Patent Document ID: 9383341
Application ID: 14066504
Patent Flag: 1

Claim One:
1. An apparatus for grading a wood lumber specimen including an electric hammer with a bimetallic armature for striking a first end of said wood lumber specimen, and an acoustic sensor means for detection of sonic reverberation in said wood lumber specimen and a computer processing means whereby said wood lumber specimen is struck on the first end of the wood lumber specimen by the bimetallic armature thereby inducing a sonic reverberation in the wood lumber specimen, and a property information value is calculated for the wood lumber specimen from the wood lumber specimen density and the sonic reverberation in the wood lumber specimen: and, the electric hammer includes a solenoid coil wound with electrically conductive wire and a cylindrical open center extending from a first end of the solenoid coil to a second end of the solenoid coil; and, a magnetic circuit means composed of ferromagnetic material whereby a magnetic field is conducted externally around the solenoid coil; and, a first linear bearing means arranged at the first end of the solenoid coil such that the first linear bearing means is maintained in coaxial alignment with the cylindrical open center of the solenoid coil; and, a second linear bearing means arranged at the second end of the solenoid coil such that the second linear bearing means is maintained in coaxial alignment with the cylindrical open center of the solenoid coil: and, the bimetallic armature is composed of a magnetic steel portion and a nonmagnetic steel portion with a transition there-between and with constant circular cross section of a diameter that provides a loose running fit between the bimetallic armature and the first and the second linear bearing means and the cylindrical open center of the solenoid coil, the first and the second linear bearing means allowing axial movement of the bimetallic armature: and, the magnetic circuit means and the bimetallic armature do not include an operative air gap; and, a return spring whereby the bimetallic armature is urged into a preferred starting position when said solenoid coil is not conducting electric current: and, a stop-bumper means arranged adjacent to the second linear bearing means to set the position of the preferred starting position: and, an electric circuit means for supplying an electric current impulse to the solenoid coil whereby the electrical current impulse causes the magnetic field to be generated in the solenoid coil and the bimetallic armature is caused to accelerate rapidly in a direction that extends the bimetallic armature outwardly and away from the stop-bumper to a preferred distance at which point it strikes the first end of the wood lumber specimen with a single impact thereby producing a compressive stress wave and sonic reverberation in said wood lumber specimen and the wood lumber specimen density is determined in any conventional manner.