Heat exchanger

A heat exchanger includes: heat exchanger bodies arranged in parallel, each allowing a fluid to be cooled to flow therethrough in one direction; a housing that forms a coolant passage that allows a coolant to flow therethrough around each of the heat exchanger bodies; a coolant inlet portion and a coolant outlet portion located in a position corresponding to first ends of the heat exchanger bodies in a flow direction of the fluid to be cooled; a separating portion that separates the coolant passages in a position corresponding to second ends of the head exchanger bodies in the flow direction of the fluid to be cooled so that a communicating portion that allows the coolant passages to communicate with each other is left; and a flow passage area increasing portion that increases a flow passage area of the communicating portion. This structure achieves good cooling performance in the heat exchanger.

CROSS-REFERENCE TO RELATED APPLICATION

This is a national phase application based on the PCT International Patent Application No. PCT/JP2013/062952 filed May 8, 2013, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention is related to a heat exchanger.

BACKGROUND ART

There has been conventionally known a variety of heat exchangers. For example, Patent Document 1 discloses a heat exchanger including a first fluid flow portion formed of a honeycomb structure having a plurality of cells to allow a heating medium as a first fluid to flow therein, and a second fluid flow portion located on an outer peripheral face of the first fluid flow portion. A coolant flows through the second fluid flow portion, taking heat from the heating medium flowing through the first fluid flow portion to cool the heating medium. Patent Document 1 also discloses layered honeycomb structures having gaps to allow the second fluid to flow therein.

PRIOR ART DOCUMENT

Patent Document

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

However, when multiple honeycomb structures, i.e., multiple heat exchanger bodies, are provided as with the layered honeycomb structures disclosed in Patent Document 1, a coolant may stagnate or come to a boil depending on their arrangement. More specifically, the relation between the heat exchanger body and inlet and outlet ports of the coolant and the handling of the coolant may cause stagnation of or a boil of the coolant. The stagnation or a boil of the coolant decreases cooling efficiency. The technique disclosed in Patent Document 1 can be improved in these respects.

The present invention has an object to allow a heat exchanger to have good cooling performance.

Means for Solving the Problems

In order to overcome the above problem, a heat exchanger disclosed in the present description includes: heat exchanger bodies arranged in parallel, each allowing a fluid to be cooled to flow therethrough in one direction; a housing that forms a coolant passage that allows a coolant to flow therethrough around each of the heat exchanger bodies; a coolant inlet portion and a coolant outlet portion located in a position corresponding to first ends of the heat exchanger bodies in a flow direction of the fluid to be cooled; a separating portion that separates the coolant passages, each formed around the corresponding heat exchanger body, so that a communicating portion allowing the coolant passages to communicate with each other is left in a position corresponding to seconds ends of the head exchanger bodies in the flow direction of the fluid to be cooled; and a flow passage area increasing portion that increases a flow passage area of the communicating portion.

This structure reduces stagnation of the coolant, and allows the heat exchanger to have good cooling performance.

The coolant inlet portion and the coolant outlet portion may be located at a downstream side of the flow direction of the fluid to be cooled. This arrangement of the coolant inlet portion and the coolant outlet portion allows the coolant to be introduced from a downstream side of a flow of the fluid to be cooled, turn back its flow direction at an upstream side, flow toward the downstream side, and be discharged. The above described path of the coolant allows the flow of the coolant introduced from the coolant inlet portion and having a lower temperature to be countercurrent to the flow of the fluid to be cooled, enabling to increase cooling efficiency. Additionally, the temperature of the fluid to be cooled is low near the coolant outlet portion at which the temperature of the coolant is high, and thus a boil of the coolant in the heat exchanger is prevented.

A coolant guide portion that rectifies the coolant may be located in the coolant passage. The coolant guide portion may be helically located around each of the heat exchanger bodies. The efficient flow of the coolant enables to increase cooling efficiency.

A flow passage area of the coolant passage, a flow passage area of the communicating portion, a flow passage area of the coolant inlet portion, and a flow passage area of the coolant outlet portion may be equal to each other. Making the flow passage areas of the portions through which the coolant flows equal to each other enables to prevent a part at which pressure loss of the coolant enormously increases from being formed, and to improve cooling efficiency.

