Abstract:
A heat exchanger stack includes two or more nestable plates formed of a plate material being substantially unresponsive to electromagnetic impulse welding, and wherein each plate includes a generally flat central portion having a plurality of protrusions protruding from one or more surfaces thereof and one or more pairs of edge portions generally formed non-coplanar relative to the generally flat central portion. The two or more plates are arranged in a nesting arrangement and spaced apart by the protrusions so as to define therebetween a space through which a heat exchange medium may flow. Further, two or more plates are affixed together by electromagnetic pulse welds at a plurality of welding locations which include the protrusions and one or more pairs of edge portions. Also, the two or more plates are mutually connected at the welding locations via a facilitator substrate, which is highly responsive to electromagnetic impulse welding, and which is disposed on one or more of the two plates.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates, generally to heat exchangers and, more specifically, to forming a stack of heat exchanger plates.  
       GLOSSARY  
     Facilitating Substrate  
       [0002]     An applied coating, layer or covering of material substantially responsive to applied electromagnetic impulse energy for application to a surface of an object substantially unresponsive to electromagnetic impulse energy, thereby to effectively provide the object with substantial responsiveness to electromagnetic impulse energy.  
       BACKGROUND OF THE INVENTION  
       [0003]     It is known in the art to provide for forming a stack of heat exchanger plates which are welded together using a high energy, short duration electro-magnetic pulse.  
         [0004]     With reference to U.S. Pat. No. 6,513,240 dated Feb. 4, 2003 entitled “Method of forming a heat exchanger stack” to Pessach Seidel, who is also the inventor of the present invention, there is described a method for forming a heat exchanger stack from a plurality of plates. The plurality of plates includes at least first and second nestable plates formed of an electrically conductive material. Each plate has a generally flat central portion and at least one pair of edge portions generally non-coplanar relative to the respective central portions of the plates. Each plate has a plurality of protrusions, which are formed so that, when the plates are in a stacked, nested position, the respective pluralities of protrusions of the first and second plates engage each other. In addition, the respective central portions of the plates are spaced apart, thereby to define therebetween a space through which a heat exchange medium may be passed. The method includes placing the first heat exchanging plate on a support, placing the second heat exchanging plate in nesting arrangement with the first heat exchanging plate such that the central portions and the edge portions of the two plates are spaced apart, and exposing at least the edge portions of the second heat exchanging plate to pulsed electromagnetic energy, so as to apply thereto a kinetic force causing the edge portions to bend away from the pulsed electromagnetic energy source, such that they impinge on the respective edge portions of the first plate, so as to become joined thereto.  
         [0005]     With reference to  FIG. 1 , there is shown in accordance with the prior art U.S. Pat. No. 6,513,240 a lower static plate referenced  10  having down-turned edges referenced  14  and  16  positioned on a supporting base referenced  2 . If plate  10  is formed of a thick material, the support of base  2  is not required.  
         [0006]     A second plate referenced  20  usually formed having a similar shape to plate  10 , formed having two down-turned edges referenced  24  and  26 , is positioned over plate  10 . Plate  10  and plate  20  are designed so that gaps formed therebetween may be varied according to the welding requirement.  
         [0007]     There is formed a region between plates  10  and  20  that provides turbulent flow of fluid passing therethrough causing high heat transfer, this area including protrusions referenced  18  and  28  respectively.  
         [0008]     Due to the application of electro-magnetic impulses by an electromagnetic pulse welding source referenced  33 , upper plate  20  is projected as indicated by arrow referenced  30  and  32  against lower plate  10 , causing a change of shape of edges  24  and  26  respectively, inducing an electromagnetic weld in areas referenced  34  and  36 . Between protrusions  18  and  28  a weld is similarly formed by electromagnetic impulses projected as indicated by arrow referenced  38 .  
         [0009]     The drawback to the prior art invention is that, while the weld is formed between protrusions  18  and  28 , there is the lack of internal support within flow area between areas referenced  12  and  22  respectively of plates  10  and  20 . The entire surface area  12  becomes projected towards area  22 , not merely in the vicinity of protrusions  18  and  28 , thereby causing distortion of the shape of areas  12  and  22 .  
