An upright type of vacuum cleaner is a self-contained unit which has the motor, main cleaning nozzle, filtering system, etc. all built together in an overall vertical shape. All upright types today have motor driven revolving brush rolls and are used primarily for cleaning carpeted floors. They are pushed forward and pulled backward in front of the user by gripping the narrow handle extending upward from the main case.
The general upright type can be subdivided into three basic types having three unique design characteristics. They are the Traditional Upright, the "Clean-Air" Upright and the Two-Motor Upright. The "clean-air" upright design has been around for many years, originally introduced by The Hoover Company with their innovative Dial-a-Matic series.
The "clean-air" upright designation is used since the air which passes through the suction producing fan or fans is already "clean", having passed through most of the filtering system before reaching it. While two-motor uprights usually fit this description as well, this designation typically is used to refer to an upright using only one motor to create the suction and drive the brush roll. As such, it is often used when comparing "clean-air" uprights to "dirty-air" (traditional) uprights.
The air enters the nozzle near the floor and travels toward the paper or cloth filter bag, carrying the dirt with it. The bag retains most of the dirt and dust while allowing the air to pass through its filter media. The air then travels through a filter pad to be cleaned further before entering the high speed suction fan or fans. Since the air is quite clean, it is allowed to flow through the motor to cool it. After leaving the motor the air is often filtered by additional exhaust filters to remove even more fine particles and carbon from the motor brushes before it leaves the vacuum cleaner.
The "clean-air" upright combines a canister type motor and filtration system in the main body with a more traditional type nozzle for cleaning carpeted floors. The basic vertical configuration of the upright is maintained while performance with the attachments is improved. Most uprights having this design conveniently carry the attachments on-board with the hose always attached and ready to use.
The canister motor design creates significantly more actual suction (pressure difference) than the traditional upright motor design. This is important for effective cleaning with a hose and attachments due to the higher resistance to air flow present in the hose. The velocity of the air flow plus the amount of the carpet agitation determines how well a vacuum cleaner will pick up the dirt so the shorter the distance the air travels and the larger the air passages, the better the performance will be. Some "clean-air" uprights pull all the air through a long hose even when cleaning with the main carpet nozzle, reducing their performance slightly. For more about suction motor and fan designs, see our articles on Suction Motor Design & Operation and Fan or Impeller Types & Performance.
In summary, "clean-air" uprights typically produce better performance when using on-board attachments. They also have significantly longer fan and motor lives compared to most "dirty-air" uprights with on-board attachments. Operating noise levels are typically much lower than from their "dirty-air" counterparts. This design can be identified by looking at the filter bag and the supporting container. If the paper bag is supported by a flexible outer cloth or vinyl bag you can be sure that it is the "dirty-air" design. If the bag is supported by a rigid enclosure, open it and look for seals around the edges. If none are present, it is probably the "dirty-air" design as well. If the rigid bag enclosure is sealed and a foam or fiber filter pad is at the bottom of the enclosure, it is probably the "clean air" design.
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