Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
This invention relates to volatile liquid injection
systems and to processes and apparatus for the preparation of
plastomer compounds and more particularly volatile liquid supply
equipment and to production processes and apparatus for intro-
ducing volatile cross-linking agents which may be flammable
into cross-linkable polyolefin compounds and Eor the continuous
extrusion of cross-linkable polyolefin compounds with a maln-
tenance of safe operating conditions.
The cross-linking processes assoc:La~ed wlth plastomer
compounds from polyolefin polymers such as polyethylenes or the
like is well known and is disclosed in U.S. Patent No. 2,628,214
entitled Curing of Polyethylenes as issued to Pickney and Wiley
on February 10, 1953 and U.S. Patent ~o. 2,528~523 entitled -~
Process for Extruding And Insolubilizlng Polymers of Ethylene
as issued to R.E. Kent on November 7, 1950. Typically, these ,,
processes provide for the introduction of organic peroxides by
curing at elevated temperatures, on the order of 160 to 250C., ~-
under pressure and result in products which are highly advanta-
geous and may be emplo~ed to form insulating or scmiconductive
layers for cable and the like if the same are produced with ~ ~ -
: .
extruders. Polyolefin compounds prepared according to the - -
teachings of the prior art were required to be prepared so that
the same could accept the cross-linking agent, a protective
agent, and any filler materials to be employed in a suitable
mixture within a well defined, narrow temperature zone. This
zone, for example, in the case of a low density polyethylene
and under favourable mixing conditions, would be located between
` 105 `and 135C. The higher temperature within this range is
dictated by the cross-linking agent while the lower temperature
: 30 is mandated, in the case of polyethylene, by the viscosity of
.
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~78~
the ~atter in :itS molten stat~. The compounds thus prepare~
would then be cross-linked at the extruder output by passing
directly into a chamber under pressure of water vapor or super
heated water at elevated temperatures of approximately 180 to
250C. ~lternatively, introduction of the cross-linking agent
could occur within the extruder screw output zone ~ust prior to
a penetration oE the mixture into the extruder head; however,
mixing here occurs within a zone where the polyolefin compound
is sub~ected to very high pressure rendering the introduction
of the cross-linking agent highly impractical and resulting
in a mixture which is not homogeneoua.
In practical application within the industry, the
preparatory operations for polyolefin compounds capable of
being cross-linked were limited to a choice of organic peroxides
which were suitable for the cross-linking of such compounds
wherein suitability limited the choice of cross-linking agents to
organic compounds displaying low volatility at the temperatures
employed during the mixing operations. Therefore, certain
highly volatile, flammable, liquid organic peroxides ~hich en~oy
current use as cross-linking agents for silicone rubber and
other synthetic elastomers could not be practically employed under
industrial conditions for the cross-linking of polyolefin com-
pounds and in particular, of polyethylene compounds because of
the required high temperatures which occur during processing.
This form of exclusion extended to tertiary butyl peroxide or
di-t butyl peroxide DTBP, ~hose boiling point is approximately
110 C at 760 mm of mercury pressure despite the fact that DTBP is
a highly advantageous cross-linking agent because it exhibits
cost advantages as well as enabling the fabrication of cross-
linked polyethylenes with low photo degradability due to anabsence of aromatic cetones. Furthermore, when a liquid
~8~L 518
peroxide is employed as a cross-linking agent for polyolefin
compounds, at ambient temperatures and pressures, the peroxide
may be introduced in a single operation at, for example, the
extruder input, and avoids the need for prior preparation
of the organic compound in the manner described above. In
addition, such use of a liquid peroxide permlts complete control
of the mixing of the ingredients at a single location prior
to further processing and results in a highly homogeneous
mixture which was not available with prior art techniques.
Therefore, it is an object of this invention to provide
processes and apparatus for introducing volatile and/or
flammable cross-linking agents into polyolefin compounds.
It is a further object of this instant invention to
provide processes and apparatus for the continuous extrusion of
cross-linkable polyolefin compounds employing highly volatîle
cross-linking agents.
It is an additional object of the present invention
to provide processes and apparatus enabling the practical use of
liquid perox;des as cross-linking agents for polyolefin com-
.,.
pounds.
It is another ob~ect of the instant invention to provideprocesses and apparatus for producing cross-linkable polyolefin
compounds by mixing volatile cross-linking agents directly at
the extruder input while maintaining processing conditions at a
- ~ ... .
safe level which is continuously monitored.
It is an additional object of the present invention to
provide apparatus for sa~ely conveying liquid peroxîde to a
mixing point under conditions where the amount o~ liquid
peroxide conveyed is precisely metered and conditions within the
system are constantly monitored to ensure the safe operation
thereof.
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It is a further ob~ect oE the present invention to
provide processes and apparatus for automatically conveying
the peroxide to a mixing point at a rate which is governed by
the material processed from that mixing point under conditions
where safety conditions are monitored throughout the system
and upon failure of a signiflcant condition, the conveyi~g
system is automatically shut down and an alarm conclition
initiated.
Other ob~ects and advantages of the lnvention will be-
come clear from the following detal.led description of an examplaryembodiment thereof, and th.e novel features will be particularly .
pointed out in connection with. the appended claims. ~1.
In accordance with an exemplary embodiment of the ~ :
instant invention, a volatile cross-linking agent such as liquid
peroxide is introduced, at ambient temperature and under
atmospheric pressure directly into the input of an extruder at
the same pressure as the polyolefin compound to be cross-linked,
the resulting compounds being put under pressure within the
extruder as the temperature lncreases so that it reaches its
definitive shape at the extruder output and may be fed directly
into a hot cross-linking enclosure which is maintained under ~ -
pressure 50 that the peroxide-is incorporated in a single
operation permitting complete control of the ingredients mixed
and allowing perfect homogenization of the mixture while defusion
and consequent loss of the highly volatile peroxide are avoided~
The system for introducing the highly volatile cross-linking
agent includes a peroxide storage tank, a filling pump, a feed
vessel, and incremental feed pump with. a pressure gauge, a
flow meter and numerous safety features which control the flow,
temperature and ambient conditions of the cross-linking agent
feed system within a controlled environment to ensure the safe
and precise hanclllng Oe a highly volatile liquid while at
the same time controlling the feeding of the liquid as a function
: of the material processed by the extruder so that the percentage
of the cross-linking agent inserted at the input to the extruder '-
remains at a constant, predetermined percentage, regardless of
extruder speed variations. Additionally, as shall be seen
hereinafter, various additives which are soluble in the volatlle
cross-linking agent may be introduced within the feed system
therefor in sufficient amounts Eor effecting protection Oe
the resulting polymer without altering the eEfic:Lency of the
feed system or that of the additive so that the entire proce~s. may
be carried out at the processing site w-ithout initial preparation ::
of various mixtures to be further processed. Additional objects
Oe the present invention will be apparent from the operation
of the embodiment of the instant invention wkich is disclosed
herein and the operation of the disclosed embodiment of the . .~
present invention will be clearly understood from the following ;
description and the accompanying drawings in which: ;
Figure 1 is a pictorial view illustrating exemplary ,~.
20 continuous extrusion techniques for cross-linkable polyolefin :
compounds in accordance with the teachings of the present
invention together with housings for the volatile cross-linking
agent feed system and the electrical control and alarm
equipment therefor;
Figure 2 is a highly generalized block diagram ~:
schematically illustrating the details of the volatile cross- :
linking agent feed system for supplying the ~olatile cross-
linking agent in the manner illustrated in Figure l; and
Figures 3A and 3B depict a schematic diagram illustra- .
ting the details of the volatile cross-linking agent feed system -. .
and the electr~cal control and alarm equipment for the exemplary
i _ 5 _ .. -.:
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~781~
continuous extrusion embodiment of the invention illustrated in
Figure 1. ~s Figures 3A and 3B connect from left to right to
depict a single schematic, these figures are frequently referred
to in combination as Figure 3.
Referring now to Figure 1, there is sho~n a pictorial
view of an exemplary continuous extrusion technique for cross
linkable polyolefin compounds in accordance with the teachings
of the present invention together with housings for the volatile
cross-linking agent feed system and the electrical control and
alarm equipment therefor. The apparatus illustrated ln Figure 1
comprises an electrical control and alarm cabinet 1, a peroxide
feed cabinet 2, and extruder 3, and a continuous vulcanization
tube 4. The electrical control and alarm cabinet 1~ as shall
be seen in greater detail in conjunction with Figure 3 includes
all logic, control, alarm, condition indicia, connection
terminal boards and other electrical apparatus employed or
the control, maintenance and monitoring of the pe~oxide feed
system within cabinet 2 while all electrical moto~s which are
disposed within -the cabinet per se are of the explosion proof
type or are connected to inherently safe supplies. ~11 feed
through conduits and connectors intermediate the two cabinets
are provided with seal proof gaskets and all electrical connec-
tions are made, wherever possible, within terminal boards
mounted within the electrical cabinet 1 so that, in essence,
all circuitry required for the peroxide feed system is present
within electrical cabinet 1 except where the presence of a
specific drive or motor system within peroxide feed cabinet 2 is
absolutely necessary such as in the case of a motor or the like
and under these circumstances such motor i5 of an explosion
proof construction. On the face 5 of the electrical control and
alarm cabinet 1 are located a plurality of control, monitoring
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and alarm indicia to provide an operator with immediate visual
appraisal capabilities of the present operation of the system
as well as records regarding the past history thereof. In
addition, any alarm condition of note is further accompanied
by the sounding of a siren or horn so that both the audible
and visual senses are stimulated should an alarm condition
result. ~lore particularly, the electrical control and alarm
cabinet 1 is provided with two sets of visual condition lndicating
devices 6 ~ 7 to provide the operator with immed:Late indication6
which are advisory of the operational conditions within the
system. ~ltho~lgh the nature of these indicia will become
apparent in con~unction with Figure 3, it should here be
appreciated that condition indicia 7 ma~ take the form of ten
alphameric display panels located in a side by side manner
which are selectively illuminated by the system should the
condition to which they are assigned occur within the system.
