U.S. patent number 3,859,407 [Application Number 05/253,186] was granted by the patent office on 1975-01-07 for method of manufacturing particles of uniform size and shape.
This patent grant is currently assigned to Corning Glass Works. Invention is credited to Wendell S. Blanding, Jack A. Brothers.
United States Patent |
3,859,407 |
Blanding , et al. |
January 7, 1975 |
METHOD OF MANUFACTURING PARTICLES OF UNIFORM SIZE AND SHAPE
Abstract
Plastically formable material, which may be formed under
pressure into desired shapes, is fed while in a fluid or
plastically formable condition to a pair of cooperating surfaces
which are relatively movable into compressive relationship with
material disposed therebetween. The face of at least one of such
surfaces is patterned with a plurality of juxtapositioned
geometrical impressions of desired size and shape so as to form a
ribbon or sheet of uniformly sized and shaped particles from the
plastically formable material supplied to the cooperating surfaces.
The uniform particles are initially joined together by thin web or
edge portions which maintain the continuity of the newly formed
particles within a sheet form. However, after the ribbon of newly
formed particles has become sufficiently rigid, such as through the
cooling of a molten thermoplastic material or the drying or firing
of a green ceramic material from which such ribbon may be formed,
the ribbon may then be flexed in various directions to separate the
particles along the edge or web portions, thus providing a
plurality of individual particles having substantially uniform size
and shape.
Inventors: |
Blanding; Wendell S. (Painted
Post, NY), Brothers; Jack A. (Corning, NY) |
Assignee: |
Corning Glass Works (Corning,
NY)
|
Family
ID: |
22959233 |
Appl.
No.: |
05/253,186 |
Filed: |
May 15, 1972 |
Current U.S.
Class: |
241/3; 51/295;
51/309; 65/62; 264/133; 264/175; 51/307; 65/22; 65/101; 264/140;
425/116 |
Current CPC
Class: |
C03B
11/082 (20130101); E01C 7/085 (20130101); C03B
19/104 (20130101); C03B 19/1035 (20130101); B28B
3/14 (20130101); C03B 13/08 (20130101); B01J
2/22 (20130101); C03B 11/06 (20130101); B28B
1/004 (20130101); B29B 9/04 (20130101); C03B
2215/412 (20130101); C03B 2215/414 (20130101); C03B
2215/40 (20130101) |
Current International
Class: |
B01J
2/22 (20060101); B28B 1/00 (20060101); E01C
7/00 (20060101); E01C 7/08 (20060101); B28B
3/00 (20060101); B28B 3/14 (20060101); C03B
11/06 (20060101); C03B 19/00 (20060101); C03B
13/00 (20060101); C03B 19/10 (20060101); C03B
13/08 (20060101); C03B 11/08 (20060101); B29B
9/02 (20060101); B29B 9/04 (20060101); C04b
041/14 (); C04b 041/24 () |
Field of
Search: |
;264/67,140,144,214,332,175,133 ;65/87,93,97,101,245 ;425/115,116
;51/295,307,309,DIG.30 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
45-35720 |
|
Nov 1970 |
|
JA |
|
655,185 |
|
Jul 1951 |
|
GB |
|
875,140 |
|
Aug 1961 |
|
GB |
|
725,973 |
|
Mar 1955 |
|
GB |
|
368,073 |
|
Mar 1932 |
|
GB |
|
Primary Examiner: White; Robert F.
Assistant Examiner: Pavelko; Thomas P.
Attorney, Agent or Firm: Turner; Burton R. Patty, Jr.;
Clarence R.
Claims
We claim:
1. A method of continuously forming particles of uniform size and
shape from flowable batch material which comprises:
a. providing a pair of cooperating forming rollers,
b. providing a patterned surface having a plurality of individual
uniform recesses of desired size and shape across and about an
operating surface of at least one of said cooperating rollers,
c. supplying a flow of said flowable batch material to the bite of
said cooperating rollers,
d. roll-forming between said pair of cooperating rollers a
longitudinally continuous ribbon of particles of uniform size and
shape connected together along adjacent edge portions by a web
portion extending the width of said patterned surface, and
e. flexing the ribbon between a pair of off-set rolls out of the
plane of the ribbon to liberate the connected particles therefrom
into a plurality of individual separated particles of the same
uniform size and shape as initially produced in ribbon form.
