Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a gasket for use in
a plate type heat exchanger.
Conventionally, gaskets for use in a plate type heat
exchanger have been uniformly formed of an elastomeric material
which can be safely used on the severest conditions during heat
exchange. However, such gaskets will have higher resistances
to corrosion and elastic deformation than is necessary in a
region where the conditions are rather favourable. As a result,
if used for a long time, the gaskets deform and the plates warp.
Further, most of the gaskets used hitherto in such
plate type heat exchangers have been made of an elastomeric
material such as synthetic rubber from the standpoint of fluid
tightness. There is no problem with such gaskets so long as
non-corrosive liquid or gas is used, but when chemicals such as
organic solvents are handled, since synthetic rubber is inferior
in its resistance to chemicals the portion of the gasket which
is contacted with an organic solvent, is corroded, losing fluid
tightness. Therefore, plate type heat exchangers have been
regarded as unsuitable for heat exchange of such fluids as
organic solvents.
`In order to eliminate such disadvantages, use of a
gasket made of Teflon (trade mark) which is superior in
resistances to heat and chemicals would be contemplated, but
Teflon has no elasticity and a high degree of hardness, so that
it is unsuitable for use as a sealing material. Thus, in order
to obtain sufficient fluid tightness, it would be necessary to
clamp the plates with a considerably strong force. For this
reason, it is unsuitable for use with thin plates.
It is an object of the present invention to eliminate
the disadvantages of conventional gaskets used in plate type
heat exchangers.
Another object of the invention is to provide a gasket
having characteristics which meet the conditions for contact in
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various positions on the plates.
A further object of the invention is to provide a
gasket for use in plate type heat exchangers which is supe-
rior in elasticity and resistances to heat and chemicals.
Accordingly, the present invention provides a gas-
ket comprising an elongated elastic core describing a closed
loop of irregular configuration with a cross-section having
top, bottom, inner and outer side surfaces,and a mating elon-
gated Teflon* cover member of uniform U-shaped cross-section -
also having an irregular configuration and encasing said core
on said top, bottom and inner side surfaces, the cover member
being of substantially uniform thickness and being provided
with means positively securing the core member within the
cover member.
The elastic core material may be natural or synthe-
tic rubber and may be secured by adhesive bonding to the
Teflon* cover or by meshing of the material and cover.
Said gasket has a suitable degree of elasticity and
is capable of maintaining fluid-tightness between the plates
with a relatively small force whilst its surface of contact
with heat exchange liquid is superior in resistances to heat
and chemicals.
Other numerous features which are characteristic of
the present invention will be fully described with reference
to the accompanying drawings illustrating embodiments of the
invention and in which:
Figure 1 is a schematic front view of a plate and a
gasket generally used in a plate type heat exchanger;
Figure 2 is a schematic front view of a plate pro-
vided with a gasket according to the invention;
Figure 3 is an enlarged sectional view showing themounting of a gasket according to the invention;
* Trade Mark
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Figure 4 is an enlarged sectional view of the prin- -
cipal portion of another embodiment of the invention, similar
to Figure 3;
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Figure 5 is a perspective view of a gasket according
to a further embodiment of the invention;
Figure 6 is a perspective view, partially broken
away, of the gasket of Figure 5 installed between plates in a
heat exchanger; and
Figures 7 through 9 are cross-sectional views of
gaskets, showing the condition of engagement between an elastic
material and a Teflon sheet.
In a known kind of plate type heat exchanger, as :~
10 shown in Figure 1, each heat exchange plate, is provided at the ~:
four corners with openings 1, 2, 3 and 4 serving as inlet and
outlet ports for a heat exchanger fluid, for example, liquid
or gas. Thus, the heat exchanger includes a plate A having a
gasket 5a mounted thereon so as to surround the openings 1 and
2 disposed on a diagonal line to establish communication
therebetween while shutting off the other openings 3 and 4, and .
a plate B having a gasket 5b mounted thereon so as to surround
the openings 3 and 4 to establish communication therebetween
while shutting off the other openings 1 and 2. A plurality of
:20 such plates A and B are alternately put together with clearances
defined therebetween providing fluid channels or heat exchange
chambers ~llowing dissimilar heat exchange fluids to flow
therethrough with one plate A or B between such fluids. For
example, if high temperature fluid is supplied through the
openings 1 while supplying cold water through the openings 3,
` the high temperature fluid flowing in through the openings 1
passes along the surfaces of the plates A during which time it
exchanges heat with the fluid in the adjacent heat exchange
chambers, namely the cold water, and flows out through the
; 30 openings 2. On the other hand, the cold water passes from the
openings 3 along the surfaces of the plates B during which time
it exchanges heat with said high temperature fluid flowing
through the adjacent fluid channels with the plates A
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therebetween and flows out through the openings 4. In
addition, the entire surface of each of the plates A and B is
provided with a number of ridges and recesses in order to
improve the efficiency of heat exchange, and the gaskets 5a and
Sb are mounted by making use of the recesses.
Now, since the high temperature fluid passing from the
openings 1 onto the plates A is heat-exchanged on the plates A,
the condition of the fluid does not necessarily remain constant
but varies with different locations on each plate A and hence
the conditions for its contact with each gasket 5a vary. More
particularly, the temperature of the fluid differs between a
region near the openings 1 and a region near the openings 2 and
hence the condition of deformation of the gaskets 5a also
differs. If the fluid is a non-corrosive one, such as water,
there is no trouble, but if it is an organic solvent, there is
the problem of the contact surfaces of the gaskets being
corroded. Moreover, since organic solvents vary in their
corrosive nature according to temperature, there will be the
phenomenon of some regions of the gaskets 5a being attacked with
other regions not being attacked.
