GB1562335A - Gasket for use in plate type heat exchangers - Google Patents

Description

(54) GASKET FOR USE IN PLATE TYPE HEAT EXCHANGERS (71) We, HISAKA WORKS LIMITED, a Company organised and existing under the laws of Japan, of 4-chome, 4-banchi, Hirano ho, Higashi-Ku, Osaka-Shi, Osakafu, Japan, do hereby declare the invention, for which we pray that a Patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: 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 polytetrafluoroethylene (PTFE) which is superior in resistances to heat and chemicals would be contemplated, but PTFE 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 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 superior in elasticity and resistances to heat and chemicals.

Accordingly, the present invention is a gasket for use in a plate type heat exchanger, which comprises a sheet or strip of an elastomeric material having an edge portion thereof encased in and secured to a U-shaped cross section member formed from a sheet of polytetrafluoroethylene.

The elastomeric material may be natural or synthetic rubber and may be secured by adhesive bonding to the polytetrafluoroethylene sheet or by meshing of the material and sheet.

Such a 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 provided with a gasket according to the invention; Figure 3 is an enlarged sectional view showing the mounting of a gasket according to the invention; Figure 4 is an enlarged sectional view of the principal portion of another embodiment of the invention similar to Figure 3; Figure 5 is a perspective view of a gasket according to a further embodiment of the invention; Figure 6 is a perspective view of a gasket and plate assembly; and Figure 7 through 9 are cross-sectional views of gaskets, showing the condition of engagement between an elastomeric material and a polrtetrafluoroethylene (PTFE) sheet.

Referring to Figure 1, a 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 Sb 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 such plates A and B are alternately put together with clearances defined therebetween providing fluid channels or heat exchange chambers allowing 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 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 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 5b 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 it varies according to different positions on each plate A and hence the conditions for its contact with each gasket Sa 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 Sa also differs. If the fluid is 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 Sa being attacked with the 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 10A. The gasket 15 is formed of an elastomeric material 16 such as rubber, and a thin PTFE e.g. Teflon (Registered Trade Mark) sheet 17 highly resistant to heat and corrosion. More particularly, the elastomeric material 16 applied to a region where the conditions for contact during heat exchange are relatively favourable is formed uni formly to the size of the gasket 15, while the portion of the elastomeric material ex posed to a region where the conditions for contact are severe has the U-shaped PTFE 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 PTFE sheet 17 is pre-bent to the shape of the portion of the elastomeric material 16 on which it is to be mounted so as to facilitate the mounting of the PTFE sheet on the elastomeric material.

The surface of the late 10A on which the PTFE sheet 17 is to be seated is formed with a step lOa corresponding to the thick ness of the PTFE 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 elastomeric material 16 may be formed with steps 16a and 16b for receiving the PTFE sheet 17 ta prevent the latter from projecting out of the elastomeric material 16.

Thus, when a chemical such as a solvent is handled, the use of the gasket 15 constructed in the manner described 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 characteristics of the elastomeric material 16 and PTFE 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 Figures 5 and 6 showing a second embodiment of the invention a gasket is shown at 25. The gasket 25 comprises an elastomeric material 26 such as synthetic rubber of rectangular cross-section covered with a thin PTFE sheet 27 formed into a U-shaped cross-section.

The width of the PTFE 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 28b.

In mounting the elastomeric material 26 to the PTFE sheet 27, the PTFE sheet 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 elastomeric material 26 is then mounted to the PTFE sheet. The surface of the PTFE sheet 27 is smooth and very slippery and the gasket is long and narrow, so that if the plates 20A and 20B are clamped, there would be the danger of the elastomeric material 26 being squeezed out of the open side of the PTFE sheet 27 as it is deformed. To prevent this, the inner surface of the PTFE sheet 27 is surface-treated and an adhesive agent is applied thereto to fix the two members together.Further, if the gasket member 25 is adhesively secured to the gasket groove 28b of the plate 20B, this facilitates plate assembling operation.

