A number of types of domestic fan are known. It is common for a conventional fan to include a single set of blades or vanes mounted for rotation about an axis, and driving apparatus mounted about the axis for rotating the set of blades. Domestic fans are available in a variety of sizes and diameters, for example, a ceiling fan can be at least 1 m in diameter and is usually mounted in a suspended manner from the ceiling and positioned to provide a downward flow of air and cooling throughout a room.
Desk fans, on the other hand, are often around 30 cm in diameter and are usually free standing and portable. In standard desk fan arrangements the single set of blades is positioned close to the user and the rotation of the fan blades provides a forward flow of air current in a room or into a part of a room, and towards the user. Other types of fan can be attached to the floor or mounted on a wall. The movement and circulation of the air creates a so called ‘wind chill’ or breeze and, as a result, the user experiences a cooling effect as heat is dissipated through convection and evaporation. Fans such as that disclosed in U.S. D 103,476 are suitable for standing on a desk or a table. U.S. Pat. No. 2,620,127 discloses a dual purpose fan suitable for use either mounted in a window or as a portable desk fan.
In a domestic environment it is desirable for appliances to be as small and compact as possible. U.S. Pat. No. 1,767,060 describes a desk fan with an oscillating function that aims to provide an air circulation equivalent to two or more prior art fans. In a domestic environment it is undesirable for parts to project from the appliance, or for the user to be able to touch any moving parts of the fan, such as the blades. U.S. D 103,476 includes a cage around the blades. Other types of fan or circulator are described in U.S. Pat. No. 2,488,467, U.S. Pat. No. 2,433,795 and JP 56-167897. The fan of U.S. Pat. No. 2,433,795 has spiral slots in a rotating shroud instead of fan blades.
Some of the above prior art arrangements have safety features such as a cage or shroud around the blades to protect a user from injuring himself on the moving parts of the fan. However, caged blade parts can be difficult to clean and the movement of blades through air can be noisy and disruptive in a home or office environment.
A disadvantage of certain of the prior art arrangements is that the air flow produced by the fan is not felt uniformly by the user due to variations across the blade surface or across the outward facing surface of the fan. Uneven or ‘choppy’ air flow can be felt as a series of pulses or blasts of air. A further disadvantage is that the cooling effect created by the fan diminishes with distance from the user. This means the fan must be placed in close proximity to the user in order for the user to receive the benefit of the fan.
Locating fans such as those described above close to a user is not always possible as the bulky shape and structure mean that the fan occupies a significant amount of the user's work space area. In the particular case of a fan placed on, or close to, a desk the fan body reduces the area available for paperwork, a computer or other office equipment. The shape and structure of a fan at a desk not only reduces the working area available to a user but can block natural light (or light from artificial sources) from reaching the desk area. A well lit desk area is desirable for close work and for reading. In addition, a well lit area can reduce eye strain and the related health problems that may result from prolonged periods working in reduced light levels.