Abstract:
A combination of a plurality of heat exchange plates and sealing gaskets therefor, for use in a heat exchanger arrangement, each heat exchange plate having first and second sides, an edge, and a groove formed in the upper side thereof, extending along and spaced from the edge, and each sealing gasket having an elongate main portion, for seating in the groove of a first heat exchange plate, and for sealing between the first heat exchange plate and a second of the heat exchange plates when the second heat exchange plate is retained in compressive association therewith; and a plurality of plate gripping portions located in spaced arrangement along the length of the main portion, formed integrally therewith, and extending transversely away therefrom, for gripping predetermined portions of the plate so as to attach the gasket thereto, wherein the plate gripping portions are formed so as to provide to an assembler a visual indication as to whether the plate gripping portions and the plate are properly fastened together, at each predetermined portion of the plate.

Description:
FIELD OF THE INVENTION 
     The present invention relates to flat plate heat exchangers generally, and in particular to sealing gaskets therefor. 
     BACKGROUND OF THE INVENTION 
     It is well known in the art to construct flat plate heat exchangers, in which there is provided a plurality of plates arranged adjacent to each other and forming between them sealed passages for two mutually heat exchanging fluids. Flow passages are provided between the plates by virtue of transverse fluid ports formed therein, and by a rubber gasket located between each pair of facing plate surfaces. The gasket is generally of elongate, continuous form, and is arranged for seating in a preformed groove provided along the edge of each plate. The stack is assembled manually, by sliding each plate onto one or more elongate supports, so that the groove extends generally upwards, thereafter, a gasket is placed in the groove. Subsequently, an entire stack of plates and gaskets has been assembled on the supports, it is tightened together, thereby compression the gaskets between the plates so as to seal the spaces between the plates against leakage. 
     It is of particular importance to ensure that the gaskets are correctly positioned prior to the stack being tightened. Otherwise, the stack may not be properly sealed, leading to leakage. In the event that this happens, it is, of course, necessary to locate the improperly positioned gasket, and to partially dismantle the stack so as to align the gasket properly prior to tightening the stack once more. 
     Various efforts have been made to facilitate easier and more accurate placement and retention of gaskets prior to tightening. 
     U.S. Pat. No. 4,377,204, entitled “Plate Heat Exchanger,” describes a plate heat exchanger arrangement in which the plate is formed with a plurality of holes between the gasket seating groove, and the plate edge, and wherein each gasket are provided with a plurality of tabs extending laterally outward from the main gasket portion, and wherein each tab has formed thereon a protrusion which is arranged for insertion into an adjacent hole. The protrusion is provided facing generally downwards, out of the view of a person assembling the gasket and the plate, so as to extend towards the surface of the plate in which the groove is formed, and must be pushed through the hole - away from the in order for the gasket to become properly fastened to the plate. Moreover, if the protrusions are not pushed through properly, then the gasket will not lay properly, and the extra thickness of a non-inserted protrusion may cause a slight misalignment of the gasket relative to the stack, causing an imperfect seal, and the problems caused thereby. 
     In an attempt to overcome this problem, U.S. Pat. No. 4,635,715, entitled “Gasket Arrangement for a Plate Heat Exchanger,” teaches a gasket for placement into the gasket seating groove of a plate, and which has, on the side of the gasket closest to the plate edge, a plurality of spaced apart plate retention portions, which are arranged at a distance from each other. 
     This prior art gasket is illustrated in FIGS. A, B, C and D, herewith, and is denoted generally by the letter a. The main portion of gasket a, formed for seating in a groove b of a heat exchanger plate c, is indicated by the letter d. It will be appreciated that only small sections of both the gasket a and of the plate c are illustrated, and that, in the present drawings, and, indeed, through the present specification, they are intended to represent the entire gasket and plate, respectively. 
     FIG. A shows a section of the gasket a, and FIG. B shows proper placement thereof in groove b of heat exchanger plate c. Gasket a has a plurality of plate mounting portions e, of which a single one only, by way of illustrative example, is shown herein. Mounting portion e has one or more projections f, which are formed integrally with and perpendicular to the main gasket portion d, and thus also to the edge g of plate c. The projections f have integrally formed therewith a bridge portion h which is parallel to the main gasket portion d, and from which extend—at right angles thereto—one or more holding elements i. In the present example, a single holding element i is provided. 
     The holding elements i are parallel to and spaced longitudinally from the projections f and extend back towards the main gasket portion d, and therebetween, so that the projections f and holding elements i serve to effectively surround the plate edge g, such that the plate mounting portions serve to provide a retention force across the plate, and in the plane of the plate, thereby to reduce the chance of the gasket becoming detached from the plate. 
