Linear ball bearing

An improved linear ball bearing is disclosed which essentially comprises a bearing casing and a pair of retainer and side cover assemblies. The last mentioned assembly consists of a retainer half and a side cover and the two members are integrally secured to one another. On the inner end face of the side cover are formed U-shaped ball movement direction reversing grooves which are located corresponding to loading ball guiding grooves and non-loading ball guiding holes. The retainer half contains horizontal member, inclined members and lower holding members each of which is protruded from the inner end face of the side cover toward those of the opposite side cover. Between the adjacent concave end faces of these members are formed loading ball guides of which inner diameter is substantially same to the outer diameter of rolling balls and which are arranged so as not to cause any falling-down of the balls therefrom. The members of the respective retainer halves are dimensioned exactly to one half of the length of the bearing casing. One of the inclined members and lower holding members has engagement pins at the end thereof, while the other one has engagement holes at the end face thereof to receive the corresponding engagement pins.

FIELD OF THE INVENTION 
The present invention relates to a linear ball bearing which essentially 
comprises a bearing casing and a pair of retainer and side cover 
assemblies, said bearing casing being formed with ball guiding grooves and 
holes which are symmetrically arranged to guide a row of rolling balls, 
while said assemblies having a retainer half integrally secured to the 
side cover, and more particularly relates to an improved linear ball 
bearing having four lines of loading ball guiding grooves formed on the 
upper wall and inclined side walls of a considerably large recess having a 
substantially trapezoidal sectional configuration as well as four lines of 
non-loading ball guiding holes drilled through the bearing casing in the 
longitudinal direction and located at a predetermined distance radially 
from said loading ball guiding grooves in parallel to the same. 
Specifically, the linear ball bearing of the present invention is 
constructed such that the retainer and side cover assembly comprises a 
retainer half and a side cover and the side cover has four lines of 
U-shaped ball movement direction reversing grooves formed on the inner end 
face thereof, said U-shaped ball movement direction reversing grooves 
being located corresponding to the loading ball guiding grooves and 
non-loading ball guiding holes, while the retainer half contains a 
horizontal member, inclined members and lower holding members each of 
which is protruded from the end face of the side cover toward those of the 
opposite retainer half in such a manner that said U-shaped ball movement 
direction reversing grooves extent intermediate the adjacent members among 
the above-described ones. Further, the linear ball bearing is constructed 
such that the horizontal member, inclined members and lower holding 
members of the respective retainer halves have concave end faces so as to 
form four lines of loading ball guides therebetween of which inner 
diameter is substantially same to the outer diameter of rolling balls and 
which are arranged so as not to cause any fallingdown of the loading balls 
therefrom, the respective retainer halves are dimensioned exactly to one 
half of the length of the bearing casing, and further one of the inclined 
members and lower holding members has engagement pins at their end faces, 
while the other one of them has engagement holes at their end faces to 
receive the corresponding pins therein. 
BACKGROUND OF THE INVENTION 
The hitherto known linear ball bearing is usually constructed such that 
side covers and retainer are separately manufactured and then assembled 
onto a bearing casing (c.f. U.S. Pat. No. 4,253,709). 
The conventional retainer is made of steel plate by press working in such a 
manner that a plurality of longitudinally extending slits are punched out 
at predetermined positions and at the same time considerably small tongue 
pieces are projected out at both the ends of the respective slits for the 
purpose of ensuring scooping function for the rolling balls. To meet this 
requirement it is necessary that the tongue pieces have high mechanical 
strength and wear resistance. 
For the reason the conventional retainer is made of steel plate having 
excellent rigidity and resiliency and after completion of press working it 
is subjected to heat treatment, which causes it to be manufactured at an 
expensive cost. 
SUMMARY OF THE INVENTION 
Thus, it is a principal object of the present invention to provide an 
improved linear ball bearing without any of the drawbacks inherent to the 
conventional one as described above which is constructed in an integrally 
molded structure in the form of a side cover and retainer assembly using 
heat resistant plastic material in which a plurality of loading ball 
guides are formed through the retainer half and which provides a wide and 
successive supporting area as well as scooping function for rolling balls 
without any particular necessity for mechanical strength and rigidity of 
the retainer half. 
