Background Art Heat exchangers are used in many applications and are made of different materials, most notably metal and plastic. Such heat exchangers are disclosed in U. S. Patents 6,119,768,4,997,031; 4,907,648; 4,874,035; 4,858,685; 4,820,468; 4,738,311; and GB 2158569, and PCT Applications SE82/00393 and GB98/03368. Typically, metal heat exchangers are relatively expensive. Plastic heat exchangers tend to be more economical. Examples of recent plastic heat exchangers are shown in U. S. Patent Nos. 6,364,007 and (09/665, 462). In PCT/GB98/03368 the heat exchanger core is formed of identical sheets of plastic where every other sheet is rotated 90 degrees to construct a cross flow type heat exchanger. As is apparent, there continues to be efforts to create an economical, simply constructed and easily assembled heat exchanger to bring costs down and to enhance operation.

DISCLOSURE OF THE INVENTION The difficulties encountered in the past have been overcome by the present invention. What is described here is a heat exchanger comprising an outer housing, an elongated strip of synthetic resin material located in the outer housing, the strip having a longitudinal axis. The elongated strip also has

longitudinal sides and lateral sides and is divided into a plurality of panels. A plurality of hinges is formed in the elongated strip where each of the plurality of hinges extends generally perpendicular to the longitudinal axis and connecting lateral sides of adjacent panels. Alternate hinges are bendable in opposite directions so that the elongated strip assumes an accordion folded disposition.

Each of the plurality of panels is aligned generally parallel to and spaced from adjacent panels of the plurality of panels when folded and the plurality of panels forms first and second passages between adjacent pairs of panels where one panel of each of the adjacent pairs of panels is common to both adjacent pairs.

Latitudinal sides of a pair of adjacent panels opposite a hinge connecting them form a closure.

There are a number of advantages, features and objects achieved with the present invention which are believed not to be available in earlier related devices. For example, one advantage is that the present invention provides an economical heat exchanger and core. Another object of the present invention is to provide an economical heat exchanger and core which is simply constructed and easily assembled. Still another feature of the present invention is to provide an economical heat exchanger and core which may be easily disassembled, cleaned and reassembled.

A more complete understanding of the present invention and other objects, advantages and features thereof will be gained from a consideration of the following description of the preferred embodiment read in conjunction with the accompanying drawing provided herein.

BRIEF DESCRIPTION OF DRAWING FIGURE 1 is a plan view of a flat strip of synthetic resin material formed as disclosed herein.

FIGURE 2 is an enlarged broken sectional view taken along line 2- 2 of FIGURE 1.

FIGURE 3 is an enlarged broken sectional view taken along line 3-3 of FIGURE 1.

FIGURE 4 is an enlarged broken sectional view taken along line 4- 4 of FIGURE 1.

FIGURE 5 is a front isometric view of a partially folded heat exchanger core made from the flat strip illustrated in FIGURE 1.

FIGURE 6 is a rear isometric view of the partially folded heat exchanger core shown in FIGURE 5.

FIGURE 7 is a downward looking isometric view of the heat exchanger core shown in FIGURES 5 and 6, but in a fully folded position.

FIGURE 8 is an exploded isometric view of the heat exchanger core shown in FIGURES 5-7 installed in a heat exchanger housing.

FIGURE 9 is a plan view of another embodiment of a flat strip of synthetic resin material formed as disclosed herein.

FIGURE 10 is a sectional view taken along line 10-10 of FIGURE 9.

FIGURE 11 is a sectional view taken along line 11-11 of FIGURE 9.

FIGURE 12 is a sectional view taken along line 12-12 of FIGURE 9.

FIGURE 13 is an enlarged view taken within the circle 13-13 of FIGURE 11.

FIGURE 14 is an enlarged view taken within the circle 14-14 of FIGURE 11.

FIGURE 15 is a right side, downward looking isometric view of a partially folded heat exchanger core shown in FIGURES 9-14.

FIGURE 16 is an enlarged left side, downward looking isometric view of the heat exchanger core shown in FIGURE 15.

FIGURE 17 is an enlarged view of the heat exchanger core taken within the circle 17-17 of FIGURE 15.

FIGURE 18 is an isometric view of the heat exchanger core of FIGURES 9-17 placed in a housing.

