Abstract: A synchronized dog clutch according to the invention comprises a clutch shaft, a coupling sleeve splined to the clutch shaft and having dog claws at its end, a synchronizer ring slidably fitted to outer periphery of the coupling sleeve, said synchronizer ring having a conical face for frictional engagement and being rotatable together with the coupling sleeve, and a gear wheel coaxially and rotatably arranged with respect to the clutch shaft and having teeth at its outer periphery. The gear wheel is provided with a conical face and claws respectively engagable with the conical face of the synchronizer ring and the claws of the coupling sleeve. The conical face of the gear wheel is disposed closely and radially inside the teeth, and the claws of the gear wheel are arranged inside the conical face, and thereby torque transmitted through the conical faces for synchronization is increased.

Abstract: A decorative coating layer, unified with the succulent and fragile surface of a concrete board, is formed by a method comprising laminating an inorganic and hydraulic coating material on the surface of an unhardened concrete board placed in a mold, and immediately thereafter heat-curing the thus coated concrete board. According to this method, beautifully dressed precast concrete boards can be mass-produced by a shortened process with improved efficiency of operation.