Linear motion ball bearing

A ball bearing assembly for guiding two machine parts in linear relative motion. Upper, intermediate and lower members are assembled to an inverted U-shaped bearing body which straddles the sides of a rail base. Grooves formed between the members and the bearing body provide circulation paths on either side of the rail base for ball bearings. All components are accommodated within the width of the bearing body.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a linear motion ball bearing used for guiding 
portions which perform a linear motion such as a machine tool table, a 
positioning table, etc. 
2 Description of the Prior Art 
According to a conventional linear motion ball bearing of this type, 
generally a ball return hole is formed axially in a bearing body to let 
balls circulate in an axial direction, and a machining for curved surface 
is performed to connect end portions of the return hole and a loaded ball 
groove formed in the bearing body, and further a return cap having a ball 
turning groove for changing the direction of the balls by 180.degree. is 
applied to each end portion. 
However, in order to prevent balls from falling off when the bearing body 
is pulled out from a rail base, it is necessary to provide a separate ball 
retainer. In addition, the aforementioned return caps are required which 
increases the number of parts. 
A very different linear motion ball bearing has been proposed in U.S. Pat. 
No. 4,632,573, issued Dec. 30, 1986 to Katsutoshi Itoh, in which upper and 
lower ball circulation paths are formed surrounding a leg portion of a 
bearing body with loaded ball grooves. By fitting the circulation paths, 
one upon another, to the leg portion, upper and lower members are each 
formed with an opposingly J-shaped groove, and an intermediate member is 
formed on upper and lower sides thereof with opposingly J-shaped grooves 
and further grooves connecting the tips of said J-shapes. 
The above-mentioned bearing does not require curved surface machining at 
the ends of the loaded ball grooves of the bearing body; nor separate 
provision of ball retainers. However, it unavoidably becomes larger 
widthwise, requiring larger space. 
Therefore, an overall size becomes larger if one wants to increase the 
width of the leg with a view to increasing the rigidity of the bearing. 
SUMMARY OF THE INVENTION 
The present invention has solved the abovementioned problem in which a 
linear motion ball bearing is provided with a bearing body having a leg 
portion with upper and lower loaded ball grooves. The upper groove 
includes a substantially semi-circular section, a lower groove includes a 
substantially quarter-circular section. A recessed corner portion is 
formed on an opposite side of the grooves. Upper members, each having a 
ball turning groove, are connected to the upper loaded ball groove and the 
corner portion and arranged at both ends of the bearing body. An 
intermediate member is formed on upper and lower sides thereof with 
opposingly J-shaped grooves and ball retaining grooves connected to the 
tips of the J-shapes, and is mounted to the leg portion such that the 
corner portion serves as an unloaded ball groove and forms an upper ball 
circulation path with the upper groove of the intermediate member. A lower 
member, having an opposingly J-shaped groove and ball retaining groove, is 
connected to the tips of the J-shapes and is arranged to form a lower ball 
circulation path with the lower groove of said intermediate member. 
When the upper, intermediate and lower members are assembled to the bearing 
body, the two unloaded ball grooves are accommodated into the recessed 
corner portion of the bearing body, whereby all the members may be 
accommodated within the width of the bearing body. In addition, like the 
above-mentioned prior application, there is no need to provide ball return 
holes to the bearing body and to provide ball turning caps at both ends to 
change the direction of the balls. Furthermore, a ball retainer may be 
built-in such that balls do not fall off even when the bearing assembly is 
separated from the rail base.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings wherein like characters designate like or 
corresponding parts throughout the several views, there is shown in FIGS. 
1-4 a prior art linear motion ball bearing of said U.S. Pat. No. 
4,632,573. The linear motion ball bearing comprises upper and lower 
members 410, 420 and an intermediate member 430 fitted to a bearing body 
400 one upon another to form endless ball circulation paths. The upper and 
lower members are identically formed. Said members have opposingly 
J-shaped grooves, the sections of which are nearly semi-circular. The 
reference numerals 412 and 422 are ball-scooping pawls. 