It is other object of the present invention to provide a linear ball 
bearing which ensures smooth movement of the balls irrespective of an 
appreciable dislocation of the retainer halves at their joint part owing 
to the arrangement that the rolling balls are not brought in tight contact 
with the inner wall of the ball guides in the retainer half. 
It is another object of the present invention to provide a linear ball 
bearing which is easy to be assembled and is manufactured at a reduced 
cost under an improved working condition owing to the fact that the 
retainer and side cover assemblies are integrally constructed using 
plastic material or non-ferrous metallic material which is easily molded 
or cast to the required configuration. 
To satisfactorily accomplish the above objects there is proposed in 
accordance with a linear ball bearing which essentially comprises a 
bearing casing and a pair of retainer and side cover assemblies which have 
a symmetrical configuration and are secured to the end face of said 
bearing casing, said bearing casing having four lines of loading ball 
guiding grooves formed on the upper wall and inclined side walls of a 
considerably large recess having a substantially trapezoidal sectional 
configuration as well as four lines of non-loading ball guiding holes 
drilled through the bearing casing in the longitudinal direction in 
position at a predetermined distance radially from said loading ball 
guiding grooves in parallel to the latter, said loading ball guiding 
grooves and non-loading ball guiding holes having the substantially same 
radius of curvature as diameter of rolling balls, while said retainer and 
side cover assemblies comprising a retainer half and a side cover 
respectively, characterized in that the side cover has four lines of 
U-shaped ball movement direction reversing grooves formed on the inner end 
face thereof, said U-shaped ball movement direction reversing grooves 
being located corresponding to the loading ball guiding grooves and 
non-loading ball guiding holes, while the retainer half contains a 
horizontal member, inclined members and lower holding members each of 
which is protruded from the end face of the side cover toward those of the 
opposite retainer half in such a manner that the U-shaped ball movement 
direction reversing grooves radially extend intermediate the adjacent 
members among the above ones, wherein the horizontal member, inclined 
members and lower holding members of the respective retainer halves have 
concave end faces so as to form four lines of loading ball guides 
therebetween of which inner diameter is substantially same to the outer 
diameter of the rolling balls and which are arranged so as not to cause 
any falling-down of the loading balls therefrom, the respective retainer 
halves are dimensioned exactly to one half of the length of the bearing 
casing, and further one of the inclined members and lower holding members 
has engagement pins at their end faces, while the other one of them has 
engagement holes at their end faces to receive the corresponding 
engagement pins therein. 
Other objects and advantageous features of the present invention will be 
apparent from the reading of the following description made with reference 
to the accompanying drawings which illustrate a preferred embodiment of 
the invention.

DETAILED DESCRIPTION OF THE INVENTION 
Now the present invention will be described in more detail with reference 
to the drawings as follows. It is to be noted that the terms "loading 
ball" and "non-loading ball" are intended to represent the operating 
conditions of rolling balls and they should be identified by a so-called 
bearing ball. 
Reference numeral 10 designates a bearing casing made of steel material. As 
is apparent from the drawing, the bearing casing 10 has a geometrical 
configuration in the form of a parallepiped and is provided with a 
considerably large recess having a substantially trapezoidal sectional 
shape, wherein said recess comprises an upper wall 11, inclined side walls 
12 and 13 and open end faces 14 and 15 inwardly raised at portions 16 and 
17 (see FIG. 1). 
Further, said upper wall 11 has longitudinally extending grooves 19 and 20 
having the substantially same radius of curvature as diameter of rolling 
balls, said grooves 19 and 20 being located in the vicinity of both ends 
of the upper wall 11, while said inclined side walls 12 and 13 have also a 
longitudinally extending groove identified by reference numerals 21 and 22 
having the substantially same radius of curvature as the diameter of 
rolling balls, said grooves 21 and 22 being located at the lower part of 
the inclined side walls 12 and 13, whereby four ball rows (containing four 
lines of longitudinally extending grooves for loading balls) are 
symmetrically arranged on the inner walls of the bearing casing 10. 
