A coupling adapter for attachment to the fluid reservoir of a hydraulic system for coupling a fluid filter and a remotely located fluid circulation device to the hydraulic system, comprising in combination:
- (a) a generally disk-shaped body having first and second spaced-apart end surfaces, the first end surface being adapted for abutment adjacent the outlet surface of the fluid reservoir in place of a fluid filter, the second end surface being adapted for abutment adjacent the end surface of a fluid filter;
- (b) a first cylindrically-shaped cavity extending partially into said disk-shaped body from said first end surface;
- (c) first, second and third spaced-apart concentric ridges of different diameters formed at the first end surface of said disk-shaped body, said first ridge being adjacent to the outer peripheral surface of said first cavity, said third ridge being adjacent to the outer peripheral surface of said disk-shaped body, said second ridge being located in-between said first and second ridges;
- (d) an inner circular groove situated between said first and second concentric ridges and extending partially into said disk-shaped body from the first end surface;
- (e) an outer circular groove situated between said second and third concentric ridges and extending partially into said body from the first end surface, one of said inner or outer circular grooves being adapted for receiving a single O-ring for providing a fluid-tight seal between the first end surface of said disk-shaped body and the outlet surface of the fluid reservoir, said inner circular groove receiving an O-ring when the adapter is to be used with a fluid reservoir whose outlet surface is of a first diameter size, said outer circular groove receiving an O-ring of larger diameter when the adapter is to be used with a fluid reservoir whose outlet surface is of a second and larger diameter size;
- (f) a second cylindrically-shaped cavity extending partially into said disk-shaped body from the second end surface, the second end surface of said disk-shaped body adapted for abutment adjacent the end surface of a fluid filter includes a substantially flat annular end surface extending between the outer peripheral surface of said second cylindrically-shaped cavity and the outer peripheral surface of said disk-shaped body, the width of said flat annular end surface being sufficient to abut the end surfaces of fluid filters of at least two different diameter sizes;
- (g) a central wall section situated within said disk-shaped body between said first and second cavities for preventing the passage of fluid between said cavities;
- (h) a central bore coaxially situated within and extending through said disk-shaped body between said first and second cavities, said central wall section including a cylindrically-shaped portion surrounding said central bore, said central bore being adapted for receiving a hollow nipple having an internally-threaded portion, the hollow nipple being adapted for aligning said disk-shaped body with the fluid reservoir of the hydraulic system, the hollow nipple having an externally-threaded portion situated outside said central bore and extending beyond the second end surface of said disk-shaped body, the externally-threaded portion of the nipple being adapted for engagement with a fluid filter, the hollow nipple securing the fluid filter and the coupling adapter to the fluid reservoir of the hydraulic system;
- (i) an outlet port extending from the outer peripheral surface of said disk-shaped body and through said body into said first cavity, said outlet port being situated between said first and second spaced-apart end surfaces;
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- (j) an inlet port extending from the outer peripheral surface of said disk-shaped body and through said body into said second cavity, said inlet port being spaced apart from said outlet port and being situated between said first and second spaced-apart end surfaces, the distance between the innermost wall portions of the passageways of said outlet and inlet ports at the points of entry into said first and second cylindrically-shaped cavities being greater than the diameter of the cylindrically-shaped portion of said central wall section surrounding said central bore, the distance between the outermost wall portions of the passageways of said outlet and inlet ports at the points of entry into said first and second cylindrically-shaped cavities being substantially equal to the diameters of said first and second cavities, said outlet and inlet ports being adapted for coupling the adapter to a remotely located fluid circulation device.