SUMMARY AND BACKGROUND OF THE INVENTION The present invention relates to a convection oven for cooking of food products.

One embodiment of the invention includes a convection oven having a cooking chamber for holding the food to be cooked. The cooking chamber has an upper enclosure member and a lower enclosure member. A housing is attached to the upper enclosure member. The housing has a central portion and at least one arm extending outwardly from the central portion to beyond the outer edge of the upper enclosure member. Attached to the housing is a heater for heating air within the cooking chamber and an air-moving means for moving air within the cooking chamber. The housing is configured so that cool air flows from a peripheral portion of the arm into the central portion of the housing and then is expelled from the arm over the upper surface of the upper enclosure member.

An alternative embodiment of the invention includes a convection oven designed to rest on a supporting surface such as a countertop. The oven has a frame including a base member which rests on the supporting surface and at least two upright members which extend upwardly from the base member. A cooking chamber for holding food to be cooked is removably supported by the frame and includes an upper enclosure member and a lower enclosure member. A housing is attached to the upper enclosure member. Attached to the housing is a heater for heating air within the cooking chamber and an air-moving means for moving air within the cooking chamber.

A further embodiment of the invention includes a convection oven having a frame and designed to rest on a supporting surface such as a countertop. The oven has a cooking chamber for holding food to be cooked which includes a lower enclosure member for holding the food, and an upper enclosure member for covering the upper

enclosure member. A housing is attached to the upper enclosure member. The holster attaches to the frame of the oven and is configured to hold the upper enclosure and housing when they are separated from the lower enclosure member.

One embodiment of the present invention may also include a holster for use in a convection oven having a frame and which is designed to rest on a supporting surface. The oven further includes a cooking chamber which includes a lower enclosure member for holding the food and an upper enclosure member for covering the lower enclosure member. A housing is attached to the upper enclosure member. The holster is attached to the frame of the oven and is configured to hold the housing and the upper enclosure member when they are separated from the lower enclosure member.

Another alternative embodiment of the present invention includes a convection oven having a cooking chamber for holding food to be cooked, and a frame for removably holding the cooking chamber. The frame has a base member which rests on the supporting surface and an upright member extending upwardly from the base member. The cooking chamber has an upper enclosure member and a lower enclosure member. A housing is attached to the upper enclosure member. The housing has a central portion and an arm extending outwardly from the central portion. Attached to the housing is a heater for heating air within the cooking chamber and an air-moving means for moving air within the cooking chamber. A connecting means connects the housing to the frame such that the housing and upper enclosure member may be both separated from the frame and lower enclosure member by lifting the housing vertically and pivoted relative to the frame and lower enclosure member. The housing and upper enclosure member may be pivoted between a first position wherein the upper enclosure member rests on the lower enclosure member and a second position wherein the

upper enclosure member is separated from the lower enclosure member.

Another alternative embodiment of the present invention includes a convection oven having a cooking chamber for holding food to be cooked. The cooking chamber includes an upper enclosure member and a lower enclosure member. The oven includes heating means for heating air within the cooking chamber and air-moving means for moving air within the cooking chamber. At least one extension ring for enlarging the size of the cooking chamber is included. The extension ring includes a ring designed to be removably placed between the upper enclosure member and the lower enclosure member so as to increase the height of the cooking chamber, as well as handle means attached to the ring which can be gripped so as to selectively place the ring in between or remove the ring from between the upper enclosure member and the lower enclosure member.

Yet another alternative embodiment of the present invention includes a convection oven having a cooking chamber for holding food to be cooked. The cooking chamber includes an upper enclosure member and a lower enclosure member. The oven includes heating means for heating air within the cooking chamber and air- moving means for moving air within the cooking chamber. At least one extension ring for enlarging the size of the cooking chamber is included. The extension ring includes a ring designed to be removably placed between the upper enclosure member and the lower enclosure member so as to increase the height of the cooking chamber. The ring is shaped so as to form a ledge for supporting a rack within the cooking chamber.

