Fluid handling – Systems – Multi-way valve unit
Reexamination Certificate
1999-06-02
2001-03-06
Fox, John (Department: 3753)
Fluid handling
Systems
Multi-way valve unit
C137S312000, C137S625160, C210S340000
Reexamination Certificate
active
06196267
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a valve having a rotatable cock plug body for selectively controlling the flow of a fluid from an inlet port to a selected one of at least two outlet ports. Such a valve is particularly suitable to be used for controlling the flow of molten thermoplastic polymer material to either selected one of two melt filters of an apparatus or plant for producing thermoplastic sheet goods.
BACKGROUND INFORMATION
Melt flow control valves of the above mentioned general type are typically used in extrusion plants especially for controlling the flow of the polymer melt to large-surface-area melt filters.
Such valves are conventionally embodied as three-path valves and serve to control the flow of the melt into and out of the respective filter chamber or chambers. In double melt filter arrangements, one filter chamber is respectively operational at any given time, i.e. being used for filtering the melt during the extrusion production process, while the other filter chamber is being cleaned and equipped with a new filter cartridge. The used filter cartridge is cleaned in a space or chamber that is especially provided therefore and is then prepared for reuse.
Control of the melt flow respectively to the two filter chambers is typically provided by two conventional three-path valves, which are available and are utilized in different embodiments having single cylindrical or conical cock plug bodies, double cylindrical or conical cock plug bodies, spool-type slider valves with a plate construction or spool-type slider valves with cylindrical valve stems or valve bodies.
Spool valves or slider valves provide a disadvantageous flow guidance of the melt and furthermore have relatively long melt flow paths in comparison to the cock-type valve embodiments. Such long flow paths cause problems in cleaning, waste of material, and difficulty in controlling the characteristics of the melt material during its rather long passage through the valve.
While the conventional cock-type valves at least partially avoid the above mentioned problems of slide-type valves, they suffer other disadvantages as follows. Previously known cock-type valves with a rotational drive in an axial direction of the cock plug body conventionally have a radially directed melt inlet as well as a radially directed melt outlet. When such valves are installed in connection with typical vertically-oriented melt filter arrangements, it is disadvantageously necessary to provide respective separate valve drives from above the filter and from below the filter. With such an arrangement, it is not possible to achieve a synchronization of both valves by using a rigidly interconnected shaft, for example, especially due to the relatively high rotational moments and the opposite rotation directions that are involved in the two valves. Moreover, the space is rather limited, especially underneath the filter arrangement, and for this reason, problems arise in the installation, operation and maintenance of the respective plant utilizing such conventional embodiments of melt flow control valves having axial rotational drives.
In double cock-type valves, both the melt inlet as well as the melt outlet are provided and controlled by a single cock, whereby operating advantages are achieved, but the melt feed channels and melt lines need to be substantially longer and therefore the additional cleaning effort and complication is considerably increased.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the present invention to provide a melt flow control valve embodied in such a manner that the flow paths through the valve are kept rather short to provide improved cleaning possibilities, and that the drive for the rotatable cock plug body is arranged in such a manner to allow convenient installation and operation and to locate the drive arrangement substantially outside of the range of thermal radiation coming from a melt filter or the like. The invention further aims to reduce or completely avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as apparent from the present specification.
The above objects have been achieved in a melt flow control valve adapted to selectively control the flow of a flowable molten thermoplastic polymer from a melt inlet port to a selected one of at least two melt outlet ports provided in a valve housing. The valve further includes a rotatable cock plug body that is arranged within the valve housing and that has at least one flow channel therethrough including an inflow portion and an outflow portion to respectively provide the selected connection between the melt inlet port and the selected melt outlet port. Especially according to the invention, the melt inlet port extends substantially axially relative to the valve housing and the cock plug body, i.e. parallel to the rotation axis of the cock plug body, and axially connects to the inflow portion of the flow channel of the cock plug body, while the radially inner ends of the melt outlet ports extend substantially radially relative to the cock plug body and respectively communicate with the outflow portion of the flow channel of the cock plug body. Further according to the invention, pre-flooding passages extend from the flow channel in such a position so as to simultaneously connect both the first and second melt outlet ports of the valve housing with the flow channel when the rotatable cock plug body is in a prescribed rotation position.
An essential feature of the inventive melt valve arrangement is that it uses a single rotatable cock plug body arranged in a valve housing having a melt inlet port that is oriented axially relative to the cock plug body, and melt outlet ports that extend generally radially relative to the cock plug body. The inventive valve arrangement further includes a special packing and an additional tapering seal lip at the inlet port to achieve an effective sealing of the relatively large cross-section of the melt flow channel. Furthermore, this seal lip is so configured and arranged that it achieves an ever increasing surface pressure on the cooperating seal edge of the cock plug body as the melt pressure increases. The additional axial pressure or thrust of the melt acting on the cock plug body (which results from the axial arrangement of the inlet port) is taken up by a generally conventional axial bearing, which is permanently lubricated with a one-time high temperature resistant grease filling or packing, which is fully adequate in view of the relatively small rotational movement to which it is subjected.
In view of the narrow gap between the cock plug body and the valve housing, the sliding or gliding surfaces of the respective components are provided with a special surface treatment. Particularly in this context, the cock plug body is coated with a hard-facing or hard-casing material in the micron range, and the housing is nitrided. In this manner, the possibility of counterabrading and seizing of the cock plug body in the housing is reliably prevented. As an additional measure to prevent counterabrading and seizing of the cock plug body in the housing, the invention further provides that the cock plug body is rotated through a few minutes of rotational angle by a drive motor, either continuously or at specified time intervals. This procedure is carried out because the danger of counter-abrading and seizing is especially high after a long operating time of the system without an exchange or replacement of the filters, i.e. without a switching of the valve state.
Especially when the valve is used in connection with a melt filter arrangement, it is necessary that the valve switching process be carried out in such a manner that a small rotation of the cock plug body will leave open or maintain the previous prevailing flow direction and also already slightly open the new flow direction into the cleaned filter chamber. In this manner, the inventive valve ensures that the new filter and particularly the entire new filter chamber can be flooded with molten
Bock Udo
Mueller Friedrich
Rutz Andreas
Fasse W. F.
Fasse W. G.
Fox John
Lindauer Dornier Gesellschaft mbH
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