Abstract:
A method for filtering suspended materials from a cooking substance, e.g. oil or shortening, in a central filtration system  100 . The method including the steps of (i) receiving the cooking substance in a first tank 106 from a deep fryer and filtering in a first filtration stage through a separator  112  and returning to the first tank  106 ; (ii) transitioning to a second stage by filling a second tank  118 ; (iii) filtering in a second filtration stage through filters  120  and  112 ; and (iv) holding the cooking substance in a heated tank  126  before returning to the deep fryer. Each stage commences when a certain condition is met, e.g. a predetermine level or weight of cooking substance in a tank or a predetermined clarity of the cooking substance.

Description:
This application incorporates by reference and claims the benefit of priority of Provisional Application No.60/082,529 filed Apr. 21, 1998 in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention is directed generally to apparatus and methods for filtration of a cooking substance in a cooking systems, such as a deep fat fryer, and more specifically to a central filtration system and method. 
     2. Description of Related Art 
     Large capacity pressurized deep fat fryer cookers (referred herein as deep fat fryers, cooking devices, cookers, and the like) have been devised for cooking products in a heated and or pressurized environment. Typically such devices comprise a cooking vessel, which may be filled with a type of cooking substance (e.g., oil or shortening) and heating devices surrounding or immersed in the vessel for heating the cooking oil. Products to be cooked are placed in the vessel, either directly or possibly contained in a wire basket, and are cooked for a desired length of time. 
     While such cooking devices described above provide for a relatively effective cooking environment, a problem exists with these devices. Specifically, the cooking substance used in these cooking devices looses some of its effectiveness as it becomes contaminated with suspended particles of food, or “cracklings.” This can result in, inter alia, decreased heat capacity for the cooking substance, incomplete cooking, unappealing appearance of the cooked food, and an unappealing taste. 
     Generally, “cracklings” are pieces of breading, skin, or other items which have separated from a food item being cooked in the fryer. For example, if fried chicken pieces are being cooked within the vessel, some of the breading applied before cooking the chicken may break away from the chicken and drift to the lower zones of the vessel. In the lower portions of the cooking vessel, the cracklings are less likely to cause degradation of the cooking substance in contact with the food products. Because moisture may be found within the cracklings, such moisture may cause the cooking substance to boil over if the cracklings become mixed with the hot oil in the upper zones of the vessel. Further, if the temperature in the bottom of the cooking vessel is too high, the cracklings may burn, causing oxidation of the cooking substance. Such oxidation reduces the useful life of the cooking substance. 
     Filtration of the cooking substance is a large task. Some fryers include an internal cooking substance filtration system to remove cracklings and other undesirable solids from the cooking substance. The cooking substance from the fryer is drained into a filtration system, where the cracklings are filtered and the cooking substance is cleaned. However, fryers having internal filtration systems tend to be expensive, and the filtration systems often require a significant amount of maintenance. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a system and method for a centralized filtration that overcomes these and other disadvantages. 
     A system for filtering a suspended material from a cooking substance is disclosed. The system includes a first pump for pumping a cooking substance from at least one fryer, a first tank for receiving the cooking substance from the first pump; a second pump for circulating the cooking substance; a separator for separating the suspended material from the cooking substance, the separator in communication with the second pump; a second tank for receiving the cooking substance; a holding tank for receiving the cooking substance; and a third pump for pumping the cooking substance to at least one fryer. In one embodiment, the separator may be a cyclone separator. 
     A method for filtering a suspended material from a cooking substance is disclosed. First, a cooking substance from at least one fryer is received. Next, a suspended material from the cooking substance is separated during a first filtration stage. At the completion of the first filtration stage, a transition is made to a second filtration stage. During the second filtration stage, suspended material is separated from the cooking substance. At the completion of the second filtration stage, the cooking substance is held, and then moved to at least one fryer. 
     A technical advantage of the present invention is that a system and method for centralized filtration is disclosed. Another technical advantage of the present invention is that a cooking substance from at least one fryer may be centrally filtered. Another technical advantage is that the cooking substance is filtered in two filtration stages. Another technical advantage is that a heated holding tank is provided. 