BEST MODE FOR CARRYING OUT THE INVENTION While the present invention is open to various modifications and alternative constructions, the preferred embodiments shown in the drawing will be described herein in detail. It is understood, however, that there is no intention to limit the invention to the particular forms disclosed. On the contrary, the intention is to cover all modifications, equivalent structures and methods, and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

The simplicity and economical features of the present invention are apparent by referring to FIGURES 1-4. There is illustrated a portion of a formed elongated strip 10 of synthetic resin material. For purposes of orientation, a longitudinal axis 12 for the strip is illustrated in phantom line. The elongated strip portion is shown divided into four panels 14,16,18,20 with each panel having opposed longitudinal sides and opposed latitudinal sides, such as the longitudinal sides 22,24 of the panel 18 and the latitudinal sides 26,28 of the same panel. Each panel has two longitudinal and two latitudinal sides. It is further to be understood that while only four panels are illustrated, the elongated strip will usually contain far more panels as will be explained hereinbelow.

Between adjacent panels is an integral hinge, such as the hinge 30 between the panels 14 and 16, the hinge 32 between the panels 16 and 18 and the hinge 34 between the panels 18 and 20. Also, as will be shown in detail below, the hinges are made to fold in alternate directions to achieve an accordion like disposition when the strip is folded at the hinges during assembly.

The longitudinal sides 22,24 are each divided into first and second generally equal portions. For example, the longitudinal side 22 includes a first portion 40 and a second portion 42. In a like manner, the longitudinal side 24 includes a first portion 44 and a second portion 46. As shown more clearly in FIGURES 2 and 3, each portion of the longitudinal sides includes a bent border but in an alternating fashion. For example, the longitudinal side portion 40 has a downward or closed bend whereas the longitudinal side portion 42 has an upward

or open bend. The opposite longitudinal side portions of a panel are bent in opposing directions. For example, the longitudinal side portion 44 is bent upwardly or in an open position whereas the longitudinal side portion 46 is bent downwardly or in a closed position. The concept of opened and closed portions will also be explained in more detail below. Each of the latitudinal sides, such as the sides 26,28 has a raised border which will act as a spacer to separate the adjacent panels when the strip is folded. The latitudinal sides of each panel are integrally formed adjacent a hinge except for the end latitudinal sides 50,52 of the end panels 14,20, respectively of the strip.

Referring now to FIGURES 5 and 6, the elongated strip 10 is shown enlarged and in a partially folded position where the folded hinges bend in alternate directions, accordion-like. It can now be appreciated that the longitudinal side portions alternately provide openings to form first and second sets of fluid flow passages through the folded stack of panels, the fluid flow passages being generally parallel to the latitudinal sides of the panels. For example, the first portion 44a of the longitudinal side 24a of the panel 14 is bent downwardly to meet the upwardly slanting second portion 46b of the longitudinal side 24b of the panel 16. When these side portions come together, a closure is formed against fluid flow entering or leaving through the left side portion of the space between the panels 14,16 as viewed in FIGURE 5. The right side portion of the space, however, formed by the side portion 46a and the side portion 44b are bent upwardly so as to provide an opening to fluid flow on the right side between the panels 14 and 16. On the opposite longitudinal side of the panel, the edge portions 40a and 42b are bent upwardly to form an opening whereas the edge portions 42a and 40b are bent downwardly to form a closure.

Referring to the latitudinal sides 28 and 26a surrounding the hinge 34, FIGURE 4, it is seen that there are raised borders for the purpose of spacing adjacent panels from one another. This can be seen by way of example between the two panels 18,20, FIGURE 6. It can also now be observed by referring to FIGURE 5 that the hinges alternate in the direction of folding from counterclockwise to clockwise to counterclockwise, etc. When the elongated strip is fully folded as shown in FIGURE 7, two sets of fluid passages are formed.

This is clearly shown in FIGURE 6 where there is formed a first set of fluid passages, exemplified by the passage 60 formed between the panels 18 and 20, and a second set of fluid passages, exemplified by the passage 62 formed between the panel 20 and its adjacent panel 64. A passage identical to the passage 62 is also formed between the panels 16 and 18 whereas an identical passage to the passage 60 is formed between the panels 14 and 16. The two types of passages alternate between adjacent pairs of panels where one panel of the adjacent pairs is common to both pairs. Thus, the two pairs of panels 14,16 and 16,18 have the panel 16 in common. It is also noted that because of the alternating design, the set of passages, like the passage 60, is open on the right side of the stacked panels when viewed from the front (FIGURE 5) and is open on the right side when viewed from the rear (FIGURE 6). Stated another way, the passages"cross"the panels when moving in a direction generally perpendicular to the longitudinal axis 12 of the strip. In a similar but opposite manner the other set of passages, like the passage 62, also cross the panel. Nevertheless, most of the flows in the passages are such that it can be said that the core produced is of the counterflow variety.

