Abstract: Sound boards having an elongate, approximately trapezoid shape, provided on the front face with a central longitudinal profiled string-carrier member and on the reverse side with a central profiled reinforcing member or beam, and with two side profiled members or sound bars, symmetrically disposed with respect to the reinforcing beam are provided. In such sound boards the cross-section of the reinforcing beam has a central portion with an increased height or thickness and two adjacent, symmetrical side portions or wings having a height or thickness which tapers gradually towards the outside through a concave arcuate profile up to a predetermined minimum value.

Abstract: Sound chests having a sound board connected to a hollow body which includes a bearing structure to which there is connected an outer shell are provided. In such sound chests the bearing structure includes a bottom wall or chest-bottom, and a top member or upper block, a central longitudinal batten or backboard, and two side battens or planks, which extend between the chest-bottom and the upper block, remote from and close to the sound board, respectively; and a plurality of longitudinally staggered, transverse stiffening members or bridges each of which is connected centrally to the backboard with its ends connected to the side planks. Methods for making such sound chests are also provided.

Abstract: Sound chests having a sound board connected to a hollow body which includes a bearing structure to which there is connected an outer shell are provided. In such sound chests the bearing structure includes a bottom wall or chest-bottom, and a top member or upper block, a central longitudinal batten or backboard, and two side battens or planks, which extend between the chest-bottom and the upper block, remote from and close to the sound board, respectively; and a plurality of longitudinally staggered, transverse stiffening members or bridges each of which is connected centrally to the backboard with its ends connected to the side planks. Methods for making such sound chests are also provided.

Abstract: Sound boards having an elongate, approximately trapezoid shape, provided on the front face with a central longitudinal profiled string-carrier member and on the reverse side with a central profiled reinforcing member or beam, and with two side profiled members or sound bars, symmetrically disposed with respect to the reinforcing beam are provided. In such sound boards the cross-section of the reinforcing beam has a central portion with an increased height or thickness and two adjacent, symmetrical side portions or wings having a height or thickness which tapers gradually towards the outside through a concave arcuate profile up to a predetermined minimum value.

Abstract: The surface of a metallic substrate is coated with wear-resistant material by depositing on the surface a layer of a mixture of a coating powder including a metallic carbide with powdery silicon and heating said layer by exposure to a source of high density energy to bring about simultaneous evaporation of said silicon and fusion of said coating powder with bonding to said substrate. A coating of high surface porosity can be obtained.The substrate may be a piston ring for heavy-duty internal combustion engines.