High-frequency welding principle and application of drainage bags

I. High-Frequency Welding Principle

High-frequency welding utilizes the resistance heat generated when a high-frequency current (typically in the range of 10-500kHz) passes through a workpiece. This heats the joint surfaces of the workpieces locally to a molten or plastic state, thus achieving the connection of metal or plastic materials. Its core principles include:

1. Skin Effect: When a high-frequency current flows through a conductor, the current density concentrates on the conductor surface, creating the "skin effect." This characteristic concentrates heat on the workpiece surface, achieving rapid localized heating.

2. Proximity Effect: When a high-frequency current flows in opposite directions through two adjacent conductors, the current concentrates on the adjacent sides of the conductors, further enhancing the localized heating effect.

3. Resistance Heat Generation: When a high-frequency current passes through a workpiece, the resistance of the workpiece material generates a large amount of heat, causing the contact surfaces to rapidly heat to their melting point or plastic state.

4. Pressure Effect: During the heating process, applying a certain pressure (or not applying pressure) ensures a tight bond between the workpiece contact surfaces, forming a strong weld after cooling.

5. High-frequency welding is divided into contact high-frequency welding and induction high-frequency welding:

Contact high-frequency welding: High-frequency current is transmitted to the workpiece through electrodes in direct contact with it.

Induction high-frequency welding: High-frequency current is coupled through an external induction coil to generate an induced current within the workpiece, achieving heating.

II. Application of High-Frequency Welding in Drainage Bag Production

Drainage bags are medical devices used to collect accumulated fluid in the body, typically made of medical-grade polymer materials (such as PVC, TPU, PE, etc.). The application of high-frequency welding in drainage bag production is mainly reflected in the following aspects:

1. Bag Body Welding

Film Welding: The bag body of a drainage bag is usually welded from two or more layers of plastic film. High-frequency welding locally heats the contact surfaces of the films, causing them to melt and bond, forming a sealed bag structure. Weld Strength: High-frequency welding produces uniform and strong welds, ensuring that the drainage bag will not leak during use.

2. Tubing Connection

Drainage Tube to Bag Body Connection: The drainage tube of a drainage bag is usually connected to the bag body using high-frequency welding. High-frequency welding ensures a tight seal between the tubing and the bag body, preventing liquid leakage.

Valve welding: Some drainage bags are equipped with check valves or drain valves. These valves are connected to the bag body via high-frequency welding to ensure their proper function.

3. Anti-backflow design

Check valve welding: The core component of the anti-backflow drainage bag is the check valve. High-frequency welding connects the check valve to the bag body, ensuring proper valve operation and preventing liquid backflow.

Sealing: High-frequency welding ensures a tight seal between the check valve and the bag body, preventing increased infection risk due to leakage.