Abstract: A repairing method using a lance for repairing an oven wall surface of a coke oven comprises the steps of arranging a distance sensor at a top end of the lance, quantitatively measuring a depth of a worn or a damaged area by the distance sensor, and blowing a repairing material from a repairing nozzle to the worn area in accordance with a measurement result to thereby repair the worn area. The lance used in this repairing method has a multistage structure having a polygonal cross section and is extendable. With this structure, the oven wall surface can be scanned in a linear fashion or along a plane. If the top end of the lance is movable in accordance with a basic motion pattern and/or a travelling pattern, it is possible to readily repair a repair range having a complicated shape.

Abstract: A telescopic hydraulic damper includes an outer tube filled with working oil, a pipe member mounted on the bottom of the outer tube, and an inner tube slidably disposed in the outer tube. A valve structure disposed in an inner end of the inner tube comprises a valve body lossely fitted over the pipe member, and a plurality of valve seats mounted in the inner end of the inner tube and spaced from each other across the valve body. The valve seats include an oil locking seat for shutting off working oil between the oil locking seat and the valve body upon engagement with each other, and a rebound seat for allowing working oil to flow between the rebound seat and the valve body upon engagement with each other. The oil locking seat having a surface for engaging the valve body, the surface being inclined at an acute angle with respect to the longitudinal axis of the damper.

Abstract: A hydraulic damper includes a cylinder filled with working oil, a piston rod extending axially in the cylinder, and a piston slidably disposed in the cylinder and fixed to the piston rod, the piston having an oil passage defined therein. A valve structure in the hydraulic damper has a spacer disposed around the piston rod and on one surface of the piston, a leaf valve disposed around the spacer for normally closing an end of the oil passage at the piston surface, and a restriction plate disposed around the piston rod and mounted on the spacer and the leaf valve for allowing the leaf valve to open the end of the oil passage only during one of compression and expansion strokes of the piston with respect to the cylinder.