Cooking grill heated from deep fat fryer

A cooking grill structure for utilizing the heat from deep fat fryers has a grill plate and a heat pipe extending into the cooking oil. Water is utilized as the liquid medium in the heat pipe, and condensation is distributed over the grill plate to provide uniform heating and prevent accumulated forces. Distribution is achieved by a relatively small channel that uniformly spreads the heat while preventing the production of unduly large pressure forces. To achieve greater transfer of heat from the cooking oil to the liquid medium in the heat pipe, heat transfer assistance approaches, such as fins or small diameter tubes to provide a flash boiler effect may be used. Also, more than one heat pipe may be used, and the grill plates may be interlocked to provide a continuous grill surface.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates generally to a cooking grill, and more specifically, 
this invention relates to a cooking grill heated from a deep fat fryer. 
2. Description of the Prior Art 
Fast-food facilities normally have deep fat fryers to cook items such as 
french fries. Also, foods such as hamburgers are now frequently cooked by 
devices such as chain conveyor broilers or charcoal grills, rather than a 
general purpose grill. While this approach works well for these foods, 
there are various types of foods, such as eggs, that are not readily 
susceptible to cooking by such devices. Thus, some fast-food facilities 
are limited in the types of food and the meals that they can serve. For 
example, they may find it difficult to provide a full range of breakfast 
foods, which limits the usefulness of their facility. 
Separate grills could be provided, but this involves additional cost and 
space, with the attendant increase in capitalization and overhead expense. 
Also, the grills might be utilized only for a portion of the day. A 
preferable approach would be to utilize the available heat source (i.e., 
the deep fat fryers) to provide a heated grilling surface when required. 
Since the peak time usages for the deep fat fryers (e.g., lunch time or 
supper time) normally differs from the peak time usage of the grills 
(e.g., breakfast, when the deep fat fryers would not usually be required), 
this would provide a very desirable combination that would tend to 
maximize utilization of these components. Specifically, the deep fat 
fryers may be utilized as a heat source for the grills at breakfast. 
Further, since the cooking oil in the deep fat fryers must usually be kept 
heated for possible use, the heat lost when they were not in use could be 
put to work. 
Two previous attempts to provide such a deep fat fryer grill have been 
made. One involves placing a grill plate on top of the deep fat fryer and 
increasing the temperature of the cooking oil to grill by heat radiated 
from the cooking oil. The other utilizes a grill plate floating directly 
on the cooking oil. Each of these attempts has defects that prevents 
successful use. 
In connection with the first, the increased temperature of the cooking oil 
causes it to degrade (i.e., particles of the oil carbonize). This results 
in a lower smoking temperature that causes foods cooked in that oil to 
have an undesirable taste and smell. Also, of course, the increased 
temperature requires greater energy consumption. 
With respect to the second approach, the cooking oil must be kept below the 
top of the vat or container, so that the insertion of food to be cooked 
does not cause the cooking oil to overflow. Thus, the grill plate must be 
small enough to be inserted into the top of the deep fat fryer. This 
reduces grill surface and prevents the joinder of adjacent grill plates. 
Further, the grill surface is not maintained flat as the grill plate 
floats on the cooking oil. 
Accordingly, it would be highly desirable to have an effective system for 
converting a deep fat fryer into a grill. 
SUMMARY OF THE INVENTION 
With the present invention, a relatively lightweight grill system is 
provided by which a deep fat fryer can be easily converted for grilling 
and re-converted for deep fat frying. 
This system includes a generally flat grill plate that is arranged to be 
mounted on top of the deep fat frying vat or container. In a preferred 
form, the grill plate could rest directly on the top of the deep fat 
frying container. 
Heat for the grill plate is obtained from the heated cooking oil by an 
appropriate heat transfer arrangement. This could take various forms, such 
as a solid heat conducting structure, but the preferred approach disclosed 
herein utilizes a heat pipe that extends from the grill plate down into 
the cooking oil. With such a heat pipe, a liquid medium, such as water, is 
vaporized by heat from the cooking oil and then condensed adjacent the 
grill plate to provide the heat for cooking. A distributing structure may 
be utilized to spread the heat of condensation evenly over the grill 
plate, and preclude development of excessive forces on the grill plate. 
