Brushing – scrubbing – and general cleaning – Machines – With air blast or suction
Reexamination Certificate
2001-10-29
2004-06-01
Till, Terrence R. (Department: 1744)
Brushing, scrubbing, and general cleaning
Machines
With air blast or suction
C015S340100, C015S347000
Reexamination Certificate
active
06742219
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a surface cleaning apparatus and more particularly to an air sweeping apparatus.
2. Description of the Prior Art
Recirculating air systems have been in use for many years and are preferred over vacuum based systems for sweeping large areas. They generally comprise an air stream that is constrained to move along an air circulation loop. The air stream is pressurized, directed onto a surface to entrain debris, drawn by low pressure into a suitable receptacle, filtered and then re-pressurized. In some recirculating air systems some of the air is diverted from the loop and discharged to the atmosphere. These machines may also include brooms to assist in debris removal.
There are at least three types of head assemblies commonly used on recirculating air sweepers. The first type uses a broom or brooms to mechanically sweep debris into a row where it is then drawn up by a relatively small, lower pressure suction head. The second type of head assembly is a cross flow head. This is typically a single chambered head which extends transversely to the direction of motion of the head as it moves along a surface being swept. With this head, air is blown into one end of the head, travels along the length thereof and is then drawn out the other end. The third type of head assembly is a two-chambered head. Here, air fills a first pressure chamber that is above or behind a second pick-up or sweeping chamber. Pressurized air from the first chamber is fed into a gap or nozzle that extends along the sweeping chamber of the head. As the pressurized air exits the gap, it is formed into an air curtain or sheet which is directed towards the surface being swept in a direction substantially coincident with the direction of travel. The pressurized air entrains debris in high velocity turbulent air flow and transports the debris along the sweeping chamber of the head assembly until it is drawn out of the head to a suitable receptacle by low pressure. Once the air stream/debris mixture leaves the head, it is conveyed into a hopper where the debris is separated out of the air stream and collected for later disposal. The air then continues out of the hopper to be re-pressurized after which a majority of the air stream is directed back into the head assembly and the remainder is exhausted to the atmosphere. One example of a sweeper for road or other surfaces is disclosed in U.S. Pat. No. 4,660,248, the sweeper including a pickup head, a hopper into which debris is adapted to be discharged, and a centrifugal separator for filtering the air stream. Other aspects of recirculating air sweepers are disclosed in U.S. Pat. Nos. 4,006,511, and 4,109,341.
The aforementioned recirculating air systems have their drawbacks. One drawback is that as the air stream moves along the sweeping chamber of the head and exits the head, the air stream must make a series of sharp angular turns and starts to spin into a vortex. This results in a reduction in the efficiency of the air stream to entrain and convey debris. This relative inefficiency can be overcome by providing greater air flow through the system, but this requires larger fans, motors, etc.; each of which add to the cost, power requirements, and/or weight of the system.
Another drawback with the aforementioned recirculating air system occurs at the head. Since there is high velocity turbulent air flow in the head, steps must be taken to prevent air from escaping the head while letting debris enter. This is typically achieved with front and rear skirts made from elastomeric materials. The skirting used, however, has limitations. One limitation, for example, is that a relatively pliable front skirt that is able to be deflected by light debris as it passes thereover and is not able to resist the force of air as it is drawn into the pick-up chamber. This results in the skirt being lifted away from the ground and toward the pick-up chamber creating a situation in which clouds of dust may get ejected from the head. This dusting may be reduced by providing a second skirt in front of the first skirt. However, use of such a second skirt has its drawbacks. Some of the debris which is captured between the skirts escapes at the ends, particularly when the air sweeper is cornering, to form trails. Conversely, another limitation is that a relatively stiff front skirt (one that is able to resist the force of air as it is drawn into the pick-up chamber) will not deflect when it encounters light debris. As a result, the skirt plows the lighter material in front of the head. This debris may accumulate between the skirting where it reduces overall efficiency and facilitates dusting and trailing. Yet another drawback occurs at the end wall of the pick-up chamber as it travels over an uneven surface. In operation, a localized high pressure zone is created at the end wall of the chamber. This does not present too much of a problem with relatively smooth surfaces. However, when the end wall of a pick-upchamber passes over a depression such as a pot hole, some of the air and entrained debris blows out of the chamber in yet another dust cloud.
Once debris has been entrained and transported to a suitable receptacle, the debris is usually separated from the air stream. There are several methods used to separate the debris from the air stream. One method mixes water with the dirty air stream. With this system, screens are used to separate larger debris from the mixture leaving the heavy debris to settle out of the water in a holding tank. The water is then recycled through the system. This method has its drawbacks. The water adds excess weight to the hopper and must be periodically cleaned. An additional concern is that of leakage and degradation. The hopper or bin may initially be water tight, but it may develop leaks over time. In other systems, small quantities of water are injected into the air stream to help separate dust from the air stream. This presents a problem, however, because when water is mixed with small or fine particulate matter, mud is formed. This mud clogs filters and reduces the efficiency of the air sweeper. The filters must, therefore, be periodically inspected and serviced to ensure that the air sweeper is operating within normal parameters.
Another method of separation uses the centrifugal force of debris to separate it from a cyclonic air stream. This is not without its drawbacks. One drawback is that the debris extracted from the air stream is often allowed to settle out in a main hopper. There, the debris is subject to internal air currents and may become re-entrained as the air stream swirls about the hopper. Alternatively, the extracted debris is collected in a secondary hopper internal to the main hopper. This alleviates some of the problems of re-entraining, however, the secondary hoppers are usually an afterthought. Additionally, the secondary hopper is usually provided with its own cover. Often, the secondary hoppers are not sealed and are loosely hinged. This allows dust contained therein to leak into the main hopper. Moreover, when emptying the hoppers, the secondary hopper is emptied into the main hopper as the main hopper is being dumped. This precludes continued separation of the differently sized debris and may complicate disposal.
There is a need for an air sweeper which may be adjustably configured depending upon the size and type of debris to be removed and collected from a surface. There is a need for an air sweeper with a collection chamber which is configured to suspendingly contain and transport debris in a predetermined pathway as the debris travels therealong. There is also a need for an air sweeper in which debris is separated according to size and weight, and collected in separate containers which may be accessible for emptying through a common access panel. And there is a need for an air sweeper which is able to remove and collect fine particulate matter from a surface without the assistance of liquids.
SUMMARY OF THE INVENTION
An air sweeper having a head ass
Lenzmeier Michael H.
Wydra Larry D.
Tennant Company
Till Terrence R.
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