It is unlawful for any person, firm or corporation to use or occupy any public sidewalk in the city for the display of goods, wares of merchandise, or to use the exterior walls of any building abutting upon any public sidewalks, street, alley or passageway, for the display of goods, wares, merchandise, boxes, barrels, trucks or other articles upon any street or public sidewalks or a portion thereof in the city; provided, however, that the above restrictions shall not apply when said goods, wares, merchandise, boxes, barrels or other articles are in actual process of being loaded into or discharged from a vehicle. The actual loading of such articles shall not consume a period of time in excess of thirty (30) minutes. (Prior code § 3200)