2. A method of continuously forming uniform abrasive grains of
desired size and shape from flowable thermoplastic vitreous or
thermosetting ceramic material comprising:
a. providing a pair of cooperating forming rollers rotatable about
parallel longitudinal axes,
b. providing patterned particle-forming surface portions on opposed
surfaces of said forming rollers,
c. supplying a flow of said material to the bite of said
cooperating rollers,
d. synchronizing said pair of cooperating rollers so that opposed
patterned surface portions cooperate with one another,
e. roll-forming between said cooperating rollers a longitudinally
continuous ribbon of a plurality of adjacent particles connected
together by means of a continuous connecting thin web portion
extending across the width of the patterned surface portions and
having opposed apexes which extend outwardly from opposite sides of
the ribbon such that the plane of said web portion perpendicularly
bisects an axis extending between a pair of opposed apexes, and
f. flexing said ribbon between a pair of off-set rolls in various
directions out of the plane of the ribbon to separate the newly
formed abrasive particles therefrom along adjacent edge portions
into individual particles of desired uniform size and shape for use
as abrasive grains.
3. A method of continuously forming uniform abrasive grains of
desired size and shape from flowable siliceous material
comprising:
a. providing a pair of cooperating forming rollers rotatable about
parallel longitudinal axes,
b. providing patterned particle-forming surface portions on opposed
surfaces of said forming rollers,
c. supplying a flow of siliceous material to the bite of said
cooperating rollers,
d. roll-forming between said cooperating rollers a longitudinally
continuous ribbon of particles of uniform size and shape connected
together along adjacent edge portions by interconnected web
portions,
e. metallizing said particles of siliceous material while in said
ribbon form to form cermet abrasive grains, and
f. flexing said ribbon of abrasive grains between a pair of off-set
rolls in various directions out of the plane of the ribbon to
separate the newly formed abrasive grains therefrom along adjacent
edge portions into individual abrasive particles of desired uniform
size and shape.
Description
BACKGROUND OF THE INVENTION
The present invention resides in the field of discrete particle
manufacture, and particularly is concerned with the problem of
repeatably forming particles having virtually identical size and
shape.
The granules or particles manufactured by the present invention
have utility in numerous fields including gripping elements for
road surfaces and abrasive grains for use in bonded abrasive
articles such as grinding wheels and snagging wheels, and coated
abrasive articles such as abrasive papers and the like. One of the
problems that has plagued the industry in the manufacture of
discrete particles for use as abrasive grains has been the
inability to continually reproduce grains of the same size and
shape. That is, it has been customary in the past to manufacture
abrasive grains by crushing abrasive type material into granular
form. However, in the case of heavy duty abrasive grits, usually
less than 50% of the total material is recovered in a usable size
range, with the majority of the material being crushed into useless
fines. Further, that material which is usable must then be
classified into standard grain sizes. However, since the crushing
process cannot be accurately controlled, the shape of the grains
even within a particular classification will vary materially, thus
producing grains with dissimilar cutting rates and variable useful
lives, thereby resulting in less than optimal efficiencies. The
shape of crushed abrasive particles can be improved somewhat by
mulling, however such process is not only costly but results in
even lower recoveries.
U.S. Pat. No. 3,481,723 illustrates a method of producing shaped
abrasive grains by extruding predetermined lengths of a green
ceramic mixture which is then sintered to form hard abrasive
grains. However, due to the extrusion forming thereof, the shape of
such grains is severely limited to a pre-shaped cylindrical or
prismatic configuration, with the only variable cross-section lying
in a plane perpendicular to the axis of extrusion. Therefore,
although the extruded sintered abrasive grains were an improvement
over the randomly crushed grains, they have not been entirely
satisfactory since variable three-dimensional geometric solids are
not obtainable and the manufacturing process is not particularly
economical.
