1. Field of the Invention
This invention relates to structure for diverting articles out of a continuous conveying path and, more particularly, to a structure for controllably discharging diverted articles to prevent localized accumulation.
2. Background Art
In conventional glass molding operations, molten glass at approximately 2300.degree.-2600.degree. F. is conveyed continuously in discrete volumes called gobs to mold cavities at a molding station. The size of the gob is dictated by the size of the part, such as a bottle or the like, that is being formed on a particular run.
Typically, a continuous stream of molten glass flows from a furnace and is separated or cut into the gobs, which are conveyed continuously to the molds. As a general rule, once the furnace is tapped and molten glass flow starts, conveying of gobs from the furnace is carried out continuously through a campaign, which may last from 3-5 years.
In the event that a mechanical problem is encountered at the molding station downstream of the furnace or in the event that a mold change is required, it may be necessary to interrupt the molding operation. However, the conveying of the gobs will nonetheless proceed and provision must be made to divert the gobs from their normal route taken to the molding station. Handling the diverted gobs has posed a serious problem to the industry. The high temperature gobs must be accumulated in a form that facilitates recycling and cooled without endangering workmen operating the system.
Heretofore, two types of structure have been used to accommodate the diverted gobs. One of these is called a tap box. A tap box is essentially a steel container with drilled holes to allow the escape of a cooling fluid which is used to quench the gobs collected in the container. However, the industry is moving away from tap boxes principally because they require the supervision of several workmen to keep up with glass flow and are extremely dangerous to work around. The high temperature gobs, when quenched, may tend to explode into shattered particles generally the size of pea gravel and pose a serious health hazard to those in the vicinity of the tap box. Additionally, the glass gobs accumulate to form a solid mass which is difficult to handle and recycle.
As an alternative to the tap box, water filled, vibratory conveyors have been used to intercept, cool and accumulate the diverted gobs. An apparatus suitable for use in a glass molding system is shown in U.S. Pat. No. 4,171,948, to Kraus et al. In Kraus et al a trough contains a predetermined level of cooling fluid and is vibrated to continuously convey material through the fluid between an entry and an outlet end, with the latter residing above the level of the cooling fluid. The gobs entering the fluid explode due to thermal shock upon encountering the fluid.
One problem with conventional systems, such as that in Kraus et al, is that the chute which directs the gobs onto the conveyor is fixed so that the gobs are directed onto a single location on the conveying trough. With a steady flow of gobs, such a system is highly acceptable. However, during an upset period, wherein all gobs are diverted out of the main stream, maximum reject rate occurs and several problems may develop.
First, the chutes and conveyor may experience a substantial temperature elevation. The gobs contacting the heated chute remain partially melted and may adhere thereto. Rapid buildup as far back as the molding station may occur and with the resulting heat concentration a fire may erupt and/or dangerous overflow of molten glass may occur.
Another problem is that as the temperature of the bath increases, the gobs will not effectively explode and distribute themselves in the trough, which action is normally relied upon by systems designers, resulting in a buildup at the entry portion of the conveying trough. At high flow rates, this condition can deteriorate to the point that some of the gobs may not be immersed and may move off of the trough end in clumps at dangerously high temperatures. Again, a serious threat to the health of workmen is apparent.
Still further, the unexploded gobs do not convey at the same rate through the fluid as the shattered glass particles. This may result in a backup as far as the chute, with the consequences apparent.