Reference numerals 23 and 24 designate non-loading ball guiding holes which 
extend through the bearing casing 10 at a predetermined distance from the 
loading ball guiding grooves 19 and 20 on the upper wall 11 in parallel to 
the latter. 
Reference numerals 25 and 26 designate another non-loading ball guiding 
holes which extend also through the bearing casing 10 at a predetermined 
distance radially downward of the loading ball guiding grooves 21 and 22 
in parallel to the latter (see FIG. 1). 
Reference numerals 27 and 28 designate a threaded hole for a set screw 
respectively. Said threaded holes 27 and 28 are provided in a spaced 
relation on the center line of the upper wall 11 of the bearing casing 11 
and receive set screws 33 and 34 which are inserted through drilled holes 
27' and 28' on horizontal members 31 and 32 which are an integral 
extension from side covers 29 and 30, said set screws 33 and 34 being 
inserted and tightened after the horizontal members 31 and 32 come in 
abutment against one another at their end faces. 
Reference numeral 35 designates a threaded hole provided on the end faces 
of the bearing casing 10, into which a set screw is tightened for firmly 
securing the side covers 29 and 30 thereto. The horizontal members 31 and 
32 which serve as a part of a retainer have an outer concave end face 45 
at both sides thereof, said end face 45 having the substantially same 
radius of curvature as the diameter of rolling balls. 
Reference numerals 36 and 37 designate inclined members which are another 
integral extension of the side covers 29 and 30. Said inclined members 36 
and 37 have bottom ends 38 and 39 which are integrally secured to the 
inner end face 40 of the respective side covers 29 and 30, and they are 
longitudinally protruded therefrom. Further, they have outer inclined 
faces 41 and 42 of which width is dimensioned exactly same to that of the 
inner inclined walls 12 and 13 of the bearing casing 10, whereas they have 
upper and lower concave faces 43 and 44 which are symmetrically located 
opposite to the outer concave faces 45 of the horizontal members 31 and 
32. It is to be noted that the radius of curvature of the respective 
concave faces 43, 44 and 45 is dimensioned such that there is no danger of 
falling-down of any of rolling balls even when a track rail 55 is removed 
in the longitudinal direction (see FIGS. 1 and 2). 
Reference numeral 47 designates an engagement pin which is located at the 
right side seen toward the end face of the bearing casing 10. Said 
engagement pins 47 are protruded from the end face of the inclined member 
36, whereas drilled holes 48 are provided in the opposite inclined member 
37 to receive them. 
Reference numerals 49 and 50 designate upper and lower cornered portions 
formed intermediate the upper and lower concave faces 43 and 44, wherein 
the upper cornered portion 43 is flush with the lower face 51 of the 
horizontal members 31 and 32 and the lower cornered portion 50 has a 
downward inclination. 
Reference numerals 52 and 53 designate lower holding members which are also 
another integral extension of the side covers 29 and 30. Said lower 
holding members 52 and 53 are longitudinally protruded from the end face 
40 of the side covers 29 and 30 in the same manner as the inclined members 
36 and 37. Further, they have an upper concave face 54 which is 
symmetrically located opposite to the lower concave face 44, wherein said 
concave faces 44 and 54 are dimensioned such that no rolling ball falls 
down when the track rail 55 is removed in the longitudinally direction. 
Reference numeral 56 designates an engagement pin which is longitudinally 
protruded from the end face of the lower holding members 52 and 53 to be 
received in a corresponding drilled hole 57 on the end face of the bearing 
casing 10. 
Reference numerals 58, 59, 60 and 61 designate an U-shaped ball movement 
direction reversing groove respectively each of which is formed on the end 
face 40 of the side covers 29 and 30 by machining. Among them the U-shaped 
grooves 58 and 59 are located between the side concave faces 45 of the 
horizontal members 31 and 32 and the upper concave faces 43 of the 
inclined members 36 and 37, while the U-shaped grooves 60 and 61 are 
located between the lower concave faces 44 of the inclined members 36 and 
37 and the upper concave faces 54 of the lower holding members 52 and 53. 