Certain of these indicia merely are advisory of normal operating
conditions while others are indicative of a condition which will
cause system operation to terminate if the same are not quickly
corrected. The conditions for which an alphameric display panel
is provided within the condition indicia array 7 are as follows;
Maximum Flow Empty Hopper
Dangerous Flow Extruder Sync
Minimum Flow Line Sync
Maximum Level Heat Rise
Minimum Level Leak ~ :
In addition, the condition indicia 6 comprise a plurality of
colored panels which are selectively enabled in conJunction with
selected ones of the condition indicia in array 7 to indicate -~
normal operating conditions, abnormal operating conditions or
the onset of dangerous conditions which, as will be seen below, ~ :
are accompanied by a shutting down of the system. The colored
panels associated with the condition indicia 6 are nor~ally
: ~ 7 -
78~88
selectively illu~inated in conjunction with the alphameric panels
within the condition indicia array 7 so that the operator is apprised
both as to the urgency of the cond~tion which has occurred and
its precise nature. The condition indicia 6 may typically com-
prise five differently colored panels, such as red, orange,
green, blue and white wherein the wh~te, blue and green panels
are indicative of normal system operation, the orange panel 1
indicative of an abnormal condition while the red panel is
indicative of a dangerous condition which may cause system shut
down to occur. Addltionally, while the white, blue and green
panels will be continuously illuminated during normal forms of
operation, the illumination of the orange and red panels occurs
on an intermittent or flashing basis and is accompanied by the
sounding of a horn, siren or the like~ Preferably, the
condition indicia ~ are rather large panels and are prominently
located on the housing in a manner to be visible throughoot -
an operating area; however, the placement, size and colors for
the panels chosen are merel~ a design choice. The operation
and actuation of the condition indicia array 6 and 7 as well
as the conditions to which they respond will be described in
greater detail in con~unction with Figure 3.
The face 5 of the electrical control and alarm cabinet
1 is also provided with a digital display 8 and a pair of
chart recorders 9 and 10. The digital takes the form of a flow
rate counter providing a digital output which displays the flow
rate in liters per hour ~herein the measured flow-rate corresponds
to the flow rate of the liquid peroxide ~eing provided at the
output of the peroxide feed cabinet 2. The chart recorder 9 -
takes the form of a two track analog recorder which maintains
a record of both the metered flow and the line or extruder speed,
2S measured in the manner to be described in con~unction with
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Figure 3, so that a history oE the system operation with respect
to that set is automatically maintained and displayed. Similarly,
the chart recorder 10 is a six track event recorder which
indicates graphically the time and condition of any system .
warnings which may have been issued by the system in a manner
to be further described in conjunction with Flgure 3.
The face 5 of the electrical control and alarm cab:inet
1 is also provided with an hour meter 11 which is used to record
the cumulative operating time of a system incremental pump~
as shown in Figures 2 and 3. Additionally, power On and Off
switches 12 and 13 are provided as well as a pair of rate control
potentiometers 14 and 15. The power on control switch 13 is a
two position, mode control s~witch which automatically returns
to a home position identified with the automatic mode of operation
when not held in its second position. This second position is .:
: a manual mode or a mode which is independent of the level control
: employed for protective purposes within the fluid feed vessel,
and will be described in detail in conjunction with Figure 3,
In the home or automatic position, th:e power On switch 13 .:-.
causes the system operation to be controlled in response to an ^ ..
error signal which is derived from the difference between
the actual flow rate of the s~stem and a referenced condition
established by a mode control switch 16, also pro~-ided on the ~ :
face 5 of the electrical control and alarm cabinet. The
referenced condition is set by the operation of the mode control
switch 16 which employs, in a first or start up position, the ~ :
speed of the extrudier 3 screw and in the second posit~on employs .~::
the product output rate from the continuous vulcanization tube
4 as th.e reference standard so that, in this manner~ the flow
rate at which li~uid peroxide is in~ected is made to identically .~ .
correspond to the rate at which processing is occurring to .; ;
_ g _
i- . . : .
78~
ensure that a precisely metered amollnt of liquid peroxide is
injected for the rate at which the polyolefin compound is being
processed. The electrical control and alarm cabinet l is also
provided with a lock means to prevent access by unauthorized
personnel.
The peroxide feed cabinet 2 as shall be seen in greater
detail in connection with Figure 3 is. a vent:Llated cabinet in
which the liquid peroxide is stored wh.ich contains all necessary
ducts and conduits Eor conveying precisely metered liquid peroxide
to the output thereof at conduit 17. The output 17~ as shall be
described hereinafter, is connected to the extruder i.nput at
the base of the hopper employed to suppl~ cross-linkable polyole-
fine to the extruder. The fron~ of the peroxide $eed cabinet 2
is provided with a float type glas6 tube 18 which permits th.e
visual monitoring of the actual flow in a manner illustrated in ~ : :
greater detail in connection with Figure 3. The construction :
of the peroxide feed cabinet 2 is~such that a highly constrained
and controlled environment is provided for both the liquid .. ::.
peroxide storage and feed equipment so that safe conditions ~-
are maintained or else system shut down is initiated~ Thus,
the peroxide feed cabinet 2 is ventilated and should proper ~.
ventilating action terminate, an abnormal condition is indicated. ;- --.
Similarly, the peroxide fill tank is monitored and should the
temperature rise, an abnormal condition is indicated. In addition2
feed vessel is refrigerated and ventilation is insured th.rough .
an under pressure venting system, in a manner ~ell known to those .
of ordinary skill in the art which is implemented th.rough leak-
proof tubing. All feed throughs of conduits and electrical cables
utilize seal proof gaskets and any electrical equipment contained ..
within the cabinet is either explosion proof or connected to
supplies which are inherently safe. Furthermore, the pow-er levels
employed are calculated to avoid.arcing and all electrical
connections are ~rought to a terminal board within the electrical
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10~8188
¦ control and alarm cabinet 1. Catch basins are additionally provided
¦ throughout in case of leaks and leaks are monitored by a sump and a
pneumatic level indicator to cause the indication of an abnormal or
dangerous condition. The entire peroxide feed cabinet 2 is separate and
apart from the electrical control and alarm cabinet 1 and it may be
located at a variable distance from the extruder to en~ure safety in
ope~ation. All parts within the peroxide feed cabinet which come into
contact with metered liquids are strictly non-corrosive and neutral with
l respect to the liquid peroxide being employed and hence should take the
~ form of stainless steel, glass,TeflonOpolyethylene or similar types of
~eutra~ non-corrosive tubings. The connecting ducts for the installation
are also of stainless steel and heavy metals such as copper, are avoided -
throughout. A closedcycle refrigeration system is also provided
¦ herein and a fire detection system may be provided, if desired, throug~
the installatlon of ionization chambers for detection of gases emitted
through combustion and upon such detection, sensory means may be
activated to initiate alarms, and/or subsequent to a delay cause
extinguishing gas to be discharged into the chamber. Furthermore, in t~ e
case of an external fire hazard, alternate detectors, located on top of
the electrical cabinet for the purposes of monitoring the external
environment may also be employed to initiate an alarm and the extinguis~ er~
¦ Thus, as shall be seen in greater detail hereinafter, the peroxide feed
cabinet 2 is constructed and monitored so that safe operating conditions
are maintained throughout or else system operation is terminated.
~ The extruder 3 may take the conventional form of extruder
apparatus having a hopper39inwhich the'compound to be cross-linked such
as polyolefin is fed. At thebase OI the hoppeF, the conduit 17 is
. ~
.. . . .
I . . .
~onnec~ed to directly ln~ect the liquid cross-linking agent 7 which
in the exemplary embodiment has been ~escribed as a liquid
peroxide, directly into the input of the extruder. In addition,
the extruder, takes the conventional form of a hollow outer core
20 with a centrally disposed and rotating extruder screw 21 caus-
ing extrusion to occur in the well known manner. Thus it will
be seen that granules of the compound to be cross-linked are
initially mixed at the input oE the extruder and thereafter the
increase in temperature and pressure induced by the operation
of the extruder will cause a highly homogeneous mixture of the
liquid peroxide and polyolefin to occur and to be process.ed
through to the output thereof. Accordingly, it will be ap-
preciated that the initial third of the extruder acts to effec- :
tively cause the mixing of the liquidous cross-linking agent and .
the solidus compound to be cross.-linked and thereafter an increase ~ :
in temperature within the extruder, resulting in temperatures
from 100 - 140 C, will cause the resulting mixture to assume ~
a highly homogeneous state. Th.e resulting mixture of compounds: .
rhich occurs from the output of the extruder is introduced into : .
the continuous vulcanization tube 4 wherein the same is disposed
about a core and thereafter subjected to elevated temperatures
so that actual cross-linking ~ay occur. .. :
More particularly, the continuous vulcanization tube 4
takes the form of a steel tube 22 forming a heating chamber 24
which receives steam or super h.eated water, under pressure. The
input portion of the continuous vulcanization tube 4, is provided
with a central opening 26 adapted to accept core material about
which an insulating layer of cross-linked polyolefin 23 is to
be disposed and an annular conduit portion 28 adapted to receive
the output of the extruder screw from th.e extruder head 25.
As will be readily appreciated by those of ordinary skill in the
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art, the liquidous output mixture from the extruder is
continuously disposed about core mater~al as the same is fed into
the central opening of the extruder head 25 so that this material
is vulcanized in a continuous manner about the core material being
fed in the direction indicated by the arrow A. Thereafter, the
core thus coated with the extruded mixture is run through the
heated zone of the continuous vulcanization tube so that cross-
linking of the mixture occurs in the manner lndicated on a
continuous basis so that continuous processing techniques may
be employed throughout. ~s indicated in Figure 1, the length of
the cross-linking zone is sufficient so that-cross-linking of the homogeneous
mixture from the output of the extruder can be completed prior to leaving the
continuous vulcanization tube ~and hence, all processing which occurs
is carried out on a continous basis,
As the exemplary embodiment of the instant invention
being disclosed in association with Figure 1 has presumed that
polyolefin compounds are supplied to the hopper 19 and liquid
peroxide is injected at a precisely metered flow into the
conduit 17 for mixing within the extruder and subsequent
continuous vulcanizing about a core 27, it may be assumed that
the core 27 comprises electrical cable or conductor means as
the resulting compound is a highly advantageous insulator.
However, it wlll be appreciated by those of ordinary skill
in the art that any liquid material of a volatile nature may
be injected at a precisely metered basis from the output of
the peroxide feed cabinet 2 and similarly, any compounds which
call for organic peroxides for their cross-linking or
vulcanization of any other compounds which require highly
volatile cross-linking agents may be employed. Typically,
compounds which could be introduced into the hopper means
for advantageous combination w th organic peroxides for cross- ~
: ~-
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7~
link:ing or vulcanization are as follows:
polyethylene
ethylene propylene copolymer (EPM) :
ethylene propylene diene terpolymer (EPDM)
chloride polyethylene (CM)
chlorosulfone polyethylene (CSM)
tolyethylene polyethylene (CSM)
vinyl acetate ethylene copolymer (EV~)
natural rubber (NR)
polyisoprene (IR)
butadiene styrene rubber (SBR)
polyisobutylene
silicone rubber .-
acrylonitrile butadiene rubber (~BR~ .
