Drying and gas or vapor contact with solids – Apparatus – With means to treat gas or vapor
Patent
1986-05-12
1988-05-17
Schwartz, Larry I.
Drying and gas or vapor contact with solids
Apparatus
With means to treat gas or vapor
34 30, 34 34, 34 48, 34 54, 34 55, 34100, F26B 2022
Patent
active
047441542
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a method of measuring and controlling the moisture content of hair using a hair-drying hood with an air humidity sensor in the return air duct, and to a hood for use in such a method.
BACKGROUND ART
A drying process is known from the European Patent Application EP-A-0 073 944, in which the heating capacity is controlled automatically as a function of the relative air humidity measured by means of an air humidity sensor arranged in the return air duct. The disadvantage here is that the degree of moisture in the hair is not compared with the relative humidity of the outside air, so that a process of this type is extremely inaccurate and may lead to overdrying. In this connection a remedial measure is said to be provided in the form of a second air humidity sensor, which includes the relative humidity of the outside air in the drying process. The disadvantage here is still a large degree of measurement inaccuracy, since it is necessary to work from the fact that a comparative relative air humidity measurement is only possible when the temperatures of the return air and the outside air are the same; another disadvantage is the use of two sensors with characteristics which are not identical. An improvement in the accuracy of measurement is possible by means of a selected (expensive) pair (extensive correlation of the characteristics), but this also makes the device for performing the method expensive as a result of large circuit costs.
German Auslegeschrift DE-A2-10 79 801 discloses a drying process with two air humidity sensors. The relative humidity of the return air and the outside air is detected; the return air temperature is said to be brought to the temperature of the outside air by means of cooling fins and the application of outside air, in order that a comparative measurement of the relative air humidity can be made at equal temperatures. As a result of the strong return air flow an adjustment to the outside air temperature is not possible. In addition, the already mentioned disadvantages are present.
What is desired is a hair drying method which does not have the disadvantages or which makes exact measurement and control of the moisture content of the hair possible and prevents overdrying.
DISCLOSURE OF INVENTION
The present invention provides a method of measuring and controlling the moisture content of hair using a hair drying hood with an air humidity sensor in the return air duct, in which when the drying phase commences, a measuring device connected to the air humidity sensor produces mean values at equal time intervals, a first stop signal being transmitted from the measuring device to a hair drying programme device in order to introduce an automatic programme stop when a predetermined differential value of the measured air humidity mean values is not reached.
Proceding from the concept that the hair is considered to be dry when there is no longer any significant change in the moisture content of the exhaust air, this state and thus the end of the drying process can be determined using the method according to the invention.
In order to adapt the treated hair to the temperature and humidity of the surroundings and in order to reduce the excess remaining moisture of the hair without overdrying the hair, once a predetermined differential value (e.g. 0.1) of the measured mean values of the air humidity has been reached, the drying process continues at a reduced heat capacity and also a reduced fresh air capacity until a predetermined period of time has elapsed (e.g. 5 min).
To signal a warning for the end of the drying process a stop signal can advantagsously be used which, after a predetermined period of time and after a predetermined period of time of the reduced drying phase (reduction of the heat capacity/fresh air flow), also indicates by means of a timer the time which remains until the drying hood switches off. This device enables the operating personnel to adapt themselves optimally to the operation cycle.
Since the sensitivity of air humidity
REFERENCES:
patent: 2271857 (1942-02-01), Dwyer
patent: 3052038 (1962-09-01), Harris
patent: 3082540 (1963-03-01), Hiltenbrand
patent: 4385452 (1983-05-01), Deschaaf et al.
Bollinger Heribert
Hollmann Siegfried
Mattinger Detlef
Schwartz Larry I.
Striker Michael J.
Wella Aktiengesellschaft
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