     A disadvantage, however, of the solution suggested in the above cited patent, is that it does not securely fasten a gasket to a plate, and, due to the relative flexibility of the gasket, does not provide sufficient purchase on the plate so as to prevent its dislodgment therefrom during assembly. 
     Furthermore, and referring now to FIG. C, it may happen during assembly, that the holding portion f thereof, instead of being fastened underneath the plate edge, instead remains on the top surface thereof. As now seen FIG. D, the assembling of a subsequent plate onto the improperly placed holding portion f, causes a misalignment in the assembled stack, thereby causing leakage therefrom. In practice, the misalignment is not normally discovered until use of the stack, which is a source of great inconvenience, as the system has to be properly emptied and disassembled, and, furthermore, as it is difficult to determine the location of the improperly placed holding portion, and it is required to disassemble much or all of the stack in order to determine its location. 
     SUMMARY OF THE INVENTION 
     It is an aim of the present invention to provide a gasket for use with a plate heat exchanger arrangement, in which each gasket has formed thereon a plurality of gripping elements for applying a positive gripping force transversely to the heat exchanger plate, thereby to positively retain the gasket in a desired position on the plate prior to tightening of a stack. 
     A further aim of the invention is to provide a gasket for use with a plate heat exchanger arrangement, in which each gasket has formed thereon a plurality of gripping elements for gripping an associated heat exchanger plate, and wherein, in the event that the gripping element is not properly positioned during assembly, there is provided a visual indication as to the location thereof, thereby facilitating easy correction of the problem prior to use of the assembled plate stack. 
     There is thus provided, in accordance with a preferred embodiment of the invention, a combination of a plurality of heat exchange plates and sealing gaskets therefor, for use in a heat exchanger arrangement, each heat exchange plate having first and second sides, an edge, and a groove formed in the upper side thereof, extending along and spaced from the edge, and 
     each sealing gasket having an elongate main portion, for seating in the groove of a first heat exchange plate, and for sealing between the first heat exchange plate and a second of the heat exchange plates when the second heat exchange plate is retained in compressive association therewith; and a plurality of plate gripping portions located in spaced arrangement along the length of the main portion, formed integrally therewith, and extending transversely away therefrom, for gripping predetermined portions of the plate so as to attach the gasket thereto, wherein the plate gripping portions are formed so as to provide to an assembler a visual indication as to whether the plate gripping portions and the plate are properly fastened together, at each predetermined portion of the plate. 
     Further in accordance with a preferred embodiment of the present invention, each heat exchange plate has formed therein a plurality of openings extending between the first and second sides, and each plate gripping portion includes: 
     one or more connector portions associated with the first side of the plate and extending transversely across the plate edge so as to define a bridge portion thereat; 
     a holding tab connected to the one or more bridge portions, and extending generally inwards, transversely across the edge, in association with the second side of the plate; and 
     a locking element formed on the holding tab and facing the second side of the plate, and operative, when the main gasket portion is seated in the groove, to be in registration with one of the openings, 
     wherein the locking element is arranged for mating engagement with the opening, and a portion of the locking element is visible from the first side when in mating engagement with the opening. 
     Additionally in accordance with a preferred embodiment of the present invention, the one or more connector portions include two, spaced apart, connector portions so as not to cover the opening, there is provided a single bridge portion extending transversely between the connector portions, and the connector element is formed on the holding tab so as to be visible between the connector portions. 
     Further in accordance with a preferred embodiment of the present invention, each opening also opens out directly to the plate edge, thereby to facilitate a lateral movement of the connector element into an associated opening, generally in the plane of the plate, during engagement of the gripping portions with the plate. 
     Preferably, each gripping portion is operative to apply to the plate a gripping force in a direction transverse to the plate. 
     In accordance with an alternative embodiment of the invention, each gripping portion includes: 
     one or more connector portions associated with the first side of the plate and extending transversely from the main portion across the plate edge; 
     one or more flexible elongate gripping tabs; and 
     hinge apparatus connecting the one or more tabs to the one or more connector portions, 
     wherein each tab has an at rest position, prior to fastening of the gasket to the plate, whereat the tab projects generally away from the plate, 
     and wherein, a rotation of the one or more tabs towards the first side of the plate and subsequent positioning of the one or more tabs in touching contact with the second side of the plate, causes the one or more tabs to be urged into gripping contact with the second side of the plate, thereby also to exert a generally equal and opposite force on the one or more connector portions, thereby urging the one or more connector portions into gripping contact with the first side of the plate. 
     Additionally in accordance with a preferred embodiment of the present invention, each tab has a locking element which, when each tab is in gripping engagement with the second side of the plate, is oriented so as to face the second side of the plate, and the plate has formed therealong a plurality of mating portions for mating engagement with the locking element of each tab. 