The distributing structure may take the form of a channel having a 
multiplicity of branches distributed under the grill plate, so that a 
branch of the channel is in relatively close proximity to a major portion 
of the surface of the grill plate. This distributing structure should be 
slightly evacuated to prevent an air layer from interfering with heat 
transfer to the grill plate. 
In order to increase heat transfer for the cooking oil to the heat pipe, 
heat fins may be located on the portion of the heat pipe that extends into 
the cooking oil. Alternatively, a relatively small diameter tube may be 
connected to the heat pipe to provide a flash boiler effect, and thus 
greatly enhance the heat transfer characteristics. Also, additional 
interconnected heat pipes, each with a flash boiler tube, may be used to 
increase heat transfer from the cooking oil to the grill plate. 
Each of the grill plates may be provided with a converting structure that 
permits grill plates mounted on adjacent deep fat fryers to be interlocked 
to provide a continuous grill surface. This provides a large grill 
surface, when required, with considerable efficiency. 
These and other objects, advantages and features of this invention will 
hereinafter appear, and for purposes of illustration, but not of 
limitation, exemplary embodiments of the subject invention are shown in 
the appended drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
A deep fat frying container 11 is illustrated in FIG. 1. Deep fat frying 
container 11 is partially filled with a cooking oil 13. Cooking oil 13 is 
kept at a raised temperature, generally in the 350.degree.-400.degree. 
Fahrenheit range, for cooking french fried potatoes or other foods 
immersed therein. 
To provide a cooking grill heated from the cooking oil 13, a grill plate 15 
is appropriately mounted on the deep fat fryer 11. In this preferred 
embodiment, the grill plate 15 may be mounted directly on the top 17 of 
the container 11. 
A heat pipe 19 is appropriately secured to the bottom of grill plate 15 to 
extend down into the cooking oil 13. Heat pipe 19 is filled with a 
suitable liquid medium 21, such as freon, alcohol, oil of turpentine or 
water. In this preferred embodiment, water is utilized for purposes of 
safety as well as efficacy. 
In operation, heat from the cooking oil 13 vaporizes the liquid medium 21, 
the vapor being represented by bubbles 23. The vapor 23 rises to a 
distributing chamber or channel 25. Vapor 23 condenses in channel 25, and 
the heat of condensation provides the cooking heat for grill plate 15. 
Channel 25 is constructed to evenly distribute the heat over the surface 
of grill plate 15 and to prevent the development of cumulative forces at a 
given area. Channel 25 is also partially evacuated to prevent an air 
barrier from being created that could interfere with the transfer of heat 
to grill plate 15. In addition, to increase heat transfer from the cooking 
oil to heat pipe 19, heat fins 27 may be attached to heat pipe 19. 
FIG. 2 illustrates another embodiment in which grill plates 15' are 
provided with connecting elements 29 and 31. When elements 29 and 31 are 
mated, a continous grill surface heated from adjacent deep fat fryers 11' 
is provided. Any appropriate form of a connecting structure may be 
utilized, and the grill surface can extend along as many deep fat fryers 
as desired or needed. 
To increase the efficiency of heat transfer from the cooking oil to the 
heat pipe, an arrangement such as that illustrated in FIG. 3 may be 
utilized. In this embodiment, a tube 33 is associated with the heat pipe 
19", such as by being wrapped around it. A first end 35 of tube 33 is 
connected in fluid communication with the interior of heat pipe 19" at the 
bottom thereof to provide for flow of the liquid medium from the heat pipe 
19" into the tube 33. 
An end 37 of tube 33 is connected to heat pipe 19" at a point, preferably 
although not necessarily, below the surface of the cooking oil, 
represented by the wavy line 39. End 37 of tube 33 is also preferably, 
although not necessarily, located above the level of the liquid medium in 
heat pipe 19". As in the case of end 35, end 37 of tube 33 is in fluid 
communication with the interior of heat pipe 19". 
