Modular extruder barrel construction

Details Modular extruder barrel construction Modular extruder barrel construction

1985-07-03

1987-02-03

Czaja, Donald

Plastic article or earthenware shaping or treating: apparatus

With apparatus assembly or dismantling means or with idle part

For extrusion or injection type shaping means

366 79, 425205, 425208, B29B 713

Patent

active

046406727

DESCRIPTION:

BRIEF SUMMARY
This invention is concerned with an extruder barrel construction for an extruder, especially an extruder suitable for homogenising and extruding plastics or rubber materials.


TECHNICAL FIELD

In the field of extruders it is known to enhance the homogenisation of materials by providing in the extrusion chamber a screw having interrupted helical flights and obstacles projecting from the sides of the chamber arranged to cooperate with the flights of the screw, namely so-called "pin-barrel" extruders.


BACKGROUND ART

U.K. Pat. No. 1440682 for example, discloses one such single screw extruder for mixing and homogenising viscous materials wherein the extrusion zone of the extruder comprises a screw having two discontinuous flights enclosed in an extruder barrel containing a series of obstacles projecting from the sides thereof towards the root of the screw. The interruption of the flights thus provides channels at the root of the screw into which the series of obstacles project. Each series of obstacles comprises eight obstacles distributed around the circumference of the barrel.
As a result of extensive wear of the internal surface of the extruder barrel caused by abrasion and wear as the flights convey the material to be homogenised through the extrusion chamber, it is common practice to provide a very hard and wear-resistant lining. Such linings may be of bi-metallic material and are very brittle. They are also very expensive to produce. For those extruders heretoforeknown comprising obstacles projecting into the extrusion chamber, it is necessary to drill holes through both the sides of the barrel and the hard lining material so that the obstacles may be inserted into the holes thus provided and secured therein by fastening means. Drilling of holes through the lining is difficult if damage to the lining is to be avoided; damage to the lining can lead to unsatisfactory performance and, if severe, may necessitate provision of a new lining.
As a result of breakage of one or more of the obstacles, thus requiring replacement thereof, or wear or damage to the lining material, it is commonly necessary to replace the lining material and/or obstacles. Such a process is time consuming and laborious, involving removing the lining from the barrel (also, if any of the obstacles have been bent, removing and replacing these may be a problem), providing a new lining in replacement and furthermore drilling holes in the lining to accommodate the obstacles. In a large bore extruder this may prove to be very expensive both in capital outlay and lost production time.
It is an object of this invention to provide an improved extruder which may be assembled and dismantled easily for replacement of inner parts.


DISCLOSURE OF THE INVENTION

The invention provides in one of its aspects an extruder comprising a plurality of barrel modules arranged in alignment, at least two adjacent barrel modules having a plate secured therebetween, the plate having an opening passing therethrough and comprising projections extending into said opening, the opening of the plate and internal surfaces of the barrel modules forming a substantially continuous passageway which provides an extrusion chamber of a barrel of the extruder, and a screw in the extrusion chamber having one or more helical flights projecting from a root portion of the screw, the flights being discontinuous and arranged to leave annular spaces between adjacent flight sections into which the projections extend towards the root of the screw.
An extruder according to the invention may be of any convenient size with respect to the diameter of the extrusion chamber and the length thereof, however it is envisaged that the construction according to the invention will particularly be used in large extruders where there is a high cost in terms of time and materials in replacing the lining material. The invention is particularly suitable for extruders having an extrusion chamber greater than twenty centimeters in diameter.
For ease of construction of an extruder barrel, in an extruder ac

REFERENCES:
patent: 4408887 (1983-10-01), Yamaoka

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