     Further in accordance with a preferred embodiment of the present invention, the mating portions are openings, and the locking element is a protrusion arranged for mating engagement with one of the openings. 
     Additionally in accordance with a preferred embodiment of the present invention, the mating portions are recesses formed in the second side of the plate, and the locking element is a tooth portion arranged for mating engagement with one of the recesses. 
     Further in accordance with a preferred embodiment of the present invention, the sealing gasket is formed of a single portion of a rubber-like material, the one or more tabs are connected to the one or more connector portions so as to form a joint thereat, and the hinge apparatus includes a natural hinge formed by a rotation of the one or more tabs relative to the one or more connector portions, about the joint. 
     Additionally in accordance with a preferred embodiment of the present invention, the hinge apparatus defines a hinge axis at a predetermined position relative to the plane of the plate, and each gripping portion further defines a raised bridging portion about which the one or more tabs must be flexed in order to insert it between the hinge apparatus and the plate so as to bring the one or more tabs into touching contact with the second side of the plate, so as to cause the one or more tabs to be urged into the gripping contact with the second side of the plate. 
     Further in accordance with a preferred embodiment of the present invention, the hinge apparatus defines a hinge axis generally parallel to the gasket main portion, and the one or more flexible elongate gripping tabs extend generally perpendicular thereto. 
     Additionally in accordance with a preferred embodiment of the present invention, the hinge apparatus defines a hinge axis generally perpendicular to the gasket main portion, and is constituted by the one or more connector portions, the one or more flexible elongate gripping tabs extend parallel to the one or more connector portions, and has an intermediate joining element connected to the one or more connector portions, extending generally perpendicular thereto. 
     Further in accordance with a preferred embodiment of the present invention, the one or more connector portions are constituted by a pair of elongate connector portions spaced apart along the gasket main portion, and there is provided a single elongate gripping tab mounted for insertion between the pair of elongate connector portions. 
     Additionally in accordance with a preferred embodiment of the present invention, the one or more connector portions are constituted by a single elongate connector portion, and there is provided a pair of elongate gripping tabs mounted to either side of the single elongate connector portion. 
     Further in accordance with a preferred embodiment of the present invention, each connector portion defines a free end which extends beyond the plate edge and defines a mounting portion thereat, there is provided a single elongate gripping tab mounted in the fork by the hinge apparatus so as to at least partially overlap the elongate connector portion when in gripping engagement with the second side of the plate. 
     In accordance with yet a further embodiment of the invention, there is provided a sealing gasket for use in a heat exchanger arrangement having a plurality of heat exchange plates, each plate having first and second sides, an edge, and a groove formed in the first side thereof, extending along and spaced from the edge. 
     In this embodiment of the invention, each sealing gasket includes: 
     an elongate main portion, for seating in the groove, and for sealing between the first heat exchange plate an a second of the heat exchange plates when the second heat exchange plate is retained in compressive association therewith; 
     one or more connector portions engaging, on the first side, a predetermined portion of the plate, formed integrally with the main portion and extending transversely therefrom across the edge of the plate, so as to define a free end; and 
     one or more flexible gripping tabs connected via hinge apparatus to the free end of the one or more connector portions, the hinge apparatus being operative to permit folding of the one or more flexible tabs about an axis which is perpendicular to the one or more connector portions, so as to engage, on its second side, the predetermined portion of the plate, such that the predetermined portion of the plate is enclosed therebetween. 
     Additionally in accordance with the present embodiment of the invention, the hinge apparatus is operative to urge the one or more flexible tabs towards the one or more connector portions, such that, in the absence of the plate, the one or more flexible tabs and the one or more connector portions would be pressed together in mutual registration, and wherein, when mounted about the plate, the one or more flexible tabs and the one or more connector portions cooperate so as to grip the predetermined portion of the plate therebetween. 
     More particularly, the hinge apparatus and the free end of the one or more connector portions define therebetween an opening, and prior to mounting of the gasket onto the plate, the one or more tabs is in an at rest position, whereat the tab projects generally away from the plate; the one or more tabs being rotatable towards the first side of the plate, and insertable through the opening, thereby to be urged by the hinge apparatus into gripping contact with the second side of the plate. 
     Further in accordance with a preferred embodiment of the present invention, each elongate connector portion has a rear portion connected to the main gasket portion; a relatively raised main stem portion defining the free end; and a generally diagonal, intermediate portion, formed integrally with the rear portion and the stem portion and connecting therebetween. 
     Preferably, each flexible gripping tab is configured to be folded beneath the relatively raised main stem portion, so as to be in generally coplanar registration with the rear portion, thus as each rear portion is in generally coplanar registration with the main portion, also in generally coplanar registration with the main portion. 
