Movable table

A movable table is provided with a guide rail, a movable block capable to move along with the guide rail, a driving means, and a power transmitting means transmitting from the driving means to the movable block; the movable block has a hole to contain the power transmitting means therein, and a bearing is formed between the guide rail and the movable block, and therefore, when a pre-load is applied on the movable block, the parts thereof on which the bearing is formed do not bend in any direction, and proper pre-loaded state is constantly kept.

FIELD OF THE INVENTION AND RELATED ART STATEMENT 
1. Field of the Invention 
The present invention relates to a movable table, and particularly pertains 
to a movable table widely used for general industrial equipments such as a 
machine tool. 
2. Description of the Related Art 
Recently, a movable table is used for various industrial equipments such as 
a machine tool and an industrial robot, and demand therefor has rapidly 
increased. In the following, a related art to the movable table is 
described with reference to the drawings. 
A conventional movable table has a construction as shown in FIG. 5 and FIG. 
6 of Japanese Patent Gazette of unexamined patent application No. Sho. 
59-137616. 
In FIG. 5 and FIG. 6, a movable block 41 has a pair of ball or roller 
(hereinafter merely refer to as ball) traveling grooves 42, 42 on inner 
side of both vertical protrusions and a pair of ball circulation passages 
43 bored in both vertical protrusions. A driving system 44 comprises a 
motor 45 for giving driving force to the movable block 41 through a ball 
thread 48 comprising a screw bolt 46a, nut part 46b, and a screw bolt 
bearing 46c. A fixed base 47 containing the screw bolt 46a of ball thread 
46 has a pair ball traveling grooves 48, 48 which form a pair of ball 
traveling passages 42a in together with the ball traveling grooves 42, 42 
provided on the movable block 41. And balls 49 inserted in each other 
facing ball traveling passages 42a, 42a operate as balls for a 
ball-and-roller bearing used for a rectilinear motion. In the movable 
table having the above-mentioned constitution, the movable block 41 is 
given a rectilinear motion by translating a rotary motion of the motor 45 
into a rectilinear motion by use of the ball thread 46. 
However, in the above-mentioned conventional movable table, the fixed base 
47 has a U-shape in cross section to accommodate the ball thread 46 
therein. The movable block, therefore, 41 also has U-shape in 
cross-section so that ball traveling grooves 42 can be defined between 
base 47 and block 41. Because both the fixed base 47 and the movable block 
41 have U-shaped cross-sections, the rigidity of block 41 against external 
forces in the direction of X indicated by arrow is inferior to rigidities 
against the external force from the other directions, and deflection of 
the depending arms is likely. 
More particularly, because both base 47 and block 41 of this prior art 
structure are U-shaped in cross-section, when the block 41 is loaded and 
exposed to forces from various direction, because fo the lack of 
structural rigidity, as discussed above, the downwardly depending legs 
will tend to deflect outwardly. Therefore a spacing between ball traveling 
grooves 42, 48 and balls 49 is produced and smooth sliding action of the 
movable block 41 is not possible. Thus, it is difficult to make it in a 
proper pre-loaded state. 
OBJECT AND SUMMARY OF THE INVENTION 
The present invention aims at solving the above-mentioned problems pointed 
out with respect to the prior art, and has for its object to provide an 
improved movable table having a strength capable of accepting a pre-load 
between ball or roller of a ball-and-roller bearing and traveling groove 
thereof, and to prevent a generation of spacing between the ball or roller 
and the traveling groove thereof, even when external force is applied on a 
movable block. 
A movable table of the present invention comprises: 
a guide rail extending in one horizontal direction, 
a movable block being movable along with the guide rail, and being provided 
with a hole in a moving direction thereof, by means of a linear bearing 
formed in cooperation with the guide rail, 
driving means, and 
power transmitting means for transmitting a force from driving means to the 
movable block, at least a part of the power transmitting means being 
disposed in the hole. 
In the movable table of the present invention, the ball thread is inserted 
in the hole of the movable block, the movable block has a hollow rectangle 
shape in cross section, but has a bottom part connecting both side parts. 
And therefore, when a pre-load is applied on the ball-and-roller bearing 
and an external force operates on the movable block, the side parts having 
ball travelling grooves do not bend in outward direction.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A preferred embodiment of the moving table in accordance with the present 
invention is described referring to FIGS. 1 and 2. 
