JPS5872432A - Barrel segment of extruding machine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention generally relates to apparatus for extruding thermoplastic materials. In particular, the present invention relates to the barrel of a multi-screw extruder for vinyl chloride (PVC).

It is known that in order to economically extrude thermoplastic materials, the materials must be maintained in a plastic state within a relatively narrow temperature range. Within this temperature range, the material should be sufficiently fluid to flow through the extrusion die, but not near chemical decomposition temperatures that would cause defects in the structure or finish of the final product. For PvC, the allowed temperature range is 175
to 215°C. The material enters the extruder at room temperature, so
The importance of temperature control is typically localized in the portion of the extrusion barrel closest to the exit of the extruder. In this section, the combined action of convective heat released to the outside and self-generated heat generated from shearing of the material must be balanced by each of the eight cooling devices to achieve the desired temperature control.

In multi-intermeshing screw extruders, there are heat transfer complications within the vicinity of the screw hole intersections where the combination of large thermal mass and self-generated heat of the material makes temperature control more difficult. In the prior art, the barrel segments are shaped to follow the cross-sectional shape of the holes in the engaged screws and are surrounded by a jacket containing a heat exchange fluid outside the barrel body. This method eliminates the cooling effect at the interface. but on the other hand increases the production cost of the barrel segment.

It has also been shown in the prior art to retain a wear insert defining a screw bore within a housing and to have fluid bores configured to follow the contour of the insert.

Therefore, one object of the present invention is to provide a simplified barrel segment for a multi-intermeshing screw extruder equipped with an internal and external heat transfer device to obtain a heat transfer effect partially utilizing a heat exchange fluid. Another object of the present invention is to provide a barrel segment for a multi-intermeshing screw extruder with a cooling system with internal and external heat exchange fluids responsive to the actual barrel temperature.

Another object of the present invention is to provide a multi-intermeshing screw extruder equipped with a cooling device with internal and external heat exchange fluids and an external heating device, controlled according to the actual barrel temperature.

Other objects and advantages of the present invention will become apparent from the following description.

In accordance with the foregoing objects, there is provided a barrel segment for a multi-intermeshing screw extruder having at least one closed internal bore located within the barrel segment body near the intersection of the screw bores. The barrel body is surrounded by an outer tube through which a heat exchange fluid is directed.

Inlet and outlet passages are provided for connecting the fluid bore and the fluid introduction tube.

In the preferred embodiment, a twin screw barrel segment with two fluid holes is described. inside the fluid bore to ensure maximum contact of the heat exchange fluid with the inside of the fluid bore and to ensure passage of the force fluid from the inlet passage to the outlet passage disposed at one end of the barrel body. A fluid guiding device is fitted. The barrel segment also has a groove on its outer surface for receiving a fluid guide tube. A heating band surrounds the fluid guide tube, and a thermocouple senses the temperature of the barrel body within the vicinity of the fluid bore to control the flow rate of the heat exchange fluid and the operation of the heating band. Alternative fluid guiding devices are described for generating a dilute flow of fluid within the fluid bore.

To explain the invention, a twin screw extruder for the production of PVC pipes will be described in some detail. This extruder incorporating a preferred embodiment was manufactured by the Cincinnati Milacron Company, the assignee of the present invention.
Inc.).

Referring to FIG. 1, a twin screw extruder 1 includes a machine base 2 and an extruder drive train including a drive motor 14, a speed reducer 10, a screw drive force distribution gearbox 8, and a screw 6. The appearance is shown as follows. An extruded barrel 4, partially shown by breaking away the cover 12, is supported on the base 2 by supports 22 and 24. The raw material for PvC extrusion is supplied to the extruder through a hopper 15, and is passed through a hopper feed tube 16 to the extruder barrel 4.
sent to the entrance. Within the hopper feed tube 16, a material feed screw (not shown) is connected to a motor 20.
It is rotated via a drive device 1B driven by. The hopper and material feed drive mechanism are supported on the extruder screw drive frame extension 42 by supports 26.

The barrel segment 30 at the exit end of the extruder has a flange 40
It is attached to the barrel 4 by a flange 32 bolted to the barrel 4. Following this barrel segment is an extrusion die 50 that is attached to the die inlet adapter 36. This segment is supported on extruder base 2 and support 22 by support member 28 . Along the length of barrel segment 30, heating bands 38 and 3
9 are distributed. A thermocouple 34 is inserted into the barrel body downstream of its length and near its top.

The raw material fed through the feed tube 16 is guided over the length of the extruder barrel 4 by internal mating feed screws (not shown).

These screws also process the material inside the screw hole and act to convectively heat the material from the heat provided externally by heating bands such as bands 38 and 39, while at times shearing the material. promote self-heating of the material.

