1. Partial separators, which must be used in conjunction with another separator in order to effect a complete removal of the dust from the air. These separators are again divided into two sub-classes, i. e., primary, or those removing the heavy particles of dust and dirt only, and secondary, or those removing the finer particles of dirt which have passed through the primary separator.
2. Complete separators, or those in which the removal of both the heavy and the finer particles of dust is effected in a single separator.
Separators may also be classified, according to the method employed in effecting the separation, into dry separators in which all operations are effected without the use of liquid, and wet separators in which water is employed in the removal of the dust.
Primary Separators.
—Primary separators are nearly always operated as dry separators and depend largely on centrifugal force to effect the separation. The first type of primary separator used by the Vacuum Cleaner Company is illustrated in [Fig. 67]. This consists of a cylindrical tank, with hopper bottom, containing an inner cylinder fixed to the top head. The dust-laden air enters the outer cylinder near the top on a tangent to the cylinder. The centrifugal action set up by the air striking the curved surface of the outer cylinder tends to keep the heavy dirt near the outside of same, and as it falls towards the bottom the velocity is reduced and its ability to carry the dust is lost. When the air passes below the inner cylinder the velocity is almost entirely destroyed and all but the very lightest of the dust particles fall to the bottom, while the air and the light dust particles find their way out of the separator through the opening in the center at the top.
FIG. 67. EARLY TYPE OF PRIMARY SEPARATOR USED BY VACUUM CLEANER COMPANY.
FIG. 68. PRIMARY SEPARATOR USED BY THE SANITARY DEVICES MANUFACTURING COMPANY.
The primary separator used by the Sanitary Devices Manufacturing Company is illustrated in [Fig. 68]. The inner centrifugal cylinder is omitted and the air enters through an elbow in the top of the separator, near its outer extremity, which is turned at such an angle that the air is given a whirling motion resulting in the dust being separated much the same as in the case of the Vacuum Cleaner Company’s apparatus.