The invention also may include an extension ring for enlarging the size of the cooking chamber of an oven. The extension ring includes a ring designed to be removably placed between the upper enclosure member and the lower enclosure member so as to increase the height

of the cooking chamber, and handle means attached to the ring which can be gripped so as to selectively place the ring in between or remove the ring from between the upper enclosure member and the lower enclosure member. In an alternative embodiment, the extension ring includes a ring designed to be removably placed between the upper enclosure member and the lower enclosure member, with the ring being shaped so as to form a ledge for supporting a rack within the cooking chamber. Yet another alternative embodiment of the invention may include a convection oven having a cooking chamber for holding the food to be cooked. The cooking chamber has an upper enclosure member and a lower enclosure member. A housing having a central portion is attached to the upper enclosure member. Attached to the housing is a heater for heating air within the cooking chamber and an axial-type hot-air fan for moving air in a substantially axial direction within the cooking chamber. The oven may also include a fan shroud surrounding the hot-air fan for providing an air duct around the periphery of the hot-air fan such that the radial component of the hot air is initially routed in a substantially axial direction off of the hot-air fan into the cooking chamber. A yet further embodiment of the invention may include a convection oven having a cooking chamber for holding the food to be cooked. The cooking chamber has an upper enclosure member and a lower enclosure member. A housing having a central portion having a cooling fan for imparting cool air therein is attached to the upper enclosure member. Attached to the housing is a heater for heating air within the cooking chamber and an air moving means for moving air within the cooking chamber. The oven also may include a thermostat adjacent to but isolated from the cool air in the central portion of the housing so that the thermostat more accurately reflects the temperature of the cooking chamber in the oven.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of one preferred embodiment of a convection oven;

Figure 2 is a vertical cross sectional view of the convection oven shown in Fig. 1;

Figure 3 is a side view of the convection oven shown in Fig. 1, with part of one arm cut away to show the interior of the housing;

Figure 4 is a bottom view of the end portion of an arm of the convection oven shown in Fig. 1.

Figure 5 is a perspective view of a second preferred embodiment of a convection oven;

Figure 6 is a sectional view of the hinge of the convection oven shown in Fig. 5, shown in the closed position;

Figure 7 is a sectional view of the hinge similar to Fig. 6, but showing the oven in the separated position;

Figure 8 is a sectional view of the hinge similar to Fig. 6, but showing the oven in the open position;

Figure 9 is a perspective view of the oven of Fig. 1, together with a preferred embodiment of an extension ring; Figure 10 is vertical cross-section of one end of the extension ring of Fig. 9;

Figure 11 is a sectional view of the extension ring of Fig. 9, taken along lines 11-11 in Fig. 10; Figure 12 is a perspective view of a third preferred embodiment of a convection oven;

Figure 13 is a vertical cross sectional view of the convection oven shown in Fig. 12;

Figure 14A is a perspective view of the holster of the convection oven shown in Fig. 12; Figure 14B is a vertical cross sectional view of the convection oven shown in Fig. 12 showing an upper

enclosure member and a housing resting in the holster of Fig. 14A.

Figure 15 is a vertical cross sectional view of the convection oven shown in Fig. 12 with a preferred embodiment of a hot-air fan design, and thermostat configuration; and

Figure 16 is a vertical cross sectional view of the hot-air fan design and thermostat configuration of the convection oven shown in Fig. 12.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One preferred embodiment of a convection oven is shown in Figs. 1-4. With particular reference to Figs. 1 and 2, the convection oven 10 includes a cooking chamber 12 removably supported by a frame 14.

The cooking chamber is made up of a lower enclosure member 16 and an upper enclosure member 18. The upper and lower enclosure members are preferably made out of heat resistant glass, such as PYREX. A cooking rack 19 is preferably placed within the cooking chamber to support the food to be cooked. The lower enclosure member has a bottom wall 20 and a generally- cylindrical side wall 22. A ridge 24 is formed along the upper edge of the side wall to support the upper enclosure member. The upper enclosure member has a centrally-located opening for receiving a heater and fan as will be hereinafter described.

Frame 14 is preferably made up of a base member 28 and at least two upright members 30. The base member may be generally circular in shape, and is designed to rest on the supporting surface, such as a countertop. The upright members are preferably located on diametrically opposed sides of the base member, and are made up of two riser portions 31 connected together by a connecting portion 33. The riser portions 31 extend outwardly at the upper end thereof to form supporting surfaces 34.

