US2066629A - Pulpstone - Google Patents

Description

Jan. 5, 17937. T LARSSON 2,066,629

PULPSTONE Filed March 25, 1936 3mm THL/RE L HRS-SUN Patented Jan. 5, 1937 1 UNITED STATES PULPs'roNF.

Thure 'Larsson, Worcester; Mass, assignor to Norton Company, Worcester, Mass, a corporation of Massachusetts Application March 25, 1936, Serial o. 70,813

4 Claims.

The invention relatesto grinding wheels, and with regard to its more specific features to a pulp grinding-wheel or stone for the grinding of logs into fibre which is converted into pulp and thereafter made into paper.

One objectof the invention is to provide a simple and practical pulpstone construction. Another object of the invention is to provide an expansible pulpstone construction embodied in a particular shape of the segments or sectors. Anotherobject of the invention is to provide a freely cutting pulpstone. Another object of the invention is to provide a segment or sector which is substantially non-fracturable. Another object of the invention is to provide a simplified method for the manufacture of an expansible pulp-stone. Other objects will be in part obvious or in part pointed out hereinafter.

'I'he'invention accordingly consists in the features of construction, combinations of elements, arrangements of parts, and in the several steps and relation and order of each of said steps. to one or more of the others thereof, all as will be illustratively describedherein, and the scope of the application of which will be indicated in the following claims;

Inthe accompanying drawing, in which is shown one of several possible-embodiments of the mechanical features of this invention,

- 5 Fig. '1 is an elevation of a pulpstone;

Fig. 2 is a' fragmentary radial sectional view, on an enlarged scale, taken on the line 2-2 of Fig. 1;

' Figx3' is an isometric view of a segment or sector. v

' Referring'first to Figures 1 and 2, there is provided a driven spindle l0 to'which is keyed the hub, not 'sh6wm of 'a drum l2, and the construction in this respect may be the same as disclosed in U. SsLetters Patent No. 1,850,231 issued on application of Wallace W. Greenwood. I preferably provide Wedge blocks 20, studs 22 and nuts 23 as in the aforesaid Greenwood patent.

Considering now more particularly certain specific features of my invention, and referring particularly to Figure 3, I provide a plurality of sectors 25 (parts of this general type being sometimes referred to as segments). Each sector 25 has a flat or plane side 26 which, together with others, forms one radial face of the entire wheel. Each sector 25 has a face 21 originally in an axial plane of the Wheel but having V- grooves 23 cutting its surface leaving dihedral angle apexes 29 which are in said original plane.

The surface soformed is also altered by one-half of a dovetailed groove 30.

Referring now to Figures 1 and 2, the side 3| opposite the side 21 of each sector has V-grooves 32 leaving dihedral angle apexes 33 which are in the original radial axial plane of the sector. Whereas the apexes 29 are radial lines, the apexes 33 are not radial but parallel to the wheel axis. When two sectors are put together, therefore, apexes 29 cross apexes 33. More specifically, they are perpendicular to each other, but it must be understood that they might cross each other at different angles with similar results so far as this invention is concerned. The radial axial side 3! is modified by the other half 35 of a dovetailed grove. The wedge blocks 20 are dovetailed andrest against opposite grooves 30, 35 and against facings or shoes 36, 31 respectively and hold the sectors in position, as described in the aforesaid Greenwood patent.

Considering now Figure 1, I prefer to stagger the line joining sectors in the manner illustrated in order that there shall not be a circle on the wheel surface which is entirely in a line of division. In other words, any circle in a plane normal to the wheel axis on the surface of the wheel passes over solid abrasive.- Accordingly, considering now sectors individually, and referring again to Figure 3, I provide two side faces 40 and M; the planes of which are not perpendicular to the wheel axis and the planes of which are disposed to each other to form a very obtuse dihedral angle. The surface 40 is grooved by V- grooves 42 having apexes 43 which are substantially radial." The surface 41 is grooved by V- grooves 44 having apexes 45 which are perpendicular to adjoining apexes 43 on a different sector, but again contiguous apexes 43 and 45 may cross each other at other angles.

