Adjustable die mechanism

An adjustable die mechanism (10) for extruding a profiled strip of plastic or elastomeric material wherein a plurality of adjacent segments (44) is located upstream and in spaced relation from a final extrusion die assembly (32), having a predetermined profiled opening (38), with this plurality of segments (44) being mounted for individual and independent adjustment thereof, each segment having one end (46) capable of extending into the extrudate flow channel (26). Means for actuating (64) move the segments (44) relative to the profiled opening (38) in a predetermined manner such that moving the segments (44) into the profiled opening (38) modifies the flow of the extrudate material downstream of the segments (44) as the profiled strip emerges from the die assembly (32). The die mechanism includes control means (82) for selectively operating the means for moving the segments so as to produce a strip of material having the desired characteristics.

TECHNICAL FIELD 
The field of art to which this invention pertains is that of adjustable die 
mechanisms for extruding profiled strips of plastic or elastomeric 
material, specifically profiled extrusion dies with adjustable upstream 
segments. 
In the rubber industry, particularly in the tire industry, it is quite 
common to utilize profiled extrusion dies for producing elastomeric tire 
components such as tire treads used in the manufacture of pneumatic tires. 
The set up for extruding a profiled shape of elastomeric material is a 
costly process, since the desired extrusion has to have both the correct 
shape or profile as well as weight. Generally, several die trials with 
recutting or reshaping of the die are often necessary. During these 
trials, the extrudate is usually scrapped and must then be reworked into 
the process. Similar problems generally also occur when a previously-run 
die is utilized and the operator at each run must still adjust equipment 
speeds until dimensionally correct on-weight profiles are obtained. 
There are many problems that occur in this type of an operation because 
profile variations can also be caused by the extrusion process or the 
material being extruded. For example, day-to-day line variations require 
different equipment speed settings with the same production die. 
Similarly, because of unbalances in the extruder die head, non-symmetrical 
dies may even be required to obtain a symmetrical profile. Stock 
variations and temperature variations also can cause dimensional and 
weight changes during a production run. 
BACKGROUND ART 
U.S. Pat. No. 2,720,679 to Ratliff, discloses a plurality of dam segments 
that may be individually adjusted so as to provide the desired cross 
sectional contour of the tire tread being extruded. However, FIG. 6 
discloses that the variable dam segments are not disposed upstream from 
the final die, but in fact, form the final die. A similar die wherein 
again the adjustable extrusion die appears to be the final die is shown in 
U.S. Pat. No. 3,195,183 to Phillips. 
U.S. Pat. No. 3,323,169 to Vitellaro also discloses a plurality of dam 
segments which may be adjusted independently with this adjustment being 
carried out via a motorized adjusting means. 
U.S. Pat. No. 3,884,611 to Anderson, et al., discloses an extrusion die 
wherein a section of the die is thin-walled in construction and extends 
across the width of the flow channel prior to the outlet from the die. An 
adjusting mechanism is operative to decrease the cross sectional dimension 
across a pre-land area by flexing or distorting the thin-walled segment. 
U.S. Pat. Nos. 3,940,221 to Nissel and 4,125,350 to Brown are cited for 
their showing of a controllable die lip so as to control both the position 
and size of the die lip, with the patent to Nissel further disclosing a 
control and measuring apparatus. 
U.S. Pat. No. 3,870,453 to Howard is cited for its disclosure of an 
adjustment mechanism for an extruder die having an adjustable and a 
movable die portion. 
U.S. Pat. No. 3,830,610 to Ohkawa, et al., discloses an adjustable contour 
die having a plurality of vertically adjustable individual upper die 
sheets for achieving specific contours and a control system for effecting 
same. 
DISCLOSURE OF THE INVENTION 
The present invention provides a solution to the prior art problems 
pertaining to the profiled extrusion of elastomeric materials by utilizing 
a variable preform die upstream and in spaced relation from the normal 
extrusion die assembly. 
This preform die takes the form of a series or pluralities of adjacent 
segments that are mounted for individual and independent adjustment 
thereof wherein each segment has an end capable of extending into the 
extrudate channel and thus into the strip of material being extruded. 
