back into the fryer vat.

Description:
BACKGROUND 
     The present invention pertains to a recirculating deep-fat fryer used for cooking various types of food products within a heated bath of cooking oil; and more particularly, to a recirculating deep-fat fryer having a combination continuous and batch filtration system. 
     A typical recirculating deep-fat fryer will include a fryer vat containing a heating bath of cooking oil. The cooking oil is adapted to receive baskets of food products such that the food products will be immersed within and cooked by the heated cooking oil. Such recirculating fryers will also include a heat exchanger and a pump. The pump is responsible for continuously pumping the cooking oil from the fryer vat, through the heat exchanger and back into the fryer vat such that the cooking oil remains at a substantially constant temperature, thereby allowing the food products to be evenly and consistently cooked within the fryer vat. 
     To extend the useful life of the cooking oil, it is a common practice to filter the particulate food matter from the cooking oil to minimize the carbonization of such food matter within the cooking oil. Some conventional fryers utilize a batch filtration system, in which the cooking oil is drained from the fryer vat and then manually or mechanically filtered before returning the cleansed cooking oil back to the fryer vat. Other conventional recirculating fryers utilize a continuous filtration system, in which a continuous filter is placed within the fluid path of the cooking oil, so as to continuously filter the cooking oil as being recirculated between the fryer vat and the pump. 
     Even with such continuous filtration recirculating fryers, there is often a need to perform the batch filtration process on the cooking oil at the end of a predetermined period of time, if a more thorough filtration of the cooking oil is desired. Alternatively, the cooking oil in such continuous filtering recirculating flyers must periodically drained from the fryer vat so that the fryer vat may be cleaned out. Once cleaned, it is often desirable to return this drained cooking oil back to the fryer vat. 
     Accordingly, with either of such conventional systems, it is often necessary to provide extra floor space for a separate batch filtration system that is typically wheeled from fryer to fryer, performing the batch filtration operation. A disadvantage with such batch filtration systems is that during use, they will need to be positioned to the side or the front of the fryer vat, taking up aisle space and work space within the kitchen. 
     SUMMARY OF THE INVENTION 
     The present invention provides a combination continuous and batch filtration system for a recirculating fryer where the continuous filter and batch filter assemblies are integrated into a single unit, utilizing a common pump. This unit is substantially compact and is therefore able to fit within the frame of most recirculating fryers. The outlets of the continuous filter and the batch filter are connected to a two-way valve, which is, in turn, connected to the inlet of the common pump. The valve allows an operator to selectively pump cooking fluid from either the continuous filter or the batch filter back into the fryer vat. 
     The continuous filter assembly includes of a box-like enclosure with an inlet and an outlet and a filter disposed between the inlet and outlet. During normal operation, the continuous filter assembly is preferably seated within the batch filter assembly and is sized to hold only a portion of the entire fryer vat cooking fluid volume at any given time. The present invention therefore provides a continuous filtration system that increases the efficiency of a recirculating fryer as less cooking fluid is required during normal operation and heat loss is minimized. 
     The batch filter assembly includes another box-like enclosure or “holding tank”, open at the top to allow the continuous filter assembly to fit inside of it. The continuous filter assembly is supported inside the batch filter holding tank by brackets, or other supports, fixed to the inside walls thereof. A filter element for the batch filter assembly is situated in the flow path of cooking fluid through the batch filter. The batch filter holding tank is substantially larger than the continuous filter assembly and is capable of holding the entire cooking fluid volume of the fryer vat. 
     During normal operation of the recirculating fryer, the continuous filter assembly is seated within the batch filter assembly holding tank and the valve is engaged to allow pumping of cooking fluid from the fryer vat, through the continuous filter, through the valve, through the common pump and back into the fryer vat. At the end of a period of use for the recirculating fryer in continuous filter mode, such as the end of a day, the operator may desire to run a batch filter operation where the entire contents of the fryer vat are filtered while the fryer is not being used to cook food. The operator may then turn off the pump and engage the valve to discontinue flow through the continuous filter assembly. The continuous filter assembly is then removed from its position within the batch filter assembly holding tank and the entire contents of the fryer vat are allowed to be emptied into the holding tank. The operator engages the valve to allow pumping of fluid from the outlet of the batch filter and turns on the pump, thereby pumping fluid from the batch filter holding tank, through the batch filter element, and back into the fryer vat. 