Further, fixing of the elastomeric material 26 to the PTFE 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 said adhesive agent. Thus, in an embodiment shown in Figure 7, a projection 27b is formed on the inner surface of the PTFE sheet 27 and fixing is effected by said projection eating into the elastomeric material. In Figure 8, the inner surface of the PTFE sheet 27 is roughened or corrugated. In Figure 9, cores 29 in the form of piano wires or the like are embedded in the elastomeric material 26 to increase the resistance of the elastomeric material 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 plates. 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 fluid contacts only the PTFE sheet 27 of the gasket 25. Thus, handling of organic solvents for heat exchange becomes possible.

Further, the function described above prevents the elastomeric material 26 from being squeezed out of the PTFE sheet 27 when the plates 20A and 20B are clamped, and hence reliable sealing is assured.

Whilst there have been described herein what are at present considered 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 invention as claimed.

WHAT WE CLAIM IS: 1. A gasket for use in a plate type heat exchanger, which comprises a sheet or strip of an elastomeric material having an edge portion thereof encased in and secured to a U-shaped cross section member formed from a sheet of polytetrafluoroethylene.

2. A gasket as claimed in Claim 1 wherein the elastomeric material is in the form of a sheet the peripheral edge of which is encased in a U-shaped cross section member formed from a sheet of polytetrafluoroethylene.

3. A gasket as claimed in Claim 1 or 2 wherein the elastomeric material is natural or synthetic rubber.

4. A gasket as claimed in Claim 1 substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. differences and corrosiveness even if used for a long time, and hence the plates will not warp. Referring to Figures 5 and 6 showing a second embodiment of the invention a gasket is shown at 25. The gasket 25 comprises an elastomeric material 26 such as synthetic rubber of rectangular cross-section covered with a thin PTFE sheet 27 formed into a U-shaped cross-section. The width of the PTFE 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 28b. In mounting the elastomeric material 26 to the PTFE sheet 27, the PTFE sheet 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 elastomeric material 26 is then mounted to the PTFE sheet. The surface of the PTFE sheet 27 is smooth and very slippery and the gasket is long and narrow, so that if the plates 20A and 20B are clamped, there would be the danger of the elastomeric material 26 being squeezed out of the open side of the PTFE sheet 27 as it is deformed. To prevent this, the inner surface of the PTFE sheet 27 is surface-treated and an adhesive agent is applied thereto to fix the two members together.Further, if the gasket member 25 is adhesively secured to the gasket groove 28b of the plate 20B, this facilitates plate assembling operation. Further, fixing of the elastomeric material 26 to the PTFE 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 said adhesive agent. Thus, in an embodiment shown in Figure 7, a projection 27b is formed on the inner surface of the PTFE sheet 27 and fixing is effected by said projection eating into the elastomeric material. In Figure 8, the inner surface of the PTFE sheet 27 is roughened or corrugated. In Figure 9, cores 29 in the form of piano wires or the like are embedded in the elastomeric material 26 to increase the resistance of the elastomeric material 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 plates. 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 fluid contacts only the PTFE sheet 27 of the gasket 25. Thus, handling of organic solvents for heat exchange becomes possible. Further, the function described above prevents the elastomeric material 26 from being squeezed out of the PTFE sheet 27 when the plates 20A and 20B are clamped, and hence reliable sealing is assured. Whilst there have been described herein what are at present considered 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 invention as claimed. WHAT WE CLAIM IS:

1. A gasket for use in a plate type heat exchanger, which comprises a sheet or strip of an elastomeric material having an edge portion thereof encased in and secured to a U-shaped cross section member formed from a sheet of polytetrafluoroethylene.

2. A gasket as claimed in Claim 1 wherein the elastomeric material is in the form of a sheet the peripheral edge of which is encased in a U-shaped cross section member formed from a sheet of polytetrafluoroethylene.

3. A gasket as claimed in Claim 1 or 2 wherein the elastomeric material is natural or synthetic rubber.

4. A gasket as claimed in Claim 1 substantially as hereinbefore described with reference to the accompanying drawings.