Diaphragm Pump

FIG. 1 is a perspective view of a diaphragm pump showing our new and ornamental design; FIG. 2 is a front view of FIG. 1 ; FIG. 3 is a rear view of FIG. 1 ; FIG. 4 is a left side view of FIG. 1 ; FIG. 5 is a right side view of FIG. 1 ; FIG. 6 is a top view of FIG. 1 ; FIG. 7 is a bottom view of FIG. 1 ; FIG. 8 is an alternative perspective view of FIG. 1 ; and, FIG. 9 is an alternative perspective view of FIG. 1 . The portions of the diaphragm pump shown in broken lines shown in the figures attached hereto form no part of the claimed design.