| Type of Renovator. | A | C | F | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Vacuum in renovator, in. hg. | 2 | 4¹⁄₂ | 1 | 2¹⁄₂ | 4 | 3¹⁄₂ | ||||||
| Air exhausted, cubic feet per min. | 16 | 27 | 24 | 37 | 44 | 59 | ||||||
| Material removed, per cent. of total, 1 min. | 48 | 54 | 45 | 48 | 50 | 50 | ||||||
| Material removed, per cent. of total, 2 min. | 70 | 87 | 60 | 63 | 65 | 73 | ||||||
| Material removed, per cent. of total, 3 min. | 91 | 100 | 73 | 75 | 77 | 87 | ||||||
| Material removed, per cent. of total, 4 min. | 100 | —— | 76 | 81 | 88 | 100 | ||||||
| Material removed, per cent. of total, 5 min. | —— | —— | —— | 88 | 97 | —— | ||||||
| Material removed, per cent. of total, 6 min. | —— | —— | —— | 92 | 102 | —— | ||||||
| H. P. per ounce sand | 0. | 047 | 0. | 143 | 0. | 06 | 0. | 195 | 0. | 44 | 0. | 223 |
| Ounces sand per minute | 1. | 5 | 2. | 0 | —— | 0. | 92 | 1. | 02 | 2. | 11 | |
The results of these tests at the higher vacua are shown graphically in [Fig. 19]. Comparison of these curves with those obtained when removing sand from a long napped carpet ([Fig. 18]), shows:
First, a marked increase in the efficiency of Type A renovator, this being slightly better than obtained when cleaning a dirty carpet.
Second, practically no change in the efficiency of Type C renovator.
Third, a small decrease in the efficiency of Type F renovator, which still shows a much higher efficiency than when cleaning dirty carpets.
In order to determine how much, if any, of these changes in the behavior of the renovators was due to the increase in the quantity of material to be removed, the horizontal line, representing 1 oz. of sand remaining in the long-napped carpet, was drawn on [Fig. 18] and, using this as a base line, it will be seen that Type A renovator removes this remaining material in three minutes, the same time as was required to remove the same amount from the short-napped carpet. However, the first 4¹⁄₂ oz. of sand have been removed from the long-napped carpet in three minutes, or at a rate 4¹⁄₂ times as fast as the last 1 oz. was removed. This indicates that the narrow slot renovator is capable of handling more material than is likely to be encountered in any dirty carpet and that the apparent decrease in the efficiency of this renovator is not due to the increased quantity of material to be removed.
FIG. 19. CLEANING TESTS USING 1 OZ. OF SAND PER SQUARE YARD OF CARPET.
It will be noted that the Type C renovator removed the last 1 oz. per square yard from the long-napped carpet in the same time that was required by Type A renovator, while it needed nearly twice as long to remove this amount of material from the short-napped carpet ([Fig. 19]). This renovator, however, was slower in removing the first 4¹⁄₂ oz. per square yard.
Type F renovator removed the last 1 oz. per square yard from the long-napped carpet in two minutes, while it required twice this time to remove the same amount from the short-napped carpet. This renovator also removed the first 4¹⁄₂ oz. per square yard from the long-napped carpet in two minutes, while it required three minutes for Type A and 3-³⁄₄ minutes for Type C renovators to remove the same quantity. It is, therefore, evident that sand is removed more rapidly from a long than from a short-napped carpet when a wide slot renovator is used. The same time is required to remove small quantities of sand from a long or short-napped carpet with a narrow slot.