Considering now the manufacture of the sectors 25, I provide a quantity of abrasive grain, for example fused alumina, emery or corundum, or silicon carbide or any other desired type. I provide a quantity of suitable bond, preferably ceramic bond intending to include preformed frits and the like. Forming a desired mixture of the abrasive grains and bond, preferably coating each granule with some bond, and including in the mixture a suitable plasticizer or temporary binder, or using a plastic clay such as ball clay and a certain amount of water, I place a regulated quantity of the mixture in a mold which is shaped to form a sector in outline, that is to say with the two cylindrical surfaces, the plane surface 26 and surfaces 21, 3|, 40 and 4| to true planes,

but with the half dovetailed grooves 30 and breaking said planes. I press the mixture in the mold, preferably to a predetermined volume content of abrasive grains and bond and to the described shape, and upon removing the mass from the mold it is in the so-called "gree condition and by reason of the temporary binder or plasticizer or plastic clay or all of these will hold its shape. I then form the grooves 28, 32, 42 and 44 by means of gang milling cutters, or shaping tools or like operations analogous to a machining operation on metal.

After the grooves are formed as described, the sectors are placed in a kiln and the bond is burned or otherwise treated to convert it to the desired condition. In the case of ceramic bonded articles I use any suitable type of kiln and kiln temperatures. In the case of organic bonded articles, the heat treating or maturing temperature may be described as a baking rather than a burning or firing. It must be understood that the wheel may be formed of sectors bonded with any type of bond and is not limited to any particular one. For example, rubber may be used, or phenolic resinoids or other types of resinoids. Shellac or sodium silicate may also be used. Various cements have been found satisfactory for the manufacture of pulpstones and I may use any one thereof. But so far as certain features of the invention are concerned, I prefer to use a fired ceramic or a vitrified bond, and certain advantages follow from the use thereof.

After the wheel is assembled, it may be used in the usual manner for the grinding of logs to form pulp. While various fillers may be placed between sectors, one characteristic of my invention is that the stone may be used without any filler. After a short period of pulp grinding, the spaces between sectors become filled with a packing of wood pulp, at least to some extent. Furthermore, the absence of any foreign material between sectors has certain advantages, and the relatively open space between sectors (filled only with a deposit of wood pulp which has a negative action on wood) provides an open clearance space which facilitates cutting. Furthermore, sectors may readily be replaced with a minimum of difiiculty.

Pulpstones are preferably made to withstand ordinary conditions involving use in practically Arctic localities, at least so far as temperature is concerned, and a particular pulpstone may have to withstand a change from a temperature of minus 20 or 30 F. to a temperature of several hundred degrees Fahrenheit. During the normal operation of grinding pulp, no such high temperatures are usually reached, but occasionally the supply of water is cut off accidentally and the pulpstone rapidly overheats. Furthermore such heating is not uniform throughout the stone. As a result thereof there is an expansion which, unless provision is made, may fracture sectors and may ruin the stone.

According to the present invention, when excess expansion occurs, the apexes 29, 33, 43 and 45, or some or all of them, are crushed. Contacting apexes crush each other, especially owing to the crossed arrangement. This constitutes a safety feature to prevent fracture of the sectors under unusual conditions. When the emergency is over and the stone has cooled off, there is simply a little wider gap between sectors which will rapidly fill up.

I may provide one set of grooves and apexes resting against a plane face of an adjacent sector in certain cases, as where mixtures are used resulting in sectors of less grade hardness. With the described construction, however, there is substantially point contact and the apexes crush before the sectors can fracture.

It will thus be seen that there has been provided by this invention a method and an article in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As various possible embodiments might be made of the mechanical features of the above invention and as the art herein described might be varied in various parts,

all without departing from the scope of the invention, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawing is to be interpreted as illustrative and not in a limiting sense.

I claim:

l. A grinding wheel comprising a drum, 9. plurality of sectors attached to said drum, and radial faces of some sectors being grooved so that crushable apexes are provided at all joints.

2. A grinding wheel comprising a central support, sectors attached to the central support, some sides of some sectors being grooved to provide crushable apexes.

3. In a grinding wheel, a central support, a plurality of sectors attached to said central support, radial sides of adjacent sectors being grooved leaving apexes, and the apexes being disposed to cross each other.

4. In a grinding wheel, a drum, a plurality of sectors each having one half of a dovetailed groove, bolts and wedge blocks to attach the sectors to the drum, there being a plurality of rows of sectors so shaped that the joint between rows is a staggered line, each sector being grooved leaving apexes, and the apexes running in difl'erent directions so that each set of apexes contact apexes running across them.

THURE LARSSON.

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