Renovator No. 2 had a cleaning slot 9¹⁄₂ in. long and ¹⁄₄ in. wide, the face of the renovator being approximately ⁷⁄₈ in. wide and practically a plain surface, a typical Type B renovator.
Renovator No. 3 had a cleaning slot 7¹⁄₄ in. long and ¹⁄₈ in. wide, the face of the renovator being ³⁄₈ in. wide and the edges slightly rounded, a typical Type A renovator.
The carpet used was a Colonial velvet rug with ¹⁄₈-in. nap, closely woven, containing 6 sq. yds. This rug was filled with 12 oz. of dirt taken from separators of cleaning machines, from which the lint and litter had been screened. This was rubbed into the carpet until no dirt was visible on the surface, the surface being then lightly swept with a brush and weighed.
In cleaning this carpet the renovator was passed once over the entire surface at the rate of about 70 ft. per minute. This required six strokes and 50 seconds for No. 1 cleaner, nine strokes and 77 seconds for No. 2 cleaner, and 12 strokes and 100 seconds for No. 3 cleaner.
The carpet was then weighed, spread down and gone over three times, weighed, spread down and gone over four times. This operation was repeated until the carpet came within ¹⁄₂ oz. of its weight when received.
Each of the three renovators was operated with a vacuum of 2 in. at the renovator.
The results of these tests are illustrated by curves 1A, 2A and 3A in [Fig. 23]. This shows that to remove 95% of the dirt the renovator had to be passed over the carpet 20 times for No. 1 renovator, 15 times for No. 2 renovator and 8 times for No. 3 renovator.
Similar tests were then made with each of the renovators, with a vacuum of 4.5 in. of mercury at the renovator. The results are shown by curves 1B, 2B and 3B ([Fig. 23]) These show that to remove 95% of the dirt the renovator had to be passed over the carpet 11 times with No. 1 renovator, 6¹⁄₂ times with No. 2, and 4¹⁄₂ times with No. 3.
These tests are all on the same carpet, with the same quantity of the same dirt and with the renovators moved at the same speed in each case. The comparison of the results should give a fair indication of the efficiency of the different types of renovators at different degrees of vacuum within the renovator and, therefore, form the most conclusive proof of the statements relative to the efficiency of renovators as given in this chapter.
All cleaning tests that the author has observed indicate that the higher the vacuum within the renovator the more rapid and effective the cleaning, and that the efficiency of the renovator is fully as high with a small as with a large volume of air passing through the renovator and with the same degree of vacuum within same. Therefore, the most effective and economical renovator should be that which gives the highest vacuum with the least air passing.