It is to be added that the U-shaped grooves 58 and 59 extends in the 
vertical direction such that they are located in alignment with the 
loading ball guiding grooves 19 and 20 as well as the non-loading ball 
guiding holes 23 and 24, while the U-shaped grooves 60 and 61 extend in 
the downwardly inclined direction such that they are located in alignment 
with the loading ball guiding grooves 21 as well as the non-loading ball 
guiding holes 25 and 26 in the bearing casing 10. 
The side cover 30 and its associated members are constructed and arranged 
symmetrically relative to the side cover 29. 
Reference numeral 62 designates a drilled hole through which a fitting bolt 
63 is inserted and screwed into a threaded hole 35 provided on the end 
face of the bearing casing 10 so that the assemblies of the side covers 29 
and 30 with the retainer means are firmly secured to the bearing casing 
10. 
Reference numeral 55 designates a track rail which is adapted to be 
slidably incorporated through the linear ball bearing of the invention, 
having a X-shaped cross-sectional configuration. Said track rail 55 has 
raised portions 163 and 64 at the both sides of the upper part thereof, 
said raised portions 163 and 64 extending in the longitudinal direction 
and being formed with loading ball guiding grooves 65 and 66 located in 
the vicinity of both ends of the upper surface corresponding to the 
loading ball guiding grooves 19 and 20 on the inner upper wall 11 in the 
bearing casing 10 as well as with another loading ball guiding grooves 69 
and 70 located at the bottom of the raised portions 163 and 64 
corresponding to the loading ball guiding grooves 21 and 22 on the 
inclined side walls 12 and 13 in the bearing casing 10. The respective 
loading ball guiding grooves 65, 66, 69 and 70 have the substantially same 
radius of curvature as the diameter of the rolling balls (see FIG. 2). 
Reference numeral 71 designates a fitting hole which is intended to fixedly 
mount the track rail 55 on a moving part or stationary part of a machine, 
equipment, apparatus or the like such as machine tool by tightening a 
fitting bolt (not shown) inserted through said fitting hole. Further, 
reference numeral 73 designates a threaded hole which is intended to 
firmly set the bearing casing 10 to a table of a machine tool or the like 
by screwing a fitting bolt (not shown) into said threaded hole. 
The members or components for the linear ball bearing of the invention are 
designed and constructed as described above. Now a description will be 
made below as to how they are assembled. 
First, the retainer half of the retainer and side cover assembly 30 is 
inserted into the bearing casing 10 and then is fixed thereto by means of 
the bolts 63. Thereafter the horizontal member 32 of the retainer is 
firmly secured to the upper wall 11 of the bearing casing 10 by means of 
the set screw 33 inserted through the drilled hole 27'. 
Next, a number of balls 46 are charged into the bearing casing 10 through 
the respective non-loading ball guiding holes 23 to 26, until the loading 
ball holding passages in the retainer, the U-shaped ball movement 
direction reversing grooves 58 to 61 and the non-loading ball guiding 
holes 23 to 26 are filled with the charged balls. 
On the other hand, the retainer and side cover assembly 29 is charged with 
another balls 46 and thereafter it is inserted into the bearing casing 10 
with the engagement pins 47 being fitting into the engagement holes 48 on 
the retainer of the other assembly 29. At the same time the engagement 
pins 47 on the retainer of the other assembly 29 are fitted into the 
engagement holes 48 on the retainer of the one assembly 30. 
Finally, the retainer and side cover assembly 29 is firmly secured to the 
bearing casing 10 by means of the bolts 63 inserted through the fitting 
holes 62. 
Since the linear ball bearing of the invention is constructed in the 
above-described manner, it is ensured that as the linear ball bearing 
slidably mounted on a track rail moves forward and backward, loading balls 
held in the loading ball guiding grooves on the bearing casing and track 
rail are smoothly displaced into the non-loading ball guiding holes in the 
bearing casing via the U-shaped ball movement direction reversing grooves 
owing to the wide supporting area provided by the retainers as well as the 
scooping function through the U-shaped ball movement direction reversing 
grooves.