Column type hydraulic tappet

A column type hydraulic tappet, comprising:

• a housing,
• wherein the housing comprises an external circumferential groove disposed on an outer diameter for passing the hydraulic medium, and an inner circumferential groove disposed on an inner diameter for passing the hydraulic medium, and wherein one or more oil holes disposed between the external circumferential groove and the inner circumferential groove of the housing;
• a plunger correspondingly installed in the housing,
• wherein the plunger comprises a sealed hemisphere head portion, a shaft portion, and a body portion, wherein an indent neck portion is formed between the head portion and the shaft portion of the plunger, and wherein a wall thickness of the neck portion is 105%-120% of a wall thickness of the other portions of the plunger;
• and
• a high-pressure chamber for a hydraulic medium formed between a sealed base of the plunger and a bottom of the housing,
• wherein the high-pressure chamber is sealed by a check valve opening towards the high-pressure chamber.