Note: Descriptions are shown in the official language in which they were submitted.
~6~80~
BACKGROUND OF THE INVENTION
This invention relates to an improved method and
apparatus for extruding articles and to improved products
made thereby. The invention relates more particularly to
the fabrication of an extruded article having a profile as
seen in cross sec~ion which varies along the length of the arti le.
The need exists for elongated articles having a
cross section or pro-Eile which varies along the length of
the article. More particularly, in the field of horticul-
ture, -for example, it is often desirable to provide a means
for staking saplings and young trees with an elongated stake
which exhibits different requirements with respect to the
profile of the stake at different elevations along its lengt~ .
A sapling stake is intended to be inserted into the soil
and to securely form an anchor fox maintaining the sapling
at a prede-termined attitude. A lower segment of the stake
proLile should be tapered to ~acilitate insertion into the
soil, but nearer the surface of the soil it should exhibit
substantial lateral projected area and cross-sectional
dimensions in order to resist lateral displacement in the
soil to establish a firm anchor in the soil and correspond-
ing relatively greater strength, i.e. greater section
modulus, to resist the maximum bending moment which occurs `,
near the soil surface. On the other hand, a resilience or
predetermined flexibility in that segment of the stake above
the soil is desired to enable the sapling to flex somewhat
during its growth under varying atmospheric conditions.
A stake having these differing requirements can be provided
by varying the pro~ile of the sapling s-take along its length
and by Eabricating it oE a material which exhibits a memory
.
ll
-2~ ~ ~
601309 ~ ~
characteristic.
When a sapling is suppor-ted by unduly rigid
stakes, its trunk is not allowed to flex in a natural
manner under wind loads. The resul-t is that the trun~ o~
the tree does not develop proper strength for supporting
itself under heavier wind loads later on in its life. By
suitably tapering the stake a predetermined flexural
resilience is provided which tends to match the natural
flexibility of the tapering trunk o~ the sapling. Thereby,
the sapling is allowed to flex naturally in all directions
under ambient wind conditions. Its trunk develops
appropriate strength, and a healthier young tree results
when the stake support is removed. In addition to sapling
stakes, other articles such as fence posts and the like have
differing profile requirements at different elevations along
their lengths. Further desirable characteris-tics ~or these
articles which are generally maintained outdoors are a
resistance to corrosionl fungus, and to decay.
Prior articles in~ended at least partially to
satisfy these requirements have been fabricated of metal or
of wood. Metal fence post or stake articles have been
formed by the usual well known metal fabricating techniques,
and have been relatively expensive, have not exhibited the
desired resilience, and are subject to corrosion over a
period of time in an ou-tdoor environment. Alternatively,
articles of this type are Eabricated by woodworking techni-
ques and are conventionally o-E uniEorm cross-sectional area,
thus being unmatched to the tapering trunk of a sapling.
They do not provide the desired flexural xesilience and
generally do not exhibit the deslred overall strength and
~.~ LiOt309
we~thering characteristics. Moreover, wood stakes of uni-
form cross-sectional area often do not provide sufficient
lateral projected area at the soil surface and within the
soil. Accordingly, if the soil becomes softened by rain,
the stake may readily become displaced laterally and tilt
over. Furthermore, unless specially treated, they are
readily susceptible to decay and to rotO
. These articles may be formed of thermoplastic
polymer materials which exhibit the desirable memory,
resistance to corrosion and which are not susceptible to
decay, fungus and to rot. ~owever, thermoplastic polymer
articles are generally fabricated by extrusion or by injection
molding. In prior extrusion techniques, a plastic stock
material in plasticized or in a liquid form is forced through
a die having an orifice of fixed dimensions and having a .
desired profile or cross-sectional configuration. The
article thus extruded has a substantially uniform profile
along the entire length of the extruded section.
With respect to injection molding, which
involves high pressures, Eor example, such as 20,000 pounds
per square inch, the fabrication of elongated stake or
fence post articles requires relatively large, strong ex-
pensive dies for injection molding presses. In addition,
it is often not possible to produce some of the articles
by injection molding because of the need fo.r complex, multi-
ple parting lines in the injection molding die to enable
stripping of the product from the molds. Thus, articles
having undercuts or multiple fins, for example,
_4_
~ 9
could not be stripped from the die without damaging the
articles.
Accordingly, it is an object of this invention
to provide a method and apparatus for extruding an elongated
article having a variable profile along its length.
Another object of -this invention is to provide
an elonyated article formed of a polymer plastic and haviny
a variable profile along the length of the article.
Still another object of the invention is to
provide an elongated article o~ the type described haviny
mechanical characteristics of relative rigidity and relative
flexibility at different locations along the length of the
article.
SUMMARY OF THE INVENTION
.
In accordance with eatures of the method of
this invention, an elonga-ted article having a profile which
varies alony the length o ~he article is fabricated by
forcing an extrudate stock material in plasticized or liquid
form through an orifice which is formed by a plurality of
extrusion die members defining an orifice profile. The
position of at least one oE said members is varied while
forcing the stock material through ~he orifice thereby vary-
iny the profile of the orifice and forming an elonyated
ex-trudate having a varying profile which conforms to the
varying profile of the orifice. In accordance with other
features of the method of the invention, the position of a
plurality o the extrusion die members is varied inter-
mittently or continuously in an extrusion cycle duriny which
an elongated extruded article is formed.
