I claim the ornamental design for a contact spring for electrical switch, as shown and described.
FIG. 1 is a perspective view of a contact spring for electrical switch according to the present invention;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is a side view showing the portion of the contact spring for electrical switch defined by lines 8-8 in FIG. 6.
The broken lines show parts of the contact spring for electrical switch that represent unclaimed subject matter and form no part of the claimed design.