The present invention includes means for moving these segments relative to 
a profiled opening in the final extrusion die assembly in such a 
predetermined manner that moving the segments into the projection of the 
profiled opening modifies the flow of the extrudate material downstream of 
the segment as the material emerges from the die assembly. 
The present invention further includes control means for selectively 
operating the means for moving the segments, thereby producing a strip of 
plastic material having the desired characteristics, wherein this desired 
characteristic may be strip profile, weight and/or mass. 
The present invention also includes a plurality of various control means 
for monitoring, checking, correcting and implementing control strategies 
to produce materials having the desired characteristics. 
The placement of the adjustable segments upstream of the fixed die modifies 
the flow of the extrudate to the final die assembly and thus the final 
extrudate characteristics. The use of the final extrusion die assembly 
downstream from the adjustable segments eliminates the discreet steps on 
the profile and the possible consequent curing defects which could be 
caused by such steps. 
The adjustable die mechanism of the present invention compensates, to a 
large extent, for the everyday variables present in most extrusion process 
systems. The benefits achieved include better profile uniformity, 
resulting in better final product uniformity; material and energy savings 
by target shifting to the light side of gauges and weight; reducing or 
eliminating die tryouts; as well as achieving higher productivity. In 
addition, extrusion die making can be simplified and use of the present 
invention may possibly even lead to the mechanization of die making. For 
example, the final die can be made to produce approximately the desired 
extrusion with the movable segments adjusted to the mid position, such 
that raising or lowering individual segments, or a combination of them, 
will increase or decrease the extrudate flow at particular areas of the 
extrusion as it emerges from the final die, thereby achieving such 
modification of the extruded shape as is necessary to produce a strip of 
elastomeric material having the desired characteristics. 
One preferred embodiment of the adjustable die mechanism control means is 
shown by way of example in the accompanying drawings and described in 
detail without attempting to show all of the various forms or 
modifications in which the invention might be embodied. The features and 
advantages of the invention will become more readily understood by persons 
skilled in the art when following the best mode description in conjunction 
with the several drawings.

BEST MODE FOR CARRYING OUT THE INVENTION 
Referring now to the drawings, specifically FIGS. 1 and 2, numeral 10 
denotes an adjustable die mechanism mounted upon the delivery end 12 of 
any desired type of an extruder (not shown) for producing a profiled strip 
or sheet of plastic or elastomeric material (not shown). 
Adjustable die 10, which includes an apertured die block 20, together with 
adaptor plates 22 and 24 attached thereto, is affixed, in any desired 
manner to extruder delivery end 12. Die channel or cavity 26, extending 
through die block 20 and adaptor plates 22 and 24, registers with extruder 
delivery channel 28, with extruded material entering die channel 26 
therefrom. 
The outer or exit end of die channel 26 is provided with a recess 30 
adapted for the insertion and fastening of a final extrusion die assembly 
32, having an opening 38 of predetermined profiled shape which is of a 
cross sectional size less than that of die channel 26. If desired, die 
assembly 32 may include a separate base plate 34 and a separate upper 
plate 36, said plates cooperating to define profiled opening 38. 
Die block 20 is provided with a transverse slot or opening 40, preferably 
perpendicular to the major axis of die cavity 26 and of a transverse 
extent at least as great as the transverse extent of profiled opening 38. 
Slot 40, which is parallel with die assembly 32, but located upstream 
therefrom a predetermined distance, contains a series or pluralities of 
adjacent blocks, segments, dams, or baffles 44, with all of segments 44, 
while being adjacent to one another, being capable of individual and 
independent reciprocal adjustment, via generally rectilinear motion 
thereof, in a manner to be discussed hereinafter. Segment inner ends 46 
are at least capable of partially (or if desired, fully) extending into 
die channel 26 and thus into the strip of elastomeric or plastic extrudate 
being conveyed therethrough. 
Each segment outer end 48 extends out of die block channel 40 and is 
pivotally connected, via pin 52, to an intermediate portion of an 
actuating arm 54 which in turn is pivotally connected on one end, via pin 
56, to a pivot link 58. The other end of arm 54 is also pivotally 
connected, via pin 60, to a piston rod and clevis assembly portion 62 of 
an actuating means 64 which may take the form of a dual acting fluid 
pressure operated piston and cylinder apparatus. A clevis cap 66, on the 
other end of actuating means 64 is pivotally attached, via pin 68, to one 
longitudinal edge of a retainer plate 70 rigidly affixed to die block 20 
in any desired manner. 
