Machine element or mechanism – Mechanical movements – Reciprocating or oscillating to or from alternating rotary
Reexamination Certificate
2000-06-02
2002-06-25
Herrmann, Allan D. (Department: 3682)
Machine element or mechanism
Mechanical movements
Reciprocating or oscillating to or from alternating rotary
C384S029000, C384S042000, C403S359200
Reexamination Certificate
active
06408706
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rotation-preventive device and an electric actuator having a rotation-preventive function which make it possible to prevent, for example, a spline shaft from rotation in the circumferential direction by means of engagement of the spline shaft with a hole of a boss.
2. Discussion of the Background
For example, a spline has been hitherto used to prevent a shaft member from rotation in the circumferential direction. As shown in
FIG. 23
, the spline
1
includes a spline shaft
4
which has a plurality of teeth
3
a
to
3
h
having a substantially trapezoidal cross section formed in the circumferential direction along the outer circumferential surface between adjoining grooves
2
a
to
2
h
separated from each other by a predetermined angle, and a boss
6
which is provided relatively slidably in the axial direction of the spline shaft
4
and which is formed with a hole
5
having a shape corresponding to the cross-sectional shape of the spline shaft
4
in a direction perpendicular to the axis.
In this case, as shown in
FIG. 24
, a predetermined clearance A is formed between the teeth
3
a
to
3
h
of the spline shaft
4
in the circumferential direction and the inner wall surface of the hole
5
of the boss
6
corresponding to the teeth
3
a
to
3
h
. The clearance A is formed as follows. That is, the spline shaft
4
is formed, for example, by means of the thread rolling. The boss
6
is formed, for example, by means of the drawing. After that, the finishing machining is applied to the teeth
3
a
to
3
h
of the spline shaft
4
and the inner wall surface of the hole
5
of the boss
6
.
However, the spline
1
concerning the conventional technique as described above involves the following inconvenience. That is, the clearance A is dispersed due to an error occurring in machining accuracy. Further, the teeth
3
a
to
3
h
of the spline shaft
4
are abraded due to the sliding friction with respect to the inner wall surface of the hole
5
of the boss
6
, and the clearance A is increased so as to be larger than a preset predetermined value. As a result, backlash is caused when the spline shaft
4
and the boss
6
make the relative sliding displacement in the axial direction.
An electric actuator
10
has been hitherto used as a means for transporting a workpiece. As shown in
FIG. 25
, the electric actuator
10
comprises a motor
14
which is arranged at one end of a body
12
of the electric actuator
10
, and a feed screw
18
which is coupled to a rotary shaft of the motor
14
and which is inserted into a hole
16
of the body
12
. A feed nut
20
is meshed with the feed screw
18
. The feed nut
20
is secured to one end of a cylindrical member
22
. The other end of the cylindrical member
22
is secured to a movable member
24
. A guide block
26
is secured to the movable member
24
. The guide block
26
is slidably engaged with a guide rail
28
.
When the motor
14
is energized in the electric actuator
10
, then the feed screw
18
is rotated to move the feed nut
20
in the axial direction of the feed screw
18
, and the movable member
24
, which is secured to the cylindrical member
22
, is linearly displaced. In the electric actuator
10
, the guide block
26
, which is coupled to the movable member
24
, slides along the guide rail
28
which is provided at the outside of the body
12
. Thus, the rotation-preventive function is effected to prevent the movable member
24
from rotation together with the feed screw
18
.
An electric actuator
30
concerning another conventional technique is shown in FIG.
26
. The electric actuator
30
comprises a movable member
32
which is secured to one end of a cylindrical member
22
. One end of a guide shaft
34
is secured to the movable member
32
in parallel to the cylindrical member
22
. On the other hand, an end plate
36
is secured to one end of a body
12
. A bush
38
for inserting the guide shaft
34
therethrough is provided in the end plate
36
.
In the electric actuator
30
, the guide shaft
34
is guided by the bush
38
. Accordingly, the rotation-preventive function is effected to prevent the movable member
32
from rotation together with the feed screw
18
.
However, the electric actuators
10
,
30
involve the following drawback. That is, the rotation-preventive mechanism for preventing the movable member
24
,
32
from rotation is provided at the outside of the body
12
. Therefore, the entire shape of the electric actuator
10
,
30
becomes large.
In order to realize a compact size, it is conceived that the rotation-preventive mechanism for preventing the movable member from rotation is provided at an inside portion of the body of the electric actuator. For example, as shown in
FIG. 27
, a ring-shaped guide member
42
is secured to one end of a cylindrical member
22
of an electric actuator
40
. A groove
44
is defined on the guide member
42
so that the groove
44
is parallel to the axis of the cylindrical member
22
. On the other hand, a rail section
48
, with which the groove
44
is slidably engaged, is formed on the wall of a hole
46
of the body
12
. When the groove
44
of the guide member
42
makes sliding movement along the rail section
48
, the rotation-preventive function is effected to prevent the cylindrical member
22
from rotation.
An electric actuator
50
concerning still another conventional technique is shown in FIG.
28
. In the electric actuator
50
, a guide member
54
, which is formed with a spline
52
, is secured to one end of a cylindrical member
22
. A spline groove
58
, with which the spline
52
is slidably engaged, is formed on the inner wall of a hole
56
defined in a body
12
. In the electric actuator
50
, the engagement between the spline
52
and the spline groove
58
effects the rotation-preventive function to prevent the cylindrical member
22
from rotation.
An electric actuator
60
concerning still another conventional technique is shown in FIG.
29
. The electric actuator
60
comprises a spline
64
which is formed over the entire outer circumference of a lengthy cylindrical member
62
. An end plate
66
is secured to an end of a body
12
. A spline groove
68
, with which the spline
64
is slidably engaged, is formed on the end plate
66
. In the electric actuator
60
, the engagement between the spline
64
and the spline groove
68
effects the rotation-preventive function to prevent the cylindrical member
62
from rotation.
However, the electric actuators
40
,
50
,
60
, each of which is provided with the rotation-preventive mechanism at the inside of the body
12
, require the exclusive part having the specified structure as the rotation-preventive mechanism to prevent the cylindrical member
22
,
62
from rotation, including, for example, the guide member
42
formed with the groove
44
, the guide member
54
with the spline
52
formed on the outer circumferential surface, and the cylindrical member
62
formed with the spline
64
. Therefore, a problem arises in that the production cost of the electric actuators
40
,
50
,
60
is expensive.
An object of the present invention is to provide a rotation-preventive device which makes it possible to conveniently and freely adjust the clearance in the circumferential direction between teeth of a spline shaft and an inner wall surface of a hole of a boss.
Another object of the present invention is to provide an electric actuator having a rotation-preventive function which makes it possible to reduce the production cost by using parts hitherto used generally so that any exclusive part is unnecessary.
SUMMARY OF THE INVENTION
According to the present invention, a first spline shaft member and a second spline shaft member, which are divided into two, are rotated and displaced in mutually opposite directions about a center of rotation of the axis. Thus, it is possible to freely adjust the clearance in the circumferential direction between an inner wall surface of a boss section a
Nagai Shigekazu
Shirai Yousuke
Herrmann Allan D.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
SMC Kabushiki Kaisha
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