     Preferably, removal of the continuous filter assembly is facilitated by having the outlet of the continuous filter assembly connected to the inlet of the flow selection valve via a quick-disconnect fitting. It is also preferred that the batch filter assembly have wheels fixed to the base of the holding tank allowing the entire unit to be moved away from within the frame of the recirculating fryer. 
     The filter element of the continuous filter assembly is preferably comprised of a perforated filter media encapsulated by a nylon bag. This allows larger food particles from the used cooking fluid to be captured on the outside of the bag. Periodically during operation of the filter assembly in continuous filter mode, the pump is activated, either manually or automatically, to reverse flow thereby dislodging food particles from the nylon bag and extending the operating time of the filter assembly. The filter element of the batch filter assembly is preferably comprised of a removable screen that is placed at the bottom of the batch filter holding tank just above the outlet. 
     In another aspect of the present invention, a recirculating fryer assembly includes a fryer vat for holding cooking fluid and receiving food for cooking, an inlet and an outlet port, a heating element within the fryer vat or within a recirculating path of the cooking fluid, a frame for supporting the flyer vat, and a filtration system having a continuous filter assembly and a batch filter assembly integrated into a single unit and sharing a common pump for pumping fluid from the fryer vat through either the continuous filter assembly or the batch filter assembly and back into the fryer vat. 
     In yet another aspect of the present invention, a method for filtering the cooking fluid of a recirculating fryer, which has a fryer vat and a pump for recirculating cooking fluid, includes the steps of: (a) providing a continuous filter, a batch filter, and a valve with a first inlet connected to the outlet of the continuous filter, and a second inlet connected to the outlet of the batch filter, and an outlet connected to the inlet of the fryer assembly pump; (b) coupling the inlet of the continuous filter to the outlet of the fryer vat; (c) switching the valve to allow cooking fluid to flow from the continuous filter assembly through the valve and pump; (d) activating the pump so that cooking fluid is pumped from the fryer vat, through the continuous filter, through the valve, through the pump and back into the fryer vat; (e) at the end of a period of running the fryer in continuous filter mode, shutting off the pump; (f) switching the valve to allow flow from the batch filter assembly through the valve and pump; (g) decoupling the continuous filter from the outlet of the fryer vat; (h) removing the continuous filter assembly from its position within the batch filter assembly; (i) draining the cooking fluid from the fryer vat into the holding tank of the batch filter; and (j) activating the pump to pump cooking fluid from the batch filter through the valve, through the pump and back into the fryer vat. 
     Accordingly, it is an object of the present invention to provide a filtration system for a recirculating fryer assembly where the continuous filter assembly and the batch filter assembly comprise a single unit. It is another object of the present invention to provide a continuous filter assembly that holds substantially less than the entire volume of cooking fluid of a recirculating fryer so that efficiency of the fryer is increased during normal operation. It is a further object of the present invention to provide a filtration system for a recirculating fryer where the continuous filter assembly is removably seated within the batch filter assembly. These and other objects and advantages of the present invention will be apparent from the following description, the appended claims and the attached drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic drawing of a fryer assembly for use with the present invention; 
     FIG. 2 is a schematic, side view of a fryer assembly and an embodiment of the combination continuous and batch filtration system according to the present invention and illustrating the flow of cooking fluid through the continuous filter assembly during normal operation of the fryer; 
     FIG. 3 is a perspective view of an embodiment of the batch filter assembly of the present invention; 
     FIG. 4 is a perspective view of an embodiment of the continuous filter assembly of the present invention, with sections removed to show detail; and 
     FIG. 5 is a schematic view of the fryer assembly of FIG. 2 with the continuous filter removed and illustrating the flow of cooking fluid from the batch filter assembly during a batch filter operation of the fryer. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     It is to be understood that the following dimensions disclosed with respect to the invention are exemplary and pertain to the preferred embodiment of the invention as it exists as of the date of filing; and that such dimensions are not necessarily for use with a commercial embodiment of the invention, if and when such commercial embodiment is developed. 
