Agitating – Stirrer within stationary mixing chamber – Rotatable stirrer
Reexamination Certificate
2000-12-27
2003-02-25
Cooley, Charles E. (Department: 1723)
Agitating
Stirrer within stationary mixing chamber
Rotatable stirrer
C366S325100, C366S326100
Reexamination Certificate
active
06523996
ABSTRACT:
BACKGROUND OF THE INVENTION
The field of the proposed invention relates to high intensity blending apparatus and processes, particularly for blending operations designed to cause additive materials to become affixed to the surface of base particles. More particularly, the proposed invention relates to an improved method for producing surface modifications to electrophotographic and related toner particles.
High speed blending of dry, dispersed, or slurried particles is a common operation in the preparation of many industrial products. Examples of products commonly made using such high-speed blending operations include, without limitation, paint and colorant dispersions, pigments, varnishes, inks, pharmaceuticals, cosmetics, adhesives, food, food colorants, flavorings, beverages, rubber, and many plastic products. In some industrial operations, the impacts created during such high-speed blending are used both to uniformly mix the blend media and, additionally, to cause attachment of additive chemicals to the surface of particles (including resin molecules or conglomerates of resins and particles) in order to impart additional chemical, mechanical, and/or electrostatic properties. Such attachment between particles is typically caused by both mechanical impaction and electrostatic bonding between additives and particles as a result of the extreme pressures created by particle/additive impacts within the blender device. Among the products wherein attachments between particles and/or resins and additive particles are important during at least one stage of manufacture are paint dispersions, inks, pigments, rubber, and certain plastics.
A typical blending machine and blending tool of the prior art is exemplified in
FIGS. 1 and 2
.
FIG. 1
is a schematic elevational view of a blending machine
2
. Blending machine
2
comprises a vessel
10
into which materials to be mixed and blended are added before or during the blending process. Housing base
12
supports the weight of vessel
10
and its contents. Motor
13
is located within housing base
12
such that its drive shaft
14
extends vertically through an aperture in housing
12
. Shaft
14
also extends into vessel
10
though sealed aperture
15
located at the bottom of vessel
10
. Shaft
14
is fitted with a locking fixture
17
at its end, and blending tool
16
is rigidly attached to shaft
14
by locking fixture
17
. Before blending is commenced, lid
18
is lowered and fastened onto vessel
10
to prevent spillage. For high intensity blending, the speed of the rotating tool at its outside edge generally exceeds 50 ft./second. The higher the speed, the more intense, and tool speeds in excess of 90 ft./second, or 100 ft./second are common.
Turning now to
FIG. 2
, a perspective view of blending tool
16
of the prior art is shown. Center shank
20
has a central fixture
17
A for engagement by locking fixture
17
(shown in FIG.
1
). In the example shown, the central fixture
17
A is a simple notched hole for receiving a male fixture
17
(from
FIG. 1
) having the same dimensions. Arrow
21
shows the direction in which tool
16
rotates upon shaft
14
. Vertical surfaces
19
A and
19
B are fixed to the end of center shank
20
in order to increase the surface area of the tool at its point of greatest velocity. This increases the tool's “intensity”, or number of collisions per unit of time. In addition to the surface area of the tool's face, the intensity of a tool is influenced by tool speed and the shape of the tool. The importance of the shape of the tool will be discussed below. Vertical surfaces
19
A and
19
B combined with the leading edge of center shank
20
are the surfaces of tool
16
that collide with particles mixed within vessel
10
(shown in FIG.
1
). The area through which these surfaces
19
and leading edge of center shank
20
sweep during rotation of tool
16
can be thought of as the working profile of the tool. In other words, the “profile” of a tool equals the 2-dimensional area outlined by collision surfaces of the tool as it sweeps through a plane that includes the rotational axis of shaft
14
. In
FIG. 2
, the space or zone immediately behind rotating tool
16
is labeled
22
.
Various shapes and thicknesses of blending tools and collision surfaces are possible. Various configurations are shown in the brochures and catalogues offered by manufacturer's of high-speed blending equipment such as Henschel, Littleford Day Inc., and other vendors. The tool shown in
FIG. 2
is based upon a tool for high intensity blending produced by Littleford Day, Inc. Among the reasons for different configurations of blending tools are (i) different viscosities often require differently shaped tools to efficiently utilize the power and torque of the blending motor; and (ii) different blending applications require different intensities of blending. For instance, some food processing applications may require a very fine distribution of small solid particles such as colorants and flavorings within a liquid medium. Similarly, the processing of snow cones requires rapid and very high intensity blending designed to shatter ice cubes into small particles which are then mixed within the blender with flavored syrups to form a slurry.
Most high-speed blending tools of the prior art do not have raised vertical elements such as surfaces
19
A and
19
B (collectively “surface
19
”) shown in FIG.
2
. Instead, a typical blending tool has a collision surface formed simply by the leading edge of its central shank
20
. In many tools, the leading edge is rounded or arcurately shaped in order to avoid a “snow plow” effect wherein particles become caked upon a flat leading face much as snow is compressed and forms piles in front of a snow plow. The tool shown in
FIG. 2
attempts to avoid this snow plow effect on raised collision surfaces
19
by slanting the forward face of surfaces
19
at an acute angle, thereby causing particles to either bounce upward from the tool or be swept by friction upward along the face of the tool until carried over its top and into the lee of the tool. However, a problem with the tool shown in FIG.
2
and with other tools in the prior art is that an enlarged collision surface tends to create vortices in the wake of the tool as well as to decrease the overall density of particles in the zone
22
behind the tool. The degree of such density variations depends primarily upon the speed of the tool through the particle mixture as well as the height, width, and depth of the collision surface
19
.
Because of the above snow plow, vortex, and density limitations, conventional tools such as shown in
FIG. 2
are limited both in height and in the width of any enlarged collision surface. Indeed, it is believed that in tools of the prior art that have elements raised above center shank
20
, the height (defined below as the y-axis dimension) of such vertically raised elements is less than the depth (defined below as the z-axis dimension) of center shank
20
in its region proximate to the attachment point of the enlarged element. It is also believed that the width (defined below as the x-axis dimension) of any vertically raised element of a conventional tool has not exceeded the height, or y-axis, of center shank
20
in the region of center shank
20
proximate to where the raised element is attached. Lastly, it is believed that in high-speed blending tools of the prior art that have raised elements, the z-axis dimension, or depth, of the raised element greatly exceeds its width, or x-axis, dimension. For clarification, the height, or y-axis, dimension of a blending tool and its elements shall mean the dimension of the tool or element in the plane that contains shaft
14
around which the tool rotates. The depth, or z-axis, of the tool and its elements shall mean the dimension perpendicular both to the axis of the tool's center shank and to the y-axis. The x-axis of the tool and its elements shall be measured in the direction of the axis of the tool's center shank. For center shan
Cooley Charles E.
Spoone Richard F.
Xerox Corporation
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