Note: Descriptions are shown in the official language in which they were submitted.
This invention relates to processing equipment having endless twin
metal belts which move together while holdin~ a product captive between them,
and relates particularly to improvements in systems for the manufacture of
products in continuous sheet form and of the types which require such treat-
ment by heat and/or pressure.
An object of this invention is to provide improved methods and
apparatus for treating materials between two belts. Another object is to
provide improved systems for treating products between metal belts. A
further object is to provide for the above in a manner which overcomes
difficulties which have been encountered with such systems in the past. These
and other objects will be in part obvious and in part pointed out below.
The present invention involves producing products by feeding a
layer of materials into the nip between two metal belts as the belts pass on-
to and around a series of drums. The illustrative embodiment of the present
invention involves a twin-belt system for producing a continuous sheet of a
product from a filler and a material which requires heat-treatment under
pressure. The continuous sheet is heat treated to perform the curing or re-
acting of the product while holding the sheet captive between the pair of
steel belts and passing the belts around a series of hollow heating drums.
One system is disclosed in U.S. Patent No. 2,069,589 to J. Meijling et al.
It has been found that the present invention overcomes difficulties which
were encountered with such systems.
According to the invention, there is provided guide means between
each belt and the drum upon which it rests which forms a combination of the
drum and the belt, said ~uide means comprising guide structures a~tached to
the respective belts and presentin~ guide surfaces which are spaced from the
belt surface which contacts the drums and extend toward the drum axis and
guide surfaces on the drum which are parallel with and mate with the first-
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named ~uide surfaces, respectively, said guide surfaces on said guide
structures and on said drums forming a first set of cooperating guide sur-
faces which prevent movement of the belt in one direction parallel to the
drum axes and another set of guide surfaces which prevent such movement in
the opposite direction whereby said guidc structuresact thro-ughout the
length of each belt contacting one of the drums to exert continuous forces
opposing deviation of the belt movement from true alignment.
'. Referring to the drawings:
, Figure 1 is a schematic side elevation of a system constituting
one embodiment of the invention;
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Figures 2 and 3 are enlarged plan and sectional
views of a portion of one of the belts of Figure l;
Figure 4 is a view similar to Figure 2 but showing
another embodiment of the invention;
, 5 Figure 5 is a greatly enlarged sectional view of
? the central portion of one of the drums in the system of
Figure 1, showing a belt resting on the drum; and,
Figure 6 is an enlarged somewhat schematic view of a
portion of Figure 1 showing the steel belts passing from one
drum to another.
? . In manufacturing certain sheet products it is
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desirable to hold the materials captive between two belts
during a curing or finishing process. That is particularly
important in certain processes for manufacturing sheet products
which require heating and/or cooling under pressure. With some
such processes, a continuous product sheet or strip may be
passed from a hopper type tank as shown in U. S. Patent No.
2,069,589 or it may pass from a roll on an unwinder or from a
tank and then is fed between two mating steel belts. The belts ~ ~
20 with the product sheet held captive between them pass around a -
series of hollow cylindrical drums or rolls. The product sheet
is heated by supplying steam to the one or more drums, and there
may be a drum upon which the product is cooled. The product
can then pass to a winder or other receiving means thus com-
pleting the process.
The present invention overcomes a very serious
problem which was encountered in a system of that type. In -~
~: passing around the drums in a series, the two belts alternate
between being the inner belt which wraps directly against the :
drum, and being the outer belt which wraps around the layer of
the product sheet. That is, when the two belts approach -the
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first drum, the product sheet is fed between them and one
belt is the inside belt and contacts the drum, while the
other belt is the outside belt and presses the product sheet
against the inside belt. And when the belts pass from that
first drum to the second drum, the relative positions of the
belts on the drum are reversed so that the belt which contacted
the first drum is the outside belt on the second drum and holds
the product sheet against the other belt which lies on the
second drum.
~hen passing around each drum, the inside belt is
at a lesser radius than the outside belt, so that the outside
belt tends to move at a more rapid rate than the inside belt.
But the inside belt is drawn away as the outside belt on the
next drum so that it is the belt which tends to move around
the next drum at the more rapid rate. That difference in the
- relative rates of the movement of the two belts tends to cause
: the outside the belt leaving a drum to bulge outwardly away
from the other belt. Also, it was found that there was a very -
marked tendency for at least the outside belt to move axially
with respect to the drums, i.e., depart from the tracking
position on the drums. When such a condition developed, it :
was found to be impractical to try to adjust the axis of the
drum because adjusting one drum disturbed the relationship
; between the belts and the next adjacent drum and subsequent ;~
!;25 drums. For solving that problem there was a proposal to hold
the belts in alignment by flanges on the pulleys and drums
around which the belts pass. However, it has been found that `
flanges on the pulleys or drums will not overcome the problems
referred to above. The belts still tend to depart from true
alignment so that the belt edges become seriously damaged by
;scraping on the flanges and the belts even tend to ride up on
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. top of the flanges thus rendering the machine completely
~ inoperative. The result was that the belts would not remain
:. in tracking relationship with respect to the drums, and the
product sheet also deviated from true alignment and developed
i 5 bulges w~ich became large enough to produce folds or pleat$
in the edge portion of the product sheet. The present
~$ invention overcomes that difficulty, and insures that the
product sheet will be of uniform high quality.
