US 3071432 A
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Jan. 1, 1963 H. w. GESCHKA ETAL 3,071,432
PROCESS FOR OPERATING A WASHING MACHINE FilQd Sept. 30, 1958 h'uo WEE/YER GESCHKH, A: 5531 racemes/cu 4 Trekker;
i tats 3,071,432 PROCESS FQR UPERATHNG A WASHHNG MACHENE Hugo Werner Geschka, Dusseldorf, and Albert Heidenreich, Monheim-Baumberg, Rhineland, Germany, assignors to Maschinentabrik Peter Pfenningsherg G.m.b.l-l., Dusseldorf-Oherirassel, Germany Filed Sept. 30, 1958, Ser. No. 764,419 Claims priority, application Germany st. 11, 1957 4 Claims. (Cl. 8159) Very many different washing processes have been carried out in the course of time in automatic drum washing machines of the kind having a washing drum which is disposed in a container and which is rotated about a horizontal axis. Thus, for example, it is known to allow a predetermined amount of water provided with a washing agent to flow into the container before the beginning of the washing process, and to treat mechanically the articles to be washed for a certain length of time in the washing bath prepared in this manner. In this case it is of no consequence whether the water flows in at once at its prescribed final temperature, which is kept constant during washing, or whether the washing water is heated up during the course of the washing process to a predetermined final temperature during which the washing agent removes the dirt from the fibers of the articles being washed or disperses or entrains it. The amount of washing agent required depends on the dirtiness of the articles to be washed. The dirt-carrying capacity of the washing agent is then of great importance because the particles of dirt are kept in suspension by the washing agent. The above mentioned washing process, which has hitherto usually been employed, has the disadvantage that the dirt removed from the fibers remains in the washing liquid from the beginning until the end of the washing process and, therefore, comes into contact again and again with the articles being washed.
Another known washing process obviates the aforesaid disadvantage by allowing a definite amount of water to flow continuously into the washing liquid in the drum and discharging an equal amount through an overflow. This process is based on the idea that the dirt separated from the fibers is continuously removed owing to the continuous discharge of the upper layers of the washing liquid from the washing container. The amount of Water flowing in and flowing out must, however, not be too great because if it is the .efiiciency of the process will be doubtful owing to the increased consumption of washing agent and heat. The amount of water usually employed in this process is 0.08 to 0.15 liter per minute per kilogram of dry articles to be Washed. In this way, the entire washing bath is renewed in 75 minutes with the minimum inflow mentioned and in 40 minutes at the maximum inflow mentioned. Owing to the continuous removal of the particles of dirt the number of the individual washing stages can be reduced without impairing the washing effect because an appreciable quantity of the dirt is removed from the drum immediately after being released from the fibers. The process is, therefore, economical, but if the degree of whiteness is used as a measure of the effectiveness of the washing, the process is somewhat inferior compared with the first-mentioned process.
The efliciency of the flow process depends on whether it is carried out at the above-mentioned lower or upper limits of inflow and outflow of water with which both heat and washing agent are lost with the water which flows in and out. At the above-mentioned upper limit the aforesaid losses are great, whereas at the lower limit there are difliculties in the construction of a suitable regulating device.
According to a modification of the last-mentioned process it has been proposed to work with a relatively large water inflow but to allow the water to enter the washing drum only at definite intervals. In this case,
however, the washing effect is necessarily reduced, be-
cause the dirt is removed from the drum container or the washing liquid also only at certain intervals and is again deposited on the articles being washed between two periods of water inflow and water outflow.
The object of the present invention is to provide a washing process which does not processes the disadvantages of the above-mentioned processes and enables their advantages to be fully utilized to produce an improved washing effect with economy of washing agent and heat consumption. According to the present invention the washing process is carried out in two stages during the first of which a continuous supply and discharge of water takes place to and from the washing container and the washing liquid in the container is heated and during the second of which the supply and discharge of water is discontinued but heating is maintained until the end of the washing process.