         [0010]     Referring now to  FIGS. 2 and 3  there are seen views according to another embodiment of the prior art, showing the welding impulse process applied from the concave side of similar shaped plates referenced  40  and  50  as opposed to that indicated in  FIG. 1 . In  FIG. 2 , there is seen preformed plate  40  disposed on base referenced  4  and plate  50  is positioned over plate  40 . Plates  40  and  50  are formed having turned-up edges referenced  44  and  46  and  54 , and  56  respectively. Plate  50  is so disposed relative to plate  40  so as to provide an acceleration gap therebetween.  
         [0011]     In  FIG. 3 , there is shown the disposition of plates  40  and  50  after electromagnetic impulse welding using source referenced  53  as indicated by arrows referenced  51  and  49 . Edge  54  is projected towards edge  44 , creating a welded area referenced  55  therebetween and edge  56  is projected towards edge  46  creating welded area referenced  57  therebetween. The flow region between plate areas referenced  42  and  52  are similarly welded together utilizing electromagnetic impulse source  53  directing impulses as indicated by arrow referenced  58  at protrusions  48  and  58 . However, during this welding process there occurs distortion of plates  40  and  50  in areas referenced  42  and  52  respectively.  
         [0012]     According to another embodiment of the prior art, referring now to  FIG. 4 , there is shown the disposition onto base referenced  8  of lower plate  60  and upper plate  70  on the left side of  FIG. 4  referenced  71  prior to welding and on the right side referenced  79 , after welding. Plates  60  and  70  are formed having a pair of edges  64  and  66  and  74 , and  76  respectively. There is further shown the welding impulse process applied from source  73  as indicated by arrows  80  and  82  to the convex, upper surface of edges  74  and  76  of plate  70  causing edges  74  and  76  to be projected towards edges  64  and  66  respectively, thereby to provide welding therebetween. Also, electromagnetic impulses are applied from source  77  as indicated by arrows  88  to the concave, lower side of plate  60  as opposed to that indicated in  FIG. 1 . Plate  60  is projected towards plate  70  thereby causing protrusions referenced  68  to impinge against opposing protrusions  78  and thereby providing welding therebetween.  
         [0013]     There arises a problem in regard to the above prior art embodiment, however, in so far as severe distortion is found to occur to plates  60  and  70 .  
         [0014]     Furthermore, the above-mentioned process is efficient for heat exchanger plates made from highly conductive metals such as copper, aluminum, magnesium, etc. Materials that are not good conductors, such as tin, steel, stainless steel, titanium, etc., require the application of additional force or energy.  
       SUMMARY OF THE INVENTION  
       [0015]     The present invention aims to provide a heat exchanger stack in accordance with a preferred embodiment of the present invention, including two or more nestable plates formed of a plate material being substantially unresponsive to electromagnetic impulse welding, and wherein each said plate includes a generally flat central portion having a plurality of protrusions protruding from one or more surfaces thereof and one or more pairs of edge portions generally formed non-coplanar relative to the generally flat central portion. The two or more plates are arranged in a nesting arrangement and spaced apart by the protrusions so as to define therebetween a space through which a heat exchange medium may flow. Further, two or more plates are affixed together by electromagnetic pulse welds at a plurality of welding locations which include the protrusions and one or more pairs of edge portions. Also, the two or more plates are mutually connected at the welding locations via a facilitator substrate, which is highly responsive to electromagnetic impulse welding, and which is disposed on one or more of the two plates.  
         [0016]     In accordance with an embodiment of the present invention, the facilitator substrate is selectively applied to one or more surfaces of the edge portions of one of the two or more nestable plates.  
         [0017]     In accordance with another embodiment of the present invention, the facilitator substrate is selectively applied to one or more surfaces of the protrusions of two or more nestable plates.  
         [0018]     In accordance with a further embodiment of the present invention, a substrate of a non-conductive material is selectively applied to one surface of the edge portions and to the generally flat central portion of one or more of the two or more nestable plates, thereby to provide resistance to electromagnetic impulse welding thereto.  
