Finishing machine for concrete surfaces

Claim 1

AN APPARATUS FOR FINISHING THE SURFACE OF FRESH CONCRETE INCLUDING A VIBRATORY BEAM, SAID BEAM COMPRISING AN ELONGATE FLEXIBLE METALLIC SHEET PROVIDED WITH A LONGITUDINAL ARCUATE CREASE FORMING TWO ANGULARLY DISPOSED FLANGES THEREOF, ONE OF SAID FLANGES BEING VERTICAL AND THE OTHER SUBSTANTIALLY HORIZONTAL, MEANS PROVIDING A REINFORCING RIB ALONG THE FREE MARGIN OF THE VERTICAL FLANGE, AND VIBRATORY MEANS ENGAGING SAID REINFORCING RIB FOR IMPARTING VIBRATION TO SAID BEAM, SAID MEANS VIBRATING NORMAL TO THE LONGITUDINAL AXIS OF SAID BEAM, SAID REINFORCING RIB IMPARTING SUFFICIENT RIGIDITY TO SAID BEAM TO PREVENT RESONANT TRANSVERSE VIBRATION OF SAID BEAM EXCEPT AT FREQUENCIES HIGHER THAN THAT IMPRESSED BY SAID VIBRATORY MEANS, AND SAID ARCUATE CREASE HAVING SUFFICIENT FLEXIBILITY TO PREMIT RESONANT VIBRATION OF SAID HORIZONTAL FLANGE ABOUT A LONGITUDINAL AXIS DEFINED BY SAID CREASE AT THE FREQUENCY OF VIBRATION IMPRESSED BY SAID VIBRATORY MEANS, SAID FLANGES BEING SUFFICIENTLY SIMILAR IN WIDTH TO ACCOMPLISH SUCH VIBRATION.