In FIGS. 1 and 2, a guide rail 1 is fixed to a fixed base 13 with bolts 14 
and nuts 15. The guide rail 1 has a pair of straight and parallel ball 
traveling grooves 2 on its side walls for holding and enabling traveling 
of balls 7 therein. A moving block 3 slides on and along with the guide 
rail 1 in the same direction as the ball traveling grooves 2 shown by 
arrow A. The moving block 3 has a flat top 3a in which tool, work or parts 
to be assembled are carried. The moving block 3 also has a hole 10 in 
which a ball thread 6 penetrates. A driving system 4 comprises a motor 5 
and the ball thread 6. The ball thread 6 comprises a screw bolt 6a, nut 
part 6b, and a screw bolt bearing 6c. The nut part 6b is slidably coupled 
to, for example, guide groove 3d on side wall 3b of the moving block 3. 
The side wall 3b is vertical to the direction shown by arrow A. The nut 
part 6b is not movable against the moving block 3 in the direction shown 
by arrow A. But the nut part 6b is movable against the moving block 3 in a 
direction shown by arrow B which is vertical to the moving direction of 
the moving block 3. Namely, the nut part 6b and the moving block 3 are 
slidably coupled in the direction shown by arrow B. Both side walls 3c, 3c 
of an inner channel part of the moving block 3 has ball traveling grooves 
8. Ball (or roller) traveling passage 8a is formed by cooperation of the 
ball traveling grooves 8 with the ball traveling grooves 2. Ball 
circulation passages 9 are continuously formed on the ball traveling 
grooves 8 in the moving block 3. The ball circulation passages 9 hold and 
circulate the balls 7. A ball and roller bearing for rectilinear motion is 
constructed of the guide rail 1, the moving block 3 and the balls 7. The 
moving block 3 has an upper part 12 and a lower part 11 around the hole 
10. And both sides 30, 30 give enough strength to prevent a bending of the 
moving block. 
Operation of the movable table having the above-mentioned construction is 
described with reference to FIG. 1 and FIG. 2. 
Rotational motion of the motor 5 is changed into rectilinear motion by the 
ball thread 6. The rectilinear motion is transmitted to the movable block 
3. The balls 7 are circulated through the ball traveling passage 8a formed 
by ball traveling grooves 2 and 8, and the ball circulation passage 9. For 
actual use, a pre-load is applied on the ball-and-roller bearing formed by 
the guide rail 1, the movable block 3 and balls 7, in order to prevent an 
undesirable small downward motion of the movable block 3 when a load is 
applied on the movable table. When the pre-load is applied on the 
ball-and-roller bearing and the external force operates to the movable 
block 3, a tensile force is applied on the lower thin part 11 of the 
movable block 3. On the other hand, to the upper thin part 12 of the 
movable block 3, a force in horizontal and inward direction is applied. 
However, although the movable block 3 is provided with the hole 10, the 
upper and lower thin parts 11 and 12 have enough thickness, hence enough 
strength, to withstand the above-mentioned forces. Furthermore, since the 
guide rail 1 does not have hollow parts, it is very strong against the 
external force from horizontal direction. And therefore, the spacing 
between the ball traveling grooves 2, 8 and balls 7 is not made. 
As mentioned above, according the present invention, it is possible to 
apply the pre-load between the ball travelling grooves 2, 8 and balls 7, 
and to keep a proper pre-loaded state, even when the external force is 
applied on the movable block 3. Because the guide rail 1 with two grooves 
2 and the movable block 3 are combined, and because the lower part 11 and 
the upper parts 12 of the movable block 3 gives enough strength to 
withstand the load without bending to the movable block 3. 
Next, FIG. 3 shows a movable table as another embodiment of the present 
invention, and FIG. 4 is a perspective view thereof. The movable table of 
this embodiment is different from the first embodiment shown in FIG. 1 and 
FIG. 2 in that a driving means comprises a motor 5, a driving pulley 
(gear) 16, a timing belt 17, a subordinate pulley 18, and idle pulleys 19, 
and a timing belt fixing part 20 for fixing the timing belt 17 to the 
movable block 3. And other parts are almost the same as the first 
embodiment. 
In the movable table having the above-mentioned construction, a rotary 
motion is changed into a rectilinear motion by the driving pulley 16 and 
the timing belt 17. The rectilinear motion is transmitted to the movable 
block 3 through the timing belt fixing part 20 connecting the timing belt 
to the movable block 3. The timing belt 17 can performs a reciprocating 
motion along with hole 10. 
As mentioned above, by using the driving means comprising the moro 5, the 
driving pulley 16 and the timing pulley 17, it is possible to obtain the 
same effects as that of the first embodiment. 
In the above-mentioned embodiments, the balls 7 can be replaced by rollers.