The coating feeding system of a coating machine (or composite machine) consists of an upper pressure roller, a coating roller, and a metering roller. Depending on process requirements, the metering roller can be a single roller or an anilox roller. The lower portion of the metering roller is submerged in the paint tank. The coating roller is positioned very close to the metering roller, with a small gap between them. During operation, the surface speed of the coating roller matches the forward speed of the substrate. As the metering roller rotates, it picks up paint from the tank and transfers it to the coating roller. The roller then evenly spreads the paint onto the surface of the metering roller. The substrate is held between the rotating coating roller and the upper pressure roller and is fed forward. The upper pressure roller, controlled by a cylinder, applies pressure to the substrate, ensuring the paint is transferred from the coating roller onto the substrate.

In this process, the gap between the coating roller and the metering roller directly influences the thickness of the paint applied to the coating roller's surface. This, in turn, affects the coating amount (thickness), and uniformity of the coating amount is a crucial factor in determining coating quality. Therefore, precise control of the gap between the coating roller and the metering roller is essential.

During scraping, a specific point on the surface of the coating roller is scraped only when it rotates closest to the metering roller. Hence, the scraping position corresponds to the point where the coating roller is closest to the metering roller. Assuming negligible gap between the two rollers, the scraping position aligns with the tangent point between the coating roller and the metering roller. In existing technology, due to difficulties in machining the coating roller into a perfect circle, its radius exhibits errors and inconsistencies in all directions. Although these radius errors compared to the absolute value of the radius may be small, they result in significant fluctuations in the gap size between the metering roller and the coating roller due to the small gap between them. This, in turn, causes noticeable periodic fluctuations and unevenness in the paint thickness applied to the coating roller's surface, ultimately leading to uneven coating amounts.

The purpose of the described device is to address these issues by providing an automatic adjustment mechanism for the gap between the metering roller and the coating roller, mitigating the problem of uneven coating amounts caused by radius errors in the coating roller.

The automatic adjustment device comprises a coating tank, an upper pressure roller, a coating roller, and a metering roller. The lower part of the metering roller resides within the coating tank cavity, with the coating roller positioned close to the metering roller but maintaining a gap between them. The upper pressure roller applies pressure onto the coating roller. Metering roller supports are provided at both ends of the metering roller, and a laser displacement sensor is installed adjacent to the coating roller, equipped with a laser head. The laser head's irradiation direction is perpendicular to the coating roller's central axis, pointing towards its surface. The metering roller supports are movably installed on linear guide rails and equipped with servo drive mechanisms, allowing synchronous movement along the guide rails. Additionally, a central control processor is included, connected to the laser displacement sensor. The processor commands the servo drive mechanism based on the laser displacement sensor's detection results, adjusting the position of the metering roller to maintain the desired gap when the specific point on the coating roller's surface rotates to the scraping position.

Preferably, the laser rays emitted by the laser head are positioned in the same plane as the coating roller's central axis.

The automatic adjustment method for the gap between the metering roller and the coating roller involves the continuous rotation of both rollers. The laser displacement sensor measures the distance between a reference point on the coating roller's surface and a specific target point, with measurements taken every 5° to 20° of the coating roller's rotation. The central control processor receives these distance measurements, calculates the coating roller's radius at the target point, and commands the servo drive mechanism to adjust the metering roller's position accordingly as the target point approaches the scraping position. This ensures that the actual gap between the target point on the coating roller and the metering roller aligns with the set ideal gap value when the target point reaches the scraping position.