The ornamental design for a cap for aircompressor, as shown and described.
FIG. 1 is a front and upper perspective view of a cap for air compressor showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom plan view thereof;
FIG. 6 is a left side elevational view thereof;
FIG. 7 is a right side elevational view thereof, the broken lines in FIG. 7 are included for the purpose of illustrating portions of the cap for air compressor that form no part of the claimed design;
FIG. 8 is a rear and upper perspective view thereof;
FIG. 9 is a rear and bottom perspective view thereof;
FIG. 10 is a front and upper perspective view thereof, the openings and the recesses and the ribs depicted by means of broken lines being for illustrative purposes only and forming no part of the claimed design; and,
FIG. 11 is a rear plan view thereof, the openings and the recesses and the ribs depicted by means of broken lines being for illustrative purposes only and forming no part of the claimed design.