~1116U~ 9
In accordance with features of the apparatus
of this nvention, a die block assembly means is provided
having a plurality of die bloc~ members and an extrusion
orifice ormed therein by the members. The orifice has a
periphery establishing an orifice profile which is defined
by edge segments of the plurality of die block members.
A means is provided for forcing an extrudate stock material
through the orifice to form an elongated extrudate article
having a profile conforming to the profile of the orifice.
A means is also provided for automatically varying a position
of an edge segment of at least one of the die block members
for varying the profile of the orifice as the stock material
is forced therethrough. An elongated extrudate article
having a varying profile is thus provided.
In accordance with other features of the
invention, an elongated extrudate article formed o thermo-
plastic polymer material and having a profile which varies
along the length of the article is provided. The article
comprises, for e~ample, a sapling stake, a post or other
similar article which exhibits the desired resistance to
outdoor environment and which is fabricated without the use
of relatively expensive injection molding forms and dies.
Examples of other articles which can be made to
advantage using the present invention are trim strips or
decorative moldings having changing profiles to provide
attractive scalloped, serrated or other formed edges or sur-
faces. Such trim strips may be usecl For home decoration,
both in the interior or exterior~ They may be applied on
613~0~ ~ ~
gable ends, eaves, soffits, and so forth, to provide a
finished appearance. At the present time, such trim strips
and moldings are commercially available as unpainted lengths
of wood which have been machined to shape. The user must
paint and maintain these decorative wood items to resist
weathering. Care in installation to avoid splitting or
breaking away of delicate cross-grain contours is ~equired.
It is among the advantages of the present
invention that such variable profile decoractive trim strips
can be extruded continuously with relatively low tooling
costs in p:re-colored and finished appearance in readiness
to be cut into 8, 10, 12 or 16 foot lengths, as may be
desired for marketing. They are durable and do not require
the maintenance which is associated with wood trim. Further-
more, commercially available wood trim strips and moldings
can exhibit undesired variations in machining techniques from
length-to-length, or even several noticeable changes in
pattern along various regions of the same strip. In marked
distinction to such problems, variable profile extruaate
articles produced in accordance with the present invention
are produced under controlled conditions to provide pre-
determined repeatability of the desired patterns with con~
sistent quality and pre-finished appearance read~ for instal- !
lation.
Other types of ar-ticles which can be produced
to advantage by employing this invention are tapered, mul-ti-
faceted furniture legs, fancy banisters and dowels, and the
like. As compared with wood from which such furniture parts
i and decorative dowels have conventionally been produaed, therej
_7_
1 ~6~09 ~ I
are the same kinds of advanta~es as discussed above oE
consistent quality, durability, attractive pre-finished
appearance and lack of grain. Although such furniture
parts and decorative dowels may be înjection molded in
certain cases, the present invention enables them to be
produced at a lower tooling and lower production costs.
In addition, the present invention enables
changes in variable contouxs and stylized patterns to ~e
made relatively quickly and easily with short 'idown time" and
low changeover costs. Consequentl~, articles of elongated
shape subject to low volume production, runs of multiple
pattern styles, can be produced economically.
BRIEF DESCRIPTION OF THE DRP~WINGS
These and other objects and features of the
invention will become apparent with reference to the follow-
ing specification and to the drawings wherein:
FIGURE 1 is a side elevational view of a
sapling stake of varying profile constructed in accordance
with features of this invention;
-
FIG. 2 is an e~,larged view of a cross section
taken along the lines 2-2 oE FIG. 1, being a cross sec-tion
at an elevation near the sur-face of the earth w'nen -the stake
is ins-talled in use;
FIG. 3 is an enlarged view of a cross section
taken along the lines 3-3 of FIG. 1, being a cross section
at an elevation which is more than half of the way up along
the stake above the location of the section shown in FIG. 2;
FIG. 4 is a front elevational view of a post of
varying profile constructed in accordance with features of
this invention;
FIG. 5 is a side elevational view of the post
of FIG. 4; . .
FIG. 6 is an enlarged view of a cross section
taken along lines 6-6 of FIG. 4;
FIG. 7 is an enlarged view of another. cross
section taken along the lines 7-`7 of FIG. 4;
FIG. 8 is a fragmentary view of a portion of a
die assembly for forming the post of FIG. 4 and constructed
in accordance with the features of this invention;
FIG. 9 is a front elevational view of an
extrusion die constructed in accordance with the features
of this invention and illustrating the die orifice profile
for the stake of FIG. 1 at its maximum profile;
FIG. 10 is a front elevational view, par-tly in
section, of the extrusion die of FIG. 9 and illustrating li
the die orifice profile for the stake of FIG. 1 a-t its .
minimum proEile;
. , ,.
~6~ 9
FIG. 11 is a view taken along the lines 11-11
of FIG. 10;
FIG. 12 is a front elevational view, partly in
section, of an extrusion die constructed in accordance
with an alternative embodiment of the invention;
FIG. 13 is an alternative arrangement for a die
profile actuating means of FIG. 12; and
FIG. 14 illustrates a further alternative
arrangement for a die profile actuating means of FIG. 12.
DETAILED DESCRIPTION
Referring now to FIGS. 1-7, elongated articles
having a varying proile along their length and which are
formed of a polymer plastic are illustrated. The plastic
material used is thermoplastic, as for example high density
polyethylene, polyvin~l chloride, polypropylene, and other
thermoplastic materials can be used having the desired
properties for the particular end use application involved. A
sapling stake 20, shown in FIGS. 1-3, has a varying profile.
