GB2271827A - Mounting a bearing race on a shaft - Google Patents

Abstract

An anti-friction bearing assembly includes a housing 60 for securing to a stationary structure, an outer ring 62 including an outer race, an inner ring 52 including an inner race and a plurality of rolling elements disposed between the inner and outer races. A substantially circular bore 54 delineates an inner surface of the inner ring. A V-shaped protrusion 56 extends into the bore, the bore and the V-shaped protrusion are suitable for mounting the bearing assembly on a shaft having a substantially identical V-shaped groove. <IMAGE>

Description

ANTI-FRICTION BEARING ASSEMBLY The present invention relates to an anti-friction bearings comprising spherical, conical or cylindrical rolling elements disposed between two raceways, commonly referred to as radial bearings, and more particularly radial bearings that are not secured to the shaft on which they are mounted.

Radial bearings are generally used to longitudinally support a shaft by eliminating radial play of the shaft.

Radial bearings are characterized by a structure including spherical, conical or cylindrical rolling elements disposed between an inner raceway and an outer raceway. The shape of the rolling element determines the type of radial bearing, such as ball bearings, needle bearings and roller bearings.

Each type is suitable for particular arrangements. For example, for shafts rotating at a high speed with a light load, radial ball bearings are typically used. For each type of radial bearing there are different styles each of which is suitable for a particular use of the radial bearings. The structure associated with the mounting of the inner and outer raceways determine the style of the radial bearing. Typically, the outer raceway includes a housing adjoining the outer raceway for securing the outer raceway to a frame member. The mounting structure of the inner raceway may be simply an aperture through which the shaft is inserted, or may include means to secure the inner raceway to the shaft, such as a setscrew.

In some applications, the inner raceway is not secured to the shaft but must rotate with the rotation of the shaft. For such applications it is known to use "D" bore radial bearings which are designed for shafts with a milled or ground flat. The "D" bore shape provides a built in anti-rotation feature which eliminates press fits or the need for auxiliary locking devices. It also offers the time saving advantages of slip on assembly and easy removal for fast maintenance. An example of this style radial bearing is the "D" bore bearings manufactured by Torrington Bearing Co. of Torrington, Connecticut, U.S.A.

The D bore radial bearings are useful in assemblies where there may be axial movement of the shaft within the inner raceway of the bearings. Such axial movement generally is the result of heat resulting from high rotational speed of the shaft. Although D bore radial bearings are suitable for such use, there is an inherent noise problem in the use of such bearings. For each rotation of the shaft there is an audible click or knock sound caused by the flat in the shaft abruptly striking the flat in the bore of the inner race. The loudness of the knock depends on the size of the gap between the flat of the shaft and the flat of the bore when the bearing is mounted on the shaft. The larger the gap the louder the knock. The material of the bearing also contributes to the loudness of the knock.For example, bearings with a nylon inner race will cause a smaller knock than bearings with a metal inner race having the same bore dimensions as the nylon bearing.

In accordance with the present invention a new radial bearing with a V-shaped protrusion is used in place of the D bore radial bearing. The present invention provides an anti-friction bearing assembly comprising a housing including means for securing said housing to a stationary structure; an outer ring contiguous to said housing and including an outer race on an inner surface of said outer ring; an inner ring including an inner race on an outer surface of said inner ring, said inner race being coaxial with said outer race; a plurality of rolling elements disposed between said inner and outer races; a substantially circular bore delineating an inner surface of said inner ring; and a V-shaped protrusion extending into said bore, said bore and said V-shaped protrusion being suitable for mounting on a shaft having substantially identical V-shaped groove.

Advantages of the present invention will be apparent upon consideration of the following detailed description, taken in conjunction with aczoapaying drawings, in which like reference characters refer to like parts throughout, and in which.