As seen in better detail in Fig. 2, the lower enclosure member 16 is configured to rest on the lower curved region 36 of the riser portions. Because of this arrangement, a small air space 38 is formed between the bottom wall 20 of the lower enclosure member and the base member 28. This air space helps to prevent the transfer of heat from the cooking chamber to the base member, so as to avoid excessive heating of the countertop. Alternatively, the air space may also be formed by placing a number of spacer members (not shown) between the bottom wall of the lower enclosure member and the base member.

The design of the frame provides passive cooling so as to keep the countertop cool. Specifically, air trapped in the region 42 between the connecting portion 33 of the upright members and the cooking chamber is heated by the cooking chamber. This hot air rises along the upright member. The rising air creates a suction effect, drawing cooler air into the region 42 from around the base member. This flow of air helps cool the base member and hence helps to keep the countertop cool.

A number of cushioning members 40 may be attached to the connecting portion 33 of the upright members. These cushioning members help provide support to the cooking chamber when it is held by the frame.

Frame 14 is preferably made of a thermoplastic material, such as by molding. For ease of manufacture, the upright members of the embodiment of Fig. 1 are preferably identical. As such, only two molds are required (one for the base member and one for the upright member) . After molding, two of the upright members may be connected to a base member, for example using screws, to form the frame. As best seen in Fig. 1, a housing 44 is attached to the upper enclosure member 18. Like the frame, the housing is preferably made out of a

thermoplastic material. The housing is made up of a central portion 46 and two arms 48 which project outwardly from the central portion. The central portion 46 is generally circular in horizontal cross section. A handle 50 may be attached to the central portion of the housing.

The arms 48 project past the outer edge of the upper enclosure member 18. The arms are made up of a top wall 76, two side walls 77 and a middle wall 78 (see Fig. 2). The arms are configured so that the outer peripheral portion of the arms rest on the supporting surfaces 34 of the upright members. In this way, the housing 44 is supported and stabilized by the frame 14. The arms define two air channels. The upper channel 79 is defined by the top wall 76, the two side walls 77, and the middle wall 78. An air inlet 80 (Fig. 4) located at the outer end of the arms communicates with the upper channel 79. The lower channel 82 is defined by the two side walls 77, the middle wall 78, and the upper surface of the upper enclosure member 18. A small space 81 is present between the side walls 77 and the upper surface of the upper enclosure member. This space provides for the exit of cool air for cooling the upper surface of the upper enclosure member, as will be described below.

As shown in Fig. 2, a dividing member 53 divides the interior space of the central portion 46 into an upper space 71 and a lower space 72. The dividing member has an opening 75 located in the center thereof which connects the upper space 71 and the lower space 72. A motor 52 is mounted on the dividing member 53 and is located within the upper space 71. The motor is connected by a shaft 54 to a hot-air fan 56 located within the cooking chamber. The hot-air fan 56 is preferably permanently attached to the shaft 54, such as by a hexnut.

Also located within the cooking chamber is a heater. The heater preferably may be thermostatically regulated to maintain cooking temperatures ranging from 150 to 500+ degrees F. The heater generally consists of heater coils 57 and heat spacer members 58 for separating the heater coils and for providing support thereto. The heat spacer members 58 are preferably made of ceramic. A heater base 60 is also provided for isolating the heater from the lower region 72, and is preferably made of metal. The heater coils 57 are located at opposite ends of the heater base 60. The heater coils 57 and spacer members 58 are mounted to the heater base 60, such as by screws. In addition, two insulating layers 63 are provided on opposite sides of the heater coils 57, and are preferably made of Mica. The heater coils are preferably an open coil, resistance wire type. Open heater coils are used in order to achieve the lowest possible surface watt density. With adequate air flow, such an element is capable of transferring maximum heat to the air stream via conduction, while operating in the "black" heat range. In order for other types of heating elements, such as tubular types, to give off the same wattage given the same space and airflow, the heater would glow. Such a high surface watt density would result in overheating of the motor, the food being cooked, and plastic parts through an excessive radiation of heat. In the present oven, the heater preferably operates in the "black" heat range or with only minimal glow. In addition, such an element would retain too much heat when the unit is shut off, causing additional over- temperature problems. The heater assembly also preferably incorporates an over-temperature device (not shown) capable of shutting off power to the heater should the thermostat fail.