For the purpose of this specification and the appended claims,
the term profile means the cross-sectional configuration or
the cross-sectional area of an article. In FIG. 2, the stake
is shown to have a central segment 22 and fin segments 24,
26 and 28 which extend in a radial direction from the
central segment 22. The profile of the stake 20 varies .
from a maximum at a location 30 along its length to minimum
cross-sec-tional areas a-t the location 32 and 34 along its
length. The sapling stake provides desired characteristics,
as enumerated hereinbefore, since it includes a segment
extending from location 30 to 34 which is tapered to facili-
tate insertion into the soil and, at the same time, provides
.
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1~L60:309 ~ ~
substantial strength and rigidity for anchoring the stake
in the soil.
In further explanation, the location 30 is at
an elevation along -the stake when it is ins-talled in the
soil whichis near the surface of the soil. The ~in seg-
ments 24, 26, 28 extend laterally outward and thereby
provide a relatively large pro~ected area as seen fro,m any
lateral direction. This large projected area is embedded
in the soil and strongly resists lateral displacement of the
stake in the soil, even when the soil may be soft or .
spongy after a severe rainstorm. In addition, the section
modulus of the stake 20 has a maximum value at the elevation
30 which is intended to be near the soil su.rface Ik is
at the soil surface wnere the bendiny moment of applied
loads on the installed stake are greatest. Consequently,
the stake 20 advantageously exh.ibits its ma~imum flexural
stiffness and strength where the maximum bending moment is
applied to it.
On the other hand, the profile of the stake
varies continuously providing a continuous tapering leng-th
segment 31 from the location 30 to the location 32 which
is at an elevation more than half of the way up the stake .
from the location 30 of maximum section modulus. This
changing profile provides various lengths of the stake
with a resilient characteristic enabling saplings and other .
larger plants which are secured thereto a degree of flexure
during growth and adverse wea~her conditions.
By virtue o-f -the Eact that the stake 20
tapers over the major por-tion of i.-ts exposed length above
the soil surface from location 30 to location 32, it
ll
1`1
11- j 1,
provides a progressively chan~ing fle~ural resilience which
tends to match the na-tural flexibility of the tapering trunk
of the sapling. As explained above, allowing the trunk of
the sapling to sway naturally under incident wind loads
occurring from day-to-day from the different compass
directions advantageously causes the growing trunk to develop
strength analogous to the result ~hat appropriate exercise
strengthens the li~bs of an animal. Fabrication o the
stake from a stiffly flexible polymer plastic provides a
memory characteristic so that the resilien~ deflec~ion of the
stake length between locations 30 and 35 thereof results in
the restoration of the stake to an undeflected attitude upon
removal oE the deflecting force.
In a particular embodiment, the sapling stake 20
is formed of thermoplastic polymer material, for example
such as translucent polypropylene or high density polyethyl-
ene, and has an overall length of approximately 8-1/2 feet.
The lower portion of the stake varies in profile from the
lower tip 34 to the location 30 of maximum section modulus
and is approximately 18 inches long. The next portion 31
varies in profile from the location 30 to the location 32 and
is approximately 48 inches long. The upper portion 37 from
the location 32 to the top 35 is of constant profile and,
for example may have a length of 36 inches. The fins 24,
26 and 28 along this upper portion 37 may each be notched
slightly to form a set of notches. Such sets of notches
may be provided at several different elevations along the
upper portion 37 to prevent longitudinal slippage of the
cord, -twine, fabric s-trips or bands which may be used to
support a sapling from the stake 20 a-t one or several
elevations along the trunk of the sapling. ~or example,
there may be six sets of such notches spaced approximately
six inches apart in elevation along the upper stake
portion from 32 to 35.
Also, as an illustrative example, the central
segment 22 of the stake is shown as being round in section
having a radius of approximately 3/16ths of an inch. Each
of the fin segments 24, 26 and 28 has a thickness of approxi-
mately 1/4th of an inch. Its outer surface is rounded in a
semi-circle, as seen in FIGS. 2 and 3, which has a radius of
approximately 1/8th of an inch, thereby ~urther protecting
the sapling bark from abrasion or scuffing injury. In FIG.
3, the distance from the axial center of the stake to the
point on the centerline of each fin segment at the outer sur
face thereof is approximately 5/16ths of an inch. In other
words, at the elevations 32 and 34 each of the fin segments
24, 26 and 28 protrude 5/16ths of an inch from the axial
centerline of the stake 20. At the elevation 30 of maximum
cross-sectional area, as shown in FIG. 2, each of the fin
segments protrudes 1/2 of an inch from the axial centerline
of the stake.
Furthermore, this sapling stake 20 is advan-
tageously formed of translucent plastic material, as indicated
above, at least in portions 31 and 37 which are intended to
project above the ground. A tree, particularly a sapling,
tends to grow away from a dark shadow. Thus, when suppor-ted
from a wood stake, or a metal pipe, the sapling -tends to
grow away From the s~pportlng ob~ect This tendency is
-13-
undesirable because the tree starts ou-t growing somewha-t
crooked as a result of the shadow eEfect of the supporting
object, resultiny in a less attractive or weaker tree than
if the trunk were straigh-t and truly vertical. By ~irtue
of the fact that -the stake 20 is translucent, ~or example
having an overall pale, milky appearance, light is allowed
to pass through the stake and shadow e~fects are markedly
lessened, thereby encouraging the supported sappling to grow
straight up along beside a stake which is essentially
"invisible" to the young growing tree.