     However, other objects, features, and advantages will be understood from the following detailed description of preferred embodiments of the invention, in connection with accompanying drawings. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 depicts a schematic of the filtration system according to one embodiment of the present invention. 
     FIG. 2 is a flowchart depicting the filtrating process according to one embodiment of the present invention. 
     FIG. 3 a  depicts a front view of a central filtration system in accordance with one embodiment of the present invention. 
     FIG. 3 b  depicts a side view of a central filtration system in accordance with one embodiment of the present invention. 
     FIG. 4 depicts a schematic of the filtration system according to another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 depicts a depicts a schematic of the filtration system according to one embodiment of the present invention. It will be understood by one of ordinary skill in the art that the present invention, which will be described below, may be readily implemented with various other fryer types and configurations and that the specific fryers in these figures are shown merely as a preferred embodiment and for illustration purposes. 
     Referring to FIG. 1, filtration system is provided. Filtration system  100  includes supply line  102 , which is provided to connect with at least one deep fat fryer. This line may be connected to drain valves on at least one deep fat fryer, or it may be a connection which is submerged into a deep fat fryer to drain the cooking substance. Supply line  102  is connected to pump  104 , which is used to fill tank  106 . Any suitable pump may be used. In one embodiment, pump  104  may be a roller pump, such as a series 0500 roller pump, manufactured by Hypro, Inc., of New Brighton, Minn. 
     Because the cooking substance being pumped by pump  104  may contain a significant amount of crackling, other types of pumps may be used. These pumps may be pumps that crush the crackling and other suspended material, and then pumps the cooking substance with crushed crackling. 
     First tank  106  and second tank  118  are used to temporarily hold the cooking substance during the first and second filtration stages. These tanks may be standard tanks. In one embodiment, first tank  106  and second tank  118  are made of stainless steel and, the exception of at least one supply line and at least one exit line, may be otherwise sealed. First tank  106  and second tank  118  may have any suitable capacity; in one embodiment, they have a 20 gallon capacity. 
     First tank  106  and second tank  118  may include at least one sensor (not shown). In one embodiment, several sensors are provided. These sensors may be used to determine information about the cooking substance in the tanks, such as, inter alia, the weight of the cooking substance, the clarity of the cooking substance, the temperature of the cooking substance, the level of the cooking substance in the tanks, and the type of cooking substance present in the tank. This information may be used to determine the completion of the filtration stages, which will be discussed in detail below. In another embodiment, the information may be sent to a controller (not shown) for processing. 
     Second tank  118  may include filter  120 . Filter  120  may include at least one screen (not shown) covered with a paper medium (not shown) for filtering the cooking substance passing through filter  120 . Powdered diatomaceous earth (not shown) may also be used in conjunction with the paper medium (not shown) and at least one screen (not shown) to aid in filtering the cooking substance. 
     Valves  108 ,  114 ,  116 ,  122 ,  124 , and  128  control the flow of the cooking substance throughout filtration system  100 . Any suitable valve which is made of a material acceptable for use with a cooking substance may be used. In one embodiment, valves  108 ,  114 ,  116 ,  122 ,  124 , and  128  may be 2-way direct series 8267 solenoid valves, manufactured by Automatic Switch Company, of Florham Park, N.J. Before they are used with the cooking substance, these valves may be nickel-plated. Valves  108 ,  114 ,  116 ,  122 ,  124 , and  128  may be controlled by a controller (not shown), or they may be individually controlled. 
     Valves  108 ,  114 ,  116 ,  122 ,  124 , and  128  control the flow at different locations within filtration system  100 . Valve  108  controls the flow of cooking substance from first tank  106 , valves  114  and  116  control the flow of cooking substance to either first tank  106  or second tank  118 , valves  122  and  124  control the flow of cooking substance from second tank  118 , and valve  128  controls the flow of cooking substance from holding tank  126 . 
     Pump  110  circulates the cooking substance through filtration system  100 . Any suitable pump may be used. In one embodiment, pump  110  may be a roller pump, as a series 0500 roller pump, manufactured by Hypro, Inc., of New Brighton, Minn. 
