Abstract:
A ball bearing which includes a cage which defines recesses for receiving balls in a single row. The cage is in the form of a ring obtained by casting or machining and is intended to be interposed between an inner ring and an outer ring of the bearing. The cage includes recesses of a first group each having an opening for positioning a ball located on a first side of the cage, while recesses of a second group each have an opening for positioning a ball located on a second side of the cage, opposite the first side.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a ball bearing cage, to a ball bearing comprising such a cage, and to a process for assembling such a bearing. 
   2. Description of the Related Art 
   In the domain of ball bearings, so-called “rigid” bearings are known, comprising a single row of balls arranged between two so-called “inner” and outer” rings, and allowing a relative movement of rotation of the inner ring with respect to the outer ring without pivoting about an axis perpendicular to the central axis of the bearing. U.S. Pat. No. 5,015,105 describes a ring-shaped cage that may be used with such bearings. 
   It is also known to equip such a bearing with a cage for separating the balls, such a cage defining recesses in which the balls are received, separated from one another. Such a cage is formed by two elements assembled by fastening, riveting or clipping and requiring high-precision machinings, in order not to increase friction in the bearing too greatly. The necessity of producing such a cage in two parts results from the fact that the cage must be maintained in place in the internal space of the bearing defined between the two rings, failing which it might be driven outside this space. 
   The different known means for assembling the two parts of a cage most often lead to an increase in the dimensions of the joints between these two parts. For example, when rivets are used, a certain quantity of matter must be provided around each rivet, in order to reduce the risks of rupture of the cage. This leads to relatively large gaps for separation between two adjacent balls and the fact that a bearing equipped with such a cage generally cannot be subjected to an intense load. 
   In order to allow a maximum load capacity of a bearing, it is also known to manufacture cage-less bearings which are filled with contiguous balls, this solution leads to friction between the balls, which friction may generate considerable wear of the balls, in particular when ceramic balls are used. This solution also involves a risk of the balls escaping from the internal space of the bearing as they are not maintained in place. 
   As it is necessary to provide a zone for positioning the balls between the rings, the balls can be driven outwardly through this sone, when the bearing is being used. 
   Finally, EP-A-0 288 334 discloses producing a bearing cage from a flexible band, this cage being provided with a slot which constitutes a zone of weakness of the cage that may lead to deformations likely to release the balls, particularly in the event of axial vibrations of the bearing. 
   It is a particular object of the present invention to overcome these drawbacks by proposing a novel bearing cage which said cage open on a second side of said cage. avoids friction between the balls and ensures that they are held in the internal volume of a bearing without requiring complex or high-precision assembly. 
   SUMMARY OF THE INVENTION 
   To that end, the invention relates to a ball bearing cage in the form of a ring obtained by machining or casting, defining recesses for receiving balls in one row and intended to be interposed between an inner ring and an outer ring of a bearing, characterized in that the recesses are distributed in two groups, each recess of the first group having an opening for positioning a ball located on a first side of the cage, while each recess of the second group has an opening for positioning a ball located on a second side of the cage, opposite the first side. 
   Thanks to the invention, the cage performs its role of separation of the balls efficiently and enables them to be maintained in position in the internal volume of the bearing as the balls introduced in the recesses of the second group are, to some extent, mounted in opposition with respect to the balls of the first group and act as members for maintaining the cage in the internal volume of the bearing, without requiring complex means for connecting two parts of a cage. The cage of the invention does not necessitate reserving a large volume for assembling two parts, which allows a high density of balls to be implanted, the number of balls of a bearing of given diameter being close to that of a cage-less bearing, which allows a bearing equipped with a cage according to the invention to be used under a high load. 
