The present invention relates to a crown-shaped cage which is used, for example, in a deep groove ball bearing, and particularly to a crown-shaped cage which is able to positively hold balls inserted easily in its pockets using the elasticity of its component material, and can, particularly, have the balls inserted in the pockets even when it is made of a material with nominal flexibility.
When made of plastics, bearing cages can be made lightweight and can be manufactured using monolithic molding processes offering higher mass productivity, and the flexibility of the plastics can be used for press insertion of each ball in the respective pockets. For these reasons, plastics are widely used for crown-shaped cages. Among these, nylon is widely used as plastic material mainly because it provides sufficient flexibility to cages.
However, demand has risen in recent years for bearings which can be used in high temperature environments, resulting directly in growing demand for cages with high heat resistance. Various plastics with higher heat resistance than nylon, including polyphenylene sulfide (hereinafter referred to as PPS), polyether ether ketone (hereinafter referred to as PEEK), and other plastics with resistance to heat of 200.degree. C. or more, have therefore been tested recently for their suitability as a material for crown-shaped cages. PPS and PEEK, however, are less flexible than nylon.
A conventional crown-shaped cage has multiple pockets that are open on both ends in the radial direction and open on one side in the axial direction. Each of the entrances to the pockets, which are open in the axial direction as described above, is smaller in width in the circumferential direction than the diameter of each ball by a given dimension. Insertion of a ball into its pocket is performed by pressing the ball from the entrance in the axial direction, flexibly forcing the walls, which are on both sides of the entrance to form the pocket, out in the circumferential direction. After the ball is completely inserted, the entrance returns to the original width, thereby holding the inserted ball in the axial direction. When all balls are inserted in such a way in their respective pockets the balls are held at specified regular intervals in the circumferential direction.
Since the construction of the conventional crown-shaped cage as described above is such that walls on both sides of an entrance are simply spread flexibly in the circumferential direction when a ball is inserted in the axial direction into the cage, the entire walls must give or deflect flexibly when the pocket is opened. When the cage is constructed of nylon or a similar flexible material, the walls can be elastically deformed in the circumferential direction to expand the entrance to the diameter of the ball so that the ball can be inserted. However, when the cage is made from PPS or PEEK, materials with excellent heat resistance but much less flexibility, the entrance cannot be spread to the diameter of the ball and it is therefore not possible to insert the ball into the pocket.