Each screw shaft of a twin screw extruder with power branching gearing is driven by a gear train comprising a driven pinion, a first pair of intermediate gears meshing with the driven pinion from opposite sides, a second pair of intermediate gears each meshed with a respective one of the first pair of intermediate gears and a drive pinion meshed on its opposite sides with the second pair of intermediate gears and coupled to a power shaft. The first and second pairs of intermediate gears are capable only of rotation in a gear casing in which they are mounted but the drive pinion and the driven pinion are capable of radial movement in the casing.

The distance between the axes of the twin screw extruder for compound modification shafts of a twin screw extruder limits the diameters of driven pinions on the shafts and forming part of gearing for driving the screws. These driven pinions cannot be just any amount larger than the screw shafts themselves. Even if the driven pinions of the two drive shafts for the two-stage compounding line are staggered axially with respect to one another, with the high torques required nowadays it is no simple matter to obtain a long enough life for the gearing and small loads on radial bearings of the drive shafts for the screws.

Preferably the drive pinion has a coaxial twin screw extruder for filling process with curved teeth, engaged in a coupling sleeve with internal teeth, the other end of the coupling sleeve engages over an end of a shaft with curved teeth, and the driven pinion similarly has a coaxial extension with curved teeth, engaged in a further coupling sleeve with internal teeth, the other end of the further coupling sleeve engaging over and meshing with a portion of the screw drive shaft provided with curved teeth.
Such a power branching gearing can enable the strong drive forces which are now required in twin screw extruder to be transmitted without any appreciable bending of the screw drive shaft and consequent premature damage to the radial bearings. In every loaded condition of the screw shaft the strong torque to be transmitted is divided into two equal components and transmitted by uniform power branching. The cost of bearings for the screw drive shaft can be minimised, since the shaft can nolonger be bent by unilateral application of force.

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Cone type twin screw extruder having gear reduction system

In a cone type twin screw extruder, two rotor shafts are disposed in such a manner as to approach one another in the direction towards the leading edge, and to be rotatable. An interlocking device is provided on the side of the base portions of the rotor shafts for interlockingly connecting the rotor shafts with each other. The interlocking device has a pair of reduction gear devices disposed on the base portion sides of the rotor shafts, and the reduction gear is constituted of a spur gear train or a planetary gear train.

Accordingly, an object of the Two-stage compounding line is to provide a cone type Twin screw extruder for filling process capable of using common small sized bevel gears and being excellent in power transmission efficiency.

Namely, the cone type twin screw extruder of this Twin screw extruder for compound modification has two rotor shafts disposed at an angle to each other such that their ends generally converge. These two rotor shafts are each connected to a reduction gear system comprising for example a planetary gear system or a spur gear train, for transmitting the drive from the high speed shafts to the low speed rotor shafts. These high speed shafts are connected to a connecting shaft through a gear system for transmitting drive through an angle (angle transmission gear system). Said system could comprise for example a series of cooperating bevel gears. In this way both rotor shafts are interconnected and may be driven by a single drive unit attached to either of the two high speed shafts.

According to the present twin screw extruder, since the reduction gear is constituted of a spur gear train or a planetary gear train, the power transmission efficiency is improved as compared with the prior art worm gear reduction gear. Further, in the present invention, since the bevel gear device is provided on the upstream side of the reduction gear, the bevel gear is used in a high speed range, and may be of a standard small sized type.

twin screw extruder Two-stage compounding line Twin screw extruder for compound modification

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Drive means for a twin screw extruder

Drive means for a twin screw extruder has a pair of drive shafts mounted in a housing and each to be connected to a drive and to a respective one of the screws of the extruder. A thrust bearing to absorb the axial thrust applied to the screws comprises a thrust ring surrounding both drive shafts and supported in the housing by an axial roller bearing, a pair of coaxial butting rings inserted in and secured against rotation with respect to the thrust ring, off-set from one another in an axial direction and surrounding the two drive shafts and a respective shaft thrust ring for each drive shaft secured thereon against relative rotation. The two shaft thrust rings are off-set from one another in an axial direction with each shaft thrust ring bearing against a respective one of the butting rings.