     According to yet a further aspect of the invention, there is provided a heat exchanger plate having defined edge topography which includes 
     an elongate groove extending parallel to the plate edge for seating a main gasket portion; 
     one or more channels formed transversely to the elongate groove and communicating therewith, extending towards the plate edge, for supporting the rear portion of each of the above-mentioned connector portions; 
     a raised portion, located between each channel and the edge, for supporting a single main stem portion of each of the above-mentioned connector portions; and 
     an intermediate portion, joining between the channel and the raised portion, for supporting a single intermediate portion of each of the above-mentioned connector portions, 
     wherein the raised portion defines therebeneath a hollow, in parallel registration with the raised portion, configured for receiving therein a flexible gripping tab. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be more fully understood and appreciated form the following detailed description, taken in conjunction with the drawings, in which: 
     FIGS. A-D are schematic illustrations of a PRIOR ART gasket, showing use thereof; 
     FIG. 1 is an edge portion of a flat plate for use in a heat exchanger, having an opening formed therein for use with gaskets formed in accordance with any of the embodiments of FIGS. 2A and 2B; 
     FIGS. 2A and 2B are schematic illustrations of a portion of a gasket and flat plate attachment arrangement, constructed in accordance with a first embodiment of the present invention; 
     FIG. 3 is a schematic illustration of a portion of a gasket and flat plate attachment arrangement, constructed in accordance with a second embodiment of the present invention; 
     FIG. 4 is a schematic illustration of a portion of a gasket having resilient gripping portions for gripping the edge of a flat heat exchanger plate in accordance with a third embodiment of the present invention, in an at rest position, prior to assembly with a plate; 
     FIGS. 5A and 5B are cross-sectional views of the resilient gripping portion seen in FIG. 4, wherein a resilient holding element thereof is seen to be formed in a range of different possible positions, which, inter alia, serve to determine the gripping force applied thereby; 
     FIG. 6 is a schematic cross-sectional view of the gasket and a gripping portion thereof, fully mounted on the plate; 
     FIGS. 7A and 7B show the gasket of FIGS. 4-6 mounted in a plate stack in properly and improperly mounted positions, respectively; 
     FIGS. 8A,  8 B and  8 C show a gasket which is generally similar to that of FIGS. 4-7B, but wherein the resilient gripping portions thereof each have a single projection and a pair of resilient holding elements connected thereto, wherein the gasket is seen in an at rest, non-mounted position, an at rest position after initial mounting thereof, and in a fully mounted, gripping position, respectively; 
     FIGS. 9A and 9B show a gasket employing, in combination, resilient portions for gripping and becoming matingly engaged with the edge of a flat heat exchanger plate, seen prior to and after full mounting, respectively; 
     FIGS. 10A,  10 B and  10 C show a gasket which is generally similar to that of FIGS. 8A-8C, but wherein the resilient holding elements are connected thereto for rotation about an axis perpendicular to the main gasket portion; 
     FIG. 11 is a perspective view of a portion of a gasket having hinged, resilient gripping portions for gripping the edge of a flat heat exchanger plate in accordance with a fourth embodiment of the present invention, in an at rest position, prior to assembly with a plate; 
     FIG. 12A is a perspective view of the gasket of FIG. 11 in position on a flat plate, prior to attachment therebetween; 
     FIG. 12B is a cross-sectional view of the gasket and plate of FIG. 12A, taken along line B—B therein; 
     FIG. 12C is a perspective view of the gasket of FIG. 11 in position on a flat plate, after full mounting thereon of the gasket; 
     FIG. 13 is a view similar to FIG. 12C, but wherein the gasket employs, in combination, resilient portions for gripping and becoming matingly engaged with the edge of a flat heat exchanger plate; 
     FIGS. 14A and 14B are perspective views of a portion of a gasket having resilient gripping portions for gripping the edge of a flat heat exchanger plate in accordance with a fifth embodiment of the present invention, employing a single resilient gripping element supported on a single projection, seen in an at rest position, prior to assembly with a plate; 
     FIG. 15 is a portion of a flat heat exchange plate for use with the gasket of FIGS. 14A and 14B; 
     FIG. 16 is a perspective view of the gasket of FIGS. 14A and 14B mounted onto the flat plate of FIG. 15; 
     FIG. 17 is a perspective view of a portion of a gasket having a pair of resilient gripping elements supported on a pair of projections, constructed and operative in accordance with a sixth embodiment of the present invention, in an at rest position; 
     FIG. 18 is a perspective view of a portion of a gasket having a pair of resilient gripping elements, also supported on a pair of projections, constructed and operative in accordance with a seventh embodiment of the present invention, in an at rest position; 
