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Manual actuators are levers, wheels, or buttons controlled by humans. They can be simple switches or complex control wheels. Examples include door handles, toilet flush arms, and accelerator pedals. They are used in irrigation, flood control, and industrial processes. Hand calculators also used manual actuators until electronic calculators became more common.
A hand actuator is a lever, wheel or button used to control something through human action rather than a power source. These can be as simple as an on-off switch or as complex as large control wheels for opening the floodgates. The key to any manual actuator is that one person operates the device, rather than a computer or power source of any kind.
Simple manual actuators are common and familiar to many people in their homes. Electric switches are a manual actuator for turning on lights or other electrical appliances. Toilets can be flushed by pressing a flush arm or, in some designs, a button on the top of the tank, which then allows the water to flow. Electric, gas or microwave ovens may have electronic systems for their operation, but the user chooses the cooking and timer settings, making the commands manual actuators.
Over hundreds of years and into the 21st century, many people have come to depend on a manual actuator to enter or exit their homes. Door knobs or handles are simple actuators that move a latch mechanism as needed. In the late 20th century, some companies switched to automatic door openers for customer convenience, but a handle remained a common and effective way to open and close doors.
Vehicles have a variety of manual actuators, including climate controls, external wipers in vehicles without automatic rain sensors, and even the accelerator pedal. The throttle may be a wire connection to the throttle assembly, or it may be an electronic switch depressed by the foot pedal, often referred to as a “fly-by-wire” since there is no physical connection to the motor. There is a manual override for people who don’t want to use the accelerator, called cruise control, which is activated by a switch.
Where water is used for irrigation, manual irrigation valves are often used to control the flow of water to fields. They are simple to use, robust and require little maintenance. Manual gate or butterfly valves, which describe the shape of the valve seat, are the most common and allow reasonable control over water flow rates.
Water can also be a nuisance, and flood control in smaller rivers and streams can use manual control valves. The valves can control sluice gates and direct water to small generators or water wheels. Larger dams and water works may use motorized control systems, but a manual valve can operate reliably for years. This can be especially useful for flood control systems in remote areas with no power or systems that operate intermittently.
Industrial and chemical operations rely on manual valves as backup controls for powered systems. A manual control valve can be used in an emergency to control processes in the event of a power failure. Manual valves are often used as shut-off devices, isolating parts of the process for maintenance and locked out by maintenance personnel to prevent injury.
In the 19th and early 20th centuries, calculators and early calculating devices used levers and control arms to provide mathematical functions. Adders commonly had rows of buttons that were pressed and a control arm pulled to activate each addition or subtraction. A hand actuator operated the machine, and hand calculators were used extensively until electricity became more common, and electronic calculators eventually replaced calculators in the 19th century.