Fig. 1 is a schematic illustration of a typical application for radial bearings; Fig. 2A is an axial view of a prior art D bore bearing with a line of force towards the center of the flat of the shaft; Fig. 2B is the D bore bearing shown in Fig. 2A rotated to where the line of force is towards one end of the flat of the shaft; Fig. 2C is the D bore bearing shown in Fig. 2B rotated to where the line of force is 1800 from the line of force in Fig. 2A:: Fig. 2D is the D bore bearing shown in Fig. 2C rotated to where the line of force is towards the other end of the flat shown in Fig. 2B; Fig. 3 is an axial view of a bearing according to one example of the present invention; Fig. 4 is a cross section view of the bearing of Fig. 3; Figs. 5A, 5B, 5C and 5D are axial views of the bearing of Fig. 3 shown with lines of force as the bearing rotates with the shaft.

Detailed DescriDtion of the Invention Referring now to Fig. 1, a typical application for radial bearings is shown. A pair of driven shafts 12 and 14 are rotatably mounted to frame members 16 and 18 by radial bearings 40 and 50, respectively. Shafts 12 and 14 are driven by a conventional pulley drive system, generally designated 24, which includes pulleys 30 and 32 and belt 34.

Pulleys 30 and 32 are secured to one end of shafts 12 and 14 respectively. It will be understood by those skilled in the art that the respective linear line of force, i.e., the load, on shafts 12 and 14 is caused by pulley drive system 24, and are in the direction of arrows A and B respectively.

The rotational load associated with rotation of shafts 12 and 14 are not discussed herein because they do not cause or add to the noise generated by the D bore radial bearings.

For the purpose of describing the present invention, shaft 12 is shown and described as having a flat 16 suitable for use with a D bore radial bearing. Shaft 14 is shown with a groove 18 suitable for use with the present invention.

Referring now to Figs. 2A through 2D, there is shown an axial view of shaft 12 with the inner race 42 of a prior art D bore radial bearing, generally designated 40, mounted thereon and the effect of the line of force, i.e., load A, on bearing 40 as shaft 12 makes one revolution. In Fig. 2A, the load A is directly into the flat 16 of shaft 12, thereby causing shaft 12 to be urged against the round portion of bore 44 of bearing 40. It will be understood by those skilled in the art that bore 44 must be slightly larger than the axial dimensions of shaft 12. A reasonable tolerance in size provides a low cost but reliable D bore radial bearing which supports shaft 12 but which is not a tight or secured fit to shaft 12. Generally, the D bore radial bearing is not intended to be secured by auxiliary locking devices.

Referring now to Fig. 2B, shaft 12 has been rotated counterclockwise approximately 1350. Load A is now urging one end of the flat 16 of shaft 12 against a corresponding flat end of bore 44 at 46. As shown in Fig. 2B, a gap "d" between the flat 16 of shaft 12 and the flat of bore 44 at 48 is at its maximum distance. As shaft 12 rotates approximately another 450 counterclockwise, load A urges the flat 16 of shaft 12 against the flat of bore 44, as shown in Fig. 2C. At this point in each rotation, a click or knock is heard as the flat of shaft 12 strikes the flat of bore 44 at 48. As shown in Fig. 2D, as shaft 12 rotates further counterclockwise, the flat 16 of shaft 12 moves away from the flat of bore 44 at 46 because load A, urges the flat 16 of shaft 12 against the end of the flat of bore 44 at 48.

The D bore radial bearing described above, is suitable for its intended applications, such as shown in Fig. 1. However, the clicking noise is a problem as faster and quieter machines are desired.

Referring now to Figs. 3 and 4, a radial bearing 50 in accordance with the present invention is shown. Bearing 50 includes a housing 60 (Fig. 3 only) having apertures at each end for mounting bearing 50 to a stationary frame member, such as 16 or 18 in Fig. 1. Bearing 50 includes an outer ring 62 having an outer race 64 adjoined to housing 60. There is an inner ring 52 which includes an inner race 58 which has a common axis with outer race 64. There are a plurality of roller elements, such as balls 66, disposed between inner race 58 and outer race 64.

The present invention provides a bore 54 which is substantially circular except for a V-shaped protrusion referred to herein as V-jut 56 into bore 54. The V-shape protrusion 56 is matched to a corresponding V-shaped groove 18 in shaft 12 (Fig. 1).

