Mechanism for driver head adjustment

An uncapping apparatus for a test tube cap, comprising:

• a drive head configured to drivingly engage with the test tube cap, the drive head comprising at least two drive head elements, at least one of the drive head elements being rotatable about a rotary shaft, the drive head elements each comprising a first section that is close to the test tube cap when the drive head engages with the test tube cap and a second section that is located away from the test tube cap when the drive head engages with the test tube cap, wherein the first section and the second section are located on two opposite sides of the rotary shaft, and wherein the first sections engage with the test tube cap from an inside thereof;
• an elastic element configured to act on the second sections to provide a tensioning force to the drive head elements;
• and
• a switching element configured to be movable between a first position and a second position, wherein in the first position, the second sections are under the action of the tensioning force of the elastic element to cause the first sections to form a first drive head size, and in the second position, the switching element is capable of acting on the elastic element to change the tensioning force acting on the second sections, so that by means of the rotation of the drive head elements, the first sections form a second drive head size different from the first drive head size.