     FIG. 19 is a perspective view of a portion of a gasket having a single resilient gripping element supported on a pair of projections, constructed and operative in accordance with a eighth embodiment of the present invention, in an at rest position; 
     FIG. 20 is a perspective view of a portion of a gasket having a pair of resilient gripping elements supported on a pair of projections, constructed and operative in accordance with a ninth embodiment of the present invention, in an at rest position; 
     FIG. 21A is a perspective view of a portion of a gasket having a single resilient gripping element supported on a pair of projections, but also having an adjacent plate locator element, constructed and operative in accordance with a tenth embodiment of the present invention, in an position of full engagement with a plate; 
     FIG. 21B is a perspective view similar to FIG. 21A, but illustrating the positioning of an additional plate in mating engagement with the plate locator element of the gasket; 
     FIGS. 22A and 22B are plan views of a portion of a gasket having a single resilient gripping element supported on a pair of projections, constructed and operative in accordance with an eleventh embodiment of the present invention, in respective partially an fully mounted positions, respectively; 
     FIG. 23 is a cross-sectional view of the gasket and plate seen in FIG. 22B, taken along line  23 — 23  therein; and 
     FIG. 24 is a plan view showing the topography of an edge portion of the plate seen in FIGS. 22A,  22 B and  23 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention seeks to provide, in combination, sealing gaskets for use with a plurality of flat plate heat exchange plates for arrangement in a stack, thereby providing a flat heat exchange stack assembly which is more easily assemblable, is less prone to leakage, and in which gaskets not properly positioned are more easily noticeable prior to use. 
     In the description that follows, various embodiments incorporating the principles of the invention are described. All of the embodiments have basic components in common, however, including a heat exchanger plate and portions thereof, and a gasket and portions thereof. For purposes of brevity and ease of understanding, these portions are generally described the first time that they are introduced only, and typically are not specifically described again, except as may be required for understanding of a particular embodiment. These portions are, however, normally denoted in the description with a one or two digit prefix, indicative of the drawing in which they are illustrated or, if a single embodiment is described in conjunction with more than one drawing, the prefix indicates the first drawing in which they are illustrated. 
     Referring now initially to FIG. 1, there is seen an edge portion  110  of a flat heat exchanger plate  112 , whose topography is such that it can accommodate either of the gaskets shown and described below in conjunction with FIGS. 2A and 2B. In particular, and referring now also to FIGS. 2A and 2B, the heat exchanger plate  112  has an elongate, continuous groove  114 , formed in a first side  115  thereof, parallel to the edge  116  of the plate, for seating the main portion  218  of a gasket  220  (FIGS.  2 A and  2 B). The plate also has formed therein a gasket mounting portion, referenced generally  122 , which, in the present embodiment, is provided by a pair of channels  124  which extend at right angles from groove  114  to plate edge  116 . Between the channels  124  and extending parallel thereto is a generally elongate, intervening ridge portion  126 , which defines a on a second, underside  125  of the plate, a corresponding hollow or recessed portion  128 . Ridge portion  126  also has an opening  127  formed therein. 
     Referring now particularly to FIGS. 2A and 2B, gasket  220  has a plate gripping portion, referenced generally  230 , which provides for improved attachment of the gasket to the plate. Plate gripping portion  230  has a pair of elongate connector portions  232 , which are formed integrally with and project perpendicularly from main gasket portion  218 , and are thus oriented perpendicular to plate edge  116 , when the main gasket portion  218  is seated in groove  114 . 
     Connector portions  232  are joined to each other by an integral bridge portion  234  which is parallel to the main gasket portion  218 , and from which extends—at right angles thereto—a holding tab  236 . A connector stud  238 , or the equivalent thereof, is formed onto holding tab  236 . Holding tab  236  is configured for sliding into hollow  128 , beneath ridge portion  126  of gasket mounting portion  122 , such that, when main gasket portion  118  is properly seated in groove  114 , and plate gripping portion  230  is fully engaged with gasket mounting portion  122 , stud  238  is brought into registration with opening  127 . 
     As seen in the drawings, stud  238  may take any suitable form, and may be, by way of example, a simple, generally cylindrical protrusion, as seen in FIG.  2 A. Alternatively, however, it may have a conical widened end portion, as seen at  240  in FIG.  2 B. As the entire gasket is made of a rubber-like material, the end portion  240  can be easily passed through opening  127 , so as to lock the gasket in place. 
