The ornamental design for a dustcollector, as shown and described.
FIG. 1 is a top perspective view of a dust collector showing my new design;
FIG. 2 is a left side plan view thereof;
FIG. 3 is a right side plan view thereof;
FIG. 4 is a front plan view thereof;
FIG. 5 is a back plan view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken lines shown in the figures are included for the purpose of illustrating portions of the dust collector and form no part of the claimed design.