Note: Descriptions are shown in the official language in which they were submitted.
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Backqround Of The Inventlon
The present invention relates to briq~etting ma-
chines and, in particular, to briquetting rolls and removable
segments therefore
Briquetting machines are known devices which gener-
ally comprise a pair of wheel-like rolls geared together to
cooperatively turn in opposing directions on parallel axes
with ~he peripheral surfaces of each respective roll posi-
tioned in linear axial alignment with one another so that
material introduced to the rolls is captured by the molding
surfaces of the rolls and compressed into briquets by passage
through the adjoining molding surfaces.
Briquetting apparatus and techniques have been used
to compact and/or mold materials at both low temperatures and
pressures as well as high temperatures and pressures for mate-
rials such as charcoal, iron ore, metal chips, ekc. Gener-
ally, high pressure briquetting at elevated temperatuees places
additional demands upon the commonly employed rotary molds.
In particular, rotary mold segments are subject to cracks
from stress and to wear due to rocking and abrasion of the
mold surface by the material to be molded.
It has been recognized that briquetting roll designs
incorporating replaceable mold segments should permit easy
removal and replacement of worn or broken segments with as
little down time as possiblè. Also, inexpensive fabrication
of durable segments which may be firmly secured in proper
alignment are long known goals of segment design. The use of
rolls comprised in part of a plurality of replaceable mold
segments having surface cavities capable of receiving mate-
rial to be briquetted is described in many prior art patents
ncluding U.S. Patent Nos. 3,907,485; 4,306,846; and 4,097,215.
U.S. Patent No~ 3,907,485 describes replaceable
mold segments adapted for placement upon the periphery of a
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cylindrical central member. These mold segments are affixed
to the cyl;ndrical central member by fasteners engaging pro-
jections extending outwardly from the side walls of the mold
segment. This configuration of the mold seqment cooperates
with the central member such that radial compression forces
applied to the mold segment are transmitted through the bot-
tom surface of the mold segment, which bottom surface is co-
planar with the projections from the side walls. The appli-
cation of such forces to the mold segments produces bending
stresses in the mold segment that can result in premature
failure due to cracking of the strong part brittle mold seg-
ment.
V.S. Patent No. 4,306,846 describes the use of a
symmetrically shaped replaceable mold segment for a briquett-
ing roll. These segments have side walls including upper and
lower portions, the upper portions of which are disposed at
an angle convergent with respect to a top working surface,
and the lower portions of said side walls are divergent with
respect to the axis of rotation of the rolls.
U.S. Patent No. 4,097,215 describes a briquetting
press roll which comprisés a cylindrical core having a regular
polygonal cross-section and a plurality of equal planar sec-
tions around its peripheral surface to which are attached a
plurality of removable mold segments each having a flat bot-
tom surface with said segments being attached by retaining
rings.
Thus, prior art processes, techniques, and apparatus
have been employed with varying degrees of success to alleviate
the foregoing problems relating to premature failure or wear
of roll segments. Some prior art devices go to great lengths
to overcome these wear and cracking problems. For example,
U.S. Patent No. 2,9~8,902 describes the use o~ exchangeable
segments which when a~ttàched to a briquetting rcll are aligned
so that the separation ga~p between segments forms an acute
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angle with cylinder generatrices which are parallel to the
roller axis. The foregoing arrangement purportedly reduces
wear by reduction of non-uniform forces clue to overlapping
separation ~aps (Col. 1, lines 25-67). This device has the
disadvantage of high machining costs due to it complicated
design as best illustrated in Figures 2, 3, 11 and 14.
As mentioned abo~e, prior art segments suffer from
wear due to rocking of the segment in its seatO This movement
of a segment with respect to its seat occurs as a force tra-
vels across the arcua~e molding surface of the segment causing
the segment to pivot due to aberrations in surface contact.
Since this rocking movément causes undesirable wear, attempts
are made to minimize rocking in order to prolong segment life.
