US3367068A - Grinding wheel mounting - Google Patents

Description

Feb. 6, 1968 P. c. DOOLEY, JR 3,367,068

GRINDING WHEEL MOUNTING Filed March 25, 1965 INVENTOR ATTORNEY United States Patent 3,367,068 GRHNDING WHEEL MOUNTING Peter C. Dooley, Jr., Lewiston, N.Y., assignor to The Carborundum Company, Niagara Falls, N.Y., a corporation of Delaware Filed Mar. 25, 1965, Ser. No. 442,574 3 Claims. (Cl. 51-168) ABSTRACT OF THE DISCLOSURE A grinding wheel mounting spindle having flanges on opposite sides of the wheel. A plurality of studs radially spaced from the wheel axis are fixed at their one ends to one flange and extend through aligned bores of the wheel and the other flange. Nuts on the other ends of the studs are tightened against the other flange. Both flanges have surfaces that are radially disposed beyond the studs and bear directly against the sides of the wheel.

This invention relates to grinding wheels and, more particularly, to high speed rotary grinding wheels and spindles for supporting such grinding wheels.

A typical resin bonded grinding Wheel of the type having a peripheral grinding edge is mounted on an arbor for rotation. The arbor extends through a central hole in the wheel and flanges are mounted on the arbor on opposite sides of the wheel. One of the flanges is keyed to the arbor and the other flange presses the grinding wheel against the fixed flange. A large nut is threaded on the arbor adjacent the movable flange. Tightening the nut urges the movable flange toward the fixed flange to clamp the grinding wheel between them.

Due to improved bonding formulations and techniques during recent years, it has become practical to increase the surface speed of grinding wheels. An increase in wheel speed is desirable because there is a corresponding increase in the rate of metal removal. In order to have available a large amount of usable abrasive, it is customary to use wheels having a large diameter. As the size of the grinding wheel increases, however, the sizes of the arbor, the flanges, and the clamping nut also must be increased. When the clamping nut is very large, a large torque is required to overcome the frictional resistance between the threads on the arbor and the threads on the nut. The frictional resistance increases as the nut is tightened against the flange due to the axial load imposed on the threads. Consequently, the thread friction may become so great that the nut cannot be tightened sufliciently to clam the grinding wheel rigidly between the flanges.

An abrasive wheel wears as it is used, and accordingly, it has to be replaced periodically. A large wheel is particularly diflicult to replace because the Wheel is awkward to handle. As the wheel passes over the threaded portion of the arbor while it is being installed and removed, it may engage the threads and the abrasive material in the wheel may damage the threads. Therefore, it may become necessary to replace the arbor due to the wear on the threads caused by the wheel.

Another problem related to the high speed operation of conventional grinding wheels is the danger of fracturing the Wheel due to internal stresses. When a bonded abrasive wheel rotates, centrifugal forces impose tangential and radial stresses in the wheel. These internal stresses increase as the speed of the wheel increases. When the stresses become excessively high, the wheel flies apart. This is a serious hazard to personnel.

in view of the difficulties arising from the use of conventional rotary, bonded abrasive wheels at high speeds, it is an object of this invention to provide a grinding wheel and a spindle assembly capable of safe high speed operation.

3,367,068 Patented Feb. 6, 1968 "ice It is a further object of this invention to provide a rotary grinding wheel spindle assembly for rigidly supporting large diameter wheels.

It is a still further object of this invention to provide a grinding wheel and a spindle assembly which permit eflicient replacement of the grinding wheel.

These objects are accomplished in accordance with a preferred embodiment of the invention by a spindle assembly having flanges on opposite sides of a wheel. The wheel has no central opening, but a plurality of studs extend through holes in the wheel that are spaced from the central axis of the wheel. The studs have one end mounted in one of the flanges and the other end of each stud extends through a hole in the opposite flange. A nut on each stud is tightened against the flange to clamp the grinding wheel rigidly between the flanges. Each of the holes in the Wheel is lined with a bushing.

This preferred embodiment of the invention is illustrated in the accompanying drawings in which:

FIG. 1 is a cross sectional view of the grinding wheel and spindle assembly; and

FIG. 2 is a cross sectional view of the grinding wheel and spindle assembly along the line 2-2 in FIG. 1.