     Attachment of the gasket to the plate is thus completed by pressing on the back or underside of holding tab  236 , as indicated by arrow  242 , thereby to push stud  238  through opening  127  from behind, so as to be clearly visible when protruding therethrough. It will thus be appreciated that, in accordance with the present embodiment, due to the fact that the stud is pushed through from behind, in clear view of a person attaching the gasket to the plate, it is much easier to ensure that the gasket is mounted correctly. 
     Referring now briefly to FIG. 3, it is seen that gasket mounting portion  322  may alternatively be formed such that, rather than a simple hole, plate opening  327  is formed so as to have a widened, generally funnel shaped opening  342  to edge  316 , so as to enable stud  238  to be inserted simultaneously with the mating of connector portions  232  and holding tab  236  with edge portion  310  of plate  312 . 
     Referring now to FIGS. 4-7B, gasket  420  has a plurality of plate gripping portions  430 , each of which has a pair of elongate connector portions  432  which are formed integrally with and extend away from main gasket portion  418 , and across plate edge  416  (FIGS.  5 - 7 B). Elongate connector portions  432  are also seen to be spaced longitudinally apart along the gasket main portion  418 . A single gripping tab  436  is disposed between connector portions  432 , and are supported thereat by means of an integrally formed hinge  440 , defining a hinge axis  441  parallel to plate edge  416 . 
     In the present embodiment, the entire gasket  420  and all the various portions of the gripping portions  430  are preferably formed of a single piece of molded, rubber-like material. Accordingly, gripping tab  436  is formed so as to have an initial, at rest orientation which, in order to bring it into engagement with the plate, requires a relative rotation about hinge  440 , thereby generating an elastic, rotational force, in the direction opposite to that of the rotation of the gripping tab  436 . In an alternative embodiment, hinge  440  may be a separately formed rod like element, but also having additional resilient means (not shown) so as to provide a desired gripping force. 
     Referring now to FIGS. 5A-6, it is seen that main gasket portion  418  is formed so as to be seated in groove  414  of plate  412 , and that after initial placement of the gasket on the plate, the gripping tab  436  has an initial, at rest orientation which is angled generally away from the plate, and from gasket main portion  418 . The initial disposition of tab  436  is preferably in the range 90°-180° relative to the respective planes of plate  412  and connector portions  432 , as seen in FIGS. 5A and 5B, thereby to ensure that when assembling a plate stack, gripping tab  436  of a non-properly fastened gasket is easily visible. 
     As indicated by arrow  442  (FIGS.  4  and  6 ), a rotational force is applied to gripping tab  436  so as to bring it from its at rest position, shown in FIG. 4 in solid lines, to a position of full gripping engagement with the underside or second side  425  of plate  412 , shown in solid lines in FIGS. 5A,  58  and  6 . The force required to rotate gripping tab  436  about a hinge axis  441 , results in a gripping force transverse to the plate  412 , as indicated by arrow  444  in FIG. 4, thereby causing an equal and opposite force to be applied to plate  412  by connector portions  432 . It will be appreciated that the gripping force is thus a function of the rotational resistance provided by hinge  440 , which, in turn is a function of the material properties, the cross-sectional area of the hinge, and the angle through which the gripping tab  436  must be rotated. 
     As is clear from FIG. 6, in the present embodiment of the invention, tab  436  must be inserted in the space between hinge  440  and the plate edge  416 , in order to enable ultimate insertion into hollow  428 . The proper positioning of gasket  420 , including full mating and gripping engagement of plate gripping portion  430  with plate  412 , is seen in FIG.  7 A. FIG. 7B, on the other hand, clearly shows an improper or incomplete mounting of the gasket  420 , indicated by gripping tab  436  standing out in flag like fashion. 
     Referring now briefly to FIGS. 8A,  8 B and  8 C, there is shown an embodiment of the invention which is generally similar to that shown and described above in conjunction with FIGS. 4-7B, but wherein the gasket  820  has a single elongate connector portion  832  to which a pair of gripping tabs  836  are fastened, parallel thereto, via a pair of hinge elements  840 , defining a hinge axis  841 . In order to accommodate the illustrated gasket  820 , plate  812  is provided with a single channel  824 , which is bounded by a pair of ridge portions  826 , defining therebeneath hollows  828 . Mounting of the gasket  820  is generally as described above in relation to gasket  420 , and is thus not described again herein. 
     FIGS. 9A and 9B show both a gasket  920  and a plate  912  which, while being generally similar to those described above in conjunction with FIGS. 4-7B, is also provided with an additional locking facility, by means of an opening  927  formed in ridge portion  926  of plate edge portion  910 , and a locking protrusion  938  arranged for mating engagement with opening  927 , once the remainder of plate gripping portion  930  had been brought into complete mating engagement with plate edge portion  910 . 
