Plastic article or earthenware shaping or treating: apparatus – With apparatus assembly or dismantling means or with idle part – Means permitting removal or substitution of elements during...
Reissue Patent
2000-05-26
2002-04-30
Mackey, James P. (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
With apparatus assembly or dismantling means or with idle part
Means permitting removal or substitution of elements during...
C210S236000, C210S447000, C210S489000, C210S498000, C425S197000, C425S199000
Reissue Patent
active
RE037681
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to filter members for use in resin extruders (inclusive of kneaders and molding machines) and to screen changers for use in such resin extruders.
2. Discussion of the Background
A filter member for filtering off impurities contained in a resin material is incorporated in the resin passage of resin extruders (inclusive of kneaders and molding machines) adapted to extrude resin materials such as polyolefins and compounds.
A flat-type filter member is known comprising a screen for filtering off impurities and a breaker plate attached to the rear side of the screen for backing up the screen, as disclosed in Japanese Examined Patent Publication No. SHO 59-27698.
Conventional breaker plates have a multiplicity of circular resin passageways, and the ratio of opening thereof is set to about 50% to maintain a strength sufficient to back-up the screen.
For this reason, the filter member has a decreased effective filtering area within a limited area and hence tends to have a larger diameter.
It is a general practice to provide a screen between the resin melt outlet of an extruder or the like and the inlet of a mold (hereby meant to include a granulating die) to filter off impurities contained in resin melt, and to provide a device for changing the used screen soiled by much accumulation of the impurities and the like on the mesh of the screen for a new screen without the need of stopping the operation of the extruder or the like.
Conventionally known ones of this type of screen changer are described in Japanese Unexamined Patent Publication No. SHO 47-39160 and Japanese Examined Patent Publication No. SHO 59-27698.
FIG. 21
shows a screen changer
60
as described in Japanese Unexamined Patent Publication No. SHO 47-39160 which includes a slide bar
65
slidably interposed between resin melt outlet
62
of an extruder
61
and inlet
64
of a molding die
63
, breaker plates
67
A and
67
B respectively provided in a pair of resin passageways
66
A and
66
B extending as intersecting the moving direction of the slide bar
65
, and screens
68
A and
68
B inserted through the breaker plates, each of the screens comprising seven bottomed cylindrical screens.
In changing the screen
68
A or
68
B for a new one by the screen changer
60
, the slide bar
65
is made to slide so as to expose the screen
68
A from between the resin melt outlet
62
of the extruder
61
and the inlet
64
of the molding die
63
and to move the other screen
68
B to a position between the resin melt outlet
62
of the extruder
61
and the inlet
64
of the molding die
63
, and in this condition the screen
68
A is changed for a new one.
FIG. 22
shows a screen changer
70
as described in Japanese Examined Patent Publication No. SHO 59-27698 which includes a body
72
having two branched resin passages
71
A and
71
B and through-holes
72
A and
72
B extending as orthogonally crossing the resin passages
71
A and
71
B, respectively, slide bars
73
A and
73
B slidably installed in the through-holes
72
A and
72
B, respectively, breaker plates
75
A and
75
B fitted in resin passage holes
74
A and
74
B defined in the bars
73
A and
73
B, respectively, and screens
76
A and
76
B.
In changing the screens
76
A and
76
B for new ones by the screen changer
70
, the slide bar
73
A is made to slide so as to close the resin passage
71
A and expose the screen
76
A. After changing the screen
76
A for a new one while allowing resin to pass through the other screen
76
B, the slide bar
73
A is made to slide back so as to open the resin passage
71
A. Subsequently the other slide bar
73
B is made to slide for the screen
76
B to be changed for a new one.
With the former conventional changer
60
, though the resin filtering area can be increased by increasing the number of bottomed cylindrical screens
68
A and
68
B, the flow of the resin melt is interrupted during the changing operation and, in addition, the screens has to be changed together with the breaker plate
67
A or
67
B because the number of the screens is large. Furthermore, the breaker plates
67
A and
67
B, if in a large plant are heavy and hot, resulting in troublesome changing operations and in difficulty in cleaning.
On the other hand, the latter conventional changer
70
has advantages that the flow of resin is never interrupted in changing the screens
76
A and
76
B because the resin passage is branched into two and that the changer facilitates the changing operations. Typically, the slide bars
73
A and
73
B are shaped like logs, and the breaker plates
75
A and
75
B are shaped circular for the ease of fabrication. With such circular breaker plates, if the filtering area is desired to be enlarged, the slide bars must be also enlarged in diameter, resulting in the body enlarged, hence, in the overall device enlarged. This raises critical problems in terms of space and cost.
SUMMARY OF THE INVENTION
It is, therefore, a first object of the present invention to provide a filter member having an increased effective filtering area in a limited area and hence allowing for minimization of the size thereof by forming slit-like resin passageways in a breaker plate so as to ensure an increased ratio of opening (70% to 80%) without any deterioration in the back-up capability.
It is a second object of the present invention to provide a screen changer for use in resin molding machines which permits easy screen changing operations without interrupting the flow of resin melt, facilitates cleaning operations, and provides an increased resin filtering area.
To attain the above first object, the present invention provides the following technical means in a filter member comprising in combination a screen for filtering off impurities contained in a resin material flowing in an extruder and a breaker plate having a multiplicity of resin passageways and attached to the rear side of the screen for backing up the screen.
Specifically, the present invention is characterized in that the resin passageways of the breaker plate are configured into elongated slits extending in a direction intersecting the flow direction of resin.
It is desired that the breaker plate comprise a first plate on the upstream side thereof and a second plate on the downstream side thereof which are mated to each other, the slits of one of the first and second plates being larger in width than those of the other plate and extending as intersecting those of the other plate.
Alternatively, it is desired that the breaker plate comprise a first plate on the upstream side thereof and a second plate on the downstream side thereof which are mated to each other, the resin passageways of the first plate being configured into elongated slits, and those of the second plate being configured into circular holes.
Further, the face of the breaker plate defining the resin passageways may be configured circular or rectangular, and it is desired that the screen and the breaker plate respectively comprise curved surfaces having a single curvature which protrude in the extrusion direction or the direction opposite thereto.
With the filter member according to the present invention, a resin material extruded from an extruder is filtered for its impurities by the screen of the filter member in the course of its flowing in the direction indicated by the arrow in FIG.
1
(A).
Since the resin passageways of the breaker plate in the filter member are configured into elongated slits extending as intersecting the direction of the arrow, the back-up capability of the breaker plate can be sufficiently ensured even when the ratio of opening of the slits is increased relative to that of circular holes.
To attain the foregoing second object, the present invention provides the following technical means.
Specifically, the present invention provides a screen changer for use in a resin molding machine which is adapted to change a screen disposed at a resin melt outlet of an extruder or the like to filter off impurities contained in a resin m
Fukumizu Shin'ichi
Ikeda Osamu
Nagami Nobuki
Nakata Yoshiaki
Yamasaki Nobuhiro
Kabushiki Kaisha Kobe Seiko Sho
Mackey James P.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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