Pump apparatus with pressing means

A pump apparatus comprising:

• a drive shaft supported by drive-side bearing members on both end portions of the drive shaft;
• a driven shaft supported by driven-side bearing members on both end portions of the driven shaft;
• first external gears comprising a first drive gear which is driven by the drive shaft and a first driven gear which is meshed with the first drive gear and supported on the driven shaft;
• a center plate formed with a first through-hole through which the drive shaft extends and a second through-hole through which the driven shaft extends;
• second external gears which are opposed to the first external gears so as to sandwich the center plate between the first and second external gears, the second external gears comprising a second drive gear which is driven by the drive shaft and a second driven gear which is meshed with the second drive gear and supported on the driven shaft;
• a first seal block having a first side plate portion and a first seal block portion, the first side plate portion being disposed so as to sandwich the first external gears between the first side plate portion and the center plate, the first seal block portion comprising seal surfaces sealing tooth tips of the first external gears, the first seal block portion defining a first pump chamber in cooperation with the center plate;
• a second seal block having a second side plate portion and a second seal block portion, the second side plate portion being disposed so as to sandwich the second external gears between the second side plate portion and the center plate, the second seal block portion comprising seal surfaces sealing tooth tips of the second external gears, the second seal block portion defining a second pump chamber in cooperation with the center plate;
• and
• a pressing means for applying a pressing force between the tooth tips of the respective first and second external gears and the seal surfaces of the respective first and second seal block portions in a closing region disposed between the respective first and second external gears and the respective first and second seal block portions such that the tooth tips of the respective first and second external gears and the seal surfaces of the respective first and second seal block portions are allowed to press against each other in the closing region,
• wherein contact between an inner circumferential surface of the respective drive-side bearing members and an outer circumferential surface of the drive shaft and contact between an inner circumferential surface of the respective driven-side bearing members and an outer circumferential surface of the driven shaft are established on the side of the closing region, while the tooth tips of the respective first and second external gears and the seal surfaces of the respective first and second seal block portions in the closing region are kept pressed against each other by the pressing means.