Machine element or mechanism – Gearing – Plural power paths to and/or from gearing
Reexamination Certificate
1997-11-07
2001-10-09
Bucci, David A. (Department: 3682)
Machine element or mechanism
Gearing
Plural power paths to and/or from gearing
C074S395000, C074S410000, C074S42100R, C198S625000, C198S663000, C366S100000
Reexamination Certificate
active
06298751
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a drive transmission apparatus for a twin-screw extruder. In particular, it relates to an improvement that facilitates the adjustment of the gear power-transmission apparatus that transfers rotational power from a prime mover device to screws.
A twin-screw extruder is provided with two screws that are disposed parallel in close proximity. A drive transmission apparatus transfers a rotational driving force from a prime mover to the screws of the twin-screw extruder to cause the screws to rotate. The narrow spacing between the screws sets a limit on a diameter of a gear that is linked to the screws for transferring the rotation thereto. It is not possible to increase the diameter of the gear attached to at least one of the screws.
Since a drive transmission apparatus used in a twin-screw extruder transmits a high level of torque generated by a high-power input but a low rotational speed, the prior-art drive transmission apparatus makes use of gear trains such as those shown in
FIGS. 6
to
10
.
An example of such a prior-art drive transmission apparatus is shown in
FIG. 6. A
first screw
11
and a second screw
12
provided for the twin-screw extruder are disposed in parallel. A prime mover such as a motor
30
(which also includes reduction gears) is connected to an input shaft
31
. A coupling portion
32
is provided on the end of this input shaft
31
. A rear-end portion of a transmission shaft
33
is linked to a first linkage portion
32
a
of the coupling portion
32
so that the transmission shaft
33
is connected to the input shaft
31
via the coupling portion
32
. A front-end portion of the transmission shaft
33
is connected to the first screw
11
. A transmission shaft
41
is connected to the second screw
12
. To sustain a thrust load from each of the first screw
11
and the second screw
12
, thrust bearings
43
and
44
are provided on the ends of the transmission shafts
33
and
41
, respectively.
A spur gear
34
is attached to the transmission shaft
33
on the side thereof opposite to the side that is linked to the first screw
11
, with the configuration being such that the spur gear
34
is rotated in synchronization and together with the transmission shaft
33
. An end portion of the spur gear
34
facing toward the motor
30
engages with a second linkage portion
32
b
formed in the coupling portion
32
.
A side view of the drive transmission apparatus of
FIG. 6
is shown in
FIG. 7 and a
section taken along the line VII—VII of
FIG. 7
is shown in FIG.
8
. As shown in
FIG. 7
, two idler spur gears
35
and
36
are provided at one end each of parallel idler shafts
37
and
38
, respectively, in engagement with the spur gear
34
. Two idler helical gears
39
and
40
are attached to the other ends of the idler shafts
37
and
38
, respectively. Each of these idler helical gears
39
and
40
engage with a helical gear
42
that is attached to the transmission shaft
41
of the second screw
12
. Therefore, the configuration is such that the rotation of the spur gear
34
, which is connected to the input shaft
31
by the coupling portion
32
, is transmitted to the transmission shaft
41
of the second screw
12
through the two parallel gear trains (in other words, the gear train consisting of the idler spur gear
35
, the idler shaft
37
, the idler helical gear
39
, and the helical gear
42
and the gear train consisting of the idler spur gear
36
, the idler shaft
38
, the idler helical gear
40
, and the helical gear
42
), in such a manner that the second screw
12
rotates.
The teeth of the spur gear
34
and the idler spur gears
35
and
36
extend parallel to the transmission shaft
33
and the idler shafts
37
and
38
. The helical gear
42
is configured in such a manner that it has teeth that are inclined in the same direction as those of the second screw
12
. This is to ensure that part of the thrust loading that occurs when the second screw
12
is rotationally driven is borne by the idler helical gears
39
and
40
via the helical gear
42
.
The first screw
11
and second screw
12
must be made to rotate in the same direction, at the same rotational speed. This is determined by factors such as the number of teeth of each of the gears that form the gear trains, the module of each gears, and intershaft distance.
It is necessary to adjust a phase of meshing of the gears and the tooth bearing thereof, to ensure that the two parallel gear trains (consisting of the idler spur gears
35
and
36
, the idler helical gears
39
and
40
, and the idler shafts
37
and
38
) engage uniformly with the spur gear
34
and the helical gear
42
, so that the rotational driving force is transferred uniformly to the first screw
11
and the second screw
12
.
In this prior-art drive transmission apparatus, the four gears consisting of the idler spur gears
35
and
36
and the idler helical gears
39
and
40
engage together to form a gear transfer mechanism. Therefore, to adjust the meshing phase or tooth bearing of the gears, at least one of the four gears is adjusted as described below.
The configuration is such that one of the gears, such as the idler spur gear
35
, can be released so that it no longer engages with the spur gear
34
. The freeing of this idler spur gear
35
makes it possible to make the phase adjustment, etc. The idler spur gear
35
is constructed of two components, a ring-shaped gear portion
35
a
and a boss portion
57
, as shown in FIG.
9
. The ring-shaped gear portion
35
a
has a hole
50
. A hub
51
of the boss portion
57
is designed to fit tightly into the hole
50
. An annular oil groove
52
is provided in an inner peripheral surface of the ring-shaped gear portion
35
a,
extending in the circumferential direction thereof. This annular oil groove
52
is designed to form a sealed annular passageway together with the outer peripheral surface of the hub
51
.
An oil passageway
53
that communicates with the annular oil groove
52
is formed in either the ring-shaped gear portion
35
a
or the boss portion
57
. High-pressurized oil from a hydraulic power source (not shown in the figures) is supplied from this oil passageway
53
to enable the introduction of high-pressure oil into the annular oil groove
52
. This high-pressure oil causes the inner circumference of the ring-shaped gear portion
35
a
to expand. As a result, a meshing phase adjustment becomes possible because the ring-shaped gear portion
35
a
can be made to rotate alone about the hub
51
of the boss portion
57
. When the phase adjustment is completed, reamer bolts or knock pins
54
can be used to fix the ring-shaped gear portion
35
a
firmly with respect to the boss portion
57
.
Another method that can be used for a meshing phase adjustment is shown in
FIG. 10. A
thin cylindrical portion
35
c
is formed integrally with the ring-shaped gear portion
35
a
in such a manner that it protrudes from the right-hand side thereof as seen in the figures. The boss portion
57
fits into a hole
35
b
of this thin cylindrical portion
35
c
in a manner as a clearance fit. An annular oil groove
52
is formed on an inner surface of the ring-shaped gear portion
35
a,
extending in the circumferential direction thereof. A gap is formed between the ring-shaped gear portion
35
a
and the boss portion
57
by forcing high-pressurized oil from an oil passageway
53
into the annular oil groove
52
. Since this permits the ring-shaped gear portion
35
a
to rotate alone, it enables phase adjustment and the adjustment of tooth bearing. After the adjustment is completed, a tightening means, which consists of members such as two tightening rings
62
and
63
that fit over the thin cylindrical portion
35
c
with a tapered ring
60
therebetween, is tightened by using bolts
61
. This tightening means ensures that the thin cylindrical portion
35
c
is firmly connected to the boss portion
57
by frictional force.
With the prior-art apparatus shown in
FIG
Endoh Kuniaki
Hatamoto Mitsuoki
Ide Akinori
Bucci David A.
Joyce William C
Pillsbury WInthrop Intellectual Property Group
Toshiba Kikai Kabushiki Kaisha
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