A train coupler for coupling of a train car, comprising a bar, which at a front end is adapted to engage with coupling means and at a rear end attached to an anchor, the longitudinal extension of the bar in a relaxed position defining an axial direction and a central axis of the train coupler, wherein the anchor is arranged to interact with a deformation unit, the deformation unit positioned coaxially with the anchor and after the anchor in the axial direction from the bar, the anchor and the deformation unit comprised in an housing in-between a pair of front lugs and a pair of rear lugs, and the train coupler further comprising - at least one axial expansion module inserted in-between the front lugs and the anchor or in-between the anchor and the deformation unit or in-between the deformation unit and the rear lugs, the axial expansion module arranged to be expandable in the axial direction and to be expanded after having been inserted into the housing, the axial expansion module exerting a predetermined force on the deformation unit and the anchor so that the axial expansion module, the deformation unit and the anchor are held between the front lugs and the rear lugs, wherein the axial expansion module is a wedge assembly comprising at least three separate pieces wherein at least two of the three separate pieces are wedged pieces having parallel wedged surfaces facing each other and the axial expansion is provided by moving the at least the two wedged pieces relative each other in a transversal direction to the central axis, wherein the train coupler comprises two wedged assemblies provided on each side of the centre axis and their bolt heads facing the underside of the housing, and characterized by the wedge assembly comprising: - a first wedged piece with a first wedged surface and a second wedged piece with a second wedged surface wherein the first and second wedged surfaces are parallel and facing each other, the first wedged piece provided with a threaded hole provided on its bottom surface; - a third piece with a non-wedged surface which faces the non-wedged surface of the first wedged piece; - a fixture provided in contact with the bottom surfaces of the second wedged piece and the third piece and extending at least partly over the respective bottom surfaces, the fixture provided with a hole; and - a bolt extending through the hole of the fixture and engaging with the threaded hole of the first wedged piece and a head of the bolt acting on the fixture. a central axis of the train coupler, wherein the anchor is arranged to interact with a deformation unit, the deformation unit positioned coaxially with the anchor and after the anchor in the axial direction from the bar, the anchor and the deformation unit comprised in an housing in-between a pair of front lugs and a pair of rear lugs, and the train coupler further comprising - at least one axial expansion module inserted in-between the front lugs and the anchor or in-between the anchor and the deformation unit or in-between the deformation unit and the rear lugs, - at least one axial expansion module inserted in-between the front lugs and the anchor or in-between the anchor and the deformation unit or in-between the deformation unit and the rear lugs, the axial expansion module arranged to be expandable in the axial direction and to be expanded after having been inserted into the housing, the axial expansion module exerting a predetermined force on the deformation unit and the anchor so that the axial expansion module, the deformation unit and the anchor are held between the front lugs and the rear lugs, wherein the axial expansion module is a wedge assembly comprising at least three separate pieces wherein at least two of the three separate pieces are wedged pieces having parallel wedged surfaces facing each other and the axial expansion is provided by moving the at least the two wedged pieces relative each other in a transversal direction to the central axis, wherein the train coupler comprises two wedged assemblies provided on each side of the centre axis and their bolt heads facing the underside of the housing, and characterized by the wedge assembly comprising: - a first wedged piece with a first wedged surface and a second wedged piece with a second wedged surface wherein the first and second wedged surfaces are parallel and facing each other, the first wedged piece provided with a threaded - a first wedged piece with a first wedged surface and a second wedged piece with a second wedged surface wherein the first and second wedged surfaces are parallel and facing each other, the first wedged piece provided with a threaded hole provided on its bottom surface; - a third piece with a non-wedged surface which faces the non-wedged surface of the first wedged piece; - a fixture provided in contact with the bottom surfaces of the second wedged piece and the third piece and extending at least partly over the respective bottom - a third piece with a non-wedged surface which faces the non-wedged surface of the first wedged piece; - a fixture provided in contact with the bottom surfaces of the second wedged piece and the third piece and extending at least partly over the respective bottom surfaces, the fixture provided with a hole; and - a bolt extending through the hole of the fixture and engaging with the threaded hole of the first wedged piece and a head of the bolt acting on the fixture. - a bolt extending through the hole of the fixture and engaging with the threaded hole of the first wedged piece and a head of the bolt acting on the fixture.