This application claims the benefit of US Provi- sional Application 61/591,717, filed Jan. 27, 2012; US

Provisional Application 61/591,955 filed Jan. 29, 2012 and US Provisional Application 61/593326, filed Feb. 1, 2012.

Background Of The Invention

Various spiral oven systems are known.

For example, U.S. Patent 5,850,781 describes a multi-heating zone, single spiral oven. A spiral conveyor helically winds around a rotating drum. Heating is pro- vided in zones within the oven. The zones are arranged vertically, i.e., an upper zone and a lower zone. Each zone has at least one ventilation device and heating de ^¬ vice for circulating hot air through the zone. Each zone preferably has two ventilators, each with a heating de- vice, which cover approximately half of each spiral con ^¬ veyor winding.

U.S. Patents 7,107,899 and 5,329,916 describe dual spiral ovens. In these patents two rotating drums within the oven are helically surrounded by conveyors wherein the output of one spiral conveyor communicates products onto the input of the next spiral conveyor. Heating elements in U.S. Patent 7,107,899 are arranged as helical electri ^¬ cal coils or hollow tubes that underlie the spiral convey ^¬ or. The heating elements in US Patent 5,329,916 are ar- ranged in overhead air ducts.

The present inventor has recognized that it would be desirable to provide a compact spiral oven that pro ^¬ vides an optimized and efficient cooking. Summary Of The Invention

The exemplary embodiment of the invention provides an oven having a rotating drum and a conveyor surrounding or wrapping the drum helically for transporting products to be cooked along a path from an inlet of the oven to an outlet, a ventilator for circulating air through the oven, and a heat exchanger for heating the air circulated by the ventilator. A housing provides a chamber that surrounds the drum and the conveyor that wraps the drum. A curved plenum is configured adjacent to the chamber wherein the plenum is curved substantially concentrically with the drum. The ventilator forces air in a tangential direction with regard to the drum through the plenum, through a heat exchanger that is configured to curve with the curve of the plenum. The heat exchanger preferably comprises transversely arranged hollow tubes that contain a circu ^¬ lating thermal fluid that is heated outside of the oven.

Preferably, the oven includes two drums and two spiral conveyors that surround each of the drums respec ^¬ tively. The output of one conveyor delivers product being cooked to an input of the next spiral conveyor.

The oven is designed for cooking a high amount of meat and chicken products.

The drums form the largest components of the system, and provide the main source of drive for the con ^¬ veyor belt, which can be 120 meter in length. The spiral conveyor system can be configured with the conveyor belt entering at the bottom of the drum and exiting at the top. Alternately, the in-feed and out-feed of the spiral con ^¬ veyors can be the opposite of this arrangement. During the belt's helical travel, its edge is held in tight contact with the drum, so that the friction created by the wraps of the belt around the drum is sufficient to drive the belt through the system. The drum is driven from underneath by an electric motor and can be either direct or chain-driven. The mechanism that keeps the belt tight against the drum is a secondary drive, or take-up or aux ^¬ iliary drive. The auxiliary drive provides just enough pull on the belt to keep the belt in tight contact with the drum and to help set belt speed, not to provide the driving force to the belt. This keeps belt tension low.

Numerous other advantages and features of the pre ^¬ sent invention will be become readily apparent from the following detailed description of the invention and the embodiments thereof, and from the accompanying drawings.

Brief Description Of The Drawings

Figure 1 is a front perspective view of the dual spiral oven according to one embodiment of the present in ^¬ vention;

Figure 2 is a front perspective view of the dual spiral oven of Figure 1 with an outer skin or housing removed to view underlying components;

Figure 3 is a schematic top view showing an air flow arrangement for the oven;

Figure 4 is a further schematic top view showing the air flow arrangement in the oven;

Figure 5 and 6 are schematic diagrams of spiral oven conveyor belts;

Figure 7 is another schematic top view of the oven shown in Figure 2; Figure 8 is an enlarged perspective view taken generally along line 8-8 from Figure 7 with some walls re ^¬ moved to view otherwise obscured parts;

Figure 9 is a top view taken from Figure 8 ; Figure 10 is a perspective view similar to Figure

8 but rotated a small amount with some walls removed to view otherwise obscured parts ;

Figure 11 is a perspective view similar to Figure 10 but rotated a small amount with some walls removed to view otherwise obscured parts;

Figure 12 is a schematic, partially fragmentary perspective view of a plenum taken from Figure 4.