     As shown in FIG. 1 a recirculating fryer assembly  10  has a fryer vat  12  containing a cooking fluid  14  and accommodating a food basket  16  for cooking food items. A pump and filter assembly  18 , in accordance with the present invention, is in fluid communication with the fryer vat  12  via a conduit  20 . A conduit  22  serves to return the filtered cooking fluid to the fryer vat  12 . This continuous flow of cooking fluid into the fryer vat helps to evenly and efficiently cook the food items contained in the food baskets. Preferably, the cooking fluid is dispersed within the fryer vat  12  using jets (not shown). The jets help keep the free food particles in the cooking fluid afloat in the fryer vat, which helps the food particles to enter into the pump and filter assembly  18  during operation of the fryer assembly  10 . In turn, the jets also assist in keeping the floor of the fryer vat clean. 
     A schematic diagram of the pump and filter assembly  18  in accordance with a preferred embodiment of the present invention is shown in FIG.  2 . The fryer vat  12  containing cooking fluid  14  has an outlet port  24  connected to the pump and filter assembly  18 . The pump and filter assembly includes a continuous filter assembly  26  positioned within an opening  28  of a batch filter assembly  30 . The continuous filter assembly  26  has an inlet port  32  connected to the outlet port  24  of the fryer vat  12 . The outlet port  34  of the continuous filter assembly  26  is connected, via a conduit  36  and a quick disconnect fitting  38 , to a first inlet port  40  of a valve  42  via flexible conduit  43 . The outlet port  44  of the batch filter assembly  30  is connected, via a conduit  46 , to a second inlet port  48  of the valve  42 . The outlet port  50  of the valve  42  is connected to an inlet port  52  of a pump  54 . The outlet  56  of the pump  54  is connected, via conduit  22 , to an inlet port  58  of the fryer vat  12 . 
     As shown in FIGS. 2 and 3, the batch filter assembly  30  includes a holding tank  60 , with four vertical side walls  62  and a horizontal bottom wall  64  attached at the edges to form an enclosure with an open top. Preferably, the batch filter holding tank  60  may contain the entire cooking fluid content of the fryer vat  12 ; and in the preferred embodiment is 18.5″×15.5″×15″. A mesh or screen filter  66  is removably attached to the bottom wall  64  of the holding tank  60  and is situated approximately in the center of the bottom wall  64 . The filter  66  is placed directly over the outlet port  44  of the batch filter assembly  30 . At least two angle brackets  68  are rigidly attached to the side walls  62  of the batch filter holding tank  60  for seating the continuous filter assembly  26  during normal operation of the recirculating fryer  10 . A plurality of wheels  70  are attached to the batch filter holding tank  60  near the base to provide mobility for the batch filter assembly  30 . The valve  42  is preferably a ball valve and has a handle  73  for switching the valve to either of two positions: a first position providing fluid communication between the first inlet port  40  and the outlet port  50  of the valve, and a second position providing fluid communication between the second inlet port  48  and the outlet port  50  of the valve. It is also within the scope of the invention to have additional positions for the valve, such as a third position that restricts any fluid from flowing therethrough. 
     As shown in FIGS. 2 and 4, the continuous filter assembly  26  includes a housing  71  made up of four vertical side walls  72  and a bottom wall  74 , joined at the edges to form an enclosure, and a lid  76 . The bottom wall  74  is preferably sloped downwards and inwards towards the outlet port  34 . The lid  76  fits over the opening in the top of the continuous filter housing and has a rolled edge  78  to provide a locational fit. The lid  76  may be clamped to the walls  72  of the continuous filter housing  71  with fastening hardware  80 . The inlet port  32  of the continuous filter assembly  32  is located approximately in the center of the continuous filter assembly lid  76 . The filter element for the continuous filter assembly includes a perforated filter media  82  surrounded by a nylon bag  84  and is fixed on the bottom wall  74  of the continuous filter assembly  26  between the inlet port  32  and the outlet port  34 . At least two support legs  86  are attached to the bottom wall  74  of the continuous filter assembly  26  for supporting the assembly either on the brackets  68  within the batch filter holding tank  60  or while free standing once removed from the batch filter holding tank  60 . In the preferred embodiment, the overall size of the continuous filter housing  71  is 11″×13″×8.25″ while the perforated filter  82  is 5″×5″×6″. 