     Separator  112  is used to separate crackling and other suspended material from the cooking substance. In one embodiment, separator  112  may be a DorrClone CA-25Cyclone Separator, manufactured by Dorr-Oliver Inc. of Milford, Conn. 
     Separator  112  separates crackling and other suspended materials from the cooking substance, and the cracking and other suspended materials are separated from the cooking substance, and are collected in a collector tank (not shown). 
     Holding tank  126  may be constructed similarly to first tank  106  and second tank  118 . In one embodiment, holding tank  126  may be heated. 
     Holding tank  126  may be larger than first tank  106  and second tank  118 . In one embodiment, holding tank  126  may have the capacity to hold filtered cooking substance from several fryers. Once filtered, the cooking substance may remain in holding tank  106  until it is transferred to a fryer. In one embodiment, at least one sensor  134  may be provided in first tank  106 , second tank  118 , and or holding tank  126 . Sensor  134  may be a level sensor, a liquid-type determining sensor, a temperature sensor, or a combination of these types. 
     The system operates as follows. Referring to FIG. 2, a flowchart depicting the central filtration method is provided. In step  202 , cooking substance containing crackling and other material is transferred from at least one fryer through supply line  102  into first tank  106 . This may be accomplished by pump  104 . In this step, valve  108  is closed, which causes first tank  106  to fill with the cooking substance. The other valves may also be closed. 
     In step  204 , once a predetermined condition is achieved, the first filtration stage is commenced. The first filtration stage may be commenced when a specific condition is met. This may be when the level of the cooking substance in first tank  106  reaches a predetermined level. This may be determined by an optical sensor, or by some other means. Other conditions, such as the weight of the cooking substance in first tank  106 , may also be used to commence the first filtration stage. 
     To commence the first filtration stage, valves  108  and  114  are opened, while valves  116  and  122  are closed. Pump  110  is activated, and the cooking substance is circulated through valve  108 , pump  110 , separator  112 , valve  114 , and back to first tank  106 . 
     Separator  112  separates the crackling and other material from the cooking substance, effectively filtering the cooking substance. The first filtration stage lasts until predetermined condition is met. This condition may be the amount of time that the cooking substance has been circulating. In one embodiment, the first filtration stage lasts for five minutes. Other conditions may also be used to determine when the first filtration stage is complete. For instance, the weight of the cooking substance may be used as a criteria. The first filtration stage may continue until the weight of the cooking substance is within a certain percentage of its known weight, without crackling, indicating that a sufficient amount of crackling has been separated from the cooking substance. 
     The clarity of the cooking substance may also be used to determine if the first filtration stage is complete. If clarity is used as a condition, an optical sensor (not shown) in first tank  106  may be used to determine if the cooking substance has changed a significant amount in clarity, or if it is within a desired percentage of a known clarity, indicating that sufficient crackling has been removed from the cooking substance. Because the cooking substance may darken with age, it may be necessary to calibrate the sensors to compensate for this darkening. For instance, a new cooking substance may be golden in color, while a used cooking substance will be slightly darker, even when it is free of crackling. Therefore, in order to accurately use clarity of the cooking substance as a criteria, it may be desirable to account for the darkening of the cooking substance. 
     The volume of cooking substance passing through separator  112  may also be used to determine when to end the first filtration stage. A flowmeter (not shown) may be employed between first tank  106  and separator  112  in order to determine the volume of cooking substance that has passed through separator  112 . Once a desired volume of cooking substance has passed, indicating a certain number of passes through separator  112  for the cooking substance, the first filtration stage may be determined to be complete. 
     Once the first filtration stage is complete, in step  206 , the system transitions to the second filtration stage. In order to do so, valve  114  is closed and valve  116  is opened, allowing second tank  118  to fill with cooking substance. Pump  110  and separator  112  continue to operate. Valve  108  remains open until first tank  106  is determined to be empty. This may be determined by optical sensors (not shown) or by weight sensors. Once first tank  106  is empty, valve  108  is closed. 
