DE3702975A1 - Start-up control for pressure cookers with consideration of the filling amount - Google Patents

Abstract

The heat capacity of the filling amount in a pressure cooker is approximately determined by means of timing during the heating-up of the pressure cooker. Subsequently, the heating-up process is accordingly extended beyond the beginning of the pressure build-up.

Description

The regulation of pressure cookers to a predetermined one Pressure value typically takes place in three phases:

1st phase

The pot is heated at full power, until the vent valve (to expel of air-oxygen) closes and the pressure rise begins.

2nd phase

The heating power is varied so that the Print as quickly as possible Value reached.

3rd phase

The heating output is reduced and added or turned off depending on whether the pressure is below or is above the specified value.  

The second phase is more difficult to regulate because heat Capacities play a crucial role and this with different loads of cookware also under have different values. The hybrid control (Offenle publication DE 34 37 121 A1) tries this complexity To be taken into account by different regulatory programs are provided for different pressure levels and excessive Blown off pressure with an adjustable steam valve becomes. The different loading of cookware will, however not yet taken into account in the standard programs. Deswe The hybrid control is also unreasonable in this regard reaching. So it's the inventive task, one Finding regulation for the second phase described above taking into account the heat capacity of the food.

The solution consists of two parts:

• a. Measurement of the heat capacity of the food,
• b. Appropriate programming of the second control phase.

To a:
It is proposed to measure the capacity of the food to be cooked using a time measurement. If the pressure vessel is loaded with a small amount of water, the pressure build-up begins after a time T (after switching on the full power). This time T corresponds approximately to the fixed heat capacities of the device (heating plate and pot walls). When loading with food, the pressure build-up begins at a later time T + t . The proportion of time t is characteristic of the heat capacity of the food.

To b:
The following program has proven itself for the second rule phase:
The full power is maintained after the onset of the pressure build-up (time T + t) for a time β · t , where β is a constant which depends on the pressure to be reached. Then (time T + t + β · t) the heating power is switched off completely for a certain fixed time (about 3 minutes), during which the pressure increases due to local overheating and approaches the preselected value.

The realization of the inventive concept is an electronic problem that can be solved in various ways. An analog circuit with a relay and a digital output is described below ( FIG. 1):

The essential part of the circuit is the capacitor C , which can be charged with a constant current I ₁ via the transistor T ₁ and also discharged with a constant current I ₂ via the transistor T ₂ . In this example, I ₁ is greater than I ₂ . In addition, the transistor T ₃ can be turned on with the voltage of the capacitor C as soon as it is positive. The output of the circuit can be activated by means of an AND gate.

At the beginning of the control process, the contacts K of a relay ( FIG. 1) are closed, as a result of which the capacitor C is brought into a charged state. In addition, the output of the circuit is deactivated by the AND gate (ZERO at input B) . When the fixed time T expires, the contacts K are opened (time T) . This starts the discharge of the capacitor C. When the pressure builds up (time T + t) , the contacts K are closed again and the output activated (ONE at input B from the AND gate). Now the capacitor C charges again. When its voltage becomes positive (with respect to earth), the transistor T ₃ switches through and a ONE appears at the output, whereby the heating power is switched off (time T + t + β · t) . The heating time has thus been extended beyond the time of pressure build-up (T + t) , the length of time being proportional to the heat capacity of the food. Charging and discharging currents of the capacitor C can be set by the resistors R ₁ and R ₂ .

Claims (4)

1. Start-up control for pressure cookers with pressure sensor and associated heating device with controller, characterized in that the controller contains a fixed timer (T) , which represents the fixed heat capacities of the heating device and pressure pot walls and whose timing begins when the heating power is switched on and that Controller has a device for time measurement, which is activated immediately after the time (T) and which measures the time period (t) until the pressure builds up, and that the controller has a second device which converts the time period (t) proportionally in accordance with ( β · T) ( β : Pro proportionality factor), and that the controller has a third device which switches off the heating power after the time period ( b · t) , starting from the pressure build-up. 2. Start-up control for pressure cookers with pressure sensor and associated heating device with controller according to claim 1, characterized in that the proportionality factor ( β ) is predetermined by the set final pressure. 3. Start-up control for pressure cookers with pressure sensor and associated heating device with controller according to claims 1 and 2, characterized in that the function ( β · t) is a more complicated function of (t) and the final pressure. 4. Start-up control for pressure cookers with temperature sensor and associated heater with controller according to Claims 1 to 3, characterized in that analogously measured the temperature values assigned to the pressure values are giving.