On the other hand, the intermediate member 430 has, on its upper and lower 
surfaces, opposingly J-shaped grooves complementary to the opposingly 
J-shaped grooves of the upper and lower members 410 and 420, and ball 
retaining grooves 433 connecting the tips of said J shapes. The section of 
the opposingly J-shaped groove 431 is semi-circular so that a circle may 
be formed with the corresponding grooves of the upper and lower members; 
and the section of the ball retaining groove 433 is quarter-circular. 
The assembly of said upper, lower and intermediate members 410, 420 and 430 
are fitted to the leg 401 of the bearing body 400 such that endless ball 
circulation paths are formed with loaded ball grooves 404 and 405 of 
semi-circular sections. Said members and the bearing body are secured at 
both longitudinal ends by means of a cover (not shown). 
FIG. 5, in contradistinction, shows in disassembled state, a bearing 
according to a first embodiment of this invention. A bearing body 20, a 
pair of upper members 30, 30, a pair of intermediate members 50, 50, a 
pair of lower members 70, 70 and a seal member 80 are secured firmly by 
means of bolts 90, 91, screws 93 and nuts 94. FIG. 6 depicts the state in 
which the assembled body is mounted to a rail base 96. 
The bearing body 20 has legs 21, 21 riding astride on the rail base 96, the 
section of which is shown in FIG. 11. At the inner surfaces of the legs, 
two pairs of upper and lower loaded ball grooves 22a, 22b are opposingly 
formed. The upper loaded ball grooves 22a are longitudinally extending 
grooves of semi-circular sections; and the lower loaded ball grooves 22b 
are of quarter-circular sections, as the lower ends of the legs 21 are cut 
off. These loaded ball grooves 22a, 22b and the ball rolling surfaces 97, 
97 form two pairs of upper and lower loaded areas. These loaded ball 
grooves 22a, 22b are simple, straight grooves; and curved surfaces need 
not be machined at both ends thereof like the above-mentioned U.S. Pat. 
No. 4,632,573. 
At the both side surfaces of the bearing body 20, recessed corner portions 
23 are formed, such that they are open sidewardly and downwardly. Said 
corner portions form upper unloaded ball grooves in cooperation with the 
intermediate members 50 as mentioned below, and accommodate the lower 
unloaded ball grooves. At the longitudinal ends of the bearing body 20, 
threaded holes 25 with counterbores 24 for receiving the protrusions 33 of 
the upper members 30, explained below, and screw holes 26 for securing a 
seal member 80, are provided; and at the upper surface, screw holes 27 are 
provided for securing the body, for example, to a table of a machine tool. 
To the bearing body 20, the upper member 30, the intermediate member 50 and 
the lower member 70 are secured. Each member will be explained with 
reference to FIGS. 7a, 7b, 8 and 9. 
A pair of upper members 30, 30 disposed at both ends of the bearing body 20 
have at each lower surface a U-shaped ball turning groove 31 connecting 
the upper loaded ball groove 22a of the bearing body and the corner 
portion 23. At the end of ball turning groove 31 adjacent to the upper 
loaded ball groove 22a, a ball scooping pawl 32 is provided. On the 
surface in contact with the bearing body 20, protrusions 33 for 
positioning are provided so as to fit into the counterbores 24. On the 
reverse side, counterbores 34 are provided with a through hole 35 for 
accommodating fastening bolt 90. A pair of through holes 36, 36 are 
provided for securing a seal member 80 to the bearing body 20. Vertical 
through holes 37 are provided to fasten the intermediate member 50 and the 
lower member 70; and the upper end thereof is adapted to accommodate a nut 
94. A stepped portion 38 is provided for accurate positioning in 
cooperation with a shoulder 58 of the intermediate member 50. 
As mentioned above, the upper members 30 are simply positioned adjacent to 
both ends of the bearing body 20 and do not surround the leg of the 
bearing body 21, which is different from the invention of said prior U.S. 
Pat. No. 4,632,573. 
