The US-based firm has no refilling device on the market today, though other firms are starting to sell such machines, a development which could spell trouble for HP's multi-billion dollar throwaway cartridge business.
A spokesman for HP told CNETAsia that there are no plans to manufacture the refill device, which has been dubbed a "rejuvenation station" in the patent filings.
"As a worldwide leader in printing and imaging, HP is constantly researching new ways to print and provide even greater value to our customers. The 'rejuvenation station' is part of this ongoing research," Vincent Vanderpoel, a vice president with HP's imaging and printing group said in a statement in response to CNETAsia queries.
HP filed four patents with the US Patent and Trademark Office, numbered 20030011666, 20030011665, 20030011664 and 20020135645, between September last year and January this year.
The earliest filing said "an economical, efficient and compact method for refilling a print cartridge, while maintaining high print quality, is desired." It goes on to describe a machine that clamps the cartridge while a pump injects ink into it, while automatically taking care of problems such unequal air pressure.
This method compares with a method that many third-party refill makers employ, which involves the possibly messy manual injection of ink into the cartridge using a hand-held syringe.
But the threat to HP's ink business is increasing. Recently, makers such as Singapore-based INKE have begun selling desktop automatic ink refill stations costing $49 (£29.31). The company claims savings of $329 per average user over the three-year lifespan of an inkjet printer. INKE ink tanks cost just $6 each, compared with HP's original cartridges, which can cost up to $30.
Vanderpoel said there were no plans as yet to bring HP's own ink refiller to the market.
"For the majority of customers HP offers disposable inkjet cartridges with integrated ink supplies and printheads… While these cartridges can be refilled, one thing we have not been able to solve is how to maintain the high image quality and cartridge reliability in the refilled cartridges," he said. HP, however, did have a recycling program of used cartridges, he added.
When asked why HP would try to patent a device that could hurt its own disposable cartridge business, Christina Tay, a vice-president at ink-refill device maker INKE said that "it is difficult to speculate on their motive".
She said her firm had no worries of a patent dispute with HP as their ink stations use different technology.
"We have filed patents for INKE in USA as well as other countries. These filings are now under examination and should be published soon," she said. She also said that INKE was safe from HP's filing eventually becoming a "submarine patent", a patent that stays hidden until it is used in court to claim damages for alleged infringement.
"Refilling in itself is patent free; only the way or method of refilling may be patented. In fact, in certain parts of the world, it is anti-trust or considered monopolistic in practice if you adopt anti-refilling measures," she said.
HP's and INKE's methods "have different principles of refilling, different mechanism and are for different cartridges… Our method was cleared by our R&D and legal counsel before we went into commercial production," she added.
