US2178855A

US2178855A - Grinding stone

Info

Publication number: US2178855A
Application number: US191431A
Authority: US
Inventors: John E Hassler
Original assignee: Simonds Worden White Co
Current assignee: Simonds Worden White Co
Priority date: 1938-02-19
Filing date: 1938-02-19
Publication date: 1939-11-07
Anticipated expiration: 1956-11-07

Description

Nov.v 7, 1939. J. E. HAssLER 2,178,855

GRINDING STONE Filed Feb. 19, 19:58

www

Inde/775A- Patented Nov. 7, 1939 was I arrasa n Galan-nwo s'roNn John E. Hassler, Portland, Oreg., assignor to Simcnds Worden White Cio., a corporation of Ohio Application ren-nary i9, 193s, seriali No. 191,431

4 Ciaims.

In the manufacture of mechanical wood pulp, it is necessary to grind blocks of wood by means of large kgrinding stones so as to pull out the short fibers of the wood. At first, it was coms mon practice to make such grinding stones of natural stone, but the inherent defects of natural stone made them lacking in uniformity and strength. That is, the stones frequently exhibited fracture lines or other defects which caused said stones to burst under high speed rotation. Thus, recent eorts have been directed toward producing cast or artificial pulp stones or grinder wheels. It is desirable in wheels thus made that they be reinforced, preferably by circumferential reinforcing rods or bars, so that if the wheel should burst, the central pieces will not iiy out and damage the operating parts of said pulp grinder or injure workmen employed thereat.

y Bolts of Wood are held against the peripheral grinding surface of a pulp wheel under substantial pressure. The friction of the grinding stones upon the wood generates heat within said stone, and it takes a substantial period of time for said heat to equalize itself throughout the entire stone. Thus, the peripheral portions of said stoneV are heated to a greater degree than the central portions thereof, and differential expansion due to said unequal temperatures results. Said stones are integral, and thus the tendency of 3()V the peripheral surface to elongate relatively to the remainder builds up rupturing strains in the stone, frequently causing damage.

The object of my invention is to provide a pulp stone or grinder stone of this character with means permitting the peripheral portions of said stone to elongate with relation to the central portions thereof without setting up said rupturing strains. My invention has particular application to pulp stones or other grinder wheels in which the stone is cast of grit particles embedded in cementitious material and in which circumferenential reinforcing elements are located inwardly from the peripheral grinding surface of the stone. Said reinforcing material is spaced inwardly from 45 the peripheral surface of the stone as it is originally formed, to a point within the maximum permitted wear of said stone.

Said object is attained by forming a plurality of uniformly spaced radial slots extending in- 50 wardly of the peripheral grinding surface of 4said stone and preferably laterally the full width of the grinding surface and the full thickness of the grinding portion from said reinforcing material outwardly so that said grinding portion might elongate with relation to the central portion without setting up rupturing strains in said stone. Said radial slots preferably are filled with some resilient composition or material which is preferably plastic so that it Will yield readily under relative elongation, but will flow or move back when the slots are extended *toI their original width. Said filling material is desirable so that said slots cannot become lled with foreign inatter and so that the grinding surface of the wheel will be substantiallycontinuous.

The details of my invention are hereinafter described with reference to the accompanying drawing, in which: Fig. 1 is an elevation of a pulp stone embodying my invention with a portion thereof shown broken away to disclose the manner in which the radially extending expansion' slots are formed inwardly from the grinding surface of said pulp Wheel Fig. 2 is an elevation of a lpulp wheel embodying my invention with a part shown in section, said figure being taken on the line 2 2 in Fig. l; Fig. 3 is a more or less diagrammatic detail View showing the normal arrangement of one of said slots when the grinding surface is not expanded; and

Fig. 4 is a similar detail view illustrating the vmanner in which the cementitious body of the pulp wheel adjacent said expansion slots is permitted to expand and to contract the expansion slots and the plastic material with which said slots are filled.

A pulp wheel embodying my invention'comprises a cementitious cast body a in which reinforcing material b is imbedded circumferentially but spaced substantially from the grinding sur-` face a of said body. A grinder wheel of this character is adapted to be mounted upon a rotatable shaft c, the body being supported by a central flanged collar d.. to which collar the body is secured by threaded bolts or studs e; rI'he side faces a2 of said body are engaged by a pair of opposed collars f. Said collars preferably are arranged with inwardly extending lateral hub pord tions f extending into the'central bore g of said body. Said collars f engage the side faces of said body and are held tightly there against by the threading 0f said collars j upon the threaded portion c' of the shaft.

