US1944184A

US1944184A - Manufacture of abrasive articles

Info

Publication number: US1944184A
Application number: US573004A
Authority: US
Inventors: Henry P Kirchner
Original assignee: Carborundum Co
Current assignee: Unifrax 1 LLC
Priority date: 1931-11-04
Filing date: 1931-11-04
Publication date: 1934-01-23
Anticipated expiration: 1951-01-23

Description

Jgn. 23, 1934. KlRcHNE Mmumdwunflor ABRAYSIVE ARTICLES Filed Nov. 4, 1931 T, J I

INVENTOR 1. w v HENRY V mam-mu.

ATTORN EY Patented Jan. 23, 1934 1,944,184 MANUFACTURE or anassrva ARTICLES Henry P. Kirchner, Niagara Falls, N. Y., assignor to The Carborundum Company, Niagara Falls, N. Y., a corporation of Pennsylvania Application November 4, 1931. Serial No. 578,004

' 8 Claims. (or 51-201) This invention relates to improvements in the manufacture of abrasive articles and is applicable to abrasive wheels intended for peripheral grinding, although not limited to this method of grinding.

A typical operation in which abrasive wheels are subjected to temperature changes is that-of grinding wood to produce paper pulp. Wheels intended for this type of service must resist tem- The use of these crusher leads is familiar particularly to the gun and ammunition art for measuring breach pressure. My invention is not devoted to new methods for measuring definite flange pressures, but has t'o'dowith the maintaining at a constant value any derived or predetermined flange pressure when the assembly is subjected to temperature change.

A large abrasive wheel, such as is used for- 10. perature changes at least from minus 40 degrees pulp grinding, is made almost invariably of,mate-'- centigrade to plus 100 degrees centigrade. They furthermore must be made very rugged mechanically, in order to perform under loads as high as 2000 horse power. They are made in sizes as heavy as eight tons, requiring a sixteen inch diameter steel spindle, and are mounted between right and left-hand threaded flanges to guarantee their proper mechanical functioning and safety. I

The serious difliculty encountered in the operation of an artificial abrasive wheel for such purposes is the building up of excessive flange pres-- sure which may lead to the destruction of the wheel. These pressures may also exist in the mounted natural sandstone assemblies.

The more important causes of flange pressure are due (1) to the large driving torque, and (2) to the action of differential expansion between steel spindle and abrasive body when assemblies are subjected to temperature changes. The pressure due to the first cause may amount to from 500 to 900 pounds per square inch under the flanges and is not serious, but is, in fact, essential in order th is the wheel may perform its work. The. incre e in pressure due to temperature change, such as cooling the wheel from 100 degrees centigrade to 10 degrees centigrade, however, may amount to three or four thousand pounds per square inch, and it isthe magnitude of these secondary pressures acting upon the abrasive that, to a large degree, causes cracking of such wheels.

The status of the prior art is such that constant flange pressure is an ideal but unrealized condition for assemblies which may be subjected to temperature changes. It would be still more advantageous to be able to impose a predetermined, definite, flange pressure, especially for the larger sizes of abrasive wheels which require heavy power input, but here again the inability to maintain the pressure constant has prevented proper development of this phase of the problem. There are various mechanical methods which may be used to measure pressure and place a definite flange pressure upon an abrasive wheel such as small hydraulic pistons and suitable gauges placed between the flanges, or flange pressures may be determined by measuring the distortion of crusher'leads suitably embedded in the flanges under a definite area of flange bearing.

