Conveyors: fluid current – With means to control conveying fluid or movement of load in... – Control of conveying fluid
Reexamination Certificate
1999-09-10
2001-10-30
Ellis, Christopher P. (Department: 3651)
Conveyors: fluid current
With means to control conveying fluid or movement of load in...
Control of conveying fluid
C406S093000
Reexamination Certificate
active
06309144
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to air conveyor systems and more particularly to flow control in air conveyor systems.
2. Description of the Related Art
In general, air conveyance systems are accumulators where the conveyor fills with product and then empties out. Common applications of air conveyor systems include handling two piece aluminum cans and blow molded plastic bottles.
An air conveyance system provides motive force to the product being conveyed through momentum transfer from an air jet to the product. When the system is full of product, the air pressure must be set high enough to clear out the entire weight of all the product present. When the system is empty and single items are moving through the system, there is a tendency for the single objects to move too fast and either become damaged or jammed. The difference between accumulated and unaccumulated flow may be analogized to the difference between bumper-to-bumper rush hour traffic and single cars moving at the speed they choose.
A conventional two pressure design is shown in FIG.
1
. In this design, a blower
50
pressurizes a plenum
54
which supplies air
56
to the jets
58
which impart momentum to the product. When the sensor tells the control system that the subject fan zone has become accumulated (i.e., backed up), then the automatic damper
62
opens, supplying more air
56
into the plenum
54
. Inlet dampers, outlet dampers, and variable speed drives which change the motor's revolutions per minute (RPM) have been-used as methods for changing plenum pressure.
A second conventional two pressure design is shown in FIG.
2
. In this design the plenum is split by a divider
68
. A blower
70
pressurizes the primary plenum
74
, and multiple dampers
78
in parallel regulate the flow of air
80
into the secondary plenum
82
. Louvers which form the air jets
86
that drive the product are connected to the secondary plenum
82
. U.S. Pat. No. 5,222,840 is representative of this type of conventional design.
A disadvantage with the first approach is that the length of the control zone is the same as the blower zone. Once the control zone becomes too long then the advantage of the two pressure system is lost. The sensor which switches the zone to high pressure must be located so far from the upstream end of the zone that the product has a chance to gain terminal speed before hitting the back end of the accumulated pack—thereby causing damage to the product and to the pack.
Moreover, the use of smaller blowers and a shorter blower zone in order to shorten the control zone increases both the cost of the equipment and the cost to install it. Lastly, a disadvantage with the second approach is the sheet metal fabrication cost to divide the two plenums.
SUMMARY OF THE INVENTION
The present invention is an air conveyor system which has a blower in communication with a plenum. The blower provides air to the plenum to move the objects within the plenum. The present invention includes a plurality of dampers disposed at predetermined locations along the plenum with the dampers being normally open. A sensor device senses the location where the objects have accumulated within the plenum. Furthermore, the present invention includes a closing device for closing the damper which is at the location where the objects have accumulated within the plenum. The closing of the damper is based upon the sensed accumulated location.
The present invention also includes a system for moving objects within a plenum that includes a variable speed blower for providing air to move objects within the plenum. The objects are either in an accumulated or unaccumulated state within the plenum. A velocity measuring device measures the velocity of the objects, and an adjustment device which is connected to the velocity measuring device adjusts the speed of the blower to a predetermined speed based upon the velocity of the unaccumulated objects. A velocity measuring device uses the two pressure system with short control zones.
REFERENCES:
patent: 4515503 (1985-05-01), Snowdon
patent: 4715748 (1987-12-01), Krambrock
patent: 4909676 (1990-03-01), Heep et al.
patent: 5071289 (1991-12-01), Spivak
patent: 5145253 (1992-09-01), Paul et al.
patent: 5220840 (1993-06-01), Ingraham et al.
patent: 5247722 (1993-09-01), Leifeld
patent: 5407305 (1995-04-01), Wallace
patent: 5738467 (1998-04-01), Aidlin et al.
Advanced Manufacturing Technology
Crawford Gene O
Ellis Christopher P.
Harness & Dickey & Pierce P.L.C.
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