The housing is preferably attached to the upper enclosure member by sandwiching the inner rim 70 of the

upper enclosure member between the dividing member 53 and the heater base 60. A cooling fan 74 is located in the lower space 72. The cooling fan is preferably located on the same shaft as is hot-air fan 56, so that it is also rotated by motor 52.

The upper air channel 79 opens into the upper space 71. The side wall of the dividing member 53 has a plurality of openings 84 located therein so that the lower air channel 82 communicates with the lower space 72.

The above-described configuration of the housing provides for a venting system for cooling the motor 52 as well as the upper enclosure member 18. Particularly, rotation of the cooling fan 74 causes cool air to be drawn in through the air inlet 80 and into the upper channel 79 of both arms 48. From there, the cool air enters the upper space of the central portion so as to cool the motor 52. The cool air is then drawn by the cooling fan down through the opening 75 into the lower space, and then expelled into the second channel. From there, the cool air is forced out through the small space 81 between the side walls of the arm and the upper enclosure member. These jets of cool air across the surface of the upper enclosure member provide an effective method of cooling the upper enclosure member, so as to reduce the chance of accidental burning of the user. The flow of cool air also helps cool the housing itself which, being preferably made of plastic, cannot take the high temperatures produced in the heating chamber. In addition, the draw of air through the air inlet 80 also increases the flow of air up through the region 42 between the upright members 30 and the lower enclosure member, thereby increasing the cooling of the base member. It may also be preferable to include additional air inlets 86 in the housing. These air inlets are preferably located in the underside of handle 50 so as

to minimize the chance that liquid, such as water used for cleaning, will accidentally enter the housing. The air inlets provide for additional flow of cooling air over the motor 52. The hot-air fan 56 may be a radial-type fan which, unlike conventional devices, is placed in the top center of the cooking chamber. The hot-air fan creates two air circulations. The first air circulation is throughout the cooking chamber. In particular, hot air thrown off the fan travels horizontally parallel to the upper enclosure member until it is directed downward by the corner joining the upper and lower enclosure members. The air then travels downward until it is again deflected at the bottom wall of the lower enclosure member. The air is then simultaneously pushed and drawn by the blower across the top of and beneath the cooking rack. As the air approaches the center of the enclosure, it is drawn up into the open underside of the hot-air fan where it is then recirculated through the same pattern described above.

The second air circulation passes a small portion of air over the heated coils in the heater. In other words, the small air current exits radially outwardly from the fan 56, reverses direction 180 degrees to be drawn in over the coil, then radially inwardly to the center of the heater, then downwardly into the center zone of the blade 56. This configuration provides the following advantage: most particles are unable to make the abrupt 180 degree change in direction that the air drawn through the heater does. Therefore, the air traveling through the heater assembly is virtually free of contamination, while most particles are thrown off to the sides and bottom of the cooking chamber, where they can easily be cleaned away. As a result of the above, the heater does not accumulate food, oil or grease, thereby eliminating

the need to clean the heater, extending heater element life and preventing smoke or fire hazard.

A wire guard 62 may be attached to the heater base 60 for protecting the hot-air fan 56. However, the wire guard does not substantially block the air flow created by the hot-air fan, so that hot air may be circulated within the cooking chamber in a substantially unrestricted manner. The velocity of the air is not constant within the chamber, since the heated air converges as it moves to the center of the cooking chamber and is drawn into the hot-air fan. In the convection oven, the air cools as it contacts the food, but simultaneously accelerates as it converges on the center of the chamber. This change in velocity compensates for the dropping temperature by more effectively exchanging the heat remaining in the air. The result is very uniform cooking from the outer edge to the center of the cooking rack. The velocity of the air in the oven is preferably very high, in the range of 1000-4000 linear feet per minute in the vicinity of the food, with a range of 1200-2500 being particularly preferred.