rial that has a lower coefllcient of thermal expansion than the steel shaft upon which it is mounted. The flanges that grip the sides of the wheel are threaded in left and right-hand directions, respectively, so that the power that turns the shaft tightens the flange grip upon the wheel sufliciently to carry the required load. The wheel and shaft become very hot during use and, consequently, the shaft lengthens more than the abrasive body. During this change, however, the power continues to take up this increase in shaft 'length and preserves the tight flange grip upon -mal length when cool. The abrasive cannot contract sufllciently to afford the necessary relief. Consequently high pressures upon the abrasive result. If an abrasive wheel is capable of resisting the first few cycles of heating and cooling (possibly as a result of a slight disintegration of the cement grouting material such as is commonly used under the driving flanges), the repeated cycles of operation cause the same extra tightening of the flanges, and cooling reapplies the same heavy flange pressure with its attendant threat upon the physical integrity of the wheel. The are two broad classifications into which assembly methods for these large wheels fall; viz. (1) those which provide a ribbed metallic hub or drum structure wherein the rotating forces are applied to the abrasive entirely by means of large ribs which are inserted into the abrasive, 'said ribs being parallel to the driving shaft and contacting with the abrasive essentially throughout the length of the arbor hole, and (2) those which provide no hub in the arbor hole, but which drive the wheel entirely by pressure directed upon the wheel by the flanges. My invention has to do .chiefly with this latter type of mounting but also applies to certain modified designs of the former class, and provides means for preventing any de- Fvelopment of excess flange pressure by permitting freedom of longitudinal movement of the more hlgly expansive member (usually the steel driving shaft) while still pressing the necessary flange pressure against the abrasive member by means of tie bolts which are made to possess the same expansion coeflicient as the abrasive member.

The invention is illustrated by the accompanying drawing in which:

Figure 1 is an axial section of an abrasive whee and its driving flanges;

Figure 2 is an end view of the wheel shown in Fi 1;

Figure 3 is an axial section of a reinforced seg-- mental abrasive wheel and its driving flanges; and

Figure 4 is an end view of the wheel shown in Fi 3.

A typical manner in which my invention may be carried out is shown in Figures 1 and 2, where an abrasive annulus 1 is held between flanges 3 and 4 which in turn are mounted upon a driving spindle or shaft 2. Flange 3 is threaded upon shaft 2 by threads 9 and locked firmly in position by lock nuts 7 and 8. Flange 4 is slidably mounted upon shaft 2 and is made rotatable by means of key 10 which is supported firmly in shaft 2 but is slidably connected with flange 4. Bolts 5 are passed through flanges 3 and 4, and tightening the nuts 6 causes the flanges to grip the abrasive annulus firmly enough to transmit power to the wheel and answer the requirements for operating the wheel. The degree to which the tightening is carried should not be excessive, and is easily attained by the use of ordinary judgment of those skilled in the art of assembling and using such abrasive wheels.

If the assembly in hand does require a definite amount of pressure to be imposed by the flanges, then methods such as referred to above are used to attain this end.

The bolts 5 are composed of a material possessingsubstantially the same coefficient of thermal expansion as the abrasive annulus 1. It will be seen, therefore, that no stresses due to differential contraction can be built up between the annulus 1 and the shaft 2 because the more highly expansive member, namely the shaft 2, is freeto elongate or sh'orten by sliding through one flange. It will be seen that, if the shaft were not thus free to shorten, serious pressures would be transmitted to the abrasive annulus 1 by means of the clamping members 3 and 4. One

v class of materials satisfactory for the tie rods 5 is the group of nickel steel alloys containing from 30 to 42 per cent of nickel. The coefficients of thermal expansion of artificial abrasives range from 3 x 10- per centigrade degree to '7 x 10" per centigrade degree and the coeflicients of thermal expansion obtainable by selecting definite compositions in the class of steels cited range from 1 x 10- to 12 x 10- per centigrade degree; hence, there is no diiflculty in obtaining a nickel steel alloy to match with sufficient accuracy the thermal characteristics of any abrasive selected for use.

As specific examples showing that a certain composition of steel possesses a coeflicient of expansion substantially the same as that of an artificial abrasive, I will tabulate data from results which have actually been determined and used.

