a dispenser sequentially dispenses web material from a working web roll and then a reserve web roll . a web sensing mechanism senses the presence of the working web at a back side of the main feed roller and introduces the leading end of the reserve web roll to a feed nip defined by two feed rollers immediately after the trailing end of the working web roll passes over a back side of the feed roller . web sensing , and controlled introduction of the leading end of the reserve web to the feed nip , are carried out by a simple and effective interaction of a grooved main feed roller , and a pair of pivotable lever arms — a web sensing arm mounted at the backside of the rollers , and a transfer arm mounted at the front side . the mechanism avoids double feeding of web by sensing the presence or absence of web at the back - side of the main feed roller . transfer fingers of the transfer arm are movable against the reserve roll web and into corresponding grooves in the main feed roller such that a leading end portion of the reserve roll web is reliably moved into the vicinity feed roller nip , where serrations provided in the edges of the grooves facilitate a gripping of the leading end portion to pull the web through the nip . the feed path is arranged to extend away from the transfer fingers so as to avoid interference of the transfer fingers with the subsequent feeding of the web .