Loptex: An Optosonic Sorter

Loptex: An Optosonic Sorter

Arman Hossain Akash
Department of Textile Engineering
Ahsanullah University of Science & Technology, Dhaka, Bangladesh
Email: armanakash899@gmail.com


Contamination removal systems have long been using optical sensors to detect contamination in raw cotton, but they can detect contaminations only if their color are different compared to the raw material (cotton). Colorless contamination like white polypropylene, known as white PP, or other synthetic materials cannot be detected by optical sensors. Since plastics do not absorb dyestuffs of cotton (such as reactive dye), undyed spots will then appear in finished goods which are not accepted in today’s competitive market.

The optosonic sorter (loptex), the Swiss-Italian company producing systems for the detection and removal of contamination in cotton blowroom lines, still implements the simplest and most effective solution in the market. Loptex is equipped with two different sensing devices:

(i) The raw material will first be scanned by an Acoustic Sensor. Acoustic waves will penetrate into loose cotton tufts but will be reflected by contamination having a more compact surface structure like polypropylene and other synthetic materials. The sonic system is a hardware attachment that measures the average density of the cotton and recognizes all the different density color and colorless contamination. Furthermore, since its acoustic waves penetrate the fibres flock, hidden contamination are also detected. These features carry out a double control on contamination.

Optosonic sorter (loptex)
Figure 1: Optosonic sorter (loptex)

(ii) Thereafter the raw material will be scanned by Optical Sensor detecting contamination on the basis of its shade. This sensor measures the average brightness of the raw material and recognizes colored contamination being darker.

Both sensor systems will monitor continuously the raw material in respect to its average density and brightness. Eventual changes in density, colour and brightness are automatically taken into account.

Working Principle
The Loptex Sorter includes a rectangular duct through which the raw material is transported by the fan already existing at the end of the blowroom line. The raw material will first be presented to the Acoustic Sensor and thereafter to the Optical Sensor. In case a contamination is detected it will be ejected by high speed pneumatic valves into the waste container. The Acoustic Sensor will emit ultrasonic waves which cannot be heard by human ears. Since such waves penetrate into fibrous material, only one sensor is needed. To avoid the reflection of the waves by the opposite side of the duct, an absorber box is installed. If contamination with a compact surface structure (like plastic) is transported through the duct, the ultrasonic waves will be reflected into the receiver. This receiver will thereafter trigger the ejection device.

parts of loptex
Figure 2: Parts of loptex

The Optical Sensor consists of standard fluorescent light tubes and custom made photosensor arrays. In addition, a very simple system can be achieved without the need of mirrors and focusing. If a contamination passes the set threshold, the raw material will absorb more light and less light will be reflected to the photosensors which thereafter will trigger the ejection device.

Both sensors will trigger high speed pneumatic valves for the ejection of the contamination. These valves are arranged in one line, covering the full width of the duct. Only the valves placed directly in front of the contamination will be activated. The number of valves will vary according to the setting of the user and depending on the size of the detected contamination. The duct opposite the valves presents an opening through which the contamination is blown into the waste container.

Ideal Positioning of Loptex
Loptex offers different types of Sorter systems according to the production rate required and permitting the installations in various locations of the spinning preparation line. The Sorter performs the best when positioned at the end of the opening line, after opening and cleaning. Here the fibres are opened to their maximum. The detection of foreign material will be more effective as the risk of contamination hidden in the fibres is practically non-existent. In addition, the number of fibres attached to the contamination will be lower (normally less than 0.1% of the production).

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