         [0019]     The present invention aims to provide a heat exchanger stack in accordance with another preferred embodiment of the present invention, including two or more nestable plates formed of a plate material being substantially unresponsive to electromagnetic impulse welding, and wherein each said plate includes a generally flat central portion having a plurality of protrusions protruding from one or more surfaces thereof and one or more pairs of edge portions generally formed non-coplanar relative to the generally flat central portion. The two or more plates are arranged in a nesting arrangement and spaced apart by the protrusions so as to define therebetween a space through which a heat exchange medium may flow. Further, two or more plates are affixed together by electromagnetic pulse welds at a plurality of welding locations which include the protrusions and one or more pairs of edge portions. Also, the two or more plates are mutually connected at the welding locations via an intervening facilitator material, which is highly responsive to electromagnetic impulse welding.  
         [0020]     In accordance with another embodiment of the present invention, the intervening facilitator material provides a joining medium in said plurality of welding locations.  
         [0021]     The present invention further aims to provide a method for causing a welding process by the application of a electromagnetic pulse from an electrical source thereto, so as to provide a thrust to preselected portions of a heat exchanger plate, fabricated from materials that are relatively poor electrical conductors or even non-conductors. The preselected portions become welded to an adjacent fixed heat exchanger plate. In order to accelerate the thrust created by the electromagnetic pulse, a thin layer of a facilitating substrate material such as copper, certain plastics and aluminum) is selectively applied in the preselected area to be welded, either in front of or behind the heat exchanger plate. This film is activated by the electromagnetic pulse and serves to respectively pull or push the “dynamic” plate towards its stationary partner, thereby creating a weld.  
         [0022]     In the context of the present invention, the “dynamic” heat exchanger plate relates to that heat exchanger plate which is accelerated and caused to impact or impinge against an adjacent static or fixed plate by the application of an electromagnetic impulse thereto There is provided a method of forming a heat exchanger stack from a plurality of preformed heat exchanger plates, wherein the plurality of plates includes two or more nestable plates, each having a generally flat central portion and having one or more a pairs of edge portions generally non-coplanar relative to the respective central portion of the plate. Also, each plate is formed so that, when the plates are in a stacked, nested position, the respective central portions of the plates, having similar protrusions formed on both surfaces of the central portions of the plates, are spaced apart thereby to define therebetween a space through which a heat exchange medium may be passed. The method includes the steps of 
        a) applying a facilitator substrate, which is highly responsive to electromagnetic impulse welding, to at least one surface of the edge portions and selectively to at least one surface of the generally flat central portion of each plate;     b) disposing the first and second exchanger plates in nesting arrangement on a support; such that the central portions and the edge portions of the two plates are spaced apart; and     c) exposing the facilitator substrate applied to one or more of the first and second heat exchanger plates to a source of electromagnetic impulse energy, so as to apply thereto a kinetic force causing the facilitator substrate to induce the edge portions and selected portions of the flat central portion to bend away from the source of electromagnetic impulse energy, such that the edge portions and the protrusions impinge on the respective edge portions and protrusions of the other plate, so as to become joined thereto.        
 
         [0026]     There is provided another method for forming a heat exchanger stack from a plurality of plates, wherein the plurality of plates includes two or more nestable plates, each having a generally flat central portion and one or more pairs of edge portions generally non-coplanar relative to the central portion of the plate. Each plate has a plurality of protrusions which is formed so that, when the plates are in a stacked, nested position, the respective opposing pluralities of protrusions of the first and second plates are disposed in close spaced apart proximity to each other, and that the respective central portions of the plates are spaced apart, thereby to define therebetween a space through which a heat exchange medium may be passed. The method includes the steps of 
        a) applying a facilitator substrate, which is highly responsive to electromagnetic impulse welding, to at least one surface of the edge portions of each plate and to preselected portions adjacent to the protrusions of the generally flat central portions of each plate;     b) disposing the first and second exchanger plates in nesting arrangement on a support; such that the central portions and the edge portions of the two plates are spaced apart; and     c) exposing the facilitator substrate applied to at least one of the first and second heat exchanger plates to a source of electromagnetic impulse energy, so as to apply thereto a kinetic force causing the facilitator substrate to induce the edge portions and selected portions of the flat central portion to bend away from the source of electromagnetic impulse energy, such that the edge portions and the protrusions impinge on the respective edge portions and protrusions of the other plate, so as to become joined thereto.        
