System and method for welding two thermoplastic workpieces

1. A system for welding two thermoplastic workpieces, comprising:

an ultrasonic tool;

a support; and

a cooling unit comprising a liquid tank, a pump, and a pipeline strand;

wherein the ultrasonic tool is configured to generate mechanical vibrations with a frequency of between 20 kHz and 100 kHz,

wherein a head of the ultrasonic tool faces the support such that a receiving region for the workpieces is formed between the head of the ultrasonic tool and the support;

wherein the system is configured to clamp the workpieces together in the receiving region by the ultrasonic tool and the support when at least one attachment portion of the workpieces has a mutually opposite arrangement in the receiving region;

wherein the ultrasonic tool is configured to introduce mechanical vibrations into the attachment portion of the workpieces to weld the workpieces in a joining zone;

wherein the cooling unit is configured to cool at least a part of the attachment portion of the workpieces and/or a cooling portion of the workpieces that directly adjoins the attachment portion using cooling liquid; and

wherein the cooling unit is configured to convey cooling liquid from the liquid tank through the pipeline strand to a line end of the pipeline strand by the pump such that the cooling liquid leaving the line end reaches the attachment portion and/or cooling portion of the workpieces.

2. The system of claim 1 , wherein an auxiliary body in the attachment portion between the workpieces when the workpieces are to be clamped together in the receiving region, wherein the two workpieces can be welded by the auxiliary body in the joining zone.

3. The system of claim 1 , wherein the cooling liquid is water or at least comprises water.

4. The system of claim 1 , wherein the cooling unit has a liquid container, the interior space of which is at least partially filled with cooling liquid, wherein the liquid container is on the support and or a base of the liquid container is at least partially formed by the support, wherein the head of the ultrasonic tool is immersed into the cooling liquid in the interior space of the liquid container such that the receiving space is within the interior space, filled with cooling liquid, of the liquid container.

5. The system of claim 1 , wherein the cooling unit is configured to convey the cooling liquid to the attachment portion and/or cooling portion, such that the cooling liquid that has been conveyed flows over the attachment portion and or cooling portion of the workpieces to cool the workpieces.

6. The system of claim 1 , wherein the system has a first handling unit, to which the ultrasonic tool is attached, wherein the system is configured to control the first handling unit to move the ultrasonic tool along a predetermined movement path relative to the support and or the workpieces.

7. The system of claim 1 , wherein the system has a drive which is coupled to the support to move the support along a predetermined drive path, in particular relative to the ultrasonic tool.

8. The system of claim 1 , wherein the system has a holding unit, which is configured to hold the workpieces and to arrange the workpieces such that the workpieces are mutually oppositely arranged in the attachment portion and the attachment portion of the workpieces is arranged in the receiving region, wherein the system has a first handling unit, to which the ultrasonic tool is attached, wherein the system is configured to control the first handling unit to move the ultrasonic tool along the workpieces along a predetermined movement path, and wherein the system has a second handling unit, to which the support is attached, wherein the system is configured to control the second handling unit to move the support parallel to the ultrasonic tool.