Referring to Figure 1 of the drawings, a system
is represented schematically for fabricating a continuous
sheet or strip of glass-fiber reinforced plastic. The
system of this embodiment includes two hollow cylindrical
drums 6 and 7 and a pair of endless steel belts 14 and 16
; which pass around the drums together with the product strip
held captive between them. Drum 6 is a heating drum which
is mounted at its ends upon axial stub shafts (not shown).
This drum is supplied with steam through a line 5 from a
boiler 9 and the condensate is returned through a line 11,
lines 5 and 11 being concentric and extending through one of
~ 20 the stub shafts. Drum 7 is a cooling drum and cold brine is -
:i ` delivered to it from a chiller 13 through a line 19 and the
~ brine is returned to the chiller through a line 17, lines 19
:s and 17 being concentric tubes through one of the stub shafts
j ~ of the drum.
Belt 14 passes from drum 7 to pulley 18 and thence
upwardly around the pulley and to the left and around a pulley
20. Belt 16 moves with belt 14 to pulley 18, and then onto
a pulley and downwardly around a pulley 22 and thence some-
what downwardly and to the left and around pulley 24. The
belts move from their respective pulleys 20 and 24 somewhat
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downwardly and they converge and move together as they
approach drum 6. The product strip 15 is fed between them
and the belts pull the strip captive as they move around
drum 6 and thence around drum 7.
The drums and pulleys are mounted on a frame
structure (not shown), and are enclosed with the belts in a
housing represented at 26. A product strip 15 is drawn
from a tank 28 upwardly around a pulley 30 and thence down-
wardly and to the right of the bite between belts 14 and 16
as the belts move onto drum 16. Strip 15 is compressed
between the belts and is first heated as it passes around
drum 6 and is then cooled as it passes around drum 7. The
product is further cooled as it is held captive between the
belts while moving from drum 7 to pulley 18. Belt 14 is
peeled away from the product strip at pulley 18, and the product
strip is carried by belt 16 to pulley 22 where belt 16 is also
peeled from the product strip. The finished product strip 32
is discharged ~rom housing 26 and is further treated or packed
for storage.
Separate electric motor and gear units 23 and 25
drive belts 14 and 16, respectively, through pulleys 18 and 22
and the tension on each of the belts is controlled by units
23 and 25, respectively. The drive and tension control units
are of known construction.
As indicated above, with a system of the general
type of the illus~rative embodiment, the outer belt passing
` from one drum to the next drum of a series tended to bulge
out away from the outer belt and from the product sheet, and
tended to move from its true alignment path. The basis of
the difficulty was that the inner belt 14 on drum 6 was pulled
onto drum 7 at a more rapid rate than belt 16, whereas belt 16
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tended to move around drum 6 at a more rapid rate than
belt 14. It was found that that difficulty was avoided
by providing a belt-guiding system to maintain both belts
in exact alignment at all times. For that purpose, each of
the belts 14 and 16 has a V-rope 50 (see Figure 5) extending
along its center line and projecting into a peripheral groove
52 in each of the drums which the belt contacts. Also, there
is an identical groove in each of the pulleys. That is, the
V-rope 50 on belt 14 projects into an annular groove 52 in : ;
drum 6, and the V-rope on belt 16 projects into groove 52
in drum 7. Each of the V-ropes is generally triangular in
cross-section and is formed by a continuous spiral ~see
Figures 2 and 3) of a thin narrow stainless steel strip.
Each of the flat sides 54 of the V-rope is spot-
welded to the belt at 56, so that each loop is attached to
the belt at both of its ends, and the other two sides (Figure
5) 58 and 60 are free and resilient. The arrangement is such ~ ;
; that when belt 14 is held snuggly against surface 70 of the
drum, portions 58 and 60 of the V-rope are held firmly against
surfaces 66 and 68 so as to provide a fixed relationship
between the V-rope and those surfaces. With the belt posi-
, tioned as shown in Figure 1 and a layer 15 between them, the ~ -
belts and layer 15 form a rigid stable construction around
each drum. That is, each groove 52 provides two tapered
annular or peripheral surfaces 66 and 68, each of which mates
with a surface portion of each spiral of its V-rope 50.
Each of those two pairs of mating surfaces at each spiral of
the V-rope throughout the length of each belt contacting a drum
or a pulley provide balanced opposite forces tending to hold
the belt in egact alignment.
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The belts and the product layer between them act
in the nature of a single structure in that they are held
together in hugging relationship against drums and the pulleys.
