Blender

Details Blender Blender

1998-06-15

2001-03-20

Soohoo, Tony G. (Department: 1723)

Agitating

With weighing

C366S152600, C366S153100, C366S156100, C366S163100, C366S181100, C366S179100

Reexamination Certificate

active

06203184

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a blending apparatus and method.
The invention particularly relates to a batch blending apparatus for controlled mixing and delivery of particulate blend additives into a material processing device, such as a plastics extruding device, or, in processes requiring blending of material.
BACKGROUND OF THE INVENTION
It is known to provide a blender having a mixing chamber for reception of two or more materials to be blended. A mixing paddle is mounted within the mixing chamber to stir the materials within the mixing chamber for blending the materials within the mixing chamber prior to discharge to a process. A disadvantage with these types of blender is that the mixing tends to be fairly coarse and vigorous within the mixing chamber and thus it can be difficult to achieve an accurate blending of the material additives with the process materials. Also, in these blenders, because of their constructions, there may be dead areas in the mixing chamber where unblended or only partially blended materials collect. Further, these blenders are sensitive to the density and particle size of the material to be blended. It is also difficult to process relatively small quantities of material and achieve the required blend. Thus, these blenders are somewhat limited in the range and quantities of materials that can be successfully blended.
The present invention is directed towards overcoming these problems.
SUMMMARY OF THE INVENTION
According to the invention, there is provided a blender for mixing particulate materials prior to discharge into a process line, the blender comprising a mixing chamber, the mixing chamber having an inlet for reception of additive materials to be mixed and a blended material outlet, mixing means for mixing additive materials within the mixing chamber, delivery means for delivery of blended material to the outlet at a rate greater than the rate of discharge of blended materials through the outlet, and means to direct excess blended material away from the outlet for remixing within the mixing chamber.
In one embodiment, the mixing means is operable to generate and maintain a substantially level top surface in the additive materials within the mixing chamber above the outlet.
In a preferred embodiment, the mixing means comprises a mixing screw rotatably mounted within the chamber, the mixing screw operable to mix two or more materials delivered into the chamber, prior to discharge of the blended materials through the outlet.
Advantageously the use of a mixing screw facilitates good and even blending of the material additives in a controlled manner which minimises agitation of the materials which facilitates more accurate monitoring and control of additive material throughput to the process.
In one embodiment of the invention, the mixing screw has a rotatable shaft with a pair of mixing blades of opposite pitch extending outwardly from a central portion of the shaft which is located adjacent the outlet. Thus, conveniently the mixing screw is operable to direct material towards the outlet of the mixing chamber, while at the same time circulating the material within the mixing chamber for blending of the additive material.
Preferably the mixing screw is demountably secured within the mixing chamber.
Conveniently the mixing screw is movable axially through an opening in a side wall of the mixing chamber for removal. This facilitates easy cleaning of the screw and the mixing chamber as desired.
In a further embodiment there is provided a blender comprising a mixing chamber for reception of two or more materials to be blended, the mixing chamber having a material inlet and a blended material outlet, a mixing screw mounted within the mixing chamber adjacent the outlet for circulating and mixing of materials within the mixing chamber and material level sensor mounted within the chamber, said level sensor connected to a controller which is operable to regulate the supply of fresh materials to the blending chamber for mixing.
Preferably the blender further comprises a weigh hopper having a material inlet and a material outlet, the outlet arranged to discharge material from the weigh hopper to the mixing chamber.
In another embodiment a discharge gate on the weigh hopper outlet is operatively connected to the controller.
In a further embodiment the blender further comprises raw material supply bins, each bin having a discharge valve mounted at an outlet of the material supply bin, each of said discharge valves being operatively connected to the controller to regulate discharge of material from the bin to the weigh hopper or the mixing chamber.
Preferably, each discharge valve comprises a ram operated plate slidably mounted on a complementary track, the plate engagable with a downwardly depending discharge collar at the outlet to close the outlet.
Conveniently a vacuum loader is provided associated with each material supply bin, the vacuum loader operable to draw material from a material storage reservoir into the bin, said vacuum loader having a vacuum pipe connected to the bin with a filter mounted across said vacuum pipe, cleaning means being provided to clean the filter.
Preferably the cleaning means comprises an air jet operable to automatically back-flush the filter after each fill cycle.
In another embodiment, an auxiliary supply bin is provided with a discharge screw at an outlet of the auxiliary bin for delivery of material to the mixing chamber, said screw rotatably mounted within a complementary barrel, a non-return flap valve being mounted at an outlet end of the barrel.
In a further embodiment, an access door is provided on the mixing chamber, said access door operably engagable with switches for isolating electric and pneumatic power supply to the blender when the door is open.
In another embodiment, a complementary pair of capacitor plates are mounted in each material supply bin, said plates being connected to a controller operable to determine the level of material in the bin.
In another embodiment, the blender incorporates a material bulk density measurement device.
Preferably, the bulk density measurement device comprises a chamber which is filled with material during operation of the blender, an associated pair of capacitor plates being mounted within the chamber and connected to a controller operable for determining the bulk density of material between the plates.
In another aspect, the invention provides a level measurement device for measuring the level of material in a bin or container, the device comprising a complementary pair of capacitor plates mounted within the bin, said plates being connected to a controller operable to determine the level of material in the bin.
In a still further aspect, the invention provides a bulk density measurement device comprising a chamber which is filled with material, the bulk density of which is to be measured, an associated pair of capacitor plates mounted within the chamber and connected to a controller which is operable for determining the bulk density of material between the plates.


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