US Patent 11504467 Liquid injection device and assembly including same

A liquid injection device includes: a syringe that comprises a barrel part configured to be filled with a liquid, and a needle attached to a distal portion of the barrel part and configured to discharge the liquid, a cap that covers the needle; a housing that covers at least a base end part of the syringe; and a step part that is formed on an outer peripheral surface of the cap or between the housing and the cap, the step part protruding farther outward than a side surface of the barrel part. The step part is configured to engage with a lower surface of a notch part that extends laterally inward from an outer edge of a flange part of a container such that the cap is removable from the housing by the notch part.