At the surface of one of the upper members 30, 30, a grease nipple 39 is 
provided, which serves to supply lubricating grease to the ball 
circulation paths. A grease supplying groove 40 is formed such that it may 
be closed when fastened to the bearing body 20. The grease supplying 
groove 40 extends to the center of the semi-circular portion 41 surrounded 
by the ball turning groove 31. Grease may be supplied to the ball 
circulation path through the longitudinal communicating channel 42. This 
channel 42 may be provided in the intermediate member as mentioned later. 
Opposingly J-shaped groove 71 is formed in the lower member 70, the section 
of which is semi-circular. Between the tips of the J-shapes, a ball 
retaining groove 72 is formed such that it does not interfere with the 
balls B which move between the rail base 96 and the bearing body 20. The 
central portion 73 surrounded by the J-shaped groove 71 and the ball 
retaining groove 72 abuts, as shown in FIG. 8, against the lower surface 
of the leg portion 21 of the bearing body 20 and thus the ball retaining 
groove 72 may be located close to the lower loaded ball groove 22b. 
The present invention is distinct over said prior invention in that the 
lower member 70 abuts against the lower surface of the leg portion 21 and 
does not accommodate the leg portion. 
A communicating groove 74 is formed in the central portion 73 for supplying 
lubricating grease to the J-shaped groove 71 by way of the intermediate 
member 50; and at one end of the J-shaped groove 71, a pawl 75 is provided 
for smoothly guiding the ball B from the lower loaded ball groove 22b into 
the ball turning path. Close to the end surface of the lower member 70, a 
through hole 76 is provided as mentioned before; and on the lower surface 
thereof, a counter-sink 77 is formed to receive a head of a screw 93. In 
addition, on this lower surface, a dovetail groove 78 is formed to receive 
a seal member 80. 
On the other hand, on the upper surface of the intermediate member 50, 
opposingly J-shaped grooves 51 are formed complimentary with the ball 
turning groove 31 of the upper member 30 and the corner portion 23 of the 
bearing body 20; and on the lower surface as well, opposingly J-shaped 
grooves 52 are similarly formed. A ball retaining portion 53 is formed 
with upper and lower ball retaining grooves 54, 55 so as connect the tips 
of the J-shapes (reference numeral 51a notes one of the tips of the 
J-shapes on the upper surface). The sections of the upper and lower 
J-shaped grooves are semi-circular so as to form a circle with 
corresponding grooves 31, 71 of the upper member 30 and lower member 70, 
respectively; and the sections of the ball retaining grooves 54, 55 are 
almost quarter-circular. As shown in FIG. 11, the ball retaining portion 
53 extends along the groove 98 of the rail base 96. 
At the turning portions of the J-shaped grooves 51, 52, a half 
cylinder-like portion 56 is formed; and the hollow portion 57 surrounded 
by the portion 56, J-shaped grooves 51, 52 and the ball retaining portion 
53 is adapted to accommodate the leg portion 21 of the bearing body, and 
the shoulder 58 abuts against the lower surface of the corner portion 23 
so as to form a ball circulation path with the elongated part of the 
J-shaped groove 51. Adjacent to one end of the intermediate member 50, a 
through hole 59 is formed so as to align with the holes 37, 76 of the 
upper member 30 and lower member 70, respectively. The stepped portion 38 
receives the shoulder 58 to ensure accurate positioning of each member in 
cooperation with the fastening by means of screws through holes 37, 59 and 
76. And, when the intermediate member 50 is fit to the bearing body 20, a 
channel 60 is formed at the inner side of the half cylinder portion 56 so 
as to connect the grease supplying grooves in the upper member 30 and the 
lower member 70. 
The seal member 80 (FIG. 5) comprises a pair of opposing front plates 81, 
81 and a pair of base plates 82, 82 adapted to fit into the dovetail 
groove 78 of the lower member 70. On the outer surface of the front plate 
81, through holes 84, 84 for securing to the bearing body 20 and a hole 85 
for communicating with a grease nipple 39 are respectively provided. A 
rubber material 83 is secured to the plate 84 so as to come into a sliding 
contact with the groove 97 of the rail base 96. A rubber material seal is 
also provided to the opposing inner surfaces of the base plates 82, 82. 
