Coating apparatus – Control means responsive to a randomly occurring sensed... – Responsive to attribute – absence or presence of work
Reexamination Certificate
1998-10-30
2001-11-27
Lamb, Brenda A. (Department: 1734)
Coating apparatus
Control means responsive to a randomly occurring sensed...
Responsive to attribute, absence or presence of work
C118S125000, C118S405000, C118SDIG001
Reexamination Certificate
active
06322630
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to apparatus and methods for coating elongated substrates and, more specifically, for coating substrates such as fiber optic cable, metallic cable, wire, cords, filaments, and strength members.
BACKGROUND OF THE INVENTION
During the manufacture of elongated substrates, such as wires or cables, it is common to coat the wire or cable with an exterior thermoplastic coating. These exterior coatings can serve several purposes such as thermal and electrical insulation, corrosion protection and water blocking. The quality of the wire or cable is heavily dependent upon the quality of the exterior coating. If the coating is of inferior quality, uniformity or integrity, the performance of the wire or cable may be severely diminished. The characteristics of the coating are affected by both the coating material itself and the coating apparatus.
In more basic coating techniques, a continuous length of wire or cable simply passes through a heated slurry bath of coating material. As the wire or cable pass through the bath, the coating material adheres to the exterior of the wire or cable to provide the desired protective coating. The slurry bath technique, however, may yield marginally acceptable finished coatings, especially for those substrates requiring uniform and homogenous coatings. The slurry bath technique lacks the precise control needed to produce a consistent, high-quality coating on a substrate. The coating material in a bath may also be subject to increased contamination. Additionally, during an interruption in the manufacturing process, the wire or cable may not be easily removed from the heated slurry bath. As a result, temperature sensitive substrates may be damaged when exposed for extended periods to the bath.
In an effort to improve the quality of the coating on wires and cables, for example, coating systems have been designed with one-piece heated dies to apply the thermoplastic coating instead of a slurry bath. In such systems, a wire or cable is threaded and continuously moved through an aperture in the one-piece die. The coating material is then dispensed through the die and around the wire or cable. By employing a dispensing die, the amount or thickness of coating material applied to the substrate can be controlled in a precise manner.
The one-piece die coating technique, however, does have disadvantages. For instance, if the production line stops while the wire or cable is being coated, the wire or cable typically remains within the heated die. For temperature sensitive substrates, such as fiber optic cable, the continuous contact with the heated die may cause damage to the substrate itself. Additionally, one-piece dies do not provide for easy removal of the wire or cable. For instance, to remove the wire or cable from the one-piece die, one end of the wire or cable must pass through and exit the die. Although the wire or cable could be cut at the one-piece die to facilitate easier removal of the substrate from the production line, typical manufacturing techniques require the production of continuous rolls of wire or cable.
For at least these reasons, it would be desirable to provide a coating apparatus that would have the advantages of a one-piece die, but fewer disadvantages thereof. For example, it would be desirable to easily retract the die away from an underlying substrate, such as temperature-sensitive fiber optic cable, during a production interruption. Such a retractable dispenser system would also readily permit installation or removal of the wire or cable during the manufacturing process.
SUMMARY OF INVENTION
The present invention overcomes various shortcomings of previous coating systems and techniques. The present invention is generally directed to an apparatus for coating many forms of elongated substrates, such as wire, metal cable, fiber optic cable, cords, filaments, or strength members. The coating apparatus has first and second dispensers which are preferably ON/OFF dispensing valves, guns or modules, with each dispenser having a liquid passageway adapted to connect to a source of heated liquid, such as a heated thermoplastic liquid. The dispensers may take many other forms suitable for dispensing a controlled amount of liquid. The first and second dispensers are disposed opposite one another and first and second actuators preferably move the dispenser in opposing directions to closed and open positions with respect to the elongated substrate. At least one actuator control device controls the respective actuators. Preferably, the actuators are pneumatic pistons and the actuator control device is a 4-way solenoid valve. One or both dispensers may move along straight or arcuate paths to establish the closed or open position. As one alternative, the first dispenser could remain stationary and an actuator could simply move the second dispenser relative to the first dispenser to reach the open or closed position. However, if the substrate is temperature sensitive, such as fiber optic cable, it is preferred that both dispensers automatically move away from the cable to prevent heat damage to the cable in the event that the coating process stops.
In the preferred embodiment, the apparatus also has first and second mouthpieces connected respectively with the first and second dispensers. The mouthpieces have complimentary recesses such that when the first and second dispensers are in their closed position the recesses form a throughhole, preferably oriented perpendicular to the longitudinal axes of the dispensers, for receiving the elongated substrate. The recesses in the first and second mouthpieces, for example, preferably include arcuate portions for generally conforming to a round wire or cable. Each recess communicates with the liquid passageways in the dispensers such that when the first and second dispensers are in their closed position an elongated substrate passing through the throughhole may be coated with the liquid coming from the liquid source. Generally, a stepped bore is formed in the throughhole with a smaller diameter portion thereof receiving the substrate only and a larger diameter portion receiving the substrate and the coating liquid.
The coating apparatus also includes first and second liquid discharge pieces that are respectively disposed between the first and second dispensers and the first and second mouthpieces. Each liquid discharge piece has a liquid discharge orifice which is in fluid communication with the liquid passageways of the first and second dispensers. Finally, in the preferred embodiment first and second shims are respectively disposed between the first and second liquid discharge pieces and the respective first and second mouthpieces to form a liquid discharge channel which is in fluid communication with the liquid discharge orifice.
As an additional feature, a guide member is adapted to align and support the elongated substrate as it passes through the throughhole during a coating operation. As still another feature, the mouthpieces include alignment members which align the throughhole with the substrate to further assure uniform, concentric coating of the substrate.
The present invention is also directed to methods for coating an elongated substrate, such as a wire or cable, generally involving the use of coating apparatus such as described above. Using the present invention, a continuous coating may be applied to a substrate or, in the alternative, an intermittent or broken coating may be applied to satisfy the needs of the user. Using a sensing device to detect when the substrate stops moving or when the coating process otherwise stops, the actuator control device and actuators cause the dispensers to retract away from the substrate, for example, to prevent heat damage.
The coating apparatus and methods of the present invention have several advantages. For instance, the aligned mouthpieces of the coating apparatus provide a uniform, concentric coating around, for example, wires and cables. Additionally, the dispensers and associated mouthpieces can au
Carroll Kenneth P.
Cushing David
Evans Greg
Lamb Brenda A.
Nordson Corporation
Wood Herron & Evans L.L.P.
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