This property of the renovator raises the question whether the quantity of air or the degree of vacuum in the renovator is most essential for the removal of dirt from carpets. Tests made by Mr. S. A. Reeve, consulting engineer for the Vacuum Cleaner Company, with this type of renovator, with the inrush open and repeated with the inrush closed, disclose the fact that it does more effective cleaning with its inrush closed, while the volume of air passing is considerably less with the inrush closed. The degree of vacuum was greater, which tends to indicate that the vacuum within the renovator is the most important factor.
An extract from the affidavits of Mr. Reeve in one of the numerous patent suits will show his explanation of this phenomenon: “If we examine more closely into the actual process whereby such a sweeper succeeds in extracting dust from carpets, etc., it will appear that the actual cleaning is effected at the periphery of the slot in the lower surface of the sweeper. It is accomplished chiefly by the development of local changes of air pressure at the lips defining this slot, incidentally to the movement of the tool over the carpet. These changes cause the air occupying the interstices between the dust particles to expand suddenly, thus ‘raising the dust.’ To a lesser degree, the scouring is effected by highly localized air currents of considerable velocity, engendered where the tool comes in contact with the carpet. These air currents pick up the dust which has already been expanded or raised by pressure change. They will be of higher velocity, and therefore more effective, the better the contact of the tool with the carpet. The same is true of the pressure changes.
“All this action depends for its intensity, speed and effectiveness, not on the vacuum existing at the pump or in the separators, but upon the vacuum prevailing within the sweeper head itself.”
Renovator with Two Cleaning Slots.
—Another form of renovator was introduced by the Blaisdell Machinery Company which contained two cleaning slots each ³⁄₁₆-in. wide and 12-in. long, separated by a partition ¹⁄₄-in. wide in contact with the surface of the carpet, as indicated in [Fig. 14] (Type D). While this form of renovator has a greater area of cleaning slot than Type A, its individual cleaning slots are no wider; therefore, it cannot pick up anything larger than can be picked up by Type A. As no air can enter under the partition it can do no more effective work as a dust remover when operated on a carpet with a glue-sized back and its only advantage over a cleaner of Type A is that when operated on a loose-fabric carpet more air can pass through the fabric into the cleaning slot, thus giving a greater variation in the quantity of air exhausted when operated on carpets of different texture, a condition which is undesirable when used with a system having characteristics previously described.
Tests of this type of renovator, made by Mr. Reeve, are given later in this chapter.
Renovator with Inrush Slots on Each Side.
—Another form of renovator, introduced by Mr. Moorhead, is illustrated in [Fig. 15] (Type E). This is a modification of Type A in that an inrush slot is provided on each side of the vacuum slot, these inrushes being hinged members which form the sides of the cleaning slot. This cleaner has the advantage over Type C renovator in that it can take air from either side, but in action it takes air from but one side at any time. Its inrush will not become entirely clogged, but its mechanically-moving parts in contact with the dust and lint picked up will easily become inoperative and are as like as not to become caught wide open when the air entering the cleaner will not come into intimate contact with the carpet. In that event, its cleaning efficiency will be greatly reduced. The author has not had an opportunity to make any comparative tests of this form of renovator.
When Mr. Spencer introduced the centrifugal fan as a vacuum producer, he also brought out a series of carpet renovators of various forms and sizes. One had a cleaning slot ³⁄₄-in. wide and 10-in. long, another a slot 15-in. long, ¹⁄₄-in. wide at its end, increasing to ³⁄₄-in. at the center. Another had a slot 20-in. long and ³⁄₈-in. wide, and finally he adopted a tool with a cleaning slot 15-in. long and ¹⁄₂-in. wide throughout its length. This is merely the re-entrance into the field of the wide-slot tool first used by Mr. Kenney and its successful operation depends on its use with a vacuum producer of such characteristics and a hose and pipe line of such proportions that practically a constant vacuum is maintained within the renovator, regardless of the quantity of air passing through the tool. The latest form of this renovator, as used by Mr. Spencer, is illustrated in [Fig. 16]. At the time that the writer made tests on renovators of this make, the majority of the tests were made with a renovator having a cleaning slot 10-in. long and ³⁄₄-in. wide. This renovator is designated as Type F, while the 15-in. × ¹⁄₄-in. to ³⁄₄-in. slot is designated as Type F¹.
