US 2655144 A
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gli H Oct. 13, 1953 1N VEN TOR.
Patented Oct. 13, 1953 UNITED STATES PATENT OFFICE DEEP FRYER Richard T. Keating, Chicago, Ill.
Application September 15, 1950, Serial No. 184,973
2 claims. (ci. 126-391) and increases the speed and economy with which foods may be cooked in the fryer.
The design and construction of heating devices for deep fryers presents many problems not encountered in other types of heat exchangers, and these are particularly vexing in heaters designed to burn gas or oil as fuel, primarily for the reason that While the heating tubes of the burners must have sufficient inside volumetric capacity to support combustion and afford adequate draft, yet they must be capable of effecting efficient heat .transfer from the flame within the tube to the grease on the outside thereof, without undue losses due to discharge of heated gases through the flue. At the same time, the necessity for maintaining the grease in fresh, clean condition limits the volume of grease which should be employed in a container, and this limitation of volume is ordinarily reflected in a similar limitation on the length and surface area of the combustion tubes employed in the unit. It follows that it is of prime importance to provide means whereby the combustion tubes extending through the grease tank of a deep fryer may be heated directly from a gas or oil flame, yet With means for so controlling the temperature and velocity of the burning gases within the tubes so that the heat thereof is transferred through the tube walls rather than passing into the flue.
It is, therefore, the primary object of the present invention to provide an improved deep fryer including a grease tank with heat transfer tubes of novel construction extending therethrough, With the tubes so designed, shaped and proportioned as to provide an inherent control of the velocity of the gases passing therethrough and at the same time permit almost perfect combustion. The result of this object is, of course, a fryer of greatly improved efficiency. Obviously, this improvement in efficiency brings about important economies in the consumption of gas or oil used for heating the fryer, and thus gives rise to corresponding economies in cooking of foods therein. Also, the improvement in efficiency of heat transfer effects a marked difference in the time required to bring the unit to 2 operating temperature after being vtemporarily lowered as by the immersion of a quantity of foods to be fried, and thus increases the productive capacity of the unit to a very marked degree.
The teachings of the present invention will be disclosed in connection with a present preferred embodiment of the invention illustrated in the attached drawings, wherein:
Figure 1 is a plan view of a deep fryer unit constructed according to the presentinvention;
Figure 2 is a, longitudinal sectional view taken substantially on the plane of the line 2 2 of Figure l;
Figure 3 is a detail transverse sectional view through the inlet end of one of the heat transfer tubes, and is taken substantially on the plane of the line 3--3 of Figure 1; and
Figure 4 is a detail transverse sectional view of an intermediate portion of one of the heat transfer tubes employed by the present teaching, the view being taken on the line 4 4 of Figure 1.
In the preferred form of deep fryer illustrated, the grease tank is of rectangular shape having inner walls I0 with outwardly flared portions H at their upper edges terminating in vertical exterior walls l2 surrounding the tank. The bottom I3 of the tank is tapered from a center point indicated at I4 and may be provided with a drain valve (not shown) at the lowermost point thereon.
As shown, the unit employs two identical oil burners l5, but the teachings of the present invention apply equally to burners designed for gas. The burners i5 are positioned in alignment with the inlet ends l 6 of a pair of heat transfer tubes I1, each of which is of U shape, and extend into the grease tank from a point adjacent the burners to a reverse bend I8 near the opposite end of the tank, and then double back to join conduits I9 extending to the lowermost end of the ue 20.
The inlet ends I6 of the heat transfer tubes are tapered for about half the length of the grease tank, but are inclined sufliciently so that the upper surfaces of the tapered portion are level with the rest of the tube, as shown in Figure 2. The mouth portions of each tube are thus of a diameter substantially double the diameter of their cylindrical portions (Figures 3 and 4), so that the inlet of each of the tubes is of greatly increased cross sectional area as compared to the remainder of the tube, yet extends no higher in the tank. It has been found, however, that when the unit is in use, the increased cross sectional area at the inlet end of the tube increases the efficiency of combustion, and not only raises the 3 temperature of the burning gases within the tubes. but raises the temperature of the tube walls to a marked degree.
This clearly demonstrates that a heat transfer tube according to the present teachings not only increases the efficiency of combustion, but in addition, provides an inherent regulation of the velocity of gases passing through the tube, such that the efficiency of heat transfer from the gases to the metal of the tube is also increased.
Thus, aI deep fryer having heat transfer tubes constructed in accordance .with the present teachings effects a substantial increase in e'- ciency of heat transfer from the ame of the burner to the grease in the fryer. This has been demonstrated by actual tests, in whichk it has been shown that a fryer having combustion tubes in accordance with the present teaching can be heated to operating temperature in considerably less than the time required to heat a similar vessel with conventional types of heat exchangers, At the same time, the present teaching provides a unit which is suitable for use in a deep fryer in that it is compact enough to be' practical in a grease reservoir of limited size and is so designed as to be fully accessible throughout and to thus be easily cleaned and maintained in fresh, sanitary condition.
Having thus described my invention, what I claim as new and desire to secure by United States Letters-Patent is:
1. The combination, with a deep fryer comprising a grease tank having hollow Walls, a plurality of burner-s and a plurality of flues, a pair of said ues being parallel to each other and extending in said Walls and along the oppasite sides of the tank and inr heat communication therewith, andadditional ues extending in a third hollow Wall and along the third side of said tank and being in heat communication therewith, said latter nues being connected to the exits of said pair of iiues, a pair of combustion tubes, said tubes having mouths, each mouth being located in a wall and adjacent to a burner and being located on opposite sides of said tank with each mouth being located adjacent to one of said parallel pair of ues, each combustion tube having a horizontal section and a gradually tapered section with the larger end of the tapered section of each tube terminating in one of said mouths, and said cylindrical section having means connecting the same to one of said parallel iiues, said iiue connecting means of each combustion tube being located substantially diametrically opposite from the other iiue connecting means;
2. A structure of claim 1, in which the top surface of' each tapered section is substantially parallel to the top surface of its cylindrical section, and the undersurface of the tapered section is at an angle with the upper surface of the tapered section.
RICHARD T. KEATING.
References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 412,821 Wright Oct. 15, 18,89 502,370 Lied Aug. 1, 1893 1,050,095 Betts Jan. 14, 1913 2,053,568 Levin Sept. 8,v 1936 2,176,869 Childs Oct. 24, 1939 2,429,360 Kells Oct. 2l, 194,7 2,452,472 Keating Oct. 26, 1948 2,496,113 Wollner Jan. 31, 1950 FOREIGN PATENTS Number Country Date 3,798 Great Britain of 1868