Ink supply system for an ink jet printer

An ink supply system for supplying ink to the print head of an ink jet printer for production of jet drop streams, comprising

• an ink supply tank for storing a quantity of ink,
• pump means, having a pump inlet and a pump outlet, for receiving ink from said ink supply tank at said pump inlet and for providing ink under pressure at said pump outlet,
• print head supply line means for providing flow of ink from said pump outlet to said print head,
• print head return line means for providing flow of ink from said print head to said ink supply tank,
• closed container means communicating with said pump outlet and said print head for providing a second flow of ink to said print head,
• controllable valve means for selectively directing ink from said pump outlet to said closed container means,
• a print head outlet valve for selectively preventing flow of ink through said print head return line means,
• pressure sensing means mounted in an upper portion of said closed container means and responsive to air pressure therein, and
• control means, responsive to said pressure sensing means, to control said controllable valve means and said print head outlet valve, such that a portion of the ink from said pump outlet may be directed to said closed container means so as to gradually fill said closed container means, compressing the air therein and supplying a flow of ink to said print head at a gradually increasing static pressure, said control means further operating in response to a predetermined air pressure within said closed container means as determined by said pressure sensing means to close said print head outlet valve, thereby initiating production of jet drop streams.

A method of controlling the flow of ink to an ink jet print head in an ink jet printer, said printer including an ink supply tank, a pump receiving ink from said tank at a pump inlet and providing ink under pressure at a pump outlet, and a print head supply line connecting said print head and said pump outlet, comprising the steps of

• providing a closed container communicating with said print head for holding a quantity of ink therein,
• selectively connecting said closed container to provide fluid flow between said pump outlet and said closed container, whereby a portion of the ink from said pump outlet is directed to said closed container so as to fill gradually said container and to compress the air therein, providing a flow of ink to said print head at a gradually increasing fluid pressure, and the balance of the ink from said pump outlet is supplied to said print head through said print head supply line,
• disconnecting said closed container from said pump outlet upon reaching a predetermined air pressure within said container, and
• connecting said closed container to said ink supply tank, thereby draining ink from said closed container into said tank.

A method of controlling the flow of ink to an ink jet print head in an ink jet printer, said printer including an ink supply tank, a pump receiving ink from said tank at a pump inlet and providing ink under pressure at a pump outlet, a print head supply line connecting said print head and said pump outlet, a print head return line connecting said print head and said ink supply tank, and a print head outlet valve for controllably preventing fluid flow through said print head return line, comprising the steps of

• providing a closed container communicating with said print head for holding a quantity of ink therein,
• providing fluid flow of ink from said pump outlet through said print head supply line, said print head, and said print head return line to said ink supply tank,
• selectively connecting said closed container to provide fluid flow between said pump outlet and said closed container, whereby a portion of the ink from said pump outlet is directed to said closed container so as to gradually fill said container and compress the air therein, providing a flow of ink to said print head at a gradually increasing fluid pressure, and the balance of the ink from said pump outlet is supplied to said print head through said print head supply line, and
• closing said print head outlet valve upon reaching a predetermined air pressure within said container, rapidly terminating ink flow through said print head so as to initiate production of jet drop streams.