Abstract: A relief valve for an oil filter device integrally formed with a check valve has an annular shape, and has a front end portion, a guiding portion, a sealing portion, a recess portion, and a groove portion. The relief valve is attached to a protector only by inserting a cylindrical protector end portion into the groove portion thereof. At this time, the recess portion is elastically deformed so that the sealing portion moves inwardly, while the sealing portion is elastically compressed by the protector end portion. As a result, the relief valve closes an oil flow passage defined in a wall of the protector end portion only by an elastic deformation stress thereof. The relief valve can be readily molded and attached to the oil filter device and stably provide desired valve opening characteristics.

Abstract: A filter element has a generally ring-like structure which basically comprises a plurality of generally radial sections circumferentially arranged to define a central space. Each radial section has a plurality of circumferentially zigzag pleats formed from a ribbon of a filtering sheet material. The radial sections are circumferentially connected such that radially inwardly open generally radial spaces and radially outwardly open generally radial spaces are defined. The radially inwardly open radial spaces are closed at the axially opposite ends by end walls. Fluid to be filtrated can enter the radially outwardly open radial spaces and then passes through the zigzag pleats into the radially inwardly open radial spaces and thus into the central space. The ring-like structure has many modifications.

Abstract: A filter element has a generally ring-like structure which basically comprises a plurality of generally radial sections circumferentially arranged to define a central space. Each radial section has a plurality of circumferentially zigzag pleats formed from a ribbon of a filtering sheet material. The radial sections are circumferentially connected such that radially inwardly open generally radial spaces and radially outwardly open generally radial spaces are defined. The radially inwardly open radial spaces are closed at the axially opposite ends by end walls. Fluid to be filtrated can enter the radially outwardly open radial spaces and then passes through the zigzag pleats into the radially inwardly open radial spaces and thus into the central space. The ring-like structure has many modifications.