Electrical current is fed into the device 10 by way of electric cord (not shown) . A thermostat 64 is provided in the central portion 46 of the housing 44 which adjusts the current supplied to the heater so as to control the temperature within the cooking chamber. The thermostat is preferably an anticipator-type self- heating thermostat, such as one manufactured by Abundance Thermo Control Factory, Type A228, thereby more readily holding the temperature of the oven in a narrow range to prevent major fluctuations in the temperature which may adversely affect the cooking of the food. A timer/switch mechanism 66 is also provided for turning the heater and motor on and for controlling the cooking time. A sensing mechanism (not shown) may be provided to provide shutdown of the unit in the case

of overheating in the cooking chamber 12 and/or housing 44. A sensing mechanism (not shown) may also be included which shuts down the unit when the housing is removed from the frame with the switch 64 in the "on" position.

Figs. 15 and 16 show another embodiment of a convection oven 10A. Much of the oven of Figs. 15 and 16 are preferably identical to the embodiment of Figs. 1 and 2, and hence will not be described again in detail. The primary changes in this embodiment are the hot-air fan design and the thermostat configuration. Unlike the radial-type hot-air fan 56 of the embodiment in Figs. 1 and 2, hot-air fan 56' is an axial-type fan. In addition, a fan shroud 62' replaces the wire guard 62. The fan shroud 62' has an opening in the center to provide for the preferred air flow as described below. A washer 59 is also attached to the shaft 54 directly above the fan shroud 62' for providing a safety mechanism to ensure that the blades of the hot-air fan 56' are out of reach of a user's fingers. However, as with wire guard 62, neither the fan shroud 62' nor the washer 59 substantially blocks the air flow created by the hot-air fan, so that the hot air may be circulated within the cooking chamber in a substantially unrestricted manner.

Like hot-air fan 56, hot-air fan 56' also imparts a radial component of velocity on the air. However, fan shroud 62' provides a substantially vertical air duct around the periphery of the hot-air fan 56' to minimize this effect. As a result, less heat is lost to the side walls of the lower enclosure member, and more hot air is initially directed at the food itself.

More importantly, hot-air fan 56' also on its own imparts an axial component of velocity on the air. Therefore, the axial fan and fan shroud configuration provides an additional advantage over the radial-type

hot-air fan by directing significantly more air in a downward direction, thereby more directly heating the food as well as creating a low pressure region around the shaft 54 in the lower space 72. This in turn pulls significantly more air through the heater coils 57, and thus more efficiently removes heat from the heater coils 57. As a result, the temperature by the heater coils 57 is lower, making the heater coils last much longer. The other primary difference between the embodiment of Figs. 15 and 16, and the embodiment of Figs. 1 and 2, is that the thermostat 64' is contained within a thermostat chamber 65 adjacent the cooling fan 74 and the lower space 72. The thermostat chamber 65 has an opening 61 in the bottom so that hot air from the cooking chamber may be directed therein (see Fig. 16). The thermostat chamber, however, isolates the thermostat 64' from the lower space 72 and the cooling fan 74, and thus prevents cool air from the lower space 72 from affecting thermostat 64'. This configuration allows the oven to provide a more accurate reading.

In operation, hot air from the cooking chamber is routed upward, pulled through the opening 61 of the thermostat chamber 65 up over the thermostat 64' , and then out the opening 61 toward the low pressure region near the shaft 54. Due to the low pressure region created by this new fan design, air is continually routed up and over thermostat 64. In this manner, air by the thermostat 64' is prevented from becoming stagnant. As a result, the oven is able to respond more quickly to temperature changes.

It can be appreciated that either or both of the new hot-air fan design and thermostat configuration amy be incorporated into the embodiment of the convection shown in Figs. 1 and 2. The convection ovens described above are used by first lifting up on the housing 44 so as to remove the upper enclosure member 18 from the lower enclosure

member 16. Food pieces such as potatoes, bakery goods, pizzas and the like may be placed on the rack 19. The housing 44 is then once again placed on the frame 14, so that the upper enclosure member 18 again rests on the lower enclosure member 16. The thermostat is then activated turning the heating and the motor on. With the hot-air fan rotating, air is moved within the cooking chamber. Air is circulated over the heater coils 57, thereby providing heat to the cooking chamber 12. The temperature will typically be in the range of 150-500 degrees F.