Referring now to FIG. 2, which is an end view of barrel segment 30 looking toward flange 32, internal tapered screw holes 104 and 106 are shown intersecting along line 62. . In this figure, plugs 100 and 1 for closing the internal heat exchange fluid holes 62 and 68 are shown.
02 is shown positioned on the intersecting line 62. line 62
passes through the intersection of screw holes 104 and 106 and passes through an imaginary longitudinal axis defined by the radial direction of the barrel body that bisects the interior of barrel body 60. Inlet passageways 74 and 76 to fluid holes 66 and 68 are shown in phantom in this figure. Also shown in phantom are outlet passages 70 and 72. Also shown in phantom is a thermocouple 34 set into the barrel body 60 for sensing the temperature within the interior bisected by the longitudinal plane.

Referring to FIG. 3, there is shown a partial longitudinal cross-sectional view of barrel segment 30 taken along section line 3--3 of FIG. It is shown. Die inlet adapter 36 to segment 30
Locating pins 92 are shown in phantom for positioning above.

Additionally, the barrel segment 300 has the groove 64 formed therein.
The cross section of heating bands 38 and 39 surrounding the section is shown in phantom.

Still referring to FIG. 3, a heat exchange fluid guiding tube 110 is shown in cross section walled within the groove 64 of the barrel segment 30. As can be seen from the partial surface cut-out, the groove 64 is continuous and helical on the outer part of the barrel body surrounded by the heating bands 38 and 39. Inside the barrel body 6o, the inner heat exchange fluid holes 6, 6 and 68 are shown. As can be seen with reference to FIG. 3, these holes have their longitudinal centerlines aligned with the longitudinal center of barrel segment 30 @44
It is located so that it intersects with the In this way, the hole 66
and 68 are positioned to match the taper of screw holes 104 and 106.

Supported within the bores 66 and 68 are open-ended fluid guiding tubes 86 and 88, which
They are supported by support rings 78 and 80, 82 and 84, respectively. These support rings 78 to 84 are connected to the interior of holes 66 and 68 and to fluid guiding tubes 86 and 88.
and are sealed.

Fluid entering inlet passages 74 and 76 is thus directed via tubes 86 and 88 to outlets 90 and 92;
From the outlet flows into outlet passages 70 and 72. This fluid guiding device directs the heat exchange fluid over a length K inside the fluid holes 66 and 68 to maximize heat exchange between the interior of the barrel body 60 and the heat exchange fluid.

Referring now to FIG. 4, a heat exchange fluid guide tube 110 is mounted within the groove 64 of the barrel body 60 to form an effective heat exchange interface between the tube 110 and the barrel body 60. There is. In particular, groove 64 is configured with a cutout 65 that acts to hold fluid guide tube 110 in place.

Further, referring to FIG. 4, the outer portion of the guide tube 110, shown in its normal state in phantom lines, has been modified to provide a uniform surface around which heating bands 38 and 39 are to be provided. There is. In this way, heating bands 38 and 3
Maximum heat exchange can be obtained between 9 and the barrel body 60,
Meanwhile, maximum exchange between the heat exchange fluid in the guide tube 110 and the barrel body 60 is also achieved.

1 and 6, it can be seen that the guide tube 110 is continuous from one end of the barrel segment 3Q to the other end.

Referring now to FIG. 5, an alternative fluid guiding device is shown in place within fluid bore 66. Similar to the fluid guide system described above, the heat exchange fluid is routed through the inlet passageway 76.
Entry into the fluid hole 66 is prevented by a support ring 124 that forms a seal between the open-ended tube 122 and the hole 66. The heat exchange fluid is then directed within fluid guide tube 122 to its end and enters hole 66 from that end. In this case, a ribbon 126 is wrapped around the outside of the guide tube 122 and
2 and the hole 66 such that the heat exchange fluid flows through the hole 66.
A thin flow is generated as it progresses through the length of the outlet passage 70. In this way, by generating a thin flow of the heat exchange fluid inside the fluid holes 66,
Maximizes the effective heat exchange between the interior of the barrel body 60 and the heat exchange fluid.

In FIG. 6, the barrel segment 30 is shown with a heat exchange fluid recirculation system and a heating band control system.

Heat exchange fluid is transferred by pump 150 to heat exchanger 152 via outlet side 172 and pressure relief valve 148 and to control valve 1
44 to the supply piping 140. From the supply pipe 140, the cooled heat exchange fluid is transferred to the connecting tube 11.
0 and the inlet passages 74 and 76 of the fluid holes 66 and 68. The heat exchange fluid is returned to return piping 142 via outlet passages 70 and 72 and guide tube 110. The heat-exchanged fluid from the return pipe 142 is guided to the return pipe 170 of the pump 150 via the heat exchanger 152.

