GB1030592A - Improved pulpstone and method of making the same - Google Patents

Abstract

1,030,592. Pulpstones. NORTON CO. April 21, 1965, No. 16690/65. Heading B3D. A pulpstone comprises a core having a circular cross-section and a plurality of segmental blocks secured by prestressed bolts about and in contact with the peripheral surface of the core, the blocks collectively forming an abrasive facing around the core, means being provided whereby the core is constantly constrained in compression circumferentially and means being provided on the prestressed bolts which secure the segments to the core and which also resist the centrifugal force developed in the segmental blocks while permitting constant circumferential compression on the core to be maintained. Abrasive segments 10 are assembled in a cylinder with temporary joint-forming material 52, e.g. a thermoplastic, between the segments. Each segment has secured thereto four bolts 16, the head of each bolt having a coarse thread or annular ribs anchored in a radial hole in the segment. Metal reinforcing hoops 30 are arranged in pairs on both sides of the bolts 16 within the cylinder. A retainer plate 36 is mounted on each bolt 16 so as to bear against the inner surfaces of the adjacent hoops 30 and a sleeve 34 is mounted on each bolt 16 with its outer end bearing against the plate 36. The hole in the plate 36 and the bore of the sleeve 34 are both of larger diameter than the bolt 16 to minimize heat transfer from the bolt 16 to the core. A nut 28 is threaded on the inner end of the bolt 16 with spring washers 26, 26 interposed between it and the inner end of the sleeve 34. The nuts 28 are tightened to impart a tension of approximately 2500 lbs. to each of the bolts 16 which is transmitted, through the sleeves 34 and retainer plates 36, to the hoops 30 so as to tension them. The outer surfaces of the bolts 16, nuts 28, washers 26, sleeves 34 and retainer plates 36 are coated with latex or the like, to permit movement of those parts relative to the core. A reinforcement for resisting destructive compression under the working load is arranged centrally of the cylinder. It comprises hoops 38, 40, rods 42, 44 and stirrups each having a base 48 and legs 50, 50 extending almost to the hoops 30. The hoops, rods and stirrups are secured together where they meet. Concrete or the like is poured into the space between the cylinder and a form for the central aperture 14 to form a core 12, and cured under trolled moisture conditions to minimize shrinkage. When the stone is put into use it heats up, so that the material 52 gives way. The bolts 16 hold the segments 10 against the core, and the tension in the hoops 30 is relieved to exert compression on the core.