Coating apparatus – Projection or spray type – Work-supported and guided carriage
Reexamination Certificate
1999-04-12
2001-01-09
Edwards, Laura (Department: 1734)
Coating apparatus
Projection or spray type
Work-supported and guided carriage
C118S317000, C118S215000, C118S254000, C118SDIG001, C134S16700R, C134S16800C
Reexamination Certificate
active
06171398
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of apparatus for coating a conduit surface. More specifically, the present invention discloses an apparatus to accurately elevate a coating device to coat the inner surface of a conduit.
2. Statement of the Problem
Conduits are often used to carry fluids or abrasive slurries as part of a treatment or disposal process. As the fluid passes through the conduit, frictional forces against the conduit walls can cause the conduit walls to wear. The effect of these frictional forces is magnified on the curved portions of the conduit as a result of complex flow patterns and the forces from the fluid impacting the conduit surface caused by the fluid changing direction. Abrasives suspended within the fluid (e.g., solids commonly associated with mining slurries or sludge) can be even more detrimental to the conduit walls. Whatever the cause, these forces cause the conduit walls to wear even faster, eventually causing the conduit walls to crack or burst where the walls have worn thin.
To minimize the effects of these frictional forces on the conduit walls, a protective coating is applied (e.g., welded or sprayed) to the inner surface of the conduit. To provide effective protection against wear on the conduit wall, it is important that the entire area is completely coated with the coating material. Areas left unprotected will continue to be vulnerable to fracture.
An example of the prior art in this field is disclosed in U.S. Pat. No. 4,513,443 (Kostecki). Kostecki discloses an apparatus for coating an internal wall of a curved conduit with a layer of protective material. The apparatus has a guide means, a longitudinally flexible member, means for mounting a coating means for incremental rotation by the longitudinally flexible member, a drive means to drive the longitudinally flexible member relative to the curved conduit, and a means to automatically step the flexible member and consequently rotate the coating means. However, a disadvantage of using the flexible member in Kostecki is the associated inaccuracy in translating the rotational steps along the longitudinally flexible member. Because the coating means cannot be accurately rotated, the protective material can be misapplied resulting in either gaps or overlap between the applied strips of protective material.
A need exists to provide an apparatus to coat the internal walls of a conduit without sacrificing accuracy. In other words, conventional coating apparatus use a drive means remotely located from the coating device to elevate the coating device. As a result, error is introduced as the elevation drive is longitudinally translated from the remote position of the drive means. Consequently, portions of the conduit wall may be left unprotected. Alternately, in an attempt to eliminate unprotected surfaces, the spray pattern is severely overlapped, thus wasting the coating material.
3. Solution to the Problem
None of the prior art references uncovered in the search show an apparatus to coat a surface of a conduit having a center rod that provides for longitudinal movement of an index motor having a fixed rotational orientation relative to the center rod and positioned near a coating device so that the coating device is elevated directly proportionate to the index motor step to accurately coat the conduit wall. Therefore, the elevation of the coating device must be precisely controlled so that gaps are not formed between the strips of protective layer and to eliminate wasted coating material caused by overcorrecting, both potentially introduced by conventional coating apparatus.
SUMMARY OF THE INVENTION
The present invention is an apparatus for coating an interior surface of a conduit. The apparatus has a center rod with a substantially square cross-section that extends axially along the centerline of the conduit. An index carriage slidably engages the substantially square cross-section of the center rod, which ensures that the index carriage maintains a fixed rotational orientation relative to the center rod. An index motor is provided on the index carriage to elevate a coating device to coat the interior surface of the conduit. The coating device is rotationally attached to the index carriage and the index motor has an adjustable index position. Thus, as the index motor is indexed by a fixed angular increment, the coating device is rotated to a rotational position that corresponds to the index position of the index motor. A separate drive motor is carried by a drive carriage and propels the drive carriage longitudinally along the center rod. Generally, at least one intermediate carriage that slidably engages the substantially square cross-section of the center rod translates motion of the drive carriage to the index carriage so that the index carriage, and hence the coating device moves longitudinally along the center rod within the interior of the conduit. By positioning the index motor near the coating device and providing a center rod that moves the index carriage longitudinally while maintaining a fixed rotational profile, the rotational position of the coating device can be accurately controlled so that the entire interior surface of the coating device is coated without overlap or gaps in the coating.
A primary object of the present invention is to provide an apparatus to coat an internal surface or wall of a conduit with a layer of protective coating.
Another object of the present invention is to provide an index motor mounted near the coating device to reduce elevation errors such as those associated with the translational elevation changes from an index motor that is mounted remotely from the coating device. Thus, the coating device of the present invention can be accurately elevated so that the entire conduit wall is coated without undue overlap or gaps between applied strips of protective coating.
Yet another object of the present invention is to provide a substantially square center rod and carriages that can be moved or slid longitudinally parallel to the center rod without rotating about the center rod. As such, the present invention provides increased accuracy with which the coating device is elevated.
These and other advantages, features, and objects of the present invention will be more readily understood in view of the following detailed description and the drawings.
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Dorr, Carson , Sloan & Birney, P.C.
Edwards Laura
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