Machine element or mechanism – Mechanical movements – Reciprocating or oscillating to or from alternating rotary
Reexamination Certificate
1998-10-13
2001-12-11
Luong, Vinh T. (Department: 3682)
Machine element or mechanism
Mechanical movements
Reciprocating or oscillating to or from alternating rotary
C074S089330
Reexamination Certificate
active
06327924
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an actuator for converting rotary motion of a feed screw into rectilinear motion by using a feed nut to allow a displacement member to perform rectilinear motion.
2. Description of the Related Art
An actuator, which is based on the use of a feed screw, has been hitherto used as a driving source for transporting a workpiece or the like. For example, as shown in
FIG. 8
, such an actuator
10
comprises a ball screw
16
with its one end which is connected to a rotary shaft
14
of a motor
12
. The other end of the ball screw
16
is rotatably supported by a shaft support member
18
. A feed nut
20
meshes with the ball screw
16
. The feed nut
20
is surrounded by a displacement member
22
. The displacement member
22
is formed with an attachment section
24
which protrudes at an upper portion of the displacement member
22
and which extends along its displacement direction. The attachment section
24
protrudes upwardly through a slit
28
which is formed at an upper portion of a frame
26
of the actuator
10
.
When the motor
12
is operated, the rotary motion of the ball screw
16
is converted into rectilinear motion by the aid of the feed nut
20
. The rectilinear motion is transmitted to the displacement member
22
. Thus, the displacement member
22
makes displacement along the longitudinal direction of the actuator
10
.
However, if the conventional actuator
10
as described above involves any axial deviation between the frame
26
and the ball screw
16
, then the sliding resistance with respect to the inner wall of the frame
26
is increased when the displacement member
22
makes displacement, and the displacement action of the displacement member
22
is obstructed when the displacement member
22
makes displacement in the frame
26
.
For this reason, when the ball screw
16
is assembled to the frame
26
, then it is necessary that the both ends of the ball screw
16
are subjected to centering adjustment with respect to the rotary shaft
14
and the shaft support member
18
, and it is also necessary that the ball screw
16
is subjected to centering adjustment with respect to the feed nut
20
. Therefore, a problem arises in that the assembling operation is complicated.
Further, if the central portion of the ball screw
16
is warped, for example, when the actuator
10
has a lengthy size, or when a load of a workpiece or the like is exerted on the displacement member
22
, then the sliding resistance between the displacement member
22
and the frame
26
is increased in the same manner as described above, and the displacement member
22
occasionally fails to make displacement. For this reason, it has been impossible to allow the actuator
10
to have a fairly long size, and it has been also necessary to restrict the load of the workpiece.
SUMMARY OF THE INVENTION
A general object of the present invention is to provide an actuator which is free from any fear of obstructing the displacement action of a displacement member even when the actuator involves axial deviation between a feed screw and a frame.
A principal object of the present invention is to provide an actuator which prevents the displacement action of a displacement member from being affected by positional deviation of a feed screw and warpage of the feed screw by absorbing axial eccentricity of the feed screw by using an axial eccentricity-absorbing mechanism which is displaceable in a direction perpendicular to a direction of displacement of the displacement member, making it possible to permit the positional deviation and the warpage of the feed screw.
Another object of the present invention is to provide an actuator comprising an axial eccentricity-absorbing mechanism which is composed of a first guide mechanism designed to be linearly displaceable in a direction perpendicular to a direction of displacement of a displacement member and a second guide mechanism designed to be linearly displaceable in a direction perpendicular to the direction of displacement of the displacement member but in the direction different from the direction of displacement of the first guide mechanism, thereby making it possible to absorb axial eccentricity of a feed screw by using the relatively simple mechanism.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.
REFERENCES:
patent: 3945481 (1976-03-01), Lindberg
patent: 4232562 (1980-11-01), Perkins
patent: 4276003 (1981-06-01), Perkins et al.
patent: 5170675 (1992-12-01), Kawashima
patent: 60196461 (1985-04-01), None
patent: 03277820 (1991-09-01), None
patent: 4-140546-A (1992-05-01), None
patent: 7-315773 (1995-12-01), None
patent: 8-42657 (1996-02-01), None
Miyahara Masaki
Nagai Shigekazu
Joyce William C
Luong Vinh T.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
SMC Kabushiki Kaisha
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