Gate valve with speed controller using cda

A gate valve with speed control capability, the gate valve comprising:

• a housing;
• an air cylinder configured to move a first shaft vertically up to a first position, the first shaft being connected to the air cylinder;
• a cam unit including a cam attached to the first shaft at one end;
• a second shaft connected at an opposite end of the cam and configured to move along with the cam to a certain height;
• a first bellows disposed around the second shaft;
• a seal plate disposed at an end of the second shaft and configured to close a passage to/from a chamber;
• a seal ring disposed around the seal plate and configured to seal up the passage when the seal plate closes the passage;
• and
• a CDA unit configured to control an open/close speed of the gate valve,
• wherein the CDA unit comprises:
• a casing;
• a piston configured to move vertically by air flow;
• a first air passage and a second air passage for controlling an amount of air flow;
• a separator configured to separate the first air passage and the second air passage, wherein the separator is equipped with a hole;
• and
• a first needle valve disposed in a middle of the first air passage and configured to control a flow of an air in the first passage.