1. Field of Invention
The invention relates to an ink container for inkjet printers and, in particular, to an ink container that maintains the negative pressure.
2. Related Art
The inkjet printer used in homes or offices has two parts: the ink cartridge and the inkjet print head. The inkjet print heads can be further classified into two categories: the thermal bubble system and the piezoelectric system.
Although the above-mentioned two systems are good and highly efficient inkjet print head designs, a mechanism is required to prevent ink from permeating out of the nozzles. If ink permeates out of the nozzle, it may cause ink droplets to fall imprecisely, deteriorating the printing quality. To solve this problem, a slight negative pressure has to be maintained inside the ink cartridge, so that no ink will leak out from the nozzles if the inkjet print head is paused or stops working. The negative pressure means that the pressure inside the ink chamber is smaller than that of the ambient air. However, if the negative pressure is too large, it will cancel with the pushing force of the print head to eject ink. A possible consequence is: the sizes of the ink droplets are hard to control or getting smaller. This also deteriorates the printing quality. Ink droplets may even be impossible to be ejected out as the condition gets to the worst.
To maintain normal operation conditions, the negative pressure has to be kept within a desired operating range. In other words, the negative pressure has to be greater than a value to prevent ink from permeating out of the inkjet print head, but also simultaneously smaller than the value that interferes normal printing. To satisfy the above requirement, there are many different proposals for different products.
For example, James E. Pollacek et al. proposed xe2x80x9cregulator for inkjet pensxe2x80x9d in the U.S. Pat. No. 5,040,002. According to them, a ventilation hole is opened directly on the ink cartridge. A metal valve base is installed thereon too. A magnetic force is used to keep the valve closed until the negative pressure inside the cartridge is large enough for the atmospheric pressure to push open the valve, letting the ambient air to come in. Once the negative pressure get smaller, the valve is closed airtight again, keeping the negative pressure inside the cartridge. The above mechanism can sensitively maintain the negative pressure in the ink cartridge within the desired operating range.
Although the ink cartridge structure using a magnetic valve to control the air supply channel is nice, such products are susceptible to strong magnetic fields. If they experience a strong magnetic field during transportation or use, the magnetic properties of the metal valve base and the valve will be changed. As a result, the operating range of the negative pressure cannot be correctly controlled.
In view of the foregoing, the invention provides an ink container, which has a pressure stabilizer module with a simple structure for ink stored inside the ink chamber to be fully utilized and not affected by the magnetic force.
The ink container having a pressure stabilizer module according to the invention contains a box and more than one stabilizer module. The stabilizer module is installed inside the box and protected by the strong shell of the box. The stabilizer module contains an airtight membrane that can be elastically deformed. It separates the box into an ink chamber and an air chamber. The ink chamber stores ink for printing. A passive plate in an arc or plane shape is connected to one side of the airtight membrane inside the ink chamber. An elastic device is connected to the passive plate and installed on the inner side of the ink chamber, so that it is normally suppressed. In particular, a conic spiral spring is utilized. The height of the spring under pressure is closed to the thickness of the spring wire. Therefore, as the ink gets less during use, the space of the ink chamber also shrinks. The elastic device is depressed to provide an elastic force to push the passive plate, putting a limit on the shrinking extent of the ink chamber. Under the influence of the elastic device, the ink chamber obtains a negative pressure that is maintained within a specific range. Since the height of the conic spiral spring is merely the thickness of the spring wire, it can prevent ink inside the ink chamber from remaining therein. On the other hand, one end of the box is opened with a through hole to connect to the ambient space. Ambient air can enter the air chamber via the through hole to balance the pressure inside the box. As the ambient temperature or pressure changes, it can make the corresponding adjustment. The bottom of the ink chamber is installed with an ink channel connected to a nozzle on another end of the box. Therefore, the ink stored inside the ink chamber can be ejected out for printing.
It should be noted that the separation between the ink chamber and the air chamber by the airtight membrane keep the ink chamber airtight. The design of the air chamber does not necessarily require a through hole, as long as some space is saved for the ambient air to enter the air chamber.
Another preferred embodiment of the invention is different from the previous one in that: the passive plate is connected to the outer side of the ink chamber, i.e. the air chamber on the other side of the airtight membrane. In the case, the elastic device is installed in the air chamber so that it is normally stretched. Likewise, when the ink gets less during use, the space of the ink chamber also shrinks. The elastic device provides a restoring elastic force to drag the passive plate, restricting the shrinking extent of the ink chamber. Therefore, the ink chamber obtains a negative pressure within a desired operating range. The nozzle can thus operate normally to eject ink.
The disclosed ink container having a pressure stabilizer module utilizes the connection between the conic spiral spring and the airtight membrane to maintain the negative pressure in the ink chamber within a specific range. Most important of all, the use of the conic spiral spring fully utilizes the stored ink, avoiding ink residues and unnecessary waste. According to the disclosed embodiments, the invention can be easily assembled. Each component can be readily obtained too. Therefore, the manufacturing cost is greatly reduced. Moreover, it is not affected by the external magnetic field. The printing quality is thus warranted.