 
         [0030]     In accordance with an embodiment of the present invention the method step of placing the first heat exchanger plate on a support includes placing it in supporting contact with a shaped surface defined by the support.  
         [0031]     There is provided a further method for forming a heat exchanger stack from a plurality of plates, wherein the plurality of plates includes two or more nestable plates, each having a generally flat central portion and one or more pairs of edge portions generally non-coplanar relative to the central portion of the plate. Each plate has a plurality of protrusions which is formed so that, when the plates are in a stacked, nested position, the respective opposing pluralities of protrusions of the first and second plates are disposed in close spaced apart proximity to each other, and that the respective central portions of the plates are spaced apart, thereby to define therebetween a space through which a heat exchange medium may be passed. The method includes the steps of 
        a) applying a facilitator material, which is highly responsive to electromagnetic impulse welding, to at least one surface of the edge portions and selectively to at least one surface of the generally flat central portion of each plate;     b) disposing the first and second exchanger plates in nesting arrangement on a support; such that the central portions and the edge portions of the two plates are spaced apart; and     c) exposing the facilitator applied to at least one of the first and second heat exchanger plates to a source of electromagnetic impulse energy, so as to apply thereto a kinetic force causing the facilitator material to induce the edge portions and selected portions of the flat central portion to bend away from the source of electromagnetic impulse energy, such that the edge portions and the protrusions impinge on the respective edge portions and protrusions of the other plate, so as to become joined thereto by the intervening facilitator material.        
 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0035]     The present invention will be more fully understood and its features and advantages will become apparent to those skilled in the art by reference to the ensuing description, taken in conjunction with the accompanying drawings, in which:  
         [0036]      FIG. 1  is a schematic cross-sectional view of a convex stack of heat exchanger plates in accordance with the PRIOR ART;  
         [0037]      FIGS. 2 and 3  are schematic cross-sectional views of a concave stack of heat exchanger plates in accordance with the PRIOR ART;  
         [0038]      FIG. 4  is a schematic cross-sectional view of a convex stack of heat exchanger plates having an electromagnetic impulse applied from beneath the stack in accordance with the PRIOR ART;  
         [0039]      FIG. 5  is a schematic cross-sectional view of a convex stack of heat exchanger plates prior to and subsequent to electromagnetic impulse welding in accordance with a preferred embodiment of the present invention;  
         [0040]      FIG. 6  is a schematic cross-sectional view of a convex stack of heat exchanger plates prior to and subsequent to electromagnetic impulse welding in accordance with an embodiment of the present invention;  
         [0041]      FIG. 7  is a schematic cross-sectional view of a convex stack of heat exchanger plates prior to and subsequent to electromagnetic impulse welding in accordance with another embodiment of the present invention;  
         [0042]      FIG. 8  is a schematic cross-sectional view of a convex stack of heat exchanger plates prior to and subsequent to electromagnetic impulse welding in accordance with a further embodiment of the present invention;  
         [0043]      FIGS. 9 and 10  are schematic cross-sectional views of a concave stack of heat exchanger plates respectively prior to and subsequent to electromagnetic impulse welding in accordance with an embodiment of the present invention;  
         [0044]      FIGS. 11 and 12  are schematic cross-sectional views of a concave stack of heat exchanger plates respectively prior to and subsequent to electromagnetic impulse welding in accordance with an embodiment of the present invention;  
         [0045]      FIGS. 13 and 14  are schematic cross-sectional views of a concave stack of heat exchanger plates respectively prior to and subsequent to electromagnetic impulse welding in accordance with an embodiment of the present invention;  
         [0046]      FIG. 15  is a schematic cross-sectional view of a convex stack of heat exchanger plates having an electromagnetic impulse applied from beneath the stack; and  
         [0047]      FIG. 16  is a schematic cross-sectional view of a convex stack of multiple heat exchanger plates.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0048]     The present invention discloses a means for facilitating electromagnetic impulse welding of a stack of heat exchanger plates together wherein the heat exchanger plates are formed from less conductive or even non-conductive materials which are substantially unresponsive to electromagnetic impulse welding, while reducing or preventing distortion of the plates.  