     Referring now to FIGS. 10A-10C, there is seen a gasket and plate combination in which the plate edge portion  1010  is substantially similar to that shown and described above in conjunction with FIGS. 8B and 8C, but wherein there is provided a single connector portion  1032 , which is arranged at right angles to the gasket main portion  1018 , and which also constitutes a hinge  1040 , such that a hinge axis  1041  is also generally perpendicular to both the gasket main portion  1018 , but also to the plate edge  1016 . 
     Holding tabs  1036  are formed parallel to axis  1041 , so as to be insertable beneath ridge portions  1026 , as seen in FIGS. 10B and 10C, and are connected to connector portion  1032  via an intermediate joining element  1033 , extending at right angles between connector portion  1032  and gripping tabs  1036 . 
     Referring now to FIGS. 11-12C, there is seen yet a further gasket and plate combination, but wherein the gripping force is not necessarily provided by means of an integral hinge. In the present embodiment, the hinge apparatus  1140  may either be an integral, natural hinge, or a separate hinge element with little or no rotational resistance, there also being provided a raised bridging portion  1148 . Bridging portion  1148 , as seen most clearly in FIG. 12B, defines an edge  1150  which, as seen, is located above the second side  1125  of plate edge portion  1110 , by an amount e, thereby requiring gripping tab  1136  to be bent therearound, prior to insertion into hollow  1128 . This causes a moment of resistance M to be applied by bridging portion  1148  to tab  1136 , resulting in a transverse gripping force F being applied by tab  1136  to the underside or second side  1125  of plate edge portion  1110 . 
     It will be appreciated that the magnitude of the gripping force is determined by the flexibility of the tab  1136 , the magnitude of the height difference e, and the optional provision of flexure characteristics to hinge  1140 . 
     The gripping tab  1136  of the present embodiment is seen to have a generally stepped configuration, having a rear portion  1152  connected to hinge  1140 , a front, free end portion  1154 , for engaging the plate second surface  1125 , and a diagonal, intermediate portion  1156 , connecting between rear portion  1152  and front portion  1154 . It will be appreciated, however, that this is by way of example only, and that a gripping tab having a non-stepped configuration may also be used. 
     Referring briefly now to FIG. 13, there is shown, in combination, a plate  1312  and a gasket  1320 , which are similar to plate  1112  and gasket  1120  of FIGS. 11-12C, but wherein ridge portion  1326  is provided with an opening  1327  for receiving in mating engagement a locking protrusion  1338  attached to gripping tab  1336 . 
     A feature common to the plate gripping portions of all the gaskets shown and described above in conjunction with FIGS. 2A-13, is that the flexible tabs thereof have all been spaced longitudinally from the elongate connector portions extending from the gasket main portion. 
     In the embodiments of the invention shown and described hereinbelow in conjunction with FIGS. 14A-21B, however, a feature common to all of them is that the gripping tabs thereof at least partially overlap the one or more elongate connector portions to which they are connected. Referring now initially to FIGS. 14A and 14B, there is seen a portion of a gasket  1420 , which is configured for use in combination with a flat plate  1512  (FIG.  15 ); the combination being illustrated in a fully, properly mounted orientation in FIG.  16 . Plate gripping portions  1430  of gasket  1420  each have a single elongate connector portion  1432  which extends transversely outwards from main portion  1418 , and terminates, in the present embodiment, in a forked mounting portion, referenced generally  1460 , so as to allow full registration of the single gripping tab  1436  therebeneath, so as to firmly grasp the plate edge portion therebetween. 
     Mounting portion  1460  splits into a pair of mounting elements  1462 , between which is supported a single gripping tab  1436 , via hinge elements  1440 , in much the same manner as exemplified by the arrangement seen in FIG.  4 . Accordingly, in order to properly fasten gasket  1420  to plate  1512 , it is necessary to rotate tab  1436  in a generally upward direction (as per the illustrated orientation) about hinge axis  1441 , as shown by arrow  1464  (FIG.  14 B), and to insert it between the axis  1441  and main stem  1466  of connector portion  1432 , as shown in FIG. 16 by arrow  1468 . 
     In the present embodiment, the connector portion  1432  and gripping tab  1436  overlap, and so both the plate edge topography and the plate gripping portion  1430  are formed so as to accommodate the gripping tab  1436  in generally the same plane as gasket main portion  1418 . In order to do this, connector portion has a generally stepped configuration, having a rear portion  1470  connected to main portion  1418 , and a diagonal, intermediate portion  1472  from which main stem  1466  extends. 
     Similarly, channel  1524  communicating with groove  1514  extends only part of the way to plate edge  1516 , being interrupted by ridge portion  1526 , supporting main stem  1466 . It will thus be appreciated that, when the plate and gasket combination is fully assembled, the gripping tab  1436  and main stem  1466  of each plate gripping portion  1430 , serve to apply a vice-like gripping force about the plate edge  1512 , perpendicular thereto. 