As best seen in FIG. 1, adjacent ones of actuating arms 54 are oppositely 
directed, thus resulting in two parallel rows of actuating means 64. The 
reason for this construction is that the physical size of the particular 
type of actuating means 64 is such as to discourage adjacent placement of 
successive units. As best seen in FIG. 2, the sheer number of individual 
segments 44 suggests the alternate-row spacing and attachment of actuating 
means 64 to retainer plate 70. 
Returning now to FIG. 1, it will be noted that a position indicating rod or 
member 72 is also pivotally attached to each actuating arm 54, via pin 74, 
in axial alignment with each segment 44. Members 72 extend through an 
aperture in retainer plate 70, with the outer end 76 of each member 72 
being operatively connectable with a position readout device 80 which will 
be more fully discussed hereinafter. 
In one operative example of the present invention, adjustable die mechanism 
10 included the use of 36 rectilinearly adjustable 3/4-inch wide steel 
segments 44 abutting side by side across die channel 26 about one inch 
ahead or upstream of final extrusion die assembly 32. The assembly 
containing this arrangement was part of a die mechanism having a 
263/4-inch wide die channel. 
Segments 44 are moved by actuating means 64 acting on segment ends 48 via 
actuating arm 54 pivoting around the axis of pin 56. The position of each 
segment 44 is monitored by a position readout device 80, such as an "LVDT" 
or linear voltage displacement transducer (for example, a series 240 
displacement transducer available from Trans-Tek Incorporated of 
Ellington, Conn.) or any well-known dial-type displacement gauge, 
interacting with each position-indicating member 72. 
Appropriate valving (not shown), of well-known design, for controlling 
actuating means 64 is operated by signals from an associated central die 
control system. The central die control system may have numerous 
configurations dependent upon the specific application of adjustable die 
mechanism 10. However, inasmuch as certain control functions are 
preferably common to all applications, a central die control system having 
such characteristics (generally identified in FIG. 3 with the numeral 82) 
is presented hereinwith. 
Central die control system 82, hereinafter referred to as control system 
82, performs several basic functions. First, it monitors the profile of 
the extrudate as it is produced (the "instantaneous extrudate profile"), 
compares the same to a desired profile, and, where deviations equal to or 
greater than a preselected minimum threshold are found, it generates the 
necessary signals for operating actuating means 64 to achieve the desired 
profile. Additionally, it insures that when making the comparison between 
the instantaneous extrudate profile and the desired profile the two 
profiles are properly aligned. 
It has been found preferable to correct deviations between the 
instantaneous extrudate profile and the desired profile by first suitably 
adjusting the segment 44 at the location having the greatest magnitude of 
deviation, and then proceeding to adjust the remaining segments 44 in 
descending order based upon the magnitude of deviation at their respective 
locations. When the magnitude of deviation at the location of all segments 
44 are all less than a preselected threshold, a new comparison may be made 
and the process of correction begun again. 
As best seen in FIG. 3, control system 82 includes extrudate profile sensor 
and memory circuit 84, target profile sensor and memory circuit 86, 
profile error detection circuit 88, profile alignment circuit 90, and 
correction factor generator circuit 92. Extrudate profile sensor and 
memory circuit 84 (hereinafter called "sample circuit 84"), target profile 
sensor and memory circuit 86 (hereinafter called "target circuit 86"), and 
profile error detection circuit 88 each contain a conventional digital 
memory, denoted 94, 96 and 98 respectively, for respectively storing the 
magnitude of the instantaneous extrudate profile, the magnitude of the 
desired or "target" profile, and the magnitude (if at least equal to a 
preselected threshold) of the deviation therebetween at a preselected 
number of locations across die channel 26. Where memories 94, 96 and 98 
are selected to contain an identical number of addresses of a quantity at 
least equalling the preselected number of locations across die channel 26, 
a unique correspondence will exist between the data stored in a particular 
address of each memory and a particular location across die channel 26. 
