Filter device

A filter device which is installed in a flow path and filters foreign substances from a gas which flows through the flow path to which a pressure selectively switched between a negative pressure and a positive pressure is supplied, the filter device comprising:

• a first port for selectively switching between and inputting a negative pressure and a positive pressure;
• a second port for outputting to an outside the negative pressure and the positive pressure inputted from the first port;
• and a negative pressure-side filter and a positive pressure-side filter which are disposed between the first port and the second port, and connected in parallel to the first and second ports,
• the negative pressure-side filter has a breathable negative pressure-side filter element to filter foreign substances from a gas which flows from the second port to the first port, and the positive pressure-side filter has a breathable positive pressure-side filter element to filter foreign substances from a gas which flows from the first port to the second port,
• a shuttle valve is disposed between the first port, and the negative pressure-side and positive pressure-side filters, and
• the shuttle valve has a valve disc such that when a negative pressure is supplied to the first port, the valve disc opens communication between the first port and the negative pressure-side filter to output the negative pressure from the second port, and simultaneously blocks communication between the first port and the positive pressure-side filter, whereas when a positive pressure is supplied to the first port, the valve disc opens communication between the first port and the positive pressure-side filter to output the positive pressure from the second port, and simultaneously blocks communication between the first port and the negative pressure-side filter.