Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPA~ATUS FOR MAKING A CONTINUOUS
LENGTH OF TUE3ING ~IAVING FOAMED PLASTIC WALLS
There are a variety of known types of tubing formed of insulating ma-
5 terial which may be used in many applications where good insulation and similar
properties are required. It has been found that tubing formed of foam plastic
material such as polyurethane material is particularly effective as an insulating
material.
It is known that continuous lengths of tubing of the aforesaid type may
10 be formed by utilizing a forming mold constructed of upper and lower semi-cylin-
drical mold elements arranged on continuously movable conveyors so that the
upper and lower mold elements come into contact with one another to form a
moving cylindrical mold. A mandrel is disposed centrally of the cylindrical mold,
and flexible strips of material are formed into cylinders which cover the exterior
15 surface of the mandrel and the interior surface of the cylindrical mold A liq-
uid forming material is injected into the annular space between the strips of
flexible material to be cured during its passage through the moving cylindrical
mold, or during its passage through a curing oven if required. The method and
apparatus for forming tubing of the aforesaid type are disclosed in greater de-
20 tail in U.S. Paten1s Nos 31745,621; 3,746,487; 3,754,064 and 3~816,043.
While tubing ~ormed by this known process is commercially acceptable,it will be appreciated that the moving molding cylinder arrangement is complex
in design and operation, and it is expensive to produce and run on a continuous
basis. Additionally, it is somewhat difficult to assure proper curing of the plas-
25 tic mixture during the time it is within the moving molding cylinder.
In accordance with the present invention, a method and apparatus forforming a continuous length of tubing having foamed plastic walls is provided
which obviates the disadvantages of known technology, and which provides sub-
stantial general improvements to such technology.
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The present invention provides a method and apparatus for making a
continuous length of tubing with walls formed of a foamed material~ including
a forming cylinder having a mandrel extending centrally thereof along the
5 length of the cylinder, first means for feeding or pulling a first strip of flexible
material, preferably paper, into one end and through the forming cylinder, such
first strip of flexible material being formed into a cylindrical shape about the
; mandrel9 and second means for feeding or pulling a second strip of flexible ma-
terial into one end of and through said forming cylinder, such second strip of
10 flexible material being formed into a cylindrical shape at the interior surface
of the forming cylinder. A curable foaming plastic mixture is injected into said
one end of the forming cylinder and into the annular space between the first
and second strips of flexible material, and a sensor is disposed at said one end
of the forming cylinder for sensing the point along the length of the forming
15 cylinder at which the foaming plastic oixture begins to cure into a solid across
the cross-section of the annular space between said first and second strips of
material. The signal from this sensor is utilized for selectively varying the speed
at which the first and second strips of flexible material are fed through the
forming cylinder. When the sensed point of curing is within a predetermined dis-
20 tance from said one end of the forming cylinder, the speed of the strips is in-
creased, and such speed is decreased when the sensed point of curing is beyond
such predetermined distance. E~y virtue of this control arrangement, proper cur-
ing of the foamed plastic material is obtained during the period of time that
the foamed plastic material is passing through the forming cylinder. Additionally,
25 this control arrangement may also incorporate a safety feature by which the
entire tube forming process is shut down when the sensed point of curing is at
a predetermined minimum spacing from said one end of the forming cylinder
In accordance with further features of the present invention, the two
strips of flexible material are fed into the forming cylinder from supply rolls,
30 and additional sensing means are provided for detecting any break or rupture
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of the strips of materialt and for monitoring the amount of flexible material
contained on the supply rolls. If a break or rupture of either strip of materialis detected, or if the reserve supply of flexible material on the supply rolls
reaches a predetermined rninimum, the control system of the present invention
5 will shut down the tube forming process
In accordance with a further feature of the present invention, the man-
drel is formed as a hollow cylinder with the end thereof that is adjacent to
said one end of the forming cylinder being opened, and with the other or ex-
tending end of the mandrel being closed A length of tubing is mounted interior-
10 ly of the mandrel, such tubing having an open end adjacent the closed end ofthe mandrel, and a supply of cooling fluid, preferably air, is conveyed through
the tubing so that it is introduced into the mandrel at the closed or extending
end thereof, and flows back through the mandrel toward its opened end, thereby
acting as a heat exchanger to cool the extending end of the mandrel while sim-
15 ultaneously heating the end of the mandrel adjacent said one end of the form-
ing cylinder.