Sample circuit 84 provides the necessary elements to sample and store the 
instantaneous extrudate profile. Sample sensor 100 includes a plurality of 
position readout devices (similar to LVDTs 80 described hereinabove) which 
when actuated manually by pushbutton 102 or automatically by means of auto 
restart 104 scan the instantaneous extrudate profile. The LVDTs provide a 
digital signal indicative of the thickness of the extrudate at each of the 
preselected locations across die channel 26 and this information is stored 
in sample memory 94. 
The instantaneous extrudate profile data is received by profile alignment 
circuit 90 simultaneously with the data's receipt by sample profile memory 
94. Profile alignment circuit 90, which includes a center line detector 
106, a memory shift factor 108 and a scan complete monitor 110, serves to 
correlate the center of the sensor profile data with that of the target 
profile data so that no error is introduced as a result of misalignment. 
This correlation is accomplished in two steps. First, center line detector 
106 locates the center of the instantaneous extrudate profile by 
monitoring, for example, a sharp discontinuity in the sample sensor data 
introduced in the extrudate by the placement of a small notch in the 
center of opening 38 in final extrusion die assembly 32. Upon completion 
of a scan of the entire width of the instantaneous extrudate, scan 
complete 110 generates an actuation signal which initiates the second step 
of the correlation. During this second step, memory shift factor 108 
determines the extent to which the data in sample memory 94 must be 
"shifted" such that when compared with the data in target memory 96 the 
proper correlation exists. However, instead of actually shifting the data 
in sample memory 94, the signal from memory shift factor 108 simply 
suitably alters the address of the data in sample memory 94 at which the 
comparison is begun, thereby achieving the same correction. 
It should be appreciated that the center of the instantaneous extrudate 
profile may be ascertained by any of the numerous other well-known 
techniques. For example, combination light generator and light-sensitive 
sensors are frequently utilized as edge detectors in extrusion systems and 
the center found from this information. 
A target profile may be scanned simultaneously with that of the 
instantaneous extrudate profile by means of another plurality of LVDTs 
similar to that noted hereinabove (shown in FIG. 3 as target sensor 112), 
or other suitable mechanism to examine like locations in the sample and 
target profiles at the same time. Alternately, data indicative of the 
desired profile could be electronically loaded into target memory 96 at 
any time prior to comparison of the data in sample memory 94 with the data 
in target memory 96. 
After any necessary starting address correction has been received by and 
made to sample memory 94, memory shift factor 108 simultaneously enables 
the output of both sample memory 94 and target memory 96 so that the data 
in each corresponding memory address may be sequentially compared by 
comparator 114 in profile error detection circuit 88, and an output signal 
generated therefrom proportional to the difference between the thicknesses 
of the instantaneous extrudate profile and desired profile. The output 
signal from comparator 114 (which may be referred to as the "error data") 
is received by another element of profile error detection circuit 88, 
level detector 116. Level detector 116 examines the magnitude of the error 
data and generates either an output indicative of a zero error (when the 
magnitude of the error data is less than a preselected threshold 
magnitude), or an output proportional to the error data (when the 
magnitude of the error data is at least equal to the preselected threshold 
magnitude). The output signal from level detector 116 (which may be known 
as the "significant error data") is received by and stored in significant 
error memory 98 at addresses corresponding to the location across die 
channel 26 of that particular error magnitude. Thus, only thickness 
deviations at least equal to the preselected threshold magnitude are 
deemed necessary for correction and retained. 
As significant error memory 98 receives error data from level detector 116, 
such data is simultaneously transmitted to most significant error detector 
118, which together with no error detector 120, correction factor 
generator 122 and next selector 124 make up correction factor generator 
circuit 92. Most significant error detector 118 may be a conventional peak 
hold circuit which retains the greatest error location and magnitude 
stored in significant error memory 98. Upon receipt of the last error data 
address in significant error memory, the address of the most significant 
error is sent to both target memory 96 and correction factor generator 
122, and the magnitude of the most significant error also sent to 
correction factor generator 122. Target memory 96 provides to correction 
factor generator 122 the magnitude of the desired profile thickness from 
the received address. Correction factor generator 122 then selects the 
appropriate die segment actuating means 64 to correct for the most 
significant thickness deviation and processes the error signal and the 
magnitude of the desired profile thickness to generate a signal to the 
selected actuating means of appropriate characteristic to suitably correct 
for the most significant thickness deviation found. 
