Device for transporting flat elements along a given conveyor path, comprising: - an endless transport member which is roll-guided over the whole length of the conveyor path by a succession of substantially adjacent guiding members , at least one mobile guiding member being mounted mobile offset with respect to static guiding members being mounted secured, between a retracted position wherein the mobile guiding member is placed in the direct continuity of the static guiding members , and a deployed position wherein the mobile guiding member stands at a distance from the static guiding members , and - complementary guiding members which are mounted mobile in movement between a reserve position wherein they are placed at a distance from the static guiding members and the mobile guiding member when the latter is in the retracted position, and a service position wherein they are inserted continuously between the static guiding members and the mobile guiding member when the latter is in the deployed position, characterised in that it comprises coupling means , - which are capable of driving the movement of the complementary guiding members between the reserve position and the service position, when the mobile guiding member is moved between the retracted position and the deployed position, and - which comprise a drive element which is secured to the complementary guiding members , and which engages simultaneously by sliding with - on the one hand, a guiding element secured to the static guiding members , called static drive guide , defining an oblique guiding path which will approach the conveyor path with respect to the movement direction of the flat elements, and - on the other hand, a guiding element secured to the mobile guiding member , called mobile drive guide , defining an oblique guiding path, which will extend away from the conveyor path with respect to the movement direction of the flat elements. - an endless transport member which is roll-guided over the whole length of the conveyor path by a succession of substantially adjacent guiding members , at least one mobile guiding member being mounted mobile offset with respect to static guiding members being mounted secured, between a retracted position wherein the mobile guiding member is placed in the direct continuity of the static guiding members , and a deployed position wherein the mobile guiding member stands at a distance from the static guiding members , and - complementary guiding members which are mounted mobile in movement between a reserve position wherein they are placed at a distance from the static guiding members and the mobile guiding member when the latter is in the retracted position, and a service position wherein they are inserted continuously between the static guiding members and the mobile guiding member when the latter is in the deployed position, characterised in that it comprises coupling means , - which are capable of driving the movement of the complementary guiding members between the reserve position and the service position, when the mobile guiding member is moved between the retracted position and the deployed position, and - which comprise a drive element which is secured to the complementary guiding members , and which engages simultaneously by sliding with - on the one hand, a guiding element secured to the static guiding members , called static drive guide , defining an oblique guiding path which will approach the conveyor path with respect to the movement direction of the flat elements, and - on the other hand, a guiding element secured to the mobile guiding member , called mobile drive guide , defining an oblique guiding path, which will extend away from the conveyor path with respect to the movement direction of the flat elements. <EOS>