The fluid recirculation system is controlled via thermocouple 34 and control circuit 156. As the heat exchange fluid cools within barrel body 60, thermocouple 34 generates a sensing signal proportional to the temperature that is sensed by control circuit 156 to output power distribution 1.
A control signal is generated to IJ 158 to close control valve 144 and open pressure relief valve 148. In this condition, heat exchange fluid is circulated by pump 150 through pressure relief valve 148 to heat exchanger 152 and return piping 170.
and returns to pump 150 via. When thermocouple 34 detects an increase in temperature within barrel body 60, the sensed signal on line 154 causes control circuit 156 to again generate a control signal on line 158 to open control valve 144, causing the control valve to open. By reducing the pressure in line 172 and thus closing valve 148, heat exchange fluid is again circulated through tube 110 and fluid holes 66 and 68.

At the same time, the control circuit 156 connects the wiring 134 with the thermocouple 34.
Heating bands 38 and 39 can be activated or deactivated in response to sensing signals generated by the heating bands 38 and 39.

Thus, when the sensing signal on line 154 indicates that the temperature within barrel body 60 has fallen below a critical temperature, control circuit 156 generates a control signal on line 162 to activate heating bands 38 and 39. . However, when a sensing signal on wire 154 from thermocouple 34 indicates that the temperature within barrel body 60 has exceeded a preset limit, control circuit 156 generates a control signal to cause heating bands 38 and 39 to deactivate, i.e., release.

Referring again to FIG. 2, those skilled in the art will appreciate that the large mass of material in the immediate vicinity of the intersection of screw holes 104 and 106 also constitutes a large thermal mass.

As a result, if the thermocouple 34 determines that the temperature inside the barrel has exceeded the upper limit, relying on external cooling only through the heat exchange fluid guide tube 110 will cause the temperature inside the barrel to exceed the upper limit. is insufficient to cause a rapid decline in Therefore, heat exchange fluid must be supplied to both guide tube 110 and fluid holes 66 and 68 to prevent overheating of the material along the mating plane of screw holes 104 and 106.

The present invention will now be described in some detail by means of preferred embodiments shown in the accompanying drawings, and the preferred embodiments will now be described in some detail.
However, there is no intent to limit the invention to such details. On the contrary, the intention is to cover all modifications, changes and equivalents included within the spirit and scope of the claims.

In particular, it should be noted that the barrel segment containing the internal/external heat exchange device described above is also suitable for use in parts of the extruder barrel other than the outlet section. Additionally, although the preferred embodiment is directed to the use of heat exchange fluids for cooling, the combination of guide tubes and fluid holes facilitates alternative heating and cooling for most effective material temperature control. Can be adapted to Additionally, it will be appreciated that multiple fluid holes may be provided within the barrel if the capacity within the barrel permits.

[Brief explanation of the drawing]

FIG. 1 is a side view of a twin screw extruder incorporating a barrel segment according to the invention; FIG. 2 is an end view of the extruder barrel segment showing the relative position of the screw holes and internal fluid holes; FIG. 2nd diagram line 3
Figure 4 is a detailed view of the heat exchange fluid guide tubes and grooves of the barrel segment shown in Figure 3; Figure 5 is a fluid guide for the internal fluid holes; A representative embodiment of the apparatus is shown; FIG. 6 is a schematic diagram of a recirculation apparatus for thermal exchange fluid and one control apparatus for the barrel segment. In the figure, 1... Extruder 4... Barrel 30... Barrel segment 34... Thermocouple 38
．． 39...Heating hand 6o...Barrel body 64.
...Grooves 66, 68...Fluid holes 74.
76... Passage 86, 88... Tube 90.
92... Discharge port 100, 102... Plug 110.
...Tube 144...Control valve 14B...Pressure relief valve 150...Pump 152...Heat exchanger 156...Control circuit patent applicant, Cincinnati Milacron, Inc.

Claims (1)

[Scope of Claims] 1) In a barrel segment of a multi-intermeshing screw extruder, (α) an elongated cylindrical barrel body portion through which at least two intersecting screw passages are bored; (J5) a guide tube for the heat exchange fluid attached to the outer surface of the barrel body; (C) a longitudinal plane defined by a radius of the barrel body passing through the intersection of the screw passages; a barrel interior having at least one closed heat exchange fluid hole and having an inlet passageway and an outlet passageway connecting said fluid hole to a fluid guiding tube; Barrel segment for multi-screw extruder. 2. Barrel segment for a multi-screw extruder, characterized in that the segment according to claim 1 comprises a number of barrel interiors equal to the number of longitudinal planes. 3) The segment according to claim 2, wherein the screw passages are tapered and located in intersecting longitudinal planes, and further the longitudinal centerline of the fluid hole lies in said longitudinal plane. A barrel segment for a multi-screw extruder, characterized in that the fluid hole is located within and intersects a longitudinal centerline of the barrel segment. 4) A segment according to claim 1, characterized in that: (a) a temperature sensing device inserted therein for sensing the temperature inside the barrel; and (b) connected in response to said temperature sensing device. Barrel segment 0 for a multi-screw extruder, further comprising a tube and a fluid control device for blocking the flow of fluid through the internal fluid bore.