VACUUM CLEANER. An appliance for extracting and removing dust from fabrics, such as carpets, upholstered seats, cushions, etc., by suction, designed for the primary purpose of carrying out this operation without the necessity of displacing the articles to be cleansed from the positions which they normally occupy when in use. It is also used to remove dust from such surfaces as those of floors, shelves and walls, etc. It was so named by its inventor, H. C. Booth, who made and patented the first successful appliance in the year 1901.
A vacuum cleaner consists essentially of an air suction pump, or exhauster, connected by a pipe or tube or directly to a nozzle having a slot shaped orifice which is passed over the material being cleansed, the surrounding lip of the orifice being kept in close contact with the material. An air filter which cleanses the air either before or after its entry into the exhauster serves at the same time as a chamber, or receptacle, for collecting the dust, which can be removed therefrom conveniently and without dispersal. In the light portable or domestic types, this filter is of cloth in the shape of a bag. In operation, suction from the air exhauster causes air to rush violently into the nozzle through the interstices of the fabric being cleansed and to carry away with it the imprisoned dust. The stream of dust-laden air passes from the nozzle to the filter, in which the dust is retained while the cleansed air is drawn on through the pump or filtered through the dust bag and delivered thence to the atmosphere.
In the first instance the vacuum cleaner was made in the form of a portable plant and consisted of a pump driven by a petrol or electric motor, mounted with the filter on a portable trolley, which was taken round periodically to houses, offices, etc., when cleaning was required. A long flexible hose with the cleaning nozzle attached was led into the house from the plant which remained outside. Such cleaners for house to house work are now mounted in motor vans.
Central Installations.—Shortly after the introduction of the portable type of machine, fixed installations of central plants were established in large buildings, such as hotels and theatres.
These had a permanent system of pipes running from the plants to the various floors with branch pipes to different parts of the build ing. At convenient positions in the pipe lines, valves, or nozzles with removable caps, were fitted, to which flexible hose with cleaning nozzles could be attached. It is now common practice to equip large modern buildings with such central installations.
In both forms of plant the suction pump or exhauster is now either of the positive displacement or of the multi-stage fan type, depending upon circumstances and the class of work to be done, the former being more suitable for giving a higher degree of vacuum with less volumetric capacity than the latter.
If of the positive displacement type, it should be capable of drawing from 28 to 35 cu.ft. of free air per minute per clean ing nozzle at work, while maintaining inside the nozzle a degree of vacuum equal to 5 in. of mercury. If of the multi-stage fan type, it should be capable- of drawing from 5o to 70 cu.ft. of free air per minute per cleaning nozzle at work, while maintaining inside the nozzle a degree of vacuum equal to 3 in. of mercury.
The filter is a chamber generally formed in two parts, an upper fixed part containing a filtering fabric of unbleached calico, linen or other suitable material usually made in the form of an inverted bag or cone, and a lower part, readily removable, into which falls, and is collected, the dust intercepted by the filtering material.
The cleaning nozzle for use on carpets or upholstery has a slot shaped orifice usually from 2 in. to a in. wide, and from 4 in. to 12 in. long, the rim of the orifice being formed with a continuous rounded lip so as to run smoothly over the fabric being cleansed and to ensure close contact therewith throughout its entire peri phery. Other forms of nozzle are used for various purposes— those for removing dust from surfaces such as floors, or shelves, usually have felt or bristles mounted around the orifice.