In accordance with another feature of the present invention, the ex-
tending or outlet end of the forming cylinder is provided with at least one, and
preferably several, small protrusions at the interior surface of the forming cylin-
20 der, such protrusions serving to score the outer paper covering of the tubing
as it leaves the :Eorming cylinder, such scoring being utilized to accommodate
in a neat fashion any subsequent shrinkage of the tubing after it leaves the
forming cylinder, and to provide an indexing groove or guide which may be used
during subsequent processing of the tubin~
Finally, the forming cylinder is mounted on a frame by mounting plates
having cylindrical openings for receiving the forming cylinder, and these mount-
ing plates are secured to the frame by detachable means which permits the plates
to be quickly mounted on, or removed from, the frame, whereby forming cylinders
of di:Eferent d~ameters can be alternately used in the tube forming process by
30 replacing one set of mounting plates having openings for receiving one size forming
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cylinder with mounting plates having larger or smaller openings for receiving
a forming cylinder of a different size.
Figure 1 is a diagrammatic illustration of apparatus for forming a con-
5 tinuous length of tubing in accordance with the present invention;
Figure 2 is a detailed view taken along section line 2-2 in Fig. l;
Figure 3 is a detailed view in vertical section illustrating the inlet end
of the forming cylinder;
Figure 4 is a plan view of the inlet end of the forming cylinder shown
10 in Fig. 3, with some elements being omitted for purposes of clarity;
Figure 5 is a detailed view, partly in section, illustrating the mandrel
and cooling arrangement therefor; and
Figure 6 is a detailed view showing the outlet or extending end of the
forming cylinder~
15 ~
~ ooking now in greater detail at the accompanying drawings, Fig. 1 illus-
trates in diagrammatic form, the preferred embodiment of the apparatus for car-
rying out the present invention, such apparatus including a cylindrical forming
cylinder 10 which is mounted at a horizontal disposition by a plurality of mount-
20 ing plates 12 which receive the forming cylinder 10 through cylindrical openings14 having a diameter corresponding to the exterior diameter of the forming cy-
linder 10, and which are mounted to a frame 16 by quick-disconnect couplings
1~ in the form of U-clamps having bolts for attaching and detaching the U-clamps
18 and the mounting plates 12 to the ~rame 16. It will be appreciated that if
2S it is desired to use a forming cylinder 10 having a different diameter, such new
forming cylinder 10 can be quickly mounted on the frame 16 by simply removing
the mounting plates 12 and substituting new mounting plates having a smaller
or larger opening 14 therein, and then sliding the new forming cylinder into the
aligned openings of the mounting plates.
A mandrel 20 is also mounted on the frame 16 by depending support mem-
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bers 2? located adjacent to the inlet end of the forming cylinder lO, the mandrel
20 extending in cantilever fashion into and through the fdrming cylinder 10 so
as to be disposed centrally thereof and in concentric relation to the forming
cylinder 10.
A stanchion 24 is located in spaced relation to the inlet end of the
forming cylinder 10, and a first supply roll 26 of a strip of flexible material 28
is mounted on the stanchion 24. This strip of flexible material 2~, which is pref-
erably paper, is fed from the supply roll 26 across a guide member 30 supported
by the frame 16 and into the inlet end of the forming cylinder 10. As best seen
in Fig. 3, the strip 28 passes through a shaping member 32 which forms the stripinto a cylindrical shape that is disposed about the exterior surface o-f the man-
drel 20. If desired, ccnventional equipment (not shown) can be provided for ap-
plying an adhesive to one edge of the strip prior to its being formed into a cy-lindrical shape so that such edge of the strip will adhere to the overlapping
edge of the strip when it is formed into a cylindrical shape.
