In some examples, an apparatus can include a valve body including a recirculation inlet path and a recirculation outlet path, a piston assembly located in the valve body, and a recirculation cavity between the valve body and the piston assembly, where print material is to be circulated through the recirculation cavity via the recirculation inlet path and the recirculation outlet path.

A liquid discharge apparatus includes a head including a supply path and a discharge path circulating a liquid in a liquid circulation direction, the head configured to discharge the liquid, a circulation path coupled to the head, the liquid circulates through the head in the circulation path, a bypass coupled to a downstream end of the supply path of the head and an upstream end of the discharge path of the head in the liquid circulation direction, a pressure generator configured to generate and apply a circulation pressure to the liquid circulating through the circulation path, and a deaerator configured to remove gas in the liquid circulating the circulation path.

An image forming device including a deaerator that deaerates liquid, a supply tank for storing liquid, a spray device that sprays liquid, and a controller. The controller executes a control causing supply of deaerated liquid from the deaerator to the supply tank, and from the supply tank to the spray device, and spraying of liquid by the spray device to form an image, and while waiting for image forming or while the supply of liquid from the supply tank to the spray device is stopped, the controller executes a control causing at least some of the liquid stored in the supply tank to be supplied to the deaerator in a direction opposite the supply from the deaerator to the supply tank, and causing the deaerator to deaerate the liquid so supplied.

A liquid ejecting head includes a first drive circuit including a switching element that selects, from a plurality of drive elements, a drive element to which a drive signal for ejection of liquid through a nozzle is sent, a case defining a first accommodating portion that is a space accommodating the first drive circuit, and a first gas supply passage that is in communication with the first accommodating portion and through which gas is supplied to the first accommodating portion.

A pressure fluctuation suppression device including a suppressor and a detector. The suppressor is disposed on a flow path of a liquid and suppresses fluctuations in pressure of the liquid in the flow path. The detector detects deterioration of a suppression function of the suppressor.

A recording apparatus includes a channel through which liquid to be supplied to a recording head that ejects the liquid flows and a concentration measuring unit including a light emitting unit and a light receiving unit and configured to measure the concentration of the liquid, wherein the concentration measuring unit is disposed at a direction change portion at which the liquid flowing through the channel changes in direction.

A method of recirculating printing fluid that includes with a first pump upstream of an internal reservoir, pumping printing fluid into the reservoir and with a second pump downstream of the internal reservoir and upstream of a pen assembly, pumping printing fluid from the reservoir.

A method of recirculating printing fluid that includes with a first pump upstream of an internal reservoir, pumping printing fluid into the reservoir and with a second pump downstream of the internal reservoir and upstream of a pen assembly, pumping printing fluid from the reservoir.

Fluid is continuously recirculated through a thermal fluid-ejection printhead. Prior to firing a thermal resistor of the printhead to thermally eject a drop of the fluid through a nozzle of the printhead, the fluid is recirculated on-demand through a chamber of the printhead between the nozzle and the thermal resistor. The thermal resistor is fired to thermally eject the drop of the fluid through the nozzle. The fluid has a concentration of solids greater than 12% by volume.

Since ink is not heated at a protrusion connecting an ink supplying device and a print head chip or the like, the viscosity of the ink increases, and the fluidity may not be maintained in some cases. An inkjet printer 1 for solving the above problem includes an inkjet head 300 that ejects ink; a protrusion 310 provided to protrude from the inkjet head 300 and configured to circulate the ink to the inkjet head 300; and an ink flow path portion 6 that supplies the ink to the protrusion 310; where the ink flow path portion 6 includes an ink warming block 200 that heats the ink, and a conducting portion 210 that is formed in the ink warming block 200 itself or separately from the ink warming block 200 and through which heat from the ink warming block 200 is conducted is adjacently disposed outside the protrusion 310.