     FIGS. 17 and 18 illustrate gaskets having plate gripping portions that are generally similar in function to those described above in conjunction with FIGS. 14A-16. 
     In FIG. 17, the illustrated plate gripping portion  1730  has a pair of elongate connector portions  1732 , which terminate in a mounting portion  1760  which mounts a pair of gripping tabs  1736 , in a manner similar to that in which tabs  836  are mounted to connector portion  832 , as shown and described hereinabove in conjunction with FIGS. 8A-8C. 
     In FIG. 18, however, the illustrated plate gripping portion  1830  has a pair of elongate connector portions  1832 , which terminate in an integrally formed pair of forked mounting portions  1860 , each of which mounts a single gripping tab  1836 , in a manner similar to that in which tabs  1436  are mounted to forked mounting portion  1460 , as shown and described hereinabove in conjunction with FIGS. 14A,  14 B and  16 . 
     FIG. 19 illustrates a gasket  1920  having a plate gripping portion  1930  in which a pair of spaced apart elongate connector portions  1932  terminate in a single forked mounting portion  1960 , in which a single gripping tab  1936 , whose overall width W 1  is approximately equal to the corresponding exterior dimension W 2  of the pair of connector portions  1932 . Accordingly, when plate gripping portion  1920  is in full gripping engagement with the plate edge (not shown), gripping tab  1936  is configured so as to completely overlap the pair of connector portions  1932 , thereby providing a relatively increased gripping interface between plate and the gripping portion  1930 . 
     FIG. 20 illustrates a gasket  2020  having a plate gripping portion  2030  which is generally similar to that of FIG. 19, except that a pair of gripping tabs  2036  is mounted in forked mounting portion  2060 , via a relatively elongated hinge element  2040 , as shown. 
     Referring now to FIGS. 21A and 21B, there is seen a gasket  2120  having a mounting portion  2130  which is generally similar to that shown and described in conjunction with FIG. 19, except for the addition of an indexing member  2174 . Indexing member  2174  is located between elongate connector portions  2132 , and is attached at a rear end  2175  to mounting portion  2160 , and has a front free end  2176 . 
     When mounting portion  2130  is fully engaged with plate edge portion  2110 , the indexing member  2174  extends over the ridge portion  2127 . 
     As seen in FIG. 21B, when an additional plate  2112 ′ is assembled in an adjacent position in the stack, its edge portion  2110 ′ is inserted between indexing member  2174  and ridge portion  2127  of the lower plate edge portion  2110 , thereby further securing the gasket  2120 . As seen, however, in the present embodiment, in order to utilize the indexing tab  2174 , the additional plate  2112 ′ is inverted so that ridge portion  2127 ′ thereof rests on ridge portion  2127  of the lower plate edge portion  2110 . 
     Referring now to FIGS. 22A-23, there is seen, in combination, a heat exchange plate  2212  and a gasket  2220  having plate gripping portions  2230 . Each plate gripping portion  2230  has a pair of elongate connector portions  2232  extending at right angles from main gasket portion  2218 . Connector portions  2232  are connected by a cross member  2280 , so as to have a generally H-like shape, and thus leaving an opening  2281 . A gripping tab  2236  is mounted to connector portions  2232  via a resilient hinge element  2240 , and is adapted for insertion into gripping contact with second side  2225  of plate edge portion  2210 , as indicated by arrow  2282  in FIG.  23 . Gripping tab  2236  has a locking protrusion  2284 , whose function is described below. It is also seen that cross member  2280  defines a generally flat, plate contact surface  2286 , and gripping tab  2236  also defines a plate contact surface  2288 , which are brought into registration with each other upon full engagement of the plate gripping portions  2230  with plate edge portions  2210 , as seen in FIG. 23, thereby providing a vice-like contact therebetween. 
     Referring now also to FIG. 24, the topography of plate edge portion  2210  is formed so as to accommodate the locking protrusion  2284 , by providing a ridge portion  2226 . The ridge portion  2226  has a generally rectangular, truncated pyramid shape, so as to define a hollow  2228  therebeneath, in the second side  2225  of the plate  2212 , thereby to enable mating engagement thereof with the locking protrusion  2284 . Furthermore, the ridge portion  2226  and the opening  2281  are formed so as to also accommodate each other in a mating arrangement, thereby providing maximum purchase between. 
     It will be appreciated by persons skilled in the art that the scope of the present invention is not limited by what has been shown and described hereinabove. Rather the scope of the present invention is limited solely by the claims, which follow.