The separating portion may include a deflation portion. If air is entrapped into a part of the coolant passage, the part at which air accumulates becomes exposed from the coolant, and the exposed part may become high in temperature. The provision of the deflation portion prevents the exposed part from being formed.

Additionally, the coolant inlet portion may be offset from the heat exchanger body. This structure enables to generate a swirl flow of the coolant.

An inlet flow of the fluid to be cooled to a first heat exchanger body of the heat exchanger bodies may be greater than an inlet flow of the fluid to be cooled to a second heat exchanger body of the heat exchanger bodies, the first heat exchanger body being located closer to the coolant inlet portion than the second heat exchanger body. As the heat exchange body becomes closer to the coolant inlet portion, the temperature of the coolant decreases, and the cooling capacity increases. Thus, the cooling efficiency as a heat exchanger is improved by allowing more fluid to be cooled to flow into the heat exchanger body having higher cooling capacity.

Effects of the Invention

The heat exchanger disclosed in the present description achieves good cooling performance in a heat exchanger.

MODES FOR CARRYING OUT THE INVENTION

Hereinafter, a description will be given of embodiments of the present invention with reference to the attached drawings. In the drawings, the dimensions of each portion, the ratio, and the like may not completely correspond to the actual ones. Some drawings omit the illustration of details.

First Embodiment

A description will first be given of an EGR cooler1of a first embodiment with reference toFIG. 1AthroughFIG. 9. The EGR cooler1is an example of a heat exchanger, and the heat exchanger disclosed in the present description can cool a variety of fluids. The EGR cooler1of the first embodiment is installed in an exhaust gas recirculation device installed in an internal-combustion engine. Thus, a fluid to be cooled in the first embodiment is EGR (Exhaust Gas Recirculation) gas.

FIG. 1Ais a perspective view of the EGR cooler1of the first embodiment viewed from a rear side, andFIG. 1Bis a perspective view of the EGR cooler1of the first embodiment from a front side.FIG. 2is an explanatory diagram schematically illustrating the inside of the EGR cooler1of the first embodiment.FIG. 3is an explanatory diagram illustrating main portions of the disassembled EGR cooler1of the first embodiment.FIG. 4is a cross-sectional view taken along line A-A inFIG. 2.FIG. 5AthroughFIG. 5Care explanatory diagrams schematically illustrating flow states of cooling water in comparative examples.

As illustrated inFIG. 1AthroughFIG. 2, the EGR cooler1includes two heat exchanger bodies arranged in parallel to each other: a first heat exchanger body2and a second heat exchanger body3. A fluid to be cooled, which is EGR gas in the present embodiment, flows through each of the first heat exchanger body2and the second heat exchanger body3. The EGR gas flows in one direction. The first heat exchanger body2and the second heat exchanger body3are made of silicon carbide (SiC) ceramic. Ceramic materials have high-efficiency thermal conduction and high corrosion resistance. Thus, ceramic materials having a high thermal conductivity are suitable for the heat exchanger body. The first heat exchanger body2and the second heat exchanger body3have the same structure. Each of them is cylindrically formed, and has a path formed therein to allow EGR gas to pass therethrough. The first heat exchanger body2and the second heat exchanger body3heat-exchange with cooling water flowing through a first refrigerant passage11and a second refrigerant passage12described in details later, thus cooling the EGR gas. The number of heat exchanger bodies is not limited to two, and more than two heat exchanger bodies may be installed. Additionally, the shape of the heat exchanger body is not limited to a cylindrical shape, and may be other shapes.

The EGR cooler1includes a housing4that forms a coolant passage allowing a coolant to flow therethrough around each of the heat exchanger bodies. More specifically, the housing4forms the first coolant passage11around the first heat exchanger body2, and the second coolant passage12around the second heat exchanger body3. The housing4is made of stainless steel (SUS). As illustrated inFIG. 3, the combination of a first halved member4aand a second halved member4balmost forms the exterior shape of the housing4. The first halved member4aincludes a first curved portion4a1to be located around the first heat exchanger body2and a second curved portion4a2to be located around the second heat exchanger body3. In the same manner, the second halved member4bincludes a first curved portion4b1to be located around the first heat exchanger body2and a second curved portion4b2to be located around the second heat exchanger body3. The first curved portion4b1of the second halved member4bhas a coolant inlet portion6described in details later. The second curved portion4b2of the second halved member4bhas a coolant outlet portion7. A coolant inlet port6ais formed in the coolant inlet portion6. A coolant outlet port7ais formed in the coolant outlet portion7. Although any type of coolant may be used, the present embodiment uses cooling water.

