The tank rotation axis should be horizontal to provide proper washing and rinsing of laundry and the tank rotation axis should be vertical to provide proper balancing during water extraction from laundry.
In the general case, a washing machine is a tank filled with a washing solution (water and detergent) and laundry. During washing, the solution in the tank is activated either by rotating the tank itself or by using special blade agitators. Then the solution is discharged and the remaining water is extracted from the laundry. To do this, the tank starts spinning rapidly and the centrifugal force removes the water. This operation is followed by several rinsing cycles. Clear water is supplied into the tank and this time is activated to wash the detergent from the laundry. Then the water is wrung out again and the 'rinsing-wringing out" cycle recurs. Some washing machines include the operation of laundry drying by hot air.
Thus, a washing machine has two main modes of operation – a detergent or water activation mode (washing or rinsing) and a water extraction mode.
The entire variety of washing machines may be reduced to two main types – machines having a horizontal axis rotation of the tank (Fig.1, a) and machines having a tank rotating about a vertical axis (Fig. 1, b).
|Fig.1. Washing machine design|
a) with a horizontally arranged drum;
b) with a vertically arranged drum.
In horizontal-axis machines, detergent is activated by slowly rotating a tank with laundry. In fact it is a drum with perforated walls which is arranged fixedly within an immovable tub filled with detergent.
In addition to the direct action of activated detergent on laundry, machines of this type produce an interesting effect. The walls of a rotating drum have several protrusions which regularly raise the laundry to some height. Then the laundry detaches from the wall and falls down. When falling into the washing solution, the solution jets penetrate the cloth with force, thereby removing soil.
Horizontal-axis machines provide a very good and simple organization of the washing and rinsing process, but have serious problems with water extraction from the laundry. The thing is that laundry in a horizontal drum is compactly arranged and causes a strong unbalance during rotation.
Balancing a rotating horizontal-axis drum is a difficult problem. The simplest way of solving it is attaching a heavy load – a concrete disk whose mass is much greater than the laundry mass – to the back wall of the drum. This is a so-called major balancing of the drum. In addition, there are a lot of patents for additional balancing of a horizontal drum, for example, by arranging an annular plane partially filled with water around the drum periphery.
The higher the drum rotation speed, the better is the water extraction from laundry. Because the rotation speed of a horizontal-axis drum is limited in principle, the water extraction process is ineffective. This increases power needed to dry laundry after washing.
In addition, a horizontal-axis front-loader is not ergonomically convenient. To load laundry or take it out after washing has finished, one should stoop.
A vertical-axis washing machine only has one rotating tank for a washing solution. The washing solution is activated by rotating an additional blade agitator mounted on the tank bottom. To extract water during wringing, the tank and the agitator are rotated at a high speed. The advantage of this type of washing machines is their simple design because we only have one tank – a tub for a washing solution and laundry. Though an additional unit – blade agitator – appears in this construction, such a washing machine does not need any tub-balancing system during spinning. The thing is that during the spinning of a vertical-axis tub, laundry is arranged more or less uniformly on its bottom and does not cause sensible unbalance. This system is also ergonomically convenient because one can load and unload the machine in a more comfortable position.
The disadvantage is the fact that a blade agitator does not always provide a proper washing quality. Attempts to make a blade agitator with developed blades or an auger-type agitator or to increase the agitator rotation speed failed. The more active the agitator operation, the stronger is the laundry wear and damage during washing.
We are not going to consider washing process improvement methods which could be equally applied to vertical-axis and horizontal-axis washing machines, such as optimization of washing solution parameters and machine operation modes, supply of air bubbles into a washing solution, use of ultrasound, etc. Our purpose is to solve the contradiction between the two main types of washing machines.
Let us present the advantages and disadvantages of both designs in the form of a table.
||Washing and rinsing
|Horizontal-axis washing machine
|Vertical-axis washing machine
What is good in one type of machines is bad in the other type and vice versa. In fact we have two alternative systems (1, 2) for performing the same function. To improve such systems, it is necessary to combine them so as to impart only positive properties of both alternative systems to a new system.