In order to incorporate balls B (FIG. 8) into the bearing assembly, the 
bearing body 20 is first put on an assembling jig (not shown) upside down; 
and then, the upper members 30, 30 each having a ball turning groove 31 
are fastened to the end surfaces of the bearing body 20 by means of the 
bolts 90 so that said grooves face upward. After forming endless ball 
circulation paths with the jig, upper members 30, 30 and the bearing body 
20, balls B are introduced. Thereafter, the intermediate members 50, 50 
are fit to the legs 21, 21 of the bearing body 20, and balls B are 
inserted into the circulation paths 52 and ball retaining grooves 55. On 
top of the assembly thus formed, the lower members 70, 70 are placed, with 
the base plates 82, 82 having been fit into the dovetail grooves 78, 78 of 
the lower members. Then, the assembly is fastened by means of the screws 
93 and nuts 94. Thus, endless ball circulation paths are formed with the 
loaded ball grooves 22a, 22b forming a part thereof. Furthermore, the seal 
member 80 may be secured by means of the bolts 91. Needless to say, the 
seal member 80 may be used only when it is required. 
In a linear motion bearing 10 thus assembled, as shown in FIG. 6, the side 
faces of the bearing body 20, the upper member 30, the intermediate member 
50 and the lower member 70 are flush with each other, and consequently, 
all members may be accommodated within the width of the bearing body 20. 
FIG. 10 is a side view of the assembled bearing showing that no extra 
space is required in the longitudinal direction as well. 
The ball retaining portion 53 having ball retaining grooves connecting the 
tips of the J-shapes of the grooves 51, 52 of the intermediate member 50 
extends along the groove 97 of the rail base 96. In the assembled state, 
only about a quarter portion of one ball B may be exposed, as shown in 
FIG. 8; and consequently, balls may be retained in cooperation with the 
loaded ball grooves 22a, 22b, even when the bearing assembly is separated 
from the rail base 96. 
A second embodiment of the invention will now be explained with reference 
to a linear motion bearing 100 which incorporates a few improvements over 
the first embodiment. The improvements may be summarized as follows. 
Firstly, as seen from FIG. 8, there is a thin portion between the upper and 
lower unloaded ball grooves of the intermediate member 50. Since a 
predetermined minimum amount of thickness is required when forming this 
member by plastics, the upper unloaded ball groove must be set 
sufficiently upward in FIG. 8 in order to reduce the embodiment of FIG. 8 
to practice. On the other hand, if the upper unloaded ball groove is set 
upward, a cavity may be formed in the direction of load applied to the 
lower loaded balls (ordinarily 45 degrees from normal line), which causes 
the rigidity of the leg portion 21 to decrease (see FIG. 13). This is the 
first point of improvements. Simplification of a grease introducing path 
to the lower ball circulation path will be effected at the same time. 
Secondly, ball turning paths are formed between the upper member and the 
intermediate member, and between the intermediate member and the lower 
member. Said ball turning paths, especially those portions for receiving 
loaded balls, are subjected to reaction forces and centrifugal forces 
during the turning of the balls. Thus, if the portions in question 
comprise only plastic material, wear will be remarkable. This is the 
second point of improvements. 
Referring to FIG. 12, there is illustrated a linear motion ball bearing 100 
(excluding balls and a rail base) according to the second embodiment of 
this invention. The bearing body 120, a pair of upper members 150, 150, a 
pair of lower members 170, 170, a seal member 180 and a seal securing 
member 190 are fastened by means of bolts 101, 102, screws 103 and nuts 
(not shown) received in the upper member. 
As shown in FIG. 12, the bearing body 120 has a pair of legs 121, 121 so as 
to ride astride on the rail base 96 as was the case with the first 
embodiment. And two pairs of opposing loaded ball grooves 122a, 122b are 
formed in the inner surfaces of the leg portions 121, 121. The upper 
loaded ball groove 122a extends longitudinally and has a semi-circular 
section; and the lower loaded ball groove 122b has a quarter-circular 
section as the lower end of the leg portion 121 is cut off. These loaded 
ball grooves 122a,122b form two pairs of upper and lower loaded ball areas 
in cooperation with the grooves formed in the rail base 96. These loaded 
ball grooves 122a and 122b are straight grooves with no curved surface 
machinings at both ends thereof as is the case with the above-mentioned 
U.S. Pat. No. 4,632,573 and the first embodiment of this invention. 