Detailed Description

While this invention is susceptible of embodiment in many different forms, there are shown in the drawings, and will be described herein in detail, specific embodi ^¬ ments thereof with the understanding that the present dis- closure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated.

US Patents 5,850,781; 7,107,899 and 5,329,916 are all herein incorporated by reference where not incon- sistent with the present disclosure.

Figure 1 illustrates an oven 30 having a housing 32 and conveyor infeed station 34 and a conveyor discharge station 36. Products, such as chicken pieces are loaded onto the conveyor infeed station, pass through the housing 32 and are output at the conveyor discharge station 36. The housing includes a hood 40 that can be raise by four lifting jacks 43. The housing 32 provides outside walls that substantially enclose the oven. Figures 2 and 6 illustrate the oven with the hous ^¬ ing removed for viewing underlying components. The oven comprises a first drum 44 and a second drum 48. Prefera ^¬ bly, drums 44, 48 are solid cylinders. A conveyor belt 54, such as a stainless steel wire mesh belt, is a contin ^¬ uous belt that moves from the product infeed, and helical ^¬ ly wraps around the first drum 44 and the second drum 48 and passes to the discharge station 36, and over a second ^¬ ary drive 60 and back to the product infeed station 34.

The secondary drive 60 maintains a tension on the belt 54. The drums 44, 48 are rotated by a motor drive (not shown) and engagement of the drums and an inside edge of the belt 54 circulates the belts helically on the drums and between the infeed station 34 and the discharge sta- tion 36 and back.

As shown in Figures 3 and 4, each drum and associ ^¬ ated length of spiral conveyor is arranged in a separate cooking volume of the housing. The drum 44 and a first as ^¬ sociated length 54a of spiral conveyor 54 are located in a first chamber 66 and the drum 46 and a second associated length 54b of spiral conveyor are located in a second chamber 68. The chamber 66 is heated by at least one ven ^¬ tilator or fan 70 contained in a substantially enclosed fan chamber 71. The fan 70 is driven by a motor 70m from outside the fan chamber. The fan 70 has a rotary axis ap ^¬ proximately radially oriented to the circumference of the drum 44. The fan 70 draws air from chamber 66 in a substantially radial direction R into an inlet 70a. The fan 70 is mounted to the fan chamber 71 with the inlet 70a in registry with a fan chamber inlet opening 71a. The fan chamber inlet 71a is preferably a funnel or flared inlet, tapered toward the fan inlet, to reduce pressure drop. The air is forced by the fan (s) 70 through an outlet 71b of the fan chamber into a curved plenum 72 that has an inner curvature that substantially conforms to the outer circum ^¬ ference of the spiral belt 54a within the chamber 66. The plenum is curved substantially concentrically with the drum 44. The air is moved through the plenum in a tangential direction T. A curved heat exchanger 76 is located within the plenum that conforms in curvature to the curva ^¬ ture of the plenum 72 to maximize heat exchange surface area in the compact oven. The heat exchanger 76 is pref- erably comprised of tubes which are transversely oriented and which carry hot heat transfer fluid. The heat ex ^¬ changer 76 can be made up of vertically aligned exchanger banks 76a, 76b, 76c, as shown in Figure 8. The heat transfer fluid can be heated outside the oven by a gas or oil fired source, or an electric source, or the like. Heat transfer fluid is conducted to and from the heat exchanger banks 76a, 76b, 76c by pipes 77. The plenum 72 is de ^¬ signed to output heated air into the chamber 66 in the tangential direction T so that the air is circulated sub- stantially around the chamber before returning the inlet of the fan 70.

Preferably two fans 70 are provided at different elevations but arranged identically when viewed from above, in plan. Both fans force air into the plenum 72 in the same way.