The first halved member4aand the second halved member4bare assembled to face each other so that two cylindrical portions are formed, forming the housing4. In the housing4, enclosed are the first heat exchanger body2and the second heat exchanger body3. Ring members8, each having a shape in which two ring-shaped parts are connected, are mounted to both ends of the housing4. This allows the first heat exchanger body2and the second heat exchanger body3to be supported by the housing4, and prevents the leakage of cooling water.

The first heat exchanger body2and the second heat exchanger body3are enclosed in the housing4and supported by the ring members8, forming the first coolant passage11and the second coolant passage12. In this structure, the first coolant passage11and the second coolant passage12are communicated with each other across almost the entire area in a longitudinal direction of the first heat exchanger body2and the second heat exchanger body3. The EGR cooler1of the present embodiment includes a plate-like separator10that forms a separating portion that separates the first coolant passage11and the second coolant passage12. To form the separating portion, the shapes of the first halved member4aand the second halved member4bmay be changed. For example, the separating portion may be formed when the first halved member4aand the second halved member4bare assembled.

As illustrated inFIG. 2, the separator10is fixed at a side at which the EGR gas is discharged. That is to say, the separator10is located between the first heat exchanger body2and the second heat exchanger body3so that a communicating portion13that allows the first coolant passage11to communicate with the second coolant passage12at the upstream side of the flow direction of the EGR gas is formed. As described above, the separator10separates the first coolant passage11and the second coolant passage12, but is fixed in the housing4so that the communicating portion13is left.

The EGR cooler1includes the coolant inlet portion6and the coolant outlet portion7in the housing4as described above. The coolant inlet portion6and the coolant outlet portion7are located in a position corresponding to a first end in the flow direction of the EGR gas. That is to say, the coolant inlet portion6and the coolant outlet portion7are located at the same end in the flow direction of the EGR gas. The present embodiment provides the coolant inlet portion6and the coolant outlet portion7at the downstream side of the flow direction of the EGR gas. The present embodiment provides the communicating portion13at the upstream side of the flow direction of the EGR gas. Therefore, cooling water, which is a coolant in the present embodiment, is introduced from the downstream side of the flow direction of the EGR gas, and flows toward the upstream side of the flow direction of the EGR gas. The cooling water then turns back its flow direction at the upstream side of the flow direction of the EGR gas, and is discharged at the downstream side of the flow direction of the EGR gas. The coolant inlet portion6is located at the lower side, and the coolant outlet portion7is located at the upper side. Both the coolant inlet portion6and the coolant outlet portion7may be located at the upstream side of the flow direction of the EGR gas.

Here, a description will be given of a positional relation between the communicating portion13and the coolant inlet portion6and the coolant outlet portion7. As described above, the coolant inlet portion6and the coolant outlet portion7are located in a position corresponding to a first end in the flow direction of the EGR gas. On the other hand, the communicating portion13is located in a position corresponding to a second end in the flow direction of the EGR gas. This structure allows cooling water to flow along the first heat exchanger body2and the second heat exchanger body3located in parallel.

As illustrated inFIG. 4, the EGR cooler1includes a flow passage area increasing portion5athat increases the flow passage area of the communicating portion13. The flow passage area increasing portion5ais formed by a protruding portion5located on the rear side of the housing4as clearly illustrated inFIG. 1AandFIG. 1B. As clearly illustrated inFIG. 3andFIG. 4, when the protruding portion5is viewed from the inside of the housing4, a recessed flow passage area increasing portion5ais formed. The flow passage area increasing portion5ais provided in a location corresponding to the location of the communicating portion13. This structure reduces stagnation of cooling water, and allows cooling water to smoothly flow from the first refrigerant passage11to the second refrigerant passage12.