One way to minimize rocking is to reduce the surface aberra-
tions which act as "pivot points" for rocking. Machining of
contact surfaces between segment and core seat will reduce
rocking. Advantageously, the present invention reduces ma-
chining time and costs by allowing machining of flat surfaces
which include at least one right angle between two flat planar
surfaces. Use of a right angle allows utilization of uncom-
plicated fixtures in the machining process. Simplifiçation
of machining is especiaiiy desired to lower the time and cost
of such operations in those countries having high labor costs.
SUMMARY OF THE INVENTION
Xt is an objec~ of the present invention to provide
replaceable mold segments having improved duraDility.
A further ob~ect of this invention is to provide
segments resistant to wear, especially wear caused by rocking.
A further object of the present invention is to
provide segments which are easy and economical to machine.
A further objedt of the invention is to provide a
design which reduces mac~ining costs while maintaining or
improving durability and wear resistance~
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A further object of this invention is to provide a
briquetting roll with easy-to-replace mold segments of econom-
ical design.
A further object of this invention is to provide a
keyless segment/core combination which resists wear and break-
age from rotational forces through a sawtooth core design.
The foregoing objects and others which will become appar-
ent from that which follows are achieved in a rotary mold
segment which comprises a top arcuate molding surface, a bot-
tom surface, two opposing end walls connecting this top sur-
face and this bottom surface whereby said segment further
having a connection between one end wall with the bottom sur-
face which defines an angle of from about 80 to 90 degrees,
and further comprising two opposing side walls connecting the
respective sides of thè top, bottom and end walls.
A preferred embodiment comprises a rotary mold seg-
ment of truncated sectorial shape (hereinafter "right angle
preferred embodimentn) which segment comprises a top arcuate
molding surface~ a bottom surface, two opposing end walls
connecting the top surface and this bottom surface whereby
said connections define a riqht angle with respect to a line
drawn tangent to the arcuate top surface at each respective
connecting end, and sai~ segment further having a connection
between one end wall with the bottom surface which defines a
right angle, and furthér comprising two opposing side walls
connecting the respectivé sides of the top, bottom and end
walls.
By the term "a line drawn tangent to the arcuate
surface at each respecti~e connecting end" is meant the tangent
line at that end po~int prèsuming a continuation of preceding
arcuate curve. It is nio~ necessary that each and every object
listed above be found i~ aII embodiments of the invention~
It is sufficient that t~é invention may be advantageously
employed when compared t~ thé prior art.
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The present invention also comprises a r~tary mold
having a roll shaft with a core portion adapted to receive
the plurality o removable mold segments and fastening means
for removably attaching mold segments to said core and a plur-
ality of the above-described mold segmentsO Fundamental to
the instant invention is the design of a replaceable mold
segment having an angle from about 80 to '30 degrees between
the generally planar bottom surface and the longer end wall
of said segment.
Each mold segment comprises a body having a bottom
planar surface which mates with a corresponding surface on
the sawtooth shaped core portion of a roll shaft. In the
preferred embodiment, the bottom right angular surface formed
by one end wall with the bottom portion of the segment mates
with the corresponding right angular L-shaped peripheral por-
tion of the core surfaces.
BRIEF DESCP~IPTION OF THE DRAWINGS
Figure 1 is a plan view of a roll shaft and segment
construction characterized by the features of this invention;
Figure 2 is an end elevation of the roll shaft taken
about the line 2-2 of Figure 1 with a partial broken away
area showing screw placement
-- Figure 3 is a sectional view taken about the line
3-3 of Figure l; and,
Figure 4 is an exploded fragmentary perspective
view depicting fastening of individual segments to the roll
core of Figure 1.
DETAILED DESCRIPTION OF THE INVENTION
Referring to Figure 1, a rotary mold 10 suitable
for use with a second similar rotary mold according to known
techniques in a briquettin~ machine ~not shown) is depicted.
The rotary mold 10 comprises a roll shaft 11 adapted for rota-
tion within a briquetting machine in coaxial alignment with a
similar roll shaft, both of whlch shafts possessing a plural-
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ity of mold segments 12 positioned about the periphery of aroll core 13 which is integral with said shaft 11~ Also
integral with said roll core is roll radius 14a and roll core
radius 14b. Shaft 11 al60 contains bearing cone surfaces 15a
and 15b positioned on either side of said roll core 13. Roll
shaft 11 may be equipped with access means 16 for temperature
control.