The present invention not only obviates the problem of repeatably
producing uniform particles of virtually identical size and shape,
but also provides a simplified continuous or repeatable process for
rapidly and economically producing such particles in mass
production.
SUMMARY OF THE INVENTION
The present invention sets forth a completely new concept in the
manufacture of particulate matter having uniform size and shape
from a flowable plastically formable material. In its simplest
form, the present invention includes the flowing of plastically
formable material to a pair of cooperating forming members having
one or more of the cooperating surfaces thereof engraved or
contoured with recesses or patterns of desired size and shape.
Accordingly, the cooperating members produce a plurality of uniform
particles of substantially identical size and shape which are
joined together along adjacent connecting edge portions by means of
a thin web portion.
Any flowable plastically formable material may be supplied to the
cooperating members including thermoplastic materials such as
basalts and molten vitreous materials, as well as thixotropic and
thermosetting materials such as ceramic batches, wherein all such
materials have the property of being able to flow and be
plastically formed during the application of forming pressure,
while also being able to become sufficiently rigid immediately
thereafter so as to maintain structural integrity. That is, when
the particles are formed of a thermoplastic material, the ribbon of
newly formed particles is cooled and solidified immediately
thereafter in order to provide sufficient rigidity so as to
maintain the structural integrity of the newly formed particles,
whereas when such ribbon is formed of a ceramic batch, it may be
dried or fired in order to obtain the necessary rigidity.
Depending upon the particular application to which the particles
are to be utilized, the cooperating forming members may be either a
pair of cooperating forming rollers or a mold and plunger set. That
is, the particles may either be roll-formed or press-formed
depending upon the particular forming device utilized, however, in
both instances the forming of the plastically formable material is
accomplished through a pressing force exerted between a pair of
forming members having one or more cooperating surfaces thereof
contoured with patterns for forming the particles of desired size
and shape. Roll-forming has the advantage of providing a continuous
forming process, whereas press-forming by means of a mold and
plunger has the advantage of greater flexibility in providing lower
volume speciality items.
In view of the fact that the basic forming operation of the present
invention, which includes the exertion of pressure by two
cooperating surfaces on plastically formable material to product
particles of a given size and shape, may be accomplished by either
roll-forming or linear press-forming, the invention will be
described in particular only with respect to roll-forming, as the
similarities between the two processes will be readily appreciated
by those skilled in the art. Depending upon the surface patterning
and the orientation of the cooperating members, it is possible to
form particles which extend solely from one surface of the ribbon
with the opposite surface being flat, such as may be utilized with
coated abrasive sheets; or the particles may project outwardly in
staggered relation from opposite sides of the resulting sheet; or
finally, the recesses in the opposed faces may be mated or aligned
and synchronized so that the resulting particles have opposed
apexes projecting equally distant on opposite sides of the ribbon
from a thin web-like plane bisecting the axis between such apexes.
In all cases, however, since the recesses or impressions formed in
the cooperating surfaces are of a desired uniform size and shape,
the resulting particles formed thereby are also virtually identical
in both size and configuration, thus providing a theoretical 100%
selection.
The newly formed particles may be conveniently conveyed or
transported in ribbon form for further processing as may be
desired, and the plurality of particles making up the ribbon may,
after becoming sufficiently rigidified to prevent deformation, then
be separated or liberated therefrom in individual form by various
means such as a pair of soft, off-set rolls. The rolls cause the
substantially rigid sheet or ribbon of particles to flex in various
directions out of the plane of the sheet, thus liberating or
separating the particles along the edge or web portions from the
sheet as individual grains of uniform size and shape which may then
be conveniently collected for bulk packaging. It will be apparent,
however, that the individual particles may be liberated from the
ribbon either before or after any additional treatment, such as
metallizing, is undertaken.
It thus has been an object of the present invention to obviate the
uneconomical and virtually uncontrollable prior art processes of
forming particulate matter usable as abrasive grains or highway
traction particles, by providing an improved process of forming,
such as by continuously rolling, a plurality of interconnected
particles of like size and shape in ribbon form from plastically
formable material such as green ceramic or molten vitreous
material, with the ribbon of connected particles, after
rigidification, being subsequently separable into uniform
individual particles.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a somewhat schematic perspective view illustrating the
process and apparatus of the present invention for continuously
forming particles of substantially identical size and shape.
