US3719180A

US3719180A - Device for heat treatment by way of forced gas convection, forming a bakery, pastry, pork-butchery oven or the like

Info

Publication number: US3719180A
Application number: US00111241A
Authority: US
Inventors: F Pere
Original assignee: CAPIC CAILLAREC Ets
Current assignee: CAPIC CAILLAREC Ets
Priority date: 1970-02-02
Filing date: 1971-02-01
Publication date: 1973-03-06
Anticipated expiration: 1990-03-06
Also published as: DE2103827A1; ES387809A1; FR2079466A5

Abstract

A device for heat treatment comprising a muffle, heating means, a fan and a treatment chamber limited on one of its sides by an inner wall of the muffle, the cross-sections of said chamber having the shape of trapezia, the larger base of which is located on the fan side of the device. The heating means are constituted by at least one gas burner. The device comprises a casing forming a heat exchanging element surrounding said heating means and being placed within the hot gases circulating in the muffle.

Description

[451 March 6, 1973 United States Patent 91 Pere 3,324,844 6/1967 Huffman............................ 126/21A 3,384,068 5/1968 3,605,717 9/1971 Sauer...............,..................126/2l A Perry et al.

[ DEVICE FOR HEAT TREATMENT BY WAY OF FORCED GAS CONVECTION,

FOREIGN PATENTS OR APPLICATIONS Francois Caillarec Pere, Quimper, 1,124,382 6/1956 France................................126/21 A France [73] Assignee: Capic-Etablissements Caillarec, Primary Examiner-Charles Myhre Quimper, France Attorney-Stemberg & Blake Feb. 1, 1971 [21] Appl. No.: 111,241

ABSTRACT [22] Filed:

A device for heat treatment comprising a muffle, heating means, a fan and a treatment chamber limited on one of its sides by an inner wall of the muffle, the cross-sections of said chamber having the shape of trapezia, the larger base of which is located on the fan France.................... ............7003575 side of the device. The heating means are constituted by at least one gas burner. The device comprises a casing forming a heat exchanging element surrounding said heating means and being placed within the hot gases circulating in the muffle.

Afi R 1/ 3 2 7 /1 6 24R6 429 C1 mR m IA mi 2 ""6 "2 "1 Th "C r. "0 Us L I0 W d td I Q- UmF 111111 2 8 555 [rlrl 7 Claims, 5 Drawing Figures [56] References Cited UNITED STATES PATENTS 3,148,674 9/1964 Boardman et a1. ....,............l26/2l A PATENTED 61975 3.719.180

SHEET EEF 2 DEVICE FOR I-IEAT TREATMENT BY WAY OF FORCED GAS CONVECTION, FORMING A BAKERY, PASTRY, PORK-BUTCHERY OVEN OR THE LIKE The present invention has for its object a device for heat treatment of food products, of the forced gas convection type, adapted to be used, in particular, as a bakery, pastry, pork-butchery oven or the like, for baking, pre-heating, or heating food products.

The few devices for heat treatment of food products by way of forced gas convection, wherein use was made of gas burners located within the very muffle of the device, had the following drawbacks a considerable part of the sensible heat of the burnt gases was lost as a result of insufficient heat exchange through the walls of the sealed sheath containing the burners and of the relatively direct escape of the burnt gases in the chimney or chimneys the arrangements which were resorted to, although relatively efficient from the heating point of view, led to a lack of sufficient available space in some portions of the muffle, so that it was not possible to use removable trolleys carrying the foodstuffs and, therefore, the baking rates were reduced the said devices were not provided with the system of circulation which is well known at the present time and particularly efficient, according to which the hot gases proceeding from the medial region of the chamber of the treatment device were sucked by a fan placed in a medial plane of the muffle and delivered symmetrically towards the side walls of the said chamber and then along the said wall, to be thereafter recycled in the medial region of the oven.

The heat treatment device according to the present invention enables the various aforesaid drawbacks to be remedied.

The heat treatment device according to the invention pertains to the general type described above and is characterized in that the heating means are constituted by at least one gas burner of the baror tube-type,or of the single-jet type, the latter being protected from the air flows produced in the oven chamber by a casing or enclosure which surrounds it at least on a portion of its periphery, the said casing or enclosure being located within the hot gases circulating in the muffle, so as to constitute a heat exchanging and distributing element.

