Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
1999-10-27
2001-01-16
Pelham, Joseph (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C099S330000, C126S020000
Reexamination Certificate
active
06175100
ABSTRACT:
FIELD OF INVENTION
The present invention relates to steam cooking ovens and more particularly to pressure regulation in such ovens.
BACKGROUND OF THE INVENTION
Steam ovens, also known as steamers, have been long used to cook food. Steam ovens operate by heating water to generate steam and then circulating the steam within a cooking cavity containing food to cook the food.
Conventional steamers are not pressure cookers; instead, conventional steamer cooking cavities are vented to the atmosphere so that the steam pressure in the cooking cavity is not greater than atmosphere. This arrangement is not thermally efficient. In order to maintain steam in the cooking cavity, steam must be continuously generated to replace that which is vented into the atmosphere. However, the amount of steam required to cook the food varies during cooking. Food can only accept steam energy at a rate that depends on its surface area and temperature. In the initial phase of cooking room temperature or frozen food products the amount of steam required is high. However, when the food products are thereafter in a heated condition, less steam is required to complete the cooking. Thus, when the food cannot absorb all of the steam being generated, the excess steam is wasted. As such, conventional steam cookers typically produce too much steam during the later portions of cooking, when the food is already at an elevated temperature. Thus, conventional steam cookers are not thermally efficient and they consume an excess of water for continuously making steam and cooling exhaust steam.
More efficient cooking performance is achieved when steamers operate at pressures above atmospheric pressure. On the other hand, if high pressure steam is used, then significant structural requirements must be met for safety reasons which increases cost. In addition, high pressure steamers may require certification as pressure vessels. As such, it is desirable for steamers to operate at pressures above atmospheric, but below the level where certification is necessary.
The food cooking industry has long sought efficient low pressure steamers. One recent approach is reflected in U.S. Pat. No. 5,549,038 to Kolvites which discloses a steamer having separate steam generation chambers which uses low pressure to cook food more efficiently. In this device, the steam is not vented directly to the atmosphere for the entire cooking cycle. Instead, a water seal and pressure valve arrangement is used to cause the steam in the cooking cavity to be at a slightly elevated pressure. This pressure is described as being somewhat above atmospheric pressure or one or two inches of water. Also, the device regulates the generation of steam according to the steam pressure so that steam is not continuously produced. When the food is absorbing all the steam, then the pressure will be low and additional steam is produced. When the food is not absorbing all the steam, then the resulting rise in pressure is directly sensed by a normally closed pressure switch which interrupts the steam generation until the pressure drops.
The Kolvites steam cooker has at least two main drawbacks. First, the Kolvites device employs separate steam generation cavities, which requires more space. Second, the Kolvites device does not reuse water that condensed from steam; this condensate is removed to a tempering water tank and then drained therefrom. Other known steamers suffer from these or other drawbacks.
Thus, there remains a need within the industry for efficient, compact low pressure steamers which conserve water.
SUMMARY OF THE INVENTION
The present invention provides an efficient way to cook food in a steamer at low pressure while conserving water and space. In one embodiment, the present invention uses a pressure sensor to regulate the pressure in the cooking cavity and modulate the production of steam accordingly. The cooking cavity of the oven has a pool for holding water to be turned into steam. Heating elements are provided, possibly in the pool, but preferably underneath the pool, which heat the water into steam. A pressure sensor is disposed in a steam outlet conduit connected to the cooking cavity. The pressure sensor may be a float switch that indirectly measures the pressure in the cooking cavity by monitoring the pressure in the steam outlet passage. The lower end of the steam outlet passage is preferably blocked by water that creates a water seal. The float switch is operable to turn off the heating elements when the float of the float switch is in a lower position, such as when pressure in the cooking cavity causes the water level in the steam outlet passage to fall. In another embodiment, the steamer includes a reservoir external to the cooking cavity. The reservoir is connected to the pool via an overflow which allows condensate from the steam outlet passage to be recirculated to the cooking cavity. Because steam is generated directly inside the cooking cavity, no separate steam chamber is required. Also, the recycling of steam condensate from the steam outlet passage to the cooking cavity allows less water to be used.
REFERENCES:
patent: 3604895 (1971-09-01), MacKay
patent: 4011805 (1977-03-01), Vegh et al.
patent: 4123969 (1978-11-01), Abbate
patent: 4506598 (1985-03-01), Meister
patent: 4722321 (1988-02-01), Meister
patent: 4995313 (1991-02-01), Delau et al.
patent: 5355840 (1994-10-01), Violi
patent: 5549038 (1996-08-01), Kolvites
patent: 5631033 (1997-05-01), Kolvites
patent: 5869812 (1999-02-01), Creamer et al.
patent: 3703539 (1988-08-01), None
patent: 7-269879 (1995-10-01), None
Creamer Kurt S.
Hartzell Richard W.
Hotard Thomas C.
Johnson Murray Van
Coats & Bennett PLLC
Middleby-Marshall, Inc.
Pelham Joseph
LandOfFree
Pressure regulator for steam oven does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Pressure regulator for steam oven, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pressure regulator for steam oven will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2476736