Deep Fat Fryer With Burner Tube End Weld Temperature Protection

This invention relates generally to deep fat fryers and specifically to an arrangement for precluding temperature-induced failures of the end-welded junctions of the fry pot and burner tubes in such fryers.

Deep fat fryers include a fry pot having opposed walls and one or more open-ended burner tube secured (by end welds) between a pair of opposed fry pot walls. The fry pot and burner tube material are generally of stainless steel and the fry pot has flanged apertures formed therein to enable the burner tube to be end-welded thereto.

In high heat or rapid recovery deep fat fryers, the burner flame is intense and in some situations, the end welds on the burner tubes may experience an excessive rise in temperature which produces stresses in, and occasional failure of, the end welds. Part of the reason for the excessive temperature rise is the end-weld design, which partially isolates the weld from the cooling effect of the cooking oil in the fry pot. While the problem can be minimized with controlled manufacturing procedures and more costly weld materials, the solution of the present invention obviates the potential problem with very little added cost and enables more efficient manufacturing while avoiding the need for specialized materials.

A principal object of the invention is to provide a novel deep fat fryer.

Another object of the invention is to provide a deep fat fryer that is less costly to manufacture.

A further object of the invention is to provide a deep fat fryer of improved reliability.

A still further object of the invention is to provide a rapid recovery deep fat fryer that minimizes the possibility of burner tube weld failure.

These and other objects and advantages of the invention will be apparent from reading the following description in conjunction with the drawings, in which:

FIG. 1 is a simplified partial perspective of a prior art deep fat fryer;

FIG. 2 is a frontal view of a front burner tube heat shield constructed in accordance with the invention;

FIG. 3 is a cross section taken along the line 3--3 of FIG. 2;

FIG. 4 is a rear view of the heat shield of FIG. 2;

FIG. 5 is a bottom view of the heat shield of FIG. 2;

FIG. 6 is a frontal view of a rear burner tube heat shield constructed in accordance with the invention;

FIG. 7 is a cross section taken along the line 7--7 of FIG. 6; and

FIG. 8 is an enlarged, partial sectional view of a burner tube end-welded in a fry pot with the front and rear heat shields of the invention installed.

Referring to FIG. 1, a prior art deep fat fryer fry pot 10 includes three open-ended burner tubes 12, 14 and 16, secured between a pair of opposed walls 17 and 19 of the fry pot. Three gas burners 18, 20 and 22 are positioned to project burner flames into corresponding ones of the burner tubes, which are supplied with gas from a manifold 24. In practice, cooking oil is in fry pot 10 and surrounds the burner tubes, which are heated by the burner flames and which, in turn, heat the cooking oil. As discussed above, the combination of the high heat burner flame in the rapid recovery deep fat fryer and the effect of the burner tube end-welded construction in restricting efficient heat transfer from the weld area to the heating oil, can create a stress failure in the weld. While the problem is more pronounced with end welds, it is also present, to a lesser degree, with conventional butt or overlap welds.

In FIG. 2, a front heat shield 26, constructed in accordance with the invention, includes three orifices 28, 30 and 32 that are shaped like the open ends of the burner tubes, but have a slightly smaller size. The orifices may be formed by stamping out the appropriate shapes from a flat stainless steel sheet 26a and have contoured lips 28a, 30a and 32a, respectively, formed therein. As shown in FIG. 4, a similar flat stainless steel sheet 26b has similarly shaped, but slightly smaller orifices 40, 42 and 44 formed therein with contoured lips 40a, 42a and 44a, respectively. The two sheets 26a and 26b are sandwiched together, preferably by a series of spot welds, and take the configuration indicated in FIGS. 3 and 5. Two L-shaped mounting plates 48 and 50 are secured to shield 26 for positioning the orifices in alignment between the burners and burner tubes, as will be seen. The cross section of FIG. 3 clearly illustrates the difference in orifice sizes.

While not required in the broader aspects of the invention, a rear heat shield is also provided for the deep fat fryer. Obviously, the welds at the rear of the burner tubes are not subjected to the direct impact of the burner flame as often occurs with the front welds. However, the hot combustion products impinging on the rear of the burner tubes can cause temperature stress problems in the rear welds, especially if they are of the end weld type.

In FIG. 6, a rear heat shield 60 is shown, In this shield construction, three openings are formed in the stainless steel plate and three individual heat deflection tubes 52, 54 and 56, with contoured lips 52a, 54a and 56a, respectively, are secured in respective ones of the orifices by any well known means. Angled portions 60a, formed along the edges of sheet 60, position the heat shield from the rear wall of the fry pot with the deflection tubes positioned in the ends of the corresponding burner tubes. The cross section of FIG. 7 clearly illustrates the relationship of the heat deflection tubes and shield plate.

In FIG. 8, the arrangement for burner tube 16 is shown, with both the front heat shield 26 and the rear heat shield 60 in position at the front and the rear, respectively, of the burner tube. The position of burner 22 is indicated by dashed lines. The end welds 16a on both the front and rear open ends of burner tube 16 are also indicated. Specifically, front and rear end welds 16a join the flange 17a of front fry pot wall 17 and the flange 19a of rear fry pot wall 19, respectively. With respect to the front heat shield 26, a space exists around the welded open end of burner tube 16 which permits ambient (cool) airflow over the weld when the burner is operating. Also, front end weld 16a is blocked off from the flame from burner 32 by the rear portion 26a of front shield 26. The combined effect of the isolation of front weld 16a from the direct burner flame and the airflow over front weld 16a, acts to restrict the temperature rise at the front weld to a level where temperature induced stress failure does not occur. The arrangement for the other burner tubes is similar to that shown and described.

At the rear of burner tube 16, rear heat shield 60 positions heat deflection tube 54 closely adjacent to, but preferably not in contact with, the inner surface of the burner tube. Insulation material 62 is placed in the space between heat shield 60 and the fry pot rear wall 19 and in the space between the inner surface of burner tube 16 and heat deflection tube 54. In this manner, the rear weld 16a is shielded from the hot combination products in the burner tube. The contoured lip 54a of deflection tube 54 aids in the free flow of combustion products out of the open-ended rear of the burner tube into a flue (not shown), where they are carried away by conventional means. It will be recognized, that details of securing the heat shields to the fry pot are not given, since such will vary depending upon the particular fry pot and deep fryer arrangement.

What has been described is a novel shielding arrangement for precluding temperature-induced stress failure in the welds between a burner tube and fry pot. It is recognized that numerous changes and modifications in the described embodiment of the invention will be apparent to those skilled in the art without departing from its true spirit and scope. The invention is to be limited only as defined in the claims.