Referring to Figure 2 showing a first embodiment of
the invention, a gasket shown at 15 is mounted on a plate lOA.
- The gasket 15 is formed of an elastic material 16, such as
rubber, and a thin Teflo ~ sheet 17 highly resistant to heat and
corrosion. More particularly, the elastic material 16, applied
to a region where the conditions for contact during heat
exchange are relatively favorable, is formed uniformly to the
size of the gasket 15, while the portion of the elastic material
exposed to a region where the conditions for contact are severe
has the U-shaped Teflon sheet 17 adhesively fixed thereto in
such a manner that its lateral surface 17a defines a surface of
contact with a heat exchange fluid. The Teflon sheet 17 is
pre-bent to the shape of the portion of the elastic material 16
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on which it is to be mounted so as to facilitate the mounting
~' of the Teflon~sheet on the elastic material.
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The surface of the plate lOA, on which the Teflon~
sheet 17 is to be seated, is formed with a step lOa
corresponding to the thickness of the Teflon sheet 17, as shown
in Figure 3, so as to avoid positional misalignment when the
gasket 15 is mounted. Further, as shown in Figure 4, the upper
and lower surfaces of the elastic material 16 may be formed
with steps 16a and 16b for receiving the Teflo~ sheet 17 to
prevent the latter from projecting out of the elastic material
16.
Thus, when a chemical such as a solvent is handled,
the use of the gasket 15 constructed in the manner described
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above allows heat exchange to be performed in the same manner
as in the past without being attacked by the heat exchange fluid
and variations in the conditions for contact at various positions
on the plate can be effectively accommodated by the character-
istics of the elastic material 16 and Teflon~sheet 17, which differ
in their resistances to heat and corrosion. Moreover, the same
state of contact exists over the entire gasket 15 irrespective
of temperature differences and corrosiveness, even if used for a
long time, and hence the plates will not warp.
Referring to Figure 5 showing a second embodiment of
the invention, a gasket is shown at 25. The gasket 25 comprises
an elastic material 26 such as synthetic rubber of rectangular
cross-section covered with a thin Teflon sheet 27 formed into a
U-shaped cross-section.
Referring to Figure 6, the width of the Teflon sheet
27 is substantially the same as the width of a gasket groove
28a or 28b in a plate 20A or 20B and the height of the lateral
surface 27a is greater than the depth of the groove 28a or 28b.
Therefore, when the gasket 25 is mounted, for example, in the
groove 28b, the upper portion of the lateral surface 27a faces
the fluid channel and the upper portion of the gasket 25 projects
above the groove 28~.
In mounting the elastic material 26 to the Teflon sheet
27, the Teflo~rsheet 26, pre-bent into a u-shaped cross-section,
is circularly or flaringly formed as by a roller while applying
heat in such a manner that its lateral surface 27a becomes an
inner peripheral surface, and the elastic material 26 is then
mounted to the Teflon sheet. The surface of the Teflon sheet
27 is smooth and very slippy and the gasket is long and narrow,
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so that, if the plates 20A and 20B are clamped, there would
be a danger that the elastic material 26 would be squeezed out
~-~,of the open side of the Teflon sheet 27 as it is deformed. To
prevent this, the inner surface of the Teflon sheet 27 is
surface-treated and an adhesive agent is applied thereto to
fix the two members together. Further, if the gasket 25 is
adhesively secured to the gasket groove 28b of the plate 20B,
plate assembling operation is facilitated.
Further, fixing of the elastic material 26 to the Teflon~
sheet 27, or their integration, may be effected by resorting to
engagement or meshing relation therebetween as shown in Figures
7 through 9 rather than resorting to the adhesive agent. Thus,
in an embodiment shown in Figure 7, a projection 27b is formed
on the inner surface of the Teflo ~sheet 27 and fixing is
effected by said projection cutting into the elastic material.
In Figure 8 the inner surface of the Teflo~ sheet 27 is roughened
or corrugated. In Fy ure 9, cores 29 in the form of piano wires
or the like are embedded in the elastic material 26 to increase
the resistance of the elastic maberial to deformation. These
forms may be suitably selected according to the clamping force
on the plates 20A and 20B.
On the plate 20B, having the gasket 25 adhesively
applied to the gasket groove 28b, is placed the back surface of the
other plate 20A, with the bottom of the groove 28a contacted with
the gasket 25, and in this condition the assembly is clamped
whereby a fluid channel or heat exchange chamber 20C is defined
between these pla~es. ThUs, intimate contact of the gasket 25
with the surfaces of the respective plates is established with a
relatively small clamping force and the heat exchange
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fluid contacts only the Teflon sheet 27 of the gasket 25.
~` Thus, handling of organic solvents for heat exchange becomes
possible. Further, the function described above prevents the
elastic material 26 from being squeezed out of the Teflo~ sheet
27 when the plates 20A and 20B are clamped, and hence reliable
sealing is assured.
While what have been described heEèin are at present
considered to be preferred embodiments of the several features
of the invention, it will be obvious to those skilled in the
art that modifications and changes may be made without departing
from the essence of the invention.
It is therefore to be understood that the exemplary
embodiments thereof are illustrative and not restrictive of the
invention, the scope of which is defined in the appended claims,
and that all modifications that come within the meaning and
range of equivalency of the claims are intended to be included
therein.
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