Similarly, while an extrusion and vulcanization techni~ue has been
employed in the exemplary embodiment for the output of the .
peroxide feed cabinet 2, any mixing or combining and forming
techniques, well known to those of ordinar~ skill in the art~
which may be performed under ambient conditions with either
liquid peroxide or highly volatile compounds on a precisely
20 metered basis may be used in combination ~ith the principles -
of the instant invention.
Referring now to Figure 2, there is shown a highly .
generalized schematic illustrating in a highly simplified manner~ :
the techni~ues employed by the instant invention for precisely .~:
metering and controlling th.e in~ection of highly volatile
.`. cross~linking agent while the maintenance of ambient conditions :~
required for safe operations are rigi.dly controlled. Th.e ~ .
apparatus illustrated in Figure 2 comprises ~he simplified ;-~
schematic for the embodiment of the invention illus:trated in :.
Figure 1 and comprises a storage tank 30, feed vessel 31, .~
incremental feed pump 32, output transducer means 33, safety . - .
' :
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~l~7~
valves 34 and 35, a flow meter 36 and the extruder 37 and with
the exception of the extruder 37 each of these elements resides
in the main channel of fluid flow. The storage tank 30 may
take any conventional form of storage tank capable of holding
liquid peroxide or such other highly volatile cross-linking
agent as is employed in a given system. In addit~on to the
volatile cross-linking agent, other addltlves such as certain
antioxidants which are soluble by direct addition to liqllid
peroxide or the like may be present within the storage tank 30
so that the cross-linking agent to be in~ected already includes
such additives as are des-ired~ The antioxidants which may be
added may take the form of:
44~thio-bis(6 terbutyl-meta~cresol),
44'-butylidene-bis (6 tert. -butyl. -meta~ -
cresol),
2.6 - di-tert. -butyl. -para-cresol,
2.2' - methylene-bis (6 tert~ butyl. -para-
cresol) Thiobiphenol
These antioxidants can be completely dissolved in peroxide in
sufficient proportions for effective protection of the polymer
without altering the efficiency of the peroxide or of the
antioxidant.
The s$orage tank 30 is connected through a conduit 38
and a pump 39 to the input of the feed vessel 31~ The feed
vessel 31 may be provided with a fill control device, represented
by the input annotated N. This fill control device may be
initiated either by manual or automat~c control in a manner to be
described more in detail in con~unction with Figure 3. How-ever,
the actual start and stop actions of the pump 39 are initiated
by a float switch within the feed vessel 31 which acts -
magnetically on contacts associated with the power input for
the pump 39 in a manner also described in greater detail in
. - - - ~
!38
connection ~i~h Figur~ 3. Additionally 7 the flo~t action within
the feed vessel 31 acts to provide a mini.mum level condition
which, acts to initiate indicia advisory that an upcoming
product shortage in the feed vessel 31 is about to occur through
audible and visual indicia in a manner to be more fully
discussed in connection with Figure 3. Switched contacts are
also employed to start and stop the automatic fill whlle a
maxlmum level sensory condition associated with the float
control automatically terminates the automatlc or manual filling
of the feed vessel 31 and provides an advisory indicative of this
condition through both visual and audible indicia. The feed
vessel 31 is connected through a conduit 41 to an incremental
Eeed pump 32 which transmits a pulsed stream of peroxide or
other cross-linking agent in response to control signals
supplied at the input thereto annotated C. The incremental
feed pump 32 is actually controlled by the production speed of .;
the product coming out of the continuous vulcanization tube or
alternatîvely by the speed of the screw ~ithin the extruder 37
in a manner to be covered in greater detail in connection with ~ -. .
Figure 3. Here, it is sufficient to recognize that a control
is provided to compare the actual flow rate of the system wh.ich
is injecting liquid peroxide or other cross-linking agents and .:
the speed of the extruder screw or the output of the continuous
vulcanization tube and the output of this control signal is . :
applied to the incremental feed pump 32 so that the rate of flow
is maintained at the precisely metered rate required by the -~`:
processing operation which is then occurring. The incremental :. ~:
',~.'
:
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feed pump may be bypassed by a pressure limiting valve ~3
connected between the input 41 and output 42 of the incremental
Feed pump. The pressure limiting valve 43 acts in the well
known manner to isolate the input and output to the incremental
feed pump 32 whenever the pressure at the output thereof remains
below a specified level while breaking down to cause the output
: to effectively be connected to the -input whenever the pressure
at the output of the incremental ~eed pump 32 exceeds such
predetermined level. The pressure limiting valve 43 may als.o be
employed as an alarm should the pressure dif~erential which
it is designed to measure exceed a predetermined level or
alternately, a direct reading gauge may be employed to provide
this Eunction as well as a direct display function ~or the
operator. The output of the incremental feed pump which transmits
the peroxide as a pulsed stream is further filtered and regulated
by a group of hydro-pneumatic dampers 44 which act in the
well known manner to smooth and order the stream of peroxide -.
pumped from the output of the încremental feed pump 32.
The output of the incremental feed pump 32 thu~
20 smoothed îs applied through. conduit 42 to the input of an
output transducer 33 which acts, i.n essence, to measure the
rate of flow and produce an output signal V representing th.e .~
flow rate, which is obtained, in a manner to be more fully .
discussed in connection with Figure 3 This flow rate .. ;
signal, as obtained from the output of the output transducer 33, .~ -~
is employed in conjunction with th.e rate signal developed from
the speed of the extruder screw or the mater~al processed at ~:
the output o~ the continuous vulcanizati.on tube 4 to
develop~-the error~signal used to control the
:
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~ 88
increment~l feed pump 32 and hence the flow rate with which peroxide is
¦ run through the system. After the rate of flow is measured by the
output transducer 33, the peroxide being pumped is supplied through
electrically actuated safety valves 34 and 35 and a flow meter 36 to the
5, input of the extruder 37 through conduits 45 - 48. The pair of electrical
safety valves 34 and 35 are disposed just at the output OI the output
transducer 33 and at the input to the extruder 37 so that She same may be
simultaneously closed off should an emergency or abnormal condition
arise to cut off the feeding of peroxide both within the system andat the
I output thereof so that the flow is immediately terminated at several
locations. The flow meter 36 is a glass tube and ball flow meter of the
well known variety and corresponds to the flow meter 18 illustrated in
Figure 1 which permits the operator to visually monitor the flow of
liquid peroxide within the peroxide feed cabinet 2. The conduit 48, it
should be noted essentially corresponds to conduit 17 in Figure 1 and the
input thereto at the extruder 37 corresponds to the input position at the -
base portion of the hopper. The pair of electrical safety valves 34 and
35 will close either when the incremental pump 32 stops or should the
electrical supply be interrupted so that the supply of liquid pera~ ide to
the injection point at the extruder 37 is immediately cut off.
Polyolefin compound or the like is supplied from the hopper49 ;, ~ `~
which would correspond to the hopper 19 illustrated in Figure 1 and
through a conduit 50 to the input portion of the extruder 37. Thus, the
~olyolefin compound will enter into the input portion of the extruder 37
~5 at the same time as the crosslinking agent is injected through conduit 48 -
under ambient temperature and pressure conditions, whereupon the
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., . ' ' ' .
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. , ~
- . - : - :. - - ~ -
1C97~
extrusion process and the continuous vulcanization and cross-
linking processes described in association with Figure 1 may take
place without any initial preparation of compounds to be sub-
jected to the process and safe operating conditions are maintained
throughout because the amount of cross-linking agent is precisely
metered to correspond to that required by the rate of processing.
~11 internal parts of the apparatus ~hich come in contact with
liquid peroxide or other volatile cross-linking agents which
may be employed are made Erom stainless steel, Elorosilasomer,
polytetrafluoroethylene or any other material not sensitive
to peroxide or other cross-linking agent action. Furthermore, since
these agents tend to be flammable, a plurality of safety devices
are added, as shall be described in more detail in connection
with Figùre 3, to ensure the safe operation of the cross-linking
agent injection system. For instance, the storage tank 30 and
the feed vessel 31 are refrigerated while an enclosure 51, as
indicated by the dashed block, is provided in the manner shown
to maintain the environment of the system w-ithîn desired
parameters. The enclosure 51 is fabricated so as to be leak
proof to the cross-linking agents conveyed should leaks or
spills develop within the system and it is sub~ected to a negative
pressure by an extractor 52 whose discharge is evacuated through
leak proof tubing and sealing arrangements. The extractor 52
may take the form of a conventional under pressure extractor
which is a fan type device wherein venting to an external
environment is accompli:hed through a sealing arrangement.
Additionally, sensory devices responsive to the ventilation
control of the extractor 52 and the temperature within the en-
- closure 51 are provided to initiate alarm conditions should
either the ventilation fail or the temperature rise~ Further-
more, catch basins (not shown) are provided throughout the
- 19 -
:
., ~ ~ - . . .
~C378~
enclosure beneath peroxide handling equipment s:hould leaks.
develop and the catch basins may be provided with fluid level
detectors to indicate the presence of a leak and initiate an
alarm condition. In addition, all electrical connections are
made to a terminal board located outside of the enclosure 51 so
as to avoid the possibility of spark ignition.
Referring now to Figures 3A and 3B which connect
from left to right, referred to generally as Figure 3, there is
shown in great detail a schematic diagranl illustrating the details
oE the volatile cross-lInking agent feed or supply system an-l
the electrical control and ala~m equipment for the e.xemplary
continuous extrusion embodiment of the invention illu6trated
in Figure 1. As should now be apparent to those of ordinary
skill in the art, although the exemplary embodiment herein
discussed includes an extruder and continuous vulcanization tube . .-
for forming a resultant mix of volatile cross-linking agent and
polyethylene about a core to form a resultant product, the .~
volatile cross-linking agent supply system according to one --
aspect of the instant invention may be employed an~ time it is
necessary or desirable to feed precisely metered quantities of
a liquid to a given location and the nature of the liquid ~:`
involved requires extremely rigorous h.andling requirements. :; ;.
Furthermore, it will be apparent that although a multitude of
safety features are included within th.e instant invention to .~ .
insure the safe operation of the volatile cros:s-linking supply ~
system, selected safety features may be added or deleted to . .:-
meet the requirements of a specific application. As a generalized .
block diagram of the exemplary embodiment of the present invention ~ -
was set forth in conjunction with Figure 2, the description of ~
~igure 3 will proceed to set forth the details of the schematic
diagram illustrated therein as an overview has already been .
- 20 -
.
.... . ..
: .
88
provided in conjunction with Figure 2~ In the description of
Figure 3, initial focus is directed to portions of the supply
system associated ~ith the flow of volat~le cross-linking agent
while control, safe~y, and metering equipment associated ~herewith
is either described in association with elements which are
controlled thereby or in separate s~ectiorls of this descr:Lption
devoted to such control circuitry.