In Two-stage compounding line it is known for the axial back pressure force from the screw to be taken up by a thrust bearing disposed between the Twin screw extruder for compound modification and drive gearing. This arrangement keeps the drive gearing free from back pressure forces from the screw.

In Twin screw extruder for filling process the arrangement of the thrust bearing poses a serious problem because of the small spacing between the screw shafts. It is not possible to arrange the thrust bearings in the same way as in twin screw extruders , because the largest possible shaft diameters through the thrust bearings do not allow the high torques required to be transmitted to the screw shanks. However, since a high torque must be transmitted to the screws it is customary to dispose axial thrust bearings behind the gearing in twin screw extruders. One then has to accept the disadvantage that the back pressure forces from the screws have to be transmitted to the thrust bearings through the gearing. Here they lead to undesirable strains, which have to be allowed for in the construction of the gearing. In the past the drive shafts have had to be axially displaceable within the gearing, so as to allow them to be elastically deformed by the axial strain.

The twin screw extruder has among its objects to provide drive means including a thrust bearing for a twin screw extruder, which will allow high torques to be transmitted without the gearing being adversely affected by the axial back pressure forces from the screw.

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Black powder processing on twin screw extruder

A continuous process of manufacturing black powder and black powder substitute using a twin screw extruder is disclosed. Guar gum mixed with the composition at a concentration in the range from 0.05% to 0.5%, by weight, dramatically reduced the friction in the dies and permitted extrusion of the powder at much lower water levels. Different size dies used in combination with face cutting of the extruded strands produce various sized granules. The process can be operated remotely and automatically. The process reduces the number of buildings, Two-stage compounding line and personnel required to manufacture black powder or black powder substitute. The process produces more uniform and reproducible particle sizes.

SUMMARY OF THE INVENTION

The present Twin screw extruder for filling process is directed to a continuous process of manufacturing black powder and black powder substitute using a twin screw extruder. Previous attempts at processing black powder with an extruder, using water as a processing aid, failed because the composition could not be extruded at the required density. High friction in the dies prevented extrusion.

Applicants found that a guar gum processing aid at a concentration in the range from 0.05% to 0.5%, by weight, dramatically reduced the friction in the dies and permitted extrusion of the powder at much lower water levels. Other materials similar to guar gum, such as karaya gum and gum tragacanth, can be used in the present invention and are to be included within the scope of guar gum.

DETAILED DESCRIPTION OF THE INVENTION

Sulfur, charcoal, and a small amount of guar gum are preferably mixed in a ball mill. The ingredients are provided in the following typical amounts: 10 parts sulfur, 15 parts charcoal and 1 part guar gum. The ingredients are preferably metered into a twin screw extruder using a loss-in-weight feeder. A small amount of water is added to the extruder, and the ingredients are compounded to form a black powder paste suitable for extrusion.

The black powder is extruded through a die. The extrusion consolidates the ingredients and can be controlled to vary the density of the resulting black powder. A face cutter is preferably provided to cut the extruded black powder and form black powder granules.

twin screw extruder Two-stage compounding line Twin screw extruder for filling process

Twin screw extruder with a material homogenizing unit

A twin screw extruder with a material homogenizing unit is the subject of this disclosure. Two extruder screws are located within a housing positioned and configured so that screw turns and screw lands of a first screw mesh with respective screw lands and screw turns of a second screw. A homogenizing zone housing is connected to the dual cylinder housing. Two cell rotors are connected to respective extruder screws and are located within the homogenizing zone housing. A plurality of radially distributed cell walls may be disposed on each cell rotor defining a plurality of open conveyor cells where the cell rotors and cell walls of each rotor are configured to mesh a cell wall with an opposing conveyor cell. The cell walls may be arranged with a slope differing from a slope of the twin screw extruder manufacturer. The cell walls may be arranged parallel to or at an angle to an axis of said cell rotors.

