The ornamental design for an armrest apparatus, as shown and described.
FIG. 1 is a front view of an arm rest apparatus of our new design;
FIG. 2 is a rear view of the arm rest apparatus shown in FIG. 1;
FIG. 3 is a top view of the arm rest apparatus shown in FIG. 1;
FIG. 4 is a bottom view of the arm rest apparatus shown in FIG. 1;
FIG. 5 is a left side view of the arm rest apparatus shown in FIG. 1;
FIG. 6 is a right side view of the arm rest apparatus shown in FIG. 1;
FIG. 7 is a perspective view of the arm rest apparatus shown in FIG. 1;
FIG. 8 is another perspective view of the arm rest apparatus shown in FIG. 1;
FIG. 9 is a view for a reference, which shows a using state of the arm rest apparatus; and,
FIG. 10 is a view for a reference, which shows a position relationship of the arm rest apparatus with respect to an arm.
The dash-dash line showing of is included for the purpose of illustrating environment and unclaimed subject matter, the dash-dot line showing is included to illustrate the bounds of the claimed design, and form no part of the claimed design.