     In step  208 , the second filtration stage is commenced. Valve  122  is opened, allowing the cooking substance to circulate through valve  122 , pump  110 , separator  112 ,  116 , second tank  118 , and filter  120 . Separator  112  continues to separate crackling and other suspended material from the cooking substance. 
     The length of the second filtration stage may be determined in the same way that the length of the first filtration stage is determined, or another method may be used. Once the second filtration stage is completed, in step  210 , valve  122  closes and second tank  118  is filled with cooking substance. Once all of the cooking substance is in second tank  118 , pump  110  is turned off. 
     In step  212 , valve  124  is opened, and the cooking substance flows through filter  120  and valve  124  to holding tank  126 . In one embodiment, holding tank  126  is located below second tank  118  to take advantage of gravity in filling holding tank  126 . In one embodiment, holding tank  126  may be heated. 
     The cooking substance remains in holding tank  126  until it is required to be transferred to a fryer. In step  214 , once the cooking substance is required, valve  128  is opened, and pump  130  is turned on. The cooking substance flows through valve  128 , and is pumped through line  132  to fill at least one fryer. 
     Referring to FIGS. 3 a  and  3   b , which show a front and side view of a central filteration system according to one embodiment of this invention, a practical layout for the system is shown. Supply line  102  is used to supply cooking substance, and is pumped by pump  104  into first tank  106 . Valves  108  and  122  are located below first tank  106  and second tank  118 , respectively, to take advantage of gravity while draining these tanks. Separator  112  is shown with separator collection tank  302  positioned beneath it, for receiving crackling and other material. Holding tank  126  is located below second tank, and cooking substance flows due to gravity from second tank  118  to holding tank  126  when valve  124  is opened. 
     Filtration system  100  may be used as a centralized filtration system for several fryers. Filtration system may be permanently connected to several fryers, and each fryer may have a valve, such as a 2-way direct series 8267 solenoid valve, manufactured by Automatic Switch Company, of Florham Park, N.J. These valves may be controlled by a central controller, which controls when the cooking substance from each fryer is cleaned, and may automatically process it through filtration system  100  and refill the fryer. This may be accomplished without human interaction. The controller may be able to record when the cooking substance in each fryer was last filtered, how many times it has been filtered, the overall quality of the cooking substance, and when the cooking substance should be replaced. 
     Filtration system  100  may include several back-up measures to increase reliability, and minimize system downtime. Referring to FIG. 4, back-up pump  402  is provided to serve as a back-up for pump  110 . This may be necessary because pump  110  is in use during both the first filtration stage and the second filtration stage, and thus is used more than any element of filtration system  100 . Any additional piping to connect back-up pump  402  to filtration system  100 , as well as any additional valves (not shown) to select the desired pump may also be provided. 
     In one embodiment, the use of pump  110  and back-up pump  402  may alternate with each filtration stage. In another embodiment, the use of pump  110  and back-up pump  402  may alternate with each complete first filtration stage and second filtration stage. 
     In addition to a back-up for pump  110 , a back-up valve for each of valves  108 ,  114 ,  116 ,  122 ,  124 , or  128  may also be provided. These valves may be the same type of valve as valves  108 ,  114 ,  116 ,  122 ,  124 , or  128 , or they may be different types. 
     A back-up pump for pump  104  and pump  130  may also be provided. These pumps may be the same type of pump as pumps  104  and  130 , respectively, or they may be different types. 
     The centralized filtration system of the present invention reduces operating cost over fryers that use their own filtration systems. With the filtration system of the present invention, several fryers can be serviced by one filtration system, resulting in a reduction in overall investment, and in maintenance costs, since only one filtration system must be maintained. By providing an automated system, the overall cooking substance quality will be more closely monitored, resulting in more efficient fryers producing a high quality product. Further, by proving a filtration system that is connected to several fryers, the potential for a spill of cooking substance is significantly reduced. 
     Other embodiments of the invention will be apparent to persons skilled in the relevant art from a consideration of this specification or practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only. Although a detailed description of the present invention is provided above, it is to be understood that the scope of the invention is not limited thereby, but is determined by the claims which follow.