   According to advantageous aspects of the invention, the cage incorporates one or more of the following characteristics:
         Each recess is defined between two arms and a bottom, the arms extending, when the cage is in configuration mounted in a bearing, in a direction substantially parallel to an axis of rotation of the bearing, while the bottom is substantially perpendicular to this axis. Certain of the arms define two adjacent recesses belonging to the same group of recesses, these arms each comprising a first end adjacent the respective bottoms of the adjacent recesses and a second free end. Certain other arms define two adjacent recesses belonging to the afore-mentioned two groups of recesses, these arms comprising a first end adjacent the bottom of one of the two adjacent recesses and a second end adjacent the bottom of the other adjacent recess.   The bottom of the recesses of a group of recesses is pierced with an orifice for passage of a member for extracting balls in place in these recesses.   The arms separating the recesses each form two concave surfaces oriented towards two adjacent recesses and adapted to cooperate with the outer surface of the balls.   The first group of recesses comprises all the recesses except two, while the second group comprises two diametrally opposite recesses.   The cage is cast or machined in one piece, of metal or a composite material.       

   The invention also relates to a ball bearing comprising a single row of balls, disposed between an inner ring and an outer ring, and a cage such as described hereinbefore. 
   Such a bearing is easier to assemble than a bearing with cage of the prior state of the art, while its cost is lower and it can operate under a greater load. 
   In addition, at least one of the rings may be provided with at least one notch for introduction of the balls in an internal volume defined between races formed respectively on the inner and outer rings. 
   Finally, the invention relates to a process for assembling a ball bearing which comprises a single row of balls, disposed between an inner ring and an outer ring, and a cage defining recesses for receiving the balls, in which process balls are introduced in a volume defined between races formed respectively on the inner and outer rings. This process is characterized in that it comprises the following steps of:
         introducing in the afore-mentioned internal volume and via at least one notch made on one side of the bearing, a number of balls less than the nominal number of balls of the bearing,   positioning the cage by causing the balls, already in place in the volume, to penetrate in recesses in the cage open on a first side of the cage, and   introducing, via the or each afore-mentioned notch, a ball in at least one recess of the cage open on a second side of the cage.       

   The introduction of the or each ball in the or each recess open on the second side of the cage makes it possible to maintain the cage in position in the internal volume of the bearing without necessitating the use of blocking members or added parts. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be more readily understood on reading the following description of an embodiment of a cage and a bearing in accordance with its principle, given solely by way of example and made with reference to the accompanying drawings, in which: 
       FIG. 1  is a view in perspective of a bearing cage according to the invention. 
       FIG. 2  is a side view on a smaller scale of the cage of FIG.  1 . 
       FIG. 3  is a section along line III—III of FIG.  2 . 
       FIG. 4  is a view on a larger scale of detail IV in FIG.  3 . 
       FIG. 5  is a view in perspective with parts torn away of a ball bearing according to the invention. 
       FIG. 6  is a view similar to  FIG. 5 , the bearing being seen from the opposite side, and 
       FIG. 7  is an exploded view in perspective of the bearing of  FIGS. 5 and 6 , from the same side as FIG.  6 . 
   

   DESCRIPTION OF PREFERRED EMBODIMENT 
   Referring now to the drawings, the cage  1  according to the invention is obtained by machining steel. The ring  1  might equally well be cast. It is a rigid structure which enables balls to be efficiently maintained in position, including in the event of vibrations of the bearing in which it is mounted. 
   The ring  1  is centred about an axis X 1 —X′ 1  and comprises two arcs  11  and  12  from which arms  13  substantially parallel to axis X 1 —X′ 1  extend. Arms  14  extend from the ends  11   a ,  11   b ,  12   a  and  12   b  of the arcs  11  and  12 . The arms  14  are connected, opposite arcs  11  and  12 , by bridges  15  and  16 . The elements  11 ,  12 ,  15  and  16  are substantially perpendicular to axis X 1 —X′ 1 . 
     13   a  and  14   a  respectively denote the ends of the arms  13  and  14  connected to the arcs  11  and  12 .  13   b  and  14   b  respectively denote the ends of the arms  13  and  14  opposite the ends  13   a  and  14   a . The ends  13   b  are free, i.e. are not joined to an arc, while ends  14   b  of arms  14  are joined to the bridges  15  and  16 . 
   The bridges  15  and  16  are each pierced with an orifice  17 ,  18 , respectively, in their central part. 
   Recesses  20  are defined between the arms  13  and  14 . More specifically, recesses  20   1  belonging to a first group I of recesses are formed between two adjacent arms  13  or between an arm  13  and an arm  14  and their respective bottoms are constituted by one of the arcs  11  or  12 . The opening  21   1  of each recess  20   1  of this first group faces upwardly in FIG.  1 . 