It should also be made clear that my invention is fully operative to maintain flange pressure constant during variations of temperature and operating conditions regardless of the relative difference in expansion coeflicients between the abrasive and the spindle; that is, it makes no difference how much the expansion of the spindle is greater or less than that of the abrasive member between the flanges, inasmuch as the use of my slidably mounted flange in conjunction with the bolts which are of the same thermal expansion as the abrasive takes care of all such differences.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is embodied in the following claims.

, I claim:

1. As an article of manufacture, an abrasive wheel adapted for peripheral grinding wherein the power is transmitted from opposed driving flanges which are pressed axially against the abrasive wheel by means of bolts and nuts threaded on said bolts, one of said flanges being slidable on the driving shaft and the'bolts having approximately the same coeflicient of expansion as the abrasive whereby stresses due to thermal change are prevented from accumulating. 4

2. As an article of manufacture, an abrasive wheel adapted for peripheral grinding and driving means for said wheel comprising a shaft, a pair of oppositely disposed driving flanges-drivingly connected to said shaft and each adapted to transmit torque from flange to wheel by simple frictional engagement, one of said flanges being free to slide on the driving shaft while not rotatable with respect to said driving shaft, and manu- 13 ally operated means for adjusting the axial pressure between the flanges and the abrasive wheel.

3. As an article of manufacture, an abrasive wheel adapted for peripheral grinding and driving means for said wheel comprising a shaft, a 1 pair of oppositely disposed driving flanges drive ingly connected to said shaft and each adapted to transmit torque from flange to wheel by simple frictional engagement, one at' least of said flanges being free to slide on the driving shaft, and means 1 for adjusting the axial pressure between then. flanges and wheel, said means comprising a plurality of tie rods possessing substantially the same coeflicient of expansion as the abrasive article and means on the tie rods for manual adjustment 3 of the tension exerted by the rods on flanges and wheel.

4'. As an article of manufacture, an abrasive wheel adapted for peripheral grinding which consists of adriving spindle, an abrasive annulus 1 surrounding the spindle, two flanges adapted to fit against the abrasive annulus and mounted upon the spindle, one of said flanges being threaded and looked upon the spindle and the other flange being slidable on but rotatable with the spindle, and rods of a metal possessing substantiallythe same coefficient of thermal expansion as the abrasive annulus and provided with clamping means to hold the two flanges tightly 4 against the abrasive annulus.

5. A method of mounting an abrasive wheel adapted for peripheral grinding which comprises mounting said wheel upon a spindle between driving flanges, fastening one of said flanges rigidly to the driving shaft, slidably mounting the other of said driving flanges on'the driving shaft to turn therewith, and clamping the two flanges against the abrasive 'wheel by means of clamps which have substantially the same coeflicient of expans onaa the abrasive wheel.

6. A method of mounting a reinforced segmental abrasive wheel adapted for peripheral grinding which comprises mounting said wheel upon a spindle between flanges, fastening one of said flanges rigidly to the driving shaft in adjustable position, slidably mounting the other of said driving flanges on the driving shaft to turn therewith, and clamping the two flanges against the abrasive wheel by means of clamps which have substantially the same coefficient of expansion as the abrasive wheel whereby stresses due to thermal changes are prevented from accumulating.

7. A method of mounting an abrasive wheel to withstand temperature changes of the order of magnitude of one hundred oentigrade degrees,

which method comprises mounting the wheel between driving flanges which are pressed against the wheel by means of clamps having the same coeflicient of expansion as the abrasive, fastening one of the driving flanges rigidly to the driving shaft in adjustable position, and slidably mounting the other of the driving flanges on the driving shaft by means which compel the lastmentioned flange to turn with the driving shaft.

8. The method of mounting a segmental abrasive wheel which comprises clamping the segments between terminal driving flanges by means of metal rods having substantially the same coeflicient of expansion as the abrasive, clamping one of the driving flanges to a shaft in adjustable position, and providing the other flange with a sliding connection with the shaft, which connection compels the last-mentioned flange to rotate with the shaft.

HENRY P. KIRCHNER.