In essence, the schematic diagram illustrating the
details of the volatile cross-l~nking agent ~eed or supply system
and the electrical control and alarm equipment for the exemplary
continuous extrusion embodiment thereof, as illustrated in
Figure 3, comprises a storage facilIty for liquid cross~-linking ~
agent 61, a pumping and metering compartment indicated by the ~-
dashed block 62, material and processing equipment indicated
by the dashed block o3~ display and alarm indicia 64 and 65 ;~
and various control, and sensing equipment to be described
hereinafter. The storage facility for liquid cross-linking
agent is disposed within a separate chamber of the peroxide
feed cabinet 2 illustrated in Figure 1 and is employed to
store a small quantity, 100 liters maximum, of cross-linking agent
in liquid form. The liquid cross-linking agents selected may
t~pically include:
di-t butyl peroxide (DTBP)
2,5-dimethyl-2,5-di(t-butylperoxy) hexane
2,5-dimethy1-2,5-di(t-butylperoxy)-3-hexyne
t-butyl cumyl peroxide
1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane
2,2-di(t-butylperoxy)propane
2,2-di(t-butylperoxy)butane or
cumyl hydroperoxide,
The storage of the cross-linking agent within the storage facility
61 is compartmented in flasks as indicated by flasks or vessels
66-69 with liquid
- 21 -
.. ~- ,: : : -
1~78~
cross-linking ~gent being pumped from the storage facility 61
through a conduit 70. For the conduit 70 shown, an operator
would be required to reposition the conduit within a full flask
each time a need for a new supply of cross-linking agent was
indicated by the minimum level indicia, to be described herein-
after; however, as will be appreciated by those of ordinary
skill in the art, branching and valving of a plt1rality of :
conduits for the flasks could be provided so tl~at a new supply
as well as the substitlltion of full flasks Eor empty Elasks
could be achieved by merely turning a val.ve and once the flask .
was isolated from the system, an empty flask could then be ~ .
replaced. The storage facility for liquid cross-linking agent 61
is an enclosed chamber as indIcated and is refrigerated by a ;i :
closed circuit refrigeration or "lost" water refrigeration
system indicated by the dashed block 71. The lost water or
closed circuit refrigeration system indicated by the dashed
: block 71 includes a motor 72 which drives a pump 73 which in
turn drives cooling liquid, maintained at a temperature wh.ich
is below 16C through the conduits 74-76 and the heat exchanging .::~
portion 77 to cool the storage facility for liquid cross-linking - :.
agent 61 in the well known manner. The closed circuit refriger- ::
ation or lost water refrigeration system indicated by the
dashed block 71 may take any conventional form of -this well
known class of devices or alternativelyS any suitable reErigeration .
system may be employed in its place.
Additionally, for the purposes of protecting the
.~ .
system against an outbreak of fire, a conventional ionization
chamber 78 of conventional construction is disposed within
the storage facility 61 for the purpose of detecting gases .:
emitted by combustion and to transmit information indicative ~:
of this condition to fire indicating means indicated by the
- 22 - :
1~78~L8~
dashed block 7~ ~hrough conductor 80. The ~ire indicating
means indicated by the dashed block 79 includes an amplifier
81, an instantaneous operating relay 82 and a delay relay 83.
Accordingly, as will be appreciated by those of ordinary skill
in the art, whenever a combustion gas- is detected by the
ionization chamber 7~, this signal is conveyed thro-lgh conductor
80 and amplified by the amplifier 81 in ~he well known manner ;:
to cause a triggering of the instantaneous relay 82 :eollowed
by delayed actuation of the relay 83. When ~he instantaneous
relay 82 is triggered in the ~oregoi.ng manner, QS shall be further
described above, system ventilation is terminated and a red
alarm signal coupled with the acutation of a horn is initiated.
Thereafter, when the delayed relay 83 is triggered, the closing
of the contacts associated therewith will cause flask 84, to
be opened whereupon fire extinguishing gases as contained therein
are conveyed through conduit 85 to extinguish any ~ire which
may be in the process of occurring wîth.in the storage facility
for liquid cross-linking agent 61. Accordingly, it will be
appreciated that the storage ~acility for liquid cross-linking
agent 61 comprises an essentially sealed storage facility which
is refrigerated to maintain the volatile cross-linking agent
in a cooled condition and is provided with an independent
fire detection and extinguish.ing system so as not only to be ~ -
isolated from its environment but additionally to be self-
protected. Alternatively, solid peroxide or other cross~linking
agents in-solidus form may be employed within the storage facility
for liquid cross-linking agent 61; ho~ever, under these
conditions J it ~ould be necessary to provide for the controlled
heating of the container and ducting so that the environment ~ .
established within the chamber is- set to maintain the peroxide
in its liquid state into which it w-ould be first rendered through
- 23 -
.: . . . . ,, . ~ .............................. . - - :
-,'' -,
:
a melting process.
The pumping and metering compartment indicated by the
dashed block 62 comprises a fill pump 88, a feed vessel 89,
metering pump 90, hydropneumatic dampers 91 and q2, a pressure
limiting valve 93, a pressure gauge 94, a ~low transducer ~5,
electric safety valves 96 and 97, a ~low meter 98, negative
pressure venting means 99 and catch basin means 100. The fill
pump 88 may comprise a conventional pump which is employed to
draw liquid cross~linking agen~ Erom the sto-rage eacility 61
through conduit 70 to the feed vessel 89 through the conduit 101,
The fill pump 88 is driven as indicated by conventional motor
means 102 which e.ither may be located within the pumping and
metering compartment 62 if the same is o~ an explosion proof
design or may be disposed without the pumping and metering
compartment and merely connected through a drive sh~ft or the
like to the fill pump loaded therein. The motor means 102
which may comprise either conventional AC or DC motor means is
energized through a set of contacts 103 ~o a conventional
power supply (not shown). Both the set of contacts 103 and
the power supply would be located outside of the pumping and
metering compartment 62 and preferably w-ithin the electrical
control and alarm cabinet 1 as shown in Figure 1. Accordingly,
as will be appreciated by those of ordinary skill in the art,
the motor means 102 is energized to cause cross-linking agent to
be pumped through conduits 70 and 101 into the ~eed vessel 89
whenever the contact set 103 is in a closed cond;t~on.
The contact set 103 which acts to cause the fill pump
88 to be energized ln the foregoing manner is controlled by the
condition of the pump relay 104 which is conventional and
acts to close contact set 103 whenever potential is applied
thereacross from the potential supply 105. The potential
supply 105 may comprise any conventional AC source of potential
~ 24 - :
:
''; '.: - '
:- : - . - . , . : - . . . . : . :,: . - . - :
~78~
or alternatively a DC source may be employed if this farm of
relay is preferred. The potential supply 105 is directly
connected to one side of the pump relay 104 through conductor
106 and to the other side thereof through conductor 107 and
the combination of switches 108 and 109, 108, 110 and 111 or
108, llO and 112 whichever group of switches is in a closed
condition to establish the serial path to the pump relay 10~.
Of course, should no serial path be established tc connect relay
10~ to conductor 107, the relay will be in a de-energized state
whereupon switch contacts 103 w~ill be in an opened condition
and the fill pump 88 will be inoperat~ve. The switches 108, 111
and 112 are controlled as a function of the level in th.e feed
vessel 89 in a manner to be described belo~ and hence it i5
here sufficient to appreci.ate that switch 108 is opened to
indicate a safe maximum level condition and terminates the
operation of the fill pump 88 while conversely, switch 112 is
acutated to indicate a mînimum level within the feed ves.sel 89
and hence indicates a condition associated with an eminent lack
of cross-linking agent in the flask presently being employed
within the storage facility for liquid cross-linking agent 61.
The opening of contacts 112 w-ill not, however, stop the action
of the fill pump 88 as no danger results when the s~ystem runs out
of fluid and warning devices which are provided are sufficient
to apprise an operator to immediateIy correct the condition~ :
In similar manner, the contacts lll are in a closed condition
when a normal level resides within feed vessel 89 and an
opening of this set of contacts will not result in pump
termination so long as th.e minimum level associated w;th contact
set 112 has not also been exceeded. This means, as will be
readily appreciated by those of ordinary skill in the art that .~.
an overlap may be established b~tween th.e normal level indicated :
- 25 ~
~C~7~
by contacts 111 and the safe mini~um level indica~ed by contact
set 112 50 that an operator is warned to input more cross-linking
agent into the storage facility for liquid cross-linking agent
prior to actual termination of the operation o~ the fill pump 88.
The switches 109 and 110 comprise a ganged pair of
switches which are biased to the condition shown. The closed
condition of switch 110 is definitive of the automatic mode oE
operation of the system which is :Lmplemented whenever an
operator depresses the Power On button at ~he electrlcal cabinet.
During the automatic mode oE operation it will be appreciated -
that the minimum and normal level controls associated with
switches 111 and 112 are operative. However, for cases where -
the system must be serviced, a push button associated with
contacts 109 is provided w-ithin the electrical control and
alarm cabinet 1 which will energize rela~ 104 and cause the
pump to be driven regardless of the condition of switches 111 and
112 so long as the push button is held depressed to overcome
the normal biased condition oP the ganged set of contacts 109
and 110. It should however be noticed that the maximum level
condition associated with contacts 108 is always operative as
it would be undesirable to let even a repairman initiate a set
of conditions where the feed vessel 89 could overflow.
The feed vessel 89 is adapted to receive pumped cross-
linking agent through conduit 101 in the manner indicated and
to sup~ly cross-linking agent to the metering pump 90 through
conduit 113, the filter 114 and the conduit 115. Within the
feed vessel 89 resides a level float 116 which acts in a
conventional manner to magnetically actuate respective ones
of the switch contacts 108, 111 and 112 and thus to control
the action of the fill pump 88 in the manner described above -~
and hence, control the level within the feed vessel ~9. It should
- " . . .
- 26 -
- . . . ... . ,....... .~ , , ,, .- , . . .. , : .
1~78~
be noted that ~henever either the maximum level condition
associated with switch 108 or the minimum level condition
associated ~ith swîtch 112 are actuated, appropriate ones of the
condition indicia 6 and 7 shown in Figure 1 are initiated.
~Iore particularly, as shown by the dashed lines 117 - 120,
appropriate condition indicia as depicted by the condition
indicia arrays 121 and 122 illustratecl in Figures 3~ and 3B
are energized. Thus, whenever a maximum level condition is
indicated magnetically by the level float 116 and switch 108
is opened, the contact set 123 is closed to illuminate the
maximum level alphameric panel indicia in the condition array
121 and as is illustrated by the conductor 125, the orange
warning light in condition indicia array 122 is energized.