FIG. 1a is a sectional view illustrating a further embodiment.
FIG. 2 is an elevational view in section through the bite of a pair
of cooperating rollers.
FIG. 3 is a greatly enlarged fragmental view in plan of a plurality
of particles in ribbon form produced by the rollers of FIG. 2.
FIG. 4 is a greatly enlarged fragmental view of a plurality of
particles after they have been liberated or separated from the
ribbon of particles shown in FIG. 3.
FIGS. 5a, 6a, 7a, 8a, 9a and 10a illustrate various shapes of
particles in ribbon form which may be produced by the present
invention, whereas corresponding FIGS. 5b, 6b, 7b, 8b, 9b and 10b
illustrate the shape of the individual particles after they have
been separated or liberated from their corresponding ribbon.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the schematic illustration of FIG. 1, a pair of
cooperating forming rollers 10, 12 which may be water cooled if
desired, and having engraved or recessed patterned surfaces 14, 16,
roll-forms a flow of plastically formable material G, such as green
ceramic batch or molten glass or basalts, into a continuous ribbon
R of interconnected particles P. The rollers are rotatable about
parallel longitudinal axes toward one another as shown by the
arrows, so that the flowable material G supplied thereto is
roll-formed as it passes through the bite. As shown, the ribbon may
be transferred along conveyor rollers 18 to a pair of soft, off-set
flexing rolls 20 which distort and flex the now rigidified ribbon R
in various directions out of its natural plane and thereby liberate
the connected particles P from the ribbon so they may fall as
separate individual particles P and be collected in a container 22.
The ribbon R is shown as being discontinuous between conveyor
rollers 18 to indicate that additional processing such as
solidifying, drying, firing and metallizing may be imparted to the
ribbon as desired prior to the liberating or separating of the
various particles therefrom into their individual state. For
example, the newly formed ribbon R, if of a siliceous vitreous
material, may be subjected to a metallizing treatment such as by
contacting it with molten aluminum as described in U.S. Pat. No.
2,702,750, so as to form cermet particles which are especially
suited for heavy-duty abrasive grain application.
The recessed or engraved patterned surface may be formed in either
or both of the cooperating rollers 10, 12 as desired. When the
recessed or engraved pattern is formed in the surface of only one
roller and the opposed surface of the other cooperating roller is
smooth, a plurality of particles are formed within the resulting
ribbon having a flat or planar back surface, with the particles
projecting outwardly only from one side of such ribbon and being
joined together along adjacent edge portions thereof. When such a
ribbon is formed having a flat or planar back surface, it may be
desirable, after appropriate treatment, to utilize the particles in
ribbon form in a coated abrasive article by applying a backing
thereto, without requiring the separating or liberating of the
individual particles from the ribbon.
As shown in the schematic illustration of FIG. 1, both of the
operating surfaces 14, 16 of the cooperating forming rolls 10, 12
may be provided with desired impressions to provide a specific
pattern on both sides of a ribbon of material which passes through
the bite of such rollers. The impressions made in the roller
surfaces are uniform with respect to one another and may be of any
desired size and shape such as tetrahedra, cubes, octahedra and
other geometric shapes. As previously pointed out, the particles
formed by the recessed surfaces are initially joined together in
ribbon form, either along common edge portions or by means of a
narrow thin web of vitreous material, with the exact manner in
which the particles are joined being dependent upon the shape being
produced.
When both of the cooperating rollers are provided with engraved
surfaces, the recesses or impressions in each such surface may be
staggered or off-set as illustrated in the embodiment shown in FIG.
