Classifying – separating – and assorting solids – Sorting special items – and certain methods and apparatus for... – Sorting bottles – ampoules – jars – drinking vessels – or like...
Reexamination Certificate
1999-12-28
2001-02-20
Walsh, Donald P. (Department: 3653)
Classifying, separating, and assorting solids
Sorting special items, and certain methods and apparatus for...
Sorting bottles, ampoules, jars, drinking vessels, or like...
C209S522000, C209S529000, C209S552000, C209S559000, C209S597000, C198S406000, C198S417000
Reexamination Certificate
active
06189701
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a device for the manufacture of hollow plastic objects, especially stretch-blown plastic bottles, with a conveyor track along which plastic preforms are transported in sequence past at least one inspection station to a molding station for molding the preforms into a desired shape.
BACKGROUND OF THE INVENTION
A type of device and a type of process for manufacturing hollow plastic objects are known in practice. It is customary, especially in the manufacture of plastic bottles, particularly PET bottles, to convey so-called preforms made of plastic from a repository to a molding station. This molding station may include, for example, a heating device in which preforms are heated to the temperature needed for the subsequent stretch blowing process. The final shape of the bottle is then created during the subsequent stretch blowing process.
However, a defectively manufactured preform can cause operating problems if it reaches the heating device and/or the stretch blowing device. For example, damage to the mouth area of a preform may result in leakage during the stretch blowing process. Consequently the preforms are moved past an inspection station in the shape of a mandrel wheel. The individual mandrels of this wheel penetrate the mouth of a preform and scan it mechanically so as to be able to detect certain defects in the mouth area. If a defect is detected, the machine is stopped and an operator must remove the defective preform. Consequently, an operator must be present and the machinery may be subject to downtimes that reduce its output. In addition, there is a risk that the penetrating action of the mandrel wheel may damage the plastic preforms.
SUMMARY OF THE INVENTION
Consequently, the objective of the invention is to further develop a generic device and a generic process so as to ensure that such drawbacks do not occur.
According to the invention, the device features a screening area in which the preforms are conveyed in such a way that they are loosely supported on only one side, and in which is provided a screening apparatus that moves plastic preforms that have been identified as being defective out of the row in response to signals from the inspection station.
The preforms are loosely supported on only one side as they move through the screening area. This enables the screening apparatus to move a plastic preform identified as being defective by the inspection station out of the row. This does not require that any substantial forces or tensions be overcome, as the preforms are only loosely supported in the screening area. An operator is no longer needed and the screening process can take place continuously. There is no need to interrupt production.
A lever-like guide that guides the plastic preforms in the screening area into a pivoted position is provided in an advantageous embodiment of the invention. Because of this pivoted position, it is possible to support the plastic preforms in the screening area on only side while continuing to guide them in a precise manner.
The plastic preforms can be pivoted to any degree, provided it is sufficient to ensure that they remain in their pivoted position. An angle of 50° against a vertical plane progressing in the direction of movement has proven to be especially advantageous.
The device according to the invention is especially suitable for use with plastic preforms that feature a collar in the mouth area. Such plastic preforms may, for example, be used in the manufacture of PET plastic bottles. This type of collar or neck ring is an area along the plastic preform with a larger diameter that allows the preform to be transported by suspending it from this collar. In an advantageous embodiment of the device according to the invention, the lever-like guide features a guide edge that engages the collars of the plastic preforms.
The pivoted position of the plastic preforms in the screening area may, for example, be generated by a surface against which the plastic preforms rest in a pivoted position. In an alternative form of the invention, a guide rail is provided that engages the lower portions of the plastic preforms so as to move them into the pivoted position.
The plastic preforms can be fed along the entire conveyor track in their unilaterally supported pivoted position. However, a method of conveyance that is particularly secure and space-saving comprises guide rails that support the plastic preforms at their collars from two sides. A break in one of these guide rails in the screening area through which the preforms are conveyed in a pivoted position allows for the removal of defective plastic preforms. The pivoted or tilted position in the screening area also provides for secure guidance when the guide rail is interrupted on the screening side.
If the plastic preforms are transported in areas outside the screening area in a primarily vertical position, i.e., a position located in a vertical plane, the lever-like guide is designed in such a way that the plastic preforms are placed into the pivoted position at the beginning of the screening area. In a design in which the lever-like guide consists of a surface, this surface is curved accordingly. If the lever-like guide is comprised, for example, of upper and lower guide rails, these rails are twisted in such a way that they transport the plastic preforms from their primarily vertical position to the pivoted position as they move along the conveyor track.
Guide rails according to the invention may have different shapes. However, it is especially advantageous if the guide rails feature support surfaces that conform to the shape of the collars and lateral surfaces of the plastic preforms. Such support surfaces are advantageously twisted in such a way that they follow the pivoting motion of the plastic preforms. This ensures especially secure guidance.
The screening apparatus can be executed in various ways. For example, a mechanism can be provided that interrupts the loose support of a plastic preform that has been identified as being defective in response to a signal from the inspection station, thus allowing the defective plastic preform to drop downward. However, a particularly simple screening apparatus can be achieved with a pusher that gives the plastic preform a lateral push in response to an error signal from at least one inspection station, thus disengaging the collar of the plastic preform from the guide rail. Disengaging the plastic preform from the guide rail causes the plastic preform that has been identified as being defective to slip downward and into a screening container, if provided. This type of design ensures that the adjacent plastic preforms are not affected by the screening process. The lateral push can be applied to the lateral surface of the plastic preform or to its mouth area.
The pusher may consist of a simple tappet. It may also be provided that the surface of the pusher that touches the preform during the screening process conforms to its external shape. In a simple design, the pusher comprises a prismatic surface that opens in a concave manner relative to the preform being screened out. This type of prismatic surface is easy to manufacture and causes the preform to become centered during the screening process.
The inspection station can be arranged directed in the screening area and can control the screening apparatus directly. A more detailed inspection can be performed if the inspection station is arranged upstream from the screening area and emits a time-delayed signal to the screening apparatus, with the time delay corresponding to the amount of a time a plastic preform needs to travel from the inspection station to the screening apparatus.
In a design of this nature, several inspection stations can be arranged in sequence to test various parameters of the plastic preforms, such as their lateral surfaces.
A fixed value may be established for the time delay between the inspection and the screening process. However, in an enhancement of the invention, an apparatus is provided that allows for monitoring
Beauchaine Mark J.
Krones AG
Tilton, Fallon, Lungmus & Chestnut
Walsh Donald P.
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