         [0049]     Referring now to  FIG. 5 , there is illustrated an application in accordance with a preferred embodiment of the present invention. On the left side generally referenced  101  of  FIG. 5 , there is shown the disposition onto base  105  of lower plate  110  and upper plate  120  before welding and on the right, generally referenced  103 , after welding. Prior to welding, there is an acceleration gap provided between opposing protrusions referenced  118  and  128 . In addition, as an improvement to what is disclosed in the prior art U.S. Pat. No. 6,513,240, facilitating substrates referenced  100 , which are substantially more responsive to an applied electro-magnetic field, are applied to upper surfaces of edges referenced  124  and  126  and similar facilitating substrates, referenced  102  are applied to upper surface of plate  120 , adjacent to protrusions  128 .  
         [0050]     An electro-magnetic pulse is applied from electromagnetic source  133 , as indicated by arrows referenced  130  and  132  to each film area  100 , and as indicated by the arrow referenced  135 , to each film area referenced  102  thereby causing a kinetic projection of edges  124  and  126  and protrusions  128  of upper plate  120  to impinge against lower plate  110 . Consequently weld referenced  134  is formed between edges  114  and  124 , and weld referenced  136  is formed between edges  116  and  126 , and weld referenced  137  between protrusions  118  and  128 .  
         [0051]     To facilitate appropriate eddy currents so as to apply impulses to facilitating substrate material disposed on parts to be welded, these facilitating substrates require to be conductively connected to each other (not shown).  
         [0052]     After welding the initial stack of two plates  110  and  120 , a further plate (not shown) is positioned thereover. Welding of edges and protrusions is then carried out as disclosed herein above.  
         [0053]     Referring now to  FIG. 6  there is shown, before welding on the left side generally referenced  201  and on the right, generally referenced  209 , after welding, the disposition onto base  207  of lower plate referenced  210  and upper plate  220 . There is seen a pushing facilitating substrates referenced  202  and a separating substrates referenced  203  disposed along the upper surface of edges referenced  224  and  226 . Similarly, pushing facilitating substrates  202  and separating substrates  205  are disposed on surface referenced  222  of plate  220  adjacent to protrusions referenced  228 . Separating substrates  203  are formed of a material that facilitates transfer of force from facilitating substrates  200  and  202  towards edges  224  and  226  and surface  222  respectively but prevents welding from occurring therebetween. There is shown on the left side  201  of  FIG. 6  the disposition of lower plate  210  and upper plate  220  before welding and on the right side  203 , after welding. After application of an electromagnetic pulse from source referenced  233  as indicated by arrows referenced  230  and  232 , edges  224  and  226  are projected by pusher film  200  and separating film  203  towards edges  214  and  216 , respectively. Welding occurs in areas referenced  234  and  236 . In addition, welding together of protrusions  218  and  228  in area  222  is facilitated by projecting pushing film  202  and separating film  205  by application of electromagnetic impulses from source referenced  233  in the direction of arrow referenced  235 .  
         [0054]     Referring now to  FIG. 7  there is shown the disposition onto base  307  of lower plate  310  and upper plate  320  before welding on the left side referenced  301  and on the right side referenced  303 , after welding. Plates  310  and  320  are provided with a selective area of a facilitating substrate, which is substantially responsive to an electromagnetic impulse. Facilitating substrates referenced  300  are disposed on the under-side of edge areas referenced  324  and  326  respectively, and also on edge areas referenced  314  and  316 , respectively, in preparation for welding. In area  312  there is a facilitating substrate (not shown) on protrusions  328  formed in area  322 . Following application of an electromagnetic impulse from sources referenced  333  as indicated by arrows referenced  330  and  332 , facilitating substrates  300  are projected towards stationary edges  314  and  316  and, in so doing, pull dynamic plate edges  324  and  326  against static edges  314  and  316 , respectively, thereby creating welding therebetween at areas referenced  334  and  336 , as shown on right side  303 . Similarly, electromagnetic pulses are projected from source  333  in the direction of arrow referenced  335  so that facilitating substrate materials on protrusions  328  are projected towards protrusions  318 , and, in so doing, pull protrusions  328  against protrusions  318 , and thereby creating welding therebetween.  