2, or the impressions on the surfaces may be synchronized by the
speed of rotation of the rollers so that the patterns on opposing
rollers are matched when in contact with the plastically formable
material at the bite of the rollers. Similarly, as illustrated in
FIG. 1a, the forming members shown as plunger 10a and mold 12a are
provided with cooperating surfaces having mating or matched
impressions so that the patterns cooperate to form a ribbon of
particles within the mold which extend outwardly from opposite
sides of the ribbon per se. Accordingly, the resultant particles
may be symmetrical about a plane perpendicularly bisecting an axis
passing through a pair of opposed apexes formed by each such
particle. Whether the opposed patterns on the forming members are
mated in synchronized relation or not, adjacent particles may be
connected to one another in ribbon form either by connecting edge
portions or by a small connecting web portion, however, in either
case the particles may be liberated from the ribbon form to their
separate state by means of a pair of off-set flexing rolls or the
like which permit the connected particles to break apart from the
ribbon while maintaining their initially formed individual
integrity. That is, since the flexing rolls do not affect the size
or shape of the individual particles per se, but merely separates
one from another, it is possible to continuously and repeatably
produce particles of a given size and shape with about 95-100%
selection, since there is no crushing or deleterious deformation of
the particles as was occasioned in the prior art processes.
Although virtually any size of particle above 0.01 inches may be
formed with the present invention, for the purpose of manufacturing
abrasive grains we prefer to form articles having an altitude, or
apex to apex distance, of between about 0.028 inches and 0.157
inches. It will be apparent that the upper size limit of particle
manufacture will be limited only by the pressing capacity of the
cooperating surfaces, whereas the lower limit of about 0.01 inches
is dictated by the minimum thickness of the resulting web which
would be sufficient to maintain the integrity of the ribbon. As
previously mentioned, the individual geometric shapes of the
particular particles may be liberated from the rigidified ribbon or
sheet by providing a sufficient deflection of the ribbon to cause a
brittle fracture along the thinnest portions thereof, such as the
common edges of the particle shapes or the thin web of vitreous
material between such shapes. The liberated particles of geometric
shapes are then collected and further processed as dictated by
their end use.
Referring now to the embodiment shown in FIG. 2, the forming
rollers 110, 112 are provided with recessed or engraved pattern
surfaces 114, 116 which are staggered or off-set with one another
at the bite 118 of the rollers. Each of the patterned surfaces 114,
116 is provided with a plurality of pyramidal or tetrahedral shaped
recesses of equal size and shape. Accordingly, the plastically
formable material G, such as molten glass, which is fed to the
forming rollers 110, 112, is formed into a ribbon R having a
plurality of off-set tetrahedral or pyramidal particles P extending
outwardly from both sides thereof. As shown in FIG. 3, the
pyramidal particles P extending outwardly from one side of the
ribbon R are bound together along connecting edges 120 of the flats
or bottoms 122 of pyramidal particles P extending outwardly from
the opposite side of the ribbon. As shown in FIG. 4, the individual
particles P, after being liberated from the ribbon R and falling
into the container 22, are all of the same size and shape as
originally formed by the cavities or recesses of the forming
rollers.
Referring now to FIGS. 5a through 10b which illustrate some of the
various forms of ribbons and particles which may be produced by the
present invention, it will be noted that the ribbons shown in FIGS.
5a, 6a, 7a and 8a all have a flat or planar back or bottom surface,
such as would be produced when only one roll or mold surface is
provided with a recessed or engraved pattern. The ribbon 50 of FIG.
5a is formed of a plurality of particles 51, shown in FIG. 5b,
having the appearance of a slightly rounded cube or frustum. The
web or connecting edge portion of the particles 51 is shown at 120.
It should be further noted, that the ribbon 100 shown in FIG. 10a
and the particle 101 of FIG. 10b formed therefrom, may be produced
by synchronizing two forming rollers having the same surface
pattern which forms ribbon 50 of FIG. 5a. That is, ribbon 100
produces particles 101, each of which has a pair of symmetrical
shapes, similar to particle 51, extending outwardly on opposite
sides of the ribbon from a plane perpendicularly bisecting an axis
extending between opposed apexes of the particle 101. The
connecting edge or web portions which lie in the bisecting plane
are shown at 120.
Ribbon 60, of FIG. 6a produces a plurality of pyramids 61 having a
square base and four triangular sides converging at an apex. If a
second roller, having a patterned recess similar to that on the
first roller forming particle 61, were synchronized with such first
roller, a particle projecting outwardly from opposite sides of the
ribbon and having an octrahedral configuration would be formed.