Although the illustration is omitted inFIG. 1A,FIG. 1BandFIG. 3, the EGR cooler1includes cone-shaped members at its upstream end and downstream end. More specifically, an upstream cone member9ais located at the upstream side of the flow direction of the EGR gas. A downstream cone member9bis located at the downstream side of the flow direction of the EGR gas. The upstream cone member9ais a member functioning as an introducing portion that introduces the EGR gas to the first heat exchanger body2and the second heat exchanger body3in the housing4. The downstream cone member9bis a member functioning as a discharging portion that discharges the EGR gas from the first heat exchanger body2and the second heat exchanger body3in the housing4. The upstream cone member9aand the downstream cone member9bare bonded to the housing4by brazing so that the end having a larger diameter covers the end of the housing4.

The EGR cooler1of the present embodiment has the above described outline structure. The EGR cooler1introduces cooling water from the downstream side of the flow direction of the EGR gas to the upstream side. The cooling water turns back its flow direction at the upstream side, flows toward the downstream side, and is discharged at the downstream side. The above described path of the cooling water allows the flow of the cooling water introduced from the coolant inlet portion6and having a lower temperature to be countercurrent to the flow of the EGR gas. Accordingly, the cooling efficiency of the EGR cooler is improved. The increase in the cooling efficiency makes cooling water easily boiled, but the EGR gas temperature near the coolant outlet portion7at which the temperature of the cooling water is high is decreased, and thus a boil of the cooling water can be prevented. The characteristics of the above described EGR cooler1will be described by presenting comparative examples with reference toFIG. 5AthroughFIG. 5C.

With reference toFIG. 5A, an EGR cooler100includes a coolant inlet portion106at the downstream side of the flow direction of the EGR gas and a coolant outlet portion107at the upstream side of the flow direction of the EGR gas. The coolant inlet portion106and the coolant outlet portion107are located at the upper side in the figure. Unlike the EGR cooler1of the first embodiment, the separator10is not provided. Cooling water in the EGR cooler100hardly reaches the periphery of the first heat exchanger body2located at the lower side. That is to say, the flow toward the coolant outlet portion107is strong in the flow of the cooling water introduced from the coolant inlet portion106, and the cooling water hardly reaches the periphery of the first heat exchanger body2. As a result, stagnation of the flow of the cooling water easily occurs in the region indicated by X1inFIG. 5A, and sufficient cooling efficiency is hardly achieved.

With reference toFIG. 5B, an EGR cooler110includes a coolant inlet portion116at the downstream side of the flow direction of the EGR gas and a coolant outlet portion117at the upstream side of the flow direction of the EGR gas. The separator10is not provided. The coolant inlet portion116is located at the upper side inFIG. 5B, while the coolant outlet portion117is located at the lower side inFIG. 5B. Thus, the coolant inlet portion116is located diagonally to the coolant outlet portion117in the EGR cooler110. Cooling water in the EGR cooler110hardly reaches the periphery of the first heat exchanger body2at the downstream side and the periphery of the second heat exchanger body3at the upper side. That is to say, the flow toward the coolant outlet portion117is strong in the flow of the cooling water introduced from the coolant inlet portion116, and the cooling water hardly reaches the periphery of the first heat exchanger body2at the downstream side and the periphery of the second heat exchanger body3at the upstream side. As a result, stagnation of the cooling water easily occurs in the regions indicated by X2and X3inFIG. 5B, and thus sufficient cooling efficiency is hardly achieved.

With reference toFIG. 5C, an EGR cooler120includes a coolant inlet portion126and a coolant outlet portion127at the upstream side of the flow direction of the EGR gas. The separator10is provided. However, the separator10is fixed at the upstream side of the flow direction of the EGR gas, and a communicating portion is formed at the downstream side. That is to say, the EGR cooler120has the structure in which the positions of the coolant inlet portion, the coolant outlet portion, and the communicating portion are switched around those of the EGR cooler1of the first embodiment. The cooling water discharged from the coolant outlet portion127is already circulated in the EGR cooler120, and is in a state where heat exchange is already performed, thus having a high temperature. The high-temperature cooling water heat-exchanges with high-temperature EGR gas introduced through the upstream cone member9a, and thus a boil of the cooling water easily occurs. Therefore, the EGR cooler120can be improved in terms of effective cooling.

As described above, the comparative examples can be improved in terms of the occurrence of stagnation or the like, and reveal that the cooling by the EGR cooler1of the first embodiment is effective.

Hereinafter, a description will be given of the flow state of the cooling water in each portion of the EGR cooler1with use of comparative examples.