Similarly, whenever a minimum level condition results in the
opening of contacts 112, a set of contacts 124 are also closed
to cause the minimum level condition indicia in condition
indicia array 121 to be illuminated and as is also indicated
by the conductor 126 to cause the red warning condition indicia
in array 122 to be illuminated~ Furthermore, as indicated by
the conductors 127 and 128, whenever either the red ~r orange
condition indicia are illuminated, a horn 129 is also sounded
to additionally solicit an operator~s attention. The feed
vessel 89 is additionally refrigerated in the same manner as
the storage facility for liquid cross-linking agent 61 by the
closed circuit refrigeration or lost water refrigeration system
71 through the winding of the conduits 74 and 75 therearound
in a serpentine fashion. Alternatively, if liquified peroxide
developed from solid peroxide w-a~ being supplied to the feed
vessel the feed vessel could be heated in the same manner,
described above, for the storage facility for liquid cross-
linking agent 61. Fluid may be drawn from the feed vessel o9
27 -- -
~078~8
by the metering pump 90 through conduits 113 and 115 and the
Lilter 114. ;:
The metering pump 90 may take the conventional form of
an incremental pump which is driven by the motor 130 disposed
outside the pumping and metering compartment 62. The speed with
which the motor drives the incremental pump 90 will be dicussed
in greater detail below, however, at thls ~uncture in the
specification, it is sufficient to appreciate that the speed
oE the metering pump is closely controlled by an error signal
so that precisely the right amount of cross-linking agent ls
injected into the base of the hopper for the rate in which
processing is occurring wherein both 10w rate and processing
rate can be measured in several fashions. The output of the
metering pump 90 in the form of a pulsed flow whose rate is
~ a function of the speed with which the motor 13Q is being ~:.
driven is supplied to the conduit 131 for application to flow
transducer 9S.
The pulsed flow applied to the conduit by the
~ incremental metering pump 90 i5 smoothed ~y a series of h.ydro-
~0 pneumatic dampers 91 and 92 which may be conventional and
act in the w-ell known manner to regulate the flow due to the . ~ .
. pressure regulating effect of the air or other media therein
; on the fluid levels ~hich are also present therein. In
addition, the metering pump is protected by a pressure limiting . .
valve 93 which may also be conventional and acts in the well
known manner to connect the output of the pump to its input t~
thus release the pressure in the exit line wheneverthe pressure in
the line exceeds the pres:sure to wh.ich. th:e s-ame is: set th.r~ugh. .:~a spring or other biasing means. The p~es:sure in th.e exit line
131 is also directly measured b~ a pressure gauge 94 to furthe.r
apprise the operator of the functions whi~ch are occurring w~ith.in
- 28 ~
": ' '
, . , , ~ . . . , . .: . .. . .
1~71~8
the syqtem.
The regulated output oE ~he metering pump 90 is thus
applied to the input of the .~low transducer 95 through conduits
131 and 132. The flow transducer 95 may take the form of a
conventional differential flow meter or alternatively, a magnetic
thermic or ultrasonic flo~ meter could be employed. In the
case of a differential flow~ me-ter, th.e relationship bet~een
the pressure being proportional to th.e square of ~he flow rate
is employed to generate a s.~ignal on conductor 133 whi.ch is thua
proportional to the square of the flow rate.
The signal on conductor 133 as developed as. a function
of the square of the flow rate through. the differential pressure
techniques employed b~ the flo~ transducer 95 is uti.llzed QS. a
preferred method of determining the flow rate within the system
so that the same may be displayed and also used where desired
to develop an error s.ignal for controlling the speed of th.e
metering pump motor 130. More particularly, the signal re- -
.. presenting the square of the flow rate i5 applied to a linear :~
amplifier 134 which may be conventional and is employed to shape : ....
the signal on conductor 133 in the well known manner~ The output
of th.e linear amplifier 134 is then applied through conductor 135 : -
to the input of a square root extractor 136 which may take the
conventional form of a differentiator or the like. Th.e output
of the square root extractor 136 wh:ich. is a signal ~hich is now-
directly proportional to the flow- rate of fluid being applied .. :~
to the flow transducer 95 i~ applied through. conducto~ 137 to . :;~
the input o~ a linear amplifier 133 for additional sh.aping and
ampl~fication in the conventioDal manner. The resulting signal .-
obtained at the output of amplifier 130 is: applied to conductor .:.
139 tc potentiometer 140, which h.ere acts as a sensitivity ad- -
justment, and is thereafter appl~ed th.rough conductors 141 and .
142 to the inputs of a digital display 145 and one input of an
. . .. - :
- 29 - `
.
. , .. ~ - - . .- ,
~.~7~
an~log recorder 146 so that the flow rate thus obt~ined may be
directly displayed to the operator in terms o:~ ]iters per hour
and recorded for reference purposes. The digital display 145
corresponds to dîgital display 8 in Figure 1 while the analog
recorder 14~ corresponds to the two track analog recorder 9 as
also shown in Figure 1.
The flow rate signal obtainecl from the output o:~
potentiometer 140 on conductor 141 is a negative signal represent-
in~ the Plow rate and is employed, after suitable manlpulation,
to develop an error signal from summing point 150, under
conditions where actual flow rate is belng utilized to develop
the error signal. Once the error signal is developed at summing
point 150, it is applied to a conventional di:~ferential amplifier
151 and a thyristor bridge 152, which also may be conventional,
so that a drive signal proport~onal to the error s~gnal is .
applied through conductor 153 to control the speed of the metering
pump motor 130 and hence the flow rate through the system as -
determined by the speed of the incremental metering pump 90. . `.
More particularly, when flow rate is to be employed in the
development of an error signal, which is the automatic mode set
:'
a-t the console to be distinguished from the manual mode, the -
s~itch 154 is- in a closed condition while the switch 155 is in ~
an opened condition, i.e,, opposite to that illustrated in Figures
3A and 3B. Under these conditions, the negative flow rate signal ~ :
developed as a negative level from the output of potentiometer
140 on conductor 141 is applied through conductors 142 and 156, a ~ :
,
- resistor 157, conductors 158 and 159, the closed switch 154 and ~ :
....
.: ..
the conductor 160 directly to the summing point 150. In addition, : -
the negative flow rate signal on conductor 141 is applied through .~
a resIstor 161 to a summing point 162 where it is combined with a ;~.
positive signal representing, as shall be seen below, either the ~- .
~ ~ 30-
, - . ~. ~. .- ; ~
rate at which completed material is being processed or the speed
of the extruder screw so that a measure of the processing rate
is effectively applied through conductor 163 to the summing point
162. Accordingly, the output of the summing point 162 on
conductor 164 represents a system error signal which is then
applied to the integrator formed ~y the capacitor 165 and the
operational amplifier 166. The error signal is thus integrated
and inverted in the well known manner ancl thereafter applied
through
'
conductor 167 tn the input of the inverting amplifier 16B. The correc-
tion signal thus obtained at the output of the inverting amplifier 168
is applied to conductor 169 where it is algehraically summed with the,
negative flow rate signal on conductor 158 whereupon the resulting signal
is applied through conductors 159, the closed switch 154 and conductor
16û to the summing point 150 where an additional component signal is
added to the modified flow rate signal applied to conductor 160 under
this set of conditions. More particularly, a tachometer generator 17û
is connected in the convention manner to measure the speed of the
motor 130 and develops a negative signal proportional to the speed
thereof. This signal is then applied -through a voltage divider ~ormed
by resistors 171 and 172 to the conductor 173. As the switch 155 is
in an opened condition due to the automatic mode of operation set by
the operator wherein actual flow rate measured by the flow transducer
95 is employed in developing an error signal, only the AC portion of
this signal is applied through capacitor 174 to the summing point 150 -
as a damping signal for the resulting signal applied on conductor 160.
Thus it will be seen that when actual flow rate is being employed in
developing an error signal at the summing point 150, the actual flow
rate is measured by the flow rate transducer 95 and displayed at the ~ ;
digital display 145 whereupon this signal through conductor 156,
resistor 157 and conductor 158 is summed algebraically with the integral
of an error signal developed at summing point 162 and added to a
damping signal developed from the output of the tachometer generator
170 whereupon the resulting sum is applied to the summing point 150.
~hen the automatic mode is established by -the operator, the
switch 154 is placed in a closed condition while the switch 155 is opened
~8~
as aforeslid. ~dclitionally, the establishment of this mode places the
s~itch 176 in the condition illustrated in Figures 3A and 3B so as to
connect a second input of the summing point 150 to conductor 177 through
a resistor 178. The conductor 177 is connected to a switch 179 which may
be set at the console by the operator and is determinative as to whether
the rate at which finished material is processed a-t the output of the
continuous vulcanization tube or the speed of the extruder scrcw i5 to
be employed as a measure oF the rate at which the processing of rnaterial
in the hopper is being processed. More particularly, iF the material
processing equipment within the dashecl block 63 is considered, it will
be seen that the items illustrated within this block include the extruder
screw 180 and material pulling equipment 181 which, in the case of the
cable making application discussed in association with Figure 1, wnuld
cornprise pulling equipment suitable for withdrawing finished cable from
the end of the continuous vulcanization chamber at -the rate at which the
same was being made. Thus, in the case of the extruder screw 180, the
speed with which the same would turn would normally be expected to
measure the rate in which material was being processed From the hopper -
while in the case of the material pulling means 181, the rate at which
actual cable was being made, in the exemplary embodiment, would be
determined by the rotation of the driven wheels thereof indicated by the
idler wheels 182 and 183. In actuality, the rate at which the idler wheels
182 and 183 are driven by the pulling of finished cable would constitute
the better measure since extruders are notorious for clogging or becoming
dirty and hence their rate of rotation will not represent a constant
measure as to the amount of material being processed from the hopper
without periodic readjustment. However, there are certain circumstances in
-32-
~ .
18~
which this type of measure is desireable such as for initiating the
operation and the like.