Referring now to Figs. 5A through 5D, there is shown an axial view of shaft 14 with the inner race 52 of a V-jut radial bearing, in accordance with the present invention, mounted thereon. The line of force, i.e., load B, is shown by an arrow. In Fig. 5A, the load B is directly into the V-groove of shaft 14, thereby causing shaft 14 to be urged against part of bore 54 that is opposite V-jut 56. As with the D bore radial bearing in Figs 2A-2D, bore 54 is slightly larger than the axial dimensions of shaft 14. Fig. 5B shows 0 shaft 14 rotated 135 counterclockwise to a position at which a maximum gap dl exists between V-jut 56 in bearing 50 and V-groove 18 in shaft 14.As shaft 14 rotates 0 approximately another 45 counterclockwise, load B urges V-groove 18 against V-jut 56 as shown in Fig. 5C. At this point in each rotation , gap dl is closed; as the lower edge of Vgroove 18 strikes the lower edge of V-jut 56. Although this will cause some sound upon impact, the sound will be significantly less than the sound made by the D-bore radial bearing 40. This will be described below in more detail. Finally, in Fig. 5D, shaft 14 further rotates counterclockwise The following provides an example of how the present invention significantly reduces the clicking noise because the gap between bore 54 and shaft 14 is minimized by the shape of protrusion.

In a typical application, for example, in an inserting machine, when a 0.372 inch, 9.45 mm., diameter shaft 12 with a 0.314 inch, 7.98 mm., flat is used, a D-bore radial bearing 40 having a 0.376 inch, 9.55 mm., bearing bore and a 0.316 inch, 8.0 mm., flat would be used. For such an application, the gap d, shown in Fig.

2B, would have a maximum clearance of 0.0051 inches, 0.13 mm. The closing of this gap as the shaft 12 rotates causes the clicking sound. It will be appreciated by those skilled in the art, that the more bearings in the machine, the more noise that will be generated.

In a comparable application using the present invention, a 0.372 inch, 9.45 mm., diameter shaft 14 with a "V" shaped groove 18 can be used with a V-jut radial bearing 50 having a 0.374 inch, 9.5 mm., diameter bore with V-jut 56. The V-jut 56 is a V-shaped protrusion having an included angle of 90" with a 0.030 inch, 0.76 mm., radius at its vertex and a height of 0.028 inches, 0.71 mm., as measured from the 0.374 inch diameter bore to the top of the 0.030 radius. In accordance with the present invention, the gap d1 has a maximum clearance of 0.00033 inches, 0.008 mm., in the position shown in Fig. 5B.

Thus, the illustrated embodiment provides a solution to the noise associated with the D-bore radial bearing in a machine operating at a high speed, such as an inserting machine. It will be understood by those skilled in the art that the dimensions of Vjut 56 and V-groove 18 may vary depending on the load B and size and speed of rotation of shaft 14.

The V-jut and V-groove combination is suitable to force the inner race into rotation with shaft 14 without the need to lock the inner race to shaft 14. This allows bearing 50 to move transversely along shaft 14 as needed as a result of changes to shaft 14 caused by heat generated by rotations at high speed.

While the present invention has been disclosed and described with reference to a single embodiment thereof, it will be apparent, as noted above, that variations and modifications may be made therein, without departing from the present invention.

Claims (5)

What is Claimed is:

1. An anti-friction bearing assembly comprising: a housing including means for securing said housing to a stationary structure; an outer ring contiguous to said housing and including an outer race on an inner surface of said outer ring; an inner ring including an inner race on an outer surface of said inner ring, said inner race being coaxial with said outer race; a plurality of rolling elements disposed between said inner and outer races; a substantially circular bore delineating an inner surface of said inner ring; and a V-shaped protrusion extending into said bore, said bore and said V-shaped protrusion being suitable for mounting on a shaft having a substantially identical V-shaped groove.

2. The anti-friction bearing assembly of claim 1 wherein said plurality of rolling elements comprises balls.

3. The anti-friction bearing assembly of claim 1 wherein said inner and outer rings are made of a plastic-like material.

4. An anti-friction bearing assembly substantially as herein described with reference to and as illustrated in the accompanying drawings.

5. Any novel combination or sub-combination of features disclosed and/or illustrated herein.