According to a preferred form of embodiment of the present invention, the said fan is secured to the rear wall of the muffle, and the said casing is constituted by two substantially parallel and vertical metal sheets perpendicular to the fan shaft and located on either side of the said burner which is preferably constituted by a horizontal gas bar or tube, the said sheets being located in front of the fan and their side edges being bent towards the front and joined together, whereas a passageway is provided transversely of and through the said sheets in confronting relationship to the said fan,

so as'to allow the passage of the hot gases proceeding 6 from the interior of the chamber towards the space provided within the said casing and the rear wall of the oven, the said bent edges being located at a certain distance from the side walls of the muffle so as to allow the passage of the hot gases proceeding from the space provided between the said casing and the rear wall of the muffle towards the interior of the chamber.

According to another preferred form of embodiment of the invention, the device comprises two casings of the aforesaid type, placed symmetrically with respect to the said medial plane, within the treatment chamber proper, in immediate proximity to the muffle walls, so that the said casing is licked on one side by the gas flow entering the said chamber and on the other side by the gas flow passing through the said casing towards the said fan.

The invention will be better understood and other objects, characteristics and advantages thereof will appear as the following description proceeds, with reference to the appended drawings given solely by way of example illustrating two forms of embodiment of the invention and wherein FIG. 1 is a horizontal sectional view of a heat treat- 7 ment device according to a first form of embodiment of the present invention FIG. 2 is a vertical sectional view upon the line II-II of FIG. 1 of the same device FIG. 3 is a perspective view of the rear metal sheet of the casing of the heat treatment device of FIG. 1

FIG. 4 is a vertical sectional view, in parallel relationship to the inlet door, of a heat treatment device according to a second form of embodiment of the invention FIG. 5 is a longitudinal sectional view upon the line VV of FIG. 4 of the said device.

Referring now to FIGS. 1 to 3, the heat treatment device comprises a muffle 1, made for instance from a refractory or heat insulating material, two fans 2 and 3 secured to the rear wall 1c of the muffle, a gas tube burner 4, a casing 5 for the latter and a trolley 6 for moving in or out the products to be treated, the said muffle being closed by means of a door 1a.

The gas tube burner 4 is fed through a gas (town gas, butane or propane) intake piping, not shown for the sake of clarity the gas tube burner is arranged on the sole or bed lb of the oven and is fed with air supplied from the exterior through two ducts 7 (portions 7a and 7b) and 8 (portions 8a and 8b) opening into the casing 5.

The treatment chamber 9 is constituted by the portion in front of the casing 5, i.e., the space comprised between the said casing and the door In the treatment chamber 9 is intended to contain the products to be treated which may be arranged on a system of removable or stationary trays or plates connected to the side wall of the muffle 1 however, as shown in FIG. 1, a trolley 6 is preferably used owing to the fact that the heating means and the means ensuring the circulation of the hot gases leave the medial portion of the internal volume defined by the muffle l altogether free, thus facilitating and accelerating the charging and discharging operations.

The general system of circulation of the hot gases within the muffle is as shown by the arrows F in FIG. 1 and results from the trapezoidal shape of the cross-sections of the inner walls of the muffle, normal to the medial plane 10 in which are placed the fans 2 and 3, in combination with the use of deflecting means which, in this case, are constituted by the casing 5 itself as well as the dihedral rounded angles of the inner

rear corners

11a and 11b of the muffle l, axial passageways such as 12 and 13 being provided through the casing 5 in alignment with the fans 2 and 3.

FIG. 3 is a detailed view of the structure of the casing 5 surrounding the gas-tube burner 4 so as to protect the latter from the hot gas flow proceeding from the treatment chamber 9 or conveyed thereto the said casing is constituted by two vertical and parallel metal sheets 14 and which are substantially perpendicular to the axes of the fans 2 and 3 the side edges such as 15a of the metal sheet 15 are bent towards the front, and so are the side edges such as 14a of the metal sheet 14 the edges such as 14a and 15a are sealingly joined together, as by welding, so as to close as completely as possible the inner space of the casing 5 for the same reason, the communication between the said inner space and the general volume of the muffle at the passageways l2 and 13 is practically completely prevented by means of cylindrical metal sheets 12a and 13a connected at their ends to the sheets 14 and 15 the metal sheets 12a and 13a are provided at least at their upper portion with openings 16, the dimensions of which may be adjustable on the other hand, the diameter of the metal sheets 12a or 13a is slightly greater than that of the fan, the said diameter being for instance on the order of 10 to 13 cm depending on the size of the oven the opening 16 may be closed if for instance a malodorous combustive material such as fuel is used according to a modified form of embodiment, no passageway is provided between the casing 5 and the general volume of the muffle (sealed casing).

The metal sheet 14 of the casing 5 is also provided on its outer surface with substantially horizontal ribs or fins 17 serving to improve heat exchange and favor the transverse flow of hot gases in the space 18 located between the casing 5 and the rear wall 1c of the muffle.