The fence post 36 of FIGS. 4-7 is similarly
an elongated body having a varying profile, as illustrated
by the differences ln the cross-sectional area o~ the
profile at the location 37 and at the location 38. There is
a tapering length segment of the post 36, as represented
~y that portion of the post extending from the location of
the lower shoulder 39 to its lower tip or distal end 40.
There is also a tapering length segment of the ~ence post
extending from the location of the upper shoulder 44 up to
the location 42. It will also be noted in FIG. 5 that a
fin segment 46 has a serrated configuration. The serratio
48 with intervening teeth enable the positive non-slip
locating and securing o~ the tie wires, fence lines or fence
mesh and the like at desired locations along the length o~
the post.
This fenc~ post has a wide rear ~in segment
.
11 ~6(~'809
41 opposite to the narrow serrated front fin segment 46.
This rear fin segment 41, as seen in FIG. 5, is of uniform
width along its length, except that it tapers from its
shoulder 39 down to the tip 40 ~or ease of driving into
the soil. This taper at the lower end of the uniformly
wide rear fin 41 can readily be formed by cutting a
triangular piece off from this fin after the variable profile
extrusion operation to produce the fence post 36 has~been
completed There are two side fin segments 43 and 45 which
are relati.vely wide in the regions between their shoulders .
39 and 44, as shown also by the cross-sectional configuration
seen in FIG. 6. These wide portions of the fin segments
43 and 45 are intended to be embedded in the soil for provid-
ing a large projected area, as seen in the lateral direction,
to resist displacement of the fence post in the soil even
iE the soil is sotened by rain. Also, the section modulus
of the fence post 36 is greatest in the region between the
shoulders 39 and 44 where the bending moments caused by the
pull of the fence are greatest.
Since both the post 36 and the sapling stake
20 are formed of a polymer plastic, they exhibit a desirable
resistance to deterioration and are not susceptible to decay,
rot, rust, corrosion and fungus although utilized primarily
in outdoor environments. Moreover, the plastic material
provides smooth surfaces which will not splinter to cause
piercing injuries to trees or people and will not corrode . .
or scale of~ to cause rough bumps which injure hands and
create rubbing injury or girdling damage to the tree bark.
~hR plastic material will no-t support insect li~e or
parasites.
61Q9
An apparatus for forming elongated extrudate
articles having a varying profile, such as the stake 20 and
the post 36, is illustrated in FIGS. 8~ As schematically
indicated in FIG. 8, the fence post 36 may be variable
profile extruded by an extrusion oriice 47 defined by a
ixed die block 49 and a plurality of movable die members
51, 53 and 55. The structure and mounting of the movable
die members 51, 53 and 55 and the way in which they may be
moved radially inwardly and outwardly in controlled cycles
will become understood from the following description of
an embodiment of the variable profile extrusion method and
apparatus for producing the sapling stake 20.
A means for provlding an extrudate stock
ma~erial in plasticized or liquid form is provided and is
shown to include a heated extruder barrel 50 (FIG. 11)
and means 52 for feeding the plastic material forward in
the barrel, for example such as an extruder screw which
rotates within the barrel 50. The ex-trudate stock ir~
pellet or powder form is continuously arawn from a hopper
(not shown) into the heated barrel by the action of the
rotating screw 52 where it is heated to plasticized or
liquid form 33 and is forced at high pressure through a
rounded exit port or aperture 54 located at the mouth o the
barrel 50. A heated master die plate 60 is mounted to a
flange 56 ~FIG. 11) surrounding the mouth of the barrel by
screw means 61 which extend through bores 62 in-this flange and engag~
internally -threaded bores 63 in the plate 60. ~he master
die plate 60 includes a throa-t aperture 64, having an axis
65 therein, which is central ~ ~rmecl in the plate and com-
municates with the extruder barrel aperture 54. Extrudatestock material is forced through the aperture 64 and then
through an extrusion orifice, discussed hereinafter.
Since the viscosity oE the stock extrudate
is an important characteristic in -the extrusion process and
is dependent upon its temperature, the master die plate 60
is heated by a plurality of resistance heaters (FIG.'lO)
66, 67, 68, 70, 72 and 74. These are thermos-tatically
controlled in accordance with the desired temperature
of the plate as determined by a temperature sensing element
76 (FIG. lOj. Although a plurality of such temperature
sensing elements will be provided, only one such element is
illustrated for purposes of ,simplifying the drawing.
During an extrusion process, it is also desirable to monitor
the pressure of the extrudate. To this end, a channel 78
(FIG. ll) communicates with the aperture 64 and a pressure
sensing element 80 is positionecl therein which generates an
electrical signal proportional to the extrudate pressure.
The master die plate 60 provides a support for .
variable profile extrusion die means referred to generally
by reference numera]. 90 and for a cam 92. It is to be
noted that the master die plate 60 and associated variable
profile extrusion die means 90 are shown as relatively
massive in structure with a multiplicity of heaters 66, 67,
68, 70, 72 and 74 for providing ample heating capacity. The
relatively massive and well heated structure provides a good
thermal conduc-tivity throughout itself for maintaining all
of the extrusion die parts at essentially the same uniform
temperature. The thick master die plate 60 serves as a
-17-
iL'16~8~)9
backing or mount of good thermal conductivity for the die
means and thereby enhances the desired tendency to maintain
temperature uniformity throughout all die parts affecting
the temperature of the thermoplas-tic material being extruded.
