Pump-equipped liquid supply system

Claim 1

A pump-equipped liquid supply system comprising: a liquid supply vessel which holds a liquid therein, a cylinder, disposed within said supply vessel, with a bottom portion having a piston hole, a first liquid suction hole with a liquid suction valve, and a second liquid suction hole, said first and second suction holes opening into said liquid supply vessel, a piston device which is slidably disposed within said cylinder, said piston device comprising (1) a piston with a liquid suction inlet, a liquid inlet valve, and a valve-pressing member which can be brought into pressure contact with said liquid developer suction valve for said first liquid suction hole so that said first liquid suction hole is tightly closed by said liquid developer suction valve, (2) a piston cover which is provided above said piston to form an inner space therebetween to hold said liquid therein, and an upper space above said piston cover within said cylinder to hold said liquid therein, said piston cover comprising a liquid suction inlet with a liquid inlet valve to draw said liquid into said inner space from said upper space, and a liquid introducing port with a valve which is connected to said second liquid suction hole of said cylinder, passing through said inner space, through which said liquid is caused to enter said upper space, (3) a piston shaft which, in a sealed state, passes through said piston hole formed in said bottom portion of said cylinder, and is integrally connected with said piston in such a manner as to slidably move said piston device along the inner side of said cylinder, when pressed upward or downward, said piston shaft including therein a liquid discharge conduit which is connected to said inner space of said piston device and from which said liquid can be discharged for use, said bottom portion of said cylinder and said piston being capable of forming a lower space therebetween when said piston device is moved upward to draw said liquid thereinto through said first liquid suction hole with said liquid suction valve from said liquid supply vessel, said liquid being supplied to said inner space of said piston device from said lower space between said bottom portion of said cylinder and said piston and to said upper space through said second liquid suction hole, and discharged from said liquid discharge conduit for use when said piston device is moved downward, and (4) an air displacement port through which air is caused to flow into said supply vessel when said liquid is drawn into said lower space from said supply vessel, a spring member which urges said piston device downward, and a cradle member which is fixed to said cylinder or said liquid supply vessel and is provided with a seal-packing member in such a configuration that said second suction hole formed in said bottom portion of said cylinder comes into close contact with said seal-packing member to tightly close said second suction hole when said piston device comes to its lowest position.