Weighing scales – Weigher responsive material control – Plural chambers
Reexamination Certificate
1999-10-13
2001-05-22
Gibson, Randy W. (Department: 2859)
Weighing scales
Weigher responsive material control
Plural chambers
C177S105000, C177S145000, C177S120000, C198S358000, C198S368000, C198S370010, C198S463400, C222S055000, C222S056000
Reexamination Certificate
active
06235998
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to an improved product conveyor apparatus and, in particular, to a product conveyor apparatus which provides for efficient dispensation of the product on the first run through the product conveyor by use of a stopper gate. A plurality of stopper gates are positioned adjacent to a plurality of slide doors in the bottom of the product conveyor and controlled in order to limit the amount of product that is recycled along the recirculation conveyor. The invention greatly reduces the potential for product staling due to excessive product recirculation.
2. Description of Related Art
A vibrating conveyor is a commonly used device in the food industry for dispensing products such as potato chips into weighers. In most packaging lines, a product is moved along vibrating distribution conveyors having multiple product weighers placed below and along the length of the conveyor. When a weigher requires product, a slide door opens in the bottom of the distribution conveyor over that particular weigher and drops product onto the weigher. It is possible that the product might pass over all of the weighers without being dropped because none of the weigher doors are open when the product passes over. Rather than simply discarding the product that was not dispensed into the weighers, a recirculation conveyor is typically used to re-route the undispensed product back to the beginning of the distribution conveyor.
An example of a prior art design in this regard is illustrated by FIG.
1
A. Throughout the specification, the same numerals are used to denote like parts.
FIG. 1A
shows a top view of a distribution conveyor
100
with a plurality of slide doors
105
and a recirculation conveyor The distribution conveyor
100
consists of multiple sections of distribution conveyor pans (not shown), each having a plurality of slide doors
105
mounted in the bottom of the conveyor pan. The conveyor pans are vibrated in the direction of product flow
125
. In operation, the pan drops downward and in the opposite direction of product flow, and then lifts upward and forward in the direction of product flow
125
. In this manner, the product is moved to a higher elevation at the end of each distribution conveyor pan before it is dumped onto the next distribution conveyor pan at a lower elevation.
The slide doors
105
are controlled by a weigher underneath the door
105
which sends a signal to open the slide door
105
when more product is needed. Thus, each slide door
105
operates independently of the other slide doors
105
. The recirculation conveyor pans are similar in operation to the distribution conveyor pans except that they do not have slide doors, operating simply to move the product back to the initial stage
120
of the distribution pan.
FIG. 2A
shows the distribution conveyor
100
in operation. The product
200
, such as potato chips, comes out of the kitchen and is deposited onto the initial stage
120
of the distribution conveyor
100
. It then passes over multiple slide doors
105
until it is dropped into an open slide door
105
. If it passes over all of the slide doors without being dropped, then it is deposited onto the upstream end
130
of the recirculation conveyor
115
and re-routed back to the initial stage
120
of the distribution conveyor
100
. In a typical system, approximately 20% of the product is re-routed down the recirculation conveyor back to the distribution conveyor. A significant portion of this 20% will get re-routed a second or third time. It is conceivable that some portion of the product will never get dropped during a given product distribution run.
The longer the product remains on the conveyor, the more it cools and, consequently, the ore moisture that is absorbed by the product. As the product is circulated from the distribution conveyor
100
to the recirculation conveyor
115
and back to the distribution conveyor
100
, it will decrease in temperature to the point that the vapor pressure of the product is exceeded by the surrounding atmosphere. When this happens, the product absorbs moisture from the atmosphere, increasing its moisture content. Excess moisture in a packaged product can lead to premature staling. The shelf life of the packaged product is therefore reduced when the product makes a subsequent pass on the distribution conveyor
100
. Furthermore, even if only a portion of the product packaged in a bag bad been recirculated, the absorbed moisture of the recirculated product would also affect the product that had not absorbed any moisture, causing it to go stale faster as well.
Environmental conditions of the room can be controlled by increasing the temperature and decreasing the humidity. This is not a feasible solution because the equipment needed to control the environment in the room is extremely expensive to purchase, operate, and maintain. Another alternative is to keep the product warmer by using infrared heaters placed above the product. Using this method to keep the product warm, the product could theoretically be circulated for hours at higher than room temperature without absorbing moisture from the ambient air. However, the obvious shortcoming of this solution is that it would require an electrical or gas energy source. This added energy cost decreases the profitability of the operation and makes it a much less attractive solution. Further, maintaining the product at an elevated temperature for an extended period of time could affect the characteristics and quality of the product.
Thus, the best solution is to develop a method and apparatus for dispensing the product into the weighing mechanism as soon as possible after it enters the packaging line, preferably on the first pass of the product through the distribution conveyor. When packaged in this manner, the product does not have time to cool down and absorb moisture from the ambient air before it is packaged in a vapor-proof bag.
SUMMARY OF THE INVENTION
The present invention decreases the length of time that the product remains on the distribution conveyor by utilizing a plurality of stopper gates to ensure that over 95% of the product is packaged on the first pass through the distribution conveyor. Each of the stopper gates are placed adjacent to a slide door near the end of the distribution conveyor. In operation, the stopper gate is rotated downward into the closed position so that the product may not get past the stopper gate. A sensor is used to determine the product level so that if the product level reaches a predefined height in the distribution conveyor, the stopper gate will automatically open and allow the product to pass on to the recirculation conveyor. Because the stopper gate is placed adjacent to a slide door in the distribution conveyor, it holds a product there for a length of time which usually allows the product to drop into that particular slide door so that it is packaged on the first run, rather than on a second or subsequent recirculation.
Although only one stopper gate is operational at any given time, multiple gates are used to provide for the situation in which the slide door closest to the downstream end of the conveyor is inoperable because the weigher associated with that slide door is not accepting product. In such a case, the next stopper gate upstream would be the operational gate. By providing three or more stopper gates, it is highly unlikely that all three of the slide doors adjacent to the stopper gates would be inoperable. Thus, more assurance is provided that the product will be packaged on the first pass through the distribution conveyor.
A computer control device is used to continually time the slide door actuation to determine which one is the last operational weigher so that the appropriate stopper gate may be closed. A timer is also provided to determine bow long the sliding door is closed. If the sliding door is closed for a pre-determined time, then it is assumed that the weigher is inoperable at that sliding door, and the stopper gate is opened.
The a
Cahoon Colin P.
Carstens, Yee & Cahoon
Gibson Randy W.
Recot Inc.
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