In addition, this relatively massive mounting plate and die
structure 60, 90 of good conductivi-ty provides a thermal fly-
wheel effect which resists varia-tions in locali~ed temperatu
in the thermoplas-tic extrudate. Thus, the termperature
of the plastic material is maintained substantially constant
to achieve good, uniform flow characteristics in spite of
variations from moment-to-moment of volumetric flow through
the die orifice, as occurs with changes in cross section o
the extrudate.
The mounting plate 60 also provides a pivotal
mount for a cylinder support bracket 93 of a pneumatic return
cylinder 96 which serves as a cpring for causing the die
means 90 to follow the motion of the cam 92, as will be
explained. The cam 92 is driven bv a shaft 114 to which
rotary motion is imparted by a motor (not shown) which is
energized in accordance with a predetermined program
for actuating a member of the die extrusion means 90. A
bore 116 is formed in a bracket segment 118 of the plate 60
and a cam shaft rotary bearing 120 is positioned in the bore.
~1L6(J'~9 ~ I
Another bracket segment 122 of the plate 60 supports the
cylinder mounting bracket 93. A spacer pivot moun-t 126,
having a threaded shank 128, is provided for supporting
the cylinder 96 at a spaced apart position Erom the plate 60.
The threaded shank 128 of mount 126 engages an internally
threaded bore 130 formed in the bracket segment 122 while
an opposite end of the mount extends as a pivot throu~gh a
bore 132 (FIGS. 9 and 10~ in the cylinder bracket 93 and
provides a pivotal mounting for this cylinder. Means, such .
as a cap nut or cotter pin (not illustrated) are provided
for maintaining the pivot 126 in engagement with the bore
132.
The extrusion die means 90, referred to here-
inbefore, comprises a plurality of die block members which
form an extrusion oriice. At: least one of the di.e block
members is movable. In FIG. :L0, the die block members are
shown to comprise an annular shaped stationary member 140 anc ~ I
a plurality of movable members 142, 144 and 146. ~he ¦ I
stationary die block member 140 includes a plurality of 1.
radially extending grooves 148, 150 and 152 formed therein
in which the movable members 142, 144 and 146 are positioned
respectively and which provide rectilinear guides for these
members.
The plurality of die block members form an
orifice which is referred to generally by reference number
154 and which has a periphery outlining an orifice profile~
This periphery and the orifice profile are defined by
edge segments 156, 158 and 160 of the sta-tionary die block
39
member 140 and by edge segments 162, 164 and 166 of the
movable die block members 142, 144 and 146, respectively.
The annular stationary die block member 140 includes an
annular flange 16~ (FIG. 11~ extending from a surface 170
and engaging an annular groove 172 formed in the master
die plate 60. The flange 168 and the groove 172 enable
alignment of the stationary die block member 140 with the
plate 60 thereby aligning and locating an axis 180 of the
orifice 154 with the axis 65 of the master aie plate 60.
A means for varying the position of an edge
segment of at least one of -the die block members and thus
the profile of the orifice 154 as stock extrudate material
is forced through this orifice,is provided and includes an
annular shaped actuator ring 191, the cam 92 and its drive,
the cylinder 96, and drive means providi.ng engagement bet-
ween the ring 191 and the movable die mem~er. The actuator
ring 191 is positioned on and rotates about a bearing surface
192 of the stationary die block member 140. A lip 194 formed
in the actuator ring limits axial movement of the ring 191
in a first axial direction relative to the stationary die
block member 154. A cam follower surface 195 (FIG. 10) is
provided on a bracket 196 of the ring and is engaged by
a peripheral surface 198 of the cam 92. The ring also
includes an integrally Formed extending bracket 199 having
a pi.n 200 supported therein -Eor engaging a bore 202 formed
in an end bracket 204 of the piston rod 206.
The s-tationary die block 140, the movable die
block members 142, 144 and 146 located in grooves of the
-20-
~ 80~
stationary die block 140 and the rotary actuator ring 191
comprise a die assembly which is mounted to the master
die plate 60 by an annular shaped retainer ring 208 (FIG. 9)
and a plurality of screws 210-220. These screws extend
through a plurality of bore holes in the plate 208 as exempli
fied in FIG. 11 by the bore 222 through which the screw 210
extends, and through a plurality of corresponding bores in
the stationary die block 140/ as exemplified by the bore 224.
These screws engage a plurality of associated internally
threaded bores in the master die plate 60, as exemplified by
the internally threaded bore 225 in this plate. As shown
in FIG.ll, a peripheral lip 209 on the retainer ring plate
208 overlaps the interior lip 194 of the movable actuator
ring 191 for preventing the ring 191 fro~ moving in the down-
stream direction.
Radial inward and outward movement of the movabl ,
die block members 142, 144 and 146 is effected by rotation
of the actuatox ring 191. The pneumatic cylinder 96 biases
the actuator ring 191 in a clockwise direction as viewed in
FIG. 10 since the cy7inder member bracket 93 is coupled to
the stationary bracket 122 while the piston rod 206 is
coupled to the bracket 199 which is integral with rotatable
ring 191. A pneumatic pressure is initially established
for creating this clockwise bias of the ring 191. As the
cam 92 rota-tes, it forces the cam follower surface 195 and
the ring 191 to rotate in a counterclockwise direction agains t
the biasing pressure wi-thin the cylinder 96. This pressure
maintains the follower surEace 195 against the cam surface
~L~.6~
198 and thereby turns the ring 191 in a clockwise direction
as permitted by motion of the cam surface.