As illustrated inFIG. 6, the coolant helically flows. That is to say, the cooling water introduced into the housing4from the coolant inlet portion6helically flows through the first coolant passage11as indicated by arrows14a,14band14cinFIG. 6. The cooling water flows into the second coolant passage12through the communicating portion13, and also helically flows through the second coolant passage12as indicated by arrows15a,15band15cinFIG. 6. The first coolant passage11and the second coolant passage12are separated by the separator10, thus enabling to generate a helical flow in each passage. The helical flow of the cooling water allows the cooling water to flow along the external walls of the first heat exchanger body2and the second heat exchanger body3, thus reducing stagnation as much as possible. This improves cooling performance.

With reference toFIG. 7A, the coolant inlet portion6is offset from the first heat exchanger body2. More specifically, the coolant inlet portion6is located on the lateral side of the first heat exchanger body2, and is located in the position offset from the center axis of the first heat exchanger body2. Thus, the introduced cooling water can form a swirl flow at the time of being introduced. Once the swirl flow is generated, it can helically flow through the first coolant passage11and the second coolant passage12. Additionally, the coolant outlet portion7is also offset from the second heat exchanger body3. More specifically, the coolant outlet portion7is located on the lateral side of the second heat exchanger body3, and is located in the position offset from the center axis of the second heat exchanger body3. This allows the cooling water helically flowing to be smoothly discharged to the outside of the housing4. In contrast, an EGR cooler20of a comparative example illustrated inFIG. 7Bprovides a coolant inlet portion26so as to correspond to the center portion of the first heat exchanger body2. A coolant outlet portion17is also provided so as to correspond to the center portion of the second heat exchanger body3. Thus, the cooling water introduced from the coolant inlet portion26easily collides with the first heat exchanger body2, and pressure loss easily occurs. In a coolant outlet portion27, the cooling water flowing around the second heat exchanger body3from one side easily collides with the cooling water flowing around the second heat exchanger body3from another side, and thus pressure loss also easily occurs. The EGR cooler1of the first embodiment can avoid the above described inexpedience.

With reference toFIG. 8A, the EGR cooler1of the present embodiment leaves a distance L in the communicating portion13and forms the flow passage area increasing portion5a, enabling to smoothly guide the helical swirl flow from the first coolant passage11to the second coolant passage12. That is to say, the occurrence of pressure loss in the communicating portion13can be reduced. In contrast, an EGR cooler30of a comparative example illustrated inFIG. 8B, no countermeasure is taken in the communicating portion, and a narrow part31is formed. As a result, the smooth transfer of the cooling water is prevented, and pressure loss occurs. The EGR cooler1of the first embodiment can avoid the above described inexpedience. As illustrated inFIG. 9, when a flow passage area increasing portion41ais formed in other than the communicating portion, i.e., in a position where a separator41is provided, it is difficult to form a swirl flow in the regions indicated by X4and X5inFIG. 9, and the cooling water easily flows in the axial direction. The presence of such a part stops the helical flow. As a result, the smooth flow of the cooling water is prevented.

Second Embodiment

A description will next be given of a second embodiment with reference toFIG. 10throughFIG. 12. An EGR cooler50of the second embodiment differs from the EGR cooler1of the first embodiment in the following point. That is to say, the EGR cooler50of the second embodiment differs from the first embodiment in that it includes coolant guide portions16that rectify the cooling water in the first coolant passage11and the second coolant passage12. More specifically, the coolant guide portion16is formed of wire members helically located around the first heat exchanger body2and the second heat exchanger body3. The provision of the helically located coolant guide portions16enables to form the swirl flow even when the flow rate of the cooling water introduced in the housing4is slow and the inertia force is weak. This reduces the occurrence of stagnation. Additionally, the coolant guide portions16located at intervals of an arrangement width (pitch) W reduce the flow passage cross-sectional area as illustrated inFIG. 11A, and thus increase the flow rate of the cooling water of the same quantity. As a result, heat-transfer efficiency increases, and temperature efficiency increases.FIG. 11Billustrates a flow passage area S1without the coolant guide portion16. When the coolant guide portion16is not provided, the ring shape of the first coolant passage11or the second coolant passage12defines the flow passage area, and thus the flow passage area is greater than the flow passage area S2with the coolant guide portion16illustrated inFIG. 11A. In other words, the provision of the coolant guide portions16allows the flow passage area to be defined by the arrangement width of the coolant guide portions16, i.e., the pitch W and the gap between the heat exchanger body and the housing4, thus enabling to make the flow passage area S2less than the flow passage area S1.