At both side surfaces of the bearing body 120, longitudinally extending 
recessed corner portions 123, 123 are respectively formed so as to open 
sidewardly and downwardly. The upper and lower unloaded ball grooves 112a, 
112b are formed at this portion in cooperation with the intermediate 
member 150 and lower member 170 as will be explained later (see FIGS. 13 
and 14). 
As illustrated in FIGS. 13 and 14, the corner portion 123 has three grooves 
and one protrusion. The first groove 123a has an acutely angled corner and 
is for receiving the intermediate member 150; the second groove 123b is of 
substantially semi-circular section for forming an upper unloaded ball 
groove 112a; and the third groove 123c is of substantially 
quarter-circular section for forming a lower unloaded ball groove 112b. 
The groove 123c may be done away with by displacing the lower unloaded 
ball groove slightly downwardly in FIG. 13 (see FIG. 8). A protrusion 123d 
is formed between the second and third grooves. 
The longitudinal end surfaces of the bearing body are provided with 
threaded holes 125 with an annular enlargement 124 for receiving a 
protrusion 133 of the upper member 130, and threaded holes 126 for 
securing a seal member 190. On the upper surface of the bearing body, 
threaded holes 127 are formed for connection, for example, with a table of 
a machine tool. 
The upper members 130, 130, the intermediate members 150, 150 and the lower 
members 170, 170 are fastened to the bearing body 120. Each member will be 
explained with reference to FIGS. 12 and 13-16. 
At the lower surface of the upper member 130, a U-shaped ball turning 
groove 131 is formed so as to connect the upper loaded ball groove 122a of 
the bearing body 120 and the second groove 123b of the corner portion 123 
(FIG. 14), and a ball scooping pawl 132 is formed at the end of the ball 
turning groove 131 adjacent to the upper loaded ball groove 122a. At the 
abutment surface with the bearing body 120, protrusions 133 are formed so 
as to engage with the aforementioned annular enlargements 124; and at the 
reverse side, a pair of through holes 135 having counterbores for 
receiving the head of bolts 101, and a pair of through holes 136 for 
securing a seal member 190 are respectively formed. At the lower surface, 
tapped holes are provided to fasten the intermediate and lower members. 
In addition, a grease nipple 105 may be provided to the hole 138 of the 
upper member 130, which enables the supply of grease to the ball 
circulation paths. Grease supply groove 140 is formed so as to be closed 
when the upper member 130 is secured to the bearing body 120, which groove 
extends to the center of the semi-circular portion surrounded by the ball 
turning groove 131; and grease may be supplied therefrom to the ball 
circulation paths through a longitudinally extending groove 142 (see FIG. 
14). 
Opposingly J-shaped grooves 171 are formed in the lower member, the section 
of which is almost semicircular. Between the tips of said J-shapes, ball 
retaining groove 172 is formed so as not to interfere with the balls B 
held between the rail base 96 and the bearing body 120. The central 
portion 173 surrounded by the J-shaped grooves 171 and the ball retaining 
groove 172 abuts, as shown in FIG. 13, the lower surface of the bearing 
body 120; and thus, the ball retaining groove 172 comes adjacent to the 
lower loaded ball groove 122b. 
At both ends of the J-shaped grooves 171, ball scooping pawls 175, 175 are 
provided for smoothly introducing the balls from the lower loaded ball 
grooves into the ball turning paths. Through holes 176 are provided for 
fastening by means of screws 103, the heads of which are received in the 
recesses 177. Moreover, on the lower surface, stepped portions 178, 179 
are provided for receiving a seal member 180 and seal fixing member 190, 
respectively (FIG. 15). 