As seen in FIG. 2, the lower end of the casing 5 is connected to the sole or bed 1b whereas its upper end is connected to the muffle vault 1d thus, the combustion gases may escape through the chimney 18 opening at 18a into the upper medial portion of the rear wall 10 of the muffle, a short metal sheath being provided to connect the opening 18a with an opening 18b located opposite the opening 8a in the rear metal sheet 14 of the casing 5.

Thus, the only communication between the general volume of the muffle and the inner space of the casing 5 is through the orifices 16.

The operation of the heat treatment device just described is obvious; the heating takes place in a particularly efficient and uniform manner. Indeed, in addition to the advantages resulting from the use of the means already described in French patent No. 1,515,884 and its two certificates of addition, respectively No. 92,009 and No. 92,659, in the name of the Applicant, as regards the system of hot gas circulation in the treatement chamber, the present device provides the following improvements as compared with the already known types of gas ovens the required temperature within the treatment chamber 9 is attained more rapidly owing to the fact that a greater proportion of the sensible heat of the combustion gases than in the known gas ovens is transferred directly to the gases which are made to circulate in the chamber 9 by the fans 2 and 3, owing, on the one hand, to the fact that the heat of the flames is not stored in a heat insulator which subsequently restores it to the circulating gases and, on the other hand, to the fact that the combustion gases conveyed to the chimney are not as hot as in the known devices owing to the remoteness of the chimney with respect to the gas tube burner and owing to the particular position of the lower orifice of the chimney which is not located in the muffle vault (braking effect at exit) 1 thermal efficiency is improved, for as already stated, a greater proportion of combustion heat is transferred to the gases circulating in the treatment chamber 9, as a result, mainly, of the good heat conductivity of the large metal surface developed by the metal sheets 14 and 15 of the casing 5, between the region where heat is produced at the burner 4 and the region where the fumes or burnt gases are eliminated at the opening 18a moreover, heat exchange is still more improved owing to the ribs 17, an additional function of which is, as already mentioned, to facilitate the transverse flow of the gases conveyed to the treatment chamber 9 the cold primary air sucked at the inlet of the ducts 7 and 8 is pre-heated owing to a sufficiently long path within the muffle 1, whereas a direct supply of cold air at the gas tube burner 4 would result in the absorbtion of a non-negligible fraction of the heat produced at the lower portion of the casing 5.

The orifices such as 16 ensure direct passage into the circulating hot gases blown back into the chamber 9 by the fans 2 and 3 of a portion of the burnt gases produced in the casing 5, thus imparting more flexibility to the heating means in operation without prejudicing the stability of the flames.

The heat treatment device shown in FIGS. 4 and 5 comprises a muffle 20 and at least one fan 21 secured to the vault 20a of the muffle and located in the medial plane 25 thereof, opposite an opening 22 provided in an inner wall 23 of the muffle, defining a treatment chamber 24 in the general volume of the muffle, the said inner wall 23 being preferably constituted by a metal sheet which is for instance suspended by suitable means from the oven vault 20a (in the case considered, the number of fans used depends upon the depth of the muffle, measured from its front wall provided with the access door to its rear wall).

The heating means are constituted by two gas-tube burners 26a and 26b, each surrounded by a

casing

27a or 27b constituted by an invagination of the metal sheet 23, the said invagination being open at the level of the flames of the gas burner tubes, so that the combustion gases are conveyed back into the general circulation system of the gases in the treatment chamber the flames are protected from the direct effect of the flow owing to the end portions such as 27'a, the combustible gas being injected at the rear end of the gas burner tubes by an injector 30 supported by an arm or bracket 300, which allows auxiliary atmospheric air to be carried along by the gas. Primary air necessary for the combustion of the gas is fed from the atmosphere through a sheath 280; one of the sides of the sheath 38 is advantageously constituted, as seen in FIG. 4, by a portion 28 of the casing the supply of air at the level of the flames of the burner tube takes place through a series of orifices 29. Part of the front door 32a is schematically illustrated in FIG. 5.

It is thus possible to make the gas burner flames emerge in the baking chamber itself while at the same time protecting the flames and, as a result of the supply of primary air, ensuring good gas combustion in order to compensate for the said supply, discharge means such as, for instance, a chimney or a vent, are provided.

Generally, in the devices according to the present invention, the primary air supply orifices are at least two in number and arranged either in the front portion or in the side portion of the device of course, the said primary air may also be mixed beforehand with the fuel, a secondary air supply being possibly provided at the level of the flames. Although the examples illustrated apply solely to the case where bar-type or tube-type gas burners are used, it is obvious that other types of gas burners such as, for instance, single-jet flame type burners, may be used, such single-jet flame burners being for instance constituted by an airfuel mixture injector at the outlet of which the said mixture is inflamed.