In this way, in addition to a noticeable economy in the consumption of heat and of washing agent, a surprising improvement in the cleanliness ofthe washed articles if obtained. It has been found that by far the greatest part of the dirt which is removed from the articles being washed is removed early in the washing operation, that is to say Whilst the washing liquid is still at a relatively low temperature, whereas towards the end of the washing process hardly any accumulation of particles of dirt in the Washing liquid occurs. Because of this, the first stage of the washing process is of particular importance for removing the dirt and dispersing the dirt in the washing liquid because the particles of dirt adhering to the articles being washed must be transferred as rapidly as possible to the washing liquid at the beginning of the washing process and must be discharged from the container. As the temperature of the washing liquid rises the loss of heat from the liquid also becomes greater; If the temperature of the washing liquid is plotted against time the temperature/time curve becomes increasingly flatter towards the end of the washing process. According to the amount of heat supplied and the amount of water discharged through the overflow it will sooner or later happen that a state of equilibrium is reached and the temperature of the washing liquid does not rise any longer. If the flow of water through the container in the first stage is too great, it is possible that the final temperature of 85 to 90 C. which is necessary for the washing process is never reached.
At the moment when, at the end of the first stage, the supply of water is shut off, the constant outflow of water also ceases. The temperature of the washing liquid then rises rapidly so that the necessary washing temperature of, for example, 90 C. is quickly reached.
The characteristic feature of the first stage is that a relatively large quantity of dirt is removed because the removal and dispersal of the coarse dirt at the beginning of the process is much more rapid than the removal of the last traces of dirt. The capacity of the washing agent for 60 carrying away the dirt is considerably better in the second stage of the process because the liquid does not flow through the container and in this stage only a relatively small quantity of dirt is present. Therefore, a high degree of cleanliness is also obtained. The choice of the 65 correct moment for changing over from the first washing stage to the second depends mainly on the material being washed, on how dirty it is, on the temperature of the water and on the amount of water which is continuously passed through the container. It is preferably determined by 70 experiment.
If, for example, the articles to be washed are contaminated by oil or fat, the particles of dirt which are combined with the oil or fat can be removed only with difiiculty at low temperatures. Under these circumstances, it is preferable to heat the washing liquid additionally during the first stage when there is a continuous inflow and outflow of water, the liquid being preferably heated to a temperature of approximately 90 0., whereas in the final stage the additional heating is cut off and the washing is carried out to the end of the process at an approximately constant temperature.
With washing machines having a pre-heating boiler it is possible to pre-heat the washing liquid before it flows into the container during the first washing stage. Further, it may be advantageous to use pre-heated Water for the water which is continuously supplied during the first stage. In any case, it is possible with the above-mentioned machines to use the method of the invention when the materials or articles to be washed are heavily contaminated by fats, oils or the like and to clean them to the necessary extent.
An automatic washing machine which is suitable for carrying out the process of the invention and a process for operating it is illustrated, by way of example, in the accompanying drawing in which:
FIGURE 1 is a diagrammatic illustration of the washing drum container of an automatic washing machine having a washing drum which rotates about a horizontal axis;
FIGURE 2 is a graph of the temperature of the washing liquid plotted against time;
FIGURE 3 is another temperature/time graph;
FIGURE 4 shows one form of control knob for the machine; and
FIGURE 5 shows another form of control.
As shown in the drawing, a perforated washing drum 3 which rotates about a horizontal axis 2 is mounted in a container 1. The container 1 is provided, below the washing drum, with a water outlet 4 and an adjacent water inlet 5. An overflow outlet 7 is provided at the level 6 up to which the container 1 is to be filled with liquid. A number of heating elements 9 are provided in the lower part of the annular space 8 between the washing drum 3 and the container 1. A valve 10 is provided in the water inlet pipe for controlling the inlet of water and is preferably actuated by electromagnetic means.
The new washing process will now be explained with the aid of the graph shown in FIGURE 2. In this graph time is plotted as the abscissa and the temperature of the washing liquid as the ordinate. The washing process begins at the point P at which the water flows into the washing drum 1, for example, at a temperature of C. The heaters 9 are switched on and the inlet valve is opened to allow a continuous inflow of water. The heat output Q and the amount of water M introduced per unit of time are indicated in FIGURE 2 by the chain-dotted lines. At first the temperature rises continuously and relatively quickly. The rate of temperature rise becomes smaller as the time increases and would finally become zero at the point P From this point onwards equilibrium occurs between the introduction and the loss of heat. A definite temperature T and time t are reached at the point P depending on the output of the heaters 9 and the amount M of the inflowing and outflowing water. Therefore, if after a certain time a temperature T is reached, the output of the heaters 9 is fixed for a given volumeof liquid in the washing drum and for a fixed inflow and outflow of water. The point P corresponds in practice usually to a temperature of 90 to 95 C. and the time taken to reach this point should, in general, be less than 60 minutes.