During an extrusion cycle, the movable die
block members are advanced in a radial direction toward
the axis 180 of the orifice 154 thereby varying the oriEice
profile for decreasing the width of the fin segments, as
viewed in FIG. 10, during one portion of an operating cycle,
or are retracted from the axis 180 in a radial direction for
varying the orifice profile for increasing the width of the
fin segments, as viewed in FIG. 9, at another position of the
operating cycle. This movement is effected by rotary motio
of the actuator ring 191. A plurality of grooves 230, 232
and 234 are formed in the actuator ring 191 thereby providin
control cams for controlling the respective positions of the
movable die block members 142, 144, 146, as will be explaine
later.
Each of the movable die block members, as
exemplified by the die block member 144 in FIG. 11, is
generally L-shaped in the radial plane and includes an ori- .
fice forming inner edge segment in the form of a first leg
164 of khe L~shape, and a radially outwardly extending stem
segment 236 forming a second leg of the L-shape. A pin 23~ , .
is press fitted into a bore 240 formed in a lower portion
of the second leg 236 of the L-shape. A roller or bearing
slee-~e 242 is positioned about the pin 238. This assembly
of the pin 238 and the roller bearing 242 extend into the
groove 230 formed in the actua-tor ring 191. Similar cam
follo~er pin and roller assemblies 250, 251, 252, 253 (FIG. 10) æe
posi~oned.in o-~er cam grooves 232 and 234 of the actuator ring. It
can be seen that the grooves 230, 232 and 23~ are each inclined in the
radial direction for providing that the respective ends
of these inclined cam grooves are located at a different
radial distance from the axis lB0 of the orifice. Thus.
upon rotation of the actuator ring 191, the inclined cam
grooves will cause the cam follower asse~blies 238, 242:
250, 251: and 252. 253 of the movable die members to move
in a radial direction with resPect to the axis 180 of the
orifice 154. The edge segments of the movable die b;ock
members are caused to advance or retract correspondingly,
and the profile of the orifice is thereby varied. The
particular movement of the edge segments of the movable die
block members and thus the profile of the orifice will be
determined during an extrusion cycle by the configuration
of the cam 92 and by the configuration of the cam grooves
230, 232 and 234.
As seen in E'IG. 11 t the fixed die block 140 has
a streamlined convergent entry region 255 extending downstrea n
from -the entry face of orifice 154. Similarly, each of the
movable die block members, as exemplified by the movable die
block member 144, has a streamlined convergent entry region
257 extending downstream from this entry face. These stream _
lined convergent regions 255 and 257 guide the extruding
plastic material 259 to flow unimpeded into the die orifice
154 without upstream disturbances.
As shown in FIG. 11, in order to allow for -the
escape of any plastic material which may force itself out-
wardly along the outwardly extending side surfaces of the
stem portion 236 of the movable die block member 144, there
is a small bleed port 263 in the retainer cover ring plate
~1~6(~309
208. This bleed port 263 communicates with the clearance
space 261 outside of the inner segment 164 of the movable
die block member 144. Similar bleed ports 263 (as seen in
FIG. 9) are provided for the corresponding clearance spaces
of the other rnovable die block members 142 and 146. A small
amount of plastic material 259 can be seen issuing from the
bleed port 263.
For producing the sapling stake 20, an
extrusion cycle will be completed after the cam 92 makes
one full revolution. During this movement of the cam, the
extruder screw 52 is continuously Eorcing stock extrudate
material in plasticized or liquid form from the extruder
barrel 58, through the maste~ clie plate aperture 64 and
through the orifice 154. An elongated article having a cross sectior al
profile corresponding to the pro-Eile of the orifice 154, as
it is varied during the cycle~ will thus be extruded through
the orifice 154. An elongated article having a varying
profile along its length is thereby provided during one
extrusion cycle. Extrusion is generally continuous and a
plurality of articles will thus be formed, which can sub-
sequently be cu-t one from another to complete the finished
article.
~ n addition to the apparatus illustrated in
FIGS. 9, 10 and 11 of the drawings Eor providing the
extruda-te article r various other known means employed in an
extrusion apparatus including extrudate stock hopper, heat-
ing means for the extruder barrel, cooling ba-th means for
the ex-trudate, and extrudate puller means which are well
known in the extrusion ar-ts are employed but are not il~us-
trated Eor purpose of simplif~ing the drawings and the
description thereof.
The variable proile extrusion method and
apparatus thus described exhibi-ts several advantages.
In addition to providing the desired variable profile for
an extruded article, the assembly of dies, actuator ring
and cam is readily mounted and demounted for substituting
various different arrangements o-E die members in oraer to
effect various different profile configurations. It will
be noted from the drawings that the rotary actuator ring,
the stationary and movable die block members, and the cam
can be readily demounted by the steps of disengaging the
mounting screws 210-220 and the piston rod from the pin 200.
Thus, the apparatus described is versatile in that various
die block members adapted to provide desired profiles can be
readily substituted.
FIG. 12 illustral:es an alternative means for
rotating an actuator ring 299 during an extrusion cycle.
