I claim the ornamental design for an air compressor, as shown and described.
FIG. 1 is a front perspective view of an air compressor showing our new design.
FIG. 2 is a right-side view of the air compressor of FIG. 1.
FIG. 3 is a left-side view of the air compressor of FIG. 1.
FIG. 4 is a front view of the air compressor of FIG. 1.
FIG. 5 is a rear view of the air compressor of FIG. 1.
FIG. 6 is a top view of the air compressor of FIG. 1; and,
FIG. 7 is a bottom view of the air compressor of FIG. 1.
The broken lines shown represent unclaimed subject matter only and form no part of the claim. Where broken lines abut a claimed surface it is understood that those broken lines represent an unclaimed boundary between claimed and unclaimed surfaces. None of the broken lines forms any part of the claimed design.