Segment position comparator 126 receives a signal from the selected die 
segment actuating means 64 indicative of the necessary correction and 
receives a signal from the die segment LVDTs associated with the segment 
operated by the selected die segment actuating means 64. When the 
necessary correction is determined to have occurred, segment position 
comparator 126 furnishes an output signal to next selector 124. Next 
selector 124 loads a number indicative of no error into the address 
containing the error data for the location at which the deviation was just 
eliminated, and resets significant error memory 98 such that it again 
scans through all error data therein. As previously described, most 
significant error detector 118 receives and retains the magnitude and 
location of the remaining greatest error and the correction process 
continues. When no error is found in significant error memory 98, all 
corrections have been completed and no error detector 120 furnishes a 
signal to auto restart 104 to make another scan of the instantaneous 
extrudate profile as delineated hereinbefore. 
It should be understood that in order for segments 44 to operatively effect 
the extrudate, segment inner ends 46 must extend into die channel 26 for a 
distance sufficient to enter into the projection or silhouette of profiled 
opening 38 in extrusion die assembly 32. Furthermore, segments 44 must 
move individually and differentially in order to produce a specific change 
in the profile. 
It should be further understood that since there are different profiles 
which can be produced, the exact number and transverse extent of segments 
44 may be substantially varied, depending on the desired resulting 
contour. In addition, the resulting profile will depend upon additional 
variables, which include the type of material being processed (physical 
characteristics, temperature, uniformity and plasticity), the ratio of the 
height of the die channel to the average height of the profiled opening in 
the final extrusion die assembly, as well as the distance upstream of 
segments 44 from the rear surface of extrusion die assembly 32. 
The action of series or pluralities of adjacent segments 44 may be 
analogized, for discussion purposes, to that of a variable preform die. 
The benefit of such a plurality of segments 44, or preform die, upstream 
of the final die is that segments 44 tend to preshape or preform the 
extrudate, with the final shaping being done by die assembly 32, thereby 
avoiding the striations or stair-step effect that results when the 
variable dam segments in fact form the only or final die. Furthermore, the 
use of a variable preform die in combination with a final or finish die 
not only simplifies construction and increase the permissible dimensional 
tolerances of the final extrusion die assemblies, but also permits 
compensation for the extrusion profile variation caused by the extrusion 
process itself or the material being extruded. 
In addition, where the speed of a take away conveyor is utilized in 
conjunction with adjustable die mechanism 10 to control various extrudate 
characteristics, the use of a preform die may be expected to at least 
reduce the need for conveyor speed variations. 
Preferably, the profiled opening 38 in final extrusion die assembly 32 may 
be up to 10% oversize at least in terms of dimensional height, in order to 
provide the maximum benefit in terms of profile or shape control through 
the use of the preform die in the manner previously described. 
As previously noted, the placement of segments 44 upstream of final die 
assembly 32 modifies the flow of the extrudate to die 32 and thereby 
modifies the final shape. Furthermore, the use of the final die assembly 
32 eliminates the discrete steps on the profile and the consequent curing 
defects which may be caused by such steps. If desired, a flexible 
diaphragm may be interposed between segments 44 and the extrudate to 
promote an even more uniform gauge change and to seal the segments against 
any extrudate which may leak between them and thereafter jam them, and 
thus prevent the adjustment thereof. 
Testing of prototypes has shown a correction in the range of at least plus 
or minus 10% of the original gauge and profile. It should be understood, 
however, that due to the plurality of influencing factors in an extrusion 
process of this type, changes in the detail of construction may be 
resorted to and different results may be obtained. 
From the foregoing description, when read in the light of the several 
drawings, it is believed that those familiar with the art will readily 
recognize and appreciate the novel concepts and features of the present 
invention. Obviously, while the invention has been described in relation 
to only a limited number of embodiments, numerous variations, changes, 
substitutions and equivalents will present themselves to persons skilled 
in the art and may be made without necessarily departing from the scope 
and principles of this invention. As a result, the embodiments described 
herein are subject to various modifications, changes and the like without 
departing from the spirit and scope of the invention with the latter being 
determined solely by reference to the claims appended hereto.