As can be seen from FIG~ 12, the profile of the article bein
extruded has a T-shaped configuration. The T-shaped profil
can be altered in that the length of the stem fin segment
300 can be varied by movement of a die block member 302,
while the thickness 304 of the head of the T can be altered
by movement of the die block member 306. The die block
member 302 is actuated by a cam follower assembly 308
located in an inclined cam groove 310. This cam follower
assembly 308 is similar to the cam follower assemblies 238,
242; 250, 251; and 252l 253 shown most clearly in FIG. 10.
The movable die block member 306 is actuated by movement
~l~6~
of two cam follower assemblies 312 and 314 which extend into
a pair of identical inclined cam grooves 316 and 318, res-
pectively. Because of the relatively large radial forces
exerted during the extrusion process on the relatively large
die surface 307 of the movable die block member 306, this
movable die block member is provided with the dual cam follo _
er assemblies 312 and 314 acting in concert for transmitting
the actuating force to this member at two separate places
spanned across its relatively large width.
It is to be understood that the movable die
block members 302 and 306 cooperate with the stationary
die block member 140A in a manner analogous to tha-t shown
and descr:ibed in detail in conjunction with FIG. 9. The
machine screws 210-218 serve to secure the variable profile
die means 90A to a corresponding master die plate 239 which
is generally similar to the master die plate 60 as shown in
FIG. 11. The variable proile die orifice 154A communi-
cates with an aperture corresponding to the aperature 64
~FIG. 111.
In FIGS. 9-11, movement of the actuator ring
191 was effected by the mechanical transmission of an
actuating torque to the ring 191 from the cam 92 via the cam
follower surface 195 while the restoring toxque on this ring
was provided by the pneumatic cylinder 96 acting on a movabl
arm 199.
In FIG. 12, rotary movement of the actuator
riny 299 during an extrusion cycle is accomplished by
hydraulic cylinders 320 and 322, a spring loaded hydraulic
:~16~9
tracer valve 324 which is mounted on and rotated with the
ring 299 and by a cam 325. Brackets 326 and 328 of the
hydraulic cylinders 320 and 322, respectively, are pivotal-
ly mounted to a mas-ter die plate 329 by pins 330 and 332,
respectively. Piston rods 334 and 336 are coupled to
bracket segments 338 and 340 of the actuator ring 299 by
pins 342 and 344, respectively. The piston rods are
coupled to the ring 299 at di-fferent,circumferential
locations in push-pull tor~ue relationship for producing
a powerful driving torque on the rotary ring i~ eaeh res-
pec-tive direetion when the hydraulie cylinders 320 and 322
are appropria-tely pressurized.
An hydraulic fluid 350 is supplied from a
reservoir 352 via a pump 35~ and a eonduit 356 to -the traeer
valve 324. A hand operated by-pass pressure-relief valve
355 is provided in parallel circuit relationship with the
pump 354 for relieving any exeess pressure which might occur
downstream of the pump. The tracer valve 324 whieh is
actuated by the cam 325 distribu-tes the hydraulic fluid 350
under pressure through a conduit 358 for causing elockwise
rotation of the ring 299, as viewed in FIG. 12l or to a eon-
duit 360 for eausing counterclockwise rotation of the ring.
The hydraulie fluid under pressure in the conduit 358 is
coupled to the hydraulic eylinders 320 and 322 by Elexible
braneh lines 361 and 359 for causing extension of the piston
334 from the cylinder 320 and simultaneous retraction of
the piston 336 into the cylinder 322, thus providing a
power~ul push-pull effec-t in exerting clockwise. torque
on the rotatable ring 299. Sim,ilarly, the hydraulic fluid
~l~L6l~8~9 ~ ~
under pressure in -the conduit 360 is distributed -to the
cylinders 320 and 322 by flexible branch lines 363 and 365
for causing retraction of the piston 334 into t~e cylinder
320 and extension of the ?iston rod 336 from the cylinder as
illustrated in FIG. 12. Thus, powerful counterclockwise
torque is exerted on the rota~.able ring 299.
The use of dual hydraulic cylinder means for
actuation of the ring 299 enables the application of relative _
ly higher die actuation forces than is provided with the
cam drive arrangement of FIGS. 9-11. It also results in
balancing the torque forces being applied on the opposite
sides of this ring and the reaction forces of the driven
cam follower assemblies 308, 312 and 314, thereby minimizing
frictional effects during the actuation of the movable die
members in a variable profile extrusion process.
The advantageous actuation of the hydraulic
cylinders through the use of a control cam 325 which is not
bearing any significant load and a tracer roller 362 oper
ating the tracer (or servo) valve 324 enables relatively l,
abrupt changes in cylinder control motion and rapid changes
in the profile o extruded articles. The cam 325 may be
rotated by any convenient source of rotary motion applied to
its shaft 367 which is journalled in a bracket 369 on the
master die plate 329. The spring 371 in the tracer valve 324 ll
biases the valve spool plunger 373 toward the right in FIG. ,.
12 and maintains the follower roller 362 in contact with the
revolving cam surface 325.
Thus, when the valve spool 373 moves to the
j ight oF its neutral pos~tion, it causes the hydraulic
-28-
8~g
cylinders 320 and 322 to produce clockwise rotation of the
actuator ring 299. When the valve spool is in its neutral
position, it causes the actuator ring 299 to be held
temporarily stationary. When it moves to the left of
neutral position, it produces countercloc~wise rotation of
the actuation ring.
The hydraulic fluid returns through either of
the conduits 358 or 360, as the case may be, and is discharg~ d
through a valve passage 375 and a line 377 returning to the
reservoir 352.
