Expansible chamber devices – With flexible transmission element secured to working member
Reexamination Certificate
1999-08-27
2001-08-14
Ryznic, John E. (Department: 3745)
Expansible chamber devices
With flexible transmission element secured to working member
Reexamination Certificate
active
06272972
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, in general, to rodless cylinder actuators for feeding workpieces in machining tools and, more particularly, to a rodless cylinder actuator having a piston slidably positioned within the cylinder, the piston being pnewmatically hydraulically reciprocable within the cylinder, thus reciprocating a slide table installed outside the cylinder housing.
2. Description of the Prior Art
A conventional rodless cylinder actuator for feeding workpieces in machining tools may be referred to Japanese Patent Laid-open Publication No. Sho. 62-266,206 published on Nov. 19, 1987.
FIGS. 1
to
4
show the above Japanese rodless cylinder actuator. As shown in the drawings, the actuator
1
has a slit
3
that longitudinally extends from one end to the other end on its top surface of the cylinder
1
. A longitudinal bore
2
is formed within the cylinder
1
and communicates with the outside of the cylinder
1
through the slit
3
. A piston
4
, consisting two piston bodies
5
, is slidably received within the bore
2
. Each of the two piston bodies
5
has a circumferential groove
6
on its external surface, with a sealing member
7
being set in the groove
6
to be brought into close contact with the interior surface of the bore
2
.
A longitudinal groove
26
is formed along each top edge of the slit
3
. The width of each groove
26
is narrower than that of the slit
3
. A longitudinal subsidiary sealing strip
27
is set into the grooves
26
at both side edges thereof, thus sealing the top portion of the slit
3
. A movable block
11
is slidably received within the bore
2
. The movable block
11
is integrated with a connection block
14
at its top section, with a guide groove
28
being formed on the top surface of the connection block
14
. A guide surface
29
is formed on the bottom of the guide groove
28
. The above guide surface
29
is brought into contact with the lower surface of the subsidiary sealing strip
27
, thus allowing the strip
27
to escape from the grooves
26
. On the other hand, two pressure plates
30
are provided at both sides of the connection body
14
. The above pressure plates
30
come into contact with the top surface of the subsidiary sealing strip
27
, thus pressing down the strip
27
into the grooves
26
. A sealing strip
19
is positioned within the lower portion of the slit
3
while being set in a groove
16
formed in the lower portion of the slit
3
. A rail
20
is longitudinally formed along the central axis of the top surface of the sealing strip
19
. The above sealing strip
19
is also fitted into the lower portion of the slit
3
at the rail
20
.
A cap
31
, having an air hole
32
, is tightened to each end of the cylinder
1
. An air pipe
33
extends from the inside end of each cap
31
while communicating with the air hole
31
. The above air pipe
33
is designed to be selectively inserted into a relief hole
34
formed on each piston body
5
. Each end of the two sealing strips
19
and
27
is mounted to the junction between the cap
31
and a mount plate
36
using a pin
37
. In such a case, the mount plate
36
is provided on the top surface of the subsidiary sealing strip
27
. A slide table
38
, carrying a workpiece thereon, is seated on and mounted to the connection body
14
using a plurality of pins
39
.
The above rodless cylinder actuator
1
is operated as follows. When pressurized air is applied to the rear chamber
40
of the piston
4
, with the front chamber
42
of the piston
4
discharging air therefrom, a pressure difference is generated between the two chambers
40
and
42
. The piston
4
is thus moved forwardly within the cylinder
1
. When the piston
4
moves forwardly as described above, two elastic protrusions
21
of the sealing strip
19
are elastically deformed to be removed from two protrusion rails
17
of the cylinder
1
, thus allowing the sealing strip
19
to be removed from the groove
16
. The strip
19
is inserted into a passage
24
at its front portion.
As both the piston
4
and the movable body
11
further move forwardly within the bore
2
of the cylinder
1
, the rear piston body
5
pushes the sealing strip
19
into the groove
16
, thus allowing the protrusions
21
to engage with the protrusion rails
17
while elastically deforming the protrusions
21
of the sealing strip
19
.
On the other hand, when pressurized air is applied to the front chamber
42
of the piston
4
, with the rear chamber
40
discharging air, a pressure difference is generated between the two chambers
40
and
42
. Both the piston
4
and the movable body
11
are thus moved backwardly within the cylinder
1
. In such a case, the sealing strip
19
is removed from the groove
16
and is inserted into the passage
24
at its rear end. Therefore, it is possible for both the connection body
14
and the slide table
38
to be reciprocable along the slit
3
. When the piston
4
and the movable body
11
are moved within the cylinder
1
, the sealing strip
19
partially closes the strip
3
at a position free from the piston bodies
5
. That is, at the position free from the piston bodies
5
, the elastic protrusions
21
of the strip
19
engage with the protrusion rails
17
of the cylinder
1
, thus closing the strip
3
at that position. Therefore, even when the internal pressure of the front or rear chamber
42
or
40
is reduced to a low pressure, the sealing strip
19
is free from sagging into the chamber
42
or
40
, but completely closes and seals the slit
3
at the position around the chamber
42
or
40
. Therefore, the sealing strip
19
almost completely prevents air leakage through the slit
3
.
During a reciprocating motion of the connection body
14
along the slit
3
, the leading portion of the subsidiary sealing strip
27
is partially raised up at its lower surface by the leading end of the guide surface
29
of the connection body
14
, thus escaping from the grooves
26
of the slit
3
prior to being laid on the guide surface
29
of the body
14
. On the other hand, the trailed portion of the sealing strip
27
is pressed down at its upper surface by a trailed pressure plate
30
, thus being brought into engagement with the grooves
26
of the strip
3
. Therefore, the slit
3
is always sealed by the subsidiary sealing strip
27
at the front and rear of the reciprocating connection body
14
. It is thus possible to almost completely prevent an introduction of foreign substances, such as dust, into the cylinder
1
through the slit
3
during a reciprocating motion of the connection body
13
along the slit
3
.
In addition, when the sealing strip
19
engages with the groove
16
of the slit
3
, the lower surface of the sealing strip
19
may be somewhat protruded into the bore
2
as shown in
FIG. 4
due to a designing tolerance of the strip
19
and the groove
16
. In such a case, the chambers
40
and
42
may fail to be completely sealed, thus causing an air leakage between them. However, such an air leakage between the chambers
40
and
42
is completely prevented by a pressure contact between the sealing member
7
of the piston
4
and a thin plate
22
of the sealing strip
19
. The sealing member
7
of the piston
4
is designed to be elastically extendible or contractible, while the thin plate
22
totally covers the lower surface of the sealing strip
19
while extending outside both side edges of the strip
19
. Therefore, when the lower surface of the sealing strip
19
is protruded into the bore
2
as described above, the elastic sealing member
7
compresses both side edges of the thin plate
22
, thus appropriately bending and deforming both side edges of the plate
22
. The sealing member
7
is thus brought into close contact with both the inner surface of the bore
2
and the thin plate
22
without leaving a gap between them. Therefore, the actuator is free from air leakage between the chambers
40
and
42
.
However, the above rodless cylinder actuator has the fo
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