GB584433A - A portable grinding machine - Google Patents

Abstract

584,433. Grinding valve-seats. DEHN, F. B. (Hall Manufacturing Co.). Jan. 18, 1944, No. 962. [Class 60] A portable valve seat grinding - machine, wherein the grinding-disc has an orbital movement, has the axis of the grinding-disc inclined slightly to the axis of the pilot supporting the machine, the arrangement being such that the axes intersect approximately at a point spaced inwards from the outer end of the shaft. The machine, supported on a pilot 4 mounted in the valve stem guide 3 of the valve seat 2 being ground, comprises a body A having therein an electric motor 14, the hollow shaft 15 of which is coaxial with a shaft 10 adapted to rotate on the pilot, the shaft 10 carrying a sleeve 20 journalled in a bushing 21 in a part 22 of a gear casing 18 carried by the body A. The sleeve 20 has a worm-wheel 23 thereon, and also supports on ball bearings 25 a hollow spindle 11, coaxial with the shaft 10 and carrying at its lower end the grinding disc 5. The spindle 11 has thereon a spur gear 30 in mesh with a gear 34 on a counter-shaft 31 driven by the motor shaft 15 through gears 33, 32, and driving the wormwheel 23 through worm-gears 35, 36 ; the shaft 10 thus rotates slowly and the spindle 11 rotates at high speed. The bore 40 of the shaft 10, which receives the pilot 4, has its axis a inclined slightly to the axis b of the shaft, the axes a, b intersecting at the point 41 which is the centre of balance of the machine ; the grinding-disc 5 thus engages the seat 2 at one side of its axis and the point of engagement moves round the seat, the body A swinging round on the opposite side of the axis, so that the tool as a whole is balanced. A depth gauge rod 50 passes down the shaft 15 to engage the top of the pilot 4, thus suspending the machine in predetermined relation to the seat 2 ; the rod 50 is adjustably secured by a screw 52 in an adjusting head 51 screwing on a sleeve carried by the body A and locked by a spring detent 53. In a modification, the machine has the motor on an axis offset from the axis of the shaft and grinding-disc spindle, a handle projecting laterally from the top of the machine and including a fixed member and a slidable member with interposed spring means, whereby a predetermined balancing force may be applied. The pilot engaging bore may be formed in a sleeve fitted into the lower end of the hollow shaft, either the bore receiving the pilot or the bore of the shaft being inclined and the sleeve rotating either on the pilot or in the bore of the shaft.