On the other hand, as shown in FIGS. 12 and 14, the upper surface of the 
intermediate members 150 is formed with opposingly J-shaped groove 151 so 
as to be complementary with the ball turning groove 131 of the upper 
member 130 and the corner portion 123 of the bearing body 120; and a 
similarly opposingly J-shaped groove 152 is formed. Furthermore, the ball 
retaining portion 153 is formed with upper and lower ball retaining 
grooves 154, 155 connecting the tips of said J-shapes (see reference 
numeral 151a). Each of said ball retaining grooves 154, 155 has a 
substantially quartercircular section. The ball retaining portion 153 
extends along the groove 98 of the rail base 96 as shown in FIG. 11. 
Denoted by 163 in FIG. 13 is a protrusion which opposes the protrusion 123d 
of the leg portion 121 with a space therebetween. The upper unloaded ball 
groove 112a having a substantially circular section is formed by the 
second groove 123b of the corner portion 123 and the J-shaped groove 151 
of the intermediate member 150. Moreover, the lower unloaded ball groove 
112b of a similarly substantially circular section is formed by the third 
groove 123c of the corner portion 123, the lower J-shaped groove 152 of 
the intermediate member 150 and the J-shaped groove 171 of the lower 
member 170. 
The gap between the protrusions 123 and 163 is a slit which connects the 
upper unloaded ball groove 112a and the lower unloaded ball groove 112b in 
the longitudinal direction of the J-shaped grooves 151, 152. A similar 
slit may be provided between the upper and lower J-shaped grooves 51, 52 
at the thin central portion in the first embodiment. The slit may be 
provided only partly in the longitudinal direction. 
The slit enables uniform lubrication of both the upper and lower ball 
circulation paths. In the first embodiment, grease supply paths are 
provided to all of the upper, lower and intermediate members; however, 
such a path is provided only to the upper member 130. This of course 
serves to simplify the whole structure of the bearing. 
The grease supplied at the nipple 105 may be supplied to the upper unloaded 
ball groove 112a by way of the hole 138, the supply groove 140 and the 
communicating groove 142. Since the lower unloaded ball groove 112b can 
communicate with the upper unloaded ball groove 112a through the slit 160, 
the grease may be distributed to each groove with the balls as media. This 
means that not only the slit but the upper unloaded ball groove 112a is 
utilized as the grease supply path. 
By comparing FIG. 13 with FIG. 8, it will be appreciated that in the FIG. 
13 embodiment, the separation of the upper and lower unloaded ball grooves 
by means of the intermediate member only is replaced by the separation by 
means of the two opposing protrusions with a gap therebetween. Thus, the 
thin portion of the intermediate member as seen in FIG. 8 may be done away 
with; and furthermore, since the position of the upper unloaded ball 
groove 112a may be made lower, it is possible to eliminate cavities 
between the line normal with respect to the center of the lower loaded 
balls and the line inclined 45.degree. outwardly therefrom. This serves to 
increase rigidity of the leg portions and simplify the grease supply path 
by virtue of the slit 160 as mentioned above 
Another improvement reinforces the ball turning paths. As mentioned before, 
ball turning paths are formed in the portions held by the upper member and 
the intermediate member, and between the intermediate member and the lower 
member to turn the moving directions of the balls by 180.degree.. These 
ball turning paths (especially the portions where the loaded balls are 
introduced) are subjected to the reaction force during the turning of the 
balls and the balls are pushed toward the bottom of the groove because of 
the centrifugal force; and consequently, if these paths are formed by 
plastics only, significant wear is unavoidable. Therefore, it is 
preferable to reinforce at least the quarter portion where the loaded 
balls are received. The improvement is explained in detail as follows. 
As shown in FIG. 12, at the ball retaining portion 153 of the intermediate 
member 153, notches 164, 164 are formed. In addition, beyond the notch 
164, a retaining groove 166 is formed so as to cover almost half of the 
ball turning path. The section of said retaining groove is almost 
semi-circular. The retaining groove comes to an end at the insertion hole 
167 which is provided at the end of the upper and lower J-shaped grooves. 