It has already been disclosed that alternate portions of the longitudinal sides of the panels are closed and open. Referring now to the latitudinal sides, they are, in all cases, closed. For example, each of the hinges 30, 32,34 connect adjacent panels as a solid integral piece. Further, between hinges a closure is formed by abutting raised latitudinal sides, such as the sides 26b, 28, FIGURES 5 and 6. In a similar manner a closure or seal 68, FIGURE 6, is formed along the latitudinal sides of the panels 18 and 20.

When the elongated strip is fully folded as shown in FIGURE 7, two sets of fluid flow passages are formed which alternate along the stack as exemplified by the fluid flow passages 60,62. The passages are formed between alternate pairs of panels and by the structure of the individual panels and related hinges. Seals or closures are formed by abutting panels to keep the two sets of fluid passages separate. Thus, a fluid flow entering from the front, right side through the passage 60 is separated from another fluid flow entering from the rear, left side through the passage 62. This latter fluid flow will exit from the left, front side of the stacked panels. The flow passages are sealed because the hinges

are solid material and the contacting portions of opposite latitudinal sides may be pressed together to prevent leakage. Or, an adhesive may be used to seal the contacting portions or heat may be used to cause bonding of these portions. The flow passages are further separated by the panels themselves. It is readily understood that if opposing fluid flows are at different temperatures, heat transfer will take place across each panel from the flowing higher temperature fluid to the flowing lower temperature fluid. It is to be noted that abutment between panels may also be made by projecting borders of one panel and mating recess borders of another panel where the two are nested. This also will form a closure.

Referring to FIGURE 8, the folded strip of material 10 in the form of a core is placed within a simply constructed four piece heat exchanger housing comprising a lower housing member 70, a housing cover 72, and two trapezoidal partitions 74,76. The partitions are provided to engage housing partitions 78,80 respectively to maintain separated fluid flows in the housing. For example, an inlet as exemplified by the arrow 82 may be formed with a mating outlet, exemplified by the arrow 84. This flow can use the first set of passages, such as the passage 60. In a like manner, an inlet, exemplified by the arrow 86, is mated with an outlet, as exemplified by the arrow 88. This flow can use the second set of passages, such as the passage 62. It is to be noted that fluid flows may also be in generally the same direction. That is, both flows may move from left to right in the heat exchanger shown in FIGURE 8.

The elongated strip is formed of a synthetic resin material, such as PVC film having a starting thickness of about 0.12 to about 0.18 inches. As explained in International Application No. PCT/GB98/03368 and incorporated herein by reference, the elongated strip of material may be thermoformed in an assembly line fashion to achieve the structural detail described for the panels and hinges. Each panel emerges with a panel length, parallel to the latitudinal sides of the strip of between 1 and 3 feet and a panel width, parallel to the longitudinal sides of the strip, of between 1 and 2 feet. It is contemplated that the space between stacked panels is within the range of about 0.200 to 0.800 inches. Each stack of folded panels may be approximately 7 inches tall although it is to be understood that a stack may be made higher or of the desired heat transfer. The

same is true of the dimensions of the panels. These may also change depending upon the heat transfer characteristics desired.

The simplicity and versatility of the present invention is shown by reference to FIGURES 9-17. There is illustrated another embodiment of a heat exchanger core which is similar to the embodiment illustrated in FIGURES 1-8 except that the second embodiment is for a cross-flow heat exchanger rather than a counterflow heat exchanger. There is illustrated a portion of an elongated strip 110 of synthetic resin material having a longitudinal axis 112. The elongated strip is formed into a series of connected or integral panels 114,116,118,120.

Each of the panels includes longitudinal sides and latitudinal sides, such as the longitudinal sides 122,124 and latitudinal sides 126,128 of the panel 118.

Hinges 130,132,134 are formed integral with the panels and are positioned between panels to allow the strip to be alternately folded in an accordion fashion.

The longitudinal and latitudinal sides have raised borders so that when folded, each panel is spaced from an adjacent panel whereby fluid flow passages between panels are created.

