The ornamental design of a "bed elevator," as shown and described.
FIG. 1 is a perspective view of the present invention;
FIG. 2 is a top plan view of the present invention;
FIG. 3 is a front elevation view of the present invention which is also illustrative of all side elevation and rear elevation views of the present invention; and,
FIG. 4 is a bottom plan view of the present invention.
The broken lines shown in the drawings illustrate environment and do not form any part of the claimed design.