Hence, while the belts move continuously, a rigid construction
of unchanging configuration is provided which is formed by the
. belt and the drums and pulleys. Throughout that construction
the V-ropes resist the tendency for the belts to deviate from
the true alignment path. For example, belt 14 is held in
; exact alignment when it passes around drum 6 and pulleys 18
10 and 20, and that alignment is maintained by the cylindrical -
forms as it passes around drum 7. Simultaneously, belt 16 is
held in exact alignment when passing around the drum 7 and
pulleys 22 and 24 and the cylindrical forms maintain it in
; alignment while passing aro~nd the drum 6.
The maintenance of the belts in exact alignment ~
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has overcome the above-mentioned difficulty which was encoun-
tered in a system of the general type disclosed herein which
did not have the V-ropes on the belts and the mating grooves
in the drums and pulleys. With the present system, the belts
; 20 do not tend to bulge out, and in fact the belts and product ~ -
layer stay together as they pass from one drum to the next.
An explanation for the achievement of that result will now be
discussed.
As pointed out above, the optimum posture of the
: 25 belts is for each of them to be formed into a series of
partial cylinders and with each partial cylinder being
connected to each adjacent partial cylinder by a flat belt
portion which is tangential to the two partial cylinders.
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Referring to Figure 6, the belts are formed into partial
cylinders extending around drum 6 from tangential point
80 to tangential point 82, and then the belts move away
from drum 6 to tangential point 84 on drum 7. The belts
i 5 have portions 86 between points 82 and 84 which are flat
and tangential to their respective partial cylinders on
the adjacent drums.
The portion 86 of belt 14 is under tension because
it is being drawn into drum 6 at a lesser radius than is
belt 16, and portion 86 of belt 16 tends to be slack because
it has moved at a greater radius than belt 14 around drum 6.
The above-mentioned bulging effect is avoided only because
the belts are forced to move around both drums at the same
rate. It is believed that the flat portion 86 of belt 16
j 15 acts in effect as a column to exert forces at the tangential
zone of point 82, those forces are of a magnitude to retard
the movement of belt 16 around drum 6. As long as portion 86
of belt 16 does not buckle or bulge and is under compression
at the nip at 84 between drum 7 and belt 14, belt 16 cannot
move forwardly from drum 6 any faster than the surface of
drum 7 is moving. Nevertheless, it is held against the drum
and is being pushed forwardly from drum 6 at point 82. However,
even a thin belt can withstand longitudinal compression forces
when acting as a column, provided the forces are below the
limit at which the belt would buckle when acting as a column.
That limit is based upon the physical characteristics of the
belt, i.e., its cross-section and length and the material of
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i which the belt is constructed. Accordingly, belts 14 and 16 are
` caused to move around drum 6 at the same rate so that between
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points 80 and 82, there is preogressive relative longitu-
dinal movement between the belts with belt 16 lagging
behind belt 14.
Similarly, if the system were to include a
third drum in the series downstream from drum 7, in moving
around drum 7, belt 14 would be restrained from moving
freely beyond point 88 because of compression forces ex- ;
erted by the portion 92 of the belt. It is thus seen that
the inside belt on each drum is caused to lag behind the
10 outside belt. However, the belts would alternate as the
inside and outside belts on successive drums so that neither
belt moves more than "one step" ahead of the other. The
total amount that one belt lags behind the other on a drum
. ~ equal the difference between the mean circumferential
15 lengths of the two partial cylinders of the belts.
V-rope 50 cooperates with the other belt and
drum structure to provide adequate heat transfer between
,
the heat exchange fluids in the drums and the product
layer. Other forms of V-ropes may be used, for example~
` 20 in the embodiment of Figure 4 the V-rope is in the
form of individual triangular clips 100 spot welded to
.:` the belt.
" The invention contemplates that additional drums ;~
~; for heating or for cooling may be added to the series, and
25 that the number of drums and the construction will be such
as to produce the desired results. Various heat ~ransfer
; and/or pressure effects may be produced upon the product,
for example, by changing the belt tension to control the
i~ pressure and by changing the temperature of the heat exchange ;
30 fluids to control the heat transfer rates. Also, if the
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product is to be frozen, the drums can be evaporators of
a refrigeration system. The single V-rope attached along
. the center line of each of the belts can be replaced by
two V-ropes on each of the belts mating with V-grooves at
the ends of the drums and pulleys. Also, the belts can
, overhang the ends of the drums with a V-rope at each edge
',. of each of the belts, and with the drums and pulleys
j beveled at their ends to produce surfaces identical with
surfaces 66 and 68 in Figure 5. With that arrangement,
the V-rope at the left-hand edge of the belt (as in Figure
5) would mate with a beveled surface like 68, and at the
right-hand edge of the belt, the V-belt would mate with a
: surface like 66. It is understood that other modifications
~` in the constructlon and other embodiments may be provided
within the scope of the claims.
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