Patent ID: 8016300

Claim:
A mobile cart for carrying a plurality of fluid canisters, the cart being adjustable between a standing mode and a rolling mode and comprising: a platform configured to support the fluid canisters during operation of the cart; a base connected adjacent the platform including a right base system and a left base system on which the mobile cart stands and rolls during operation of the cart, each of said base systems including: a base body having an outer wall having a bottom, multiple slots extending generally vertically, a first outer wall pin opening, and a second outer wall pin opening and having an inner wall having a bottom, multiple slots extending generally vertically and aligned with the outer wall slots, and a first inner wall pin opening and a second inner wall pin opening aligned with the first and second outer wall pin openings, respectively; a cartridge positioned at least partially within said base body including: a cartridge body having a first cartridge body pin opening and a second cartridge body pin opening; multiple axles extending from the cartridge body and through corresponding slots of the multiple slots in the outer wall and in the inner wall; and multiple in-line wheels connected to respective axles of said multiple axles so that the wheels can rotate about the axles and the cartridge is slidable up and down with respect to the base body; and at least two pins including a first pin and a second pin sized and shaped for sliding into and out of the first and second pin openings of the outer wall, the inner wall, and the cartridge body; wherein each cartridge may be selectively moved up with respect to the respective base body to a retracted position, wherein none of the wheels of the cartridge extend below the bottoms of the inner and outer walls, and may be held in that position by the first and second pins being positioned in the respective first and second pin openings of the respective outer wall, cartridge body, and inner wall; wherein each cartridge may be moved down with respect to the respective base body to an extended position, wherein all of the wheels of the cartridge extend below the bottoms of the inner and outer walls, and may be held in that position by the first and second pins being positioned in the respective first and second pin openings of the respective outer wall and inner wall; and wherein the mobile cart is in the rolling mode when the cartridge of each base system is in the extended position and the mobile cart is in the standing mode when the cartridge of each base system is in the retracted position.