Here, a description will be given of the flow passage area of each portion of the EGR cooler50of the second embodiment with reference toFIG. 12. InFIG. 12, the flow passage areas of the first coolant passage11and the second coolant passage12are represented by S2. The flow passage area of the coolant inlet portion6, more specifically, the area of the coolant inlet port6ais represented by S3. The flow passage area of the coolant outlet portion7, more specifically, the area of the coolant outlet port7ais represented by S4. The flow passage area of the communicating portion13, more specifically, the flow passage area of the flow passage area increasing portion5ais represented by S5. These flow passage areas S2through S5are equal to each other. Making the flow passage areas of the portions equal to each other as described above prevents the occurrence of local pressure loss. As a result, the cooling water can smoothly flows through the entire path, and good cooling performance can be obtained.

Third Embodiment

A description will be given of a third embodiment with reference toFIG. 13.FIG. 13is an explanatory diagram schematically illustrating an EGR cooler60of the third embodiment. The EGR cooler60of the third embodiment includes a deflation portion61in the separator10that forms a separating portion. When air is entrapped into a part of the coolant passage, the part in which air accumulates becomes exposed from the cooling water, and the exposed portion may become high in temperature. Especially, when the separator10is located as described in the present embodiment and the first coolant passage11and the second coolant passage12are separated, air may be accumulated in a part such as a corner of the flow passage. The part in which air accumulates becomes exposed from the cooling water. Thus, the deflation portion61is provided. The EGR cooler60is tilted and installed in a vehicle. More specifically, the EGR cooler60is tilted so that the deflation portion61is located further upper than the communicating portion13and installed in a vehicle. This allows the air to move directly to the coolant outlet portion7side, and to be discharged from the inside of the EGR cooler60.

Fourth Embodiment

A description will next be given of an EGR cooler70of a fourth embodiment with reference toFIG. 14.FIG. 14is an explanatory diagram schematically illustrating the EGR cooler70of the fourth embodiment. The EGR cooler70of the fourth embodiment makes the inlet flow of the EGR gas to a heat exchanger body located closer to the coolant inlet portion6, i.e., to the first heat exchanger body2, greater than the inlet flow of the EGR gas to the second heat exchanger body3. As a position becomes closer to the coolant inlet portion6, the temperature of the coolant decreases, and the cooling performance increases. Thus, cooling efficiency as a heat exchanger is improved by allowing more fluid to be cooled to flow into the heat exchanger body having higher cooling performance. More specifically, the shape of an upstream cone member79is changed to increase the inlet flow of the EGR gas to the first heat exchanger body2. The length of a lower edge79a1of the upstream cone member79is made to be greater than that of an upper edge79a2to change the volume allocation of the inside of an upstream cone member79. That is to say, the volume at the first heat exchanger body2side is increased to achieve the state where the EGR gas more easily flows into the first heat exchanger body2. This enables to cool the EGR gas more effectively.

Fifth Embodiment

A description will next be given of an EGR cooler80of a fifth embodiment with reference toFIG. 15.FIG. 15is an explanatory diagram schematically illustrating the EGR cooler of the fifth embodiment. The EGR cooler80of the fifth embodiment makes the inlet flow of the EGR gas to the first heat exchanger body2greater than the inlet flow of the EGR gas to the second heat exchanger body3as with the EGR cooler70of the fourth embodiment. The fifth embodiment differs from the fourth embodiment in the means of changing the inlet flow of the EGR gas. In the EGR cooler80of the fifth embodiment, a first heat exchanger body82has a diameter Din greater than the diameter Dout of a second heat exchanger body83. That is to say, the diameter of the first heat exchanger body82, which is located closer to the coolant inlet portion6, is made to be greater than the diameter of the second heat exchanger body83to increase the quantity of the EGR gas cooled in the first heat exchanger body82. This enables to cool the EGR gas more effectively.

While the exemplary embodiments of the present invention have been illustrated in detail, the present invention is not limited to the above-mentioned embodiments, and other embodiments, variations and modifications may be made without departing from the scope of the present invention.

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