         [0055]     Referring now to  FIG. 8  there is shown a lower plate referenced  410  and upper plate referenced  420  before welding on the left side referenced  401  and, after welding, on the right side referenced  403  disposed onto base referenced  407 . Facilitating substrate  400  is disposed on the external, convex side of both pairs of edges referenced  414  and  416  and  424  and  426  of plates  410  and  420  respectively. Similarly, Facilitating substrate referenced  402  is disposed on the external, convex side of both areas referenced  412  and  422  adjacent and over protrusions referenced  418  and  428 . Directing electromagnetic impulses from source referenced  433  as indicated by arrows referenced  430  and  432  causes facilitating substrate  400  and associated edges  424  and  426  to be projected towards edges  414  and  416  and to be welded thereto incorporating facilitating substrate  400  thereon into the welded areas referenced  434  and  436  respectively. Similarly, directing electromagnetic impulses from source  433  as indicated by arrow  425 , facilitating substrate material  402  projects protrusions  428  on surface  422  towards protrusions  418 , coated with facilitating substrate material, on surface  412  to form welds referenced  437  therebetween incorporating the facilitating substrate material therein.  
         [0056]     In accordance with another embodiment of the present invention, referring now to  FIGS. 9 and 10 , concave heat exchanger plates referenced  140  and  150  are nestingly disposed on concave base referenced  106 . A facilitating substrate referenced  155  is disposed on the concave edge areas referenced  156  of plate  140  and facilitating substrate referenced  149  is disposed on the concave surface in area referenced  152  adjacent to protrusions referenced  158 . As seen in  FIG. 10 , with application of an electromagnetic impulse from source referenced  153  as indicated by arrows referenced  151 , facilitating substrates  155  are projected towards areas  156  of static plate  140 . In so doing, areas  156  of plate  150  are respectively projected towards areas  146  of plate  140  thereby to provide welds therebetween. In  FIG. 10  there is shown the disposition of edges  114  and  116  after application of electromagnetic impulses from source  153  as directed by arrow referenced  159  to facilitating substrates  149  thereby to cause welding between opposing protrusions  148  and  158  formed respectively in areas referenced  142  and  152 .  
         [0057]     Referring now to  FIGS. 11 and 12 , similar heat exchanger plates referenced  340  and  350  are nestingly disposed in base referenced  366 . In accordance with a further embodiment of the present invention, relating to a facilitating substrate material both facilitating and forming welds between nested plates  340  and  350 , intermediate facilitating substrate material referenced  355  is disposed on plates  340  and  350  on both surfaces of edges referenced  346  and  356  and, also, over and adjacent to protrusions referenced  348  and  358  formed in areas referenced  342  and  352 , where welding is required.  
         [0058]     In  FIG. 12 , with application of electromagnetic impulses from source referenced  353  as indicated by arrows referenced  351  and  352 , facilitating substrate materials  359  is seen to pull and project edges  356  towards edges  346 , thereby welding therebetween referenced  355  with facilitating substrate material  359 . Similarly, with application of electromagnetic impulses as indicated by arrow referenced  361  from source  353 , facilitating substrate material  349 , as indicated in  FIG. 11 , is seen to pull and project protrusions referenced  358  towards opposing protrusions referenced  348 , thereby welding therebetween with facilitating substrate material  349 .  