In each case, a tachometer generator 184 and 185 is employed
to measure the speed of the extruder screw or the idlerwheels 182 and
183 respectively and the positive DC voltage developed thereby is
applied through the voltage dividers formecl by the resistors 185 and
186 or 187 and 188 to the inputs of potentiometers 189 and 190. Tlle
inputs to the potentiometers 189 and 190 are applied through conductors
191 and 1~2 to the inpu-ts of the switch 17~. Thus it will be seen that
depending upon the setting of the switch 179, the voltage level applied
through conductor 177, the switch 176 and the resistor 178 to the sum- ;~
ming point 150 will be a measure of either the ra-te a-t which completed
cable is being pulled from the continuous vulcanization chamber or the :
rate at which the extruder is turning which is an indirect measure of
the material being drawn from the hopper. When this positive signal -
is algebraically summed with the negative going flow rate signal
applied to the summing point 150 it will be seen that the output of the '
summing point 150 which is applied to the amplifier 151 effectively is an
error signal representing the difference between the flow rate and the
rate at which processing is occurring measured in one of two selected
manners. Thus this signal, when applied to the thyristor bridge 152
will drive the motor for the metering pump 90 at a rate to reduce the
error signal to zero and hence cause the rate of fluid flow as governed
by the incremental metering pump to correspond to that at which volatile
cross-linking agent is being employed for processing. It will be
appreciated that when switch 176 is in the condi-tion indicated, the
lower input to the differential amplifier 151 is zero and hence the
summing point 150 in actuality develops the error signal employed. The ~ -
-33- ~ ~
.' '~
`'-''~:
8~
processing rate applied to the input to switch 179 is also
applied through conductor 193 and resistor 19~ to the conductor
163 and hence this rate information is applied to summing point
162 in the manner aforesaid. It should additionally be noted that
switch 195 is ganged to switch 179 ~nd hence wil~ receive ~he
output of the voltage divider 185' and 186 or 187 and 188 through
potentiometers 196 or 197. These potentiometers are set in
substantially the same manner as potent:lometers 189 and 190 so
that the resulting signal applied to ~he switch 195 and conductor
198 may also be recorded at the two channel analog recording
device 146 so that actual flow rate information is recorded with
the rate of material processing measured in the manner elected
by the operator. The flow rate signal on conductor 144 and the
processing rate information on conductor 193 are additionally
applied to conductors 199 and 200, respectively.
The signals on conductors 199 and 200, representing the
actual flow rate as measured by the flow transducer 95 and the
preset flow rate, established by potentiometers 189 and 190,
measured as a function of the processing speed, as elected by the
operator through ganged switch 179 are applied through conductors
201-206 to individual ones of threshold comparators 207-209~ ~The
threshold comparators 207-209 may take the conventional form of
deadband amplifiers which each act to compare on a continuous basis,
the magnitude oE the error signal as measured between the actual
flow rate within the system as established by the signal on con-
ductor 199 and the rate at which material is being processed as
present on conductor 200. The settings of each of the threshold
comparators 207-209 differ and are associated with specific
conditions which must be detected for safety indicia and/or auto-
matic shut down to occur. More particularly, the threshold am~plifier 207 is associated with a maximum flow condition
- 34 -
which is measured by stepping the threshold comparator 207 to a level
which is calculated to be 10o above a norrnal flow condition. Therefore,
as will be appreciated by those of ordinary skill in the art, whenever
the difference in the signals supplied to conductors 201 and 204 is less
than a value which is 10~o above normal flow no output is produced by
the threshold comparator 207. ~lowever, when the diFFerence hetween
these input signals exceed the 10o of normal flow value cstablished, an
output level is supplied on concluctor 210 which thus triggers the
maximum Flow relay 211. When the maximum Flow relay 211 is
triggered, the contact set therein is closed 90 that an energizing
level is applied through conductor 212 -to cause the maximum flow
indicia within the alphameric indicia array 121 to be energized and in
addition thereto, as indicated by the conductor 213, the orange warning
indicia is energized in an intermittent or flashing manner and the horn
129, as indicated by conductors 127 and 128 is also enabled. Thus,
whenever a maximum flow condition is measured, the maximum flow
relay 211 is triggered to initiate a flashing orange alarm and the horn
129 while the appropriate panel within the alphameric display 121 to
define the nature of the condition measured is illuminated.
In a similar manner, the threshold comparator 208 is set to
measure dangerous flow conditions which are defined as those which
exceed a normal flow condition by 50O. Accordingly, the level of -the
threshold comparator 208 is set to this magnitude and whenever this
condition is detected, an output signal is applied to conductor 214 to
trigger the dangerous Flow relay 215. Whenever the contacts within the
~ ~ .
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'``'` ' ^11`''
l ~
l ~78~8~
dangerous flow relay 215 close, as indicated by the conductors 216 and
~17, tne dangerous flow alphameric indics within the indicia array 121
is illuminated and additionally~ the red in(licia within the array 122 is
I illuminated on an intermittent or flashlng basis together with the horn
¦ 1~9. Thus, the closure of relay 215 which indicates the presence of a
¦ dangerous flow condition, initiates the sounding of an alarm in terms of
¦ a red flashing light and horn while the appropriate one of the alpha-
I meric indicia in array 121 to define this condition is illuminated. In
¦ addition, a second set of contacts 218 which are associated with the .
dangerous flow condition relay 215 are opened to terminate the operatia .
of the metering pump through the control logic associated with the bloc
219 which is subsequently described. Here, however, it is sufficient to
appreciate that the control logic within block 219 enabLes the metering
pump 90 to be driven in the manner described above so long as the .
- contact set 220 associated therewith is in a closed condition; however,
whenever the contact set 220 r~sides in an opened condition, the driving
¦ current for the metering pump motor 130 will not be provided thereto.
Thus, whenever a dangerous flow condition is detected, the metering
pump 90 is stopped and an alarm in the form of a red flashing light and
a horn is initiated together with an illumination of the appropriate
I indicia panel within the alphameric indicia display 121. It should also :
¦ be noted that the contact set 218 associated with relay 215 or the
operation of the purnp control logic associated with block 219 may be
I timed so that upon detection of a dangerous flow condition, the pump is
initially stopped for a short interval, such as five ~5) seconds, and then . ~ . .
is restarted to ascertain if the condition persists; however, should the -
. -36
. . . . "~
-.- . . ': ~ '
~7151~
condition persist~ shut down in a Final manner may then be initiate~l.
The threshold comparator 209, as indicated, is associated
with a minimum flow condition and hence, this threshold comparator
is preset to establish an output signal on conductor 221 when the
di~f~erential measured between the input signals on conductors 2n6 ancl
203 drops below the level corresponding to lOno below normal flow.
When this occul:s, an output signal is provided on conductor 221 to
energize the minimum flow relay 222 and hence, signal a minimum flow
condition. When the minimum flow relay 222 is triggered, as indicated
10 by conductors 223, and 22~, the minimum Flow display indicia within the
alphameric display 121 is illuminated together with the illumination of
the flashing red panel and the horn 29. Although not shown in Figures
3A and 3B, the minimum flow relay 222 may have a second se-t of
contacts associated therewith to stop the action of the metering pump
90 through a disposition of such second set of contacts in much the
same manner as the contacts set 218. Alternatively, a timing
- arrangement could also be employed with this second set of contacts
to cause a stopping of the pump after a short interval such as five (5)
seconds, if this condition should persist or alternatively, the timing
20 could be achieved by the pump variation control logic indicated by the
- block 219. Thus, it will be seen that whenever a dangerous flow
condition is detected, the metering pump 90 is stopped and an alarm
condition is indicated by a flashing red light, the sounding of a horn
and the illumination of an alphameric display indicia indicating the
condition. Similarly, should a maximum flow condition be detected,
a flashing orange light is initiated together with a horn and a display
indicia indicating the condition while for minimum flow detection, an
--37--
..
. ~ f~3~1L88
,alarrtl in the lorm of a flashing red light and horn together with an
¦appropriate display panel is issued and the action of the metering pump
may be stopped.
Upon a setting of the manual mode control switch by an operato ~,
the switch cont~cts 176 are changed in position to cvnnect with the input
to potentiometer 225 through conductor 226 Additionally, as
was stated above, the switch 154 is opened while the switch contacts
155 are closed so as to reside in the condition illustrated in Figure 3
so that manual operation of the pump may be initiated for the purposes
of testing or calibration. Additionally, as shall be seen below,
switch contacts 227 associated with the relay 228 and the metering
pump control logic 219 are closed to effectively by-pass the dangerous
flow and other sa~ety feature interlocks so that relay 228 is
maintaine-d in an energized condition to thereby retain the contacts
22û of the metering pump control logic closed so t~at the same can be
operative. Although the mode control switch associated with manual
nd automatic operation has been stated as present on the face of the
electrical control cabinet illustrated in Figure l, the same may be
modified so that manual operation OI the pump for testing and
calibrating purposes rnay only be inLtiated by an opening of the cabinet
and the depression of this switch which would then reside therein to ; -
insure that only authorized personnel can implement the manual
operation of the metering pump 90 for testing or calibration purposes.
In the manual mode of operation, associated with the switching of contacts
178 to the input~ potentiometer 225 and conductor 226, the metering
pump rnotor 130 is essentially driven from a DC level and feedback
. ' - ' ' . ."' '' "
. , . ' . ' "" :'
. . '.'
0781~8
rep~csel~till" the spc.~ of ihe motor per se is employed thrc~ugh feedbac¦
techniques to form an error signal from summing point 150. More
particularly, when switch 176 is placed in contact with the conductor
226, the 15 volt supply of voltage to the potentiometer 225 is stepped
down and applied through conductor 226, the switch 176, and the
resistor 178 to the summing point 150. Similarly, the negative signal
developed by the tachometer 170 as a function of the speed of the
metering pump motor 130 is stepped down through the voltage divider
formed by the resistors 171 and 172 and applied through conductor 173,
the resistor 175, the switch 155 which is now in a closed condition and
¦ the conductor 160 to a second Input to the summing point 150. The
¦ difference between the positLve level from the output of resistor 178
¦ and the negative level on conductor 160,as thus obtained,is applied from
I the summing point 150 to the differential amplifier 151 whereupon the
-15 difference signal is applied to the thyristor bridge 15Z and a ¦
driving signal for the pump motor 130 is developed therefrom and
I applied thereto through conductor 153. In this manner, the metering
¦ pump motor 130 may be driven for calibraticn or testing purposes under
¦ operator control.
