Patent ID: 7758174

Claim:
An ink supply system for an inkjet printhead, said ink supply system being configurable for printing onto media and for printhead purging, said ink supply system comprising: (a) an ink reservoir for storing ink, said ink reservoir being contained in a pressurizable chamber; (b) an ink conduit providing fluid communication between said ink reservoir and said printhead; (c) an air compressor in fluid communication with said chamber via a switchable first valve, (d) a second valve positioned in said ink conduit between said ink reservoir and said printhead, said second valve being configured for delivering a predetermined amount of positively-pressurized ink to said printhead during said purging, and said valve being always open during said printing; wherein said first valve is switchable between a positively-pressurizing configuration for said purging and a negatively-pressurizing configuration for said printing, wherein said air compressor has an air inlet in fluid communication with said chamber in said positively-pressurizing configuration, and said air compressor has an air outlet in fluid communication with said chamber in said negatively-pressurizing configuration.