Each rotary mold segment 12 contains three complete
mold cavities 17 and two separate cavity halves 18, at either
end of each segment 12. Each segment member is adapted to
cooperate with a segment member adjacent thereto in forming a
complete mold cavity in the assembled roll. Thus, each segment
member in Figure 1 has three complete mold cavities formed in
the center and has half pockets formed thereon at the ends.
The present invention contemplates the use of differing
numbers of mold cavities and designs, e.g. more than one row
of mold cavities could be provided, or blank segments without
molds or segments having different or varying shapes. Mold
cavities may be either completely contained within each seg-
ment or not according to design needs. Advantageously, a
roIl comprising a plurality of segments made according to the
present invention may contain 12 to 16 segments. The use of
12 segments provides a reduction in the number of machining
operations and allows stronger fastenin~ of segments to the
roll core, while the use of 16 segments allows reduced costs
with respect to modifying present roll cores and for produc-
tion of segments from readily available stock materials. Of
course, fewer than 12 or greater than 16 segments may also be
employed, depending upon roll size. Rolls of any diameter
are contemplated.
Referring now to Figure 2, an end eleva~ional view
of rotary mold 10 including roll shaft 11 taken about line
2-2 of Figure 1 is depict d. Roll shaft 11 supports roll
core 13 about which are attached twelve roll mold segments 12
which are removably attached by fastening means such as sunken
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screws 19 treated with a suitable lubricant such as a solid
film molybedenum disulfide lubricant known as Molykote (not
shown).
Each segment 12 comprises two end walls 20 and 21
connecting a top arcuate working surface 22 with a bottom
surface 23. In the right angle preferred embodiment, each
end wall 20 and 21 is coplanar with axia'Lly disposed planes
24a and 24b which extend from the axis of rotation 25 to ro-
tar mold perimeter 26. Thus the angle ~ between said planes
24a and 24b which may define the location of said end walls
20 and 21 i5 app~oximately 30 degrees for a twelve-segmented
rotary mold. Of course, angle ~ may vary to accommodate a
greater or fewer number of segments. By use of the term ap-
proximate is meant an angle sufficient to create the segment
size desired for the particular roll core.
The skilled artisan upon reading this disclosure
will understand that the precise angle will vary, not only
upon the number of segments to be emp~oyed in forming periph-
eral arcuate surface 26, but also upon such application depend-
ent variables as: the desired degree of machining of end
walls 20 and 21; necessary tolerances between segments to
allow the desired degree of ease of attachment and removal,
space necessary for thermal expansion and/or constriction
(oper~ting temperatures may vary depending upon--other design
variables), etc.
By remachining is meant the process whereby working
surface 22 may be machined to re-obtain a sharp ~old cavity
periphery thereby extending the useful lif~ of the segment
12. Remachining will remove aberrations in the working sur-
face 22 of segments 12 and thereby reduce the diameter of the
rotary mold. Some excess material may be left on the segment
working surface initially (before first use) to allow for
remachining after wear from operation.
Generally, the segments wil be constructed of a
wear-resistant metal such as steel. The particular material
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used to construct the segments 12 will depend pri~arily upon
the intended applications for the particular rotary mold.
Generally, steels and irons havinq application-dependent com-
positions will be employed.
End walls 20 and 21 may also be defined or the
right angle preferred embodiment by reference to imaginary
lines drawn tangent to the top arcuate surface 22 at each
point 27a connecting top surface 22 to either end wall 20 and
21. Two such tangent lines 28 and 29 form right angles ~
with each respective end wall 20, 21. Thus, the connections
27a between each end wall 20, 21 with the top arcuate surface
22 defines a right angle with respect to a line 2~ drawn tan-
gent to the arcuate top surface 22 at each respective end 20,
21.
