Machine element or mechanism – Mechanical movements – Reciprocating or oscillating to or from alternating rotary
Reexamination Certificate
2001-03-29
2003-04-29
Butler, Douglas C. (Department: 3683)
Machine element or mechanism
Mechanical movements
Reciprocating or oscillating to or from alternating rotary
C384S013000
Reexamination Certificate
active
06553855
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a drive system having a wide width structure integrally assembled with a feed screw and a linear guide device, for example.
There is known a drive system having a structure provided with a feed screw as driving means such as ball screw, slide screw or like and a linear guide device. Such drive system essentially comprises a screw shaft formed, at its outer surface, with a spiral groove, a linear guide rail as longitudinal track table arranged in parallel to the screw shaft and a block as movable member assembled with the linear guide rail to be movable along the longitudinal direction thereof, and this movable block is provided with a nut member to be screwed with the screw shaft.
Further, in general, a machine tool, a machine table or like is operatively mounted to such drive system and moved to a desired position and stopped there. This positional control of the machine tool, for example, is performed by controlling the rotational motion of the screw shaft through the operation of a motor or like drive means. As mentioned above, such drive system may be said as a compact feed unit having a good assembling performance and adjustment, and accordingly, has been utilized for various industrial robots, conveying equipments and the like.
For example, as shown in Japanese Utility Model Laid-open Publication No. HEI 2-12554, the drive systems of the type mentioned above generally includes the following two types, one being a straddle-type in which a movable table, having a bottom portion and lateral side portions extending in the longitudinal direction thereof, is straddled on the track table to be movable therealong and the other one being an idly groove-fitting type in which a movable member having a rectangular section is idly fitted into a recessed groove of a track member having box-shaped section to be movable in the longitudinal direction thereof.
In the case where both the above two types are compared with each other at the same rated load, a linear guide device utilizing the idly groove-fitting type can be formed to have a height lower than that of the straddle type, and hence, can be made compact, thus being arranged in a small space. In this meaning, it may be said that the idly groove-fitting type structure is effectively utilized for robots or conveying units which are likely to be used with restricted or reduced space.
The idly groove-fitting type structure will be described more in detail hereunder with reference to
FIGS. 7 and 8
.
A track table
90
having box-shaped section and having longitudinal extension is composed of a horizontally flat portion as a bottom portion
90
a
and a pair of lateral side portions standing upward from the bottom portion
90
a
as viewed in
FIG. 7
or
8
so as to form a recessed portion therebetween. The lateral side portions are formed with inner side surfaces
91
,
91
to which two rows of upper and lower ball rolling grooves
92
,
92
are respectively formed so as to extend in the longitudinal direction in parallel to each other. Further, a screw shaft
93
for the ball screw is arranged in the lateral central portion of the box-shaped track table
90
to be parallel to the ball rolling surfaces
92
,
92
.
A movable table
94
is a member having a top surface on which a table T or like is mounted to convey a machine tool or like tool, or other articles disposed on the table T. The movable table
94
has a rectangular section and is formed with a nut portion (member)
95
so as to be screwed with the screw shaft
93
. The movable table
94
has a width dimension slightly smaller than an inner width dimension of the recessed portion of the track table
90
as can be seen from FIG.
8
.
The movable table
94
is hence idly fitted to the recessed portion (groove) of the track table
90
. The movable table
94
is formed with lateral side surfaces to which loaded ball rolling surfaces
94
a
,
94
a
are formed so as to be opposed respectively to the ball rolling grooves
92
,
92
formed to the inside surfaces
91
,
91
of the track table
90
. Furthermore, ball return passages, each composed of a linear through hole, are formed in a solid portion of the movable table so as to extend in parallel to the loaded ball rolling surfaces
94
a
, and U-shaped rolling direction changing passages are also formed to the movable table at both longitudinal end portions thereof so as to communicate the loaded ball rolling surfaces
94
a
with the ball return passages
94
b
, respectively, thereby constituting an endless ball circulation passage in which a number of balls
97
as rolling members circulate while rolling therealong.
In the operation, when the screw shaft
93
is rotated through the driving of a servo-motor, not shown, the movable table
94
is moved in association with the rotational motion of the screw shaft
93
and guided along the track table
90
in its longitudinal direction. In this operation, the movement of the movable table
94
can be smoothly performed through the rolling motions of steel balls B arranged between the nut member
95
and the screw shaft
93
and the balls
97
arranged between the track table
90
and the movable table
94
. Further, a load of an article such as machine tool, table or like article applied to the movable table
94
through the table T on which the article is mounted to be conveyed is directly applied to a number of balls
97
arranged and rolling between the ball rolling surfaces
92
,
92
and the loaded ball rolling surfaces
94
a
,
94
a
. Furthermore, the ball rolling surfaces
92
, the loaded ball rolling surfaces
94
a
and the balls
97
are arranged so as to make minus the gaps, in dimension, between each of the ball rolling surfaces
92
and each of the balls
97
and between each of the loaded ball rolling surfaces
94
a
and each of the balls
97
to thereby apply a preload to the balls
97
.
However, in a conventional drive system in which the structure mentioned above is simply applied to a drive system having a wide width structure, the bottom portion
90
a
of the track table
90
having a wide width dimension is likely deformed or bent by a moment load Mc (
FIG. 8
) in a rolling direction applied to the movable table
94
, thereby opening outside the both lateral portions having the inside surfaces
91
,
91
to which the ball rolling grooves are formed. As a result, there causes a case where the tight close contact between the ball
97
, the ball rolling surface
92
and the loaded ball rolling surface
94
a
is loosened and it becomes difficult to give a sufficient preload to the ball
97
and a case where the movable table
94
causes a rolling, yawing or pitching motion because of the reduced preload and, hence, a smooth linearly advancing motion cannot be expected, thus being inconvenient.
In order to obviate the defect mentioned above, a prior art has provided one idea that a plurality of such drive systems are arranged side by side in parallel to each other. However, such plural lateral arrangement requires a wide space in the width direction and is not usable for disposing in a narrow limited space. Moreover, such parallel arrangement will require a high performance in the parallel alignment and location working for such requirement and for making minimum an operational resistance also requires much time and labor for an operator, as well as increasing in manufacturing cost for plural drive systems.
SUMMARY OF THE INVENTION
An object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art mentioned above and to provide a drive system having a wide width structure in which there is less change in preload between a rolling member and a rolling member rolling surface even in a case where a load, particularly, a moment load in the rolling direction, is relatively large, and the dimension in the width direction of the drive system is made compact, and an assembling working can be performed easily and smoothly with reduced manufacturing cost.
This and other obje
Michioka Hidekazu
Takahashi Kenji
Takamatsu Hiroshi
Armstrong Westerman & Hattori, LLP
Butler Douglas C.
Pezzlo Benjamin A
THK Co. Ltd.
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