One method of supporting a conventional grinding wheel for rotation is to mount the wheel on an arbor. The arbor is supported in journal boxes on opposite sides of the wheel housing. The spindle assembly 2 of this invention is adapted to be mounted in wheel housings of conventional grinding machines. The spindle assembly 2 includes a pair of hollow sleeves 4 and 6. The sleeve 6 has an axle 8 extending outwardly from one end and a similar axle 10 is provided on the corresponding end of the sleeve 4. Conventional ball bearing assemblies 12 and 14 are mounted on the respective axles 8 and 10. The ball bearing assemblies 12 and 14 are secured on the axles 8 and 10 by internally threaded rings 16 and 18 which engage the threaded ends of the axles. The outer race of each of the bearings 12 and 14 is received in a collar 20 and 22, respectively, and caps 24 and 26 cover the ends of the axles and the bearings. The caps 24 and 26 are secured to the collars by screws 28. A wavy spring washer 36 is mounted between the outer race of the bearing 12 and the cap 26 to provide limited axial displacement of the sleeve 4 relative to the collar 22. The collars 20 and 22 are adapted to be clamped in conventional supports in a wheel housing and they remain stationary while the sleeves 4 and 6 rotate.

A grinding wheel 32, as shown in FIGS. 1 and 2, having a solid center is clamped between a flange 34 on the sleeve 4 and a flange 36 on the sleeve 6. The flanges have radial bearing portions 38 and 40 which project axially beyond the end of their respective sleeves so that the opposite radial faces of the wheel 32 are supported by the bearing portions 38 and 40. The remaining portions of the sleeves 4 and 6 are spaced from the radial faces of the wheel 32.

The grinding wheel 32 is mounted on a plurality of studs 42 which extend between the flanges 34 and 36. The studs preferably are spaced equally around the circumference of the flanges. In this preferred embodiment there are eight studs, four of which are shown in FIG. 2. The studs 42 are press-fitted in holes 44- in the flange 36. Counterbores 46 are provided to receive the heads 48 of the studs 42. The studs fit tightly in the bores 44 and do not turn relative to the flange. Additional means, such as welding, may be used to prevent the studs from turning in the bores 44. It is very important to align the studs 42 with the central axis of the sleeve 6 and to position them accurately relative to the central axis. The inner axial 0 edge of the flange 36 adjacent the bearing surface 40 may 50 are provided in the flange 34 for receiving the studs 42. The studs have a conical end portion to guide the Wheel 32 and the flange 34 over the ends of the studs. The studs also are threaded at the end to receive nuts 52. The nuts 52 cooperate with the studs 42 to clamp the bearing surfaces 38 and 40 directly against the radial faces of the wheel 32. Preferably, the nuts 52 are lock nuts, so that they are not loosened by vibration.

The wheel 32 has a plurality of holes 54 which extend through the wheel and are located to correspond with the positions of the studs 42. It will be seen that the bearing portions 38 and 40 are disposed a substantial distance radially outwardly away from the holes 54 in order to preclude any stress concentration adjacent said holes. Each hole 54 has a liner 56 formed of rigid, nonahrasive material. The liners 56 preferably are formed of fibrous mate rial bonded together by a resin. The liners 56 may be in the form of hollow cylinders which are placed in the abrasive wheel mold before the abrasive material is cast. Then, during the baking of the wheel, the resin liner 56 becomes bonded to the abrasive of the wheel 32. Initially, the liners may be in the form of solid plugs. After the wheel has been formed, the plugs are drilled out carefully using a gang drill, so that the holes through the liner 56 are accurately positioned with respect to the studs 42. The internal diameter of the liners 56 is only slightly larger than the external diameter of the studs 42 to allow easy assembly of the wheel, while providing good radial location.

A conventional sheave 58 is mounted on the exterior of the sleeve 6 and is secured rigidly to the sleeve by a set screw 60, or a key or other suitable means. Drive belts are positioned in the grooves of the sheave 58 for rotating the sleeve 6. Since the wheel 32 and the sleeve 4 are secured to the sleeve 6 by the studs 42, the wheel assembly rotates as a unitary structure. Furthermore, since there is no arbor passing through the center of the grinding wheel 32, the internal stresses in the wheel are minimized.