Furthermore, for all embodiments, segment 12 may be
defined by a ratio of the length of the longer end wall 21 to
the length of the shorter end wall 20 and the angle between
the longer end wall 21 and the bottom surface 23. A suitable
range of such e~ld length ratios is 22:16 to 17:6; with a pre-
ferred range being 18:11 to 16:9. As further depicted in
Figure 2, the connection 27b between end wall 21 and bottom
surface 23 forms an angle ~ . A suitable range for~ would
be from about 80 to about 90 degrees. It is believed that
when '-~"'I'S 90 degrees or less, then tipping or rotational action
about the corner forming the angle is reduced.
Advantageously, when ~ is a right angle, this facili-
tates machining o~ segment surfaces thereby reducing machining
costs. Roll core 13 and attached segments 12 will rotate
during normal operation in the direction sh~wn by arrow A.
Advantageously, the indicated direction of rotation in combina-
tion with the design of the segments 12 and segment attachment
to the roll core 13 is believed to reduce wear due to rocking.
Also, the novel segment is adapted to withstand rotational
forces ~resented as the roll mo~es from the shorter segment
end to the longer segment ends,
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The sawtooth design of the perimeter of roll core
13 resists rotational forces exerted against the segments 12
relative to core 13. The torque produced during acceleration,
deceleration and use of the rotary mold operates to cause the
segments to slip rela~ive to the core perimeter. In the pres-
ent invention, this "slippage~ is counteracted by the saw-
tooth design which, when the mold is rotated as indicated, is
believed to decrease wear while providing a substantially
flat bottom surface without necessitating the use of keys or
other core and/or segment weakening grooves.
-The mating roll which runs adjacent to the roll
depicted will be adapted to rotate in a clockwise direction
since roll 11 is shown rotating in a counterclockwise direc-
tion. However, it should be understood that both rolls will
rotate in the direction shown by arrow A with respect to the
positioning of the segments, i.e., while both rolls will turn
in opposite direction on parallel axes, nonetheless, the seg~
ments on each roll will be positioned so that as each sepa-
rate segment passes a chosen point during rotation, the shorter
end surface of the segment will pass that point first. Rever-
sal of the direction of rotation depicted will normally occur
only after unloading in order to remove a jam or plug and
then only for a short time.
~~ Referring now-~o Figure 3, rotary mold segment 12
and roll core 13 are shown in a sectional view taken about
the line 3-3 of Figure 1. Segment 12 has a top surace 22
(with raised mold cavity 17) connected to bottom surface 23
by side walls 30 and 31. Segment 12 is attached to planar
core surface 32 in substantial coplanar alignment by a plural-
ity of threaded screws 19, which are recessed below surface
22 and removably secured to core 13 through a plurality of
holes 33a adapted to removably receive, align, and secure
together segment 12 with core 13. Advantageously, at least a
~portion of the holes 33a which extend into core 13 are threaded
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for connection with screws 19. Alternative attachment means
or removably fastening segme~s ~o a roll, which means are
well known in the art, sueh as clamp rings, may also be em-
ployed.
Referring now to Figure 4, an exploded fragmentary
perspective view depic~ing attachment of a segment 12 having
a top surface 22 with raised mold cavity 17, side wall 31 and
end wall 21 connected so that wall 21 forms an angle ~ with
bottom surface 23. Four holes 33a extencl from top surface 2
through an otherwise solid segment body 12 through bottom
surface 230 ~hese holes 33a align with threaded holes 33b in
roll core surface 32. Holes 33b extend a sufficient distance
below surface 32 to provide adequate securing of segment 12
to core 13 when segment 12 is seeured to core 13 by threaded
screws l9a and l9b. Serews l9a whieh seeure segment 12
through a lesser segment thickness (sueh as that nearer side
20) and screws l9b (which are loeated nearer longer segment
side 21) may be of lesser and greater length, respeetively,
to avoid weakening of the eore roll by intersection of holes
33b between adjaeent core surfaces 32.
It will be understood that various changes and modi-
fications may be made in the segment and mold described ~whieh
provide the characteristics of the invention) without depart-
ing from the spirit thereof particuarly~as defined in the .
following claims.
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