The most striking difference between the heat exchanger core embodiment shown in FIGURE 1 and that shown in FIGURE 9 is that the core in FIGURE 9 has a region of every second hinge which is mostly open. When the elongated strip is folded, this opening forms an inlet or outlet for a fluid flow passage. Also, longitudinal sides of the panels either form a closure or an opening. In this manner, two series or sets of fluid flow passages are provided, the passages being at right angles to each other. One set of passages conducts flows parallel to the longitudinal axis 112 whereas the other set of passages conducts flows perpendicular to the first mentioned set and to the longitudinal axis.

Referring to FIGURES 9-16 in more detail, the openings between the panels are seen in more detail. For example, between the panel 114 and the panel 116 the hinge 130 includes a forward portion 130a and a rearward portion 130b separated by an opening 150. The hinge 132 extends across the strip of material without any opening. The hinge 134 is also divided between a forward portion 134a, a rearward portion 134b and a central opening 152. Following the

open hinge 134 is a closed hinge 154 which is identical to the hinge 132. In this fashion, closed and open hinges alternate with each other.

Referring again to FIGURE 16, the raised borders 156,158 are illustrated along the upper and lower longitudinal sides 122,124, respectively, of the panel 118. The longitudinal sides of the adjacent panel 120 also include projecting borders 155,157. When the projecting borders 155,157 of the panel 120 engage or abut the projecting borders 156,158 of the panel 118, closures are formed longitudinally. However, between the adjacent pair of panels 116,118, the longitudinal sides do not have raised or abutting borders and thus openings are formed. Referring now to FIGURES 16 and 17, the alternating openings 160,162 in the longitudinal sides between panels is shown alternating with closed or sealed longitudinal sides 161,163 caused by raised or projecting borders, such as the raised borders 164,166. The latitudinal sides have openings, such as the opening 170, alternating with closed hinges, such as the hinges 154,172. As with the earlier embodiment, nesting elements of two panels may also be used to close sides of the panels to fluid flow.

The cross flow may best be seen by reference to FIGURES 16 and 17 where a fluid flow passage having the opening 170, parallel to the longitudinal axis, has an inlet, depicted by an inlet arrow 180, and an outlet 181, depicted by an outlet arrow 182. A fluid flow passage having the opening 162 includes an inlet, depicted by the inlet arrow 190, and an outlet, depicted by the outlet arrow 192, FIGURE 16.

Referring to FIGURE 18, there is illustrated the folded stacked strip 110 forming a core. The core is positioned in a heat exchanger housing 200 having a cover 202, a first inlet 204, a first outlet 206, a second inlet 208 and a second outlet 210. One corner 212 of the core is sealed against a wall 214 of the housing, an opposing corner 216 of the core is sealed to an opposite wall 218, a third corner 220 of the core is sealed to a third wall 222 and a fourth corner 224 of the core is connected to a partition 226 which is sealed to a fourth wall 228. This arrangement also allows for oppositely directed fluid flows if desired.

In operation, the core is formed from a long strip of PVC material which is formed by any suitable process, such as vacuum forming or embossing,

to fold in an accordion-like fashion. The folded core may be used as is and placed in a heat exchanger housing or the abutting borders or edges or surfaces may be bonded and sealed in some fashion such as with an adhesive polymeric cure-in- place compound, a preformed seal system, such as a molded or die-cut gasket or by the use of an RF welder, thermal border or a combination of these or other methods. The heat exchanger housings include two inlets and two outlets which define flow paths to and from the fluid passages formed in the core. In the case of the embodiment shown in FIGURES 1-8, a counterflow heat exchanger is formed whereas with the embodiment shown in FIGURES 9-18, a cross-flow heat exchanger is formed.

The specification describes in detail two embodiments of the present invention. Other modifications and variations will, under the doctrine of equivalents, come within the scope of the appended claims. For example, dimensional differences for the core, a greater or lesser number of panels in a core, differences in geometries and the like are all considered equivalent structures. Also, fluid flow directions designated first and second may be perpendicular to each other, or parallel to each, and when parallel, they may be in opposite directions or in the same direction. That is, the first and second directions may be generally the same though separated. Further, the fluid in one flow may be a gas such as air while the fluid in the second flow may be a liquid.

These are all equivalent. Still other alternatives will also be equivalent as will many new technologies. There is no desire or intention here to limit in any way the application of the doctrine of equivalents.