         [0059]     In accordance with an alternative embodiment of the present invention, relating to a facilitating substrate material applied onto a single surface both facilitating and actively forming the welds between nested plates, reference is now made to  FIGS. 13 and 14 . In  FIG. 13 , similar heat exchanger plates referenced  640  and  650  are nestingly disposed in base referenced  606 . Only the upper surfaces of edges referenced  646  and  656  of both plates  640  and  650  receive a facilitating substrate material referenced  659  and areas referenced  642  and  652  adjacent to protrusions referenced  648  and  658  receive a facilitating substrate material referenced  657  only on the upper surface thereof. In  FIG. 14 , with application of electromagnetic impulses as indicated by arrows referenced  651  and  652  from source referenced  653 , facilitating substrate materials referenced  654  push and project edges referenced  656  towards edges referenced  646 , thereby causing welding therebetween at areas referenced  658  with intermediate facilitating substrate material  659 . With application of electromagnetic impulses as indicated by arrow referenced  661  from source  653 , facilitating substrate material (not shown) on the upper surface of areas referenced  642  and  652  adjacent to protrusions referenced  648  and  658 , respectively, is seen to push and project protrusions  658  towards opposing protrusions  648 , thereby welding therebetween with facilitating substrate material (not shown) disposed on protrusions  648 .  
         [0060]     Referring now to  FIG. 15 , in accordance with an added embodiment of the present invention, there is shown lower plate referenced  760  and upper plate referenced  770  disposed onto base referenced  708  such that the left side referenced  771  of  FIG. 15  indicates the status before welding and the right side referenced  773 , after welding. There is illustrated facilitating welding of edges referenced  774  and  776  of plate  770  respectively to edges referenced  764  and  766  of plate  760 , and of protrusions referenced  778  to opposing protrusions referenced  768 , either simultaneously or separately. This is facilitated by applying a facilitating substrate material referenced  779  to the upper surface of edges  774  and  776  of plate  770  and by applying a facilitating substrate material  783  to the lower surface of area referenced  762 . Electromagnetic pulse source referenced  773  acts as indicated by arrows referenced  780  and  782  on facilitating substrate referenced  779  on edges  774  and  776 , which are projected, respectively, towards edges  764  and  766  so as to provide welding therebetween. Simultaneously or separately, electromagnetic pulse source  773  acts as indicated by arrows referenced  781  on facilitating substrate  783  disposed adjacent to protrusions  768  on lower area  762  (of plate  760 . Consequently, facilitating substrates  783  are projected towards area  772  of plate  770 , against support  709 , thereby causing impingement of protrusions  768  against opposing protrusions  778 , so as to provide welding therebetween, without causing significant distortion of areas  762  and  772 , in contrast to the prior art as disclosed hereinabove in relation to  FIG. 4 .  
         [0061]     Due to the accuracy of the positioning of the electromagnetic impulses  783  and the self-support that develops in the plate stack, there is no need for additional support between plates  760  and  770  since these become internally self-supporting. Only two welded plates are shown but, after welding the first pair,  760  and  770 , another plate is added from below and welding is continued as disclosed hereinabove in relation to  FIG. 15 .  
         [0062]     In accordance with an additional embodiment of the present invention, referring now to  FIG. 16 , there is shown disposed onto base referenced  802  the upper plate referenced  810  and lower plate referenced  820  with edges referenced  816  already electromagnetically impulse welded to edges referenced  826 . An additional plate  830 , having a facilitating substrate material referenced  800  applied to the upper surface of edges referenced  836 , is placed beneath joined plates  810  and  820 . There is further indicated the disposition before welding plate  830  to plates  810  and  820 , on the left side referenced  801  of  FIG. 16 , and on the right side  803 , after welding. In order to facilitate electromagnetic impulse welding, source referenced  833  is caused to direct electromagnetic impulses towards facilitating substrate  800 , as indicated by arrows referenced  852 . This causes edges  816  of plate  810  to be accelerated and projected respectively towards edges  826  and then towards edges referenced  836  of plate  830  thereby welding these together. Similarly, protrusions referenced  828  on area referenced  832  are directed to impinge against opposing protrusions referenced  838  on area referenced  832  and thereby to be welded together as shown on the right side  803  of  FIG. 16 . Similarly, by adding further plates from below, one after another, a plurality of plates are welded together. Welding in the flow area  812 ,  822 ,  832 , and so on, of protrusions referenced  838  to opposing protrusions  828  is facilitated generally as disclosed hereinabove in relation to  FIG. 15 .  
         [0063]     It will be appreciated by persons skilled in the art that the present invention is not limited by the drawings and description hereinabove presented. Rather, the invention is defined solely by the claims that follow.