Patent ID: 6619932
Filing Date: 2003-09-16
Classification: F04B

Abstract:
A pump comprising:a pump main body including a first fluid delivering chamber, a first driving chamber, a second fluid delivering chamber, a second driving chamber, and a balancing valve having a first end facing said first driving chamber and having a second end facing said second driving chamber; and a change-over valve communicating with said pump main body, and including a supply port for receiving a driving fluid, a first pressure chamber at a first end of said change-over valve, a second pressure chamber at a second end of said change-over valve opposite said first end, and a valve body operable to reciprocate between said first pressure chamber and said second pressure chamber based on a difference between a pressure of the driving fluid in said first pressure chamber and a pressure of the driving fluid in said second pressure chamber, said change-over valve being operable to shift an operation of said pump main body between a first mode and a second mode by controlling a supply of the driving fluid to said pump main body and by controlling an exhaust of the driving fluid from said pump main body, said pump main body and said change-over valve being arranged such that in the first mode: a volume of said first driving chamber is increased by supplying the driving fluid to said first driving chamber, thereby decreasing a volume of said first fluid delivering chamber so as to discharge a fluid-in-transfer from said first fluid delivering chamber; and simultaneously a volume of said second driving chamber is decreased by exhausting the driving fluid from said second driving chamber, thereby increasing a volume of said second fluid delivering chamber so as to suck the fluid-in-transfer into said second fluid delivering chamber; said pump main body and said change-over valve being arranged such that in the second mode; a volume of said second driving chamber is increased by supplying the driving fluid to said second driving chamber, thereby decreasing a volume of said second fluid delivering chamber so as to discharge a fluid-in-transfer from said second fluid delivering chamber; and simultaneously a volume of said first driving chamber is decreased by exhausting the driving fluid from said first driving chamber, thereby increasing a volume of said first fluid delivering chamber so as to suck the fluid-in-transfer into said first fluid delivering chamber; and wherein said pump main body and said change-over valve are further arranged such that if said change-over valve remains in an intermediate position so that pressures in said first driving chamber and said second driving chamber of said pump main body are substantially identical, said balancing valve of said pump main body is operable to induce a pressure difference between said first pressure chamber and said second pressure chamber of said change-over valve so that said change-over valve moves from said intermediate position.