Similarly, the stanchion 24 includes a second supply roll 34 of a wider
strip of flexible material 36, also preferably paper, which extends from the sup-
ply roll 34 over a guide member 38 attached to the frame 16, and into the inlet
end of the forming cylinder 10. As best seen in Figs 3 and 4, the strip 36, as
it enters the inlet end of the forming cylinder 10, is formed into a cylindricalshape and extends along the interior surface of the forming cylinder 10. Again,
apparatus (not shown) may be provided for applying an adhesive to one edge of
the strip 36 for the same purpose as that indicated above.
As best seen in Figs. 3 and l~, the inlet end of the forming cylinder 10
is cut away in a plane disposed in angular relation to the center line of the form-
ing cylinder 10 so that the strip 36 comes together in an overlapping "V" disposed
above the bottom surface of the forming cylinder 10, and a plastic injecting noz-
zle 40 is mounted on a vertical support member 41 extending downuardly from
the frame 16, with the tip of the nozzle 40 being disposed just within the "V"
of the strip 36 and above the lower surface fo the forming cylinder 10 as best
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seen in Fig. 4.
In the present invention, the foamed plastic material to be used is pref~
erably polyurethane~ and the nozzle 40 is of generally conventional construction
for mixing and injecting a plastic mixture therefrom, as is well known in the
5 art. Briefly? a first reservoir 42 is provided which contains a first ingredient
consisting essentially of a plastic resin, isocyanate and a promoter combined
as a liquid which is fed through a supply.conduit 42' and a conventional metering
device 43 to header 44 of the nozzle 40 having an internal passageway therein
for receiving this first ingredient and directing it to the nozzle 40. A second
10 reservoir 46 is provided which contains a second ingredient consisting essential-
ly of a plastic resin and a catalyst combined as a liquid to be fed in a similar
fashion to the nozzle 40 through supply conduit 46', metering device 43, and
the header 44. The two ingredients are mixed as they flow from the internal
passageways in the header 44 to the nozzle 40, and this mixing starts a chemical
15 reaction which results in the plastic mixture ultimately expanding and foaming
whereby a cellular structure 48 is formed as an annular wall of the tubing 50
as illustrated in Fig. 2, the cellular character being retained in solid form after
the mixture has been cured~ A pneumatically or hydraulically operated motor
52 is mounted on the header 44 for selectively opening and closing the internal
20 passageways in the header 44 under the control of an electrically operated sole-
noid valve 54 which is disposed in the fiuid line 54' extending to the motor 52.
Electrically operating the solenoid valve 54 to one position thereof will result
in the two ingredients being fed into the nozzle 40 and injected thereby, and
electrically operating the solenoid valve 54 to its other position will result in
25 the flow of both ingredients being stopped before they reach the nozzle 40 and
become mixed.
rhus, in the present invention, the two ingredients for forming polyure-
thane are mixed in the nozzle 40 and immediately injected from the nozzle 40
into the annular spacing between the first and second cylindrical strips 28 and
30 36, as best seen in Fig. 3. The mixture which is injected by the nozzle 40 is
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essentially in liquid form, but the mixture immediately begins to cure as it
leaves the nozzle 40 and in a relatively short period of time the mixture will
be cured to an extent tha-t it will form a solid extending across the entire cross-
section of the annular spacing between the strips 28 and 36. As the foamed
5 mixture continues to be moved along the length of the forrning cylinder 10, final
curing occurs so that, as shown in Fig. 2, a cellular structure 52 is formed be-
tween the cylindrically shaped strips 28 and 36, and the cellular structure 52
is completely cured by the time the tubing 54 leaves the outlet or extending
end of the forming cylinder 10 It should be noted that since the plastic mixture
10 sets up into a solid at a point near the inlet end of the forming cylinder and
continues thereafter in a solid form, this solid form acts as a support for the
cantilever-mounted mandrel 20, so that no aWitional support for the mandrel
is necessary.