In the embodiment shown in the drawings, the grinding wheel 32 is mounted between a pair of sleeves 4 and 6. The grinding wheel mounting of this invention also may be applied to an open ended spindle, in which the grinding wheel is mounted on the end of the spindle. In accordance with this invention, a flat plate is substituted for the sleeve 4. The plate has equally spaced holes corresponding to the holes 50 for receiving the studs 42. The spindle is provided with a flange corresponding to flange 36 and with studs corresponding to the studs 42. The plate, the grinding wheel 32, and the spindle are assembled in the same manner as the apparatus shown in FIG. 1.

The grinding wheel 32 may be replaced readily when it becomes worn. The nuts 52 are unscrewed from the studs 42 to allow the flange 34 to be separated from the studs. The wheel 32 then may be displaced off of the ends of the studs 42 and a new wheel may be installed in its place.

The liners 56 of the replacement wheel are accurately posi tioned so that their central bores are aligned with the studs 42. The internal diameter of the liners 56 is only slightly larger than the external diameter of the studs 42,

to allow easy assembly of the wheel, while providing good radial location.

After the wheel 32 is mounted on the studs 42, the flange 34 is installed over the ends of the studs 42 and the nuts 52 are threaded on the studs until the wheel 32 is tightly clamped between the bearing surfaces 38 and 40.

The fibrous liners 56 serve another purpose, and that is to protect the threads on the studs when the wheel 32 is being replaced. Since the abrasive material of the wheel is hard enough to cut steel, the threads of the studs 42 may be severely damaged as the wheel passes over the ends of the studs 42, if it were not for the fibrous liners 56. Furthermore, the liners 56 protect the studs from the abrasive material of the wheel. Direct engagement of the wheel and the studs 42 would cause the studs to be abraded, thereby reducing the diameter of the studs and, consequently, the tensile strength of the studs.

In installing the wheel 32, suflicient pressure should be provided between the flanges 34 and 36 to grip the wheel tightly. This pressure is obtained by tightening of the nuts 42 uniformly around the flange 54. It is preferred that the clamping force provided by the studs be so great that the wheel resists radial displacement almost entirely by the friction force at the bearing surfaces 38 and 40, rather than by the studs 42. After the wheel 32 is assembled between the flanges 34 and 36, the wheel may be dressed in a conventional manner.

he spindle assembly of this invention is a rigid unitary structure that in capable of operating efficiently at high speeds. The axles 8 and 10 are integral with the sleeves 6 and 4, respectively, and the sleeves are tightly clamped against the wheel 32.'It has been found that the spindle assembly of this invention has a greater beam strength than the arbor type mounting because the assembly is more rigid. This permits the spindle assembly of this invention to be operated at substantially higher speeds than the arbor type mountain.

While this invention has been illustrated and described in one embodiment, it is recognized that variations and changes may be made therein without departing from the invention as set forth in the claims.

I claim:

1. A grinding wheel spindle assembly comprising: a sleeve having a first radial flange at one end thereof; axle means secured to said sleeve for rotation therewith; means forming a second radial flange separate from said sleeve; a rotary grinding wheel between said first and second flanges; said grinding wheel having a plurality of holes; a plurality of studs firmly secured at their one ends, respectively, in said first radial flange and disposed radially, outwardly from the central axis of said first flange; said studs extending substantially parallel to said central axis of said first flange and extending outwardly fromsaid first flange through said holes of said grinding wheel; said second flange having a plurality of holes in position to receive said studs therein; nuts mounted on the other end of said studs, respectively, whereby said grinding Wheel may be clamped between said first and second flanges; said flanges having surfaces, respectively, hearing directly against the sides of the grinding wheel and spaced in their entirety a substantialvdistance radially outwardly away from said holes of said grinding wheel.

2. A grinding wheel spindle assembly as defined in claim 1 in which said studs have conical end portions,

respectively, remote from said first flange.

3. A grinding wheel spindle assembly as defined in claim 2 in which said means forming a second radial flange comprises a sleeve.

References Cited UNITED STATES PATENTS 1,918,392 7/1933 Hohnhorst 51-168 2,021,536 11/1935 Bath 5l168 2,173,461 9/1939 Wagner 51168 2,476,234 7/1949 Balsiger 5ll68 2,741,070 4/1956 Muehling 51 -35 X HAROLD D. WHITEHEAD, Primary Examiner.

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