The chamber 68 is heated by at least one ventila ^¬ tor or fan 80 contained in a substantially enclosed fan chamber 81. The fan 80 is driven by a motor 80m from outside the fan chamber. The fan 80 has a rotary axis ap- proximately radially oriented to the circumference of the drum 48. The fan 80 draws air from chamber 68 in a substantially radial direction R into an inlet 80a. The fan 80 is mounted to the fan chamber with the inlet 80a in registry with a fan chamber inlet 81a. The fan chamber inlet 81a is preferably a funnel or flared inlet, tapered toward the fan inlet, to reduce pressure drop. The air is forced by the fan (s) 80 through an outlet 81b of the fan chamber into a curved plenum 82 that has an inner curva ^¬ ture that substantially conforms to the outer circumfer ^¬ ence of the spiral belt 54b within the chamber 68. The plenum is curved substantially concentrically with the drum. The air is moved through the plenum in a tangential direction T. A curved heat exchanger 86 is located within the plenum that conforms in curvature to the curvature of the plenum 82 to maximize heat exchange surface area in the compact oven. The heat exchanger 86 is preferably comprised of tubes which are transversely oriented and which carry hot heat transfer fluid. The heat exchanger 86 can be made up of vertically aligned exchanger banks 86a, 86b, 86c as shown in Figure 8. The heat transfer fluid can be heated outside the oven by a gas or oil fired source, or an electric source, or the like. Heat transfer fluid is conducted to and from the exchanger banks 86a,

86b, 86c by pipes 87. The plenum 82 is designed to output heated air into the chamber 68 in the tangential direction T so that the air is circulated substantially around the chamber before returning the inlet of the fan 80.

Preferably two fans 80 are provided at different elevations but arranged identically when viewed from above, in plan. Both fans force air into the plenum 82 in the same way.

The drums 66 and 68 are rotated clockwise when viewed from above in Figure 3. The belt 54 in the chamber 66 circulates helically up the drum 44 and the belt in the chamber 68 helically circulates helically down the drum The structure of the fans, heat exchangers and plenums are mirror image identical across a vertical cen ^¬ ter plane CP of the oven 30. The air flow rotation direction in the chamber 66 is with the drum rotation and belt circulation direction, and the air flow rotation direction in the chamber 68 is counter to the drum rotation direction and belt circulating direction.

The chambers 66, 68 are defined by outside walls of the housing 32 and separated by inside walls 102, 104, 106, 108 (Figure 4) provided in the housing 32. The walls 102, 104 are curved and form side walls of the plenums 72, 82 and extend vertically from a bottom wall of the housing to a top wall of the housing. Opposite sidewalls 103, 105 are curved and form side walls of the plenums 72, 82.

Different cooking temperatures and conditions can be main ^¬ tained within the chambers 66, 68, for controlled cooking. Products, such as chicken pieces are input into the infeed station 34, move on the conveyor 54 up the drum 44 across to the drum48, down the drum 48 to the discharge station 36. Hot cooking gas, such as air is introduced into the first and second chambers 66, 68 to cook the products while resident in the respective chambers 66, 68.

Figure 7 illustrates that each chamber 66, 68 in ^¬ cludes an overhead cleaning manifold 202, 204. A pressur- ized water and soap mixture or solution is provided to the manifolds 202, 204 and periodically, during a cleaning procedure, a plurality of nozzles 210 spray water and soap mixture or solution S into the respective chamber.

Figures 8, 10 and 11 illustrate construction of the exchangers 76, 86 with the walls 102,104 removed in the figures.

Figure 8 illustrates a further cleaning manifold 230 arranged above the exchanger 76. A cleaning manifold 250 is arranged above the exchanger 86 and is a mirror im ^¬ age duplicate of the manifold 230 across the vertical cen ^¬ ter plane CP of the oven. The manifolds 230, 250 contain a pressurized water and soap mixture or solution.