After the tubing leaves the outlet end of the forming cylinder IQ, it
15 enters the nip of a traction device 56 f~r pulling the tubing through the proces-
sing steps described akove. The traction device 56 includes two vertically
spaced traction belts 58 which are driven by an electric motor 60 so that the
spaced, horizontally extending reaches of the two traction belts 58 move in
a direction away from the forming cylinder IOJ and the frictional engagement
20 Of the tubing 54 by the tracticn belts 58 will pull the tubing 54 horizontally
through the forming cylinder 10. A conventional slitting device 62 is disposed
at the exit end of the traction device 56 for cutting the tubing into pieces hav-
ing any desired length, such pieces of tubing then being carried away by a con-
veyor system 6~.
The basic operation of the apparatus described above is as follows.
To commence the operation, the operator, using a pulling line or the like, manu-
ally pulls the two strips 28 and 36 through the forming cylinder 10, with the
strips being formed in the cylindrical shapes described above Preferably, the
traction device 56 includes an external capstan (not shown) about which the
30 pulling line can be wound to assist the operator in initially pulling the strips
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28 and 36 through the cylinder lO, The nozzle 40 is then energi~ed to inject
the plastic mixture into the forming cylinder 10, and the operator continues
to manually pull the paper strips at a linear speed approximating the linear speed
at which the tubing is normally passed through the apparatus so that the plastic5 mixture is cured during its passage through the forming cylinder 10. When the
tubing 54 has a sufficient length to reach the traction device 56, the tubing
is inserted in the traction device 56 and the motor 60 therefor is energized
Thereafter, the traction device 56 will automatically and continuously pull the
tubing 54, and the strips 28 and 36 which form a part thereof, through the form-
10 ing cylinder 10 at a predetermined speed determined by the motor 60, so thata continuous length of tubing having foamed plastic walls is formed by the appa-
ratus.
1r-. Iooking at Fig. 3, it will be appreciated that the plastic mixture
flowing from the nozzle 40 is deposited on the moving strips 28 and 36 and is
15 carried along the length of the forming cylinder lO thereby. Accordingly, the
point along the length of the forming cylinder lO at which the plastic mixture
is initially cured as a solid across the entire cross-section of the annular spacing
between the strips 28 and 36 is a function of the speed at which the strips 28
and 36 are pulled through the forming cylinder lO by the traction device 56.
20 More specifically, if the strips 28 and 36 are pulled through the forming cylinder
at a relatively slow speed~ the quantity of the plastic mixture being injected
will accumulate more quickly with respect to the speed of ~he moving strips
28 and 36 and will set-up as a solid across the annular spacing at a point rela-
tively close ~o the inlet end of the forming cylinder lO, whereas pulling the
25 strips 28 and 36 at a relatively fast speed will result in such injected plastic
mixture accumulating less quickly and the set-up point being spaced substanti-
ally further from the inlet end of the forming cylinder 10. After the plastic
mixture initially sets-up, the chemical reaction between the ingredients continues
to tah;e place as the plastic is pulled through the forming cylinder lO, resulting
30 in a con-tinuing cxpansion or foaming of the plastic. It is important, in terms of
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the q~lality of the end product formed by the process of the present invention,
that this chemical reaction or final curing take place while the plastic mixture
is fully contained between the mandrel 20 and the forming cylinder 10. In accor-
dance with one feature of the present invention, proper curing of the plastic
5 material within the forming cylinder 10 is obtained by providing a sensor 66 mounted
on the support 42 adjacent the inlet end of the forming cylinder 10 as shown in
Fig. 3. This sensor 66 is a conventional ultrasound-type sensor which generates
ultra-high-frequency sound waves, indicated by reference numeral 66', that are re-
flected back when they strike a solid surface and are detected by the sensor 66.