     FIGS. 2 and 5 illustrate the operation of the combination continuous and batch filter of the present invention. Referring to FIG. 2, during normal operation of the recirculating fryer, the continuous filter  26  is positioned within the housing  60  of the batch filter assembly  30  and is supported within the batch filter assembly  30  by the angle brackets  68 . The outlet port  34  of the continuous filter assembly  26  is coupled to the inlet  40  of the selection valve  42  by a quick disconnect fitting  38  and conduits  36 ,  43 . The selection valve  42  is switched to the first position, providing fluid communication between the first inlet port  40  of the valve and the outlet port  50  of the valve, so that cooking fluid received from the outlet port  34  of the continuous filter assembly  26  flows through the valve and into the pump. Therefore, while the fryer is in use, the pump  54  is activated to pump cooking fluid  14  from outlet port  24  of the fryer vat  12 , into the continuous filter assembly  26  through the filter  82 , through the outlet port of the  34  of the continuous filter assembly  26 , through the conduit  36 , through the inlet  40  of the selection valve  42 , through the outlet of the selection valve  50 , through the inlet  52  of the pump  54 , through the outlet  56  of the pump  54 , through the conduit  22  and back into the fryer vat  12 , through the inlet  58 . Periodically (preferably, every 3-5 minutes), the pump  54  is activated (either automatically or manually) to temporarily reverse flow so that fluid is pumped back through the conduit  36 , through the outlet  34  of the continuous filter  26  and back into the continuous filter, thereby loosening particles from the outside of the continuous filter element  82 , so that such particles settle to the floor of the continuous filter housing. It is also noted that if any leakage occurs from the continuous filter during normal operation, such leakage will end up in the holding tank  60  of the batch filter and not on the ground. 
     Referring to FIG. 5, after a period of operation in the continuous filter mode, it may be desired to filter the entire contents of the fryer vat  12  in a batch filtration operation. At this point, pump  54  is de-energized and the continuous filter assembly  26  is uncoupled from the inlet  40  to the selection valve  42  by disengaging the quick-disconnect fitting  38 . The continuous filter assembly  26  may then be removed from the holding tank  60  of the batch filter assembly  30 . The entire cooking fluid volume  14  of the fryer vat  12  is then allowed to drain through the outlet port  24  into the holding tank  60  of the batch filter assembly  30 . After draining the contents into the batch filter holding tank  60 , the outlet port  24  of the fryer vat  12  is plugged. Selection valve  42  is then switched to the second position, providing fluid communication between the second inlet port  48  and the outlet port  50  of the valve. Thereafter, pump  54  is activated to pump the cooking fluid  14  from the batch filter assembly holding tank  60  through the filter  66 , through the outlet to the  44  of the batch filter assembly  30 , through conduit  46 , into the second inlet  48  of the selection valve  42 , out of the selection valve outlet  50 , into the inlet  52  of the pump  54 , out through the outlet  56  of the pump  54 , through the conduit  22  and back into the fryer vat  12  through the inlet port  58 . 
     The wheels  70  allow the unitary pump and filter assembly  18  to be rolled away from the fryer vat  12 . Accordingly, it is within the scope of the invention that the above batch filtration process may be performed to pump the filtered cooking fluid to a separate article or container, rather than back into the fryer vat  12 . The wheels will facilitate easy transportation of the pump and filter assembly  18  to this alternate article or container. The holding tank  60  of the batch filter is also useful for holding the cooking fluids while the fryer vat  12  is being cleaned. The wheels  70  allow the holding tank  60  to be rolled away from the fryer vat  12 , facilitating drainage of the cleaning fluids from the fryer vat  12  to a separate container or drain. While it is preferred that the cooking fluid be returned to the fryer vat  12  using the pump  54 , after cleaning, it is within the scope of the invention to use a wash down hose. 
     Having described the invention in detail and with reference to the drawings, it will be apparent to those of ordinary skill in the art that changes can be made to the embodiments disclosed herein without departing from the scope of the invention as defined in the following claims.