FIG. 23. TESTS SHOWING EFFICIENCY OF DIFFERENT TYPES OF RENOVATORS AT DIFFERENT DEGREES OF VACUUM.
If the degree of vacuum within the renovator be carried to an abnormally high degree, there will be a tendency for the renovator to cling so close to the carpet that its operation will be difficult and the wear on the carpet rapid. The production of this high vacuum, with a larger quantity of air exhausted, will result in the expenditure of power at the renovator in excess of the gain in efficiency and speed of cleaning.
It is evident that the wider the cleaning slot, the greater will be the tendency of the renovator to stick to the carpet with a high vacuum within the same. The author has experienced no difficulty in operating the 10-in. renovator, with ³⁄₁₆-in. cleaning slot, with a vacuum as high as 9 in. of mercury, but wider-slot renovators always push hard when any high degree of vacuum exists within them.
Effort Necessary to Operate Various Types of Renovators.
—The author made a series of tests to determine the effort necessary to operate the various types of renovators under different conditions. In making these tests the renovator was attached to a spring balance and pulled along the floor, the pull required to move the renovator being observed by the reading of the balance. Three types of renovators were used in this test: Type A, having a cleaning slot ⁵⁄₁₆ in. wide and 12 in. long; Type C, having a cleaning slot ⁵⁄₁₆ in. wide and 12 in. long, with an auxiliary inrush slot ¹⁄₄ in-wide and 12 in. long; Type F, having a cleaning slot ³⁄₄ in. wide and 10 in. long. The results were as follows:
TABLE 5.
Effort Necessary to Operate Cleaning Tools.
| Kind of Carpet. | Type of Renovator. | Vacuum at Renovator, In. Hg. | Pull, Pounds. | Air, cu. ft. per min. | ||
|---|---|---|---|---|---|---|
| Brussels, short | A | 8 | 20 | 27 | ||
| Napped, close back | C | 6 | ¹⁄₂ | 17 | 31 | |
| F | 3 | ¹⁄₂ | 11 | 59 | ||
| Axminster, long nap | F | 3 | ¹⁄₂ | 14 | 59 | |
| Velvet, with glue | A | 8 | ¹⁄₂ | 18 | 28 | |
| Sized back | C | 6 | ¹⁄₂ | 17 | 31 | |
| Velvet, without glue | A | 3 | ¹⁄₂ | 15 | 40 | |
| Sized back | C | 1 | 12 | 45 | ||
| Linoleum | A | 13 | 23 | 12 | ¹⁄₂ | |
| C | 1 | 10 | 40 | |||
It may be noted that, when operating on the Brussels and the glue-sized velvet, the pull required to move all types of renovators bears a direct ratio to the degree of vacuum under the renovator, and that the quantity of air exhausted is the same for each renovator on either carpet, but different for each type of renovator. It is evident that, in this case, very little air enters the renovator by passing up through the carpet, and hence the action of the inrush slot on Type C renovator is noticeable only to a slight degree. When operating on velvet carpet, without glue-sized back, the inrush slot, in conjunction with the greater quantity of air coming through the carpet, has caused the passage of a large quantity of air, while the vacuum maintained at the renovator is greatly reduced over that which was maintained under Type A renovator when the same quantity of air was passing. In this case, nearly all of the air entering Type A renovator came from the under side of the carpet. The effect on the efficiency of cleaning with Type C renovator under these conditions can readily be imagined, by reference to former tests, as being greatly reduced over that of Type A when passing the same quantity of air. With linoleum, the action of the inrush slot of the Type C renovator has again greatly reduced the vacuum under the renovator, although the quantity of air is much in excess of that passing Type A renovator. The difference in the behavior of the renovators on different makes of carpet is seen to be due largely to the difference in the quantity of air which passes up through the carpet into the renovator.
It is evident that, with the same degree of vacuum within the renovator, all types are equally easy to push and that, if the vacuum within the renovator becomes higher than is necessary to produce good cleaning results, unnecessary effort will be required to operate the renovator.