A spring tension control system for the front and rear application roller arms, and for the sealing tape application rollers mounted thereon, of a tape cartridge assembly of a case sealing machine comprises a first spring-biasing mechanism to control the disposition and movement of the front and rear application roller arms upon which are respectively mounted the front and rear case sealing tape application rollers for applying the sealing tape to the vertically oriented front and rear surface portions of the case. In addition, there is also provided a second spring biasing mechanism which operatively cooperates with the first spring biasing mechanism so as to effectively impart an enhanced amount of tension and speed to the rear case sealing application roller in order to achieve enhanced case sealing processing speeds.