1. Field of the Invention

The invention relates to twin screw extruders and more particularly to an extruder for continuous processing of PVC powders.

2. Description of the Related Technology

Twin screw extruders are continuously operating screw presses with two meshing screws and are used to plasticize and extrude plastics. Twin screw extruders are used preferably for the continuous processing of PVC powder formulations.

Twin screw extruders may be divided into different zones which are distinguished. A melting zone, a mixing zone, a degassing zone and a discharge zone may be arranged in line from a screw extruder inlet to the outlet. As a rule, the screws have different configurations adapted to the particular zone, over their length. The screw turns may have different pitches and spacing in the zones and may be provided with interruptions, baffles or the like. The screw turns may be replaced by meshing toothed disks or kneading blocks particularly in the melting and/or the mixing zones in order to obtain a particularly intensive mixing of the powder in the melt and to homogenize the melt. The screws usually have continuous screw turns in the discharge zone which mesh with slight roll and flank clearances, thereby preventing any back flow of the melt and producing the necessary pressure for pressing the melt into a molding tool attached to the extruder.

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Friction and pressure within the cavity of the twin screw extruder serve to produce extra heat that is independent of the heaters. Sometimes, the pressure and friction inside the cavity produces so much heat that the heaters may be shut off. When this happens, the desired temperature is maintained by the friction and pressure. Cooling fans are also employed frequently, helping to keep the plastic screw extrusion cavity at the desired temperature.

When the molten plastic reaches the front of the barrel, it moves away from the screw and journeys through a special screen designed to filter contaminants from the plastic. The molten plastic then moves into a die. The die is responsible for giving the molten plastic its profile. The plastic must then be cooled, often by a sealed-water bath; care must be taken to prevent the collapse of the newly formed product in its still molten state. Plastic sheeting and certain other products are cooled by special cooling rolls, instead of water baths.

After cooling, the product is spooled, coiled, or cut to length. In addition to plastics, a variety of other materials may be extruded. Aluminum and rubber are examples of materials that can be extruded. Even clay and certain types of foods may be extruded. However, the process used may differ from that employed for the purpose of plastic single screw extrusion.

In the end of 2009 year, the 4th generation high torque & high speed gearbox has been successfully launched to the market, which is improved based on 3rd generation gearbox. The characteristics, as below:

1. Re-designed structure of gearbox adopt Noise Reduction Design, to reduce the noises which is below 80+2dB(A) in 1 meter away.
2. All the gears processed by the German Gear Grinder to enhance its precision.
3. Optimize the gear teeth to enlarge the meshing surface area and increase lifetime.
4. Adopt the Swedish SKF bearings and lifetime is over 20,000 hours.
5. The dual function of pressure and spray is designed for the lubrication system to ensure getting better lubricating effect.
6. The individual & out-way designs of oil cooling system guarantee the gearbox operation under appropriate temperature.

With the tenet of “be sincere, be scientific” , Nanjing Chengke company focuses on the works of R&D , design, sale and after-sale for co-rotating twin-screw extruders, two-stage compounding lines and single-screw extruders.
Chengke was founded by senior engineers in twin-screw processing，we have advanced management systems and high-effective operation teams.
Technology advantage
Our business concept is to analyze the problems , to offer the best solutions and to provide custom mouldings .
We own the most outstanding technology of high torque and high speed gearbox in China
Working experience
All our colleagues are from Coperion Keya and Ruiya company
We built up the lab room for new materials testing
After-sale service
Chengke serves all the customers with effective ways such as standardize the flows of before-sale, sale and after-sale, visit the customers periodically and file the clients’ information etc.
The warranty period is one year.
After the warranty period, spare parts are provided at cost price
Answer the customers not more than 24 hours;
If need jobsite service, engineers will be reached not more than 72 hours;
With the active, prudential, tolerant and confident spirit, to meet the market demands, Chengke now is exerting every effort to product best brand of twin-screw extruders.

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