This invention relates to a gasket for a plate of a plate heat exchanger, which plate is provided with a gasket groove, the gas- ket being made of an elastic material and intended to be applied into the gasket groove of the plate.

A plate heat exchanger comprises a number of essentially rectangu¬ lar plates as a rule fastened into a frame, which plates are sea- led from each other by means of peripheral gaskets and between which are formed heat transferring areas in the form of parallel- connected heat exchanging passages for through-flow of heat ex¬ changing media that are conducted to and from the heat exchanger via inlets and outlets preferably arranged at the one end of the plate heat exchanger, the plates at their corner parts being pro¬ vided with openings for forming inlet channels and outlet channels for the heat exchanging media.

The peripheral gaskets sealing between the plates essentially con- sist of rubber, the sealing pressure of the gaskets being obtained when the plate package is tightened by the frame by means of set bolts.

In order that a rubber gasket shall function satisfactorily there has among other things to be sufficient space in the gasket place for an expansion of the rubber partly when the gasket is compres¬ sed during the tightening procedure and partly as a consequence of possible temperature expansion.

There is already today such an expansion space-on certain types of heat exchanger plates due to the fact that recesses are made in the flank of the gasket groove in the heat exchanger plate.

Another type of plate is disclosed in the Swedish patent No 116 638. This plate is provided with a gasket groove having a

square cross section and cooperating with a gasket having a circu¬ lar cross section. Owing to this form the gasket obtains an expan¬ sion space in the gasket groove but instead problems arise regard¬ ing the holding of the gasket in the gasket groove, because the contact surface of the gasket towards the walls of the gasket groove becomes small. Due to that fact the gasket has to be held in the groove by means of special projections.

The purpose of this invention is to solve the problem of the ex- pansion and the holding of the gasket in a gasket groove having for instance square, rectangular or dovetailed-formed cross sec¬ tion. This is achieved by the fact that the gasket at least at certain places along its extension fills up essentially the whole gasket groove and that the gasket has such a design that necessary expansion space is created for the same in the gasket groove of the plate.

Three preferred embodiments of the invention shall be described more closely in connection with the accompanying drawings, in which

Figs. 1, 4, 7 show a plane view of a part of the gasket according to the three different embodiments,

Figs. 2, 5, 8 show a cross section of the gasket along the lines II-II, V-V and VIII-VIII of Figs. 1, 4 and 7 , respectively, the gasket being put jLnto a groove in a heat exchanger plate and

Figs. 3, 6, 9 show a cross section of the gasket along the lines III-III, VI-VI and IX-IX in Figs. 1, 4 and 7, respectively, the gasket being put into a groove in a heat exchanger plate.

The first embodiment is disclosed in the Figs. 1-3. The gasket 1 preferably made of rubber extends along the periphery of a plate 2 and seals off the interspace between two plates. A cross section

II-II of the gasket according to this embodiment has essentially the form of a trapezoid, two sides 3, 4 connecting two essentially parallel sides 5, 6 of the cross section II-II of the gasket.

The gasket 1 is put into a dovetail-formed groove 7 in the heat exchanger plate 2. In this connection the side 3 of the gasket co¬ operates with the flank 9 of the groove 7 and the side 4 of the gasket with the flank 10 of the groove 7 so that the gasket 1 fills up essentially the whole gasket groove 7. The advantage of this t e _^ of grooves is that the gasket is held in the groove in a secure way. The disadvantage, however, is that when using a con¬ ventional gasket filling up all the space in ^' the groove there is not sufficient expansion space for the rubber.

According to Fig. 1 one side 3 of the gasket 1 has recesses 8 so that. the cross section III-III at these places is redued in rela¬ tion to the cross section II-II. The reduction of the cross sec¬ tion is preferably made in that side 3 _, of the gasket that does not come into contact with the heat exchanging media.

The recesses 8 are made at certain places along one of the sides 3, 4 of the gasket and preferably recur with even interspaces along the gasket. Recesses, however, can be made in both these sides 3, 4 of the gasket 1 which are in contact with both flanks 9, 10 of the gasket groove 7.

Due to the reduction of the cross section there is created space for expansion of the gasket during the tightening of the plate package. Thus, during the tightening of the plate package the re- cesses are filled up by the expanding rubber. Further, due to the fact that the reduction of the cross section is preferably only made in parts of the one flank of the gasket the feature of the dovetail groove to hold the gasket is preserved at the same time as the sealing features of the gasket are not changed.

In Figs. 4-6 a second embodiment of the invention is shown. The gasket 11 according to this embodiment has an appearance that looks like that according to Figs. 1-3 with that difference that one o£ the flanks of the gasket is cut away, whereby the one side 12 of the gasket extends essentially perpendicularly to the bottom surface 13 of the gasket. This side 12 cooperates with a side sur¬ face 14 of the gasket groove extending essentially perpendicularly to the plane of the plate 15. The other side 16 of the gasket has such a form that it is in contact with the dovetail-formed flank 17 of the gasket groove. Due to that fact the gasket fills up essentially the whole gasket groove. The gasket 11 in conformity with the gasket according to Figs. 1-3 has recesses 8 preferably with even interspaces along the gasket in that side of the gasket that does not come into contact with the heat exchanging media. By these recesses 8 space is created for the expansion of the gasket in the gasket groove.

Due to the fact that the gasket 11 fills up essentially the whole gasket groove along a great part of its extension, and that the flank 16 of the gasket is in contact with the dovetail-formed flank 17 of the gasket groove, the gasket is securely held in the gasket groove.

In Figs. 7-9 there is disclosed a third embodiment of the inven- tion. The gasket 18 according to this embodiment has a square cross section and cooperates with a gasket groove of a correspond¬ ing form. In this connection the gasket 18 fills up essentially the whole gasket groove. In order to make expansion of the gasket possible this one is provided with recesses 19 preferably made in that side 20 of the gasket which does not come into contact with the heat exchanging media. These recesses 19 can suitably comprise a square or rectangular cut out from the side 20 of the gasket and recur with even interspaces along the gasket.

OMPI

LA>„ wipo Λ>

Due to the fact that the gasket 18 at the unrecessed places fills up the gasket groove, the gasket is held in the same in a secure way.

Other embodiments within the scope of the invention, of course. are possible. Thus, the gasket according to the third embodiment may have rectangular cross section at the unrecessed places in¬ stead of square. Furthermore, it is possible at least in certain applications to have in all three embodiments recesses also in that side- of the gasket that is in touch with the heat exchanging media.