As has been found by comprehensive experiments, a great part of the dirt has already been removed from the article being washed when a temperature of 60 to 65 9 C. is reached corresponding to the point P At this point the ratio of the amount of heat supplied to the washing liquid by the heaters 9 to the heat loss is still approximately 221. The second stage of the washing process is now begun at the point P by closing the valve 10. The temperature then rises quickly, for example, along a straight line. The point P corresponding to the temperature of the point P is now very quickly reached, in a time interval At which is only a fraction of the corresponding time interval At with constant water supply.
The temperature/time graph illustrated in FIGURE 3 shows corresponding conditions for washing articles which are heavily contaminated with fat or oil. In this case, in a first phase of the washing process in which there is a continuous inflow and outflow of an amount M of water, the temperature is raised to the point P which corresponds approximately to the boiling point of the liquid, by switching in an additional heater having a heat output AQ. After this, the additional heater is cut off and the supply of water is also shut off either immediately or a short time afterwards. The temperature falls while the inflow of water still continuous at first by the amount AT until a condition of equilibrium is reached at the point P If then at the point of time P the continuous inflow of water is cut off the temperature again rises, for example, to C. at the point P and the washing process is completed.
The change-over of the washing machine from the first washing stage in which there is a continuous inflow and outflow of water to the second washing stage in which the washing liquid remains in the container can be effected with many different kinds of devices. For example, the shutting of the regulating valve which adjusts the continuous inflow of water during the first washing stage can be effezted by control means which provides a control impulse in dependence on the predetermined duration t of the first phase. The control impulse is preferably provided by the program switch which is always present in automatic washing machines. It is also possible to shut the valve 10 by a temperaturesensitive device, for example one having several switch ing stages, which, when the temperature of the washing liquid reaches a predetermined temperature corresponding to the change-over point P cuts off the further supply of water. A further way of controlling the washing machine is to provide control means which control the shutting of the valve 10 and, therefore, the cutting off of the inflow of water in dependence on the total amount of water which flows in and out during the first washing stage. A washing machine which operates in accordance with the process of the invention is preferably provided with control knobs for carrying out the preliminary adjustment of the control means which actuates the valve 10 and, if desired, the time during which an additional heating device provided in the machine is connected. This will depend on the nature of material to be washed and on its dirtiness. Preferably, the washing machine is constructed and electrically connected in such a way that it can be arranged to work in accordance with the customary washing process or also in accordance with the two-stage process of the invention with or without additional heating.
FIGURES 4 and 5 show embodiments of the control knobs provided on the machine. FIGURE 4 shows a switch knob 12 which can be moved over a scale 11. The knob 12 can be set in three different positions 13, 14 and 15, namely in the economy, normal and power positions. In the normal position the machine operates in accordance with the customary washing process, whereas in the economy and power position it operates according to the new two-stage process with or without additional heating.
Further control knobs are shown in FIGURE 5 in which, in addition to the starting and stopping knobs further knobs 16, 17 and 18 for providing economy, normal and power processes are also provided.
1. A process for operating a washing machine provided with a rotatable drum, comprising the steps of charging said drum with articles to be washed, setting said drum in rotation, continuously supplying fresh water to the rotating drum and removing overflowing liquid from said drum While continuously heating said drum during a first operating stage at a rate resulting in a substantially linear rise of the temperature of said water, discontinuing the water supply upon said temperature attaining a predetermined level substantially below the boiling point of water, maintaining the supply of heat during a second operating stage at a rate resulting in a more rapid rise of the Water temperature toward the boiling point of Water, and continuing the heating of the rotating drum until the water temperature has reached a value close to said boiling point.
2. A process according to claim 1 wherein the water is supplied to said drum during said first stage at a rate of substantially 0.08 to 0.15 liter per minute per kilogram of its charge in dry weight.
3. A process according to claim 1 wherein the water supply is discontinued upon said water temperature reaching a value between substantially and C.
4. A process according to claim 1 wherein the heating of said drum during said first stage is continued until the water temperature reaches a value above said predetermined level and the rate of heating is thereupon reduced to lower the temperature to said level prior to discontinuance of the water supply, the drum being heated at the reduced rate during said second stage.
References Cited in the file of this patent UNITED STATES PATENTS Re. 22,375 Chamberlin et al. Sept. 14, 1943 2,161,604 Watts June 6, 1939 2,193,495 Rolkern Mar. 12, 1940 2,676,088 Bilde et al. Apr. 20, 1954 2,722,119 Constantine Nov. 1, 1955 2,730,887 Howlett June 17, 1956 2,757,065 Castner July 31, 1956