The wear on these felt faced renovators was found to be so rapid that hard felt or composition rubber strips, placed so that the wear comes on the edges of the same, have been substituted. The felt or rubber was screwed on to the outside of a metal shell and projected sufficiently below the face of the metal to permit considerable wearing off of same before the surface of the metal came in contact with the surface cleaned. When this occurs, the felt strips can readily be replaced with new ones. The ends are left open about ¹⁄₂ in. to form an inrush for the entering air. Such a type is shown in [Fig. 29].
FIG. 29. BARE FLOOR RENOVATOR WITH HARD FELT OR COMPOSITION RUBBER STRIPS.
This renovator, in either of the above-described forms, is a great improvement over the bristle brush in that the air passing into the body of the renovator must come into intimate contact with the surfaces cleaned, but it still has the disadvantage of tending to push the dirt before it.
A modification of the above-described renovators has been introduced, in which the wearing surface of the renovator, which is covered with felt, is rounded as shown in [Fig. 30]. With this form of bare floor renovator, the air passing into same is not only brought into intimate contact with the surface cleaned but the dust is also crowded under the curved surface of the renovator as the same is pushed over the floor and thus brought directly into the path of the air current.
FIG. 30. BARE FLOOR RENOVATOR WITH ROUNDED WEARING SURFACE.
The last named type is by far the most effective for cleaning either polished or unpolished floors. It must be provided, however, with inrush slots in order to prevent its sticking and preventing easy operation. When operated with hose pipe and a vacuum producer necessary to produce 2 in. of vacuum in Type A carpet renovators, at least 30 cu. ft. of air must be permitted to pass the renovator. When operated with systems adapted to produce 4¹⁄₂ in. of vacuum in Type A carpet renovators, at least 70 cu. ft. of air must pass the renovator in order to permit easy operation.
This increase in the air quantity without change in the degree of vacuum in the case of these renovators, is not without increase in efficiency, as in the case of the carpet renovators, because large quantities of dust and also small litter are met with much more frequently on bare floors than on carpets. With the increase in the volume of air passing, it is possible to pick up much heavier articles than with the smaller quantity. It is also possible to pull dust out of deep cracks or from surfaces which are not in contact with the renovator face, such as the spaces between the slats of floors of trolley cars. This would not be possible with the small air quantity. The use of the larger quantity of air prohibits the use of small-sized hose and pipe and, therefore, larger articles can be conveyed through them. Where a large amount of bare floor must be rapidly cleaned the use of the larger air quantity is recommended.