   In the example shown, the cage  1  comprises two series of three recesses  10   1  defined opposite the arcs  11  and  12 . 
   Two recesses  20   2  belonging to a second group II of recesses, are defined between two arms  14  and their respective bottoms are constituted by the bridges  15  and  16 . The openings  21   2  of these recesses are oriented downwardly in  FIG. 1 , i.e. contrary to the openings  21   1  of the recesses of the first group I. 
   A denotes the side of the cage  1  visible from underneath in FIG.  1  and on the right of FIG.  3 . The respective openings  21   2  of the recesses  20   2  open out on side A of the cage  1 . 
   B denotes the side of the cage  1  by which it is seen in  FIG. 2 ; this side is opposite side A. The respective openings  21   1  of the recesses  20   1  open out on this side B. 
   The lateral faces  13   c  and  14   c  of the arms  13  and  14  are concave, with a radius of curvature greater than or equal to the radius of the balls  100  intended to be introduced in the recesses  20  through the openings  21   1 ,  21   2 . 
   The bottoms of the recesses  20  are also concave, as will be seen in FIG.  4 . Towards a recess  20   2 , the bridge  15  presents a concave surface  15   c  with, in transverse section, the shape of an open V allowing partial engagement of a ball. 
   The situation is similar concerning the arcs  11  and  12  and the bridge  16  of which the surfaces  11   c ,  12   c  and  16   c  are also concave at the level of the bottoms of the recesses  20 . 
   As is more particularly visible in  FIGS. 5  to  7 , a bearing  101  according to the invention comprises an inner ring  102  and an outer ring  103  centred on an axis X 2 —X′ 2  which is the axis of rotation of the bearing. When the bearing is in mounted configuration shown in  FIGS. 5 and 6 , the axes X 1 —X′ 1  and X 2 —X′ 2  merge. 
   The inner ring  102  defines a race  102   a  for balls  100 , this race  102   a  being formed by the outer radial surface of the ring  102 . The inner radial surface of the ring  103  also defines a race  103   a  for balls  100 . V denotes the internal volume of the bearing  101  included between races  102   a  and  103   a . A′ denotes the side of the bearing  101  shown on the left-hand side of  FIGS. 6 and 7  and B′ the side of this bearing shown on the left-hand side of FIG.  5 . 
   On side A′ of the bearing, the rings  102  and  103  are each provided with a notch  102   b ,  103   b  allowing the successive introduction of the balls  100  in the volume V, as represented by arrow F 1  in FIG.  7 . 
   When the bearing  101  is to be assembled, six balls  100  are introduced in the volume V, via the opening made at the level of the notches  102   b  and  103   b . The cage  1  is then introduced in the bearing  101 , as represented by arrow F 2 , the balls  100  being distributed in the six recesses  20   1  of the first group I of recesses  20 . 
   A ball  100 ′ is then positioned, via side A′ of the bearing, in the recess  20   2  shown in the upper part of  FIG. 7 , this being represented by the arrow F 3 . The cage  1  is then rotated about axes X 1 —X′ 1  and X 2 —X′ 2 . The angle of rotation of the cage is about 180°, which makes it possible to bring the second recess  10   2  of the second group II opposite the notches  102   b  and  103   b  and to introduce a second ball  100 ″ in this notch as represented by arrow F 4 . It is then possible to impart to the ring  1  a fresh movement of rotation in order to move ball  100 ″ away from the notches  102   b  and  103   b.    
   Due to the positioning of the balls  100 ′ and  100 ″, the cage  1  is maintained in position in the volume V and efficiently performs its function of separation and distribution of the efforts between the balls  100 ,  100 ′ and  100 ″ without it being necessary to add a blocking piece on this cage. 
   When the bearing  101  is to be dismantled, the balls  100 ′ and  100 ″ are driven from the recesses  20   2  by bringing these recesses successively opposite the notches  102   b  and  103   b  and by exerting a thrust on the balls by means of a rod  200  passing through an orifice  17  or  18 , as schematically represented by arrow F 5  in FIG.  5 .