This arrangement is provided at both sides of the intermediate member 150. 
Denoted by the numeral 161 is the reinforcing member in the form of a 
clip, the ends of which are inserted into the holes 167, 167 and placed 
along the retaining grooves 166, 166 with the middle portion held in the 
notch 164. The reinforcing member 161 comprises an elastic metal wire and 
is placed into position as mentioned above. 
The notch 164 is larger than the wire diameter so that the reinforcing 
member 161 will not interfere with the rail base 96. On the other hand, 
the retaining groove 166 has a depth to receive one half of the wire 
diameter. Therefore, the respective complimentary grooves are provided in 
the upper member 130 and the lower member 170 in the opposing surfaces 
thereof. 
As the balls B move from the loaded ball groove to the unloaded ball 
groove, the pawls 132, 175 scoop the balls in cooperation with the ball 
retaining portion 153. The balls turn in direction while being pushed 
against the reinforcing member 161. Thus, the reinforcing members serve to 
increase the service life of the bearing. 
A half cylindrical portion 156 is formed at the ball turning portion of the 
J-shaped grooves 151, 152. The hollow portion surrounded by the half 
cylindrical portion 156, opposingly J-shaped grooves 151, 152, and the 
ball retaining portion 153 fits into the leg portion 121 of the bearing 
body 120, and the shoulder 158 abuts the groove 123a of the corner portion 
123. The shoulder 158 has an acute angle and serves to accurately position 
the intermediate member 150 relative to the bearing body 120. 
Adjacent one end of the intermediate member 150, a through hole 159 is 
formed so as to align with the through hole 176 of the intermediate member 
170 and the tapped hole in the upper member 130. 
As shown in FIG. 15, the assembled upper, lower and intermediate members 
have, at both longitudinal ends, a first stepped portion 110 for receiving 
a seal securing member 190, and a further recessed stepped portion 111 for 
receiving the seal member 180. The seal member 180 is inserted into the 
second stepped portion 111 for sealing the gap in the longitudinal 
direction; and the connecting portions 182 are fitted into the stepped 
portion 178 of the lower member 170 to seal in the vertical direction. 
Thus, foreign matter may be prevented from entering the bearing assembly 
from both the longitudinal and vertical directions 
Outwardly of the second stepped portion 111, the seal securing member 190 
is fastened into the first stepped portion 110. 
The seal securing member 190 comprises a pair of opposing front members 
191, 191, and a pair of connecting members 192, 192 fitting into the 
stepped portion 179 of the lower member 170. The front members have 
through holes 194, 194 with countersinks for connection to the bearing 
body 120, and a notch for mounting a grease nipple 105 to the upper 
members 130. 
In order to incorporate balls, the bearing body 120 is first placed on an 
assembly jig (not shown) upside down. Next, a pair of the upper members 
130, 130 are secured to the front ends of the bearing body 120 such that 
the grooves face upward. After forming an endless ball circulation path 
with the jig, upper members 130, 130 and the bearing body 120, balls are 
put into the groove. Thereafter, the intermediate members 150, 150 are fit 
to the respective leg portions 121, 121 and the balls are put into the 
J-shaped grooves 152, 152 and the ball retaining groove 155. 
Then, the lower members 170, 170, each fitted with the connecting member 
182 of the seal member 180 into the stepped portion 178, and the lower 
member 170 into the stepped portion 179 are placed thereon. The assembly 
thus formed is fastened by means of the screws 103 threaded into the 
tapped holes in the upper members 130, 130. Thus, the upper and lower ball 
circulation paths are formed with the upper and lower loaded ball grooves 
122a, 122b forming a part thereof. The seal securing members 190, 190 are 
finally fastened to the bearing body 120 by means of the bolts 102. 
The linear motion ball bearing 100 thus assembled is capable, like the 
first embodiment, of accommodating all the members within the width of the 
bearing body 120 and the balls may be retained even when the bearing 
assembly is separated from the rail base 96. 