The main contradiction of a washing machine may be formulated as follows.
- The tank rotation axis should be horizontal to provide proper washing and rinsing of laundry.
- The tank rotation axis should be vertical to provide proper balancing during water extraction from laundry.
When thinking about some compromise version, there immediately occurs an idea about the inclined position of a tank. Some manufacturers took this way and put inclined-axis washing machines on the market. For example, in a Samsung washing machine, the drum is inclined at an angle of 12 degrees with the horizon (Fig.2). The apparent advantage of such a machine is its improved ergonomic properties because it makes it easier to put laundry into the drum. However, it is difficult to state that inclination really contributes to better balancing.
|Fig. 2. Inclined drum washing machine. |
With the contradiction aggravated to its ultimate, the requirements for the tank become mutually exclusive – the tank rotation axis should be both horizontal and vertical.
Such contradictory requirements for the same element of the system may be separated in time.
Indeed, the tank should rotate vertically during loading and water extraction by spinning while during washing and rinsing, it would be better for the tank to rotate about its horizontal axis. During unloading, it is desirable for the throat to be inclined down and for laundry to fall out into a basin.
This contradiction may be solved by means of additional dynamization. Suppose we have an ordinary vertical-axis washing machine hinged to an additional frame (Fig.3). To wash, it is enough to incline the washing machine so that its axis of rotation becomes horizontal. To extract water and unload laundry, it is enough to reset the machine.
The tank shape needs to be slightly changed. It is better to make the throat tapered so as to prevent water outflow.
The presence of the additional frame and hinged device slightly complicates the washing machine construction, but then a blade agitator and balancing device may be removed from it.
|Fig.3. Washing machine turning scheme.|
By trimming the produced construction, that is, by removing unnecessary elements from it and optimizing the remaining ones, we can arrive at a conclusion that the washing machine should be spherical (Fig.4). A spherical tank filled with water and laundry is mounted on a base where electric motors and water-supply pipes are also located. Four rollers protrude from the base, each being actuated by its own electric motor.
|Fig.4. Spherical washing machine design|
A spherical water tank is supported by rotating rollers which can spin it in different directions and change it from the vertical position to horizontal position and back. Fig.5 shows positions during the main operating modes of the washing machine.
|Fig.5. Alternative positions of driving rollers|
The rollers are arranged in parallel and rotate slowly in the same direction – the tank turns from a vertical position to a horizontal position (Fig. 5, a). For the axis of rotation of the tank to pass through the loading door of the machine during washing and rinsing in a horizontal position, the rollers should be rotated through 90 degrees (Fig. 5, b).
If the rollers are set so that their axes of rotation intersect in the center of a circumference (Rig. 5, c), the spherical tub for extracting water from the laundry may be rotated. Because water will be removed towards the sphere equator during spinning, it is necessary to provide an additional netlike frame for laundry inside the sphere and to rotate the drum with stops so that the accumulated water can drain off.
|Fig. 6. Decelerating the drum.|
In addition, in would be expedient for the rollers to be retracted inside the base (Fig.6). If the rollers are extended, the water-filled tank is raised and can rotated freely; if they are retracted, the tank rests on the base and is connected to the pipes for water supply and removal.
As a result, we have a washing ball. Probably, something of the kind has already been invented but so far, we have not got any information about manufacture of this type of machines, though we do no see any special technological difficulties while advantages are evident.
As to the practical realization of such a construction, the rotating ball may be hidden under a transparent housing. It would be more practical though not too beautiful.
1. Litvin, S., and V. Gerasimov. “Development of Alternative Systems by Combining them into a Supersystem”, TRIZ Journal, 1990, 1.1.
2. Vladimir Gerasimov. Wattled Fence. Inventor's Yarn. http://www.trizminsk.org/e/212003.htm