Due to the communication between heat pipe 19" and tube 33, the liquid 
medium in heat pipe 19" tends to rise to the same level in tube 33 that it 
reaches in heat pipe 19". However, since the tube 33 has a diameter small 
in comparison to the diameter of heat pipe 19", heat transfer from the 
cooking oil to the relatively small amount of liquid medium in tube 33 
rapidly raises the temperature of the liquid medium. The result is that 
the liquid medium in tube 33 is quickly vaporized, and thus tube 33 
provides a flash boiler effect. 
Upon vaporization in flash boiler tube 33, the vaporized medium passes back 
into heat pipe 19" for conveyance to distributing channel 25". Although 
the discharge of vaporized medium into heat pipe 19" normally is above the 
level of the liquid in the heat pipe, even if the level of the liquid were 
to rise above end 37 of the flash boiler tube 33, the operation of the 
system should not be significantly affected. 
By utilizing the small dimensions of the tube 33 to achieve a flash boiler 
effect, the process of heat transfer from the cooking oil to the liquid 
medium in the heat pipe 19" is greatly accelerated. As the vaporized 
medium condenses and conveys heat to the grill plate 15", the condensed 
liquid is returned to heat pipe 19" and, in part, to the flash boiler tube 
33 to once again be vaporized. 
It is not necessary that only one heat pipe be used with the grill plate, 
as a multiplicity of such heat pipes could be employed in various 
situations. Thus, in FIG. 4 there is illustrated another embodiment 
utilizing two heat pipes 41 and 43. Heat pipes 41 and 43 are essentially 
the same as heat pipe 19 and utilize a common liquid medium. 
Heat pipes 41 and 43 are provided with flash boiler tubes 45 and 47, 
respectively. Flash boiler tubes 45 and 47 are essentially identical to 
flash boiler tube 33. 
In order to prevent an accumulation of liquid medium in one or the other of 
heat pipes 41 or 43, the bottoms of these heat pipes are interconnected by 
a tube or conduit 49. Not only does conduit 49 provide for the maintenance 
of an equal distribution of the liquid medium, it also aids in the 
transfer of heat from the cooking oil to the liquid medium, due to its 
relatively small diameter. As a matter of fact, in another version the 
flash boiler tube 45 and 47 could be connected between the heat pipes 41 
and 43, thus eliminating the need for conduit 49. 
Grill plate 51 is a modified version of grill plate 15, having a chamber or 
channel structure 53 adapted to distribute the steam or other vaporized 
medium from the two heat pipes 41 and 43. Of course, further heat pipes 
could also be employed, which would involve further modification of the 
grill plate. 
The shape of chamber or channel structure 53 is illustrated schematically 
in FIG. 5. While various shapes could be utilized, the shape of FIG. 5 is 
that preferred in this embodiment. It should also be recognized that the 
channel structure is not flat, but is angled to provide for return flow of 
the condensed medium, as illustrated in FIG. 4. 
As may be seen, a pair of openings 55 and 57 communicate with the heat 
pipes 41 and 43, respectively. Steam, or other vaporized medium, rises 
through these openings and water, or other condensed liquid medium, flows 
back to the heat pipes through these openings. 
Radiating outwardly from opening 55 are channel branches 59, 61, 63 and 65. 
Branch 65 also communicates with opening 57, which has additional channel 
branches 67, 69 and 71 radiating outwardly therefrom. Channel branches 63 
and 67 communicate with a larger branch 73, while branches 61 and 71 
communicate with a similar larger branch 75. 
This arrangement of the branches of the channels of chamber 53 provides for 
uniform distribution of heat over grill plates 51, without generating 
unduly excessive pressure forces on the grill plate. Of course, any 
appropriate shape of the chamber or channel structure 53 that would 
realize these goals could be utilized. 
It should be understood that various modifications, changes and variations 
may be made in the arrangement, operation and details of construction of 
the elements disclosed herein without departing from the spirit and scope 
of this invention.