¦ The final element associated with the driving of the metering
pump motor 130 is associated with the metering pump variation control ¦ -
¦ logic indicated by the block 219. This logic, when in an op~ative
condition, will close a set of contacts, not shown, to cornplete the circ~it
to the input ~e the metering pump drive motor which resides between
~ the differential amplifier means 151 and the motor 13~ wherein any
location therein is suitable. Alternat;vely, the control of the metering
_39_
pump logic indicated by the block 219 may be associated with a triggering
function of the -thyristor bridge 152. In any event, the pump variation
control logic associated with the block 219 may serve to moni-tor any
functions of the me-tering pump motor 130 or the me-tering pump 90
which are deemed desireable and in addition thereto an external set of
contacts 220 associated with the metering pump variation control 219
are employed to terminate the action of the metering pump any time an
abnormal or dangerous condition occurs within the system. More
part:icularly, the contacts for the metering pump con-trol logic indicated
10 by the blocks 219 are controlled by a relay 228 which additionally controls
the set of contacts indicated as 229 and 230. Thus, when the me-tering
pump relay 228 is in an energized condition, the contacts 220, 229 and
230 are in a closed condition whereupon the pump variation control logic
indicated by the rectangle 219 may control the operation of the metering
pump motor as aforesaid. Additionally, with contacts 229 in a closed ;
condition, a signal level is applied through conductor 231 to the display
indicia array 122 to cause the illumination of a green lamp or panel
therein and thus indicate to an operator that a normal operation is :-~
occurring. The closure of contacts 230, as shall be seen below, enables
electrical safety valves 96 and 97 to be retained in an opensd condition
where the flow is permitted to pass therethrough in a manner to be
described subsequently. The energizing circuit for the relay 228 is
supplied through either the contact set 227 or the grouped sets of
contacts 218, 232 and 233 to a potential supply which has not been
illustrated. The set of contacts 227 are automatically closed, as afore-
said, when manual pump operation is the commanded mode through a
switching of the mode switch associated with switch 176 as a~oresaid, ;
and whenever this
.:
-40-
--- . -. , --, - , - . . . - , . ,. -: : .
~)7~
condition persists automatic energization of the relay 228 is
initiated together with the operation of the pump. However,
during automatic operation, the pump relay 228 is energized
through the set of contacts 218, 232 and 233 which all must be in
a closed condition Eor the pump to operate since an opening o~
any of these switches will cause the relay 228 to open whereupon
the contacts 220, 229 and 230 open causing the pump to be dis~
abled, the green light to be ext:lnguished and the e:Lectrical
safety valves 296 and 297 to be closed~ The con~act set 218 ~s -.
controlled by ~he dangerou~ flow relay 215, as aforesaid, and
hence any time this condition occurs, the pump relay 218 is
disabled. Similarly, contact set 232 is ln a closed condition ~:
only when the extruder screw 180 is operatlng as the same is .-
driven by a relay which is actuated as a function thereof and hence
if at any time during normal operation the extruder screw should
jam, the set of contacts 232 will open to shut down the system~
Similarly, the contact set 233 wh.~ch. may~ operate in res~ponse tQ a
delay as indicated, is controlled by th.e conditi.on of the hopper :
level relay 234 which is driven from th.e output o~ a deadband -
amplifier as a function of a level control 236 withtn th.e h.opper . -
~237 of the extruder. When the hopper has a sufficient level of
compound to be cross-linked th.erein~ a normal level i5 provided
from the level control 236 to the deadband amplifier 235 wh.ere-
upon no output i6 provided to th.e hopper level relay 234, Under ~;
these conditlons, the deIayed contact set 233 rema~.ns clos:ed and
the pump relay 228 iS energi.ze.d, However, sh:ould the level of
polyolefin in the h.opp~r drop beIow-a specified amount, an out
put is produced from the output of th.e deadband amplifier to
energize the hopper level relay 234 and cause the delayed contact -
set 233 to open and th.ereby disable the pump motor relay andhence the metering pump per se through the opening of switch
contacts 220. The level control 236 for the hopper may be a
41 -
~C~751~
conventional mechanical or capacitive level detection device
well known to those of ordinary skill in the art. Accordingly,
it will be appreciated by those of ordinary skill in the art that
the pump motor relay 228 is disabled any time a dangerous flow
condition occurs, the level in the hopper 237 becomes tQo low-,
or the extruder screw is not turning. Thls immedlately causes
~he pump motor to be disabled tllrough contact set 220, the green
normal operating light to be extinguished through contactæ 224
while the electrical safety valves 96 and 97 are closed through
the operation of safety relays 238 and 242 in response to the -
opening of contacts 230.
The description of the pumping and metering compartment
62 set forth above has outlined how cross-linking agent is pumped
from the storage facility for liquid cross-linking agent 61
into the feed vessel 89 by the action of the fill pump 88 and ~ -
the operation of the fill pump 88 is strictly and precisely con- -
trolled by levels residing within the feed vessel 89. Thereafter,
the manner in which liquid cross-linking agent is d~awn from tne
feed vessel 89 through the conduits 113 and 115 by the metering
pump 90 and then supplied, after appropriate smoothing of the
pulsed flow, to the flow transducer 95 wai~ described together
with the manner in which the speed of the metering pump is
controlled as a precise function of the difference between the
flow rate within the system and the rate of use of material in
processing. A similar description was also prov;`ded for the many ,-
safety features employed within the sy~stem to ensure that a
safe flow within the system is maintained. After the flow rate -
is measured by the flow transduce-r 95, it is applied through the
; electric safety valve 96-to the flow- meter 98. The electric
safety valve 96 may take any of the well
'
- 42 -
- - . , . . - . ,-
' iO'78188
¦ known forms of this conventional class of device which functions to
¦ convey fluid therethrough only when po~ver is supplied to the actuating
relay therefor illustrated as 23g. Therefore, as the relay 238 is
¦ connected throu~h conductor 239 to the contacts 230 which are controlle ~ :
I by the pump motor relay 228,it will be appreciated that any time power
is not applied by the system or the metering pump is disabled, the
electric safety valve 96 is immediately closed to close off the flow of
liquid cross-linking agent through the system prior to the flow meter
98.
¦ The flow meter 98 may take any conventional form of flow .
l meter but the float type employing a glass tube for visual inspection of
¦ the flow is preferred to permit an operator to view the flow on a period c¦ basis so that not only may its rate be ascertained but its characteristic
, . I visually Lnspected. The flow meter 98 corresponds to the glass tube
¦ flow meter illustrated as 18 in Figure 1. After passage through the
¦ flow meter 98, the liquid cross-linking agent being pumped through the
system is supplied through conduit 241 through a second electrical
safety valve 97. The electrical safety valve 97 may take the same forn
I as the electrical safety valve 96 described above and the operatlng
¦ relay 242 therefor is energized through conductor 243 and the pump
relay contacts 230 in the same manner as was descrlbed for the operati
relay 238 of the eledrical safety valve 96~ This means that any time -
power-is not applied to the system or the metering pump is disabled
through the action of the pump relay 228, the electrical safety valve 97
¦ Ls closed. The physical location of the electrical safety valve 97 has I
¦ been shown outside of the pumping and metering compartment 62; howe~ r,
~ its location is preferably just inside this compartment at a location whe
. . ' ~"
. ' , , . ,'...... ~
~(~78~
the peroxide is in~ected from the cabinet into the base of the
extruder. This means that any time the pump operation is termin-
ated, peroxide injection will immediately terminate and virtually
no drippings from the cabinet into the hopper ba~e will occur.
This has been indicated by the positioning of the electric safety
valve 97 at the beginning portion of the injector tube for peroxide
in the hopper cabinet. The injector tube 244 corresponds to the
conduit 17 shown in Figure 1 and is positioned to inject liquid
cross-linking agent into the base of the hopper.
The pumping and metering compartment indicated by the
dashed block 62 is provided with a negative pressure venting means
99 to maintain a pressure therein which is less than atmospheric
pressure while to additionally cause the venting of the cabinet.
Tn this manner, any liquld cross-linking agent which should spill
or evaporate within the environment of the pumping and metering
compartment 62 will be quickly vented to a safe environment,
While the negative pressure venting means 99 has been schematically
illustrated, it should be noted that seal proof construction is
used throughout and that ducting to an external environment carried
out through the port includes essentially a one way flow from the
interior and metering compartments 62 to its external environment.
The negative pressure venting means 99 has been illustrated in
Figure 3 as being driven by a fan blade 246 which in turn, is
driven by a motor 250 which is located externally with respect to
the pumping and metering compartment. The motor 250 is energized
through a relay contact set 251 and a current sensing device 252,
the potential supply to the motor not being shown. Thus, it will
be seen that whenever the relay contact set 251 is in a closed
condition, the fan motor 250 will be energized to thus energize the
- 44 -
~LC978~
negative pressure venting means 99, The relay contact set 251 i$
actuated by the condition o~ the vent-~ng relay 253 which is
connected across the potential supply 105 directly through con~
ductor 106 and indirectly through relay contact sets 254 and 255
to the conductor 107. Accordingly, it will be appreciated by thos.e
of ordinary skill in the art that so long as contact sets 254 and
255 are in a closed condition, the venting relay 253 will be
energized to close contact set 251 and hence energize the venting
motor 250. The contact set 255 is connected as indicated to the
instantaneous relay 82 wlthln the fire indicatlng means 79 and
hence this contact is opened by the instantaneous acting relay
~2 only when ~umes indicating a combu$tion situation have been
indicated. Thus, when such fumes are detected it will be seen
that contact set 255 is opened to deenergize the venting relay
253 to cause the contact set 251 to open and hence, deenergize
the venting motor 250. Similarly, contact set 254 i5 energized
as a function of the current sensor 252 in the same manner as a
relay contact set. Thus, whenever a normal current level is being
sensed by the current sensor 254 in well known manner, contact
set 254 is energized to energize the venting relay 253 and
hence to continue the motor 250 in an energized cond~tion. How~-
ever, when excess current is sensed by the current sensor 252, the
contact set 254 is opened to de-energize the venting relay 253.
It will be appreciated by those of ordinary skill in the art th.at
should excess current be sensed by the current sensor 252, the
venting motor 250 is operating improperly and hence, appropriate -:
ventilation i.s not occurring. There~ore, to avoid ~urther damage, .
the venting relay 253 is opened to disable the motor 250 and an .-.
additional contact set 256 is closed, The contact set 256 is
30 connected between ~
- 45 - .
'~ ' '
a potential supply indlcated by the horizontal line and the conductor 257
to the temperature ventilation alphameric indicia within the alphameric
indicia display array 21 and through the conductor 258 to the re~
indicia within the warning light array 122. This means that both the
temperature ventilation indicia wi-thin array 121 will be illuminated
together with a flashing red warning light and the horn 129. Accordingly,
it will be appreciated that whenever a failure of ventilation motor
250 is de-energized while should a fire condition any place :in the system
be detected, de-energization of the venting motor 250 occurs through
direct de-energization of the switch contacts 255.
In a similar manner, a heat sensor 260 is disposed within the ;
pumping and metering compartment 62 to monitor the temperature therein.
The heat sensor 260 may take the form of a conventional thermal couple
... .... .
or the like and is connected as indicated to energize a relay 261 any
time a high temperature condition is detected. Upon energization9 the
relay 261 closes contact set 262 to connect a supply indicated by the
horizontal line annotated V through conductors 263 and 257 to the
temperature ventilation indicia within the array 121 and the red warning
light within the array 122 to cause both indicia to be illumina-ted and
sound the warning horn 129. Accordingly, it will be appreciated by
those of ordinary skill in the art that should either the ventilation
or an abrupt rise in temperature occur within the pumping and metering
compartment 62, a warning of abnormal conditions is issued to the
operator together with the illumination of advisory indicia specifying
the precise condition which has caused the warning indicia to be issued.