What is claimed is:

1. In a gas-fired, forced-air convection heating device for food-stuffs, a muffle having a front wall provided with a door, a rear wall opposite said front wall, opposed side walls extending between said front and rear walls and connected thereto, and top and bottom walls extending between and connected to the remaining walls, said muffle having a vertical medial plane situated midway between and being parallel to said side walls, said top and rear walls of said muffle forming a pair of walls which with said opposed side walls and said bottom and front walls define an interior treatment chamber which in a plane normal to said medial plane is of trapezoidal configuration on each side of said medial plane, at least one fan situated in close proximity to and carried by one of said pair of muffle walls, in said medial plane with the interior space of trapezoidal configuration on each side of said medial plane in said plane normal to the latter having its largest base situated in the region of said fan, an an inner wall situated adjacent that one of said pair of walls which carries said fan with the latter situated between said inner wall and said one of said pair of walls, said inner wall being formed with an opening in alignment with said fan, and heating means for heating the interior of said muffle, said heating means comprising a gas burner and a casing extending at least partly around said gas burner, forming an extension of said inner wall, and having a heat-exchanging relationship with the interior of said muffle for transferring heat from said burner to the interior of said muffle for generating in the latter hot gases circulated by said fan through said opening of said inner wall into the space between the latter and said one of said pair of muffle walls, said casing having elongated side portions situated adjacent but spaced from said side walls to define with the latter a pair of elongated gaps through which the hot gases flow from the space between said inner wall and said one of said pair of walls into an interior treating portion of said treatment chamber situated on the side of said inner wall opposite from said fan and in which the food-stuffs are located to be treated.

2. The combination of claim 1 and wherein said one of said pair of walls is said rear wall of said muffle, said inner wall being situated in front of said rear wall and being in the form of a metal sheet, said casing including a front metal sheet situated forwardly of said inner wall and having a pair of opposed vertical side edges, said inner wall also having a pair of opposed vertical side edges respectively fixed with said ogpiostgdvertictzlill sidce1 e ining wi sa1 edges of said front metal sheet, an opposed side walls of said muffle said gaps through which the hot gases flow, at least one of said metal sheets having a rounded configuration and said casing having a lower interior region in which said burner is located, and a chimney connected to an upper portion of said casing and communicating with the interior thereof, and a circular wall defining an air channel, extending between and connected to said inner wall and from metal sheet, the latter being formed with an opening aligned with said opening of said inner wall so that said circular wall defines an air channel for flow of air through the latter channel toward said fan, so that said channel has a rear end communicating with the space between said inner wall and rear wall and a front end communicating with said treating portion of said treatment chamber.

3. The combination of claim 2 and wherein a supporting means for supporting food-stuffs is located in said treating portion of said treatment chamber and is in the form of a removable trolley.

4. The combination of claim 2 and including a means for supplying primary air, the latter means including at least one air duct having an elongated section embedded in one of said side walls and a relatively short section extending between said elongated section and said casing, communicating with the interior of the latter in the region of said burner for supplying primary air to the latter.

5. The combination of claim 2 and wherein said circular wall extending between said front sheet metal wall and said inner wall and defining said channel is itself formed with openings providing communication between the interior of said casing and the interior treatment chamber.

6. The combination of claim 2 and wherein said inner wall is provided at its surface which is directed toward said rear wall with a plurality of elongated horizontal ribs which improve the heat-exchanging relation between said casing and the interior of the muffle.

7. The combination of claim 1 and wherein said one of said pair of walls is said top wall, said casing including a pair of casing portions situated adjacent the opposed side walls of said muffle and said heating means including a pair of burners respectively situated in said pair of casings.

Claims

2. The combination of claim 1 and wherein said one of said pair of walls is said rear wall of said muffle, said inner wall being situated in front of said rear wall and being in the form of a metal sheet, said casing including a front metal sheet situated forwardly of said inner wall and having a pair of opposed vertical side edges, said inner wall also having a pair of opposed vertical side edges respectively fixed with said opposed vertical side edges of said front metal sheet, and defining with said opposed side walls of said muffle said gaps through which the hot gases flow, at least one of said metal sheets having a rounded configuration and said casing having a lower interior region in which said burner is located, and a chimney connected to an upper portion of said casing and communicating with the interior thereof, and a circular wall defining an air channel, extending between and connected to said inner wall and front metal sheet, the latter being formed with an opening aligned with said opening of said inner wall so that said circular wall defines an air channel for flow of air through the latter channel toward said fan, so that said channel has a rear end communicating with the space between said inner wall and rear wall and a front end communicating with said treating portion of said treatment chamber.