Patent ID: 7284414

Claim:
A hardness testing device for measuring a hardness of a work piece surface, comprising: an elongated guiding tube having a bottom impact opening for contacting with said work piece surface and a coil seat formed on an outer circumferential surface of said guiding tube at a position close to said impact opening, wherein said coil seat has two spaced apart guiding slits; a test member slidably moving within said guiding tube; an impact actuator provided on an upper portion of said guiding tube for applying a force against said test member such that said test member travels within said guiding tube at an impinging velocity before impacting with said work piece surface and at a rebound velocity after impacting with said work piece surface; and a transducer, which comprises: an electric coil coaxially wound on said coil seat to minimize a clearance between said electric coil and said test member when said test member slidably passes through said coil seat is adapted to electromagnetically communicate with said test member for detecting said impinging velocity and said rebound velocity of said test member when said test member slidably passing through said coil seat; and a hardness interpreter arranged for measuring a hardness of said work piece surface with respect to said impinging velocity and said rebound velocity, wherein two end portions of said electric coil are extended from said coil seat to said upper portion of said guiding tube along said outer circumferential surface thereof to electrically connect to said hardness interpreter through said guiding slits respectively so as to retain said two end portion of said electric coil on said outer circumferential surface of said guiding tube.