As seen best in Fig. 2, the outer edges of the arms 48 extend below the lower surface of the upper enclosure member 18. This is a useful feature because, when the housing 44 and upper enclosure member 18 are lifted off the frame 14 and placed on the countertop, the hot upper enclosure member 18 does not come into direct contact with the countertop. Hence, the chances of burning the countertop are reduced. Figure 5 shows yet another embodiment of a convection oven 10B. Much of the oven of Fig. 5 is preferably identical to that of Fig. 1, and hence will not be described again in detail. It can be appreciated, however, that either or both of the hot-air fan designs and thermostat configurations previously described herein may be incorporated in this embodiment.

The primary change in this embodiment is that the convection oven has only one upright member 30 and arm 48 as described in connection with the first embodiment. The other upright member 30' and arm 48' have been modified as described below. The upright member 30' and arm 48' are connected together by a connecting mechanism 90. This connecting mechanism acts as a "passive hinge" which allows the housing and upper enclosure member to be either lifted off and removed from the frame and lower enclosure member, or simply

tilted back so as provide access to the interior of the cooking chamber.

The connecting mechanism includes two hubs 92 attached to the upright member 30' and two engagement members 94 attached to the arm 48'. As seen best in Figs. 6-8, the hubs 92 are generally circular in vertical cross-section and have an opening 93 in the upper surface thereof. Two stop surfaces 95 are preferably located within the hubs. The engagement members may be generally triangular in shape, and are designed to fit through the opening 93 and rotate snugly within the hubs 92.

Connecting mechanism 90 is designed to allow the convection oven to function in three positions, as shown in Figs. 6-8. The oven is shown in the closed position in Fig. 6. In this position, the engagement members 94 are located within the hubs 92. The arms 48 and 48' are resting on the upright members 30 and 30', respectively. The upper enclosure member 18 is resting on the lower enclosure member 16.

From the closed position of Fig. 6, the housing may be lifted vertically to the separated position shown in Fig. 7. The engagement members 94 pass through the openings 93 so as to disconnect the housing 44 from the frame 14. In this way, the upper enclosure member can be completely removed from the lower enclosure member, so as to provide access to the interior of the cooking chamber.

Alternatively, the housing may be rotated from the closed position of Fig. 6 to the open position of Fig. 8. In moving between the closed and open positions, the engagement members 94 rotate within the hubs 92. In the open position, the engagement members contact the stop surfaces 95, so as to prevent rotation of the housing past the open position. In this way, the upper enclosure member can simply be tipped back so as

to provide access to the interior of the cooking chamber.

While in Figs. 6-8, the engagement members 94 are attached to the arm 48' and the hubs 92 are attached to the upright member 30', this configuration can be reversed. Specifically, the engagement members may be formed on the upper portion of upright members, with the hubs mounted on the end of arm 30'. In this instance, the openings 93 are positioned in the lower surface, rather than the upper surface, of the hubs. The engagement members are still preferably triangular in shape, but would taper upwardly, instead of downwardly as shown in Fig. 6.

The hubs 92 are preferably well spaced apart on opposite sides of the upright member 30'. The upper enclosure member and motor assembly are relatively heavy, and can exert substantial sideways torque when the housing is moved to the open position. By spacing the hubs wide apart, the connecting mechanism is better able to withstand this torque created when the oven is opened.

The other primary difference between the embodiment of Fig. 5 and the embodiment of Fig. 1 is that the mechanisms for controlling the oven temperature and fan speed are located on the upright member 30'. Specifically, a control panel 96 is attached to the front of the upright member 30'. The control panel preferably has a digital display panel 97 and a plurality of buttons 98 for controlling the cooking temperature and programming cooking times.

A base extension 99 extends outwardly from the upright member 30'. The purpose of this base extension is to provide extra stability to the oven when the housing and upper enclosure member are tilted to the open position.

Figures 9-11 shows a preferred embodiment of an extension ring 101 used to enlarge the cooking chamber

of an oven, such as that of Fig. 1. As seen in Fig. 9, the extension ring includes a ring 103 and two handles or spacers 105. The ring is designed to removably fit in between the lower enclosure member 16 and upper enclosure member 18, while the spacers fit between upright members 30 and arms 48.

