Keystone set

Keystone set for installation in a transition region (30) between two sections (14a, 14b) of a support structure (14), which is formed as an arch and is comprised of fire-resistant stones (22), each of which has a trapezoid cross-section when viewed from the side and is joined on its face corresponding to adjacent stones (22) via substantially radial tongue-and-groove arrangements (24, 28), the keystone set comprising two transitional stones (32a, 32b), which on their outer side, adjacent the respective last stone (22a, 22b) of the corresponding section (14a, 14b) of the support structure (14), have a corresponding tongue or groove profile for positive locking and are formed on their opposite faces with a substantially axial step (34), the keystone set also comprising at least one keystone (36a, 36b), whose shape is such that it is axially insertable with positive locking into the space between the transition stone (32a, 32b),

• the keystone (36a, 36b) being divided into two structurally identical sections (36a, 36b) lying opposite one another in a symmetrical manner,
• the contact faces (40) of the keystone sections (36a, 36b) being flat,
• further including positive locking means for joining the keystone sections (36a, 36b) together,
• said locking means including tongue-and-groove joints formed in the keystone sections (36a, 36b),
• the keystone sections (36a, 36b) (seen in the radial direction from the outside inward) being conically formed,
• the transition stones (36a, 36b) being structurally identically formed,
• the tongue-and-groove devices of the transition stones (viewed in the radial direction from the outside inward) being tapered, and
• the tongue-and-groove devices of the transition stones (view in the radial direction from the outside inward) having a step.