10 Thus, the sensor 66 is able to sense the point along the length of the forming cy-
linder 10 at which the plastic mixture begins to cure into a solid that extends across
the cross-section of the annular space between the cylindrical stips 28 and 36.
The electrical signal generated by the sensor 66 is transmitted through electrical
line 68 to a control panel 70, and a further electrical line 7Z extends from the
15 control panel to the variable speed motor 60 which operates the traction device
56. The control panel 70 is designed so that when the aforesaid sensed point
~f set-up of the plastic material is within a predetermined distance from the
inlet end of the forming cylinder 10, the speed of the motor 60 is increased to
thereby increase the speed at which the strips 28 and 36 are pulled through the
20 forming cylinder 10 by the traction device 56 as described above. Similarly, if
bhe sensed set-up point of the plastic material is beyond such predetermined dis-
tance from the inlet end of the forming cylinder 10, the speed of the motor 60
is decreased to slow the speed of the strips 28 and 36 through the forming cy-
linder 10. Thus, the sensor 66 is utilized to vary the speed of travel of the strips
25 28 and 36, which in turn varies the set-up point of the plastic mixture as des-
cribed above so that this set-up point can be substantially maintained at a pre-
determined distance from the inlet end of the forming cylinder 10 which will pro-
ide proper curing of the plastic mixture while it is within the confines of the
forming cylinder lO. Preferably, the control panel 70 is designed to proportion-
30 ately increase or decrease tlle speed of the motor 60 as the sensed set-up point
- lo -
moves a greater distance away from the desired point of set-up along the length
of the forming cylinder 10.
The control panel 70 is also preferably designed to include a safety
feature by which the entire tube forming process is shut down if~ for any reason,
5 the sensed set-up point of the plastic mixture comes within a predetermined min-
imum spacing from the inlet end of the forming cylinder 10, thereby avoiding
a very undesirable situation in which the liquid plastic mixture being injected
from the nozzle 40 would flow out of the inlet end of the forming cylinder 10
and onto the floor or surrounding equipment More particularly, the control panel
10 70 includes an electrical line 74 extending therefrom to the above-described
solenoid valve 54 which controls the fluid motor 52. If the sensor 66 determines
that the set-up p~int is within the aforesaid predetermined minimum spacing from
the end of the forming cylinder 10, an electrical signal is transmitted through
the line 74 to operate the solencid valve ~4 so that the further flow of the plas-
15 tic ingredients to the nozzle 40 is stopped, and a signal is also transmittedthrough the line 70 to stop the motor 60 of the traction device 56, whereupon
the operation of the entire system is shut down.
In accordance with a further feature of the present invention, a pair
of photoelectric sensing devices 76 are disposed on each side of the strip of
20 flexible material 28 as it is fed from the supply roll 26, and an electrical line
78 extends therefrom to the control panel 70. Corresponding sensing devices
80 are also disposed on each side of the strip 36, with an electrical line 82 ex-
tending therefrom to the control panel 70. If a break or rupture occurs in either
of the strips 28 or 36, this break will be detected by the sensing devices 76 or
25 80 to transmi-t a signal to the control panel 70 which, in turn, will shut down
the apparatus by operation of the solenoid valve 54 and stopping the motor 60
in the same manner as that described above.
~ lso, sensing devices 8~ and 86 are disposed immediately adjacent the
supply rolls 26 ~nd 34, respectively, ~or sensing the diameters of such supply rolls,
30 which is a function of the quantity of material which remains on the supply rolls
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at any given time. When either of the supply rolls 26 or 34 approaches exhaus-
tion, this condition will be sensed by the sensing devices 84 or 86, and a signal
will be transmitted therefrom through electrical lines 88 or 90, respectively7 to
the control panel 70, which will transmit electrical signals to the solenoid valve
5 54 and the motor 60 to shut down the apparatus and permit a fresh supply roll,
such as the supply rolls 26' and 34' located on the stanchion 24, to be substitut-
ed for the exhausted supply rolls.