It is to be notecl that the tracer valve 32~ is
mounted on a brac~et 379 e~tending from the periphery of the
rotatable ring 299. Therefore, the movement of the valve
spool plunger relative to the housiny o the tracer valve
324 is a resultant of the action of the cam 325 plùs the
action of the movable bracket 379. Consequently, fairl~
rapid and complex variations in profile of the orifice 154A
can conveniently be produced.
At times it may be desirable to provide even
more rapid changes in positioning o~ the actuating ring 299.
While the arrangement of FIG. 12 enhances such movement,
relatively quick changes in the position o~ the actuating
ring are limited to some extent by the ability o~ the
tracer roller 362 to ollow the pro~ile and ramp angles of
the control cam 325. In FIG. 13, there is illustrated
an apparatus for further multiplying and amplifying the
ampli~ude and slopes of the cam con~iguration with a
tracer valve mechanical lever linkage ~hich accomplishes
relatively quicker and multiplied response of the actuator
ring 299 for very rapidly varying the profile of the extruder
die.
In FIG. 12, the tracer valve 324 is supported
on an arm 379 on the actuator ring 299 and was transported .
therewith during its rotary motion, as discussed above.
In the arrangement of FIG. 13, the tracer valve 324 is .
supported on a lever arm 364 of a lever system 366 forming
a me~hanical linkage for coupling the tracer valve in an
articulated manner to the periphery of the rotatable ring
299. This arm 364 is pivotally supported by a fixed pivot .
368 at an elbow region 370 of the lever linkage 366. A
coupling slot 372 is formed at the end of another longer arm
374 of the lever 366, and a pin 376 which is secured to a
bracket 378 near the periphery of the ring 299 engages in the
slot 372.
Thus, relatively small movements of the servo
valve 324 cause mechanically multiplied movements of the
rota-table actuator ring 299, depending upon the relative
lengths of the two lever arms 364 and 37~. The servo
valve plunger 373 is advantageously enabled to follow the
cam profile in sp.te of relatively rapid or abrupt movements
of the actuator ring 299. Moreover, the angular attitude
of the axis of the valve plunger 373 relative to the axis
of the cam shaft 367 changes as the arm 364 swings about the
pivot 368 for providing various control effects. As a
result, the tracer valve i5 permitted to accomplish relatively
more complex, varied higher speed and larger amplitude control
actions in p:roducing the resul-tant movement of the extrusion
die members and accordingly to provide relatively more
abrupt, repeatable and complex variations in the article
profile as desired.
At times, a linear cam profile rather -than an
annular cam profile may be desired for actuating the tracer
valve 324. FIG. 14 illustrates an arrangement for linear
actuation of this valve. A longitudinally movable cam
plate 380 is provided having a first ramp 382 of relatively
steep slope and a second ramp 384 of relatively less steep
slope. The tracer roller 362 is maintained in engagement
with the edge 385 of the cam plate which is reciprocated
within a track or groove 386 of a fixed support frame 388.
The linear cam plate 380 is actuated by a pis-ton rod 390 of
a pneumatic cylinder 392 mounted on the support 388.
This linear cam arrangement can be used to
provide the same general pattern of variable profile
extrusion as the annular cams of FIGS. 9-13. The ramp
segments 382 and 384 can be adapted to have equivalent
profiles, if desired, in which case the cam plate 380 can
be reciprocated in opposite directions at the same rate to
provide the same variable profile. In other words, each
extension and each retraction of the piston rod 3~0 can be
arranged to produce a complete operating cycle, if desired~
If it is desired to produce two lengths of
elongated articles having the same relative proportions in
the same production run, the cam plate 380 can be driven
back and -forth in opposite directions at different speeds.
Thus, an alternating sequence of relatively longer and short-
er articles oE varying profile are produced as a continuous l,
extrusion. They are then cut apart from each other and
are ready for marketing.
io~og
There has thus been described an improvedmethod and apparatus for fabricating an improved elongated
extruded article of variable profile. Althouc3h particular
embodiments of the invention have been described herein,
it will be apparent to those skilled in the art that
variations may be made thereto without departiny from the
spirit of the invention and the scope of the appended
claims.
It is to be understood that when using the motio
amplifying lever linkage 366 on FIG. 13 7 the hydraulic con- ¦
nection for causing retraction and extension of the piston
rods 334 an~ 336 are reversed from those as shown in FIG. 12;
so that the valve 324 will continue to operate as a servo
valve. Thus, when the valve spool 373 moves to the right
of its neutral position in FIG. 13, it produces counterclock
wise rotation of the actuator ring 299, thereby causing the
lever arm 364 and the valve 324 to move toward the right..
When the valve spool 373 is in its neutral posit1on, it caus~
the actuator ring to be held temporarily stationary. When
it moves ~o the left of its neutral position, it
produces c].ockwise rotation of the actuator ring, thereby
ca~sinc3 the lever arm 364 and the valve 324 to move toward
the left. The movement of the servo valve 324 is much less
than the multiplied movement of the actuator ring 299.
If desired, a lever system similar to that show~
in FIG. 13 can be employed for moving the servo valve 324 in
FIG. 14. The connection to the hydraulic cylinde.rs should
always be such that the valve 324 in FIG. 14 will operate
as a servo valve. Thus, when the cam :Eollower 326 moves to.
the ric3ht oE i-ts neutral position in FIG. 14, the servo
valve 324 should move to the ri~ht, and vice vexsa.