FIG. 7a illustrates a ribbon 70 for forming a multi-surfaced
particle 71 having numerous edges which are useful when the
particle is used as a cutting grain. FIG. 8a illustrates a ribbon
80 which produces particles 81 having an eight-sided configuration.
As previously mentioned, ribbons 50, 60, 70 and 80, which are
provided with a flat or planar back surface, may be utilized in the
as-produced ribbon form, after being suitably treated, by providing
the same with backing sheets so as to form coated abrasive
articles.
FIG. 9a illustrates a ribbon 90 for producing particles 91 having a
hexahedral configuration. Such configuration would be formed by
rollers 110, 112, when the speed thereof is adjusted so that the
impressed or recessed portions 114, 116 are synchronized and
cooperate with one another as they pass through the bite 118 of the
rollers. Also the mating surfaces of plunger 10a and mold 12a could
produce the hexahedral particle configuration of FIGS. 9a and 9b.
Accordingly, particle 91 is characterized by a pair of opposed
pyramids projecting outwardly from opposite sides of the ribbon 90
such that the connecting web 120 or plane of the ribbon 90 bisects
and axis extending between opposed apexes 92 of the hexahedral
configuration of the shaped particle 91.
The fact that the present invention permits a highly controlled
geometric shape of the particle is of particular significance when
such particle is used as an abrasive grain. That is, improved
abrasive performance can be achieved by controlling the shape to
maximize grain sharpness and grain toughness. Also, the shape can
be designed to supply anchors for the resin or other bond utilized
to hold the grains on a grinding or snagging wheel and thereby
increase the strength and life of such a wheel. Further, the shape
may be optimized to increase the particle packing of the grains and
thus increase the volume of grains per wheel. Finally, the present
process allows for very accurate control of the particle size
distribution of the grains produced, and therefor permits the
manufacture of highly reproducible abrasive products from such
grains.
From the foregoing it will be appreciated that virtually any
desired geometric shape of particle may be continuously or
intermittantly reproduced either in a single patterned surface or
in cooperating patterned surfaces, and such particles may be formed
of virtually any desired plastically formable material which
becomes rigid and sets-up after forming, such as by firing or
cooling. Preferably, the particles are formed from green ceramic
material or thermoplastic materials, such as basalts or siliceous
glass compositions, with the latter providing a basis for
transforming the particles into cermets by known metallizing
processes. Such metallizing processes are described in U.S. Pat.
No. 2,702,750, however, we prefer to subject the newly formed
siliceous particles into contact with molten aluminum at about
700.degree.C for about 2 1/2 to 10 hours, for No. 20 to No. 6 grit
sizes, respectively. Although it will be appreciated that operating
parameters may vary over wide limits depending upon the material
being produced, the following specific example is given merely for
purposes of illustration.
A 17.6% MgO-29.7% Al.sub.2 O.sub.3 -9.1% B.sub.2 O.sub.3 -43.6%
SiO.sub.2 glass was melted at 1,650.degree.C and poured at about
1,400.degree.C between a pair of cooperating water cooled stainless
steel forming rolls. Each of the rolls was provided with an
engraved or recessed patterned surface in the form of one half of
an octrahedral impression, and the rolls were then synchronized so
that the patterns on opposing rolls were matched when in contact
with the molten glass at the bite thereof. The rolls were rotated
at approximately 28 RPM and spaced about 0.005 inches apart. The
formed glass ribbon was pulled vertically downwardly from the rolls
and contained small glass octrahedra measuring 0.069 inches from
point to point along an axis extending between opposed apexes
thereof. The octrahedra were separated by a thin web of glass which
laid within a plane bisecting the axis extending between the
apexes. On cooling, the ribbon was easily broken to liberate the
small glass octrahedra which were then collected for further
treatment.
Although we have disclosed the now preferred embodiments of our
invention, it will be apparent to those skilled in the art that
various changes and modifications may be made thereto without
departing from the spirit and scope thereof as defined in the
appended claims.
* * * * *