The improvement resulting from the provision of the slit between the upper 
and lower unloaded grooves; and the reinforcement of the ball turning 
paths should not be limited to the illustrated embodiment comprising the 
upper members 130, intermediate members 150 and the lower members 170. 
Accordingly, a third embodiment of this invention will be explained with 
respect to a conventional block type linear motion ball bearing with 
reference to FIGS. 17-20. Only the different structures will be explained. 
The ball retaining portion 253 of the intermediate member 250 is provided 
with notches 264, 264. The grooves 265, 265 connect said notches to the 
ball retaining grooves 254, 254; and the retaining groove 266 is provided 
so as to extend along the ball turning groove 251. Namely, the retaining 
groove 266 is formed in the region where the loaded balls are received. 
The retaining groove 266 ends at the hole 267 provided at one longitudinal 
end of the J-shaped grooves 251. The lower surface of the intermediate 
member 250 is similarly formed. Denoted by the reference numeral 261 is a 
reinforcing member placed into the notch 264, grooves 265, 266 and 
inserted into the hole 267 at both ends. The reinforcing member 261 is 
made of a metallic wire and positioned as mentioned above. 
The width of the notch 264 is greater than the diameter of the reinforcing 
member 261 and the grooves 265 and 266 are adapted to receive 
approximately one half of the reinforcing member 261. Moreover, on the 
opposing surface of the upper member 230 and the lower member 270, the 
retaining grooves 236, 276 are respectively formed for receiving the 
reinforcing member 261. The three members placed one upon another as shown 
in FIG. 19 are fit to the leg portion 221 of the bearing body 220 such 
that the assembled members surround the leg portion. The reinforcing 
member 261 functions as mentioned before with reference to the second 
embodiment. 
Another improvement is to communicate the upper and lower J-shaped grooves 
by means of a slit 260. As illustrated in FIGS. 17, 19, a slit 260 is 
provided at a thin portion between the upper and lower J-shaped grooves 
251, 252 so as to communicate said two grooves. 
Thus, as mentioned with reference to the second embodiment, grease may be 
evenly supplied to both grooves. 
A more conventional bearing body 320 having longitudinal ball return bores 
312a, 312b may also be provided with a slit 360 so as to achieve the same 
effect. 
Application of the present invention is not limited to such a symmetrical 
bearing shape as shown in FIG. 6. A linear motion ball bearing may be 
constituted by forming an only one-side bearing body portion having a ball 
circulation mechanism and a rail base as separate unit type modules and 
bolting these modules to other machine parts (e.g. table and bed of a 
machine tool). It goes without saying that the ball groove may be formed 
in a circular shape to receive loading equally in four directions. In this 
case, an angle of contact, between the rail base and ball shown in FIG. 11 
is set about 45 relative to the horizontal direction. 
The plan shape of the ball turning portion of the J-shapes may be 
semi-circular, U-shaped, or rectangular with chamfered corners, etc. 
ADVANTAGES OF THE INVENTION 
Being structured as mentioned above, the linear motion ball bearing of the 
present invention is capable of accommodating all the members within the 
width of the bearing body, and consequently, can be made compact. In 
addition, the bearing body need not be provided with conventional ball 
return holes and need not be given curved surface machining at the ends of 
the loaded ball grooves. Moreover, since the section of the lower loaded 
ball groove of the bearing body can be quarter circular, the machining 
thereof can be simpler. Such a structure does not require separate members 
for turning the balls, such as, ball return caps. Furthermore, being 
equipped with ball retainers, the balls will not fall off even when the 
bearing assembly is separated from the rail base. Therefore, the number of 
the parts may be less, which also serves to reduce the manufacturing 
costs. 
As a result, even if the width of the leg portions of the bearing body is 
made somewhat larger to increase the rigidity, the overall size of the 
bearing assembly can be relatively small. 
The provision of the slits between the upper and lower unloaded ball 
grooves serves to evenly distribute grease to the entire ball circulation 
paths, which is useful to simplify the grease supply paths and to 
facilitate manufacturing. 
By providing reinforcing members, wear of the ball turning paths may be 
reduced, which is useful for increasing the service life.