Patent ID: 7150828

Claim:
A drain structure for a fluid filter, the drain structure comprising: a cap that defines a drain hole; a drain member that is attachable to the drain hole of the cap from an outside of the cap such that the drain member blocks the drain hole when the drain member is attached to the drain hole; a valve member that is provided inside the cap; and a resilient means that biases the valve member in a direction in which the valve member blocks the drain hole, wherein the cap is attachable to a drain tool when the drain member is detached from the cap, the drain tool has a hooking portion that is detachably hooked to a hooked portion provided to the cap, when the drain tool is inserted into the drain hole of the cap and the hooking portion displaces the valve member in a direction in which the drain hole is unblocked, the drain tool is rotated around an axis of the drain hole so that the hooking portion and the hooked portion are attached to and detached from each other, when the drain tool is inserted into the drain hole and the drain hole is unblocked, the drain tool is inserted into the drain hole so that the drain tool displaces the valve member against resilience of the resilient means to unblock the drain hole blocked by the valve member, the hooking portion of the drain tool is formed on one axial end of the drain tool, the one axial end being located on the side of the valve member, the hooking portion protrudes in an axial direction of the drain tool, the hooking portion outwardly protrudes in a radial direction of the drain tool, and when the hooking portion and the hooked portion are attached to each other, the hooking portion is interposed between the valve member and the hooked portion.