Another feature of the present invention involves the distribution of
the heat generated by the chemical reaction of the plastic mixture as it flows
10 through the forming cylinder 10 This chemical reaction tends to generate progres-
sively higher levels oE heat as the plastic mixture approaches the outlet end
of the forming cylinder 10, so that there is a significant inbalance in the heat
that is transmitted to the enclosed mandrel at the inlet and outlet ends of the
forming cylinder lQ. To correct this inbalance, and distribute the heat more even-
15 ly along the length of the mandrel which lies within the length of the formingcylinder 10, the mandrel 20 is preferably formed as a cylinder as shown in Fig.
S, with the end of the mandrel 20 that is adjacent the inlet end of the forming
cylinder IQ being open, and with the opposite or extending end of the mandrel
being closed, A length of tubing 92 is disposed interiorly of the mandrel 20 by
20 supporting spokes 9~, and the extending end of the tubing 92 is open. A cooling
fluid, preferably air, ls conveyed from a source 96 through an inlet conduit ~8
to the tubing 92, with the flow of cooling fluid being regulated by a valve 100
As shown in Fig. 5, this cooling fluid passes through the tubing 92 so as to be
admitted into the mandrel 20 at the extending closed end thereof, and this air
25 is therefore forced to flow back along the interior surface of the mandrel 20
for exhaustion at the open end of the mandrel 20, and this flow of fluid acts
in the nature of a heat exchanger to transmit heat from the extending end of
the mandrel 20 back to the open end of the mandrel 20, thereby assisting in
equalizing the temperature of the mandrel 20 along the length thereof.
It is a well known phenomenon that tubing formed of a foamed plastic
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material such as polyurethane will con-tract or shrink slightly a~ter it is fully
cured and cools to room temperature. While this contraction is not great, it
will nevertheless tend to create an irregular crease in the outer paper layer
formed by the strip 36. This irregular crease does not effect the structural in-
5 tegrity of the tubing, but it is somewhat unslightly, and it is sometimes mistaken-
ly thought to represent a partial defect in the tubing. The drawbacks associated
with this irregular crease are eliminated by a further feature of the present
invention which, as best seen in Fig. 6, includes the mounting of small protrusions
at the inner surface of the forming cylinder 10, adjacen-t the outlet end thereof.
10 In the preferred embodiment of the present invention, these protrusions are in
the form of small lengths of wire 102 having the ends 104 thereof passing out-
wardly through the forming cylinder 10 and being bent to hold the wire elements
in place. While it may be suitable in some applications to use only one wire 102,
it is generally preferable to provide a plurality of wires 102 which are equally
15 spaced from one another in a radial direction as shown in Fig. 6. With this ar-
rangement, when the formed tubing 50 passes through the extending or outlet
end of the forming cylinder lOj the wires 102 will indent or score the outer paper
layer 36 to form creases that extend along the length of the tubing 50 When
the foamed plastic material subsequently shrinks or contracts as described above,
20 this shrinkage will be accommodated in the outer paper layer 36 by the creases
formed by the wires 102 without the formation of any additional, irregular creases
- in such paper. Moreover, these formed creases may be advantageously utilized
as indexing grooves to properly orient and guide the tubing if it is passed through
subsequent processing operations.
Finally, it will be noted that the control panel 70 can also be utilized
to control the operation of the above-described slitting device 62 through an
electrical line 106, and the above-described metering device 43 may be similarly
controlled through an electrical line 108.
The present invention has been described in detail above for purposes
30 of illustration only and is not intended to be limited by this description or other-
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wise to exclude any variation or equivalent arrangement that would be apparent
from, or reasonably suggested by the :Eoregoing disclosure to the skill of the
art.
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