Extending radially inwardly from said grinding surface are a series of uniformly spaced radial slots h. Said slots extend the f-ull width of the pulp stone, as is shown in Fig. 2, and extend substantially the full thickness of the grinding portion a3 of said stone. The grinding portion a3 55 of said stone is that portion extending outwardly from the reinforcing material b. That is, when said stone is worn down to a point adjacent the reinforcing material, it is considered to have outlived its usefulness. The wearing down of the pulp stone correspondingly diminishes the radius thereof, and when the stone is worn down to such small diameter that the reinforcing material is exposed, it is thrown away.

Said radial slots are preferably filled with some plastic resilient material such as an asphaltic composition. Said sections i of plastic material prevent foreign -matter from becoming lodged within the radial slots and also bridge over the gap which would be left in the grinding surface if said sections were not in place. If said slots were not filled, it would be possible for them to be filled up and the material to become lodged therein to such a degree that it would prevent the stone from expanding freely and permit said expansion slots from functioning. When said stones are operated, the friction generated by applying the grinding surface to a block of wood relatively causes the said surface to become heated substantially greater than the central portions thereof. A cast stone of this character is a poor conductor of heat, and thus relatively severe differential expansion takes place in said stone.

To limit the absorption of heat in the stone, it is common practice to run water over the face of the stone during the grinding operation. The water not only functions to cool the stone but carries away the small shredded fibers ground off. It is impractical, however, to provide sufficient water to keep said stone cool, because this would produce too thin a pulp stock. Of course, after a long operating period, the stone becomes more or less uniformly heated and the central portions are heated somewhat similarly to the periphery, thedifferential expansion which produces rupturing strains is eased, and the expansion slots take their original shapes. As is shown diagrammatically in Fig. 4, the slots have a normal width at. Under induced increase in temperatures, particularly at the grinding surface a', said slots may narrow to a width y under the stresses imposed by differential expansion. Uniform temperature throughout the stone, yof course, will cause said slots to approximate their original Widths.

I claim:

1. A pulp grinding stone comprising an integral cylindrical body having a peripheral grinding surface, and a plurality of uniformly spaced radial slots extending inwardly from said grinding surface, the total width of said slots being proportioned to accommodate the overall greater relative circumferential expansion of the grinding surface of said stone than the remainder thereof in the presence of increased temperatures set up in said stone by the heat generated in grinding, said slots being lled with a plastic composition adapted to yield under said greater relative Vcircumferential expansion.

2. A pulp grinding stone comprising an integral cylindrical body having a peripheral grinding surface, and a plurality of uniformly spaced radial slots extending inwardly from said grinding surface, the total width of said slots being proportioned to accommodate the overall greater relative circumferential expansion of the grinding surface of said stone than the remainder thereof in the presence of increased temperatures set up in said stone by the heat generated in grinding, said slots being lled with a resilient composition` adapted to yield under said greater relative circumferential expansion.

3. A pulp grinding stone comprising an integral cylindrical body having a peripheral grinding surface, and a plurality of uniformly spaced radial slots extending inwardly from said grinding surface, the total width of said slots being proportioned to accommodate the overall greater relative circumferential expansion of the grinding surface of said stone than the remainder thereof in the presence of increased temperatures set up in said stone by the heat-generated in grinding, said slots being lled with an asphaltic composition adapted to yield under said greater relative circumferential expansion.

4. A cast pulp grinding stone comprising an integral cementitious cylindrical body having a peripheral grinding surface, said stone having circumferential reinforcing elements embedded therein lying inwardly from said grinding surface a substantial distance, the portion 0f said grinding stone lying between said reinforcing elements and said surface constituting the active grinding portion of said stone, and a plurality of uniformly spaced radial slots extending inwardly from said grinding surface, laterally the full width thereof, and the full thickness of said grinding portion, the total width of said slots being proportioned to accommodate the overall greater relative circumferential expansion of the grinding surface of said stone than the remainder thereof in the presence of increased temperatures set up in said stone by the heat generated in grinding, said slots being lled with a plastic, resilient, asphaltic composition adapted to yield under said greater relative circumferential expansion.

JOHN E. HASSLER.