Planetary-type lapping device for finish-grinding the valve seat of a safety relief valve

Claim 1

A planetary-type lapping device for finish-grinding the surface of the valve seat of a safety relief valve, said lapping device comprising: a gear housing which confines a gear receiving space, said gear housing having a top end with a rotatable axial shaft which extends upwardly therefrom and a bottom end, a primary gear means mounted rotatably to said gear housing in said gear receiving space; at least one secondary gear unit provided in said receiving space and meshing with said primary gear means, each said secondary gear unit being provided with an axle that is mounted rotatably to said gear housing and that has a lower end which extends downwardly through said bottom end of said gear housing; and a grinding disc mounted on said lower end of said axle of each said secondary gear unit, each said grinding disc having a lower side formed with a grinding compound; said primary gear means being mounted statically to the safety relief valve, said axial shaft being axially rotated to rotate said gear housing and cause each said secondary gear unit to revolve around said primary gear means, revolution of said secondary gear unit around said primary gear means causing axial rotation of said secondary gear unit, said grinding disc rotating with the respective said secondary gear unit to permit said grinding compound to lap the surface of the valve seat, said primary gear means further comprises: a gear member mounted rotatably to said gear housing and being formed with an axial positioning hole; and a positioning rod having a top end which is fittingly received in said positioning hole and a lower end which extends through said bottom end of said gear housing, said lower end of said positioning rod being adapted to extend through the valve seat and being adapted to be mounted statically to the safety relief valve.