Pressurized tennis ball container

A cover assembly for use with a metal tennis ball can to form a pressurized tennis ball container, comprising a transparent cover member sized to overlie the top of said can and having a integral pump cylinder upstanding therefrom, a pump piston extending into said pump cylinder, piston seal means mounted on said piston including a sealing ring slidably mounted on said piston and providing a wiping seal between said piston and said pump cylinder for preventing the flow of air past said piston on the downstroke of said piston and with said means opening to permit airflow past said piston on the upstroke of said piston to refill said cylinder, valve means disposed to permit the flow of air from said cylinder into said tennis ball can and to prevent the flow of air in the reverse direction, means for mounting said cover member on said tennis ball can, pressure release mounted on said cover member for venting pressure from said tennis ball cans, and pressure indicator means on said cover for indicating the attainment of a selected pressure within the can upon which said cover member is mounted by operation of said pump piston, said pressure indicating means including a transparent cylinder formed integrally with said transparent cover member and upstanding therefrom, said transparent cylinder having a closed top end and an open bottom end communicating with the interior of said can, a piston slidably mounted in said cylinder and visible therethrough, and a reference line on said cylinder at a location to indicate the attainment of said selected pressure within said can when said piston registers with said reference line, said pressure indicator means providing a continuous visual indication of the pressure within said can until said pressure is released by said pressure release means.