Ring 103 is preferably made of metal. As better seen in Fig. 10, preferred ring 103 is not of uniform diameter. A ridge 107 may be formed at the upper edge of the ring. This ridge is similar to the ridge 24 formed at the top of the lower enclosure member, and is designed to receive the upper enclosure member. Similarly the lower edge 109 of the ring preferably is dimensioned to rest on the ridge 24. A ledge 111 may also be formed in the middle of the ring 103. This ledge is designed to support a further rack (not shown) which may be placed within the enlarged cooking chamber so as to provide an additional level for cooking. It is to be noted that an extension ring configured with a ledge or other protrusion for removably supporting a cooking rack need not employ spacers or handles 105, although such handles are preferred.

The spacers 105 are preferably made up of plastic. The spacers may include two side walls 113, a top wall 115, and a back wall 117. The top wall 115 preferably has the same general shape as the supporting surface 34 of the upright members 30, and hence is configured to support the arms 48. Likewise, the lower edge of the spacers has the same general shape as the lower end of arms 48, and hence is configured to rest on supporting surface 34.

The back wall _. 117 preferably has a recessed portion 119. The recessed portion defines a lifting surface 120 which provides for a convenient location to grip the extension ring when placing the extension ring on or removing the extension ring from the convection

oven. In this way, the spacers 105 serve as a handle means for the ring 103. It will be recognized that many other configurations of spacers or handles 105 are possible; for example, in an oven configuration where upright members 30 and arms 48 are not employed, handles 105 could have virtually any configuration.

The spacers preferably have a plurality of bosses 121 projecting inwardly from the back wall 117. These bosses have holes in them for receiving screws or rivets used to connect the ring 103 and the spacers 105 together. The bosses 121 preferably extend slightly past the edge of side walls 113 and top wall 115 so that a small space 123 is maintained between the walls of the spacers and the ring. This space improves air circulation and helps to prevent heat damage to the plastic spacers.

Figures 12 and 13 show another embodiment of a convection oven IOC. Much of the oven of Figs. 12 and 13 are preferably identical to the embodiment of Figs. 1 and 2, and hence will not be described again in detail. Again, it can be appreciated that either or both of the hot-air fan designs and thermostat configurations previously described herein may be incorporated in this embodiment. One primary change in this embodiment is that the mechanisms for controlling the oven temperature and hot-air fan speed are located on the upright member 30. This embodiment includes a control panel 96 like that shown in the embodiment of Fig. 5. However, unlike the embodiment shown in Fig. 5, this embodiment still includes two upright members 30 and two arms 48.

The other primary difference between the embodiment in Figs. 12 and 13, and Figs. 1 and 2 is that the convection oven of Figs. 12 and 13 includes a holster 51 which may be attached to the frame 14 of the oven for holding the upper enclosure member 18 and housing 44 against the side of the oven when they are

separated from the lower enclosure member 16. In this manner, the upper. enclosure member 18 and the housing 44 need not take up valuable countertop space. In addition, it should be appreciated that often the upper enclosure member 18 becomes dirty during cooking. With the holster 51, the upper enclosure member 18 is kept off of the countertop, thus reducing the amount of clean up after cooking.

As can best be seen in Figure 14A, the holster 51 has a substantially vertical wall 100 and a substantially flat, substantially horizontal base 104 attached to the substantially vertical wall 100. The substantially vertical wall 104 preferably includes two side walls 102 which define a cut-out portion for receiving the upper enclosure member 18 and housing 44 on edge. A portion 106 of the holster base 104 attaches to the frame 14 of the oven. Preferably, the portion 106 is attached to the underside of the base member 28 of the frame 14, such as by screws. Figure 14B shows the upper enclosure member 18 and the housing 44 in its resting position in the holster 51. Due to the low focus of weight of the holster 51, it provides support to the upper enclosure member 18 and housing 44 when they are placed therein, and ensures their stability.

The foregoing constitutes a description of various preferred embodiments. Numerous changes to the preferred embodiments are possible without departing from the spirit and scope of the invention. Hence, the scope of the invention should be determined with reference not to the preferred embodiments, but to the following claims.