.~.".': '
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8151
All parts within the pumping and metering compartment 62
which come in contact with the metered liquid are strictly non-corrosive
and neutral in construction with regard to the product being provided
and such materials may be made from stainless steel, glass, TeFlon,
polyethylene, etc. In addition, the connecting ducts for the insulation
are also preferably formed of stainless steel and heavy metals such as
copper are deliberately avoided. All electrical apparatus contained
within the pumping and metering compartment 62 are either oF an
explosion type design or are inherently safe and the power levels
selected are chosen so as to be incapable oF arcing. Similarly, all
feed throughs oF conduits and electric cables utilize leak proof gaskets
so the integrity oF the environment on either side of -the gasket is
maintained. Furthermore, a catch basin lO0 is positioned within the
pumping and metering compartment 62 so as to underlie all
components handling metered liquid and hence, serves to prevent the
leakage of material out of the container. A sump 265 is provided
within the catch basin lO0 so that all fluid which has been caught thereby
will be collected in the sump whereupon the level thereof may be sensedO
More particularly, the sump is provided with a pneumatic or similar
level monitor 266 ~vhich is arranged to close a se-t of con-tacts 267 when-
ever the level in the sump exceeds a predetermined level. When the
contacts 267 are closed, potential is applied from the source indicated
as V through conductor 26E~ to illuminate the alphameric indicia
within the alphameric indica array 121 annotated LEAK. In addition, as
indicated by the conductor 269, the red flashing indicia within array 122
is also illuminated to cause a red flasing warning to be issued and a
sounding of the horn 1 2g.
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-47- -
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10~78188
. ~'
Fire detection and correction equipment may also be provided
within the pumping and metering compartments 62 through the provisio~
of an ionization chamber 270 therein which acts to detect gases
associated l,vith combustion. The ionization chamber 270 may be
the same as ionization chamber 78 described above and is connected
through conducSor 271 to the fire indicating means 79 described above.
This means, it will be recalled, acts in response to the detection of
a fire condition to immediately terminate the operation of the ventilatio
system through immediate acting relay 82 and the contact set 255 while
- acting through the operation of delayed relay 83 to initiate the operationof extinguishing equipment. In the case of the pumping and metering
compartment 62, an extinguisher flask 272 is mounted on the side of
the pumping and metering compartment 62 as shown and when -enabled
, by the output of the slow acting relay 83 through conductor 273, causes
extinguishing fluids to be vented into the system through the conduit 274
¦ It should additionally be noted that any time the immediate acting relay
- 82 within the f~re indicating means 79 is actuated, a slgnal is supplied
thereby through the conductor 275 to cause the red warning indicia
¦ within the indicia array 122 to be actuated while a fire horn 276 is
¦ additionally actuated. When fire indicating means 79 are ernployed
¦ within the system, additional ionization chambers such as 277 may be
disposed about the syst em to warn of externally developed fire hazards
and to cause extinguisher fluid to be supplied to hazardous areas handli ;
metered nuids, -
~5 Though not previously described, the switch 17~ which acts,
as aforesaid, to determine whether the error signal is developed as a
-48- '~
. , . .
, ' .' ''
~7~18~3
function of the speed of the extruder screw or the speed of the
actual production line is ganged in the manner indicated to the
switch 278 associated with the alphameric indicia display 121.
Accordingly, this switch 278 thus defines the mode of synchroni~
zation being employed to the alphameric indicia display and
accordingly, will couple the voltage source indlcated by the
horizontal line annotated V to the appropriate one o~ the con-
ductors 279 or 280 to cause the approprIate :lndlcla, extruder sync
or line sync, to be illuminated to thux apprise the operator as
to the method of synchronization employed to develop the error
signal whlch controls the speed of the metering pump. When
the extruder sync indicia is illuminated, the blue warning indicia
within the array 122 is illuminated as indicated by the conductor
281 while when line production synchronization is being employed,
as indicated by the conductor 282, the white indicia associated
with the array 122 is employed.
An event recorder 290 is also provided so that a con-
tinuous record is made of the critical warnings issued as a
function of time as well as the modes of operation taking place
when such warnings were issued. The timing function is provided
by means of a synchronous motor 291 driving the record paper at
a speed which is exactly proportional to time. Similarly, the ~-
occurrence of the red and orange warnings, regardless of origin, -~
are the critical factors which need be noted in a continuous
record of operation and the energized or de-energized condition oE
the red and orange display indicia within the array 122 may be
conveyed through conductors 292 and 293 and recorded on appropriate
ones of the tracks of the six track event recorder 290. Similarly,
as the nature of the synchronization employed to develop the error
signal is defined as a function of either the actuated condition
- 49 -
~ - - . , , - .
: of the blue or white warning lights, the enabled or dis.abled
level thereof ~ay be supplied from the array 122 through conducto~s
294 and 295 and recorded onto additional independent tracks of the
six track event recorder serving as the event recorder 290,
Finally, the condition oE switch 176 deEining either the manual
or automatic mode oE operation may be gated to the base of the
warning light array 122, through means not shown ? ~nd conveyed
- for recording purposes on an additional track of the six track
event recorder through the conductor 296, Thus, in this manner~
a continuous record is malntained as: a function of time b~ the
event recorder ~hich record includes the modes of operation initi-
atedl the type of synchronization employed therewith and the nature
of the dangerous conditions which occurred during such operation~ -
Such records may be quite important in further analyzing the .
operation of the instant embodiment of the invention wherein
highly volatile cross-linking agents are supplied from a closely
controlled and monitored supply system and injected into the base
of an extruder under ambient conditions~
The p~esent invention is viewed as highly advantageous - :
~ 20 since it permits precisely metered amounts of a liquid agent such .~
- as an organic peroxide or any other highly volatile liquid to be .~.
: injected under ambient conditions for combination with other com-
pounds in a manufacturing process under circumstances which require ~:
no preliminary preparation of materials-. Furthermore, the supply ;~ . -
system proposed is e~quisitely configured for the safe handling
of highly volatile materials such as: volatile cross-linking agents
because th.e metered output thereof is controlled as: a function of
an error signal developed bet~een the rate at which liquid cross-
linking agent is injected and the rate at which the same is bei.ng
used during processing. This means, that under no
- 50 -
~7~ 8~3
conditicnswill more cross-linking agent be delivered than is effectively
being employed so that a dangerous build up of volatile material is
avoided. Furthermore, through the provisions of internal monitoring
and safety features as well as arranging the fluid conducting components
within the pumping and metering cabinet l and on an inclined plane
upwards towards the output, should arly dangerous conditions arise, the
cut-off of injected material from the extruder is immediate and also
self-imposed by the system. Furthermore, the supply system per
se provides an operator with timely warning~ so that abnormal
conditions which become hazardou~ may be timely corrected and alarm
features calculated to call immediate attention to the condition are
employed. Thus, while possible devia-tions in the metering rate of the
liquid injected are constantly monitored and automatically corrected,
they are also displayed and recorded so as to be readily available for
operator analysis. ~
The supply system employed also warns of dangerous flow,- ;
maximum flow and minimum flow conditions so that flow rates which are
either hazardous or improper are immediately called to the attention of
the operator and should a hazardous condition exist, the metering pump
2û
is terminated to immediately cure the condition. Similarly, maximum
and minimum level contrb~s within the feed vessel 89 are monitored so
that both overflow conditions and conditions wherein the system is
about to run out of cross-linking agent are indicated to the operator
while the fill pump 88 is terminated to permit the condition to be
corrected. Similarly, in areas where the volatile cross-linking agent
are handled per se, venting is provided and monitored while refrigera-tion
techniques with temperature monitoring are also employed to avoid
hazardous conditions. In a similar manner, the metering pump which
controls injection is interlocked with the operation of the extruder or
~8~
a slmilar processin~ device so that injection is precluded unless
processing operations are occurring and the only exception to this
is provided in a manual mode of operation which is necessitated
for testing and calibration procedures. ~lectrically operated
valving is also provided to ensure immediate cut ofE oE the in-
jected cross-linking agent should power failure or termination o~
the metering pump arise and combustion detection equipment to-
gether with automatic extinguishlng equipment may be employed in
appropriate portion of the supply system to further reduce the
chance of accidental ;Eire or the like, Similarly, the use of
the inventive supply system in connection with the extrusion of ~
polyolefin compounds or the like is highly advantageous ~ecause `
using a cross-linking agent in its volatile form in the example -
cited is much less expensive than forms of the cross-linking agents
which are currently employed, does not require special preparation
and the combination may be initiated under ambient conditions where-
in the extruder per se is employed to mix the same into a homo-
geneous relationship while cross-linking may be per~ormed on a
continous processing basis.
~hile the invention has been disclosed in con~unction `
with a rather specific embodiment which is rendered highly de-
tailed due to the need to show specific safety and monitoring fea-
tures, it will be appreciated by those of ordinary skill in the -
art that many variations and alternatives to the specific em-
bodiMents set forth may be employed without deviating from the
teachings of the instant invention. More particularly~ while
specific sensors and monitoring techniques are disclosed
herein, it will be apparent that alternate forms of sensing or
.. , ~ . , . .- - . . ., -, . . : ::
monitoring devices may be employed in association with different
forms of monitoring techniques. Furthermore, while a great number
of safety and monitoring features were disclosed in conjunction with
the supply system for the volatile cross-linl<ing agent disclosed, it
will be appreciated by those of ordinary skill in the art that when the
supply system is employed for diFFering types oF cross-Linking agent
or volatile materials, either a greater or lesser number oF saFety
and monitoring Features may be utilizecl dependillg upon the speciFic
application contemplated and the practical requirements dictated by
1û circumstance. In addition, while the use oF the instan-t supply system
in conjunction with an extruder is highly advantageous, it will be seen
that direct combination of a volatile agent or cross-linking agent as
provided by the supply system may occur in an advantageous manner
with other types of processing equipments where the precisely metered
output of the instant supply system may be employed to great advantage.
Therefore, this aspect of the instant invention should not be viewed as
limited to use with an extruder or any of the specific combinations
set forth in conjuction with the instant exemplary embodiment.
Accordingly, while the invention has been described in
conjunction with a rather specific exemplary embodiment thereof, it ~ ;
will be understood that many modifications will be readily apparent to
those of ordinary skill in the art; and that this application is intended
to cover any adaptations or variations thereof. Therefore, it is
manifestly intended that this invention be only limited by the claims and
the equivalents thereof.
~'~,,'.
53
