Washing Machines and Principles of Operation

Washing Machines and Principles of Operation

Soil removal in a modern washing machine is a combination of chemical and mechanical processes.

1. Chemical action. The detergent or soap solution dissolves and loosens the soil in the fabric.
2. Mechanical action. Flexing the clothes and forcing the detergent or soap through removes the soil. The functioning of the washer is aided by the heat and softness of the water, which increases the chemical action of the detergent or soap used.

Almost all modern automatic washers employ one of two types of mechanical action, tumbler or agitator. The latter is by far the more popular and more commonly used. But all automatic washers, regardless of type, model, or make, have only four basic functions of operation: (1) fill, (2) wash, (3) pump out, and (4) extraction (spin).

The heart of the agitator-type washing machine is the agitator, which usually consists of vanes or blades on a cone that fits over a central shaft in the washer tub. As the agitator turns back and forth, the blades or vanes catches clothes and move them about. This movement also creates currents in the water, which contribute to the cleaning action.

There are almost as many agitator designs as there are washers that use agitators. Agitators have vanes or blades of various numbers, designs, and sizes, which are arranged in a vertical or spiral position. Agitators may be of solid or perforated plastic or metal (usually aluminum).

Most agitator-type washing machines employ an oscillating (back-and-forth) action during the wash cycle. To produce this oscillating action, the arm is generally connected off-center to a low-speed gear wheel. As this gear wheel turns, it imparts a back-and-forth motion to the arm. This motion, in turn, is transmitted to a pinion gear which drives the agitator.

There are also other methods of driving the agitator. For instance, a few models provide a slow-speed, off center, wobbling motion to the agitator, while some others impart an up-and-down, pulsating motion to it. While the oscillating action is the one most commonly used for the washing operation, some machines of this type employ a rotating or revolving motion to spin the tub or basket for the extraction operation. To accomplish this, a clutch action of some type is used to disengage one set of gears and engage the other. One such clutch used in washers consists of a pin dropping in place in a hole in the drive gear to engage it or it may be a friction type, as is frequently found in automobiles. Incidentally, agitator-type washing machines are top loading, meaning that the clothes are placed in the washer through a door or lid that opens on the top of the unit.

The front-load type of automatic washer has gained in popularity in recent years. The tumbler mechanism is a perforated cylinder, usually aluminum or porcelain-enameled steel, which holds the clothes; it revolves in a larger tub that holds the water. Within the cylinder are baffles, which are projections designed to carry the clothes along, through, and out of the water, until the position of the clothes causes them to fall downward again, and the process is repeated.

The axis of rotation of the washing cylinder usually is either parallel to the floor or inclined upward from the floor at approximately a 30 degree angle. A few have a vertical cylinder. Most tumbler-type washers are loaded from the front, but some can be loaded from the top or at an angle. During the washing cycle, the cylinder revolves slowly, tumbling the clothes about in soapy water. During the damp-dry cycle, the cylinder revolves rapidly, and centrifugal action helps to throw the water out of the clothes. The low speed for washing and the high speed for damp-drying are provided by the gears in a transmission as in an automobile. In a similar manner, there is a gear-shifting arrangement and a clutch to engage the gears.

The needs and components of both tumbler and agitator washers are about the same. For example, both require hot and cold water. This water is fed into valves in the washer which turn on and off the hot and cold water and mix them at appropriate times. While a few washers control water temperature with a thermostat, most operate on a simple on-off principle. When the hot water is on and cold is off, the water in the washer is hot-whatever temperature the water-heater tank provides. When the cold water is on and whatever temperature the cold-water tap provides. When both hot and cold are on, they are evenly mixed to provide warm water; with average cold water temperatures out of the tap (about 50F), the mixture comes out at about 100F.

All automatic washers have an electric motor as well as a pump. The motor on most models, in driving the washer through the wash and rinse cycles, operates in both the counterclockwise and clockwise directions when viewed from the top of the machine. It operates counterclockwise during the wash cycles and agitate-rinse operation and clockwise during the pump out and spin operations. The motor turns the pump and drive pulleys through a belt or motor-coupler arrangement. After the completion of the agitation or rinse, the water is pumped from the washer before the start of the rinse cycle. In this operation the motor is operating in the clockwise direction as it is in the spin; however, and overriding clutch disengages the transmission spin tube so the basket will not spin. At the end of the pump out period a solenoid releases the clutch spring and the spin basket rotates to extract the water from the clothes. The pump is usually in operation continuously. When the agitator is in operation, power is transferred directly into the transmission from the drive pulley through the transmission drive shat and clutch spring located inside the transmission case. During the pump out and spin periods the clockwise rotation of the motor releases the clutch.

Solenoids play a very important part in the operation of an automatic washer. In addition to operating the clutch and gearshift arrangements, they control water flow, detergent application and the like. Of course, the overall control of the automatic washer is left to the timer or the electronic control. While part of the control is selected by the user – for instance, washing time and water temperature-most of the automatic action is performed at certain preselected time intervals by the timer/control.