The manifold 230 has a plurality of nozzles 210 for spraying water and soap mixture or solution S onto the top exchanger bank 76a during a periodic cleaning procedure. Further manifolds arranged between the banks can be used to spray water and soap mixture or solution S onto the banks 76b and 76c respectively. The manifold 250 has a plurality of nozzles 210 arranged to spray water and soap mixture or solution onto the top exchanger bank 86a during a periodic cleaning procedure. Further manifolds arranged between the banks can be used to spray water and soap mixture or solution onto banks 86b and 86c respec ^¬ tively.

Figure 8 also shows an extension guide plate 260 and an adjustable spoiler plate 266 that is hinged by a plurality of hinges 270 to the extension guide plate 260 arranged between the heat exchanger 76 and the chamber 66. The extension plate 260 and the spoiler plate 266 can be part of the respective wall 103, 105 of an extension thereof and have a vertical length equal to the respective wall 103, 105. An identical extension guide plate and spoiler plate are arranged between the heat exchanger 86 and the chamber 68, configured as a mirror image duplicate of the guide plate 260 and the adjustable spoiler plate 266 across the vertical center plane CP of the oven.

The combination of the two plates 260, 266, with proper adjustment thereof allows for fine tuning of the air flow delivered by the fans 70, 80 to the chambers 66, 68. The hinges 270 include a portion 271 fixed to the ex ^¬ tension guide plate 260 and a portion 272 fixed to the spoiler plate 266. The portions 271, 272 are rotatable with respect to each other about a bolt 273, when the bolt is loosened for adjustment of the angle between the plates 260, 266. One the angle is adjusted the bolt 273 is tightened which prevents any further rotation of the plates 260, 266.

Particularly, the air flows circumferentially around the respective drum 44, 48 in the respective cham ^¬ bers 66, 68.

Figures 10 and 11 illustrate a vertically arranged steam header 320 that is adjacent the heat exchanger banks 76a, 76b, 76c. The header 320 contains pressurized steam. The header has a plurality of holes 320a arranged spaced- apart in the vertical direction. A mirror image identical header 330 with holes 330a is provided at the outlet of the exchanger 86. Steam under pressure is ejected from the holes 320a, 330a into the air stream downstream of the exchangers 76, 86 such that a proper cooking humidity is maintained in the oven chambers 66, 68.

The plenums 72, 82 are mirror image identical across the vertical center plane CP of the oven. There ^¬ fore, only the plenum 82 will be described in detail in Figure 12.

Figure 12 illustrates the plenum 82. The plenum includes the curved vertical sidewalls 102, 103 that are substantially concentric with the drum 48. A top wall 400 substantially closes the space between the walls 102, 103 at a top end thereof and a bottom wall 404 substantially closes the space between the walls 102, 103 at a bottom end thereof. A fan chamber wall 408 provides at least one and preferably two outlets 81b, 81b for two fans 80. Alt ^¬ hough a flat wall 408 is shown in Figure 12, it is benefi ^¬ cial to provide an expanding or funnel outlet 81d, expand- ing in a direction away from the fans and toward the heat exchangers in the direction T (Figure 3) as shown in Figure 7, to minimize pressure drop. Otherwise, the wall 408 closes an opening defined by the walls 102, 103, 400, 404. An outlet open face 412 defined by the walls 102, 103, 400, 404, at an end opposite the wall 408, allows air to pass from the plenum 82 into the chamber 68. The extension 260, and the spoiler 266, as an adjustable part of inside wall 103, can be adjusted to most effectively di- rect forced air flow around the circumference of the drum 48. The walls 102, 103, 400, 404 form a curved rectangu ^¬ lar tube for directing air in a curved path from the outlets 81b, 81b within the chamber 68. The heat exchanger 86 is contained within the walls 102, 103, 400, 404. The walls 400, 404 can be regions or portions of an overall housing hood and floor respectively.

From the foregoing, it will be observed that nu ^¬ merous variations and modifications may be effected with ^¬ out departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred.

All references, including publications, patent ap ^¬ plications, and patents, cited herein are hereby incorpo- rated by reference to the same extent as if each reference were individually and specifically indicated to be incor ^¬ porated by reference and were set forth in its entirety herein, to the extent that the references are not incon ^¬ sistent with the present disclosure.